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SOLID WASTE MANAGEMENT BASICS IGNACIO MANZANERA 2011
SOLID WASTE MANAGEMENT
BASICS
IGNACIO MANZANERA
2011
2
Foreword
Environmental protection is an engineers’ responsibility and it should not be taken
lightly.
Environmental concerns have forced many engineering schools to run their syllabus
following engineering subjects embedded in ecological scenarios to emphasize the fact
their graduates will be meeting communities’ green codes where ever they are.
It is the intention of this book to promote basic knowledge on the different alternatives
available to handle waste sources.
The book has been published with an environmental impact assessment guide from the
Scientific Council on Problems of the Environment (SCOPE) as a helpful tool for project
developer.
Every project must have an environmental impact assessment and it should be an integral
part of all planning for major actions. It should be carried out at the same time and given
the same importance as engineering, economic, and socio-political assessments.
In order to provide guidelines for environmental impact assessments, national goals and
policies should be established which take environmental considerations into account;
these goals and policies should be widely promulgated, promoted and applied.
The institutional arrangements for the process of environmental impact assessment
should be determined and made public. Here it is essential that the roles of the various
stakeholders of the project be designated.
It is also important that timetables for the impact assessment process be established, so
that proposed actions are not held up unduly and the assessor and the reviewer are not so
pressed that they undertake only superficial analyses.
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Table of Contents
Subject Page Chapter I Waste Characterization 7
Durable Goods Waste 8
Containers and Packing Waste 9
Waste Characterization Results 10
Chapter II
Best Practical Environmental Option 11
Diversification Requirements 12
Operating and Control Philosophy 12
Design Basis 15
Analysis of Different Operational Scenarios 16
Chapter III
Waste Collection of Residential Waste 18
Cost Accounting Procedures for Solid Waste Collection Systems 19
Enterprise Fund Accounting 20
Labor Relations Staff and Strategy 21
Motivation 22
Collection Routing 24
Collection Equipment Maintenance Program 26
Components in a Maintenance Program 27
Codes for Maintenance 28
Optimizing the Performance of Collection Services 29
Factors Affecting Productivity and Costs 30
The Five Stage Process to Improve Solid Waste Collection Systems 35
Chapter IV
Transfer Stations 42
Transfer Stations Concepts 42
Conceptual Design 49
Site Development and Ancillary Facilities
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Table of Contents
Subject Page Chapter V Sorting and Recycling Facilities 50
Design Requirements 51
Conceptual Design 52
Vibratory Desk Screens 53
Rotary Screens 55
Screen Selection 56
Size Reduction Equipment 57
Magnetic Separation 60
Baling 62
Chapter VI
Sanitary Landfills 64
Design Requirements 64
Conceptual Design 67
Liner System and Leachate Control System 68
Gas Collection 69
Support Facilities 71
Chapter VII
Medical Waste 75
Steam Autoclaving 75
Chemical Decontamination 77
Microwaving 79
Disposal of Medical Waste 80
Landfill 80
Sanitary Sewer 81
Incineration 81
Design Requirements 82
Medical Waste Collection 83
Medical Waste Handling and Disposal 85
Rotoclave System Specifications 96
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Table of Contents
Subject Page Chapter VIII Construction & Demolition Waste 99
Collection, Disposal and Reuse of C&D Waste Materials 104
Conceptual design 105
Processing Building Structures 106
Chapter IX
Compost Technologies and Engineering 112
Digestion in Horizontal Drums 117
Digestion in Vertical Drums 119
Windrows 119
Aeration in Windrows 122
Static Piles 126
Other Composting Technologies 127
Engineering a Compost Plant 129
Odor Control Calculations 140
Compost Facilities Water Requirements 145
Chapter X
Hazardous Waste Treatment 151
Design Requirements 152
Pre-shipment Waste Analysis 153
Residuals Management 156
Conceptual Design 157
Steam Stripping 157
Carbon Adsorption 159
Chemical Oxidation 160
Attached-Growth Systems 161
Aerobic Batch Reactor Systems 162
Liquid Injection Incineration 165
Solidification 169
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Table of Contents
Subject Page Chapter XI Hazardous Waste Landfill 171
Construction Quality Assurance 175
Design Requirements 177
Security and Fencing 180
Chapter XII
Standards of Hazardous Waste Management 184
General Facility Standards 184
General Waste Analysis 185
Waste Analysis Plan 186
General Inspection Requirements 188
Personnel Training 189
General Requirements for Ignitable, Reactive or Incompatible Wastes 191
Location Standards 192
Construction Quality Assurance Program 193
Preparedness and Prevention 195
Contingency Plan and Emergency Procedures 197
Cost Estimate for Closure 199
Financial Assurance for Closure 200
7
Chapter I Waste Characterization
The foundations of solid waste management rest on a good understanding of the
characteristics of the waste stream being considered.
Waste characterization is an essential activity of any solid waste management program
and it is a required permanent function contributing to good short, medium and long
range planning.
Waste characterization should provide a clear picture of the solid waste generation rates
or the amount of materials and products in municipal solid waste as they enter the waste
stream before any treatment takes place.
Sizing of the operations should always be tied to the waste characterization results and
their corresponding projections. Underestimated or overestimated waste figures will
result in over- or undersized facilities.
The main sources of municipal solid waste are as follows:
Residential;
Commercial;
Institutional; and
Industrial.
Residential waste comes from family homes. Commercial garbage includes waste from
office buildings, shopping malls, warehouses, hotels, airports, and restaurants.
Institutional rubbish comprises waste form schools, medical facilities, government
institutions and prisons. Industrial waste comes from packaging of components, offices
waste, and cafeterias garbage and excluding industrial process waste.
There are two procedures to characterize municipal waste, one is by sampling the other is
material flows. Sampling can be expensive while done with large enough samples and
frequently enough to contribute accurate results.
The material flow methodology was developed by the US environmental protection
agency in the 1970s and since then has been refined by the EPA and other interested
organizations.
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The foundation of the material flow methodology is data collected by department s of
commerce, industrial associations, chambers of commerce and the like. Material flow
technology focuses on consistency of data series from year to year instead of data in a
single point in time.
Data adjustments are obviously required:
Product life times
Assumption that all containers and packaging and most non-durables are disposed the
same year they are produced. Durables such as appliances and tires are assigned product-
life times and analyzed for location behavior before they are assumed to be discarded.
Production scrap
Deduct industrial production scrap, which is classified as industrial waste.
Imports/Exports
Due to obvious reasons, the characterization data should be adjusted according to
reported import and export figures.
Sampling studies must be a complement of material flow methodology when
determination of food waste generation, yard trimmings, and other inorganic wastes is
required.
Durable Goods Waste
Products lasting more than 3 years are usually called durable goods. Durable goods
waste includes among others:
Furniture and furnishings;
Carpets and rugs;
Rubber tires;
Lead-acid batteries; and
Major appliances.
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Durable goods waste also called bulky items, are extremely difficult to forecast due to
wide open opinions on products life time and local way of life. Also, they are not
accounted for during sampling exercises.
Nondurable Goods Waste
Products lasting less than 3 years are cataloged as non-durable goods although
experience shows that most of them are discarded the same year they were manufactured.
Products made of paper are the largest contributors to this category of waste.
Non-durable goods waste, among many others, includes:
Newspapers;
Office papers;
Commercial printing;
Tissue paper and towels;
Clothing and footwear;
Phone books; and
Junk mail.
Containers And Packaging Waste
Packaging is usually divided in primary, secondary and tertiary packing. Primary
packing is used as containers to hold food, beverages, toiletries and the like. Secondary
packing is used for product display. Tertiary packing is utilized for shipping purposes.
It should be assumed that containers and packaging are discarded the same year they
were manufactured. Paper and paperboard are, of course, the prevailing materials in this
category of waste.
Other Wastes
Total municipal waste generation is obtained adding durable wastes, non-durable wastes,
containers waste, packaging waste to other wastes including:
Food wastes;
Yard trimmings; and
Miscellaneous inorganic wastes
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Waste Characterization Results
A waste characterization study should end up with a clear image of the solid waste
management problem at hand. As such, it should define waste quantities generated:
Households;
Commercial dealings;
Institutions;
Industry;
Agricultural production;
Hospitals and clinics;
Construction sites; and
Hazardous wastes
This information will provide the background required for:
Collection routing solutions;
Recycling programs;
Treatment needs;
Manpower estimates;
Equipment estimates;
Operational cost estimates;
Capital cost estimates;
Investment; and
Waste minimization programs.
Marketing organizations are also interested in waste characterization results since,
among others things, they provide population:
Eating habits;
Products preference sorted by community areas; and
Seasonal consumer’s variations.
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Chapter II
BPEO
The Best Practicable Environmental Option (BPEO) can be defined as an evaluation of
the non-hazardouos and hazardous waste management options, which are deemed to be
practicable and environmentally acceptable for the local authorities.
The BPEO concept was first outlined in the UK in the fifth report of the Royal
Commission on Environmental Pollution 1976, and defined for a given waste stream as
the optimum combination of available methods of disposal so as to limit damage to the
environment to the greatest extent achievable, for a reasonable and acceptable total
combined cost to industry and to the public in general.
The concept of BPEO has been further defined as the outcome of a systematic
consultative and decision making procedure which emphasizes the protection of the
environment across land, air and water. The BPEO procedure establishes for a given set
of objectives, the option that provides the most benefit or least damage to the
environment as a whole, at acceptable cost in the short term as well as in the long term.
BPEO has not been designed to provide the best environmental option as the objective of
waste management should be to protect the environment as a priority. Instead, it is to put
forward what is believed to be the best overall approach that will provide a long-term
and workable solution to non-hazardous and hazardous waste management in a
community.
Analysis of the situation includes consideration for the practicalities of waste collection,
storage and transfer, the combination of treatment methods for the diversity of waste
streams and a rational approach to assessing the most worthy service provider in this
field.
At least two BPEO service coverage scenarios should be selected for discussion rounds
with working groups at the local community.
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Market volatility due to production optimization
Environmental awareness means households adopting new habits and industrialists
modifying processing methods to produce less waste or at least reduce its hazardous
nature. It also means possible substitutions of raw materials being used for the same
purpose.
Although this situation is good news for the environment, it is not necessarily so for a
concession contractor. There will always be the risk of planning solutions for 25 five
years ahead and ending up with an oversized facility that will not produce the expected
revenues.
Local authorities are obviously not interested in accepting clauses guaranteeing market
volume on privatization contracts, so a suggested solution comes through
accommodating other productive and less volatile waste market segments into the
concession agreement.1
Diversification Requirements
One of the most difficult parts of waste management systems is the diversification of
wastes to be treated.
No all non-hazardous and hazardous waste can be given the same transportation
methods, the same treatment method, or the same disposal method. This situation
obviously increases the investment and the risks of the investors. There are several
solutions to this problem, some of them are:
Sizing treatment options according to market volume;
Changing hazardous waste nature and using landfills;
Encapsulation of small waste streams;
Postponing solutions (adequate storage);
Including all hazardous waste in a concession agreement; and
Pricing services according to investment requirements;
1 Should be included in a Feasibility Study as an additional Scenario
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Range of Services to be provided
Treatment and disposal are obviously included in the range of services to be provided but
collection and transportation of the waste to the concession facility is a matter of concern
due to the range of waste characteristics.
There will be generators who produce several truckloads of compatible wastes, those
who produce less than a full truckload amount, those who produce one or two barrels
periodically, and households with very small but important quantities.
Transfer stations are the preferred solution to consolidate full payloads and make prices
and treatment accessible to all generators.
Operating and Control Philosophy
Facilities should be designed to handle and treat liquid, solid and semi-solid waste in a
safe, efficient and environment-friendly way. It will ensure complete compliance with
the local authorities standards and environmental regulations for all discharges
(solid/liquid/gaseous) emanating from anyone or all of the waste facilities outside the
overall plant battery limits.
The best affordable and sustainable concept will be the guiding principle for
selecting/designing suitable equipment/process systems. All facilities created under the
project should use commercially proven technology and the plant design should ensure
maximization of energy and utility conservation.
As a minimum, a solid waste management project should include the following facilities:
i. A liquid hazardous waste treatment facility (LHWTF);
ii. A land farming facility;
iii. Non-Hazardous and Hazardous Waste Landfills facility;
iv. A solidification & stabilization facility (SSF);
v. A drum processing facility;
vi. Medical waste treatment facilities;
vii. Used oil treatment facilities;
viii. Non-Hazardous and Hazardous Wastes transfer stations;
ix. Used Tires Processing facility;
x. A Non-hazardous Waste treatment facility;
xi. A Non-Hazardous Recycling treatment Facility;
xii. A Composting Facility; and
xiii. A Waste Transportation Fleet
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The specific purposes of each of these facilities will be as follows:
i. Liquid Hazardous Waste Treatment Facility (LHWTF): This facility will be designed
to treat all types of aqueous waste streams comprising of acidic wastes, basic wastes and
liquids with heavy metal contamination. The treatment technology will consist of
neutralization and sedimentation of liquid waste.
ii. Land farming facility: This facility will be used for the treatment of oil-contaminated
soil, which constitutes the main component of hazardous organic wastes to be treated by
the plant. Fresh water, nutrients like fertilizers and PH regulators will be required to be
added to this facility periodically.
iii. Landfills facility: This facility will receive treated and separated wastes from the
LHWTF, SSF, and Non-Hazardous waste facilities in addition to wastes received directly
by the local authorities.
iv. Solidification and Stabilization Facility (SSF): This facility will be designed to
inactivate and immobilize mobile contaminants prior to land filling in order to minimize
contaminant migration and to comply with the landfill operational regulations and
requirements.
Contaminated solid wastes, sulphured wastes, miscellaneous solid hazardous wastes and
sludge from the LHWTF will be treated at this facility. Processed materials will be sent
to landfills.
v. A drum processing facility to ascertain proper handling of contaminated drums and
safe disposal of them.
vi . Medical Waste Treatment facilities at major cities to ensure proper transportation,
treatment and disposal of medical hazardous wastes generated at these locations.
vii. Used Oil Treatment Facilities at convenient locations to reduce its toxicity and
contamination and add value to the processed oil.
viii. Non-Hazardous and Hazardous Waste Transfer Stations to professionally structure
the collection, consolidation and transportation of waste to their final treatment and
disposal site.
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ix. A Used tires processing facility to process them into useful products.
x. A Non-Hazardous waste treatment facility for separation of main waste streams.
xi. A Recycling plant to add value to the recyclable products obtained from the waste
separation procedures.
xii. A composting facility to add value to organic recyclable materials.
xiii. A Waste Transportation Fleet to ensure safe, flexible and economical transfer of
wastes from generators sites to the corresponding treatment facilities.
Design Basis
Within the Concession documentation the prospective contractor should receive:
Details of solid, liquid, and sludge wastes generation quantities in the local
community as they have been identified by the local authorities. The Concessionaire will
be required to verify this data; The facilities to be designed under the Concession should
be conceived to process the 25-year forecast waste quantities in one shift operating 8
hours/day, 6 days /week and 260 days/year;
Conceptual details of the type of facilities/processes selected by local authorities to
treat the various wastes. The Concessionaire should be advised that the selected
facilities/ processes should be considered as minimum requirements. The Concessionaire
may offer different facilities/processes to those selected by the local authorities, however
the local authorities may insist on using the facilities/ processes already selected; and
The Concessionaire will be request to independently verify all engineering
information and drawings provided by the local authorities if the Concessionaire intends
to incorporate these into its design.
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Analysis of Different Operational Scenarios
Several different operational scenarios should be taken into consideration in order to
establish various service coverage scenarios before deciding on the best practicable
environmental option for the local community.
Before deciding on a scenario as the most practicable operational scenario for the local
community, various service coverage scenarios should focus on the local authorities’
priorities, which are usually as follows:
1. Medical Waste Treatment and Disposal
2. Hazardous Waste Current Backlog.
3. Affordable Transportation, Treatment, and Disposal of Hazardous and Non –
Hazardous Waste.
Service Coverage Scenarios
Order of magnitude capital and operational cost estimates should be developed to go
along with the proposed service coverage scenarios. As an example, the following 25
year scenario has been divided in five, 5-year scenarios:
First Service Coverage Scenario
The First Service Coverage Scenario may be described as follows:
Estimated coverage quantities estimated at current levels and growing at 1.5% per year.
First 5-year Plan:
Medical Waste Collection, Treatment and Disposal implementation within six
months after Concessionaire reception of Notice to Proceed. (NTP);
Partial Development of a hazardous waste treatment facility including storage
capacity, landfill operations, use oil treatment, and stabilization and solidification
operations; and
Development of Transfer Stations at different locations including transportation
fleet;
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Second 5-year Plan:
Development of Sorting and Recycling Stations at specific locations to be
decided; and
Project Major overhaul at year 8th
Third 5-year Plan:
Development of Liquid Hazardous Waste Treatment and disposal;
Major Sorting and Recycling Stations overhaul at year 12th
; and
Project Major overhaul at year 14th
;
Fourth 5-year Plan:
Major LHWTF overhaul at year 17th
; and
Major Sorting and Recycling Stations overhaul at year 19th
;
Fifth 5-year Plan:
Major Project Overhaul at year 25th
.
Second Service Coverage Scenario
The second service coverage scenario should, as a minimum, be envisioned to follow
the same pattern of the first service coverage scenario with a substantial change in
quantities to be treated and investment to be made in every facility. This scenario will
provide the worst available situation the project can face to help develop intermediate
situations and eventually provide a sensitivity analysis to guide potential concessionaires.
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Chapter III
Collection of Residential Solid Waste
The collection of residential solid wastes should be provided to citizens to assure the
protection of public health and environmental quality. Since government officials
realized that they had to do something about the garbage piling up in the streets and
gutters, responsibility of public cleanliness has been passed to the public sector.
As the character and amount of solid wastes have changed in our urban centers, the
methods and techniques for collection have also changed. Residential solid waste has
became bulky and more difficult to collect.
Commercial and industrial enterprises have introduced wastes that are totally different
from those the homeowner. These changes have brought about the evolution of
compaction equipment and containerization, and the need for greater speed and capacity
to collect and move waste.
Perhaps the most important change has not been in technology but in institutional
arrangements. The result is a partnership that today exists between government and
industry providing solid waste management services to citizens and businesses. Public
and private sector solid waste employees work side by side to collect the vast amounts of
waste generated by business, commercial enterprises, and industry. Generally speaking,
the private sector has accepted the lion's share of residential, commercial and industrial
solid waste collection.
It makes little difference which resources collect solid wastes, as long as the public
interests are protected. Local governments must ascertain a satisfactory delivery of
collection services to their local communities.
The commitment to assure that the public is served by an effective, efficient, and well-
managed election program has to be supported by a determination of what level and type
of service is best for the community and its citizens. This can only be done with the
involvement of the public. No matter how difficult or unpleasant it may be for the public
officials, the public must be involved in determining the level and character of the
service to be provided.
This requires that the responsible public officials, both elected and career ones, prepare
the public for such involvement. The officials must do their homework so that they can
provide the public with the information necessary for public participation into this
policy-making exercise.
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The public has to know exactly how much does it cost to provide different levels and
quality of services and what can and cannot be done with today's collection technology.
The citizen has to understand that the more he wastes the more he will have to pay for
the service. Citizens must understand they are part of the solid waste management
problem and therefore must effectively contribute to the solution.
The selection or determination of the level and type of service guides the delivery of
services. In engineering terms, it is technical specifications describing the service to be
provided regardless of whether the service is provided by government or private forces.
Technical specifications depend heavily on the professional in the community
responsible for solid waste management. With an adequate public policy on what the
community requires, the job of the local solid waste manager becomes easier to plan and
forecast.
A local government is responsible to see that their community is kept clean and the
public health is protected. If state legislation is unclear in assigning this responsibility,
then local government should work toward a clarification of that responsibility.
Cost Accounting Procedures for Solid Waste Collection Systems
Management control of a solid waste system develops around its budgeting-accounting-
reporting system. Generally accepted government accounting principles require solid
waste activities to be accounted for on the same basis as a similar enterprise in private
industry.
In governmental accounting, the vehicle for accomplishing this objective is usually
referred to as an enterprise fund. Even if a solid waste system is funded through general
tax revenues, accounting concepts and principles should be utilized by management to
the maximum extent possible.
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Enterprise Fund Accounting
The principles that distinguish enterprise fund accounting from general fund accounting
are:
Accrual basis of accounting;
Use of a self-balancing chart of accounts (i.e., assets, liabilities, equity, income,
and expenses);
Classification of income and expenses as operating versus non-operating, and
classification of revenues as income versus contributions of fund capital;
Recording of fixed assets and recognition of depreciation as an operating
expense; and
Use of inter-fund billings to account for services rendered for and provided by
other agencies of the same governmental unit.
For cost accounting principles to be truly a management tool, the solid waste manager
must make every effort to assign all costs to various cost centers. This allows for a more
realistic analysis of costs to be made.
Furthermore, by assigning costs and budgets to various line managers, the solid waste
manager is able to assign responsibilities for budget control and fiscal management to
those line managers and through such responsibility, a cost accounting system can be
used as a management tool.
System Deficiencies
Total costs of solid waste collection systems should be accounted for. Simply stated,
principles of enterprise fund accounting should be adhered to in all instances. Examples
of costs that should be charged to a solid waste collection operation, but often are
charged to other departments, are as follows:
Capital costs (i.e., depreciation or principal portion of debt in lieu thereof)
associated with the acquisition and/or construction of facilities and equipment
(e.g., collection vehicles, garages, and administrative services);
Interest cost of debt incurred in the acquisition of equipment and construction of
facilities;
Costs (i.e., labor, parts, oil, tires) of repairing and maintaining facilities and
equipment;
Employee benefits, including pension contributions, for solid waste personnel;
Cost of temporary employees borrowed from other departments to fill short-term
needs;
Overhead costs associated with the city executive and supporting staff agencies;
Costs associated with budgeting, accounting, and report activities;
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Costs associated with billing and collecting user charges;
Liability and damage claims paid by a city which is self-insured; and
Insurance premiums related to solid waste personnel, facilities, and equipment
(e.g., personnel liability, fire, accident).
Obviously, the exclusion of such items from the costs of a solid waste collection
department could understate significantly the result of the operations. In turn, any
analysis of operating costs or any comparison of such costs with other governmental
entities, private enterprise, and/or alternative collection methods could lead to erroneous
conclusions and improper decisions.
Financial management of a solid waste system involves a number of complex issues and
principles. Depending upon the organization of a particular solid waste system, and the
economic and political environment in which it functions, some of the principles may not
be necessary or practical.
However, all should be seriously considered in formulating alternative approaches to
solid waste management. It should be obvious that financial management and
operational management are necessarily linked. A decision in one area usually
influences the available alternatives of the other. The solid waste manager must become
familiar with and understand these financial concepts.
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Unions and Solid Waste Collection
Collective Bargaining in Residential Solid Waste Collection
Strikes
The most important and basic difference between private and public sector collective
bargaining is the almost universal prohibition against public employee strikes.
Labor leaders argue that the absence of the strike weapon results in collective begging,
rather than collective bargaining. A bargaining atmosphere is often created in spite of the
strike ban because of an implied or expressed threat of the union to strike, regardless of
the law.
Supervisory Personnel
In contrast to the private sector, supervisory personnel in the public sector frequently
bargain on a formal basis with the governments that employ them. This is partly due to
the fact that the demarcation between management and non-management employees in
the public sector is much more obscure than in the private sector.
In other words, public sector supervisors, even more than their private sector
counterparts, are the proverbial middle men. Often they perceive themselves as
supervisors in name only and, consequently, seek to define their position more explicitly
through unionism and collective bargaining.
Labor Relations Staff and Strategy
If local authorities expect to meet the challenge of unionism, it must establish a labor
relations staff function as a permanent part of the organization and develop the
competence of the individuals who staff this function. All too often, the responsibility
for collective bargaining is not fixed with any degree of certainty.
If labor relations are not recognized as a distinct function, then the individuals who must
assume this responsibility are generally expected to perform their normal duties as well
as creating a situation that is less than satisfactory. These individuals may not be
prepared by either training or background to deal with a skilled negotiator representing
the employees.
The private employer generally orients a significant portion of management toward
personnel and collective bargaining matters and maintains a well-ordered strategy
concerning the labor relations function.
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Operation divisions are probably assisted by an industrial relations or personnel director
who negotiates with one or more unions and provides advice on day-to-day contract
matters. His future with the company depends on how effectively he manages his area of
responsibility.
Establishing a separate labor relations function and holding its staff to high standards of
performance is not enough. In the public sector, the political element must also be
considered. Because the union may be a potent force, elected officials may permit the
union to circumvent the collective bargaining process and make a direct appeal to the
legislative body. This process is called an "end run" and, if successful, seriously
undermines the effectiveness of a negotiating team. If collective bargaining is going to
work in the public sector, the "end run" must be eliminated.
Motivation
There is also a difference in motivation between public sector management and managers
in the private sector. The most important of these differences are:
The following suggestions on what can be done to properly motivate public managers
should be taken into consideration:
a. Every effort should be made to make it understood to public managers
that it is their duty to represent and protect the interests of the local
authorities agency employing them, just as it is the duty of unions to
represent public employees.
b. Negotiators in the public sector must recognize the importance of
retaining the right to manage. This is critical if we are to retain the right
to operate efficiently, to utilize technological change to reduce labor
costs, and to avoid restrictive work rules.
c. All persons who hold supervisory positions should be considered part of
the management team.
d. An attempt should be made to provide public managers with some form
of financial reward for outstanding performance.
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Collection Routing
The community should determine to some extent the configuration of the service needed
and to do some homework makes sense as far as routing goes. Certainly, there may be a
need to indicate which portions of the city should be served on which days, if that makes
a difference. If the community is going from a community-operated system to a
contractor system, past routes and other operating information should be provided to
assist the bidders.
The community should decide on the type and level of service to be provided including
any acceptable alternatives. A community must clearly determine what it wants and
needs in a collection service. Some communities that change to contract services fall to
recognize and consider the variety of services that their community forces have provided.
When they start to develop the scope of work, they should carefully review past services.
As an example, a community should determine who is to provide:
Street Washing and its timetable;
Dead animal pickup;
Snow removal. City systems equip their collection trucks with the ability to
plough snow;
Special clean-up programs. Many community-owned systems provide this
service; if the contractor is to continue to do so, it must be included in the scope
of work;
Emergency (e.g., storm, hurricane, etc.) service. What is the role of the
contractor in these instances; and
Waste pick-up at schools and public buildings, street sweeping, and so on.
Many of these special services often are provided by city forces as part of the business of
sanitation. It should be established if the contractor will be expected to do the same. It is
obvious that when a community decides it is going to contract out for public cleanliness,
it had better do its homework on exactly what is to be cleaned up by the contractor.
Communities must decide on how proposals will be evaluated and selections made.
Anyone who has ever made a proposal for any type of work knows how important it is to
have an understanding of how the proposals are to be judged. A community should
identify the factors to be considered in judging proposals such as:
Lowest bid;
Past experience and past demonstrated capabilities and corresponding
weigh factors;
Contractor’s own resources, human and equipment;
Current workload; and
Evaluation procedure.
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Communities must decide on how the local government solid waste manager will
evaluate performance under the terms of the contract; what procedures will be followed
when service is not consistent with the specifications; and how the manager will oversee
and supervise the contractor in the performance of the contract.
Any community that makes an award for contract services and then neglects to oversee
that service will eventually run into trouble. In overseeing that service, however, the
community should clearly identify who should be overseen; what should be the nature of
the force that should be supervising; and what factors should be used to measure
satisfactory completion of the service (missed stops, the number of complaints,
responsiveness to unique occurrences, etc.). The determination and measurement of
acceptable service must be defined in the scope of work.
Payment procedures, what financial requirements are expected of a contractor, and other
financial matters that will affect the success of the contract. Local authorities are
notorious for slow payment for services and products received. This really is unfair to a
vendor or contractor. Everyone has a problem of cash flow.
A community should be sensitive to the fact that if it is slow in paying, a contractor
might have to get commercial financing to continue to provide the service that the
community is supposed to be paying for. Prompt payment is essential. The scope of
work should commit the community to a payment schedule that is fair, and if it fails to
meet that schedule, the community should pay a penalty for its lack of financial
planning.
The rights of the community in regard to the continuation of services when a contractor
defaults or for some reason is not able to perform according to the terms of the contract
should be clearly established. Circumstances such as strikes may occur that prevent the
contractor from meeting the terms of the contract. The contract document itself must deal
with how the community will assure the protection of the public service in these
instances. If the failure is one of a temporary nature (say several weeks) the community
will have to find alternative collection methods on an emergency basis, or perhaps take
over the operation of the system. How this is to occur and who is to pay for it must be
specified in detail.
In the case of default, the contract document has to fully describe what kind of penalties
should be placed on the defaulted contractor, what should be the disposition of the
contract, and what should be the role of the contractor's equipment and facilities in this
situation. This is a very complex set of issues, but one that must be comprehensibly
addressed in the contractual documents.
As a community develops its contract documents, it can seek professional advice to
assure that the bid documents are adequate to achieve the objectives of the community.
26
A bid document and the supporting specifications need not be overwhelming in either
language or length. The specifications related to the level of service, quality of service,
and so on, can be written in terms that are simple and understandable.
Although it is desirable to have counsel review and assist in the development in the
offering, the professional responsible for the documents and the project should not let
counsel dictate the nature and content.
It also seems advisable to avoid the common practice of cut and paste. Do not take an
old bid document and attempt to adapt it. Although this may make the job easier, it does
not assure that the resultant product will be on target for the particular project to be
initiated. Previously used bid documents are certainly helpful as guidance in the
development of the new bid document and specifications. However, the work should be
original, with the specific objectives of the job in mind, and be prepared in the tone and
language of the person(s) responsible for the project.
Collection Equipment Maintenance Programs
Any maintenance program must be built upon planned and preventive maintenance and
must avoid at all costs a system based on demand of maintenance. A responsible
manager cannot depend on a system that permits a truck or piece of equipment to break
down before repairs are made. Preventive maintenance can normally prevent most major
breakdowns such as engine failures because systematic inspections will permit a
manager to detect problems before they occur. In addition, preventive maintenance
programs can extend the useful life of vehicles and equipment by the establishment of a
planned maintenance program.
Planned Maintenance
Planned maintenance is accomplished by inspecting a vehicle systematically at regular
intervals and by replacing, readjusting, tightening, repairing, or adding to it any part or
system that shows a need for repair or adjustment during the inspection. Replacement is
done also when the maintenance records on a vehicle indicate that an assembly or a
component is nearing the end of its useful life.
Some advantages of planned maintenance are:
Fewer part failures, fewer emergencies, and fewer road calls;
Development of the records necessary to assist in preparing annual
maintenance budgets; and
Development of information to help determine the best specifications for new
vehicles and equipment.
27
Components in a Maintenance Program
The following records should, at least, be part of a maintenance program:
A standard repair order;
A standard vehicle history jacket;
Standard codes for use with the repair order and the vehicle history jacket;
and
A liquid usage report.
Repair Order
The repair order, when properly filled out, will provide the information needed to
complete maintenance records. This form should be used for all work performed so that
the shop manager can allocate labor costs and spare parts costs to each vehicle. This will
allow to know the operational cost of each vehicle of the working fleet. All repair orders
should be filed permanently in the individual vehicle jackets (on the computer bank if the
operation has access to computer capability).
A standard repair order should provide the following advantages:
It will provide written orders to the shop personnel and will eliminate
misunderstandings about the work to be accomplished;
It will be the document that authorizes the spare parts department to supply
a required part to a mechanic;
It will provide an accurate record of the labor spent and the spare parts used
for each repair;
It will provide a complete record of the work done at a given mileage
(preferably given as hours of use) and on a specific date;
It will pinpoint the responsibility for the quality of the repairs done by
listing the names of the mechanics who performed the work;
It will provide a means to check the productivity of the mechanics because
it is possible to check work times against standard time allowances;
It will provide the date and the times for scheduling PM (preventive
maintenance) intervals and inspections;
It will permit a check out of unscheduled shop visits and determine the
reasons for them; and
It will provide a running history of all mechanical work done on each
vehicle.
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Vehicle History Jacket
The repair order probably will be the most important and useful document used in the
shop by the mechanic and maintenance manager. The most important management
document, however, will be the vehicle history jacket.
This jacket should be designed to mirror the repair order so that the most important
information placed on a repair order can be transferred quickly to the jacket. In that way,
the jacket will highlight the critical maintenance actions on each truck, and will give a
manager a quick and accurate picture of the truck's problems.
The maintenance manager should study a truck's history jacket before he ever issues a
repair order. The maintenance manager should determine if a complaint is a current one,
if repairs have been excessive, or if maintenance has been performed at proper intervals.
Based upon this information, the manager can determine what kinds of repairs should be
made, if replacement is called for, and if planned repairs and/or replacements are cost
effective.
Ultimately, the jacket can be used to determine whether a vehicle should be replaced.
The vehicle history jacket should be kept for the life of a vehicle. More than any other
record, the jacket is a management tool.
Codes for Maintenance
To simplify entries on the repair order, the manager should consider using a standard
brevity code. Many Trucking Associations in Europe and America have developed
standard codes to that purpose.
Liquid Use Record
The last record that should be mandatory in any simplified system should deal with
liquids. It is essential to keep a daily record of fuel consumption, oil usage, and the
usage of special liquids such as hydraulic fluid and antifreeze.
29
Other Factors to Consider
Although the already mentioned records can provide the essentials for a good
maintenance system, there are other matters that should be considered in a maintenance
program.
For example, more complete records, such as: purchase orders, purchase lead times,
weekly preventive maintenance forms, quarterly or 250-hr preventive maintenance
forms, annual or 1000-hr preventive maintenance forms, work to be done sheets,
workmen's time tickets, daily truck cost reports, mechanical downtime reports, fuel
pump readings reports, tire inventory reports, bearings working hours, and similar items
might be included.
Equipment dealers can be of great assistance in planning preventive and planned
maintenance.
In summary, maintenance programs must be professionally managed. A simple system
built upon planned maintenance should be the basis for any maintenance program. Keys
to any planned maintenance program are:
Managerial interest and support;
Competent mechanics;
A simple system of procedures and records;
Standardization of components and fleets, if possible; and
Attention to big dollar expenses.
Optimizing the Performance of Collection Services
The provision of residential collection services is emphasized upon the need to protect
public health. The provision of public health protection, however, need not and should
not be used as a justification for inefficient, unproductive, and ineffective service. These
factors can result only in one outcome: an expensive system that fails to properly utilize
is work force and equipment.
The keys to assuring the optimal collection system are a combination of equipment
selection, maximum productivity, and effective routing. The selection of equipment is
dependent upon the determination of type and level of service to be provided and which
type of equipment can be the most productive within the configuration of the community
to be served.
30
Factors Affecting Productivity and Costs
Work supported by solid waste management programs and conducted by waste
associations identified a number of factors that when applied to a residential solid waste
management system can result in substantial improving of service. A summary of their
findings will follow:
Crew Size
The productivity per crewman in terms of homes served and tons collected per collection
hour is greatest with a one-man crew. On the average, the productivity of one two-man
crew is less than the productivity of two one-man crews. Likewise, the productivity of
one three-man crew is less than the productivity of three one-man crews.
The percentage of on-route productive collection time for one-man crews is significantly
greater than the percentage of productive time for two- and three-man crews. For one-
man crews, the on-route productive time is about 97%. For the two- and three-man
crews, the on-route productive time is approximately 70%. There is no significant
difference in the percentage of productive time between the two- and three-man crews.
In going to the route and in transporting the collected waste to the final destination, only
the driver is productive. All other crewmen, riding with the driver are non-productive in
these operational phases. With these phases consuming approximately 30% of the work
day, one-half and two thirds of the man-hours of this effort are wasted for two- and
three-man crews, respectively.
Frequency of Collection
Increasing the frequency of collection from once a week to twice a week requires
approximately 50% more crews and equipment than the once-a-week systems. The
average number of homes served per week for a twice-a-week collection system is
approximately two-thirds the number for a once-a-week collection system. Conversely,
to decrease the frequency of collection from twice a week to once-a-week, requires
approximately 33% fewer crews and equipment than the twice a week systems.
In terms of productivity factors, the twice-a-week collection systems served
approximately 50% more homes per collection hour than the once-a-week collection
systems. The weight collected per collection hour, however, was only 80% of the weight
collected per collection hour by the once-a-week collection system.
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Storage Point Locations
The productivity of a backyard system in terms of' homes served per collection hour and
tons collected per collection hour, is approximately one-half the productivity of a
corresponding curb or alley system.
Incentive Systems
Collection systems operating under the task incentive system tend to work a smaller
percentage of the normal work week than the standard day systems. The work effort of
standard day collection systems has a tendency to expand into overtime operations. The
collection production and productivity of the task incentive systems tend to be greater
than the collection production and productivity of standard day systems.
Storage Containers
The percentage of one-way items (bags and miscellaneous items) does have a significant
effect on the system productivity. An increase in the percentage of one-way items
reduces the time required to service a home, and conversely, increases the number of
homes served per collection hour.
The weight per home per collection also affects the system productivity, and this effect is
greater and opposite in direction to the effect of one-way items. An increase in weight
per home increases the time required to service a home and decreases the number of
homes served per collection hour.
Productivity and Efficiency
Curb-side is more productive and cost efficient than backyard service.
For the curb and alley systems:
Systems that have a collection frequency of twice a week tend to serve
more homes per collection hour, but collect fewer tons per collection
hour, than their once-a-week counterparts;
Larger crew sizes have a tendency to collect more tons per collection
hour; and
When productivity and cost efficiency are considered on a per crew basis,
there is a strong tendency for the smaller crew sizes to have the greatest
productivity and best cost efficiency.
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For backyard systems:
Systems using task incentive programs have greater productivity than
systems using standard day system; and
There is no clear pattern between backyard systems regarding collection
cost efficiency.
System Costs
Regardless of the kind of equipment used, the initial cost of the equipment, or the
number of days per week the equipment is being used, the daily equipment costs are of
the same general magnitude for all systems. (Note: This conclusion may or may not
apply to a fully automated one-man system, given the costs of containers, etc. It is
recommended to consider additional cost analysis to make a true comparison).
The daily personnel costs were related directly to the crew size. For every system
studied, using the standardized cost data, the daily personnel costs were significantly
more than the daily equipment costs. The manpower to equipment ratios averaged 1.4 for
one-man crews, 3.0 for two-man crews, and 4.5 for three-man crews. The incremental
effect of an increase in equipment costs of $1000 was small in comparison with an
effective increase in labor costs per crewman of $0.50/hr.
Since daily personnel costs were significantly more than the daily equipment costs, cost
reduction programs should look first in the area of personnel costs. Personnel costs can
be lowered by improving personnel productivity, by reducing the numbers of personnel
or both. There was a strong tendency for personnel productivity to increase as crew size
decreases.
Since marginal cost effects of an increase in equipment cost of $1000 were small in
comparison with a marginal cost effects in the effective labor rate of $0.50/hr;
compromising equipment performance for the sake of a lower equipment cost appears to
be counterproductive.
Factors which are most important to productivity and cost efficiency have been ranked
and, although they may not be totally applicable to any specific system, the rankings
clearly do demonstrate the conclusions that were established from their study (see table
below).
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For each of these factors, the direction to improve productivity and costs is, from less to
more, point of collection (backyard to curbside), crew size (larger to smaller, but depends
on the point of collection, amount of waste and distance between stops), frequency of
collection (twice to once-a week), incentive systems (standard 8-hr day to task system),
and percent one-way items (less to more, the impact is significantly greater with curbside
collection than backyard collection).
Rank Order of Factors Affecting Residential Solid Waste Collection,
Productivity, and Costs
Factor Order of
Productivity
Relative
Magnitude of
Effect
Order for Cost
Efficiency
Relative
Magnitude of
Effect
Point of
collection 1 58 1 52
Crew size (per
crewman) 2 38 3 9
Frequency of
collection 3 36 2 28
Incentive
system 4 26 4 1
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Measuring Productivity in Residential Solid Waste Collection Systems
It is not the speed at which collection crews work that affects productivity. Rather, as
reviewed earlier, there are a number of nonhuman factors and sub-factors related to the
type and level of service provided and the equipment used to provide that type and level
of service that affects productivity and costs.
The most costly portion of collection, labor, and its productivity is greatly affected by
that portion of the total work day actually devoted to productive collection activities.
Consequently, increasing the productivity of work crews is not necessarily predicated
upon making the crews work harder and faster, but the application of equipment and
methodologies that will allow the worker to devote more time to actually collecting solid
wastes.
Stearns2, in a series of studies, developed several models that allow solid waste managers
to measure the productivity of systems. The determination of productivity will
necessitate that solid waste management managers conduct field studies and analyses of
their current system to establish the basic data necessary to define the various
characteristics that affect productivity.
Stearns determined that route-related sub-factors are those that most directly affect
productivity. These sub-factors must be measured and compared when a solid waste
manager is attempting to measure and improve productivity.
Application of the methodology identifies the reasonable level of productivity which
should be expected for a existing mix of men and equipment, and a collection situation,
that is, a "fair day's work." Maximum utilization of the methodology is achieved by
using the models to estimate expected productivity levels if alternative collection
equipment and crew sizes are used in the same collection situation.
Following categorization of the collection situation and identification of the optimal
refuse collection vehicle for that situation, and subsequent application of local cost
factors, accurate cost estimates may be developed.
These accurate estimates of productive time requirements allow development of total
service cost comparisons between existing and alternative collection crew
size/equipment combinations. Thus, the most cost-effective residential solid waste
collection systems for a specific collection situation and desired service level can be
readily identified and documented.
2 See references
35
The model developed by Stearns to measure the productivity of two-man crews (rear
loaders) is:
P = 0.001D + 0.16 N + 0.09 T + 0.03S + 0.02 (1)
The model developed by Stearns to measure the productivity of one-man crews is:
P = 0.005 D + 0. 15 N + 0.08 T + 0.08 (2)
Where,
P = Productive collection time required per stop, in minutes, including the driving
time from the previous stop.
D = Distance between stops in meters.
N = Number of refuse containers at a service stop.
T = Total number of throwaway items (including paper or plastic garbage
bags) serviced at a stop.
S = Number of services collected at each stop.
The Five-Stage Process to Improve Residential Solid Waste Collection Systems
Shuster3, identified five steps which when combined with the measurement of
productivity and a commitment by managers and policy officials can result in improved
cost-efficiency and optimal delivery of collection services.
The five stages of the process are:
1. Review existing policies and methodologies and the alternative of these,
including institutional structure and objectives of the delivery system.
2. Macro-routing, that is, determine the optimum assignment of the daily
collection routes to existing or proposed processing and disposal facilities.
3. Perform route balancing and districting to determine a fair day’s work, to
evaluate performances and costs for different policies and methods, and to
divide the collection areas into equal workloads for each crews.
4. Micro-routing, that is, determine the path or route the collection vehicle is
to follow as it collects waste from each service in a specified area.
5. Implement changes.
The stages are generally performed in the order listed, with the exception that some of
the policies and methodologies of stage 1 should be determined or revised after the route
evaluations of stage 3 have been performed. Implementation, of course, must be
considered in each stage.
3 See references
36
Stage 1 is greatly dependent upon a political and policy commitment to take steps that
might lead to change and perhaps community disruption during the period of change. A
frank and analytical judgement of the current practices must be done so that a
community will move forward and implement needed change.
Stage 2 is very much an effort to determine the current productivity and to determine and
define the current practices followed in the delivery of collection services.
Route balancing (stage 3) is the process of determining the optimum number of services
that constitutes a fair day’s work and dividing the collection task among the crews so that
they have equal workloads. Route balancing can be sued to:
Eliminate the number of trucks and men required to collect waste in a new or
revised solid waste system;
Develop or evaluate a bid price for a collection contract;
Evaluate crew performances, as a whole of individuality;
Determine a fair’s day work or a work standard necessary to task and wage
incentive (bonus) systems;
Balance or equalize the workloads among collection crews; and
Determine the optimum size for new trucks or optimize the use of existing ones.
Route balancing can be accomplished by analyzing each component of time in the
collection day, or how time is spent. Adding these component times results in an
equation for the total time in the workday:
Y = a + b + n (c1 + c2 + d) – c2 +e + f + g (3)
Where,
a = Time from garage to route;
b = Total collection time on route;
c1 = Time from route to disposal site;
c2 = Time from disposal site to route;
d = Time at disposal site;
e = Time from disposal site to garage;
f = Time for official breaks;
g = Slack time: lost time due to breakdowns and other delays, incentive time, lunch
time.
Equation (3) is the basis for determining a fair’s day work and for route balancing. The
data required for this analysis are:
Time and distance related to the component of the collection day;
The number and type of services and where they are located;
37
The average amount of waste generated per service, including seasonal
variations; and
Basic equipment and labor cost data.
To determine the appropriate number of services per crew per day and being able to tell
how many men and trucks are required, the following equation is necessary:
N = x1 x2 / x3 (4)
Where,
x1 = Vehicle capacity (m3/load);
x2 = Vehicle density (kg/m3);
x3 = Kg/service/collection;
N = Number of services per load.
Reasonable values for variables a, c1, c2, d, e and f are readily obtainable. For example,
variable a the time for the garage to route, is easily derived by considering the distance
and route covered and the reasonable driving time to run it. Likewise, the number of
formal breaks to be taken is a policy decision and is typically two 15-min breaks ( in a
task incentive system, crews frequently skip the breaks).
Variable n (number of loads per day) is based on equation (4). It is determined by
dividing the number of services that can be collected in the workday (calculated with the
procedure described below) by N and rounding up to the next whole number.
A variable b (total collection time on route) is a function of' the number of' services that
can be collected per hour, or the on-route minutes per service. These values may be
obtained in four ways: (1) conducting time and-motion studies on the existing system or
a similar one; (2) using regression equations developed from data on similar systems; (3)
implementing experimental routes and trying different crews; or (4) utilizing the Stearns
work with some modifications. Obviously, the values for variables n and b, and the time
per service, vary seasonally as the amount of waste per service varies.
38
It makes a great deal of sense, therefore, for the values for the variables n, b, and the time
per service be calculated for the peak, normal, and low waste generation periods.
The steps necessary to determine the number of services per crew per day (a fair day's
work), the number of men and trucks required, and the system cost are described in the
following procedure. These steps are based on equations (1) and (2), and determine
values for variable b (collection time), variable n (number of loads), and the number of
services per crew per day. The time required for on-route collection and transport for
each load is compared with the time that is left in the workday until the total time in the
collection day is accounted for.
1. Select the level of service, truck type and size, and crew size.
2. Determine N (number of services per load) from Equation (2) using normal waste
generation rate.
3. Starting with Y, the total hours in the workday (e.g., 8 hr) from equation (3)
subtract variables a, e and f, and add c2. Then subtract the round-trip haul time
per load ( c1 + c2 + d) and the collection time per load [services per load (N)
times the minutes per service]. Continue to subtract transport and collection
times, load by load, until all the time in the workday is used up.
4. Multiply the resultant number of loads (including partial loads if any) by the
services per load (N) to get the total number of services per day for each crew.
5. The number of trucks required is determined as follows (rounding the result to
the next highest whole number).
Total number (collection frequency
services) per week)
Trucks required =
(services per (number workdays
truck per day) per week)
6. Calculate the annual cost of a crew and truck by adding vehicle costs and labor
costs: Vehicle Cost = depreciation + maintenance + consumables + overhead +
license fees and insurance. Labor Cost = salary of driver + salary of collectors) +
fringe benefits + indirect labor + supplies (e.g., gloves) + administrative
overhead.
7. Evaluate the effects of peak and low generation periods on overtime and
incentive time respectively by repeating steps 2 through 5 using peak and low
generation rates.
8. Multiply the cost per crew (from step 6) by the number of crews needed (from
step 5) and add overhead expenses including overtime cost (from step 7) to obtain
the total system cost. Divide the total cost by the total number of services to
obtain the annual cost per customer.
39
9. Repeat steps 1 through 8 for any other level of service, equipment, crew size, or
other system alternatives being considered. Comparison of crew productivities,
system slack, and total cost (and cost per customer) for each system alternative
helps give a clear picture of which alternative is most acceptable.
The slack time, variable g, is built into this procedure by rounding to whole numbers and
by using conservative estimates. For example, if the average number of loads is 2.3 (step
3), the number of trips is 3, giving a slack capacity of 70% for the last load for all trucks.
Slack also results from rounding the number of trucks required up to the next whole
number. For example, if the number of trucks required is 7.2 (step 5), then the actual
number of trucks required is 8.
If the number of services per truck per day is computed to be 650, based on 7.2 trucks
(step 4), then the actual number of services per day for each of the 8 trucks is 585. This
also means more slack in the number of loads. In this case, the actual length of the
workday should be recalculated using 8 trucks and 585 services per truck.
Once the equitable number of services per crew (step 4) has been determined for each
truck districting and micro-routing can be performed to develop the individual routes.
Districting is the process of dividing the collection area into equal workload sections
according to the days of the week, and then dividing each daily section into specified
routes for each truck, based on the equitable number of services per crew determined by
the route balancing procedure.
Total collection and haul time should be reasonably constant for each route. Developing
the daily routes may be done in conjunction with micro-routing or before. When they
are done together, a starting point is selected and a path or route is developed
(continuous and concentrated in an area) until enough services to make a route are
reached. This process is continued until the whole collection area is routed. In
distracting and micro-routing, natural boundaries should be used where possible for route
boundaries. These include rivers, lakes, streams, mountains, valleys, railroads,
highways, major roads, parks, cemeteries, hospitals, and other areas without services.
Routing can be done in a number of ways using complex computer approaches to more
common sense techniques. The heuristic routing approach developed by the solid waste
management program has broad application to many different-sized systems. The
heuristic approach to routing is a relatively simple and expedient method for obtaining an
efficient route layout that minimizes dead distances and delay times. The heuristic
approach could also be called a pattern method of routing since it relies heavily on the
application of specific routing patterns to certain block configurations.
Admittedly, efficient routing requires both skill and aptitude. But guided by certain
heuristic rules and patterns, and through experience, a router can readily develop the
ability to scan a map and rapidly and systematically plot timesaving routes.
40
The heuristic rules for micro-routing are:
Rule 1. Routes should not be fragmented or overlapping. Each route should be compact,
consisting of street segments clustered in the same geographical area.
Rule 2. Total collection plus haul times should be reasonably constant for each route in
the community (equalized workloads).
Rule 3. The collection route should be started as close to the garage or motor pool as
possible, taking into account heavily travelled and one-way streets (see rules 4 and 5).
Rule 4. Heavily-travelled streets should not be collected during rush hours.
Rule 5. In the case of one-way streets, it is best to start the route near the upper end of the
street, working down it through the looping process.
Rule 6. Services on dead end streets can be considered as services on the street segment
that they intersect, since they can only be collected by passing down that street segment.
To keep left turns at a minimum, collect the dead end streets when they are to the right of
the truck. They must be collected by walking down, backing down or making a U-turn.
Rule 7. When practical, steep hills should be collected on both sides of the street while
vehicle is moving downhill for safety, ease, speed of collection and wear on vehicle and
to conserve gas and oil.
Rule 8. Higher elevations should be at the start of the route.
Rule 9. For collection from one side of the street at a time, it is generally best to route
with many clockwise turns around blocks.
Heuristic rules 8 and 9 emphasize the development of a series of clockwise loops in
order to minimize left turns, which generally are more difficult and time-consuming than
right turns; right turns are safer, especially for right-hand drive vehicles.
Rule 10. For collection from both sides of the street at the same time, it is generally best
to route with long, straight paths across the grid before looping clockwise.
Rule 11. For certain block configurations within the route, specific routing patterns
should be applied.
41
REFERENCES
Helsel, D., “Government Policies for Solid Waste Collection” (Proceedings, GRCDA
33th International Seminar and Equipment Show, 1992), in Residential Solid Waste
Collection.
Kerton, D., “Making the Change from Backyard to Curbside Collection” (Proceedings,
GRCDA 35th International Seminar and Equipment Show, 1995), in Residential Solid
Waste Collection.
Larson, H. G., “Cost Accounting Techniques for Solid Waste Collection Systems
“(Proceedings, GRCDA 37th International Seminar and Equipment Show, 1997), in
Residential Solid Waste Collection.
Stearns, R. A.., “Measuring Productivity in Residential Solid Waste Collection Systems”
(Proceedings, GRCDA International Seminar and Equipment Show, 1998), in
Residential Solid Waste Collection, GRCDA, 1989, pp. 3-1/3-19.
Shuster, K. A., “A Five Stage Improvement Process for Solid Waste Collection
Systems”, USEPA/OSW (SW- 131), 1994.
Schur D.A. and Shuster, K.A., “Heuristic Routing for Solid Waste Collection Vehicles”,
U S EPA/OS W (SW- 113), 1984.
42
Chapter IV
Transfer Stations
Design Requirements
Transfer Station facilitate the transportation of waste to distant places and make Solid
Waste Management feasible by gathering the required quantities of waste to justify
collection, treatment and processing latest technologies. Transfer Stations should be
affected by the selection of the design concept, as well as the design quantity of waste in
each Lebanese region.
Transfer Station Concepts
The three primary design concepts for Transfer Stations may be summarized as follows:
Pit;
Direct dump; and
Compaction.
Pit stations have gained popularity in recent years. Collection vehicles unload wastes
into a large pit. The wastes are then pushed from the pit into an open-top transfer trailer
by a tractor with a dozer or landfill-type blade. The pit provides storage of waste during
peak period, and provides an opportunity to pre-sort the waste and remove oversized and
hazardous materials. Some compaction of the waste, especially bulky items is achieved
by the tractor in the pit as shown in the figure below.
43
At direct dump stations, see figure below, collection vehicles dump directly into open-
top transfer trailers. Large hoppers direct the waste into the transfer trailers. Stationary
or mobile clamshell equipment can be used to distribute the waste in the transfer trailer
and can also accomplish some compaction of the waste. Very large transfer trailers are
used since there is only minimal compaction of the waste in the trailers. The direct dump
stations are inherently efficient because there is no intermediate handling required to
transfer the waste from the collection vehicle to the transfer trailers.
Direct Dump Station
Two types of compaction stations are commonly constructed. In smaller stations, the
collection vehicles dump into a hopper from which the waste drops by gravity into a
compactor, which then packs the waste into the trailers as seen in the figure below.
Other stations use a push pit. After waste from the collection vehicle is dumped into the
push pit, a large hydraulically operated blade moves the waste to the stationary packer.
The stationary compactor then packs the waste into the transfer trailer. Each of the
station concepts has advantages and disadvantages as explained below.
44
Pit Stations Advantages
With uncompacted material crushed in the pit by the bulldozer, maximum
loads are attainable without further processing;
Waste can be pre-sorted to remove oversized and hazardous materials;
Top trailers are less costly than enclosed compactor trailers;
Peak loads may be handled easily with many incoming vehicles capable
of being unloaded at the same time;
Drive-through arrangements for transfer vehicles can be easily provided;
Simplicity of equipment and operation minimizes possibility of complete
station shutdown; and
The long-haul vehicles owned by the Municipality are open top vehicles.
These vehicles could be used for the Pit Station alternative, and it would
not be necessary to purchase new long-haul vehicles.
Pit Station Disadvantages
Construction of receiving pit and purchase of the bulldozer require
considerable capital investment; and
Top loading trailers are more difficult and time consuming to unload than
enclosed compactor trailers.
Compaction-Hopper Station Advantages
Maximum payloads can be obtained from compacted or uncompacted
waste;
Nearly all bulky material that can be placed in the hopper can be
handled by the stationary compactor because of the large hydraulic force
available; and
The compaction equipment can handle light, fluffy types of waste; and
Trailers can be unloaded quickly and efficiently.
45
Compaction-Hopper Stations Disadvantages
No alternative way of loading trailers exists if compactor fails;
If most of the waste received is pre-compacted in collection trucks, the
heavier enclosed trailer offers little advantage since maximum payloads
can be achieved in lighter top loading trailers with top tamping;
Limited hopper storage space causes queuing problems during peaks;
therefore, more suitable for low-volume Transfer Stations;
Extra dead weight of the hydraulic ram ejection system and the required
trailer reinforcement reduces legal payloads; and
Procurement costs are more than for top loading trailers.
Compaction-Push Pit Stations Advantages
Pit provides some storage for peak waste loadings;
Maximum payloads can be obtained from compacted waste;
Nearly all bulky material that can be placed in the hopper can be
handled by the stationary compactor because of the large hydraulic
force available;
Incoming waste usually receives minimum exposure because it is
rapidly pushed into the enclosed trailers;
Canvas or metal tops do not have to be dealt with when loading and
unloading the transfer trailer because it is enclosed; and
Trailers can be unloaded quickly and efficiently.
Compaction-Push Pit Stations Disadvantages
Construction of push pit and purchase of hydraulic ram results in
considerable capital expense;
No unloading into push pit possible when charging the stationary
compactor;
No alternate way of loading trailer if compactor fails;
Extra dead weight of the hydraulic ram ejection system and the
required trailer reinforcement reduces legal payloads;
Procurement costs are higher;
If most of the waste received is pre-compacted in collection trucks
the heavier enclosed trailer offers little advantage since maximum
46
payloads can be achieved in lighter top loading trailers with top
tamping; and
Cycle time for loading of trucks is high compared to top load
vehicles.
Design Recommendations
Based on the analysis of design alternatives, existing equipment, and the requirements of
the local authorities, the following design recommendations are made:
The Transfer Stations should be designed with a tipping floor and pit
construction;
Waste receiving pits should be designed with hydraulic doors to minimize odor
and decrease cycle time;
The large Transfer Stations should be designed for a waste transfer capacity of
250 tons/day; and
The small Transfer Stations should be designed for a waste transfer capacity of
100 tons/day.
Conceptual Design
Preliminary Design Calculations
Station capacity should be controlled by one of two factors:
Rate at which wastes can be unloaded from collection vehicles; or
Rate at which transfer trailers can be loaded.
Therefore, two calculations must be made for most types of stations. The formulas are
slightly different for different types of stations and are not applicable to stations where
the tipping floor is used for storage. Without the peaking factor, F, the equations provide
a peak capacity. With the peaking factor, the equations provide station capacity with
minimal queuing of collection vehicles.
47
For pit stations, the capacity, based on the rate at which wastes can be unloaded from
collection vehicles into the pit, is calculated by the following equation:
C = Pc {(L/W) (60 Hw/Tc)(F)}
Where,
C = Station capacity in tonnes per day;
Pc = Collection vehicle payload in tonnes;
L = Total length of dumping space in meters;
W = Width of each dumping space in meters;
Hw = Hours per day waste is delivered;
Tc = Time in minutes to unload each collection vehicle; and
F = Peaking factor equal to the ratio of number of
collection vehicles received during an average
30-min period to the number received during
a peak 30-min period.
The capacity for a pit type station, where the rate of loading into transfer trailers controls
the system, may be calculated by the following equation.
C = 60 Pt N Ht / (Tt +B)
Where,
C = Station capacity in tonnes per day;
Pt = Transfer trailer payload in tonnes;
N = Number of transfer trailers loading simultaneously;
Ht = Hours per day used to load trailers (empty trailers must be available);
B = Time in minutes used to remove and replace each loaded trailer; and
Tt = Time in minutes to load each transfer trailer.
For direct dump stations, capacity can be calculated using the following equation:
C = 60Hw Nn Pt F / {[(Pt/Pc) (W/Ln) Tc] + B}
48
Where, C, Pt, F, Hw, Pc, W, Tc and B are as previously defined, and Nn equal to
number of hoppers, and Ln equal the length of each hopper in meters.
Capacity for compaction stations (hopper type), based on the rate at which wastes are
unloaded from collection vehicles, can be determined using the following equation.
C = 60 Hw Nn Pt F / { [(Pt/PC)Tc] + B}
The rate at which transfer trailers can be loaded at a hopper-type compaction station is
calculated using equation:
C = 60 Pt N Ht ( Tt +B)
Push pit-type compaction stations have capacity as determined by the following
equation:
C = Nn Pt F 60Hw / { [(Pt/Pc) ( W/Lp) Tc] + Bc + B}
where C, Pt, F, Hw, Pc, W, TC, and B are as previously defined, and
Lp = Length of push pit in meters;
Np = Number of push pits; and
Bc = Total cycle time for clearing each push pit and compacting waste into the
trailer.
The equation is based on the assumption the hopper holds a quantity of waste equal to
one transfer trailer load.
49
The pictures below show a typical Transfer Station.
Waste Loading Pit with an Open Top Long-Haul Transfer Trailer
Site Development and Ancillary Facilities
Site development should include on-site roads, parking, drainage, fencing, landscaping,
fuel storage, and utilities. Ancillary facilities should include scales, office, and employee
facilities. These facilities complement the Transfer Station and should be carefully
planned.
On-site roads must accommodate the expected traffic as safely and efficiently as
possible. Site drainage structures should be sized to handle peak storm flow to avoid
disruption of station operation. The fence should serve several purposes, including
keeping the public away from the heavy traffic areas, providing security for the facilities,
and assisting in control of blowing litter.
Landscaping and screening should be design to fit surrounding areas and to provide a
pleasing look for the facilities. Berms may be used to screen the vehicles. Landscaping
should enhance the facility and make the station appearance more pleasing. Plantings
should be selected to minimize maintenance requirements.
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Chapter V
Sorting and Recycling Facilities
There are three main separation approaches to recycling:
Source separation by either the generator or the collector with consolidation for
transport to markets;
Commingled recyclables collection with processing at centralized materials
recovery facilities (MRFs); and
Mixed municipal solid waste collection with processing for recovery of the
recyclable materials from the waste stream at mixed waste processing or “front-
end processing” facilities.
Materials collected and fully separated at curbside (after initial separation by the
resident), may have too low a density to be sold directly to an end user. Bottles may need
to be crushed, metals flattened or baled, plastics granulated or baled, and waste paper
baled.
For commingled recyclables (not fully separated before collection), more complex
separation and processing systems are employed to first separate the commingled
recyclables into their component materials, remove impurities from them, and then
densify them or otherwise prepare them for shipment to the end user.
Commingled waste processing facilities, called materials recovery facilities or MRFs, are
typically of larger volume or tonnage that the systems required to process source
separated materials. MRF equipment is also normally of larger capacity and more
rugged. Very complex, heavy-duty, capital-intensive processing systems are required for
mixed waste processing facilities with the goal of recovering materials from the entire
solid waste stream.
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The basic process system unit operations are similar regardless of whether the
materials to be processed or separated are obtained from source separation, commingled
collection, or mixed waste collection programs. The unit operations employed in
processing recyclable materials includes:
Screening;
Size reduction;
Air classification;
Eddy current separation;
Can flattening and densification;
Magnetic separation; and/or
Baling.
Design Requirements
Design parameters should be derived from a Waste Characterization study.
The following example planning data accepted for dimensioning of a plant assumes an
annual generation and increase of the amount of waste generated of approximately 3
percent. The composition of the assumed waste delivered to the compost plant will be as
follows:
Plastic Bags: 2.0 to 6.0 percent;
PVC Plastic: less than 1 percent;
Clear HDPE: 1 to 2 percent;
Colored Glass: 1 to 5 percent;
Clear Glass: 1 to 3 percent;
Paper: in the range of 1 to 7 percent;
Aluminum: 0.25 to 0.50 percent;
Other Metals: 0.7 to 2.4 percent;
Cloth and Carpet: 1.4 to 4.8 percent;
Wood: 0.3 to 4.2 percent;
Cardboard: 0.35 to 7.7 percent; and
Food and Biowaste: 66 to 84 percent.
52
Conceptual Design
Conceptual design plans should be based upon the requirements already mentioned and
the selection of equipment available in the international and local markets. A layout
drawing of a Sorting and Recycling Facility is presented at the end of the chapter.
Equipment included in this layout will be discussed in this section.
The layout is specifically designed to process MSW as fast as possible to avoid
unpleasant, unnecessary situations as having a tipping floor full of overnight decaying
waste for hours at the front-end of the plant.
The process should feature the following equipment:
A bag-opening machine;
Two hand separation platforms;
A Sorting Trommel to separate most of the organic waste;
Multiple magnetic separators to ascertain no metals go to composting
operations or the landfill;
Multiple shredding machines to control the size of the composting
material;
2 front-end loaders to move recyclable materials to their
corresponding locations;
Recyclable processing departments to present recyclables in the most
marketable fashion;
Baling machines for paper, cartons, cans, and plastics to reduce their
volume and improve handling;
A blue bag sorting and separation system; and
An automatic loading dock to send refuse materials to the landfill as
they are produced.
53
The efficiency of the screens is usually evaluated in terms of the percentage of recovery
of the material to be separated from the feed stream by the following expression:
Recovery % = U w1 / (F w2 *100)
Where, U = weight of material passing through screen (underflow);
F = Weight of material fed to screen;
w1= weight fraction of material of desired size in underflow; and
w2 = weight fraction of material of desired size in feedstock.
Screens operate at the highest efficiency when the materials to be separated are either
much larger or much smaller that the screen opening. Specifically, when a spherical
particle of diameter d imposes on a square or round hole of size a where a > d, the
probability that it will pass through the hole is expressed as follows:
p = [1 –(d/a)] * Q
The quantity Q is the ratio of the hole area to the total screen surface area. As the ratio of
d/a approaches 1, the probability of material falling through the screen approaches zero.
Therefore, as the material to be screened approaches the size of the screen opening, the
screening efficiency becomes very low and approaches zero.
Meanwhile, very large materials flow on top of the screen as if it were a solid surface,
and very fine materials fall through the openings of the screen with a very high
efficiency or probability of passage.
The most common types of screens in recycling applications are the vibrating deck
screen, the rotary drum or trommel, and the disc screen.
Vibratory Deck Screens
Vibratory Deck Screens typically have flat decks and are mounted on an incline to assist
in material movement. The screens may be designed with one deck to make a bimodal
product or may have multiple decks, however, Vibratory Deck Screens normally have
not more than two layers in which three different-sized products can be handled.
54
The screen, which is often a wire mesh but can also be a solid metal or rubber plate with
holes punched into it, is powered by an electric motor and a material vibrating drive
mechanism forcing the material to jump up and down on the screen so the material
imposes many times on the deck, providing multiple opportunities to pass through an
opening.
The screen is often supported on springs and a motor turns an eccentric weight imparting
motion to the material sitting on the deck. The throw or length of stroke, the inclination
of the screen, its overall length, and its vibration frequency are selected to handle the
throughput and screening efficiency.
Vibrating screens are very efficient and cost-effective for screening fine particles such as
glass and stones, however, Vibratory Screens are not very efficient for separation of
large materials such as paper which tends to bridge over the screen openings.
55
Rotary Screens (Trommels)
A typical rotary screen is shown below. The screen is normally set at a downward slope
in the range of 2 to 5 degrees to help the material flow down the screen as it is dropped
and tumbled.
A Rotary screen should be operated at a velocity that is 50 percent less than the critical
velocity. Rotary Screens are extremely efficient and require less cleaning than any other
type of screen. Depending on the materials processed, screen plates need to be replaced
every 5 years on average. The figure next page shows the conceptual design of a trommel
screen. Discs Screens
Discs Screens are composed of a series of horizontal bars or shafts running across the
screen in a direction that is perpendicular to the material flow. There are several serrated
or star-shaped discs spaced evenly across the width of the screen. As the shaft turns, it
carries material across the discs and bounces it into the air. The action is not as
aggressive as the trommel, but it is much more aggressive than the horizontal vibratory
screen. Long stringy objects tend to flow across the bars, while smaller objects such as
glass, grit, bottles, and cans tend to fall between the discs, normally onto a take-away
conveyor.
56
Screen Selection Considerations
The following factors should be taken into consideration while selecting a screen:
Particle size and distribution;
Bulk density;
Moisture content;
Particle shape;
Sticking potential;
Separation efficiency and overall effectiveness;
Construction materials;
Shape of screen openings;
Total screening surface;
Rotational speed of drum screens;
Oscillation rate for vibrating screens;
Energy requirements;
Routine maintenance requirements;
Simplicity of operation;
Reliability;
Noise;
Vibration; and
Plugging potential.
Hand sorting
Although considered low-tech systems for sorting, handpicking stations have been and
will be used for solid waste management for a long time. They are usually more efficient
than machines and are favored by municipalities for providing additional jobs to the local
workforce.
The ideal design for MSW is to have a combination of a high-tech screen and a
handpicking station. This will ascertain total sorting of the waste stream.
57
Size Reduction Equipment
Size reduction equipment are utilized to rip, cut, tear, and pulverize commingled
recyclables, liberating materials that are bound together so they can be separated from
each other in downstream unit operations. They are also used for densifying materials to
reduce storage, handling, and transportation costs.
Types of size-reduction equipment include:
Horizontal shaft hammermill;
Vertical shaft hammermill;
Vertical shaft ring grinder;
Flail mill;
Glass crusher and pulverizer;
Granulator and knife shredder; and
Rotary Shear Shredder.
Horizontal Shaft Hammer mill
Material is fed through a hopper, which then falls into a hammer circle where a hammer
attached to a rotor or shaft impacts the material, crushing, pulverizing, and tearing it into
smaller pieces. Below the hammer circle there are a series of cast grates which are
similar to a screen with very wide openings, which may range in size from 76 mm to 500
mm. The material remains inside the hammer mill and is crushed and torn between the
hammers and the grates, until its size is sufficiently reduced to pass through the grates,
where it is discharged to a conveyor.
The figure below shows a section of the configuration of a horizontal shaft hammer mill.
HOPPER
HAMMER
CIRCLE
GRATES
58
Vertical Shaft Hammer-mill
A Vertical Shaft Hammer-mill differs from the horizontal mill in that there is no grate.
Instead, the discharge material passes through an annulus controlling the exit particle
size. This type of equipment offers less control over maximum particle size that the
horizontal shaft hammer-mills.
The material to be shredded is fed into the top of a hopper feeding into a breaker plate
and hammer area. As the material is beat and hammered, it works its way down the cone-
shaped machine. The distance between the hammer and the breaker plate constantly
decreases, thus continuously working to reduce the particle size.
The figure below shows a section of the configuration of a vertical shaft hammermill.
DRIVE MOTOR
BALLISTIC
CHARGE EJECTION
DISCHARGE
59
Vertical Shaft Ring Grinder
A Vertical Shaft Ring Grinder is similar to a vertical hammer-mill, except that a gear-
type device is positioned in place of a hammer. These mills provide more of a mashing
and grinding action rather than the tearing, pulverizing, and ripping action of the
horizontal and vertical shaft hammer-mills.
Flail Mill
A Flail Mill is like a hammer-mill without grates. Material is fed into the top of the
single or double shaft mill through a feed chute. The flails attached to the rotating shaft
function as knives. These knives can cut open bags, liberating their contents. Paper is
torn and ripped. Cans will go through the mill unaffected. Glass is pulverized into very
fine sizes. Flail mills are not good devices for controlling particle size because they do
not have grates.
Pulverizer and Glass Crusher
A pulverizer is very much like a flail mill but it utilizes a breaker plate and hammer
rather than knives. It has impact bars and impact plates to assist in the pulverization of
glass and other friable materials. As materials fall into the mill, glass is struck by the
hammers and thrown against the impact blocks where it is again smashed into smaller
pieces. Pulverizers do not usually have grates and they are much smaller in size than
hammer-mills.
Granulator and Knife Shredder
This machine employs very sharp, long knives for cutting materials such as rags and
plastic bottles into small pieces for later separation. The knives are attached to a rotor
and are positioned horizontally across the entire width of the shredder. As the rotor
moves, the knives pass by an impact or cutting block at high speeds.
Material caught between the impact block and knife is cut with a cutting action that
allows size reduction down to the order of 6 to 18 mm.
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Rotary Shear Shredder
A Rotary Shear Shredder is essentially a continuous rotary shear or scissor. Two counter-
rotating shafts rotate in opposite directions with very close spacing between the cutters
placed on each shaft.
This type of shredder tends to cut feed material into strips, which are the same dimension
as the cutter width or spacing. Since the cutters tend to be not less than 25 mm in size,
this would be the smallest cutting dimension.
Size Reduction Equipment Selection Considerations
Selection depends primarily on waste characterization and process needs of the size-
reduced materials. Pulverizers, flail mills, and hammer-mills tend to be noisy and are
likely to generate dust during operations. They are also susceptible to explosions due to
the presence of flammable materials and pressurized containers.
Shear shredders are selected where the potential for explosions is high and the need to
minimize dust generation is important. Knife mills are employed where fine particle-
sized discharge is required and tight control over size distribution is important.
Magnetic Separation
Magnetic separators are utilized to remove ferrous metals from commingled recyclables.
Magnets can be classified as:
Electromagnets using electricity to magnetize or polarize and iron core; or
Permanent magnets utilizing permanently magnetized materials to create a
magnetic field.
61
Magnetic Separators are usually located in the field in the following three configurations:
Suspended stationary magnet over a passing conveyor;
Conveyor on the production line with a magnetic pulley at the end; and
Suspended magnetic drum at the discharge of a conveyor
The figure below shows a typical magnetic separator installation.
62
Baling
Baling is an integral part of sorting and recycling operations, Baling is an efficient means
of reducing volume, improving handling, and reducing costs. Rejects and residues may
also be baled for the same reasons. There are two main types of baling machines, vertical
and horizontal.
Baling machines have the following features:
Feed hopper or area to feed the recyclables or rejects;
One or more hydraulic or mechanically driven rams to compress the
material fed;
Compression area where the materials are densified; and
Discharge area opening from which the completed bales are ejected.
Wire ties are normally used in either a manual or automatic configuration to wrap wire
around the bale and tie it off to avoid post baling expansion and breaking.
63
REFERENCES
United Nations Industry and Environment Programme. Executive Summary of the
Workshop on country-Specific Activities to Promote Cleaner Production. (Paris, France,
Sept. 17-19, 1992).
Glenn Jim, “The Sate of Garbage in America”, Biocycle, May 1992.
Fishbein, Bette, Germany, Garbage, and the Green Dot. New York, 1994.
Decision Maker’s Guide to Solid Waste Management, EPA/530-SW-89-072, U.S. EPA,
Washington, D.C., 1989.
A Business Guide for Reducing Solid Waste, EPA/530-K-92-004, U.S. EPA,
Washington, D.C., 1990.
Variable Rates in Solid Waste: Handbook for Solid Waste Officials, vol. II, Detailed
Manual, EPA/530-SW-90-084B, NTIS: PB90-272 063, Washington, D. C., 1990.
64
Chapter VI
Sanitary Landfills
Future projections of waste quantities according to updated characterization studies are
the design basis for sanitary landfill development. Key issues like recycling and
construction and demolition waste should be given due consideration. Though recycling
is usually carried out on a small scale, it has always the potential to grow into a large
industry.
Keeping in mind local trends of recycling, and local authorities’ plans for implementing
it should give an idea of this ever growing activity to factor landfill quantities
accordingly. It should also be assumed that about 50 percent of the aggregates from the
construction and demolition (C&D) waste and 80 percent of the potentially recyclable
materials will be recycled. The remaining quantities will be sent to the landfill.
Design Requirements
Design of a sanitary landfill should provide protection of human health and the
environment. The lining system and leachate collection system of the landfill will be
designed to minimize or prevent leachate migration to ground water, protect ground-
water quality, and prevent landfill gas migration. The final cover system of the landfill
will be designed to minimize the potential for leachate generation, prevent landfill gas
migration, and prevent direct exposure of the waste.
Design requirements of a municipal waste sanitary landfill should be as follow:
A design life of at least 25 years;
A growth rate should be decided usually between 2 and 4 percent per year;
Recycling programs should be built into the forecasted quantities to be
landfilled in future years;
A landfill should be divided into cells that may be developed based on the
actual growth rate of the waste, and the needs of the local authorities;
Leachate generation should be predicted and collection and treatment
designed accordingly;
Gas generation should be predicted and collection and treatment designed
accordingly;
65
Visual screening barriers should be constructed along the site boundaries to
prevent the public from being able to view the site operations;
A lining system should be specified according to geological conditions and
designed capacity;
Cells should have a design life of 1 to 2 years;
An odor management system should be designed to prevent landfill odors;
An operations plan should be developed for the landfill describing how the
landfill should be operated to minimize odors, be acceptable to the public,
and protect human health and the environment;
A final cover system should consist of a geo-membrane plus additional soil
cover specifically design to avoid as much water filtration as possible;
The side slope of the final cover system should be 3H:1V;
The support facilities for the municipal solid waste landfill should include:
Main access road;
Fencing, gate, and gatehouse at main entrance;
Truck parking lot;
Scale house;
Inbound and outbound scales;
Truck wash facility;
Office and laboratory;
Maintenance garage and storage building;
Fuel depot;
Leachate treatment facility; and
Gas treatment facility.
The leachate collection system should be designed for the following
minimum factors of safety;
Flow capacity of leachate collection system, FS > 2.5;
Flow capacity of polyethylene pipe, FS > 2.5;
Flow capacity of leachate pump, FS > 2.0; and
Flow capacity of leachate forcemain, FS > 2.5.
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The lining system should be designed for the following minimum factors of
safety;
Leakage rate through the lining system less than 0.2 liters/hectare/day;
Bearing capacity, FS > 1.5;
Static short-term slope stability, FS > 1.2;
Static long-term slope stability, FS > 1.35; and
Dynamic long-term slope stability, FS > 1.0, and acceptable strain in the
lining system.
The final cover system of the landfill should be designed as follows:
The side slopes of the landfill will not be steeper than 3H:1V;
Static short-term slope stability, FS = 1.2;
Static long-term slope stability, FS = 1.35; and
Dynamic long-term slope stability, FS > 1.0, and acceptable strain in the
lining system.
The main access road should have a paved width of at least 10 m, with side
slopes not greater than 3H:1V;
The sanitary landfill should not adversely impact human health or the
environment. Ground-water modeling should be performed for a minimum
period of 100 years after the closure of the landfill to assess potential impacts
on human health and the environment; and
The sanitary landfill should be designed in such a way that it can be expanded
in the future without adversely impacting the performance of the landfill.
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Conceptual Design
Prior to the design of a sanitary landfill, a site and soil investigations should be
conducted to assure the suitability of the site, and to obtain data and information
regarding geologic and hydrogeologic conditions. This information is needed to evaluate
the potential impact of the facility on the environment in the future, and to evaluate the
design methodology.
A municipal solid waste landfill will be divided into cells, each with a leachate collection
sump. Each cell should be approximately 100 m wide by 300 m long, and should be
sloped towards the center of the cell, and towards the sump adjacent to the site boundary.
The minimum slope along the center of each cell should be 0.05 percent, and the
minimum slope from the side of the cell to the center of the cell should be approximately
2 percent.
The leachate sumps should be located along the centerline of each cell, adjacent to the
berm at the cell boundary. Each leachate sump should cover an area of approximately 3
m by 3 m, and should be approximately 1 m deep.
Cells can be constructed in phases in response to the growth rate of the local conditions,
and the growth rate of the waste stream. If the rate of growth of the waste stream is
greater than anticipated, the schedule for construction of the individual cells can be
advanced. In addition, the landfill should be designed in such a way that it can be
expanded should the need arise.
Visual Barriers
A sanitary landfill should not be operated in a way that is a danger or a nuisance to the
public. Burning of waste should not be allowed at a sanitary landfill, the waste should be
covered on a daily basis, and the tipping area should be kept as small as possible.
In addition, visual barriers should be designed to be constructed around the perimeter of
the landfill to prevent observation of site operations. An exterior screening berm should
be constructed along the closest main road, adjacent to the fence line.
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The exterior screening berm should be 3 to 4 m high, 3 m wide at the top, and should be
landscaped with trees and shrubs or rock, to create a visual barrier between the main road
and the landfill.
A perimeter berm should be constructed around the landfill. This perimeter berm should
increase landfill capacity, provide a barrier to leachate and gas migration, protect the
lining system, and provide an additional visual barrier for landfill operations.
Liner System and Leachate Control System (LCS)4
The lining system at the base of the sanitary solid waste landfill should consists of, from top
to bottom:
A 2-ft (0.6-m) thick LCS drainage sand layer;
A LCS geo-textile filter;
A LCS geo-net drainage layer;
top of a geo-synthetic clay layer; and A composite liner composed of a 60-mil
(1.5-mm) thick high density polypropylene (HDPE) geo-membrane placed
on a minimum 0.3 m prepared sub-base.
In addition, at the LCS collector swale and LCS sump there should be:
A LCS geo-textile cushion located between the pipe bedding/drainage gravel and
the HDPE geo-membrane; and
A LCS geo-textile filter located between the LCS drainage sand layer and the
pipe bedding/drainage gravel.
4 See drawing at the end of the chapter
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Gas Collection System
The active gas collection system should be located within the perimeter of the waste
disposal area. The purpose of the gas collection system is to actively collect the landfill
gas produced at the landfill and convey the landfill gas to the gas disposal system and/or
gas processing system.
The gas collection system for the Sanitary Landfill should actively collect landfill gas from
the landfill. The gas collection system consists of a vertical gas collection (VGC) system.
This VGC system should provide effective collection and removal of the landfill gas and is
designed to function for the entire design period of the landfill. In addition, the VGC
system should be designed to withstand all landfill operating conditions.
The VGC system for collection of landfill gas includes vertical extraction wells. The
vertical extraction wells should be nominally spaced in plan at about 100-m intervals,
penetrate the final cover system, and extend into the waste to a depth equal to
approximately three-quarters of the waste thickness or liquid level, whichever is the highest.
The vertical extraction wells should consist of an HDPE pipe with a standard dimension
ratio (SDR) of 17 and a nominal diameter of 150 mm. The HDPE pipe should be rated by
the manufacturer as safe for use in hazardous or explosive environments and is resistant to
corrosion and constituents of landfill gas. The upper one-quarter of the vertical extraction
well should be solid HDPE pipe while the bottom three-quarters of the HDPE pipe should
be perforated. The lengths of solid and perforated HDPE pipe may be adjusted during
installation depending on field conditions.
The vertical extraction wells, via the connector pipes, should be tied to the gas collection
header pipe. The gas collection header pipe should be buried within the perimeter berm.
The gas collection header pipe conveys the landfill gas to the flare station for disposal.
The gas collection system should be considered part of the facility. It should be designed
such that the system will not compromise the integrity of the liner, leachate collection, or
cover system.
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Final Cover System
A final cover system should be designed for the municipal solid waste landfill. The final
cover system provides a barrier over the waste materials that prevents contact with the
public, and minimizes leachate generation and gas migration. The Final Cover System
should have a maximum of 3H: 1V side slopes and top slopes graded at five percent.
These side slopes should be consistent with the side slopes at many other landfills, which
have demonstrated good structural stability. A stone cover layer should minimize wind
erosion of the final cover sand layer.
The final cover system on top of the landfill should consist of, from top to
bottom;
0.3-m thick stone layer;
0.3-m thick granular (sand) cover protective layer;
40-mil (1.0-mm) thick polyethylene (PE) geo-membrane liner; and
0.15 to 0.3-m thick daily or intermediate cover layer.
The geo-membrane and stone final cover on the side slopes should be identical to
the final cover system on top of the landfill except that a geo-composite cover drainage
layer should be included on the side slopes above the PE geo-membrane. This geo-
composite cover drainage layer is required for slope stability, as it will provide drainage
in the event of precipitation at the site. In the event of precipitation at the site, the sand
layer above the geo-membrane would become saturated. This layer would become
unstable if not properly drained. The geo-composite drainage layer should be designed
to prevent saturation of the overlying sand cover protective layer. The geo-composite
drainage layer of the final cover system should be designed for the maximum flow rate
with a safety factor of 2.5.
The final cover system on the side slopes of the landfill should consist of from
top to bottom:
0.3-m thick stone layer;
0.3-m thick granular (sand) cover protective layer;
Geocomposite cover drainage layer;
40-mil (1.0-mm) thick polyethylene (PE) geomembrane liner; and
0.15 to 0.3-m thick daily or intermediate cover layer.
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Support Facilities
The support facility for the proposed new Landfill should include the following:
Access Road and Truck Parking;
Scales and Scale house;
Offices and Laboratory;
Leachate Treatment System;
Gas Treatment System;
Maintenance and Storage Buildings; and
Staff Cafeteria Building.
These facilities are briefly described below.
Access Road and Truck Parking Lot
A paved access road should be constructed from the main road to the solid waste landfill.
The Truck Parking Lot should be located near the main access road. The Truck Parking
Lot should cover an area of approximately 30 m by 50 m, and the parking lot should be
paved to protect the subgrade soils and ground water from contamination.
Scales and Scalehouse
Scales should have sufficient capacity to accommodate up to and including the large
open back trucks (18 wheel) used to transport waste materials from the Compost Plant
and Transfer Stations to the landfill. The scalehouse should be approximately 5.0 m by
6.0 m, with window counters on each side. The scalehouse should also be designed with
an observation deck to view waste loads prior to disposal in the landfill.
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Office and Laboratory
An office and laboratory building should be designed. The office building should be
designed with a 4 m by 6 m office for the Landfill Manager, and 3.5 m by 5 m offices for
the Laboratory Manager and Landfill Operations Supervisor. Kitchen, restrooms, and
open work areas should be provided. The laboratory should be constructed in a large
open area of approximately 100 sq m.
Leachate Treatment System
The leachate treatment system for the landfill should consist of a leachate recirculation
system with a leachate evaporation pond. The leachate recirculation system should be
used to reduce constituent concentrations, and minimize leachate treatment rates and
volumes.
The leachate evaporation pond might cover an area of approximately 40 m by 80 m. The
leachate evaporation pond should be designed to store a minimum of 7 days of leachate
at the maximum leachate generation rates for the conditions just prior to closure of the
landfill, when all of the cells are full except for the active cell, and there is 3 m of waste
on the base of the final cell.
Gas Treatment System
The gas collected by the gas collection system should be conveyed through gas header
pipes to a gas force main. The gas header pipes and gas forcemain should be installed
with a safety factor of 4.0 for flow capacity.
Condensate traps should be included in the design of the forcemain and prior to the
industrial flare. The condensate traps should be designed to drain into the landfill, or
into the leachate collection system.
An industrial flare should be used to destroy the landfill gas to meet appropriate air
quality standards. The flare should be designed to handle the maximum gas generation
rate with a minimum safety factor of 2.0.
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Maintenance and Storage Buildings
A Maintenance Building should be constructed to maintain the site vehicles. The
Maintenance Building should be designed with 3 working bays, each of approximately
10 m by 20 m. A Storage Building should be designed adjacent to or as part of the
Maintenance Building. The Storage Building should be approximately 6 m by 20 m.
In addition, a truck wash facility should be designed to accommodate all of the various
types of vehicles that will deliver waste to the landfill.
Staff Cafeteria Building
The Staff Cafeteria Building should be designed to accommodate a staff of up to 30 at
the landfill operations site. The Staff Cafeteria Building should include a cafeteria,
restrooms, and a common area. The Staff Cafeteria Building should be a one floor
facility, with a footprint of approximately 10 m by 15 m.
74
REFERENCES
Bagchi, A., Design, Construction, and Monitoring of Sanitary Landfill, John Wiley &
Sons, New York, 1990.
California Waste Management Board. “Landfill Gas Characterization,” Sacramento,
1988.
Crawford, J.F., and P.G. Smith. Landfill Technology, Butterworths, London, 1991.
75
Chapter VII
Medical Waste Treatment
There are many proven technologies that may be used to treat medical wastes. Only the
most popular medical waste treatment technologies will be considered in this chapter.
Steam Autoclaving.
Steam autoclaving is an appropriate method for treating microbiology laboratory waste,
human blood and body fluid waste (if applicable), waste sharps, and non-anatomical
animal wastes. It must not be used for treating either human or animal anatomical waste.
Personnel who operate steam autoclaves must be thoroughly trained in the use of the
equipment. Specific guidelines and regulated requirements for operating and using
autoclaves must be developed for the local authorities.
The effectiveness of decontamination of biomedical waste is dependent upon the
temperature to which the waste is subjected, as well as the length of time it is exposed to
steam. Because the waste is heated by both steam penetration and heat conduction, air
must be displaced to allow proper steam treatment.
Typical operating conditions for decontamination include temperatures of at least 121oC
at a pressure of 15 lbs/in2
for more than 60 minutes. Laboratory wastes, such as Petri
dishes and syringes that are liable to melt and trap air or liquids, may require longer
sterilization times.
The penetration of steam into the waste is crucial to the effectiveness of the autoclaving
process. For this reason, particular attention must be given to packaging to ensure
effective steam penetration.
76
Special consideration must be given to the type of plastic bags used within the autoclave.
Some bags may impede steam penetration while others may melt during the autoclave
cycle. Plastic bags should therefore be assessed under actual working conditions to
assure their effectiveness and integrity throughout the autoclave cycle.
The effectiveness of decontamination is also affected by the volume and size of the waste
load in the autoclave. For small-capacity laboratory autoclaves, two separate small loads
may be more effective for treatment than a single larger load. Also since there is no
"standard load" for an autoclave, the operator may need to adjust to the autoclaving
parameters. As with other treatment technologies, proper operation of the autoclave is
essential to its effectiveness.
To monitor the effectiveness of the autoclaving cycle, either chemical indicators or
biological indicators are typically used. Chemical indicators are not recommended,
however, as they indicate only the attainment of a temperature, not its duration.
Biological indicators, such as the presence of bacillus stearothennophilus, are typically
found to be more reliable. The effectiveness of the autoclave should be verified
regularly, based on its frequency of use.
The facility should keep records of the time, temperature, and pressure to which each
load of decontaminated waste is subjected as evidence that the load has been properly
treated. Such records may be useful if landfill operators require a certificate, signed by
an official of the waste generator, stating that the waste has been treated in a steam
autoclave. Records of routine preventative maintenance and problem maintenance for
the steam autoclave must be also kept. These records must be available at all times.
Wastes containing cytotoxic agents, such as chemotherapy drugs and other chemical
wastes, must not be subjected to autoclaving. Such wastes are not degraded at normal
autoclave temperatures.
State of the art rotating autoclaves have improved the performance of conventional
autoclaving systems. Modern systems have the advantage of not being capital or
operating intensive. A typical autoclave system layout is shown in the figure next page.
77
Plan View of Typical Autoclave System Layout
Chemical Decontamination
Chemical decontamination may be appropriate for treating microbiology laboratory
waste, (regulatory approval required), human blood and body fluid waste (if applicable),
and waste sharps. It must not be used for treating anatomical waste.
Chemical decontamination is most often applied to liquid wastes before disposal. It may
be useful in decontamination of spills when they occur. Chemical treatment alone does
not render sharps safe for additional handling. This treatment option applies to filled
sharps containers that may undergo further treatment after chemical decontamination as
part of a process, e.g., chemical decontamination coupled with mechanical shredding.
78
If chemical decontamination is used, the following factors should be considered:
Type of microorganisms;
Degree of contamination;
Type of disinfectant used; and
Concentration and quantity of disinfectant.
Other relevant factors include temperature, pH, degree of mixing, and the length of time
the disinfectant is in contact with the contaminated waste.
Sodium hypochlorite (household bleach) is often used as an intermediate-level
disinfectant, with the commercial product normally being a 5.25% solution of sodium
hypochlorite (50 000 mg/L of free available chlorine). If diluted hypochlorite solution is
used, it should be made up daily to prevent loss of germicidal action. A 5,000 mg/L
(5,000 ppm) sodium hypochlorite solution (1:10 dilution) is recommended for
disinfecting blood spills and soiled equipment.
Records of the chemical decontamination protocol to which each load of the waste is
subjected should be kept by the facility as evidence that the load has been treated. Such
records may be useful if landfill operators require a certificate, signed by an official of
the waste generating facility, stating that the waste has been appropriately treated.
79
Microwaving
The introduction of microwaves to treat medical waste is relatively young but extremely
effective both technically and economically. Microwaving treatment units have been
successfully used in hospitals in America, Europe and the Middle East in recent times.
The Microwave treatment system procedures are quite simple. The Microwave unit
resembles a shipping container and it is very easy to install and accommodate in any
hospital. The system features a shredder at the front-end of the operation and then a
conveyor belt taking the shredded waste through three consecutive microwave
generators. The procedure takes about 10 minutes and renders the infectious medical
waste sterile.
Figure below shows a typical microwave installation.
Typical Section of a Microwave Treatment Unit
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Disposal of Medical Wastes
Landfill
It is technically acceptable to dispose of some types of decontaminated biomedical waste
in a landfill. The following are recommended protocols for the handling of
decontaminated biomedical wastes at landfill sites. Standards and regulations for the
disposal of medical waste in landfills must be developed.
Waste generators should prearrange with the landfill site operator such
specific details as time of delivery, volume of waste, and evidence of
treatment.
Decontaminated microbiology laboratory waste, or decontaminated and
shredded waste sharps should be buried immediately upon receipt or
following a schedule designated by the authority with jurisdiction; and
To prevent direct contact with compaction equipment or other equipment
operating at the surface, the wastes should be covered with either earth or
other waste at the site.
If requested, the waste generator should provide information to the landfill operator and
other staff, about the nature and handling of decontaminated microbiology laboratory
waste or decontaminated waste sharps. Such information may include:
Where the waste was generated;
What treatment it has undergone; and
Quantities of waste generated.
Human anatomical waste and animal waste must not be disposed of in a sanitary landfill.
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Sanitary Sewer
Fluids associated with the exotic communicable diseases (ECD's) require special
handling. These diseases are: Lassafever, Marburg virus disease Ebola virus disea, the
two South American hemorrhagic fevers - Junin and Machupo, and the Crimean-Congo
hemorrhagic fever. Because of the potential infectivity of the agents causing these
diseases, and their relatively high case fatality rates, wastes contaminated by these
diseases should be managed in consultation with the laboratory center for disease
control.
Microbiological laboratory waste consisting of laboratory cultures, stocks or
specimens of micro organisms, live or attenuated vaccines, human or animal cell
cultures used in research, and laboratory material that has come into contact with the
above, must be autoclaved or subjected to other treatment technologies considered
acceptable to the regulatory authority before disposal to the sanitary sewer system.
Regulations for disposal of medical wastes to the sanitary sewer system must be
developed.
Solid wastes, if they are not being disposed to a sanitary sewer after appropriate
treatment, should be placed in leak-proof containers before treatment and/or disposal.
Liquid wastes contained in this way must not be disposed of by landfill, as sanitary
landfills are not designed to accept waste liquids.
Incineration
Modern incineration equipment, complying with all environmental regulations, is being
designed and fabricated for medical waste disposal. Medical Waste Incinerators are very
effective but they require high capital investment and the cost of operations is higher
than any other alternative disposal systems.
82
Design requirements
Preliminary design should be based on the following information about the medical
facilities and their working conditions.
Sources of Medical Waste
The major sources of medical waste are hospitals, clinics, pharmacies, health centers,
dental clinics, nursing homes, police hospitals and clinics, hospitals and clinics at the
military bases, medical laboratories, and veterinary facilities. These medical facilities
may be divided into two broad categories: (i) government facilities; and (ii) private
facilities. However, significant quantities of medical waste are also generated in private
households, schools, offices, and commercial and industrial facilities.
Quantities of Medical Waste
Based on the data and information provided by local authorities, the number of patients
treated in a given year may be organized as in the following example:
Admitted patients in different hospitals = 84,619;
Surgical operations in different hospitals = 31,984;
Outpatient visits in hospitals = 2,271,733;
Outpatient visits to consultants in hospitals = 1,646,913; and
Individuals having dental treatment = 353,107.
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The total estimated quantity of medical waste generated in the government medical
facilities in the past year was approximately 3,200 kg/day (1,156 tons/yr). The total
estimated quantity of medical waste generated in the private medical facilities was
approximately 1,20 kg/day (432 tons/yr). Therefore, the total combined quantity of
medical waste from the government and private hospitals, health clinics (including dental
clinics), pharmacies, health centers, nursing homes, and laboratories was approximately
4,400 kg/day (1,588 tons/yr). These totals are expected to increase at different percent
rates per annum.
These quantities should be added to medical waste generated in veterinary clinics,
households, businesses, or schools. If the total medical waste generated in veterinary
clinics, households, businesses, and schools is estimated to be approximately 100 kg/day,
the estimated total quantity of medical waste to be generated in a given year should be
approximately 4,500 kg/day (1,643 tonnes/yr).
Medical Waste Collection
Medical waste is usually collected by private cleaning companies working in hospitals
and clinics. The medical waste is placed in different types and colors of waste bags and
containers then placed in specially designed bins. These bins should be located at the
medical facilities in protected areas.
The colored bags and containers should be strictly used for the collection of medical
waste only. The type, color, and classification of the bags and containers are as follows:
Red Heavy Duty Bags. The red heavy duty bags are used for Type A
materials, which are considered to be highly infectious. The red heavy duty
bags are made of 400 gauge (100 micron) polyethylene, and are filled only to
a 40 percent capacity before collection and disposal. A warning sign is
located on the exterior of the bag indicating “Highly Infectious Material Type
A Medical Waste for Incineration Only”.
84
Yellow Heavy Duty Bags. The yellow heavy duty bags are used for Type D
waste materials, which are considered to be toxic. The yellow heavy duty
bags are made of 400 gauge (100 micron) polyethylene, and are filled only to
40% capacity before collection and disposal. A warning sign is located on
the exterior of the bag indicating “Toxic Material Type D Medical Waste.
Sterilize Before Disposal.”
Transparent Blue Bags. The transparent blue bags are used for Type C waste
materials, which are considered to be highly infectious, and must be sterilized
before disposal. The transparent blue bags are made of 160 gauge (40
micron) polyethylene, and may be filled to capacity prior to disposal. A
warning sign is located on the exterior of the bag indicating “Highly
Infectious Material Type C Medical Waste, Sterilize Before Disposal.”
Yellow Medium Duty Bags. The yellow medium duty bags are used for Type
E waste materials, which are considered to be hazardous materials, and must
be incinerated. The yellow medium duty bags are made of 200 gauge (50
micron) polyethylene, and may be filled to 40 percent capacity before
collection and disposal. A warning sign is located on the exterior of the bag
indicating “Hazardous Material Type E Medical Waste, for Incineration
Only”.
Yellow Rigid Container. The yellow rigid containers are used for Type B
waste materials, which are sharp objects. The yellow rigid containers are
made of hard, puncture and chemical resistant, non-polluting, translucent
plastic. The containers are equipped with a leak-proof closure device that
prevents spillage and leakage. Each container is filled to no more than 75
percent capacity prior to disposal. A warning sign is located on the exterior
of each container indicating “Contaminated Sharp Objects Type B Medical
Waste, Sterilize Before Disposal”.
85
Medical Waste Handling and Disposal
As stated previously, medical waste should be collected and transported by private
cleaning companies under contract with the various facilities and government
departments. All medical waste is collected and placed in specially designed waste bins
at each facility. The medical waste should then be collected by private companies for
treatment and disposal at their corresponding facilities.
Radioactive Medical Waste
Radioactive medical waste consists of radionuclides used in medical diagnostics and
therapy. After use, the radioactive medical wastes are temporarily stored at the medical
facilities. Based on available data and information, most of the radioactive medical
waste is returned to the suppliers or manufacturers for treatment and disposal.
The most frequently used radionuclides in the hospitals for the purpose of medical
therapy and medical diagnostics are Co-7, Co-60, Selenium, I-131, Cs-137, Sr-90, Y-90,
NB-1, 201Ti.
Collection and Storage of Radioactive Waste
All hospitals and clinics should have storage areas for radioactive waste and the sealed
sources.
86
Conceptual Design
Based on the result of a Waste Characterization Study, it should be anticipated that the
medical waste treatment system will consist of an autoclaving system, and an incinerator.
A typical plan view of a medical waste treatment facility is a figure next page. The
facility should comply with international safety and environmental requirements,
including adequate accident prevention systems and emergency treatment in case of
accident. Laboratory facilities should be supplied and they should be specifically design
to support the medical treatment activity. Additional regulations and guidelines should
be developed for the collection, storage, transport, treatment, and disposal of medical
waste.
Waste Incinerator (Pyrolisis)
The waste incineration system is comprised of six major parts as follows:
Primary Waste Chamber;
Breech (Ducting) Assembly;
Afterburner Combustion System;
Automated Control System;
Operator’s Computer Monitoring System;
Industrial Ash Vacuum System;
Ram Feeder; and
Gas Conditioner (where necessary).
It is recommended that the medical waste incinerator be an indirect burn, zero air
discharge system as the one shown in a figure below. One of the many unique and
distinct features of this system is the automated control and operation thereby,
eliminating the need for bag houses or precipitators for MSW. Tests have indicated that
there is no need for further air processing because of the low particulate levels and low
level of complex chemical emissions.
For medical waste, if there is air discharge, the use of stack-gas conditioning is
recommended such as a Pollution Control Scrubber to reduce the acid gases, which
contain a high content of HCl originating from the plastics.
87
The primary waste chamber is a steel panel fabrication, either square or rectangular
depending on the customer’s size requirements. Each panel is lined with a total of 0.15
m. of insulation and high temperature refractory material suited for the waste to be
processed at high temperatures. To make use of new and lighter materials available on
the market, a ceramic blanket material is also used on the walls and on the door of the
primary waste chamber and afterburner to lighten the weight of the machine for
shipping.
When the primary waste chamber is full, the lid will close by pushing a button on the
control panel, and the chamber will be essentially airtight. The afterburner chamber and
the primary waste chamber are purged of air and the process begins with a temperature
increase in the afterburner.
Once the appropriate temperature is reached, the primary waste chamber is ignited with
propane, natural gas, or fuel oil burners. The primary burner (s) run for approximately
eight minutes to raise the interior temperature to 1,000 oF. Once this temperature is
achieved, the primary burner automatically shuts off.
88
The principle of the oxidation process is that it occurs under a starved air environment.
The bottom of the primary waste chamber is equipped with a series of perforated tubes,
to allow for only traces amount of air to maintain substoichiometric conditions.
As the gas by-product of the process begins to accumulate in the primary waste chamber,
a modulated damper opens and allows the air to be drawn into the afterburner
combustion system. Here, secondary burners bathe the gas stream in a turbulent manner
and ignite it. The processed and spent gas may be mixed with outside air, expanded, and
kept in the high temperature environment of 1,400 oC (2,552
oF) for two seconds before
being vented through an exhaust stack.
All of these operations are monitored and computer controlled with the control panel.
Using a combination of automatically controlled set points, checks and balances, the
waste oxidizer system will perform reliably and consistently for many years.
The secondary chamber is specifically designed and engineered so that particulates and
emissions are resident for sufficient time for their destruction. Typical operating
temperature is 1,000 oC.
The system is a prefabricated assembly, which streamlines field assembly and gives solid
and liquid processing capability.
89
The systems features:
Virtually no moving parts to maintain;
Simple and inexpensive maintenance;
Minimized labor costs;
Same system can be used for MSW, medical and liquid waste, and tires;
Easy installation on existing foundations;
Air intake manifolds;
Non-conventional insulating and refractory materials; and
Modular, portable, expandable and easily customized to start small and grow.
Operations design will also include waste reduction planning, segregation schemes,
waste packaging directives, and containers management as will be discussed below.
90
Rotoclave Treatment Specifications
Typical Rotoclave Treatment Unit
The overall dimensions of a typical unit are:
Length: 10 meters;
Height: 3 meters;
Width: 2 meters;
Height: (open) 5.7 meters; and
Weight: (Approx.) 12 tons.
The rated capacity of a typical system is 200-500 k/hr
The Shredder specifications are as follows:
HP: 20;
Amperage: 46 (3 phases, 230 V.);
Knife Thickness: 5/8”; and
Cutting Chamber: 38´x 14”
91
The Electrical Requirements are:
Input voltage: 460/480 Vac;
Amperage: 200 amp.;
Frequency: 60 Hz;
Phase: 3 (3w/ground); and
Consumption: 75 Kw/hr. (nominal).
The required steam generator specs are as follows:
Capacity: 518 lbs/hr;
Gross BTU Output: 516,000 (100% rating);
Amperage: 15 amperes; and
Water usage per cycle: 65 gallons.
The Autoclave Specifications are as follows:
Gallons: 396;
Waste load: 226 kg;
BTU/hr: 472,140; and
Boiler HP: 15.
Segregation
Whether the method of disposal is on-site or off-site, medical waste must be segregated
from the general waste stream. If medical waste is mixed with general refuse, the total
waste stream would require special treatment and handling. Waste segregation relies on
the waste being segregated at its point of generation and placed into appropriate waste
containers. Segregation permits facilities to effectively divert those materials that are
recyclable.
92
Medical waste must be segregated at the point of generation into the following waste
categories:
Human anatomical waste;
Animal waste; microbiology laboratory waste;
Human blood and body fluid waste;
Waste sharps;
Although not considered a medical waste, cytotoxic wastes and pharmaceutical wastes
must also be segregated from the remainder of the waste stream.
Waste Packaging
Waste must be safely contained during handling and to the point of its disposal. The
packaging must remain intact throughout handling, storage, transportation, and
treatment. When selecting packaging, the following factors should be considered: (i) the
type of waste being contained; (ii) appropriate colour-coding and labelling; (iii) special
transportation requirements; (iv) the method of disposal; (v) local regulatory
requirements; and (vi) requirements of the disposal facility.
To simplify their selection and use, waste containers should be classified as reusable or
single-use/disposable.
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Reusable Containers
Reusable waste containers must be made of metal or rigid plastic and able to withstand
exposure to common cleaning agents. They must be colour-coded according to the type
of waste for which they are intended, and labelled with the biohazard symbol.
Reusable waste containers should be inspected for holes or leaks each time they are
emptied and their colour-coding and labelling renewed if necessary. Holes or leaks must
be repaired or the waste container replaced. Reusable waste containers must be cleaned
regularly to prevent odours and as soon as possible if waste materials leak or spill within
the containers.
The facility's infection control committee bio-safety officer, or other appointed person's
should be consulted about the frequency of cleaning and the type of cleaning agent to be
used. New regulations should be developed to address the requirements for inspection
and monitoring of reusable containers.
Modular Indirect Burn Incinerator.
94
The primary waste chamber is a steel panel fabrication, either square or rectangular
depending on the customer’s size requirements. Each panel is lined with a total of 0.15
m. of insulation and high temperature refractory material suited for the waste to be
processed at high temperatures. To make use of new and lighter materials available on
the market, a ceramic blanket material is also used on the walls and on the door of the
primary waste chamber and afterburner to lighten the weight of the machine for
shipping.
When the primary waste chamber is full, the lid will close by pushing a button on the
control panel, and the chamber will be essentially airtight. The afterburner chamber and
the primary waste chamber are purged of air and the process begins with a temperature
increase in the afterburner.
Once the appropriate temperature is reached, the primary waste chamber is ignited with
propane, natural gas, or fuel oil burners. The primary burner (s) run for approximately
eight minutes to raise the interior temperature to 1,000 oF. Once this temperature is
achieved, the primary burner automatically shuts off.
The principle of the oxidation process is that it occurs under a starved air environment.
The bottom of the primary waste chamber is equipped with a series of perforated tubes,
to allow for only traces amount of air to maintain substoichiometric conditions.
As the gas by-product of the process begins to accumulate in the primary waste chamber,
a modulated damper opens and allows the air to be drawn into the afterburner
combustion system. Here, secondary burners bathe the gas stream in a turbulent manner
and ignite it. The processed and spent gas may be mixed with outside air, expanded, and
kept in the high temperature environment of 1,400 oC (2,552
oF) for two seconds before
being vented through an exhaust stack.
All of these operations are monitored and computer controlled with the control panel.
Using a combination of automatically controlled set points, checks and balances, the
waste oxidizer system will perform reliably and consistently for many years.
The secondary chamber is specifically designed and engineered so that particulates and
emissions are resident for sufficient time for their destruction. Typical operating
temperature is 1,000 oC.
95
The system is a prefabricated assembly, which streamlines field assembly and gives solid
and liquid processing capability.
The systems features:
Virtually no moving parts to maintain;
Simple and inexpensive maintenance;
Minimized labor costs;
Same system can be used for MSW, medical and liquid waste, and tires;
Easy installation on existing foundations;
Air intake manifolds;
Non-conventional insulating and refractory materials; and
Modular, portable, expandable and easily customized to start small and grow.
Operations design will also include waste reduction planning, segregation schemes,
waste packaging directives, and containers management as will be discussed below.
96
Rotoclave Treatment Specifications
The overall dimensions of a typical unit are:
Length: 10 meters;
Height: 3 meters;
Width: 2 meters;
Height: (open) 5.7 meters; and
Weight: (Approx.) 12 tons.
The rated capacity of a typical system is 200-500 k/hr
The Shredder specifications are as follows:
HP: 20;
Amperage: 46 (3 phases, 230 V.);
Knife Thickness: 5/8”; and
Cutting Chamber: 38´x 14”
The Electrical Requirements are:
Input voltage: 460/480 Vac;
Amperage: 200 amp.;
Frequency: 60 Hz;
Phase: 3 (3w/ground); and
Consumption: 75 Kw/hr. (nominal).
The required steam generator specs are as follows:
Capacity: 518 lbs/hr;
Gross BTU Output: 516,000 (100% rating);
Amperage: 15 amperes; and
Water usage per cycle: 65 gallons.
The Autoclave Specifications are as follows:
Gallons: 396;
Waste load: 226 kg;
BTU/hr: 472,140; and
Boiler HP: 15.
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Segregation
Whether the method of disposal is on-site or off-site, medical waste must be segregated
from the general waste stream. If medical waste is mixed with general refuse, the total
waste stream would require special treatment and handling. Waste segregation relies on
the waste being segregated at its point of generation and placed into appropriate waste
containers. Segregation permits facilities to effectively divert those materials that are
recyclable.
Medical waste must be segregated at the point of generation into the following waste
categories:
Human anatomical waste;
Animal waste; microbiology laboratory waste;
Human blood and body fluid waste;
Waste sharps;
Although not considered a medical waste, cytotoxic wastes and pharmaceutical wastes
must also be segregated from the remainder of the waste stream.
Waste Packaging
Waste must be safely contained during handling and to the point of its disposal. The
packaging must remain intact throughout handling, storage, transportation, and
treatment. When selecting packaging, the following factors should be considered: (i) the
type of waste being contained; (ii) appropriate colour-coding and labelling; (iii) special
transportation requirements; (iv) the method of disposal; (v) local regulatory
requirements; and (vi) requirements of the disposal facility.
To simplify their selection and use, waste containers should be classified as reusable or
single-use/disposable.
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Reusable Containers
Reusable waste containers must be made of metal or rigid plastic and able to withstand
exposure to common cleaning agents. They must be colour-coded according to the type
of waste for which they are intended, and labelled with the biohazard symbol.
Reusable waste containers should be inspected for holes or leaks each time they are
emptied and their colour-coding and labelling renewed if necessary. Holes or leaks must
be repaired or the waste container replaced. Reusable waste containers must be cleaned
regularly to prevent odours and as soon as possible if waste materials leak or spill within
the containers.
The facility's infection control committee bio-safety officer, or other appointed person's
should be consulted about the frequency of cleaning and the type of cleaning agent to be
used. New regulations should be developed to address the requirements for inspection
and monitoring of reusable containers.
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Chapter VIII
Construction and Demolition (C&D) Waste
The key to lessening landfill dependency is not simply recovering materials, but being
able to sell what you recover. As a result, municipalities have targeted a recoverable
portion of the waste stream with good end-markets: construction and demolition (C&D)
debris. Not only is C&D highly recyclable, it also represents between 15 percent and 30
percent of all waste headed to landfills.
Construction and Demolition waste is one major source of waste everywhere in the
world. Fortunately, construction and demolition processing technologies are changing
dramatically the approach to handling and disposal of this kind of waste. It may be said
that Municipalities and/or the private sector can nowadays benefit from the management
of this activity.
If there is a straight forward, clean, profitable waste recycling business, it is the recycling
of construction and demolition waste. Construction materials always have been and they
always will be in high demand for obvious reasons and modern technologies are now
available to add value to the waste with proven, affordable processing machinery.
There are an ever-increasing number of recyclables and applications derived from
construction and demolition waste. The obvious ones are metals, wood, glass, plastics,
and aggregates and its derivatives. Even asphalt from old roads is being recycled with
modern equipment specifically designed for the job.
Successful municipalities have reached their construction and demolition waste treatment
and disposal goals by proper planning with a vision of the practical procedures needed in
place to guarantee the outcome of the business.
The first important step into management of the sector is to introduce legislation in
agreement with all industrial, contracting, and developing sectors to ascertain new
procedural rules will be followed on disposal of construction waste.
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Construction permits should introduce waste disposal procedures and certification of
compliance as part of conditional clauses. Certification of compliance means the
contractor has to have a written contract with a specialized company to dispose of all the
construction waste generated for the duration of the development.
License to function should also be tied to construction waste disposal certification and it
should be extended to revamping and modification projects so the whole spectrum of the
construction industry is included.
The second step should be promotion of sectors awareness of the new legislation and the
available procedures to avoid fines, permit revoking, and license withdrawals.
The third step should be accomplished by full commitment from the municipality to
make the procedures available and eventually utilize the law to enforce them.
C&D waste is defined as non-putrescible waste materials that are generated in the normal
course of construction or demolition of structures and facilities. C&D waste consists of
construction and demolition debris from both construction and demolition projects.
C&D waste typically consists of materials that are not generally water soluble and are
non-hazardous in nature, including steel, glass, brick, concrete, asphalt, pipe, gypsum
wallboard, and wood.
C&D would also typically include rock, soil, tree remains, and vegetative matter
resulting from land clearing and land development activities. Construction materials
would typically consist of clean cardboard, plastic, paper, wood, metal scraps, forms, and
pallets. C&D waste may also include hazardous constituents such as paints, foams,
caulking materials, adhesives, epoxy grouts, surface treatments, and roofing materials.
Diversion of C&D materials (excluding C&D materials contaminated with hazardous
substance) is a key strategy for reaching landfill diversion goals. This is because:
There are well-established C&D processing technologies, improved equipment
and new systems are continuously coming on line;
C&D materials are heavy and high in volume;
C&D materials are highly recyclable;
There are good end-uses and markets for most types of C&D materials;
C&D materials can be source-separated, transported, and processed cost-
effectively;
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C&D recycling centers provide good business and job creation opportunities;
Costs for processing C&D materials often are much lower than the cost of
landfilling them; and
C&D can be a significant portion of the waste stream;
Design Requirements
In order to evaluate the quantity, type, characteristics, and sources of C&D waste, field
studies and investigations should be performed. In addition, responsible parties from the
Municipality, construction and demolition companies, and C&D waste collectors and
transporters should be interviewed and researched. These studies and investigations
included placing personnel at the current dump sites to examine each truck load of waste
delivered to the dump sites, and detailed analysis of their composition.
Municipalities and other government organizations usually generate less than 1 percent
of the C&D waste. However, the quantities of waste hauled by each company,
organization, or group to the landfill appear to be highly variable, depending on the
projects that are permitted and under construction or demolition.
Types and Characteristics of C&D Waste
The following information is given as a guide basis for engineering design. When
each load of waste material is spread out to facilitate examination and evaluation,
C&D waste materials are segregated according to the following types:
Aggregates (rock and soil);
Metals;
Cardboard;
Paper;
Wood;
Plastic;
Municipal Solid Waste;
Tires;
Furniture;
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Residuals;
Vegetation;
Carpet;
Polystyrene Insulation;
Drums (55 gallon);
Air Filters;
Wall Board; and
Glass.
Ranges and quantities of the C&D waste materials should be organized as in the
following example:
Aggregates Range = 0 to 100% Average = 78.2%;
Metals Range = 0 to 4% Average = 1.4%;
Cardboard Range = 0 to 15% Average = 2.0%;
Paper Range = 0 to 5% Average = 0.8%;
Wood Range = 0 to 80% Average = 11.1%;
Plastic Range = 0 to 3% Average = 1.3%;
Municipal Solid Waste Range = 0 to 85% Average = 3.6%;
Tires* Range = 0 to 5 Average = 0.02%;
Furniture Range = 0 to 3 Average = 0.2%;
Residuals Range = 0 to 5% Average = 0.6%;
Vegetation Range = 0 to 1% Average = 0.03%;
Carpet Range = 0 to 10% Average = 0.5%;
Polystyrene Insulation Range = 0 to 2% Average = 0.3%;
Drums (55 gallon) Range = 0 to 1 Average = 0.03%;
Air Filters Range = 0 to 1 Average = 0.01%;
Wall Board Range = 0 to 1% Average = 0.03%; and
Glass Range = 0 to 1% Average = 0.03%.
* This value does not usually include tires disposed of directly in tire disposal areas. The
aggregate materials usually consist of rock, concrete, brick, stone, and soil (primarily sand). As
shown above, the total quantity of aggregate is usually found in the range of 50 to 80 percent,
with an average value of 78.2 percent. Therefore, aggregate was by far the most common
constituent of the C&D waste.
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Quantity of C&D Waste
For a Middle East city of more than 2 million inhabitants the following breakdown of
C&D waste materials is usually found:
Aggregates (rock and soil) 800 tonnes/day 320,000 tonnes/yr;
Metals 16 tonnes/day 5,700 tonnes/yr;
Cardboard 22 tonnes/day 8,200 tonnes/yr;
Paper 9 tonnes/day 3,300 tonnes/yr;
Wood 125 tonnes/day 45,500 tonnes/yr;
Plastic 15 tonnes/day 5,300 tonnes/yr;
Municipal Solid Waste 40 tonnes/day 14,700 tonnes/yr;
Tires 0.2 tonnes/day 82 tonnes/yr;
Furniture 2 tonnes/day 820 tonnes/yr;
Residuals 6 tonnes/day 2,500 tonnes/yr;
Vegetation 0.3 tonnes/day 120 tonnes/yr;
Carpet 5 tonnes/day 2,000 tonnes/yr;
Polystyrene Insulation 4 tonnes/day 1,200 tonnes/yr;
Drums (55 gallon) 1 tonnes/day 410 tonnes/yr;
Air Filters 0.1 tonnes/day 41 tonnes/yr;
Wall Board 0.3 tonnes/day 123 tonnes/yr; and
Glass 0.3 tonnes/day 123 tonnes/yr.
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Collection, Disposal, and Reuse of C&D Waste Materials
The majority of the C&D waste is usually collected and transported by the construction
and demolition contractors. Private companies also provide collection and transportation
services for C&D waste from the construction sites.
Waste is typically placed in roll-off boxes at each construction site. When the boxes are
full they are picked up by Crane Truck and transported to the Landfill.
Recycling and Reuse of C&D Waste Materials
Waste materials having recognized value, such as wood and metal, are often segregated
at the construction site. These materials are then sold to recycling companies. In some
cases individual scavengers rummage through the bins to remove wood, cardboard, and
other waste materials that can be recycled. Materials are then transported to the recycler,
where the materials are consolidated and transported to the markets.
However, based on experience in the USA and Europe, recycled C&D waste materials
have good value as construction materials as long as they are processed and presented in
a customer-oriented fashion. Rock, concrete, and stone materials may be crushed and
used as aggregate for highway base course and drainage. The metal, wood, glass, paper,
and cardboard may also be recycled. These materials may be collected, consolidated,
and sold to recycling companies, or they may be sold directly to industries that use the
recycled materials.
Tires Shredder
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Conceptual Design
Construction and Demolition waste plans should be based upon the requirements already
mentioned and the selection of processing equipment available in the international and
local markets.
A drawing at the end of the chapter shows a preliminary sorting facility layout,
equipment included in this layout will be discussed in this section.
The layout is specifically designed to process C&D waste starting with sorting facility to
avoid damaging machinery and materials that could otherwise reach better bids in the
market. The layout is specifically oriented towards segregation and treatment of popular
aggregates, processing wood into extruded pellets and recovery of cartons, plastics,
glass, and metals.
The typical process should feature the following equipment,
A reception hopper;
Two hand separation platforms;
A heavy-duty crusher for aggregate products;
Multiple magnetic separators to ascertain no metals into aggregate products;
Multiple shredding machines to ascertain the size of the final products
2 front-end loaders to move recyclable materials to their corresponding
locations;
Recyclable processing departments to present recyclables in the most
marketable fashion;
Baling machines for paper, cartons, cans, and plastics to reduce their volume
and render them easy to handle;
A palletizing machine to produce saleable pellets; and
An automatic loading dock to send refuse materials to the landfill as they are
produced;
Some technical aspects related to preliminary design selection are presented in the
following pages.
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Processing Building Structures
Structural steel sections and welded plate members should be designed in accordance
with the applicable section, relating to the design requirements and allowable stresses of
the AISC Specification for the Design, Fabrication, and Erection of Steel for Builings,
effective November 1, 1978.
Cold-formed structural members and exterior covering should be designed in accordance
with the applicable sections, relating to the design requirements and allowable stresses of
the AISI Specification for the Design of Cold-Formed Steel Structural Members, 1977
edition.
The building manufacturer should furnish complete erection drawings showing anchor
bolt settings, sidewall and roof framing, transverse cross- sections, covering and flashing
details, and necessary installation details to clearly indicate the proper assembly of all
building parts.
Framing members should be shop-fabricated for bolted field assembly.
Primary structural framing should include transverse rigid frames, wing unit rafter
beams, and columns, canopy beams, intermediate columns, bearing end frames, endwall
columns and wid bracing.
Secondary structural framing should include the purlins, first, eave struts, flange bracing,
sill support, clips, and other miscellaneous structural parts. Cold-formed sections are
manufactures by roll or brake forming.
Welds should be designed to meet the stress requirements of the AWS Structural
Welding Code.
Field connections should be bolted with A-325 High strength bolts for primary
connection and A-307 machine bolts for secondary connections.
Structural framing members which are not galvanized should be given one shop coat of
iron oxide zinc chromate alkyd primer.
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Roof and Walls
General
Roof, wall, and interior panels should be 0.5 mm or 0.6 mm thick made of either hot
dipped galvanized steel, hot dipped Aluminium –Zinc coated steel or pre-painted cold-
formed panels.
Panel Materials
Materials for galvanized steel panels should conform to ASTM specidifcation A-446,
galvanizing class G-90. Translucent panels should match standard panel profiles, should
be 1.5 mm thick and should be white with a granitized top surface.
Fastners
Self-tapping sheet metal screws should have Type A or Type AB threads. Where
required for weather tightness, screws should be equipped with metal and neoprene
washers. Screws should have hez heads, and are zinc plated.
Anchorage
The building anchor bolts and related anchorage should be designed to resist the column
reactions resulting from the specified loading combinations.
Design loads
Live load 100 kg/m2
Wind load 125 kg/m2
(to be checked against local conditions)
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Grinding Machine Technical Specs
40 CY per hour with large hopper of at least 2 CY capacity;
Expected size turned out: 5 cm max. Extra wide 4 meter drag link conveyor
with 2.54 cm x 7.6 cm solid steel bars spaced 12” apart eliminate bridging;
11 CY hopper build in such a fashion that a ramp for the loader is not
needed. Integral stacking conveyor up to 210 cm-high;
Heavy duty performance gear and ancillary equipment;
Pull over mechanism to resolve working congestion and cleanup problems
associated with steel tunnel walls, which tend to accumulate thick layers of
sticky material;
1.300 HP diesel power plant with flexaire fan; and
Pressure compensated, load sensing hydraulic system. No flying debris and
automatic metal ejection. Ladder and service platforms should provide
access vital areas for ease of service.
C&D Debris Sorting Machine Specifications
Throughput Capacity: 35 T/hr;
Overall dimensions: 10,530 mm;
Internal drum diameter: 2,400 mm;
Overall drum length: 12,510 mm;
Length of screening drum: 10,000 mm;
Diameter of screening openings:
1 section: 50 mm; and
2 section: 120 mm;
Design of screening zone: Exchangeable plates;
Devices incorporated in the drum: Material infeed plates;
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Speed of screening drum: Approx. 8 rpm;
Driving Power of screening drum: 30 HP;
Voltage Data: 380 V;
Operating voltage: 50HZ; and
Weight of the drum: 24,000 kg
The machine should also include supporting structure, maintenance platform & staircase
Baling Machines
Capacity: 10 tons per hour;
Produced bales must be cubes of 1x1x1 meter with a tolerance of 3 cms each
side. Baling machine should be able to produce consistent, high density bales
that are cube efficient and stack well;
The machine must have a heavy-duty structural construction;
Hydraulic system must be market available best for high efficiency, low
operating costs, and decreased maintenance;
The baler must have replaceable liner plates to prolong baler life and increase
productivity;
Release mechanism to allow easy ejection of oversized bales and
minimization of downtime; and
Hopper feeding machine must be appropriate for loading directly from a
front-end loader or a feeding conveyor.
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Front-end Loader (3 cubic meter) Specifications
Engine:
Rated flywheel at 2,200 rpm: 145 hp;
Net power: ISO 9249 145 HP, EEC 80/1269 145 hp;
Peak torque (net) at 1,400 rpm: 765 Nm;
Total torque rise: 54%;
Bore: 110 mm;
Stroke: 127 mm;
Displacement: 7.2 liters;
Exhaust emissions exceeds the following requirements: EU Oct. 98 to 2002,
US; and
EPA Jan. 97, Japan MOC April 1997.
Transmission:
Automatic power shift transmission with four speeds forward and three
reverse;
Single lever to control both speed and direction;
Separate control to lock in neutral;
Single-stage, single-phase torque converter;
Automatic shift;
Quick gear kickdown button;
F-37 high energy friction material provides long clutch life;
Externally mounted controls for easy diagnostic checks; and
High contact ration for quick operation.
Axles:
Fixed front, oscillating rear (+- 12o);
Maximum single-wheel rise and fall: 420 mm;
Patented Duo-Cone Seals between axle shaft and housing; and
Uses SAE 30W (oil change interval: 2,000 hours or one year).
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Steering:
Full hydraulic power steering. Meets ISO 5010-1992;
Maximum turning radius: 5,480 mm;
Steering angle, each direction: 40o ;
Hydraulic output at 2,597 rpm and 6,90 kPa: 102 liters/min;
Relief valve setting: 22,800 kPa;
Center-point frame articulation;
Load sensing hydraulic steering pump;
Front and rear wheels track;
Flow-amplified, closed-center, pressure-compensated system;
Full-flow filtering; and
Adjustable steering column.
Tires:
Tubeless, loader-design tires. Wide range of brand and type of tires available in the
following sizes: 20.5 R 25, 555/70 R 25, 625/70 R 25
Service Refill Capacities:
Fuel Tank: 254 liters;
Cooling system: 52.5 liters;
Crankcase: 20 liters;
Transmission: 30 liters;
Hydraulic system: 90 liters; and
Hydraulic tank: 55 liters.
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Chapter IX
Compost Technologies and Engineering
Being a natural phenomenon, composting occurs everywhere. Over time, different
organic materials break down or decompose by action of microorganisms such as
bacteria and fungi. The rich, dark soil like materials that result after full decomposition
is called compost. It is dark brown, almost black in color and has a woody or earthy
smell. Compost is like humus, the black crumbly material found on the forest floor.
However, technically, compost is a natural product of decomposition when organic waste
is carefully managed.
Worms and other soil creatures help too in the process of composting. As
microorganisms and soil creatures turn organic material into compost, they use the
organic material as food for their own growth and activity. Eventually these nutrients are
returned to the soil to be used again by trees, crops and other plants.
Decomposition occurs when organic material decays into its basic components.
Decomposition is the way nature disassembles natural products and recycles them back
into raw materials to be used again. In general terms, organic material is anything that
started out as a plant or animal. Such material becomes waste when it is no longer
usable or desired in its present form. Examples include harvest leftovers, food, leaves,
wood, manures, plant trimmings and even paper.
The process of making compost primarily consists of the following three phases:
Heating phase: The process in which the piled organic waste material begins
to heat up because of the active growth of the microorganisms is called the
heating phase. As a result, the organic waste material heats up to 55-60o C
and the microorganisms die. This phase starts after 2 - 3 days and ends after
1 - 2 weeks;
Cooling phase: It is the process when the piled material slowly starts cooling
down, until it reaches approximately 30o C. Here, a new type of
microorganism starts decomposing the organic matter. This takes about 1
month; and
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Maturation phase: The process in which the temperature of the organic waste
material becomes the same as that of soil. Microorganisms, earthworms as
well as ants help in maturation. When these organic waste materials start
drying and become like that of brown and black soil, then the compost is
ready.
The process of composting is the microbiological conversion of raw organic waste into
stable, soil enriching humus. Understanding the compost process can help produce a
high quality product, and prevent many common operating problems. Many problems
can be avoided by ensuring optimal conditions for the microorganisms that expedite
composting.
All organic material is compostable but the composition of the different materials affects
the rate of decomposition. A major factor is the carbon and nitrogen content, which
means that the more carbon in the material, such as wood, the slower the rate of
decomposition, and the more nitrogen, such as grass or manures, the faster the process.
Bacteria and fungi get their energy from carbon, found in carbohydrates such as the
cellulose in wood chips or leaves. Nitrogen, a component of protein, is necessary to
support a large population of these beneficial microorganisms. The ideal ratio of these
elements for composting is 30 parts carbon to 1 part nitrogen. If the carbon-to-nitrogen
ratio deviates too much from this ratio, the microorganisms important for composting
will not thrive.
By blending different materials, it is possible to improve the balance of carbon and
nitrogen and hasten decomposition. Leaves usually have 40-80 parts carbon to 1 part
nitrogen. With such low levels of nitrogen, they compost slowly by themselves. Grass
clippings, in contrast, have high levels of nitrogen, which are often released as ammonia
gas. Blending waste materials, to balance these nutrients, results in faster composting
with less potential for odor problems. Blending different organic wastes is an important
part of composting.
Generally, it is estimated that 60% of municipal waste is compostable organic matter.
For certain types of commercial enterprises, the compostable organic component of the
waste can be much higher, approximately 80% or more. For businesses in this category,
such as food processors, supermarkets, health care institutions, restaurants and resorts,
commercial composting may be a practical alternative to landfilling or incineration.
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A composting program for the organic wastes from these businesses can reduce disposal
expenses by 10 - 50%, depending on the type of business, the local disposal markets and
the program configuration.
Compost can improve the quality of both sandy and clay soils when used as a soil
amendment. As mulch, compost can retain soil moisture, moderate fluctuations in
temperature and keep down weeds. Compost can also substitute for peat moss in potting
mixes and protect peat bogs that are a limited natural resource. Composting can be a
cost effective waste management alternative. Composting has many advantages such as:
It is a cheap way to produce soil amendments reducing the need for artificial
fertilizers;
It reduces the amount of open garbage and is a way to keep organic waste
from being left in rotten smelly piles, as composting reduces smell;
It reduces weight of organic waste material for carrying and transport and
reduces pressure on landfill site;
It improves the quality of soil, improves its acidity, serves as a nutrient for
plants, increases water absorption capacity and helps to prevent soil erosion;
It helps to increase the population of friendly microorganisms and
earthworms in the soil;
If the compost is added to plants in large amounts, there is no danger of
spoiling plants as in the case of chemical fertilizer;
Composting helps complete the carbon cycle by returning the carbon to the
non-living environment by decomposing plant and animal matter;
Composting, as an enterprise, creates employment and generates income;
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Anaerobic composting is concealed and thus can be used for generating
biogas for use as fuel or for generating electricity; and
It can be used as an activator for further biological decomposition of the
garden/kitchen and farm waste faster.
Municipal composting offers an environmentally sound and economically affordable
way to manage a significant fraction of our solid waste problem. Implementation of an
effective composting program can work in tandem with the Government’s efforts
towards environment protection. In a broader perspective, by practicing composting, we
will send back to nature what we get from it in the first place.
One should also bear in mind that a poorly managed compost facility can be a nuisance
both to the public and the environment. It is a fact that composting is environmentally
benign, but any composting facility needs to be backed up by many precautions.
Government regulations should require a wide range of constraints, including potable
water well and residence setback distances, dust control measures, surface-water runoff
requirements, and minimum static water table depths. Water quality protection should
be one of the primary aims of regulatory restrictions on compost facility siting.
As organisms decompose waste, they generate heat. This heat is important, since
decomposition occurs most rapidly when the temperature is between 32 and 60o C.
However, if the temperature rises above 60o C, many organisms will start to die.
Overheating results in drastic microbial-population fluctuations and possibly unpleasant
odors, as the pile sterilizes itself and microorganisms die.
As it can be seen a thermometer is an essential instrument for monitoring a composting
operation. One with a 1 to 1.25 meter stem and 0-100° C range works best.
Temperature readings help determine the most appropriate time to turn over the material.
When the temperature rises above 60o C, operators should turn and mix windrows.
Turning the compost will cool the pile, and break up any anaerobic pockets, where
oxygen is lacking.
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Microorganisms need water to maintain their metabolic activity. Ideally, the moisture
content should be between 40 and 60%.
Surface area is another important consideration in the composting process. Millions of
microorganisms are working to break down an already partially decomposed organic
matter. Shredding organic waste before composting increases surface area. This
expedites decomposition and hence reducing the time to produce finished compost.
Minor variations in most of these requirements of the compost process will not cause
significant problems. The goal is to promote rapid composting without creating
anaerobic conditions, which will result from too much moisture, excess nitrogen, or
inadequate aeration.
Although, composting is one of nature’s natural systems, it can pose a number of
problems from the commercial point of view. Time scale, safety, quality, quantity, and
repeatability all become important factors when it comes to designing a compost facility.
Fortunately, there is no shortage of machinery in the market to help us in this direction.
Although the machinery doesn’t actually do the composting, it helps to create the right
conditions for nature to take its course in as short a time as possible.
Creating the right conditions centers on three distinct pieces of equipment; shredders,
turners and screens - and the selection of these equipments will depend on the sort of
tonnages intended to be handled. The shredder’s role is simple - to expose as much of
the material’s structure as possible. This is one of the essentials to ensure speedy and
effective breakdown during the composting process.
The shredder is one key piece of equipment needed but should not be confused
with a chipper (a chipper chips and a shredder shreds). Shredders range from tiny units
to units handling upwards of 600 cubic meters per hour. If the need is to compost on a
commercial scale, then it involves handling of material in excess of 150,000 tonnes per
year and volumes to be processed at peak times need to be calculated.
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Another important aspect to the purchasing decision is running costs; not only
fuel but maintenance as well. Some shredders use discs rather than flails to shred and
claim great savings in operating cost. Further, compost needs plenty of oxygen for
various organisms that will breakdown the material.
To aid this situation, the windrow has to be turned. It does not take much to turn a small
compost heap but if the compost heap is on much greater scale, then a turner becomes
essential if anaerobic digestion is to be avoided. Screens are another item that do not
really affect the small operator. However, if large volumes are to be processed, then a
screen is essential for creating a uniform material and removing larger particles not
suited to final specifications.
Digestion in Horizontal Drums
Dano Ltd. in Denmark developed the “Dano” drum about 1933 for composting
biodegradable refuse. The reactor is a rotating drum and it is slightly inclined from the
horizontal, 2 to 4 meters in diameter and up to 45 meters long. The drum is kept about
70 % full of refuse and rotates at 0.2 to 2 rpm.
As the drum rotates, the waste moves in a helical path towards the outlet at the end of the
drum and are mixed and granulated by abrasion. Typical digestion is 1 to 3 days in the
drum and is usually followed by screening and windrow/static pile curing. Water and
nutrients can be added to the drum and forced aeration is usually provided. The rotary
drum, being one of the techniques of In-vessel composting, has become one of the most
popular reactor processes for municipal solid wastes, with several hundred installations
worldwide.
Following is a brief summary of the processes and requirements occurring in the rotary
drum:
Rotation mixes and aerates the compost mix;
Second - stage curing/composting is needed;
Food waste grinding and mixing with bulking agent is needed prior to feeding
drum; and
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Usual recipe for drum composting food wastes is as follows:
2 parts wood chips;
1 part sawdust; and
2 parts food waste.
Rotating-drum composting digesters have been used both for large-scale facilities and
backyard composting for many years. Although the various drums differ in details and
process management, they share the basic idea of promoting decomposition by tumbling
material in an enclosed reactor.
The typical small drum is 1.2 to 1.7 meters in diameter and 2 to 4 meters in length, but
drums up to 3 meters in diameter and 20 meter-long are available. Drums are oriented
horizontally, sometimes at a slight incline, to facilitate helical movement of the waste.
Biodegradable organic materials are loaded at one end and unfinished compost is
removed at the opposite end.
While various devices are used, loading with augers or conveyors and unloading by
gravity are the normal practices adopted. Inside the drum, the tumbling action mixes,
agitates and generally moves material through the drum. Regarding the composting
process, the key function of the rotation is to expose the material to air, add oxygen and
release heat and gaseous products of decomposition.
Forced aeration is frequently, but not always, provided. Passive air movement through
the openings at the end delivers sufficient oxygen in most cases but a fan is sometimes
used with longer drums. Some systems take the unique approach of injecting the closed
drum with an oxygen-rich atmosphere (80 percent plus) from an oxygen generator. The
design of the drum and the loading and unloading devices create a closed system that
allows the high oxygen concentrations to be maintained.
Rotating-drum composting reactors always have been associated with very short
retention times. In the past, drums have served as an intense first stage of composting
followed by an extended curing period or additional composting in windrows or another
secondary system. A seven-day retention time is suggested if the drum is used for initial
decomposition followed by additional composting outside the drum.
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For complete composting within the drum, three weeks are usually recommended. Short
retention time is attributed to the high oxygen environment, special microbial inoculant,
and close control of the process environment. Such abbreviated retention periods are
cause for skepticism. Currently prevailing knowledge says that a minimum of six weeks
is necessary to achieve a compost product that is mature enough for general horticultural
use. Nevertheless, vendors of horizontal rotary drums advocating a short retention time
are supporting their claims with research projects.
Digestion in Vertical Drums
Employed as a primary system for treating the compostable material, the vertical
digestion drums receive the crushed refuse from a magnetic chamber. In the vertical
digestion chamber, enough water is added to the mixture to raise the water content to 50
– 55 percent.
This rise in the moisture content allows quick onset of fermentation process, i.e. the
mixture undergoes chemical change accompanied with liberation of heat and alteration
of properties. Sometimes chemicals are added to increase the nitrogen content of the
mixture and hence, further expedite the maturation process. The mixture is stored
normally at 60 – 70o C for 24 hours. This rise in temperature is due to the fermentation
process and not due to external heat sources.
From the vertical digestion drums, the semi-treated mixture is subjected to the final
phase of treatment. After being processed in the vertical digester drum, the compostable
materials are shifted to the windrow/static pile pavilions and are cured for approximately
one month. During this period, temperature and moisture content are regularly
monitored and maintained at an appropriate level.
Windrows
In order to maximize the biological action of decomposition, environmental factors, such
as oxygen, temperature and moisture, are controlled in the composting process. Compost
is the result of the normal activity of many microscopic bacteria and fungi.
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The process of composting never really finishes, but does stabilize to the point where the
product is ready to use. In order to achieve the stability point, compost needs plenty of
oxygen for the various organisms that will breakdown the material.
The most common approach to processing yard waste is the windrow-and-turn method.
Leaves and grass clippings are formed into long narrow piles, called windrows. The
piles should be 6 to 8 feet high and 12 to 16 feet wide. The length of the windrows will
depend on the size of the composting facility. To achieve this organic materials are
placed in long triangular rows called windrows.
Windrows are turned and watered occasionally to ensure that the microorganisms get an
adequate supply of oxygen and that any clumps of organic material are broken up.
Turning of a windrow helps composting process in a number of aspects.
If the supply of oxygen is not as required, some areas inside a compost heap become
anaerobic, and release offensive odors. As oxygen moves into the pile primarily by
diffusion, therefore if a pile is too large, not enough oxygen can get to the center of the
pile. Forced aeration is sometimes used to supply oxygen in large compost piles. An
oxygen analyzer is useful for determining the aerobic quality of the compost. Keeping
oxygen levels above 5% will help avoid the odors caused by anaerobic decomposition.
Once windrows are formed, the Carbon to Nitrogen ratio can be adjusted by depositing
nitrogen rich feedstock (manure and sludge) or carbon rich feedstock (dead leaves and
wood chips) along the top of the windrows. The Carbon/Nitrogen rich feedstock and
seeding compost are turned into the windrows with a compost turner.
The windrows are monitored for temperature, oxygen and moisture continously. The
windrows are turned as many times as needed per week to insure high oxygen levels and
a good mixture of organic material. The windrows usually remain in the compost
building for 40 days or more. They are then transferred to an outdoor asphalt-curing pad.
On the curing pad, the compost is reformed into windrows measuring 2 – 2.5 meter-high,
6 to 7 meter-wide and up to 80 meter-long. The windrows remain on the pad for
approximately 1 to 2 months. The windrows are monitored regularly, turned and
moistened when necessary. Hosing piled waste as the windrow is turned can help get
water into the pile. Portions of compost from windrows that have been actively
composting for a couple of weeks can be incorporated into the newly formed windrows.
This process is called "seeding the windrow".
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Windrows should be formed within one day of receiving yard waste at the facility and
should be formed perpendicular to the slope of the site to prevent water from ponding
around the base.
If leaves and grass are to be composted together, the materials should be mixed before
windrow formation.
The yard waste should be fluffed to break up clumps. Water should be added to dry
leaves to achieve the optimum 50 percent moisture content and aid in the composting
process.
Windrows should be turned regularly to ensure proper oxygen levels in the piles and to
help control the temperature. Turning of a windrow can be accomplished with:
Front-end loaders that scoop and fluff materials in a cascading fashion;
Windrow turning attachments used with front-end loaders or tractors; and
Self-propelled windrow turners that straddle the windrows and turn materials.
After an initial high temperature period (of a few days to several weeks), compost pile
temperatures will gradually drop. Turning the compost rejuvenates the oxygen supply
and exposes new surfaces to decomposition, causing temperatures to rise. If
temperatures rise above 71°C, the compost can sterilize itself, killing off the beneficial
microorganisms. Extremely high temperatures can also start the chemical process of
spontaneous combustion, which might lead to the outbreak of a fire. Turning the
compost when temperatures exceed 60°C can prevent both these potential problems.
Turning the compost whenever temperature gets above or below the optimum range will
help produce high quality compost in the shortest possible time. When the temperature
drops below 21°C, the composting process is nearly complete. However, it is also
possible that imbalances of oxygen or moisture are causing the pile to cool.
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If the compost is properly moist, and turning does not cause temperatures to rise, the
compost is probably finished. Windrows should not be turned quite often during cold
weather because heat losses can slow the composting process. If grass and leaves are
composted together, a more frequent turning schedule may be needed to prevent odor
problems.
Aeration in Windrows
Composting is an aerobic process, which means it occurs in the presence of oxygen. The
air we breathe is about 21 percent oxygen, whereas, compost organisms can survive with
as little as 5 percent oxygen. However, if the oxygen level falls below 10 percent in the
large pores, parts of the compost pile can become anaerobic.
As anaerobic organisms decompose wastes, they produce methane gas, which is an
odorless gas, and hydrogen sulfide, which smells like rotten eggs. Because odor
complaints are the most common problem at composting sites, maintaining an adequate
oxygen supply is critical.
Provision of oxygen in a compost pile can be both natural and mechanical. These two
methods are discussed below.
Natural Aeration
Windrows can be aerated naturally by either passive or active means. The windrows are
aerated "passively" by natural convection currents, formed as warm air generated in pile
centers moves upward through the center of the pile and pulls in cooler air from the
sides. If pile size remains moderate, fresh air can flow in to the center of the pile from
the outside. The passive processes, supplying air in this way, include diffusion and
natural convection.
Natural convection is driven by a chimney effect, with warm air from the center rising
out of the top of the pile, and cool fresh air sucked in at the bottom sides. Leaf compost
piles 1.8 to 2.5 meter-high and 3.5 to 5 meter-wide will get most of their air from
diffusion and natural convection. Passive piles are generally smaller than are piles in
other systems, and take longer to mature. Passive piles are suitable for small to moderate
size operations (such as farms) where available land space and time are not limiting
factors.
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Materials that decompose more quickly, such as a mixture of grass clippings and leaves,
must be placed in smaller piles or oxygen will be depleted. Moisture content and the size
of composting particles will also affect the effectiveness of natural convection.
Mechanical Aeration
The importance of oxygen in a compost pile cannot be overemphasized. For survival
and efficient action of compost-beneficial microorganisms, it is one of the most
important factors. The natural oxygen available is sometimes insufficient to cater for
these microorganisms. Therefore, in order to create a favorable atmosphere for
microorganisms involved in the process of decomposition and composting, it is
sometimes necessary to provide additional oxygen. This can be done mechanically by
two methods, namely:
(i) An air system: In some compost operations, additional oxygen is supplied by
a system of blowers and perforated pipes. These forced aeration systems are
somewhat more expensive, but the cost is justified if there are consistent odor
problems, or if the waste is being composted with other materials such as
sludge; and
(ii) Turning of the composting pile: This method involves turning the compost
with a front-end loader or a specialized compost turner. Although the oxygen
added by turning only lasts a few hours, turning also loosens the piles so that
air can flow more easily by natural convection.
Windrows with Positive Aeration
In simple terms positive aeration of a windrow mean increased air pressure inside the
windrow. Actually, in order to compensate for insufficiency of oxygen available for
survival of compost-beneficial microorganisms, air is pushed up from the bottom of a
compost pile. This is achieved through a system of perforated pipes and pumps. Since
air has to be pumped up through the compost pile, therefore, high-pressure pumps are
employed.
Though quite beneficial for compost-beneficial microorganisms, positive aeration has
some drawbacks as well. Positive aeration system for windrows should be conceived
carefully with due consideration to the following factors:
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Since air is pushed from the bottom of the compost pile, generation of odors
can be quite considerable. However, efficient management of air along with
other factors fairly reduces chances of this paradox. Reason for this being the
fact that with efficient air regulation chances of anaerobic pockets are reduced
considerably. Therefore, any air forced up from the bottom of the compost
pile is less likely to encounter any anaerobic pockets, and hence generation of
odor is minimized;
Density of the compost pile is another governing factor affecting the positive
aeration system. The denser the compost pile the difficult it is to aerate it
properly. It is obvious that for this type of aeration to work effectively,
compost particle size is of critical importance. The bigger the particle size,
the denser will be the compost pile, and hence the harder to push air through
the pile;
The above factor also implies that under positive aeration, before piling
compost in windrows, the compost should be shredded very effectively;
Regulation of temperature is of utmost importance in this type of aeration
system. Due to the shape of compost pile, some sections are thinner than
others, meaning that while pushing air upwards through a compost pile,
temperature of thinner sections get lower than others, killing beneficial
microorganisms; and
Installation of an efficient air-collection system to control odors is very
crucial to the survival this method of aeration. A state of the art air-scrubbing
system needs to be installed as a complement to this method of aeration.
Since air-scrubbing systems are expensive, it increases the cost of positive
aeration method quite considerably.
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Windrows with Negative Aeration
Under this method of aeration, as is evident from its name, air is sucked downwards from
the bottom of the pile by a suction pump, through a system of perforated pipes, creating a
negative pressure inside the pile itself and hence giving it the name of negative aeration.
Technically it is, more or less, an air-draining system. Since, suction of air from the
compost pile causes negative pressure inside the pile, air from outside the compost pile
rushes inwards towards the center of the pile, where it is readily absorbed by
microorganisms.
Suction of air is achieved by providing a system of perforated pipes and suction pumps.
A number of problems have been associated with negative aeration of a compost pile,
they are discussed briefly as follows:
There is a considerable generation of leachate. This is primarily due to two
factors, namely (i) by downward suction of air from the composting pile; and
(ii) due to gravity;
This system of forced aeration needs very efficient management and
maintenance, because leachate generated during the process expedites
corrosion of the pipes and pumps used in the air system;
In this system blockage of aeration pipes is very common. The air system
pipes are blocked by leachate, thus compromising the efficiency of the
system;
Since water is already under the action of gravity in a compost pile, therefore,
application of this type of aeration system sometimes causes the compost pile
to become over-dried; and
The balance of maintaining the appropriate temperature and moisture content
for the microorganisms to thrive and the compost to mature is very fine. It
gets even more critical when this type of aeration system is adopted, because
a thinner section of the compost pile readily gives air than a thicker section.
This sometimes leads to imbalance of oxygen and temperature in some parts
of a compost pile.
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Static Piles
Aerated pile systems are often arranged into a windrow configuration. They may be
turned or left to decompose in their original configuration (i.e. "aerated static piles").
These systems utilize the added technology of aeration devices to deliver oxygen to pile
cores. This is usually achieved by means of perforated pipes running underneath the
length of the piles. The aeration may be passive, or may be driven by blowers.
Positive pressure forced aeration involves the blowing of air up through the bottom of
piles. Negative pressure systems draw air into the pile from the top of piles via suction
into tubes at the bottom. Negative pressure systems can be useful in situations where
odor is a problem, because exhaust air can be driven through a bio-filter designed to
"scrub" the exhaust before its release into the atmosphere. Aerated systems are usually
more energy intensive but allow the construction of larger piles that would be
inadequately ventilated in more passive systems.
The shape of a static compost pile has an important effect on moisture content. Scooping
out the top of the pile to create a concave shape will maximize water absorption, so that
rainfall can help replenish the moisture that is lost from the piles as steam. However, if
the pile is overly saturated, anaerobic odors and leachate will be produced. Therefore, in
prolonged wet conditions, the pile should be shaped to form a peak that will minimize
absorption by shedding water.
Water can be added to a static compost pile in various ways. Overhead sprinklers on a
concave shaped pile work well. By applying water slowly, it is more likely to infiltrate
the pile, rather than running off the surface. Another method uses a drilled pipe as an
injection probe, delivering pressurized water from a water truck to the center of the pile
where it can be readily absorbed.
As organisms decompose waste, they generate heat. Decomposition is most rapid when
the temperature is between 32 and 60°C. Below 32°C, the process slows considerably,
while above 60°C most microorganisms cannot survive. Compost pile temperature
depends on how the heat produced by microorganisms is offset by the heat lost through
aeration or surface cooling.
During cold weather, piles may need to be larger than usual to minimize surface heat
loss. When composting high nitrogen wastes, like grass clippings in the summer, smaller
piles and efficient temperature regulations are needed to provide both oxygen and release
excess heat.
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Temperature monitoring of a static pile is very important for managing the compost
process. By measuring temperatures regularly, one can tell how fast material is
composting, and whether there are hot or cold spots in the pile. Aeration in a static pile is
provided by mechanical blowers, and can shorten composting time to 3 - 5 weeks
(followed by 30 days curing). These blowers can provide either negative or positive air
to the static pile.
As explained earlier, in case of negative air, the air is sucked downwards from the pile
through a system of pipes, and in case of positive air, the air is pushed upwards from the
bottom of the pile. The advantages and disadvantages of both these systems are the same
as discussed in the preceding subsections.
The pros and cons of the static pile method for composting waste are as follows:
Better suited to larger volumes (landscape debris and food waste);
May not be suited to wastes that need mixing during composting, like food
wastes;
Difficult to adjust moisture content during composting, if needed;
Odor control difficult with positive aeration;
Small footprint area, i.e. less land area than windrows; and
Labor intensive.
Other Composting Technologies
Factors To Consider In Selecting Technology
Composting can be done in many different ways. Types of composting range from
residential or backyard composting to mid-scale and central municipal or industrial
composting systems. Selecting the most suitable method depends on the amount and
type of organic materials to be composted.
Residential or backyard composting means that an individual household composts most
of its food and yard waste in a container located outside the home. However, not all food
and yard waste can be managed so simply. Organic material from commercial sources,
such as restaurants, supermarkets, apartment buildings and food manufacturers, needs to
be managed differently.
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This is where mid-scale and centralized composting fits in. Both mid-scale and
centralized composting involves significantly larger quantities and a larger variety of
organic wastes.
Mid-scale composting is the on-site management of organic waste generated by a group
of people, such as in an apartment complex, office building or hospital. This avoids the
transportation of organic waste. Centralized composting involves the collection and
transportation of organic materials to a special facility where it will be prepared and
processed into compost.
Due to the importance of composting in waste reduction process, and it being
environmentally friendly, a lot of research has been carried out for devising newer and
more effective ways of composting. Selection of a composting technology depends
primarily on the following factors:
Available space;
Available labor;
Vendor previous experience with same organic materials;
Control of odors, vermin, and vectors; and
Life - cycle costs.
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Engineering a Compost Plant
Area Engineering for Municipal Solid Waste Composting
Area Calculation for Fermentation and Maturation of MSW
A number of factors have to be taken into consideration to design the dimensions of the
area required by a Compost Facility. The most important of the factors, is the total
volume of the material to be housed during all the steps of the composting process. This
includes all stages from formation of the windrows to refining and storage of the finish
product.
Other factors include, configuration design for to the windrows, space required for the
associated materials handling equipment, space for the maneuvering of windrow turning
machines, space for the maneuvering of front-end loaders, and space for the forced
aeration system. The following is the summary of the steps involved in calculating the
required area for a 1,000 tons/day plant:
Volume of material to be composted:
Assuming an organic compostable material density of 1.2 tonnes/m3
1,000 tons / day = 833.33 m3
/ day say, 835 m3
/ day
Composting period (detention time) =75 days
Total volume of material on floor = 75 days x 835 m3
/ day = 62,625 m3
Design measures of windrow:
Height: 2.5 meters
Width: 5 meters
Length : 92 meters
Volume of Windrow:
V = (2/3) (2.5 x 5 ) x 92 = 766.66 say 767 m3
Number of Required Windrows:
Total Volume of Material / Total Volume of Windrow:
62,625 / 767 = 81.64 say, 82
Design Distance between Windrows = 1.5 meters
Distance around Perimeter of Composting Area: 3 meters
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Length of Composting area = Windrow Length + Perimeter Space =
= 92 + 6 = 98 meters
Width of Composting Area:
Width of Windrows + Distances between Windrows + Perimeter Space =
= (92x5) + (91x1.5) + (2x3) = 460+136.5+6 = 602.5 say, 603 meters
Required Composting Area = 603 x 98 = 59,094 m2 say, 59,100 m
2
Nine separate buildings accounting for 86,436 m2 should be designed to compost the
required material volume, thus each of the six buildings will need a calculated area of
9,604 m2 and design dimensions of 98 x 98 meters. Among the reasons to have separate
buildings the following are outstanding:
Production Flow Control;
Maintenance operations; and
Odor Control Systems.
Calculations for 60 Days Production of MSW Compost Storage Area
Additional area has been required for storage of finished compost of at least 60 days of
production to create a commercial buffer. The calculations for this area are as follows,
Volume of compost to be stored:
1,000 tons of compost / day = 833.33 m3
/ day say, 834 m3
/ day
Storage period = 60 days
Total volume of material on floor = 60 days x 835 m3
/ day = 50,100 m3
Windrow Design Measures:
Height: 4 meters
Width: 6 meters
Length : 92 meters
Volume of Windrow:
V = (2/3) (6 x 4 ) x 92 = 1,472 m3
Number of Required Windrows:
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Total Volume of Material / Total Volume of Windrow:
50,100 / 1,472 = 34.03 say, 35
Design Distance between Windrows = 1.5 meters
Distance around Perimeter of Storage Area: 3 meters
Length of Storage area = Windrow Length + Perimeter Space =
= 92 + 6 = 98 meters
Width of Storage Area:
Width of Windrows + Distances between Windrows + Perimeter Space =
= (35x6) + (34x1.5) + (2x3) = 210+51+6 = 267 meters
Required Storage Area = 267 x 98 = 26,166 m2 say, 26,170 m
2
As a result, the total area required for the compost facility can be calculated as follows:
Composting Area 59,100 m2
Compost Storage Area 26,170
Area for Corridors 4,000
Area for Polishing Plants 300
Area for Bagging Plants 500
Area for Biofilters 900
Area for Leachate Treatment 100
Total Required Area for MSW composting activities: 91,070 m2
Area Engineering for Green Waste Composting
Area Calculation for Fermentation and Maturation of Green Waste5
As stated before, a number of factors have to be taken into consideration to design the
dimensions of the area required by a Compost Facility. The most important of the
factors, is the total volume of the material to be housed during all the steps of the
composting process. This includes all stages from formation of the windrows to refining
and storage of the finish product.
5 Green waste is unpolluted waste generated by farming
132
Other factors include, configuration design for to the windrows, space required for the
associated materials handling equipment, space for the maneuvering of windrow turning
machines, space for the maneuvering of front-end loaders, and space for the forced
aeration system.
The following is the summary of the steps involved in calculating the required area
for a 700tons/day, Green Compost Facility;
Volume of material to be composted:
Assuming a green waste density of 0.9 tons/ m3,
700 tons / day = 777.77 m3
/ day say, 780 m3
/ day
Composting period (detention time) = 75 days
Total volume of material on floor = 75 days x 780 m3
/ day = 58,500 m3
Design measures of windrow:
Height: 2.5 meters
Width: 6 meters
Length: 92 meters
Volume of Windrow:
V = (2/3) (2.5 x 6 ) x 92 = 920 m3
Number of Required Windrows:
Total Volume of Material / Total Volume of Windrow: 58,500 / 920 = 64
Design Distance between Windrows = 1.5 meters
Distance around Perimeter of Composting Area: 3 meters
Length of Composting area = Windrow Length + Perimeter Space =
= 92 + 6 = 98 meters
Width of Composting Area:
Width of Windrows + Distances between Windrows + Perimeter Space =
= (64x6) + (63x1.5) + (2x3) = 384+94.5+6 = 484.5 meters
Required Composting Area = 484.5 x 98 = 47481 m2 say, 47,500 m
2
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Six separate buildings accounting for 57,624 m2 have been designed to compost the
required material volume, thus each of the six buildings will need a calculated area of
9,604 m2 and design dimensions of 98 x 98 meters. As stated before, among the reasons
to have separate buildings the following are outstanding:
Production Flow Control;
Maintenance operations; and
Odor Control Systems.
Area Calculation for Green Compost Storage Area
Additional area will be required for storage of finished green compost of at least 60 days
of production. The calculations for this area are as follows,
Volume of material to be stored:
700 tons / day = 777.77 m3
/ day say, 780 m3
/ day
Storage period = 60 days
Total volume of material on floor = 60 days x 780 m3
/ day = 46,800 m3
Windrow Design Measures:
Height: 4 meters
Width: 7 meters
Length : 92 meters
Volume of Windrow:
V = (2/3) (7 x 4 ) x 92 = 1,717.33 say, 1,718 m3
Number of Required Windrows:
Total Volume of Material / Total Volume of Windrow:
46,800 / 1,718 = 27.24 say, 28
Design Distance between Windrows = 1.5 meters
Distance around Perimeter of Storage Area: 3 meters
Length of Storage area = Windrow Length + Perimeter Space =
= 92 + 6 = 98 meters
Width of Storage Area:
Width of Windrows + Distances between Windrows + Perimeter Space =
= (28x7) + (27x1.5) + (2x3) = 196+40.5+6 = 242.5 say, 243 meters
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Required Storage Area = 243 x 98 = 23,814 m2
Calculation of Area Required for Manure Composting
Additional area has been required by the Abu Dhabi Municipality for composting of
animal manure. The calculations for this area are as follows,
Volume of material to be composted:
Assuming a green waste density of 0.5 tons/ m3,
82 tons / day = 164 m3
/ day
Composting period (detention time) = 60 days
Total volume of material on floor = 60 days x 164 m3
/ day = 9,840 m3
Design measures of windrow:
o Height: 2.5 meters
o Width: 5 meters
o Length: 92 meters
Volume of Windrow:
V = (2/3) (2.5 x 5 ) x 92 = 766.66 say 767 m3
Number of Required Windrows:
Total Volume of Material / Total Volume of Windrow: 9,840 / 767 = 12.82 say, 13
Design Distance between Windrows = 1.5 meters
Distance around Perimeter of Composting Area: 3 meters
Length of Composting area = Windrow Length + Perimeter Space =
= 92 + 6 = 98 meters
Width of Composting Area:
Width of Windrows + Distances between Windrows + Perimeter Space =
= (13x5) + (12x1.5) + (2x3) = 65+18+6 = 89 meters
Required Animal Manure Composting Area = 98 x 89 = 8,722 m2
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As a result, the total area required for the 700 tons/day Green Compost Facility
can be calculated as follows:
Composting Area 47,500 m2
Compost Storage Area 23,818
Area for Corridors 4,000
Area for Polishing Plants 300
Area for Bagging Plants 500
Area for Biofilters 900
Area for Leachate Treatment 100
Area for Animal Manure` 8,722
Total Required Area 85,840 m2
Air for Composting Engineering
There is not a universally applicable numerical rate of oxygen uptake for use as a design
parameter due to the unpredictable character of factors influencing oxygen demand of the
biomass. Temperature, moisture content, size of bacterial population, and availability of
nutrients may be cited as the main controlling factors.
A scientific report on oxygen demand by Chrometska [1968] range between 9 mm3/g*h
for ripe compost to 284 mm3/g*h for raw substrate. A technical publication on oxygen
demand by Lossin [1971] reports average oxygen demand ranging from almost 900 mg/g
on the first day of composting to about 325 mg/g on the twenty-fourth day.
Regan and Jeris [1971] in a review for Compost Studies, part II Vol. 12, observed that
oxygen uptake was as low as 1 milligram of oxygen per gram of volatile matter per hour
when the temperature of the mass was 30 oC and the moisture content was 45%, and it
was as high as 13.6 mg/g volatile matter per hour when the temperature of the mass was
45 oC and the moisture content 56 percent.
The capacity and performance of the air equipment has to be designed on the highest
reported characteristics and with the flexibility to reduce needed flows by means of
control devices and the like.
136
Schulze [1960] publication for Compost science suggests a range of 562 to 623.4
m3/Mton volatile matter per day. Since it is the highest researched figure available and
some over design is advisable due to the impossibility of aerating a mass in such a way
that all the microorganisms have access to sufficient oxygen simultaneously.
An important operational consideration is that although the input air stream may be
sufficiently and even over design to meet the theoretical microbial oxygen demand,
localized anaerobic zones may be present6. These zones may exist due to inadequate
mixing or to short-circuiting of air through the biomass. In practice the complete
prevention or elimination of these zones would be economically, if not technologically,
unfeasible. Fortunately, the complete elimination is not essential for a nuisance-free
operation, provided the number and size of the zones does not become excessively large.
According to L.F. Diaz, G.M. Savage, and C. G. Golueke [1982], in their “Resource
Recovery from Municipal Solid Wastes” book, four generalizations can be made despite
the many uncertainties mentioned or implied before. The generalizations are:
An oxygen pressure greater that 14 percent of the total indicates that not more than one-
third of the oxygen in the air has been consumed.
The optimum oxygen level is 14 to 17 percent.
Aerobic composting supposedly ceases if the oxygen concentration drops to
10 percent.
If CO2 concentration in the exhaust gas is used as a parameter for oxygen
concentration, then the CO2 in the exhaust gas should be between 3 and 6
percent by volume.
As a result of the above discussion, the 1,000 ton/day Compost Facility design will use
the highest oxygen requirement with computerized regulation according to operational
parameters.
6 Kreith, 1994
137
The air blowers capacity design has been calculated as follows:
Theoretical row volume: 600 m3
Theoretical row tonnage: 720 tons
Schutlz [1960] air requirement: 600 m3 /ton/day
Design air requirement per row per day: 301,320 m3
Blower capacity in cubic meter per minute: 209.25 say, 210 (7,415 cfm)
Blower aeration capacity will be complemented by windrow turning on specified
schedules according to field-measured parameters.
MSW Trommel (screen) Engineering
The MSW trommel will be a robustly constructed cylinder fitted with a perforated plate
or wire mesh screen barrel. The size of the holes will be determined by the application,
and selected to ensure maximum open area. The screen plates are designed in sizes
convenient for handling and their installation has been design for easy removal and
maintenance. The running surfaces of the barrel tracks will be machined after fabrication.
A two-start spiral at the feed end and a single start spiral along the length and at the
discharge end of the barrel have been designed to permit a continuous flow of material.
The barrel will revolve on four supporting rollers arranged in pairs for each rolling track.
Each roller will be fitted with a solid rubber tire to ensure silent running. Two roller on
one side of the screen will be idlers, whilst the two on the opposite side will be
interconnected by a shaft and flexible coupling to a variable speed drive. The rollers will
be mounted on a mild steel frame supported from the main under-frame. The idler roller
frames will have screw adjustment to enable the barrel to be kept in position by
compensating for tyre wear.
The screen will be retained longitudinally by a rubber-tired roller running within the
support roller track at the feed end of the barrel. The screen under-frame and supporting
structure has been designed from rolled steel section and its construction will be bolted.
138
The whole of the barrel and supporting rollers will be enclosed in a sectionalized steel
plate dust cover and hinged access doors will be provided down one side and at the ends
for maintenance and inspection. The screen dust cover will be connected to the dust
extraction system.
Chutes will be provided at the discharge end for the oversized waste and underneath the
full length of the barrel for the undersized material.
Trommel design follows the following equation:7
t = 18.98 (L/D) / SN
Where,
t = Mean Resident Time in Minutes;
L = Trommel Internal Length in meters;
D = Trommel Internal Diameter in meters;
S = Trommel rake Slope in centimeters per meter of length; and
N = Trommel Rotational Speed in rotations per minute.
Desired Retention time: 18-20 minutes
Slope design: 2 percent (1.998 cm/m.)
Engineered Rotational Speed (empirical): 3 rotations per minute
Now, clearing L/D on the Kuntz equation for 20 minutes retention,
L/D = tSN / 18.98 = (20 x 1.998 x 3) / 18.98 = 6.316
Design length: 12 meters
Resulting internal diameter: D = 12 / 6.32 = 1.8987 say, 2 meters.
7 Developed by J. Kuntz [1987]
139
Sludge Mixing Trommel Engineering
Sludge from water treatment plants is used in composting operations and it added with a
simplified combination of equipment.
A Sludge mixing trommel has been designed with a required capacity of mixing 10
tonnes per hours. Engineering has been developed as follows:
Trommel design follows the following equation:8
t = 18.98 (L/D) / SN
Where,
t = Mean Resident Time in Minutes;
L = Trommel Internal Length in meters;
D = Trommel Internal Diameter in meters;
S = Trommel rake Slope in centimeters per meter of length; and
N = Trommel Rotational Speed in rotations per minute.
Desired Retention time: 2 to 3 minutes
Slope design: 2 percent (1.998 cm/m.)
Engineered Rotational Speed (empirical): 20 rotations per minute
Now, clearing L/D on the Kuntz equation for 2 minutes retention,
L/D = tSN / 18.98 = (2 x 1.998 x 20) / 18.98 = 4.21
Design length: 6 meters
Resulting internal diameter: D = 6 / 4.21 = 1.42 say, 1.5 meters.
Mixing action will be complemented by a spraying system of the sludge inside the
trommel.
8 Developed by J. Kuntz [1987]
140
Odor Control Calculations
Engineering of the volume of air to be handled by the air collection system and
processed by a scrubber and a biofilter has been performed as follows:
Building Dimensions: 98x98x8 in meters
Building air volume: 76,832 m3
Number of buildings for 1 filter: 3
Air volume for 3 buildings: 230,496 m3
Recommended air changes per day: 6
Total air volume to be handled during a day: 1,382,976 m3
Total air volume to be handled per hour: 57,642 m3
Total air volume to be handled per minute: 1,921 m3
Based on the above calculations, the system has been designed with the following
characteristics:
Max capacity: 58,000 cm/h;
Length: 9.500 mm;
Width: 4.300 mm;
Height: 4.700 mm;
Material: PVC;
Material used for the filling units: Polyethylene; and
No. Cleaning beds: 2.
Drop Separator:
Cleaning bed length: 1.200 mm;
Drop separator length: 200 mm;
pH value during the 1st phase: 1to2; and
pH value during the 2nd
phase: 9 to10.
141
The biofiltering station will have the following technical characteristics:
Intake effluent unit : 60,000 nmc/h
Temperature of the effluent to be treated: environment
Purification procedure: deodorizing procedure of the air from the
composting reactor unit
Designed Dimensions:
Rate of flow: ranging from 1000 to 5000 cm/sqm/h;
Height of the bed: 1.5 m;
Humidity level of the bed: ranging from 25 to 50%;
Operation temperature: max 40°C;
pH value of the bed: ranging from 4.5 to 6.5;
Load loss: 10 to 1000 mm H2O; and
Square 5 x 4 meters.
There will be 4 equally designed scrubber-biofilter combinations working at all times
and 2 for the MSW Compost Facility and 2 for the Green Compost Facility.
Additionally, there will be one scrubber-biofilter combination in standby for each
Facility to eliminate breakdown situations and facilitate maintenance of the systems.
Slat conveyor Engineering and speed calculations
The slat conveyor is and overlapping steel plate feeder. This conveyor is a simple and
efficient method of accepting crude waste material to be processed and conveying it at a
controlled and even rate to any Sorting and Recycling Facility.9
The slat conveyor has been designed and sized to suit the application at the Abu Dhabi
Sorting and Recycling Facility. The plates, which have a flat bar welded to each alternate
plate to assist the movement of the material are attached to an endless conveyor chain
which in turn is fitted with flanged rollers that run in guide tracks. The guide tracks are
an integral part of the framework which is designed in a robust manner of lattice braced
construction using rolled steel section. The slat will be provided with a hopper and side
plates and underframes to ensure no spillage.
9 Usually the first step in the sorting plant previous to the compost facility.
142
Conveyor Speed calculation:
Waste quantity to be handled per hour: 32 tonnes
Volume to be handled per hour: 27 m3
Volume to be handled by second: 0.007 m3
Designed length: 6 meters
Volume of waste on the conveyor at any time: 0.3297 (width)2 length
Required volume per second: 0.007 = 0.3297 (width)2 6 meters
Therefore, width = 0.59 meters say, 60 cm
Recommended design width: 90 cm ( designed at safety factor 1.5)
Conveyor speed: Volume/ Area = 0.3297 / 0.2670 = 1.23 meters per second.
Power Requirements
Power requirement have been calculated according to design layouts10
and distributed in
kWh as it is discussed below.
SWM Waste Composting Power Requirements:
Weighbridge: 10;
Outdoors Lighting: 15;
Sorting and Recycling Facility: 160;
8 Composting hangars: 20x8 = 160 (includes water system, biofilters,
air blowers, and leachate treatment);
One Storage hangar: 45 (includes mixing, bagging, and polishing
plants);
Laboratory: 8;
Administration Building: 20;
10
See drawing at the end of the chapter.
143
Employees Building: 25;
Sludge management system: 8; and
Pump Station: 5.
That takes us for a total power requirement at the MSW composting facility of 456
kWh.
Green Waste Composting Power Requirements:
Outdoors Lighting: 15;
8 Composting hangars: 20x8 = 160 (includes water system, biofilters,
air blowers, and leachate treatment);
One Storage hangar: 45 (includes mixing, bagging, and polishing
plants);
Storage Facilities: 10;
Heavy Equipment Workshop: 25;
Industrial Workshop: 40;
Sludge management system: 8; and
Pump Station: 5.
This takes us for a total power requirement at the Green Waste composting facility of
308 kWh. As a result the power needs for the all the composting facilities can be
estimated at 920 kWh including a safety factor of 1.2. A 1,000 Kva generator with the
following technical specifications will be installed at the transformers room.
Generator Frame:
Type: Permanent magnet excited, static regulated, brushless
Construction: Two bearing, close coupled
Three phase: 12 lead reconnectable
Insulation: class H with tropicalization and anti-abrasion
Enclosure: Drip proof IP22
Alignment: Pilot shaft
Over speed capability: 150%
Wave form: Less than 5% deviation
Paralleling capability: Standard
144
Voltage regulator: 3-phase sensing with D.V.R.
Voltage regulation: Less than +- 0.5% (steady state)
Less than +-1% (no load to full load)
Voltage gain: Adjustable to compensate
TIF: Less than 50
THD: Less than 5%
Generator Engine:
V-8, 4 stroke-cyle Watercooled Diesel
Bore: 170 mm
Stroke: 190 mm
Displacement: 34.5 liters
Compression ratio: 14:1
Aspiration: Turbocharged, separate circuit aftercooled
Fuel system: Direct Unit Injection
Control Panel:
24 Volt DC Control
NEMA 1, IP22 enclosure
Electrically dead front
Lockable hinged door
Instrument meet ANSI C-39-1
Terminal box mounted
EC compliant – segregated AC/DC connection
The following standard equipment shall be included with the generator:
Modular air cleaner single element, radiator with guard, coolant drain line with valve, fan
and belt guards, low coolant level shutdown. Stainless steel exhaust flex and ANSI weld
flange. EMCP II control panel, 13-in structural steel rails spring-type anti-abrasion
isolators. 45 amp. charging alternator, fuel shutoff solenoid, 24 volt starting motor,
batteries with rack and cables, battery disconnect.
145
Compost Facilities Water Requirements
MSW Compost Plant Water Requirements
Water Requirements engineering for the MSW Compost Plant are concerned with
the following water consuming activities:
Composting operations;
Fire Fighting operations;
Equipment Washing and Cleaning;
Administration Building;
Employees Building;
Workshops;
Weighbridges; and
Landscaping
Composting Operations
Composting indoor operations consume a range of 4 to 5 gallons of water per day
per cubic meter during the first 30 days11
and less than a gallon during the rest of the
composting operation. If sprinklers having a reach of 3 to 4 square meters are to be used
to spray water when necessary, and knowing that one sprinkler consumes 2 gallons per
minute,12
the following water requirements for composting operation at the MSW
Compost Facility can be calculated as follows,
Volume of Compost during 30 days: 835 m3
/ day x 30 days = 25,050 m3
Number of windrows needed for the calculated volume of compost =
Volume during 30 days / vol. of windrow = 25,050 / 767 = 33
Area cover for 33 windrows with dimensions 92x5x2.5 = 5 x 92 x 33 = 15,180 m2
Number of sprinklers required: 15,180 / 4 = 3,795
Water consumption per day: 3,795 sprinklers x 5 gallons per day = 18,975 gallons
Water consumption per day in cubic meters: 72
11
According to J. Kunz [1994] 12
Metcalf and Eddy, [1991].
146
The quantity for the rest of the composting operation can be assumed as one fifth the
calculated amount per day or 15 m3/day.
Fire Fighting Operations
Considering only consumption of one drill a month with fire hoses 32 cm in diameter,
12.5 cm nozzle, and 22 meter head during 30 minutes the water consumed will be 38
gal/min,13
or 38 x 30 = 1,140 gallons plus the a reserve tank with 8 times the calculated
amount to fight a fire lasting two hours with four hoses:
1,140 x 8 = 9,120 gallons or 34.5 m3
Equipment Washing and Cleaning
Equipment washing and facilities cleaning will require water as follows:
Equipment Washing once per week (30 items @ 40 gal/item): 1,200 gallons/week
Facilities Cleaning: 900 gallons per week (Order of Magnitude Estimate)
Total water required for this section = 8 m3/week = 1.2 m
3/day
Administration Building
According to Metcalf and Eddy [1991] and estimating at 50 the staff working at the
building,
15 gallons/employee x day
Water consumption = 15 x 50 = 750 gallons/day or 3 m3/day
13
Metcalf and Eddy, [1991]
147
Employees Building
According to Metcalf and Eddy [1991] and estimating at 150 the staff working at the
building,
50 gallons/employee x day
Water consumption = 50 x 150 = 7,500 gallons/day or 28 m3/day
Workshops
According to Metcalf and Eddy [1991] and estimating at 10 the staff working at the
building,
50 gallons/employee x day
Water consumption = 50 x 10 = 500 gallons/day or 2 m3/day
Weighbridges
According to Metcalf and Eddy [1991] and estimating at 12 the staff working at the
building,
50 gallons/employee x day
Water consumption = 50 x 12 = 600 gallons/day or 2 m3/day
Landscaping
According to Metcalf and Eddy [1991] 1 gallon of water per square meters of
landscaping per day is required.
Water consumption = 580 x 1 = 580 gallons/day or 2 m3/day
148
As a result the total water consumption of the MSW Compost Facility has been
estimated at 125.2 cubic meters per day, taking into consideration that firefighting
calculations are not going to be consumed per day.
Storage capacity of the MSW Compost Facility can be designed at 5 times the daily
consumption rate or 625 cubic meters plus firefighting capacity of 35 cubic meters at a
total of 660 cubic meters.
Green Compost Plant Water Requirements
Water Requirements engineering for the Green Waste Compost Plant is concerned with
the following water consuming activities:
Composting operations;
Fire Fighting operations;
Administration Shed;
Landscaping
Composting Operations
Composting indoor operations consume a range of 4 to 5 gallons of water per day per
cubic meter during the first 30 days according to J. Kunz [1994] and less than a gallon
during the rest of the composting operation. If sprinklers having a reach of 3 to 4 square
meters are to be used to spray water when necessary, and knowing that one sprinkler
consumes 2 gallons per minute, Metcalf and Eddy, [1991] the following water
requirements for composting operation at the New Abu Dhabi Compost Facility can be
calculated as follows,
Volume of Compost during 30 days: 780 m3
/ day x 30 days = 23,400 m3
Number of windrows needed for the calculated volume of compost =
Volume during 30 days / vol. of windrow = 23,400 / 920 = 26
Area cover for 33 windrows: 92x6x 26 = 14,352 m2
Number of sprinklers required: 14,352 / 4 = 3,588
149
Water consumption per day: 3,582 sprinklers x 5 gallons per day = 17,910 gallons
Water consumption per day in cubic meters: 68
The quantity for the rest of the composting operation can be assumed as one fifth the
calculated amount per day or 14 m3/day.
Fire Fighting Operations
Considering only consumption of one drill a month with fire hoses 32 cm in diameter,
12.5 cm nozzle, and 22 meter head during 30 minutes the water consumed will be 38
gal/min, Metcalf and Eddy, [1991] or 38 x 30 = 1,140 gallons plus the a reserve tank
with 8 times the calculated amount to fight a fire lasting two hours with four hoses:
1,140 x 8 = 9,120 gallons or 34.5 m3
Administration Building
According to Metcalf and Eddy [1991] and estimating at 5 the staff working at the
building,
15 gallons/employee x day
Water consumption = 15 x 5 = 75 gallons/day or 0.5 m3/day
Landscaping
According to Metcalf and Eddy [1991] 1 gallon of water per square meters of
landscaping per day is required.
Water consumption = 580 x 1 = 580 gallons/day or 2 m3/day
As a result the total water consumption of the Green Waste Compost Facility has been
estimated at 84.5 cubic meters per day, taking into consideration that firefighting
calculations are not going to be consumed per day.
Storage capacity of the Green Waste Compost Facility has been designed at 5 times the
daily consumption rate or 425 cubic meters plus firefighting capacity of 35 cubic meters
at a total of 660 cubic meters.
150
REFERENCES
Manzanera, I., M., Composting in the Context of Municipal Solid, Publicaciones Medio-
ambientales, Sevilla, 1996.
Moller, F., Oxidation-Reduction Potential and Hygienic State of Compost from Urban
Refuse, International Research Group on Refuse Disposal, Information Bulletin 32,
August 1988.
Willson, G.B., J.F. Parr, E. Epstein, P.B. Marsh, R. L. chaney, D, Colacicco, W.D. W.D.
Burge, L.J. Sikora, C. F. Tester, and S. Hornick, Manual for Composting Sewage by the
Beltsville Aeration Pile Method, EPA 600/S-80-022, Office of Research and
Development, U.S. EPA, Cincinnati, Ohio, May 1990.
Lossin, R.D., Compost Studies, Part III, Measurements of Chemical Oxygen Demand of
Compost, Compost Science, March 1991.
Obrist, W., Enzymatic Activity and Degradation of Matter in Refuse Digestion:
Suggested New Method for Microbiological Determination of Degree of Digestion,
International Research Group on Refuse Disposal, 1995
Chaney R.L., The Establishment of Guidelines and Monitoring System for Disposal of
Sewage Sludge to Land, Proceeding, International Symposium on Land Application of
Sewage Sludge, Tokyo 1994.
Frank, Kreith, Handbook of Solid Waste Management, McGraw-Hill, Inc, 1994
151
Chapter X
Hazardous Waste Treatment
There are as many ways to manage hazardous wastes as there are types of hazardous
wastes. In fact, there are at least 50 commercially proven technologies for the recovery
and treatment of hazardous waste.
A hazardous waste facility may function with just one technology, or it may combine
multiple technologies. This is particularly true if it is a commercial facility serving a
number of generators. The predominant type of facilities is shown in the figure below.
Recovery/recycling facilities recover material as a salable product. Treatment facilities
change the physic al or chemical characteristics of the waste, or degrade or destroy waste
constituents, using any of a wide variety of physical, chemical, thermal, or biological
methods. Land disposal facilities are permanent repositories for the disposal of waste
materials.
There are some differences between a commercial, off-site facility and a captive, on-site
facility. The off-site facility accepts waste from outside its own community, while an on-
site facility handles only that waste generated by what could be a long-standing and
important economic activity in the community.
WASTE GENERATION
RECOVERY/RECYCLING
Solvent recovery Products
Fuel blending
Metal recovery
Oil recovery
Energy recovery
TREATMENT
Residuals
Thermal destruction
Aqueous treatment
Stabilization/Solidification
Biological treatment
LAND DISPOSAL
Landfill
Deep well injection
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From the technical perspective, the off-site facility generally handles a wider range of
waste types and is typically larger and more complex. Ignoring this, however, the risks
posed by off-site and on-site facilities are comparable, and depend far more upon types
of waste received, design, operation, and other site-specific factors. The two types of
facilities must meet the same hazardous waste regulations.
Design Requirements
Operations design at the hazardous waste facility should be guided by the following five
subsystems:
Pre-shipment analysis;
Waste receiving;
Waste Storage and preparation;
Container processing;
Waste treatment; and
Residuals management.
A typical layout for a hazardous waste facility is shown at the end of the chapter.
It is important to keep in mind that all the above components operate under the umbrella
of a number of special measures. These special precautionary measures include:
Security;
Inspections;
Maintenance;
Training;
Incident Prevention;
Emergency Planning;
Safety;
Monitoring; and
Auditing.
153
Pre-Shipment Waste Analysis
A waste analysis plan is a critical part of the facility. The plan should be specified the
parameters for which each waste should be analyzed, the sampling and analytical
procedures to be used, and the frequency of analysis. Before the facility treats, stores, or
disposes of a waste, it must profile the waste. This is also called full characterization of
the waste, by the generator, prior to shipment.
Representative sampling of a waste shipment is conducted upon arrival at the facility to
verify that the composition of the shipped waste matches the fully characterized waste.
The purpose of the full characterization before shipment is to satisfy the following
requirements:
Determination if the waste is acceptable for receipt at the facility in terms of
the capability of the facility to treat or dispose of the waste;
Identification of inherent hazards of the waste so that appropriate precautions
can be taken during its handling and storage at the facility to prevent
incidents;
Determination of physical characteristics and chemical constituents of the
waste to allow selection of effective waste processing and disposal methods;
Selection of verification parameters to be tested upon arrival at the facility.
These parameters will ensure that each shipment of waste is the same as the
fully characterized waste;
Selection of any treatability parameters to be tested which could vary so as to
influence how waste processing would be programmed; and
Development of a cost estimate for treatment and disposal.
Waste Receiving
Waste shipments typically arrive by truck at the facility’s gatehouse. Upon accepting the
waste, the facility should sign the manifest and send a copy to the generator.
154
At that point, the facility will share liability with the generator and the transporter. Thus,
it is critical that pre-shipment waste analysis has already been completed and the
shipment scheduled. Without prior scheduling of the incoming shipment or if the
shipment is improperly documented, the gatehouse will have to refuse entry to the truck.
Scheduled and properly documented shipments are directed to the receiving station
where any packaging is checked, the loaded truck is weighed, and representative samples
are collected for testing the verification parameters.
The waste may arrive as bulk liquids in a tank truck, containerized liquids or sludge in
drums, bulk shipments of contaminated soil in dump trucks, or by a number of other
methods. Collecting a representative sample can pose a difficult task considering that a
waste may be in multiple phases and states, or have pockets of high concentrations. The
receiving station should use previously established procedures for each situation to
ensure the collection of a representative sample.
Upon collection of a sample, the laboratory should analyze a portion for the verification
parameters and should retain the remainder for subsequent testing of treatability
parameters. Upon verification of the waste shipment, the truck should be directed to an
unloading area, where it should be emptied and then reweighed before it leaves the
facility.
The mere emptying of a truck can pose a difficult challenge if the waste has stratified, a
container has leaked, or a solidification reaction has occurred. It is important to have plan
procedures and have prepared special equipment to resolve such problems. Furthermore,
the truck may need to be decontaminated to remove any trace residues.
Waste Storage and Preparation
After unloading, the wastes should be moved into storage that can consist of tanks or
impoundments for bulk liquids, hoppers for solids and sludge, or pads and warehouses
for containers. The objectives of storage and preparation are fourfold:
Store waste safely before introduction as feed into the system of unit
treatment and disposal processes;
Provide adequate accumulation time during periods when treatment and
disposal processes systems are out of service;
155
Facilitate mixing, blending, and repackaging of waste as deemed necessary;
and
Allow staged input of various wastes with regard to the subsequent unit
treatment processes.
An obvious important safety consideration is fire prevention and protection. The storage
of certain types of hazardous waste requires automatic alarms and possibly sprinklers.
The facility must provide adequate water supply for extinguishing fires plus the
capability to collect and store fire waste runoff. The storage and treatment of any water-
reactive waste necessitates an alternative type of fire protection system.
A key issue in providing safe storage is compatibility. This has two independent
considerations:
The compatibility of the waste with the material used to construct the
container, tank, or liner in contact with the waste; and
The compatibility of the waste with other waste stored together.
Container Processing
Wastes could be delivered to the Hazardous Waste Treatment Facility in various sizes
and types of container. The wastes should then be extracted form the containers and the
containers will be processed and cleaned. Clean, competent containers could be sold
back into the market for reuse. Clean, punctured or defective containers should be
crushed and transported to the Sorting and Recycling Facility.
Waste Treatment
While waste is maintained in storage, a treatment schedule is developed that will identify
the waste to be treated, its storage location, any necessary preparations, the method of
treatment, and the rate at which the waste is fed. Upon commencement of waste
treatment operations, the waste is typically fed by bulk materials handling systems such
as pipelines or conveyors to the equipment used to perform the prescribed treatment
steps.
Treatment operations may be carried out on a batch or continuous basis. The facility
should monitor operations carefully to assure that the performance attains the desired
results.
156
Operational monitoring should be done with instrumentation, direct human observation,
and chemical analysis. This typically involves extensive record keeping using a
combination of computers, chart recorders, and manually entered paper logs.
Hazardous waste should be treated using any of a large number of commercially proven
unit processes. The treatment methods fall into the following four categories:
Phase separation (sedimentation, steam stripping, etc.);
Component separation (ion exchange, electrodialysis, etc.);
Chemical transformation (chemical oxidation, incineration, etc.); and
Biological transformation (fixed film aerobic treatment, etc.).
The selected method of treatment not only depends upon the type of waste, but on the
waste’s individual physical and chemical characteristics and the specifications for the
treated waste. The unit treatment processes can be interconnected to attain more efficient
and more effective treatment.
Residuals Management
Each waste treatment process produces gaseous emissions, wastewater effluents, or
residuals requiring subsequent management, if not additional treatment. An incinerator,
for example, produces combustion gases that require scrubbing, that in turn produce an
acidic wash-water requiring wastewater treatment. Incineration may also produce fly ash
and bottom ash requiring disposal, if not treatment. The unit treatment processes are not
the only operations that generate residuals. Spillage and runoff from storage areas may
also require treatment.
The opening of containers may need to be done under negative atmospheric pressure
with the fumes collected and treated. A full-service facility can usually provide all
necessary treatment of residuals. Smaller facilities may have to collect the residuals and
transport them as hazardous waste to another facility capable of treating them.
157
Special Measures
A Waste Treatment Center should take a number of special precautionary measures for
all of its day-to-day operations to prevent incidents. These measures can be listed as
follows:
Security;
Daily Inspection;
Emergency planning;
Continuous Employee training;
Safety;
Monitoring; and
Strict Auditing procedures.
Conceptual Design
As part of the conceptual design, the designer should take into consideration the waste
characterization studies to propose the most adequate processes to be included at the
treatment facility. Based on input from the local authorities, incineration and
solidification facilities are usually included at the treatment facility.
Steam stripping, Carbon Adsorption, and Chemical Oxidation may also be included as
part of the physico-chemical methods. Attached-growth, Aerobic Batch Reactor,
Conventional liquid phase treatments will also be considered as part of the biological
methods included in the Hazardous Waste Treatment Center.
A brief discussion on these methodologies is provided below.
Steam Stripping
This process is utilized for the removal of volatile and sometimes semi-volatile
compounds from wastewaters. The process is capable of reducing volatile organic
compounds (VOCs) in water to very low concentrations. Steam strippers are based on
the transfer of organics from the liquid phase to the gas phase. Higher concentrations of
organics in a steam stripper require complex process design techniques.
158
A schematic diagram of a steam stripper operating at atmospheric pressure is presented
next page.
The bottom portion of the steam stripper is stripping wastewater in a manner similar to
an air stripper. This is known as the stripping section of the column. The top section of
the column, above the feed point, is known as the rectifying section. This section of the
column enriches the organics content of the steam to a point where a separate organic
phase can be achieved in the overhead decanter. The steam is enriched because it is
(theoretically) in equilibrium with the saturated liquid that is fed to the top of the
column.
The combination of the stripping and rectifying section is a mass transfer process known
as distillation in the chemical process industry.
The contaminated water feed to the steam stripper is preheated to near-boiling
temperature by exchanging heat with the stripped water exiting from the bottom of the
stripping column. The contaminated water enters the column at the feed point, and the
water flows downward through the stripping section of the column. Steam passes
counter-currently up through the column.
C OOLIN G
V A POR W A T ER
A QU EOU S R EF LU X
OF F - GA S
R EC T IF Y IN G
SEC T ION OV ER HEA D D EC A N T ER
D R A W - OF F
F OR OR GA N IC
PHA SE
ST R IPPED W A ST ER ST R IPPIN G A QU EOU S
SEC T ION PHA SE
D ISC HA R GE ST EA M
B OT T OM S
F EED W A T ER
159
The column operates at a temperature that is slightly higher than the normal boiling point
of water, usually in the range of 215 to 220 oF. The temperature difference between the
top and the bottom of the column is modest, generally on the order of a few degrees
Fahrenheit.
At the elevated temperatures inside the column, the volatile organics in the water exert a
higher vapor pressure than at ambient conditions. As the organics vaporize in the
column, they are transferred from the liquid phase into the gas phase. As the stream
travels up the column, the concentration of organics increases in the striping steam.
The steam exits the top of the column where it undergoes a phase change to a liquid in
the overhead condenser. This liquid is supersaturated with the organics so a separate
organic layer forms in the decanter. The aqueous phase from the decanter is returned to
the top of the column where it flows down the column. This aqueous phase is saturated
with the organics because the organic concentration in the aqueous phase is in
equilibrium with the separate organic phase in the decanter.
An analysis of phase-equilibria thermodynamics and a mass balance will show that,
because this fed to the top of the column is saturated with the organics, the steam leaving
the top of the column will contain a high enough concentration of organics to form a
separate organic phase when the steam is condensed to a liquid phase.
Carbon Adsorption
In the Carbon Adsorption process, a soluble contaminant (the adsorbate) is removed
from water by contact with a solid surface (the adsorbent). The adsorbent most widely
used in environmental applications is carbon that has been processed to significantly
increase the internal surface area (activated carbon). Use of different raw materials and
processing techniques results in a range of carbon types with different adsorption
characteristics.
Activated carbon is available in both powdered and granular form. Granular activated
carbon (GAC) will be used for removal of a wide range of toxic organic compounds
from ground water and industrial waste streams. Powdered activated carbon is often used
in biological treatment systems.
Typical activated carbon contactors are cylindrical tanks where carbon is held in place by
a plenum plate. Contaminated water enters the top of the cylinder or column, it makes
contact with the carbon and exits through a drain system at the bottom.
160
The system will be accompanied by air scouring and back washing facilities to avoid
head loss due to accumulation of solid particles present in the influent.
Furthermore, the system will allow removal of spent carbon for regeneration, and the
addition of new carbon.
The system will comprise a continuous flow of columns, set up in series so that the final
column in the system is in effect a polishing unit. Because the downflow beds also act as
filtration units, they will be periodically backwashed.
Chemical Oxidation
The objective of having chemical oxidation treatment at the facility is to be able to
detoxify waste by adding oxidizing agents to chemically transform waste components.
Chemical oxidation of wastes is a well-established technology that is capable of
destroying a wide range of organic molecules, including chlorinated VOCs, mercaptans,
phenols, and inorganics such as cyanide.
This section focuses on the oxidizing agents most commonly used for hazardous waste
treatment:
Ozone;
Hydrogen peroxide;
Chlorine; and
Ultraviolet light (UV).
Oxidation and reduction reactions occur in pair to comprise an overall redox reaction. In
chemical oxidation for hazardous waste treatment, an oxidizing agent is added to oxidize
the waste components of concern, which serve as the reducing agents. Oxidizing agents
are nonspecific and will react with any reducing agents present in the waste stream.
Therefore, these processes are most economical when organics other than the ones of
concern are in low concentration.
Although chemical oxidation is typically applied to liquid hazardous wastes and
contaminated ground water, soils may also be amenable to these processes.
Contaminated soils can be excavated and treated in a slurry form in reaction vessels.
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However, because excavation is an expensive process, the tendency in soil cleanup
technology is to use in situ processes.
Chemical oxidation will be conducted in completely mixed tanks or plug flow reactors.
The contaminated water is introduced at one side of the tank and the treated water exits
at the other side. The oxidizing agent is either injected into the contaminated water just
before it enters the tank or is dosed directly into the tank.
Complete mixing, which prevents short-circuiting in the tank, is necessary to ensure
contact of the contaminants with the agent for a minimum period of time, and, thus,
reduce the chemical dosage required to obtain a specific effluent concentration.
Ozone is produced from atmospheric oxygen using electrical energy to split the oxygen
into two oxygen radicals, which readily combine with other oxygen molecules to form
ozone. Ozone is unstable under normal environmental conditions and readily
decomposes back to oxygen. Ozone is added to the liquid waste as a gas, either through
porous diffusers at the bottom of a tank, of through an injector where the pressure drop
produced draws ozone into the injector and mixes it with the liquid.
Attached-Growth Systems
These systems rely on the ability of the microorganisms to attach to surfaces of inert
media. Contaminated water will be passed through a bioreactor housing the media. The
resulting microbial growth attaches to the media and forms a thick film. The biomass
remains in the reactor except that which sloughs off the supporting media. Part of the
effluent and biomass may be recycled.
These systems can develop high concentrations of biomass in relatively small reactors
because relatively little biomass is lost with the effluent. This results in a low food to
microorganism ratio and the long solids retention time necessary to foster slow-growing
microorganisms. Both enhance degradation of hazardous contaminants, particularly
waste with low concentrations of organics.
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Attached-growth systems require that the microbes have the ability to attach to the
appropriate media; such ability varies among strains of microbes and will be examined
during the definitive design phase.
The field of municipal sewage treatment historically has relied extensively on trickling
filters, a form of attached-growth treatment using rock as the inert media. Fluidized bed
reactors may be utilized. The fluidized bed is achieved by growing the biofilm not on a
fixed media but on particles of sand or other inert media. The influent is introduced from
below the bed in an upflow reactor; the upflow velocity must be sufficiently high to keep
the particles suspended.
Withdrawal of treated effluent from the top of the reactor maintains the upflow velocity.
A portion of the inert media is withdrawn periodically as the bed expands. These systems
can remove more organic loading per unit reactor volume than other fixed-film
processes. Two examples of modern attached-growth systems are shown below.
Aerobic Batch Reactor Systems
Batch reactors may be utilized due to their proven capability to foster genetic exchange
in the microbial community of a bioreactor.
Batch reactors combine equalization, bio-treatment, and sedimentation in a single tank.
The systems are called sequencing batch reactor (SBR) because they conduct the
equalization, bio-treatment, and sedimentation sequentially.
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The figure next page shows an aerobic batch reactor system.
The biomass will be maintained by discharging only the clarified effluent after the
sedimentation step. The time allocated to each step will be adjusted within the constraint
of the incoming flow. This provides much greater flexibility than continuous flow
systems, allowing SBRs to achieve high performance when treating variable wastewater.
The simplicity and the flexibility of the SBR approach makes it especially appropriate
for small-scale processes.
Aerobic Batch Reactor System
If the flow to be treated is continuous, at least two SBRs will be needed. Placing the
SBRs in series helps ensure that the biomass in each tank is acclimated to the
transformed compounds being discharged from the previous tank.
IN FLU EN T
TR EA TED EFFLU EN T
SLU D GE
D IFFU SED A IR
EQUALIZATION BIOTREATMENT SEDIMENTATION
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Conventional Treatment
Conventional liquid-phase treatment consists of technologies, or variants, originally
developed for treatment of industrial wastewater. The typical hazardous wastes treated
by this method include contaminated ground water and industrial process wastewater
containing toxic organic substances.
This method will consist of passing aqueous hazardous waste through a reactor
containing either suspended or attached biomass of highly active and acclimated
microorganisms.
The flow can be continuous or batch, and the reactor can be operated under aerobic or
anaerobic conditions. Oxygen is added in aerobic systems by diffused aeration. The
liquid waste receives treatment both before and after biological treatment.
Pretreatment consist of several steps dependent upon the types of waste to be treated:
Equalization to dampen/modulate hydraulic surges and variable organic loading
in continuous flow systems;
Chemical treatment to precipitate toxic metals, if present, but could involve other
steps such as breaking of emulsions;
Physical removal by sedimentation of metallic precipitates, removal of floating
material and others; and
Conditioning to supply nutrients and to adjust pH to optimum range.
After pretreatment, the liquid waste will flow into the bioreactor where the dissolved
organics are metabolized by the biomass with a resulting growth of cellular mass. This
can be achieved only by biodegradation. The actual yield of biomass depends on
numerous factors. Not all utilization of substrate results in synthesis of cells; some
substrate is oxidized to produce energy.
Additional treatment will be required after the reactor by adsorption, ion exchange, or
microfiltration methods. The removal of a portion of organic waste occurs by methods
other than biological.
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Volatilization can result in significant removal of some organics, especially in aerated
systems. Some organics may not be metabolized but absorbed with colloidal
contaminants onto the biomass. In sum, abiotic losses can account for significant amount
of the organic waste removed with no reduction of the toxic nature of the waste. The
chemical constituents have merely been transferred to other media which may require
their own particular treatment.
Liquid Injection Incineration
When it comes to incineration of hazardous waste, there is more experience with liquid
injection (L.I.) incinerators than all other types combined. The greatest proportion of
hazardous waste incinerators in operation today are the LI type.
The waste in burned directly in a burner (combustor) or injected into the flame zone or
combustion zone of the incinerator chamber (furnace) through atomizing nozzles. The
heating value of the waste is the primary determining factor for the location of the
injection point.
Liquid injection incinerators are usually refractory-lined chambers (horizontal or vertical
flow, either up or down), generally cylindrical in cross section, and equipped with a
primary burner (waste and/or auxiliary fuel fired). Often secondary combustors or
injection nozzles are required where low heating value materials such as dilute aqueous-
organic waste are to be incinerated.
LI incinerators operate at temperature levels ranging between 1,000 oC (1,832
oF) and
1,700 oC (3,092
oF). The residence time for the combustion of products in the incinerator
may vary from milliseconds to as much as 2.5 seconds. An atomizing nozzle in the
burner or the incinerator is a critical part of the system because it converts the liquid
waste into fine droplets.
The viscosity of the waste determines whether good atomization of a liquid is possible.
Two-fluid atomizers, using compressed air or steam as an atomizing fluid, are capable of
atomizing liquid with viscosities up to 70 centistokes (2.7 ft2/hr).
The physical, chemical, and thermodynamic properties of the waste must be considered
in the basic design of any incinerator system. Any commercial facility receiving
hazardous waste requires a complete analytical laboratory on site. Most commercial
operators require a sample of the waste before they will provide a treatment cost to the
generator.
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The following information about the waste to be burned in the incinerator is required to
design and properly engineer the total system and the auxiliary components.
Chemical composition;
Heat of combustion;
Viscosity;
Corrosivity;
Reactivity;
Potential for polymerization;
Ash content; and
Ash fusion temperature.
The atomizer design in the burner or incinerator usually dictates the pressure
requirements of the transport system. Where a hydraulic (pressure type) atomizing nozzle
is used, requiring high pressures, a pump design with close clearances between the
impeller and the housing is needed. High viscosity materials and liquids containing
solids will erode the pump surface causing excessive wear and rapid deterioration of
pump pressure resulting in a reduction of flow as well as poor atomization.
Waste transport is critical in proper design of any incinerator. Some liquid wastes and
sludge must be maintained at above ambient temperatures to permit pumping. When
cooled, these wastes will solidify in the pipeline. Conversely, if these wastes are heated
too much, they may polymerize. Once polymerized, it may be impossible to re-liquify
the material. With heated liquids, pump bearings may become overheated or centrifugal
pumps may cavitate, so pump selection is also critical.
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The method of injection of the liquid into the burner or incinerator furnace is one of the
most important features of a well-designed system. The reasons for injecting the liquid as
a fine spray are to:
Break up the liquid into droplets;
Develop the desired pattern for the liquid droplets in the combustion zone
with sufficient penetration and kinetic energy; and
Control the rate of flow of the liquid discharged to the combustion system.
Organic and aqueous liquids pass through three phases before oxidation takes place
(Hydrocarbons ignite at temperatures as low as 20oC and as high as 650
oC). The liquid
droplets are heated, vaporized, and superheated to ignition temperature.
These droplets must receive heat by radiation and convection from the furnace as rapidly
as is practical. At the same time, they must be in intimate contact with oxygen from the
combustion air. If the droplet diameter is large, fewer droplets will be produce per unit
flow of waste, and the total surface available for heat transfer is small.
In a good atomizer, the droplet size will be small providing greater surface area and
resulting in rapid vaporization.
It should be taken into consideration that that the burning time for a 300-micron droplet
is 150 milliseconds, while only 30 milliseconds are necessary to burn a 125-micron
droptlet.
There are two basic types of atomizers for liquid wastes. The first is the mechanical or
pressure atomizer, which is a small orifice through which high-pressure liquid expands
as they go from a high pressure to the low pressure of the combustion chamber. The
higher the pressure to the nozzle the better the atomization.
Droplet size at full flow is usually on the order of 100 to 150 microns, and atomization
deteriorates as the flow is decreased. The mechanical atomizing nozzle is simple in
construction, subject to fouling and plugging by small particles, and has poor turndown
characteristics.
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The second type of atomizer is the two fluid internal mix atomizer, where steam or
compressed air acts as the second fluid, and the waste or fuel as the first. The two fluids
are mixed within the atomizer, and the energy of the steam or compressed air achieves
the atomization. Droplets down to 50 microns can result from good internal mix nozzle
design.
This nozzle still has small orifices so it should not be selected for a dirty liquid waste. It
is an excellent atomizer with good turndown.
Proper mixing of combustion air with the atomized liquid droplets is very important. As
the liquid is vaporized and superheated to ignition temperature, oxygen reacts with the
hydrocarbon vapor to produce combustion. As this occurs, there is a sudden rise in
temperature increasing the velocity of the gases in the area surrounding the droplets
causing greater mixing and completing the reaction.
As the viscosity of the liquids increases, droplet size tends to get larger. To completely
vaporize and superheat the droplet, more time is needed. Increased turbulence created by
high-intensity burners permits this reaction to be achieved rapidly.
Greater energy, imparted to the combustion air by fan or blower, provides higher
velocities in the combustion zone improving the mixing of the air and the fuel droplets.
In many burners this turbulence causes internal recycling of the hot product of
combustion providing better heat transfer to the atomized droplets achieving the ignition
point more rapidly.
If the vaporize liquid contains solids, the incinerator design must allow the particles to be
carried into the gas stream without agglomeration. A high swirl or a cyclonic design may
cause the solids to be re-agglomerated into larger particles becoming more difficult to
burn.
Proper design of the air mixing device and the nozzle location are therefore very
important. Proper oxygen concentration at the surface of these solids is needed to ensure
that gradual oxidation will occur.
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Because they are solid, the particles will burn at the surface, and heat will be transferred
inwardly to the core of the particle. Sufficient time must be provided to permit complete
burnout of the solid particles in suspension. It is for this reason that coal is finely
pulverized before combustion in a fluid system.
Inorganic compounds are carried with the liquid into the gas stream as particulates.
Depending on the type of atomizer, the composition of the solid, and the temperature of
the primary oxidizer chamber, many particles will be reduced to submicron size and
diffused into the gas stream.
The heavier particulates may become molten and agglomerate into a molten ash. The
combustor must be designed to collect the molten ash without plugging the passages of
the incinerator and quench system. A slanted horizontal design or a downward vertical
orientation is most often used for these types of waste.
Primary and secondary combustion units are utilized in the liquid injection type
incinerator systems. Primary units are used to burn wastes having sufficient heating
value to burn without the need for auxiliary fuel. With good burner design, heating
values from approximately 2,500 kcal/kg (4,500 Btu/lb) and above can be burned
without the use of auxiliary fuel.
The burner design determines the minimum heating value waste that can be burned
without the need for auxiliary fuel.
Solidification
Solidification is the process of mixing liquid or semi-solid waste materials with
pozzolanic materials such as cement kiln dust, lime or flyash. The pozzolanic materials
either react directly with the waste materials, taking them up through ionic or covalent
bonding, or encapsulate the materials within the structural matrix.
Inorganic waste materials are typically bonded to the matrix and may participate in the
chemical reactions. Organic chemicals are typically encapsulated within the structural
matrix, and do not generally participate in the chemical reactions.
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Solidification systems are extremely versatile, and can be used to treat virtually all types
of liquid hazardous wastes. However, solidification is considered to be most cost-
effective for inorganic waste constituents.
REFERENCES
Freeman, H.M., Standard Handbook for Hazardous Waste Treatment and Disposal,
McGraw-Hill, 1999.
Shah, K.L., Basic Solid and Hazardous Waste Management Technology, Prentice Hall,
1999.
Tchobanoglous, G., Theisen, H., Vigil, A.S., Integrated Solid Waste Management
Principles and Management Issues, MacGraw-Hill, 1993.
Lagrega, M.D., Buckingham, P.H., Evans, J.C., Hazardous Waste Management,
MacGraw-Hill, 2000.
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Chapter XI
Hazardous Waste Landfill
A Hazardous Waste Landfill will provide protection of human health and the
environment. The lining system and leachate collection system of the landfill will be
designed to minimize or prevent leachate migration to ground water to protect ground-
water quality. The final cover system of the landfill will be designed to minimize the
potential for leachate generation, and prevent direct exposure of the waste for long-term
closure and post-closure conditions.
Design requirements for a Hazardous Waste Landfill are as follows:
The landfill should be divided into cells that may be developed based on the
actual growth rate of the waste, and the needs of the local authorities;
The Phase 1 landfill construction for the Hazardous Waste Landfill should
include the construction of 2 landfill cells;
Leachate generated at the landfill, if any, should be collected and treated;
The landfill should be surrounded by a perimeter berm, and daily and
intermediate cover should be placed over the waste. Site management and
operations should be performed to modern standards, which will minimize the
potential for problems that could potentially impact human health and the
environment;
An Operations Plan should be developed for the landfill to describe how the
landfill will be operated in a way that will be safe and acceptable to the
public, prevent observation of operations from surrounding areas, and protect
human health and the environment;
The support facilities for the Hazardous Waste Landfill should include the
already mentioned for a municipal solid waste landfill as well as:
A well-equipped laboratory;
A Unit with emergency procedures for possible spills and fires;
A Staff decontamination building; and
A Truck decontamination facility.
The lining system should cover the area of the cell and its immediate
surroungings;
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The side slope of the final cover system will be 3H:1V;
The top elevation of the landfill should be no more than 30 m;
The leachate collection system should be designed for the following
minimum factors of safety;
Flow capacity of leachate collection system, FS > 2.5;
Flow capacity of polyethylene pipe, FS > 2.5;
Flow capacity of leachate pump, FS > 2.0; and
Flow capacity of leachate force main, FS > 2.5.
The lining system should be designed for the following minimum factors of
safety;
Leakage rate through the lining system less than 0.01
liters/hectare/day;
Bearing capacity, FS > 1.5;
Static short-term slope stability, FS > 1.35;
Static long-term slope stability, FS > 1.5; and
Dynamic long-term slope stability, FS > 1.0, and acceptable strain in
the lining system.
The maximum depth of leachate in both the primary and secondary leachate
control system (LCS) should be less than the thickness of the leachate
collection layer;
The maximum depth of the leachate in the leachate collection sump should be
less than 1 m;
The final cover system of the landfill should be designed for the following:
The side slopes of the landfill will not be steeper than 3H:1V;
Static short-term slope stability, FS = 1.35;
Static long-term slope stability, FS = 1.5; and
Dynamic long-term slope stability, FS > 1.0, and acceptable strain in the
lining system.
The main access road should have a paved width of 10 m, with side slopes
not greater than 3H:1V;
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Ground-water modeling should be performed for a minimum period of 100
years after the closure of the landfill to assess potential impacts on human
health and the environment; and
The landfill should be designed in such a way that it can be expanded in the
future without adversely impacting the performance of the landfill.
Prior to a landfill design, a site investigation should be conducted to assure the suitability
of the site, and to obtain detailed data and information regarding geologic and hydro-
geologic conditions. This information will be needed to evaluate the potential impact of
the facility on the environment in the future, and to evaluate the design methodology.
The leachate sumps should be located along the centerline of each cell, adjacent to the
perimeter berm at the cell boundary. Each leachate sump should cover an area of
approximately 3 m by 3 m, and should be approximately 0.5 to 1.2 m deep.
Visual Barriers
Visual barriers should be designed and constructed around the perimeter of the landfill to
prevent observation of site operations. An exterior screening berm should be constructed
adjacent to the fence line. The exterior screening berm should be at least 3 to 4 m high, 3
m wide at the top, and should be landscaped with trees and shrubs or rock.
A perimeter berm should increase landfill capacity, provide a barrier to leachate
migration, protect the lining system, and provide an additional visual barrier for landfill
operations. The outside of the perimeter berm should be faced with a 0.3-m thick layer
of crushed stone and concrete, which will provide an aesthetically pleasing view.
Liner System and Leachate Control System
The lining system of the Hazardous Waste Landfill should be graded in a sawtooth
configuration with minimum 2 percent grades, sloping towards leachate collection pipes.
The leachate collection pipes should be located at the valley between the high point of
the sawtooth and at the toe of the perimeter berm. The leachate collection pipes are high
density polyethylene (HDPE) perforated pipes embedded in gravel.
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The lining system at the base of the Hazardous Waste Landfill should be a double
composite lining system. This lining system, should exceed international standards,
consisting of the following components, from top to bottom:
2-ft (0.6-m) thick granular soil liner protective layer;
Primary leachate collection system (LCS) geo-textile filter;
Primary LCS geo-net drainage layer;
Primary 60-mil (1.5-mm) thick HDPE geo-membrane;
Primary geo-synthetic clay liner;
Secondary LCS geo-textile filter;
Secondary LCS geo-net drainage layer;
Secondary 60-mil (1.5-mm) thick HDPE geo-membrane;
Secondary geo-synthetic clay liner; and
Prepared sub-base of at least 0.80 m.
A leachate collection sump should be designed to collect leachate from both the primary
and secondary LCSs (leak control systems). The sump should be segregated so leachate
from the primary and secondary LCSs are not mixed. The LCSs should be designed with
side slope risers, so there should not lining system penetrations, or leachate manholes that
could be a potential source of leakage.
Final cover system
A final cover system should provide a barrier over the waste materials that prevents
contact with the public, minimizes leachate generation, and prevent gas migration. The
final cover should have maximum 3H: 1V side slopes and top slopes graded at five
percent. These side slopes should be consistent with the side slopes at many other
landfills that have demonstrated good structural stability. A stone cover layer should
minimize wind erosion of the final cover sand layer.
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The proposed final cover system profile on top of the landfill should consist of, from top
to bottom;
0.3-m thick stone and/or crushed concrete layer;
0.3-m thick granular (sand) cover protective layer;
40-mil (1.0-mm) thick polyethylene (PE) geo-membrane liner; and
0.15 to 0.3-m thick daily or intermediate cover layer.
The geo-membrane and stone final cover on the side slopes should be identical to the
final cover system on top of the landfill except that a geo-composite cover drainage layer
is included on the side slopes above the PE geo-membrane. This geo-composite cover
drainage layer is required for slope stability, as it will provide drainage in the event of
precipitation at the site.
In the event of precipitation at the site, the sand layer above the geo-membrane would
become saturated. This layer would become unstable if not properly drained. The geo-
composite drainage layer is designed to prevent saturation of the overlying sand cover
protective layer. The geo-composite drainage layer of the final cover system should be
designed for the maximum flow rate with a factor of safety of 2.5. Based on the local
precipitation data some adjustments must be performed.
The final cover system on the side slopes of the hazardous waste landfill should consist
of, from top to bottom:
0.3-m thick stone and/or crushed concrete layer;
0.3-m thick granular (sand) cover protective layer;
Geo-composite cover drainage layer consisting of geo-textile filters, geo-net
drainage layer, and geo-textile cushion;
40-mil (1.0-mm) thick textured polyethylene (PE) geo-membrane liner; and
0.15 to 0.3-m thick daily or intermediate cover layer.
A geo-textile and geo-net layers comprising the geo-composite cover drainage layer
should be heat bonded to increase the interlayer shear strength.
Construction Quality Assurance
A Construction Quality Assurance (CQA) plan should be developed describing
construction, inspection, oversight, material inspection, acceptance requirements, and
management duties and responsibilities. In addition, the CQA plan will describe the
material testing requirements, inspection requirements, and reporting requirements.
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Landfill Buildings
Several Buildings and support facilities should be constructed at the landfill, they should
include:
• Office and Laboratory Building;
• Garage and Maintenance Workshop Building;
• Scales and Scale house;
• Gate and Gatehouse;
• Access Road; and
• Parking Lots.
The design and requirements for these buildings are briefly described in the following
sections.
Office and Laboratory Building
Design
The design of the proposed landfill Office and Laboratory building shall be based on
architectural theories and concepts.
The basic principle of simplicity should be inducted into the concept and design of the
office and laboratory building. In addition, strong consideration shall be given to the
functional requirements and suitability, shape, and appearance of the building.
While designing the landfill Office and, Laboratory Building, consideration should be
given to the surrounding areas and the location of site. The external courtyards shall be
designed within the framework of better environment, cross ventilation, and good natural
lighting. A claustrophobic effect created by totally closed areas shall be compensated by
provision of open areas and glazed windows, which should not only give a pleasant
feeling but will also reduce the cost of the various items and will give economy to the
systems.
The landfill Office and Laboratory Building should be designed to provide balance,
harmony and elegance at an appropriate cost. The building design shall incorporate at
least the following:
• Symmetry around the central axis;
• Spacious reception area, generous office space, conference room, staff rooms,
and facilities located off the lobby; and
• Separate access for the laboratory and staff areas.
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Throughout the design of the Building, the factors of easy-accessibility and functionality
should be considered. Keeping these factors in mind, special consideration should be
given to provide separate entrance for the landfill workers and staff, away from the main
entrance. Another important aspect is the provision of a separate entrance for laboratory,
changing areas, and the rest room for the workers and staff at the landfill.
Design Requirements
Prior to the construction process of the new building, a site investigation should be
conducted to evaluate the geotechnical properties of the site soil. The geotechnical
investigation will be conducted by the General Contractor and will include a minimum of
one soil boring at each building location to evaluate the design requirements for the
foundations.
The landfill Office and Laboratory Building shall be provided with the following
facilities;
• The landfill office area is designed with approximately 50 sq m space for the
office and the meeting room for the Landfill Manager;
• The Laboratory covers an area of approximately 96 sq m; and
• The remaining main building area includes provision for offices, conference
room, changing area, restroom, reception area, offices for the Laboratory
Manager and Landfill Operations Supervisor, kitchen, restrooms, and open
work areas.
The landscaping and car park area for the staff and landfill site vehicles should be
enough for 30 employees and 10 visitors at a time. The external surrounding area will be
developed with pavement tiles.
Construction Requirements
The Contractor should be required to prepare and submit final design drawings and
specifications to the local authorities for review and approval. The local authorities
should approve all drawings and specification prior to the start of construction.
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Maintenance Building
Design
The concept for the design of the proposed landfill maintenance building should be based
on the amount of trucks and equipment to be serviced.
The landfill maintenance building should be designed to provide balance, harmony and
elegance at an appropriate cost. The building design should incorporate the following:
Maintenance Garage with hydraulic hoist and oil changing facilities;
Mechanical Workshop for heavy equipment;
Spare Parts Warehouse;
Office space for the Maintenance Garage Manager and Parts Manager;
Reception and Waiting area;
Restrooms and Changing areas; and
Small kitchen.
The garage and warehouse should be designed to be accessible by heavy equipments
including typical equipment. A spare parts warehouse should be designed including the
latest technology to controll inventories.
Design Requirements
Prior to the construction process of the new landfill maintenance muilding, a site
investigation should be conducted to evaluate the geotechnical properties of the site soil.
The geotechnical investigation should be conducted by the general contractor and should
include a minimum of three soil borings at the proposed building location to evaluate the
design requirements for the foundation.
The Maintenance Building should be designed for maintenance of site vehicles as
required at the Landfill. Design should include the following facilities;
A reception area to accommodate the number of activities in the premises;
Two working bays, each with an area of 150 sq m allocated for vehicle
maintenance and heavy equipment maintenance;
Office space for the Workshop Manager of approximately 35 sq m
Spare parts warehouse with approximately 98 sq m area; and
Kitchen, restrooms, and open work areas.
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Scales and Scale house
A scale house and both inbound and outbound scales should be designed with sufficient
capacity to accommodate all refuse vehicles, including large open back trucks (18 wheel)
used to transport waste materials from the transfer stations to the landfill.
The scale house should be approximately 5 m by 6 m, with window counters on each
side.
The scale house should be equipped with an observation deck to monitor and observe
waste loads. Additionally, a waste sample collection facility should be designed along
with the scales system.
Gate and Gatehouse
A gate and gatehouse should be constructed at the landfill, to monitor and control the
incoming and out going traffic to the landfill. The gatehouse shall be designed to
accommodate 2 guards. The gate should have sufficient clearance for all passing refuse
vehicles, including large open back trucks (18 wheelers) used to transport waste
materials from the transfer stations to the landfill. The gatehouse should be
approximately 3 m by 4 m, with window counters on each side.
Access Road and Parking Lots
A paved access road should be constructed from the main road to the buildings at the
landfill. This road should comply with all the engineering specifications required by the
local authorities and with capacity for heavy vehicles.
The parking lot should be located near the main entrance. It should cover an area of
approximately 50 m by 50 m, and it will be paved with the interlocking tiles to protect
sub-graded soils.
General Contractor Requirements
The General Contractor should be required to perform a Geotechnical Investigation to
evaluate site conditions for the Office and Laboratory Building, Maintenance Building,
Scalehouse and Gatehouse. The General Contractor should submit a Geotechnical
Investigation Plan to the local authorities for review and approval prior to the start of
fieldwork.
Following the completion of fieldwork, the General Contractor should prepare detailed
design drawings, specifications, and material boards for the local authorities for review
and approval prior to the start of any construction work.
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Security and Fencing
Description of Tile Work
The Contractor should be responsible for the security of the Works in their entirety
whilst in possession of any part of, or the whole of, the Site. The Contractor should erect
suitable and appropriate permanent fencing and gates around the boundaries of the Site,
or around parts of the Site, possessed by the Contractor, constructed at the locations
detailed, and in accordance with, the lines, grades, levels, designs and dimensions given
on the drawings.
In establishing the part(s) of the Site requiring fence, the Contractor should pay due
attention to, but shall not be limited to, the following matters:
Safety of the public and local residents;
Health and safety on Site;
Prevention of unauthorised entry to the landfill facility;
The nature of the Works proposed; and
Preservation of established and existing rights of way.
The Contractor should erect permanent fencing to enclose the following facilities
and infrastructure:
1) Perimeter of the landfill as delineated on the drawings;
2) Leachate treatment plant; and as and if applicable:
o Landfill gas plant;
o Plant workshop and compound;
o Fuel storage area;
o Transformer compound; and
o Vehicle and trailer parks.
As far as practicable, where the Contractor should provide permanent fencing, this
should be installed as soon as the Contractor takes possession of the Site.
Responsibilities
A. Where, for practical reasons, permanent fencing cannot be erected at the start of
the construction phase, the Contractor should erect and remove, and as necessary,
re-erect and maintain, temporary fencing.
B. If temporary fencing is removed for any reason it should be re-instated as soon as
possible. Whilst the temporary fencing is not in place the Contractor should
arrange for the gap in the fencing to be patrolled in order to prevent unauthorised
entry.
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Submittals
A. The Contractor should submit to the Owner all details of the proposed fencing
before commencing erection on site. The information required should include,
but not be limited to:
Manufacturer’s details;
Material properties;
Erection procedures; and
Maintenance requirements.
Products
Materials
Temporary Fencing
A. Temporary fencing should be post and wire type fencing, a minimum of 1.25 mm
height, of a type acceptable to the Owner, generally complying with BS 1722 or
equivalent and installed in a manner that is secure and provides adequate support.
B. Posts should be treated and weather-proofed to a standard acceptable to the
Owner. Wire, if not PVC coated or manufactured from stainless steel, shall be
galvanized in accordance with the relevant provisions of BS 443 or equivalent.
Permanent Fencing
A. Permanent fencing proposed by the Contractor should comply generally to the
provisions of BS 1722 or equivalent and be acceptable to the Project Manager.
C. Permanent fencing should be a minimum of 2.4 m in height inclusive of anti-
climber, raked over spikes.
D. All steelwork should be PVC coated over a galvanized sub-finish to comply with
the relevant provisions of BS 443 or an equivalent standard.
E. All fastening, nuts and bolts should be manufactured of stainless steel complying
with BS 970 or BSl449 or equivalent.
F. The standard colour of finish must be black.
G. All components which are not coated with PVC or are not manufactured from
stainless steel must be galvanized to the relevant provisions of BS 443 or
equivalent and finished with one coat acid etch primer and two coats black paint
matt finish before delivery.
H. Timber should be well-seasoned and pressure treated and shall be sound, free of
shakes, splits, wavy edges and heart wood.
I. Cable, chain link, barbed wire, hinges and fittings should be of the gauge,
weight, size and type indicated on the drawings and as approved by the Owner.
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Execution
Setting Out
A. Permanent fencing should be set out in accordance with the following
requirements:
In straight lines or smoothly flowing curves in plan and elevation;
Tops of posts following the profile of the ground;
Posts set rigid, vertical and to a depth necessary to ensure adequate
support;
All straining and intermediate posts and struts fixed and anchored
securely;
Straining posts at all ends, corners and changes of direction;
Straining posts at acute variations in level;
Correct fastenings and all components fixed, taut and installed securely;
Ground along line of fence trimmed as necessary; and
Provisions and measures to preclude intruders.
B. Gates should be installed only at the position shown in the engineering drawings.
C. Gates shouldl conform to the requirements of the appropriate BS or equivalent
for the fence into which the gate is to be installed and should be of a standard
equal to the fencing.
Maintenance
A. The Contractor should inspect all fencing and gates on a regular basis to check
for damage.
B. The Contractor should repair all fencing, gates and ancillary works, and replace
damaged fencing, gates and ancillary works as necessary, to the satisfaction of
the Owner.
C. Areas of finish damaged during erection should be made good with the same
protective system. The Contractor should apply sufficient material to provide a
zinc coating at least equal in thickness to the original layer, and PVC covering or
paint to the specifications given in BS 443 or equivalent.
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REFERENCES
Caldwell, J.A., Reith, C.C., “Principles and Practice of Waste Encapsulation”, Lewis
Publishers, 1993.
Blackman, W.C. Jr., “Basic Hazardous Waste Management, Lewis Publishers”, 2001.
Wagner, J., “The Complete Guide to Hazardous Waste Regulations: RCRA, TSCA,
HMTA, OSHA, and Superfund”, John Wiley & Sons, 1998.
Martin, W.E., “Hazardous Waste Handbook”, Butterworth-Heinemann, 1999.
Dayton, L. Davis, J., “Basics of Solid and Hazardous Waste Management Technology”,
Prentice Hall, 2000.
Haxo, H.E., “Liner Materials for Hazardous and Toxic Wastes and Municipal Solid
Waste Leachate”, Noyes Publications, 1995.
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Chapter XII
Standards for Hazardous Waste Management
Purpose, Scope, and Applicability
The purpose of this chapter is to establish minimum standards that define the acceptable
management of hazardous waste. They apply to owners and operators of all facilities that
treat, store, or dispose of hazardous waste, except as specifically provided otherwise.
General Facility Standards
Applicability
The regulations in this chapter apply to owners and operators of all hazardous waste
facilities.
Identification Number
Every facility owner or operator must apply to the local authority for an identification
number in accordance with local authority notification procedures.
Required Notices
The owner or operator of a facility that receives hazardous waste from an off-site source
(except where the owner or operator is also the generator) must inform the generator in
writing that the owner or operator has the appropriate permit(s) for, and will accept, the
waste the generator is shipping. The owner or operator must keep a copy of this written
notice as part of the operating record.
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Before transferring ownership or operation of a facility during its operating life, or of a
disposal facility during the post-closure care period, the owner or operator must notify
the new owner or operator in writing of the requirements of this Part.
General Waste Analysis
A. Analysis
1. Before an owner or operator treats, stores, or disposes of any hazardous wastes,
or non-hazardous wastes, the owner or operator shall obtain a detailed chemical
and physical analysis of a representative sample of the wastes. At a minimum, the
analysis must contain all the information that must be known to treat, store, or
dispose of the waste in accordance with this Part.
2. The analysis may include data developed under local authority code and existing
published or documented data on the hazardous waste or on hazardous waste
generated from similar processes. The owner or operator of an off-site facility
may arrange for the generator of the hazardous waste to supply part or all of the
information required by subsection (a)(1) above, except as otherwise specified. If
the generator does not supply the information, and the owner or operator chooses
to accept a hazardous waste, the owner or operator is responsible for obtaining
the information required to comply with this Section.
3. The analysis must be repeated as necessary to ensure that it is accurate and up to
date. At a minimum, the analysis must be repeated:
When the owner or operator is notified, or has reason to believe, that the
process or operation generating the hazardous waste, or non-hazardous waste
has changed; and for off-site facilities, when the results of the inspection
required in subsection (a)(4) below indicate that the hazardous waste
received at the facility does not match the waste designated on the
accompanying manifest or shipping paper; and
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The owner or operator of an off-site facility shall inspect and, if necessary,
analyze each hazardous waste shipment received at the facility to determine
whether it matches the identity of the waste specified on the accompanying
manifest or shipping paper.
B. Waste Analysis Plan
The owner or operator shall develop and follow a written waste analysis plan that
describes the procedures that it will carry out to comply with subsection (a) above. The
owner or operator shall keep this plan at the facility. The plan must specify:
1. The parameters for which each hazardous waste, or non-hazardous waste will be
analyzed and the rationale for the selection of these parameters (i.e., how analysis
for these parameters will provide sufficient information on the waste’s properties to
comply with subsection above);
2. The test methods that will be used to test for these parameters; and
3. The sampling method that will be used to obtain a representative sample of the
waste to be analyzed. A representative sample may be obtained using either:
One of the sampling methods prescribed by the local authority; or
An equivalent sampling method.
4. The frequency with which the initial analysis of the waste will be reviewed or
repeated to ensure that the analysis is accurate and up to date.
5. For off-site facilities, the waste analyses that hazardous waste generators have
agreed to supply.
6. Where applicable, the methods that will be used to meet the additional waste
analysis requirements for specific waste management methods.
7. For surface impoundments exempted from land disposal restrictions, the
procedures and schedules for:
Sampling of impoundment contents;
Analysis of test data; and
Annual removal of residues that are not delisted or which exhibit a
characteristic of hazardous waste and either: Do not meet applicable
treatment standards; or where no treatment standards have been
established, such residues are prohibited from land disposal.
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C. Waste Analysis Plan for Off-Site Facilities
For off-site facilities, the waste analysis plan required in subsection (b) above must
also specify the procedures that will be used to inspect and, if necessary, analyze each
shipment of hazardous waste received at the facility to ensure that it matches the
identity of the waste designated on the accompanying manifest or shipping paper. As
a minimum, the plan must describe:
1. Procedures that will be used to determine the identity of each movement of
waste managed at the facility;
2. Sampling method that will be used to obtain a representative sample of the
waste to be identified, if the identification method includes sampling; and
3. Procedures that the owner or operator of an off-site landfill receiving
containerized hazardous waste will use to determine whether a hazardous
waste generator has added a biodegradable sorbent to the waste in the
container.
Security
A. The owner or operator must prevent the unknowing entry, and minimize the
possibility for the unauthorized entry, of persons or livestock into the active portion of
the facility, unless the owner or operator demonstrates to the local authority that:
Physical contact with the waste, structures or equipment within the active
portion of the facility will not injure unknowing or unauthorized persons or
livestock which may enter the active portion of a facility; and
Disturbance of the waste or equipment, by the unknowing or unauthorized
entry of persons or live-stock onto the active portion of a facility, will not
cause a violation of the requirements of this Part.
B. Unless the owner or operator has made a successful demonstration under paragraph
(a), a facility must have:
1. A 24-hour surveillance system (e.g., television monitoring or surveillance
by guards or facility personnel) which continuously monitors and
controls entry into the active portion of the facility; or
2. An artificial or natural barrier (e.g., a fence in good repair or a fence
combined with a cliff), which completely surrounds the active portion of
the facility; and
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3. A means to control entry, at all times, through the gates or other
entrances to the active portion of the facility (e.g., an attendant, television
monitors, locked entrance or controlled roadway access to the facility).
C. Unless the owner or operator has made a successful demonstration under paragraph
(a), a sign with the legend, “Danger--Unauthorized Personnel Keep Out”, must be posted
at each entrance to the active portion of a facility, and at other locations, in sufficient
numbers to be seen from any approach to this active portion. The sign must be legible
from a distance of at least 25 feet. Existing signs with a legend other than “Danger--
Unauthorized Personnel Keep Out” may be used if the legend on the sign indicates that
only authorized personnel are allowed to enter the active portion, and that entry into the
active portion can be dangerous.
General Inspection Requirements
A. The owner or operator shall conduct inspections often enough to identify problems in
time to correct them before they harm human health or the environment. The owner or
operator shall inspect the facility for malfunctions and deterioration, operator errors, and
discharges that may be causing or may lead to:
1. Release of hazardous waste constituents to the environment; or
2. A threat to human health.
B. Inspection schedule.
The owner or operator shall develop and follow a written schedule for
inspecting monitoring equipment, safety and emergency equipment, security
devices, and operating and structural equipment (such as dikes and sump
pumps) that are important to preventing, detecting, or responding to
environmental or human health hazards.
The owner or operator shall keep this schedule at the facility.
The schedule must identify the types of problems (e.g., malfunctions or
deterioration) that are to be looked for during the inspection (e.g., inoperative
sump pump, leaking fitting, eroding dike, etc.).
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The frequency of inspection may vary for the items on the schedule.
However, it should be based on the rate of deterioration of the equipment and
the probability of an environmental or human health incident if the
inspections. Areas subject to spills, such as loading and unloading areas, must
be inspected daily when in use. As part of this review, the local authority may
modify or amend the schedule as may be necessary.
C. The owner or operator shall remedy any deterioration or malfunction of equipment
or structures that the inspection reveals on a schedule which ensures that the problem
does not lead to an environmental or human health hazard. Where a hazard is imminent
or has already occurred, remedial action must be taken immediately.
D. The owner or operator shall record inspections in an inspection log or summary. The
owner or operator shall keep these records for at least three years from the date of
inspection. At a minimum, these records must include the date and time of the
inspection, the name of the inspector, a notation of the observations made and the date,
and nature of any repairs or other remedial actions.
Personnel Training
1. Facility personnel must successfully complete a program of classroom instruction or
on-the-job training that teaches them to perform their duties in a way that ensures the
facility’s compliance with the requirements of this Part. The owner or operator must
ensure that this program includes all the elements described in the document required.
2. This program must be directed by a person trained in hazardous waste management
procedures, and must include instruction which teaches facility personnel hazardous
waste management procedures (including contingency plan implementation) relevant to
the positions in which they are employed.
3. At a minimum, the training program must be designed to ensure that facility
personnel are able to respond effectively to emergencies by familiarizing them with
emergency procedures, emergency equipment and
Procedures for using, inspecting, repairing and replacing facility
emergency and monitoring equipment;
Key parameters for automatic waste feed cut-off systems;
Communications or alarm systems;
Response to fires or explosions;
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Response to groundwater contamination incidents; and
Shutdown of operations.
4. Facility personnel must successfully complete the program required in paragraph (a)
within six months after the effective date of these regulations or six months after the date
of their employment or assignment to a facility, or to a new position at a facility,
whichever is later. Employees hired after the effective date of these regulations must not
work in unsupervised positions until they have completed the training requirements of
paragraph (a).
5. Facility personnel must take part in an annual review of the initial training required in
paragraph (a).
6. The owner or operator must maintain the following documents and records at the
facility:
a. The job title for each position at the facility related to hazardous waste
management, and the name of the employee filling each job;
b. A written job description for each position listed. This description may be
consistent in its degree of specificity with descriptions for other similar
positions in the same company location or bargaining unit, but must include
the requisite skill, education or other qualifications, and duties of
employees assigned to each position;
c. A written description of the type and amount of both introductory and
continuing training that will be given to each person filling a position
listed;
d. Records that document that the training or job experience required under
paragraphs (a), (b) and (c) has been given to, and completed by, facility
personnel.
7. Training records on current personnel must be kept until closure of the facility;
training records on former employees must be kept for at least three years from the date
the employee last worked at the facility. Personnel training records may accompany
personnel transferred within the same company.
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General Requirements for Ignitable, Reactive or Incompatible Wastes
A. The owner or operator must take precautions to prevent accidental ignition or reaction
of ignitable or reactive waste. This waste must be separated and protected from sources
of ignition or reaction including but not limited to: open flames, smoking, cutting and
welding, hot surfaces, frictional heat, sparks (static, electrical or mechanical),
spontaneous ignition (e.g., from heat -producing chemical reactions) and radiant heat.
While ignitable or reactive waste is being handled, the owner or operator must confine
smoking and open flame to specially designated locations. “No Smoking” signs must be
conspicuously placed wherever there is a hazard from ignitable or reactive waste.
B. Where specifically required by this part, the owner or operator of a facility that treats,
stores or disposes ignitable or reactive waste, or mixes incompatible waste and other
materials, must take precautions to prevent reactions which:
1. Generate extreme heat or pressure, fire or explosions, or violent reactions;
2. Produce uncontrolled toxic mists, fumes, dusts or gases in sufficient
quantities to threaten human health or the environment;
3. Produce uncontrolled flammable fumes or gases in sufficient quantities to
pose a risk of fire or explosions;
4. Damage the structural integrity of the device or facility;
5. Through other like means threaten human health or the environment.
C. When required to comply with paragraphs (a) or (b), the owner or operator must
document that compliance. This documentation may be based on references to published
scientific or engineering literature, data from trial tests (e.g., benchmark scale or pilot
scale tests), waste analyses, or the results of the treatment of similar wastes by similar
treatment processes and under similar operating conditions.
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Location Standards
A. Seismic considerations
1. Portions of new facilities where treatment, storage or disposal of hazardous
waste will be conducted must not be located within 61 meters (200 feet) of a
fault which has had displacement in Holocene time.
2. As used in subsection (a)(l):
“Fault” means a fracture along with rocks on one side have been
displaced with respect to those on the other side;
“Displacement” means the relative movement of any two sides of a
fault measured in any direction; and
“Holocene” means the most recent époque of the Quarternary period,
extending from the end of the Pleistocene to the present.
B. Floodplains.
1. A facility located in a 100 year floodplain must be designed, constructed, operated and
maintained to prevent washout of any hazardous waste by a 100-year flood, unless the
owner or operator can demonstrate to the environmental agency’s satisfaction that:
i. Procedures are in effect which will cause the waste to be removed safely,
before flood waters can reach the facility, to a location where the wastes
will not be vulnerable to flood waters; or
ii. For existing surface impoundments, waste piles, land treatment units,
landfills and miscellaneous units, no adverse effects on human health or
the environment will result if washout occurs, considering:
The volume and physical and chemical characteristics of the waste in
the facility;
The concentration of hazardous constituents that would potentially
affect surface waters as a result of washout;
The impact of such concentrations on the current or potential uses of
and water quality standards established for the affected surface waters;
and
The impact of hazardous constituents on the sediments of affected
surface waters or the soils of the 100-year floodplain that could result
from washout;
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2. As used in subsection (b):
i. “100-year floodplain” means any land area, which is subject to a
one percent or greater chance of flooding in any given year from
any source.
ii. “Washout” means the movement of hazardous waste from the
active portion of the facility as a result of flooding.
iii. “100-year flood” means a flood that has a one percent chance of
being equaled or exceeded in any given year.
Construction Quality Assurance Program
A. Construction quality assurance (CQA) program.
1. A CQA program is required for all surface impoundment, waste pile and landfill units
that are required to comply with the local authority regulations. The program must
ensure that the constructed unit meets or exceeds all design criteria and specifications in
the permit. The program must be developed and implemented under the direction of a
CQA officer who is a registered professional engineer.
2. The CQA program must address the following physical components, where
applicable:
Foundations;
Dikes;
Low-permeability soil liners;
Geomembranes (flexible membrane liners);
Leachate collection and removal systems and leak detection systems; and
Final cover systems.
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B. Written CQA plan. The owner or operator of units subject to the CQA program
under subsection (a) above must develop and implement a written CQA plan. The plan
must identify steps that will be used to monitor and document the quality of materials
and the condition and manner of their installation. The CQA plan must include:
1. Identification of applicable units, and a description of how they will be constructed.
2. Identification of key personnel in the development and implementation of the CQA
plan, and CQA officer qualifications.
3. A description of inspection and sampling activities for all unit components identified
in subsection (a) (2) above, including observations and tests that will be used before,
during and after construction to ensure that the construction materials and the installed
unit components meet the design specifications. The description must cover: Sampling
size and locations; frequency of testing; data evaluation procedures; acceptance and
rejection criteria for construction materials; plans for implementing corrective measures;
and data or other information to be recorded and retained in the operating record.
C. Contents of program.
1. The CQA program must include observations, inspections, tests and measurements
sufficient to ensure:
Structural stability and integrity of all components of the unit identified in
subsection (a) (2) above;
Proper construction of all components of the liners, leachate collection and
removal system, leak detection system and final cover system, according to
permit specifications and good engineering practices and proper installation
of all components (e.g., pipes) according to design specifications;
Conformity of all materials used with design and other material
specifications.
2. The CQA program must include test fills for compacted soil liners, using the same
compaction methods as in the full scale unit, to ensure that the liners are constructed to
meet the hydraulic conductivity requirements of requirements in the field. Compliance
with hydraulic conductivity requirements must be verified in-situ testing on the
constructed test fill. The local authority shall accept an alternative demonstration, in lieu
of a test fill, where data are sufficient to show that a constructed soil liner will meet the
hydraulic conductivity in the field.
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D. Certification. Waste must not be received in a unit until the owner or operator has
submitted to the local authority by certified mail or hand delivery a certification signed
by the CQA officer that the approved CQA plan has been successfully carried out and
that the unit meets the requirements has been completed. Documentation supporting the
CQA officer’s certification must be furnished to the local authority upon request.
Preparedness and Prevention
Design and Operation of Facility
Facilities must be designed, constructed, maintained and operated to minimize the
possibility of a fire, explosion or any unplanned sudden or non-sudden release of
hazardous waste or hazardous waste constituents to air, soil or surface water which could
threaten human health or the environment.
Required Equipment
Facilities must be equipped with the following, unless the owner or operator
demonstrates to the local authority that none of the hazards posed by waste handled at
the facility could require a particular kind of equipment specified below:
A. An internal communications or alarm system capable of providing immediate
emergency instruction (voice or signal) to facility personnel;
B. A device, such as a telephone (immediately available at the scene of operations) or a
hand-held two-way radio, capable of summoning emergency assistance from local police
departments, fire departments or State or local emergency response teams;
C. Portable fire extinguishers, fire control equipment (including special extinguishing
equipment such as that using foam, inert gas or dry chemicals), spill control equipment
and decontamination equipment; and
D. Water at adequate volume and pressure to supply water hose streams, or foam
producing equipment, or automatic sprinklers or water spray systems.
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Testing and Maintenance of Equipment
All facility communications or alarm systems, fire protection equipment, spill control
equipment and decontamination equipment must be tested and maintained as necessary
to assure its proper operation in time of emergency.
Access to Communications or Alarm System
A. Whenever hazardous waste is being poured, mixed, spread or otherwise handled, all
personnel involved in the operation must have immediate access to an internal alarm or
emergency communication device, either directly or through visual or voice contact with
another employee.
B. If there is ever just one employee on the premises while the facility is operating, the
employee must have immediate access to a device, such as a telephone (immediately
available at the scene of operations) or a hand-held two-way radio, capable of
summoning external emergency assistance.
Required Aisle Space
The owner or operator must maintain aisle space to allow the unobstructed movement of
personnel, fire protection equipment, spill control equipment and decontamination
equipment to any area of facility operation in an emergency, unless the owner or operator
demonstrates to the local authority that aisle space is not needed for any of these
purposes.
Arrangements with Local Authorities
A. The owner or operator must attempt to make the following arrangements appropriate
for the type of waste handled at the facility and the potential need for the services of
these organizations:
1. Arrangements to familiarize police, fire departments and emergency response teams
with the layout of the facility, properties of hazardous waste handled at the facility and
associated hazards, places where facility personnel would normally be working,
entrances to and roads inside the facility and possible evacuation routes;
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2. Where more than one police and fire department might respond to an emergency,
agreements designating primary emergency authority to a specific police and a specific
fire department, and agreements with any others to provide support to the primary
emergency authority;
3. Agreements with state emergency response teams, emergency response contractors
and equipment suppliers; and
4. Arrangements to familiarize local hospitals with the properties of hazardous waste
handled at the facility and the types of injuries or illnesses, which could result from fires,
explosions or releases at the facility.
B. Where state or local authorities decline to enter into such arrangements, the owner or
operator must document the refusal in the operating record.
Contingency Plan and Emergency procedures
Purpose and Implementation of Contingency Plan
A. Each owner or operator must have a contingency plan for the facility. The
contingency plan must be designed to minimize hazards to human health or the
environment from fires, explosions or any unplanned sudden or non-sudden release of
hazardous waste or hazardous waste constituents to air, soil or surface water.
B. The provisions of this plan must be carried out immediately whenever there is a fire,
explosion or release of hazardous waste or hazardous waste constituents, which could
threaten human health or the environment.
Content of Contingency Plan
a. The contingency plan must describe the actions facility personnel in response to fires,
explosions, or any unplanned sudden or non-sudden release of hazardous waste or
hazardous waste constituents to air, soil, or surface water at the facility.
b. If the owner or operator has already prepared a Spill Prevention Control and
Countermeasures (SPCC) Plan or some other emergency or contingency plan, the owner
or operator need only amend that plan to incorporate hazardous waste management
provisions that are sufficient to comply with the requirements of this Part.
c. The plan must describe arrangements agreed to by local police departments, fire
departments, hospitals, Contractors, and local emergency response teams to coordinate
emergency services.
d. The plan must list names, addresses, and phone numbers (office and home) of all
persons qualified to act as emergency coordinator, and this list must be kept up to date.
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Where more than one person is listed, one must be named as primary emergency
coordinator and others must be listed in the order in which they will assume
responsibility as alternates. For new facilities, this information must be supplied to the
local environmental agency at the time of certification, rather than at the time of permit
application.
e. The plan must include a list of all emergency equipment at the facility fire
extinguishing systems, spill control equipment, communications, alarm systems (internal
and external) and decontamination equipment. This list must be kept up to date. In
addition, the plan must include the location and a physical description of each item on
the list, and a brief outline of its capabilities.
f. The plan must include an evacuation plan for facility personnel where there is a
possibility that evacuation could be necessary. This plan must describe signal(s) to be
used to begin evacuation, evacuation routes and alternate evacuation routes (in cases
where the primary routes could be blocked by releases of hazardous waste or fires).
Copies of Contingency Plan
Copy of the contingency plan and all revisions to the plan must be:
a. Maintained at the facility; and
b. Submitted to all local police departments, fire departments,
hospitals and state and local emergency response teams that may
be called upon to provide emergency services.
Amendment of Contingency Plan
The contingency plan shall be reviewed, and immediately amended, if necessary,
whenever:
a. The facility permit is revised;
b. The plan fails in an emergency;
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c. The facility changes -- in its design, construction, operation, maintenance or
other circumstances -- in a way that materially increases the potential for
fires, explosions or releases of hazardous waste or hazardous waste
constituents, or changes the response necessary in an emergency;
d. The list of emergency coordinators changes; or
e. The list of emergency equipment changes.
Cost Estimate for Closure
A. The owner or operator shall have detailed a written estimate, in current dollars, of
closing facility. The estimate must equal the cost of final closure at the point in the
facility’s active life when the extent and manner of its operation would make closure the
most expensive; and
The closure cost estimate must be based on the costs to the owner or operator of hiring a
third party to close the facility. A third party is a party who is neither a parent nor a
subsidiary of the owner or operator. The owner or operator may use costs for on-site
disposal if the owner or operator demonstrates that on-site disposal capacity will exist at
all times over the life of the facility.
The closure cost estimate must not incorporate any salvage value that may be realized
with the sale of hazardous wastes, or non-hazardous wastes if applicable, facility
structures or equipment, land and other assets associated with the facility at the time of
partial or final closure.
B. During the life of the facility, the owner or operator shall adjust the closure cost
estimate for inflation within 60 days prior to the anniversary date of the establishment of
the financial instrument(s). For owners and operators using the financial test or corporate
guarantee, the closure cost estimate must be updated for inflation within 30 days after the
close of the firm’s fiscal year and before submission of updated information to the local
authority. The adjustment may be made by recalculating the maximum costs of closure
in current local currency, or by using an inflation factor derived from the annual Implicit
Price Deflator for Gross National Product as published by the Local authorities. The
inflation factor is the result of dividing the latest published annual Deflator by the
Deflator for the previous year.
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The first adjustment is made by multiplying the closure cost estimate by the
inflation factor. The result is the adjusted closure cost estimate; and
Subsequent adjustments are made by multiplying the latest adjusted closure
cost estimate by the latest inflation factor.
C. During the active life of the facility the owner or operator shall revise the closure cost
estimate no later than 30 days after the Agency has approved the request to modify the
closure plan, if the change in the closure plan increases the cost of closure. The revised
closure cost estimate must be adjusted for inflation.
D. The owner or operator shall keep the adjusted closure cost estimate and when this
estimate has been adjusted, at the facility during the operating life of the facility.
Financial Assurance for Closure
The owner or operator of each facility shall establish financial assurance for closure of
the facility. The owner or operator shall choose from the options as specified in
subsections (a) through (f).
A. Closure trust fund.
1. An owner or operator may satisfy the requirements of this Section by establishing a
closure trust fund which conforms to the requirements of this subsection and submitting
an original signed duplicate of the trust agreement to the local authority. An owner or
operator of a new facility shall submit the original signed duplicate of the trust
agreement to the Agency at least 60 days before the date on which hazardous waste is
first received for treatment, storage or disposal. The trustee must be an entity which has
the authority to act as a trustee and whose trust operations are regulated and examined by
the local Central Bank.
2. The wording of the trust agreement must be as specified by the local authority and the
trust agreement must be accompanied by a formal certification of acknowledgment.
Schedule A of the trust agreement must be updated within 60 days after a change in the
amount of the current closure cost estimate covered by the agreement.
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3. Payments into the trust fund must be made annually by the owner or operator over the
term of the initial local authority permit or over the remaining operating life of the
facility as estimated in the closure plan, whichever period is shorter; this period is
hereafter referred to as the “pay-in period.” The payments into the closure trust fund
must be made as follows:
3.1. For a new facility, the first payment must be made before the initial receipt of
hazardous waste for treatment, storage or disposal. A receipt from the trustee for this
payment must be submitted by the owner or operator to the local authority before this
initial receipt of hazardous waste. The first payment must be at least equal to the current
closure cost estimate, except as provided in subsection (g), divided by the number of
years in the pay-in period. Subsequent payments must be made no later than 30 days
after each anniversary date of the first payment. The amount of each subsequent payment
must be determined by this formula:
Next payment = (CE - CV) / Y
Where,
CE is the current closure cost estimate,
CV is the current value of the trust fund and
Y is the number of years remaining in the pay-in period.
3.2 If an owner or operator establishes a trust fund as specified and the value of that trust
fund is less than the current closure cost estimate when a permit is awarded for the
facility, the amount of the current closure cost estimate still to be paid into the trust fund
must be paid in over the pay-in period as defined in subsection (a)(3). Payments must
continue to be made no later than 30 days after each anniversary date of the first payment
made. The amount of each payment must be determined by this formula:
Next payment = (CE - CV) / Y
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Where, CE is the current closure cost estimate, CV is the current value of the trust fund
and Y is the number of years remaining in the pay-in period.
4. The owner or operator may accelerate payments into the trust fund or may deposit the
full amount of the current closure cost estimate at the time the fund is established.
However, the owner or operator shall maintain the value of the fund at no less than the
value that the fund would have if annual payments were made.
5. If the owner or operator establishes a closure trust fund after having used one or more
alternate mechanisms specified in this Section, its first payment must be in at least the
amount that the fund would contain if the trust fund were established initially and annual
payments made according to specifications of this subsection.
6. After the pay-in period is completed, whenever the current closure cost estimate
changes, the owner or operator shall compare the new estimate with the trustee’s most
recent annual valuation of the trust fund. If the value of the fund is less than the amount
of the new estimate, the owner or operator, within 60 days after the change in the cost
estimate, shall either deposit an amount into the fund so that its value after this deposit at
least equals the amount of the current closure cost estimate, or obtain other financial
assurance as specified in this Section to cover the difference.
7. If the value of the trust fund is greater than the total amount of the current closure cost
estimate, the owner or operator may submit a written request to the local authority for
release of the amount in excess of the current closure cost estimate.
8. If an owner or operator substitutes other financial assurance as specified in this section
for all or part of the trust fund, it may submit a written request to the local authority for
release of the amount in excess of the current closure cost estimate covered by the trust
fund.
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9. Within 60 days after receiving a request from the owner or operator for release of
funds as specified in subsections (a)(7) or (8) above, the local authority shall instruct the
trustee to release to the owner or operator such funds as the local authority specifies in
writing.
10. After beginning partial or final closure, an owner or operator or another person
authorized to conduct partial or final closure may request reimbursement for closure
expenditures by submitting itemized bills to the local authority. The owner or operator
may request reimbursement for partial closure only if sufficient funds are remaining in
the trust found to cover the maximum costs of closing the facility over its remaining
operating life.
Within 60 days after receiving bills for partial or final closure activities, the local
authority shall instruct the trustee to make reimbursement in those amounts as the local
authority specifies in writing if the local authority determines that the partial or final
closure expenditures are in accordance with the approved closure plan, or otherwise
justified.
If the local authority determines that the maximum cost of closure over the remaining
life of the facility will be significantly greater than the value of the trust fund, it shall
withhold reimbursement of such amounts as it deems prudent until it determines, in
accordance with subsection (i), that the owner or operator is no longer required to
maintain financial assurance for final closure of the facility. If the local authority does
not instruct the trustee to make such reimbursements, the Agency shall provide the
owner or operator with a detailed written statement of reasons.
11. The local authority shall agree to termination of the trust when:
An owner or operator substitutes alternate financial assurance as
specified in this Section; or
The local authority releases the owner or operator from the requirements
of this Section.
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b. Surety bond guaranteeing payment into a closure trust fund.
1. An owner or operator may satisfy the requirements of this Section by obtaining a
surety bond which conforms to the requirements of this subsection and submitting the
bond to the local authority. An owner or operator of a new facility shall submit the bond
to the local authority at least 60 days before the date on which hazardous waste is first
received for treatment, storage or disposal.
The bond must be effective before this initial receipt of hazardous waste. The surety
company issuing the bond must, at a minimum, be among those listed as acceptable
sureties with the local Central Bank.
2. The wording of the surety bond must be as specified by the local authority.
3. The owner or operator who uses a surety bond to satisfy the requirements of this
Section shall also establish a standby trust fund. Under the terms of the bond, all
payments made thereunder will be deposited by the surety directly into the standby trust
fund in accordance with instructions from the local authority. This standby trust fund
must meet the requirements specified in subsection (a) except that:
a. An original, signed duplicate of the trust agreement must be submitted to the local
authority with the surety bond; and
b. Until the standby trust fund is funded pursuant to the requirements of this Section, the
following are not required by these regulations:
o Payments into the trust found as specified in subsection (a);
o Updating of Schedule A of the trust agreement to show current closure
cost estimates;
o Annual valuations as required by the trust agreement; and
o Notices of nonpayment as required by the trust agreement.
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4. The bond must guarantee that the owner or operator will:
a. Fund the standby trust fund in an amount equal to the penal sum of the bond
before the beginning of final closure of the facility; or
b. Fund the standby trust fund in an amount equal to the penal sum within 15 days
after an order to begin final closure is issued; or
c. Provide alternate financial assurance as specified in this section, and obtain the
local authority’s written approval of the assurance provided, within 90 days after
receipt by both the owner or operator and the local authority of a notice of
cancellation of the bond from the surety.
5. Under the terms of the bond, the surety will become liable on the bond obligation
when the owner or operator fails to perform as guaranteed by the bond.
6. The penal sum of the bond must be in an amount at least equal to the current closure
cost estimate.
7. Whenever the current closure cost estimate increases to an amount greater than the
penal sum, the owner or operator, within 60 days after the increase, shall either cause the
penal sum to be increased to an amount at least equal to the current closure cost estimate
and submit evidence of such increase to the local authority or obtain other financial
assurance as specified in this section to cover the increase. Whenever the current closure
cost estimate decreases, the penal sum may be reduced to the amount of the current
closure cost estimate following written approval by the local authority.
8. Under the terms of the bond, the surety may cancel the bond by sending notice of
cancellation by certified mail to the owner or operator and to the local authority.
Cancellation may not occur, however, during the 120 days beginning on the date of
receipt of the notice of cancellation by both the owner or operator and the local authority,
as evidence by the return receipts.
9. The owner or operator may cancel the bond if the environmental agency has given
prior written consent based on its receipt of evidence of alternate financial assurance as
specified in this section.
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c. Surety bond guaranteeing performance of closure.
1. An owner or operator may satisfy the requirements of this by obtaining a surety bond
which conforms to the requirements of this subsection and submitting the bond to the
local authority. An owner or operator of a new facility shall submit the bond to the local
authority at least 60 days before the date on which hazardous waste is first received for
treatment, storage or disposal. The bond must be effective before this initial receipt of
hazardous waste. The surety company issuing the bond must, at a minimum, be among
those listed as acceptable sureties by the local Central Bank.
2. The wording of the surety bond must be as specified by the local environmental
agency.
3. The owner or operator who uses a surety bond to satisfy the requirements of this
section shall also establish a standby trust fund. Under the terms of the bond, all
payments made thereunder will be deposited by the surety directly into the standby trust
fund in accordance with instructions from the local authority. This standby trust must
meet the requirements specified in subsection (a), except that:
a. An original, signed duplicate of the trust agreement must be submitted to the local
authority with the surety bond; and
b. Unless the standby trust fund is funded pursuant to the requirements of this section,
the following are not required by these regulations:
Payments into the trust fund as specified in subsection (a);
Updating of Schedule A of the trust agreement to show current closure cost
estimates;
Annual valuations as required by the trust agreement; and
Notices of nonpayment as required by the trust agreement
4. The bond must guarantee that the owner or operator will:
a. Perform final closure in accordance with the closure plan and other requirements of
the permit for the facility whenever required to do so; or
b. Provide alternate financial assurance as specified in this Section, and obtain the local
authority’s written approval of the assurance provided, within 90 days after receipt by
both the owner or operator and the local authority of a notice of cancellation of the bond
from the surety.
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5. Under the terms of the bond, the surety will become liable on the bond obligation
when the owner or operator fails to perform as guaranteed by the bond. Following a final
judicial determination or Board order finding that the owner or operator has failed to
perform final closure in accordance with the approved closure plan and other permit
requirements when required to do so, under the terms of the bond the surety will perform
final closure as guaranteed by the bond or will deposit the amount of the penal sum into
the standby trust fund.
6. The penal sum of the bond must be in an amount at least equal to the current closure
cost estimate.
7. Whenever the current closure cost estimate increases to an amount greater than the
penal sum, the owner or operator, within 60 days after the increase, shall either cause the
penal sum to be increased to an amount at least equal to the current closure cost estimate
and submit evidence of such increase to the local authority or obtain other financial
assurance as specified in this section. Whenever the current closure cost estimate
decreases, the penal sum may be reduced to the amount of the current closure cost
estimate following written approval by the local authority.
8. Under the terms of the bond, the surety may cancel the bond by sending notice of
cancellation by certified mail to the owner or operator and to the local authority.
Cancellation may not occur, however, during the 120 days beginning on the date of
receipt of the notice of cancellation by both the owner or operator and the local authority,
as evidenced by the return receipts.
9. The owner or operator may cancel the bond if the local authority has given prior
written consent. The local authority shall provide such written consent when:
A. An owner or operator substitutes alternate financial assurance as specified in this
section; or
B. The local authority releases the owner or operator from the requirements of this
Section.
The surety shall not be liable for deficiencies in the performance of closure by the owner
or operator after the local authority releases the owner or operator from the requirements
of this section in accordance with subsection A.
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Letter of Credit
1. An owner or operator may satisfy the requirements of this Section by obtaining an
irrevocable standby letter of credit which conforms to the requirements of this subsection
and submitting the letter to the local authority. An owner or operator of a new facility
shall submit the letter of credit to the local authority at least 60 days before the date on
which hazardous waste is first received for treatment, storage or disposal. The letter of
credit must be effective before this initial receipt of hazardous waste. The issuing
institution must be an entity which has the authority to issue letters of credit and whose
letter-of-credit operations are regulated and examined by the local Central Bank.
2. The wording of the letter of credit must be as specified by the local authority.
3. An owner or operator who uses a letter of credit to satisfy the requirements of this
Section shall also establish a standby trust fund. Under the terms of the letter of credit,
all amounts paid pursuant to a draft by the local authority will be deposited by the
issuing institution directly into the standby trust fund in accordance with instructions
from the local authority. This standby trust fund must meet the requirements of the trust
fund specified in subsection (a), except that:
a. An original, signed duplicate of the trust agreement must be submitted to the local
authority with the letter of credit; and
b. Unless the standby trust fund is funded pursuant to the requirements of this section,
the following are not required by these regulations.
i. Payments into the trust fund as specified in subsection (a);
ii. Updating of Schedule A of the trust agreement to show current closure cost
estimates;
iii. Annual valuations as required by the trust agreement; and
iv. Notices of nonpayment as required by the trust agreement.
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4. The letter or credit must be accompanied by a letter from the owner or operator
referring to the letter of credit by number, issuing institution, and date and providing the
following information: the local authority Identification Number, name and address of
the facility, and the amount of funds assured for closure of the facility by the letter of
credit.
5. The letter of credit must be irrevocable and issued for a period of at least 1 year. The
letter of credit must provide that the expiration date will be automatically extended for a
period of at least 1 year unless, at least 120 days before the current expiration date, the
issuing institution notifies both the owner or operator and the local authority by certified
mail of a decision not to extend the expiration date. Under the terms of the letter of
credit, the 120 days will begin on the date when both the owner or operator and the local
authority have received the notice, as evidenced by the return receipts.
6. The letter of credit must be issued in an amount at least equal to the current closure
cost estimate, except as provided in subsection (g).
