ENVIS ENERGY AND ENVIRONMENTAL SYSTEMS RESEARCH AND DEVELOPMENT LTD.

TRAINING REPORT

MARMARA UNIVERSITY

ENGINEERING FACULTY

DEPARTMENT OF ENVIRONMENTAL

ENGINEERING

DATE : 04.09.2015

STUDENT NAME : NİLGÜN KADAK

TABLE OF CONTENTS

ABOUT COMPANY .................................................................................................... 1

INTRODUCTION ........................................................................................................ 5

SEWAGE SLUDGE PYROLYSIS ............................................................................. 6

Sewage Sludge ................................................................................................... 6

Solar Drying Technology for Sewage Sludge ........................................ 7

Thermal Drying Technology for Sewage Sludge ................................... 7

Screw Press Technology for Sewage Sludge ......................................... 8

Pyrolysis ............................................................................................................. 9

Advantages of Pyrolysis Process ............................................................ 9

Pyrolysis vs. Inciniration ...................................................................... 10

Products of Pyrolysis and Their Features ............................................. 10

Types of Pyrolysis Technologies ......................................................... 11

Basic Description of Pyrolysis Process ................................................ 13

Calculations about Drying and Pyrolysis Processes ............................ 13

CUMULATIVE ENVIRONMENTAL IMPACT ASSESSMENT (CEIA) .......... 15

Cumulative Impacts .......................................................................................... 15

Cumulative Environmental Impact Assessment (CEIA) and Management ..... 16

Cumulative Environmental Impact Assessment (CEIA) Process ......... 17

WASTEWATER TREATMENT DESIGN ............................................................ 18

Biological Nutrient Removal Activated Sludge (BNRAS) Systems ................ 18

The University of Cape Town (UCT) Method for Enhanced Biological

Phosphorus Removal ........................................................................... 19

The Modified University of Cape Town (UCT) Process .......... 20

REFERENCES ........................................................................................................... 21

ABOUT COMPANY

ENVIS has taken development and application of R&D projects aiming at providing solutions

in the area of environment and energy technologies as a mission in line with the clean

production technologies and sustainable waste management concepts [1].

ENVIS aims to establish cooperation between university and industry for research and training

purposes to develop tailor-made solutions to the problems in the area of environment and

energy; and using the outputs of such cooperation to provide solution oriented technological

support compliant to national and international standards [1].

Area of Services

~ Resource Recycling and Re-use

~ Innovative Technologies

ENVIS contributed to the development of innovative technologies in the international

scale and has the scientific and technological infrastructure to provide all sorts of services

regarding innovative technologies in the design, application and operation phases [2].

~ Experimental Analysis and Treatability

ENVIS provides technical support on

realization of successful applications by

establishing resource recycle principles for different

types of wastes of both residential and industrial

origin. Recycle and re-use are the basic principles in

ENVIS’ project approach for all waste management

projects [2].

ENVIS has the privilege to exploit all laboratory

facilities of the Istanbul Technical University, Environmental

Engineering Department, which acquires equipment and

experience rarely found in universities in the international scale

[2].

The technical staff of ENVIS is an experienced group

which has conducted extensive studies on almost every type of

municipal and industrial wastes in these laboratories and the

published the results in international scientific arena [2].

~ Industrial Pollution Control and Treatment Plant Rehabilitation

Industrial wastes have significantly different characteristics depending on the industrial

activity. All studies within the scope of industrial pollution control are ENVIS’ field of

specialization [2].

Technical staff of ENVIS has implemented numerous studies on almost all industries

and in different organized industrial districts. Technical staff of ENVIS realizes the

rehabilitation of wastewater treatment plant, which are not being well operated or employing

an old technology, by implementing on-site diagnosis/treatment/remediation applications. In

this way, it becomes possible to make significant savings on operation costs as well as to meet

required conditions imposed by the stricter regulations [2].

~ Management of Wastes and Wastewater Treatment Plant Sludges

ENVIS is one of the companies having the level of expertise and experience found very

rare in Turkey, able to conduct both scientific research and applications in the field of waste

management and wastewater treatment plant sludge management [2].

~ Environmental Impact Assessment and Risk Assessment

ENVIS, provides scientific and technical support on assessment of environmental

impacts, definition of mitigation measures and design of systems for the investments within the

framework of scope defined by national and international legislation. ENVIS conducts

environmental impact assessment studies with its experienced staff within the framework of

Equator Principles, which is a requirement for the investor in his crediting applications [2].

ENVIS, identifies all possible environmental hazards and risks in all plants, establishes

and organizes plant-specific risk management application plans which include risk reduction,

risk control, reduction of harm, intervention and restoration processes [2].

~ Wastewater Management and Wastewater Treatment Plant Design

ENVIS, with its experienced technical team, is among the exceptional companies who

are able to offer services in both residential and industrial areas. The long list of design and

feasibility studies concluded by ENVIS in both fields is the result of research and development

studies which are recognized as leading examples [2].

~ Treatment Plant Management, Operation and Maintenance

~ Carbon Inventory and Energy Management

ENVIS implements studies on greenhouse gas (GHG) inventories and footprints

defining sector-specific methods and technologies by identifying process modifications which

can be employed towards achieving GHG emission reductions. ENVIS provides consultancy

services on verification of GHG emissions and certification under ISO 14064, which forms the

basis for emission trading [2].

ENVIS determines energy management tools, targets and programs and defines an

effective energy management system which minimizes the energy costs and reduces GHG

emissions through identification of high energy consumption areas [2].

ENVIS has the expertise and experience

required by plant management approach towards

operation and maintenance services. ENVIS has

the privilege to exploit both the laboratory

facilities and applied training and documentation

potential required for the operation of the Istanbul

Technical University, Environmental Engineering

Department [2].

~ Environmental Audit and Management

ENVIS determines the basis of environmental management by making use of scientific

data and in relation to that investigates and evaluates the industrial plants on-site considering

all environmental data with its expert team having extensive know-how. ENVIS re-organizes

the existing environmental management systems in accordance with the changing conditions

and determines the measures to be taken in order to fulfill the requirements of environmental

audits [2].

ENVIS determines possible improvement measures by evaluating

resource/energy/waste relation at all plants, defines saving opportunities and within the

framework of the investigations and evaluations. ENVIS prepares a new environmental

management plan and environmental action plan compatible with the legislation [2].

Certificates Possessed by ENVIS Energy and Environmental Systems

Research&Development LTD.

Figure [1]: ISO 9001 certification Figure [2]: ISO 14001 certification

possessed by ENVIS [1] possessed by ENVIS [1]

ISO 9001: 2008

ISO 14001: 2004

INTRODUCTION

ENVIS is a multi-functional company that has well-experienced instructors and highly

qualified staff. Therefore, my training in the office of ENVIS is considerably efficient from

every angle.

The main points I have learnt throughout my training;

What sewage sludge is and which drying processes of sewage sludges must be applied

to meet the regulations in Turkey.

How to obtain energy from sewage sludge by using pyrolysis method and how to make

the basic calculations of drying and pyrolysis process.

How to write Cumulative Environmental Impact Assessment (CEIA) and which

parameters are to be considered while writing CEIA.

How the University of Cape Town Process works and what happens during the

biochemical process of each unit.

SEWAGE SLUDGE PYROLYSIS

Sewage Sludge

Sewage sludge is a by-product of the municipal and industrial wastewater treatment

plants. It is the residual slurry of settleable solids. In recent years, environmental issues have

increasingly focused on sewage sludge treatment because wastewater treatment standards have

become more stringent [3].

Figure [3] : Sewage sludge [4]

According to the related regulation in Turkey, dryness ratio of treatment sludge must

provide a ratio of 30%. [5].

Within the scope of the recent regulations in Turkey,

~ The sewage sludges that have the dryness ratio of 30 % are landfilled, or

~ The sewage sludges that have the dryness ratio of 30 % are dried untill the dryness ratio

reaches to 80-90 % and then energy is obtained by applying pyrolysis process. [5]

Figure [4]: Sludge phases according to the dryness ratio [6]

1000 kg 160 kg 44 kg 20 kg

Wet Sludge Dewatered Sludge Dried Sludge Ash

4 % DS 25 % DS > 90 % DS > 99 % DS

40-80 % organic

in DS

40-80 % organic

in DS

40-80 % organic

in DS 0-3 % organic

The methods mentioned below can use to dry the sewage sludges that have the dryness

ratio of 30 % ;

Solar Drying Technology for Sewage Sludge

Solar drying is a process for sludge drying by convection: under the effect of solar

radiation, water evaporates from the sludge. When the solar system is completely covered with

a transparent roof and walls (glasshouse), the greenhouse effect accelerates sludge drying. Solar

drying of sludge has low operating costs for energy [7].

Figure [5]: Solar drying of sewage sludge [7]

Thermal Drying Technology for Sewage Sludge

The pinnacle technology utilizing waste heat for thermal drying. Various heat sources

and heat transfer media starting with a temperature level of approximately 100°C (212°F) can

be utilized [8].

It's a technology that limits greenhouse gas emissions and insures control of odor

problems. Furthermore, the recovery of low calories present on the site (cogeneration, heating

and air conditioning systems, residual energy etc.) allows a decrease in energy consumption

[9].

Solar drying technologies can be more preferable than thermal drying systems

considering the initial investment cost, operating cost, field conditions and

meteorological conditions [5].

In summer months, the sludge that has dryness ratio of 80-90 % due to the drying

processes can be more than at the other months. Because evaporation is much more than in

the other months depending on the weather temperature [5].

Screw Press Technology for Sewage Sludge

Screw Press is one of the dewatering equipment for sewage sludge. It increases the dry

matter of sludge from 1 % to 30 % . For this reason, this technology is more advantageous than

the other known drying technologies like filter press, belt press etc [5].

Figure [6]: Screw press technology [10]

Figure [7]: A screw press while working [11]

Pyrolysis

Pyrolysis is one of the methods of thermal utilization of wastes. It is a distillation process

affected by the application of heat in an insufficiency of air. Pyrolysis gases (syngas), untreated

oils (biodiesel), and solid matter in a form of char (bio-char) are the main products of the

process. The low-temperature pyrolysis runs at the temperatures between 350-400 °C, and

above 600 °C runs high-temperature pyrolysis [3].

Advantages of Pyrolysis Process

The advantage of the pyrolysis process is the effective reduction of volume and mass of

the dewatered sludge and vaporization of organic toxic agents from the sludge into harmless

substances in the combustion chamber. Mercury and its compounds are thermo decomposed

and vaporized as well. Pyrolysis also performs energy recycling [12]. The other advantages of

pyrolysis process are mentioned below as main topics;

~ Reduces greenhouse gas emissions and waste going to landfill

~ Produces electricity

~ Low risk of water pollution

~ Low risk of odours

~ High recovery rate of resources

~ Minimal risk of health consequences

~ Commercially proven technology [13]

Pyrolysis is a method which is used to produce energy from 80 % dry sludge [5]. Not

only sludge but also other kind of wastes can be used in this process.

Table [1]: Inputs and outputs of pyrolysis process [14]

Application Feedstock to Pyrolysis System Products of Pyrolysis

Waste-to-

Energy

Municipal Solid Waste (MSW)

Waste plastics Electrical energy

Medical waste Steam

Rubber and tyres Black carbon

E-waste Oil

Biomass/wood Non-oxidized metals

Organic sludge (sewage/oil/paper

sludge)

Pyrolysis vs. Incineration

Pyrolysis has a number of important advantages over incineration. The pyrolysis system

for treatment of MSW and other wastes demonstrates excellent practical performance in

controlling the emission of harmful substances such as dioxins with levels dramatically lower

than regulation values [14].

The pyrolysis facility is self-sustainable. Steam and/or electricity generated during

operation is further supplied outside of the facility to the customers. The pyrolysis plant does

not produce waste water effluent from the gas cleaning system. Along with this obvious

environmental advantage it also makes the system less expensive [14].

Another environmental aspect is the reduction of the residuals to be sent for landfill

disposal. Some remaining non-toxic ashes can also be used in the building industry. Recovered

Metals are non-oxidized and can be further used. Pyrolysis system can treat both low calorific

and high calorific waste [14].

Products of Pyrolysis and Their Features

The main products of pyrolysis process are;

Biochar Biodiesel Syngas

~ Biochars are created by pyrolysis of biomass. They have the potential to help reduce

the climate change effects, via carbon sequestration. Independently, biochar can

increase soil fertility of acidic soils, increase agricultural productivity, Furthermore,

biochars reduce pressure on forests. They are stable solids, rich in carbon, and can

endure in soil for thousands of years [15].

Figure [8]: Biochar produced as a result of pyrolysis process [15]

~ Biodiesels are produced from the condensation of vapour of a pyrolysis reaction. The

biodiesels have heating values of 40%–50% of that of hydrocarbon fuels. The main

advantages of biodiesels are: clearly positive CO2 balance, possibility of utilisation in

small-scale power generation systems as well as use in large power stations, storability

and transportability, high-energy density compared to biomass gasification fuel, and

potential of using pyrolysis liquid in existing power plants [16].

Figure [9]: Biodiesels and biochars produced as a result of pyrolysis process [17]

~ Syngases, or synthesis gases, are a fuel gas mixture consisting primarily of hydrogen,

carbon monoxide, and very often some carbon dioxide.They are usually product of

pyrolysis and the main application is electricity generation [18]. There are lots of

benefits of syngas utilization like generation of renewable power, conversion of

problematic wastes to useful fuels, economical onsite power production and reduced

transmission losses, reduction in carbon emissions [19].

Types of Pyrolysis Technologies

Pyrolysis processes can occur as slowly or rapidly. Slow Pyrolysis occurs during a much

longer reaction time span than fast pyrolysis and the main usable product is the solid char.

During fast pyrolysis process , the biomass must be heated very quickly with a large amount

of heat. The time period for the reaction must be very short and the vapor products must be

condensed immediately [20].

Although the main product types of slow and fast pyrolysis are the same as “biochar,

biodiesel and syngas”, the percentages of the product distribution are generally different. Slow

pyrolysis creates much less liquid products than fast pyrolysis [20].

The differences between the product distributions of slow and fast pyrolysis

technologies are shown in the graphs below;

Graph [1]: Slow pyrolysis product distribution pie chart [20]

Graph [2]: Fast pyrolysis product distribution pie chart [20]

35%

30%

35%

SLOW PYROLYSIS PRODUCT

DISTRIBUTION

Biochar

Biodiesel

Syngas

12%

75%

13%

FAST PYROLYSIS PRODUCT

DISTRIBUTION

Biochar

Biodiesel

Syngas

Basic Description of Pyrolysis Process

Drying is essential to avoid adverse effects of water on stability, viscosity, pH,

corrosiveness and other liquid properties in the pyrolysis product [16]. For this reason, the

treatment sludge that has dry content of 30 % ratio is dried with drying systems untill dryness

of the sludge reaches 80-90 %. After drying process, the dewatered sludge is fed into the

pyrolysis reactor and the pyrolysis process takes place. During the pyrolysis process, only dry

content of the dewatered sludge is used. At the end of the process, approximately 60 % of dry

content is converted into syngas. The rest of dry content (ash,dirt etc.) is sent to landfills.

Diagram [1]: Drying and pyrolysis processes diagram [5]

Calculations about Drying and Pyrolysis Processes

As an example, it is assumed that the sewage sludge (has 25 % dry solid) is dried in a

solar drying system untill dryness of the sludge reaches 80 %. After drying process, pyrolysis

process occurs. To calculate the vaporized water amount;

Assumption: The plant discharges 50 tons of sewage sludge per day. It means that this plant

discharges 18250 tons of sewage sludge per year.

For the sludge before drying process (25% dry content - 75% water content)

𝐴𝑛𝑛𝑢𝑎𝑙 𝑠𝑒𝑤𝑎𝑔𝑒 𝑠𝑙𝑢𝑑𝑔𝑒 𝑎𝑚𝑜𝑢𝑛𝑡 = 50 𝑡𝑜𝑛𝑠

𝑑𝑎𝑦∗ 365

𝑑𝑎𝑦𝑠

𝑦𝑒𝑎𝑟= 18250 𝑡𝑜𝑛𝑠

𝑦𝑒𝑎𝑟⁄

𝐴𝑛𝑛𝑢𝑎𝑙 𝑑𝑟𝑦 𝑐𝑜𝑛𝑡𝑒𝑛𝑡 𝑜𝑓 𝑡ℎ𝑒 𝑠𝑙𝑢𝑑𝑔𝑒 = 18250 𝑡𝑜𝑛𝑠

𝑦𝑒𝑎𝑟∗

25

100= 4562,5 𝑡𝑜𝑛𝑠

𝑦𝑒𝑎𝑟⁄

𝐴𝑛𝑛𝑢𝑎𝑙 𝑤𝑎𝑡𝑒𝑟 𝑐𝑜𝑛𝑡𝑒𝑛𝑡 𝑜𝑓 𝑡ℎ𝑒 𝑠𝑙𝑢𝑑𝑔𝑒 = 18250 − 4562,5 = 13687,5 𝑡𝑜𝑛𝑠𝑦𝑒𝑎𝑟⁄

For the sludge after drying process (80% dry content – 20% water content)

The annual dry content of the sludge was calculated as 4562,5 tons/year. After drying

process, the amount of solid content is the same but the percentage of it is changed from 25%

to 80%. So;

𝐴𝑛𝑛𝑢𝑎𝑙 𝑑𝑟𝑦 𝑐𝑜𝑛𝑡𝑒𝑛𝑡 𝑜𝑓 𝑡ℎ𝑒 𝑠𝑙𝑢𝑑𝑔𝑒 = 4562,5 𝑡𝑜𝑛𝑠𝑦𝑒𝑎𝑟⁄

𝐴𝑛𝑛𝑢𝑎𝑙 𝑠𝑙𝑢𝑑𝑔𝑒 𝑎𝑚𝑜𝑢𝑛𝑡 =4562,5 𝑡𝑜𝑛𝑠

𝑦𝑒𝑎𝑟⁄

80100⁄

= 5703,1 𝑡𝑜𝑛𝑠𝑦𝑒𝑎𝑟⁄

𝐴𝑛𝑛𝑢𝑎𝑙 𝑤𝑎𝑡𝑒𝑟 𝑐𝑜𝑛𝑡𝑒𝑛𝑡 𝑜𝑓 𝑡ℎ𝑒 𝑠𝑙𝑢𝑑𝑔𝑒 = 5703,1 − 4562,5 = 1140,6 𝑡𝑜𝑛𝑠𝑦𝑒𝑎𝑟⁄

According to these calculations;

𝑇ℎ𝑒 𝑣𝑎𝑝𝑜𝑟𝑖𝑧𝑒𝑑 𝑤𝑎𝑡𝑒𝑟 𝑎𝑚𝑜𝑢𝑛𝑡 𝑑𝑢𝑟𝑖𝑛𝑔 𝑑𝑟𝑦𝑖𝑛𝑔 𝑝𝑟𝑜𝑐𝑒𝑠𝑠

= 𝑇ℎ𝑒 𝑎𝑛𝑛𝑢𝑎𝑙 𝑤𝑎𝑡𝑒𝑟 𝑐𝑜𝑛𝑡𝑒𝑛𝑡 𝑏𝑒𝑓𝑜𝑟𝑒 𝑑𝑟𝑦𝑖𝑛𝑔

− 𝑇ℎ𝑒 𝑎𝑛𝑛𝑢𝑎𝑙 𝑤𝑎𝑡𝑒𝑟 𝑐𝑜𝑛𝑡𝑒𝑛𝑡 𝑎𝑓𝑡𝑒𝑟 𝑑𝑟𝑦𝑖𝑛𝑔

𝑇ℎ𝑒 𝑣𝑎𝑝𝑜𝑟𝑖𝑧𝑒𝑑 𝑤𝑎𝑡𝑒𝑟 𝑎𝑚𝑜𝑢𝑛𝑡 = 13687,5 − 1140,6 = 𝟏𝟐𝟓𝟒𝟔, 𝟗 𝒕𝒐𝒏𝒔𝒚𝒆𝒂𝒓⁄

Assumption: Average solar vaporization amount is assumed as 1000 L/m2*year. It means that

1 m3/m2 of water vaporizes in each year. So;

𝐴𝑟𝑒𝑎 𝑜𝑓 𝐷𝑟𝑦𝑖𝑛𝑔 𝐵𝑒𝑑 =12546,9 𝑡𝑜𝑛𝑠

𝑦𝑒𝑎𝑟⁄

1 𝑚3

𝑚2 ∗ 𝑦𝑒𝑎𝑟⁄= 12546,9 𝑚2

As a result of these calculations, 6 drying beds are sufficient and each of them has length

of 140 m and width of 15 m.

Length = 140 m

Width = 15 m

Number of bed = 6

CUMULATIVE ENVIRONMENTAL IMPACT ASSESSMENT

Cumulative Impacts

Cumulative impacts are the combined impacts of a single activity or multiple activities.

The individual impacts from a single development may not be significant on their own but when

combined with other impacts, those effects could become significant [21].

Cumulative effects have been defined as “the net result of environmental impact from a

number of projects and activities” [21].

Cumulative effects can occur from the following situations:

~ Combined impacts of a plan with impacts of another plan, affecting the same

receptor.

Diagram [2]: Diagram of cumulative impacts of plans [21]

~ Interaction of policies within a plan on the same receptor.

~ Interaction of impacts from proposals within a plan affecting the same receptor.

[21]

Cumulative effects occur when there is:

~ Spatial crowding or temporal overlap between plans, proposals and

actions

~ Repeated removal or addition of resources due to proposals and actions

~ Repeated alteration of the landscape in the plan area

[21]

Some examples of cumulative impacts include the following:

Effects on ambient conditions such as the incremental contribution of

pollutant emissions in an airshed.

Increases in pollutant concentrations in a water body or in the soil or

sediments, or their bioaccumulation.

Reduction of water flow in a watershed due to multiple withdrawals.

Increases in sediment loads on a watershed or increased erosion

[22]

Multiple and successive environmental and social impacts from existing developments,

combined with the potential incremental impacts resulting from proposed and/or anticipated

future developments, may result in significant cumulative impacts that would not be expected

in the case of a stand-alone development [22].

Cumulative Environmental Impact Assessment (CEIA) and Management

CEIA is the process of (a) analyzing the potential impacts and risks of proposed

developments in the context of the potential effects of other human activities and natural

environmental and social external drivers on the chosen VECs (Valued Environmental and

Social Components) over time, and (b) proposing concrete measures to avoid, reduce, or

mitigate such cumulative impacts and risk to the extent possible [22].

The key analytical task is to discern how the potential impacts of a proposed

development might combine, cumulatively, with the potential impacts of the other human

activities and other natural stressors such as droughts or extreme climatic events. VECs are

immersed in a natural ever-changing environment that affects their condition and resilience.

VECs are integrators of the stressors that affect them [22].

VECs are environmental and social attributes that are considered to be important in

assessing risks; they may be:

~ physical features, habitats, wildlife populations (e.g., biodiversity),

~ ecosystem services,

~ natural processes (e.g., water and nutrient cycles, microclimate),

~ social conditions (e.g., health, economics), or

~ cultural aspects (e.g., traditional spiritual ceremonies). [22]

Good CEIA focuses on understanding whether cumulative impacts will affect the

sustainability or viability of a VEC as indicated by the predicted condition of the VEC.

Consequently, the significance of cumulative impacts is judged in the context of thresholds or

limits of acceptable change, within which the VEC condition is considered to be acceptable but

beyond which further change in condition is not acceptable [22].

Cumulative Environmental Impact Assessment (CEIA) Process

The main stages of CEIA is shown in the diagram below;

Diagram [3]: Steps of Cumulative Environmental Impact Assessment [21]

WASTEWATER TREATMENT DESIGN

Biological Nutrient Removal Activated Sludge (BNRAS) Systems

Nitrogen and phosphorus are limiting nutrients in most freshwater systems and cause

eutrophication. Recently, interest has been developed in the use of biological, rather than

chemical processes for phosphorus and nitrogen removal from wastewater [23].

Biological nitrogen removal is a two step process including ammonia oxidation by

nitrification, followed by reduction of nitrogen oxides to nitrogen gaseous compounds by

denitrification. In other words, a sequence of oxic and anoxic conditions is required for

nitrogen removal [23].

Biological phosphorus removal from wastewaters exploits the potential of some

microorganisms, known as Phosphate Accumulating Organisms (PAOs), to accumulate

phosphate in excess of their normal metabolic requirements under aerobic conditions.

In metabolism of PAO under anaerobic condition, PAO uptakes excess phosphorus and

stores it as polyphosphate in the cell mass using the energy from the heterotrophic oxidation of

organic materials (BOD/COD). If PAO is exposed to anaerobic condition, where little

molecular and combined oxygen molecules are available, it obtains energy from the hydrolysis

of the accumulated polyphosphate to uptake volatile fatty acids (VFA) as poly-

hydroxyalkanoates (PHA) and poly-hydroxybutyrates (PHB) [24].

Diagram [4]: Metabolism of PAO under anaerobic conditions [24]

Diagram [5]: Metabolism of PAO under aerobic conditions [24]

The University od Capetown (UCT) Method for Enhanced Biological

Phosphorus Removal

One of the most commonly applied BNRAS methods for urban wastewater treatment

relies on the University of Cape Town (UCT) concept [23].

The UCT process was designed to minimize the effect of nitrate to the anaerobic contact

zone, which is crucial for maintaining truly anaerobic conditions and thus, allowing biological

phosphorus release. In fact, the higher the phosphorus concentration released in the anaerobic

tank, the higher is the phosphorus concentration taken up under aerobic conditions [23].

Diagram [6]: UCT process diagram [25]

The Modified University of Capetown (Modified UCT) Process

It modifies the UCT process with the first anoxic zone designed to reduce only the

nitrate nitrogen in the return activated sludge. The second anoxic zone is designed for a much

higher quantity of nitrate nitrogen removal as mixed liquor is recycled to it from the nitrification

zone [26].

Diagram [7]: Modified UCT process diagram [25]

REFERENCES

1. http://www.envis.com.tr/en/index.html (05.10.2015)

2. http://www.envis.com.tr/en/services.html (05.10.2015)

3. Leszczynski S. , Pyrolysis of Sewage Sludge and Municipal Organic Waste, 2006, page

257

4. https://en.wikipedia.org/wiki/Sewage_sludge (04.10.2015)

5. Envis Çevre ve Enerji Sistemleri Araştırma Geliştirme LTD. ŞTİ. , Arıtma Çamurlarının

Nihai Uzaklaştırılmasında Düzenli Depolama ve Enerji Kazanımı Alternatiflerinin

Değerlendirilmesi, 2015.

6. http://www.grad.hr/rescue/state-of-the-art/sastav-spaljenog-mulja-pepela/ (04.10.2015)

7. http://www.veoliawater2energy.com/en/water2energy-services/invest-in-renewable-

energy/ (30.08.2015)

8. http://www.thermo-system.com/en/products/thermal-drying-of-sewage-sludge/

(04.10.2015)

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