DEPARTMENT OF CIVIL, ENVIRONMENTAL & GEOMATIC ENGINEERING
MSc DISSERTATION SUBMISSION
STUDENT NAME: CHRYSOULA SFYNIA
PROGRAMME: MSC ENVIRONMENTAL SYSTEMS ENGINEERING
SUPERVISOR: DR. LUIZA CINTRA CAMPOS
DISSERTATION TITLE:
URBAN WASTEWATER REUSE - TREATMENT TECHNOLOGIES & COST
I confirm that I have read and understood the guidelines on plagiarism, that I understand the meaning of plagiarism and that I may be penalised for submitting work that has been plagiarised.
I declare that all material presented in the accompanying work is entirely my own work except where explicitly and individually indicated and that all sources used in its preparation and all quotations are clearly cited.
Should this statement prove to be untrue, I recognise the right of the Board of
Examiners to recommend what action should be taken in line with UCL’s regulations.
Signature: Date: 06/09/2013
Urban Wastewater Reuse - treatment technologies and costs
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EXECUTIVE SUMMARY
Arup and University College London’s (UCL), Civil, Environmental and Geomatic
Engineering Department, have launched a joint project for the design configuration of
urban water reuse networks.
This master thesis is part of the venture “Water Reuse Networks Project” and of the
ongoing research in the field with regards to wastewater treatment options for reuse
and their costs. The present study “Urban Wastewater Reuse – treatment
technologies and costs” involves a detailed review of the current trends and reuse
applications with emphasis on possible efficient scenarios.
The project is concerned how increasing pressures on the water environment
necessitate the implementation of sustainable water management practices and
regimes. It is argued that this can be achieved through the design, the application
and the optimal operation of water reuse infrastructure and management of both
supply and demand.
Wastewater reuse can be a tool of rational management of water resources. The
reasoning of the appropriate reuse of treated municipal or industrial wastewater has
intrinsic benefits associated with saving water resources and producing
environmental and economic benefits. However, the reuse of wastewater requires a
comprehensive and rational planning, taking into account possible risks and
limitations.
This study summarizes the current trends concerning urban wastewater reuse
focusing in the case of greywater reclamation. In addition, it outlines the objectives
and scope of the collaborative project. Overall, the report consists of 7 Chapters, a
glossary, an appendix and the appropriate referencing.
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The study reviews the following main issues (Chapter 4-6):
● Legislation of urban wastewater reuse
● Available technologies for greywater treatment for reuse
● Costs for these treatment schemes
Chapter 7 introduces the reader to the planning of water reuse networks. This
Chapter analyses four different possible greywater treatment scenarios that can be
implemented and have proved to be effective. These scenarios have been formed
after extensive research in literature, case studies and communication with
wastewater treatment specialists.
Finally, another significant component of this project is the discussion parts at the
end of each of the core chapters that illustrate briefly the main findings and comment
on the outcomes.
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ACKNOWLEDGEMENTS
First and foremost, I would like to thank my supervisor Dr. Luiza Cintra Campos for
giving me the opportunity to carry out this project as my master thesis together with
her invaluable guidance and support throughout the whole period. Her great
experience and professionalism inspired me to progress in my research and further
explore my capabilities. Secondly, I am also thankful to Eleni Georgiou for her
contribution and feedback review for this thesis.
Special thanks to ARUP and the WReN group for all the confidence, advice and
flexibility I was given, which ensured the smooth completion of the first part of the
collaborative project. I would also like to thank the wastewater treatment companies
that kindly provided technical and financial information of their technologies.
Last but not least, I would like to thank the “family” we created in London for all the
unconditional and endless support and help during my studies.
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To the inspiration in my life,
My father, Constantinos Sfynias,
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TABLE OF CONTENTS
EXECUTIVE SUMMARY ................................................................................................. 1
ACKNOWLEDGEMENTS ................................................................................................ 3
1. INTRODUCTION .................................................................................................... 9
1.1 Water Scarcity & Urbanization................................................................... 10
1.2 Water Use around the World ..................................................................... 12
2. AIMS & OBJECTIVES .......................................................................................... 16
3. BACKGROUND RESEARCH .................................................................................. 17
3.1 Water Reclamation & Reuse – A Sustainable Solution .............................. 18
3.2 Challenges of Water & Wastewater Reuse................................................ 19
3.3 Advantages of Water Reuse ..................................................................... 21
3.4 Types of Water Reuse Applications .......................................................... 22
3.5 Case Studies ............................................................................................. 24
4. WASTEWATER REUSE FRAMEWORK ................................................................... 28
4.1 Regulations by International Organizations ............................................... 29
4.2 Regulations by the State of California ....................................................... 38
4.3 Regulations by Other Countries ................................................................ 40
5. WASTEWATER TREATMENT FOR REUSE .............................................................. 44
5.1 Wastewater for Reuse – Greywater .......................................................... 46
5.2 Greywater Treatment Stages .................................................................... 50
5.3 Discussion................................................................................................. 71
6. WATER REUSE & COSTS .................................................................................... 72
6.1 Capital Costs ............................................................................................. 73
6.2 Operation & Maintenance Costs ................................................................ 82
6.3 Discussion................................................................................................. 86
7. SETTING UP WATER REUSE NETWORKS ............................................................. 87
7.1 Treatment Scenarios ................................................................................. 91
7.2 Discussion............................................................................................... 100
8. CONCLUSIONS & RECOMMENDATIONS .............................................................. 102
REFERENCES ......................................................................................................... 104
APPENDIX .............................................................................................................. 111
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LIST OF FIGURES
Figure 1.1: The Percent of Population with access to improved Water Sources (%) ............. 10
Figure 1.2: The Percent of Population with access to improved Sanitation (%) ..................... 11
Figure 1.3: Map of Worlds Water Stress in 1995 and in 2020 ................................................ 11
Figure 1.5: Water Use by Sector in European Countries ........................................................ 13
Figure 1.6: Agricultural water withdrawal as a percent of total withdrawal (%) ....................... 14
Figure 1.7: Industrial water withdrawal as a percent of total withdrawal (%) .......................... 14
Figure 1.8: Municipal water withdrawal as a percent of total withdrawal (%) .......................... 15
Figure 3.1: Water Reuse Applications .................................................................................... 22
Figure 3.2: Water Reuse Projects in Europe (Size & Application) ......................................... 27
Figure 4.1: California’s Warning Sign for Recycled Water ...................................................... 39
Figure 5.1: Treatment Technologies for Any Type of Reuse ................................................. 45
Figure 5.2: Sources of Household Wastewater ...................................................................... 46
Figure 5.3: Greywater Categories ........................................................................................... 47
Figure 5.4: Typical Flow Diagram of Basic System – Coarse Filtration ................................. 53
Figure 5.5: Typical Flow Diagram of Basic System – Sedimentation ..................................... 54
Figure 5.6: Typical Flow Diagram of Physical System – Sand Filter ...................................... 55
Figure 5.7: Typical Flow Diagram of Physical System – Membranes .................................... 57
Figure 5.8: Typical Flow Diagram of Chemical System – Coagulation .................................. 58
Figure 5.9: Typical Flow Diagram of Chemical System – Photobioreactor ............................ 60
Figure 5.10: Typical Flow Diagram of Biological System – SBR ............................................ 62
Figure 5.11: Typical Flow Diagram of Biological System – MBR ........................................... 64
Figure 5.12: Typical Flow Diagram of Biological System – RBC ........................................... 66
Figure 5.13: Typical Flow Diagram of Extensive Systems–Constructed Wetlands ............... 70
Figure 6.1: Typical Water & Drainage Pipelines ..................................................................... 80
Figure 6.2: Typical Pumping Station....................................................................................... 81
Figure 6.3: Breakdown of Running costs of a Wastewater Treatment Plant ......................... 82
Figure 7.1: Water Network Configuration ............................................................................... 89
Figure 7.2: Summary of Treatment Scenarios for Greywater Reclamation ............................ 90
Figure 7.3: Flow Diagram of Scenario 1- Constructed Wetland ............................................. 92
Figure 7.4: Flow Diagram of Scenario 2- RBC ....................................................................... 94
Figure 7.5: Flow Diagram of Scenario 3- SBR ........................................................................ 96
Figure 7.6: Flow Diagram of Scenario 4- MBR ........................................................................ 98
Figure 7.7: Diagram of Scenarios Costs per Equivalent Population ..................................... 101
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LIST OF TABLES
Table 3.1: Categories of Reclamation and Reused Water ...................................................... 23
Table 3.2: Worldwide Wastewater Reuse Projects in chronological order from 1912-1989 ... 24
Table 4.1: Directive Limits for Monitoring Parameters in Agriculture and Aquaculture ........... 31
Table 4.2: Health-based Targets & Helminth Reduction Targets from WHO.......................... 32
Table 4.3: Health Based Targets for Water Reuse by WHO ................................................... 33
Table 4.4: Suggested Guidelines for Urban & Agricultural Reuse .......................................... 35
Table 4.6: Suggested Guidelines for Indirect Potable Reuse ................................................. 37
Table 4.7: California’s Title 22 Pathogen Limits ...................................................................... 39
Table 4.8: Water Reuse Practices & Criteria in European Countries...................................... 41
Table 4.9: Existing Water Reuse Criteria in European Countries ........................................... 41
Table 4.10: Existing Water Reuse Criteria in the UK .............................................................. 42
Table 4.11: Reuse Criteria in Japan ........................................................................................ 43
Table 5.1: Average Greywater Yield & Demand ..................................................................... 48
Table 5.2: Summary of Greywater Characteristics .................................................................. 49
Table 5.3: Removal of various components using Membranes .............................................. 56
Table 6.1: Cost of Basic Systems ............................................................................................ 74
Table 6.2: Cost of Physical Systems ....................................................................................... 75
Table 6.3: Cost of Chemical Systems ..................................................................................... 76
Table 6.4: Cost of Biological Systems ..................................................................................... 77
Table 6.5: Cost of Extensive Systems ..................................................................................... 78
Table 6.6: Unit Cost of Water Distribution &Transmission Pipelines ...................................... 80
Table 6.7: Unit Cost of Water Transmission Pumping Station ................................................ 81
Table 6.8: Cost of Microbiological Monitoring Analysis ........................................................... 84
Table 6.9: Cost of Physicochemical Monitoring Analysis ........................................................ 85
Table 7.1: Summarized table for Scenario 1 ........................................................................... 93
Table 7.2: Summarized table for Scenario 2 ........................................................................... 95
Table 7.3: Summarized table for Scenario 3 ........................................................................... 97
Table 7.4: Summarized table for Scenario 4 ........................................................................... 99
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GLOSSARY
CFU Colony Forming Unit
DIY Do It Yourself
EU European Union
FAO Food and Agriculture Organisation
FC Faecal Coliforms
GAC Granular Activated Carbon
HRT Hydraulic Retention Time
MF Microfiltration
NF Nanofiltration
OECD Organisation for Economic Co-operation and Development
RO Reverse Osmosis
TC Total Coliforms
TDS Total Dissolved Solids
TSS Total Suspended Solids
UF Ultrafiltration
UN United Nations
UNDESA United Nations/Department of Economic and Social Affairs
UV Ultraviolet
WCED World Commission on Environment and Development
WHO World Health Organisation
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1. INTRODUCTION
Water has a significant importance in the creation, preservation and the development
of life in our planet and human civilization. On July 2010, through Resolution 64/292,
the United Nations recognized the “human right to water and sanitation” and
acknowledged that “clean drinking water and sanitation are essential to the
realization of all human rights” (UNDESA, 2010). Large quantities of fresh water are
needed daily in many parts of the world for domestic, agricultural, industrial use
(Eltawil, 2009).
Regarding the current situation, almost a quarter of the world’s population suffers
from inadequate fresh water supply (Fiorenza, 2003). Because of the impending
global population growth (especially in developing countries), the situation is
expected to become even worse in the next two decades (Eltawil, 2009).
The current water crisis is not subjected only to scarcity, but also to difficulties in
accessibility and unequal distribution. According to the latest statistical information
from the WHO/UNICEF Joint Monitoring Program for Water Supply and Sanitation
(JMP), released in 2013, 36% per cent of the of the world’s population, approximately
2.5 million people lack access to proper sanitation amenities and 768 million people
still consume unsafe drinking water. This dire situation results in thousands of
deaths and leads to “impoverishment and diminished opportunities” for thousands
more (WHO, 2013).
Furthermore, the pollution and uncontrolled exploitation of groundwater aquifers and
surface waters for anthropogenic activities have led to a reduction of both quantity
and quality of the available natural water resources (WHO, 2013).
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1.1 WATER SCARCITY & URBANIZATION
The planet could be called the “blue planet”, since the two thirds of its surface are
covered by water. According to several studies (Gleick, 2006), the total water volume
reaches 1.3 billion cubic kilometres. From this amount, 97% is salt water (sea), 2% is
trapped in glaciers and icebergs and the majority of the remaining 1% is bound into
great depths. So, less than 1% of fresh water is available for human consumption.
Despite the technological development, the stocks of renewable fresh water will be
only 0.3% of global water (Eltawil, 2009).
Increasingly in recent years, the problem of water shortage is becoming an actuality.
The views can be characterised as ranging from extremely scaremongering to
extremely optimistic and reassuring.
The maps below (Figures 1.1, 1.2) were published in 2013 by the United Nations and
highlight the accessibility of the population to improved water sources and sanitation,
respectively.
FIGURE 1.1: THE PERCENT OF POPULATION WITH ACCESS TO IMPROVED WATER SOURCES (%)
(FAO, 2012)
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FIGURE 1.2: THE PERCENT OF POPULATION WITH ACCESS TO IMPROVED SANITATION (%)
(FAO, 2012)
According to estimates, in 2025, when the Earth's population will be approaching or it
will have exceeded 10 billion people, one in three inhabitants of the planet, - 3.5
billion people- will live in water scarcity conditions or will be directly threatened by it.
This trend is being illustrated in Figure 1.3, which shows the freshwater scarcity of
1995 and that of 2025.
FIGURE 1.3: MAP OF WORLDS WATER STRESS IN 1995 AND IN 2025 (WMO, 1996)
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In addition, water is projected to become a cause of conflicts in neighbouring
countries, since about 40% of Earth's inhabitants live in more than 200 transnational
river basins, from which they share water resources (Eltawil, 2009).
According to all the above statistics and owing to the foreseen growth of the world‘s
population (especially in the developing countries), the problem is expected to
become more and more critical over the next two decades (Eltawil, 2009), bringing
water shortage to the top of the international agenda.
1.2 WATER USE AROUND THE WORLD
Large quantities of fresh water are needed every day in many parts of the world for
domestic, agricultural, industrial use (Eltawil, 2009). However, the distribution of
water in these three activities depends on the extent and type of development in
every country. At the same time it is influenced by both the climatic conditions and
the type of crops cultivated, which determine the irrigation requirements of the
country.
FIGURE 1.4: TYPICAL BREAKDOWN OF FRESHWATER USE (FAO, 2012)
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Worldwide, it is estimated that 70% of fresh water is consumed for irrigation needs
(FAO, 2012), but in countries like India, Mexico, Iran and Greece the figure is even
higher (FAO, 2013). In Japan, agriculture does not contribute significantly to the
economy of the country but the amount of water needed for agricultural use is vast as
all of its crops are based on irrigation. The different allocation of water use which
characterizes the U.S., Poland, UK and Germany’s irrigation policies not only
indicates greater water consumption by the industry, but also that the agriculture is
depended on the rainfalls.
FIGURE 1.5: WATER USE BY SECTOR IN EUROPEAN COUNTRIES (Aquarec, 2006)
In industrially developed countries, such as England and Germany, the largest
percentage of disposable water is being distributed into the industry (Figure 1.5).
Conversely, in countries where the developed agriculture is based on irrigated crops,
more water goes to agriculture. A visual impression is provided in the following maps
(Figure 1.6, 1.7) where it is shown the amount of water withdrawn by the agricultural
and the industrial sector, respectively.
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FIGURE 1.6: AGRICULTURAL WATER WITHDRAWAL AS A PERCENT OF TOTAL WITHDRAWAL (%)
(FAO, 2012)
FIGURE 1.7: INDUSTRIAL WATER WITHDRAWAL AS A PERCENT OF TOTAL WITHDRAWAL (%)
(FAO, 2012)
Generally, the consumption of water for domestic use is proportional to the living
standards of a country. Higher living standards and higher income per person implies
higher consumption of water (larger homes, better conditions of cleanliness and
hygiene, lifestyle change, etc.). However, this is not the rule, as in modern countries
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where the state and the communities have realised the importance of saving water
resources, serious efforts have been made to reduce the use of household level. This
also follows from the calculations of FAO, which states that the U.S. consumes far
more water for domestic uses (210 m3/person per year), whereas the United
Kingdom is an exception and consumes 35 m3/person per year (FAO, 2013). A map
of the municipal water withdrawal globally is displayed below in Figure 1.8.
FIGURE 1.8: MUNICIPAL WATER WITHDRAWAL AS A PERCENT OF TOTAL WITHDRAWAL (%)
(FAO, 2012)
According to Shiklomanov (1999), the three main sectors mentioned that consume
water will become more demanding in the near future. Specifically, the percentage of
irrigated surfaces is projected to increase by one third in 2010 and by 50% by 2025,
while water for industrial and domestic use is growing at twice the rate of the
population growth. The water consumption is observed that since 1900 has sevenfold
in total, as the water demand doubles every 20 years (Shiklomanov, 1999).
Under these circumstances, an increased trend towards the reclamation and reuse of
wastewater is observed around the world as a means to reduce current or future
water scarcity.
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2. AIMS & OBJECTIVES
Arup and University College London (UCL) have entered into a collaborative project
to investigate and develop a methodology for the design configuration of wastewater
reuse networks of sub-municipal scale. This project aims to provide an optimum
configuration of these networks, taking into consideration the input and output water
quality, the treatment schemes and their costs.
“Urban Wastewater Reuse – treatment technologies and costs” is a review of the
water reuse framework and the current urban wastewater treatment options
combined with the costs involved that can be used as a guide for water reuse
network designing. This study has three overarching aims:
● Assess the urban wastewater treatment technologies
● Evaluate the economic factor of wastewater technologies
● Develop efficient possible wastewater treatment scenarios
The objectives have been accomplished with the following:
● Collection and recording of the existing water reuse framework
● Understanding of the wastewaters nature (quality and quantity)
● Determination of water reuse applications and final recipients
● Evaluation of existing wastewater treatment systems
● Calculation of the wastewater treatment costs (literature and companies)
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3. BACKGROUND RESEARCH
The continuous population growth, pollution and the continuing deterioration of both
surface and groundwater aquifers, the unequal distribution of water resources and
periodic droughts have necessitated the exploration and development of new water
sources (Metcalf & Eddy, 1991). In industrialized countries the problems associated
with ensuring water supply and disposal of urban and industrial waste have been
intensified. In contrast, in developing countries and especially in arid or semi-arid
regions, there is a need for affordable technology in order to increase the exploitable
quantities of water, along with the protection of the environment and the natural
resources.
It is estimated that the use of "marginal" water could decisively contribute to the
sustainable use of water resources through the implementation of integrated water
resources management plans, where the recycled water will be considered an
essential component for increasing the availability and control of pollution (Angelakis
et al., 2002).
In the path for water sustainability, a key concern of the international community is
finding alternative water sources. In this direction, the practice of reclaiming and
reusing municipal waters wins more territory and is the objective of several academic
projects. Thus, the necessity for establishing criteria for wastewater recycling and
reuse has been widely recognised in many countries of the world. Development of
criteria to minimize the microbial health risks associated with wastewater recycling
and reuse should take into account other water related exposures such as through
the food-chain, drinking water and contact with water in recreational areas.
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3.1 WATER RECLAMATION & REUSE – A SUSTAINABLE SOLUTION
The new environmental practice around the world is based on the five «Rs» which
represent the basic principles of environmental protection; Reclamation, Recycle,
Reuse, Renewable and Reduce (Paranichianakis et al, 2009). Under this prism, a
few hundred thousand cubic meters of liquid waste generated worldwide could be
reclaimed, reused, thus creating a form of recycling, which will result in the reduction
of the amount of fresh water used in various fields, creating a renewable source of
water.
In this context, reclaimed and reusable water promotes an alternative reliable water
source. “Reusing treated wastewater basically compresses the hydrological cycle
from an uncontrolled global scale to a controlled local scale” (Durham et al., 2005).
Water reclamation and reuse: Definitions (Durham et al., 2005)
Reclaimed water: Wastewater that has been treated to meet specific water quality standars with
the intention to be used for a series of purposes.
Water Reuse: The use of appropriately treated wastewater.
Non-potable reuse (NPR): The use of reclaimed water for purposes other than drinking water
(e.g. irrigation).
Direct potable reuse (DPR): The use of reclaimed water directly into drinking water after
advanced treatment.
Greywater: Used water discharged from homes, business, industry, and agricultural facilities.
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3.2 CHALLENGES OF WATER & WASTEWATER REUSE
The effective planning and operation of water reuse projects as well as the safe use
of treated wastewater implies the understanding of the challenges of this practice.
Some of these issues are briefly addressed below (USEPA, 2004; Bixio, 2006).
Establishment of criteria
An important issue is the need for the establishment of a legislative framework that
enhances water and wastewater reuse. This framework should take into
consideration all risks that may arise (health and environment), including
microbiological and physicochemical quality parameters and proposing strategies for
motivation and public acceptance.
Public health protection
The reclaimed and treated water should not pose any risk to public health. So in this
direction, regulations set limits on the amount of pathogenic microorganisms. Also
special emphasis should be given to the frequent monitoring of the water quality
reused. Finally, some guidelines suggest protective measures to be in place for the
safety of the public that may be exposed directly or indirectly with the treated water
(see Chapter 4).
Environmental cost
The reuse of wastewater should be done with respect to the natural environment.
The protection of ecosystems, the flora and fauna, the avoidance of further
degradation of the natural resources are main targets. The calculation of the
environmental footprint and the potential impact would be very useful at a preliminary
level.
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Economic factors
The economic factor is one of the most important challenges in the issues of water
and wastewater reuse. Financing such projects is possibly the main obstacle for the
wider use of treated water. However, researchers are working on new technologies
that may reduce the capital, the operation and the maintenance costs.
Public acceptance & opinion
The authorities responsible for the distribution of reclaimed water (local communities,
councils, organizations) should not only make sure of the safety of the provided water
but also need to build trust and credibility with the public. This can be achieved with
water reuse campaigns, educational programs or further motives.
Aesthetics
In some cases and also for aesthetic reasons, reusable water should be colourless
and odourless (e.g. for irrigation in gardens or parks, recreation areas). Also,
attention should be given in harmonising the treatment process, chosen for the
wastewater treatment, with the landscape and the environment.
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3.3 ADVANTAGES OF WATER REUSE
The reclamation and reuse of treated wastewater is shown to have significant
advantages (Durham, 2005):
i. The development of a new water resource
ii. The protection of water resources, particularly in coastal areas with saltwater
intrusion in aquifers
iii. The policy development of water resources, with emphasis on preserving
resources and the environment
iv. The protection of public health and the environment
v. The reduction of the water cost
vi. The reliability of water supply, specifically in rural areas
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3.4 TYPES OF WATER REUSE APPLICATIONS
Throughout the centuries, water and wastewater reuse has developed from a simple
disposal method of polluted water to an advanced process of reclamation providing
agricultural, industrial, urban and even domestic reuse.
The most common form of reuse is for non-potable purposes such as agricultural and
urban water supply, for industrial uses (e.g. cooling), for fire fighting and others (Bixio
et al., 2006). These require adequate treatment of the effluent in order to correspond
to quality obligations upon the intended use. A schematic description of the
applications is shown in Figure 3.1 (Asano, 1989).
FIGURE 3.1: WATER REUSE APPLICATIONS (Asano, 1989)
Water reuse can be direct or indirect. In recent years it has attracted more and more
interest in the indirect reuse field even for indirect potable use (Leverenz et al., 2011).
In the first case, water is reclaimed from wastewater transported from the treatment
units for irrigation of agricultural land and recreational areas without the mediation of
natural water sources or other aquatic formations. In the second case, indirect water
reuse happens after the reclaimed water is mixed with surface or underground water
resources that can be used as drinking water sources (Leverenz et al., 2011).
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The improvements in technology for wastewater and drinking water treatment have
ensured that a range of new and emerging challenges from both microbial and
chemical contaminants are met. Hence, the indirect recycling developed in many
parts of the world for many years is demonstrated to be safe (UKWIR 2004).
Table 3.1 summarizes the fields for reclaimed water use and the applications that
treated water can have in these fields.
TABLE 3.1: CATEGORIES OF RECLAMATION AND REUSED WATER (USEPA, 2004)
Categories Characteristics
Agricultural use
Irrigation of food crops Other type of irrigation livestock, plant nurseries, lawn
Urban & Recreational use
Irrigation in areas open to the public: parks, schools, fountains, fire protection, cooling, toilet cleaning Irrigation in areas with limited access: golf courts, cemeteries, motorways Restricted use fishing, boating
Industrial use cooling, boiler feed, process water
Environmental use maintain / increase watercourses flow, strengthening natural wetlands, aquaculture, enrichment of underground aquifers
Domestic use garden irrigation, car washing, toilet flushing, cooling
Drinking use
Direct
Indirect mixing with surface or underground drinking water sources
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3.5 CASE STUDIES
The reuse of wastewater, particularly for irrigation, has been practiced for centuries
and seems to have originated from the ancient Greek civilizations (Angelakis et al.,
2005). In Europe, the use of sullage was a common practice in Germany since the
16th century (De Turk et al., 1978) and in England since the 18th century (Wolman,
1977). In USA the reuse of water was reported to have started in 1870 (Rafter, 1899).
In addition, increased interest in the use of recycled water for agricultural purposes
began to occur in developed countries during the decade 1980-1990 mainly due to
the capabilities and advantages that it presents. Table 3.2 shows some big scale
reclamation and reuse of wastewater projects in chronological order of development.
TABLE 3.2: WORLDWIDE WASTEWATER REUSE PROJECTS IN CHRONOLOGICAL ORDER FROM 1912-1989 (Angelakis et al., 1995)
Year Location Capacity
[m3/d]
Water Reuse Type
1912 Golden Gate Park,
San Francisco, USA
Landscape irrigation
Recreational ponds
(Metcalf & Eddy, 1991)
1926 Grand Canyon National
Park, Arizona, USA
Landscape irrigation
WC cleaning
Water cooling & heating
1929 City of Pomona, California,
USA
Landscape and garden irrigation
1942 City of Baltimore, Maryland,
USA
Cooling in metal and steel
industry (Bethlehem Steel
Company)
1960 City of Colorado springs,
Colorado,USA
Irrigation of golf courts, parks,
cemeteries & sidewalks
1961 Irvine Ranch Water District,
California,USA
60,000 Irrigation
Industrial use
WC cleaning in high buildings
1962 Soukra, Tunisia Irrigation of citrus fruits
Reduction of aquifer salinisation
1968 City of Windhoek,Namibia 21,000 Drinking water after mixing
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1969 City of Wagga Wagga,
Australia
10,000 Irrigation of public spaces
WC cleaning
1970 Sappi Pulp and Paper
group, Enstra,South Africa
Paper industry reuse
1975 Valley o river Salt, Arizona,
USA
10,000 Enrichment of aquifers with
effluents of secondary treatment
1976 Orange County Water
District,California, USA
200,000 Enrichment of aquifers with
direct injection (Nellor et al.,
1985)
1977 Dan Region Project,
Tel-Aviv, Israel
500,000 Enrichment of aquifers with
filtration ponds
1977 City of St. Petersburg,
Florida, USA
150,000 Irrigation of golf courts, parks,
school yards & public spaces
1984 Tokyo Metropolitan
Government, Japan
Large scale WC cleaning
1985 City of El Paso, Texas, USA 38,000 Enrichment of aquifers
1987 Monterey Regional Water
Pollution Control Agency
Monterey Wastewater,
California, USA
5,500 Irrigation of agriculture spaces
1989 Shoal haven Heads,
Australia
120,000 Irrigation of gardens
WC cleaning
1989 Consorci de la Costa Brava,
Girona,Spain
Irrigation of golf courts
The reclamation and reuse of wastewater seems to be a rapidly growing practice
mainly in arid and semi-arid regions. Similar projects of increased number and extent
are being programmed and implemented each year in several countries, particularly
in the U.S., Australia, Israel, Japan, the countries of the Maghreb and South Africa
(Paranichianakis et al., 2009).
Urban Wastewater Reuse - treatment technologies and costs
26
Because of its wealthy water resources and the existing differences between the
member countries, the EU has not particularly dealt so far with reclamation and reuse
water. However, the recent drought in Spain, Greece and other countries has posed
serious questions for the crucial issue of water recycling.
The most experienced country in reclamation and reuse of municipal wastewater is
the U.S.A. In the 70s, 216 million cubic meters of treated wastewater were annually
used (Asano & Tchompanoglous, 1991), while today this quantity has reached 555-
715 million cubic meters, which are distributed in more than 4,800 applications. Israel
has a similar experience (Fine et al., 2006), where it is estimated that 20% of the
needs are covered today with the use of reused wastewater. Moreover, Spain uses
recycled water for four types of uses: watering golf courses, irrigation of crops,
enhance aquifer of coastal areas to prevent the inflow of seawater and flow increase
of rivers in order to protect riverside ecosystems (Castro, 2010). In Italy today treated
wastewater is used to irrigate about 4000 hectares, whereas in Southern Italy the
irrigation areas that use untreated wastewater is undefined (Barbagallo, 2001).
Belgium is another example of water recycle for industrial purposes, as 38%
(expected 60% in near future) of the wastewater is used in industrial operations.
In the UK, treatment and recycling of waste water is limited. The recycled water is
used mainly to maintain river levels and protect their ecosystems. It is also used to
irrigate golf courses, parks and wash cars.
Figure 3.2 shows the geographic distribution of recorded water reuse projects in
conjunction with their capacity and reuse in applications. It is observed that the
majority of these projects are large scale (> 5∙106 m3/s) with applications in
agriculture.
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FIGURE 3.2: WATER REUSE PROJECTS IN EUROPE (SIZE & APPLICATION) (Bixio, 2006)
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4. WASTEWATER REUSE FRAMEWORK
A specific quality of water is required for every beneficial use of treated wastewater
effluent in order to minimize the potential public health risks and environmental
impacts. This ultimately determines the required treatment processes and
technologies to be implemented and the costs involved. Therefore, each type of
reuse requires special legislative criteria.
In recent years, the reclamation and reuse of wastewater effluents is a matter of
priority and one of the main activities of the water and wastewater managing bodies
at international, European and national level. Many countries in the developed world
and international organizations have established criteria for reclamation and reuse of
wastewaters effluents, including the U.S. (State of California), Israel, Australia, the
Food and Agriculture Organization of the UN (FAO), the World Health Organization
(WHO) and the Environmental Protection Agency of the USA (US EPA). However, it
is worth noting the absence of legislation in European Union on the required quality
for reuse of treated wastewater. A general reference to the issue is in the Directive
91/271 (EU, 1991) of the EU (Article 12 paragraph 1), while many European
countries have set their own criteria for the reuse of wastewater effluent.
The purpose of this chapter was to describe the established criteria for the reuse of
wastewater from countries and organizations within and outside the European Union.
Particular emphasis was given to cases in which the standards have been the basis
of several other criteria worldwide, such as the criteria by the World Health
Organisation, the State of California, the US EPA and Australia. Also, there are
comments on the prevailing trends and innovations in this field.
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4.1 REGULATIONS BY INTERNATIONAL ORGANIZATIONS
At international level, Directives and/or regulations for reclamation and reuse of
wastewater effluents is based on two main "philosophies"; that of WHO, FAO and
World Bank and that of the State of California. These are currently used as standards
to establish criteria for the reuse of treated wastewater, even though they incorporate
basic differences and to some extent they are contradictory.
The revised guidelines by WHO (WHO, 2006) provide a new method of risk
assessment for public health and the environment by setting quality levels similar to
that used for drinking water. In addition, the revised guidance of the Environment
Agency of the United States (US EPA, 2004) and California (State of California, 2004)
give particular emphasis to uses such as irrigation, the underground aquifers
enrichment and indirect potable uses.
● WHO
In 1973, World Health Organization proposed the first criteria and treatment methods
for various water reuse applications. The criteria established for the crop irrigation,
have been characterised as particularly severe (100 FC/100 ml for unrestricted
irrigation) and were based on the philosophy of “zero risk” (WHO, 1973).
In 1989 the organization reviewed the directive and issued a new set of criteria,
mainly of microbiological quality that emphasized on the type of irrigated crops.
Irrigation is separated into two categories with the following limits (WHO, 1989):
∞ Unrestricted (crop irrigation, garden and recreational areas watering)
200 FC/100 ml
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∞ Restricted (irrigation of crops not eaten raw).
1 helminth egg per litter
In addition, the WHO directive takes in account, for the first time, the methods of
wastewater treatment, the irrigation system and the exposed human groups. So, it
recommends additional specific precautions such as using special clothing, high
levels of hygiene, careful cooking, special washing facilities, control of human
exposure, promoting of sanitation (WHO, 1989).
In 2006, the Organization issued the third edition of the directives for safe wastewater
reuse that replaced the previous two editions (Table 4.1). The main purpose of the
new Directive is to protect the health of people that may come directly or indirectly in
contact with the treated water. In this direction, WHO developed further information
on issues relating with:
∞ Diseases of the population that contacts with the reclaimed wastewater
∞ Risk Analysis
∞ Risk managing strategies (quantification of safety measures)
∞ Chemical compounds in wastewater, whose acceptable limits are summarized in
Appendix F.
∞ Strategies for the implementation of the Directives
The current water quality parameter limits are described in Table 4.1 together with
the proposed application.
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TABLE 4.1: DIRECTIVE LIMITS FOR MONITORING PARAMETERS FOR WASTEWATER REUSE IN
AGRICULTURE AND AQUACULTURE (WHO, 2006).
Activity / Exposure Water Quality Parameters
Agriculture E.coli per 100 ml Helminth eggs per litre
Unrestricted irrigation
Root crops 103 1
Leaf crops 104
Drip irrigation, high-growing crops 105
Restricted irrigation
Labour-intensive, high-contact agriculture 104 1
Highly mechanized agriculture 105
Septic tank 106
Aquaculture
Produce consumers
Pond 104 Not detected
Wastewater 105 Not detected
Excreta 106 Not detected
Workers, Local communities
Pond 103 No viable eggs
Wastewater 104 No viable eggs
Excreta 105 No viable eggs
For the establishment of the appropriate legislation to protect public health, experts
have defined specific levels of protection according to the type of exposure (health
based targets). These levels are based on the fact that any disease that results from
the use of reclaimed wastewater should not cause a "loss" greater than 10-6 DALYs
(Disability - Adjusted Life Years) per person per year, as shown in Table 4.2 (WHO,
2006).
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TABLE 4.2: HEALTH-BASED TARGETS & HELMINTH REDUCTION TARGETS FROM WHO
Irrigation type Target for viral, bacterial
& protozoan pathogens
Microbial reduction target for
helminth eggs
Unrestricted 10-6
DALY per person per year 1 per litre
Restricted 10-6
DALY per person per year 1 per litre
Localized
(e.g. drip irrigation)
10-6
DALY per person per year Low-growing crops
1 per litre
High-growing crops
No recommendation
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Finally, WHO proposes a series of measures to protect consumers, workers, their
families and local communities, as presented in Table 4.3.
TABLE 4.3: HEALTH BASED TARGETS FOR WATER REUSE BY WHO (WHO, 2006)
Exposed
group Hazard
Health-based
targets
Quality parameters Health protection
measures E.coli/100 ml Viable
trematode/l
Consumers,
workers & local
communities
Excreta-related
diseases
10-6
DALY
per person per
year
104
(consumers)
103
(contact)
Not detected
- Wastewater treatment -Excreta treatment -Health & hygiene promotion -Chemotherapy & immunization
Consumers
Excreta-related
diseases
10-6
DALY
per person per
year
104 Not detected
-Produce restrictions -Waste application timing -Depuration -Food handling -Produce washing/disinfection -Cooking foods
Foodborne
trematodes
Absence of
trematode
infections
Chemicals Tolerable daily intakes [CAC]
Workers & local
communities
Excreta-related
diseases
10-6
DALY
per person per
year
103
(contact)
-Access control -Use of protective equipment -Disease vector control -Intermediate host control -Access to clean drinking water & sanitation -Redusing vector contact
Skin irritants Absence of skin disease
Schistosomiasis Absence of schistosomiasis
No viable schistosome
eggs
Vector-borne
diseases
Absence of vector-borne disease
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● US Environmental Protection Agency
The US EPA issued its first directive on the reuse of municipal wastewater in 1980.
The Directive was revised in 1992 and recently in 2004 in order to include more
information and the advanced technologies (US EPA, 2004).
US EPA revised Guidelines for Water Reuse published in 2004 contains updated
information on water use and water reuse practices in the United States (USEPA,
2004). The revised guidelines propose treatment processes, safety distances,
monitoring frequencies and define the limits of water quality parameters for each
intended use of the output (Tables 4.4-4.6). Faecal coliforms (FC) are adopted as
indicators to assess the microbiological quality of the treated wastewater and
concentration limits for BOD and turbidity are also set. Furthermore a minimum level
of disinfection for all purposes is recommended to avoid effects from accidental
contact.
Generally, for the majority of the applications the expected turbidity, TSS and pH are
2 NTU, 30 and 6-9, respectively, whereas BOD values vary due to the sensitivity
of each recipient (Tables 4.4, 4.5). As shown in Table 4.6 emphasis is given on the
categories related to indirect potable reuse taking into account the findings of recent
research studies which suggest groundwater recharge and surface water
augmentation with treated wastewater. As expected, these standards are very strict
with no detected coliforms, low turbidity ( 2 NTU) and mean pH values (6.5-8.5).
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Reuse Category & Description
Treatment Reclaimed Water Quality
Reclaimed Water Monitoring Setback Distances
Urban Reuse
Unrestricted Secondary
(4)
Filtration(5)
Disinfection
(6)
pH=6.0-9.0 ≤10mg/l BOD
(7)
≤2 NTU(8)
No detectable faecal coliform/100ml
(9,10)
1mg/l Cl2 residual (min) (11)
pH – weekly BOD – weekly Turbidity – continuous Faecal coliform – daily Cl2 residual – continuous
50 ft (15 m) to potable water supply wells; increase to 100 ft (30 m) when located in porous media
(18)
Restricted Secondary
(4)
Disinfection(6)
pH=6.0-9.0 ≤30mg/l BOD
(7)
≤30mg/l TSS ≤ 200 faecal coliform/100ml
(9,13,14)
1mg/l Cl2 residual (min) (11)
pH – weekly BOD – weekly TSS – daily Faecal coliform – daily Cl2 residual – continuous
300 ft (90 m) to potable water supply wells
100 ft (30 m) to areas accessible to the public (if spray irrigation)
Agricultural Reuse
Food Crops Secondary
(4)
Filtration(5)
Disinfection
(6)
pH=6.0-9.0 ≤10mg/l BOD
(7)
≤2 NTU(8)
No detectable faecal coliform/100ml
(9,10)
1mg/l Cl2 residual (min) (11)
pH – weekly BOD – weekly Turbidity – continuous Faecal coliform – daily Cl2 residual – continuous
50 ft (15 m) to potable water supply wells; increase to 100 ft (30 m) when located in porous media
(18)
Processed Food Crops Non-Food Crops
Secondary(4)
Disinfection
(6)
pH=6.0-9.0 ≤30mg/l BOD
(7)
≤30mg/l TSS ≤ 200 faecal coliform/100ml
(9,13,14)
1mg/l Cl2 residual (min) (11)
pH – weekly BOD – weekly TSS – daily Faecal coliform – daily Cl2 residual – continuous
300 ft (90 m) to potable water supply wells
100 ft (30 m) to areas accessible to the public (if spray irrigation)
TABLE 4.4: SUGGESTED GUIDELINES FOR URBAN & AGRICULTURAL REUSE (USEPA, 2012)
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Reuse Category & Description
Treatment Reclaimed Water Quality Reclaimed Water
Monitoring Setback Distances
Impoundments
Unrestricted
Secondary
Filtration
Disinfection
pH=6.0-9.0
≤10mg/l BOD
≤2 NTU
No detectable faecal coliform/100ml
1mg/l Cl2 residual (min)
pH – weekly
BOD – weekly
Turbidity – continuous
Faecal coliform – daily
Cl2 residual – continuous
500 ft (150 m) to potable water supply wells (min) if bottom not sealed.
Restricted Secondary
Disinfection
≤30mg/l BOD
≤30mg/l TSS
≤ 200 faecal coliform/100ml
1mg/l Cl2 residual (min)
pH – weekly
TSS – daily
Faecal coliform – daily
Cl2 residual – continuous
500 ft (150 m) to potable water supply wells (min) if bottom not sealed.
Environmental Reuse
Environmental Reuse Variable
Secondary and disinfection(min)
Variable, but not to exceed:
≤30mg/l BOD
≤30mg/l TSS
≤ 200 faecal coliform/100ml
1mg/l Cl2 residual (min)
BOD – weekly
SS – daily
Faecal coliform – daily
Cl2 residual – continuous
Industrial Reuse
Once-through Cooling Secondary
pH=6.0-9.0
≤30mg/l BOD
≤30mg/l TSS
≤ 200 faecal coliform/100ml
1mg/l Cl2 residual (min)
pH – weekly
BOD – weekly
TSS – daily
Faecal coliform – daily
Cl2 residual – continuous
300 ft (90 m) to areas accessible to the public.
Recirculation cooling towers
Secondary
Disinfection (chemical
coagulation and filtration may be needed)
Variable, depends on recirculation ratio:
pH=6.0-9.0
≤30mg/l BOD
≤30mg/l TSS
≤ 200 faecal coliform/100ml
1mg/l Cl2 residual (min)
300 ft (90 m) to areas accessible to the public. May be reduced if high level of disinfection is provided.
Groundwater Recharge – Nonpotable Reuse
Site specific and use dependent
Primary (min.) for spreading
Secondary (min) for injection
Site specific and use dependent
Depends on treatment and use Site specific
TABLE 4.5: SUGGESTED GUIDELINES FOR ENVIRONMENTAL & INDUSTRIAL REUSE (USEPA, 2012)
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Reuse Category & Description
Treatment Reclaimed Water Quality
Reclaimed Water Monitoring Setback Distances
Indirect Potable Reuse
Groundwater Recharge by Spreading into Potable Aquifers
Secondary
Filtration
Disinfection
Soil aquifer treatment
Includes, but not limited to, the following:
No detectable total coliform/100ml
pH=6.5-8.5
1mg/l Cl2 residual (min)
pH=6.5-8.5
≤2 NTU
≤2 mg/l TOC of wastewater origin
Meet drinking water standards after percolation through vandose zone
Includes, but not limited to, the following:
pH – daily
Total coliform – daily
Cl2 residual – continuous
Drinking water standards – quarterly
Other – depends on constituent
TOC – weekly
Turbidity – continuous
Monitoring is not required for viruses and parasites: their removal rates are prescribed by treatment requirements
Distance to nearest potable water extraction well that provides a minimum of 2 months retention time to the underground.
Groundwater Recharge by Injection into Potable Aquifers
Secondary
Filtration
Disinfection
Advanced wastewater treatment
Includes, but not limited to, the following:
No detectable total coliform/100ml
pH=6.5-8.5
1mg/l Cl2 residual (min)
pH=6.5-8.5
≤2 NTU
≤2 mg/l TOC(7)
of wastewater origin
Meet drinking water standards
Includes, but not limited to, the following:
pH – daily
Total coliform – daily
Cl2 residual – continuous
Drinking water standards – quarterly
Other – depends on constituent
TOC – weekly
Turbidity – continuous
Monitoring is not required for viruses and parasites: their removal rates are prescribed by treatment requirements
Distance to nearest potable water extraction well that provides a minimum of 2 months retention time to the underground.
Augmentation of Surface Water Supply Reservoirs
Secondary
Filtration
Disinfection
Advanced wastewater treatment
Includes, but not limited to, the following:
No detectable total coliform/100ml
pH=6.5-8.5
1mg/l Cl2 residual (min)
pH=6.5-8.5
≤2 NTU
≤2 mg/l TOC(7)
of wastewater origin
Meet drinking water standards
Site specific – based on providing 2 months retention time between introduction of reclaimed water into a raw water supply reservoir and the intake to potable water treatment plant.
TABLE 4.6: SUGGESTED GUIDELINES FOR INDIRECT POTABLE REUSE (USEPA, 2012)
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4.2 REGULATIONS BY THE STATE OF CALIFORNIA
Today, the applicable criteria in the state of California include four categories of
recycled water quality (Table 4.7) (State of California, 2003). The criteria for reuse
apart from the determination of limits of pathogens, the turbidity and the processes
requirements include standards for the reliability of the treatment.
These standards indicate backup power and security systems, multiple or redundant
process units, storage or disposal of treated wastewater in emergency situations,
advanced monitoring mechanisms and automation functions. Furthermore the
proposed additions to the reuse criteria include the following distance security
requirements (State of California, 2003):
i. Irrigation is prohibited with wastewater discharges which have not been
disinfected within 50 m of any drinking water wells,
ii. The accepted distance for secondary treatment effluents which have not been
disinfected is 30 m,
iii. The accepted distance or tertiary treatment effluents (secondary, filtration and
disinfection) the distance should be 15 m and finally;
iv. The storage of treated wastewater that has been under tertiary treatment is
prohibited in less than 30 m from residences or places, where the risk of
accidental exposure is high.
(State of California, 2003)
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TABLE 4.7: CALIFORNIA’S TITLE 22 PATHOGEN LIMITS (State of California, 2003)
Water Quality Total Coliform [MPN]
Disinfected Tertiary recycled water < 2.2 per 100 ml
Disinfected Secondary – 2.2 recycled water 2.2 -23 per 100 ml
Disinfected Secondary – 23 recycled water < 23 per 100 ml
Direct beneficial Use (no disinfection) -
Other space control measures include the reduction of runoffs while using recycled
water, the protection of recreational places of human contact, the placement of
warning signs like: "Recycled water–Non potable" and others.
The state of California has also established criteria of the enrichment of underground
aquifers (directly and indirectly) with treated wastewater since 1974, which were
recently revised. More details on the allowable uses for recycled water according to
the State of California can be found in Appendix G.
FIGURE 4.1: CALIFORNIA’S WARNING SIGN FOR RECYCLED WATER (State of California, 2003)
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4.3 REGULATIONS BY OTHER COUNTRIES
4.3.1 EUROPEAN COUNTRIES
One of the major factors that have limited the reuse of wastewater in Europe and
especially in the Mediterranean region is the absence of a unified, international or
even regional, legislative framework. Noteworthy is the absence of legislation on the
reuse of treated wastewater in the EU as the only reference which is quite generic
was made in Directive 91/271/EC where in Article 12, § 1 states that " treated
wastewater should be reused whenever appropriate” (EU, 1991). Specifically for the
European Countries, one other important aspect for the lack of unified framework is
the variations in the availability of water resources and their uses in the northern,
central and southern parts.
However, the reuse of treated wastewater for irrigation is already a widely applied
practice, especially in Mediterranean countries. Most of these countries, promote the
establishment of criteria, but often not in the form of specific, national law, but with
the form of guidelines. Table 4.8 summarises the water reuse trends and the criteria
in several European countries, whereas Table 4.9 indicates the specific criteria in the
countries where there is an existing framework.
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TABLE 4.8: WATER REUSE PRACTICES & CRITERIA IN EUROPEAN COUNTRIES (Angelakis et al., 2002)
Country
Urban
use
Unlimited
Agricultural &
Industrial use
Restricted
Agricultural
use
No
Recycling
Established
Criteria
Criteria
pending
No
Criteria
Albania
Belgium
Croatia
Cyprus
France
Greece
Italy
Malta
Monaco
Spain 1
UK
1: Only in certain regions (Andalucía, Balearic & Catalonia)
TABLE 4.9: EXISTING WATER REUSE CRITERIA IN EUROPEAN COUNTRIES (Bixio et al., 2006)
Country Type of Criteria Notes
Belgium Aquafin proposal to the Government (2003)
Based on Australian EPA Guidelines
Cyprus Provisional Standards
TC < 50/100 ml in 80% of the
cases on a monthly basis and < 100/100
ml always
France Art. 24 décret 94/469 3 1994 Circulaire DGS/SD1.D./91/n°51
Based on WHO standards
Italy Decree of Environmental Ministry 185/2003
-
Regional authorities: Sicily, Emilia Romagna & Puglia
Guidelines Based on WHO standards and Title 22,
respectively
Spain Law 29/1985, BOE n.189, 08/08/85 Royal Decree 2473/1985
Based on California’s Title 22
Regional authorities: Andalucía, Balearic & Catalonia
Guidelines Based on WHO standards
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In the UK, British Standards has published BS8525-1: 2010 for greywater systems.
These recently published standards provide tables with the water quality
requirements for reuse purposes and include guidelines for the designing, the
implementation and the maintenance of greywater treatment systems. Table 4.10
describes these water quality requirements.
TABLE 4.10: EXISTING WATER REUSE CRITERIA IN THE UK (BSi, 2010)
Parameter Spray application Non-spray application
Escherichia coli /100 ml Not detected 250
Intestinal enterococci/ 100 ml Not detected 100
Legionella pneumophila / 100 ml 10 N/A
Total coliform / 100 ml 10 1000
Turbidity [NTU] <10 <10
pH 5-9.5 5-9.5
Residual chlorine [mg/l] <2 <2
Residual bromine [mg/l] 0 <5
4.3.2 OTHER COUNTRIES
In addition to all the above mentioned legislation which exists in Europe at local level,
other countries have established strict water reuse criteria in order to enhance water
reclamation techniques in them.
● Australia
Since 1984, the Environmental Policy Agency of the State New South Wales (NSW)
has established a council to develop guidelines and promote the reclamation and
reuse of treated wastewater. Recent studies estimate that in the area of Sidney
approximately 1.3 Mm3/d are being treated of which 0.031 Mm3/d are being reused
(NSW, 2008).
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The initial Australian EPA guidelines provided criteria for three categories of reuse of
secondary treated water after disinfection for agricultural and industrial use, with the
following quality criteria:
i. Category A: < 300 cfu/100 mL FC, after 30 days storage
ii. Category B: <750 cfu/100 mL FC , after 20 days storage
iii. Category C: <2.000 cfu/100 mL FC, after 10 days storage
A couple of years later, the same organization established criteria for urban and
unlimited use of wastewater effluents, with the following qualitative characteristics:
FC <1/100 mL, TC <10/100 mL, viruses <5/50 L, parasites <1/50 L (NSW, 2008).
● Japan
In Japan, unlike other countries in arid or semi-arid areas, the main categories in
wastewater reuse are based on the enhancement of the environment, toilet cleaning,
industrial use and snow production (Nagasawa, 2009). The quality requirements
seem to be strict (Table 4.11) as they are the same for all reuse purposes (Jefferson
et al., 1999).
TABLE 4.11: REUSE CRITERIA IN JAPAN (Jefferson et al., 1999)
Total coliforms/
100 ml
Faecal coliforms/ 100
ml
BOD5
[mg/l] Turbidity [NTU] pH
< 10 < 10 10 5 6-9
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5. WASTEWATER TREATMENT FOR REUSE
The urban wastewater belongs to the broader category of wastewaters. Wastewater
is characterised by types of water which has undergone a change of physical,
chemical and biological properties due to human activities (Metcalf & Eddy, 1991). It
is therefore impossible to be used for the same purposes because it may cause
adverse health or environmental problems. Wastewaters can be defined according to
their origin, in the following categories (Metcalf & Eddy, 1991); Domestic
wastewater (from residential areas that mainly comes from household activities and
functions of the human organism, Commercial wastewater (from commercial
activities, such as restaurants and hotels), Industrial wastewater (from premises
used for any industrial or commercial activity), Surface water runoff (Rainwater
along with the road materials).
This project focuses in the case of reclamation and reuse of greywater, which is part
of domestic wastewater. Greywater has considerable advantages in that it is a large
resource of low organic content (Pidou, 2007).
The growing importance given to the protection and conservation of water resources
has led to the development and implementation of wastewater treatment techniques,
from which the uncontrolled disposal is one of the main causes of water resources
degradation. The particular conditions of each region (temperature, climate), the
nature of wastewater (high or low load, with or without toxic substances) and the
problems encountered in the implementation of various methods led to the
development of various wastewater treatment systems.
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The purpose of wastewater treatment is to return the water in nature with acceptable
quality characteristics that are compatible with the desired uses, in order to protect
public health and natural ecosystems, preserve the environment and avoid depletion
of water resources, which despite their apparent abundance, are not inexhaustible in
front of the growing human population and multiple needs (Metcalf & Eddy, 1991).
The following figure (5.1) demonstrates that wastewater reclamation technologies
have progressed to such an extent, that the produced treated water can be of higher
quality than that of drinking water .
FIGURE 5.1: TREATMENT TECHNOLOGIES FOR ANY TYPE OF REUSE (USEPA, 2012)
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5.1 WASTEWATER FOR REUSE – GREYWATER
Understanding the wastewater nature is a key parameter in the sizing, configuration
and operation of environmental engineering systems for the collection, treatment and
disposal of used water.
Greywater is a “reflection of the household activities and its characteristics are
strongly dependent on living standards, social and cultural habits, number of
household members and the use of household chemicals” (FBR, 2013). One of the
most interesting and understandable approaches of greywater nature was made by
Prof. Cedo Maksimovic (2012), which illustrated that greywater consists of bath,
shower, washing machine and dishwasher discharges (Figure 5.2), whereas,
blackwater consists of wastewater from toilets and kitchen sinks.
FIGURE 5.2: SOURCES OF HOUSEHOLD WASTEWATER (Maksimovic, 2012)
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In addition, greywater is divided in two categories according to its load, as high load
greywater needs a different type of treatment than low load greywater. Figure 5.3,
describes the two types of greywater loading.
FIGURE 5.3: GREYWATER CATEGORIES (FBR, 2013)
Specifically, greywater corresponds to up to 70% of the total domestic consumed
water (44% in the UK) but contains only 30% of the organic fraction and 9-20% of the
nutrients (Pidou et al., 2007). However, greywater has several other characteristics,
considering the quantity and quality, which are described further in the following
section (5.1.1).
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5.1.1 GREYWATER CHARACTERISTICS
The quantity of greywater discharged from households in the UK is calculated by the
British Standards (2010) with the use of “Water Efficiency Calculator” developed by
the Communities and Local Government (CLG). This tool determines easily the
average greywater yield and the demand for the sizing of treatment plants. Below,
Table 5.1 provides some typical greywater quantities linked with certain occupancies
that may describe from single households to small towns.
TABLE 5.1: AVERAGE GREYWATER YIELD & DEMAND (BSi, 2010)
Occupancy Yield [litres] Demand
WC Laundry Other uses 1
1person 50 25 15 10
2 people 100 50 30 20
4 people 200 100 60 40
8 people 400 200 120 80
10 people 500 250 150 100
15 people 750 375 225 150
20 people 1,000 500 300 200
30 people 1,500 750 450 300
50 people 2,500 1,250 750 500
100 people 5,000 2,500 1,500 1,000
150 people 7,500 3,750 2,250 1,500
200 people 10,000 50,000 3,000 2,000
500 people 25,000 12,500 7,500 5,000
1000 people 50,000 25,000 15,000 10,000
10000 people 500,000 250,000 150,000 100,000
1: For instance, garden watering or car washing
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As far as greywater quality is concerned, the main polluting parameters are:
Suspended Solids (TSS) - Organic load (COD, BOD5) - Nitrogen and Phosphorus
compounds - Dissolved solids (DS) and the microbes (coliforms, bacteria, viruses,
protozoa). Table 5.2, summarizes the physicochemical characteristics of greywater,
as found in literature (Metcalf & Eddy, 1991).
TABLE 5.2: SUMMARY OF GREYWATER CHARACTERISTICS (Metcalf & Eddy, 1991)
Parameters Units Value
pH - 6.4 - 8.1
Conductivity μC/cm 82 - 1845
Turbidity NTU 0 - 240
TSS mg/L 48 - 435
Raw COD mg/L 100 – 795
Filtered mg/L 82 – 472
DO mg/L 0 – 176.9
BOD5 mg/L 50 – 539
NT mgN/L 3.8 – 17
PT mgP/L 0.1- 2
Anionic Surfactant mg/L LSS 9 – 86
E.Coli CFU/100 mL 0 – 2.51∙107
Fecal Enterococci CFU/100 mL 0 – 2.51∙105
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5.2 GREYWATER TREATMENT STAGES
The main stages of greywater treatment are (Darakas, 2010):
Pre-treatment in which materials, such as cloths, gravels, sand particles,
small pieces of wood or plastic, oil, grease, etc. are being removed because
they usually cause damage to the mechanical equipment and problems in the
maintenance/operation of the system.
Primary treatment in which part of the suspended solids and organic
substances are being removed.
Secondary treatment in which the biodegradable organic substances, the
suspended solids and the nutrients (nitrogen and phosphorus) are being
removed with the use of biological and chemical processes. Noted that
disinfection is also included in the standard definition of conventional
secondary treatment.
Tertiary treatment in which the remaining suspended solids from the
secondary treatment are being removed, typically using filtration means.
Advanced treatment for the removal of suspended and dissolved
substances of the waste those remain after the usual biological treatment
when this is required in various applications of water reuse.
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Research on greywater treatment and reuse has been observed in literature since
1970 (Hall et al., 1974; Hypes et al., 1975; Arika et al., 1977). The primary
technologies investigated were physical based treatment schemes, such as coarse
filtration and membranes, usually followed by disinfection. These technologies were
implemented and tested years later, initially in single houses (Brewer et al., 2000).
Between 1990-2000 more advanced biological treatment options were studied for
greywater treatment, such as rotating biological contactors (Nolde, 1999), biological
aerated filters (Surendran and Wheatley, 1998) and aerated bio-reactors (Shin et al.,
1998; Brewer et al., 2000). Later researches have suggested the use of more
complex technologies like membrane bioreactors (MBRs) (Friedler, 2005; Liu et al.,
2005) and in lieu of these expensive options, natural treatment systems such as
constructed wetlands (Shrestha et al., 2001; Dallas et al., 2004; Gross et al., 2007).
As far as chemical based greywater treatment options are concerned, only three are
mentioned in literature; conventional coagulation (Sostar-Turk, 2005), electro-
coagulation (Lin et al., 2005) and photocatalysis (Parsons et al., 2000).
The choice of the appropriate treatment highly depends on the reuse application and
the influent flow rate. Overall greywater treatment systems can be categorised
according to their treatment type as follows (Pidou, 2007):
● Basic systems (coarse filtration, sedimentation and disinfection)
● Physical systems (sand filter, adsorption and membranes)
● Biological systems (biological aerated filter, rotating biological contractor
and membrane bioreactor)
● Chemical systems (conventional coagulation, electro-coagulation and
advanced oxidation methods)
● Extensive systems (ponds and reed beds)
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In the extensive systems physical, chemical and biological processes take place. The
main distinction is that treatment in extensive systems flows naturally, thus in slow
velocities, whereas in conventional systems treatment is being done rapidly, because
of the imposed artificial conditions.
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5.2.1 BASIC SYSTEMS
Basic greywater treatment systems provide elementary level of treatment for not
demanding water reuse applications. Usually basic systems are preferred in small
scale projects, such as a house or a limited number of houses. They are generally
two-phase systems based on coarse filtration or sedimentation, coupled with
disinfection (Figure 5.4, 5.5). According to literature these systems are not as
efficient as the average removal of pollutant indicators (Darakas, 2010).
TSS: 40-50% COD: 70% BOD5: 25-30% Turbidity: 50%
● Coarse Filtration
The purpose of coarse filtration is the removal of the sizeable materials or particles
that greywater may contain (sand, pieces of wood, plastic, branches, rags, etc.), in
order to eliminate the suspended solids. However, it provides only a restricted
treatment in terms of organics and solids (Pidou, 2007). Nevertheless, it is a simple
filtration system which can be easily installed in households by anyone with even
limited DIY skills.
FIGURE 5.4: TYPICAL FLOW DIAGRAM OF BASIC SYSTEM – COARSE FILTRATION (Pidou, 2007)
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● Sedimentation
The aim of sedimentation is to separate the substances that float and the ones that
precipitate from greywater (Metcalf and Eddy, 1991). It is a physical separation
process of the suspended particles based on gravity, of which the specific weight is
greater than that of water (d>100 μm and C>50 mg/L). The widespread
implementation of sedimentation systems is due to the simplicity of the method,
despite the complications often occurred in sedimentation tanks, and the low energy
consumption.
FIGURE 5.5: TYPICAL FLOW DIAGRAM OF BASIC SYSTEM – SEDIMENTATION (Pidou, 2007)
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5.2.2 PHYSICAL SYSTEMS
Physical schemes for greywater treatment can be classified in two groups; sand
filters and membranes. Sand filters can be applied alone or together with adsorption
techniques, with or without disinfection (Hypes et al., 1975; Pidou, 2007).
● Sand Filters
Sand filters are used for the removal of suspended particles, turbidity and bacteria
from greywater. The basic principle of filtration through a bed of sand (and in some
cases a combination of sand and anthracite) is already adopted by nature (Darakas,
2010). Sand filters usually offer high speeds of filtering and can have an increased
lifetime when properly maintained through frequent backwashing. Thus, their
implementation has low operation and maintenance costs (Pidou, 2007).
However, when used alone sand filters offer coarse filtration, which means weak
treatment levels, so they are often combined with disinfection (Hypes et al., 1975).
Hypes et al. (1975) reported good removal of total coliforms but inadequate removal
of suspended solis and turbidity. The addition of an adsorption technique, like
activated carbon, interestingly may not provide considerable improvement to the
results (Pidou et al., 2007). A typical flow diagram of a sand filter system is illustrated
in Figure 5.6 below.
FIGURE 5.6: TYPICAL FLOW DIAGRAM OF PHYSICAL SYSTEM – SAND FILTER (Pidou, 2007)
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● Membranes
The application of membranes in advanced water and wastewater treatment is a new
and promising technology in that it is increasingly attracting interest from
environmental researchers. The main disadvantage of this technology is the high
cost and energy consumption. Despite this, literature shows surprisingly positive
results (Tsonis, 2004), concerning the efficiency of the method (Table 5.3):
TABLE 5.3: REMOVAL OF VARIOUS COMPONENTS USING MEMBRANES (Tsonis, 2004)
Parameters MF UF NF RO
Biodegradable Organic Compounds -
TDS - -
TSS - -
Heavy Metals - -
Hardness - -
Nitric ions - -
Synthetic Organic Compounds - -
Priority Organic Compounds -
Bacteria
Protozoa, Helminth eggs
Viruses - -
Membranes are usually made of cellulose acetate (rayon) or proprietary polymers
such as polyamides (Judd and Jefferson, 2003). Each membrane presents best
performance values in a certain range of temperature, pH and qualitative
characteristics of the liquid, which requires experimental data for the selection. In
Figure 5.7, a flow diagram of a typical membrane physical treatment is illustrated,
where MF, UF, NF or RO membranes can be implemented.
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FIGURE 5.7: TYPICAL FLOW DIAGRAM OF PHYSICAL SYSTEM – MEMBRANES (Pidou, 2007)
The main advantages of using membrane technologies for greywater treatment are
the excellent removal capacity of dissolved and suspended solids and the good
removal of organic compounds. On the other hand, limitations in membrane
implementation include the high operation and maintenance costs, which are mainly
due to the large energy consumption needed to achieve the required overpressure,
the demands for regular replacement or cleaning of the membranes and the disposal
of the produced concentrate (Sostar-Turk, 2005; Pidou, 2007).
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5.2.3 CHEMICAL SYSTEMS
As far as chemical based treatment options are concerned, only three are mentioned
in literature for greywater reuse.
● Coagulation - Electro coagulation
Chemical coagulation in wastewater treatment is the process in which flocculants of
the suspended matter are created in colloidal dimensions. This process is necessary
in order to allow the precipitation of these substances which precipitate with a very
slow pace because of their small size (10-3
μm – 1 μm). Therefore the flocculants
generated during the process, which are larger and denser, facilitate and accelerate
sedimentation alongside easing filtration (Gregory, 2013).
Sostar- Turk (2005), proposes coagulation coupled with a sand filter and activated
carbon for the treatment of high load greywater, with impressive results in the
removal of suspended solids (100%) and satisfying removal of COD and BOD, 93%
and 95% respectively. These results can be found in more detail in the summarised
tables in Appendix C.
FIGURE 5.8: TYPICAL FLOW DIAGRAM OF CHEMICAL SYSTEM – COAGULATION (Darakas, 2010)
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The electrochemical flocculation or electro coagulation is an advanced and efficient
electrochemical technology for removal of organic and inorganic contaminants from
wastewaters (Lin et al., 2005). This method differs from the conventional chemical
coagulation in the fact that the coagulants (Al(OH)3, Fe(OH)3 and Mg(OH)2) are not
added into the wastewater but are being generated in situ due to electro dialysis of
the anodes of Al, Fe or Mg (Tsonis, 2004). This method has been tested for low load
greywater in Taiwan by Lin at al. (2005), showing good levels of treatment.
● Photocatalysis
Photocatalysis (PCD) is an advanced oxidation method which is becoming
increasingly important in wastewater treatment especially in cases when greywater
contains small quantities of refractory organic substances (Mills et al., 1997). This
method is based in the ability of the UV light to extract constantly electrons from TiO2
and create pairs of holes (h+) and electrons (e) that with the combination of water
create hydroxyl radicals (OH-). Hydroxyl radicals are one of the most powerful
oxidants, which react and degrade all harmful organic compounds in greywater
(Tsonis, 2004). This technique can be applied in special photobioreactors installed in
greywater treatment plants. A detailed flow diagram is illustrated in Figure 4.8.
Parsons (2004) tested the efficiency of a bench scale system that used
photobiorector (TiO2/UV) that showed interesting findings which can be found in
Appendix C.
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FIGURE 5.9: TYPICAL FLOW DIAGRAM OF CHEMICAL SYSTEM – PHOTOBIOREACTOR
(Parsons, 2004)
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5.2.4 BIOLOGICAL SYSTEMS
There are a variety of biological based treatment schemes for greywater as these
seem to achieve a very good treatment level with an exceptionally good removal of
organic compounds (Pidou et al., 2007). Each biological system meets differently the
performance and cost requirements, as according to the desirable scale simple
biological systems or more advanced ones can be chosen. Systems such as
membrane bioreactors (MBRs), sequencing batch reactors (SBRs), fixed film
reactors, rotating biological contractors, anaerobic filters and biological aerated filters
(BAFs) have already been reported in literature for greywater treatment. These
systems are usually coupled with other treatment options (disinfection,
sedimentation, and screening) in order to meet the quality demands (Pidou, 2007).
Pidou et al. (2007) in their publication, state that biological systems are “the type of
treatment most commonly seen” in big scale treatment projects. In fact, these
schemes have been reported to treat greywater generated in multi-storey buildings
(Nolde, 1999) and student accommodation (Brewer, 2000).
This Section demonstrates the three most applied systems, as these seem to be very
promising and differ significantly among them.
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● Sequencing Batch Reactor (SBR)
This system, which can also be applied to large settlements, is particularly attractive
in the case of small settlements, because of its simplicity and its ability to respond
very well to flow and pollutant load frequent fluctuations (MEECC, 2012). The system
is characterised by the high level of organic load removal, which can exceed 95%
(Shin et al., 1998).
One of the main features of the system is the combination, in a common reservoir, of
activated sludge bioreactor functions and these of secondary sedimentation. An SBR
has three basic alternating operating phases (2, 3, and 4) as demonstrated in Figure
5.10. The main difference with a conventional activated sludge system lies in the fact
that in the SBR reactor the distinction of biochemical reactions and sedimentation is
not spatial but temporal (Darakas, 2010).
FIGURE 5.10: TYPICAL FLOW DIAGRAM OF BIOLOGICAL SYSTEM – SBR (MEECC, 2012)
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The main advantages of this system are (Shin et al., 1998; Darakas, 2010):
Good removal of organic load expressed as BOD5.
Satisfactory removal of nitrogen and phosphorus.
Small area requirement.
Relative simplicity of the system. Absence of sedimentation tanks, pipes for
handling wastewater and pump stations.
Minimum staff requirement, because operation phase is easily automated.
Sludge bulking problems are almost nonexistent, and in any case can be
easily controlled.
The main disadvantages of an SBR are:
High construction and operation costs (generally lower than conventional
activated sludge and extended aeration systems).
High energy consumption.
Advanced electrical equipment and automation systems.
Construction of equalization tank.
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● Membrane Bioreactors (MBRs)
Membrane Bioreactors is a relatively recent development in the field of wastewater
treatment. This method is essentially a combination of the classical and widespread
method of activated sludge with filtration (MF or UF), thus eliminating the use of
sedimentation tank as a means of final effluent clarifier and sludge condenser
(MEECC, 2012).
Specifically, the novelty of the method lies in the use of special new technology
membrane films which are submerged in the stream and through which the influent is
moving (Darakas, 2010). The flow diagram of the bioreactor is presented below in
Figure 5.11.
The high concentration of biomass in the bioreactor, results in the accomplishment of
full decomposition of the organic matter (small amount of excess sludge) and
nitrification within 3 hours. The method can be an autonomous process, after a
simple pretreatment, as literature provides very promising results about the efficiency
of the system.
FIGURE 5.11: TYPICAL FLOW DIAGRAM OF BIOLOGICAL SYSTEM – MBR (MEECC, 2012)
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MRB presents the following advantages (MEECC, 2012):
High outflow quality (removal of organic load expressed as BOD5 > 95%).
Presents no problems of sludge sedimentation
Reduced volume system requirements
Works perfectly even as a decentralized wastewater treatment system with
great flexibility depending on the population served
Needs limited but skilled personnel
It can fit perfectly with the natural environment
Causes minimal disturbance
Among the major drawbacks of MBR are (MEECC, 2012):
High fixed costs of membranes
High operating costs (due to the need of regular membrane replacement)
Limited application (relatively modern technology)
Require delicate screening upstream of the membranes to avoid fouling
problems
Requires an equalization tank
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● Rotating Biological Contactors (RBCs)
Rotating biological contactor is a system that combines many of the advantages of
traditional activated sludge systems (small area requirement) and these of biological
filters (simplicity of operation, low operational costs). The rotation of the biological
discs provides effective ventilation and sufficient contact with the effluent and
biomass so as to achieve high organic load removal and in some cases nitrification
(Darakas, 2010).
FIGURE 5.12: TYPICAL FLOW DIAGRAM OF BIOLOGICAL SYSTEM – RBC (MEECC, 2012)
An RBC has the following advantages:
High removal of organic load
Small area requirement
Simplicity of operation
Low operating cost
Easy biomass and effluent separation
Stability of both hydraulic and organic load fluctuations
System flexibility
Denitrification potential using appropriate devices
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The main disadvantages of RBCs are:
May encounter operational problems, mainly in the support and rotating
mechanism of the filters
Require to be combined with sedimentation tanks
Odour problems
Appendix D includes a detailed table with the performance data of the biological
based systems found in literature.
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5.2.5 EXTENSIVE SYSTEMS
Extensive or natural systems for greywater treatment make use of different
physical, chemical and biological processes that occur in nature. All of these
processes in natural systems take place in an "ecosystemic" reactor (Tsonis,
2004). One of the main characteristics of these systems is the low velocities of
biochemical processes (which in any case are lower than that of the mechanical
systems). As seen in literature, the most common practice for greywater
treatment in extensive systems is constructed wetlands, such as reed beds and
ponds (Shrestha et al., 2001; Dallas et al., 2004; Gross et al., 2007). Extensive
systems are commonly used in low flow rates.
● Reed beds
These systems are usually soils flooded with an amount of shallow water (<0.6 m), in
which specific flora is being cultivated for treatment reasons. There is a variety of
plants that may be used for this process in reed beds such as Phragmites australis
(Shrestha et al., 2001), Coix lacryma-jobi (Dallas et al., 2004) and many other
hydrophilic species.
The vegetation is the substrate for the bacteria growth that assists in filtering and
adsorbing the components of waste, transports the oxygen in the water mass and
reduces the growth of algae by controlling the amount of solar radiation (Darakas,
2010). Both artificial and natural wetlands are used for greywater treatment.
Reed beds are a simple and effective solution for small treatment units, to serve even
until 2,000 inhabitants, when the required output has low organic load (BOD5 <5mg /
l) and solids (TSS <10mg /l).
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The advantages of reed beds are summarised below (Tsonis, 2004):
Low construction, operation and maintenance costs
Resistance in hydraulic and pollution load fluctuations
Easy to customise it with the surrounding ecosystem and aesthetics of the area
Enhances “green” technology
Some disadvantages include:
Low nitrogen and phosphorus removal.
Odour and insect problems.
Large areas requirement
Strong dependence on climatic factors
Inability to treat greywater with high organic load.
● Ponds
The most common natural scheme for greywater treatment systems are the systems
of artificial ponds (Gross et al., 2007). It is usually earthen basins used for the
treatment of municipal sewage and rarely for industrial wastewater. Ponds are
classified depending on the frequency of evacuation they undergo. Despite this
classification, they are divided in categories according to their depth and biological
processes (Tsonis, 2004). So, ponds may be aerobic, anaerobic or aerated.
The advantages of artificial ponds are (Tsonis, 2004):
The low manufacturing and operation costs.
The possibility to adjust the effluent flow rate.
The stability in the fluctuations of the organic load, due to dilution.
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The disadvantages of ponds are:
Requirement for large areas.
Possible odours (especially where anaerobic decomposition takes place).
The high concentration of suspended solids in the effluent (due to high
concentrations of algae) (Gross et al., 2007).
Strong dependence on climatic factors.
A typical flow diagram of constructed wetlands is shown in Figure 5.13 and a detailed
table with the literature findings on the performance of these systems in included in
Appendix E.
FIGURE 5.13: TYPICAL FLOW DIAGRAM OF EXTENSIVE SYSTEMS–CONSTRUCTED WETLANDS
(Pidou, 2007)
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5.3 DISCUSSION
The literature review indicates that sand filters and simple technologies have been
shown to attain a limited treatment of the greywater, whereas membranes have been
reported to provide great elimination of the solids but could not deal with the organic
fraction efficiently. On the other hand, extensive and biological schemes can
accomplish a reliable general treatment of greywater with a significant removal of the
organics. However, the most proficient by and large performances were reported
within the schemes that combined different approaches to guarantee efficient
treatment of all the fractions. Finally, all the above technologies cannot be completely
evaluated without an investigation of their economic feasibility, which can be found in
the next chapter.
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6. WATER REUSE & COSTS
In a period when energy and financial resources are limited, an engineer or
otherwise the decision maker should, in the context of sustainable development,
select technical solutions that meet the environmental and social constraints, have
lower energy requirements and minimum cost.
As part of the effort to achieve the environmental and social goals, the engineer can
choose between a variety of technological schemes, as analysed in Chapter 5. The
range, however of this choice is restricted, by several factors, of which the most
important is cost.
The aim of this Chapter was to provide a comparative evaluation of the total costs
(construction, operation and maintenance) of some of the most important greywater
treatment systems, suitable for a range of units (from domestic to municipal) and
costs of wastewater treatment plant that may implement these technologies. The
findings of this Chapter followed a long term literature research and communication
with wastewater treatment companies and specialists.
This Chapter can be useful for the preliminary assessment of these systems, but also
constitute the basis for estimates and other options.
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6.1 CAPITAL COSTS
The most important elements of the capital costs for a wastewater treatment plant for
reuse can be broadly categorised as follows (NRC, 2012):
Plant type, size and location
Tanks and other structures of concrete or steel
Equipment installed
Buildings and insulation
Transmission and pumping
Electromechanical equipment and control systems
The first five elements generally correspond to 85% of the total capital expenditures
(Andreadakis et al., 1992). However, the structure costs together with the building
and insulation costs are not included in this study as the study focuses on the
treatment costs.
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6.1.1 COST OF TREATMENT SCHEMES
The construction and operating costs depend on the treatment system and therefore
the analysis of the methodology varies according to the main characteristics of the
systems. However, there is not sufficient data for all the systems individually, as
usually they are implemented in combination for better performances.
● Basic systems
Basic systems are “marketed and promoted as being simple to use with low
operational costs” (Pidou et al. 2007). Usually these systems are coupled with
disinfection in order to provide a satisfactory treatment level. For this reason there is
no economical data for individual basic systems. However, there are three case
studies that provide costs (Table 6.1) for complete treatment systems that include
coarse filtration or sedimentation (Brewer et al. 2000; Hills et al., 2001; March et al.,
2004).
TABLE 6.1: COST OF BASIC SYSTEMS
Location Structure System HRT/
Flow rate
Capital
Costs O&M Costs
UK1 House
Filtration +
Disinfection N/A £ 1195 £50/year
UK2
Houses Coarse filtration +
Disinfection 28 m
3 /day £ 1625 £49/year
Spain3 Hotel
Screening +
Sedimentation +
Disinfection
38 hours £11,500 £0.50/m3
1: Brewer et al. 2000, 2: Hills et al., 2001, 3: March et al., 2004
From literature, only the system located in Spain was observed to be cost effective
as it had savings of “£0.75/m3 and a payback period of 14 years” (Pidou, 2007).
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● Physical systems
Physical systems, as analysed in Chapter 4, seem to incorporate promising
technologies in the case of greywater reclamation, as they provide an excellent
treatment level. The economical data concerning these systems was provided from
wastewater treatment companies in the UK and from one case study, summarised in
Table 6.2.
TABLE 6.2: COST OF PHYSICAL SYSTEMS
Location Structure System HRT/
Flow rate
Capital
Costs O&M Costs
UK1 Houses Sand filter N/A £ 45–350 /m3 5% of capital
Slovenia2
Houses Activated carbon filter 200 m3/day £ 0.11 /m3 £ 0.4 /m3
Slovenia2
Houses
Membrane plant
UF/RO 200 m3/day £ 0.63 /m3 £ 0.72 /m3
1: Xylem UK Ltd, 2013 , 2: Sostar-Turk et al., 2005
When comparing the costs of the above schemes, the filters coupled with activated
carbon seem to be cost effective and with high pollutants removal rates, at the same
time (Sostar-Turk, 2005). However, membrane plants are a more sustainable option,
“because only 25% of effluent water ends in the environment and about 75% is
recycled” ((Sostar-Turk, 2005). This means that larger amounts of water are recycled
annually, thus more money is being saved. Nevertheless, site specific scenarios
should be studied because even though the percentage of the recycled water may be
high the membranes cost is still 50% higher than that of GAC.
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● Chemical systems
As far as the chemical systems are concerned, there are some costs data in
literature (Table 6.3) from already tested wastewater treatment plants, yet evidence
of photobioreactor costs is not available.
TABLE 6.3: COST OF CHEMICAL SYSTEMS
Location System HRT/
Flow rate
Capital
Costs
O&M
Costs
Slovenia1
Coagulation +
Sand filter + GAC 40 min £ 0.07/ m3
£ 0.27/ m3
Taiwan2
Electro-coagulation +
Disinfection 28 m
3/day £ 0.04/ m3 £ 0.10/ m3
1: Sostar-Turk et al., 2005, 2: Lin et al., 2005
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● Biological systems
The biological schemes that can be implemented for greywater reclamation are
usually coupled with other treatment schemes and an although expensive option can
also be effective (Pidou et al., 2007). A summary of the cost data for biological
systems can be found in Table 6.4.
TABLE 6.4: COST OF BIOLOGICAL SYSTEMS
Location Structure System HRT/
Flow rate Capital Costs O&M Costs
UK1
Student hall
Screening +
Aerated bio filter+
GAC
N/A £ 1720 £ 128 /year
UK2
Student hall
Biological reactor+
Sand filter+ GAQ+
disinfection
0.65 m3/day £ 30,000 £ 611/year
Australia3
House Biofilm +
UV disinfection N/A £ 2514-3325 N/A
Germany4
Houses Modular biological
system 0.6m
3day £ 4300 £ 17-20/year
UK5
Houses Membrane bioreactor
(coated fibre membrane) 125 m
3/day
£ 80/m2
(membrane area
needed 1.92 m2/m
3)
>£ 20/m3
UK5
Houses Membrane bioreactor
(Al flocs on substrate) 4,000 m
3/day
£ 35/m2
(membrane area
needed 0.292 m2/m
3)
£ 17-21/m3
UK5
Houses Membrane bioreactor
(polypropylene membrane) 3,750 m
3/day
£30-40/m2
(membrane area
needed 0.72 m2/m
3)
£ 12/m3
USA6
House SBR N/A £ 5500 -7700 £ 160-260/year
1: Surendran et al., 1998, 2: Brewer et al., 2000, 3: Pidou et al., 2007, 4: Nolde, 2005,
5: Visvanathan et al., 2000, 6: Obropta, 2005
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● Extensive systems
Apart from being considered as sustainable technologies, extensive or natural
systems are also regarded as low cost options for greywater recycle. In fact,
literature has provided some interesting data concerning the costs of constructed
wetlands, compiled in Table 6.5. In addition, further cost data are shown in the
following table, for modular reed beds, gathered from a wastewater treatment
company that specializes in natural treatment systems.
TABLE 6.5: COST OF EXTENSIVE SYSTEMS
Location Structure System HRT/
Flow rate Capital Costs
O&M
Costs
Costa Rica1
3 Houses 2 Reed beds +
Pond
>10 days
0.76 m3/day
£ 531 £ 12/year
Nepal2
House Sedimentation +
Reed bed 0.5 m
3/day £ 230 Negligible
Sweden3
Student hall 3 Ponds +
Sand filter 1 year £ 240 /person N/A
Ireland4
- Vertical flow reed beds 0.1–0.3
m3/day
£ 1300 N/A
Ireland4
- Horizontal flow reed
bed
0.1–0.3
m3/day
£ 950 N/A
1: Dallas et al., 2004, 2: Shrestha et al., 2001, 3: Gunther, 2000, 4: Herr Ltd., 2013
The only economic constraint of constructed wetlands is the cost of the substrate
media which may be 50% of the total construction costs, thus raising significantly the
budget for small scale treatment plants (USEPA, 1999).
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6.1.2 TRANSMISSION & PUMPING
The construction of wastewater treatment facilities depends not only on the treatment
processes of the unit, but also on the supporting water network and pipes, which
should also be completed in order to create a functional plant. In addition, costs can
also differ significantly for varied landscapes, when the wastewater treatment plant is
situated at “lower elevations and the recipients are in the higher elevations”, thus
requiring pumping stations (Figure 6.2) (NRC, 2012).
These expenditures have been found to account for 35% to 50% of the total
construction costs (Metcalf and Eddy, 1995) and are demonstrated in Tables 6.6 and
6.7, in relation to pipes diameter and the capacity of water transmission, respectively.
Usually water pipelines (Figure 6.1) are ductile cast iron due to their resistance to
corrosion and centrifugal pumps are being used for water transmission (COSTwater,
2013).
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TABLE 6.6: UNIT COST OF WATER DISTRIBUTION &TRANSMISSION PIPELINES (COSTwater, 2013)
Diameter of water pipes
mm
Frost areas
£/ m
Non frost areas
£/ m
150 143.2 91.2
200 140.6 96.3
250 152.8 111.1
300 165.0 125.9
350 210.0 159.3
400 254.3 193.3
450 284.5 227.3
500 314.0 260.7
600 319.8 298.0
750 373.7 373.7
900 539.4 539.4
1050 745.6 745.6
>1050 and <1500 800.2 800.2
>1500 and <2100 1103.3 1103.3
>2100 and <2250 1116.1 1116.1
>2250 and < 2400 1251.0 1251.0
>2400 and <3000 1326.7 1326.7
>3000 1819.3 1819.3
FIGURE 6.1: TYPICAL WATER & DRAINAGE PIPELINES (NRC, 2012)
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TABLE 6.7: UNIT COST OF WATER TRANSMISSION PUMPING STATION (COSTwater, 2013)
Water transmission capacity
m3/d
Unit Cost
£/ m3/d
3785 77.1
7570 60.4
18925 43.7
37850 34.0
75700 26.3
189250 19.3
378500 14.8
FIGURE 6.2: TYPICAL PUMPING STATION (COSTwater, 2013)
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6.2 OPERATION & MAINTENANCE COSTS
The analysis of operational and maintenance costs include the factors listed below
which are also displayed in Figure 6.3, as percentages of their contribution to the
expenses.
Employee salaries
Energy requirement for operation.
Chemicals and other requirements
Water application and sludge disposal
Replacement program.
Material required for repairs.
The personnel needed of each treatment plant depend on its size and complexity.
The replacement costs apply to those design elements that have shorter lifetime than
the planned period and should therefore be replaced sooner (e.g. membranes).
Replacement cost is the same as the original cost of the items (Metcalf and Eddy,
1995).
FIGURE 6.3: BREAKDOWN OF RUNNING COSTS OF A WASTEWATER TREATMENT PLANT (adapted from COSTwater, 2013)
18%
26%
6% 13%
18%
9%
10% Water discharge fee
Electric fee
Chemical fee
Sludge transport and disposal
Staff cost
Administration cost
Maintenance & Replacement cost
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6.2.1 COST OF ENERGY REQUIREMENTS
“Energy is needed in many stages of the reclaimed water production cycle, including:
wastewater treatment, transmission to the water reclamation plant, advanced
treatment, and possible distribution to the recipient” (NRC, 2012). However, the
energy cost may differ among areas and depend on the size and the type of the
wastewater treatment plant. For instance natural systems require low energy
resources, whereas an SBR consumes big amounts of electricity.
Generally, the energy requirements of reclaimed water treatment may vary from 0.4
to 1.53 kWh/m3 (or 1.4 to 5.5 MJ/m3) (NRC, 2012).
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6.2.2 COST OF QUALITY CONTROLS
As already mentioned, the reuse of treated wastewater should not pose any risks to
public health and the environment. For this reason apart from the treatment
processes quality monitoring should also be taken into account within the
maintenance costs. During monitoring two types of parameters are being analysed;
microbiological (Table 6.8) and physicochemical (Table 6.9). The following tables
provide the costs of these analyses individually. In the case of physicochemical
parameters, monitoring frequency is also provided, as some parameters need to be
monitored in a regular basis (daily/weekly) whereas others do not need frequent
analysis.
● Microbiological Parameters
TABLE 6.8: COST OF MICROBIOLOGICAL MONITORING ANALYSIS (adapted from Salgot et al., 2006)
Parameter Cost per analysis
Legionella £170
E.coli and similar £5
Enterococci (Salmonela) £5 - £17
Nematode eggs £17 - £50
Taenia £17 - £50
Giardia and Cryptosporidium £50 - £170
Bacteriophage £5 - £17
Enterovirus £50 - £170
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● Chemical & Physicochemical Parameters
TABLE 6.9: COST OF PHYSICOCHEMICAL MONITORING ANALYSIS (adapted from Salgot et al., 2006)
Parameter Indicators Costs
per analysis
Monitoring
frequency1
Physico-
chemical pH, EC, Turbidity, TSS £5
Organic matter COD, BOD, DO, AOX £5 - £17
Nutrients Total –N, NH4+-N, Total-P £5 - £17
Minerals NO3-, SO4
2+, CN-, F-, Cl- £5 - £17
Residual
chlorine
Cl2 (if chlorination)
Disinfection products
£5 - £17
£170
(Heavy) metals
As, Cd, Cr, Hg, Pb, B, Al, Ba,
Be, Co, Cu,
Fe, Li, Mn, Mo, Ni, Se, Sn,
Th, V, Zn
£17 - £50
£17 - £50
Organic micro-
pollutants
Surfactants
Mineral oil
Pesticides
EDTA
Chloride solvents
Aldehyde
Aromatic organic solvents
PAHs
Phenols
Pharmaceuticals
£17 - £50
£17 - £50
£50 - £170
£50 - £170
£50 - £170
£17 - £50
£50 - £170
£50 - £170
£17 - £50
£170
1: Frequency: (permanently-weekly), (monthly – once a year), (once per 1-
5 years)
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6.3 DISCUSSION
The cost information provided in this Chapter is an initial level of details and can be
useful for basic financial evaluations, as it does not include building construction and
water disposal system costs.
However, demonstrates cost trends concerning the capital, the operational and the
maintenance costs. Primarily, energy requirements of the plant seem to determine
the operating expenses. As far as the treatment schemes are concerned, they show
many economical variations. In brief, it is observed that natural processes (e.g. reed
beds) that do not require mechanical equipment and large amounts of energy are
generally the most economical option. Whereas advanced treatment schemes (e.g.
MRB) have high capital and operational costs. Gratziou (2005) used mathematical
modelling in order to rank the cost of some schemes according to the equivalent
population as shown in Table 6.10.
TABLE 6.10: RANKING OF TREATMENT SCHEMES ACCORDING TO THEIR COST (Gratziou, 2005)
Equivalent Population [E.P]
100-5000 5000-8000 8000
Constructed Wetlands Constructed Wetlands Constructed Wetlands
SBR SBR MBR
RBC MBR RBC
MBR RBC SBR
In any case the overall and the running costs of greywater treatment plants depend
on of the type and capacity of the unit thus is difficult to evaluate their cost-
effectiveness.
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7. SETTING UP WATER REUSE NETWORKS
Setting up water reuse networks is the following step of the previous analysis, which
is essential in order to provide a complete study for urban water reclamation.
The ultimate selection of the appropriate series of greywater treatment technologies
will be governed by the Treatment Scenarios. The Treatment Scenarios need to be
designed to take into account a wide range of selection criteria as it is imperative that
these consider technological, environmental as well as financial key factors within the
scope of the project and within a reasonable timeframe. Primary input elements to
consider when selecting the appropriate sequence of technologies are (Siraj, 2012):
● Wastewater origin and quantity
The composition and origin of wastewater (domestic, commercial, industrial) should
be determined. In the case of greywater, it can be characterised as “low or high load”
greywater. In addition, the quantity (flow) of the produced greywater will determine
the area footprint of the treatment facility and the selection of treatment processes
that need to be employed.
● Desired quality performance
This is determined by the final recipients of the reclaimed water, which may have
quality requirements for specific reuse applications, always in accordance to the
legislation.
● Legislation
The regulatory determinants and discharge standards for the quality of treated
effluents in accordance with the regional and national standards and guidelines that
must be met for the end use of the reclaimed wastewater.
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88
● Economic factors
Economic affordability of the various treatment processes used in wastewater
reclamation should be taken into consideration, with the analysis of the capital,
operational and maintenance costs.
● Environmental conditions
These may include the land availability, geography and climate.
● Location
The availability of local skills for design, construction as well as operation and
maintenance may dictate the technical acceptability of the various treatment options.
Unlike in developed and industrialised countries, capital is scarcely found in poor and
developing countries and therefore, available treatment options tend to be less
automated and energy intensive.
Furthermore, setting up water reuse networks requires not only the understanding of
the network connections, but also the correlation between the suggested treatment
schemes in the processing stages. Figures 7.1 and 7.2 were designed in order to
ease this understanding and are the basis of Treatment Scenarios (Section 7.1).
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These diagrams illustrate the user configuration of the network with water transfer
between the supplier and the recipients. In details, Figure 7.1a, is the central supply
core, in which a group of suppliers deliver their outputs after treatment to other users.
On the other hand, Figure 7.1b represents a network of individual users, in which the
supplier is also the user after recirculation. Finally, the third diagram, Figure 7.1c,
illustrates the demand relationship of “one to many and many to one”.
FIGURE 7.1: WATER NETWORK CONFIGURATION (adapted from Arup, 2012)
Figure 7.2 shows the summarised figures of all the suggested greywater treatment
schemes (Chapter 5) organised in the relevant treatment stages in order to support
the design of the networks treatment scenarios.
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FIGURE 7.2: SUMMARY OF TREATMENT SCENARIOS FOR GREYWATER RECLAMATION (adapted from Tilley et al., 2008)
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7.1 TREATMENT SCENARIOS
This section aims to investigate four (4) potential scenarios for greywater treatment,
which have been selected after extensive research in order to meet both the
legislative and the economic standards.
In the first part, four flow diagrams, one for each scenario describe the stages of the
treatment processes selected. The second part presents the relevant summarizing
tables for the quality performance and cost effectiveness of these scenarios.
The flow diagrams include solid lines that illustrate the core treatment stages and
dashed lines that describe the optional steps. The corresponding tables on the other
hand incorporate three main subjects; systems performance, legislative criteria and
costs.
Scenario 1 - Constructed wetland system, combines a natural treatment system with
primary sedimentation (basic system), leading the effluent into UV disinfection before
storage or distribution.
Scenario 2 – Rotating Biological Contactors system employs two sedimentation
processes before and after the RBC, with a final disinfection stage.
Scenario 3 – Sequencing Batch Reactor system includes a pre-treatment stage with
a sieve filter and then introduces the effluent in the SBR system and the UV
disinfection tank.
Scenario 4 – Membrane Bioreactor system, unlike all the above systems is a one
stage treatment that may need only disinfection.
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7.1.1 SCENARIO 1 – CONSTRUCTED WETLAND
FIGURE 7.3: FLOW DIAGRAM OF SCENARIO 1- CONSTRUCTED WETLAND
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TABLE 7.1: SUMMARIZED TABLE FOR SCENARIO 1
Scenario 1 – Constructed Wetland
Quality Parameters Legislative criteria1 System Performance
2 Design Capacity System Costs
3
BOD5 < 10 mg/l < 17 mg/l 0.1–0.3 m3/day £ 950 - 1200
TSS < 30 mg/l < 13 mg/l 0.5 m
3/day £ 800
COD N/A < 50 mg/l 0.75 m
3/day £ 1000
Turbidity < 10 NTU < 10 NTU
Faecal Coliform < 250 CFU /100ml < 102 CFU /100 ml
Escherichia coli < 250 CFU /100ml < 102 CFU/100 ml
1: (BSi, 2010; USEPA, 2012) , 2: (EPA, 2000), 3: (Herr Ltd, 2013)
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7.1.2 SCENARIO 2 – RBC SYSTEM
FIGURE 7.4: FLOW DIAGRAM OF SCENARIO 2- RBC
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TABLE 7.2: SUMMARIZED TABLE FOR SCENARIO 2
Scenario 2 – RBC
Quality Parameters Legislative criteria1 Systems Performance
2 Design Capacity Systems Costs
3
BOD5 < 10 mg/l < 8 mg/l Hydraulic load
TSS < 30 mg/l < 13 mg/l 0.01 m
3/day /m
2 £ 1,625,000
COD N/A < 40 mg/l
Turbidity < 10 NTU < 2 NTU
Faecal Coliforms < 250 CFU /100ml > 1 CFU /100 ml
1: (BSi, 2010; USEPA, 2012) , 2: (Pidou, 2007) 3: (Ovivo, 2013)
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7.1.3 SCENARIO 3 – SBR SYSTEM
FIGURE 7.5: FLOW DIAGRAM OF SCENARIO 3- SBR
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TABLE 7.3: SUMMARIZED TABLE FOR SCENARIO 3
Scenario 3 – SBR
Parameters Legislative criteria1
Systems Performance2
Design Capacity
[m3/day]
Systems Costs3
[£]
BOD5 < 10 mg/l
10 mg/l 45.4 61,100
TSS < 30 mg/l
10 mg/l 56.8 89,050
Turbidity < 10 NTU
N/A 3785.4 220,350
Total Nitrogen N/A
5 - 8 mg/l 5299.6 263,250
Phosphorus N/A
1 - 2 mg/l 5526.7 263,250
7570.8 366,600
16088.0 474,500
18927 760,500
1: (BSi, 2010; USEPA, 2012) , 2: (Pidou, 2007) 3: (EPA, 1999; COSTwater, 2013)
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7.1.4 SCENARIO 4 – MBR SYSTEM
FIGURE 7.6: FLOW DIAGRAM OF SCENARIO 4- MBR
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TABLE 7.4: SUMMARIZED TABLE FOR SCENARIO 4
Scenario 4 – MBR
Quality Parameters Legislative criteria 1
Systems Performance 2
Typical Design Flux Systems Costs
3
[£]
BOD5 < 10 mg/l < 2.0 mg/l 25 LMH (l/m2 /hour)
TSS < 30 mg/l < 2.0 mg/l 36 40,131 – 114,660
COD N/A < 45 mg/l 360 401,310 – 1,146,600
Turbidity < 10 NTU < 1 NTU 3600 5,000,000-6,032,000
Faecal Coliform < 250 CFU /100ml < 2.2 CFU/100 ml 36000 36,800,000-40,300,000
Total Nitrogen N/A < 10.0 mg/l
NH3 N/A < 1.0 mg/l
Phosphorus N/A < 1.0 mg/l
1: (BSi, 2010; USEPA, 2012) , 2: (Pidou, 2007; Nalco, 2013) 3: (COSTwater, 2013)
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7.2 DISCUSSION
The above Treatment Scenarios constitute four possible greywater treatment
systems which were selected after extensive literature research and personal
communication with wastewater treatment companies. However, Figure 7.2 can be
used to form other possible scenarios, as part of supplementary future studies in the
field.
From the findings analysis, it is shown that all the selected systems comply with the
standards, concerning the quality parameters. This means that they accomplish very
good removal levels of the organic load and solids found in greywater. It is worth
noting that for the performance evaluation, the strictest legislative limits were chosen,
in order to show the performance for demanding applications (BSi, 2010; USEPA,
2012).
From the analysis of the systems costs, it is observed that these vary according to
the capacity and scale of the treatment system, with the most expensive choice this
of Membrane bioreactor, following the Rotating biological contactor, the Sequencing
batch reactor and the Constructed wetland.
Furthermore, Gratziou (2005) has developed a mathematical model that calculated
the cost of treatment systems according to the equivalent population. Figure 7.7
illustrates the results for our scenarios and it is shown that increased systems
capacities correspond to lower costs per m3 of wastewater per capita. This means
that large scale reuse projects may be more cost effective than these of domestic
scale.
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FIGURE 7.7: DIAGRAM OF SCENARIOS COSTS PER EQUIVALENT POPULATION
0.0
1000.0
2000.0
3000.0
4000.0
5000.0
6000.0
7000.0
8000.0
9000.0
0 500 1000 1500 2000 2500
Syste
m C
osts
[£/c
ap
ita]
Equivalent Population [E.P]
Constructed wetland
RBC
SBR
MBR
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8. CONCLUSIONS & RECOMMENDATIONS
Within the framework of sustainable development, one of the key concerns of the
international community is the discovery of alternative water sources. In this direction,
the practice of reclamation and reuse of wastewater should be recognised as
common practice and an essential protection method for the environment and
economies. Significant amounts of water can be saved while favouring all segments
“of the human centric water cycle”. Crop irrigation, urban spaces irrigation, industrial
cooling, reuse for environmental purposes, even indirect potable uses are some of
the application categories of treated wastewater that have already gained worldwide
acceptance.
The rational management of water resources requires a serious and responsible
planning at many levels. Several parameters should be taken into consideration, from
which the most important is the protection of public health and ecosystems. This can
be accomplished not only with the establishment of quality standards and the
protection measures, but also with the responsible monitoring programs of the
reused waters.
As far as the technical and financial issues of the project are concerned, greywater
reclamation is a feasible and sustainable practice that incorporates a variety of
treatment schemes and costs. Greywater treatment plants size and costs may vary,
offering reuse options from single households to municipal range projects. However,
the production of clear conclusions, and in particular a precise hierarchy of the
greywater treatment options reviewed, in the form of a selection guide is an attractive
idea but poses serious risks of failure. This is not only because it was impossible to
analyse all the existing and developing systems in the present study but also for the
Urban Wastewater Reuse - treatment technologies and costs
103
reason that the advantages, disadvantages and limitations of each option had
different weighting and degree of importance in each individual reuse project.
For these reasons it was considered appropriate that this work should focus on the
registration of the legislation, the treatment options and their costs, aiming that a
review of the reuse trends will provide ideas for further advances.
This study covered the fields and objectives set in the beginning of the project,
regarding greywater treatment systems and costs. However, there are still many
fields that could be investigated in urban water reuse networks. Some suggestions of
further research are as follows:
● Conduct the same technical and economical research for commercial or industrial
wastewater for urban reuse applications.
● Investigate the case of reusing reclaimed waters for indirect or even direct
potable use.
● Research the technical and economical feasibility of other Treatment Scenarios.
Finally, the problem of adequacy, quality and management of water resources needs
to be perceived from local as well as international perspectives. It is a complex issue
with various social and economical dimensions and conflicting views. The issue of
water intersects the relationship between society, nature and ecological balance, the
relationship of production and economy, the relationship of society with political and
social values, thus water is and should be considered as a collective good.
“The world has enough for everyone's need, but not enough for everyone's greed.”
Mahatma Gandhi
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APPENDIX
APPENDIX A: Data of Basic Systems
APPENDIX B: Data of Physical Systems
APPENDIX C: Data of Chemical Systems
APPENDIX D: Data of Biological Systems
APPENDIX E: Data of Extensive Systems
APPENDIX F: WHO Regulation - Maximum permissible concentration for chemical
compounds
APPENDIX G: California Title 22 - Allowable uses for Recycled water
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APPENDIX A: Data of implemented Basic Systems (Pidou et al. 2007)
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APPENDIX B: Data of implemented Physical Systems (Pidou et al. 2007)
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APPENDIX C: Data of implemented Chemical Systems (Pidou et al. 2007)
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APPENDIX D1: Data of implemented Biological Systems (Pidou et al. 2007)
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APPENDIX D2: Data of implemented Biological Systems (Pidou et al. 2007)
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APPENDIX E: Data of implemented Extensive Systems (Pidou et al. 2007)
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APPENDIX F: WHO Regulation - Maximum permissible concentration for toxic
chemical compounds (WHO, 2006)
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APPENDIX G: California Title 22 - Allowable uses for Recycled water
(State of California, 2003)