26325 Water Resources and Environment Technical Note F.3 Wastewater Reuse Series Editors Richard Davis Rafik Hirji WATER RESOURCES AND ENVIRONMENT TECHNICAL NOTE F.3 Wastewater Reuse SERIES EDITORS RICHARD DAVIS, RAFIK HIRJI The World Bank Washington, D.C. Water Resources and Environment Technical Notes A. Environmental Issues and Lessons Note A.1 Environmental Aspects of Water Resources Management Note A.2 Water Resources Management Policy Implementation: Early Lessons B. Institutional and Regulatory Issues Note B.1 Strategic Environmental Assessment: A Watershed Approach Note B.2 Water Resources Management: Regulatory Dimensions Note B.3 Regulations for Private Sector Utilities C. Environmental Flow Assessment Note C.1 Environmental Flows: Concepts and Methods Note C.2 Environmental Flows: Case Studies Note C.3 Environmental Flows: Flood Flows Note C.4 Environmental Flows: Social Issues D. Water Quality Management Note D.1 Water Quality: Assessment and Protection Note D.2 Water Quality: Wastewater Treatment Note D.3 Water Quality: Nonpoint-Source Pollution E. Irrigation and Drainage Note E.1 Irrigation and Drainage: Development Note E.2 Irrigation and Drainage: Rehabilitation F. Water Conservation and Demand Management Note F.1 Water Conservation: Urban Utilities Note F.2 Water Conservation: Irrigation Note F.3 Wastewater Reuse G. Waterbody Management Note G.1 Groundwater Management Note G.2 Lake Management Note G.3 Wetlands Management Note G.4 Management of Aquatic Plants H. Selected Topics Note H.1 Interbasin Transfers Note H.2 Desalination Note H.3 Climate Variability and Climate Change Copyright © 2003 The International Bank for Reconstruction and Development/THE WORLD BANK 1818 H Street, N.W., Washington, D.C. 20433, U.S.A. All rights reserved. Manufactured in the United States of America First printing March 2003 2 CONTENTS Foreword 5 Acknowledgments 7 Introduction 8 As demand for water increases and new sources of supply become increasingly expensive to develop, there is a growing need to use water more than once during the hydrological cycle. Reclaimed Wastewater Quality 9 Because of the potential dangers to public health from wastewater reuse, many countries have developed water quality standards for different reuse purposes. These country standards are usually based on WHO Author standards. Hugo van Gool Reuse Applications 11 Technical Adviser Stephen Lintner Wastewater can be reused for irrigation, industrial re- cycling, groundwater recharge, recreational and Editor environmental uses, nonpotable urban uses, and po- Robert Livernash table reuse. Production Staff The Planning Process for Wastewater Reuse 19 Cover Design: Cathe Fadel Planning for water reuse projects should be integrated, involving a number of disciplines, institutions, and Design and Production: beneficiaries. Special emphasis should be given to The Word Express, Inc. market assessment for reuse options, and to public acceptance of the reuse project. Notes Unless otherwise stated, all dollars = U.S. dollars. Awareness and Education 22 All tons are metric tons. Public awareness and education programs are an important aspect of water reuse project management Cover photo by because of the potential sensitivities about reusing Walter Ochs, World Bank water. Reuse of drainage water, near Fresno, California Economic and Legal Aspects of Wastewater Reuse 25 This series also is available on the Even when there appears to be a commercially ac- World Bank website ceptable rate of return on the investment, there are (www.worldbank.org). large risks associated with water reuse schemes, partly because of the limited experience with these schemes and partly because of public perceptions. In these cases, the government may need to accept part of the risk in order to attract private investment. To be effective any legal regime should be accom- panied by appropriate standards and enforcement mechanisms, including financial incentives, sanctions, and ultimately possibilities of criminal prosecution. 3 WATER RESOURCESANDENVIRONMENT · TECHNICAL NOTE F.3 Conclusion 30 Wastewater reuse is a potentially viable component of integrated water resources management along with demand-side management and supply augmentation. Further Information 31 Boxes 1. Definitions 9 2. Agricultural use of treated wastewater in Jordan 11 3. Aquaculture in San Juan, Lima, Peru 14 4. Recycling of industrial effluents, Jamaica 14 5. Reclaimed city sewage as industrial water in Chennai, India 15 6. Groundwater recharge in Israel 16 7. Wastewater reuse in Cyprus 17 8. Wastewater reclamation for drinking water purposes in Windhoek, Namibia 18 9. Public evaluation of reuse alternatives in San Diego, California 21 10. Reuse of wastewater in the Gulf region 23 11. Water education program, Queensland, Australia 24 12. Managing the risks in the Virginia Pipeline Scheme, South Australia 26 13. Collection of urban stormwater for potable water supply, Singapore 30 Figures 1. Public participation program for water reuse 22 Tables 1. Microbiological criteria for different applications of wastewater reclamation 10 2. An overview of various national standards for wastewater reused 10 for irrigation of food crops for human consumption 3. Categories of municipal wastewater reuse and potential constraints 12 4. Summary of key elements in the planning of wastewater reuse 20 5. Percentage of respondents opposed to various types of water reuse (USA) 24 6. Examples of parameters for estimating construction costs of water supply 27 and reclaimed wastewater systems 7. Examples of parameters for estimating operation and maintenance costs 28 of water supply and reclaimed wastewater systems 4 WASTEWATER REUSE FOREWORD The environmentally sustainable development and priority in Bank lending. Many lessons have been management of water resources is a critical and learned, and these have contributed to changing complex issue for both rich and poor countries. It attitudes and practices in World Bank operations. is technically challenging and often entails difficult trade-offs among social, economic, and political con- Water resources management is also a critical de- siderations. Typically, the environment is treated velopment issue because of its many links to pov- as a marginal issue when it is actually key to sus- erty reduction, including health, agricultural tainable water management. productivity, industrial and energy development, and sustainable growth in downstream communi- According to the World Bank's recently approved ties. But strategies to reduce poverty should not lead Water Resources Sector Strategy, "the environment to further degradation of water resources or eco- is a special `water-using sector' in that most envi- logical services. Finding a balance between these ronmental concerns are a central part of overall objectives is an important aspect of the Bank's in- water resources management, and not just a part terest in sustainable development. The 2001 Envi- of a distinct water-using sector" (World Bank 2003: ronment Strategy underscores the linkages among 28). Being integral to overall water resources man- water resources management, environmental agement, the environment is "voiceless" when other sustainability, and poverty, and shows how the 2003 water using sectors have distinct voices. As a con- Water Resources Sector Strategy's call for using sequence, representatives of these other water us- water as a vehicle for increasing growth and re- ing sectors need to be fully aware of the importance ducing poverty can be carried out in a socially and of environmental aspects of water resources man- environmentally responsible manner. agement for the development of their sectoral in- terests. Over the past few decades, many nations have been subjected to the ravages of either droughts or floods. For us in the World Bank, water resources man- Unsustainable land and water use practices have agement--including the development of surface and contributed to the degradation of the water resources groundwater resources for urban, rural, agriculture, base and are undermining the primary investments energy, mining, and industrial uses, as well as the in water supply, energy and irrigation infrastruc- protection of surface and groundwater sources, pol- ture, often also contributing to loss of biodiversity. lution control, watershed management, control of In response, new policy and institutional reforms water weeds, and restoration of degraded ecosys- are being developed to ensure responsible and sus- tems such as lakes and wetlands--is an important tainable practices are put in place, and new predic- element of our lending, supporting one of the es- tive and forecasting techniques are being developed sential building blocks for sustaining livelihoods and that can help to reduce the impacts and manage for social and economic development in general. the consequences of such events. The Environment Prior to 1993, environmental considerations of such and Water Resources Sector Strategies make it clear investments were addressed reactively and prima- that water must be treated as a resource that spans rily through the Bank's safeguard policies. The 1993 multiple uses in a river basin, particularly to main- Water Resources Management Policy Paper broad- tain sufficient flows of sufficient quality at the ap- ened the development focus to include the protec- propriate times to offset upstream abstraction and tion and management of water resources in an pollution and sustain the downstream social, eco- environmentally sustainable, socially acceptable, logical, and hydrological functions of watersheds and economically efficient manner as an emerging and wetlands. 5 WATER RESOURCES ANDENVIRONMENT · TECHNICAL NOTE F.3 With the support of the Government of the Nether- The Notes are in eight categories: environmental lands, the Environment Department has prepared issues and lessons; institutional and regulatory is- an initial series of Water Resources and Environ- sues; environmental flow assessment; water qual- ment Technical Notes to improve the knowledge ity management; irrigation and drainage; water base about applying environmental management conservation (demand management); waterbody principles to water resources management. The management; and selected topics. The series may Technical Note series supports the implementation be expanded in the future to include other relevant of the World Bank 1993 Water Resources Manage- categories or topics. Not all topics will be of inter- ment Policy, 2001 Environment Strategy, and 2003 est to all specialists. Some will find the review of Water Resources Sector Strategy, as well as the past environmental practices in the water sector implementation of the Bank's safeguard policies. useful for learning and improving their perfor- The Notes are also consistent with the Millennium mance; others may find their suggestions for fur- Development Goal objectives related to environmen- ther, more detailed information to be valuable; while tal sustainability of water resources. still others will find them useful as a reference on emerging topics such as environmental flow assess- The Notes are intended for use by those without ment, environmental regulations for private water specific training in water resources management utilities, inter-basin water transfers, and climate such as technical specialists, policymakers and variability and climate change. The latter topics are managers working on water sector related invest- likely to be of increasing importance as the World ments within the Bank; practitioners from bilateral, Bank implements its environment and water re- multilateral, and nongovernmental organizations; sources sector strategies and supports the next gen- and public and private sector specialists interested eration of water resources and environmental policy in environmentally sustainable water resources and institutional reforms. management. These people may have been trained as environmental, municipal, water resources, ir- rigation, power, or mining engineers; or as econo- mists, lawyers, sociologists, natural resources Kristalina Georgieva specialists, urban planners, environmental planners, Director or ecologists. Environment Department 6 WASTEWATER REUSE ACKNOWLEDGMENTS The Bank is deeply grateful to the Government of Technical Note F.3 was drafted by Hugo van Gool the Netherlands for financing the production of this of DHV Water, Amersfoot, The Netherlands. It was Technical Note. reviewed by David Hanrahan and Hans Olav Ibrekk of the World Bank. Safwat Abdel-Dayem provided comments and information for the case studies. 7 WATER RESOURCES ANDENVIRONMENT · TECHNICAL NOTE F.3 INTRODUCTION As the demand for water increases and new sources and is a feature of the new Rural Development Strat- of supply become more expensive to develop, there egy. Technical issues associated with wastewater is an increasing need to use water more than once reuse are explored in a number of World Bank pub- during the hydrological cycle. Wastewater from point lications, such as Technical Papers 51 and 64. The sources--such as sewage treatment plants, indus- Bank has invested in projects that contain a water tries, and thermal power stations--can provide an reuse component, and will continue to support so- excellent source of reusable water because this cially and environmentally acceptable and economi- water is usually available on a reliable basis, can cally efficient reuse projects. be accessed at a single point, and has a known qual- ity. These sources can be reused within the same This document is one in a series of Water Resources industry or for completely different purposes. Waste- and Environment Technical Notes that have been water reuse can not only help maintain upstream prepared by the Environment Department to apply environmental quality by reducing the demand for environmental management principles to water new water sources, but can also offer communities resources management. an opportunity for pollution abatement by reduc- ing effluent discharge to surface waters. This Note provides an overview of water reuse ap- plications, the planning of water reuse projects, the In many parts of the world, wastewater has long development of public education programs, and the been used in an unplanned way for agriculture. The economics of reuse schemes. However, every indi- planned reuse of wastewater is less common but vidual country has its own legislation, cultural re- increasing, particularly in water-short regions. strictions, and financial opportunities, so this general However, there are financial and social impediments information needs to be customized for each cir- to both planned and unplanned reuse. Treatment cumstance. to a desired quality and transport of the water to the reuse location can make the project uneconomic; This Note begins with a definition of terms used lack of social acceptance, particularly of reused sew- in water reuse management and an overview of age flows, can also limit the adoption of reuse tech- reclaimed wastewater quality criteria and stan- nologies in countries where dards. It then discusses pos- a these technologies have not sible reuse applications, ankL been traditionally applied. Sri, including irrigation, indus- trial use, groundwater re- Institute The World Bank supports wa- charge, and potable use. It ter reuse where it is an ap- describes a planning pro- propriate strategy. The Management cess for wastewater reuse potential of water reuse strat- ater and discusses public aware- W egies for promoting water ness and education pro- conservation was recognized grams. The Note concludes in the Bank's 1993 Water Re- International with discussions about the by sources Management Policy economics of wastewater re- Photo Wastewater irrigation fields, Hanoi, VietNam use and some legal aspects. 8 WASTEWATER REUSE RECLAIMED WASTEWATER QUALITY Wastewater reuse (see Box 1 for terminology) is ac- where wastewater is used to irrigate crops for hu- cepted in principle in most industrialized and de- man consumption without any treatment or admin- veloping countries, as well as in urban and rural istrative oversight. All these occurrences are termed areas. In developing countries, almost all wastewa- unplanned reuse. In this Note, we will primarily be ter reuse is applied to agricultural purposes. In gen- concerned with planned wastewater reuse, where eral, planned reuse of municipal or industrial waste- the water is diverted to a specific use in a controlled water occurs in regions where the demand for water way, including management of water quality. is high and the supply is limited because of either limited rainfall or environmental or health restric- Unplanned reuse can sometimes act as an impedi- tions on development of further water resources. The ment to planned reuse because water managers best-known regions are the Middle East, the south- argue that there is no need to invest in wastewater western United States, Namibia, northern Africa, and treatment and management when unplanned re- Australia. In large, dense urban areas where space use is already occurring. However, the unplanned is precious, wastewater is reused for nonpotable uses may not be the most efficient uses of the dis- purposes such as toilet-flushing, and stormwater is charged water, particularly when environmental stored and used later for irrigation of lawns and parks. impacts are considered. There can also be obvious This occurs in Japanese cities such as Tokyo and in health and environmental implications from un- several counties in the greater Los Angeles area. planned activities. Wastewater has been reused in an unplanned way Wastewater reuse is closely related to water con- in many parts of the world for centuries. For example, servation. Both approaches aim at making maxi- wastewater that is discharged to streams or infiltrates mum use of existing water supplies in order to groundwater systems without deliberate manage- reduce the need to tap new sources of high-quality ment activities is often reused for other purposes. water for both financial and environmental reasons. There are many examples of river water being used Municipal and agricultural water conservation are for municipal purposes, discharged (often treated to described in Notes F.1 and F.2. some extent) back to the river, and later withdrawn for water supply for cities further down the same Many countries have developed guidelines and stan- river. There are also many places, particularly in Asia, dards to establish an appropriate level of treatment BOX 1. DEFINITIONS Wastewater reuse. Use of reclaimed wastewater for a beneficial use such as agricultural irrigation or industrial cooling. Planned reuse. Direct or indirect use of reclaimed wastewater without losing control over the water during delivery. Unplanned reuse. Use of wastewater after surrendering control of the water after discharge (including incidental use of water from a river downstream of a treated wastewater discharge point). Wastewater reclamation. Treatment or processing of wastewater to make it reusable. Direct reuse. Use of reclaimed wastewater without intervening discharge to a natural body of water. Indirect reuse. Use of reclaimed wastewater with intervening discharge to a natural body of water. Wastewater recycling. Use of wastewater that is captured and redirected back to the water-use scheme from which it originates. This technique is applied particularly in industry. 9 WATER RESOURCES AND ENVIRONMENT · TECHNICAL NOTE F.3 TABLE 1. solids and significant removal of parasite eggs) to MICROBIOLOGICAL CRITERIA FOR DIFFERENT potable reuse. In the latter application, secondary APPLICATIONS OF WASTEWATER RECLAMATION treatment followed by filtration, nitrification, deni- trification, chemical clarification, carbon adsorption, Application Fecal coliforms (geometric mean; no. per 100 ml) ion exchange or membrane filtration, and disinfec- tion is recommended. Many countries base their Irrigation (restricted) No standards recommended standards on those published by the World Health Organization (WHO). Irrigation (unrestricted) 1000* Aquaculture 1000* The WHO guidelines emphasize microbiological (measured in the fish ponds) safety because more than half of the world popula- tion is still exposed to waters that contain pathogenic Landscape irrigation 200* organisms to some degree. Chemical contaminants Groundwater recharge 23** normally cause health effects after prolonged peri- ods of exposure. Of particular concern are chemi- Non-potable urban use 3-1000** cals that have cumulative toxic properties, like heavy Recreation 2.2-1000** metals and carcinogenic substances, for which sev- eral countries have developed their own standards. Drinking water Must not be detectable* * WHO standards Table 1 summarizes some microbiological criteria ** USA-EPA standards for different wastewater reuse applications accord- ing to the WHO guidelines. Apart from health con- cerns, use of wastewater for irrigation of crops can for wastewater reuse. In developing countries, lead to the buildup of toxicants-such as heavy met- where wastewater is often reused without treatment, als-in the soil, eventually rendering it unsuitable any treatment of untreated wastewater represents a for crop use. Table 2 provides an overview of some significant health improvement. Applications range national standards for selected chemical and mi- from irrigation of crops not intended for human con- crobial parameters for wastewater reused for irri- sumption (for which the criteria are absence of gross gation of food crops for human consumption. TABLE 2. AN OVERVIEW OF VARIOUS NATIONAL STANDARDS FOR WASTEWATER REUSED FOR IRRIGATION OF FOOD CROPS FOR HUMAN CONSUMPTION Parameter Unit Saudi Arabia Jordan USA WHO 1989 1985 Chemical BOD mg/l 10 150 30 na COD mg/l -- 500 na na TSS mg/l 10 200 30 na Oil and grease mg/l absent 8 na na pH 6.0 - 8.1 na 6 ­ 9 6 ­ 9 Chlorine residual mg/l na 0.5 1 na Health Fecal coliforms MPN/100ml 2.2 1,000 200 1,000 Nematodes eggs/l 1 < 1 na < 1 Saudi Arabia: Draft Standard, MAW 1989 na = not available Jordan: Jordan Standard 893/95 USA: EPA recommendations 10 WASTEWATER REUSE REUSE APPLICATIONS Wastewater can be reused in many different ways. The WHO guidelines for viable intestinal nema- Table 3 provides a summary of the most common tode eggs are set at less than 1 per liter for restricted possibilities. and unrestricted irrigation (arithmetic mean), and at less than 1,000 per 100 ml (geometric mean) for IRRIGATION fecal coliform bacteria for unrestricted irrigation. A more stringent guideline--less than 200 fecal Worldwide, crop and landscape irrigation is the coliforms per 100 ml--is appropriate for landscape major reuse purpose for domestic and municipal irrigation such as public lawns or school wastewater. Health risks and soil damage are mini- grounds, where frequent direct contact by the public mal if the wastewater is treated and the necessary is expected. precautions are taken (see Box 2). However, inad- equate funding for operations and maintenance Treatment in wastewater stabilization ponds will (O&M) in treatment plants in developing countries produce effluent complying with the WHO micro- means that irrigation with ostensibly treated waste- biological guidelines with high reliability and at low water carries many of the same risks as irrigation cost, although a relatively large area of land is re- with untreated effluent. In these circumstances, quired. Another possibility is disinfection such as wastewater quality can be highly variable, and ag- chlorination, although this will leave most helm- ricultural workers and nearby communities can be inth eggs unharmed and is costly. If the WHO guide- exposed to pathogens and other contaminants when lines are not fully met, it may still be possible to they believe they are safe. grow selected crops without risks to the consumer, but protection for field workers is needed. BOX 2. AGRICULTURAL USE OF TREATED WASTEWATER IN ORDAN J In Jordan, the demand for water is high and sources are limited. Consequently, wastewater reuse is a central part of national water policy. The use of wastewater has grown rapidly from 4 percent of total water supply in 1990 to 6.5 percent in 1995, and was projected to increase to 9 percent in 2000 and 16 percent in 2020. Groundwater abstrac- tions will be reduced during this period to eliminate over-abstraction and protect highland aquifers from salinization. Treated wastewater has been used for agricultural irrigation in the Jordan River Valley since 1968. If current plans are fulfilled, the share of treated wastewater in the valley is projected to increase from 18 percent in 1998 to 34 percent in 2020. This water is used to produce an additional winter crop and contributes to the irrigation of perennial crops. In addition, treated effluent--about 18,000 m3 per day from the Mafraq, Aqaba, Ramtha, Al-Samra, and Kufranja treatment plants--is used to irrigate 600 ha of forage crops, forests, olives, and palm trees. Health and environmental standards are a critical part of this program. Existing water quality standards have been reassessed and N and BOD targets have been made more stringent. Wastewater treatment plants are being up- graded as part of the reuse activities. Water quality is now monitored independently of the treatment facilities by the Royal Scientific Society. Laboratories have been upgraded and an early warning system has been instituted. In addi- tion, treated effluent is mixed with freshwater from the Talal dam before delivery to the irrigation districts to help mange water quality. There is widespread public support for wastewater reuse, although debate continues about the best agricultural uses for the wastewater. Sources: UNDP/FAP/World Bank/WHO. 1998. Wastewater treatment and reuse in the Middle East and North Africa Region: Unlocking the potential. Report of a Joint mission to the Middle East Region. Subramanian, A. 2001. The Hashemite Kingdom of Jordan Water Sector Review Update. World Bank Report 21946-JO. Washington: The World Bank. 11 WATER RESOURCES AND ENVIRONMENT · TECHNICAL NOTE F.3 TABLE 3. CATEGORIES OF MUNICIPAL WASTEWATER REUSE AND POTENTIAL CONSTRAINTS Wastewater reuse categories Potential constraints Agriculture and landscape irrigation Crop irrigation Surface- and groundwater pollution, if not properly managed Commercial nurseries Park/School yards Marketability of crops and public acceptance Freeways (median strips) Golf courses Effect of water quality, particularly salts, on soils, grasses, and crops Cemeteries Greenbelts Public health concerns related to pathogens (bacteria, viruses, and Residential areas parasites) Industrial recycling and reuse Cooling Constituents in reclaimed wastewater cause scaling, corrosion, Boiler feed biological growth, and fouling Process water Heavy construction Public health concerns, particularly aerosol transmission of pathogens in cooling water Groundwater recharge Groundwater replenishment Organic chemicals in reclaimed wastewater and their toxicological effects Salt water intrusion control Subsidence control Total dissolved solids, nitrates, and pathogens in reclaimed wastewater Recreational/environmental uses Lakes and ponds Health concerns from bacteria and viruses Marsh enhancement Streamflow augmentation Eutrophication due to nitrogen and phosphorus in receiving waters Fisheries Snowmaking Toxicity to aquatic life Nonpotable urban uses Fire protection Public health concerns on pathogens transmitted by aerosols Air conditioning Toilet flushing Effects of water quality on scaling, corrosion, biological growth, and fouling Potable uses Blending in water supply reservoirs Constituents in reclaimed wastewater, especially trace organic chemicals Pipe-to-pipe water supply and their toxicological effects Aesthetics and public acceptance Health concerns about pathogen transmission, particularly viruses Source: Metcalf & Eddy, Inc. (1991) Irrigation with wastewater can result in soil and Nutrients--such as nitrogen and phosphorus--in groundwater pollution. The quality of irrigation wastewater are beneficial to the plants and reduce water is of particular importance in arid zones with the need for artificial fertilizers. However, most high rates of evaporation because of the accumula- nonindustrial wastewater streams contain nutrients tion of salts in the soil profile. The salinity of the in excess of plant needs. Environmental problems, wastewater must be low enough to maintain favor- such as eutrophication of surface waterbodies (see able osmotic pressures for plants to take up water Note G.4) from agricultural run-off and infiltration (different crops have different salt tolerances). of nitrate to groundwater (see Note G.1), can occur 12 WASTEWATER REUSE production yields. However, it is expensive, requires prevention of clogging, and may cause soil salin- ization in arid climates unless sufficient freshwa- ter is added to leach the salts below the root zone (see Note E.1). This leachate fraction can be inter- cepted in sub-surface drains. Health protection re- quires regular monitoring of wastewater quality, Bank rldo crop quality, and medical surveillance of farm W, workers. Marino Although the above discussion focuses on the Manuel by planned reuse of wastewater for agriculture, the re- ality is that in many parts of Asia, Central America, Photo Wastewater ponds and Africa wastewater is used in an unplanned way for raising crops. These crops, which are central to the livelihoods of farmers and of considerable im- if these sources are not diluted with other, lower- portance to local communities, could not be grown nutrient sources of water. without this source of water and nutrients. It is un- realistic to expect that these wastewaters will re- Heavy metals, persistent organics, and ions such ceive treatment, so the issue is to understand how as boron, chloride, and sodium can harm crops and to continue to apply the effluent at minimal risk soils. Heavy metals pose the greatest long-term en- to both human health and soil productivity. vironmental risk because they accumulate in the Although research is under way in this area, there upper soil. If a soil is highly permeable or if the are currently no well-founded guidelines for these groundwater table is close to the surface, pollution practices. of groundwater can also occur. Many heavy metals and pollutants such as chlorinated hydrocarbons AQUACULTURE may accumulate in sufficient concentrations in crops to pose a serious hazard to the health of livestock About two-thirds of the world yield of farmed fish and humans. In most cases, harmful levels of chemi- is produced from ponds fertilized with wastewater. cals can be prevented by avoiding the use of un- These fish represent a cheap source of animal pro- treated wastewater and by pre-treatment of tein for poor people. Box 3 describes an economi- industrial discharges to the wastewater reclama- cally successful and safe example of wastewater tion system. References providing guidance on man- reuse for fish production. With a few exceptions, aging harmful chemical constituents are provided health aspects, treatment processes, and monitor- in the Further Information section of this Note. ing are comparable to those for irrigation. Some sub- stances may accumulate in the fish or aquatic plants The health risk depends on the method of applying more readily than in agricultural plants. However, the irrigation water. Flooding involves the least in- few standards have been set for chemical contami- vestment, but the greatest risk to field workers if nants in wastewater reused for aquaculture.1 Keep- the wastewater is not fully treated. Sprinkler irri- ing fish in clean water for at least 2 to 3 weeks before gation should be avoided if the WHO guidelines are harvest will remove residual odors and reduce con- not fully met. Even with treated wastewater, sprin- kler irrigation may promote aerosol transmission of viruses, although this is likely to be rare. Sub- 1Zweig, R.D., J.D. Morton and M.M. Stewart. 1999. Source surface irrigation gives the greatest degree of health water quality for aquaculture: A guide for assessment. protection, more efficient water use, and often higher Washington: World Bank. 13 WATER RESOURCES ANDENVIRONMENT · TECHNICAL NOTE F.3 BOX 3. AQUACULTURE IN AN UAN S J , LIMA, PERU Between 1985 and 1990, CEPIS (Centro Panamericano de Ingeniería Sanitaria y Sciencias del Ambiente, a research centre of WHO) ran a test program on the use of effluent from the San Juan wastewater treatment plant, 15 km south of Lima, for aquaculture. The effluent had a coliform concentration between 1,000 and 10,000 per 100 ml. It was used to grow tilapia (Oreochromis niloticus) in tanks designed for aquaculture. No pathogenic bacteria or viruses could be detected in the fish as long as the concentration of coliforms in the aquac- ulture tanks was less than 10,000 per 100 ml. Production of tilapia is influenced strongly by temperature. In the warmest four months of the year, tilapia could be produced with a final commercial weight of 250 g, at a density of 2 fishes/m2, from an initial weight of 60 g. In this way, an initial fish biomass of 1,000 kg/ha could be increased to 4,400 kg/ha during four warm months. The revenues from the tilapia production were such that the investment in the aquaculture tanks proved to be an economically viable operation. Much of the cost of wastewater treatment could be recovered by this reuse option. tamination from fecal microorganisms. When plan- are being used increasingly, opening the possibil- ning or managing aquaculture, consideration ity of producing high quality water from conven- should be given to the effects of the discharge from tionally treated wastewater. the ponds on surface waterbodies and on ground- water. Major uses in industry are cooling system augmen- tation, once-through cooling systems, process wa- INDUSTRIAL REUSE ter, boiler feedwater, washdown water, and miscellaneous applications such as fire protection Wastewater reuse is increasingly used to supple- and dust control. Reclaimed water for industrial use ment or replace freshwater demands from indus- may be derived from recycling within the plant it- try. Industrial reuse has the twin advantages of a self (Box 4) or from secondary effluent from mu- generally continuous demand and the ability to uti- nicipal wastewater treatment plants (Box 5). lize secondary treated wastewater. The major fac- tors that influence industrial wastewater reuse Quality requirements for cooling towers are set by include availability and reliability of the water the build-up of impurities in these closed-loop sys- source, the industry's discharge requirement, and tems as water is evaporated from the cooling tower. the required water quality and quantity. Membrane If concentrations of impurities are too high, scale technologies (ultra filtration and reverse osmosis) deposits will form on heat exchanger surfaces, low- ering the heat transfer capacity. Excessive impu- BOX 4. RECYCLING OF INDUSTRIAL EFFLUENTS , JAMAICA Bauxite/alumina companies have spearheaded the recycling of industrial effluent in Jamaica. The bauxite/alumina industry produces a waste product known locally as "red mud," which consists of over 70 percent water enriched with caustic soda and organics. The waste is thickened to 28 percent solids and sprayed on a sloping drying bed. The drying beds are sealed to prevent infiltration of effluent to the groundwater. The liquid fraction is collected at the toe of the drying bed and is channeled to a sealed holding pond. Pumps move the effluent from the holding pond back to the plant via a pipeline, where it is recycled through the process. The technology is now used at four bauxite/alumina plants in Jamaica. The system is very effective at reducing contamination of groundwater resources. Moreover, the project reduces annual freshwater consumption by 4 to 5 million cubic meters. The main disadvantage is the large area required for the drying beds. 14 WASTEWATER REUSE BOX 5. RECLAIMED CITY SEWAGE AS INDUSTRIAL WATER IN CHENNAI, INDIA The Chennai Metropolitan area, with scant rainfall, no river sources, and no major nearby watersheds, has long been chronically short of water. Demand is increasing substantially due to increases in population and industrial development. Lately, water shortages have resulted in several stoppages of water supplies to industries, leading to cessation of produc- tion and related financial losses to industries. As a result, a fertilizer company has explored alternative sources, including the use of desalinated seawater and treated wastewater to provide process and cooling water for its operations. The company has decided to reclaim water from city sewage using advanced wastewater treatment followed by reverse osmosis (RO) as an additional purification step. Wastewater used by the plant is treated to tertiary standards using an activated sludge process, with the treated water being further reclaimed through excess lime addition, ammonia stripping, recarbonation, chlorination, multimedia filtration, activated carbon filtration, cartridge filtration, and reverse osmosis. The capital cost of the entire project is estimated at $18 million. Due to the sewage reclamation project, 13,700 m3/day of potable water, previously supplied to the fertilizer company, has been redirected to domestic use in the city. rity concentrations may cause accelerated corro- the wastewater stream is used for food process- sion, sliming, or clogging. Chemical additives are ing, water quality must also meet potable water used to control these problems. Control of Legionella standards. bacteria is an increasingly important issue in cool- ing systems. These bacteria are not introduced spe- cifically by the reuse of wastewater, but may be promoted by, for example, nutrients from reclaimed water, which may accelerate the growth of the Legionella bacteria. Once-through cooling involves substantial water volumes, but does not require as stringent quality requirements as does cooling tower augmentation. The primary water quality concerns are slime and suspended solids. Scaling and corrosion are usu- ally not a problem. Discharge water quality is es- sentially unchanged, except for a temperature increase. a Boiler feedwater has similar but more stringent Lank quality requirements to cooling tower augmenta- Sri, tion. Removal of hardness is required to prevent Institute scale formation and deposits in boilers. Process water quality requirements are highly de- Management pendent on the particular industry involved. ater W Generally it is desirable to minimize the suspended solids concentration, water turbidity, and color. International Other concerns are silica, aluminium, hardness, by microorganisms and pH. Generally, the water qual- Photo ity must meet near-potable water standards. If Spinach fields, wastewater irrigation 15 WATER RESOURCES AND ENVIRONMENT · TECHNICAL NOTE F.3 GROUNDWATER RECHARGE soil, although very soluble contaminants such as nitrate will still enter the groundwater. The effec- Groundwater recharge is used to preserve ground- tiveness of this treatment is affected by tempera- water levels, to prevent land subsidence, to protect ture, rainfall characteristics, and the physical and coastal aquifers against saltwater intrusion, and to mechanical characteristics of the soil. In special store reclaimed wastewater and surface runoff for cases, some soils--such as those with high arsenic future use (called aquifer storage and recovery, or concentrations--may contribute contaminants to the ASR). Recharge methods commonly used are sur- leachate. Direct injection to groundwater bypasses face spreading in basins, direct injection into this "natural soil treatment," but there is evidence groundwater aquifers, and riverbank infiltration that contaminants are removed from wastewater in (Box 6). the aquifer matrix. A problem with recharge is that boundaries between There are several advantages to ASR. The cost of potable and nonpotable aquifers are rarely well- artificial recharge may be less than the cost of us- defined (see Note G.1). Recharging "nonpotable" ing surface reservoirs; the aquifer serves as an even- aquifers carries the risk of contaminating high-qual- tual distribution system, reducing the need for ity potable groundwater sources. Therefore, the pipelines and canals; and the aquifer is not sub- health effects from prolonged exposure to low lev- jected to evaporation, to taste and odor problems, els of contaminants must be considered, as well as or to ambient pollution. The physical transition be- the acute health effects from pathogens or toxic tween reclaimed wastewater and the water's later substances. The lack of knowledge about the fate emergence as groundwater also provides an impor- and long-term health effects of contaminants found tant psychological and aesthetic barrier for even- in reclaimed water--together with the extreme dif- tual potable uses. However, ASR is sensitive to ficulty of rectifying water quality problems once the leakage or poor placement of injection wells. Fre- groundwater has been contaminated--means that quent monitoring of groundwater quality is essen- a conservative approach should be taken when re- tial, because it takes as much as 100 years for soil charging a nonpotable aquifer. and groundwater to recover once it has been con- taminated. Because recharged water may be an eventual source of potable water, pre-treatment is necessary before RECREATION AND ENVIRONMENT groundwater recharge. Particular attention has to be paid to contamination by pathogenic microor- There are three broad uses of reclaimed water for ganisms. If the reclaimed wastewater is being in- recreational purposes, each with their own specific troduced through soil infiltration, many constituents quality requirements: primary body-contact such will be removed during their passage through the as swimming and water-skiing; secondary body- BOX 6. GROUNDWATER RECHARGE IN SRAEL I Partially treated effluent has been used to recharge aquifers in the Dan region (Greater Tel Aviv) of Israel for almost 20 years. The effluent is discharged into spreading basins, from which it percolates through the unsaturated zone until it reaches the groundwater system. Most of the remaining contaminants are removed from the effluent during this Soil- Aquifer Treatment (SAT) process. The water then moves laterally until it reaches a series of recovery wells that surround the recharge area. The recovered effluent is pumped to the Negev Desert and used for irrigation. With proper design, the zone between the recharge area and the recovery wells can be separated hydrologically from the rest of the aquifer, which can then continue to be used for potable supply. Source: UNDP/FAP/World Bank/WHO. 1998. Wastewater treatment and reuse in the Middle East and North Africa Region: Unlocking the potential. Report, Joint mission to Middle East region. 16 WASTEWATER REUSE contact such as boating and fishing; and non- this high-density urban renewal, but it reduces the contact such as ornamental fountains and aquac- pressure on existing sewerage and wastewater treat- ulture. ment facilities, which were not designed to handle the increased flow of wastewater. The water quality criteria for primary body-con- tact are the most stringent. The water has to be aes- Similar uses of wastewater are being investigated thetically attractive, and have acceptable physical in several pilot projects in Europe and China, mostly parameters such as color, taste, and odor. Most im- as locally treated "grey" water (that is, all house- portantly, the water must be free of toxic compounds hold wastewater except that from toilets) for toilet and hygienically and microbiologically safe. Most flushing and washing machines. Special attention national standards range from 100 to 1,000 fecal is given to the possibility of biological contamina- coliforms per 100 ml. Water quality requirements tion through aerosols, with tentative microbiologi- are less strict for secondary body-contact. The re- cal standards being established for Cryptosporidium quirements for non-contact recreational water are (< 2 organisms per 10 litres), Giardia (< 5 organ- a reasonable temperature to sustain aquatic life, a isms per 10 litres), and entero-viruses (< 1 organ- suitable concentration of dissolved oxygen, a suit- isms per 10 litres). able chemical quality, the absence of nutrients to avoid eutrophication, and reasonable microbiologi- POTABLE WATER cal quality. The fundamental concern is public health, but the biological health of receiving water Potable water can be reused directly or indirectly. must also be considered in recreational/aesthetic Direct potable water reuse is a "pipe to pipe" con- reuse. Cyprus illustrates a special case where the nection between the reclaimed water treatment fa- sensitivity of tourists to wastewater reuse had to be cility and the potable water distribution system. In considered (Box 7). indirect potable water reuse, the highly treated re- claimed water is introduced to a surface water or NONPOTABLE URBAN USES groundwater system that is ultimately used as a potable water supply. The reclaimed water is Wastewater has long been used for nonpotable ur- blended with water from the natural system, and ban reuse in Japan. For example, treated wastewa- there may be a significant delay between the point ter is used in 19 buildings in a development in the of reclaimed water discharge and the point of with- Shinjuku District of Tokyo for toilet flushing. Not drawal into the potable water treatment facility. The only does this reduce the need for water supply for choice of direct or indirect potable reuse is based BOX 7. WASTEWATER REUSE IN CYPRUS By 2010, the Republic of Cyprus expects to have developed all readily available ground and surface water resources. The government has ambitious plans to use wastewater for agricultural production, particularly around Limassol, Nicosia, Larnaca, and AyiaNapa/Paralimni. However, the country's economy is heavily dependent on tourism, an industry where reuse is also widely practiced. More than 250 package treatment plants service hotels and tourist sites. About 75 percent of these use tertiary treatment and reuse the water for landscaping around the tourist sites. Tourists are particu- larly sensitive to health and aesthetic issues, and great care is taken to make sure that wastewater is used safely and with minimal environmental impact around the tourist sites. For this reason, the tourist industry opposed the introduction of the discharge of treated wastewater in coastal areas. This opposition led to the delay and eventual cancellation of a proposed treatment plant and ocean outfall for wastewater from Larnaca. The wastewater was eventually collected, treated, and reused for nonpotable uses around tourist areas Source: UNDP/FAP/World Bank/WHO. 1998. Wastewater treatment and reuse in the Middle East and North Africa Region: Unlocking the potential. Report, Joint mission to Middle East region. See also World Bank. 1996. Environmental Assessment Sourcebook Update 13. Washington: World Bank. 17 WATER RESOURCES AND ENVIRONMENT · TECHNICAL NOTE F.3 on technical factors--such as quality criteria, costs, organic (bacteria, viruses, protozoa, and helminths) distribution requirements, treatment technologies, contaminants that remain in the water, even after and necessary reliability--and nontechnical factors the most advanced treatment methods. Box 8 pro- such as public acceptance, and legal requirements. vides an example of direct reclamation in a water- deficient environment. The most serious problem of direct potable reuse is public acceptance of water with a wastewater ori- There are several means for indirect, reclaimed gin, particularly chronic health effects that might water to be introduced into water supplies. The most result from ingesting the mixture of inorganic and common are ASR (as discussed earlier), and sur- BOX 8. WASTEWATER RECLAMATION FOR DRINKING WATER PURPOSES IN WINDHOEK, NAMIBIA In the 1960s, the city of Windhoek was approaching the limit of its conventional drinking water sources (groundwater and surface water) and was forced to implement direct reclamation of wastewater for potable use in 1968. Twenty-five years later, the existing capacity of 4,800 m3/d was exceeded by the demand, and the existing plant was extended to 21,000 m3/d in 1998. From the start, it was clear that reclamation could only be successful if three important matters could be controlled: diversion of industrial and potentially toxic wastewater; wastewater treatment to produce an adequate and consistent effluent quality; and effluent treatment to produce acceptable potable water. As a safe- guard against pathogens, a maturation pond and multiple chlorination steps were applied. As shown in the schematic below, the wastewater is treated in two separate treatment plants--a conventional biological wastewater treatment plant (activated sludge) and a wastewater reclamation plant. alum lime Dissolved Reactor Reactor Settling air flotation secondary effluent y primar sludge Drying beds Activated Carbon CI2 AC AC CI2 Breakpoint Sand combination filtration tertiary effluent AC AC Wastewater reclamation plant in Windhoek, Namibia The cost of reclaimed potable water is high compared to potable water from conventional sources due to the high costs of chemical dosage. For this reason, the reclamation plant was operated on an intermittent basis. For the 1968- 91 period, the average production was 27.3 percent of the plant capacity, contributing only 4 percent to the total water supply in Windhoek. In 1982, after a series of dry years, the plant ran at 80 percent of its capacity. From the start of the project, an extensive monitoring program, representing 20 percent of the total production cost, was conducted. Samples were taken at different points--varying from the treatment plant to consumer taps--and epidemiological research on the health effects of the consumption of water focused on diarrheal disease and hepatitis A. The study showed that a marginally lower incidence of diarrheal disease was found in the population receiving direct potable reuse water. The hepatitis study concluded that consumption of direct potable reuse water did not result in the occurrence of hepatitis A infections. 18 WASTEWATER REUSE face water augmentation by direct discharge to a tation, and exchange of contaminants needs to be raw water storage reservoir or an intervening stream assessed between these two points, preferably followed by withdrawal for use. Surface water aug- through water quality models. Short-circuiting of mentation with reclaimed wastewater must be done reclaimed water to the water supply intake should carefully and with thorough evaluation of several be avoided. The amount of effluent relative to the important considerations, such as the proximity of ambient water flows has to be considered for both a reclaimed water discharge point to the supply in- average and extreme conditions, such as those that take. The attenuation of pollutant concentrations occur during drought periods. from biological degradation, adsorption, sedimen- THE PLANNING PROCESS FOR WASTEWATER REUSE Wastewater reuse plans, programs, and projects not SCOPE, OBJECTIVES, AND only include technical implications, but can have BOUNDARIES OF THE PROJECT important environmental, economic, social and public health impacts. Planning water reuse projects Reuse projects can be incorporated in national should be integrated, involving a number of disci- masterplans, basinwide programs, to locally de- plines, institutions, and beneficiaries. Special em- fined projects. Every project should start with a phasis should be given to market assessment for definition of its scope and objectives. This should reuse options, and to public acceptance of the re- include a sketch of the present and desired future use project. situation in order to clarify the priorities of the objectives. In principle, a water reuse project is Because of the complexity and sensitivity of waste- multi-purpose, because it is at least both a pollu- water reuse, the planning process should occur in tion control project and a water supply project (po- a number of phases from a broad "rough-sketch" table or nonpotable). However, one objective may stage to the technical design and construction: be more important than the others. For example, I Scope, objectives and area boundaries of the public health will be the dominating issue with re- project use of raw sewage in and around many cities in I Preliminary investigations developing countries. A clear definition of the main I Screening of potential markets objectives simplifies the screening and evaluation I Detailed evaluation of selected alternatives phases. Nevertheless, to enable a broad perspec- I Implementation plan for most feasible alterna- tive in the following phases, it is recommended that tive(s) secondary effects be identified in the first phase as I Agreements with users and institutions much as possible, including possible effects out- I Design side the project area. I Construction I Operation and evaluation. PRELIMINARY INVESTIGATIONS The first four phases define the feasibility of the re- use project. The remaining five phases cover the This phase is dedicated to gathering background actual implementation of the project, following more information, gaining insight into the present situa- or less the normal process of technical facilities plan- tion, and listing all potential wastewater sources for ning. This section of the Note includes guidelines reuse and all potential markets for the reclaimed for the first four phases. Table 4 summarizes the water. Typically the following elements need to be elements to be addressed in these phases; Box 9 addressed in a general way: provides an example of the operation of these steps. 19 WATER RESOURCES AND ENVIRONMENT · TECHNICAL NOTE F.3 TABLE 4. SUMMARY OF KEY ELEMENTS IN THE PLANNING OF WASTEWATER REUSE Planning phase Technical Institutional Social Environmental Market assessment Scope and objectives IMain objectives IPositive IPositive IProject area effects effects Preliminary investigations IPresent situation ILaws and ISurvey of IPotential IPotential IWastewater regulations attitudes of impacts markets for sources suitable IInstitutions and the public reclaimed for reuse their level of water involvement Screening of potential IEstimation and IPublic IRequirements markets comparison information of user groups of costs program matching IStakeholders with and their level reclaimed of involvement water Detailed evaluation IOptimization of IOwnership and IStart of public IEnvironmental IRequirements alternatives management education impact and interest assessment of each user group I Local sources of (treated) wastewater suitable for which specific technical, social, legal and envi- for reuse ronmental data are all necessary. This phase is also I Potential local markets for reclaimed water used to establish contact with relevant institutions, I Present uses of other (fresh) water resources in define the level of involvement of the different in- the area stitutions (partnership, influence on decisions, ad- I Present and future water costs of freshwater in visory, to be informed only), and draft a plan for the area public participation and communication. In some I Publichealthconsiderationsassociatedwithre- developing countries, this phase may also include use the development of specific institutions or a regu- I Potential environmental impacts of reuse latory framework. I Laws, regulations, and legal liabilities affecting reuse options SCREENING OF POTENTIAL MARKETS I Identification of local and national institutions, involved in regulation, permits and/or advice In this phase, the options identified in the preced- I Sources of funding available to support the re- ing phase are reduced to a limited number, prefer- use program ably between two and four, to reduce the cost of the I General survey of attitudes, (potential) support detailed evaluation in the following phase. If the and opposition of the public, as well as cultural number of options identified is large (greater than and religious concerns. 10), a first quick screening should be done by a team of experts, based on their evaluation of the general The information gathered should support the information gathered in the preceding phase. The screening of alternatives in the following phases, next screening should be based primarily on a com- 20 WASTEWATER REUSE parison between the cost of freshwater delivery to be used in the screening process (for example, the a market and the cost of reclaimed water to the same possibility for future expansion, technical and/or market, for which the following steps have to be institutional complexity, reliability, use of energy, made: production of wastes, and expected user accep- I Estimation of the water quality and quantity re- tance). quired for each type of application I Expectation of the regulatory requirements for A public participation and information program has each type of application to be defined, based on the survey information from I Estimation regarding probable reclaimed wa- the preceding phase (Box 9). This is discussed ex- ter quality that would be available in the future tensively later in this Note. with various levels of treatment, and compari- son with regulatory and user requirements DETAILED EVALUATION OF I Estimation of the quantity of reclaimed water available and the ability to meet fluctuating SELECTED ALTERNATIVES demand for each type of application I Estimation of the present and future cost of The most promising alternatives from the preced- freshwater for each user or group of users ing phase are evaluated in more detail, including a I Estimation of the cost of reclaimed water treat- detailed survey of potential users, technical opti- ment and distribution for each type of appli- mization, more refined calculation of investments cation. and operational costs, and a more refined compari- son between costs of reclaimed water and costs of Apart from the comparison of costs, other criteria freshwater systems. As far as possible, the follow- derived from the technical, social, and environ- ing information should be obtained from each po- mental data gathered in the preceding phases can tential user: BOX 9. PUBLIC EVALUATION OF REUSE ALTERNATIVES IN AN S DIEGO, CALIFORNIA Planning of a wastewater reclamation and reuse project in the San Diego Clean Water Program included public involvement from the early stages of assessing the system options to ratifying the selected alternative. The initial technical evaluation identified 21 alternatives, which were reduced through further analyses to seven before presentation to the public. A survey of the general population in the greater metropolitan area of San Diego was conducted in 1989. A total of 600 respondents, selected to represent the area's residents, were interviewed to assess attitudes toward various forms of reuse, assess the seven alternatives and their associated costs, and obtain an assess- ment and ranking of each alternative. Concurrent with the interview process, technical planners performed a comprehensive analysis of the seven alterna- tives. The technical and public rankings agreed on four alternatives, with both groups ranking the same alternative as their first choice. Based on these results, the Clean Water Program proceeded with development of plans and specifications for the preferred alternative. Two more surveys were conducted, each using 600 new respondents and focusing only on the selected alternative. These surveys confirmed the favorable evaluations of the first survey, and indicated a strong inclination to support public ratification of the program. The San Diego survey illustrates several interesting points: I Technical findings and public opinion may be in concert with one another when reuse alternatives are being considered. I Preliminary surveys reliably predicted project acceptance for the reuse program. I When the public is involved in the planning process in a substantial way from an early stage, it is more likely that funding will be obtained for the project. 21 WATER RESOURCES ANDENVIRONMENT · TECHNICAL NOTE F.3 I Interest in using reclaimed water systems, application of multiple barriers in the re- I Potential uses of reclaimed water (e.g. type of moval of substances, and functioning during crops, type of process) emergencies. During this phase, ownership and I Present and future quantity needs management of installations, sale of reclaimed I Timing and reliability of needs water, and competition elements have to be dis- I Quality needs and constraints on specific uses cussed by the institutions involved. The public in- I Modifications to on-site facilities necessary to formation program starts implementation with the convert to reclaimed water, and estimate of as- first steps of targeted education activities for the sociated costs general public. Also, the process of environmental I Fraction of current demand that could be re- and/or public health impact assessment is identi- placed by reclaimed water. fied, which may be necessary for obtaining permits. A first outline of the elements to be discussed in This detailed information is used in the basic de- the impact assessment process can be used in the sign and technical optimization of the alternatives. evaluation of alternatives and the final assessment The technical aspects should include reliability of of the feasibility of the reuse project. AWARENESS AND EDUCATION Public awareness and education programs are a meet direct and obvious needs of the public. More- particularly important aspect of water reuse projects over, accountability and transparency of agencies in both industrialized and developing countries. and agency activities instills public trust and im- There is a close association in the public's mind proves public perceptions; this is essential to over- between water quality and health, while there is a come major social and cultural barriers. general lack of knowledge of wastewater treatment processes. Modern public information, education, Figure 1 shows a flowchart of a general public par- and participation programs should be designed to ticipation program. Education and information is FIGURE 1. PUBLICPARTICIPATION PROGRAM FOR WATER REUSE General Specific Users Survey Survey Plan of Alternatives Plan Project Study Identification & Selection Implementation Evaluation Public Public Customer Public Customer-Specific Notification/ Meetings Specific Notification/ Information Involvement Workshops Involvement Program 22 WASTEWATER REUSE not a single intervention, but an ongoing process with income and education. Table 5 provides an that runs through all stages of the project. Public overview of average responses from the different meetings and workshops provide a way to educate surveys. the public about a project, obtain information, and ascertain the level of support. A general survey may The results from San Diego, described above in Box be helpful in identifying the level of interest, poten- 9, have been found to be true elsewhere. Water re- tial customers, and any initial concerns that the use projects show that the best results are obtained population might have. Specific surveys can serve when communities are involved early in the plan- to confirm earlier results and monitor the effective- ning and execution of projects and are encouraged ness of the ongoing education program. After a to play an active and decisive role. Since social, eco- project is completed and is technically successful, nomic, educational, and other conditions differ from the goal of education activities is to influence the one community to another, the form and degree of users to maximize benefits by making full use of people's involvement may vary. Nevertheless, it is the facilities (Box 10). important to encourage all relevant groups within a community to participate, irrespective of ethnic Surveys in the United States over the last two de- origin, religion, social or economical status, or cades indicate a high degree of public support for gender. water reuse programs, although the public's reluc- tance to support reuse increases as the degree of In many countries, it will require significant changes human contact with the reclaimed water increases. in policy, together with the reorganization and re- Several surveys also indicate that socioeconomic and orientation of agency staff, to switch from centrally environmental factors play a role in the perception managed projects to community-based projects. It of water reclamation. Acceptance tends to increase also requires considerable effort and funding to BOX 10. REUSE OF WASTEWATER IN THE GULF REGION In the arid countries of the Middle East, where water demand outstrips supply, conserving existing water resources and using innovative technologies to tap new sources is a priority. Although desalination has long been accepted as a new source of potable water, the reuse of treated wastewater for agriculture and industry has met with regulatory and cultural resistance. Stringent water quality standards have been established, which many suppliers feel are so restrictive they discourage the reuse of treated effluent. Even when wastewater reuse has been permitted, problems have arisen. Inadvertent or unin- tended uses of wastewater have occurred, sometimes when the public is unaware of the meaning of signs indicating wastewater transport and points of discharge. Also, the hot dry climate encourages the aerosol transmission of viruses and disease when inadequately treated wastewater is used for sprinkler irrigation. These health hazards are a particular concern during pilgrimage times, when the Holy Shrines of Mecca and Medina are visited by millions of worshippers,. Islamic religious beliefs, which require cleanliness and "purity" of water, also affect attitudes toward wastewater reuse. Since the introduction of wastewater reuse programs, the fulfillment of religious requirements for water purity has been an issue of debate among religious scholars in the Islamic world. After a thorough investigation, including both scientists and specialists, the Council of Leading Islamic Scholars of Saudi Arabia expressed its approval in 1978 of wastewater reuse, after proper treatment, for all purposes. However, they stated that they preferred to avoid using treated wastewater for drinking purposes. Faced with the extent of the water shortage and reassured by this ruling, wastewater is now used for a wide range of purposes in Saudi Arabia. For example, 9,000 ha of date palms and forage crops near Riyadh and municipal parks in Jeddah, Jubail, Riyadh, and Taif are now irrigated with treated wastewater Source: Abderrahman, W.A. 2001. "Water demand management in Saudi Arabia," in Faruqui, N.I., A. K. Biswas, and M. J. Bino, eds., Water Management in Islam. Tokyo: UN University Press. 23 WATER RESOURCES AND ENVIRONMENT · TECHNICAL NOTE F.3 TABLE 5. Some communities participate only in advisory PERCENTAGE OF RESPONDENTS OPPOSED TO committees, while others may make a financial con- VARIOUS TYPES OF WATER REUSE (USA) tribution or contribute labor to the implementation of a project. A citizen advisory or participation com- Type of reuse percent opposed to reuse mittee may help ensure that a project's technical Drinking water 55 staff has not neglected an aspect of the project that could build public confidence. Food preparation 50 Bathing at home 35 Media coverage may be important to a project, de- pending on the degree of development of a coun- Swimming 21 try. Background information should be provided to the media. It is important that community lead- Laundry 21 ers are made aware of a proposed reuse project Irrigation of vegetable and its benefits prior to the media being informed. crops, vineyards etc. 12 Stakeholder briefings may be a useful strategy to Toilet flushing 5 accomplish this objective, especially for those who may be contacted by the media for comments about Irrigation of lawns, parks, the proposed project. Further, in a stakeholder golf courses etc. 4 interview other individuals in the community who have a logical interest in the project can be identified. engage the community in a participatory approach, and to support them so they are able to participate THE IMPORTANCE OF effectively. It is clear that political commitment at TERMINOLOGY the highest level is required to make such impor- tant changes in project approach. Early commu- It is important to use water reuse terminology care- nity participation will provide an insight into fully with the public. For example, "water" and community attitudes regarding a water reuse project "wastewater" suggest radically different properties and, if necessary, allow time for education to in- and are perceived differently by the general public. crease awareness of the benefits of the project. One should not hide the fact that recycled water is BOX 11. WATER EDUCATION PROGRAM , QUEENSLAND, AUSTRALIA The Australian Water & Wastewater Association, together with the Sunshine Coast Environment Council, has developed a Water Education Program. The program will try to improve public knowledge of wastewater, including what is in it, and how it can be treated and monitored. It will not "market" the concept of reuse as potable water, but rather provide people with knowledge and understanding, so they have an informed opinion. The program will avoid describing the quality of effluent by the amount of treatment it receives; its quality is what matters, not its history. It will be aimed at all ages and groups in the community and recognize all learning styles. Only a small proportion of residents are sufficiently motivated to come to meetings; all others have to be reached in more subtle ways. Two of the problems that will need to be addressed are the reluctance of water managers to consult with the community about future water supplies, which results in the community being unaware of the need for reuse, and gaps in knowledge about some of the health issues. Terminology is of critical importance. In the past, the water industry seems to have had a penchant for negative terminology. Now, the word "disposal" has almost disappeared from the vocabulary. Water is now discharged if it can't be reused. 24 WASTEWATER REUSE produced from wastewater (Box 11), but public dis- it safe by using conservative, worst-case scenarios cussions should carefully distinguish between with likely risks couched as deaths-per-million. This "wastewater reuse" and "treated wastewater reuse." can give a wrong impression to many people, be- Omission of the latter term could give rise to the cause they wonder if that one case could apply to impression that raw sewage will be used, when in them. Personal control over risks is an important fact the wastewater will be treated to a high stan- factor. People are willing to assume more risk if they dard, making it comparable to freshwater. perceive that they have control, such as when driv- ing an automobile. Risks that are outside an In general, professionals implementing water re- individual's control are met with considerably use schemes need to be aware of the perceptions of greater resistance, even if the risks are much lower their target audience. Technical people often play in comparison with voluntary risks. ECONOMIC AND LEGAL ASPECTS OF WASTEWATER REUSE BENEFITS AND COST FACTORS cluded as part of irrigation/aquaculture costs (see Box 2). The complete wastewater treatment plant Wastewater reuse projects are diverse and can in- can be defined as a production unit for irrigation volve improvements in sanitation such as waste- water, and can be designed and built to meet the water collection, water pollution control such as standards for the proposed use rather than for dis- reduction of waste discharges in streams, alterna- charge into receiving waters. In most other cases tive water production, and social or economic im- (for example, wastewater reuse as potable or non- provements such as the development of an potable urban water, or for industrial purposes), al- agricultural area. The benefits to be included in an ternative freshwater sources will be present or economic analysis will depend on the purpose of planned, and so the evaluation of costs and ben- the project. For example, in a project where no efits will involve a comparison of alternatives. To wastewater infrastructure is present and where the prevent overestimation of the cost of the wastewa- goal is to use the wastewater for agricultural pro- ter reuse alternative, the following costs should be duction in an area where freshwater sources are included when assessing the alternative: scarce, the cost of the wastewater reuse system I Wastewater treatment and discharge would include all elements of the wastewater col- I Collection and transport of wastewater to the lection system, wastewater treatment, transport, and wastewater treatment plant distribution to the users. The benefits would include I Wastewater treatment to standards for disposal health improvements (for example, reduction of to receiving waters medical costs), environmental benefits such as re- I Transport of effluent to discharge location duction of oxygen depletion in streams, social/eco- I Costofeffluentdischarge(pollutiontaxesshould nomic benefits, an increase in agricultural be set by government). production, and a reduction in the cost of fertilizer. The following should be included when assessing In developing countries, part of the wastewater col- the reuse scheme: lection system may often be present, but wastewa- I Wastewater reuse alternative ter treatment typically is absent or inoperative due I Wastewater treatment to reclaimed water stan- to lack of funds. Wastewater treatment may not be dards felt by the government to be a priority, if direct short- I Transport and distribution to the users. term benefits are not obvious. However, if the waste- water can be reused for agriculture or aquaculture, In this way, any savings on effluent transport to the then the costs of wastewater treatment can be in- receiving waters, in discharge taxes, and in (addi- 25 WATER RESOURCES AND ENVIRONMENT · TECHNICAL NOTE F.3 tional) treatment to meet increasingly stringent dis- ness of wastewater reuse. Where the treated waste- charge limits are measured as benefits. An example water is intended for agriculture, there is the addi- is the use of advanced wastewater treatment to re- tional risk because of the inter-annual variability move nutrients before discharge into surface wa- in demand from agricultural users. In these cases, ter susceptible to eutrophication. Such advanced the government may need to accept part of the risk treatment can be avoided if effluent is reused, es- in order to attract private investment. Box 12 pro- pecially for agriculture or aquaculture, where the vides an example of public-private sector coopera- nutrients are beneficial. If the treated water is in- tion in a wastewater reuse scheme. tended for potable use and drinking water or other freshwater infrastructure is already present, then ECONOMIC AND FINANCIAL ANALYSES the cost of the reuse system should be compared to the cost of the expected increase in capacity of the The economic evaluation of wastewater reuse present water system if the reuse system is not projects seeks to determine the net benefit to soci- implemented. ety of the proposed investment. The tools commonly used are: Increasingly, the role of governments is seen as I Net-PresentValue (NPV).Ifallormostoftheben- coordinating and regulating water infrastructure efits can be expressed in financial terms (as de- projects; private sector finance is sought to build scribed in the preceding paragraph), the net and operate these schemes. This is also true with present value represents the present value of wastewater reuse schemes. However, even when the benefits minus the present value of the costs. there appears to be a commercially acceptable rate If NPV is greater than zero, the activity has a of return on the investment, there are large risks net economic value. It is also possible to com- associated with water reuse schemes, partly because pare the NPVs of different alternatives (Maxi- of their novelty and partly because of public wari- BOX 12. MANAGING THE RISKS IN THE VIRGINIA PIPELINE SCHEME, SOUTH AUSTRALIA. The Virginia area near Adelaide, Australia, has used groundwater for horticulture for over 50 years. In recent years, water yields have been dropping and salinity has been increasing. At the same time, the operators of the major wastewater treatment plant for the nearby city of Adelaide (1 million people) were required by the Environmental Protection Authority to reduce nitrogen concentrations in their discharges to coastal waters. They decided that the most cost- effective solution was to sell their wastewater to the horticulturalists at Virginia, 120 km away. The government took the roles of promoting and demonstrating large-scale wastewater recycling and providing start-up finance. A private sector operator, who was granted the rights to build and operate the project, supplied the capital investment. The operator, Euratech, a pipe manufacturer, was selected early in the project to give them the opportunity to negotiate agreements with all parties from the beginning. Euratech assumed the construction, financing, and operations risks. The horticulturalists faced risks from the unknown effects of the wastewater quality on their crops. Both operator and horticulturalist risks were reduced by the government, which provided some of the project development costs, assisted with the necessary approvals, and undertook research into the suitability of the water for horticulture. The wastewater plant operators faced the risk that, if the reuse scheme did not achieve its targets, they would have to incur the additional expense of constructing nitrogen removal facilities. The contracts between the parties specified the water quality standards for pathogens, metals, and salinity, and the responsibilities for maintaining the standards. Once the scheme was operational, the horticulturalists were able to obtain contracts with the major Australian super- market chains to accept produce grown with recycled wastewater. They are also selling their produce to Asia. Source: Croke, G., B. Kracman, and C. Wright. 1999. "The Virginia Pipeline scheme, Adelaide South Australia - Commercial solutions to environmental problems," in Medina, J. A., Proceedings of the 17th International Congress on Irrigation and Drainage, Granada, Spain, pp. 93-106. 26 WASTEWATER REUSE mum Net-Present Value Criterion). be necessary to set the price of the water lower than I Cost-Effectiveness Analysis. Cost-effectiveness the price needed to cover costs. In most instances, analysis can be used if it is difficult to express the price should be set lower than the (sometimes the benefits in financial terms. It is a system- subsidized) drinking water price in order to make atic method to compare the costs of alternatives the reuse water attractive for the potential users, that produce the same result. This technique re- particularly during the first few years of operation. quires a single base criterion for the evaluation. Grants, subsidies, and support from national or in- I Impact Analyses or Multi-Criteria Analysis. If ternational organizations can be employed. For long- benefits are difficult to express in financial terms term sustainability, however, prices should and impacts and results of projects are diverse eventually be raised to ensure that capital and op- and difficult to express as a single base crite- erating costs are covered. rion, impact analysis or multi-criteria analysis can be used. A number of positive and negative ESTIMATION OF COSTS impacts are compared qualitatively, including costs, and weighed in a more or less subjective The estimated costs for reclaimed wastewater and manner. reuse projects can be divided into capital costs (Table 6) and operation and maintenance costs (Table 7), Financial analysis refers to the cost and benefits for and include the following costs: a specific user or participant, and determines the I Additional treatment required to meet reuse feasible price of the product. Even if the reuse project standards proves to be economically feasible, compared to the I Conveyance and distribution of the treated cost of developing new freshwater sources, it may wastewater TABLE 6. EXAMPLES OF PARAMETERS FOR ESTIMATING CONSTRUCTION COSTS OF WATER SUPPLY AND RECLAIMED WASTEWATER SYSTEMS Item Main factors influencing cost Key parameters of cost functions Water pipes Diameter, material, class of pipe Diameter of pipe, length Ground storage Storage capacity, construction materials, shape Storage capacity reservoir and structure of reservoir, soil conditions Elevated storage Storage capacity, height, construction Storage capacity and height of reservoir materials, shape and structure, wind and reservoir above ground level earthquake loadings, soil conditions Pumping station Pump capacity, pump head, no. and type of Pump capacity and pumping head pumps used, construction material for station, class and material for pressure pipe Water treatment Plant capacity, type of process and treatment Plant capacity facilities, construction materials, topography of plant site, soil conditions, raw water intake Sewers Diameter of sewer, depth of sewer, materials, Diameter of sewer, mean sewer shape of trench, type of soil, water table level, invert depth, length static and dynamic loading on sewer Wastewater Type of treatment, construction material, area, Area, population equivalent, treatment plant capacity, influent BOD standard 27 WATER RESOURCES ANDENVIRONMENT · TECHNICAL NOTE F.3 TABLE 7. EXAMPLES OF PARAMETERS FOR ESTIMATING OPERATION AND MAINTENANCE COSTS OF WATER SUPPLY AND RECLAIMED WASTEWATER SYSTEMS Item Main factors influencing cost Key parameters of cost functions Water pipes Total length of pipes, material and quality of Total length of pipes, or percentage construction, topography of area, pressure in of construction cost pipes Sewers Total length of pipes, materials and quality of Total length of sewers, or construction, topography of area percentage of construction cost Storage tank Quality of construction, size of structure Percentage of construction cost Water treatment Plant capacity, type of process and facilities, Plant capacity quality of raw water Wastewater Plant capacity, designed efficiency of plant Population equivalent, or BOD treatment type of process and facilities, quality of of influent wastewater construction Pumping station Pump capacity, pumping head, no. and type of Percentage of construction cost pumps, pump efficiency, quality of and pumping head construction, energy cost I Storage to accommodate diurnal and/or sea- nomic situation, local reuse options, and abundance sonal fluctuations of alternatives. Nevertheless, the following examples I Connection,additionalon-sitetreatmentanduse provide indicative costs of wastewater treatment: I Operation, maintenance, and replacement I InTheNetherlands,thecostforwastewatercol- I Monitoring reclaimed water quality and health lection is around $0.50 per m3. The cost for trans- and environmental impacts port to the wastewater treatment plant and I Customerbilling,administration,andoverhead. advanced biological treatment (including nu- trient removal) amounts to another $0.50 per Normally capital cost is a large part (50-80 percent) m3 (2000). of total costs. The capital cost is directly related to I InEgypt,thecostsforwastewatercollectionand the transport, distribution, and storage of the re- wastewater treatment were reported at $0.40 per claimed water. Strong seasonal fluctuation in de- m3 (1990). mand for, or production of, reclaimed water I In Middle Eastern countries, the cost of ad- necessitates very large storage reservoirs. The cost vanced wastewater treatment was reported be- of constructing these facilities may render the re- tween $0.20 and $0.50 per m3 (1997). use scheme economically less feasible. Economi- cal feasibility can be expected to be high if a few Indications for the cost of wastewater reuse large continuous users can be identified close to schemes: the origin of the wastewater, such as an existing I In the Middle East, the use of treated wastewa- wastewater treatment plant. ter as a source for drinking water (high level treatment by reverse osmosis) was calculated It is difficult to provide general guidelines for waste- at $0.40 to $1.00 per m3. This was cheaper than water reuse costs. Total costs vary greatly, because reverse osmosis of seawater at $1.50 to $2.00 they strongly depend on the local physical and eco- per m3 (1980). 28 WASTEWATER REUSE I CEPIS (see Box 3) reported the cost of waste- LEGAL ASPECTS water treatment by a series of disinfection la- goons, followed by fish breeding lagoons in Peru, Legislation for wastewater management usually at $0.10 to $0.20 per m3. The cost was more than consists of a water management component and a balanced by the revenues from the production public and environmental health component. Con- of fish (1985). sequently, different departments of government may I A large chemical industry in the Netherlands be involved, so water supply planners and manag- studied the production of demineralized water ers must address the legal aspects of water reuse in from effluent from their own biological waste- a coordinated way. Depending on the legal require- water treatment plant, instead of producing it ments of different countries and states, the follow- from drinking water. Drinking water cost was ing items may need to be regulated: $1.00 per m3, and demineralized water from I Protection and creation of water rights and al- drinking water cost $0.50 per m3, resulting in a location of water among competing users. Wa- total cost of $1.50 per m3. Demineralized water ter abstraction from a system may result in net from effluent by ultra-filtration followed by re- loss of water as a consequence of return flows versed osmosis cost $1.00 per m3 (1998). not reaching the water system. As a result, the I In India, a petrochemical company decided to rights of legitimate users who rely on such re- reuse secondary treated municipal effluent for turn flows need to be protected. cooling water (15,000 m3/d). Additional treat- I Ensuring adequate protection of public health ment included coagulation by iron, sedimenta- and the environment from changes in flows as tion, filtration, ion-exchange, and chlorination. well as changes in water quality. Total cost of the additional treatment was $0.15 I Apermitsystemforauthorizingwastewaterdis- per m3 (1990). charges. I In Japan, secondary treated municipal effluent I Controls over land uses and activities in the was used for toilet flushing in a business area catchment area (see Box 13). with high-rise buildings (4,000 m3/d). Additional I Water quality standards appropriate to various treatment included filtration and chlorination. uses. Total cost was $3.00 per m3, with a large part of the cost attributed to the extensive distribution To be effective, any legal regime should be accom- system. panied by appropriate standards and enforcement I In Clayton County (USA), secondary treatment mechanisms, including financial incentives, sanc- of municipal wastewater was reported to cost tions, and ultimately possibilities of criminal pros- $0.25 per m3. The effluent was then reused in a ecution (see Note B.2). nature conservation area at a cost of $0.10 per m3. Via groundwater flow and streams, the wa- ter finally reaches the area where potable wa- ter is abstracted (1987). 29 WATER RESOURCES AND ENVIRONMENT · TECHNICAL NOTE F.3 BOX 13. COLLECTION OF URBAN STORMWATER FOR POTABLE WATER SUPPLY , SINGAPORE Singapore has reached a point where around half its total land area is harnessed for water resources. The recent Lower Seletar / Bedok Water Scheme utilizes runoff from residential areas as the main source of raw water. The scheme collects surface runoff and transfers it to two new raw water storage reservoirs. The reservoirs are connected by pipeline to the Bedok waterworks, where there are extensive pre-treatment and treatment processes. The design and operation of the stormwater collection systems also ensures that only the cleaner part of the stormwater is abstracted and pumped into the reservoir. This prevents the low-quality dry weather flow and the first flush during storms from entering the reservoirs. Since its commissioning in 1986, the scheme has delivered raw water comparable in quality to raw water obtained from an upland reservoir with a largely forested catchment. The use of urban stormwater as a raw water source for potable water supply implies that the runoff should not contain excessive concentrations of organic matter and other urban pollutants. Consequently, pollution control measures are incorporated into the spatial planning of the urban area, especially regarding potentially polluting industries. Pollution control measures are imposed where necessary as a condition for planning approval. This is made possible by close and continuous consultations between government agencies to ensure that all new developments in the catchment are non-polluting and that suitable measures are implemented to prevent pollution of the stormwater. CONCLUSION Reuse of wastewater is one of a number of water such high-quality uses as potable supply to lower- conservation measures that are increasingly being quality requirements such as toilet flushing and implemented in water-scarce regions. Reuse of con- cooling water. However, reuse is not a pancea; costs taminated effluent can also provide the additional of treatment can be high, adequate sources of wa- benefit of protecting sensitive downstream environ- ter may be remote from the needs, and the volumes ments from damage. The source of the wastewater required may not match the supply. Nevertheless, can vary-from industrial discharges to urban efflu- there are enough economically successful examples ent to thermal power stations. The treated waste- of reuse schemes to show that it is a viable option water can be used for a range of purposes, from that should be considered in water supply projects. 30 WASTEWATER REUSE FURTHER INFORMATION General information on wastewater reuse can be León, G. and J.M. Cavallini. 1996. Curso de tratamiento y found in: uso de aguas residuales. Lima: Centro Panamer- icano de Ingeniería Sanitaria y Ciencias del Ambiente (CEPIS)/Organización Panamericana U.S. Environmental Protection Agency/Agency for Inter- de la Salud (OPS/PAHO/WHO). national Development. 1992. Guidelines for Wa- ter Reuse. Washington: U.S . Environmental Protection Agency/Agency for International De- Some case studies of reuse schemes are described velopment. in: Water Pollution Control Federation. 1989. Water Reuse, Manual of Practice SM-3. Alexandria, VA: Water Rosenblum, E. 1999. "Selection and implementation of Pollution Control Federation. non potable water recycling in "Silicon Valley" Metcalf & Eddy Inc. 1991. Wastewater Engineering - treat- (San Jose area) California." Water Science & Tech- ment, disposal, and reuse. New York: McGraw- nology 40 (4­5): 51­57. Hill Fong, L.M. and H. Nazarudeen. 1996. "Collection of ur- Rowe, D.R. and I.M. Abdel-Magid. 1995. Handbook of ban stormwater for potable water supply Wastewater Reclamation and Reuse. Boca Raton, in Singapore." Water Quality International FL: Lewis Publishers. May/June: 36­40. Water Environment Federation/American Water Works Husain, T. and A.H. Ahmed. 1997. "Environmental and Association. 1998. Using Reclaimed Water to Aug- economic aspects of wastewater reuse in Saudi ment Potable Water Resources. Alexandria, VA: Arabia." Water International 22: 108­112. Water Environment Federation/Denver, CO: Asano, T., M. Maeda, and M. Takaki. "Wastewater recla- American Water Works Association. mation and reuse in Japan: Overview and imple- World Health Organisation. 1986. Guidelines for Planning mentation examples." Water Science and Community Participation Activities in Water Sup- Technology 34 (11): 219­226. ply and Sanitation Projects. Geneva: World Health Mansour, M. and F.J. McNeill. 1998. "Wastewater reuse Organisation. is key to solving Jordan's water problems." Wa- Khouri, N., J.M. Kalbermatten, and C.R. Bartone. 1994. ter Environment & Technology 10 (11): 44­48. The reuse of wastewater in agriculture: a guide for planners. Water and Sanitation Report No. 6. UNDP-World Bank Water and Sanitation Pro- The International Water Management Institute gram. Washington: World Bank. (IWMI) maintains contact information on waste- water reuse at the following address: Information on handling harmful chemical contami- nants in wastewater can be found in: Citations: http://www.iwmi.org/library/dbsearches/ wwcitations.htm Contacts: http://www.iwmi.org/library/dbsearches/ Chang, A.C., A.L. Page, T. Asano, and I. Hespanhol. 1996. wwcontacts.htm "Developing Human Health-related Chemical Organizations: http://www.iwmi.org/library/dbsearches/ Guidelines for Reclaimed Wastewater Irrigation." wworganizations.htm Water Science & Technology 33 (10­11): 463­472 Projects: http://www.iwmi.org/library/dbsearches/ Mara, D. and S. Cairncross. 1989. Guidelines for the Safe wwprojects.htm Use of Wastewater and Excreta in Agriculture and Aquaculture. Geneva: World Health Organisation (WHO). 31