Wastewater aquaculture: perpetuatingvulnerability or opportunity to enhancepoor livelihoods?

Stuart W Bunting*Institute of Aquaculture, University of Stirling, Stirling FK9 4LA, Scotland, UK

* Corresponding author: s.w.bunting@stir.ac.uk

Submitted 26 January 2004; Accepted 16 July 2004

AbstractDefinitions for wastewater, aquaculture and direct and indirect reuse addressing bothtechnical and sociopsychological considerations are presented to guide the review. Evi-dence of wastewater aquaculture from historical and contemporary accounts demonstratesthat the practice has a long tradition, and it is currently widespread, with examples citedfrom diverse geographical, environmental and sociopolitical settings. Outcomes of thisreview demonstrate that some poor people depend both directly and indirectly onwastewater aquaculture for a significant part of their livelihood, whereas society moregenerally benefits from appropriately managed wastewater reuse. Wastewater reuse con-tributes to environmental protection, reduced public health risks and the supply ofenvironmental goods and services, which often play an important role in poor livelihoods.However, various constraints, including urbanisation, labour migration, erosion of a com-petitive advantage, uncertainty over wastewater supplies, contamination, health concerns,operational constraints and ineffective policies, institutions and processes, combined withrising expectations and changing perceptions, mean traditional farming practices andcoping strategies are threatened. Conclusions of this review include the need to under-stand better the importance of wastewater aquaculture in poor livelihoods and to com-municate this effectively to policymakers, enabling them to confront the realities ofwastewater aquaculture, and where appropriate, support livelihood diversification,thereby lessening the vulnerability associated with this practice.

Keywords Wastewater, Aquaculture, Vulnerability, Poor, Livelihoods, Diversification, Policy

Introduction

The fact that wastewater is routinely and widelyexploited in various agricultural practices is gaininggreater recognition, as exemplified in the recent‘Hyderabad declaration on wastewater reuse in agri-culture’ that stated:

Wastewater (raw, diluted or treated) is a resource ofincreasing global importance, particularly in urbanand peri-urban agriculture1.

Furthermore, the signatories:

strongly urge policy-makers and authorities in thefield of water, agriculture, aquaculture, health,

environment and urban planning, as well as donorsand the private sector to: Safeguard and strengthenlivelihoods and food security, mitigate health andenvironmental risks and conserve water resourcesby confronting the realities of wastewater use inagriculture through the adoption of appropriatepolicies and the commitment of financial resourcesfor policy implementation1.

This review provides a contemporary account of thenature and extent of wastewater aquaculture to high-light aspects of the practice that may create orperpetuate vulnerability, especially in poor livelihoods,and to contextualise, in a highly descriptive manner,opportunities for enhancing poor livelihoods throughthe formal adoption of wastewater aquaculture. The

g CAB International 2004 Aquatic Resources, Culture and Development 1(1), 51–75

ISSN 1477-903X DOI: 10.1079/ARC20041

review draws heavily not only on scientific and greyliterature surrounding the topic, but also on interviewswith key informants and recent findings from multi-disciplinary research projects. Critical knowledge gapsdemanding attention are identified and actions toaddress them are discussed. This review provides aresource to assist decision-makers and policy formersto develop appropriate policies, institutions and pro-cesses and thus be able to confront the realities ofwastewater aquaculture.

Some definitions are offered to guide better and focusthe review. Wastewater is defined here as water dis-charged through sewers and drainage channels fromblue water societal systems once it has fulfilled itsprimary function2. The United Nations, Food and Agri-culture Organization (FAO) has defined aquaculture as

farming of aquatic organisms, including fish, mol-luscs, crustaceans and aquatic plants. Farmingimplies some form of intervention in the rearingprocess to enhance production, such as the regularstocking, feeding, protection from predators, etc3.

A further delineation of wastewater aquaculturepractices is possible through consideration of thesociopsychological dimension, based on which twodistinct categories can be defined:

� first, direct reuse, the planned and deliberate use ofwastewater as a nutrient and water resource,

� secondly, indirect reuse, without recognition of itsprevious use, in waterways contaminated or in-directly enriched through wastewater4.

However, to consider indirect use as well in thisreview, a further clarification is needed regarding thefull definition of aquaculture presented by FAO thatcontinued:

Farming also implies individual or corporate owner-ship of the stock being cultivated. For statisticalpurposes, aquatic organisms that are harvested byan individual or corporate body that has ownedthem throughout their rearing period contributeto aquaculture, whilst aquatic organisms that areexploitable by the public as common propertyresources, with or without appropriate licenses, arethe harvest of fisheries3.

Here, however, some key criteria proposed byBeveridge and Little to distinguish between farmingand hunting or fishing are invoked, namely:

there is some form of intervention(s) to increaseyields; and there is either ownership of stock orthere are controls on access to and benefits accruingfrom the interventions5.

Historical accounts

Based on the above definitions, wastewater aquacul-ture has been practised for millennia, with the historicalrecords containing references to both direct andindirect practices. Archaeological evidence suggestsaquaculture was practised in wastewater from Romanvillas; excavations across England have demonstratedthat fishponds dating from the first to fourth centuriesAD were often associated with complex engineeringworks for water management, and that fishponddesigns permitted the control of flow rates and pre-vention of flooding. Significantly, however, channelsconveying water from rivers, streams or springs to theponds often passed first through the villa complexwhere the water was used for various purposes6.Evidence from monastic sites at Vauclair, France andMaulbronn, Germany shows that during the thirteenthcentury, fishponds were constructed downstream of theabbey latrines, where they received wastewater rich innutrients7. Direct wastewater aquaculture was revivedin Germany during the first half of the twentieth cen-tury; 90 sites have been identified across the country8,9.The practice was also adopted in Czechoslovakia,Poland and the Soviet Union and accounts of directwastewater aquaculture in sewage treatment pondsduring the second half of the century have come fromThika, Kenya; Dwangwa sugar estate, Malawi; KwaMashu, Durban, South Africa; and Marandellas,Zimbabwe4.

The history of wastewater aquaculture in Asia ismore recent, with large-scale systems in China, India,Indonesia and Vietnam emerging only during the lastcentury. Development of sewers by the occupyingcolonial powers in cities such as Bandung, erstwhileCalcutta and Hanoi gave rise to substantive wastewaterflows that were exploited by local people to culture fish.Earlier, sewers were constructed around 2500 BC by theAssyrians and Babylonians, for example at Eshnunna,northeast of present Baghdad, and excavations haverevealed widespread sanitation in the Indus civilisationaround 2550 BC and, slightly later, examples developedby the Minoans10. However, in discussing sanitation atthe Palace of Minos, Crete, it was noted that

in the Middle Minoan Period, dated about 1900–1700 BC, elaborate systems of well-built stone drainswere constructed, which carried sewage, roof waterand general drainage. The main drain transportedthese wastes a considerable distance beyond thepalace, but we do not know the method of theirfinal disposal10.

This account highlights that, although physical proofexists of sewers from many early civilisations, there isan absence of documented or archaeological evidenceto suggest either direct or indirect wastewater reuse in

52 Stuart W Bunting

agriculture. However, where nutrient-rich wastewaterwas being collected and channelled through sewers,it appears reasonable to expect that local farmerswould have exploited wastewater for agriculturalpurposes, and where the practice was established,for aquaculture.

A comprehensive review of wastewater aqua-culture, conducted a decade ago, identified two Asiancountries (Indonesia and Sri Lanka) where indirectreuse was an established and ongoing practice4.Surface water containing human waste was used inIndonesia to grow fish in ponds, raceways and cages;local farmers from Bogor devised a strategy to culturecommon carp (Cyprinus carpio) in bamboo cagespositioned in canals containing diluted wastewater.Beira Lake in Colombo, Sri Lanka, received significantvolumes of wastewater from surface drains and thebusinesses and tenements bordering the lake, andfollowing an initial stocking with tilapia (Oreochromismossambicus), local fishermen were able to harvestaround 2.5 t ha-1 yr-1 from the freely breeding fishpopulation. Unintentional reuse of wastewater was alsoreported for fort moats, village tanks and ditches inBangladesh and India; however, it was also noted that

The unintentional reuse of excreta in aquaculture,especially the use of fecally polluted surface waterin fishponds, is probably widespread, but it hasrarely been documented4.

The contemporary situation

Uncertainty concerning the extent of indirect waste-water reuse in aquaculture persists. However, thepractice may be widespread and of significance inmany poor livelihoods, since around 2 billion peoplelack adequate sanitation and 4 billion are not served bywastewater treatment, and there is increasing pressureto produce food using any accessible resource. Thissection outlines contemporary accounts drawn fromvarious sources, the objective being to show thatwastewater aquaculture is a reality, diverse in characterand widespread, and that the nature and location ofproduction means external forces and pressures arehighly influential. As a result, trajectories of change inmanagement, location and distribution and the bene-fits afforded to society are dynamic.

Although providing the earliest examples reviewedhere, wastewater aquaculture in Europe is now largelyconfined to reusing wastewater from industrial pro-cesses. Cooling water from power stations is used toproduce ornamental fish in Bulgaria, to raise juvenilefish in France for on-growing in sea cages, and inEngland, to culture marine worms for fishing bait andfeed for shrimp broodstock11. In countries around theMediterranean, many of which are arid and semi-arid,

the need to integrate wastewater reclamation andreuse in water resource planning and managementis gaining recognition; wastewater irrigation is alsoincreasingly being adopted12. Furthermore, article 12 ofthe European Wastewater Directive (91/271/EEC) hasstated that

Treated wastewater shall be reused wheneverappropriate13.

However, research in Egypt showed that wastewateraquaculture practices which satisfy health andhygiene guidelines and standards will not be viableif consumers are unwilling to accept products culturedthis way14.

Recent accounts of wastewater aquaculture fromAfrica focus mainly on fish culture in ponds or lagoonsdesigned for sewage treatment. Ampofo and Clerk15

report that in southern Ghana, tilapia (Oreochromisniloticus) are grown in ponds at Akuse, Many KroboDistrict; whereas no data are presented on the volumeof fish produced, on management and marketingstrategies in operation or the extent of the practiceacross the country, the authors do note that

The cost of inorganic fertilisers to enrich fishpondsis making the practice less attractive to fish farmersin Ghana. This has, accordingly, diverted interest toother sources of enrichment of their ponds. A grow-ing trend in fish farming in Ghana today is to feedthe fish with products from agricultural waste andby-products from sewage treatment.

Another account of direct wastewater aquaculturecomes from Nigeria, where sewage water from a resi-dential area was used to raise common carp andSarotherodon galilaeus16.

Wastewater aquaculture is most widespread in Asiaand is known primarily from accounts of systemsaround Kolkata (Calcutta), India and Hanoi, Vietnam.Ponds managed for wastewater aquaculture wereestablished in Kolkata early last century in wetlandsclose to sewerage canals draining away from the city;horticultural plots distributed amongst the fishpondsand rice paddies further from the urban fringe are alsoirrigated with wastewater17,18. Ponds managed forwastewater aquaculture cover around 3500 ha, withproduction of carp and tilapia recently estimatedby Little et al.19 at �18 000 t yr-1; fish is sold throughnearby markets in central Kolkata, many of which servepoor communities. Wastewater aquaculture is widelypractised around Hanoi and is concentrated in ThanhTri district. During the 1960s, a central canal system wasconstructed to transport wastewater away from urbanareas, and fishponds were subsequently developedadjacent to this canal from which wastewater waspumped into them. Fish yields averaging 5.6 t ha-1

Wastewater aquaculture 53

have been reported for a 10-month grow-out period;in 1992, the system produced 3900 t of fish20.

Contemporary accounts, however, indicate thatwastewater aquaculture, especially indirect reuse, isprevalent in other countries in the region, in particulararound major cities, including Phnom Penh inCambodia, Ho Chi Minh City in Vietnam and Bangkokin Thailand. In southeast Asia, aquatic plant productionconstitutes an important and widespread but generallyunacknowledged wastewater aquaculture practice.Reviewing the status of wastewater aquaculture inChina, it was noted that in 1985 there were over 30 sites,covering an area of 8000 ha and producing 30 000 t offish annually21. Ponds managed for wastewater aqua-culture were concentrated around Wuhan, Hubei Prov-ince (4200 ha), followed by Changsha, Hunan Province(1500 ha), and Tianjin, Hebei Province (800 ha). Therehas been a recent decline in the use of wastewater inaquaculture in China since it has been constrained byeutrophication, causing fish kills and industrial pollu-tion leading to undesirable taste and odour in fish22.

Although wastewater reuse for irrigation is wide-spread in central and south America, with notableexamples from Mexico and Peru, direct wastewateraquaculture in the region is limited. During the 1980s,a demonstration unit was established at the San Juande Miraflores waste stabilisation pond complex, Lima,Peru with the following objectives: to optimise theeconomics of fish production; to establish a practicalprotocol for public health monitoring to enable con-sumer safety to be certified; and to conduct a detailedsocioeconomic study to assess the potential of waste-water aquaculture for Peru and other countries23. Itwas demonstrated that tilapia (O. niloticus) cultured inthis way was safe from a public health point of view,was acceptable to consumers and that the proposedapproach was economically viable24. Aquatic plants,covering lagoons and planted in wetlands, are widelyused to treat wastewater in north America, althoughthe biomass produced is largely used for animal fodderor is composted. Using fish to graze periphytongrowing in wastewater to sequester nutrients has beenstudied and indeed patented, but its commercialviability in a north American context appears limited.

Summary

Historical and contemporary accounts, as describedabove, demonstrate that wastewater aquaculturehas developed under a wide range of geographical,biophysical and socioeconomic settings. Wastewateraquaculture has often been developed by local peopleto exploit unutilised resources and, consequently, adiverse range of practices has emerged to suit localenvironmental, sociopolitical and market conditions.Furthermore, the absence of differentiation between

wastewater and non-wastewater aquaculture by agen-cies responsible for collecting and collating productiondata makes it difficult to state with any authority theactual extent of the practice. Potential problems inestablishing monitoring programmes to evaluate theextent and importance of wastewater aquaculture arediscussed in the section ‘Policies, institutions and pro-cesses’ dealing with policies, processes and institutionalissues. However, briefly addressing the practical issues,even where an intensive monitoring programme isimplemented, it may be difficult to distinguish betweenwastewater and non-wastewater production, especiallywhere indicators such as faecal coliforms are used; arecent study of fish production in Saudi Arabia showedsignificant loadings of faecal coliforms in the ponds,originating from pigeon droppings25. Regional reviewsof sanitation coverage, wastewater treatment, surfacewater quality and aquaculture production practiceswould be required to assess more fully the extent andimportance of wastewater aquaculture.

Contextualising vulnerability associated withwastewater aquaculture

This section reviews some aspects of wastewateraquaculture that seemingly lead to weak sustainabilityand which may increase the vulnerability of poorpeople. Despite several recent accounts showing thatwastewater aquaculture is a widespread and estab-lished practice in several countries, other studies havesuggested that the practice is on the decline. Furedy26

reported such a decline in several countries, i.e. Japan,Malaysia and Taiwan, and that in China, aquacultureusing human excreta was due to be phased out.Furthermore, Muir et al.27 reported a general decreasein production from fishponds in peri-urban Kolkata,widely regarded as a model system for what can beachieved through wastewater aquaculture. Otherindicators, including the area managed for wastewateraquaculture and the number of people employed alsoportrayed a general decline. Considering traditionalwastewater aquaculture practices, a number of factorsappear to threaten continued operation and constrainthe development of more refined management strate-gies; however in the case of Kolkata, a complex arrayof factors have impinged upon this established andproductive system. More recently, Edwards28 in a state-of-the-art review of wastewater aquaculture, paintedan overall negative picture. The following sectionsoutline the main factors implicated in the decline ofwastewater aquaculture.

Urbanisation

Varied forces contribute to the process of urbanisation:increased access to the urban fringe, associated with

54 Stuart W Bunting

new roads and improved public transport, increasesthe attractiveness of land at the edge of towns andcities to industry and commuters; newly establishedindustries on land at the urban fringe represent astimulus to the development of settlements foremployees; migration of people from rural areas insearch of employment and other perceived benefits ofurban dwelling contributes to the pace of urbanisation,with recent migrants joining peripheral shanty townsand setting up shelters and dwellings on marginal land.Labour migration as a factor undermining traditionalwastewater aquaculture practices is discussed furtherin the following section. These processes, in combina-tion, constitute important factors contributing todevelopment pressure at the peri-urban interface,and as a result, traditional extensive waste treatmentand reuse strategies are often seen as archaic andredundant, especially when alternative technologiesrequiring less land area exist.

This conflict was made explicit by the proposedscheme to abandon 52 ha of oxidation ponds on theoutskirts of Gaborone, Botswana, in favour of anactivated sludge wastewater-treatment system29. TheGaborone oxidation ponds received �25 000 m3 d-1 ofwastewater from the city and achieved a reasonablyhigh level of treatment; the final effluent was used toirrigate vegetables, a golf course and hotel gardens,water livestock, meet the demand of constructionactivities and was discharged to Gaborone Gamereserve to rehabilitate swamps and marshes. Further-more, treatment employing oxidation ponds requiredno machinery or energy. However, the Gaborone CityCouncil considered that the land area required foradditional ponds to service the needs of the growingurban population was unacceptable. This techno-centric approach to development is not necessarilyan answer in itself; more intensive technologicalwastewater treatment merely concentrates thewaste flow, which ultimately still requires disposal30.Concomitantly, treated water produced may be lessdesirable for subsequent reuse due to its reducednutrient status, although of some use in meeting plantwater needs.

Urban development encroaching into peri-urbanareas affects the physical environment and leadsto more subtle changes in social interactions. TheGovernment of India in the recent past imposedcompulsory acquisition notices on peri-urban areas ofKolkata used for horticulture and wastewater aqua-culture; this had a direct impact on the people dis-placed and generated feelings of insecurity within themore general community. The largely unregulatedsprawl of the urban fringe is seen as an irresistibleforce, once again generating feelings of insecurity,which manifest themselves in what have been termed‘law and order’ problems; it appears that disgruntledlabourers, confused as to the legal basis of ownership,

dewater the ponds and poach the fish prior to theseemingly inevitable cessation in operations18.

Poaching has been described as a key constraint tothe sustained operation of ponds managed for waste-water aquaculture around Kolkata, a sentimentconfirmed by key informant interviews. Wastewateraquaculture emerges mainly in peri-urban areas, whichare characterised by poor communities that are highlytransient and seldom interact for shared aims. Thesefactors contribute to the absence of communityidentity, and this has been proposed as one reasonwhy individuals and groups poach fish from localponds, reducing financial returns to pond managersand operators. Harrison et al.31 analysed poachingfrom fishponds in rural societies in Africa from theperspective of asset redistribution from the better offand more socially and politically active communitymembers towards poorer groups and individuals.Where this was a broadly tolerated levelling mechan-ism, the process might be seen as satisfactory;however, poaching is often an orchestrated andfrequently violent affair in Kolkata and is unlikely tobe of equal benefit to members of the poorercommunity. Anti-social behaviour such as poaching,theft and vandalism represents a serious constraint toinvestments in infrastructure and improved manage-ment strategies in peri-urban production systems.

Distribution of the benefits from aquaculture toa wider section of the community can occur throughpresentation of fish to family and friends as gifts.Such practices are common as a means of socialexchange and regulation, and may be importantmechanisms for acceptance of new or modifiedactivities. A pond owner in Saidpur, Bangladesh,found that by distributing some fish at harvest timeto community members residing closest to his ponds, itwas possible to reduce the proportion of unaccountedfor fish32. This was attributed to either a reduction inthe poaching carried out by the recipients or greatervigilance on their behalf, reducing the incidence ofboth poaching and predation. The pond owner alsoengaged in another socially oriented managementstrategy; by allowing landless people to settle onembankments surrounding his ponds, poaching andpredation were again reduced through greater vigi-lance, whereas the excavation of pond sediment by thesettlers to build up the embankments upon which theirdwellings stood, protected both their property and thepond from flooding.

In contrast with the scenario presented above, thedemand for land and potential benefit from selling thisasset may encourage some land owners to limit accessto their property; from the perspective of the owner,restricting access may prevent others from laying claimto rights over the property and reduce the potential forconflict that could delay or disrupt the sale. Mechan-isms employed to restrict access may include the

Wastewater aquaculture 55

termination of leases or actively discouraging thecontinued operation of production practices. Feelingsof insecurity engendered through the common prac-tice of issuing only short-term leases have been cited asstifling innovation and constraining investment in themaintenance of the existing infrastructure supportingwastewater aquaculture in peri-urban Kolkata.

Labour migration

Many studies suggest that migration of householdmembers from rural to urban areas is prompted by anumber of ‘push’ and ‘pull’ factors, e.g. limitedlivelihood options in rural communities or opportu-nities for livelihood enhancement in urban settings,respectively. However, in many cases, rural–urbanmigration reflects traditional patterns of labour move-ment determined by social and cultural institutions,and societal strategies to obtain livelihoods33. Con-sidering the status of those families involved inhorticulture and aquaculture around Kolkata, a sig-nificant number of those sub-letting vegetable plotsand employed by operators of ponds managed forwastewater aquaculture were migrants from otherstates34. Furthermore, informal tenure arrangementsdescribed by this author indicate that tenants com-monly sub-let vegetable plots to their relatives,suggesting that access to land may be restrictedthrough family patronage. Tenure over land resourcesin peri-urban areas is frequently governed by anumber of structures and processes that may conflictwith traditional and less formal tenure agreements.Therefore, the farmers interviewed were generallyreluctant to discuss issues of tenure.

Migration of people within rural areas and from ruralto urban areas has been documented in a number ofsettings. In contrast, studies focusing on migration ofindividuals from peri-urban to urban livelihoods arefew, possibly because this type of migration is notconsidered significant or the difficulty in assessing ifand where it is occurring has constrained detailedanalysis. However, after an investigation of the prob-lems affecting farmers in peri-urban Kolkata, Kundu18

noted that loss of labour to more lucrative employmentrepresents a constraint to continued operation. Experi-ences from other regions also demonstrate that theopportunity cost of labour is a determining factor inthe livelihoods adopted by household members.Traditional low-input aquaculture in northeast Thai-land, based largely on buffalo manure and some off-farm inputs, is declining because it contributes lessthan 10% to the income of small-scale farmer house-holds, with much of the household income now beingderived from off-farm employment35.

Enhancing the benefits derived by the poor fromwastewater aquaculture, through increased wages and

more secure employment arrangements, may contri-bute to the retention of skilled employees in theseactivities. However, where such arrangements aredifficult to implement, it may be necessary to explorevarious options to transfer skills more effectively tonew employees. Although not reported in the litera-ture, it could be inferred that if dynamic labourmarkets exist in peri-urban areas with the frequentmovement of individuals to more attractive urbanemployment, then this would create opportunitiesfor underemployed community members and recentmigrants to capitalise on these vacancies, permittingthem to consolidate their asset base and, in turn, gainaccess to better employment opportunities in urbanactivities. However, despite apparent benefits from thisprocess of livelihood enhancement to the individualinvolved, broader issues, such as access to informationregarding opportunities, transaction costs, loweredlabour intensity in rural areas, remittances and expecta-tion of returns from inheritance of or continued accessto rural income-generating activities, may stronglyinfluence the potential benefit derived by the indivi-dual, household and community. In combination,these and other factors will influence the decision ofwhether or not an individual should migrate.

Erosion of a competitive advantage

When threatened by development during the 1950s, akey argument for retaining the network of ponds,paddy fields and horticultural plots in the Salt Lakearea located northeast of Kolkata was that it wasan ideal location from which to supply fresh produceto urban markets18. With the advent of new roadsand increased access to transportation, these marketsbecame easily accessible to more distant producers.Morrice et al.36 noted that the majority of large Indianmajor carp on sale at wholesale markets in Kolkata hadbeen brought from other States, by truck from UttarPradesh and train from Chennai, Orissa, Gujarat andPunjab. However, these larger fish were usually cutinto steaks for sale in middle-class retail markets andwere found rarely in markets serving poorer com-munities. These authors have also described thechanging market demand for fish with respect to size,species and freshness depending on prosperity of thecommunity served. Furthermore, they have describedhow operators of wastewater ponds tended to producesmall fish to reduce risk, highlighting the diversity ofmotivations for aquaculture producers. Investigatingthe diversity and price of fish for sale in suburbanmarkets serving the poor, these authors observed thedominance of small freshwater fish harvested fromlocal ponds managed for wastewater aquaculture.

Despite the higher price per unit weight for largerfish, managers of these systems continue to harvest

56 Stuart W Bunting

small fish to reduce risks posed by flooding, poachingand poisoning, both intentionally and through thecontamination of wastewater inputs; managementstrategies, which include multiple stocking and harvest-ing, and selling live fish which command a premium,have been adopted to optimise small fish productionand compensate for the price differential between largeand small fish. In one market, the authors observedthat small (100 g) live tilapia commanded a higherprice compared with equivalently sized Indian majorcarp, although wild fish attracted the highest prices inboth urban and suburban markets.

Uncertain waste resource supplies

Individuals engaged in wastewater aquaculture inKolkata have no say concerning the water level inthe main drainage canals, and consequently, the waste-water supply is largely unpredictable; the KolkataMetropolitan Corporation and Department of Irrigationand Waterways which oversee drainage operations areapparently under no obligation to meet the needs ofthese local farmers. Muir et al.27 noted that since farmersdid not pay for wastewater, there was little incentivefor the authorities to meet their needs. Recent researchconducted with 56 farm managers in peri-urbanKolkata, summarised in Table 1, showed that uncertainwastewater supply constituted the most widespreadand significant constraint.

Factors other than institutional difficulties alsoconstrain the equitable distribution of wastewateramongst users. Siltation of urban drainage systemshas been implicated in limiting the degree of controlurban authorities have over water levels in the canalsused to supply fishponds; problems with pumping

station maintenance and regulating the operation ofsluice gates have also been implicated in hamperingwastewater delivery. A further factor to consider is thatof competition between those farmers and groups ex-ploiting the wastewater resource. Introducing a pricingsystem for the waste resource may be one approach tooptimise the efficiency of resource utilization. Althoughsuch a strategy would probably disadvantage somepoor people, those engaged in service provision,labouring, seed and table fish distribution and poorconsumers would benefit. The potential for develop-ing markets for waste resources through stimulatingimproved supply channels has been further highlightedby Furedy et al.37; where traditional solid waste reusepractices have declined, establishing markets fororganic waste may promote separation and collection,increasing the value of this resource to farmers andproviding income for those involved in waste pro-cessing.

Contamination

Contamination of wastewater resources represents apotential constraint to the sustainability of the tradi-tional irrigation and aquaculture practices that haveevolved in many and varied locations. In Dhapa,Kolkata, ponds managed for wastewater aquacultureare frequently contaminated with industrial pollutants;farmers have been observed filling fishponds withindustrial wastewater that appeared purple due to thehigh concentration of chromium. Following a periodof time, after which the water had lost its distinctivepurple appearance, fish were stocked in the belief thatthe water had been purified. However, among stake-holders in the region, there is widespread concern that

Table 1. Constraints to peri-urban aquaculture based on the perceptions of farm managers (n = 56)

Constraint

Proportion ofrespondents affected(%)

Mean rankassigned by participants

Overall ordinalrank

Uncertain wastewater supply 86 1.1 1.0Financial problems 25 2.0 2.5Declining wastewater quality 9 2.0 2.5Poaching 34 2.5 4.0Labour problems 30 2.6 5.5Siltation in fishponds 23 2.6 5.5Management problems 5 3.0 8.0Poor road infrastructure 5 3.0 8.0Poor seed quality 2 3.0 8.0Limited access to electricity 9 3.2 10.0Disease 29 3.3 11.0Threat from land developers 7 4.0 13.0Law and order problems 4 4.0 13.0Inundation during flooding 2 4.0 13.0Declining production 5 4.3 15.0Transport problems 2 5.0 16.0

Note: 5% of respondents were unable to identify specific constraints to production (Source: Bunting et al.17).

Wastewater aquaculture 57

products from wastewater aquaculture are being conta-minated with heavy metals from tanneries operatingat the eastern edge of the city. Anecdotal evidence sug-gests that the problem of contamination with tannerywastewater is a cause for concern, although it isimpossible to assess the extent of the problem due tothe absence of a formal monitoring programme.

The heavy metal content of fish and vegetablespurchased from urban and suburban markets inKolkata was higher than that in similar productspurchased from rural markets, although all concentra-tions recorded were within permissible limits forhuman consumption38. Studies on the bioaccumula-tion of metals in fishponds receiving a high proportionof industrial effluents in peri-urban Kolkata demon-strated that fish from these ponds had accumulatedhigher levels of copper, lead, zinc and chromium thanthose from neighbouring ponds; the accumulation wasfound to vary between species and between tissuetypes39. Focusing on the dynamics of mercury infishponds receiving wastewater from Kolkata, it wasfound that fish from these ponds did not containmercury levels above the permissible level40. Theauthors do report, however, that highest mercurylevels were recorded in sediment-dwelling fish speciesand this may have implications for stocking andmanagement practices. Cage culture, which has beenpractised successfully at ponds receiving wastewater inSouth Africa, represents one management practicehaving the potential to reduce the risk of fish beingexposed to contaminated sediments41,42. The fre-quency with which people consume fish will alsoinfluence the degree of exposure to contaminants;therefore, consumption patterns and dietary intake,which may change with respect to age, gender orwell-being, also require consideration in developinga comprehensive risk assessment.

Under other circumstances, increased industrialpollution has led to changes in reuse access; consider-ing wastewater aquaculture in Thanh Tri district,Hanoi, Vietnam, the Set River is now the main sourceof wastewater, since the To Lich River is not used dueto industrial pollution. In fact, the entire wastewaterreuse system is apparently in decline as the canalsystem has fallen into disrepair with the end of thecommunes and the change to a free market economy.Inadequacies of the wastewater supply system haveresulted in fish producers purchasing by-products fromthe local breweries; reduced usage of wastewater hasalso resulted in an increased discharge of untreatedwater to the local river. Problems of contaminationhad also been encountered in a Chinese wastewateraquaculture system in Wuhan, China, where the fishcultured were reported to smell and taste of phenols.Therefore the grow-out system was converted intonursery ponds, thereby removing any problem withconsumer acceptability4.

When considering the potential of wastewater aqua-culture, the risk posed by its chemical and biologicalconstituents should be carefully assessed; it may benecessary to conduct preliminary monitoring to estab-lish the suitability of the wastewater. In small-scalesystems, it may be sufficient to conduct a generalsurvey of the area from which wastewater is collected;local knowledge may be invaluable in identifying small-scale industries that could potentially pollute waste-water derived largely from domestic sources. A rangeof such activities associated with hazardous wasteproblems have been identified in developing countries,including tanneries, textile dyeing plants, dyestuffproducers, metal working and electroplating shops,foundries, vehicle-repair shops and petrol stations43.

In addition to the possible contamination associatedwith wastewater reuse, other sources of pollutionrequire consideration. Indiscriminate dumping of solidwaste and refuse may cause serious problems foroperators of peri-urban farming systems; physicalfilling of waterways with rubbish may interfere withdrainage and affect wastewater distribution to farmers,whereas dumping of toxic or hazardous chemicals maycontaminate water supplies or waste resources. Theseeffects are in evidence at the Kolkata peri-urbaninterface, where a large land area has been designatedto receive the majority of solid waste collected by themunicipal authorities. Agrochemical drift or leachingfrom neighbouring agro-ecosystems represents afurther constraint to peri-urban production, especiallyconcerning aquaculture, where the effect of pesticidesand herbicides applied in terrestrial farming may havea severe effect on the aquatic environment andpossibly contaminate the plants and animals beingcultured. Consequently, the management of agricul-tural land close to canals, ponds and lakes in peri-urban areas may require modifications to preventcontamination. Practical steps to safeguard againstagrochemical contamination may include creatingbuffer zones between aquatic and terrestrial farmingsystems and developing guidelines for those apply-ing chemicals. Buffer zones between landfill sites andproduction systems would also assist in preventingcontamination. However, leachate management mayrequire prior planning to facilitate collection andtreatment to prevent this potentially diffuse pollutionsource from contaminating neighbouring farms,surface-water and groundwater resources.

A further threat of contamination, especially inwastewater reuse systems, is indiscriminate defecationof local residents and workers, resulting in pathogenloads at inappropriate places. Where water supply andsanitation are not adequate, local residents probablyuse ponds managed for wastewater aquaculture forbathing and defecation44. Therefore, these authorspropose that provision of water supply and sanitationfor local communities is important for controlling

58 Stuart W Bunting

human exposure to contamination. However, imposi-tion of modified defecation practices on target groupsis widely regarded as an ineffective means of achievingsustainable behavioural change. The key feature inachieving long-term behavioural change is coopera-tion of the community with the decision process,leading to the proposed behavioural change. Thesuccess of this methodology ultimately depends onthe perspective of the target group, although theseperceptions are open to external influences suchas education and peer pressure. Consequently, it maybe possible to increase the proportion of the targetgroups that adopt the proposed modified system bybeginning the project with a period of communityeducation or, where appropriate, demonstration orpilot projects.

Health concerns

A number of authors have described possible healthhazards associated with wastewater aquaculture,wastewater irrigation, garbage-fed horticulture andperi-urban livestock farming4,44–49. Although thesereports make the hazards associated with each farmingstrategy explicit, it is much more difficult to quantifythe associated level of risk. The risk associated withproducts grown using waste resources varies, depend-ing on the characteristics of the waste resource, degreeof treatment prior to use, nature of the culture system,husbandry and processing practices, subsequent hand-ling and preparation and susceptibility of the consumer.A review of the health hazards, associated with usingwastewater and excreta in agriculture identified fourgroups of people at risk: field workers, crop handlers,local residents and consumers44. The following sectionsdescribe hazards faced by different groups, factors thatinfluence the degree of risk and potential mitigationstrategies.

Field workers and crop handlersEnsuring the health and safety of employees engagedin farming practices exploiting waste resources is anessential component in managing the risks associatedwith such practices. Protective clothing and, whereappropriate, regular treatment of workers for intestinalhelminths will limit the transmission and negativehealth impacts of parasites and bacteria. Continuoususe of appropriate footwear can reduce and even elim-inate infection of workers with hookworm, althoughpersuading employees to follow this procedure maybe difficult44. As with encouraging modified defecationpractices in local communities, the key to implement-ing these safeguards is to encourage behaviouralchange through the education of employees. Further-more, the need for education regarding health risksposed by products cultured using wastewater extends

to those involved in handling and processing. Buras50

noted that

During cleaning and evisceration of fish, anypathogens present contaminate the hands of han-dlers and cleaners before the fish are cooked. Thus,contaminated fish can be vectors for the trans-mission of pathogens from the pond water tohandlers. The handlers and cleaners constitute theprimary foci for the transmission of pathogens totheir families, and later when the infection hasensued, to other people.

Although the risk to these individuals may be less thanthat posed to field workers who may come into contactwith raw wastewater, precautions such as wearinggloves and close attention to personal hygiene aredesirable; prophylactic use of chemical control agentsand provision of adequate facilities to treat diarrhoealdisease are also recommended for highly exposedgroups44.

Local residentsA study concerning pathogenic protozoan transmis-sion as a result of wastewater reuse around Marrakeshhighlights the possible negative impact of suchpractices on local communities51. Stool samples takenfrom two groups of children showed that those livingin areas where wastewater was used to irrigate agri-cultural land were more than twice as likely to beinfected with protozoa as a control group living inan area where surface water was used. The authorsconcluded that exposure to wastewater used forirrigation was the main causative agent of increasedprotozoan infestations among children living in peri-urban areas. Providing local residents with informationabout waste reuse practices in the area, e.g. the locationof all fields and ponds where human wastes were used,was recommended so that they could avoid thesefarms and prevent their children from entering theseareas. Warning signs were also considered necessary,especially where fences were absent; where sprinklerirrigation was employed, a distance of 50–100 m wasrecommended to be maintained between the irrigatedarea and houses or roads44.

ConsumersTo assess the risk posed by the transfer of water-bornediseases via wastewater aquaculture, it is important tostudy the prevalence of these diseases in the popula-tion served by the collection system. Having ascer-tained the possible level of pathogens in the wasteresource, it will be apparent what level of treatment isrequired to safeguard the aquatic organisms beingcultured. Buras50 proposed that wastewater loadingsshould ensure pathogen numbers remain under a‘threshold concentration’, i.e. the level above which

Wastewater aquaculture 59

the immune system of the cultured fish is over-whelmed, leading to contamination of the blood andinternal organs. From a review of epidemiologicaldata, guidelines for the acceptable level of pathogensin wastewater for use in restricted and unrestrictedirrigation and aquaculture have been developed44.Furthermore, on the basis of a review of wastewaterreuse practices, it was proposed that only systemsincorporating pretreatment should be employed sincethey represent the most appropriate methodologies forsafeguarding products from contamination. The prob-lem of pathogens from inadequately treated wastecontaminating products destined for human consump-tion is exemplified in the following account concern-ing the culture of fish in cages in the river Tjibunut,Bandung, Indonesia:

natural food production in the river was relativelyunimportant as a source of fish food . . . gut con-tents of all five fish sampled were mainly humanfeces (including a large number of eggs of humanhelminths Ascaris lumbricoides, Ancylostomaduodenale, and Trichocephalus dispar)4.

Even in direct wastewater reuse systems, ubiquitousorganisms, e.g. Escherichia coli and Salmonella spp.,represent a potential hazard, although the level of riskmay again be difficult to determine. Furthermore,where products are not prepared and stored in anappropriate manner, the risk to consumers may beincreased. Failing to prepare aquaculture products inclean water may allow pathogenic microbes tocolonise the final product, whereas storing produceincorrectly, e.g. on unhygienic market stalls, maypermit bacteria to proliferate52. The level of risk willalso vary depending on the mode and degree ofexposure and the resistance of the consumer toinfection.

Considering the risk posed by fish cultured in pondsmanaged for wastewater aquaculture around Kolkata,traditional food preparation methods, whereby fish isroutinely cooked at very high temperatures, provide asafeguard against pathogen transmission. However, itmay not be prudent to suggest that the onus lies withthe consumer to ensure that the produce is preparedin such a way as to counter any public health risk.Responsibility for safeguarding the quality of theproduct must lie primarily with the producer, althoughthe consumer and those involved in processing andmarketing have a role to play in ensuring that theproduce is handled and prepared so as to minimisepossible health risks.

Depuration has been suggested to be an essentialcomponent of wastewater aquaculture to ensureproducts are safe for consumers53. The depurationperiod should be sufficient to allow the gut contents inthe wastewater aquaculture systems to be expelled,

and in an ideal situation, a longer depuration periodshould be provided to reduce the population ofbacteria and parasites that colonise both the externaland internal structures of the cultured organism.Studies have also shown that the concentrations ofpersistent chemicals and heavy metals found in tissuesof organisms cultured in wastewater were lowerfollowing depuration54.

Other than contamination, factors such as socialrestrictions on direct wastewater reuse and limitedmarket demand for products from aquaculture maylimit the potential benefits associated with wastewateraquaculture. However, culturing of intermediate plantand animal products as feed inputs for secondaryaquaculture enterprises or terrestrial agriculture andlivestock farming represents a promising strategy.These not only help to ensure that the final productis safe but dissociate the product for consumption fromthe farming system exploiting the wastewater resourcein the mind of the consumer. Edwards et al.55 present aschema summarising alternative pathways for waste-water reuse employing intermediate aquacultureproduction systems. Strategies proposed includedusing wastewater to culture either fish or duckweedto produce feed for carnivorous fish or livestockdestined for human consumption.

Considering the use of aquatic macrophytes asintermediaries in farming systems exploiting waste-water, investigations concerning duckweed culture inseptage-loaded ponds resulted in extrapolated annualyields of Spirodela polyrrhiza and Lemna perpusilla of20.4 and 10.9 t ha-1, respectively56. Duckweed produc-tion may be inhibited as a result of fluctuating tem-peratures, competition from phytoplankton blooms forboth nutrients and space and infestations with mothlarvae. The NGO, PRISM Bangladesh developed asystem with conventional sewage, where, on a weeklybasis, the flow-through system received �2000 m3 ofpre-settled wastewater from 2000 to 3000 residents ofKumidini Hospital, Mirzapur, Bangladesh, and esti-mates based on work by Alaerts et al.57 suggest that thedry weight of duckweed harvested from the 0.6 halagoon ranges from 21.2 to 38.3 t ha-1 yr-1. Duckweedis harvested daily and fed to fish in adjacent ponds; thelocal community readily accepts carp and tilapiacultured in this manner.

Commercial outlets also exist for duckweed at bothlocal and regional markets. In Jessore District, Bangla-desh, traders purchase duckweed to feed fingerlings inlocal hatcheries. Previously, duckweed was collectedfrom the wild to supply these hatcheries, but wildduckweed is increasingly difficult to find, and whereit does occur, it is probable that exploitation alreadyoccurs either to feed fish or livestock. In Taiwan,duckweed produced using wastewater was fed toeither grass carp or ducks, whereas surplus productionwas sold in local markets; in the mid-1980s, a region

60 Stuart W Bunting

close to Chai Yi was converted from paddy fields intoponds suitable for duckweed culture. In Vietnam,duckweed was in demand during the early 1980s tofeed golden snails cultured for export. Evidence sub-sequently showed that introducing the golden snail inthe Philippines, Taiwan, Vietnam and throughout Asiahad severe negative impacts on rice yields due to thesnails feeding on newly transplanted rice seedlings;after an emergency meeting, the government ofVietnam banned snail farming in July 1992.

Introducing intermediate production components towastewater aquaculture has the potential to help re-duce both real and perceived risks. However, to assessadequately the benefit of using intermediaries, a riskassessment framework is required, which, in additionto considering the role of inputs, farming practice,market chain and consumer behaviour, may be ex-tended to include an analysis of all aspects of waste-water reuse that constitute a potential hazard. A recentinnovation for improving food safety that is preventa-tive in nature and focused on the consumer is theHazard Analysis Critical Control Point (HACCP) frame-work58–61. The FAO Fish Utilization and MarketingService outlines a code of hygienic practice foraquaculture products, including recommendations forthose cultured using wastewater62. In summary, theserecommendations state that only treated wastewatershould be used and that the microbiological andchemical quality of products should be monitored andmust conform to WHO guidelines. These guidelinesalso cover the use of wastewater in agriculture,although Blumenthal et al.63 have recommended revi-sions based on the type of delivery mechanism andwhether children are exposed.

Despite possible health hazards associated withwastewater aquaculture, it should be noted that theadoption of direct reuse practices incorporating treat-ment components and procedures for monitoringproduct quality represents a significant improvementon unregulated, indirect waste reuse practices. Muiret al.27 surmise that

There is an important cultural/ethical issue con-cerning the degree to which [it] is consideredacceptable to promote a system which may carryincidental health risks, particularly if wrongly orcarelessly adopted. One of the primary argumentsfor doing so is that a system of low and largelycontrolled risk with known and identifiable locationand characteristics must be better than the lack ofany system.

This sentiment is supported by research showing thatwater samples and organs from fish cultured inconventional rain-fed ponds contained certain patho-genic bacteria at concentrations two orders of magni-tude greater than samples from wastewater ponds in

peri-urban Kolkata64. This suggests that conventionalponds receiving water contaminated with humanexcrement may represent a greater consumer risk thandirect wastewater aquaculture systems. However, risksfrom reusing wastewater should not be underestimatedand those responsible for managing and regulatingproduction should be provided with knowledge onlimiting the risks associated with reuse practices;schema for risk identification and evaluation have beenproposed by a number of authors44,46,65,66. However,the development of appropriate materials for operatorsand local authorities may assist in implementing suchmeasures.

Rising expectations and changing perceptions

Changing expectations and perceptions of farmers,consumers and society in general may also hasten thedecline of once productive wastewater aquaculturesystems. As mentioned previously, the migration ofskilled and experienced employees from waste reusepractices at the Kolkata peri-urban interface representsa possible constraint to the continued operation ofthe traditional systems. However, it is important toacknowledge that expectations of managers andemployees are not limited to financial considerations;sociocultural factors such as social status and con-formity also require consideration. During interviewsconducted in the field, key informants suggested thatworkers in Bangladesh who are engaged in acti-vities associated with human excreta, e.g. sweepers,are sometimes ostracised or victimised in society.In Zambia, Tanzania and Zimbabwe, levellingmechanisms, such as social pressure and obligation,have been identified as constraints to the adoptionof aquaculture activities that have the potential toelevate individuals above their defined social role in acommunity67. Education of society to raise the statusof groups involved with resource-recovery farmingsystems may represent one approach to avoidingthe marginalisation of individuals within their owncommunity.

Within households, using modified farming strate-gies that exploit waste resources or working in a large-scale production system may cause conflicts. Investinghousehold resources, especially money and labour, insmall-scale farming enterprises may divert the resourcesaway from potentially more productive or rewardinglivelihood strategies. The chances of conflict betweenhousehold members is especially pronounced wherethe costs, benefits and risks associated with the farm-ing practice are difficult to establish and resources,including labour, may be diverted away from morereliable or beneficial activities. Harrison et al.31 havedescribed how adoption of aquaculture by householdsin Africa altered the distribution of labour, leading to

Wastewater aquaculture 61

intra-household disputes. Where women, children orelderly relatives undertake tasks associated withhomestead farming, including aquaculture, this mayaccount for a significant proportion of their workloadand result in time and energy being diverted awayfrom other important activities such as education, nur-turing and socialising. If external agents are involved, itwould be valuable to prepare daily activity charts andseasonal calendars of activities and labour demand,disaggregated by gender and age, to highlight poten-tial conflicts associated with the use of modifiedfarming practices68.

In addition to direct effects on production andincome, adopting wastewater aquaculture may haveindirect impacts. Although conversion of a pond closeto the home may seem desirable in reducing the risksof poaching and predation, this could result in anincrease in the distance that family members have totravel to collect water. Constructing impact diagramsand asking community members to map their percep-tions may indicate potential conflicts. Maps producedby men and women in Gbulon village, Sierra Leone,indicated that the men’s world view was considerablymore extensive than that of the women, and thelocations and landmarks identified differed betweenthe two gender groups68. Where males most com-monly offer inputs to ‘collective’ decision-making, thismay distort the real costs and benefits of adoption.

Loss of experienced workers to more lucrative em-ployment has been cited as limiting investment andthreatening the continued operation of traditional wastereuse practices around Kolkata. This suggests that theopportunity cost of labour in peri-urban productionsystems must be considered when assessing therelative benefit associated with such activities. Invest-ment of time, money or other resources in developinginnovative or improved farming practices may also belimited by poorly defined or inequitable inheritanceand marital allocations within communities. An inabilityto transfer established systems to future generationsdue to an absence of clearly defined inheritancemechanisms could limit the sustainability of systemsin terms of intergenerational equity, although this issueis also common to other sectors.

As consumers become more aware of the origins ofthe food they consume, knowledge of the productsbeing derived from farming systems exploiting wasteresources may influence consumer perceptions, pos-sibly restricting the acceptability of such products.Consumer perception of farming practices employingwaste reuse may be more problematic where thesepractices contravene cultural restrictions, social taboos,religious edicts or local beliefs, and operators of suchenterprises become stigmatised by association. Thisnot only restricts the market potential but may alsoaffect social interactions, possibly resulting in victimi-sation or ostracism. However, it should be noted that

beliefs, values and customs regarding excreta reuse arenot fixed but evolve, and that this evolution couldpotentially be stimulated by demonstrating that excretareuse represents a low-cost disposal option thatbenefits the population and does not represent a riskto public health. Ya’akov Zemach, advisor to Israel’sWater Commissioner, stated that

The Arab populace has a psychological and evenreligious aversion to using sewage water, but theyare coming to realise that it is necessary andworthwhile69.

The mechanisms for this fundamental shift in attitudeare not reported; however, the benefits have beendemonstrated through irrigated crop production on theWest Bank.

The perception of farming practices that exploitwastewater by key institutional functionaries maystrongly influence the prospects for such practices.Authorities in certain countries may distance themselvesfrom waste reuse practices to present a more accept-able image to foreign visitors and tourists. Tourism canmake a significant contribution to economies of poorercountries. However, to avoid potential offence tovisitors, troublesome features or practices may beremoved from tourist areas or outlawed altogether.The decline in several wastewater aquaculture systemscan be attributed to this phenomenon, which in manycases is not accompanied by any increase in overallsanitation quality, as testified by the acceptance prob-lems of sewage discharged from coastal hotel andbeach resort developments.

Abolition of wastewater aquaculture in a country isalso sometimes seen as portraying a more developedimage on the world stage. Until recently, wastewateraquaculture was widespread in southern Vietnam;however, this excerpt from a report on fisheries, fromthe Interim Committee for Coordination of Inves-tigations of the Lower Mekong Basin, highlights therole that changing attitudes are playing in the declineof this practice:

A few farmers stock common carp and Puntiussp. in cages and feed them with nightsoil fromthe city. A public latrine was observed in 1990 inChau Doc on top of floating cages stocked withPuntius altus. At a ferry stage on the road to CanTho there was a public latrine on floating cagesstocked with common carp, which were alsostocked in a pond with an overhung latrine. Untilrecently there was one toilet above a floating cage atthe Can Tho market and one at the Can Tho ferrylanding stage but the Governor of the provinceordered them removed as he was concerned abouttourists seeing them (1990 was Viet Nam TouristYear)70.

62 Stuart W Bunting

Use of fresh excreta as a fertiliser in both terrestrial andaquatic systems has now been outlawed by an officialdecree issued by the Government of the SocialistRepublic of Vietnam. Nevertheless, as noted in a reportprepared by the Ministry of Construction and Ministryof Agriculture and Rural Development:

Fishpond latrines have been the traditional solutionin the south and they are the cheapest types oflatrines but there has been a ban on the use of suchlatrines. However, there is not yet an alternativesolution71.

Information disseminated by CBOs and NGOs andgovernment agencies, e.g. health departments, mayresult in the public receiving conflicting messagesregarding the appropriate management of domesticwaste. Where behavioural development programmeshave highlighted the link between, for example, handwashing after defecation and an associated reductionin disease, it may be difficult to promote or evensustain existing waste reuse practices. Although thehealth education message is not concerned directlywith waste reuse practices, the message that disease isassociated with faeces could mean that the targetgroup will have trouble understanding how wastereuse constitutes a safe option. However, if agenciesconducting health education programmes could beinformed as to the potential role of direct waste reusepractices, in a safe and effective strategy for maximis-ing the benefit derived from waste resource, this mayrepresent an important channel for knowledge dis-semination.

Returning to the issue of fresh excreta use inagriculture in Vietnam, the authorities note:

Reuse of human excreta as fertiliser has economicimplications for many farmers in agricultural pro-duction. Therefore, it is not possible to ban the useof human excreta as fertiliser. The important thing isto help farmers with guidelines on how to composthuman excreta to get fertiliser without polluting theenvironment and causing harmful effect to humanhealth. There should be regulations on standards ofcomposted human excreta, process of composting,and a strict ban on the reuse of fresh (non-composted) human excreta71.

Operational constraints

Constraints to wastewater aquaculture outlined abovesuggest that farmers face a number of problems thatare largely out of their control but have a significantinfluence on the type of management strategies em-ployed. Insecurity of tenure has been cited as a keyfactor in constraining innovation and investment.

Managers are unwilling to invest in new technologiesas they wish to limit their exposure to financialrisks. However, limited access to information andcredit has also been cited as constraining the adoptionof enhanced management strategies18. A survey of60 operators of ponds managed for wastewater aqua-culture around Kolkata showed 45% obtained loans tofinance investment, 37% used their own savings and18% took an advance; loans and advances came fromvarious sources, including moneylenders, seed-sellers,aratdars (wholesalers) and banks, although the role ofbanks was considered to be of ‘marginal importance’;vegetable farmers in the same area appeared morewilling to obtain loans, with 53% of respondentshaving mortgaged their land18. Where loans had beentaken, repayment rates were considered exceptionallyhigh; this was attributed to poorly defined tenurearrangements that permit moneylenders to exploitthe situation. The problem is compounded further asoperators are keen to introduce improved manage-ment strategies but are unable to access bank loanssince they lack documentary evidence of ownershipand cultivation rights.

Kundu18 found that almost three-quarters of vege-table growers interviewed had introduced improvedtechnologies, including high-yielding varieties, fertil-isers and pesticides; pond operators cited limited accessto information as constraining their adoption ofimproved management techniques. The need for im-proved access to knowledge concerning constraintsand opportunities for operators of wastewater aqua-culture systems is further highlighted by reports thatproductivity in peri-urban Kolkata is declining as aresult of seemingly not insurmountable problems(Table 1). Therefore, developing effective dissemina-tion pathways for information, contributing toimproved collective decision-making, would be animportant component for ensuring continued opera-tion. Greater knowledge about health risks associatedwith farming, processing and marketing of productsgrown in wastewater systems would also help reducethe associated health risks. Problems of accessingcredit and information suggest that local institutionsor private organisations have a role to play inproviding such services. However, to identify appro-priate extension materials and pathways and todevelop suitable credit arrangements may requirefurther research and strengthening of capacity withinlocal institutions; the following section addressesfurther institutional constraints and opportunities forcapacity building.

Policies, institutions and processes

The previous discussion raises the fundamental ques-tion of who is responsible for wastewater aquaculture,

Wastewater aquaculture 63

providing support and technical advice, ensuring thesafety of products and informing the consumer andother stakeholders about such activities? From aregional or local government perspective, suchresponsibilities might be integrated into existingorganisational structures. Where this is the case,various institutional strengthening procedures may berequired to establish appropriate management strate-gies, and to develop clearly understood cross-institu-tional agreements. When job descriptions are notformally implemented and documented, as may oftenbe the case, informing key individuals concerningimportant strategic issues, assigning responsibility forissues pertaining to wastewater aquaculture and prov-iding appropriate training for operational staff will beimportant. Where basic elements are found to beinadequate, a more fundamental approach of institu-tional development may be required, concerning therelationships key institutions have with the externalenvironment, including internal issues, such as busi-ness objectives, technology, structure, systems andprocedures, and matters relating to employees, e.g.job descriptions, skill levels and motivation72. Whereinstitutional structures are well defined, these may notsuit the evolving needs, and a process of stimulus andchange may still be required.

Considering organisation within many local govern-ments, it has been noted, for example in the cases ofBihar, Uttar Pradesh and West Bengal, that theircentralised and hierarchical structures, and absenceof any over-arching thematic or strategic forces, makesit extremely difficult to identify effective mechanismsto support, extend and control wastewater aquaculturein spite of local interest and enthusiasm among someinstitutional sectors27. Unless there is a historical pre-cedent or a strong interdisciplinary mechanism, thecomplex needs and societal implications of waste-water aquaculture may be difficult to address. Suchconcerns are not unique to this issue, of course, andsimilar issues can be observed, for example, in urbandevelopment, watershed and coastal zone managementand the management of common property resources.Lessons may be learnt from successful approachesintroduced in such areas, and in some cases, it may beeffective to link wastewater aquaculture with devel-opment initiatives in other sectors. Furthermore, it isindeed important that potential benefits are recognisedand agreed by key opinion formers and decisionmakers within the communities concerned; positiveoutcomes associated with wastewater aquaculture arereviewed and discussed below.

A primary responsibility for institutions dealing withwastewater aquaculture, or other farming practicesexploiting waste resources, will be to protect thehealth of consumers, and this may involve implement-ing standards, guidelines and regulatory safeguards.Where public perception of wastewater-grown

products is of concern, such measures may beinstrumental in ensuring consumer acceptance.Externally, products cultivated using waste resourcesmay be indistinguishable from those grown inconventional farming systems. Therefore monitoringprogrammes may need to be based on microbiologicalassays or chemical analysis; any sampling programmewould have to include processors and retailers.Implementation of such a programme, and framingof legislation for its support, may represent a sig-nificant cost to regional authorities; in many situations,more pressing issues may hold priority within institu-tions. However, if defined better, the benefits gener-ated directly and indirectly by wastewater aquaculturecould potentially justify an increase in spending. Oneway to achieve this would be to conduct a compre-hensive cost–benefit analysis considering alternativewaste disposal options; assessment of wastewatermanagement options for Ra’anana, Israel, demon-strated that local irrigation represented the most cost-effective strategy73. Where products are supplied fromconventional systems to export markets, possible neg-ative impacts of food scares associated with productsgrown using waste resources demand consideration;during the first 10 weeks of a cholera epidemic inPeru, a decrease in agricultural exports and tourismcost the country an estimated 1 billion dollars74. In-cluding possible losses such as these in any cost–benefit analysis may further justify implementing amonitoring programme.

Establishing a monitoring programme for productsfrom wastewater aquaculture may make explicit therisks posed by such production strategies, which inturn, may lead to changes in consumer perception,reducing demand and causing a decline in productvalue. Furthermore, introducing a monitoring pro-gramme may demand that indirect approaches towaste reuse are brought within the regulatory frame-work, which may highlight the role of waste inputs insuch farming, again leading to changes in consumerperception and acceptance of the products. As men-tioned previously, the status of indirect approachesto wastewater aquaculture has been described to alimited extent and a number of health risks and othernegative impacts have been reported. However, thepossible impacts of such policy developments shouldnot be underestimated; indirect approaches to wastereuse, especially wastewater aquaculture, are wide-spread in many developing countries and changes inthe acceptability or value of products from suchpractices may have serious consequences for thelivelihoods of many poor people.

Although bringing indirect and uncontrolled wastereuse practices into a regulatory framework mayinfluence consumer perception of products cultured,safeguarding the health of workers and consumers inthe long-term should be a priority. Implementation of

64 Stuart W Bunting

health and safety standards, whether by a governmentagency or a private sector body, would help reducepossible public health risks and ensure consumeracceptance. However, the process of informingconsumers regarding newly introduced protectionmeasures and associated implications for food safetymay require further support from local authorities; inmany cases, poorly developed communication path-ways to reach consumers may make such initiativesimpractical and ineffective.

Continued operation of large-scale wastewateraquaculture systems, such as those around Hanoi, HoChi Minh City, Kolkata and Phnom Penh, may alsocome into conflict with local and regional planninginitiatives. Institutions may have preconceived devel-opment plans for a region and, consequently, bereluctant or unwilling to promote or support anyactivity that could come into conflict with these.Development plans formulated for urban areas suchas Hanoi and Ho Chi Minh City, and covering a 10-yrperiod, are currently being implemented and willsignificantly alter the nature, extent and distribution ofwastewater aquaculture practices within and aroundthese cities. Considering Hanoi, priorities set for themanagement of urban lakes dictate that all wastewatershould be diverted away from these waterbodies, andthat tourism and environmental functioning should begiven priority over fish culture, although fish culture isstill considered important, both for sustaining foodsupplies and demonstrating to the public that the waterquality is good.

Reports from planning agencies in Kolkata haveproposed that further expansion of Kolkata shouldproceed towards the north of the city18,75. Despitethese recommendations, urbanisation continuestowards the east, encroaching further into the low-lying wetlands where wastewater aquaculture takesplace, suggesting that policy decisions may becomplicated by other considerations. The recentconstruction of the Eastern Metropolitan Bypass hasimproved access to the east of Kolkata from boththe city and airport. Furthermore, despite beingconsidered a wetland area, the environment isnot homogeneous and selected areas representattractive development opportunities requiring littleexpenditure in site preparation. However, the impactof development on the periphery of extensive wet-lands may have profound effects, especially wherelocal hydrological conditions are disrupted and pres-sure on the surrounding land resource increases as aresult.

Opportunities for livelihoods enhancement

Despite numerous constraints outlined in the previoussection, direct and indirect wastewater aquaculture

persists as a major farming activity under manysituations, at the peri-urban interface of cities such asBangkok, Hanoi, Ho Chi Minh City, Kolkata andPhnom Penh and, on a smaller scale, at provincialwastewater treatment plants in Africa, South Americaand throughout Asia. The following section reviewsthe benefits associated with these systems andexamines whether a greater knowledge of thesebenefits could contribute to a constructive dialoguebetween planners, key actors and stakeholders regard-ing the development of policies and initiatives topromote wastewater aquaculture.

Employment and income

Operation and maintenance of ponds managed forwastewater aquaculture can create a significant num-ber of employment opportunities. Estimates suggestthat wastewater aquaculture in peri-urban Kolkataprovides direct employment for �8000 individuals.However, this figure may not represent the true labourdemand within the system. Traditional wastewateraquaculture practices depended on employment ofworkers when required, for example at harvest time;however, intervention of unions has apparently re-sulted in the permanent employment of an excessivelylarge workforce. This situation has been described as‘disguised unemployment’, since only �25% of thoseworking in peri-urban aquaculture are engaged infull-time employment, the remainder being temporaryemployees76. Permanent employees include managers,skilled workers, who weave nets and look afterequipment and infrastructure, and unskilled workerswho undertake menial tasks, including cooking.Temporary employees are engaged in harvesting,guard duties and transporting fish to wholesalemarkets. Lower wages received by temporary workerscompared with full-time employees reflect the amountof time spent actively engaged in employmentactivities. Carriers, harvesters and guards work for,on average, 1, 3 and 6 h d-1, respectively, whereastemporary employees work, on average, for only halfthe year.

From a regional perspective, creating work inassociated upstream and downstream support services,e.g. supplying inputs and marketing of products, canbenefit populations not directly involved in waste-water aquaculture. Inputs required include fry, sup-plementary feed, nets, bamboo and boats, the supplyof which provides a range of employment opportunitiesfor all sectors of society. Adoption of managementstrategies employed in Kolkata, including multiplestocking and harvesting and marketing of live fish, mayhave implications for labour demands in other systems,both in terms of amount and timing. Recent researchalso showed wastewater aquaculture constitutes an

Wastewater aquaculture 65

important component in the livelihood strategies ofmany individuals from poor and marginal commu-nities77.

At the household level, full-time employment ofone or more individuals in large-scale productionsystems, e.g. shrimp farming, can provide a valu-able source of income78. However, although employ-ment in major wastewater aquaculture operationsmay play a similar role, homestead level productionor part-time employment may be an importantcomponent in the livelihoods of poor households.Owing to the physical dominance of large-scalesystems around Hanoi and Kolkata, the role ofhomestead ponds managed for wastewater aqua-culture in the livelihood strategies of poor householdshas been largely neglected. Studies have shown thathomestead farming can play an important role in thelivelihoods of poor households79,80, suggesting thatthis facet of wastewater aquaculture requires con-sideration. Le81 reported that poor households inHanoi derive between 3 and 40% of their incomefrom rearing livestock, fed primarily on householdwaste. However, the contribution of homesteadfarming activities to food security in poor householdsis probably more important than income genera-tion and this is discussed in the next section.Although wastewater aquaculture may contributesignificantly to the income of households throughthe provision of employment and the sale of pro-duce from homestead farming enterprises, inequalitymay result in benefits being divided unfairly amongsthousehold members31. Furthermore, inequalitywithin households may influence the distributionof tasks associated with adoption of homesteadfarming.

Inequitable distribution of benefits derived fromwastewater aquaculture has also been suggested tolimit the motivation of those operating and managinglarge-scale systems, and to constrain investment andinnovation. With respect to the situation in peri-urbanKolkata, there is sometimes a lack of incentive toimprove the efficiency of the system owing to theinability of stakeholders, i.e. employees, managers,landowners and institutions, to agree on a mutuallyacceptable strategy for dividing the risks and potentialrewards associated with investment. To address thisproblem, it is suggested that division of the benefitsderived from waste reuse practices operating under avariety of management regimes, for example, individ-ual ownership, absentee owners and cooperatives,needs to be defined clearly. Government insti-tutions may be in a position to ensure that potentialoperators are in a situation where they can reap thebenefit of their labour. The development of guidelines,contracts and legislation to clarify the rights of variousstakeholders could be a key element of any develop-ment.

Contribution to food security in poor householdsand communities

Recovery of nutrients from solid waste, agricultural by-products and wastewater produced by households willcontribute to the poor resource base of small-scalefarmers. Furthermore, products from farming systemsexploiting waste resources may make a significantcontribution to household food security. Edwardset al.82 noted that farmers in northeast Thailandemploying traditional artisanal production techniquesin small ponds produce 0.4–0.5 t ha-1 of fish annually,whereas, production levels of 5 t ha-1 yr-1 werereported for similar ponds in West Java receivingmanure (human and livestock), bran and vegetation.Typical production figures presented by Mara et al.83

indicate that recycling of nutrients in the waste from afamily of five through aquaculture has the potential toalmost meet the expected demand from a householdwhere fish consumption represents an importantcontribution to the diet82. However, if fish culturedare destined for market, the relatively low level ofproduction from a household pond may be difficultor uneconomic to market; a similar constraint wasidentified for operators of small-scale fishponds inAfrica31.

Developing small-scale wastewater aquaculturepractices that may be carefully integrated into existingsubsistence farming systems, for example the tradi-tional inland artisanal aquaculture operationsdescribed by Edwards et al.,82 could potentially helpsmall-scale farmers realise their rising expectations.Realistically, however, most poor households areunlikely to have access to sufficient land or assets toconstruct a pond in which to undertake wastewateraquaculture. Furthermore, individual households maynot generate sufficient nutrient or wastewater flows tojustify investment in a system for wastewater aqua-culture, especially when the possible need for wastestorage and treatment is considered. Exploitation ofwastewater and agricultural residues at the householdor farm scale through biogas production in simplepolythene tube digesters, with resulting digestereffluents being used to enhance production in fish-ponds, is being promoted by a number of agencies.This approach presents a useful strategy for localisedwastewater reuse through aquaculture, although suc-cess with uptake and the current extent of the practicehas not been evaluated.

In peri-urban settings, homestead horticulture andlivestock husbandry have been shown to be importantin the food security of poor households79,84,85. How-ever, little work has been done to assess the rolehousehold fishponds managed for wastewater aqua-culture are playing in poor livelihoods. Consideringthe case of peri-urban Kolkata, probably the moststudied system of wastewater aquaculture, the

66 Stuart W Bunting

literature is dominated by large-scale wastewateraquaculture practices and the contribution productsfrom these enterprises make to the food security ofpoor communities, both peri-urban and urban. Keyinformant interviews suggested that some 400 house-hold ponds are managed for wastewater aquaculturein peri-urban Kolkata. Furthermore, ponds managedby households are evident in many peri-urban settings,and it is not uncommon for water flowing into theseponds to contain domestic waste32. However, thesesystems represent an indirect approach to wastewateraquaculture, where the benefits of waste reuse areexploited, but not given public recognition. Risks,possible costs and potential benefits associated withwaste reuse in small-scale peri-urban farming systemsare poorly defined and understood and this lack ofknowledge may prohibit investment of time, money orresources in developing direct systems. Risk assess-ment in relation to household level farming practicesin peri-urban areas may be critical if sustainablepractices are to be identified and promoted morewidely.

Owing to the limited distance between farm andmarket place and the prospect of a constant supply ofwastewater for aquaculture, peri-urban farms have thepotential to supply fresh, low-cost produce to urbanand peri-urban markets all year round. This is animportant consideration for poor communities thatdepend on these markets for their food supply and areunable to store perishable products. Morrice et al.36

found that small fish harvested from ponds managedfor wastewater aquaculture were available in marketsservicing the poor; however, the profiles of peopleactually purchasing fish were not investigated. Demon-strating that fish and other produce from peri-urbanfarms are accessible to, and purchased by, members ofpoor communities would have important implications.For example, assisting local institutions in ensuringfood security in poor communities, contributing to thepositioning, design and development of improvedmarketing outlets and sources of consumer informa-tion and assessing the health risks associated withproducts; farmers might also benefit from improvedknowledge regarding the consumers they supply.Those without access to employment, or unable topurchase products from markets, may still benefit fromthe productivity of major peri-urban farming systems.Depending on rights of access and availability, poorpeople may be able to appropriate unexploitedresources such as fodder, fuel wood, medicinal plantsand self-recruiting aquatic species.

Household and community health

The potential contribution of products from waste-water aquaculture to food security in poor households

and communities was discussed in the previoussection. However, access to such food sources mayalso play a role in improving the nutrition and healthof poor people. The diet of many poor people in Asiais dominated by rice, and Thilsted et al.86 described theproblems this causes in Bangladesh. These authorsnote that rice is a poor source of nutrients such asvitamins A and C, iron, calcium, zinc and iodine, andvegetables and fish make a significant contribution tothe availability of these nutrients in the diets of poorpeople. Therefore, it appears reasonable to assumethat aquatic vegetables and fish cultivated using waste-water and sold in markets servicing the poor maymake a significant contribution to the vitamin andmineral intake of poor people; vitamin A deficiencycauses blindness in children and iron deficiency causesanaemia in women and children.

Managed wastewater reuse through farming is animportant component in the sanitation strategies ofseveral poor communities in developing countries44.The World Bank estimated that in 1990, a total of1.7 billion people were without access to adequatesanitation, and by 2030, this could increase to around3.2 billion74. Providing sanitation is an importantdevelopment process, and is recognised as being ofprime importance in improving the general health ofthe population. By providing sanitation, infant mortal-ity resulting from communicable diseases, e.g. cholera,typhoid and diarrhoea is greatly reduced, as is theincidence of severely malnourished individuals withassociated physical and mental health problems87.More generally, life expectancy can be expected to in-crease when people have access to sanitation, whereasinadequate sanitation results in the degradation andcontamination of groundwater and surface water74. Insuch situations, it is often recommended that con-taminated water be boiled, thus consuming largeamounts of fuelwood, the burning of which results inatmospheric pollution leading to increased respiratorydisease48.

Economic benefits to society

Wastewater management by operators of aquaculturesystems reduces the resource demands placed on localauthorities, although responsibility for sewerage anddrainage infrastructure will probably remain withurban authorities. Processing waste through reuse inperi-urban production systems operated by the privatesector removes the need for direct management oftreatment and disposal by local authorities. Wetlandsaccommodating wastewater aquaculture, whetherproducing fish or plants, facilitate a wide range ofphysical, chemical, biochemical and biological con-taminant removal processes88. Furthermore, comparedwith conventional waste treatment and management

Wastewater aquaculture 67

strategies, wetlands constitute an ecologically soundand, provided land is available at agricultural asopposed to urban prices, a cost-effective means ofsanitation89,90. Operating and maintenance costs areminimal, construction and maintenance require rela-tively basic earthmoving and hydrological manipula-tions and management is not technically demanding.Economic benefits generated through productive re-use of wastewater by aquaculture could potentiallysubsidise the development and maintenance of collec-tion, treatment and delivery strategies for wastewaterand liquid waste used in the farming system. InTrujillo, Peru, the recommended cost allocation for-mula for constructing a lagoon-based wastewatertreatment facility was to charge the municipality theconstruction costs and to charge local farmers, whowere to use treated water for irrigation, the cost of landand operation44. Responding to a survey, local farmersindicated that this was an equitable solution, and insome cases, the expected cost of treated wastewaterwas half that being paid for groundwater. Further-more, to avoid potential constraints of transferringeven such a relatively simple technology, severalagencies and donors have produced manuals forlagoon-based treatment91–93.

Employing pond-based wastewater treatment priorto irrigation or aquaculture represents an appropriatesolution for the water to be of a sufficient quality tosafeguard the microbiological quality of the product,and in the case of aquaculture, to maintain waterquality within the culture ponds91. Locally, reuse ofwastewater in sanitary systems managed by operatorswith a vested interest in correct functioning ensuresthat both production and treatment are monitoredand maintained. An experimental wastewater aqua-culture facility developed in association with a sewagetreatment plant in Kalyani, West Bengal, India, ismanaged by a cooperative; members maintain bothmaturation ponds in which fish are cultured and thepreceding anaerobic and facultative lagoons. It is note-worthy that cooperatives, with responsibility sharedamongst members, frequently result in the establish-ment of effective management regimes; therefore, itmay be prudent to suggest that the level of main-tenance achieved will depend to some extent on thecapabilities and organisation of those responsible foroperation as well. Cooperative management seeminglyplays a key role in both the establishment andsuccessful operation of new wastewater aquaculturefacilities in West Bengal32.

Establishing structures and processes such as coop-eratives that contribute to the efficient collection,transportation and treatment of waste resources priorto use may be critical in ensuring that production isconstant and quality is safeguarded. Under certain cir-cumstances, products destined for export markets maybe grown using wastewater; although economic

benefits associated with selling products to exportmarkets may be considerable, the cost of failing tosafeguard the microbiological quality of such productsmay have severe consequences. As mentioned pre-viously, loss of export earnings and tourist revenueduring a cholera epidemic in Peru cost the country anestimated one billion dollars. Recent research inKolkata and Hanoi has demonstrated that fish culturedin wastewater aquaculture systems are being trans-ported to other cities and provinces, and this raisesconcern over the possible introduction of parasites tocommunities that were, in the past, free of infection.Ensuring only treated wastewater is used for farmingwould mean that consumer safety is protected and thatexport crops meet stringent safety standards in targetcountries.

Boiling contaminated water supplies prior to drink-ing may contribute indirectly to negative environmen-tal and public health impacts; however, the financialcost involved is also significant. The population ofJakarta spends in excess of 50 million dollars per yearon boiling water, equivalent to 1% of the city’s grossdomestic product74. The impact of inadequate sanita-tion is most pronounced in those sections of the com-munity that have little choice in the water resourcesthey have access to, most commonly the poor. InBangladesh, the cost of boiling drinking water hasbeen estimated to account for as much as 11% of theincome of poor families; in Peru, an outbreak ofcholera prompted the Ministry of Health to recom-mend that all residents boil drinking water for 10 min;it was estimated that this could cost families living insquatter camps almost one-third of their income74.

Resource recovery

Reusing waste resources, garbage, wastewater and by-products from agriculture and food processing in farm-ing systems offers a possible solution to the problem,faced by many in developing countries, of limitedaccess to nutrient inputs and water resources. Ensuringthat the maximum possible benefit is derived fromappropriated water resources and from nutrients con-tained in both solid and liquid wastes will reducepressure on the remaining renewable freshwaterresource and non-renewable mineral resources. Thiswill reduce conflict over controversial dam buildingand mining schemes, and limit environmental degra-dation. Furthermore, compared with conventionalapproaches to managing domestic waste, productivereuse in farming may offer a greater degree ofenvironmental protection.

NutrientsRecycling nutrients in wastewater flows from societalsystems also reduces the loss of non-renewable

68 Stuart W Bunting

resources, e.g. phosphorus, in the unidirectional flowof material entrained in the hydrological cycle.Furthermore, assimilation of nutrients through eco-logical systems as opposed to mechanical removalavoids the problem of developing ‘hampered effluentaccumulation processes (HEAP) traps, where formerpoint-source pollution is ultimately converted intonon-point source pollution30. Wastewater aquaculturecould be exploited to avoid creating HEAP traps, asnutrients would be assimilated into biomass that canbe harvested and either recycled through the city,integrated into agricultural systems or removed fromthe watershed. Wastewater aquaculture could permita reduction in the ecological footprint of a town orcity94, effectively decreasing the area from whichecological goods and services are appropriated tosupport societal functioning.

WaterWastewater reclamation and reuse is currently prac-tised in a number of countries and performs a widevariety of functions. With adequate treatment, watercan be returned to consumers; lower-quality water maybe reused by industry or to grow a multitude of biomassproducts including food, fodder, fibre, fuelwood andtimber. Productive wastewater reuse, through irrigationand macrophyte production is of particular importancein dry climates where photosynthesis consumes 600–6000 m3 of water per tonne of biomass produced95.Postel et al.96 estimated that in 1990, approximately2880 km3 of freshwater was used by agriculture toirrigate 240 million hectares of land. Depending onclimatic factors, the crops under cultivation and theefficiency of the irrigation system, between 50 and 80%of irrigation water is consumed; assuming a rate of65%, global agriculture consumes 1870 km3 of water,equating to 82% of that consumed directly for humanpurposes.

Overexploitation of renewable freshwater resourceshas been widely recognised, and according to some:

we have come to a point where water scarcity isincreasingly perceived as an imminent threat, some-times even the ultimate limit, to development,prosperity, health, even national security97.

Not unnaturally, many consider this a serious cause forconcern, and some, a prelude to international con-flict98. To quote Ismail Serageldin of the World Bank:

The wars of the next [this] century will be overwater97.

Where groundwater and surface-water resources havebeen polluted, uncontaminated water supplies are oftenappropriated through sinking wells into previouslyuntapped aquifers, adding to extraction rates, energy

demands and potentially depleting local aquifers. InWest Bengal and south Bangladesh, major publichealth problems are being created by the mobilisationof arsenic in tube-well water supplies. In certainaquifers, shallow tube-wells can also become con-taminated by wastewater, thereby increasing risks tothe communities or families who consider and expectsuch water to be safe. Excess abstraction can lead tosubsidence, damaging infrastructure and increasingthe likelihood of flooding; in coastal regions, seawatercan intrude into underground aquifers. Subsidencedue to groundwater abstraction has been observedalong the Mediterranean coast in Israel; in Bangkok,both subsidence and saline intrusion have beenrecorded99. Protecting water quality in surface water-bodies reduces the need to tap alternative sources, e.g.tube wells, desalination plants and rainwater harvest-ing to appropriate potable water. This also leads toreduced exploitation of underground water resources,which limits potential disruptions in soil waterchemistry.

Although uncertainty remains as to the ultimateextent of global freshwater resources98, evidenceprovided by Postel et al.96 supports the hypothesisthat human appropriation of accessible runoff, includ-ing sub-surface flow, is approaching an upper limit.Alternatives to using accessible runoff include majorwater transfer schemes, desalination and constructingnew dams with the attendant economic, social andenvironmental costs. However, in several arid and semi-arid regions where freshwater resources are beingdepleted from surface and groundwater sources at arate exceeding replenishment, wastewater reclamationis the most economically viable source of water100.Protecting surface-water quality locally enables the safereuse of water resources for various non-productivefunctions, e.g. drinking, laundering cloths, bathing,washing utensils and recreation; sometimes, theseactivities may have a greater priority in poor commu-nities compared with using the water in agriculture orfor growing fish. At the regional level, augmentingsupply through wastewater reuse may contribute todissipating tensions amongst communities, states andindeed nations that depend on shared freshwaterresources.

Functional and non-functional values

Burbridge101 reviewed key functions associated withwetlands, including biomass production, sediment andcarbon storage, water filtration and cleansing, provid-ing linkages among ecosystems, buffering downstreamenvironments against flooding and shock nutrientloadings and regulating surface runoff and ground-water recharge within catchments. He also presented aframework for integrated planning and management

Wastewater aquaculture 69

of wetlands incorporating biophysical, economic andsociocultural factors. A similar range of benefits tothose outlined above could be realised through thedevelopment of wetlands for wastewater aquaculture.Potentially, the most important of these functions is theregulation of local hydrological conditions. Extensivewetland areas have the capacity to contribute to thestabilisation of the local hydrology, providing a spillarea for floodwaters, acting as a buffer againstdownstream flooding, increasing rainwater infiltrationto recharge groundwater resources and promotingpercolation to recharge underground aquifers. Floodprotection afforded to cities such as Hanoi, Kolkataand Phnom Penh, by peri-urban wetlands that accom-modate wastewater aquaculture, may represent asignificant benefit that would be lost should urbandevelopment encroach.

As discussed in the previous section, aquaculturehas the capacity to recover nutrients from wastewaterand agricultural by-products, and nutrient assimilationwill contribute to reducing environmental degradation.Agro-ecosystems supporting wastewater aquacultureconstitute a valuable wildlife habitat, and may act asa refuge for both aquatic and terrestrial plants andanimals displaced through urbanisation. While thismay generally be positive, animal and insect vectors ofdiseases are of serious concern, and care is needed toensure these are not encouraged. Where wastewateraquaculture is integrated with practices such as dike-cropping, trees planted on the embankments provideshade and increase the thickness of the boundarylayer, reducing the loss of water via evaporation; thesetwo factors contribute to an enhanced microclimate.Furthermore, integration of additional cropping strate-gies, e.g. aquatic macrophytes, homestead gardens andorchards, has the potential to produce a diverse mosaicof microhabitats. From a social perspective, plantingbanana trees around the duckweed lagoons operatedby PRISM Bangladesh created additional employmentfor local workers, many of whom were landlessfarmers or net-less fishers.

On a cautionary note, conversion of natural wet-lands to agriculture or aquaculture could represent areduction in value as a wildlife habitat. Conversion ofshallow wetlands to deeper ponds and lagoons suitablefor aquaculture may physically preclude colonisationby emergent plants and insects that inhabit littoralareas; fish culture in these wetlands could also increasepressure from predation on aquatic insects. Introduc-tion of non-native aquatic organisms may result indegradation of the environment, disrupting the hostcommunity, causing genetic degradation of the hoststock and introduction of disease102. Species diversitymay thus be reduced. However, where wetlandsdemand conservation as a result of their recognisedvalue, the development of a designated area for waste-water aquaculture followed by discharge of treated

water to the remaining wetland, may well result innet benefits that exceed the alternatives of adoptingconventional wastewater treatment technologies, ornot treating the wastewater.

Wetlands supporting fish culture in peri-urbanKolkata have an ecological value and the InternationalUnion for Conservation of Nature and NaturalResources (IUCN) has recognised this, leading to therecognition of wastewater fishponds as a specialcategory of man-made wetlands due to their contribu-tion to preserving nature103. Further to providing avaluable habitat for migratory birds, these wetlandssupport a diverse range of species contributing toglobal biodiversity; the 12 500 ha East Kolkata Wet-lands were designated a Ramsar Site (no. 1208) on 19August 2002. The value of such systems in environ-mental protection, providing habitats and sustaininglivelihoods, also means that an individual may attributea value for preserving the resource in order that theindividual, other individuals and future generationshave the option of using the resource at a later date104.The impact of an activity, such as urbanisation, onthis option value may be estimated by assessing thechange in an individual’s willingness-to-pay for thepreservation of the resource. Environments alsohave an intrinsic or existence value that is unrelatedto humans and their present or potential direct orindirect use of the resource104,105. Changes in existencevalue arising from environmental impacts associatedwith solid waste and wastewater disposal have notbeen widely described; however, they may beexpected to be negative. This suggests that environ-mental protection afforded to downstream ecosystemsthrough the managed reuse of waste resourcescontributes to their having a more positive existencevalue.

Conclusions

Based on definitions presented in this review forwastewater, aquaculture and direct and indirect reuse,it is apparent from historical and contemporaryaccounts that wastewater aquaculture has a longtradition and is currently widespread; it was practisedunder diverse geographical, environmental and socio-political settings and was concentrated mainly in south,east and southeast Asia. However, from the reviewpresented here, it appears that many contemporarywastewater aquaculture practices are threatened on anumber of fronts. Encroachment of urban develop-ment leads to the physical loss of land and aquaticresources once accessible to farmers and poor com-munities. Such change in access also leads to the dis-ruption of local communities and engenders feelingsof insecurity. Uncertainty over the future of wastewateraquaculture and the prospect of more rewarding

70 Stuart W Bunting

employment also result in the loss of experiencedworkers, although recruitment of replacement labour-ers may not constitute a serious problem as migrantsfrom rural areas and members of displaced commu-nities are often without work. Improved access tourban markets for rural producers, through improvedcommunications, diminishes the competitive advan-tages of urban and peri-urban producers. The risk ofcontamination, a public health threat, and changingconsumer perceptions may further reduce demandfor products from such systems. Changing institutionalperceptions have also led to the abandonment oftraditional waste-reuse practices in several countries.Farmers have to manage with uncertain and variablewaste resource inputs and contend with the limitedaccess to information and credit. In combination, thesefactors have led to a reluctance to innovate and investin enhanced management approaches. Furthermore,concerns over contamination, disease problems andenvironmental degradation, combined with the adop-tion of risk-averse management strategies, may havecontributed to the widely perceived decline in pro-duction from wastewater aquaculture.

Despite the numerous constraints elucidated here, anumber of factors contribute to the continued opera-tion of wastewater aquaculture in various settings anddemand for products from such practices remainshigh. Considering poor communities, the principalbenefits associated with wastewater aquaculture areincome generation, employment and enhanced foodsecurity; this review has consolidated knowledgerelating to these factors. Wider benefits afforded tosociety by direct wastewater aquaculture include (i)managed waste reuse, which in many cases contri-butes to reduced public health risks and to environ-mental protection; (ii) environmental goods andservices derived from agro-ecosystems that supportwastewater aquaculture, and which support societalsystems; (iii) additional functional and non-functionalvalues, which often play an important role in poorlivelihoods; and (iv) providing a sanctuary for wildlifeand repository for biodiversity, and various non-useand existence values.

According to Goodland106, the World Bank hasacknowledged the need to include a wider range ofissues in economic decisions and to revise theeconomic appraisal of projects to include externalitiesand sustainability. Increased awareness among stake-holder groups regarding the wider social and environ-mental benefits from agro-ecosystems supportingwastewater aquaculture, for example in peri-urbanKolkata, has led to legislation protecting the fishpondsand designation of the area as a wetland of interna-tional importance under the terms of the RamsarConvention. A more thorough assessment of the wideranging benefits associated with wastewater aquacul-ture would inform target institutions, planners and

policymakers of the true value of such strategies toboth poor people and society in general.

Although much is known regarding the manage-ment and operation of large-scale wastewater aqua-culture, little work outside Kolkata has been done toassess the role of employment and products from thesepractices in poor livelihoods. Consequently, knowl-edge gaps concerning the role of wastewater aqua-culture in the livelihoods of poor people are proposedfor further investigation. Such studies would requireanalysis of who is engaged in wastewater aquaculture,and what contribution such activities make to thelivelihoods of those involved and their households.This assessment should include those engaged inactivities supporting and servicing wastewater aqua-culture, such as seed suppliers, boat builders,net makers and people transporting and selling aquaticproducts. The wider benefits afforded to society bywastewater aquaculture, in particular its contributionto environmental protection and food security shouldbe considered. Despite the proposition that waste-water aquaculture delivers affordable fish and aquaticvegetables to urban markets, it is not known whetherpoor households have access to this produce, there-fore, it is suggested that this issue is investigatedfurther. Constraints associated with specific wastewateraquaculture practices also demand close attention.When addressed, these may lead to enhanced liveli-hoods for poor people and enable policy formersand decision makers to formulate natural resourcemanagement strategies that benefit the poor, particu-larly for peri-urban areas where wastewater commonlyoccurs. Furthermore, to facilitate appropriate policyrecommendations that address the constraints andopportunities associated with wastewater aquaculture,knowledge emerging from ongoing research projectssuch as the EC-funded PAPUSSA and SEARUSYN mustbe communicated effectively to target institutions anddecision makers.

However, Ellis and Sumberg107 suggest a note ofcaution when considering food production in urbanand peri-urban areas, stating that

The significance of food production in and aroundtowns for the overall quality of life in developingcounties should not be exaggerated, and nor,too, should its claims for scarce developmentresources.

The same could be said of wastewater aquaculture.Through a balanced and ongoing programme of moni-toring, which takes account of technical, economic,social, political and environmental factors, it will bepossible for policymakers to allocate appropriateresources and formulate suitable management plansto confront the reality of wastewater aquaculture,mitigating health and environmental risks, conserving

Wastewater aquaculture 71

nutrient and water resources and safeguarding andstrengthening livelihoods and food security.

Outcomes of this review demonstrate that somepoor people depend both directly and indirectly onwastewater aquaculture for a significant part of theirlivelihood. However, various constraints, includingurbanisation, labour migration, erosion of a competi-tive advantage, uncertainty over wastewater supplies,contamination, health concerns, operational constraintsand ineffective policies, institutions and processes,combined with rising expectations and changingperceptions, mean traditional farming practices andcoping strategies are under threat. ConsideringKolkata, problems with wastewater supplies, limitedfinancial returns and increasing insecurity of tenure,have resulted in households dependent on wastewateraquaculture developing diversified livelihood strate-gies. However, livelihoods diversification is oftenlimited to natural-resources-based activities. Infra-structure and service provision in peri-urban areashas enhanced many poor livelihoods, although itremains difficult for the very poor to benefit fromsuch developments. Education, training and skillsprovision combined with assistance in accessing off-farm income would lessen the vulnerability experi-enced by poor people faced with encroaching urbandevelopment and uncertainty over the prospects forwastewater aquaculture.

Acknowledgement

This publication is an output from a project fundedby the UK Department for International Development(DFID) for the benefit of developing countries. Theviews expressed are not necessarily those of DFID.

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