Del importe del IVA causado (cobrado) sobre

Wastewater aquaculture has been practised for centuries in countries across Asia. It encompasses the production of aquatic organisms, including finfish, molluscs and crustaceans, and aquatic plants (including seaweeds and freshwater macrophytes) and implies some form of intervention in the rearing process to enhance production, such as regular stocking, feeding and protection from predators (Edwards and Demaine, 1998; Bunting, 2004). In terms of the wastewater element, like agriculture, this can be divided into direct reuse, which is the planned and deliberate use of wastewater as a nutrient and water resource; indirect reuse, through the use of water bodies that have received wastewater; and use of treated wastewater.

Although still practised, wastewater aquaculture appears to be on the decline in many areas due to rising peri-urban land prices, industrial pollution and demand from urban populations for higher value fish (Edwards, 2010). However in some countries there have been attempts to develop both plant and animal aquaculture as part of wastewater treatment systems, for example in Ghana, Bangladesh and Peru (Murray et al., 2011b; Buijs et al., unpublished; UNEP, 2001).

89 Direct Use of Untreated Wastewater 4.4.1

The direct use of untreated wastewater for fish cultivation is found across Asia, including China and India, Latin America and Europe, including, Germany, Hungary, Czechoslovakia, Poland and the Soviet Union (Bunting, 2004; Edwards, 1985). It has been estimated that there are more than 132 sewage-fed fisheries in India alone, covering about 12,000 ha (Edwards, 1992) and the most

extensive and well documented system in the world is probably the Kolkata wetlands (Ghosh, 2001). Sewage fish culture also occurs in several areas across China. However, the lack of reticulated sewage systems in developing countries reduces the extent of this practice (Edwards, 1992), but in areas where sewers have been introduced wastewater flows have been exploited (Bunting, 2004). An advantage of using sewage for aquaculture and horticulture is that it results in high yields and economizes on fertilizer and feed costs, resulting in higher profits (Tripathi and Sharma, 2001). Intentional, direct use is reported to be on the decline because of expanding urban areas, the cost of land and its use for higher value activities (WHO, 2006).

Indirect Use of Untreated Wastewater or Contaminated Water 4.4.2

The indirect use of untreated wastewater or the use of faecally polluted surface water is, in the opinion of Edwards (1992), probably widespread wherever fish cultivation takes place near human habitation, and where there is inadequate sanitation. As with indirect wastewater agriculture, the producers may not be fully aware of the content or quality of the water; they may be concerned about pollutants, especially if commercial or industrial waste is entering the system; or they may value it for its nutritive value. Indirect use of wastewater for aquaculture has been reported in Sri Lanka5_{, Indonesia and Taiwan (Edwards, 1992).}

Use of Treated Wastewater 4.4.3

The use of treated wastewater for aquaculture usually takes the form of raising fish or aquatic plants within WSPs or treatment wetlands, or may be the result of higher water quality in open water bodies that receive treated wastewater and where stocking and fish management take place. For example, in the USA, use of duckweed-covered lagoons for tertiary treatment is classified by the USEPA as an innovative or alternative technology, where the duckweed is used to purify secondary effluents from aerated and non-aerated lagoons (Iqbal, 1999). There are also examples of waste stabilization pond operators funding the treatment system by selling fish produced in the final ponds

5 _{Although the example given, of Beira Lake in Colombo, is likely to involve very few fishermen and will most}

likely have declined since the report by Bunting (1992) was written, due to the high level of contamination of the lake.

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of WSP systems, as well as fruit grown along the banks. One such example is in Mirzapur,

Bangladesh (Skilicorn, 2012). Use of treated or partially treated wastewater has been reported in Ghana, USA, India, Bangladesh, Peru, Germany and Africa (Bunting, 2004; Edwards, 1985; 1992).

Use of Faecal Sludge 4.4.4

Many examples of the use of faecal sludge exist across the world, based on direct entry of faecal matter to the pond, for example via an overhanging latrine, or indirectly when latrines are emptied and the contents tipped into water bodies where aquaculture takes place. In the case of

overhanging latrines, this has been a traditional means of introducing faecal matter to water bodies in many places, while in others it is simply a convenient form of household sanitation that also serves the purpose of providing nutrients to the fish. In many countries, such as Bangladesh, the practice is declining because overhanging latrines are not considered sufficiently sanitary and are being replaced by other systems (Edwards, 1985). The second system, often referred to as cartage, involves the transport and disposal, into fish ponds, of faecal matter that has been excavated from latrines, either manually or mechanically. This practice occurs in parts of China, and previously occurred in Malaysia, Hong Kong, Singapore and Japan but seems to have fallen out of favour for reasons including changes in sanitation practices, public opinion and cost (Edwards, 1992).

Summary of Reuse in Aquaculture Landscape 4.4.5

This section gives a summary of several cases of wastewater use in aquaculture. The cases are only divided into treated and untreated wastewater, rather than direct and indirect use because of the difficulties in identifying which system is operating, either because of the practice itself or the description provided in the literature. Furthermore, there may be some ambiguity and potential for disagreement as to whether certain cases constitute treated or untreated wastewater. This is because several of the examples involve the growth of aquatic plants and/or fish within WWTPs, principally WSPs. The level of treatment and the ponds in which the products are grown determine how to categorize the system, however, it may be that some products are grown in one pond and another in a later pond: e.g. duckweed in the early ponds followed by fish in the maturation pond. In this case, the fish could be classified as being grown in treated water while the duckweed is grown in untreated water. Furthermore, in some cases the secondary literature does not give sufficient information for definitive categorization. In all cases every attempted has been made to choose the most fitting category, however the critical point of this chapter is to showcase the variety of systems and not to neatly categorize, and therefore it is the descriptions of the systems that are of most interest, rather than the categories.

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Table 4-3. Locations and examples of aquaculture with wastewater and faecal sludge

Country Reuse Practice Reference

Use of untreated wastewater use in aquaculture Cambodia

(direct)

Phnom Penh is surrounded by wetlands that receive 1 MCM of wastewater and urban drainage daily. Numerous plots are used to cultivate aquatic vegetables. Boeung Cheung Ek Lake is the largest of these (3,403 ha) and receives 90 % of the wastewater. It acts as an effective, low cost means of biological treatment, capturing and using valuable nutrients for cultivation of aquatic plants (mainly water spinach). Cultivation increased in the 1980s when farmers saw greater incomes from water spinach than rice, because water spinach can be grown all year. Estimated average yield was approximately 5 tons/ha/year in 2003.

Dalsgaard (2006) and Khov et al. (2006); cited in Kuong et al. (2007); Marcussen et al. (2009) India, Kolkata (direct)

In Kolkata, changes to hydrological regimes brought about by human activities, including fishing and drainage resulted in the loss of traditional fishing grounds on salt lakes. Over several decades these were replaced by a complex system of aquaculture ponds, filled primarily from the sewage draining from the city. Ponds managed for wastewater aquaculture cover over 3,500 ha, with production of carp and tilapia estimated at USD 18,000 t/yr. Fish are sold through nearby markets in central Kolkata, many of which serve poor communities.

Bunting (1985); Bunting (2004); WHO (2006c); Little et al. (2002) Ghana (direct)

In southern Ghana, tilapia are grown in ponds at Akuse, Many Krobo District because inorganic fertilizers to enrich ponds are becoming expensive and farmers are looking for alternatives.

Ampofo and Clerk (2003); cited in Bunting (2004) Nigeria

(direct)

Sewage water from a residential area was used to raise common carp and Sarotherodon galilaeus.

Ogbondeminu (1993); cited in Bunting (2004) Taiwan

(indirect)

Faecally polluted surface water is used to fertilize empty fish ponds in the winter months when the ponds are drained. The water is pumped into the ponds to a depth of around 30 cm where it encourages the growth of benthic organisms. The water reduces in turbidity and is drained out before another load of wastewater is pumped in. This is repeated 3-4 times and then the water level is raised and fish introduced. The polluted surface water continues to be used to maintain the level of benthic organisms which the fish consume.

Edwards (1985)

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Country Reuse Practice Reference

Bangladesh The NGO, PRISM, introduced a system to treat wastewater from a hospital in Mirzapur in ponds with duckweed. They also implemented a similar system in Khulna to treat municipal wastewater. The duckweed was fed to fish which were harvested and sold. They also grew fruit along the banks of the WSPs. The income from selling fish and fruit was used to fund the treatment process.

Gijzen and

Ikramullah (1999); Haq and Ghosal (2000); cited in WHO (2006c); Skilicorn, 2012 India, Karnal Karnal District, in Haryana State has a community managed

8 MLD WSP that was established under the Jamuna Action Plan in 1999. Later it was used to cultivate fish and to irrigate crops. The WSP meets water quality standards and fish production is 12000-16000 kg/year bringing an income of INR 6-800000 (USD 9,220-12,294). The wastewater sold to farmers provides an income of around INR 10-15,000 per year (USD 154-230).

Kumar et al. (2014)

Europe Wastewater aquaculture in Europe is now largely confined to reusing wastewater from industrial processes. Cooling water from power stations is used to produce ornamental fish in Bulgaria, to raise juvenile fish in France for on- growing in sea cages, and in England, to culture marine worms for fishing bait and feed for shrimp broodstock.

Bunting and Little (2004); cited in Bunting (2004)

Germany The Munich sewage fish ponds started operation in 1929. They were designed to treat the sewage, following mechanical treatment, of 500,000 people, with a peak of 700,000 people, equivalent to a 2,000 population equivalent/ha. Although changes have been made to the system over the years, the fishponds still treat some 25 % of the settled sewage as a tertiary treatment system.

Edward (1985)

North America

Extensive cultivation of aquatic plants as a means to treat wastewater. The biomass is mainly used for animal fodder or composted.

Bunting (2004)

Faecal sludge use in aquaculture

China Nightsoil was extensively used in aquaculture, especially in rural areas, but use has declined for reasons such as land development, excessive nutrients in the water, industrial pollution and improved sanitation. Nightsoil is also used to cultivate duckweed to feed grass carp fingerlings.

WHO (2006c); Edwards (1985)

Peru Demonstration to test the growth of tilapia in wastewater showed that it was safe from a public health perspective and acceptable to the community.

Cavallini (1996); cited in Bunting (2004)

Indonesia In Bandong, some 200 ha of ponds are fed with surface waters that receive faecal matter. The practice is not

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Country Reuse Practice Reference

confined to this location. They also rear fish in cages placed in polluted streams and rivers.

Vietnam In Thanh Tri district, Hanoi, fishponds are filled with water pumped from a wastewater channel that was constructed in the 1960s to transport wastewater away from urban areas. Fish yields are reported to average 5.6 t/ha for the 10-month fishing period. In Than Liet commune, Thanh Tri district, the local farmers have converted unproductive land to fish ponds filled with wastewater. Aquatic vegetables and fish production can generate USD 5,760/ha-yr and USD 7,200/ha-yr), respectively which is three times higher than rice production. Examples of overhanging latrines and nightsoil use are also reported for Ho Chi Minh City and Bac Ninh in the north of the country.

Hoan (1996); cited in Bunting (2004); WHO (2006c); Lan Huong Nguyen et al. (2012)

Taiwan Used in brackish and freshwater ponds to feed fish in Taiwan. In this model faecal sludge is spread on the bottom of empty brackish ponds prior to filling with water and fingerlings or pumped into freshwater fish ponds at regular intervals.

Edward (1985)