Recycling human waste / Ivanildo Hespanhol

12 World Health • July-August 1992 Recycling human waste lvanildo Hespanhol M any wastes generated by modem societies represent a valuable resource which can be reclaimed, recycled or reused for man's benefit. This ensures that solid and liquid wastes are not dumped on soil or water courses, thus avoiding environmental degradation and safeguarding sources of fresh water for drinking and other beneficial uses. The use of wastewater for irrigat- ing crops can actually be traced back to ancient Athens. For thousands of years in the Far East, human wastes have been used to fertilize ponds to produce fish and aquatic weeds. Today, many countries in both the developing and the industrialized world utilize domestic wastewater to irrigate farm land. Well-managed wastewater irrigation systems contribute to raise food production and thus improve health, the quality of life and social conditions. There are several other advantages. Apart from avoiding The use of low-quality waters will become commonplace during the next century as freshwater resources grow scarcer. The health implications must not be ignored. pollution and protecting the drinking-water supply, such systems preserve groundwater resources in areas where their overuse in agricul- ture is causing salt intrusion or other types of damage to the aquifers. The build-up of humus helps to prevent land erosion. Nutrients available in treated wastewater, especially nitrogen and phosphorus, can, in many cases, eliminate the need to use synthetic fertilizers. And studies carried out in several countries have shown that crop In Cyprus, the coffon grows using recycled wastewafer. yields can increase if wastewater irrigation is provided under proper management. Health guidelines for the use of wastewater in agriculture and aquaculture, WHO Technical Re- port Series No. 778, is available in English , French, Spanish and Ara- bic, and can be obtained from Distribution and Sales, WHO, 1211 Geneva 27, Switzerland. Health guidelines WHO has been providing countries with health, environmental and technical guidance for establishing and improving wastewater use systems, especially in the Eastern Mediterranean Region. In the arid and semi-arid regions of the world, lack of water has become a limiting factor for agricultural and industrial develop- World Health • July-August 1992 ment. Governments are continuously searching for additional ways of supplementing the scarce water resources available. Health guidelines (see box on p. 12), published in 1989, have been used as a basis for developing national standards and codes of practice for waste water reuse. Four groups can be exposed to the risk of communicable diseases through agricultural reuse systems: consumers of crops, field workers and their families, crop handlers, and people living nearby. All have to be safeguarded by applying four integrated protective measures: • waste water treatment, to ensure that the treated wastewater applied to the crops is free from pathogenic organisms; • wastewater application techniques, to avoid as much as possible letting wastewater enter into contact with the edible parts of crops; • crop selection, to limit the use of wastewater for irrigating crops which are not consumed directly (industrial and fodder crops), or which grow well above the ground (tomatoes and chili), or crops not eaten raw (potatoes); • human exposure control, by advising farm workers and their families, crop handlers and con- sumers through programmes of health education, immunizing them against typhoid and hepatitis A, and providing regular chemotherapy and adequate medical facilities to treat diarrhoea! diseases. One of the greatest challenges of the next century will be to ensure the appropriate management of water resources. The use of low quality waters, such as wastewater, drainage waters or brackish waters, will certainly become commonplace as freshwater sources become less and less available around the world. Since the use of these waters may be associated with detrimental effects to soil , crops and human health, appro- priate protection measures should be undertaken accordingly. WHO will collaborate with any country requesting technical advice on AL·SAMRA WASTEWATER TREATMENT PLANT In hot countries, wastewater can be treated at low cost, wi thout any complex technology, simply by using nature's power to produce oxygen. The wastewater which is retained for an adequate period in well-designed ponds, becomes stabil ized under the action of solar energy, bacteria and algae. A I-Sam ra , near Amman in Jordan, is probably the largest stabilization pond complex in developing countries . it covers an area of approximately l 80 hectares and treats the domestic wastewater from Amman and Zarka , with a total of about l .5 million inhabitants. About l% of the treated pond effluent is used for irr igation around the pond. About l .5 million trees, particularly olive trees, grow in the area and are irrigated exclusively w ith the treated wastewater from the pond. The remaining effluent from the pond is diluted in the King Thalal Reservo ir and is utilized for irrigation of various crops along the Jordan Valley. 13 wastewater reuse systems in such a way that both the environment and the public are adequately protected and preserved. • Or lvanildo Hespanhol is a Scientist with the Prevention of Environmental Pollution unit of WHO's Division of Environmental Health , 1 2 1 1 Geneva 27, Switzerland.