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1 Chartres, Colin. 2008. Using waste water safely and profitably. [Abstract only]. In Stockholm International Water Institute (SIWI). Conference abstract volume - World Water Week in Stockholm on Progress and Prospects on Water: For a Clean and Healthy World with Special Focus on Sanitation, 17-23 August 2008. Stockholm, Sweden: Stockholm International Water Institute (SIWI). pp.22-23.
(Location: IWMI HQ Call no: e-copy only Record No: H042947)
(0.02 MB) (2.95MB)
The world currently faces food, water and energy crisis. All are interlinked, in that water underpins food production and water is also under competition for use in the energy sector including hydropower generation and biofuels production. However, until recently, we have continued to use water as if it is an infinite resource and we squander millions of litres through inefficient management practices in many sectors of the economy. Furthermore, once used in agriculture, industry and domestically, water is returned to the environment frequently contaminated with salts, pesticides, persistent organic compounds, sewage and heavy metals. Elsewhere, literally cubic kilometers of untreated effluent are dumped in the oceans, polluting fisheries and the environment alike. Storm water runoff is often similarly discharge straight into rivers, and lakes, or the ocean rather than being seen as a valuable resource. Whilst many developed countries have done much to clean up their act with respect to sewage treatment, there are many developing countries that have few, if any, operational sewage treatment plants. Where sewage is discharged into rivers, it is often reused almost immediately in its untreated form by poor farmers. Whilst the nutrients in the water can be regarded as useful fertilizer, other contaminants including fecal coliform bacteria, helminths, viruses and chemical and metal contaminants pose immediate health risks for those using the water for irrigation and for those who consume their produce. This paper addresses some of the key issues associated with the utilization of waste water in agriculture in terms of viewing waste water as an important resource that can assist in fighting the water and food crises. It examines the major contaminants in waste water being used in agriculture and considers these from risks that they pose to human health and the environment. It also considers the types of responses that are required from government to ensure that management, regulation and policy actions are introduced to ensure that risks are adequately minimized. The paper is focused around work in developing countries and will use examples from West Africa, India, Pakistan and Sri Lanka. Wastewater use is already a common reality on some 20 million hectares, where inadequate local sanitation facilities mean that farmers often have no alternative to the use of heavily polluted irrigation water. In many cases farmers have to stand in the polluted water to extract it and the water is then irrigated directly onto the leaves of green vegetables and fodder crops. Furthermore, little may be done between the field and the point of sale to wash off biological contaminants. In other cases, heavy metals and persistent organic compounds may also be found in the irrigation water and these may accumulate in the soil and the edible leaves and tubers of food crops causing long term damage to consumers. Whilst immediate effects of contamination are usually most noticeable in terms of hospital admissions with diarrhea and parasites, long term exposure to other compounds may cause damage to internal organs and/or be carcinogenic. Where fruits and vegetables, or the meat of animals fed on polluted water is then exported to developed countries, the presence of contaminants in such products can do untold damage to future market opportunities for the country of origin. To address these concerns, in 2006 WHO-FAO-UNEP released waste water use guidelines. IWMI was a major contributor to the development of these guidelines. The guidelines show that even in conditions where wastewater treatment is limited or negligible, risks for farmers and consumers can be significantly reduced. They aim at location specific measures for the locally best impact rather than at meeting international thresholds. The guidelines are now being translated into fact sheets for farmers, policy makers and researchers that will be launched later this year. Still there are many challenges for research and development. These include: 1. lack of health risk assessments for consumers especially in developing countries where local adaptation levels can be very different from thresholds defined elsewhere 2. limited studies on alternative options for health risk reduction including on-farm water treatment, enhanced natural systems, and combined treatment and non-treatment (multiple barrier) options 3. lack of low-cost concepts for situations where pathogens and heavy metals pose a combined threat 4. slow progress in participatory wastewater governance where ‘planning for reuse’ is shifted from wastewater suppliers to wastewater users.
(Location: IWMI HQ Call no: e-copy only Record No: H045757)
(1.18 MB)
This paper shows that winds of change are blowing in the dry zones of north-central Sri Lanka, the original hydraulic civilisation of the world. The social organisation of tank irrigation – which for centuries had combined a stylised land-use pattern, a system of highly differentiated property rights, and elaborate rules of community management of tank irrigation –has now been morphing in response to demographic pressures, market signals, technical change and modernisation. What are the lessons for south Asia and sub-Saharan Africa?
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