POTENTIAL BENEFITS AND RISKS OF WASTEWATER USE

Abstract

Wastewater is used to irrigate in many forms. It can be used as treated (reclaimed water) or untreated (raw 7 wastewater) and it can be applied directly to crops or indirectly after discharge and dilution with water from rivers or 8 reservoirs. Sometimes reuse is part of a planned project, but most of the time—and particularly in developing 9 countries—it just happens. In industrialized countries water reuse is part of a strategy to protect water bodies and to 10 reduce wastewater treatment costs. It is usually performed only after high ecological standards of wastewater 11 treatment have been achieved, and as a consequence reclaimed water has a low organic matter and nutrient content. 12 In contrast, in developing countries reuse is frequently a spontaneous response to a shortage of water and job 13 opportunities. It is generally practiced with “poor quality” water (even raw wastewater), which farmers like for its 14 fertilizing properties but mostly because it is the only way to earn a living. Wastewater can even be used for 15 agricultural irrigation in cities. This “urban agriculture” is practiced in urban and peri-urban areas of arid or wet 16 countries, depending on wastewater availability, local demand for fresh food products, and people living on the 17 verge of poverty who have no job opportunities. Wastewater flowing in open channels is used to irrigate very small 18 plots of land where trees, fodder, or any other product that can be introduced to the market in small quantities 19 (flowers and vegetables) or be used as part of the family diet are grown (Cockram and Feldman 1996; Ensink et 20 al.2004). Like any activity, the use of wastewater to irrigate has both advantages and drawbacks. The major 21 advantages of using wastewater for agricultural irrigation are- it permits higher crop yields, year-round production, 22 and enlarges the range of crops that can be irrigated, particularly in (but not limited to) arid and semi-arid areas, 23 recycles organic matter and other nutrients to soils, it reduces the cost of fertilizers (or simply makes them more 24 accessible to poor farmers) and also reduces the use of synthetic fertilizer. This paper discusses these aspects, and 25 based on practical experiences it proposes ways to obtain maximum benefits while reducing the risks.