Groundwater problems caused by irrigation with sewage effluent

Increasingly, sewage effluent will be used for urban and agricultural irrig ation, The main concern is the potential for infectious diseases in farm wo rkers and city dwellers exposed to the effluent, as well as in people who c onsume crops irrigated with effluent, especially when those crops are eaten ran; or brought raw into the kitchen. Prevention requires adequate disinfe ction of the effluent. The effluent also must meet normal irrigation water requirements for parameters such as salt content, sodium adsorption ratio, trace elements, and so forth, Unfortunately, little or no attention is paid to long-term effects of sewage irrigation on underlying groundwater. Since most of the water applied for irrigation in dry climates evaporates, the c oncentrations of non-biodegradable chemicals in the drainage or deep-percol ation water going down to the groundwater can be much higher than in the ef fluent itself (about five times higher for an irrigation efficiency of 80 p ercent), These chemicals comprise not only the salts, nitrates, and possibl e pesticide residues normally expected in irrigated agriculture, but also " sewage chemicals" like synthetic organic compounds, disinfection by-product s, pharmaceuticals and pharmaceutically active chemicals Like endocrine dis rupters, and fulvic and humic acids,These acids are known precursors of dis infection by-products that are formed when the drainage water ends up in dr inking-mater supplies that are then chlorinated, Thus, groundwater below se wage-irrigated areas eventually may become unfit for drinking, which raises questions of liability, More research on long term effects of sewage irrig ation on groundwater is urgently needed.