AGRICULTURAL REUSE OF WASTE-WATER - NATIONWIDE COST-BENEFIT-ANALYSIS

The increasing agricultural reuse of treated effluent serves goals suc h as promoting sustainable agriculture, preserving scarce water resour ces, and maintaining environmental quality. Also, irrigating with wast ewater may reduce purification levels and fertilization costs, because soil and crops serve as bio-filters. and wastewater contain nutrients . Policy decisions regarding the level of purification and location of agriculture using wastewater, should consider multifarious aspects in cluding costs, hazards and benefits of agricultural reuse of wastewate r. The present paper demonstrates, in a simple way, how to tackle deci sion-making questions regarding the disposal of wastewater from an eco nomic standpoint. It compares various wastewater reclamation and reuse options such as treatment levers and location of reuse, by computing the net national benefit as applied to a specific case study in centra l Israel. Several alternatives were compared including river disposal. local agricultural reuse of wastewater, and conveyance to the south. Estimated costs include those of treatment, storage and conveyance, wh ile benefits comprise the value of agricultural output, the decrease i n fertilization costs, and aquifer recharge. Hazard costs estimated in this analysis relate to seepage of nitrogen and health risks. Accordi ng to this analysis, wastewater irrigation in the center of Israel sav es US$0.50-0.60/m(3) compared with river disposal, and US$0.10-0.20/m( 3) compared with conveyance to the south. Conveyance to the south of t ertiary-treated effluent (as in the Dan Region Treatment Plant) instea d of discard saves US$0.12/m(3), justifying a subsidy. (C) 1997 Elsevi er Science B.V.