Agricultural reuse of wastewater: nation-wide cost-benefit analysis

The increasing agricultural reuse of treated effluent serves goals such as promoting sustainable agriculture, preserving scarce water resources, and maintaining environmental quality. Also, irrigating with wastewater 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 including costs, hazards and benefits of agricultural reuse of wastewater. The present paper demonstrates, in a simple way, how to tackle decision-making questions regarding the disposal of wastewater from an economic 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 central 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, while benefits comprise the value of agricultural output, the decrease in fertilization costs, and aquifer recharge. Hazard costs estimated in this analysis relate to seepage of nitrogen and health risks. According to this analysis, wastewater irrigation in the center of Israel saves 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 tertiary-treated effluent (as in the Dan Region Treatment Plant) instead of discard saves US$0.12/m(3), justifying a subsidy. (C) 1997 Elsevier Science B.V.