Alternative schemes for municipal sewage treatment and disposal in industrialized countries: Israel as a case study

Abstract

The selection of appropriate technology for municipal sewage treatment and disposal requires not only a proper characterization of modern municipal sewage but also the analysis of agriculture-generated pollution. Modern municipal sewage contains a wide spectrum of xenobiotic pollutants with negligible oxygen demand, and BOD is no longer the descriptor of effluent quality. Intensive sewage treatment systems (such as activated sludge) successfully remove BOD but fail to remove refractory pollutants and pathogens. A proper combination of semi-intensive reactors (such as aerated lagoons) for the partial removal of BOD, with extensive reactors (such as wastewater reservoirs) for the removal of refractory pollutants and pathogens, will release effluents of much better quality than other alternative schemes, at lower costs. Wastewater irrigation fails to assure nutrient recycling through agriculture products if not accompanied by a change in fertilization practices. The present system of subsidies to agriculture in industrialized countries promotes the over-application of fertilizers and biocides, and the over-production of agriculture commodities. The incorporation of the rural sector to the sewage treatment system of the urban sector will substitute the present conflict of interests between the two sectors by a partnership with strong environmental and economic bases.