Attenuation of microorganisms in the soil during drip irrigation with waste stabilization pond effluent

Waste stabilization ponds (WSP) are one of the most appropriate wastewater treatment methods to reduce nematode and faecal coliforms. However there is still a risk of contamination of crops and soil irrigated with this kind of effluent. The purpose of this work was to examine the fate of microorganisms (faecal coliforms, F⁺, and somatic coliphages and helminth eggs), from WSP effluent used for irrigation of a vineyard orchard, under onsurface (ODI) and subsurface drip (SDI) systems. The field is located near the City of Arad (Israel). The soil and water samples were taken during the irrigation periods of two consecutive years (1997 and 1998). During the first year the vineyard was irrigated with a low quality effluent from WSP (sedimentation and maturation ponds only) and during the second year a high quality effluent (sedimentation, anaerobic, and a series of aerobic ponds and a final reservoir) was used. The results showed a substantial elimination of microorganisms in the soil, decreasing negative impacts, and minimising environmental and health risks.