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Title: MICROBIAL TRANSPORT IN SOIL CAUSED BY SURFACE AND SUBSURFACE DRIP IRRIGATION WITH WASTEWATER

Author
item KOUZNETSOV, M - BEN GURION UNIVERSITY
item Pachepsky, Yakov
item GILLERMAN, L - BEN GURION UNIVERSTIY
item GANTZER, C - FACULTE DE FARMACIE
item ORON, G - BEN GURION UNIVERSITY

Submitted to: Waste Management and Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/15/2004
Publication Date: 7/3/2004
Citation: Kouznetsov, M.Y., Pachepsky, Y.A., Gillerman, L., Gantzer, C.J., Oron, G. 2004. Microbial transport in soil caused by surface and subsurface drip irrigation with wastewater. Waste Management and Research. 18:253-264.

Interpretive Summary: Availability of water for irrigation is one of the most important factors in agriculture of arid and semiarid regions, and wastewater becomes an important source. Potential transmission of diseases is the principal concern associated with the agricultural use of treated wastewater. Assessing the contamination risk requires knowledge of the behavior of pathogens in soils. Microorganisms are removed from the aqueous phase by adsorption to soil and die-off as wastewater moves through soil. Laboratory data on adsorption and survival of pathogens in soils are relatively easy to obtain, but their applicability to the transient conditions in irrigated soil remains unresolved issue. The objective of this work was to observe and simulate transport and fate of microorganisms for surface and subsurface irrigation with wastewater. Adsorption isotherms and water-content dependent survival were measured in batch experiments with treated wastewater and clay loam soil for fecal coliforms, somatic coliphages and F-specific RNA phages deemed to be indicators of fecal contamination. Column experiments with surface and subsurface trickle irrigation were carried out for the same soil. Simulations showed that die-off rates in the column experiments were much higher than in the batch experiments for all three organisms deemed to be indicators of fecal contamination. Somatic coliforms were the most persistent organisms probably because of the lowest adsorption and die-off. The subsurface irrigation appeared to be efficient in decreasing the pathogen content in irrigated soil and preventing pathogen appearance on soil surface that could result in produce contamination.

Technical Abstract: Availability of water for irrigation is one of the most important factors affecting agriculture in arid and semiarid regions. Treated domestic wastewater becomes an important source. Potential transmission of diseases is the principal concern associated with the agricultural use of treated wastewater. The objective of this work was to observe, compare and simulate transport and fate of microorganisms from wastewater for surface and subsurface irrigation methods. Adsorption isotherms and water-content dependent survival were measured for fecal coliforms, somatic coliphages and F-specific RNA phages in batch experiments with treated wastewater and clay loam soil. Column experiments with surface and subsurface trickle irrigation were carried out for the same soil. Results of the column experiments were simulated with a combination of Richards equation for water transport and advective-dispersive model with the first-order nonlinear adsorption and moisture-dependent first-order die-off. Simulations showed that die-off rates in columns experiments were much higher than in batch experiments for all three organisms. Somatic coliforms were the most persistent probably because of lower adsorption and die-off. The subsurface irrigation appeared to be efficient in decreasing the pathogen content in irrigated soil and preventing pathogen appearance on soil surface that could lead to the produce contamination.