|M.Sc Thesis||Department of Agricultural Engineering|
|Supervisors:||Prof. Shaviv Abraham|
|Assoc. Prof. Armon Robert|
Wastewater reclamation and reuse in agriculture irrigation is an essential need in Israel. Public health is one of the most important issues in wastewater reclamation and reuse. Viruses applied to soil through wastewater treatment (SAT) or by agricultural irrigation can possibly adsorb to soil particles or percolate into groundwater. The adsorption can be reversible, or not, and in some cases may cause inactivation of these viruses.
The aim of the present research was to examine the survival, adsorption and movement of viruses in a sandy loam soil and a grumusole (clay soil) with history of irrigation with effluent or with fresh water solely, by use of MS2 bacteriophage as a model for the fate of viruses in soil.
Bacteriophages survival at 25°C in effluent decreased more compared to fresh water, probably due to the presence of microorganisms in effluents that may secreting antiviral substances. Bacteriophages survived longer in saturated sandy loam compared to irrigation medium without soil, apparently due to particles adsorption that protects bacteriophages against inactivation factors. In unsaturated sandy loam, bacteriophage concentrations declined more than in saturated sandy loam most likely as a result of bacteriophage contact with air - liquid interface that is known to cause bacteriophage inactivation.
Bacteriophages movement in soil was also examined with column experiments. The presence of bacteriophages in the filtrate of the irrigated columns with fresh water was retarded compared to columns irrigated with effluents. The total count of bacteriophages in the filtrate of columns irrigated with fresh water was higher compared with the total count in the filtrate of similar columns irrigated with effluents. In batch experiments, bacteriophages adsorption to grumusole soil was much higher than to sandy loam soil due to clay higher content of the first soil type. The total count of bacteriophages in the outflow of the sandy loam columns was higher compared to grumusole columns as a result of higher adsorption rates to grumusole particles.
During summer, the main effluent irrigation season, the ambient temperature is high (>30oC), agricultural soils are normally unsaturated and soil microorganisms could secret antiviral substances. Under these conditions inactivation of viruses in soil can occur. In spite of these unfavorable conditions for virus survival, the unrestricted use of effluent for irrigation may increase the health risk of farmers and consumers that come in contact with irrigated crop, in addition to the environmental pollution potential of groundwater.