Evaluation of Virus Removal by Sandy Soils During Soil-Aquifer Treatment Using Indigenous Bacteriophage as Indicator Organisms

Abstract

Experiments were conducted to investigate several variables suspected of having an effect on the removal of pathogenic viruses from wastewater during soil-aquifer treatment (SAT). Virus removal during simulated SAT was evaluated through monitoring of coliphages indigenous to secondary effluent in bench-scale soil columns, including 18- cm and one-meter sandy loam soil columns and one-meter columns containing a river sand. Both soil types were taken from active or proposed wastewater recharge sites. Removal of coliphages was significantly higher after passage through the longer soil columns, and the finer sandy loam soil exhibited greater coliphage reduction (93%) than did sand (76%) in the one-meter columns. Removal of indigenous coliphages by one meter of sand was observed in all cases to be less than or equal to removal of poliovirus, supporting the use of coliphages as a conservative indicator of virus transport during SAT. Results also indicate that aerobic soil microorganisms play a role in virus removal during SAT. Increasing the hydraulic detention time from 5 hours to 20 hours resulted in an increased coliphage removal from 70% to 99% in the one-meter sand column. A linear relationship between log io reduction of coliphage and detention time was developed to provide an approximate estimate of virus removal during soil-aquifer treatment in the sand used in these experiments.