Fate of viruses in treated sewage effluent during soil aquifer treatment designed for wastewater reclamation and reuse

Land application or soil aquifer treatment of wastewater has been considered as a low-cost method for improving its quality for potential reuse. The objective of this work was to evaluate more quantitatively than in the past the fate and removal of viruses as they pass through the soil. A mini-basin (12 feet x 12 feet) was constructed at a site where secondary treated wastewater will be applied to large basins for underground storage. Suction samplers were placed at various depths in the upper 20 feet of the vadose zone directly beneath the mini-basin, and monitoring wells were placed at various distances (10 to 150 feet) from the mini-basin. Two experiments (August and September, 1990) were conducted where bacteriophage MS-2 and PRD-1 were added to the effluent before its application to the basins. High infiltration rate (up to 50 feet/day) and impeding layers at 15ft resulted in nearly saturated flow conditions and up to 150ft of horizontal transport of the viruses. The results also indicated that at least 90% removal of MS-2 and 99% removal of PRD-1 could be expected after movement of the sewage through 15ft of soil and greater removal was observed at a slower infiltration rate (3 feet/day).