Occurrence of Enteric Viruses and Parasites in Reclaimed Wastewater Used for Irrigation in Arizona

Abstract

The State of Arizona recently implemented virus and parasite standards for discharge and reuse of effluent. This study monitored for two years the enterovirus and Giardia content of reuse effluent from several Arizona wastewater treatment facilities. All treatment facilities met the restricted access irrigation virus standard of 125 enteric virus/40 L, but most plants would have to upgrade their treatment for open access year -round reuse which has a 1 enteric virus/40 L standard. Up to 43% of samples from facilities with primary treatment and oxidation ponds were positive and exceeded 1 enteric virus/40 L. Also, 27% of secondary (activated sludge) effluent samples, which were sand filtered and disinfected by ultraviolet light, were positive and exceeded the 1 enteric virus/40 L standard. Plants using sand filtration and /or chlorine disinfection of activated sludge effluent had the fewest positive samples (20% positive and only 12.5% exceeded 1 enteric virus/40 L). Parasites are monitored for presence or absence in recommended volumes. Giardia monitoring is required for effluent intended for food crop irrigation or full body contact recreation categories.