Relative abundance and treatment reduction of viruses during wastewater treatment processes--identification of potential viral indicators.

Waterborne pathogenic viruses discharged from wastewater treatment plants (WWTPs) pose potential public health risks. In the present study, we investigated the relative abundance, occurrence, and reduction of eleven different viruses at two WWTPs in southern Arizona over a 12-month period, from August 2011 to July 2012. Influent and effluent samples from the two WWTPs were collected monthly. Viruses were concentrated using an electronegative filter method and quantified using TaqMan-based quantitative PCR (qPCR) assays for each of the virus types (i.e., genogroup I, II and IV noroviruses, sapovirus, enterovirus, group A rotavirus, Aichi virus, pepper mild mottle virus, adenovirus, and JC and BK polyomaviruses), with murine norovirus internal control for the monitoring of extraction-RT-qPCR efficiencies. The pepper mild mottle virus, a plant virus, was found to be the most prevalent virus in both influent and effluent wastewater (annual mean concentration of 3.7-4.4×10(6) copies/L and 4.6-6.3×10(5) copies/L in influent and effluent wastewater, respectively), showing a low reduction by the treatment processes (0.76-0.99 annual mean log10 reduction), and no significant seasonal change in concentration. Aichi virus, a human enteric virus, was also found in greater abundance, and showed lower reduction during wastewater treatment than other human enteric viruses. Our results suggest that these viruses could be used as potential indicators of wastewater reclamation system performance, with respect to virus occurrence and removal.