Occurrence and reduction of human viruses, F-specific RNA coliphage genogroups and microbial indicators at a full-scale wastewater treatment plant in Japan

Aims To evaluate and compare the reductions of human viruses and F-specific coliphages in a full-scale wastewater treatment plant based on the quantitative PCR (qPCR) and plate count assays. Methods and Results A total of 24 water samples were collected from four locations at the plant, and the relative abundance of human viruses and F-RNA phage genogroups were determined by qPCR. Of the 10 types of viruses tested, enteric adenoviruses were the most prevalent in both influent and effluent wastewater samples. Of the different treatment steps, the activated sludge process was most effective in reducing the microbial loads. Viruses and F-RNA phages showed variable reduction; among them, GI and GIII F-RNA phages showed the lowest and the highest reduction, respectively. Conclusions Ten types of viruses were present in wastewater that is discharged into public water bodies after treatment. The variability in reduction for the different virus types demonstrates that selection of adequate viral indicators is important for evaluating the efficacy of wastewater treatment and ensuring the water safety. Significance and Impact of the Study Our comprehensive analyses of the occurrence and reduction of viruses and indicators can contribute to the future establishment of appropriate viral indicators to evaluate the efficacy of wastewater treatment.