Virus reduction at wastewater treatment plants in Nepal

Abstract

Continuous discharge of enteric viruses through treated wastewater is a potential threat to the environment and humans. This study aimed to investigate the occurrence and reduction of enteric viruses at two wastewater treatment plants (WWTPs) in the Kathmandu Valley, Nepal. Twenty-two samples (from the influent samples and effluent samples, n = 11 each) were collected at two WWTPs (WWTP A and WWTP B, installing oxidation ditch and non-aerated lagoon systems, respectively) between April and August 2018. Human adenoviruses, JC and BK polyomaviruses, Aichi virus 1, enteroviruses, noroviruses of genogroup I (NoVs-GI), group A rotaviruses, and human cosavirus, along with plant viruses (pepper mild mottle and tobacco mosaic viruses), were detected using quantitative PCR. The most prevalent enteric virus was NoVs-GI (100%), followed by human adenoviruses (95%), and enteroviruses and JC polyomaviruses (91%). Log10 reduction values of all tested viruses were found to be lower than those of fecal indicator bacteria. Both WWTPs were less efficient for the reduction of pathogens (p < 0.05). A significant positive correlation was found in the concentrations between indicator viruses (JC and BK polyomaviruses) and total enteric viruses in the effluents (p < 0.05). Both WWTPs were not adequately effective to reduce enteric viruses and indicator viruses. Our findings suggested that advanced treatment processes are needed for both WWTPs to achieve better reduction efficiency in the future.