Applicability of pepper mild mottle virus and cucumber green mottle mosaic virus as process indicators of enteric virus removal by membrane processes at a potable reuse facility

Abstract

Treatment of wastewater for potable reuse is increasingly becoming a suitable alternative water source to meet the growing urban water needs worldwide. Potable reuse requires reduction of enteric viruses to levels at which they do not pose a risk to human health. Advanced water treatment trains (e.g., microfiltration (MF), ultrafiltration (UF), reverse osmosis (RO), and ultraviolet light and advanced oxidation process (UV/AOP)) provide significant protection and reduce virus loads in highly treated final product waters. Even though viruses are a principal concern, the performance of virus removal by membrane processes is not easily determined. The objective of this study was to evaluate the applicability of Aichi virus (AiV), pepper mild mottle virus (PMMoV), cucumber green mottle mosaic virus (CGMMV), and cross-assembly phage (crAssphage) removal as possible process indicators for MF, UF, and RO. Virus log reduction values (LRVs) based on gene copies measured using molecular methods were determined for MF and UF. The median LRVs of all viruses obtained after MF and UF were 2.9 and 3.1, respectively. The LRVs of the proposed indicators were lower than those of human enteric viruses. The morphological and physicochemical difference among indicators was not found to affect LRVs. Therefore, all proposed indicator viruses were determined to be suitable candidates as process indicators for MF and UF. Regarding RO, most of the viruses measured in this study were undetectable in permeate. Only PMMoV and CGMMV were detected showing median LRVs of 2.8 and 2.5, respectively. PMMoV and CGMMV are recommended as good process indicators of physical virus removal for the overall water treatment process.