Demonstrating pathogen reduction in coagulation/flocculation/sedimentation, ozone, and biofiltration indirect potable water reuse treatment trains

ABSTRACT Exposure to pathogens remains the greatest acute health concern related to potable water reuse applications. Here, we implement high-volume sample concentration for both molecular- and culture-based analyses to evaluate pathogen and surrogate removal through a 1-MGD scale coagulation, flocculation, sedimentation, ozonation, and biofiltration treatment train. The reduction of Cryptosporidium and Giardia was quantified across the wastewater treatment plant and the advanced water treatment (AWT) process. Considering the low influent concentrations, only 2 and 4 total log-reduction values (LRVs) could be demonstrated for Cryptosporidium and Giardia, respectively. Adenovirus, rotavirus, norovirus GI, and norovirus GII concentration and reduction were quantified using droplet digital polymerase chain reaction (PCR) across the AWT process. Average enteric virus LRV, through coagulation/flocculation/sedimentation, ozonation, and biofiltration, was shown to be 1.5, 0.3, and 2 LRV, respectively. Both molecular and culture-based nonpathogenic viral surrogates were shown to be representatives of enteric virus reduction by physical removal treatment processes. Due to the low concentration of indigenous pathogens and surrogates, challenge tests were performed on the pilot scale to evaluate the inactivation and removal of pathogens by ozone and biofiltration. These full-scale monitoring data and pilot challenge testing data provide validation of the pathogen LRV credit claimed in ozone-biofiltration-based AWT, which is necessary to protect public health in reuse scenarios.