Civil and Environmental Engineering Seminar: Seeing inside the reactor - Molecular insight into viruses and antibiotic resistance fate during wastewater treatment (Dr. Philip Wang)

Biological treatment is fundamental to wastewater management and has been used for decades, primarily for the removal of organic carbon and nutrients. These same processes are now expected to control contaminants they were not initially designed for, including human enteric viruses and antimicrobial resistance. However, microbial contaminants are difficult to track through conventional bulk performance measurements, so molecular methods have become a promising approach for monitoring them. This talk presents two studies that use molecular tools to address different treatment questions at different scales. The first evaluates virus removal mechanisms at two full-scale facilities, one using conventional activated sludge and the other lagoons. Molecular and conventional culture assays produced different log reduction values, and spatial sampling within each treatment train explained the discrepancy: removal was solids-associated in the activated sludge system and decay-dominant in the lagoons. The second study asks how redox conditions shape antimicrobial resistance, applying metagenomic sequencing to parallel bench-scale aerobic and anaerobic membrane bioreactors under stepwise antibiotic loading. Separating intracellular from extracellular DNA in the effluent showed that the two reactors released resistance in different forms. The aerobic reactor discharged resistance genes inside intact cells, while the anaerobic reactor released the same genes as cell-free DNA, a distinction that total gene abundance alone would obscure. Redox conditions altered not only how many antimicrobial resistance genes were discharged but also the form in which they were released, and therefore the risk they carried. Together, these studies illustrate how molecular methods, interpreted alongside process behavior, can support biological contaminant management in water reuse and resource recovery systems.

Dr. Phillip Wang is an environmental engineer and microbiologist whose research examines how wastewater treatment processes control pathogens and antimicrobial resistance. He holds a Ph.D. in Environmental Engineering from the University of Southern California, along with an M.A. in Molecular Biology and a B.S. in Biochemistry and Molecular Biology from the University of California, Santa Cruz. Following his postdoctoral appointment at the Southern Nevada Water Authority, he continues to lead SNWA-affiliated research on pathogen surveillance in engineered water systems. He has published 18 peer-reviewed papers, including molecular work at three scales: antimicrobial resistance risks in laboratory-scale bioreactors, virus removal at full-scale treatment plants to support state regulations for turning wastewater into drinking water, and SARS-CoV-2 tracking through wastewater surveillance in Los Angeles County.