Occurences and Temporal Dynamics of Pathogens and Antibiotic Resistance Genes in Different Stormwater Reuse Systems

Abstract

Stormwater is increasingly considered as an alternative water source for both potable and non-potable uses. However, stormwater has not been widely used as an alternative water source, primarily due to a lack of knowledge about the presence and risks associated with pathogens and antibiotic resistance genes present in raw and treated stormwater and how these populations change with environmental conditions. In my thesis research, five different stormwater reuse systems (SRS) in the Twin Cities metro area were sampled from every three weeks from June to October 2019 to build a comprehensive data set for analysis of temporal dynamics of pathogens and metal and antibiotic resistance genes (MRG/ARG) in raw and treated stormwater samples. As a follow up, two sites were time intensively sampled (i.e., sampled every 20-40 minutes as the SRS ran and water flowed through to irrigate fields) twice in summer 2020, along with tap water and lake water control sites. Microfluidic qPCR, a high-throughput quantification tool provided microbial data for 23 bacterial pathogens, 11 viral pathogens and 48 MRG/ARGs along with physiochemical testing such as turbidity, free and total chlorine, and water temperature to evaluate environmental conditions. Correlations between pathogen and MRG/ARG levels and environmental parameters such as temperature and precipitation assess the impact of precipitation and other environmental variables on pathogen and MRG/ARG concentrations in stormwater both over the season (2019 research) and during an average run where hundreds to thousands of gallons of water may be used (2020 research.) Viral and bacterial pathogens were sporadically detected both years while MRG/ARGs were widely detected. Environmental variables loosely correlated along known patterns with Fecal Indicator Bacteria (FIB) but did not account for any variation and lack of distinguished patterns seen in the data. The system with UV treatment and the system with a ball and bag filter sufficiently eliminated E. coli and limited the concentrations of MRG/ARG/pathogen genes, whereas the chlorinated system did not. SRS without any microbial treatment had no effect on cultured FIB and concentrations of MRG/ARG/pathogen genes. These results will provide previously unknown information crucial to successful expansion of stormwater reuse, especially for uses with greater human exposure.