Pathogen Quantification and Risk Assessment of Water Reuse Systems in the State of Minnesota

Abstract

There is a growing interest in reusing or reclaiming water for non-potable use; however, one of the largest barriers to implementation is unknown source water quality and what risks are present. This work was conducted to determine the number of pathogens and their concentration present in currently operational water reuse systems in Minnesota, and to collect design treatment information from each reuse site and compare to pathogen and indicator quantity. Eighty-three samples were collected from 25 sites and were simultaneously analyzed for 27 bacterial and viral genes through microfluidic qPCR. Findings are that indicators and chemical tests did not correlate with type of source water. Type of treatment does not consistently correlate to log10 reduction, and only wastewater disinfection consistently removed all pathogens from treatment. Ten different pathogens were detected in water reuse systems. Quantitative Microbial Risk Assessment was performed on six pathogens in four exposure scenarios. Findings are that annual risk of infection of non-treated water is greater than recreational water benchmarks, however, the extent of risks depend on the exposure. When only considering samples from distribution or post-treatment sites, the risks are considerably lower, and often within guidelines.