Ensuring that drinking water is clean and safe is vital to human health and drinking water distribution systems (DWDSs) serve as the final barrier against contamination. To control Opportunistic Pathogens (OPs), which are very prevalent in each step of water treatment and distribution systems, they use disinfectants such as chlorine and chloramine.
However, these disinfectants can react with organic matter, e.g., naturally present fulvic and humic acids, amino acids, bacteria, etc., in the drinking water to form harmful Disinfection Byproducts (DBPs). At this time, the corresponding risk tradeoffs from persistent OPs and the formation of DBPs remain poorly understood in DWDSs.
Civil and Environmental Engineering Assistant Professor Yun Shen is working to fill this gap with researchers from the University of Texas at Austin, the University of Michigan - Ann Arbor, the University of Massachusetts Amherst, and Water Tower Institute. In the $2M project supported by the U.S. Environmental Protection Agency titled Consortium On Disinfection by-products and Opportunistic pathogens in Water Networks (CO-DOWN), they will investigate the prevalence of OPs, their free-living amoebae vectors, and (un)regulated DBPs across a wide variety of sizes and types of DWDSs. The project will be led by Professor Mary Jo Kirisits from the University of Texas at Austin, and Shen’s lab will work on understanding the occurrence and viability of OPs in drinking water.
Further, they will examine fundamental scientific hypotheses related to the occurrence of OPs and DBPs in DWDSs and their relative risks. As they are currently understood, OPs and DBPs pose particular risks to human health. For example, humans exposed to DBPs through drinking water, breathing contaminated air, or absorbing it through their skin during bathing and swimming may suffer from liver damage and decreased nervous system activity.
Respiratory tract OPs, including Legionella pneumophila, nontuberculous mycobacteria, Pseudomonas spp., etc., cause the majority of waterborne disease outbreaks associated with drinking water. They can be released from drinking water to the air during water use events such as showering, and the contaminated air infects humans. Take Legionella pneumophila, for example; each year in the U.S., this OP causes at least 5,000 cases of Legionnaire’s Disease.
“This grant will allow us to tackle the challenge of drinking water safety and public health. We will be able to provide the most valuable information on pathogens and DBPs in the real water systems, which can help us to find the best water treatment strategy to minimize the risk of pathogens and DBPs in drinking water,” Shen stated. “Additionally, we will work with the best researchers in the field of drinking water pathogens and DBPs, and I am sure we will learn a lot and have beneficial outcomes from this project.”
To identify patterns of occurrence and concentration of OPs and DBPs, the researchers will collaborate with Carollo Engineers and water utilities nationwide. Water utilities will provide information on their treatment process, distribution network, and water samples, which will come from sampling sites that best represent the water quality in the examined area.
Using the samples, the researchers will then conduct analyses, providing the interim research findings to utilities and working with select utilities to refine the research design. Utility companies not directly involved in the sampling process will still benefit from CO-DOWN as an educational component will be used to disseminate the project’s final findings.
The results of CO-DOWN will help to identify how hazard prevalence is correlated with general water quality and DWDSs. Identification of the most important factors controlling the relative risks exerted by OPs and DBPS will also allow the formulation of risk-mitigation strategies to ensure safe drinking water for all consumers. Ultimately, Shen is aiding public health through this project by contributing to the development of a deeper understanding of OPs and DBPs in drinking water and DWDSs.