Collaborative Research: Impacts of Metals on Disinfection Byproduct Precursor Formation in Bacteria

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Potable water supplies must be disinfected to protect human health. However, disinfectants can interact with organic matter in the system to cause the formation of byproducts that pose risks to human health. Understanding the disinfection byproduct formation process is a critical need for water utilities and regulatory agencies to reduce risk. This project addresses this national need by investigating how trace metals influence disinfection byproduct formation in water distribution systems. The underlying hypothesis is that exposure of biofilm microbes in the distribution system to heavy metals results in the release of small organic molecules. These molecules can then serve as the building blocks of disinfection byproducts through chemical reaction with disinfectants. This project establishes a research and education partnership between Oklahoma State University and Syracuse University at the interface of environmental microbiology and environmental chemistry. A STEM educational outreach program for elementary school students and provide summer internship research opportunities for high school students. This effort will improve the scientific literacy of the Nation and increase the capability of the STEM workforce to meet societal needs for clean and sustainable water. Disinfection byproducts are formed upon reactions of organic matter with disinfectants during water treatment. Strategies to control disinfection byproduct formation focus on removing their precursors prior to disinfection or removing disinfection byproducts after they have formed in the water treatment plant. Unfortunately, disinfection byproducts continue to form within distribution systems when precursors released by biofilms in the distribution system react with residual disinfectant. Bacterial metabolic processes and cellular regulation are highly sensitive to concentrations of trace metals, which vary significantly in distribution systems. The overall goal of this research is to characterize how trace metals affect the production of disinfection byproduct precursors from biofilms under conditions relevant to chloraminated drinking water distribution networks. The central hypothesis is that exposure to varying types and concentrations of trace metals alters metabolic pathways in biofilm microorganisms, resulting in shifts in the composition and reactivity of disinfection byproduct precursors released by the bacteria. The specific research objectives of this project are to: 1) examine the influence of metals on disinfection byproduct formation potential from bacterial isolates, 2) characterize the effects of metal exposure on changes in the composition and reactivity of biofilm-derived disinfection byproduct precursors, and 3) determine the underlying mechanisms of increased disinfection byproduct formation potential in bacterial isolates and biofilms through transcriptomic and proteomic approaches. This research addresses gaps in knowledge and model formulations with regards to predicting disinfection byproduct precursor loadings contributed by biofilms in chloraminated distribution systems. This research will provide a more complete understanding of the impacts that changes in metal speciation and concentration have on disinfection byproduct formation potential in full-scale distribution systems. The team will recruit underrepresented minority students to summer research positions to increase the diversity of STEM fields and outreach to the public will take place through seminars on safe drinking water.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.