In contrast to our understanding of disinfection by-product (DBP) formation in water treatment plants, where water quality parameters and the formation of DBPs can be monitored simultaneously, the formation of DBPs in water distribution systems is not well understood due largely to the complexity of interactions occurring in water distribution systems. Recent studies have indicated that the presence of biofilm impacts not only the biological stability of water but also the chemical stability of water in distribution systems via reaction with residual disinfectant. Moreover, biofilm can provide a dynamic repository for various organic materials present in the bulk fluid and subsequently utilize them as a primary nutrient source. Considering the persistence of biofilm and current operational responses to biofilm outbreak in water utilities, which include increasing the concentration of residual disinfectants to inactivate biofilm, biofilm may be one of the primary contributors to DBP formation in distribution systems. Beyond increased DBP formation potential from biofilm, recent studies also reported that biological degradation of DBPs in water distribution system was strongly related to the presence of heterotrophic bacteria. While many public and industrial sectors are working to overcome the persistence of biofilm formation and its dissemination in water distribution systems with disinfection practices, unwanted DBPs may be generated during biofilm disinfection. To address the current knowledge gap, this study aims to investigate the role of biofilm on DBP formation and degradation in water distribution systems. The proposed tests will apply various biochemical analysis tools, DBP analysis, microelectrode techniques, and molecular tools to monitor biofilm growth, disinfectant transport, DPB formation, and degradation, thus providing a mechanistic understanding of reactions, decay of disinfectants, and the production of DBPs by the organic matrix of biofilm.
Overall, research outcomes will address our current knowledge gap regarding DBP formation by biofilms that form in water distribution systems and improve our ability to predict and identify harmful DBP formation, which will contribute to protecting public health from both harmful biofilm and DBP formation. Tasks completed during the proposed study will generate robust information toward understanding the mechanisms of DBP formation as well as the fate of DBPs in distribution systems. This may assist many water utilities to assess and optimize disinfectant practices for biofilm control while minimizing DBP formation in water distribution systems. In addition, the proposed project will provide training and education for Ph.D students as well as summer research opportunities for undergraduate and high school students. Research findings will also be incorporated into the PI's undergraduate courses. Furthermore, research findings will be introduced in the PI's outreach and service activities for underrepresented K-12 students and for Engineers Without Borders Projects in Honduras.
