Disinfection Resiliency and Microbial Risk in Drinking Water Distribution Systems During Extreme Heat Disasters

About This Grant

Extreme heat disasters are increasingly common across the US, with many cities experiencing multiple consecutive days above 95°F (35°C). Extreme heat directly impacts drinking water quality by increasing the water temperature within distribution systems. High temperatures can compromise the efficacy of disinfection against microbial pathogens by increasing the decay rates of disinfectant residuals in distribution systems. Warmer temperatures can simultaneously stimulate growth of opportunistic pathogens which can cause acute illness or death. Thus, the failure of disinfection in drinking water distribution systems during an extreme heat disaster could cause a community outbreak of illness that would further stress hospital resources and lead to loss of life. This Disaster Resilience Research Grants (DRRG) project will contribute to understanding the risk of extreme heat to the microbial and chemical safety of drinking water and help identify engineering solutions to build water system resilience. The findings will inform water utility disaster response and preparedness plans, ensuring the ability to provide clean water during extreme heat events. Findings will be communicated to utilities through stakeholder organizations and targeted outreach to at-risk water systems, such as those serving low-income communities along the Southwestern border that experience frequent extreme heat events. This project provides an enriching experience for graduate and undergraduate trainees at two diverse public universities and will introduce underrepresented students to exciting, impactful STEM research. The transfer of knowledge between two early career investigators will prime both labs for future innovations in water quality and resilience engineering. This project will evaluate the effect of extreme heat on efficacy of disinfection in drinking water distribution systems and evaluate a novel engineering solution to increase resiliency. Most disinfection studies are limited to <30 °C, which is not informative for high water temperatures possible during extreme heat events. Simulated distribution system experiments will be conducted under extreme heat conditions (35-60 °C) to elucidate disinfectant decay kinetics of conventional chlorine and chlorocyanurates, an emerging chlorine alternative recently approved for drinking water treatment. We anticipate that chlorocyanurate disinfection will be more resilient to high temperatures and maintain higher microbial protection than conventional chlorine. The growth kinetics of legionellae and the required disinfection exposure to achieve inactivation will be determined with simulated distribution system experiments under extreme heat conditions, comparing conventional chlorine and chlorocyanurate disinfection. These experiments will produce chemical kinetics and microbial inactivation models that will be combined with a heat transfer model fit to real distribution system temperatures from a Southwestern US city to quantify the anticipated disinfection failure rate under a range of extreme heat scenarios. In each scenario, the failure rate with chlorine will be compared to the proposed chlorocyanurate intervention. This project takes an interdisciplinary approach to determine the extent to which extreme heat events compromise disinfection and microbial safety in drinking water distribution systems. The integration of aquatic chemistry, microbiology, and thermodynamics will produce holistic understanding of disinfection efficacy under extreme heat conditions. Bacterial inactivation results will provide critical insights into the persistence of this dangerous pathogen in drinking water distribution systems under extreme heat. This work will advance scientific understanding of how to mitigate health risk in US drinking water systems increasingly subjected to extreme heat. This award is co-funded by the NSF CMMI Disaster Resilience Research Grants and CBET Environmental Engineering Programs. 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.