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

极端高温灾害在美国越来越普遍，许多城市连续多天气温超过95华氏度（35摄氏度）。极端高温通过提高供水系统内的水温直接影响饮用水质量。高温会增加分配系统中消毒剂残留物的腐烂率，从而影响对微生物病原体的消毒效果。温度升高可以同时刺激机会性病原体的生长，从而导致急性疾病或死亡。因此，在极端高温灾害期间，饮用水分配系统消毒失败可能导致社区疾病爆发，这将进一步给医院资源带来压力，并导致生命损失。该抗灾能力研究资助（DRRG）项目将有助于了解极端高温对饮用水微生物和化学安全的风险，并帮助确定工程解决方案，以建立水系统的抗灾能力。研究结果将为水务公司的灾难响应和准备计划提供信息，确保在极端高温事件期间提供清洁水的能力。调查结果将通过利益相关者组织传达给公用事业公司，并有针对性地向有风险的供水系统进行推广，例如为西南边境低收入社区服务的供水系统，这些社区经常经历极端高温事件。该项目为两所不同公立大学的研究生和本科生学员提供了丰富的经验，并将向代表性不足的学生介绍令人兴奋的、有影响力的STEM研究。两位早期职业研究者之间的知识转移将为两个实验室未来在水质和弹性工程方面的创新做好准备。该项目将评估极端高温对饮用水分配系统消毒效果的影响，并评估一种新的工程解决方案，以增加弹性。大多数消毒研究仅限于30°C，这对极端高温事件期间可能出现的高水温没有帮助。模拟分配系统实验将在极端高温条件下（35-60°C）进行，以阐明常规氯和氯氰尿酸盐的消毒剂衰变动力学，氯氰尿酸盐是最近批准用于饮用水处理的新兴氯替代品。我们预计氯氰脲酸盐消毒将比传统氯更能适应高温，并保持更高的微生物保护。军团菌的生长动力学和实现灭活所需的消毒暴露将通过模拟分布系统实验在极端高温条件下确定，比较常规氯和氯氰脲酸盐消毒。这些实验将产生化学动力学和微生物失活模型，这些模型将与适合美国西南部城市实际分配系统温度的传热模型相结合，以量化在一系列极端高温情景下预期的消毒失败率。在每种情况下，使用氯的失败率将与建议的氯氰脲酸盐干预进行比较。该项目采用跨学科的方法来确定极端高温事件对饮用水分配系统中消毒和微生物安全的影响程度。水生化学、微生物学和热力学的整合将对极端高温条件下的消毒效果产生全面的理解。细菌灭活的结果将为这种危险病原体在极端高温下在饮用水分配系统中的持久性提供关键的见解。这项工作将促进对如何减轻日益受到极端高温影响的美国饮用水系统的健康风险的科学理解。该奖项由NSF CMMI灾害恢复研究基金和CBET环境工程项目共同资助。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

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.