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，许多城市连续多日超过95 ° F（35 ° C）。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。高温可通过增加分配系统中消毒剂残留物的衰减速率而损害对微生物病原体的消毒功效。温度升高同时会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，饮用水分配系统的消毒失败可能导致社区疾病爆发，这将进一步增加医院资源的压力，并导致生命损失。这个抗灾研究赠款（DRRG）项目将有助于了解极端高温对饮用水的微生物和化学安全的风险，并帮助确定工程解决方案，以建立水系统的弹性。调查结果将为水务公司的灾害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，并有针对性地推广到有风险的供水系统，例如那些服务于西南边境沿着经常发生极端高温事件的低收入社区的供水系统。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。两名早期职业调查员之间的知识转移将为两个实验室在水质和弹性工程方面的未来创新做好准备。 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，以提高弹性。大多数消毒研究限于30 ° C，这对于极端高温事件期间可能的高水温没有信息。将在极端高温条件（35 - 60 ° C）下进行模拟分配系统实验，以阐明常规氯和氯氰尿酸盐（最近批准用于饮用水处理的新兴氯替代品）的消毒剂衰减动力学。我们预计，氯氰尿酸盐消毒将更能适应高温，并保持比传统氯更高的微生物保护。军团菌的生长动力学和实现灭活所需的消毒暴露将在极端高温条件下通过模拟分配系统实验确定，比较传统的氯和氯氰尿酸盐消毒。这些实验将产生化学动力学和微生物灭活模型，这些模型将与适合美国西南部城市真实的配电系统温度的传热模型相结合，以量化一系列极端高温情景下的预期消毒失败率。在每种情况下，氯的失败率将与拟议的氯氰尿酸盐干预措施进行比较。该项目采用跨学科的方法来确定极端高温事件在多大程度上损害饮用水分配系统中的消毒和微生物安全。水化学，微生物学和热力学的整合将产生在极端高温条件下的消毒效果的整体理解。细菌灭活的结果将提供关键的见解持久性的这种危险的病原体在极端高温下的饮用水分配系统。这项工作将促进对如何减轻美国饮用水系统中日益受到极端高温的健康风险的科学理解。该奖项由NSF CMMI灾难恢复研究赠款和CBET环境工程计划共同资助。该奖项反映了NSF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.