Collaborative Research: Treatment of Cyanotoxins by UV/Chlorine: Optimizing Removal While Developing Strategies to Minimize Disinfection Byproducts and Toxicity

当有害藻类在包括湖泊、河流和河口在内的地表水系统中生长失控时，就会发生有害藻华（HABs）。这导致水中氧气含量大幅下降，并释放出通常被称为蓝藻毒素的有毒化学物质。这些毒素可引起鱼类、动物和人类的疾病和死亡。在世界范围内，有害藻华的频率和严重程度都在增加，通常是由过量的营养物（磷和氮）引发的。近年来，美国20多个州发生了严重的赤潮。然而，传统的饮用水处理工艺（混凝、絮凝、沉淀和氯化）不能完全去除蓝藻毒素（低于联邦和州机构认为有毒的浓度），特别是在大规模的赤潮事件中。该合作研究项目的总体目标是评估和优化一种新的水处理工艺的性能，该工艺将紫外线与氯（UV/氯）结合起来，以分解饮用水中存在的蓝藻毒素。该项目的成功完成将通过开发新的基础知识来造福社会，这些知识可能导致新的水处理技术（紫外线/氯），用于将蓝藻毒素去除到安全水平，同时最大限度地减少有毒消毒副产物（DBPs）的形成。进一步的社会效益将通过外展和教育活动来实现，包括1)与饮用水处理专业人员和相关利益相关者的研讨会和互动，2)课程开发，以及3)指导三名博士生。蓝藻毒素是由蓝藻细菌在有害藻华（HABs）期间释放的，是美国和全世界人类和生态系统健康的主要威胁。各种水处理技术，包括颗粒活性炭吸附、膜过滤、氯化、臭氧化和高级氧化工艺（AOPs），已经显示出去除或降解蓝藻毒素的潜力。然而，在处理过程中可能发生细胞裂解，从而增加了从处理过的饮用水中接触毒素的机会。此外，当消毒剂（如氯）与蓝藻毒素和/或藻类/浮游有机物发生反应时，可能产生有毒的消毒副产物（DBPs）。因此，迫切需要对水处理过程中蓝藻毒素的降解进行详细和仔细的检查，以确保公众的安全饮用水。本项目旨在评价紫外/氯处理对饮用水源中蓝藻毒素的降解效果，阐明相关工艺和环境条件下DBP的形成机制和毒性。为了推进这些目标，合作研究小组提出：1)研究两类常见的蓝藻毒素（微囊藻毒素和柱精子素）以及一组70个相关dbp（包括受调控的和优先不受调控的dbp）的降解；2)评价工艺条件（即辐射剂量和波长、氯剂量）和水质参数（藻类有机物、卤化物的存在和溶液pH）对降解效率的影响；3)利用转录组学确定反应动力学、转化产物（包括DBPs）的形成途径及其对人类和生态系统的潜在毒性。该项目的成功完成有可能产生变革性的影响，通过发展有关紫外线/氯水处理工艺的新基础知识，可以有效地将饮用水源中的蓝藻毒素去除到安全水平，同时最大限度地减少有毒dbp的形成。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。

Harmful algal blooms (HABs) occur when harmful algae grow out of control in surface water systems including lakes, rivers, and estuaries. This causes a large decrease in oxygen levels in the water and the release of toxic chemicals commonly referred to as cyanotoxins. These toxins can cause illness and death in fish, animals, and humans. HABs are increasing in frequency and severity throughout the world and are often triggered by excessive nutrients (phosphorus and nitrogen). In recent years, severe HABs have occurred in more than 20 states throughout the United States. However, traditional drinking water treatment processes (coagulation, flocculation, sedimentation, and chlorination) cannot fully remove cyanotoxins (to below the concentrations considered as toxic by federal and state agencies) especially during massive HAB events. The overarching goal of this collaborative research project is to evaluate and optimize the performance of a new water treatment process that combines UV light with chlorine (UV/chlorine) to break down cyanotoxins present in drinking water. The successful completion of this project will benefit society through the development of new fundamental knowledge that could lead to a new water treatment technology (UV/Chlorine) for the removal cyanotoxins to safe levels while minimizing the formation of toxic disinfection by-products (DBPs). Further benefits to society will be achieved through outreach and educational activities including 1) workshops and interactions with drinking water treatment professionals and relevant stakeholders, 2) course development, and 3) the mentoring of three doctoral students. Cyanotoxins, released by cyanobacteria during harmful algae blooms (HABs), are major threats to human and ecosystem health in the United Stated and worldwide. Various water treatment technologies, including sorption with granular activated carbon, membrane filtration, chlorination, ozonation, and advanced oxidation processes (AOPs), have shown potential to remove or degrade cyanotoxins. However, cellular lysis can occur during treatment thus increasing exposure to toxins from treated drinking water. In addition, toxic disinfection by-products (DBPs) might be generated when disinfectants such as chlorine react with cyanotoxins and/or algal/planktonic organic matter. Thus, a detailed and careful examination of cyanotoxin degradation during water treatment is critically needed to ensure safe drinking water for the public. The overarching goals of this project are to evaluate the performance of UV/chlorine treatment to degrade cyanotoxins in drinking water sources and elucidate the mechanisms of DBP formation and toxicity under relevant process and environmental conditions. To advance these goals, the collaborative research team proposes to 1) investigate the degradation of two common classes of cyanotoxins (microcystins and cylindrospermopsin) along with a group of 70 related DBPs (including regulated and priority unregulated DBPs); 2) evaluate the role of process conditions (i.e., radiation dose and wavelength, chlorine dose) and water quality parameters (algal organic matter, presence of halides, and solution pH) on degradation efficiency, and 3) determine the reaction kinetics, formation pathways of transformation products including DBPs, and their potential toxicity to human and ecosystems using transcriptomics. The successful completion of this project has potential for transformative impact through the development of new fundamental knowledge about the UV/Chlorine water treatment process that could lead to the effective removal cyanotoxins from drinking water sources to safe levels while minimizing the formation of toxic DBPs.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.