Photolysis of free chlorine to hydroxyl radical by sunlight and ultraviolet irradiation for enhanced disinfection of chlorine-resistant waterborne pathogens

1236303 Dodd游离有效氯（FAC）仍然是全世界饮用水实践中使用最广泛的消毒剂。它是廉价的，易于用作消毒剂，便携式，并且通常对于实现各种水性微生物病原体的灭活非常有效。然而，已知其作为诸如隐孢子虫（Cryptosporidium parvum）、鸟分枝杆菌（Mycobacterium avium）和蓝氏贾第鞭毛虫（Giardia lamblia）等重要病原体的主要消毒剂相对无效。这导致广泛采用更有效但通常实质上更资本、设备和能量密集的替代消毒剂，诸如UV光和臭氧。最近的研究结果表明，灭活氯-难降解的微生物病原体实际上可以实现在相当低的费用，利用阳光或单色紫外光光解FAC等高活性氧化剂物种，如羟基自由基，原子氧，臭氧在传统的氯化。在这种方法中，FAC和光化学产生的氧化剂可以协同作用，以产生比单独使用氯可实现的更大的各种水性病原体的灭活。这项调查将利用化学和微生物学工具的组合，以量化灭活耐氯病毒，细菌和原生动物病原体在传统的氯化过程中，FAC光解增强。这项工作的主要目标是评估阳光用于氯化过程的光化学增强的使用。然而，调查也将集中在单色和多色紫外线光源的潜在应用，因为它们在饮用水处理中的应用频率越来越高。该项目小组将开发和优化实验和分析程序，以量化光化学增强氯化过程中的病原体灭活，首先利用两种常见的替代品为水传播的病原体B。枯草芽孢杆菌孢子和MS 2噬菌体，其次是耐氯人类病原体M. avium、柯萨奇病毒B5（CVB 5）和C.小的随后将利用这些程序来检查这些关键参数的影响，如pH值，水温，碱度和基质氧化剂的需求灭活效率为每种病原体在模拟阳光下，自然阳光，和各种人工紫外线光源在缓冲实验室试剂水系统，以及在真实的水基质从市政供水设施在普吉特海湾地区。特别强调将放在考虑到测得的水质参数和光谱辐照度数据的病原体灭活的动力学模型的发展。最后，在应用光化学增强氯化过程中可能产生的有机和无机DBP的形成潜力（例如，三卤甲烷、卤乙酸、ClO 3-、ClO 4-和BrO 3-）将在与全面应用相关的各种情景下进行量化。除了建立光化学增强氯化过程中耐氯病原体灭活模型的理论框架外，该项目还将为M。avium、CVB 5和C.在适用于全面水处理的各种条件下（包括可变的照射波长、强度、温度、pH和碱度），这项研究可以支持光化学增强传统的饮用水氯化工艺在全面，最少的设备和工艺改造。这种方法的应用可能比现有的氯基消毒工艺的替代品有很大的好处。首先，氯化法用于绝大多数水处理设施。第二，与利用臭氧或人造UV光的工艺相比，利用太阳辐射特别是作为光源可以净节省大量成本和能量。此外，如果某个设施已经采用了紫外线工艺，则只需在紫外线反应器上游投加燃料活性炭，就可以很容易地将该工艺改造为光化学强化氯化工艺。此外，在发达国家和发展中国家的使用点应用中，阳光强化氯化可证明对确保耐氯病原体的消毒特别有用，因为其预期成本低且易于实施。

1236303DoddFree available chlorine (FAC) remains the most widely used disinfectant in drinking water practice worldwide. It is cheap, easily utilized as a disinfectant, portable, and in general highly effective for achieving the inactivation of a wide variety of waterborne microbial pathogens. However, it is known to be relatively ineffective as a primary disinfectant of such important pathogenic agents as Cryptosporidium parvum, Mycobacterium avium, and Giardia lamblia, This has led to widespread adoption of more effective, but often substantially more capital-, equipment-, and energy-intensive alternative disinfectants such as UV light and ozone. Recent findings suggest that inactivation of chlorine-recalcitrant microbial pathogens may actually be achievable at considerably lower expense by utilizing sunlight or monochromatic UV light to photolyze FAC to such highly-reactive oxidant species as hydroxyl radical, atomic oxygen, and ozone during conventional chlorination. In such an approach, FAC and photochemically-generated oxidants may act in tandem to yield substantially greater inactivation of various waterborne pathogens than would be achievable using chlorine alone. This investigation will utilize a combination of chemical and microbiological tools to quantify inactivation of chlorine-resistant viral, bacterial, and protozoan pathogens during conventional chlorination processes enhanced by FAC photolysis. The primary objective of this work will be to evaluate the use of sunlight for photochemical enhancement of chlorination processes. However, the investigation will also focus on potential applications of monochromatic and polychromatic UV light sources, on account of their growing frequency of application in drinking water treatment. The project team will develop and optimize experimental and analytical procedures for quantifying pathogen inactivation during photochemically-enhanced chlorination by first utilizing two common surrogates for waterborne pathogens B. subtilis spores and MS2 bacteriophage, followed by the chlorine-resistant human pathogens M. avium, Coxsackievirus B5 (CVB5), and C. parvum. These procedures will subsequently be utilized to examine the influence of such critical parameters as pH, water temperature, alkalinity, and matrix oxidant demand on inactivation efficiency for each pathogen under simulated sunlight, natural sunlight, and various artificial UV light sources in buffered laboratory reagent water systems, as well as in real water matrixes acquired from municipal water utilities in the Puget Sound region. Particular emphasis will be placed on development of kinetic models for pathogen inactivation that take into account measured water quality parameters and spectral irradiance data. Finally, formation potentials of organic and inorganic DBPs likely to be generated during application of photochemically-enhanced chlorination (e.g., trihalomethanes, haloacetic acids, ClO3-, ClO4-, and BrO3-) will be quantified under a variety of scenarios relevant to full-scale application. In addition to establishing a theoretical framework for modeling chlorine-resistant pathogen inactivation during photochemically-enhanced chlorination, this project will provide an extensive dataset for M. avium, CVB5, and C. parvum inactivation under a wide variety of conditions applicable to full-scale water treatment (including variable irradiation wavelength, intensity, temperature, pH, and alkalinity). This research could support the photochemical augmentation of conventional drinking water chlorination processes at full-scale, with minimal equipment and process retrofit. Application of such an approach could have substantial benefits over existing alternatives to chlorine-based disinfection processes. First, chlorination is used in the vast majority of water treatment facilities. Second, utilization of solar radiation in particular as a light source could net significant cost and energy savings in comparison to processes utilizing ozone or artificial UV light. In addition, if a UV process is already in place at a facility, that process could quite easily be adapted for photochemically-enhanced chlorination simply by dosing FAC upstream of the UV reactor(s). Furthermore, sunlight-enhanced chlorination could prove exceptionally useful for ensuring disinfection of chlorine-resistant pathogens during point-of-use applications in developed and developing societies, on account of its expected low costs and ease of implementation.