Formation of Halonitromethanes and Nitrosamines During Ozonation in Drinking Water Treatment

PI：Tanju KaranfilProposal编号：CBET-1066567机构：克莱姆森大学标题：饮用水处理中臭氧氧化过程中卤代硝基甲烷和亚硝胺的形成卤代硝基甲烷(HNMS)和亚硝胺是水处理过程中可能形成的两类重要的消毒副产物(DBPs)。HNM的细胞毒性和遗传毒性比任何受监管的有机DBPs高出一个数量级，而亚硝胺对癌症的风险很低(即ng/L)。皮？S最近的研究表明，与饮用水处理中使用的其他典型消毒方案相比，臭氧-氯化过程中HNM的生成量显著增加。随着水中溶解有机氮(DON)含量的增加，HNM的生成也随之增加。然而，关于DON组分的作用和导致HNM形成的前体的身份，人们知之甚少。此外，臭氧氧化过程中亚硝胺的形成也存在争议。虽然先前的研究表明臭氧氧化减少了N-亚硝基二甲胺(NDMA)的生成，但最近的工作报告了在实验室研究和大规模臭氧氧化工厂中臭氧氧化后相当数量的NDMA生成。因此，研究臭氧氧化过程中HNMS和亚硝胺的生成，了解其形成和形态的控制因素至关重要。PI旨在系统地研究臭氧氧化过程中HNMS和亚硝胺的形成，并深入了解它们的潜在前体和形成机理。我们假设N-DBPs的形成是前体特异性的，不同的前体/机制将参与HNM或亚硝胺的形成。因此，在这项研究中，假设了各种形成机制，并提出了实验计划来研究所提出的机制。PI和同事首先将对一组精心挑选的含氮有机化合物模型进行实验(任务1)。将对反应中间体进行分析，以检查拟议的形成机制，并深入了解HNM和亚硝胺的形成(任务2)。还计划在选定的天然水域进行一项监测研究(任务3)，以审查前体(根据任务2和任务3)与多氯联苯(HNM或亚硝胺)之间的关系(S)。这项拟议的工作是新颖的，因为这将是拟议的机制将第一次被研究。这些发现有望提供有关天然水中不同有机氮成分在臭氧过程中形成HNMS和亚硝胺的潜在作用的重要信息(S)。了解HNMS和亚硝胺的形成对于找到控制这些化合物的策略至关重要。美国大约有250家臭氧工厂，其中一些规模相当大(500-800 MGD)，服务于非常庞大的人口。研究结果将为世界各地的臭氧工厂提供重要信息(例如，臭氧在欧洲得到广泛实施)。美国有相当数量的公用事业公司一直在探索替代方法，以符合第二阶段D/DBP规则的严格要求。臭氧氧化是一种可行的替代方法。因此，研究结果将对考虑臭氧氧化的公用事业公司具有重要意义。从这项工作中获得的知识将提高我们对HNM和亚硝胺形成的性质的理解，并直接影响实践者S在处理设施中控制这些化合物形成的能力。美国环保局和州监管机构可以从这些结果中受益，制定目前和未来管理这些化合物的程序。实施这一项目还将促进对各种不同背景和水平的学生的培训和教育。PI将通过这个项目提供创造性探究研究课程，这是克莱姆森大学的一个独特项目，让来自不同系、学习不同学科的本科生参加小型团队项目并获得大学学分。参与的学生将学习水处理工艺、应用化学(即DPB的形成)以及如何进行科学研究。该项目还将为高中生和本科生提供机会，特别是来自代表性不足群体的机会。

PI: Tanju KaranfilProposal Number: CBET-1066567Institution: Clemson UniversityTitle: Formation of Halonitromethanes and Nitrosamines During Ozonation in Drinking Water TreatmentHalonitromethanes (HNMs) and nitrosamines constitute two important classes of disinfection byproducts (DBPs) that can form during water treatment. HNMs have orders of magnitude higher cytotoxicity and genotoxicity than any of the regulated organic DBPs, while nitrosamines pose cancer risk at very low levels (i.e., ng/L). The PI?s recent research has shown that HNM formation was significantly higher during ozonation-chlorination as compared with other typical disinfection scenarios used in drinking water treatment. It was also demonstrated that the HNM formation increased with an increase in dissolved organic nitrogen (DON) content in water. However, little is known about the role of DON components and the identity of precursors causing HNM formation. Furthermore, the formation of nitrosamines during ozonation is controversial. Though previous studies have shown that ozonation decreased N-nitrosodimethylamine (NDMA) formation, recent works have reported an appreciable amount of NDMA formation after ozonation in both lab studies and full scale ozonation plants. Therefore, it will be critically important to investigate the formation of HNMs and nitrosamines during ozonation, and to understand the factors controlling their formation and speciation.The PI seeks to systematically investigate formation of HNMs and nitrosamines during ozonation, and to gain insight to their potential precursors and formation mechanisms. We hypothesize that the formation of N-DBPs is precursor specific, and different precursors/ mechanisms will involve in the formation of HNM or nitrosamines. Therefore, in this study, various formation mechanisms have been postulated and experimental plans are proposed to investigate the proposed mechanisms. The PI and coworkers will initially perform experiments with a set of carefully selected model nitrogenous organic compounds (Task 1). Reaction intermediates will be analyzed to examine the proposed formation mechanisms and to gain insight to the formation of HNMs and nitrosamines (Task 2). A monitoring study (Task 3) in selected natural waters is also planned to examine the relationship(s) between the precursors(based on Task 2 and 3) and the DBPs (HNM or Nitrosamines). The proposed work is novel because it will be the first time that the proposed mechanisms will be investigated. The findings are expected to provide important information about the potential role(s) of different organic nitrogen components in natural waters in the formation of HNMs and nitrosamines during ozonation.Understanding the formation of HNMs and nitrosamines is vital for finding strategies to control these compounds. There are approximately 250 ozonation plants in the US, and some of them are quiet large (500-800 MGD), serving very large populations. Research results will provide important information for ozonation plants worldwide (e.g., ozonation is widely implemented in Europe). An appreciable number of utilities in the US have been exploring alternative approaches to comply with the stringent requirements of the Stage 2 D/DBP Rule. Ozonation is one of the available alternatives. Therefore, the findings will be important for utilities considering ozonation. The knowledge from this work will improve our understanding of the nature of HNM and nitrosamine formation and directly impact practitioner?s ability to control the formation of these compounds in treatment facilities. The USEPA and state regulatory agencies can benefit from the results in developing both present and future procedures for managing these compounds. Implementing this project will also promote training and education of a wide range of students with diverse backgrounds and levels. The PI will offer a Creative Inquiry research course through this project, a unique program of Clemson University bringing undergraduate students from different departments studying various disciplines to work in small team-projects and earn college credits. Participating students will learn about water treatment processes, applied chemistry (i.e., DPB formation) and how to conduct scientific research. The project will also allow opportunities for high school and undergraduate students, particularly from underrepresented groups.