CAREER: Establishing a New Retrosynthetic Framework for Identifying Precursors of Priority Disinfection Byproducts in Recycled Wastewater

水资源短缺是国家和世界面临的一个严重和日益严重的问题。帮助解决水资源短缺问题的一种方法是回收处理过的废水。再利用的废水需要处理到足够的质量，使其适合使用，包括灌溉，工业，甚至饮用水。水循环过程中最重要的一步是消毒，以杀死病毒和细菌。消毒通常是通过添加化学氧化剂，如氯（漂白剂）。使用这些氧化剂的问题是，它们可以与水中天然存在的有机分子反应，形成副产品化学品。这些副产品中有许多是高毒性和潜在致癌性的，必须去除。这个职业研究项目的目标是了解在水循环过程中导致有毒副产品形成的化学反应。这一知识将允许控制或消除副产物的形成，而不影响消毒。这项研究的成功完成将有助于国家制定可行的方法来解决水资源短缺问题，同时保护公众。研究结果将被用于通过与无国界工程师组织和洛杉矶当地一所高中合作的外展工作，向公众提供有关工程和水问题的信息和教育。本CAREER项目的目标是开发一个新的框架，用于识别再生废水中致癌消毒副产物（DBP）化学品的前体和形成途径。这一目标将通过具体研究来实现，重点是已知具有最高风险程度的三类DBP。DBPs仍然是更广泛地采用水再利用的严重障碍，因为它们是回收废水中最大的人类健康问题的化学品;甚至比药物或工业污染物更大。最大限度地减少它们的形成需要确定它们的前体和形成途径，以便重新设计处理系统以防止形成。在第一步中，将使用逆合成产生有关可能导致形成DBP的官能团的假设，逆合成是合成化学家开发的一种技术，用于选择合成目标的化学前体。接下来，将使用自下而上的方法来证明预测的前体官能团负责观察到的形成。将前体改性为反应性较低的衍生物，并将DBP形成潜力与对照品进行比较。然后将分析衍生的前体以鉴定特定的前体分子。最后，将采用自上而下的方法来制定最后的前体候选清单。这些分析物将在回收的废水中进行测量，其在前体池中的份额将通过地层潜力和模拟分配系统测试进行量化，以进行验证。该职业项目的教育和推广部分由三项相辅相成的活动组成。PI将与南加州大学工程师无国界组织（EWB）合作，在拉丁美洲开展水处理项目，将研究部分的工具和知识应用于本科生建造的消毒系统。PI还将在实验室中接待一名高中学生和教师，并通过远程传输原始数据进行分析，使教师的班级参与EWB项目。最后，PI将开发一个新的基于问题的“消毒权衡”模块，用于走廊级环境工程课程，使用南加州大学EWB团队在危地马拉建立的系统作为案例研究。该奖项反映了NSF的法定使命，并被认为是值得通过使用基金会的智力价值和更广泛的影响审查标准进行评估的支持。

Water scarcity is a serious and growing problem for the Nation and the world. One approach to help solve the issue of water scarcity is to recycle treated wastewater. Re-used wastewater needs to be treated to a sufficient quality to make it fit for use, including for irrigation, industry, and even drinking water. The most important step in the water recycling process is disinfection to kill viruses and bacteria. Disinfection is usually done by adding chemical oxidants like chlorine (bleach). The problem with using these oxidants is that they can react with organic molecules naturally present in the water to form byproduct chemicals. Many of these byproducts are highly toxic and potentially carcinogenic and must be removed. The goal of this CAREER research project is to understand the chemical reactions leading to toxic byproduct formation during water recycling. This knowledge will allow control or the elimination of byproduct formation without compromising disinfection. Successful completion of this research will help the Nation develop feasible approaches to address water scarcity, while protecting the public. Results will be used to inform and educate the public on engineering and water issues through outreach efforts in collaboration with Engineers Without Borders and with a local high school in Los Angeles.The goal of this CAREER project is to develop a new framework for identifying the precursors and formation pathways of carcinogenic disinfection byproduct (DBP) chemicals in recycled wastewater. This goal will be achieved through specific research focused on three classes of DBPs that are known to convey the highest degree of risk. DBPs remain a serious obstacle to wider adoption of water reuse, as they are the chemicals in recycled wastewater of greatest human health concern; even greater than pharmaceuticals or industrial contaminants. Minimizing their formation requires identifying their precursors and formation pathways so that treatment systems can be re-engineered to prevent formation. In the first step, a hypothesis will be generated about the functional groups likely to lead to formation of DBPs using retrosynthesis, a technique developed by synthetic chemists to select chemical precursors for synthetic targets. Next, a bottom-up approach will be used to demonstrate that the predicted precursor functional groups are responsible for observed formation. Precursors will be modified to less reactive derivatives and DBP formation potential will be compared to controls. Derivatized precursors will then be analyzed to identity specific precursor molecules. Finally, a top-down approach will be employed to develop the final precursor candidate list. These analytes will be measured in recycled wastewater and their share of the precursor pool will be quantified by both formation potential and simulated distribution system testing for validation. The education and outreach component of this CAREER project is composed of three complementary activities. The PI will work with the USC Engineers Without Borders (EWB) group on water treatment projects in Latin America, applying tools and knowledge from the research component to a disinfection system built by undergraduates. The PI will also host a high school student and teacher in the lab and involve the teacher’s class in the EWB project by remotely transmitting raw data for analysis. Finally, the PI will develop a new problem-based “Tradeoffs in Disinfection” module for the sophomore-level environmental engineering course, using the system built by the USC EWB team in Guatemala as a case study.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.