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.
