Modular, Chemical-Free Advanced Oxidation of 1,4-Dioxane and its Co-Contaminants in Ground Water

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ABSTRACT The ultimate goal of this remediation project is to design, fabricate, test, and implement point-of-use, small- scale, water treatment systems that can remove 1,4-dioxane (1,4-DX) and its frequently co-occurring contaminants, trichloroethylene (TCE), 1,1-dichloroethane (1,1-DCA) and 1,1,1,-trichloroethane (1,1,1-TCA), from contaminated ground water. The advanced oxidation process (AOP)–the process that employs highly reactive •OH as main oxidant–is considered to be the most effective among established water treatment methods for the destruction of these contaminants. However, enabling AOP in a small-scale, distributed system (i.e., in contrast to centralized large-scale treatment and water delivery through a network of pipe) is technically challenging due to the requirement for a precursor chemical (such as H2O2) that needs to be activated on site to produce •OH and the high energy demand. We will synthesize efficient catalyst materials, engineer various components of the system, and fabricate two highly-innovative prototype AOP reactors. The first reactor will employ a new catalyst that can selectively produce high concentrations of H2O2 using only water and oxygen as a source. The produced H2O2 will be activated by another newly-developed catalyst to produce •OH without any external energy/chemical supplies and without producing undesirable byproducts (which would otherwise require additional treatment). Coupled together, this catalytic system will enable for the first time AOP of ground water in a small, compact, distributed water treatment system. The second reactor will employ nanobubble technology. In this system, ambient air will be introduced to the water in the form of nanobubbles which collapse to produce •OH that will destroy 1,4-DX. Strategies to enhance the production of •OH through promotion of effective bubble collapse will be developed. Unlike any existing AOPs, both reactors will not require continuous supply of chemicals. In addition, they will either be solar powered (completely off-grid) or use a much smaller amount of electricity than conventional AOPs that employ ultraviolet (UV) irradiation. We will test the performance of prototype reactors and compare them with benchmark UV/H2O2 process (i.e., adding H2O2 and irradiating UV light). This will involve a comprehensive analysis of the efficiency of parent compound (1,4-DX) destruction, as well as the evolution of reaction byproducts. Reduction of the deleterious effects of consuming 1,4-DX-containing water will be investigated in collaboration with Research Project 1. The prototype reactors will undergo testing in select field sites in Region 1 (identified as being contaminated by Research Project 2) to determine their efficiency under real world situations and their activity under long term conditions (employing sensors developed by Research Project 3). By promoting the continual removal of 1,4-DX and its co-occurring contaminants from drinking water sources, this project will directly reduce human exposure to these pollutants and thereby limit their adverse health effects.