(Science for Solving Society’s Problems Challenge Grant Winner) Electrochemical Disinfection of Wastewater Using Urea Electrolysis (2016)

Wastewater treatment to recover useable water for human consumption and industrial application will always be an important area of research. In recent years, the high cost and energy intensive operation of the water and wastewater treatment facilities have caught everyone attention. Approximately 3-4 % of the United States energy consumption has been allocated for operating the drinking water and wastewater systems (1). There is a need to convert or upgrade the existing water and wastewater treatment plants into energy efficient and sustainable facilities. The United States Environmental Protection Agency (U.S. EPA) report on water and wastewater treatment facilities proposed various measures to achieve sustainable wastewater treatment plant, which included use of efficient disinfection equipment to enable faster and effective removal of disease causing microorganisms from the wastewater (2). Urea electrolysis is an established process where urea is electrochemically oxidized to nitrogen, carbon dioxide, and hydrogen (3-5). Nickel, an inexpensive metal in comparison to platinum group metals, is the best catalyst for anode where the oxidation of urea takes place in alkaline media (Eq. 1). On the cathode electrode, water is reduced to hydrogen gas as shown in equation 2. Therefore, the overall electrochemical reaction for urea electrolysis (Eq. 3) is conversion of urea to nitrogen, carbon dioxide, and hydrogen, a high-value product. Current disinfection methods employed for treating wastewater are chlorination, ultra-violet irradiation, and ozonation. These methods are expensive due to high-energy consuming equipment and they can generate chemicals that are carcinogenic in nature. In the present study, an attempt is made to electrochemically disinfect simulated wastewater containing urea and E. coli using the urea electrolysis process. Benefit of using urea electrolysis for destroying or killing microorganisms are disinfection of wastewater, chemical conversion of urea to basic compounds, and synthesis of high-value product (H 2 ) for possible energy recovery application. The electrochemical cell for this study utilizes nickel, as both anode and cathode electrode, and the electrolyte will be simulated urea solution containing E. coli . The effect of urea concentration, E. coli count, current density, pH of the solution, and flow condition will be investigated. The destructive capabilities of the current and fluctuations of localized pH on electrode surface during urea electrolysis over E. coli population will be analyzed for the above-mentioned parameters. References U.S. EPA, State and Local Climate and Energy Program: Water / Wastewater, www.epa.gov/statelocalclimate/local/topics/water.html U.S. EPA, Local Government Climate and Energy Strategy Guides: Energy Efficiency in Water and Wastewater Facilities, EPA-430-R-09-038 (2013). B. K. Boggs, R. L. King and G. G. Botte, Chemical Communications , 32 , 4859 (2009). V. Vedharathinam and G. G. Botte, Electrochimica Acta , 81 , 292 (2012). D. Wang and G. G. Botte, ECS Electrochemistry Letters , 3 , H29 (2014). Figure 1