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On-site applicability of hydrogen peroxide producing microbial electrochemical cells (MECs) coupled with UV in wastewater disinfection study
Citation:
Ryu, H., L. Boczek, J. Hoelle, AND M. R. Rodgers. On-site applicability of hydrogen peroxide producing microbial electrochemical cells (MECs) coupled with UV in wastewater disinfection study. Presented at Annual Conference American Society for Microbiology, New Orleans, LA, May 30 - June 02, 2015.
Impact/Purpose:
Results describe the ability to generate hydrogen peroxide from a microbial electrochemical cell and couple this with UV as a potential treatment system for pathogen inactivation in wastewater treatment plants.
Description:
Background: There is an increased interest in the application of microbial electrochemical cell (MEC) for the recovery of value-added products such as hydrogen gas and hydrogen peroxide (H2O2) from wastewater. H2O2 has strong oxidation capability and produces hydroxyl radicals when coupled with UV irradiation. An advance oxidation process (AOP) with H2O2/UV has been shown to be effective in removing/inactivating both chemical and microbial contaminants. In this study, we attempted to evaluate the performance of a H2O2 producing MEC and to demonstrate its on-site utilization coupled with UV in microbial inactivation experiments. Methods: A laboratory-scale MEC was operated in a continuous feed mode with synthetic wastewater (5-25 mM of acetate media). Water samples were collected from the cathode compartment on an hourly basis for 8 hours and analyzed for H2O2. Also, influent and effluent samples from the anode compartment were analyzed for COD. Anode potential and cell voltage were recorded every minute. Coulombic and H2O2 conversion efficiencies were calculated using consumption of COD and production rate of H2O2, respectively. A bench-scale AOP with H2O2/low-pressure UV at 254 nm was performed against E. coli, MS2 bacteriophages, Bacillus pumilus spores, and human adenovirus. Results: COD removal efficiency ranged from 40% to 48%. H2O2 concentrations increased gradually as time passed, resulted in the final concentration of 1.5 mM in 100 mL for 8 hours which converts to 0.3 m mol e-. H2O2 conversion efficiency during the first 2 hours averaged to 6.5% but decreased to 3.9% at 8 hour. The exact mechanisms of this significant reduction in cathode performance for converting electrons to H2O2 formation is still not clear. Further study is needed for a complete understanding of these electrochemical reactions. Among the testing microorganisms, human adenovirus was the most resistant microorganism under UV irradiation, but showed the relatively less resistance to H2O2. Compared to either UV or H2O2 treatments alone, UV can couple synergistically with H2O2 to sufficiently inactivate a range of microbial contaminants. Conclusions: Combining MEC with AOP has much promise for challenging the net-zero concept of wastewater treatment and demonstrated successfully its on-site application.
