title: Reductive dehalogenation of disinfection byproducts by an activated carbon-based electrode system.
abstract: Low molecular weight, uncharged, halogenated disinfection byproducts (DBPs) are poorly removed by the reverse osmosis and advanced oxidation process treatment units often applied for further treatment of municipal wastewater for potable reuse. Granular activated carbon (GAC) treatment effectively sorbed 22 halogenated DBPs. Conversion of the GAC to a cathode within an electrolysis cell resulted in significant degradation of the 22 halogenated DBPs by reductive electrolysis at -1 V vs. Standard Hydrogen Electrode (SHE). The lowest removal efficiency over 6 h electrolysis was for trichloromethane (chloroform; 47%) but removal efficiencies were >90% for 13 of the 22 DBPs. In all cases, DBP degradation was higher than in electrolysis-free controls, and degradation was verified by the production of halides as reduction products. Activated carbons and charcoal were more effective than graphite for electrolysis, with graphite featuring poor sorption for the DBPs. A subset of halogenated DBPs (e.g., haloacetonitriles, chloropicrin) were degraded upon sorption to the GAC, even without electrolysis. Using chloropicrin as a model, experiments indicated that this loss was attributable to the partial reduction of sorbed chloropicrin from reducing equivalents in the GAC. Reducing equivalents depleted by these reactions could be restored when the GAC was treated by reductive electrolysis. GAC treatment of an advanced treatment train effluent for potable reuse effectively reduced the concentrations of chloroform, bromodichloromethane and dichloroacetonitrile measured in the column influent to below the method detection limits. Treatment of the GAC by reductive electrolysis at -1 V vs. SHE over 12 h resulted in significant degradation of the chloroform (63%), bromodichloromethane (96%) and dichloroacetonitrile (99%) accumulated on the GAC. The results suggest that DBPs in advanced treatment train effluents could be captured and degraded continuously by reductive electrolysis using a GAC-based cathode.
authors.affiliation: Department of Civil and Environmental Engineering, Stanford University, Jerry Yang and Akiko Yamazaki Energy and Environment Building, 473 Via Ortega, Stanford, CA 94305, United States; National Science Foundation Engineering Research Center for Re-Inventing the Nation's Urban Water Infrastructure (ReNUWIt), United States.
authors.forename: Yuanqing
authors.initials: Y
authors.lastname: Li
authors.affiliation: Department of Civil and Environmental Engineering, Stanford University, Jerry Yang and Akiko Yamazaki Energy and Environment Building, 473 Via Ortega, Stanford, CA 94305, United States; National Science Foundation Engineering Research Center for Re-Inventing the Nation's Urban Water Infrastructure (ReNUWIt), United States.
authors.forename: Jerome M
authors.initials: JM
authors.lastname: Kemper
authors.affiliation: Department of Civil and Environmental Engineering, Stanford University, Jerry Yang and Akiko Yamazaki Energy and Environment Building, 473 Via Ortega, Stanford, CA 94305, United States; Adrian Wilcox High School, Santa Clara, CA 95015, United States.
authors.forename: Gwen
authors.initials: G
authors.lastname: Datuin
authors.affiliation: National Science Foundation Engineering Research Center for Re-Inventing the Nation's Urban Water Infrastructure (ReNUWIt), United States; Woodside High School, Woodside, CA 94062, United States.
authors.forename: Ann
authors.initials: A
authors.lastname: Akey
authors.affiliation: Department of Civil and Environmental Engineering, Stanford University, Jerry Yang and Akiko Yamazaki Energy and Environment Building, 473 Via Ortega, Stanford, CA 94305, United States; National Science Foundation Engineering Research Center for Re-Inventing the Nation's Urban Water Infrastructure (ReNUWIt), United States. Electronic address: wamitch@stanford.edu.
authors.forename: William A
authors.initials: WA
authors.lastname: Mitch
authors.affiliation: Department of Civil and Environmental Engineering, Stanford University, Jerry Yang and Akiko Yamazaki Energy and Environment Building, 473 Via Ortega, Stanford, CA 94305, United States; National Science Foundation Engineering Research Center for Re-Inventing the Nation's Urban Water Infrastructure (ReNUWIt), United States. Electronic address: luthy@stanford.edu.
authors.forename: Richard G
authors.initials: RG
authors.lastname: Luthy
mesh_terms: D002606:Charcoal; D004203:Disinfection; D004566:Electrodes; D054879:Halogenation; D018508:Water Purification
chemical_list: D002606:Charcoal
keywords: Activated carbon; Disinfection byproducts; Electrolysis; Potable reuse