Jasper, Justin T. and Shafaat, Oliver S. and Hoffmann, Michael R. (2016) Electrochemical Transformation of Trace Organic Contaminants in Latrine Wastewater. Environmental Science and Technology, 50 (18). pp. 10198-10208. ISSN 0013-936X. http://resolver.caltech.edu/CaltechAUTHORS:20160919-104159870
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Solar-powered electrochemical systems have shown promise for onsite wastewater treatment in regions where basic infrastructure for conventional wastewater treatment is not available. To assess the applicability of these systems for trace organic contaminant treatment, test compound electrolysis rate constants were measured in authentic latrine wastewater using mixed-metal oxide anodes coupled with stainless steel cathodes. Complete removal of ranitidine and cimetidine was achieved within 30 min of electrolysis at an applied potential of 3.5 V (0.7 A L^(–1)). Removal of acetaminophen, ciprofloxacin, trimethoprim, propranolol, and carbamazepine (>80%) was achieved within 3 h of electrolysis. Oxidation of ranitidine, cimetidine, and ciprofloxacin was primarily attributed to reaction with NH_2Cl. Transformation of trimethoprim, propranolol, and carbamazepine was attributed to direct electron transfer and to reactions with surface-bound reactive chlorine species. Relative contributions of aqueous phase ·OH, ·Cl, ·Cl_2–, HOCl/OCl–, and Cl_2 were determined to be negligible based on measured second-order reaction rate constants, probe compound reaction rates, and experiments in buffered Cl– solutions. Electrical energy per order of removal (E_(EO)) increased with increasing applied potentials and current densities. Test compound removal was most efficient at elevated Cl– concentrations present when treated wastewater is recycled for use as flushing water (i.e., ∼ 75 mM Cl–; E_(EO) = 0.2–6.9 kWh log^(–1) m^(–3)). Identified halogenated and oxygenated electrolysis products typically underwent further transformations to unidentifiable products within the 3 h treatment cycle. Identifiable halogenated byproduct formation and accumulation was minimized during electrolysis of wastewater containing 75 mM Cl^–.
|Additional Information:||© 2016 American Chemical Society. Received: June 10, 2016; Revised: August 23, 2016; Accepted: August 26, 2016. This research was supported by the Bill and Melinda Gates Foundation (BMGF RTTC Grant OPP1111246) and a Resnick Postdoctoral Fellowship to JTJ. ·Cl2– reaction rate constants were measured in the Beckman Institute Laser Resource Center at the California Institute of Technology with funding provided by the Arnold and Mabel Beckman Foundation. We thank James Barazesh and Cody Finke for useful discussions and critically reviewing the manuscript. The authors declare no competing financial interest.|
|Group:||Resnick Sustainability Institute|
|Official Citation:||Electrochemical Transformation of Trace Organic Contaminants in Latrine Wastewater Justin T. Jasper, Oliver S. Shafaat, and Michael R. Hoffmann Environmental Science & Technology 2016 50 (18), 10198-10208 DOI: 10.1021/acs.est.6b02912|
|Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Tony Diaz|
|Deposited On:||28 Sep 2016 19:04|
|Last Modified:||28 Sep 2016 19:04|
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