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Toxic Byproduct Formation during Electrochemical Treatment of Latrine Wastewater

Jasper, Justin T. and Yang, Yang and Hoffmann, Michael R. (2017) Toxic Byproduct Formation during Electrochemical Treatment of Latrine Wastewater. Environmental Science and Technology, 51 (12). pp. 7111-7119. ISSN 0013-936X. PMCID PMC5480235. http://resolver.caltech.edu/CaltechAUTHORS:20170619-084556145

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Abstract

Electrochemical systems are an attractive option for onsite latrine wastewater treatment due to their high efficiency and small footprint. While concerns remain over formation of toxic byproducts during treatment, rigorous studies examining byproduct formation are lacking. Experiments treating authentic latrine wastewater over variable treatment times, current densities, chloride concentrations, and anode materials were conducted to characterize byproducts and identify conditions that minimize their formation. Production of inorganic byproducts (chlorate and perchlorate) and indicator organic byproducts (haloacetic acids and trihalomethanes) during electrolysis dramatically exceeded recommendations for drinking water after one treatment cycle (∼10–30 000 times), raising concerns for contamination of downstream water supplies. Stopping the reaction after ammonium was removed (i.e., the chlorination breakpoint) was a promising method to minimize byproduct formation without compromising disinfection and nutrient removal. Though treatment was accelerated at increased chloride concentrations and current densities, byproduct concentrations remained similar near the breakpoint. On TiO_2/IrO_2 anodes, haloacetic acids (up to ∼50 μM) and chlorate (up to ∼2 μM) were of most concern. Although boron-doped diamond anodes mineralized haloacetic acids after formation, high production rates of chlorate and perchlorate (up to ∼4 and 25 μM) made them inferior to TiO_2/IrO_2 anodes in terms of toxic byproduct formation. Organic byproduct formation was similar during chemical chlorination and electrolysis of wastewater, suggesting that organic byproducts are formed by similar pathways in both cases (i.e., reactions with chloramines and free chlorine).


Item Type:Article
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.1021/acs.est.7b01002DOIArticle
http://pubs.acs.org/doi/abs/10.1021/acs.est.7b01002PublisherArticle
http://pubs.acs.org/doi/suppl/10.1021/acs.est.7b01002PublisherSupporting Information
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5480235/PubMed CentralArticle
ORCID:
AuthorORCID
Jasper, Justin T.0000-0002-2461-5283
Yang, Yang0000-0003-1650-4978
Hoffmann, Michael R.0000-0002-0432-6564
Additional Information:© 2017 American Chemical Society. ACS AuthorChoice - This is an open access article published under a Creative Commons Attribution (CC-BY) License, which permits unrestricted use, distribution and reproduction in any medium, provided the author and source are cited. Received: March 23, 2017; Revised: May 22, 2017; Accepted: May 24, 2017; Published: May 24, 2017. This research was supported by the Bill and Melinda Gates Foundation (BMGF RTTC Grants OPP1111246 and OPP1149755) and a Resnick Postdoctoral Fellowship to J.T.J. We thank James Queen and Harry Collini for help with sample analysis. We also thank James Barazesh, Eric Huang, and Cody Finke for helpful discussion and critically reviewing the manuscript.
Group:Resnick Sustainability Institute
Funders:
Funding AgencyGrant Number
Bill and Melinda Gates FoundationOPP1111246
Bill and Melinda Gates FoundationOPP1149755
Resnick Sustainability InstituteUNSPECIFIED
PubMed Central ID:PMC5480235
Record Number:CaltechAUTHORS:20170619-084556145
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:20170619-084556145
Official Citation:Toxic Byproduct Formation during Electrochemical Treatment of Latrine Wastewater Justin T. Jasper, Yang Yang, and Michael R. Hoffmann Environmental Science & Technology 2017 51 (12), 7111-7119 DOI: 10.1021/acs.est.7b01002
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:78321
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:19 Jun 2017 16:03
Last Modified:13 Jul 2017 16:47

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