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Onsite Graywater Treatment in a Two-Stage Electro-Peroxone Reactor with a Partial Recycle of Treated Effluent

Dobelle, Léopold and Kim, Seungkyeum and LeVan, Axl X. and Leandri, Hugo and Hoffmann, Michael R. and Cid, Clément A. (2021) Onsite Graywater Treatment in a Two-Stage Electro-Peroxone Reactor with a Partial Recycle of Treated Effluent. ACS ES&T Engineering . ISSN 2690-0645. doi:10.1021/acsestengg.1c00240. (In Press)

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The efficacy of an uncoupled electro-peroxone (E-peroxone) prototype reactor system for the treatment of synthetic graywater is determined. The two-stage E-peroxone process integrates ozonation with the in situ production of hydrogen peroxide (H₂O₂) in a first stage reactor before ozone (O₃) is converted via the peroxone reaction to a hydroxyl radical (•OH). The two-stage prototype reactor system allows for the generation of H₂O₂ via cathodic oxygen reduction in the first-stage reactor before mixing with O₃ in the second-stage reactor. This approach prevents the degradation of polytetrafluoroethylene (PTFE) coated carbon cathodes by •OH that takes place in a single well-mixed reactor that combines electrochemical peroxide generation with O₃. The dosage of H₂O₂ into the second-stage reactor is optimized to enhance graywater treatment. Under these conditions, the uncoupled E-peroxone system is capable of treating synthetic graywater with an initial chemical oxygen demand (COD₀) of 358 mg O₂/L, a total organic carbon (TOC₀) of 96.9 mg/L, a biochemical oxygen demand (BOD₀) of 162 mg O₂/L, and a turbidity of 11.2 NTU. The two-stage electro-peroxone system can reduce the initial COD₀ by 89%, the TOC₀ by 91%, BOD₀ by 86%, and the turbidity by 95% after 90 min of treatment. At this performance level, the reactor effluent is acceptable for discharge and for use in nonpotable applications such as toilet-water flushing. A portion of the effluent is recycled back into the first-stage reactor to minimize water consumption. Recycling can be repeated consecutively for four or more cycles, although the time required to achieve the desired H₂O₂ concentration increased slightly from one cycle to another. The two-stage E-peroxone system is shown to be potentially useful for onsite or decentralized graywater treatment suitable for arid water-sensitive areas.

Item Type:Article
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Hoffmann, Michael R.0000-0001-6495-1946
Cid, Clément A.0000-0002-7293-035X
Additional Information:© 2021 The Authors. Published by American Chemical Society. Attribution 4.0 International (CC BY 4.0) Received 30 June 2021. Published online 11 October 2021. This work was supported, in whole or in part, by the Bill & Melinda Gates Foundation (grant INV-003227). Under the grant conditions of the Foundation, a Creative Commons Attribution 4.0 Generic License has already been assigned to the Author Accepted Manuscript version that might arise from this submission. The authors would like to thank Nathan Dalleska, Director of the Resnick Water and Environment Laboratory for his help with TOC and TIC measurements. Author Contributions: L.D., S.K., A.L., and H.L. carried out the experiments. L.D. and S.K. co-wrote the manuscript with support from A.L., C.C. and M.H. C.C. conceived the original idea and helped supervise the project. M.H. supervised the project. The authors declare no competing financial interest.
Funding AgencyGrant Number
Bill and Melinda Gates FoundationINV003227
Subject Keywords:Redox reactions, Electrolyte solutions, Electrodes, Oxygen, Electrical conductivity
Record Number:CaltechAUTHORS:20211012-211828965
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Official Citation:Onsite Graywater Treatment in a Two-Stage Electro-Peroxone Reactor with a Partial Recycle of Treated Effluent Léopold Dobelle, Seungkyeum Kim, Axl X. LeVan, Hugo Leandri, Michael R. Hoffmann, and Clément A. Cid ACS ES&T Engineering Article ASAP DOI: 10.1021/acsestengg.1c00240
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:111389
Deposited By: George Porter
Deposited On:12 Oct 2021 22:43
Last Modified:12 Oct 2021 22:43

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