Phosphate Recovery from Human Waste via the Formation of Hydroxyapatite during Electrochemical Wastewater Treatment
Abstract
Electrolysis of toilet wastewater with TiO_2-coated semiconductor anodes and stainless steel cathodes is a potentially viable onsite sanitation solution in parts of the world without infrastructure for centralized wastewater treatment. In addition to treating toilet wastewater, pilot-scale and bench-scale experiments demonstrated that electrolysis can remove phosphate by cathodic precipitation as hydroxyapatite at no additional energy cost. Phosphate removal could be predicted based on initial phosphate and calcium concentrations, and up to 80% total phosphate removal was achieved. While calcium was critical for phosphate removal, magnesium and bicarbonate had only minor impacts on phosphate removal rates at concentrations typical of toilet wastewater. Optimal conditions for phosphate removal were 3 to 4 h treatment at about 5 mA cm^(–2) (∼3.4 V), with greater than 20 m^2 m^(–3) electrode surface area to reactor volume ratios. Pilot-scale systems are currently operated under similar conditions, suggesting that phosphate removal can be viewed as an ancillary benefit of electrochemical wastewater treatment, adding utility to the process without requiring additional energy inputs. Further value may be provided by designing reactors to recover precipitated hydroxyapatite for use as a low solubility phosphorus-rich fertilizer.
Additional Information
© 2018 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: September 7, 2017; Revised: February 1, 2018; Published: February 5, 2018. This research was supported by the Bill and Melinda Gates Foundation (Grants OPP 1069500 and OPP 1111246) and a Resnick Sustainability Postdoctoral Fellowship to J.T.J. C.A.C. and J.T.J. contributed equally to this work. The authors declare no competing financial interest.Attached Files
Published - acssuschemeng.7b03155.pdf
Supplemental Material - sc7b03155_si_001.pdf
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Additional details
- PMCID
- PMC5871340
- Eprint ID
- 84857
- Resolver ID
- CaltechAUTHORS:20180215-163923294
- Bill and Melinda Gates Foundation
- OPP 1069500
- Bill and Melinda Gates Foundation
- OPP 1111246
- Resnick Sustainability Institute
- Created
-
2018-02-21Created from EPrint's datestamp field
- Updated
-
2022-03-17Created from EPrint's last_modified field
- Caltech groups
- Resnick Sustainability Institute