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Phosphorus recovery from sewage sludge ash leachate using bipolar membrane electrodialysis for sustainable wastewater treatment

Merkel, Arthur LU orcid ; Čopák, Ladislav ; Sørensen, Nicolas Bygballe ; Eilkær, Thomas and Lipnizki, Frank LU orcid (2026) In Process Safety and Environmental Protection 221.
Abstract

Recovering phosphorus (P) from sewage sludge ash (SSA) is increasingly important due to resource criticality, supply risks and tightening environmental regulations. This study investigates the conversion of SSA leachate into orthophosphoric acid using electrodialysis with bipolar membranes (EDBM). The EDBM configuration enabled selective displacement of metallic cations by in situ-generated protons while retaining phosphate species in the leachate. Processing 300 mL of leachate to pH 0.88 resulted 92% phosphate-to-acid conversion, 96–100% P yield, and 81.8% removal of exchangeable cations, with no observable membrane scaling despite high Ca and Mg levels. The process operated at an average current density of 227 A·m−2 and... (More)

Recovering phosphorus (P) from sewage sludge ash (SSA) is increasingly important due to resource criticality, supply risks and tightening environmental regulations. This study investigates the conversion of SSA leachate into orthophosphoric acid using electrodialysis with bipolar membranes (EDBM). The EDBM configuration enabled selective displacement of metallic cations by in situ-generated protons while retaining phosphate species in the leachate. Processing 300 mL of leachate to pH 0.88 resulted 92% phosphate-to-acid conversion, 96–100% P yield, and 81.8% removal of exchangeable cations, with no observable membrane scaling despite high Ca and Mg levels. The process operated at an average current density of 227 A·m−2 and required 0.164 kWh·L−1 of leachate (12.5 kWh·kg−1 H3PO4). A pilot-scale system with 21 membrane triplets further confirmed stable, precipitation-free performance, even when reverse osmosis retentate of tap water was used as brine. These findings demonstrate that semi-metathesis EDBM is a robust and scalable approach for producing phosphoric acid from SSA leachates, contributing to circular phosphorus recovery. Unlike conventional electrodialysis or multi-step wet-chemical purification routes, which typically require separate unit operations to achieve comparable phosphate recovery and metal removal, the proposed single-stage semi-metathesis EDBM configuration combines high P recovery, scaling-free operation, and direct acid-form product generation, highlighting its potential to simplify industrial-scale phosphorus recovery from SSA leachates.

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author
; ; ; and
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
Bipolar membranes, Circular economy, Electrodialysis, Phosphorus recovery, Sewage sludge
in
Process Safety and Environmental Protection
volume
221
article number
109703
pages
11 pages
publisher
Institution of Chemical Engineers
external identifiers
  • scopus:105052549022
ISSN
0957-5820
DOI
10.1016/j.psep.2026.109703
language
English
LU publication?
yes
additional info
Publisher Copyright: © 2026 Institution of Chemical Engineers. Published by Elsevier Ltd. All rights are reserved, including those for text and data mining, AI training, and similar technologies.
id
54cc4c19-4404-43e7-889d-1288f0d87e06
date added to LUP
2026-10-15 05:03:39
date last changed
2026-10-16 03:01:20
@article{54cc4c19-4404-43e7-889d-1288f0d87e06,
  abstract     = {{<p>Recovering phosphorus (P) from sewage sludge ash (SSA) is increasingly important due to resource criticality, supply risks and tightening environmental regulations. This study investigates the conversion of SSA leachate into orthophosphoric acid using electrodialysis with bipolar membranes (EDBM). The EDBM configuration enabled selective displacement of metallic cations by in situ-generated protons while retaining phosphate species in the leachate. Processing 300 mL of leachate to pH 0.88 resulted 92% phosphate-to-acid conversion, 96–100% P yield, and 81.8% removal of exchangeable cations, with no observable membrane scaling despite high Ca and Mg levels. The process operated at an average current density of 227 A·m<sup>−2</sup> and required 0.164 kWh·L<sup>−1</sup> of leachate (12.5 kWh·kg<sup>−1</sup> H<sub>3</sub>PO<sub>4</sub>). A pilot-scale system with 21 membrane triplets further confirmed stable, precipitation-free performance, even when reverse osmosis retentate of tap water was used as brine. These findings demonstrate that semi-metathesis EDBM is a robust and scalable approach for producing phosphoric acid from SSA leachates, contributing to circular phosphorus recovery. Unlike conventional electrodialysis or multi-step wet-chemical purification routes, which typically require separate unit operations to achieve comparable phosphate recovery and metal removal, the proposed single-stage semi-metathesis EDBM configuration combines high P recovery, scaling-free operation, and direct acid-form product generation, highlighting its potential to simplify industrial-scale phosphorus recovery from SSA leachates.</p>}},
  author       = {{Merkel, Arthur and Čopák, Ladislav and Sørensen, Nicolas Bygballe and Eilkær, Thomas and Lipnizki, Frank}},
  issn         = {{0957-5820}},
  keywords     = {{Bipolar membranes; Circular economy; Electrodialysis; Phosphorus recovery; Sewage sludge}},
  language     = {{eng}},
  month        = {{11}},
  publisher    = {{Institution of Chemical Engineers}},
  series       = {{Process Safety and Environmental Protection}},
  title        = {{Phosphorus recovery from sewage sludge ash leachate using bipolar membrane electrodialysis for sustainable wastewater treatment}},
  url          = {{http://dx.doi.org/10.1016/j.psep.2026.109703}},
  doi          = {{10.1016/j.psep.2026.109703}},
  volume       = {{221}},
  year         = {{2026}},
}