Concomitant urea stabilization and phosphorus recovery from source-separated fresh urine in magnesium anode-based peroxide-producing electrochemical cells

Abstract

In this study, we investigated the recovery of nitrogen (N) and phosphorus (P) from fresh source-separated urine with a novel electrochemical cell equipped with a magnesium (Mg) anode and carbon-based gas-diffusion cathode. Recovery of P, which exists primarily as phosphate (PO43-) in urine, was achieved through pH-driven precipitation. Maximizing N recovery requires simultaneous approaches to address urea and ammonia (NH3). NH3 recovery was possible through precipitation in struvite with soluble Mg supplied by the anode. Urea was stabilized with electrochemically synthesized hydrogen peroxide (H2O2) from the cathode. H2O2 concentrations and resulting urine pH were directly proportional to the applied current density. Concomitant NH3 and PO43- precipitation as struvite and urea stabilization via H2O2 electrosynthesis was possible at lower current densities, resulting in urine pH under 9.2. Higher current densities resulted in urine pH over 9.2, yielding higher H2O2 concentrations and more consistent stabilization of urea at the expense of NH3 recovery as struvite; PO43- precipitation still occurred but in the form of calcium phosphate and magnesium phosphate solids.

Keywords

Source-separated urine; Nutrient recovery; Electrosynthesis

Published in

Water Research
2024, volume: 256, article number: 121638
Publisher: PERGAMON-ELSEVIER SCIENCE LTD

SLU Authors

• Simha, Prithvi

  • Department of Energy and Technology, Swedish University of Agricultural Sciences
    

UKÄ Subject classification

Other Environmental Engineering

Publication identifier

• DOI: https://doi.org/10.1016/j.watres.2024.121638

Permanent link to this page (URI)

https://res.slu.se/id/publ/130816