Bioelectrochemically assisted osmotic membrane bioreactor with reusable polyelectrolyte draw solutes

The aim of this work was to study reverse solute flux (RSF) from osmotic membrane bioreactor (OMBR) and consequent solute buildup in the feed side. A polyelectrolyte (PAA-Na) served as a draw solute (DS) to minimize RSF in OMBRs. In addition, a bioelectrochemical system (BES) was employed to drive accumulated cations from the feed/anode side into the cathode compartment, subsequently achieving PAA-Na DS recovery with the aid of high catholyte pH. Compared to the 1 M NH4HCO3 DS, the 0.48 g mL−1 PAA-Na DS produced consistently stable water flux, enhanced water recovery and increased ammonium removal efficiency. Due to a dynamic balance between PAA removal and continuing RSF, the residual PAA concentration was 72 mg L−1 on the feed side (27.0% of TOC). These results demonstrate the advantages of integrating a PAA-Na DS with a BES to mitigate RSF and to support further development of OMBR technology.