Biological Fouling Mitigation in a Forward-Osmosis Membrane Bioreactor

Abstract

Fouling remains a critical barrier for the continued development of forward-osmosis (FO) membrane bioreactor technology (MBR). Thermal osmotic backwashing at 23°C, 60°C, and 80°C, coupled air scouring, and the impact of frequency and duration of ambient (23°C) osmotic backwashing were evaluated as nonchemical methods for mitigation and removal of biological fouling in an FO-MBR. Results demonstrate that backwashing at elevated temperatures increases the immediate water flux recovery by 7% but does not provide mid- or long-term productivity improvements when compared to ambient temperature backwashing. Constant air scouring was the most effective for minimizing fouling in a bench-scale FO-MBR process; however, a full-scale energy analysis revealed that the high capital and operating costs of constant scouring outweigh the water productivity gains observed. Optimization of ambient backwashing duration and frequency was the most economically efficient FO-MBR fouling mitigation approach.