Performance of a Novel Fertilizer-Drawn Forward Osmosis Aerobic Membrane Bioreactor (FDFO-MBR): Mitigating Salinity Build-Up by Integrating Microfiltration

Abstract

In this paper, three different fertilizer draw solutions were tested in a novel forward osmosis-microfiltration aerobic membrane bioreactor (MF-FDFO-MBR) hybrid system and their performance were evaluated in terms of water flux and reverse salt diffusion. Results were also compared with a standard solution. Results showed that ammonium sulfate is the most suitable fertilizer for this hybrid system since it has a relatively high water flux (6.85 LMH) with a comparatively low reverse salt flux (3.02 gMH). The performance of the process was also studied by investigating different process parameters: draw solution concentration, FO draw solution flow rate and MF imposed flux. It was found that the optimal conditions for this hybrid system were: draw solution concentration of 1 M, FO draw solution flow rate of 200 mL/min and MF imposed flux of 10 LMH. The salt accumulation increased from 834 to 5400 μS/cm during the first four weeks but after integrating MF, the salinity dropped significantly from 5400 to 1100 μS/cm suggesting that MF is efficient in mitigating the salinity build up inside the reactor. This study demonstrated that the integration of the MF membrane could effectively control the salinity and enhance the stable FO flux in the OMBR.