Evaluation of Aquaporin-Incorporated Forward Osmosis Membrane and Biofilm Carrier Materials in a Novel Osmotic Membrane Bioreactor for Low-Temperature Rural Sewage Treatment

Transforming traditional membrane bioreactors (MBRs) into forward osmosis membrane bioreactors (OMBRs) is a highly challenging yet promising technological upgrade. Although both combine biological treatment and membrane separation, their core driving forces and operating mechanisms are completely different (an MBR is pressure-driven, while an OMBR is osmosis-driven). In this paper, a novel OMBR with an integrated fixed biofilm (BF-OMBR) was tested for the treatment of synthetic rural wastewater using fertilizer potassium chloride (KCl) as the draw solution (DS) and a commercial aquaporin InsideTM forward osmosis (FO) membrane. A bench-scale investigation was conducted to compare the BF-OMBR with traditional OMBRs and MBRs. The experimental data suggested that the reactor with aquaporin membranes contributed to a higher water flux than traditional TFC membranes, while immobilized biofilms improved the total nitrogen removal rate compared to normal OMBRs. The integration of these two technologies in the BF-OMBR system appears to leverage these individual benefits. Its TOC and ammonia nitrogen removal efficiencies were also better than those of the other two bioreactors. Meanwhile, the BF-OMBR successfully controlled the salinity build-up to a level not exceeding 2.5 mS/cm over 90 days of operation. This novel osmotic bioreactor may represent a possible alternative approach to overcoming the challenges of low-temperature and low-C/N-ratio rural sewage treatment.