Applicability of a novel osmotic membrane bioreactor using a specific draw solution in wastewater treatment

Abstract

This study aims to develop a new osmotic membrane bioreactor by combining a moving bed biofilm reactor (MBBR) with forward osmosis membrane bioreactor (FOMBR) to treat wastewater. Ethylenediaminetetraacetic acid disodium salt coupled with polyethylene glycol tert-octylphenyl ether was used as an innovative draw solution in this membrane hybrid system (MBBR–OsMBR) for minimizing the reverse salt flux and maintaining a healthy environment for the microorganism community. The results showed that the hybrid system achieved a stable water flux of 6.94L/m2h and low salt accumulation in the bioreactor for 68days of operation. At a filling rate of 40% (by volume of the bioreactor) of the polyethylene balls used as carriers, NH4+-N and PO43−-P were almost removed (>99%) while producing relatively low NO3−-N and NO2−-N in the effluent (e.g. <0.56 and 0.96mg/L, respectively). Furthermore, from analysis based on scanning electron microscopy, Fourier transform infrared spectroscopy, and fluorescence emission–excitation matrix spectrophotometry, there was a thin gel-like fouling layer on the FO membrane, which composed of bacteria as well as biopolymers and protein-like substances. Nonetheless, the formation of these fouling layers of the FO membrane in MBBR–OsMBR was reversible and removed by a physical cleaning technique.