Advanced treatment of municipal reverse osmosis concentrate by a hybrid ozone-membrane aerated biofilm reactor system

Municipal reverse osmosis concentrate (mROC) possesses some characteristics, such as complex composition, poor biodegradability and high salinity. If mROC is discharged directly to the environment, it will cause serious damage to the ecological system. In this study, a hybrid ozone-membrane aerated biofilm reactor (O3-MABR) system was designed to treat mROC. This hybrid system combined the high efficiency of ozone to degrade refractory substances with the simultaneous removal of carbon and nitrogen in MABR. The effects of operating conditions including the ozone oxidation time, aeration pressure, hydraulic retention time (HRT) and the content of external carbon source on the system performance were investigated. Under the optimal parameters (ozone oxidation time was 10 s, aeration pressure and HRT of MABR-1 were 0.002 MPa and 28 h, respectively, and aeration pressure, HRT and carbon source addition amount of MABR-2 were 0.01 MPa, 22 h and 125 mg COD/L, respectively.), the average effluent COD and TN concentration of the coupling system were 41.4 mg/L and 12.3 mg/L, respectively, which met the Class A of the Discharge standard of pollutants for wastewater treatment plants (WWTP) (GB18918-2002). Furthermore, it revealed that the main phyla in biofilms of MABR were Proteobacteria and Firmicutes via high-throughput sequencing technology. This work had successfully developed an effective advanced treatment process of mROC, which lays a favorable foundation for subsequent technical promotion and applied research.