Effects of dissolved oxygen concentration on the performance of sponge membrane bioreactor treating hospital wastewater

The performance of sponge membrane bioreactor (SMBR) is strongly dependent on operating conditions. Dissolved oxygen (DO) concentration is one of the key operating parameters in the SMBR process determining the mixing efficiency, floc generation, anoxic zone formation, and directly relating to pollutant removal efficiency and membrane behavior. This study aims to examine the effect of various DO concentrations on SMBR treating hospital wastewater. The objectives were to investigate the influence of three DO concentrations on (i) sludge characteristic, (ii) COD removal efficiency, (iii) nitrogen removal efficiency and (iv) membrane fouling in the lab scale SMBR. Consequently, the operation with DO1 (7.15 +/- 0.40 mg/L) achieved the highest MLSS concentration; however, it could consume excessive energy for aeration. The COD removal efficiencies were similar in three DO levels, ranging from 95% to 99%. The operation with DO3 (1.58 +/- 0.42 mg/L) resulted in the highest TN removal efficiency of 76% and TN denitrification percentage of 31%. Herein, sponges conditioned the denitrification process. The TN removal efficiency in SMBR was two times higher than the membrane bioreactor process. In addition, fouling was significantly improved at higher dissolved oxygen during operation period without any membrane cleaning.