Advanced Water Treatment of Non-nitrified Secondary Effluent with Tertiary Membrane Bioreactor and Reverse Osmosis Processes

Advanced treatment processes for reclaiming non-nitrified secondary effluents usually employ microfiltration/ultrafiltration (MF/UF) followed by reverse osmosis (RO) and an advanced oxidation process. Depending on the secondary effluent water quality, MF/UF membrane fouling can be a serious operational problem. In this study, a pilot-scale membrane bioreactor (MBR) was used to pre-treat the non-nitrified secondary effluent produced at the Joint Water Pollution Control Plant (JWPCP) to prepare feed to a downstream RO unit. The MBR polished the secondary effluent by removing biodegradable organic matter and reducing the potential for membrane fouling. It was operated at a flux of 20 gallons per square foot per day (gfd), comparable to that of MF/UF membranes, for over 9 months. During the study period, the MBR experienced no membrane fouling problems. Sampling results indicated that the MBR removed all suspended solids in the secondary effluent, stabilized ∼45% of the organic matter, and nitrified all the TKN to NO3-N. The experience gathered in this study suggested that MBR can be a viable alternative to MF/UF in an advanced water treatment process train.