Process configurations adapted to membrane bioreactors for enhanced biological phosphorous and nitrogen removal

Enhanced biological phosphorous (Bio-P) removal process was adapted to membrane bioreactor (MBR). One bench-scale pilot plant (BSP, 200-250 L) and two medium-scale pilot plants (2//MSP, 1000-3000 L each) were operated under several configurations, including pre-denitrification and post-denitrification without addition of carbon source, and two solid retention times (SRT) of 15 and 26 d, in parallel to the full-scale Bio-P removal activated sludge plant of Berlin-Ruhleben (12-18 d SRT). The trials showed that efficient Bio-P removal can be achieved with MBR systems, in both pre- and post-denitrification configurations. Bio-P dynamics could be clearly demonstrated through batch-tests, on-line measurements, profile analyses, P-spiking trials, and mass balances. High P-removal performances were achieved even with high SRT of 26 d (around 9 mgP/L was removed with P/TSsimilar to2.6%). Under similar operation conditions of sludge age and mass organic load, the MBR system achieved slightly higher P-removal than the conventional technology. This was due to the rejection of particles and colloids through the microfiltration membrane. When spiking with phosphate, high Bio-P removal of up to 35-40 mg/L could be achieved without addition of external carbon source, and P/TS stabilized around 7.5%.