Application of immersed-type membrane separation activated sludge process to municipal wastewater treatment

Pilot plant studies were carried out using actual wastewater to investigate the applicability of a membrane separation activated sludge (MSAS) process to municipal wastewater treatment. A small-scale pilot plant (8.7 m(3)/day ) with immersed flat sheet membrane was operated at the flux of 0.4 m(3)/m( 2)/day. Continuous operation for 140 days without chemical cleaning was pos sible. Average Sludge production ratio was about 0.6. No significant differ ence was observed in the dewaterability between membrane separation activat ed sludge and conventional activated sludge at the CST test. Large-scale pi lot plants (30-70 m(3)/day) with five types of membrane were also operated. In these plants nitrogen removal by nitrification and denitrification, and phosphorus removal by coagulant addition were carried out. Stable operatio n with HRT of six hours, flux of 0.4-0.8 m(3)/m(2)/day was possible. the av erage nitrogen and phosphorus removal efficiency being more than 80 and 95% , respectively.