Simultaneous nitrogen and phosphor removal in an aerobic submerged membrane bioreactor

Simultaneous nitrification and denitrification (SND) effect and phosph or removal were investigated in a one-staged aerobic submerged membrane bioreact or on pilot-scale with mixed liquor suspended solids (MLSS) 19—20 g/L. The effe cts of DO concentration, sludge floc size distribution on SND were studied. Test results suggested that SND was successfully performed in the membrane bioreact or(MBR) and about 70% total nitrogen removal efficiency was achieved when DO con centration was set to 0.2—0.3 mg/L. The main mechanisms governing SND were the suitable sludge floc size and the low DO concentration which was caused by low o xygen transfer rate with such a high MLSS concentration in the MBR. In the meant ime, phosphor removal was also studied with polymer ferric sulfate (PFS) additio n and 14 mg/L dosage of PFS was proper for the MBR to remove phosphor. PFS addit ion also benefited the MBR operation owing to its reduction of extracellular pol ymer substances (EPS) of mixed liquor.