ACTIVATED SLUDGE METHOD FOR DENITRIFICATION AND DEPHOSPHORIZATION

摘要

PURPOSE:To remove simultaneously nitrogen and phosphorus at a high removal rate by performing an activated sludge treatment for denitrification and dephosphorization in the 1st solid-liquid separating stage, nitrifying stage, the 2nd solid-liquid separating stage, sludge thickening stage and concn. sludge returning stage. CONSTITUTION:Gas contg. no gaseous oxygen generated from sludge in a space S is supplied through a circulating path 8 to a nozzle 7. The supplied gas flows through the nozzle 7 into a thickening tank 5 where the gas agitates slowly the sludge to improve the thickening treatment in an anaerobic state. The desorbed liquid from the tank 5 is extremely clean. The reason lies in that fine sludge flock particles are captured by the sludge bridges formed at around the skirt of a cover member 6. The desorbed liquid contains a phosphoric acid in a high concn. The thickened sludge drawn from the tank 5 is further treated with a thickener to decrease additionally the moisture content therein and thereafter the thickened sludge is returned to an aerobic tank 2.