Sewage treatment system by oxidation ditch method

摘要

PPROBLEM TO BE SOLVED: To provide a sewage treatment system capable of treating sewage efficiently and effectively by an oxidation ditch method. PSOLUTION: Aerobic operation wherein the circulating flow and aeration stirring of a mixed liquid 6A by an aeration stirrer 2 and oxygen-free operation wherein only the circulating flow of the mixed liquid 6A by a propeller 30 immersed in the mixed liquid 6A are alternately performed to alternately hold the whole region of an endless circulating water channel 11 to an aerobic state and an oxygen-free state. The excess sludge 61 in the endless circulating water channel 11 is directly drawn out from the water channel 11 by an excess sludge draw-out pump 42. The aeration stirrer 2, the propeller 30 and the excess sludge draw-out pump 42 are controlled by a controller 50 to be started and stopped so as to keep the stagnation time of sludge in an aerobic state set on the basis of the lowest temperature of inflow sewage 6. PCOPYRIGHT: (C)2004,JPO