SEWAGE DISPOSAL DEVICE

PROBLEM TO BE SOLVED: To prevent a deterioration of a treating capacity and to enable a continuation of treatment immediately after back washing by forming an aerobic biological membrane zone being a floatable filter material layer, an air diffuser and an anaerobic biological membrane zone being a precipitable filter material layer from the top in a tank, making a raw water to flow in from under the anaerobic biological membrane zone and making a treated water to flow out from above the aerobic biological membrane zone. SOLUTION: The aerobic biological membrane zone 12 is formed with the floatable filter material layer consisting of a filter material whose specific gravity is less than 1 at an upper part in a treating tank 11 of a sewage treating device 1. A diffusing pipe 13 is arranged thereunder and connected to a blower 13B for treating. The anaerobic biological membrane zone 14 is formed with the precipitable filter material layer consisting of the filter material whose specific gravity is more than 1 under the diffusing pipe 13. A raw water inflow part 16 is provided at the lowermost part of the tank 11, and a raw water supply pipe for treating 22 and a raw water supply pipe for back washing 24 are arranged while joining at an outside of the tank 11. A treated water outflow part 15 is provided at the uppermost part of the tank 11 and a discharge pipe 30 is disposed. The diffusing pipe 18 is provided under the diffusing pipe 13 and the diffusing pipe 20 is provided under a precipitable filter material layer supporting plate 14P for the back washing.