Abstract
Since 1973, septage (septic tank waste) have been treated by the aerobic digestion process at Waste Treatment Center in Takarazuka city. BOD, SS and other polutants in septage were easily removed, however, COD and N Components were not reduced satisfactorily. It was observed that effluent T-N was reduced remarkably when the volume of return sludge was increased. Flash-mixer, flocculater and sedimentation Unit were constructed to remove COD components after the aerobic digestion tank in June 1979, and whole plant were operated from August 1979 to July 1980. This paper reports the efficiency of T-N and COD removal under the aerobic digestion process followed by coagulation step in the septage treament plant. The results of the operation are:
1. Under BOD sludge load of 0.07kg-BOD/kg-SS⋅day, BOD removal and nitrification efficiency were not less than 98% and 95% respectively.
2. When the temperature in the aerobic tank was over 25°C, T-N removal in excess of 85% was achieved.
3. COD, BOD and PO43- in final effluent were less than 60mg/l, lOmg/l and 6mg/l respectively without dilution.
