An Activated Sludge Process without Excess Sludge Production Applying Thermophilic Aerobic Sludge Digestion.

A novel wastewater treatment process with thermophilic aerobic sludge digestor (TAD) was developed to reduce excess sludge generated from an activated sludge (AS) process. The TAD was operated at 65°C with hydraulic retention time 1day. The SS solubilization and VM removal in the TAD were 35% and 20%, respectively. A 40l-scale conventional AS and new processes with appropriate volume of the TAD were operated under BOD-SS loading of 0.3kg·kg-1·d-1 and MLSS of 2,000mg·l-1 using artificial wastewater over 100d. As a result, the amount of excess sludge was 4.9gSS·d-1 in the conventional AS process. On the other hand, excess sludge in the new process was reduced to nearly zero when 16.2gSS·d-1 was recirculated to the TAD. Effluent BOD was the same level in the both processes, however, effluent S-TOC was 25% higher in the new process than that of the conventional AS process. Furthermore, similar results were obtained from a treatment test with a petrochemical wastewater. The calculated operating cost of the new process was about one third or one half compared to dewatering and landfill processes.