Effect of intermittent aeration on the decrease of biological sludge amount

As a biochemical approach to decrease the amount of biological sludge, the sludge solubilization by repeatedly changing the microbial environments from aerobic to anaerobic was studied. The sludge reduction amount in batch operation was related to the degradation of intracellular materials released through sludge solubilization. The shorter the operation cycle time was, the more effective the sludge amount reduction was. On the other hand, under the cycle time of 3–24 h, longer anaerobic period compared to aerobic period was effective in removing nitrogenous compounds. This was partly ascribed to the excretion of enzyme such as protease and lipase.