Temperature Effects on Aerobic Digestion Kinetics

The effects of temperature upon the kinetics of waste activated sludge aerobic digestion in batch reactors were studied. Reactors were maintained at temperatures of 5°C, 10°C, 20°C, 30°C, 35°C, and 45°C—1°C, and the changes in suspended solids concentration, oxygen uptake rate, pH, specific resistance and floc particle size of the mixed liquor, as well as pH, BOD, and TOC of the supernatant, with digestion time, were measured. The specific decay rate was not affected in an Arrhenius fashion above 20°C, and the greatest solids reduction occurred in the 20°C reactor over a 15-day digestion period. A significant portion of the suspended solids destroyed at 45°C are solubilized but the soluble organics are not metabolized, therefore, the true stabilization at 45°C is somewhat less than the apparent stabilization calculated from suspended solids reduction. There appears to be no practical advantage to aerobic digestion temperatures in excess of 20°C.