A MODEL FOR EVALUATION OF ACTIVATED-SLUDGE PROCESS PERFORMANCE

The advantages of a multistage tower activated sludge process which were visualized experimentally could be shown quantitatively by use of the axial dispersion model in conjunction with the kinetics which involved the biosorption and subsequent oxidative biodegradation process of organic substances. The theoretical analysis indicated that partial fluid mixing closer to the plug flow possessed higher treatment ability. Also, the influence caused by the difference in Peclet number grew as the organic loading rate increased. A calculation showed that the upper limit of the volumetric loading rate to maintain good sludge settleability below an SVI of 100 was 2.3 kg COD(Cr)/m3.d for the complete mixing aeration tank. However, when an aeration tank with a Peclet number over 4 is used, the allowable volumetric loading rate can be increased to 4.0 kg COD(Cr)/m3.d.