Kinetic analysis of disruption of excess activated sludge by Dyno Mill and characteristics of protein release for recovery of useful materials

Solubilization of excess sludge (ES) cultivated in a laboratory and that obtained from real wastewater treatment plants by continuous Dyno Mill disruption were studied for the purpose of effective reuse of ES. The total soluble protein concentration released during the ES disruption was found to be closely dependent upon the released protease activity, which suggests the possibility of the enzyme recovery as one of the ES reuse methods. The operating parameters of Dyno Mill significantly affected the ES solubilization. A high ES solubilization ratio of about 53%, defined by soluble TOC per total carbon contained in the laboratory-cultivated ES, was achieved by using glass beads of 0.5 mm in diameter with the 60% (v/v) bead loading at the disc agitating speed of 3200 rpm. The ES solubilization by the continuous mill disruption was successfully analyzed by a kinetic model consisting of first-order disruption kinetics. The collision frequency between the moving beads correlated well with the ES solubilization rate constant under all the operating conditions. This study proposes the applicability of mill disruption to the ES solubilization and to its reuse process. (C) 2001 Elsevier Science B.V. All rights reserved.