Bench-Scale Ozonation of Waste Activated Sludge

This project involved the design, operation, and testing of a 10-liter clear PVC, semi-batch, bubble column reactor used for treating waste activated sludge (WAS) with ozone. Two separate runs were performed on a 5-L sample of WAS acquired from the Rocky Creek Wastewater Treatment Plant (WWTP) in Macon, Georgia. The Rocky Creek WWTP treats municipal wastewater in an extended aeration activated sludge process. Ozone was sparged through a porous diffuser at an application rate of 0.053 mg O₃/min during both runs. Ozone contact times of 9 and 12 days were used during Runs #1 and Run #2, respectively. The following parameters were measured frequently during the bench-scale study: pH, total and soluble chemical oxygen demand (COD), total and volatile solids, and total suspended and volatile suspended solids. The kinetics of total volatile solids (TVS) reduction and volatile suspended solids (VSS) reduction were determined to follow first order degradation rates. Degradation rate coefficients (K_D) based on TVS and VSS were 0.13 days^–1 and 0.17 days^–1 respectively, in Run #1 and 0.40 days^–1 and 0.54 days^–1 respectively, in Run #2. Total chemical oxygen demand (TCOD) removal was 43.4 and 91.1% respectively, for Run #1 and #2. The unstirred sludge volume index (SVI_u) decreased as ozonation contact time increased. Average ozone dosages observed in this study were 0.0037 and 0.0084 mg of O₃ per mg of total solids (TS) destroyed during runs #1 and #2, respectively.