In tannery wastewater treatment plants, sludge comprising of primary and secondary sludge isrngenerated. If the concentration of Cr (III) exceeds 5000 mg/kg, then it is considered asrnhazardous wastes and this sludge has to be disposed in hazardous waste landfill site as perrnexisting statutory requirements in India. Further, for disposal of wastes into hazardous landfill,rnthe amount of organics concentration in the sludge shall not exceed 20% and if so, then thesernwastes are not permitted to be disposed in hazardous wastes landfill. Currently, lime and fly ashrnare added to the wastes to reduce the concentration of organics. Hence, there is urgent need forrntreatment methods to reduce of organic content in sludge before disposal into hazardous landfill.rnIn this study, attempt was made to reduce the volatile solids generated from secondary biologicalrnsludge using advanced oxidation process (AOP) i.e., ozonation. Lab scale aerobic process usingrnsequential batch reactor (SBR) for treatment of tannery wastewater and ozonation of excessrnsludge generated from SBR were carried out with 24 hrs cycling time. SBR was operated withrnprimary treated tannery wastewater and excess sludge generated was ozonated and returned backrnto SBR reactor. The performance of sequential batch reactor (SBR) operated with tanneryrnwastewater alone as control and another SBR operated with tannery effluent along withrnozonated excess bio-sludge were studied and compared. It was observed that 15 minutes is thernoptimum ozonation time for oxidation of excess sludge from SBR treating primary treatedrntannery waste water as influent and the optimum ozone dose respective to optimum ozonationrntime is found to be 0.168g-O3/g-MLSS.rnIt was observed that COD in the final effluent was reduced to total and soluble CODrnconcentrations in the range of 548.2mg/l and 379.2mg/l for control SBR and 537.581mg/l andrn376.049 mg/l for SBR with ozonated sludge respectively at total cycling time of 24 h. In termsrnof overall sludge reduction, 35.1% reduction of the excess sludge could be achieved by ozonerntreatment at 0.168 g-O3/g-MLSS.