Investigating ozonation and lime coagulation effects on urban wastewater treatment sludge enhancement

Treatment and disposal of surplus sludge is a problem in wastewater treatment plants worldwide in terms of economic, environmental, social, and legal factors. To reduce the excessive costs of investment and management of the wastewater treatment plant, it is necessary to reduce the amount of sludge produced in wastewater treatment plants to the greatest possible extent. Also, the turbidity of the supernatant that remains after the process needs to be reduced to a possible extent so it can be reused for irrigation and recreational use. To achieve this aim, sludge thickening and dewatering methods are used. Since the modified sludge is easily condensed and dehydrated, sludge preparation operations are important in sewage treatment plants. In this study, the effects of ozone and lime on the quality improvement of the excess sludge in the Shiraz sewage treatment plant were investigated. In this regard, the use of lime as a coagulant and the injection of ozone as an oxidizer into excess sludge was studied separately and in combination. A glass cube with a size of ۳ liters was used as a pilot model, and the parameters SS, TSS of sludge, and supernatant’s turbidity were measured. First, pH and dosage for ozone and lime were optimized as variable parameters. According to the achieved optimum parameters, the sludge sedimentation improved by ۳۴.۳%, and the total suspended solids Increased by ۲۲.۷% by using ozone injection. sludge sedimentation improved by ۲۹.۳%, and the total suspended solids increased by ۳۱.۵% by adding lime under the optimum parameters amount. In the next step, the results of using lime and ozone combined were analyzed. The best results were obtained when lime adding was done after ozonation. In this case, the volume of sludge was reduced by ۴۱.۶%.

کلیدواژه ها:

Ozonation ، coagulation ، lime ، Sludge improvement ، wastewater