The investigation of sludge disintegration using oxidation processes

In this thesis, the feasibility of oxidation techniques as biological sludge disintegration purpose was investigated to improve anaerobic digestion performance, to increase stabilization degree and to increase biogas production with experimental studies. Fenton process, ozone oxidation and ultrasonic treatment as advanced oxidation processes were applied to biological sludge samples preceding anaerobic sludge digestion. Biological sludge was sampled from the municipal wastewater treatment plant in Izmir, Turkey, which has extended aeration activated sludge plant with nutrient removal facilities.In the first stage of the study, experiments were carried out to optimize the process conditions for floc disintegration. All applied methods allowed to destruction of microbial sludge cells resulting in an increased biodegradability. Among the methods, ultrasonic treatment gave the maximum disintegration degree.In the second stage of the study, sludge digestion studies were carried out using lab-scale anaerobic reactors. Reactors were operated both as batch and as semi batch system. The reactors were operated in mesophilic conditions for thirty days. Experimental results showed higher volatile solids reductions and higher biogas productions for the digesters fed with disintegrated sludge. All applied method showed a positive effect on anaerobic sludge biodegradability. When comparing the applied methods in terms of sludge digestion performance, ozone oxidation and ultrasonic treatment gave much closed results and ultrasonic treatment gave the best results in terms of methane production. Fenton process had lower efficiencies then the other two methods in terms of methane production. When comparing the operation types in terms of sludge digestion performance, semi batch systems had better digestion performance than batch system. On the other hand, disintegration processes had no positive effect of sludge dewatering properties.