Mesophilic anaerobic digestibility of pre-trated sludges

Anaerobic digestion has an important role in sludge management as stabilization method. Disintegration methods have taken important role before stabilization to disrupt the sludge flocs and microbial cell walls and improve the stabilization quality. So, these methods improve sludge biodegradability in terms of more biogas production and sludge minimization.In this thesis, among the pretreatment methods microwave pre-treatment, alkaline pre-treatment and the combination of these methods were investigated with experimental studies to see the effectiveness of biodegradation and biogas production on anaerobic digestion. Sludge sample was taken from the return line of secondary sedimentation tank of the municipal wastewater treatment plant in Izmir.At the beginning of the studies, disintegration applications have taken part for deciding the most appropriate method. According to the results, application of microwave pre-treatment improved anaerobic digestion performance as more stabilization and biogas production.At the continuation of the experiments, lab-scale anaerobic reactors were used. Reactors were operated as batch and semi batch system under mesophilic conditions for thirty days. Results showed that volatile solids reductions and biogas productions were higher for the digesters fed with disintegrated sludge than non-disintegrated digesters. All applied method showed a positive effect on anaerobic sludge biodegradability. When comparing the applied methods in terms of sludge digestion performance, batch reactor that include 75 percent microwave pretreated sludge gave higher volatile solids reductions and higher biogas in comparison with 50 percent microwave feeded reactor. But, anaerobic semi-continuous reactors were operated with the 75 percent feeding ratio gave the best results with respect to methane production and volatile solids reduction. 50 percent microwave feeded batch reactor gave lower efficiencies then the other two reactors in terms of methane production. At the same time, disintegration processes did not affect sludge dewatering properties positively.