Effects of microwave, H2O2, S2O82-, MD/H2O2 and MD/S2O82- pre-treatments on biochemical methane production potential of the sewage sludges

The considerable increase in the sewage sludge production in wastewater treatment plants becomes a serious problem for a modern society. The treatment of excess sewage sludge is a significant issue. Many different methods and pre-treatment techniques can be applied for the stabilization of the sludge and enhancement of energy production from the sludge. This study investigated the effects of sludge pre-treatments (microwave (MW), H2O2, S2O82-, MW/H2O2 and MW/S2O82-) and also the presence of antibiotics on anaerobic stabilization and biochemical methane production potential of sewage sludges. The pre-treatments applied to sludge samples prior to anaerobic digestion speeded up the hydrolysis step and improved the biodegradability of the organics by increasing their solubility. Application of MW, H2O2 and combined MW/H2O2 (1 g H2O2/g TS (total solids)) pre-treatments increased the methane yields by 65.5%, 20% and 40%, providing 626 mL CH4/g VS, 453 mL CH4/g VS and 529 mL CH4/g VS methane yields, respectively. However, persulfate pre-treatment (1 g S2O82-/g TS) decreased the biogas production and eliminated the methane production due to inhibiting effect of the S2O82- dose on the survival of the methanogenic bacteria. The presence of antibiotics (1 mg CIP/g TS) in sewage sludge samples decreased methane yields in the anaerobic digestion process. The methane yield, obtained in antibiotic contaminated sludge containing reactor, decreased 22% to 275 mL CH4/g VS, while uncontaminated sludge containing control reactor had a methane yield of 352 mL CH4/g VS. The presence of antibiotic in sewage sludge did not show negative effect on the sludge stabilization.