This study investigated the electrochemical oxidation of stabilized leachate from Pulau Burung semi-aerobic sanitary landfill by conducting laboratory experiments with sodium sulfate Na(2)SO(4) (as electrolyte) and graphite carbon electrodes. The control parameters were influent COD, current density and reaction time, while the responses were BOD removal, COD removal, BOD:COD ratio, color and pH. Na(2)SO(4) concentration was 1 g/L. Experiments were conducted based on a three-level factorial design and response surface methodology (RSM) was used to analyze the results. The optimum conditions were obtained as 1414 mg/L influent COD concentration, 79.9 mA/cm(2) current density and 4 h reaction time. This resulted in 70% BOD removal, 68% COD removal, 84% color removal, 0.04 BOD/COD ratio and 9.1 pH. Electrochemical treatment using graphite carbon electrode was found to be effective in BOD, COD and color removal but was not effective in increasing the BOD/COD ratio or enhancing biodegradability of the leachate. The color intensity of the treated samples increased at low influent COD and high current density due to corrosion of electrode material.
Palm oil mill effluent (POME) is a highly polluted wastewater that consists of a high organic content of 4-5% total solids; a potential renewable energy source. A waste to energy study was conducted to improve biogas production using POME as substrate by ultrasonication pretreatment at mesophilic temperatures. The effect of temperature on the specific growth rate of anaerobes and methanogenic activity was investigated. Five sets of assays were carried out at operating temperatures between 25 °C and 45 °C. Each set consisted of two experiments using identical anaerobic sequencing batch reactors (AnSBR); fed with raw POME (control) and sonicated POME, respectively. The ultrasonication was set at 16.2 min ultrasonication time and 0.88 W mL-1 ultrasonication density with substrate total solids concentration of 6% (w/v). At 25 °C, biogas production rate and organic matter removal exhibited lowest values for both reactors. The maximum organic degradation was 96% from AnSBR operated at 30 °C fed with sonicated POME and 91% from AnSBR operated at 35 °C fed with unsonicated POME. In addition, the methane yield from AnSBR operated at 30 °C was enhanced by 21.5% after ultrasonication pretreatment. A few normality tests and a t-test were carried out. Both tests indicated that the residuals of the experimental data were normality distributed with mean equals to zero. The results demonstrated that ultrasonication treatment was a promising pretreatment to positively affect the organic degradation and biogas production rates at 30-35 °C.