Abstract
This study examined the effects of microwave treatment on the physicochemical characteristics of faecal sludge (FS). FS from Ventilated Improved Pit (VIP) latrines were treated in a microwave oven at varying microwave power levels and treatment times. Changes in total solids (TS), volatile solids (VS), total chemical oxygen demand (TCOD), and soluble chemical oxygen demand (sCOD) were measured. A response surface methodology (RSM) was used to optimize organic matter solubilization during microwave treatment. A central composite design was employed, and the observed responses were used to fit a second-order response surface model. Microwave treatment at 14,000kJ/kg.TS reduced FS volume by 58%. The VS/TS ratios remained similar before and after microwave treatment. The solubilization of organic matter (measured by sCOD/TCOD ratio) increased after microwave treatment, showing an initial linear increase with specific energy, followed by a decrease. The highest solubilization was 38%, achieved at microwave power level of 630W for 3 minutes. It was observed that organic matter solubilization was more sensitive to contact time than microwave power. The optimized conditions were determined by RSM to be 617.7W and 2.4 minutes, which were within the experimental design boundaries. These findings align with similar observations from other studies using wastewater sludge. The results suggest that microwave treatment can achieve multiple FS treatment objectives. Optimal operating conditions should be identified if the aim is to solubilize organic matter in FS.