Abstract
Abstract
Microwave (MW) pretreatment is a recent method used for anaerobic sludge stabilization. Most of the studies focus on MW pretreatment at temperatures lower than boiling point of sludge and limited information on high temperature MW irradiation as pretreatment method is known. This work focused on the effect on high temperature (110–175°C) MW irradiation on biodegradation pathway of soluble organics. Microwave pretreatment at different operating conditions was applied to municipal waste-activated sludge. Ultrafiltration was used to determine the molecular weight (Mw) distribution of soluble organics. Effects of MW pretreatment temperature (110 and 175°C) and MW intensity (1.25 and 3.75°C/min) on biodegradability and rate of degradation were compared to an untreated sample. It was observed that solubilization increased as MW temperature increased. Although lowering MW intensity did not show significant improvement in overall solubility, Mw distribution profiles were found to be very different, confirming that MW intensity has an impact on thickened waste activated sludge solubilization at the molecular level. The overall (Mw < 5 μm) biodegradable chemical oxygen demand (COD)/refractory COD ratio increased with the combination of athermal effect of low MW intensity combined with the thermal effect of high pretreatment temperature.
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