Microwave-assisted chemical oxidation of biological waste sludge: Simultaneous micropollutant degradation and sludge solubilization

Microwave-assisted hydrogen peroxide (MW/H2O2) treatment and microwave-assisted persulfate ( MW / S 2 O 8 2 - ) treatment of biological waste sludge were compared in terms of simultaneous antibiotic degradation and sludge solubilization. A 23 full factorial design was utilized to evaluate the influences of temperature, oxidant dose, and holding time on the efficiency of these processes. Although both MW/H2O2 and MW / S 2 O 8 2 - yielded ⩾97% antibiotic degradation with 1.2 g H2O2 and 0.87 g S 2 O 8 2 - per gram total solids, respectively, at 160 °C in 15 min, MW / S 2 O 8 2 - was found to be more promising for efficient sludge treatment at a lower temperature and a lower oxidant dosage, as it allows more effective activation of persulfate to produce the SO 4 - radical. Relative to MW/H2O2, MW / S 2 O 8 2 - gives 48% more overall metal solubilization, twofold higher improvement in dewaterability, and the oxidation of solubilized ammonia to nitrate in a shorter treatment period.