Abstract:
The effects of sonication, potassium ferrate (K2FeO4) oxidation and their simultaneous
combination (called “sono-oxidative pre-treatment”) on chemical properties and anaerobic digestion of waste
activated sludge (WAS) were investigated and compared comprehensively. Based on chemical parameters, the
optimum operating conditions were found to be 0.3 g K2FeO4/g total solids (TS) dosage for 2-h individual
K2FeO4 oxidation, 0.50 W/mL ultrasonic power density for 10-min individual sonication and, lastly, the
combination of 2.5-min sonication at 0.75 W/mL ultrasonic power density with 2-h chemical oxidation at 0.3
g K2FeO4/g TS dosage for sono-oxidative pre-treatment. The disintegration efficiencies of these methods
under the optimized conditions were in the following descending order: 37.8% for sono-oxidative pretreatment
> 26.3% for sonication > 13.1% for K2FeO4 oxidation. The influences of these methods on
anaerobic biodegradability were tested with the biochemical methane potential assay. It was seen that the
cumulative methane production increased by 9.2% in the K2FeO4 oxidation reactor, 15.8% in the sonicated