Effects of microwave irradiation at various temperatures onbiosludge disintegration

The waste biological sludge disintegration by using microwave irradiationwas investigated at a ramping rate of 2°C/min and 5 min holding time atvarious target temperatures. Significant disintegration of biosludge wasobserved and the highest disintegration degree was determined about82% at the temperature of 110°C. Increase of target temperature elevatedthe energy needs to 98, 123 and 148 kWh/kg TS at the temperatures of75°C, 90°C and 110°C, respectively. The gradual increase of sugar andprotein in the sludge slurry with increasing temperatures indicates suc-cessful degradation. The microwave pretreatment increased the specificsurface area of the sludge by particle size reduction. The specific surfacearea of raw sludge was 70 m2/kg and rose to approximately 253.7 m2/kg at110°C with an increment ratio of 260%. Although a significant NH4–Nrelease was not observed, PO4–P concentrations increased from 11.0 mg/Lto 16.3, 20.7 and 29.2 mg/L at the temperatures of 75°C, 90°C, 110°C,respectively. While the specific filter resistance of waste biological sludgewas about 1.0 × 1013, increasing the microwave target temperature, theability of dewatering decreased and the highest SFR value of 5.1 × 1014was observed at the temperature of 110°C.