| Sewage sludge thermal hydrolysis experiments with 2 450MHz microwave energy were carried out under 80～170℃ with 1～30min. Max. microwave output power was 1kW. Volatile suspended solid (VSS) dissolving ratio, COD dissolving ratio, liquor COD and TOC, sludge particle size distribution, micro-structure, and elements(C, H and N) hydrolysis were measured. Also, sludge dewaterability improvement was inspected. Results show that microwave heating leads fast sludge hydrolysis reaction. Temperature was the controlling process factor. Under 150℃ and 170℃ with 5min, 15.8% and 29.4% VSS dissolved respectively. While, with 10min 19.07% and 25.75% COD moved to liquor. Release of organic materials increased liquid sludge COD and TOC concentration. Under 170℃ with 10min, COD and TOC concentration were 9 860.0 mg/L and 2 949.70 mg/L respectively. More than 5 to 10min, VSS and COD dissolving trend turned slow down. SEM test showed cell disruption of hydrolyzed sludge. N could dissolve more easily than C and H. 67% N hydrolysiszed under 170℃ with 5min. Bacterial cell disruption and organic solid hydrolysis improved sludge dewaterability. Sludge cake moisture content decreased from 82% to 73.1% and 65.5% under 150℃,170℃ with 10min microwave hydrolysis. Accordingly, sludge amount reduction ratios were 33.9% and 51.7% respectively. |
