Simultaneous Enhancement of Volatile Fatty Acids Production and Dewaterability of Waste-Activated Sludge Using Calcined Alkaline Residue

This study reported a novel and resource-economical strategy for enhancing volatile fatty acids (VFAs) production and sludge dewaterability from sludge anaerobic digestion via codigesting with calcined alkaline residue (CAR) generated from ammonia-soda process. Batch tests were performed with CAR calcined at various temperatures from 400 degrees C to 1,000 degrees C. Results showed that maximum VFAs production of 2,038 mg/L was achieved at 800 degrees C (CAR800), which was similar to 3.4 times higher than the control test. Moreover, sludge dewaterability by adding CAR800 was comparatively close to the control test, indicating that CAR treatment was effective in improving dewaterability of digested sludge. Mechanism investigation revealed that CAR played a buffering role in maintaining the alkaline pH, which likely inhibited methanogenesis activity. It was also found that more readily bioavailable soluble organics were released by adding CAR800 in comparison with control. Microbial community analysis indicated that microbial hydrolysis and acidification were remarkably improved in the presence of CAR800.