Anaerobic digestion of biosolids at elevated thermophilic temperatures: Inactivation of pathogens for Class A biosolids designation.
The objective of this study was to evaluate the effects of two different thermophilic operating temperatures on single-stage thermophilic anaerobic digestion of biosolids. Past studies on thermophilic anaerobic digestion have rarely utilized operating temperatures above the standard 55 degreesC, nor have there been any studies to determine the optimum temperature for a single-stage thermophilic anaerobic digester. In order to study the effects of operation at 63 degreesC and 55 degreesC, two laboratory-scale, completely-mixed, fed-batch anaerobic digesters were operated with a once-aday feeding of 1:1 mix of primary and secondary clarifier biosolids. Both of the bench-scale digesters had an effective volume of 3 liters and were operated initially at a 15 day hydraulic and solids retention time (HRT/SRT). Approximately 2-log removals of Escherichia coli and fecal coliform were observed at both temperatures while the reactor operating at 63 degreesC achieved slightly higher levels of pathogenic inactivation. A similar trend was observed in Salmonella inactivation. Statistically significant improvements were observed at 63oC operating temperature in comparison to 55 degreesC in terms of CH4 production (11% higher), volatile solids destruction (4.9% higher), and dewaterability of the digested biosolids (10% higher).
|Main Author:||Do, J.|
|Other Authors:||Daileader, K., Duran, M.|