Article ID Journal Published Year Pages File Type
5740245 International Biodeterioration & Biodegradation 2017 9 Pages PDF
Abstract

•Ultrasonic pretreatment to improve anaerobic digestion of waste activated sludge.•Linear increase of the solubilization degree was observed with the specific energy.•The maximum solubilization degree of soluble chemical oxygen demand was 26%.•A biogas overproduction of 31.43% (219.5 mL/g VS) was achieved at 35000 kJ/kg TS.•Pathogen inactivation is most effective at lower TS (2%) and continuous stirring.

Waste activated sludge (WAS) is a polluting waste with severe management problems that must be treated to prevent pollution and human health risks. Anaerobic digestion (AD) is the most used process to stabilize sludge; however, it must be improved because the biomethanation of sludge entails low biodegradability, pathogen inactivation, and biogas production. This study investigated the effects of ultrasonic pretreatment (USp) of WAS as a strategy to improve AD. Macromolecule solubilization, heavy metal behavior, pathogen inactivation and biogas production were evaluated. USp was applied at a range of 5000-35000 kJ/kg TS (total solids). The maximum solubilization degree of soluble chemical oxygen demand was 26%, and 22.9% of proteins at 35000 kJ/kg TS. The highest USp reduced only 2 log units of pathogens; nevertheless, a high inactivation was obtained when TS were reduced to 2% and continuous stirring was applied. AD of raw and sonicated WAS were compared with biochemical methane potential tests, and a biogas overproduction of 31.43% (219.5 mL/g VS) was achieved at highest USp. A modified Gompertz model was used for kinetic study of biogas production. The kinetic parameters at highest energy were: biogas production potential, G0 = 634.2 mL; maximum biogas production rate, Rmax = 57.23 mL/day.

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