Investigation of pre-treatments improving low-temperature anaerobic digestion of waste activated sludge

tThis work analyzed the feasibility of pre-treatments to improve the anaerobic digestion (AD) of wasteactivated sludge (WAS) at 20◦C. We investigated different physicochemical pre-treatments (thermal at115◦C, thermo-alkaline at pH 10 and 70◦C and ozonation at 190 mg-O3L−1) by comparing their perfor-mances about COD solubilization and sludge disintegration rate. Best performances were obtained bythermo-alkaline pre-treatment, followed by thermal and ozonation; results were consistent with litera-ture. Pre-treated WAS was fed to 12 1-L anaerobic digesters operated in semi-continuous mode. Thermaland thermo-alkaline reactors produced biogas yields (0.30–0.36 m3kg−1VS in standard conditions, 65–70% methane) analogous to mesophilic conditions. The economic assessment of the scale-up of the wholeprocess demonstrated that thermo-alkaline pre-treatment made AD at 20◦C economically profitable forWAS generated by a 20,000 PE WWTP.