High frequency ultrasound pretreatment for sludge anaerobic digestion: Effect on floc structure and microbial population

► Innovative approach proposing 200 kHz ultrasound irradiation as sludge pretreatment. ► 200 kHz sludge treatment lead to floc disintegration and digestion improvement. ► Gain in VS degradation and biogas production dependent on the F/I ratio. ► Key-role of Methanosarcina in the main reactions involved in biogas production.