Enhancement on biodegradation and anaerobic digestion efficiency of activated sludge using a dual irradiation process

► A dual irradiation process was proposed. ► The dual irradiation process improved waste-activated sludge digestion performance. ► The aerobic thermophilic irradiation pretreatment (ATIP) improved CH4 yield, VS and DOC removal. ► Carbon felt as an excellent bed material immobilized more microbes to improve the digestion effect. ► Intermittent irradiation increased the efficiency of anaerobic digestion over the dark condition.