State of the art of thermal sludge pretreatment and its enhancement for anaerobic sludge digestion

The treatment and disposal of excess sludge is becoming a rising challenge for municipal wastewater treatment plants due to huge amounts of sludge production resulted from wide application of biological wastewater treatment.As a traditional process used for excess treatment sludge,there are some disadvantages of the anaerobic digestion,such as low efficiency and long sludge retention time.However,recent researches clearly showed that thermal sludge pretreatment can enhance anaerobic digestion of excess sludge.In this study,the state of art of thermal sludge pretreatment was thoroughly reviewed,including thermal pretreatment processes of sludge,factors of thermal sludge pretreatment,impacts of sludge thermal pretreatment on sludge anaerobic digestion and its factors.Meanwhile,the prospects and shortages of thermal sludge pretreatment and its enhancement on anaerobic sludge digestion were also discussed.