Impact of low-thermal pretreatment on physicochemical properties of saline waste activated sludge, hydrolysis of organics and methane yield in anaerobic digestion.

This work studied the influence of low-thermal pretreatment (60-120 °C) on anaerobic digestion of saline waste activated sludge. The findings showed higher temperature and longer pretreatment time considerably improve organics hydrolysis (soluble chemical oxygen demand increased by 4.2-11.9 times) and volatile solid reduction (maximum 24.6%). Carbohydrate and proteins solubilization accelerated by 5.6-43.8 times and 8.9-35.9 times, respectively by temperature rose from 60 to 120 °C. Low temperature (60 °C) promotes faster release of ammonia and phosphate. Thermal treatment had positive effect on biogas production because methane yield was enhanced by 13.7, 27.0, 29.0 and 29.6% when pretreated at 60, 80, 100 and 120 °C, respectively. Significant positive relationships observed between pretreatment temperature/duration and sludge properties. Energy and economic assessment displayed anaerobic digestion of 80 °C pretreated sludge is more economically feasible. Thus, low-thermal pretreatment technology could be useful for improvement of methane yield in anaerobic digestion.