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 degrees 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 degrees C. Low temperature (60 degrees 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 degrees C, respectively. Significant positive relationships observed between pretreatment temperature/duration and sludge properties. Energy and economic assessment displayed anaerobic digestion of 80 degrees C pretreated sludge is more economically feasible. Thus, low-thermal pretreatment technology could be useful for improvement of methane yield in anaerobic digestion.