Thermal hydrolysis assists calcium hypochlorite pretreatment to enhance anaerobic digestion performance of waste activated sludge

This study proposed a novel pretreatment technology by combining thermal hydrolysis (TH) with calcium hypochlorite (CH) to promote sludge anaerobic digestion (AD) performance. Experimental results indicated that the optimum pretreatment condition was TH at 70 °C combined with 0.08 g/g volatile suspended solids (VSS) of CH, by which the methane production of 260.1 mL/g VSS was achieved, 59.1 % higher than control group. Kinetic analysis revealed that methane production potential enhanced from 158.9 to 257.0 mL/g VSS after TH + CH pretreatment, and methane production rate accordingly increased from 13.10 to 27.97 mL/g VSS/d. Mechanism analysis illustrated that both extracellular polymeric substances and microbial cells were damaged by TH + CH method, resulting in substantial increase of hydrolysis efficiency. Microbial analysis revealed that the abundances of hydrolytic, acidogenic and methanogenic microbes were all enhanced under co-treatment condition, with the total abundances calculated to be 12.33 % and 22.68 % in control and TH + CH pretreated reactors, respectively.