Abstract

The properties of sewage sludge-derived biochar (BC) pyrolyzed at 300–900 °C were characterized, and which exhibited the basic properties of coagulant. When 1 g BC500 was added to 100 mL waste-activated sludge (WAS), the maximum mean settlement rate reached 8.20 mL min−1 within 10 min, and the volume of the settlement with settling time decreased to 13 mL. The capillary suction time of BC500 (12 s) was superior to those of municipal solid waste incineration (MSWI) fly ash (13.40 s), coal fly ash (14.20 s), and activated carbon (12.20 s). In addition, added BC may reduce the moisture content of sludge cake, especially for BC500. It can be that soluble cations and organic functional groups neutralize the negative charge of WAS which is helpful to shorten settling time. Meanwhile, the pore structure is beneficial for reducing moisture content of sludge cake. As results shown, BC was feasible to improve sewage sludge dewatering used as a coagulant.

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