Pilot-scale study of sludge pretreatment by microwave and sludge reduction based on lysis–cryptic growth

•Studied microwave (MW) pretreatment in a large pilot-scale sludge reduction system.•The sludge quantity to be finally disposed off was reduced by 38.60% on average.•Achieved 13.64% cost savings compared to operation without MW pretreatment.

To evaluate the performance of microwave (MW)-chemical hybrid sludge treatment system, a pilot scale MW disintegration unit (treatment capacity of 500 L/d) was constructed. The results showed that organic matter, nitrogen, and phosphorus were effectively released from the MW-pretreated sludge. The values of COD released were 15.91%, 15.07%, 13.83%, 19.35%, and 15.07% for the MW, MW-acid, MW-alkali, MW-H2O2, and MW-H2O2-alkali treatment processes, respectively. Additionally, for a wastewater treatment system with a capacity of 200 m3/d, when coupled with a MW sludge pretreatment unit, the sludge production and sludge yield were greatly reduced by 38.60% and to 0.35 kg VSS/kg CODconsumed, respectively. The total operating cost of the lysis–cryptic growth system was 13.64% lower than that of the CAS system without a MW unit.