Biological power generation and earthworm assisted sludge treatment wetland to remove organic matter in sludge and synchronous power generation

Highlights: • A bioelectrochemically assisted STW for sewage sludge was achieved. • S₄ system yields a voltage of 0.832 V and maximum power density of 94.98 W/m². • Bioelectrochemically assisted STW owe a promoted organic degradation and dewatering. • More bacteria were detected under earthworm and bioelectricity combined system. In order to eliminate the weak degradation ability of organic matter in sludge treatment wetland (STW). In current work, a combined biological power generation and earthworm assisted sludge treatment wetland (BE-STW) system is proposed for the first time to accelerate degradation and dehydration process of organics in STW, thusly, recovering biomass energy in sludge. Experimental results show that S₄ system (earthworm and bioelectricity combined) yields a voltage of 0.832 V and maximum power density of 94.98 W/m² in the 5th day. The combination of earthworm, microorganism and plants in STW system can reduce the ratio of volatile solids to total solids (VS/TS) to 15% while the removal rate of total chemical oxygen demand (TCOD) reaches 92.1%. The BE-STW system increases sludge particle size while reduces absolute value of Zeta and extracellular polymeric substances (EPS) content, so that the moisture content of effluent sludge retains to 66.8%. Meanwhile, the richness of bacterial communities in S₄ proves that bioelectrochemistry and earthworm can effectively improve the sludge treatment effect.