Unraveling synergistic mechanisms of enhanced electrocoagulation sludge dewatering using modified sludge-based biochar

Abstract

Electrocoagulation (EC) is an environmentally friendly and efficient method that enhances sludge dewatering. However, EC has limited cracking efficiency for extracellular polymeric substances (EPS) and sludge cells. In this study, sludge-based biochar prepared by KOH impregnation (SB-KOH) was added to the EC process as both conductor and skeleton particles of the EC sludge dewatering system. As a result, the current transmission capacity and the “flocculation” effect of sludge were enhanced by SB-KOH. By optimizing the voltage, carbon dosage, specific resistance to filtration (SRF), and capillary suction time (CST0/CST), using enlarged plate area (EFe-EC + SB-KOH) and anode material replacement (Al-EC + SB-KOH), enhanced sludge dewatering performance was achieved. The results showed that SRF and CST0/CST were reduced by 66.29 % and 75.71 %, respectively, when using SB-KOH with optimal EC voltage of 25 V and 15 % dry solid (DS). In addition, the Zeta potential of the system and the sludge particle size were increased, and the surface roughness of flocs was reduced. Three-dimensional fluorescence (3D-EEM) analysis indicated that EC + SB-KOH greatly decomposed aromatic protein-like substances in EPS and led to internal material transfer or absorption. Scanning electron microscopy (SEM) and particle size analysis showed that EC + SB-KOH was beneficial to achieve stronger flocculation and solid-liquid separation performance. The above findings indicate that the efficiency of sludge dewatering was enhanced using SB-KOH self-circulation technology, which provides a validation basis for green and sustainable development.