Insights into the mechanism of sludge-based biochar in electro-dewatering and energy consumption optimization

Abstract

Electro-dewatering (EDW) technology allows for deep dewatering of sludge. Its synergistic effect with other dewatering techniques significantly improves dewatering efficiency. Sludge-based biochar (SBB) acts as an environmentally friendly physical conditioner with electrical conductivity. It has the potential to enhance the dewatering performance of EDW and reduce energy consumption. This study prepared Fe-loaded SBB at three different temperatures and treated the sludge using an EDW at a constant voltage of 30 V for 20 min under optimal conditions of 12 % g/g dry solids (DS). The results indicate that the presence of Fe ions on the SBB surface significantly enhances the electrical conductivity and Zeta potential during the EDW process, effectively neutralizing the negative charges of sludge flocs and promoting the disintegration of sludge cells. During dehydration, the migration of Fe ions from the anode to the cathode forms a loose, porous structure at the cathode, enhancing its filterability. SBB@800 significantly promotes the degradation of sludge extracellular polymeric substances (EPS), effectively releasing bound water. The degree of damage to fluorescent organic matter in the three-layer EPS increases, significantly reducing the content of proteins (PN) and polysaccharides (PS). The anode layer sludge treated with SBB@800 shows higher PN degradation efficiency. Protein secondary structure and hydrogen bond analysis indicate increased hydrophobicity and weakened binding forces in sludge EPS. Moreover, SBB@800 with 12 % DS significantly reduces the overall energy consumption of the EDW system and slows the rate of increase in dewatering energy consumption, demonstrating favorable economic benefits. This study elucidates the mechanism of enhanced EDW by sludge SBB, providing technical guidance for energy-saving and consumption-reduction in EDW processes.