Enhancing Sludge Dewatering and Filtrate Carbon Source Recovery via Typical Bioenzymatic Conditioning
This study systematically investigated the effects of single and composite conditioning with lysozyme, amylase, and protease on sludge dewatering performance and carbon source recovery in filtrate from residual sludge of a water treatment plant in Foshan City. Results indicated that lysozyme significantly improved sludge dewatering by reducing specific resistance of filtration (SRF), capillary suction time (CST), and water content of the filtered sludge cake (Wc). While amylase and protease decreased Wc, they elevated SRF and CST, deteriorating sludge filtration properties. Among combined enzyme treatments, lysozyme and protease exhibited synergistic effects. The asynchronous addition strategy (protease/amylase followed by lysozyme) demonstrated the best performance in reducing Wc, while simultaneous addition was more effective in improving SRF and CST. Mechanistic analysis revealed that all three enzymes reduced sludge particle size. Lysozyme primarily targeted cell lysis and wall disruption, releasing intracellular substances, reducing viscosity, and enhancing sludge hydrophobicity. Meanwhile, amylase and protease mainly disrupted extracellular polymeric substances (EPS), leading to release of proteins and polysaccharides into slime EPS, increasing viscosity and hydrophilicity. Furthermore, all three enzymes effectively promoted carbon source release, increased soluble chemical oxygen demand (SCOD) of filtrate, and transformed recalcitrant humic acid-like organic matters into readily bioavailable tryptophan-like and tyrosine-like substances. These findings provide a basis for optimizing enzyme-based sludge conditioning to achieve simultaneous dewatering enhancement and carbon source recovery.