Waste sludge conditioning for the enhanced dewaterability: A review of key factors, significant methods, post-disposal paths, and artificial intelligence integration

Large quantities of waste sludge (WS) have become a significant challenge and raised widespread concerns in China. Sludge dewatering is a critical step in reducing sludge volume, which has become the current focus in sludge treatment and management. This paper reviewed the key factors influencing sludge dewaterability, significant methods of sludge conditioning, typical post-disposal after sludge dewatering, and artificial intelligence (AI) integration technology application. Zeta potential, particle size, rheological behavior, hydrophobicity, extracellular polymeric substances (EPS) (including composition and content, spatial conformation, molecular weight, and fluorescent component), functional groups, and flocs morphology are considered to govern sludge dewaterability jointly. Especially, EPS properties are considered the central determinant controlling sludge dewaterability. Various physical, chemical, and biological conditioning methods are comprehensively discussed, and combined conditioning techniques present better dewatering performance. As to post-disposal after dewatering, the filtrate is suitable as a carbon source for returning to the biological pool, while N and P are recycled. The principle of site-specific recommendations is suggested for the ultimate disposal of sludge in different regions of China, and incineration and land application are mainstream in the future. Presently, the exploitation of rapid, efficient, and AI-integrated sludge deep-dewatering technology is still a challenge in China.