Experimental investigation on sedimentation characteristics of coastal slurry by flocculation

Abstract

Coastal waste slurry has a negative impact on the environment due to its slow, natural settling characteristics. In this study, the organic, inorganic, and composite flocculants were applied to improve the mud-water separation performance. A series of experiments with sedimentation columns and particle size analysis were conducted to investigate the effects of flocculant type, dosage and combination on slurry settling rates and its associated mechanisms. The experimental results show that different types of flocculants varied in improving the settling efficiency of slurry, while the flocculation effect of inorganic flocculants is relatively poor. The settling efficiency of organic polymer flocculants on slurry is in order of anionic polyacrylamide (APAM) > cationic polyacrylamide (CPAM) > nonionic polyacrylamide (PAM), with their optimal dosage 0.2%, 0.1%, and 0.1%, respectively. Moreover, the combination of APAM and Solid Polymeric Ferric Sulfate (SPFS) can further improve the efficiency of mud-water separation by enhancing electro-neutralization and net sweeping capability. Subsequently, the change in the particle size distribution of the slurry demonstrates that flocculation causes the aggregation of fine particles in slurry to form coarse particles. These findings have implications for improving the sedimentation characteristics of waste slurry to reduce environmental pollution.