Sedimentation Behavior of Organic, Inorganic, and Composite Flocculant-Treated Waste Slurry from Construction Works

The disposal of waste slurry from construction engineering is attracting more and more attention due to the thorny issues related to high water content (dewatering is difficult and time-consuming). The use of chemical flocculants is proposed in this study, and organic, inorganic, and composite flocculant are designed to identify the characteristics and efficiency of slurry-water separation. The influence of flocculant type and dosage on slurry settlement and its associated mechanisms are studied by a set of sedimentation column, particle size distribution, and scanning electron microscopy (SEM) tests. The experimental results prove that organic, inorganic, and composite flocculants can promote the efficiency of slurry-water separation, although inorganic flocculants may perform relatively worse in comparison with organic and composite flocculants. The conditioning performance of organic flocculants is sequentially anionic polyacrylamide (APAM) > polyacrylamide (PAM) > amphoteric polyacrylamide (ACPAM) > cationic polyacrylamide (CPAM), while their optimum dosage is 300, 300, 400, and 400 mg/L, respectively. The combined formulation of APAM+FeCl3 improves the conditioning of slurry owing to the charge neutralization, net capturing, and sweeping ability. The flocculating effect causes an aggregation of fine particles, and this induces a decrease in the amount of fine particles and an increase in the fraction of coarse flocs. The SEM results prove that the slurry particles tend to be arranged in a parallel manner and the flocculant induces an agglomeration of fine particles owning to a series of physicochemical reactions. The previous discussions can provide an experimental framework for the development of slurry-water separation technology on waste slurry from construction works.