Performance and mechanisms of dredged sludge dewaterability enhancement with slag-based polymeric titanium aluminum coagulant

Abstract

In this work, blast furnace slag was successfully used to prepare five kinds of polymeric titanium aluminium flocculant (PTAC) with different polymerization degrees by two-step acid leaching method, which were applied as the effective dredged sludge conditioners. The results indicated that PTAC can obviously improve the sludge dewaterability. Compared with other four types of PTAC, PTAC0.6 showed the best sludge conditioning efficiency under the optimum dosage of 4 mg Al + Ti/g TSS. It can reduce the capillary suction time of the sediment by 81.4%, the specific resistance to filtration by 65.1%, and the moisture content of the mud cake from 81.9% to 45.81%. PTAC can significantly increase the zeta potential of the dredged sludge, while it has no obvious effect on the floc size D0.5. The electric neutralization substantially contributed to the conditioning of PTAC on dredged sludge dewatering. The concentration of dissolved organic carbon, total phosphorus in the residual water was significantly reduced after PTAC conditioning. PTAC can also remove large molecular weight components in dissolved organic matter by flocculation, or hydrolyze large molecular components into small and medium molecular weight components, furthermore reduce the concentration of these organic components. 3D-EEM analysis results showed that PTAC can effectively remove fulvic acid-like substances and some protein-like substances by flocculation, especially the removal effect of fulvic acid-like substances was more prominent.