Enhanced coagulation for improving coagulation performance and reducing residual aluminum combining polyaluminum chloride with diatomite

The feasibility of using enhanced coagulation, which combined polyaluminum chloride (PAC) with diatomite for improving coagulation performance and reducing the residual aluminum (Al), was discussed. The effects of PAC and diatomite dosage on the coagulation performance and residual Al were mainly investigated. Results demonstrated that the removal efficiencies of turbidity, dissolved organic carbon (DOC), and UV254 were significantly improved by the enhanced coagulation, compared with PAC coagulation alone. Meaningfully, the five forms of residual Al (total Al (TAl), total dissolved Al (TDAl), dissolved organic Al (DOAl), dissolved monomeric Al (DMAl), and dissolved organic monomeric Al (DOMAl)) all had different degrees of reduction in the presence of diatomite and achieved the lowest concentrations (0.185, 0.06, 0.053, 0.014, and 0 mg L-1, respectively) at a PAC dose of 15 mg L-1 and diatomite dose of 40 mg L-1. In addition, when PAC was used as coagulant, the majority of residual Al existed in dissolved form (about 31.14-70.16 %), and the content of DOMAl was small in the DMAl.