氯化铝和聚合氯化铝(PAC)在黄河水中的混凝效果与残留铝含量及组分

Abstract

The coagulation performance of AlCl3 and polyaluminum chloride (PAC) during treatment of water from the Yellow River was investigated with different initial pH conditions and coagulant doses. Speciation of the residual aluminum was also studied. PAC showed superior coagulation performance to AlCl3, and it altered the initial pH slightly under alkaline conditions. For Yellow River water treatment with PAC and AlCl3, the optimum initial pH was 6.0 and the optimum coagulant dose was 15 mg/L (Al). Under these conditions, the removal of turbidity, UV254 and dissolved organic carbon was optimized. The organic material in the effluent after coagulation was mostly hydrophobic, and this material was removed better with higher coagulant doses and in neutral or weakly alkaline conditions. It was not easy for the Al from PAC to transfer to and remain in the effluent, and PAC’s residual aluminum ratio was lower than that of AlCl3. With a coagulant dose of 11-15 mg/L and initial pH of 8.0, there was little Al remaining in the water after treatment with either AlCl3 or PAC. The residual Al was mainly present as dissolved Al, and dissolved organically bound Al was the predominant species. Dissolved inorganically bound monomeric Al was the main component in dissolved monomeric Al. The residual Al concentration was effectively controlled using a coagulant dose of 10-15 mg/L and initial pH of 7.0-8.5. PAC treatment produced lower concentrations for several residual Al species, except for dissolved organically bound Al, than AlCl3 treatment. PAC could effectively reduce the concentration of dissolved Al and dissolved monomeric Al in water after treatment.