Coagulation performance and residual aluminum speciation of Al 2(SO 4) 3 and polyaluminum chloride (PAC) in Yellow River water treatment

Abstract

The effect of pH and coagulant dosage on the coagulation performance of aluminum sulphate and polyaluminum chloride (PAC) with respect to the treatment of Yellow River water was investigated in this paper. The separation and measurement of residual aluminum (Al) speciation were also conducted. The results indicated that PAC showed superior coagulation performance compared to that of Al 2(SO 4) 3 in most cases during the Yellow River water treatment. At a dosage of 15 mg/L as Al 2O 3, PAC achieved an optimum removal efficiency of turbidity, UV 254 and DOC of 96.3, 57.1, 32.7%, respectively, and Al 2(SO 4) 3 also achieved an optimum removal efficiency of turbidity, UV 254 and DOC of 94.5, 53.5 34.8%, respectively. For PAC and Al 2(SO 4) 3, the optimum pH during the treatment of Yellow River water could be determined at 6.0. Different residual Al speciation exhibited different trends with dosage and pH variation. For the two coagulants studied, no matter the dosage or pH, the majority of residual total Al existed most in the form of total dissolved Al, among which, dissolved organically bound Al was the predominant speciation. Most of the dissolved monomeric Al in the effluent was dissolved inorganically bound monomeric Al. PAC showed lower concentration for the several kinds of residual aluminum species, except the dissolved organically bound Al; and PAC could effectively reduce the concentration of dissolved monomeric Al.