title: Minimizing residual aluminum concentration in treated water by tailoring properties of polyaluminum coagulants.
abstract: Aluminum coagulants are widely used in water treatment plants to remove turbidity and dissolved substances. However, because high aluminum concentrations in treated water are associated with increased turbidity and because aluminum exerts undeniable human health effects, its concentration should be controlled in water treatment plants, especially in plants that use aluminum coagulants. In this study, the effect of polyaluminum chloride (PACl) coagulant characteristics on dissolved residual aluminum concentrations after coagulation and filtration was investigated. The dissolved residual aluminum concentrations at a given coagulation pH differed among the PACls tested. Very-high-basicity PACl yielded low dissolved residual aluminum concentrations and higher natural organic matter (NOM) removal. The low residual aluminum concentrations were related to the low content of monomeric aluminum (Ala) in the PACl. Polymeric (Alb)/colloidal (Alc) ratio in PACl did not greatly influence residual aluminum concentration. The presence of sulfate in PACl contributed to lower residual aluminum concentration only when coagulation was performed at around pH 6.5 or lower. At a wide pH range (6.5-8.5), residual aluminum concentrations <0.02 mg/L were attained by tailoring PACl properties (Ala percentage ≤0.5%, basicity ≥85%). The dissolved residual aluminum concentrations did not increase with increasing the dosage of high-basicity PACl, but did increase with increasing the dosage of normal-basicity PACl. We inferred that increasing the basicity of PACl afforded lower dissolved residual aluminum concentrations partly because the high-basicity PACls could have a small percentage of Ala, which tends to form soluble aluminum-NOM complexes with molecular weights of 100 kDa-0.45 μm.
authors: Graduate School of Engineering, Hokkaido University, N13W8, Sapporo 060-8628, Japan.
authors: Masaoki
authors: M
authors: Kimura
authors: Yoshihiko
authors: Y
authors: Matsui
authors: Kenta
authors: K
authors: Kondo
authors: Tairyo B
authors: TB
authors: Ishikawa
authors: Taku
authors: T
authors: Matsushita
authors: Nobutaka
authors: N
authors: Shirasaki
mesh_terms: D000535:Aluminum / Q000032:analysis* / Q000737:chemistry; D017607:Aluminum Compounds / Q000737:chemistry*; D000536:Aluminum Hydroxide / Q000737:chemistry; D011232:Chemical Precipitation; D003102:Colloids; D060766:Drinking Water / Q000737:chemistry*; D005374:Filtration; D005427:Flocculation; D006812:Humic Substances / Q000032:analysis; D006863:Hydrogen-Ion Concentration; D007202:Indicators and Reagents / Q000737:chemistry*; D007564:Japan; D008970:Molecular Weight; D009994:Osmolar Concentration; D045483:Rivers / Q000737:chemistry; D012995:Solubility; D013696:Temperature; D014874:Water Pollutants, Chemical / Q000032:analysis* / Q000737:chemistry; D018508:Water Purification; D060753:Water Quality
chemical_list: D017607:Aluminum Compounds; D003102:Colloids; D060766:Drinking Water; D006812:Humic Substances; D007202:Indicators and Reagents; D014874:Water Pollutants, Chemical; C016213:aluminum oxychloride; D000536:Aluminum Hydroxide; D000535:Aluminum