Enhanced coagulation with polyaluminum chlorides: Role of pH/Alkalinity and speciation

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• 作者：Mingquan Yan ; Dongsheng Wang ; Jianfeng Yu ; Jinren Ni ; Marc Edwards ; Jiuhui Qu
• 关键词：Alkalinity ; pH ; Polyaluminum chloride (PACl) ; Natural organic matter (NOM) ; Enhanced coagulation
• 刊名：Chemosphere
• 出版年：2008
• 期刊代码：15_00456535
• 类别：env
• 出版时间：April 2008
• 卷：71
• 期：9
• 页码：1665-1673
• 文件大小：223 K

摘要

Enhanced coagulation is considered to be among the best available techniques (BAT) for disinfection by-product (DBP) precursor removal in water treatment. Improving existing understanding requires further consideration of nuances of chemical speciation relative to source water chemistry. In this paper, the effect of alkalinity/pH and speciation on inorganic polymer flocculants, polyaluminum chlorides (PACls) for enhanced particle and natural organic matter (NOM) removal was investigated. Three kinds of well-characterized typical source waters in China with low, moderate, and high alkalinity were selected. Performance of coagulants is controlled not only by preformed species but also by those formed in situ. At neutral and basic pH values, PACls with higher basicity (ratio of OH⁻/Al), which have more stable preformed Al_b (the rapid reacted species as in ferron assay), are more efficient for turbidity and NOM removal. At slightly acidic pH, PACls with lower basicity are more efficient since more Al_b can be formed in situ. Optimal NOM removal was achieved at pH 5.5–6.5 for all PACls. Basicity, speciation, and dosage of coagulant should be optimized based on raw water alkalinity to enhance the removal efficiency of NOM.