混凝剂中的铝形态对黄河水源水中出水余铝的影响

铝系混凝剂是应用最广泛的无机混凝剂，改善混凝剂中的铝形态可有效提高混凝效果，但其在净水过程中产生的余铝对人体健康及输水过程具有显著的影响。本文研究了氯化铝(AlCl₃)和高聚十三铝(Al₁₃) 2种混凝剂在处理黄河上游水源水时的混凝过程，结合出水中的溶解态及不同分子质量余铝含量、有机物紫外吸光度(UV₂₅₄)、pH、浊度、有机物种类及含量和絮体特性的变化趋势，探究混凝剂中的铝形态对混凝过程的影响。结果表明，在实验投加量范围内，当Al₁₃做混凝剂时，出水余铝质量浓度均低于0.2 mg·L⁻¹。Al₁₃具有较高的形态稳定性，在混凝过程中对出水pH影响较小。絮体粒度随混凝剂投加量的增加而增加，Al₁₃投加量达到0.08 mmol·L⁻¹时絮体粒度下降(强度因子由于静电排斥作用而下降)。在不同投加量下，使用AlCl₃做混凝剂时出水余铝均高于Al₁₃体系，且在不同投加量下AlCl₃体系出水余铝中小于1 000 Da的余铝占比最大。Al₁₃对富里酸和腐殖酸的去除效果优于AlCl₃，且AlCl₃在较高投加量下才能实现水中有机物的有效去除。

Effects of Aluminum form in coagulant on residual Aluminum in effluent of the source water of Yellow River

Al-based coagulants are the most widely used inorganic coagulants, and the optimized Al species can improve the coagulation performances, but the residual aluminum produced in the treatment process has significant impacts on human health and water transport process. In this study, Al13 and AlCl3 were used as coagulants to treat the source water of Yellow River, and the coagulation process was investigated. Combined with variations of the concentration of dissolved residual aluminum and residual aluminum with different molecular weights, UV254, pH, turbidity, concentration or species of organic matter and flocs characteristics, effects of aluminum species on residual aluminum and coagulation performances were investigated. The results showed that when Al13 was used as coagulant, the mass concentration of residual aluminum was lower than 0.2 mg·L−1, and the concentration was less affected by the dosage. Due to its high stability of species, Al13 had less effects on pH of effluent during coagulation process. The particle size of flocs increased with the increase of coagulant dosage, but it decreased when the dosage of Al13 reached 0.08 mmol·L-1 (the strength factors decreased due to electrostatic repulsion). The residual aluminum using AlCl3 as coagulant was higher than that in Al13 system at different dosages, and the proportion of residual aluminum with molecular weight lower than 1000 Da in AlCl3 was the largest in AlCl3 system. The removal efficiency of fulvic acid and humic acid using Al13 was better than using AlCl3, the latter could achieve high effective removal of organics in water at high dosages.