聚氯化铝-聚二甲基二烯丙基氯化铵复合絮凝剂混凝行为和絮体特性对混凝-超滤工艺水处理效能和膜污染影响

Dissolved organic matter commonly considered as one of the most important predecessor of by-product of chlorination (DBPs) in water treatment processes, and the control of its existence in water bodies is one of the key matter for insurance of water supply security. This research project aiming to apply a novel norganic-organic composite flocculant, polymeric aluminium-chloride- Polydimethyldiallylammonium Chloride (PACl-PDMDAAC) in coagulation-ultrafiltration hybrid process (C-UF) for treatment of surface water source. The coagulation behavior, floc characteristics of PACl-PDMDAAC and their relationship with coagulation performance and membrane fouling mechanism would be investigated. To be specific, the research contents including: (1) PACl-PDMDAAC would be composite by PACl with different basicity (B) with PDMDAAC of various viscosities (η) at varying ratios; (2) Simulated water samples and real water samples would be chosen as target water. The optimum ratio for PACl of different B value and PDMDAAC of various viscosities would be selected according to their coagulation performance in treatment of target water. Furthermore, their organic pollutant reduction efficiencies and coagulation behavior would be studied; (3) By using on-line monitoring of coagulation dynamic process, the variation floc characteristics formed by PACl (B) –PDMDAAC (η) would be determined, and its relationship with coagulation behavior of the flocculants would be investigated; (4) The impacts of PACl (B) –PDMDAAC (η) coagulation behavior/floc characteristics on coagulation performance of C-UF process and the membrane fouling would be investigated by monitoring the change of membrane flux. Furthermore, the mechanism of C-UF system would be studied, and the relational model of PACl-PDMDAAC coagulation behavior,/floc characteristics with coagulation performance/membrane fouling mechanism would be established.

本课题拟采用不同碱化度的（B）聚合氯化铝（PACl）分别与不同粘度的二甲基二烯丙基氯化铵（PDMDAAC）按不同比例复合制备出系列新型PACl—PDMDAAC无机-有机复合混凝剂；以模拟水和实际地表水为处理对象，通过混凝试验，优选出不同B值的PACl与不同粘度的PDMDAAC的最佳复合配比，研究其混凝去除有机污染物的效果和混凝行为；通过在线监测混凝动态过程，研究不同B值的PACl分别与不同粘度的PDMDAAC在最佳复合比下产生的絮体特性与差异，研究其絮体特性与混凝行为之间的关系；通过测定膜通量变化及膜污染情况，研究PACl—PDMDAAC复合混凝剂的混凝行为和絮体特性对混凝-超滤组合工艺水处理效能和膜污染影响情况，进而研究混凝-超滤组合工艺中膜污染的机制，建立PACl—PDMDAAC混凝行为、絮体特性与混凝-超滤组合工艺的水处理效果和膜污染机制之间的关系模型。

在混凝-超滤（C-UF）水处理组合工艺中，混凝预处理后的水中若残留一定量的有机物，这不但会导致后续超滤膜的污染，还会在氯消毒环节产生具有“三致”作用的消毒副产物（DBPs），危及人类身体健康。因此，对于微污染水源水的混凝-超滤处理，急需研发对水体中有机物具有良好去除效果的新型高效混凝剂并分析建立混凝剂的混凝行为、絮体特性与混凝-超滤组合工艺的水处理效果和膜污染机制之间的关系。本课题以不同碱化度（B）的聚合氯化铝（PACl）和不同粘度的聚二甲基二烯丙基氯化铵（PDMDAAC）为原料研发出了系列PACl-PDMDAAC无机-有机复合混凝剂，研究了PACl的B值、PDMDAAC的粘度和复合配比对PACl-PDMDAAC复合混凝剂处理不同水样混凝效果的影响情况，优选出了高效的PACl-PDMDAAC复合混凝剂产品。采用优选出的PACl-PDMDAAC复合混凝剂处理具有不同水质特性的水样，深入系统地开展了PACl-PDMDAAC的混凝行为、絮体特性与混凝-超滤组合工艺的水处理效果和膜污染机制之间的关系研究。与PACl相比，PACl-PDMDAAC具有长链大分子结构，且携带大量正电荷，能够中和混凝体系中有机物所带的负电荷，捕获更多污染物胶体物质。同时能够充分发挥其吸附架桥作用，降低絮体间的静电排斥力，形成结构疏松且粒径较大的絮体。PACl与PDMDAAC结合形成的PACl-PDMDAAC复合混凝剂可强化混凝效果，形成大且结构疏松的絮体，因此在超滤过程中可通过形成疏松多孔的滤饼层减少膜孔堵塞和滤饼层阻力，从而减轻超滤膜污染减和减缓膜通量的下降幅度。该研究对新型高效PACl-PDMDAAC复合混凝剂在混凝-超滤工艺中的应用奠定了理论基础，并有助于进一步提升出水水质和降低水处理成本，促进混凝-超滤工艺技术在水处理中的广泛推广应用。