FeCl3与接枝型淀粉改性絮凝剂联用“化学沉淀-絮凝”工艺除磷去浊性能
Removal of phosphorus and turbidity by a chemical sedimentation-flocculation process using FeCl3 combined with a graft starch-based flocculant
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摘要: 过量的磷元素进入水体是引起水体富营养化的主要原因.本论文在传统化学沉淀除磷法基础上，采用"化学沉淀-絮凝"工艺，将氯化铁与一种接枝型阳离子淀粉改性絮凝剂（淀粉接枝共聚丙烯酰胺-聚甲基丙烯酰氧乙基三甲基氯化铵，St-AD）联合使用，分别在无机磷和有机磷模拟含浊废水中考察了其同时除磷及去浊性能.系统研究了天然高分子絮凝剂结构因素（电荷密度等）和环境因素（FeCl3与高分子絮凝剂投加量、pH、初始浊度以及初始总磷含量等）对上述基于FeCl3和淀粉改性絮凝剂联用的"化学沉淀-絮凝"工艺除磷去浊性能的影响.研究发现，相比于单独使用FeCl3化学沉淀除磷法，St-AD的加入使得铁盐投加量显著减少，同时形成的絮体尺寸更大，絮体结构也更为密实，进一步提高了除磷效果，同时也有效降低水体浊度；且一般情况下，St-AD阳离子取代度增高，处理效果增强；最佳工艺条件下，总磷和浊度去除率分别可达到98%和99%以上.此外，该组合工艺对有机磷模拟废水净化效果的提升优于对无机磷模拟废水.不同初始pH条件下实验结果表明，pH较高（pH>5）时该组合工艺的除磷去浊效果较好；本实验范围内初始浊度（30-300 NTU）对该组合工艺的除磷去浊效果影响较小；该"化学沉淀-絮凝"组合工艺对较高初始总磷含量（>20 mg·L-1）的模拟废水作用效果较差，该组合工艺不适于处理具有较高初始总磷含量的废水.由于该"化学沉淀-絮凝"组合工艺在除磷去浊中具有良好的性价比及环保特征，因此该工艺在水处理行业中应具有良好的应用前景.
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关键词:
- 除磷去浊 /
- “化学沉淀-絮凝”工艺 /
- 接枝型淀粉改性絮凝剂 /
- 氯化铁 /
- 除磷去浊机理
Abstract: Phosphorus has been considered the main trigger of eutrophication in water bodies. In this study, "chemical precipitation-flocculation" process has been used for simultaneous removal of phosphorus and turbidity on the basis of conventional "chemical precipitation" method. A cationic graft starch-based flocculant (Starch-graft-polyacrylamide-co-poly[(2-methacryloyloxyethyl) trimethyl ammonium chloride], St-AD), as an assisting agent, was fed after the application of traditional inorganic precipitant of ferric chloride (FeCl3) to remove inorganic and organic phosphorus from their respective simulated turbid wastewaters. The effects of various influencing factors, including cationic content of St-AD, dosage, initial pH, initial turbidity, and initial total phosphorus (TP), were investigated systematically. This modified chemical sedimentation process assisted by St-AD not only evidently reduced the required dosage of FeCl3 but also obtained larger and denser flocs, causing a higher efficiency in removing TP and turbidity than conventional "chemical precipitation" method. Besides, St-AD with a higher cationic content showed better removal effectiveness. At optimal conditions, the removal extents of TP and turbidity were higher than 98% and 99%, respectively. This combination exhibited better efficiency in removing organic TP than in removing inorganic TP from water. In addition, the combined process had better TP and turbidity removal effect at higher initial pH (pH>5); the initial turbidity measured in this work (30-300 NTU) had little effect on the TP and turbidity removal; however, this combined technique was not suitable for treating higher initial TP wastewater (>20 mg·L-1). This "chemical precipitation-flocculation" process had a good application prospect in removal of phosphorus and turbidity in water and wastewater treatment plants due to its high cost performance and environmentally-friendly characteristics. -
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