操作方式对混凝—超滤组合工艺净水性能及膜污染的影响
发布时间：2019-05-11 17:10
【摘要】：针对超滤膜应用过程中的膜污染问题,目前主要采用在膜系统前增加预处理单元的方法,而应用较普遍的预处理单元为混凝工艺。混凝与超滤联用通常有两种形式,一种为混凝沉淀后超滤,另外一种为混凝后直接超滤。本研究混凝-直接超滤组合工艺。目前关于混凝-直接超滤组合工艺的研究,主要集中于膜出水水质及膜污染两个方面,而混凝操作条件对于絮体的微观特性研究以及絮体特性与膜污染之间对应关系的研究相对较少。在不同的原水初始pH、混凝剂投加量和助凝剂投加量等操作条件下,本课题研究了出水水质、絮体特性和跨膜压差(TMP),考察了操作条件对絮体特性及膜污染的影响,选择了最佳的操作条件,为混凝-超滤组合工艺的推广应用提供一些建议。(1)当混凝剂聚合氯化铝(PACl)投加量小于4~5 mg/L时,随着投加量的增加,组合工艺对有机物的去除率增加明显,大于4~5 mg/L时,去除效果基本稳定。投加量小于2 mg/L时,尺寸小于300μm的絮体数量占79.53%,分形维数为1.60±0.05,TMP增涨明显,平均每个运行周期增加0.48 kPa;投加量为5 mg/L时,尺寸在400~500μm范围的絮体数量占51.27%,分形维数为1.38±0.07,TMP增涨缓慢,平均每个运行周期增加0.21 kPa。(2)在原水初始pH为4.5的酸性条件下,组合工艺对有机物的去除率较高,但膜池内絮体尺寸较小,分形维数为1.75±0.15,TMP增长速率较快,平均每个运行周期增长1.37 kPa,引起膜污染的主要有机物为疏水性的富里酸类和腐植酸类物质;pH为7.5时,虽然对有机物的去除略有下降,但絮体尺寸较大,分形维数为1.37±0.05,TMP增长速率较缓,每个运行周期平均增长0.40 kPa。(3)投加阳离子型聚丙烯酰胺(CPAM)对混凝-超滤组合工艺去除有机物有一定作用,但提升效果较小。未投加时,尺寸在300~400μm范围的絮体数量占45.21%,分形维数为1.55±0.087,TMP的增长速率较高,平均每个运行周期增加0.27 kPa;随着CPAM投加量的增加,尺寸大于400μm的絮体数量逐渐增加,分形维数下降,最小为1.34±0.076;投加量为0.06 mg/L时,TMP平均每个运行周期增加0.15 kPa;投加量大于0.08 mg/L后,膜池内絮体尺寸略有下降,TMP也略有上升。
[Abstract]:In order to solve the problem of membrane fouling in the application of ultrafiltration membrane, at present, the method of adding pretreatment unit in front of membrane system is mainly adopted, and the more common pretreatment unit is coagulation process. There are usually two forms of coagulation and ultrafiltration, one is coagulation and sedimentation, the other is direct ultrafiltration after coagulation. In this paper, the combined process of coagulation and direct ultrafiltration was studied. At present, the research on coagulation-direct ultra-filtration process mainly focuses on two aspects: membrane effluent quality and membrane fouling. However, there are relatively few studies on the microscopic characteristics of flocs and the corresponding relationship between flocs characteristics and membrane fouling under coagulation conditions. Under different operating conditions such as the initial dosage of pH, coagulant and the dosage of coagulant aid in raw water, the effluent quality, floc characteristics and cross-membrane pressure difference (TMP), were studied, and the effects of operating conditions on floc characteristics and membrane fouling were investigated. The optimum operating conditions were selected to provide some suggestions for the popularization and application of coagulation-ultra-filtration process. (1) when the dosage of coagulant polyaluminum chloride (PACl) was less than 4 鈮，
本文编号：2474689
[Abstract]:In order to solve the problem of membrane fouling in the application of ultrafiltration membrane, at present, the method of adding pretreatment unit in front of membrane system is mainly adopted, and the more common pretreatment unit is coagulation process. There are usually two forms of coagulation and ultrafiltration, one is coagulation and sedimentation, the other is direct ultrafiltration after coagulation. In this paper, the combined process of coagulation and direct ultrafiltration was studied. At present, the research on coagulation-direct ultra-filtration process mainly focuses on two aspects: membrane effluent quality and membrane fouling. However, there are relatively few studies on the microscopic characteristics of flocs and the corresponding relationship between flocs characteristics and membrane fouling under coagulation conditions. Under different operating conditions such as the initial dosage of pH, coagulant and the dosage of coagulant aid in raw water, the effluent quality, floc characteristics and cross-membrane pressure difference (TMP), were studied, and the effects of operating conditions on floc characteristics and membrane fouling were investigated. The optimum operating conditions were selected to provide some suggestions for the popularization and application of coagulation-ultra-filtration process. (1) when the dosage of coagulant polyaluminum chloride (PACl) was less than 4 鈮，
本文编号：2474689
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