水处理超滤理论与工艺研究

【作者】 何自琦；

【导师】 王晓昌；

【作者基本信息】 西安建筑科技大学 ， 市政工程， 2001， 硕士

【摘要】 本文主要研究了水中细菌、浊度和腐植酸的超滤特性，分析了超滤膜的分离机理，比较了不同截留分子量超滤膜对腐植酸的去除效果，同时研究了浊度物质和混凝预处理对腐植酸超滤效果的影响，初步探讨了膜渗透通量下降的规律和原因。 实验结果表明，超滤具有良好的灭菌和除浊功能，细菌去除率达99％以上，过滤出水的浊度能控制在0.02NTU以内，直接超滤对腐植酸TOC去除率为30％左右，UV254的去除率达 40％，截留分子量为 10万道尔顿和 1万道尔顿的两种超滤膜对腐植酸的去除效果无明显差别。超滤对细菌、浊度和腐植酸的去除机理主要是膜的机械筛分，滤饼层的形成是膜渗透通量下降的主要原因，但腐植酸对膜渗透通量下降的影响远大于浊度物质。 浊度物质的存在提高了超滤对腐植酸的去除能力，浊度越大，腐植酸去除率越高，但浊度物质的存在明显加剧了腐植酸对膜的污染，原因是浊度物质和腐植酸相互影响，形成的滤饼层较腐植酸单独实验时更加密实。 铝盐混凝预处理能提高超滤对腐植酸的去除能力，并能大幅度改善腐植酸对超滤膜的污染。pH=7.0条件下的混凝预处理机理主要是铝盐高分子水解产物对腐植酸的吸附网捕作用，pH=5.0时的机理主要是带正电荷低分子铝盐水解产物吸附电中和作用，从TOC和 UV254的去除率以及膜渗透通量的变化情况来看，pH=7.0条件下的混凝预处理优于pH=5.0。 高效液相色谱对腐植酸分子量的分析表明，直接超滤对小分子腐植酸的截留能力很差，对分子量＜6000道尔顿腐植酸的去除率仅为6％左右，证明实验中超滤膜对腐植酸的去除机理主要是膜的筛滤作用。pH＝7.0条件下的铝盐混凝预处理能大大提高超滤对小分子腐植酸的去除能力，这正是混凝预处理提高腐植酸超滤去除率的原因所在。更多还原

【Abstract】 This paper mainly studied the characteristics of ultrafiltration for the removal ofbacteria, turbidity, and humic acid （HA）. Experiments were also carried out to examine theeffects of turbidity and coagulation pretreatment on HA removal. The mechanism of UFseparation was analyzed, and the UF flux decline was preliminarily discussed.The results show that UF is efficient for the removal of bacteria and turbidity with the99% removal of bacteria achieved and residual turbidity within 0.02 NTU in the treatedwater; the UF resulting TOC and UV₂₅₄ removals of HA are 30% and 40%; there is noobvious difference of HA removals between the UF membrane with a MWCO of 10kdaltons and the other one with a MWCO of 1 kdaltons. Bacteria, turbidity and HA areremoved by the sieving mechanism of size exclusion which depends on the membraneMWCO. The decline of the membrane flux is mainly attributed to the cake layer formation,but the HA cake layer leads to much worse membrane flux decline than turbidity cake layerdoes.The presence of turbidity improves the UF removal of HA. the bigger the turbidity, thehigher the HA removal. But the membrane flux decline is aggravated due to the morecompact cake layer formation than HA alone.Aluminum coagulation pretreatment enhances the UF removal of HA and greatlyameliorates the effect of HA on the membrane flux decline. At pH=7.0 the mechanism isadsorption of HA on the amorphous solid-phase Al（OH）₃（s）, while at pH=5.0 themechanism is charge-neutralization. In terms of the removal of HA (TOC, UV₂₅₄) and themembrane flux decline, the effect of coagulation under pH=7.0 condition turns out to be muchbetter than that under the condition of pH=5.0.The result of HPLC indicates that direct UF has low removal of small molecule HA,while coagulation pretreatment can enhance the removal of UF of small molecule HA whichattributes to the higher removal of HA.更多还原