Development of Effective Cleaning and Pre-treatment for Membrane Filtration

以甲壳糖河水为试验对象，研究了混凝沉淀预处理对死端超滤（UF）膜的膜污染和天然溶解性有机碳去除率的影响。进行了两种类型的实验运行。一个是实验室规模的膜过滤与罐测试，另一个是连续膜过滤配备射流混合分离器作为一个单元的混凝/沉淀。在小型实验中，考察了混凝剂投加量、pH值和操作压力对膜污染和天然溶解性有机物去除率的影响。在连续膜过滤实验中，我们还考察了膜污染的减少和天然溶解性有机物的去除效率。膜过滤前的混凝沉淀工艺提高了天然溶解性有机物的去除率，改善了膜的过滤性能， 关于我们 研究了恒通量条件下，物理清洗对死端式和外-内操作方式下超滤膜污染的影响。与单纯反冲洗相比，空气洗涤与反冲洗相结合，可显著降低不可逆滤饼阻力。通过监测膜压力的增加和分析物理清洗对废水水质的影响，可以解释空气洗涤有效地提升和剪切了膜去除的高分子量腐殖物质和悬浮颗粒。通过对不同气洗、反洗次数和气洗强度的物理清洗实验，发现气洗、反洗时间越长，气洗强度越大，清洗效果越好。但物理清洗存在最佳条件，为了控制膜污染和改善水质，采用臭氧氧化工艺作为微滤的预处理。考察了臭氧投加量和微滤出液中臭氧残留量对膜污染及有机物和无机物去除率的影响。臭氧预氧化对水中腐殖物质的去除率是甲壳糖直接过滤的1.5-2.0倍。但是，预臭氧化的情况下，TOC的去除率略低于直接过滤的情况下，甲壳糖河水。臭氧氧化后空气洗涤和单独臭氧氧化对锰的去除率分别为90%和50%左右。预臭氧化处理的AOC比直接过滤甲壳糖河水的AOC高2.5-8.2倍。臭氧预氧化提高了膜的过滤性能。特别是当渗透液中存在残余臭氧时，恒压模式和恒流量模式下均能获得较高的渗透通量和较低的操作压力。分别预臭氧化提高膜过滤性能的原因可能是：首先，降解了以腐殖酸为主的高分子量有机物;第二，提高物理清洗效果，防止有机物和无机物在膜中积累。少

Effects of coagulation/sedimentation as a pretreatment on the dead-end ultafiltration(UF) membrane was studied in terms of membrane fouling and removal efficiency of natural dissolved organic carbon, using Chitose River water. Two types of experimental runs were carried out. One was bench scale membrane filtration with Jar-test and the other was continuous membrane filtration equipped with jet mixed separator as a unit of coagulation/sedimentation. In the bench scale experiment, effects of coagulant dosage, pH and operating pressure on membrane fouling and removal efficiency of natural dissolved organic matter were investigated. In the continuous membrane filtration experiment, we also investigated the reduction of membrane fouling and the removal efficiency of natural dissolved organic matter. Coagulation/sedimentation prior to membrane filtration process increased the removal efficiency of natural dissolved organic matter and improved the membrane filterability.We investigated the ef … More fects of physical cleaning on the UF membrane fouling in dead-end and outside-inside mode operation under a constant flux. By the air-scrubbing combined with the back washing, the irreversible cake resistance was drastically decreased, comparing with the back washing only. By monitoring the increase in trans-membrane pressure and analyzing the quality of wastewater caused by physical cleaning, it may be explained that the high molecular weight humic substances and suspended particles removed by membrane were effectively lifted and sheared by air-scrubbing. From the experimental results using physical cleaning with different times of air-scrubbing and back washing, and air-scrubbing intensity, it was found that the longer the air-scrubbing and back washing and the stronger the air-scrubbing, the higher the cleaning effect. But there exists the optimum condition of physical cleaning.For the control of membrane fouling and improvement of water quality, ozoneation process was used as a pretreatment of microfiltration(MF). Effect of ozone dosage and residual ozone in MF permeate were investigated in terms of membrane fouling and removal efficiency of organic and inorganic matter. Removal efficiency of humic substances in case of pre-ozonation was 1.5-2.0 times higher compared to the case of direct filtration of Chitose river water. But, the removal of TOC in the case of pre-ozonation was somewhat lower than the case of direct filtration of Chitose river water. In case of ozone oxidation followed by air-scrubbing and ozonation alone, removal efficiency of manganese are about 90 %, 50 %, respectively. AOC in case of pre-ozonation was 2.5-8.2 times higher compared with the case of direct filtration of Chitose river water. Pre-ozonation improved the membrane filterability. Especially, when residual ozone exists in permeate, high permeate flux and low operation pressure were achieved in constant pressure mode and constant flux mode., respectively. The reasons of improved of membrane filterabilty by using pre-ozonation may be considered as follows : Firstly, degradation of high molecular weight organic matter, mainly humic substances. Secondly, the improvement of physical cleaning effect against organic and inorganic matter accumulated in the membrane. Less