Development of Effective Cleaning and Pre-treatment for Membrane Filtration

以千岁河水为原料，研究了混凝/沉淀预处理对超滤（UF）膜的污染及对天然溶解性有机碳的去除效果。进行了两种类型的实验运行。一种是采用jar试验的实验规模膜过滤，另一种是采用射流混合分离器作为混凝/沉淀单元的连续膜过滤。在台架试验中，考察了混凝剂投加量、pH和操作压力对膜污染及天然溶解性有机物去除率的影响。在连续膜过滤实验中，我们还研究了膜污染的减少和天然溶解有机物的去除效率。在膜过滤前进行混凝/沉淀处理，提高了天然溶解有机物的去除效率，提高了膜的过滤性能。在恒流量条件下，研究了物理清洗对终端和由外至内运行的超滤膜污染的影响。与单纯反洗相比，空气洗涤与反洗相结合可显著降低不可逆滤饼阻力。通过监测跨膜压力的增加和分析物理清洗引起的废水质量，可以解释为膜去除的高分子量腐殖质和悬浮颗粒被空气洗涤有效地提升和剪切。采用不同水洗次数、反洗次数、水洗强度的物理清洗实验结果表明，水洗时间越长、反洗强度越大，清洗效果越好。但存在物理清洗的最佳条件。为控制膜污染，改善水质，采用臭氧氧化法对微滤进行预处理。从膜污染、有机物和无机物去除率的角度考察了臭氧投加量和残余臭氧对中膜渗透液中有机物和无机物去除率的影响。预臭氧化处理对腐殖质的去除率比直接过滤处理提高1.5 ~ 2.0倍。但预臭氧化处理对TOC的去除率略低于直接过滤处理。在臭氧氧化后再进行空气洗涤和臭氧氧化的情况下，锰的去除率分别为90%和50%左右。预臭氧化处理的AOC是直接过滤处理的2.5 ~ 8.2倍。预臭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，在恒压模式和恒流量模式下均可获得较高的渗透通量和较低的操作压力。,分别。预臭氧氧化提高膜过滤性能的原因可以考虑如下：首先，降解高分子量有机物，主要是腐殖质物质。二是提高对膜内积存的有机物和无机物的物理清洗效果。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