Development of Effective Cleaning and Pre-treatment for Membrane Filtration

以壳聚糖河水为研究对象，考察了混凝沉淀对超滤膜的影响，考察了膜污染和对天然有机碳的去除效果。进行了两种类型的试验运行。一种是小试规模膜过滤，另一种是以喷射混合分离器为混凝沉淀单元的连续膜过滤。在小试实验中，考察了混凝剂投加量、pH值、操作压力对膜污染及对天然溶解有机物去除效果的影响。在连续膜过滤实验中，我们还考察了膜污染的减少和对天然溶解有机物的去除效果。膜过滤前的混凝/沉淀提高了对天然可溶有机物的去除效率，改善了膜的过滤性能。考察了EF-…恒通量运行模式下，物理清洗对UF膜污染的影响较大。采用气洗与反冲洗相结合的方法，与单独反冲洗相比，不可逆滤饼阻力显著降低。通过对膜压力升高的监测和对物理清洗产生的废水水质的分析，可以解释膜去除的高相对分子质量腐殖质和悬浮物可以通过空气洗涤得到有效的提升和剪切。通过不同气洗反冲洗次数、不同气洗强度的物理清洗实验，发现气洗反洗时间越长、气洗强度越强，清洗效果越好。但存在最佳的物理清洗条件，为了控制膜污染和改善水质，采用臭氧工艺作为微滤的前处理工艺。考察了臭氧投加量和膜中臭氧残留量对膜污染及有机物和无机物去除效果的影响。预臭氧氧化对腐殖质的去除效率比直接过滤几丁江水高1.5~2.0倍。但是，在臭氧预氧化的情况下，TOC的去除略低于几托斯河水直接过滤的情况。在臭氧氧化+空气净化和单独臭氧氧化的情况下，除锰效率分别为90%和50%左右。臭氧预氧化的AOC是直接过滤几丁糖河水的2.5-8.2倍。预臭氧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，在恒压模式和恒流模式下分别获得了较高的渗透通量和较低的操作压力。臭氧预氧化提高膜过滤性能的原因主要有以下几个方面：第一，降解高相对分子质量的有机物，主要是腐殖质。其次，提高了对膜中积累的有机物和无机物的物理清洗效果。较少

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