1、Unit 13 Membrane Separation TechnologiesHang XuHenan University of Science and TechnologyThere are five types of membrane processes,which are commonly used in water and wastewater treatment:electrodialysis,microfiltration,ultrafiltration,nanofiltration and reverse osmosis and.电渗析、微滤、超滤、纳滤和反渗透是水处理和废水
2、处理中常用的五种膜过程。Through these processes dissolved substances or finely dispersed particles can be separated from liquids.通过这些过程，溶解的物质或细微分散的颗粒可以从液体中分离出来。All five technologies rely on membrane transport,the passage of solutes or solvents through thin,porous polymeric membranes.所有这些技术都依赖于膜输送，即溶质或溶剂通过薄而多孔的聚
3、合物膜。A membrane is defined as an intervening phase separating two phases forming an active or passive barrier to the transport of matter.膜被定义为分隔两相形成主动或被动屏障以进行物质运输的介入相。Membrane processes can be operated as dead-end filtration and cross-flow filtration.膜过程可以作为隔板过滤和错流过滤。Dead-end filtration refers to fil
4、tration at one end.A problem with these systems is frequent membrane clogging.静滤指的是一端过滤。这些系统的一个问题是频繁的膜堵塞。Cross-flow filtration overcomes the problem of membrane clogging and is widely used in water and wastewater treatment.错流过滤技术克服了膜堵塞问题，广泛应用于水处理和废水处理。The membrane itself is a polymeric coating or ex
5、trusion with inverted conical shaped pores.膜本身是聚合物涂层或具有倒锥形孔的挤出物。Membrane filters do not plug because the pore diameter is smaller at the top,which is the point of contact with the wastewater.膜过滤器不堵塞，因为在顶部的孔径较小，这是与废水的接触点。Material passing through the membrane passes unimpeded through the membrane stru
6、cture,therefore eliminating accumulation of material within the filter.材料通过薄膜不受阻碍地通过膜结构，因此消除了材料在过滤器内的积累。Wastewater is pumped across the membrane surface at high flow rates.废水以高流速被泵送到膜表面。This parallel fluid flow eliminates the cake-like build-up typical of conventional filters such as bags and cartri
7、dges which must be frequently replaced.这种平行的流体流动消除了传统过滤器典型的类似于锥形的积累，例如必须经常更换的袋子和墨盒。Some wastewater contaminants slowly accumulate on the membrane surface,forming a thin film,during normal operating conditions.在正常操作条件下，一些废水污染物会慢慢积聚在膜表面，形成薄膜。This fouling process is normal and causes the filtration rat
8、e to slowly decrease with time.这种结垢过程是正常的，导致过滤速率随时间缓慢下降。When membranes no longer produce clean water at the desired rate they are cleaned in place with soap and water and returned to service.当膜不再以理想的速度产生清洁水时，它们就用肥皂和水进行清洗，然后重新投入使用。Membranes can be repeatedly cleaned for years of productive,dependable
9、 service prior to replacement.细胞膜可以进行多年的清洁工作，可靠的先决条件是更换。Most of these processes are often times used with chemical mechanical polishing(CMP),which is fast becoming the established technology for planarizing multi-level devices.这些工艺中的大部分常常用于化学机械抛光(CMP)，这种抛光技术为计划中的多级装置奠定了基础。This process requires large
10、 quantities of ultra pure water for rinsing slurry particles off the polished wafers.这个过程需要大量的超纯净水来冲洗抛光晶圆片上的吸浆颗粒。Treatment by this method is generally needed in order to maintain an acceptable level of total suspended solids(TSS)in industrial wastewater effluent.一般而言，要维持工业废水的可接受总悬浮固体水平，便需以这种方法处理。Wit
11、h large quantities of particles in the CMP wastewater stream,cross-flow filtration is the most economical method for TSS removal.由于CMP 废水中含有大量颗粒，横流过滤是去除 ss 最经济的方法。Eletcrodialysis电透析The principle of electrodialysis(ED)is that the potential gradient will allow charged molecules to gain a higher diffus
12、ion rate in a given medium.电渗析的原理是电位梯度使得带电分子在给定介质中获得更大的扩散速率。When a direct current is transmitted through a saline solution,the cations migrate toward the negative terminal,or cathode,and the anions toward the positive terminal,the anode.当直流电流通过盐水溶液传输时，阳离子朝向负极端或阴极迁移，而阴离子朝向正极端，即阳极迁移。By adjusting the p
13、otential between the terminals or plates,the electric current and,therefore,the flow of ions transported between the plates can be varied.通过调节端子或板之间的电位，可以改变在板之间传输的电流以及因此离子流的流动。Ultrafitration超滤 Suspended materials and macromolecules can be separated from a waste stream using a membrane and pressure d
14、ifferential,called ultrafitration(UF).悬浮物和大分子可以从废水中分离出来，使用膜和压差，称为超滤(uf)。This method uses a lower pressure differential than reverse osmosis and doesnt rely on overcoming osmotic effects.这种方法使用较低的压差比反渗透，并不依赖于克服渗透影响。It is useful for dilute solutions of large polymerized macromolecules where the separa
15、tion is roughly proportional to the pore size in the membrane selected.它适用于大型聚合大分子的稀溶液，其分离大致上与所选膜的孔径成正比。Ultrafiltration membranes are commercially fabricated in sheet,capillary and tubular forms.超滤膜在商业上以片状、毛细管和管状的形式制造。The liquid to be filtered is forced into the assemblage and dilute permeate passes
16、 perpendicularly through the membrane while concentrate passes out the end of the media.待过滤的液体被挤入装配体中，稀释渗透垂直通过膜，浓缩液则从介质端流出。This technology is useful for the recovery and recycle of suspended solids and macromolecules.这项技术有助回收和循环悬浮固体和大分子。This technology is useful for the recovery and recycle of suspe
17、nded solids and macromolecules.这项技术有助回收和循环悬浮固体和大分子。Ultrafiltration equipment are combined with other unit operations.超滤设备与其他单元操作相结合。The unique combination of unit operations depends on the wastewater characteristics and desired effluent quality,and cost considerations.单位行动的独特组合取决于废水的特性和期望的污水水质，以及成本考
18、虑。Microfiltration微滤膜In the case of microfiltration(MF),a more porous membrane is used than in the other membrane separation technologies,thus yielding a relatively higher flux.在微滤的情况下，微孔膜比其他膜分离技术具有更多的孔隙，从而产生较高的通量。It is mainly useful in removing turbid causing materials and can replace conventional g
19、ranular filtration processes.主要用于去除造成混浊的物质，可替代传统的颗粒过滤工艺。There have been only a few studies have evaluated membrane microfiltration of secondary wastewater effluent.目前国内外对二级出水膜微滤技术的研究还很少。Microfiltration membranes might be used to achieve very low turbid effluents with very little variance in treated
20、water quality.微滤膜可以用于处理低浊度的废水，处理后的水质变化很小。Because bacteria and many other microorganisms are also removed,such membrane disinfection might avoid the need for chlorine and subsequent dechlorination.由于细菌和许多其他微生物也被除去，这种膜消毒可以避免对氯的需要和随后的脱氯。Metal salts of iron or aluminum may also be added to enhance membr
21、ane performance.还可以添加铁或铝的金属盐以提高膜的性能。Nanofiltration纳滤膜Nanofiltration(NF)membrane process are receiving considerably more attention since they are efficient at removing the trihalomethanes(THM)and haloacetic acids(HAA).由于纳滤膜在去除三卤甲烷(THM)和卤乙酸(HAA)方面具有很高的效率，因此纳滤膜过程正受到越来越多的关注。NF systems usually operate in
22、 three stage system.NF系统通常在三级系统中运行。The first stage consists of three pressure vessels,which usually contain four to eight membrane elements;the second stage has two pressure vessels;and the final stage has one.第一级由三个压力容器组成，通常包含四到八个膜元件;第二级有两个压力容器;最后一级有一个。In full scale plants,elements are approximatel
23、y 1,000mm long and have a diameter of 200 mm.在大型植物中，元素大约1000毫米长，直径200毫米。Permeation is collected from each pressure vessel.从每个压力容器收集渗透。The concentrate from the first stage serves as the feed to the second and concentrate from the seconds tage serves as the feed to the third.从第一级到第二级的集中作为供给，从第二级到集中作为供
24、给第三级。Consequently,each successive stage of the array increases the total system recovery.因此，数组的每个连续阶段都增加了总的系统恢复。Reverse Osmosis反渗透Reverse osmosis(RO)is a means for separating dissolved solids from water molecules in aqueous solutions.反渗透是一种从水溶液中分离出溶解固体的方法。When pure water and a salt solution are intr
25、oduced on opposite sides of a semipermeable membrane in a vented container,the pure water diffuses through the membrane and dilutes the salt solution.当将纯水和盐溶液引入通风容器中的半透膜的相对侧面上时，纯水通过膜扩散并稀释盐溶液。At equilibrium,the liquid level on the saline water side of the membrane will be above that on the freshwater
26、 side;this process is known as osmosis and is depicted in Figure 1.在平衡时，膜的盐水侧的液面将高于淡水一侧，这个过程称为渗透，如图1所示。左边的视图说明渗透的开始，中心视图呈现平衡条件。The effective driving force responsible for the flow is osmotic pressure.负责流动的有效驱动力是渗透压。By applying pressure to the saline water,the flow process through the membrane can be
27、 reversed.该压力的大小取决于膜特性、水温、盐溶液的性质和浓度。When the applied pressure on the salt solution is greater than the osmotic pressure,fresh water diffuses in the opposite direction through the membrane and pure solvent is extracted from the mixed solution;this process is termed reverse osmosis(RO).当对盐溶液施加的压力大于渗透压
28、时，淡水沿相反方向通过膜扩散，并从混合溶液中提取纯溶剂，这个过程称为反渗透（RO）。The fundamental difference between reverse osmosis and electrodialysis is that in reverse osmosis the solvent permeates the membrane,while in electrodialysis the solute moves through the membrane.反渗透和电渗析之间的根本区别是在反渗透中溶剂穿过渗透膜，而在电渗析中溶质穿过膜。图1 反渗透原理Words and Expr
29、essionmembrane membren n.膜electrodialysis lektrdalss n.电渗析microfiltration makrfltren n.微滤ultrafiltration ltrfltren n.超滤reverse osmosis 反渗透dead-end filtration 死端过滤cross-flow filtration 错流过滤extrusion kstru:n n.挤压，压出inverted conical shaped pores 倒锥形孔cake-like build-up蛋糕堆积的chemical mechanical polishing
30、化学机械抛光total suspended solid 总悬浮颗粒saline solution 盐溶液cation ktan n.阳离子cathode kd n.阴极 polymerized macromolecule 聚合大分子capillary kplri n.毛细管状的tubular tju:bjl(r)n.管状的flux flks n.通量disinfection dsnfkn n.消毒trihalomethane n.三卤甲烷 haloacetic acid n.卤乙酸membrane element 膜组件pressure vessel 压力容器semipermeable membrane 半透膜
