1、Designation: F 1525 96 (Reapproved 2001)Standard Guide forUse of Membrane Technology in Mitigating HazardousChemical Spills1This standard is issued under the fixed designation F 1525; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision,
2、 the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This guide covers considerations for the use of mem-brane technology in the mitigation of dilute concent
3、rations ofspilled chemicals into ground and surface waters.1.2 This guide addresses the application of membranetechnology alone or in conjunction with other technologies.1.3 The values stated in SI units are to be regarded as thestandard. The values given in parentheses are for informationonly.1.4 T
4、his standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use. In addition, it is
5、theresponsibility of the user to ensure that such activity takesplace under the control and direction of a qualified person withfull knowledge of any potential or appropriate safety and healthprotocols.2. Referenced Documents2.1 ASTM Standards:2F 1127 Guide for Containment by Emergency ResponsePerso
6、nnel of Hazardous Material Spills3. Terminology3.1 Definitions of Terms Specific to This Standard:3.1.1 concentrate, retentatein reverse osmosis and nano-filtration, respectively, the portion of the feed solution that doesnot pass through the membrane is called concentrate, while theterm retentate i
7、s more commonly used for ultrafiltration andmicrofiltration.3.1.2 crossflow filtrationa filtration process in which thefeed flows almost parallel to the filter or membrane surface. Itis also called tangential flow.3.1.3 fluxa measure of the rate at which the permeate (orfiltrate) passes through the
8、membrane per unit area of mem-brane. It is reported in units of L/m2/day, m3/m2/day, orgal/ft2/day.3.1.4 foulingthe accumulation of unwanted deposits orscales on a membrane that results in a flux reduction.3.1.5 Langelier Saturation Index (LSI)a method used todetermine the calcium scaling potential,
9、 that is, calciumcarbonate of a membrane at concentrations below 5000 ppmTDS.3.1.6 membrane technologyseparation of the componentsof a fluid by means of a pressure gradient and a semipermeablemembrane. The various classes of membrane technology aredifferentiated primarily by the size or molecular we
10、ight, orboth, of rejected material. The main divisions are (1) micro-filtration (MF), (2) ultrafiltration (UF), (3) nanofiltration (NF),and (4) reverse osmosis (RO).3.1.7 microfiltration (MF)a pressure-driven processwhereby a contaminated liquid stream is separated using afiltration process involvin
11、g a compatible membrane. Dead-ended and crossflow techniques are used. Suspended solids andmacromolecules are removed on the basis of size. Pore size isnormally 0.1 to 5.0 m, and operating pressures usually rangefrom 20 to 350 kPa (3 to 50 psig). Membrane materials, suchas polypropylene, polytetrafl
12、uoroethylene (PTFE), and metaloxides, are frequently less susceptible to chemical degradationthan those used for other branches of this technology.3.1.8 nanofiltration (NF)a pressure-driven processwhereby a contaminated liquid stream is separated and purifiedby a process involving filtration, diffus
13、ion, and chemicalpotential across a compatible membrane. Divalent and multi-valent species with a molecular weight above 80 are removedas are uncharged and univalent molecules with a molecularweight above 200. Operating pressures normally run between1380 and 2760 kPa (200 and 400 psig).1This guide i
14、s under the jurisdiction of ASTM Committee F20 on HazardousSubstances and Oil Spill Response and is the direct responsibility of SubcommitteeF20.22 on Mitigation Actions.Current edition approved April 10, 1996. Published June 1996.2For referenced ASTM standards, visit the ASTM website, www.astm.org,
15、 orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.3.1.9 osmotic p
16、ressureas related to membrane technol-ogy, the pressure that must be applied to the more concentratedsolution to halt flow of the solvent from the less concentratedsolution through a semipermeable membrane into the moreconcentrated side.3.1.10 permeate, filtratethe stream that has passedthrough the
17、membrane and is therefore free of, or has a muchreduced concentration of, contaminants. Permeate is com-monly used for the treated water obtained from nanofiltrationand reverse osmosis processes, while filtrate is more com-monly used for the treated fluid obtained by ultrafiltration andmicrofiltrati
18、on operation.3.1.11 pervaporation (PV)a vacuum-driven membraneprocess applicable to the separation of liquid mixtures. Duringthe separation, the dissolved, more volatile constituents areremoved from a less volatile carrier stream, as a vapor, througha semipermeable membrane and then condensed on the
19、 down-stream side. This energy-intensive process is still in thedevelopment stage, but it has the potential of being a verypromising spill mitigation technology.3.1.12 reverse osmosis (RO)a pressure-driven process inwhich a liquid stream is separated and hence purified bypassing it over the surface
20、of a semipermeable membrane. Bothdissolved and suspended materials in a molecular weight rangefrom 40 to 200 are removed, with charged species beingremoved more easily. In the case of nonpolar molecules,molecular structure “bulkiness” becomes important. Some arerejected well with a molecular weight
21、of 60, while others witha molecular weight of 100 are not. Differences among mem-brane material can be very important in this aspect. Thisprocess discriminates between solutes on the basis of theirability to either (1) preferentially adsorb onto the membranepore surfaces and move through the membran
22、e pores bycapillary action, or (2) dissolve in and diffuse through themembrane. Reverse osmosis uses applied pressures between1380 and 10 350 kPa (200 and 1500 psig).As the concentrationdifference between the solutions on the two sides of themembrane increases, the osmotic pressure of the solutionin
23、creases and, in turn, the applied pressure requirement. Ingeneral, solutions containing organic and inorganic compoundsranging from low ppm up to 55 000 ppm are commonly treatedwith this technique.3.1.13 semipermeable membranemembranes that are se-lective in the components that they allow to pass th
24、rough them.3.1.14 ultrafiltration (UF)a pressure-driven processwhereby a contaminated liquid stream is separated and purifiedby a crossflow filtration process involving a compatible mem-brane. Suspended solids and dissolved molecules in the 500 to300 000 molecular weight range are removed mainly on
25、thebasis of size. This represents a membrane that has a pore sizeranging between 0.0015 and 0.2 m. Ultrafiltration usespressures of 105 to 1380 kPa (15 to 200 psig).4. Significance and Use4.1 GeneralThis guide contains information regarding theuse of membrane technology to recover and concentratehaz
26、ardous materials that have entered surface and ground wateras the result of a spill. Membrane technology may be appliedalone or in conjunction with other treatment techniques, asfollows:4.1.1 Different types of membrane are used in series withfilters to treat highly contaminated solutions reaching c
27、oncen-tration levels of several parts per million of organic andinorganic materials.4.1.2 Different types of membranes are applied in series totreat very dilute concentrations (parts per billion level) oforganic and inorganic compounds. Each membrane type hasthe ability to remove specific compounds,
28、 thus producing aconcentrated fraction. This fraction may require final off-sitetreatment but provides a significant reduction in transportationcosts due to the large volume reduction achieved.4.1.3 Membranes may be used in conjunction with destruc-tion technologies such as advanced oxidation proces
29、ses(AOPs). This method is recommended for dilute solutions. Themembrane technology portion concentrates the compounds toan optimum level for AOP destruction.5. Constraints on Usage5.1 GeneralApplication of membrane technology to thecleanup of spills results in the generation of two streams. Thefirst
30、 stream is treated and has a reduced concentration ofcontaminants, while the second is concentrated and has anincreased concentration of contaminants. This concentratedstream must be destroyed, reprocessed, or disposed of in anappropriate manner. There may also be constraints that arecreated by the
31、physical and chemical sensitivity of membranesand, as a result, characteristics of a membrane system must betaken into consideration whenever membrane units are used.These considerations are described as follows.5.1.1 Membrane Material:5.1.1.1 The material used to construct the membrane iscrucial to
32、 its success. In general, for spill remediation, the UF,NF, and RO membranes require materials that have a goodtemperature and pH resistance, as well as chemical stability, toensure that the membrane is unaffected by the solution beingtreated. The increasing demands on the performance of mem-brane m
33、aterials are exceeding the capability of organic poly-mers currently available. Consequently, inorganic membraneshave been developed in order to satisfy the need for betterperformance. Today, high-quality organic and inorganic mem-branes are commercially available.5.1.1.2 Inorganic membranes are cla
34、ssified in four groups:ceramic, carbon, metal, and polymer analog. Many develop-ments in inorganic membranes have been achieved, but manyinconveniences have yet to be overcome, such as their highcost and low surface area/volume, which retards the expansionof their application. In the case of organic
35、 materials, severalkinds of polymers are used that allow for the development ofmembranes with various properties. The following improve-ments might be noticed: lower cost, longer life time, lowerreplacement rates, reduced chemical consumption, reducedoperating pressure for given flux level, use in a
36、 broader rangeof pH, higher ion rejection, easier cleaning due to effectivefoulant removal and reduced biological attack, lower energyconsumption, as well as reduction of capital cost. Polymericmembranes with very high performance have been designed,F 1525 96 (2001)2but their great complexity makes
37、commercialization difficult.Polymeric membranes currently on the market are available insymmetric and asymmetric configurations.5.1.1.3 Asymmetric membranes are more commonly avail-able than the symmetric type, especially for UF, NF, and RO.These asymmetric membranes are made of two layers of thesam
38、e polymer. They have a thin and dense surface skin and aporous substructure that adds strength and support to the thinskin without reducing the permeate flow. The symmetricconfiguration has a homogenous structure that provides a veryhigh hydraulic resistance. Another type of membrane, verysimilar to
39、 the asymmetric, is the thin film composite. The mostobvious difference is that the two layers are made individually,from two different kinds of polymers for better performance.The characteristics of several polymeric materials currentlyavailable are listed in Table 1.5.1.2 Pretreatment:5.1.2.1 Pret
40、reatment of the feed is of primary concern whenmembranes are used in spill cleanup.Although each membraneconfiguration is affected differently by inorganic foulants, mostmembranes are affected adversely by oil, grease, and parts permillion concentrations of inorganic compounds, including iron,mangan
41、ese, magnesium, calcium, carbonate ion, and sulphatespecies. Some organic species, especially at high ppm levels,may also have detrimental effects and cause irreversibledamage to the membranes.5.1.2.2 The pH of the feed solution is often adjusted todissolve or precipitate inorganics, to prevent memb
42、rane foulingon the membrane surface that leads to a performance decline(that is, lower permeate flow rate and increased pressure dropbetween the feed and concentrate sides). The degree ofpretreatment required will depend on the concentration offoulants in the feed stream, membranes used, and membran
43、ecleaning schedule.5.1.3 Membrane Cleaning Agents:5.1.3.1 A membrane cleaning schedule will depend on theseverity of membrane fouling. As mentioned above, a decreasein permeate flow of more than 10 % of the normal flow ratewill generally be an indication that cleaning or flushing, orboth, is require
44、d. It is also good practice to conduct membranecleaning during periodic maintenance or before long shutdownperiods. It is useful to determine the type of foulants on themembrane surface before cleaning. Chemical analysis is thebest method; however, in situations in which this may not bepossible, fou
45、lants may be determined by other means such asvisual inspection. Chemical cleaning clears the membranesurface by dissolving the fouling substances with reagents.Table 2 provides a description of common inorganic foulants.5.1.3.2 Each major foulant type will require a specificcleaning procedure. If t
46、he performance does not improvesufficiently after the first cleaning procedure, the application ofanother procedure may lead to a better result. Fouling on themembrane surface is usually complex and often requiresseveral cleaning procedures successively. For example, succes-sive cleaning with deterg
47、ent and citric acid results in generallymore effective cleaning than either alone. Table 3 lists severalof the common cleaning agents used for membranes.5.1.4 Flushing and Cleaning Procedures:5.1.4.1 FlushingOne of the most convenient foulant re-moval procedures is flushing. Flushing cleans the memb
48、ranesurface using a large quantity of feedwater at low pressure. Itis effective for cleaning membranes that have been slightlyfouled. The general operating conditions are as follows:(1) Flushing WaterPermeate (treated water),(2) Pressure190 to 590 kPa (28 to 86 psi),(3) Water Flow RateHigh flow rate
49、 but pressure droplimited to less than 10 psi/element,(4) TemperatureAmbient but less than 30C (86F), and(5) Period0.5 h.5.1.4.2 Cleaning (Polymer Membranes Only)Chemicalcleaning is ordinarily used after the flushing procedure. A flushis also recommended after chemical cleaning to wash offdissolved solids and suspended solids in the modules. Thegeneral operating conditions for UF membranes are as follows:It is important to realize that the operating conditions differaccording to the type of membrane used. Therefore, it isstrongly recommended to refer to the m
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