1、Designation: D 6908 06Standard Practice forIntegrity Testing of Water Filtration Membrane Systems1This standard is issued under the fixed designation D 6908; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision
2、. 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 practice covers the determination of the integrity ofwater filtration membrane elements and systems using airbased tests (pre
3、ssure decay and vacuum hold), soluble dye,continuous monitoring particulate light scatter techniques, andTOC monitoring tests for the purpose of rejecting particles andmicrobes. The tests are applicable to systems with membranesthat have a nominal pore size less than about 1 m. The TOC,and Dye, test
4、s are generally applicable to NF and RO classmembranes only.1.2 This practice does not purport to cover all availablemethods of integrity testing.1.3 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this stan
5、dard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D 1129 Terminology Relating to WaterD 2777 Practice for Determination of Precision and Bias ofApplicable Test Methods of Commi
6、ttee D19 on WaterD 3370 Practices for Sampling Water from Closed ConduitsD 3864 Guide for Continual On-Line Monitoring Systemsfor Water AnalysisD 3923 Practices for Detecting Leaks in Reverse OsmosisDevicesD 4839 Test Method for Total Carbon and Organic Carbonin Water by Ultraviolet, or Persulfate O
7、xidation, or Both,and Infrared DetectionD 5173 Test Method for On-Line Monitoring of CarbonCompounds in Water by Chemical Oxidation, by UV LightOxidation, by Both, or by High Temperature CombustionFollowed by Gas Phase NDIR or by Electrolytic Conduc-tivityD 5904 Test Method for Total Carbon, Inorgan
8、ic Carbon,and Organic Carbon in Water by Ultraviolet, PersulfateOxidation, and Membrane Conductivity DetectionD 5997 Test Method for On-Line Monitoring of Total Car-bon, Inorganic Carbon in Water by Ultraviolet, PersulfateOxidation, and Membrane Conductivity DetectionD 6161 Terminology Used for Micr
9、ofiltration, Ultrafiltra-tion, Nanofiltration and Reverse Osmosis Membrane Pro-cessesD 6698 Test Method for On-Line Measurement of TurbidityBelow 5 NTU in WaterE20 Practice for Particle Size Analysis of Particulate Sub-stances in the Range of 0.2 to 75 m by Optical Micros-copy3E 128 Test Method for
10、Maximum Pore Diameter and Per-meability of Rigid Porous Filters for Laboratory UseF 658 Practice for Calibration of a Liquid-Borne ParticleCounter Using an Optical System Based Upon LightExtinction3. Terminology3.1 DefinitionsFor definitions of terms used in this prac-tice, refer to Terminologies D
11、6161 and D 1129.3.1.1 For description of terms relating to cross flow mem-brane systems, refer to Terminology D 6161.3.1.2 For definition of terms relating to dissolved carbonand carbon analyzers, refer to D 5173, D 5904 and D 5997.3.1.3 bubble pointwhen the pores of a membrane arefilled with liquid
12、 and air pressure is applied to one side of themembrane, surface tension prevents the liquid in the poresfrom being blown out by air pressure below a minimumpressure known as the bubble point.3.1.4 equivalent diameterthe diameter of a pore or defectcalculated from its bubble point using Eq 1 (see 9.
13、3). This isnot necessarily the same as the physical dimensions of thedefect(s).3.1.5 integritymeasure of the degree to which a mem-brane system rejects particles of interest. Usually expressed asa log reduction value (LRV).3.1.6 log reduction value (LRV)a measure of the particleremoval efficiency of
14、 the membrane system expressed as thelog of the ratio of the particle concentration in the untreated1This practice is under the jurisdiction of ASTM Committee D19 on Water andis the direct responsibility of Subcommittee D19.08 on Membranes and IonExchange Materials.Current edition approved July 1, 2
15、006. Published July 2006. Originally approvedin 2003. Last previous edition approved in 2005 as D 6908 05.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standa
16、rds Document Summary page onthe ASTM website.3Withdrawn.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.and treated fluid. For example, a 10-fold reduction in particleconcentration is an LRV of 1. The definition of LRV within thisSta
17、ndard is one of many definitions that are used within theindustry. The user of this standard should use care as not tointerchange this definition with other definitions that poten-tially exist. The USEPA applies the LRV definition to patho-gens only.3.1.7 membrane systemrefers to the membrane hardwa
18、reinstallation including the membrane, membrane housings,interconnecting plumbing, seals and valves.The membrane canbe any membrane with a pore size less than about 1 m.3.1.8 multiplexingthe sharing of a common set of physi-cal, optical, and/or electrical components across multiplesystem sample poin
19、ts. Two approaches of multiplexing areconsidered in this practice: sensor multiplexing and liquidmultiplexing. Sensor multiplexing monitors a unique samplewith a dedicated sensor. Sensors are linked to a centralizedlocation, where data processing and the determinative mea-surement is performed. Liqu
20、id multiplexing uses a commoninstrument to measure multiple process sample streams in asequential manor. Samples are fed to the common analyzer viaa system of a manifold, valves and tubing.3.1.9 relative standard deviation (RSD)a generic continu-ous monitoring parameter used to quantify the fluctuat
21、ion ofthe particulate light scatter baseline from a laser-based incidentlight source. As an example, the RSD may be calculated as thestandard deviation divided by the average for a defined set ofmeasurements that are acquired over a short period of time.The result is multiplied by 100 to express the
22、 value as apercentage and is then reported as % RSD. The samplemonitoring frequency is typically in the range of 0.1 to 60seconds. The RSD parameter is specific for laser-based par-ticulate light-scatter techniques which includes particlecounters and laser turbidimeters. The RSD is can be treated as
23、an independent monitoring parameter. Other methods for RSDcalculations may also be used.3.1.10 UCLa generic term to represent the aggregatequantity of material that causes an incident light beam to bescattered. The value can be correlated to either turbidity or tospecific particle count levels of a
24、defined size.4. Significance and Use4.1 The integrity test methods described are used to deter-mine the integrity of membrane systems, and are applicable tosystems containing membrane module configurations of bothhollow fiber and flat sheet; such as, spiral-wound configuration.In all cases the pract
25、ices apply to membranes in the RO, NF,and UF membrane classes. However, the TOC and Dye Testpractices do not apply to membranes in the MF range or theupper end of the UF pore size range (0.01 m and larger poresizes) due to insignificant or inconsistent removal of TOCmaterial by these membranes.4.2 T
26、hese methods may be used to identify relative changesin the integrity of a system, or used in conjunction with theequations described in 9.4, to provide a means of estimating theintegrity in terms of log reduction value. For critical applica-tions, estimated log reductions using these equations shou
27、ld beconfirmed by experiment for the particular membrane andsystem configuration used.4.3 The ability of the methods to detect any given defect isaffected by the size of the system or portion of the systemtested. Selecting smaller portions of the system to test willincrease the sensitivity of the te
28、st to defects. When determiningthe size that can be tested as a discrete unit, use the guidelinessupplied by the system manufacturer or the general guidelinesprovided in this standard.4.4 The applicability of the tests is largely independent ofsystem size when measured in terms of the impact of defe
29、cts onthe treated water quality (that is, the system LRV). This isbecause the bypass flow from any given defect is diluted inproportion to the systems total flowrate. For example, a10-module system with a single defect will produce the samewater quality as a 100-module system with ten of the same si
30、zedefects.5. Reagents and Materials5.1 ReagentsAs specified for the TOC analyzer in ques-tion. D 5173 lists requirements for a variety of instruments.5.2 Soluble Dye SolutionUse FD that is, the conservative situation of cosu = 1. In practicemost membranes used in water treatment have a contact angle
31、greater than zero, which is represented by the shaded regionunder the solid line in Fig. 3. If the contact angle is known orcan be determined, Eq 1 may be used. However, if the contactangle is not known, a conservative estimate of the test pressurerequired can be made by applying Eq 2.9.3.3 The test
32、 pressure is usually selected to ensure that theminimum defect diameter picked up by the test is smaller thancontaminates or particles of interest. For example, Eq 2indicates that a test pressure of 100 kPa would include alldefects larger than or equal to 3 m.Alower pressure could beused for less hy
33、drophilic membranes. For example, if thecontact angle is 60 degrees (typical for polypropylene, polysul-fone, or PVdF) Eq 1 indicates that defects of 3 m would beincluded at a test pressure of 50 kPa. An even lower testpressure may be used for larger defects, such as for exampledetection of broken f
34、ibers in a hollow fiber system.9.3.4 In practice the applied test pressure is rarely more than300 kPa, which is usually sufficient to include defects smallerthan most pathogens of interest. At this pressure limit the testis not suitable for direct validation of virus rejection as theseparticles are
35、very small (typically less than 0.01 m) with acorresponding test pressure of several thousand kilopascals.9.4 Interpreting PDR and VDR Results as Log ReductionValuesBoth the PDR and the VDR are measurements of theairflow from one side of the membrane to the other under aknown set of test conditions
36、(temperature and pressure). Thisinformation can be used to estimate the flow of liquid throughthe same defects during filtration conditions. This provides anestimate of the membrane bypass flow and thereby an estimateof the log removal of particles for the system. One approach isbased on the Hagen-P
37、oiseuille law, which assumes laminarflow through cylindrical defects. Whilst this method provides auseful estimate, its applicability is limited to small fibers ( 300 to 400 m lumen diameter) which can leadto error in the calculated LRV.As with all methods to correlateintegrity test results to LRV t
38、he relationship should be verifiedby field tests for the particular membrane and configurationused.X2. GUIDANCE TO OBTAINING RELIABLE AND QUALITY MEASUREMENT DATA FROM CONTINUOUSMONITORING SYSTEMSX2.1 Throughout Practice D, there contains several piecesof key sampling information related to instrume
39、nt setup,sampling and data handling that aid in achieving optimumreliability and sensitivity for these technologies.Asummary ofthis information is provided below:X2.1.1 Common turbimeters such as those that comply withUSEPA method 180.1 are not suggested for use due to havinglower sensitivity. Laser
40、 turbidimeters with a greater sensitivityare suggested (see 22.3).X2.1.2 Insure instrumentation is installed at appropriatesample points that insure a homogeneous and representativesample. Sample points that insure filtrate or permeate waterchanges direction (such as following a 90-degree elbow) are
41、suggested (see 23.3.1).X2.1.3 Instrument bodies (sensor bodies) must be condi-tioned prior to the establishment of any baseline that is used foran upper control limit (UCL) or alarm condition. A stablecontinuous monitoring baseline is represented by a levelmeasurement values that are void of random
42、and unpredictedspikes (see 25.1).X2.1.4 Continuous monitoring methods can be applied toeither positive or negative filtration, but both types requiredifferent sampling to minimize bubble interference. The fol-lowing information can be used as guidance for specific typesof membranes:X2.1.4.1 For UF,
43、NF and RO systems with no air backwashrequire the least amount of sampling conditioning becausebubble generation during the cleaning processes in minimal.Typically, reverse-flow cleanings do not cause spikes in themeasured values. Standard sampling protocols that are pro-vided by the instrument manu
44、facturers are adequate (see 23.3).X2.1.4.2 MF and UF systems that are outside infiltrationprocesses often use air scour at the within filtration cycle. Forthese systems, bubble generation and subsequent bubble inter-ference can occur. For these systems bubble interferences areminimized through the u
45、se of: (1) sample chambers that can bepressurized to prevent further outgassing (see 25.1); (2) addi-tional bubble traps such as those that contain a larger volumemay be added to dampen bubble interference (see 25.1); (3) theintegration of a signal from the rack that indicates the stoppageof forward
46、 filtration flow can be fed to either the plant(SCADA) system or data logging program. Under this condi-tion data is either ignored or not logged (see 25.2); and (4) atime lag should be incorporated into the data logging programto ignore data for the first 2 to 6 minutes (user changeable) afterthe c
47、ompletion of an air-scour cleaning procedure. This is to allfor air to vacate sample lines prior to resuming the logging ofmeasurement data (see 25.2). Many instruments contain mea-surement algorithms that aid in the reduction or rejection ofbubble interference (see 24.1).D69080619ASTM International
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