1、Designation: D8002 151Standard Test Method forModified Fouling Index (MFI-0.45) of Water1This standard is issued under the fixed designation D8002; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A number
2、 in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1NOTENote 12 was editorially corrected in June 2016.1. Scope1.1 This test method covers the determination of the modi-fied fouling index (MFI) of water m
3、easured at constantpressure. This test can be used to indicate the fouling potentialof reverse osmosis/nanofiltration (RO/NF) feed water dueparticulate matter and is applicable to low and high turbiditywaters. Since the size, shape, and nature of particulate matter inwater may vary, this test method
4、 is not an absolute measure-ment of the quantity of particulate matter.1.2 This test method is not applicable for reagent-gradewater Types I, II, and III of Specification D1193 or effluentsfrom most reverse osmosis and ultra-filtration systems.1.3 The values stated in SI units are to be regarded ass
5、tandard. No other units of measurement are included in thisstandard.1.4 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 standard to establish appro-priate safety and health practices and determine the a
6、pplica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D1129 Terminology Relating to WaterD1193 Specification for Reagent WaterD2777 Practice for Determination of Precision and Bias ofApplicable Test Methods of Committee D19 on WaterD3370 Practices for Sampli
7、ng Water from Closed ConduitsD4189 Test Method for Silt Density Index (SDI) of WaterD6161 Terminology Used for Microfiltration, Ultrafiltration,Nanofiltration and Reverse Osmosis Membrane ProcessesD7726 Guide for The Use of Various Turbidimeter Tech-nologies for Measurement of Turbidity in Water3. T
8、erminology3.1 Definitions:3.1.1 For definitions of terms used in this standard, refer toTerminologies D1129 and D6161.3.2 Definitions of Terms Specific to This Standard:3.2.1 modified fouling index, MFI-0.45, nindex calculatedfrom the development of filtration velocity through a 0.45-mmembrane filte
9、r. D27774. Summary of Test Method4.1 Water is passed through a 0.45-m membrane filter atconstant pressure of 200 kPa and the development of the rateof filtration is measured continuously.4.2 The MFI is calculated from the obtained data of flowversus time at constant pressure and temperature.5. Signi
10、ficance and Use5.1 This test method is an alternative for the silt densityindex (SDI) method (Test Method D4189) with the aim toovercome inaccuracies related to a nonlinear relation with thefouling potential due to particulate matter concentration, ab-sence of temperature correction, support pad, an
11、d time.5.2 The MFI-0.45 can serve as a useful indication of thequantity of particulate matter.5.3 The MFI-0.45 can be used to determine effectiveness ofvarious processes such as filtration or clarification used toremove particulate matter.5.4 The MFI-0.45 has empirically been correlated withfouling
12、tendency of some water treatment equipment such asreverse osmosis (RO) devices.6. Apparatus6.1 MFI AssemblyAs described in Fig. 1 and Fig. 2,wetted parts should be made of high-quality stainless or plasticto prevent contamination by corrosion products. Do not usereactive materials such as carbon ste
13、el, galvanized steel, castiron, and copper alloys. Suitable filter holders, designed towithstand an operational gage pressure of 350 kPa, can be1This test method is under the jurisdiction of ASTM Committee D19 on Waterand is the direct responsibility of Subcommittee D19.08 on Membranes and IonExchan
14、ge Materials.Current edition approved July 15, 2015. Published August 2015. DOI: 10.1520/D8002-15E01.2For 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 standards D
15、ocument Summary page onthe ASTM website.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1obtained from suppliers of membrane filters. The filter holdershould be equipped with a device releasing air.6.2 Membrane Filter:6.2.1 Membrane, w
16、hite hydrophilic, mixed cellulose nitrate(5075 %) and mixed cellulose acetate (MCE).6.2.2 Replaceable Highly Porous Foam Support Pad, to beplaced on the bottom of the filter holder.6.2.3 Mean Pore Size, 0.45 m.6.2.4 Diameter, 47 mm.6.2.5 Thickness, 115 to 180 m.6.2.6 Pure Water Flow, 25 to 50 s/500
17、mL.6.2.7 Pressure Difference across Membrane Filter, 200 kPa.6.2.8 Bubble Point, 179 to 248 kPa.6.2.9 Use only filters that are packaged in the same orien-tation.6.3 Thermometer or Sensor Suitable for Measuring Tem-perature of the Water Sample, capable of being read orregistered 61C.6.4 Electronic f
18、low meter or mass balance.6.5 Computer or data-collecting and processing device.7. Procedure7.1 Assemble apparatus as shown in Fig. 1 and Fig. 2including flow-measuring devices (electronic flow meter ormass balance) and set the pressure regulator at 200 kPa.NOTE 1PI is pressure indicator; PC is pres
19、sure controller.FIG. 1 Apparatus for Measuring MFI at Constant Pressure with a PumpFIG. 2 Representative Apparatus for Measuring MFI at Constant Pressure with a Pressure VesselD8002 15127.2 Before installing the membrane filter, flush the water tobe tested through the apparatus to remove contaminant
20、s. Forsampling, follow the procedure given in Practices D3370.Discrete samples can be used with appropriate pressurizingapparatus such as a pump or an air/nitrogen pressurized vessel.NOTE 1The pump should be of such a design that grinding flocs willnot occur or be minimal.NOTE 2Ensure that the sampl
21、e to be tested is not super saturated withair or nitrogen.7.3 Measure the temperature of the water.7.4 Open the membrane filter holder and place a 0.45-mmembrane filter (47 mm in diameter) on the support plate ofthe holder. A replaceable foam support pad needs to be placedon the support plate of the
22、 holder. Handle the membrane filteronly with dull tweezers to avoid puncturing. Avoid touchingthe membrane filter with fingers.NOTE 3Record the manufacturer of the membrane filter and manu-facturers identification for the membrane filter.7.5 Make sure the O-ring is in good condition and properlyplac
23、ed.7.6 Replace the top of the half of the filter holder and closeloosely.7.7 Bleed out air by opening the pressure relieve valve andopen the small air relieve valve on top of the filter holder.NOTE 4Apparatus making use of membranes of smaller diametersmight use a disposable membrane incorporated in
24、 a filter holder. Thesedisposables should be equipped with an air relieve device.7.8 Close the relieve valve and start recording flow (andpreferably pressure as well). Run the test for 30 to 60 mindepending on the rate of flow decline.NOTE 5The initial flow should be within 10 % of the flow recorded
25、with nonplugging reference water. This water can be obtained by filteringdistilled water through a 0.2-m pore size membrane filter.NOTE 6If the initial flow is more than 10 % higher than with referencewater, the filter might be cracked and a new filter should be used.NOTE 7The pressure shall remain
26、at 200 6 2 kPa throughout the test.NOTE 8In many cases, especially when dealing with raw water, thefouling rate will plug the filters very quickly, for example, in a matter ofa few minutes. A recommended time interval for data acquisition is aminimum of every 30 s.7.9 After completing the test, the
27、membrane filter may beretained for future reference.8. Calculation8.1 In this test, fouling of a flat-sheet membrane in dead-endfiltration at a constant transmembrane pressure is considered totake place in three steps: (1) pore blocking, (2) formation of anincompressible gel/cake, and (3) gel compre
28、ssion or increasingrejection or both as a result of narrowing pores in gel.8.2 During the gel filtration period, there exists a linearrelation between resistance (here expressed as reciprocal flowrate at standard conditions) and cumulative filtered watervolume (V), for which the slope (b) describes
29、the foulingtendency of a given water (Eq 1 and Eq 2).tV51Qavg5RmPA1I2PA2V (1)b 5I2PA25dtdVdV(2)where:t = filtration time, s,V = cumulative filtrate volume, L,Qavg= average flow rate, t/V, = water viscosity, Ns/m2,I = fouling index, l/m2,Rm= membrane resistance, l/m,P = applied transmembrane pressure
30、, N/m2, andA = membrane surface area, m2.8.3 The gradient of the line (b) has been defined as the MFI,as an index of the fouling potential of a feed water containingparticles for the fixed reference values of P0(200 kPa), (20C), and A0(13.8 10-4m2equivalent to 47-mm diametermembrane filter). The ter
31、m, I, represents the fouling index forthe propensity of particles in water to form a layer withhydraulic resistance:MFI 520CI2P0A02(3)NOTE 9MFI is expressed in units of s/L2. By doing this, the resultswill be in the same order of magnitude of SDI in the range 2 to 3.8.4 In conducting the MFI test, t
32、he MFI can be determinedfrom the gradient (b,dtdVdV) of the linear region of minimumslope determined in (a plot of) t/V versus V. Normalizing thisslope to standard conditions of temperature (Tcorr), pressure(Pcorr), and membrane area (Acorr) yields MFI as shown in Eq4. The MFI can also be determined
33、 from a plot of gradient overtime where gel filtration is observed as a minimum or stableMFI value depending on the length of cake filtration.MFI 5S20CTDSPP0DSAA0D2dtVdV5 Tcorr!Pcorr!Acorr!dtVdV(4)NOTE 10An alternative method for calculating MFI is based on thebasic equation:dtdV51Q5RmPA1IPA2V (5)Th
34、e calculated slope is two times higher than in the standard procedure;consequently, in calculating MFI, this factor has to be taken into account.This approach has the advantage that possible errors in time and flow atthe start of the test will not have an influence on the calculated slope incourse o
35、f the test. However, a highly accurate pressure regulator and flowmeasurement device are needed to obtain desired highly accurate MFIvalues.NOTE 11The MFI was initially developed using 0.45 and 0.05-mmembrane referred to as MFI-0.45 and MFI-0.05. Later on, the MFI-UFmethod was developed at constant
36、pressure.9. Report9.1 Report the following information:9.1.1 The MFI, with a subscript indicating the total elapsedflow time (T) in minutes,9.1.2 The water temperature before and after the test, andD8002 15139.1.3 The manufacturer of the 0.45-m membrane filterused for the test as well the manufactur
37、ers identification forthe membrane filter.10. Precision, Bias, and Quality Control10.1 The MFI test outcome is not a concentration orequivalent concentration; although some basic items are usefuland achievable in the MFI (0.45) test, this does not mean thatfull QC measures typically associated with
38、laboratory analyti-cal measurements will be sufficient for use with the MFI. TheMFI gives the fouling potential of the sample for RO/NFmembrane systems, and the use of a standard foulant is notuseful since RO/NF membranes are not/never exposed to sucha foulant. The fouling potential might change ove
39、r time (forexample, in a couple of hours). Consequently many laboratory-based statistical tests are not useful in practice. Usually a verylimited numbers of samples are tested in a series.10.2 The filtration curve plotted as t/V versus V and dt/dVversus V show usually a part that is linear suggestin
40、g thatgel/cake filtration without compression occurs. However, test-ing at a different pressure shows a clear pressure dependencyand still shows the linear relationships. Theory confirms thisobservation. Consequently, it is recommended not to deviatefrom the indicated transmembrane pressure of 200 k
41、Pa.10.3 Substantial differences have been observed in MFIvalues between membranes of different manufacturers. Thereasons for these observations are: differences in pore size,pore size distribution, surface porosity, shape of the pores, andmembrane material. Far fewer differences have been observedbe
42、tween membranes of the same manufacturer and betweendifferent batches. Empirical correction/normalization can beachieved by determining the correlation between initial nor-malized permeability (flux) and MFI. This correcting factor ismost likely specific for a certain type of membrane of a specificm
43、anufacturer and dependent on the type of water; as aconsequence, the correction factor (if required) should beaccomplished with natural water and locally.NOTE 12Typically, the higher the normalized permeability/cleanwater flux, the lower the MFI.10.4 BiasThe bias of this test method cannot be deter-
44、mined because the test method is based upon waters of choice,which may differ with each source, as provided for in PracticeD2777.10.5 It is the users responsibility to ensure the validity thetest method for waters of untested matrices.10.6 The accuracy and reproducibility depends further onthe accur
45、acy of the pressure regulators applied.10.7 In practice, MFI measurements are not performed induplicate; rather, the measurements are performed one or twotimes per shift or automatically with equipment.10.8 Conducting a test with blank water is useful to verifywhether or not the equipment releases p
46、articulate matter, forexample, corrosion products, which may result in a higher MFIvalues. A test with pure water (for example, reverse osmosispermeate or distillate) at least during initial of equipment useand thereafter once a month is recommended. A test withartificially prepared seawater is usef
47、ul if said application is forseawater purposes. In this case, pure water with sodiumchloride of a concentration equivalent to the seawater to betested can be used. Both blank test should give a MFI (0.45)value below 0.1 s/L2.10.9 In practice, the MFI test is a very basic, robust andstable test. Cali
48、bration and calibration verification will not berequired as the equipment used for the MFI (0.45) test is simpleand follows a basic procedure. The MFI target from membranemanufacturer lower or equal to 1 s/L2is equivalent to SDItarget (lower or equal 3 % per min).10.10 The quality (reproducibility,
49、accuracy, correctness) ofthe obtained MFI values depend on several parameters (forexample, pressure indicator, pressure controller, flowmeter ormass balance). In addition, the quality of the membrane filtersused also impacts quality control; consequently, the pores sizeand pore size distribution are important. This aspect is more orless covered by the requirement for pure water flow namely2550 seconds per 500 ml. This is the same as for SDI (TestMethod D4189). Should a calibration with a standard berequired,
