1、Designation: D8002 15Standard 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.1. Scope1.1 This test method covers the determination of the modi-fied fouling index (MFI) of water measured at constantpressure. This test can be used to
3、 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 is not an absolute measure-ment of the quantity of p
4、articulate 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 asstandard. No other units of measurement are included i
5、n 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 applica-bility of regulatory limitations prior to use.
6、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 Sampling Water from Closed ConduitsD4189 Test Method for Si
7、lt 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. Terminology3.1 Definitions:3.1.1 For definitions of te
8、rms 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 filter. D27774. Summary of Test Method4.1 Water is passed
9、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. Significance and Use5.1 This test method is an alternative
10、 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, and time.5.2 The MFI-0.45 can serve as a useful indicat
11、ion 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 tendency of some water treatment equipment such asrev
12、erse 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 steel, galvanized steel, castiron, and copper alloys. Su
13、itable filter holders, designed towithstand an operational gage pressure of 350 kPa, can beobtained from suppliers of membrane filters. The filter holdershould be equipped with a device releasing air.1This test method is under the jurisdiction of ASTM Committee D19 on Waterand is the direct responsi
14、bility of Subcommittee D19.08 on Membranes and IonExchange Materials.Current edition approved July 15, 2015. Published August 2015. DOI: 10.1520/D8002-15.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMS
15、tandards volume information, refer to the standards Document Summary page onthe ASTM website.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States16.2 Membrane Filter:6.2.1 Membrane, white hydrophilic, mixed cellulose nitrate(5075 %) and mi
16、xed 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 mL.6.2.7 Pressure Difference across Membrane Filter, 200
17、 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 flow meter or mass balance.6.5 Computer or data-collectin
18、g 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.7.2 Before installing the membrane filter, flush the water tobe tested through the apparatus to re
19、move contaminants. ForNOTE 1PI is pressure indicator; PC is pressure 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 152sampling, follow the procedure given in Practices D
20、3370.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 sample to be tested is not super saturated withair or nitrogen
21、.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 holder. Handle the membrane filteronly with dull tweezer
22、s 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 properlyplaced.7.6 Replace the top of the half of the filter holder a
23、nd 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 a filter holder. Thesedisposables should be equipped wit
24、h 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 recordedwith nonplugging reference water. This water can be obtai
25、ned 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 at 200 6 2 kPa throughout the test.NOTE 8In many cases, e
26、specially 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 membrane filter may beretained for future reference.8. Ca
27、lculation8.1 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 compression or increasingrejection or both as a result of narro
28、wing 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 the foulingtendency of a given water (Eq 1 and Eq 2).tV51
29、Qavg5RmPA1I2PA2V (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, N/m2, andA = membrane surface area, m2.8.3 The gradient
30、 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 term, I, represents the fouling index forthe propensity of p
31、articles 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, the MFI can be determinedfrom the gradient (b,dtdVdV) of t
32、he 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 from a plot of gradient overtime where gel filtration is
33、 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)The calculated slope is two times higher than in the standa
34、rd 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 of the test. However, a highly accurate pressure regulator
35、 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 pressure.9. Report9.1 Report the following information:9.
36、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 1539.1.3 The manufacturer of the 0.45-m membrane filterused for the test as well the manufacturers identification forthe membrane filter.10. Precision, B
37、ias, 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 laboratory analyti-cal measurements will be sufficient for
38、 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 over time (forexample, in a couple of hours). Consequently ma
39、ny 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 suggesting thatgel/cake filtration without compression occurs. Howe
40、ver, 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 kPa.10.3 Substantial differences have been observed in MFIv
41、alues 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 observedbetween membranes of the same manufacturer and betweendiffer
42、ent 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 specificmanufacturer and dependent on the type of water; as aconseq
43、uence, the correction factor (if required) should beaccomplished with natural water and locally.NOTE 12Typically, the higher the normalized permeability/cleanwater flux, the higher the MFI.10.4 BiasThe bias of this test method cannot be deter-mined because the test method is based upon waters of cho
44、ice,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 accuracy of the pressure regulators applied.10.7 In practice,
45、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 particulate matter, forexample, corrosion products, which
46、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 useful if said application is forseawater purposes. In this c
47、ase, 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. Calibration and calibration verification will not berequired
48、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, accuracy, correctness) ofthe obtained MFI values depend o
49、n 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, 1 mg/L of formazinein deionized distilled waterwillproduce a
