1、Designation: D 4692 01 (Reapproved 2006)e1Standard Practice forCalculation and Adjustment of Sulfate Scaling Salts (CaSO4,SrSO4, and BaSO4) for Reverse Osmosis and Nanofiltration1This standard is issued under the fixed designation D 4692; the number immediately following the designation indicates th
2、e year oforiginal adoption or, in the case of revision, 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.e1NOTESections 2 and 3.1 were updated editorially in February
3、 2007.1. Scope1.1 This practice covers the calculation and adjustment ofcalcium, strontium, and barium sulfates for the concentratestream of a reverse osmosis or nanofiltration system. Thecalculations are used to determine the need for scale control inthe operation and design of reverse osmosis and
4、nanofiltrationinstallations. This practice is applicable for all types of reverseosmosis devices (tubular, spiral wound, and hollow fiber) andnanofiltration devices.1.2 This practice is applicable to both brackish waters andseawaters.2. Referenced Documents2.1 ASTM Standards:2D511 Test Methods for C
5、alcium and Magnesium In WaterD 516 Test Method for Sulfate Ion in WaterD 1129 Terminology Relating to WaterD 3352 Test Method for Strontium Ion in Brackish Water,Seawater, and BrinesD 4194 Test Methods for Operating Characteristics of Re-verse Osmosis and Nanofiltration DevicesD 4195 Guide for Water
6、 Analysis for Reverse OsmosisApplicationD 4382 Test Method for Barium in Water, Atomic Absorp-tion Spectrophotometry, Graphite FurnaceD 6161 Terminology Used for Microfiltration, Ultrafiltra-tion, Nanofiltration and Reverse Osmosis Membrane Pro-cesses3. Terminology3.1 DefinitionsFor definitions of t
7、erms used in this prac-tice, refer to Terminology D 1129 and D 6161.3.2 Definitions of Terms Specific to This Standard:3.2.1 For definitions of terms relating to reverse osmosis,refer to Test Methods D 4194.4. Summary of Practice4.1 This practice consists of calculating the potential forscaling by C
8、aSO4, SrSO4, and BaSO4in a reverse osmosis ornanofiltration concentrate stream from the concentration of Ca+,Sr+,Ba+, and SO45in the feed solution and the recovery ofthe reverse osmosis or nanofiltration system.4.2 This practice also presents techniques to eliminatescaling by decreasing the recovery
9、, by decreasing the Ca+,Sr+, and Ba+concentrations in the feed water, and byaddition of scale inhibitors.5. Significance and Use5.1 In the design and operation of reverse osmosis andnanofiltration installations, it is important to predict the CaSO4,SrSO4, and BaSO4scaling properties of the concentra
10、testream. Because of the increase in total dissolved solids and theincrease in concentration of the scaling salts, the scalingproperties of the concentrate stream will be quite different fromthose of the feed solution. This practice permits the calculationof the scaling potential for the concentrate
11、 stream from the feedwater analyses and the reverse osmosis or nanofiltrationoperating parameters.5.2 Scaling by CaSO4, SrSO4, and BaSO4will adverselyaffect the reverse osmosis or nanofiltration performance. Thispractice gives various procedures for the prevention of scaling.6. Procedure6.1 Determin
12、e the concentrations of Ca+,Sr+,Ba+, andSO45in the feed stream in accordance with Test MethodsD 511, D 3352, D 4382, and D 516, respectively.NOTE 1If H2SO4is used for control of CaCO3scale, measure theSO45after acid addition.6.2 Determine the concentration of all major ions using theappropriate meth
13、ods given in Guide D 4195. At a minimum,the concentrations of Mg+,Na+, HCO3, and Clmust bedetermined.1This 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 Dec. 15,
14、 2006. Published February 2007. Originallyapproved in 1987. Last previous edition approved in 2001 as D 4692 01.2For 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
15、standards Document Summary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.7. Calculation7.1 Calculate the calcium concentration in the concentratestream from the calcium concentration in the feed solution,fro
16、m the recovery of the reverse osmosis or nanofiltrationsystem, and from the calcium ion passage as follows:Cac5 Caf31 2 Y SPCa!1 2 Ywhere:Cac= calcium ion concentration in concentrate, mg/L,Caf= calcium ion concentration in feed, mg/L,Y = recovery of the reverse osmosis system, expressedas a decimal
17、, andSPCa= calcium ion passage, expressed as a decimal.NOTE 2SPCacan be obtained from the supplier of the reverse osmosisor nanofiltration system. For most reverse osmosis and nanofiltrationdevices, SPCacan be considered to be zero, in which case the equationsimplifies to:Cac5 Caf311 2 YThis assumpt
18、ion will introduce only a small error.7.2 Calculate the SO45concentration in the concentratestream from the SO45concentration in the feed solution, fromthe recovery of the reverse osmosis or nanofiltration system,and from the sulfate ion passage by using the appropriatesubstitutions in the equation
19、given in 7.1. The simplifiedequation can be used.7.3 Calculate the concentration of the major ions in theconcentrate stream using the appropriate substitutions in theequation given in 7.1. The simplified equation can be used.7.4 Calculate the ionic strength of the concentrate stream asfollows:Ic512(
20、 miZi2where:Ic= ionic strength of concentrate stream,mi= molal concentration of ion, i (moles/1000 g ofwater) in the concentrate stream, andZi= ionic charge of ion, i.NOTE 3The molal concentration is calculated as follows:mi5Ci1000 MWiF1062 TDS106 G51000 CiMWi1062 TDS!where:Ci= concentration of ion,
21、 i, in concentrate stream, mg/L,MWi= molecular weight of ion, i, andTDS = total dissolved solids in concentrate stream, mg/L.7.5 Calculate the ion product (IPc) for CaSO4in theconcentrate stream as follows:IPc5 mCa11!cmSO45!cwhere:(mCa+)c= M Ca+in concentrate, mol/L andmSO45)c= M SO45in concentrate,
22、 mol/L.7.6 Compare IPcfor CaSO4with the solubility product (Ksp) of CaSO4at the ionic strength of the concentrate stream(Fig. 1).3If IPc Ksp, CaSO4scaling will occur andadjustment is required.NOTE 4Some suppliers use a safety factor. Check with the supplier ofthe reverse osmosis or nanofiltration de
23、vice to determine if some fractionof the Ksp, for example 0.8 Ksp, should be used to compare with IPc.3Marshall, W. L. and Slusher, R., “Solubility to 200C of Sulfate and itsHydrates in Sea Water and Saline Water Concentrates and Temperature, Concen-tration Limits,” Journal of Chemical and Engineeri
24、ng Data, Vol 13, No. 1, 1968, p.83.FIG. 1 Kspfor CaSO4versus Ionic StrengthD 4692 01 (2006)e127.7 Determine the scaling potential for SrSO4using theappropriate substitution in steps 7.1 to 7.4. Compare IPcforSrSO4with the Kspof SrSO4at the ionic strength of theconcentrate stream (Fig. 2).47.8 Determ
25、ine the scaling potential for BaSO4using theappropriate substitutions in steps 7.1-7.4. Compare IPcforBaSO4with the Kspof BaSO4at the ionic strength of theconcentrate stream (Fig. 3).48. Adjustments for Scale Control8.1 If the IPcfor CaSO4, SrSO4, and BaSO4is less than theKspor the recommended fract
26、ion of Ksp, a higher recovery canbe used with respect to scaling by the various salts. Reiterationof the calculations at higher recovery can be used to determinethe maximum conversion with respect to scaling by the varioussalts.8.2 If the IPcfor CaSO4, SrSO4, or BaSO4is greater thanthe Kspof the rec
27、ommended fraction of Ksp, a lower recoverymust be used to prevent scaling. Reiteration of the calculationsat lower recovery can be used to determine the allowablerecovery with respect to scaling by the various salts.8.3 If the maximum allowable recovery is lower thandesired, sodium cycle ion exchang
28、e (softening) can be used toremove all or part of the Ca+,Sr+, and Ba+. This will permithigher recovery of the reverse osmosis or nanofiltration systemwith respect to scaling by the various salts.8.4 Lime softening with lime or lime plus soda ash willdecrease the Ca+concentration and thus permit hig
29、her con-version with respect to scaling by CaSO4.8.5 Addition of a scale inhibitor to the feed stream permitsoperation of the reverse osmosis or nanofiltration system abovethe Kspvalue. Check with supplier of the reverse osmosis ornanofiltration system to determine compatibility of inhibitors,concen
30、tration of the inhibitor needed, and amount by which theKspcan be exceeded when a scale inhibitor is used.9. Reverse Osmosis or Nanofiltration in Operation9.1 Once a reverse osmosis or nanofiltration system isoperating, the scaling potential of CaSO4, SrSO4, and BaSO4can be directly calculated from
31、the analyses of the concentratestream and compared with the projected scaling potentialcalculated above.10. Use of Computers for the Determination of ScalingPotential10.1 The preceding calculations are adaptable to simplecomputer analysis.11. Keywords11.1 barium; calcium; membrane fouling; membrane
32、scal-ing; nanofiltration; reverse osmosis; strontium; sulfate scaling4Davis, J. W. and Collins, A. G., “Solubility of Barium and Strontium Sulfatesin Strong Electrolyte Solutions,” Environmental Science and Technology, Vol 5, No.10, 1971, p. 1039.FIG. 2 Kspfor SrSO4versus Ionic StrengthD 4692 01 (20
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35、tandardsand should be addressed to ASTM International Headquarters. Your comments will receive careful consideration at a meeting of theresponsible technical committee, which you may attend. If you feel that your comments have not received a fair hearing you shouldmake your views known to the ASTM C
36、ommittee on Standards, at the address shown below.This standard is copyrighted by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,United States. Individual reprints (single or multiple copies) of this standard may be obtained by contacting ASTM at the aboveaddress or at 610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website(www.astm.org).FIG. 3 Kspfor BaSO4versus Ionic StrengthD 4692 01 (2006)e14
