1、Designation: D1291 06 (Reapproved 2011)Standard Practice forEstimation of Chlorine Demand of Water1This standard is issued under the fixed designation D1291; 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 () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This practice provides a means of estimating the quan-tity of chlorine required to be added to a unit volume of waterto accomplish
3、a predetermined treatment objective or tocompletely react with all chlorine reactable substances in thewater, or both.1.2 Temperature, pH, and initial chlorine dosage are allvariables in estimating the optimum chlorination practice. Theeffects of these variables can be evaluated using this practice.
4、1.3 Chlorine residual is determined using Test MethodD1253.1.4 This practice is applicable to all types of water in whichthe stated treatment objective can be evaluated or residualchlorine can be measured, or both.1.5 The values stated in SI units are to be regarded asstandard. No other units of mea
5、surement are included in thisstandard.1.6 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 li
6、mitations prior to use. For a specifichazard statement, see Note 1.2. Referenced Documents2.1 ASTM Standards:2D1129 Terminology Relating to WaterD1193 Specification for Reagent WaterD1253 Test Method for Residual Chlorine in WaterD1293 Test Methods for pH of WaterD3370 Practices for Sampling Water f
7、rom Closed Conduits3. Terminology3.1 Definitions of Terms Specific to This Standard:3.1.1 chlorine demandthe amount of chlorine that mustbe added to a unit volume of water under specified conditionsof pH, temperature, and contact time to completely react withall chlorine-reactable substances in the
8、water. It is defined asthe difference between the amount of chlorine applied and theamount of free chlorine remaining at the end of the contactperiod.3.1.2 chlorine requirementthe amount of chlorine thatmust be added to a unit volume of water under specifiedconditions of pH, temperature, and contact
9、 time to achieve theobjectives of chlorination.3.2 DefinitionsFor definitions relating to this practice, seeTerminology D1129.4. Summary of Practice4.1 Known amounts of chlorine are added to a series of 500mL aliquots of sample. The treated sample aliquots arepermitted to stand for a specified conta
10、ct time (or a variety ofdifferent specified contact times) under specified conditions ofpH and temperature. At the end of the contact time, the samplealiquots are either analyzed for chlorine content by TestMethod D1253 or subjected to whatever evaluative techniqueis required to establish accomplish
11、ment of the treatmentobjective, or both.5. Significance and Use5.1 Chlorine is added to potable water, waste water, andindustrial water for a variety of purposes. Some of thesepurposes are:5.1.1 To eliminate or reduce the growth of microorganismsin water,5.1.2 To destroy or modify decomposable organ
12、ic sub-stances so as to reduce the biochemical oxygen demand of thewater,5.1.3 To eliminate or reduce taste, odors, and color in thewater,1This practice is under the jurisdiction of ASTM Committee D19 on Water andis the direct responsibility of Subcommittee D19.03 on Sampling Water andWater-Formed D
13、eposits, Analysis of Water for Power Generation and Process Use,On-Line Water Analysis, and Surveillance of Water.Current edition approved May 1, 2011. Published June 2011. Originallyapproved in 1953. Last previous edition approved in 2006 as D1291 06. DOI:10.1520/D1291-06R11.2For referenced ASTM st
14、andards, 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 Document Summary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken
15、, PA 19428-2959, United States.5.1.4 To separate grease in waste water by eliminating theprotective colloidal effect of proteins present, and5.1.5 To destroy or modify substances in the waste waterthat react directly by oxidation, such as ammonia, cyanates,cyanides, ferrous iron, nitrites, phenol, p
16、hosphorus, sulfides,sulfites, thiocyanates, and other oxidizable constituents.5.2 It is important to avoid over-chlorination in order tominimize chemical consumption, meet restrictions specified byregulatory agencies, and minimize equipment degradation.6. Apparatus6.1 All of the apparatus listed in
17、Test Methods D1293 andD1253 may be required. Any other apparatus necessary tocarry out the final evaluation of the effects of chlorination willbe required.7. Reagents and Materials7.1 Purity of ReagentsReagent grade chemicals shall beused in all tests. Unless otherwise indicated, it is intended that
18、all reagents shall conform to the specifications of the Commit-tee on Analytical Reagents of the American Chemical Society,where such specifications are available.3Other grades may beused, provided it is first ascertained that the reagent is ofsufficiently high purity to permit its use without lesse
19、ning theaccuracy of the determination.7.2 Purity of WaterUnless otherwise indicated, referencesto water shall be understood to mean reagent water conformingto Specification D1193, Type III, which has been renderedchlorine demand-free. Chlorine demand can be removed bytreating with excess chlorine an
20、d allowing this treated solutionto stand in sunlight for several hours to destroy the chlorineresiduals. Test Method D1253 may be used to assure completedestruction of these residuals.7.3 Acetic Acid Solution (1 + 1)Mix equal volumes ofglacial acetic acid and water.7.4 Calcium Hydroxide Solution (10
21、.7 g/L)Weigh 10.7 gof 100 % hydrated lime, Ca(OH)2, and suspend in water. Dilutethe suspension to 1 L. Shake well each time before using.7.5 Chlorine Solution, StandardPrepare one of the stan-dard solutions described in 7.5.1 and 7.5.2; standardize asdescribed in 7.5.3.7.5.1 Chlorine WaterPass chlor
22、ine gas through reagentwater until the solution contains from 0.5 to 10.0 mg/L Cl2.NOTE 1Warning: Use a slow rate of addition and carry out theoperation under a hood. Store in a glass stoppered amber bottle andstandardize daily before use.7.5.2 Sodium Hypochlorite Solution, StandardDilute acommercia
23、l sodium hypochlorite or bleach solution containing10 to 100 g of available chlorine per litre with water to providea solution containing from 0.5 to 10 mg available chlorine perlitre, depending upon the maximum expected chlorine require-ment for the sample. This solution must be standardized before
24、use.7.5.3 Standardize the chlorine water or sodium hypochloritesolution, standard, as follows:7.5.3.1 Transfer 10 mL of the solution to be standardized toa porcelain dish.7.5.3.2 Add 10 mL of acetic acid (1 + 1) (see 7.3) and 10mL of potassium iodide solution (see 7.8).7.5.3.3 Titrate with sodium th
25、iosulfate solution (0.10 N)(see 7.11) until the yellow color of the liberated iodine isalmost discharged.7.5.3.4 Add 1 mL of starch indicator solution (see 7.12) andcontinue the titration to a colorless endpoint.7.5.3.5 Calculate the concentration of available chlorine asfollows:Available chlorine,
26、mg/mL 5A 3 B3 35.45Cwhere:A = sodium thiosulfate solution, standard, mL,B = normality of sodium thiosulfate solution, standard,andC = chlorine solution titrated, mL.7.6 Hydrochloric Acid (1 + 1)Mix equal volumes of con-centrated HCl (sp gr 1.19) and water.7.7 Potassium Dichromate Solution (0.100 N)D
27、issolve4.904 g of anhydrous potassium dichromate (K2Cr2O7)ofprimary standard quality in water and dilute to 1000 mL in avolumetric flask.7.8 Potassium Iodide Solution (50 g/L)Dissolve 50 g ofpotassium iodide (KI) in 1 Lof freshly boiled and cooled water.Add1gofsodium bicarbonate (NaHCO3) to stabiliz
28、e thesolution. Store in an amber bottle and avoid direct exposure tosunlight.7.9 Sodium Hydroxide Solution (10 g/L)Dissolve 10 g ofsodium hydroxide (NaOH) in water and dilute to 1 L.NOTE 2Caution: Heat is generated when dissolving sodium hydrox-ide in water.7.10 Sodium Thiosulfate Solution, Standard
29、 (0.10 N)Transfer 25 g of sodium thiosulfate pentahydrate (Na2S2O35H2O) to a 1-L volumetric flask containing about 800 mLwater. Dissolve the compound in the water by shaking andperiodic inversion.Add1gofsodium carbonate (Na2CO3) anddissolve. Dilute the solution to 1 L with water.7.10.1 Standardize t
30、he sodium thiosulfate solution: Add 70mL of water to a porcelain dish, and add, with constant stirring,1 mL of concentrated sulfuric acid (H2SO4), 10.0 mL of 0.100N K2Cr2O7, and 20 mL of potassium iodide solution (see 7.8).Permit the reaction mixture to stand in the dark for about sixminutes. Then t
31、itrate with the sodium thiosulfate solution untilthe yellow color of the liberated iodine is almost discharged.Add 1 mL of starch indicator solution (see 7.12) and continuethe titration to a colorless endpoint.7.10.1.1 The normality can be calculated as:3Reagent Chemicals, American Chemical Society
32、Specifications, AmericanChemical Society, Washington, DC. For suggestions on the testing of reagents notlisted by the American Chemical Society, see Analar Standards for LaboratoryChemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeiaand National Formulary, U.S. Pharmaceutical
33、Convention, Inc. (USPC), Rockville,MD.D1291 06 (2011)2Normality, Na2S2O351Na2S2O3required in titration, mL7.10.1.2 Perform this standardization in triplicate and aver-age the results.7.11 Starch Indicator SolutionMake a paste of1gofsoluble starch and mix into 1 L of boiling water. Then, add 20g of p
34、otassium hydroxide (KOH), mix thoroughly, and allow tostand for 2 h. Add 6 mL of glacial acetic acid (99.5 %). Mixthoroughly and then add sufficient HCl (sp gr 1.19) to adjustthe pH value of the solution to 4.0. Store in a glass-stopperedbottle. Starch solution prepared in this manner will remainche
35、mically stable for 1 year.7.12 Sulfuric Acid (sp gr 1.84)Concentrated sulfuric acid(H2SO4).8. Sampling8.1 Collect the sample in accordance with Practices D3370.8.2 Conduct the test immediately following collection of thesamples.9. ProcedureNOTE 3The area used for the test must not be in direct sunli
36、ght; testsshould be run at the same temperature at which chlorination will be carriedout. The temperature of the water just prior to, or immediately after,chlorination must not exceed 50C.9.1 Transfer 500 mL portions of sample to separate 1000mL beakers.NOTE 4The number of aliquots required to deter
37、mine chlorine re-quirement or demand is left to the judgment of the analyst. It will dependupon the degree of familiarity that the analyst has with the water beingtested as well as other variables.NOTE 5One of two different sources of chlorine can be used in thechlorine addition, either chlorine wat
38、er or sodium hypochlorite solution.In general, the type of chlorine that is used in the process should be usedin the test. Chlorine water will tend to lower the pH of the water whilesodium hypochlorite solution will tend to raise the pH.9.2 If chlorine water is used for chlorination, add theestimate
39、d maximum amount of chlorine (as chlorine water) toone of the sample aliquots. If sodium hypochlorite solution isused for chlorination, add the estimated minimum amount ofchlorine (as sodium hypochlorite solution). Immediately mea-sure the pH of the sample aliquot by Test Method D1293.IfthepH is not
40、 below the lower limit of the desired pH range,continue with 9.3. If the pH does fall below the lower limit ofthe desired range, add sodium hydroxide solution dropwisewith continual stirring to bring the pH up to approximately themidpoint of the pH range, noting the amount of sodiumhydroxide solutio
41、n required. Then, discard this solution andtransfer another 500 mL aliquot of sample to a 1-L beaker toreplace it. Add the same amount of sodium hydroxide solutionas was required for pH adjustment of the first sample aliquot toall of the sample aliquots. Proceed to 9.3.9.3 If the estimated maximum a
42、mount of chlorine wasadded to the first sample aliquot, add incrementally smalleramounts of chlorine to each of the other sample aliquots, withthe estimated minimum amount of chlorine being added to thelast sample aliquot. If the estimated minimum amount ofchlorine was added to the first sample aliq
43、uot, add incremen-tally greater amounts of chlorine to each of the other samplealiquots with the estimated maximum amount of chlorine beingadded to the last sample aliquot. Stir each sample aliquotgently after addition of chlorine. Proceed to 9.4.9.4 Measure the pH of each sample aliquot by followin
44、gTest Method D1293.9.5 If the pH is higher than the desired pH range, carefullyadjust the pH downward by adding, with constant gentlestirring, hydrochloric acid (1 + 1) dropwise until the pHreaches the upper limit of the desired range.NOTE 6Care must be taken during the addition of HCl (1 + 1) to ma
45、kesure that the pH is not lowered too rapidly and that the lower limit of thedesired pH range is not exceeded.Arapid reaction (which itself lowers thepH) may ensue if the pH is taken too low.9.6 Permit each portion of sample to stand for the desiredcontact time.NOTE 7Depending upon the application,
46、a single contact time or aseries of different contact times may be used for each sample aliquot. Thisis left to the judgment of the analyst.9.7 To estimate chlorine demand, determine residual-freechlorine on all of the sample aliquots at the end of the desiredcontact time by Test Method D1253.9.8 To
47、 estimate chlorine requirement, perform whatever testis necessary on all of the sample aliquots at the end of thedesired contact time to determine whether the objectives ofchlorination have been met. If it is desired to maintain a certainconcentration of residual available chlorine, perform the chlo
48、-rine determination by Test Method D1253.10. Calculation10.1 Calculate the chlorine dosage in milligrams per litre foreach treated sample solution using Eq 1:Chlorine dosage, mg/L 5 2AB(1)where:A = chlorinating solution added to each sample aliquot,mL, andB = available chlorine per millilitre of chl
49、orinating solu-tion, mg (see 7.5.3).10.2 Chlorine demand is estimated using Eq 2:Chlorine demand, mg/L 5 C 2 D(2)where:C = chlorine dosage, mg/L, andD = free chlorine remaining at the end of contact time,mg/L.NOTE 8To calculate chlorine consumed, see Appendix X1.11. Precision and Bias11.1 PrecisionThe estimation of chlorine requirement ordemand, or both, is a practice. For measuring chlorine values,this practice refers the user to Test Method D1253. A statementfor the precision and bias of chlorine measurement is located inTest Method D1253.D1291 06 (20
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