ASTM D1252-06(2012)e1

Standard Test Methods for Chemical Oxygen Demand (Dichromate Oxygen Demand) of Water

SIGNIFICANCE AND USE
5.1 These test methods are used to chemically determine the maximum quantity of oxygen that could be consumed by biological or natural chemical processes due to impurities in water. Typically this measurement is used to monitor and control oxygen-consuming pollutants, both inorganic and organic, in domestic and industrial wastewaters.  
5.2 The relationship of COD to other water quality parameters such as TOC and TOD is described in the literature. 3
SCOPE
1.1 These test methods cover the determination of the quantity of oxygen that certain impurities in water will consume, based on the reduction of a dichromate solution under specified conditions. The following test methods are included:
1.2 These test methods are limited by the reagents employed to a maximum chemical oxygen demand (COD) of 800 mg/L. Samples with higher COD concentrations may be processed by appropriate dilution of the sample. Modified procedures in each test method (Section 15 for Test Method A and Section 24 for Test Method B) may be used for waters of low COD content (  
1.3 As a general rule, COD results are not accurate if the sample contains more than 1000 mg/L Cl−. Consequently, these test methods should not be applied to samples such as seawaters and brines unless the samples are pretreated as described in Appendix X1.  
1.4 This test method was used successfully on a standard made up in reagent water. It is the user's responsibility to ensure the validity of these test methods for waters of untested matrices.  
1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. For specific hazard statements, see Section 8, 15.6, and 24.5.

General Information

• Status: Historical
• Publication Date: 14-Jun-2012
• ICS: 13.060.50 - Examination of water for chemical substances
• Technical Committee: D19 - Water
• Drafting Committee: D19.06 - Methods for Analysis for Organic Substances in Water

Standards Content (Sample)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
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Designation: D1252 − 06 (Reapproved 2012)
Standard Test Methods for
Chemical Oxygen Demand (Dichromate Oxygen Demand) of
Water
This standard is issued under the fixed designation D1252; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
This standard has been approved for use by agencies of the U.S. Department of Defense.
ε NOTE—Editorial corrections made throughout in June 2013.
1. Scope 2. Referenced Documents
2.1 ASTM Standards:
1.1 These test methods cover the determination of the
D1129Terminology Relating to Water
quantity of oxygen that certain impurities in water will
D1193Specification for Reagent Water
consume, based on the reduction of a dichromate solution
D2777Practice for Determination of Precision and Bias of
under specified conditions. The following test methods are
Applicable Test Methods of Committee D19 on Water
included:
D3223Test Method for Total Mercury in Water
TestMethodA 2 MacroCODbyRefluxDigestionandTitration
D3370Practices for Sampling Water from Closed Conduits
TestMethodB 2 MicroCODbySealedDigestionandSpectrometry
D5905Practice for the Preparation of SubstituteWastewater
E60Practice for Analysis of Metals, Ores, and Related
1.2 Thesetestmethodsarelimitedbythereagentsemployed
to a maximum chemical oxygen demand (COD) of 800 mg/L. Materials by Spectrophotometry
E275PracticeforDescribingandMeasuringPerformanceof
SampleswithhigherCODconcentrationsmaybeprocessedby
appropriate dilution of the sample. Modified procedures in Ultraviolet and Visible Spectrophotometers
eachtestmethod(Section15forTestMethodAandSection24
3. Terminology
for Test Method B) may be used for waters of low COD
content (< 50 mg/L). 3.1 Definitions—For definitions of other terms used in these
test methods, refer to Terminology D1129.
1.3 As a general rule, COD results are not accurate if the
−
samplecontainsmorethan1000mg/LCl .Consequently,these 3.2 The term “oxygen demand” (COD) in these test meth-
ods is defined in accordance with Terminology D1129 as
test methods should not be applied to samples such as
seawaters and brines unless the samples are pretreated as follows:
3.2.1 oxygen demand—the amount of oxygen required un-
described in Appendix X1.
der specified test conditions for the oxidation of water borne
1.4 This test method was used successfully on a standard
organic and inorganic matter.
made up in reagent water. It is the user’s responsibility to
ensure the validity of these test methods for waters of untested
4. Summary of Test Methods
matrices.
4.1 Most organic and oxidizable inorganic substances pres-
1.5 This standard does not purport to address all of the
ent in water are oxidized by a standard potassium dichromate
safety concerns, if any, associated with its use. It is the
solution in 50% sulfuric acid (vol/vol). The dichromate
responsibility of the user of this standard to establish appro-
consumed (Test Method A) or tri-valent chromium produced
priate safety and health practices and determine the applica-
(Test Method B) is determined for calculation of the COD
bility of regulatory limitations prior to use. For specific hazard
value.
statements, see Section 8, 15.6, and 24.5.
4.2 The oxidation of many otherwise refractory organics is
facilitated by the use of silver sulfate that acts as a catalyst in
the reaction.
These test methods are under the jurisdiction of ASTM Committee D19 on
Water and are the direct responsibility of Subcommittee D19.06 on Methods for
Analysis for Organic Substances in Water. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Current edition approved June 15, 2012. Published June 2012. Originally contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
approved in 1953. Last previous edition approved in 2006 as D1252–06. DOI: Standards volume information, refer to the standard’s Document Summary page on
10.1520/D1252-06R12E01. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
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D1252 − 06 (2012)
4.3 These test methods provide for combining the reagents 5. Significance and Use
and sample in a manner that minimizes the loss of volatile
5.1 Thesetestmethodsareusedtochemicallydeterminethe
organic materials, if present.
maximum quantity of oxygen that could be consumed by
4.4 The oxidation of up to 1000 mg/L of chloride ion is biological or natural chemical processes due to impurities in
inhibited by the addition of mercuric sulfate to form stable and water. Typically this measurement is used to monitor and
soluble mercuric sulfate complex.Atechnique to remove up to control oxygen-consuming pollutants, both inorganic and
40 000 mg/L chloride is shown in Appendix X1 for Test organic, in domestic and industrial wastewaters.
Method B. The maximum chloride concentration that may be
5.2 The relationship of COD to other water quality param-
tolerated with the procedure for low COD, Test Method A 3
eters such as TOC and TOD is described in the literature.
(15.10), has not been established.
6. Interference and Reactivity
4.5 Thechemicalreactioninvolvedinoxidationofmaterials
by dichromate is illustrated by the following reaction with
6.1 Chloride ion is quantitatively oxidized by dichromate in
potassium acid phthalate (KC H O ):
acidsolution.(1.0mg/Lofchlorideisequivalentto0.226mg/L
8 5 4
of COD.) As the COD test is not intended to measure this
41H SO 110K Cr O 12KC H O
2 4 2 2 7 8 5 4
demand, concern for chloride oxidation is eliminated up to
→10Cr SO 111K SO 116CO 146H O
~ !
2 4 2 4 2 2
1000 mg/L of chloride by complexing with mercuric sulfate.
Since 10 mol of potassium dichromate has the same oxida-
6.1.1 Up to 40 000 mg/L chloride ion can be removed with
tion power as 15 mol of oxygen, the equivalent reaction is:
a cation based ion exchange resin in the silver form as
2KC H O 115O 1H SO →16CO 16H O1K SO described in Appendix X1 when using Test Method B. Since
8 5 4 2 2 4 2 2 2 4
this pretreatment was not evaluated during the interlaboratory
Thus 2 mol of potassium acid phthalate consumes 15 mol of
study,theuserofthetestmethodisresponsibletoestablishthe
oxygen. The theoretical COD of potassium acid phthalate is
precision and bias of each sample matrix.
1.175gofoxygenpergramofpotassiumacidphthalate(Table
6.2 Oxidizable inorganic ions, such as ferrous, nitrite,
1).
sulfite, and sulfides are oxidized and measured as well as
organic constituents.
TABLE 1 Test Method A, Recovery of Theoretical COD for
Various Organic Material
7. Reagents
Reactivity, Percent of Theoretical
7.1 Purity of Reagents—Reagent grade chemicals shall be
Component
A B C D E
1 2 3 4 5
usedinalltests.Allreagentsshallconformtothespecifications
Aliphatic Compounds
of the Committee on Analytical Reagents of the American
Acetone 98 . 96 94 .
Chemical Society, where such specifications are available.
Acetic acid 92 92 98 . .
Acrolein 62 . . . .
7.2 Purity of Water— Unless otherwise indicated, reference
Butyric acid 89 93 . . .
to water shall be understood to mean reagent water that meets
Dextrose 95 . . . .
Diethylene glycol 93 . . 70 .
the purity specifications of Type I or Type II water, presented
Ethyl acetate 95 . . 85 .
in D1193.
Methyl ethyl ketone 98 . . 90 .
Aromatic Compounds
Acetophenone 89 . . . . 8. Hazards
Benzaldehyde . . . 80 .
8.1 Exercise extreme care when handling concentrated sul-
Benzene 60–98 . 41 . .
Benzoic acid 98 . . 100 .
furic acid, especially at the start of the refluxing step (15.7).
Dioctyl phthalate 83 . . . .
8.2 Silver sulfate is poisonous; avoid contact with the
Diphenyl 81 . . . .
o-cresol 95 . . 95 .
chemical and its solution.
Toluene 83 . . 45 .
Potassium acid 100 . . . . 8.3 Mercuric sulfate is very toxic; avoid contact with the
phthalate
chemical and its solution.
Nitrogen Compounds
Acrylonitrile 48 . . 44 .
9. Sampling
Adenine . . . . 59
Aniline 80 . . 74 .
9.1 Collect the sample in accordance with Practices D3370.
Butyl amine 57 . . . .
Pyridine 0 . 1 . 2
9.2 Preserve samples by cooling to 4°C if analyzed within
Quinoline . . . . 87
24 h after sampling, or preserve for up to 28 days at 4°C and
Trimethylamine 1 . . . .
Tryptophane . . . . 87
Uric acid . . . . 61
Handbook for Monitoring Industrial Wastewater, U.S. Environmental Protec-
A
Hamilton, C. E., unpublished data.
B tion Agency, Aug. 1973, pp. 5-10 to 5-12.
Moore, W. A., and Walker, W. W., Analytical Chemistry, Vol 28, 1956, p. 164.
C Reagent Chemicals, American Chemical Society Specifications, American
Dobbs, R. A., Williams, R. T., ibid., Vol 35, 1963 p. 1064.
D
Chemical Society, Washington, DC. For suggestions on the testing of reagents not
Buzzell, J. C., Young, R. H. F., and Ryckman, D. W.,“ Behaviors of Organic
listed by the American Chemical Society, see Analar Standards for Laboratory
Chemicals in the Aquatic Environment; Part II, Dilute Systems,” Manufacturing
Chemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeia
Chemists Association, April 1968, p. 34.
E
and National Formulary, U.S. Pharmaceutical Convention, Inc. (USPC), Rockville,
Chudoba, J., and Dalesicky, J., Water Research, Vol 7, No. 5, 1973, p. 663.
MD.
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D1252 − 06 (2012)
at pH<2by addition of concentrated sulfuric acid. The oxidizable substances are present. It is the responsibility of the
addition of 2 mL of concentrated sulfuric acid per litre at the users of the test method to ensure the maximum holding time
time of collection will generally achieve this requirement. The for their samples.
actual holding time possible without significant change in the
COD may be less than 28 days, especially when easily
TEST METHOD A—MACRO COD BY REFLUX DIGESTION AND TITRATION
10. Scope
10.1 TheamountofdichromateconsumedinTestMethodA (FeSO ·(NH )SO ·6H O) in water.Add 20 mLof sulfuric acid
4 4 4 2
is determined by titration rather than the spectrophotometric (H SO , sp gr 1.84), cool and dilute to 1 L. Standardize this
2 4
procedure used in Test Method B. This test method is appro- solution daily before use. To standardize, dilute 25.0 mL of
priate where larger sample volumes would provide better 0.25 N potassium dichromate solution (K Cr O ) to about 250
2 2 7
precision and better representativeness of where equipment or mL. Add 20 mL of sulfuric acid (sp gr 1.84) and allow the
space limitations exist. solution to cool. Titrate with the ferrous ammonium sulfate
solution to be standardized, using the phenanthroline ferrous
10.2 The precision of this test method in standard solutions
sulfate indicator as directed in 15.10. Calculate the normality
containing low-volatility organic compounds has been exam-
as follows:
ined in the range of approximately 10 to 300 mg/L.
N 5 A 3B /C
~ !
11. Summary of Test Method
where:
11.1 The sample and standardized dichromate solution, in a
N = normality of the ferrous ammonium sulfate solution,
50% by volume sulfuric solution, is refluxed for a 2-h
A = potassium dichromate solution, mL,
digestion period.
B = normality of the potassium dichromate solution, and
11.2 Excess dichromate after the digestion period is titrated
C = ferrous ammonium sulfate solution, mL.
with a standard ferrous ammonium sulfate solution using
14.2 Ferrous Ammonium Sulfate Solution (0.025 N)—
ortho-phenanthroline ferrous complex as an internal indicator.
Dilute100mLof0.25 Nferrousammoniumsulfatesolutionto
12. Interferences
1 L. Standardize against 0.025 N potassium dichromate solu-
tion as in 14.1. This solution is required only if COD is
12.1 Thetestmethoddoesnotuniformlyoxidizeallorganic
determined in the range of 10 to 50 mg/L.
materials.Somecompounds,forexample,arequiteresistantto
oxidation, while others, such as carbohydrates, are easily
14.3 Mercuric Sulfate— Powdered mercuric sulfate
oxidized. A guide to the behavior of various types of organic
(HgSO ).
materials is provided in Table 1.
14.4 Phenanthroline Ferrous Sulfate Indicator Solution—
12.2 Volatile organics that are difficult to oxidize may be
Dissolve 1.48 g of 1,10-(ortho)-phenanthroline monohydrate,
partially lost before oxidation is achieved. Care in maintaining
together with 0.70 g of ferrous sulfate (FeSO ·7H O), in 100
4 2
a low-solution temperature (about 40°C) and permitting oxi-
mL of water. This indicator may be purchased already pre-
dation to proceed at the lower temperature for a period of time
pared.
before reflux is initiated will result in higher recoveries of
14.5 Potassium Acid Phthalate Solution, Standard (1
theoretical COD of volatile organics.
mL=1 mg COD)—Dissolve 0.851 g of potassium acid phtha-
13. Apparatus late (KC H O ), primary standard, in water and dilute to 1 L.
8 5 4
13.1 Reflux Apparatus— The apparatus consists of a 14.6 Potassium Dichromate Solution, Standard (0.25 N)—
500-mLErlenmeyer or a 300-mLround-bottom flask, made of Dissolve12.259gofpotassiumdichromate(K Cr O )primary
2 2 7
heat-resistant glass connected to a 300-mm (12-in.) Allihn standard grade, previously dried at 103°C for 2 h, in water and
condenser by means of a ground-glass joint. Any equivalent dilute to 1 L in a volumetric flask.
reflux apparatus may be substituted, provided that a ground-
14.7 Potassium Dichromate Solution, Standard (0.025 N)—
glass connection is used between the flask and the condenser,
Dilute 100.0 mLof 0.25 N potassium dichromate solution to 1
and provided that the flask is made of heat-resistant glass.
L.This solution is necessary only for determination of COD in
13.2 Sample Heating Apparatus—A heating mantle or hot the range of 10 to 50 mg/L.
plate capable of delivering sufficient controlled heat to main-
14.8 Sulfuric Acid-Silver Sulfate Solution—Dissolve15gof
tain a steady reflux rate in the reflux apparatus is satisfactory.
powdered silver sulfate (Ag SO ) in 300 mL of concentrated
2 4
13.3 Apparatus for Blending or Homogenizing Samples—A sulfuric acid (sp gr 1.84) and dilute to 1 L with concentrated
household blender is satisfactory. sulfuric acid (sp gr 1.84).
14. Reagents 15. Procedure
14.1 Ferrous Ammonium Sulfate Solution (0.25 N)— 15.1 Homogenize the sample by blending if necessary.
Dissolve 98.0 g of ferrous ammonium sulfate solution Place50.0mLofthesampleinarefluxflask.Iflessthan50mL
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D1252 − 06 (2012)
ofthesampleisused,makeupthedifferenceinwater,thenadd round-bottom flask has
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