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1、BRITISH STANDARD BS ISO 15705:2002 BS 6068-2.80:2002 Water quality Determination of the chemical oxygen demand index (ST-COD) Small-scale sealed-tube method ICS 13.060.50 ? Licensed Copy: sheffieldun sheffieldun, na, Sun Nov 26 03:23:51 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS ISO 15705:2002 Th
2、is British Standard, having been prepared under the direction of the Health and Environment Sector Policy and Strategy Committee, was published under the authority of the Standards Policy and Strategy Committee on 10 December 2002 BSI 10 December 2002 ISBN 0 580 40924 4 National foreword This Britis
3、h Standard reproduces verbatim ISO 15705:2002 and implements it as the UK national standard. The UK participation in its preparation was entrusted by Technical Committee EH/3, Water quality, to Subcommittee EH/3/2, Physical, chemical and biochemicals, which has the responsibility to: A list of organ
4、izations represented on this subcommittee can be obtained on request to its secretary. This is one of a series of standards on water quality, others of which have been, or will be, published as Sections of BS 6068. The various Sections of BS 6068 are comprised within Parts 1 to 7, which, together wi
5、th Part 0, are listed below. Part 0 Introduction Part 1 Glossary Part 2 Physical, chemical and biochemical methods Part 3 Radiological methods Part 4 Microbiological methods Part 5 Biological methods Part 6 Sampling Part 7 Precision and accuracy NOTE. The tests described in this British Standard sho
6、uld only be carried out by suitably qualified persons with an appropriate level of chemical expertise. Standard chemical procedures should be followed throughout. Cross-references The British Standards which implement international publications referred to in this document may be found in the BSI Ca
7、talogue under the section entitled “International Standards Correspondence Index”, or by using the “Search” facility of the BSI Electronic Catalogue or of British Standards Online. This publication does not purport to include all the necessary provisions of a contract. Users are responsible for its
8、correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. aid enquirers to understand the text; present to the responsible international/European committee any enquiries on the interpretation, or proposals for change, and keep the UK interests
9、 informed; monitor related international and European developments and promulgate them in the UK. Summary of pages This document comprises a front cover, an inside front cover, the ISO title page, pages ii to v, a blank page, pages 1 to 18, an inside back cover and a back cover. The BSI copyright da
10、te displayed in this document indicates when the document was last issued. Amendments issued since publication Amd. No. DateComments Licensed Copy: sheffieldun sheffieldun, na, Sun Nov 26 03:23:51 GMT+00:00 2006, Uncontrolled Copy, (c) BSI Reference number ISO 15705:2002(E) INTERNATIONAL STANDARD IS
11、O 15705 First edition 2002-11-15 Water quality Determination of the chemical oxygen demand index (ST-COD) Small-scale sealed-tube method Qualit de leau Dtermination de lindice de demande chimique en oxygne (ST-DCO) Mthode petite chelle en tube ferm BS ISO 15705:2002 Licensed Copy: sheffieldun sheffi
12、eldun, na, Sun Nov 26 03:23:51 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS ISO 15705:2002 ii Licensed Copy: sheffieldun sheffieldun, na, Sun Nov 26 03:23:51 GMT+00:00 2006, Uncontrolled Copy, (c) BSI IS:50751 O2002(E) I SO 2002 All irthgs ersedevr iii Contents Page Foreword iv Introduction. v 1 Sc
13、ope 1 2 Normative references 1 3 Terms and definitions. 2 4 Principle . 2 5 Interferences 2 6 Reagents 2 7 Apparatus. 5 8 Sample collection and preservation 6 9 Preparation of tubes and instrument set-up 6 10 Analytical procedure for measurement of samples 7 11 Calculation of results 8 12 Expression
14、 of results 9 13 Test report 9 14 Precision 9 Annex A (informative) Comparison between the COD method according to ISO 6060 and the method described in this International Standard 10 Annex B (informative) Hazards 11 Annex C (informative) Information on the use of commercial small-scale ST-COD test k
15、its utilizing photometric detection. 12 Annex D (informative) Low-range sealed-tube photometric method (up to 150 mg/l) 13 Annex E (informative) Low-range sealed-tube titrimetric method (up to 150 mg/l) 14 Annex F (informative) Screening test for samples with high chloride concentrations. 15 Annex G
16、 (informative) Precision data. 16 Bibliography 18 BS ISO 15705:2002 iii Licensed Copy: sheffieldun sheffieldun, na, Sun Nov 26 03:23:51 GMT+00:00 2006, Uncontrolled Copy, (c) BSI IS:50751 O2002(E) vi I SO 2002 All irthgs ersedevr Foreword ISO (the International Organization for Standardization) is a
17、 worldwide federation of national standards bodies (ISO member bodies). The work of preparing International Standards is normally carried out through ISO technical committees. Each member body interested in a subject for which a technical committee has been established has the right to be represente
18、d on that committee. International organizations, governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization. International Standards are draf
19、ted in accordance with the rules given in the ISO/IEC Directives, Part 3. The main task of technical committees is to prepare International Standards. Draft International Standards adopted by the technical committees are circulated to the member bodies for voting. Publication as an International Sta
20、ndard requires approval by at least 75 % of the member bodies casting a vote. Attention is drawn to the possibility that some of the elements of this International Standard may be the subject of patent rights. ISO shall not be held responsible for identifying any or all such patent rights. ISO 15705
21、 was prepared by Technical Committee ISO/TC 147, Water quality, Subcommittee SC 2, Physical, chemical and biochemical methods. Annexes A to G of this International Standard are for information only. BS ISO 15705:2002 iv Licensed Copy: sheffieldun sheffieldun, na, Sun Nov 26 03:23:51 GMT+00:00 2006,
22、Uncontrolled Copy, (c) BSI IS:50751 O2002(E) I SO 2002 All irthgs ersedevr v Introduction The chemical oxygen demand, ST-COD value, of water as determined by this dichromate method can be considered as an estimate of the theoretical oxygen demand, i.e. the amount of oxygen consumed in total chemical
23、 oxidation of the organic constituents present in the water. The degree to which the test results approach the theoretical value depends primarily on how complete the oxidation is. The ST-COD test is an empirical test and the effects of any oxidizing or reducing agents are included in the result. Un
24、der the conditions of the test, many organic compounds and most inorganic reducing agents are oxidized to between 90 % and 100 %. For waters that contain these compounds, such as sewage, industrial waste and other polluted waters, the ST-COD value is a realistic measure of the theoretical oxygen dem
25、and. However, for waters that contain large quantities of other substances that are difficult to oxidize under the conditions of the test, such as nitrogenous and heterocyclic compounds (e.g. pyridine and aliphatic and aromatic hydrocarbons), the ST-COD value is a poor measure of the theoretical oxy
26、gen demand. This may be the case for some industrial effluents. The significance of an ST-COD value thus depends on the composition of the water studied. This should be borne in mind when judging results obtained by the method specified in this International Standard. Detailed testing has shown good
27、 comparison between this method and the method of ISO 6060. However, it should not be assumed that this method is comparable in all cases to that of ISO 6060 without testing, particularly when there is a problem in obtaining a 2 ml representative sample (e.g. samples with high content of suspended s
28、olids). BS ISO 15705:2002 v Licensed Copy: sheffieldun sheffieldun, na, Sun Nov 26 03:23:51 GMT+00:00 2006, Uncontrolled Copy, (c) BSI Licensed Copy: sheffieldun sheffieldun, na, Sun Nov 26 03:23:51 GMT+00:00 2006, Uncontrolled Copy, (c) BSI INTENRATIONAL TSANDADR IS:50751 O2002(E) I SO 2002 All irt
29、hgs ersedevr 1 Water quality Determination of the chemical oxygen demand index (ST-COD) Small-scale sealed-tube method WARNING Persons using this standard should be familiar with normal laboratory practice. This standard does not purport to address all of the safety problems, if any, associated with
30、 its use. It is the responsibility of the user to establish appropriate safety and health practices and to ensure compliance with any national regulatory conditions. 1 Scope This International Standard specifies a method for the determination of the chemical oxygen demand (ST-COD) using the sealed t
31、ube method. The test is empirical and is applicable to any aqueous sample, which includes all sewage and waste waters. The method is applicable to undiluted samples having ST-COD values up to 1 000 mg/l and a chloride concentration not exceeding 1 000 mg/l. Samples with higher ST-COD values require
32、predilution. For samples with a low COD, the precision of the measurement will be reduced and the detection limit will be poorer. Samples with a high chloride concentration will need to be prediluted to give a chloride concentration of approximately 1 000 mg/l or less before analysis. The method oxi
33、dizes almost all types of organic compounds and most inorganic reducing agents. It has a detection limit (4,65 times the within-batch standard deviation of a blank or very low standard) of 6 mg/l for photometric detection at 600 nm, and 15 mg/l for titrimetric detection as reported by one laboratory
34、 comparing the photometric and titrimetric techniques using a commercial test kit with a range up to 1 000 mg/l. The titrimetric part of this International Standard is applicable to samples exhibiting an atypical colour or turbidity after the digestion stage. NOTE A comparison between the full-scale
35、 method (ISO 6060) and the method of this International Standard is given in annex A. A discussion of possible hazards is given in annex B. Information on commercial small-scale test kits is given in annex C. The method can be used over a reduced range (see annexes D and E). For checking the chlorid
36、e concentration, see annex F. 2 Normative references The following normative documents contain provisions which, through reference in this text, constitute provisions of this International Standard. For dated references, subsequent amendments to, or revisions of, any of these publications do not app
37、ly. However, parties to agreements based on this International Standard are encouraged to investigate the possibility of applying the most recent editions of the normative documents indicated below. For undated references, the latest edition of the normative document referred to applies. Members of
38、ISO and IEC maintain registers of currently valid International Standards. ISO 3696:1987, Water for analytical laboratory use Specification and test methods ISO 5667-3:1994, Water quality Sampling Part 3: Guidance on the preservation and handling of samples BS ISO 15705:2002 1 Licensed Copy: sheffie
39、ldun sheffieldun, na, Sun Nov 26 03:23:51 GMT+00:00 2006, Uncontrolled Copy, (c) BSI IS:50751 O2002(E) 2 I SO 2002 All irthgs ersedevr 3 Term and definition For the purposes of this International Standard, the following term and definition applies. 3.1 chemical oxygen demand ST-COD mass concentratio
40、n of oxygen equivalent to the amount of dichromate consumed by dissolved and suspended matter when a water sample is treated under the conditions specified in this International Standard NOTE 1 Adapted from ISO 6060. NOTE 2 1 mol of dichromate (Cr2O72) is equivalent to 3 mol of oxygen (O). 4 Princip
41、le 4.1 Samples are oxidized in a standard manner by digesting with sulfuric acid and potassium dichromate in the presence of silver sulfate and mercury(II) sulfate. Silver acts as a catalyst to oxidize the more refractory organic matter. Mercury reduces the interference caused by the presence of chl
42、oride ions. The amount of dichromate used in the oxidation of the sample is determined by measuring the absorbance of the Cr(III) formed at a wavelength of 600 nm 20 nm for a range up to 1 000 mg/l. Absorbance measurements are made in the digestion tube, which acts as a cuvette, and are converted to
43、 an ST-COD value. 4.2 For the reduced calibration range up to 150 mg/l, an alternative wavelength 440 nm 20 nm may be used (see annexes D and E). For a further reduced calibration range up to 50 mg/l, an alternative wavelength of 348 nm 15 nm may be used. At 348 nm and 440 nm, the absorbance of the
44、remaining chromium(VI) is measured. 4.3 For turbid and atypically coloured digested samples, titration with standardized ammonium iron(II) sulfate is used. 5 Interferences 5.1 High concentrations of chloride give a positive bias caused by the oxidation of chloride ions to chlorine. The interference
45、from chloride ions is reduced but not totally eliminated by the addition of mercury(II) sulfate. This binds the chloride ions as a soluble chloromercurate(II) complex. 5.2 Manganese can give a positive bias using photometric detection at 600 nm. Using a 0 mg/l to 1 000 mg/l commercial test kit, dupl
46、icate analysis of a 500 mg/l manganese solution (as sulfate) gave ST-COD results of 1 080 mg/l and 1 086 mg/l and of a 50 mg/l manganese solution gave ST-COD results of 121 mg/l and 121 mg/l. The effect is much less with lower range (0 mg/l to 150 mg/l) kits at 440 nm (5.1). At this wavelength the i
47、nterference is expressed as a negative bias. For a 0 mg/l to 150 mg/l commercial test kit, duplicate analysis of a 500 mg/l manganese solution (as sulfate) gave ST-COD results of 7 mg/l and 8 mg/l. See also note in C.6. 5.3 Many aromatic hydrocarbons and pyridine are not oxidized to any appreciable
48、extent. Some volatile organic substances may escape the oxidation by evaporating. 5.4 Ammonium ions are not oxidized (organic nitrogen is normally converted to ammonium ions). 6 Reagents 6.1 Water, complying with ISO 3696:1987, Grade 3. BS ISO 15705:2002 2 Licensed Copy: sheffieldun sheffieldun, na,
49、 Sun Nov 26 03:23:51 GMT+00:00 2006, Uncontrolled Copy, (c) BSI IS:50751 O2002(E) I SO 2002 All irthgs ersedevr 3 6.2 ST-COD sealed tubes Whenever possible it is recommended to use ST-COD sealed tubes purchased ready for use. This minimizes the handling of toxic chemicals by laboratory staff. Commercial tubes can be purchased covering different analytical ranges (e.g. up to 50 mg/l, 160 mg/l, 1 000 mg/l or 1 500 mg/l). If tubes cannot be purchased