BS ISO 15705:2002

Foreword
Introduction
1 Scope
2 Normative references
3 Terms and definitions
4 Principle
5 Interferences
6 Reagents
7 Apparatus
8 Sample collection and preservation
9 Preparation of tubes and instrument set-up
10 Analytical procedure for measurement of samples
11 Calculation of results
12 Expression of results
13 Test report
14 Precision
Annex A (informative) Comparison between the COD method
        according to ISO 6060 and the method described
        in this International Standard
Annex B (informative) Hazards
Annex C (informative) Information on the use of commercial
        small-scale ST-COD test kits utilizing
        photometric detection
Annex D (informative) Low-range sealed-tube photometric
        method (up to 150 mg/l)
Annex E (informative) Low-range sealed-tube titrimetric
        method (up to 150 mg/l)
Annex F (informative) Screening test for samples with
        high chloride concentrations
Annex G (informative) Precision data
Bibliography

Defines a method for the determination of the chemical oxygen demand (ST-COD) using the sealed tube method. The test is empirical and is applicable to any aqueous sample, which includes all sewage and waste waters.

This International Standard specifies a method for the determination of the chemical oxygen demand (ST-COD) using the sealed tube 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 1000mg/l and a chloride concentration not exceeding 1000mg/l. Samples with higher ST-COD values require 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 1000mg/l or less before analysis.

The method oxidizes 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 6mg/l for photometric detection at 600nm, and 15mg/l for titrimetric detection as reported by one laboratory comparing the photometric and titrimetric techniques using a commercial test kit with a range up to 1000mg/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 method (ISO6060) and the method of this International Standard is given in annexA. A discussion of possible hazards is given in annexB. Information on commercial small-scale test kits is given in annexC. The method can be used over a reduced range (see annexesD and E). For checking the chloride concentration, see annexF.