DANSK DS/ISO 15705 PDF

This standard specifies a method for the determination of 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 wastewaters. The method is applicable for undiluted samples having ST-COD values up to 1000 mg/l and a chloride concentration not exceeding 1 000 mg/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 concentraton will need to be prediluted to give a chloride concentration of approximately 1 000 mg/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 6 mg/l for photometric detection at 600 nm, and 15 mg/l for titrimetric detection as reported by one laboratory comparing the photometric and trimetric techniques using a commercial test kit with a range up to 1000 mg/l. The trimetric part of this standard is applicable ro samples exhibiting an atypical colour or turbidity after the digestion stage.