Lumex Instruments Group

Determination of the chemical oxygen demand (COD) in water - Water and Wastewater


Chemical Oxygen Demand (COD) is one of the most common integral indicators of anthropogenic pollution of water bodies. COD is widely used in the analysis of natural water, to control wastewater treatment from organic various substances.

Lumex Instruments provides the method and equipment (FLUORAT-02 analyzer and TERMION thermoreactor) for accurate, easy-to-use and cost-effective COD determination using the small-scale sealed tube method (ST-COD).

Sampling should be performed in accordance with ISO 5667-3.

The COD measurement method is based on the photometric determination of residual quantities of Cr (VI) ions, or newly formed Cr (III) ions depending on the selected measurement range. Samples are oxidized vials in a standard manner by digesting with sulfuric acid and potassium dichromate in the presence of silver sulfate and mercury(II) sulfate. Silver is the catalyst to enable the full oxidizing of organic matter. Mercury reduces the interference caused by the presence of chloride ions.

The method fully corresponds to the standard ISO 15705:2002 and the result represents ST-COD value.

A photometric determination is performed by the FLUORAT-02 analyzer. COD value is calculated automatically and displayed by PC-operated software FLUORATE.