The Determination of Chemical Oxygen Demand (COD) in Water by Photoelectrochemical Measurement
Ontario Ministry of the Environment and Climate Change Laboratory Services Branch. Method Catalogue Code: E3515. Revision: 2. (February 2018)
To view the full experiment and results, click the link: COD E3515- The determination of chemical oxygen demand (COD) in water by photoelectrochemical measurement.
Chemical oxygen demand (COD) is a measure of the oxygen requirement of the oxidizable component of organic matter by a strong chemical oxidant. The test is most widely used in measuring waste loadings of treatment plants and in evaluating the efficiency of treatment processes.
Principle of Method
The COD is determined following a photo-electrochemical measurement of chemical oxygen demand. The sample enters a microcell which contains UV activated TiO2 nanoparticles. Under UV light an electrical signal is generated by the TiO2 nanoparticles, which is directly proportional to the amount of oxidizable species being present. As the organic matter in the cell gets oxidized, electrons are released, with the signal converted into an equivalent COD measurement.
Relationship to Other Methods
Method E3515 follows ASTM International standard method D8084-17 “Standard Test Method for Photoelectrochemical Oxygen Demand of Freshwater Sources for Drinking Water Treatement Plants and Treated Drinking Water”. Method E3515 replaced the standard dichromate methods E3170 and E3246, eliminating the use of harmful and toxic reagents.
The procedure determines the oxygen demand of that portion of the chemical constituents in a sample which are oxidized under the conditions of the test. The LIMS Product Code is COD E3515. Results are reported in mg/L as O2.
This procedure is routinely used on precipitation (WP), groundwater (WG), and surface water (WS). Drinking water (WD) matrix is validated but not licensed for analysis.