Ask the Expert: COD Analysis for Drinking Water
Question: Why is Chemical Oxygen Demand (COD) a useful parameter for drinking water analysis?
Answer: At very basic level Chemical Oxygen Demand or “COD” allows us to understand the oxidation potential of an organic molecule… so what does this mean? Well, consider when wood burns in a fire pit; the wood (in this case the “organic matter”) burns with heat and, most critically, oxygen. Depending on the type of wood it will completely oxidize to carbon dioxide (CO2), but some wood will burn hotter and/or leave more ash reflecting the difference in types of wood. .
Now let’s think about natural organic matter in water. Some organic material will convert to CO2 more readily than others when exposed to biological processes or treatment chemicals, such as ozone, chlorine and potassium permanganate (of course the treatment chemicals also influence the degree to which the organic matter is oxidized). Thus by measuring the COD or organic matter prior to, and following different treatment processes, we can understand the potential to oxidize organic material.
Ultimately, COD along with other measurements helps the industry design and operate water treatment processes.
This month’s Ask the Expert was answered by Dr. Graham Gagnon, Professor at the University of Dalhousie.
For more information on PeCOD and drinking water analysis please contact Camlab below.