Chemical Oxygen Demand (COD) utilizes chemical oxidation to measure the amount of oxygen required to oxidize both organic and inorganic matter in wastewater.
COD measures the amount of oxygen consumed by chemical oxidation of the wastewater sample.
The COD test is favored for its speed and comprehensiveness, offering results within 3-4 hours, making it the preferred choice for process control in wastewater treatment facilities.
The principle behind the COD test involves adding a 2ml wastewater sample to a strong chemical oxidant, potassium dichromate in a sulfuric acid solution. The mixture is then heated under reflux conditions, which accelerates the oxidation process. The amount of oxygen required to complete this reaction corresponds to the COD value, which is expressed in milligrams of oxygen consumed per liter of sample (mg O2/L).
COD measures oxygen consumed by chemical oxidation, verse BOD (Biological Oxygen Demand) oxygen consumed by biological organisms.
In comparison to Biological Oxygen Demand (BOD), another commonly used water quality parameter, COD offers a broader measure of water quality by including both biodegradable and non-biodegradable substances. While BOD specifically assesses the amount of oxygen aerobic organisms consume to break down organic matter in water over five days, COD captures the total chemical oxidation potential of the water sample, including substances that bacteria cannot readily decompose.