Chemical oxygen demand

Chemical oxygen demand (COD) measures the amount of oxygen that is needed to break down organic matter in a certain amount of water. It is a measure of how much organic pollution is in the water. To measure it, scientists add a chemical mixture to the water which causes the organic material to break down into simpler forms and the amount of oxygen needed to do this is measured. COD is important as it helps us understand how polluted the water is, and if it is safe enough to use for drinking or swimming.