Chemical Oxygen Demand (COD) Explained | Definition, Principle, Procedure, Calculation & Importance
Chemical Oxygen Demand (COD) – Definition, Principle, Procedure & Importance Chemical Oxygen Demand (COD) is one of the most important parameters used in environmental science and water/wastewater quality analysis. It indicates the amount of oxygen required to chemically oxidize oxidizable substances present in a water sample. What is Chemical Oxygen Demand (COD)? COD is the amount of oxygen required to oxidize organic and certain inorganic substances present in water or wastewater by a strong chemical oxidizing agent. It is generally expressed as: mg/L of O₂ (milligrams of oxygen per litre) A high COD value usually indicates a high concentration of oxidizable pollutants and therefore greater pollution potential. Principle of COD Test In the conventional dichromate method, a known quantity of water sample is heated under acidic conditions with a strong oxidizing agent, usually potassium dichromate (K₂Cr₂O₇). The oxidation is carried out in the presence of sulfuric acid ...