CODgehalte

CODgehalte, often written as COD, refers to the chemical oxygen demand of a water sample. It is the amount of oxygen that would be consumed if all oxidizable substances in the sample were completely oxidized, expressed as milligrams of oxygen per liter (mg/L). The CODgehalte is a common indicator of the total pollution level in water or wastewater, encompassing both biodegradable and non biodegradable organic matter, as well as some inorganic compounds.

The standard measurement uses a chemical oxidation method, most commonly the CODcr procedure. In this method potassium dichromate is used as the oxidant in strongly acidic solution, and the sample is heated to about 150°C for around two hours. The amount of dichromate that is reduced during oxidation is then titrated or measured, and the result is expressed as mg/L COD. Alternative methods, such as CODMn, employ permanganate oxidation at lower temperatures, but are generally less precise for routine wastewater analysis. Results can be affected by sample composition, temperature, reaction time, and interferences such as chlorides or reducing substances.

CODgehalte is widely used in environmental monitoring and wastewater treatment design. It provides a rapid estimate of the organic load and is related to, but not identical with, biological oxygen demand (BOD). Typically, COD values are higher than BOD because COD measures all oxidizable substances, including non biodegradable matter. In municipal wastewater, COD is commonly in the hundreds of mg/L, while natural surface waters usually have COD in the low mg/L range. Interpreting COD alongside BOD and other parameters helps assess treatment needs and compliance with discharge limits.