Waterworks treating groundwater may need a removal of iron and manganese to prevent deposits in their pipelines. To this end, iron and manganese are oxidised with oxygen and retained as insoluble oxide particles in filters. Stoichiometrically, the oxidation of iron and manganese requires only small amounts of oxygen. This is therefore often carried out with air oxygen which is limited by it's efficiency. A proper oxygenation system provides the DOC levels needed for supporting the oxidation.