Natural waters contain variable amounts of iron depending on the geological area and other chemical components of the waterway.
Iron in groundwater is normally present in in the Ferrous form, Fe (II), which is soluble. It is easily oxidised to Ferric Iron Fe (III) or insoluble iron upon exposure to air. This precipitate is orange-coloured and often turns streams orange (this is especially seen in the soft, acidic waters of the Eastern Cape). In addition, in areas where iron ductile pipes are used without adequate stabilisation, iron corrosion by-products may result.
Why test for Iron?
In small concentrations, iron is a vital trace element required by both animals and plants.
At larger concentrations, iron is more of an aesthetic concern as iron precipitates as insoluble ferric hydroxide which settles as a rust-coloured salt and is visible in stained laundry, stained enamelled basins and baths. It can also impart a bitter flavour.
Iron is an essential element for good nutrition, but excessive amounts can cause iron poisoning, which cause depression, respiratory problems and cardiac diseases in animals. Lethal doses can lead to death.
Criteria in South Africa:
0.3 mg / litre for discharge of effluent water to rivers – for discharge of effluent water to other areas
* DWA – Requirements for the Purification of waste water or effluent, Act No. 991 – 18 May 1984
< 300 µg / L – aesthetic
< 2 000 µg / L – chronic health
* SANS 241-1: 2011 Drinking Water Standards