Mineral / ion
Iron
One of the most common causes of consumer complaint, producing orange or brown discoloured water and staining laundry, without generally posing a health risk at the concentrations involved.
Key facts
- Chemical form
- Fe
- Typical range
- Should be below 200 µg/l in supply; groundwater before treatment can exceed 10 mg/l.
Where it comes from
Dissolved from soils and rock under reducing conditions, so it is common in deep groundwater and in the anoxic bottom water of stratified reservoirs. Also from corroding cast iron mains.
Typical concentrations
Should be below 200 µg/l in supply; groundwater before treatment can exceed 10 mg/l.
What it does
- Dissolved iron is colourless; it turns orange on contact with air as it oxidises and precipitates
- Stains laundry and sanitaryware
- Supports iron bacteria, which form slimes in mains
- A regulatory indicator parameter set for acceptability rather than health
Removal
Removed by aeration followed by filtration, by greensand or catalytic media, and by ion exchange at low concentrations. Discoloured water from old mains is addressed by flushing and mains renewal rather than by treatment.
Related intelligence
Sources
- World Health Organization — Guidelines for Drinking-water Quality. Public but restricted · CC BY-NC-SA 3.0 IGO
- British Geological Survey — Groundwater levels, aquifer mapping and baseline chemistry. Open — attribution required · Open Government Licence v3.0
- National Center for Biotechnology Information — PubChem chemical database. Open · US Government work — public domain