Mineral / ion
Sulphate
Contributes permanent hardness and, at higher concentrations, a bitter taste and a laxative effect that is the basis of several historic spa waters.
Key facts
- Chemical form
- SO₄²⁻
- Typical range
- Typically 10–80 mg/l; the EU and UK limit is 250 mg/l.
Where it comes from
Dissolution of gypsum and anhydrite, oxidation of sulphide minerals such as pyrite — which also generates acid mine drainage — and industrial discharge.
Typical concentrations
Typically 10–80 mg/l; the EU and UK limit is 250 mg/l.
What it does
- Bitter taste above roughly 250 mg/l
- Laxative effect at high concentrations, the reason Epsom water was historically taken medicinally
- Under anaerobic conditions, sulphate-reducing bacteria produce hydrogen sulphide and its rotten-egg odour
- Forms permanent hardness that does not precipitate on heating
Removal
Removed by reverse osmosis, nanofiltration and anion exchange.
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