Mineral / ion
Chloride
A conservative ion that moves with water essentially unchanged, which makes it a useful tracer of saline intrusion, road salt and wastewater influence.
Key facts
- Chemical form
- Cl⁻
- Typical range
- Inland supplies 10–50 mg/l; the EU and UK limit is 250 mg/l, set for taste and corrosivity.
Where it comes from
Halite dissolution, marine aerosol, seawater intrusion, road de-icing salt and sewage effluent.
Typical concentrations
Inland supplies 10–50 mg/l; the EU and UK limit is 250 mg/l, set for taste and corrosivity.
What it does
- Salty taste above roughly 250 mg/l, depending on the accompanying cation
- Accelerates corrosion of steel and stainless steel
- A rising chloride trend in a coastal borehole is the classic early signal of saline intrusion
Removal
Removed by reverse osmosis, distillation, electrodialysis and anion exchange. Not removed by carbon or softening.
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