Mineral / ion
Silica
Dissolved silicon, present in almost all natural water and a persistent operational problem for membranes and boilers because it forms a hard, difficult scale.
Key facts
- Chemical form
- SiO₂
- Typical range
- Typically 2–20 mg/l; higher in volcanic terrains.
Where it comes from
Weathering of silicate minerals — quartz, feldspar, clays. Volcanic and geothermal waters carry the highest concentrations.
Typical concentrations
Typically 2–20 mg/l; higher in volcanic terrains.
What it does
- Forms a glassy scale on reverse osmosis membranes and boiler surfaces that is much harder to remove than carbonate scale
- Limits recovery in reverse osmosis systems, because silica reaches saturation in the concentrate
- No health significance at natural concentrations
Removal
Removed by reverse osmosis, though it constrains system recovery, and by strong-base anion exchange and lime 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