Aluminium
Present naturally in acidic waters and introduced deliberately as a coagulant during treatment. Its regulation is an operational indicator — high aluminium means the coagulation process is not being controlled well.
Key facts
- Contaminant group
- Metal
- World Health Organization — guideline
- 100–200 µg/lA practical value based on treatment optimisation rather than on a health effect.
- European Union — legal limit
- 200 µg/lAn indicator parameter, set for acceptability and process control.
- United Kingdom — legal limit
- 200 µg/l
- United States — guideline
- 50–200 µg/lA secondary standard, not federally enforceable.
Where it comes from
- Residual from aluminium sulphate coagulation at treatment works — the dominant source in treated supply
- Natural dissolution from soils in acidic, low-alkalinity catchments
- Acid deposition mobilising aluminium from soil
How it behaves in water
Solubility is strongly pH-dependent, with a minimum around pH 6.5 and rising sharply either side. Coagulation is therefore operated within a narrow pH window, and drifting outside it leaves residual aluminium in the treated water.
How it is measured
Micrograms per litre. Total and dissolved aluminium differ substantially where floc has carried over.
Regulatory position
| Jurisdiction | Value | Status | Notes |
|---|---|---|---|
| World Health Organization | 100–200 µg/l | guideline | A practical value based on treatment optimisation rather than on a health effect. |
| European Union | 200 µg/l | legal limit | An indicator parameter, set for acceptability and process control. |
| United Kingdom | 200 µg/l | legal limit | — |
| United States | 50–200 µg/l | guideline | A secondary standard, not federally enforceable. |
Table sources
- World Health Organization — Guidelines for Drinking-water Quality. Public but restricted · CC BY-NC-SA 3.0 IGO
- European Commission — Drinking Water Directive (EU) 2020/2184 and reporting. Open — attribution required · European Commission reuse policy (Decision 2011/833/EU)
- Drinking Water Inspectorate — Drinking water quality in England and Wales. Open — attribution required · Open Government Licence v3.0
- United States Environmental Protection Agency — Safe Drinking Water Information System. Open · US Government work — public domain
Health context
A proposed link between aluminium in drinking water and Alzheimer’s disease has been examined repeatedly and is not supported by the weight of evidence. WHO and other authorities treat aluminium as an operational rather than a health parameter. Dietary intake exceeds drinking water intake by a wide margin.
What removes it
| Row | Effective | Not reliably effective |
|---|---|---|
| 1 | Optimising coagulation pH — the real answer, applied at the works | Boiling |
| 2 | Switching to an iron-based coagulant | Activated carbon alone |
| 3 | Filtration to remove carried-over floc | Water softening |
| 4 | Reverse osmosis at point of use | — |
Relationships
Related intelligence
Sources
- World Health Organization — Guidelines for Drinking-water Quality. Public but restricted · CC BY-NC-SA 3.0 IGO
- Peer-reviewed scientific literature — Open-access hydrology, water chemistry and water use research. Public but restricted · Publisher terms — public access, reuse not clearly granted