Aluminum (Al) in Water Treatment

Quick Answer

Aluminum (Al) is a post-transition metal with atomic number 13. PubChem lists its standard state as solid and its relative atomic mass as 26.981538.

Aluminium salts are widely used as coagulants, while residual dissolved or particulate aluminium can be a treatment-control concern. Coagulant dose, pH, mixing and filtration performance should be optimized together.

Interesting Facts

• Aluminium is Earth’s most abundant crustal metal, yet it is rarely found as free metal because it bonds readily with oxygen.
• A thin, self-repairing oxide film is why aluminium metal can resist corrosion despite being chemically reactive.
• In treatment plants, “aluminium” usually means dissolved or particulate aluminium species from raw water or coagulants—not pieces of metal.

Water-treatment Design Implications

An element name alone is not enough to select treatment equipment. Confirm chemical form or speciation, total and dissolved concentration, pH, alkalinity, competing ions and the product-water target. Send the water-analysis results to Watermart to identify additional testing and shortlist processes before equipment is specified.

Summary Data Sources

• PubChem — Aluminum
• IUPAC Periodic Table of Elements
• WHO chemical hazards in drinking-water

Aluminum (Al)

1. Basic Information

Atomic Number	13
Symbol	Al
Atomic Mass	26.98 g/mol
Electron Configuration	[Ne]3s² 3p¹

2. Physical and Chemical Properties

Aluminum is a light metal with a silver-white appearance. It has a melting point of 660.4°C and a boiling point of 2467°C. Aluminum is highly reactive but is protected by an oxide layer that forms quickly when exposed to air. In water, dissolved aluminum hydrolyzes and can form different charged or neutral species as pH changes; it may also occur in colloids or particles. Organic and inorganic ligands further affect its solubility.

3. Presence in Water and Health Effects

Aluminium can enter water through mineral weathering and can also remain after treatment with aluminium-based coagulants. Its solubility depends strongly on pH and on whether the result represents dissolved aluminium, colloids, or floc carry-over. WHO does not establish a health-based drinking-water guideline value for aluminium; operational control is instead important for coagulation performance, appearance, deposits, and distribution-system management.

4. Water Treatment Applications and Removal Methods

In water treatment, aluminum is often used as a coagulant in the form of alum (aluminum sulfate) or polyaluminum chloride (PAC). The main methods for removing excess aluminum from water include:

• Coagulation and flocculation followed by sedimentation or filtration
• Ion exchange using cation exchange resins
• Membrane filtration such as nanofiltration or reverse osmosis
• Adsorption using activated carbon or specialized adsorption media

For water with a mildly acidic pH, strong acid cation exchange resins such as sulfonate-based ones can be used. For pH between 3-6, weakly acidic cation exchange resins may be more effective. For saltwater streams, selective chelating resins can be used to selectively remove aluminum.

5. Industrial Uses in Water Treatment

Besides being used as a coagulant, aluminum also has several industrial applications related to water treatment:

• Manufacture of aluminum oxide filtration media for the removal of contaminants such as arsenic and fluoride
• Production of aluminum oxide-based ceramic membranes for water filtration
• Use in electrolytic processes for wastewater treatment

6. Case Study and Real World Application Example

Actual coagulation performance is water-specific. Jar testing should establish dose and pH, followed by checks on turbidity, dissolved organic carbon where relevant, filter performance, and residual aluminium rather than relying on an unrelated case-study percentage.

8. Environmental Impact and Sustainability Considerations

Although aluminum is considered relatively harmless to the environment, excessive use in water treatment can cause problems. Accumulated aluminum sludge from water treatment processes can contaminate soil and groundwater if not managed properly. Some studies show that elevated aluminum concentrations in water bodies can negatively affect aquatic organisms, especially in water environments affected by acid rain.