Aluminium occurs naturally in many water sources, particularly acidic groundwater and surface water from upland or peaty areas. It can also enter drinking water through certain treatment processes.
Removing aluminium is not always straightforward because it can exist in different forms depending on the water's pH and chemistry.
The most important question is whether the aluminium is dissolved in the water or present as suspended particles. This determines which treatment methods are likely to be effective.
What Is the UK Drinking-Water Limit for Aluminium?
The UK drinking-water standard for aluminium is 200 µg/L (0.2 mg/L).
This is primarily an indicator standard associated with water quality and appearance, rather than a direct health-based limit.
Elevated aluminium concentrations can contribute to:
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Cloudiness or discolouration.
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Deposits within pipework and water treatment equipment.
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Problems with the performance of certain downstream treatment processes.
An aluminium result above 0.2 mg/L should be investigated, but choosing the correct treatment requires more information than the concentration alone.
Dissolved vs Particulate Aluminium
Aluminium can occur in several forms in water.
Dissolved Aluminium
Dissolved aluminium is more commonly encountered in acidic water, although its behaviour depends on pH and other dissolved substances.
Because it is present in solution, it cannot reliably be removed using an ordinary sediment cartridge.
Possible treatment approaches include suitable ion-exchange processes, reverse osmosis or controlled pH adjustment followed by filtration.
Particulate Aluminium
Particulate aluminium consists of solid or suspended material.
If aluminium is present as filterable particles, suitable sediment filtration may reduce its concentration.
However, filtration performance depends on particle size, filter rating and the amount of material present.
Very fine colloidal particles may pass through ordinary sediment filters.
Why pH Matters
Aluminium chemistry is strongly influenced by pH.
Under certain conditions, adjusting the pH can cause dissolved aluminium to form insoluble aluminium hydroxide particles. These particles may then be removed through filtration.
However, simply increasing the pH does not guarantee aluminium removal.
Aluminium can become soluble again under more alkaline conditions, and naturally occurring organic compounds may keep some aluminium in solution.
Consequently, pH correction followed by filtration should be treated as a process requiring verification, not as a guaranteed removal method.
The correct operating pH depends on the complete water chemistry.
Methods of Removing Aluminium from Water
1. Sediment Filtration
Sediment filters can reduce aluminium when it is present in particulate form.
Suitable options may include:
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Spun polypropylene cartridges.
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Pleated sediment filters.
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Backwashing multimedia filtration systems.
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Other filtration systems selected for the particle size and loading.
Advantages
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Straightforward treatment where aluminium is already particulate.
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Suitable for a wide range of flow rates.
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Can also reduce other suspended solids.
Limitations
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Does not reliably remove dissolved aluminium.
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Very fine particles may pass through.
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High sediment loading can cause rapid cartridge blockage.
Best suited to: Water containing filterable aluminium particles, confirmed by appropriate testing.
2. pH Correction Followed by Filtration
For some acidic supplies, pH adjustment can encourage dissolved aluminium to form particles that can subsequently be filtered out.
This may involve a suitable neutralisation system followed by sediment or backwashing filtration.
Advantages
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Can address acidic water and aluminium together.
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May also improve conditions for other treatment processes.
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Potentially suitable for whole-house or commercial installations.
Limitations
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Aluminium removal depends on the final pH and water chemistry.
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Precipitation may be incomplete.
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Particles formed during treatment must be removed.
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Media beds can become fouled if precipitation occurs within them.
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Performance must be confirmed by testing the treated water.
Best suited to: Acidic supplies where testing or treatment trials demonstrate that pH correction produces removable aluminium particles.
3. Ion Exchange and Water Softeners
Under suitable conditions, positively charged dissolved aluminium species may be taken up by cation-exchange resins.
This means a water softener can sometimes reduce low concentrations of dissolved aluminium.
However, a conventional water softener is designed primarily to remove calcium and magnesium, not aluminium.
The effectiveness of aluminium removal depends heavily on its chemical form, water pH and competing ions.
Advantages
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May provide some aluminium reduction alongside hardness removal.
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Could be useful where aluminium concentrations are relatively low.
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Existing softening equipment may sometimes be considered as part of a treatment trial.
Limitations
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Aluminium removal cannot be assumed.
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Aluminium precipitates may foul the resin.
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Normal salt regeneration may not adequately remove accumulated aluminium deposits.
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Low-fouling resin can improve resistance to certain deposits but does not eliminate the problem.
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Specialist resin selection may be necessary.
Anion-exchange resins may be relevant to particular negatively charged aluminium complexes, but they should not be considered a general-purpose aluminium removal solution.
Best suited to: Carefully assessed applications involving low concentrations of suitable dissolved aluminium species, with performance confirmed by testing.
4. Reverse Osmosis
Reverse osmosis (RO) uses a membrane to separate water from many dissolved contaminants, including aluminium species under suitable operating conditions.
RO may be particularly useful when aluminium reduction is required alongside removal of other dissolved substances.
Advantages
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Can substantially reduce many dissolved contaminants.
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Suitable for point-of-use and commercial applications.
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Useful when several water quality problems need addressing together.
Limitations
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Aluminium rejection depends on its chemical form, membrane selection and operating conditions.
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Suspended aluminium and other solids can foul membranes.
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Appropriate pretreatment may be required.
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RO produces a concentrate stream that must be discharged.
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Water production varies with pressure, temperature and feedwater quality.
There is no single aluminium removal percentage or wastewater ratio that applies to every RO system.
Best suited to: Applications requiring broad dissolved-contaminant reduction, provided the feedwater is suitable for the selected membrane.
Does Activated Carbon Remove Aluminium?
Ordinary activated carbon should not be selected as the primary treatment method for dissolved aluminium.
Carbon filtration is generally used for contaminants such as chlorine, certain organic compounds, tastes and odours.
Although some aluminium associated with particles or organic matter may be retained in particular systems, there is no reliable universal aluminium removal percentage for standard activated carbon cartridges.
Why Aluminium Water Testing Can Be Misleading
A water analysis may report aluminium without clearly identifying which form was measured.
This is important because the result may include both dissolved aluminium and aluminium associated with suspended material.
Total Aluminium
A total aluminium result represents the aluminium measured in the sample using the laboratory's specified preparation and analytical method.
It does not tell you how much can be removed by a sediment cartridge.
Dissolved Aluminium
Dissolved aluminium is generally assessed using a sample filtered through a specified laboratory-grade membrane, commonly 0.45 microns, before preservation and analysis.
However, even this is an operational definition: some extremely fine colloidal material can pass through the filter.
Sampling technique matters. Aluminium can change form after collection as pH, temperature and other conditions change.
For reliable comparisons, the laboratory should specify the required sampling, filtration and preservation procedures.
What Should You Ask the Laboratory For?
When investigating aluminium contamination, we recommend requesting:
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Total aluminium.
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Dissolved aluminium, where appropriate.
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pH.
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Alkalinity.
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Total hardness.
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Iron and manganese.
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Turbidity.
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Colour or organic content, particularly for surface water.
The laboratory should be consulted before sampling to ensure the correct bottles and procedures are used.
For private drinking-water supplies, use appropriately accredited testing.
How to Choose the Correct Treatment
| Water condition | Treatment to investigate |
|---|---|
| Aluminium mainly present as filterable particles | Sediment or backwashing filtration |
| Dissolved aluminium in acidic water | Controlled pH correction and filtration, subject to trials |
| Low dissolved aluminium alongside hardness | Suitable ion exchange, with performance verification |
| Dissolved aluminium plus other dissolved contaminants | Reverse osmosis with appropriate pretreatment |
| High or variable aluminium with organic matter and turbidity | Specialist treatment assessment, potentially coagulation and filtration |
Coagulation followed by filtration can be effective for aluminium removal, particularly in larger treatment installations. However, it requires careful control of chemical dosing, pH, sludge removal and ongoing monitoring, making it less practical for many smaller private supplies.
Always Test the Water After Treatment
The effectiveness of any aluminium treatment system should be confirmed by analysing treated water.
Ideally, compare samples taken before and after treatment using consistent laboratory methods.
For systems that depend on pH adjustment or ion exchange, testing should also be repeated after a period of operation to identify changes caused by media exhaustion, fouling or variations in source water quality.
A clear appearance or normal pH reading does not prove that aluminium has been removed.
Aluminium Removal Products from GAPS Water Treatment
GAPS supplies filtration equipment, ion-exchange resins and reverse osmosis systems for domestic and commercial water treatment.
Explore our ranges:
If you need help assessing treatment options, email your water analysis and required flow rate to sales@gapswater.co.uk.
We can help identify suitable equipment, although treatment performance must ultimately be confirmed through appropriate commissioning and water testing.
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