Aluminum Sulfate for Water Treatment | Low-Iron 17% Alum, Bulk

Water treatment chemicals · Bulk export from Türkiye & UAE

Aluminum Sulfate for Water Treatment: How Alum Clears Water

Aluminum sulfate for water treatment, better known as alum (aluminium sulphate in British English), is the most widely used coagulant in drinking water and wastewater plants. It turns fine clay, silt, colour and organic matter into floc that settles and filters out, so cloudy raw water leaves the plant clear. This guide is for plant operators, engineers, tender buyers and chemical distributors. It explains how alum works, how to find the right dose, how to protect pH and alkalinity, how alum compares with PAC and ferric chloride, and what to specify when you buy aluminum sulfate by the container. Water and wastewater treatment is the largest single market for alum: in the United States it accounts for about 45% of total consumption, according to the US EPA.

Process chemistry

How Aluminum Sulfate Works in Water Treatment

Particles that make water cloudy, such as clay, silt, algae and natural organic matter, are tiny and carry a negative surface charge. They repel each other and stay suspended for days. Alum breaks that stability in four steps:

1. Coagulation (rapid mix). Alum dissolves and its aluminium ions neutralise the particle charge within seconds. Good mixing at the dosing point is essential.
2. Flocculation (slow mix). Aluminium hydroxide precipitates and gentle mixing over 15–30 minutes builds the destabilised particles into visible floc.
3. Sedimentation or flotation. The heavy floc settles in the clarifier, or is floated off in a DAF unit, and leaves as sludge.
4. Filtration. Sand or multimedia filters remove the remaining fine floc before disinfection.

In water with natural bicarbonate alkalinity, the overall reaction is:

Al₂(SO₄)₃·14H₂O + 3 Ca(HCO₃)₂ → 2 Al(OH)₃↓ + 3 CaSO₄ + 6 CO₂ + 14 H₂O

The aluminium hydroxide is the floc. The reaction also adds sulfate, releases carbon dioxide and consumes alkalinity, which is why the pH falls after alum dosing.

Two coagulation mechanisms

Applications

Where Alum Is Used in Water and Wastewater Treatment

Outside water treatment, the same product is used for rosin sizing in pulp and paper mills, as a mordant in textile dyeing, and in leather tanning, where tanneries also buy sodium sulfide for dehairing.

Terminology

Alum, Aluminium Sulphate and Other Names for the Same Coagulant

Buyers, tenders and customs documents use many names for aluminum sulfate. They all mean the same water treatment coagulant, Al₂(SO₄)₃·xH₂O (CAS 10043-01-3, HS 2833.22):

Note that "alum" in water treatment means aluminum sulfate. Potassium alum (potash alum), sold for crafts and cosmetics, is a different compound and is not used as a bulk coagulant.

Dosing

Alum Dose for Water Treatment and the Jar Test

There is no single correct dose of aluminum sulfate for water treatment. Typical doses range from 5 to 200 mg/L of alum (as Al₂(SO₄)₃·14H₂O), and very dirty water can need up to 500 mg/L. Clear reservoir water sits at the low end; turbid river water in the rainy season at the high end. The dose depends on turbidity, colour, natural organic matter, alkalinity, pH and water temperature, so it is found by a jar test and checked whenever raw water quality changes.

How to run a jar test

1. Fill the jars. Fill six beakers with the same raw water sample, typically 1 litre each.
2. Dose a range. Add increasing alum doses, for example 10, 20, 30, 40, 50 and 60 mg/L, from a fresh stock solution.
3. Mix as the plant does. Rapid mix for about one minute, then slow mix for 15–20 minutes to build floc.
4. Settle. Stop the stirrers and let the floc settle for about 30 minutes.
5. Measure. Measure settled turbidity, colour, pH and, ideally, residual aluminium in each jar.
6. Pick and refine. Choose the lowest dose that meets your targets, then repeat with pH adjustment if needed.

Mixing times and speeds should match your own plant's rapid-mix and flocculation stages. Dose ranges on this page are for guidance only; your plant design and local regulations set the final dose.

The calculator uses 0.5 mg/L alkalinity (as CaCO₃) consumed per mg/L of alum (14-hydrate), about 19 MT per 20ft container in bags, and pure-basis equivalents of 0.80 mg/L caustic soda, 0.74 mg/L hydrated lime or 1.06 mg/L soda ash per mg/L of alkalinity as CaCO₃.

pH control

pH and Alkalinity Control with Alum

Alum is acidic. Each 1 mg/L of aluminum sulfate (14-hydrate) consumes about 0.5 mg/L of alkalinity as CaCO₃ and releases carbon dioxide. In hard, well-buffered water this hardly matters. In soft or coloured water with little alkalinity, a normal dose can push the pH below the working range, so the floc forms poorly and residual aluminium rises.

Plants correct this by dosing an alkali before or with the alum:

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After filtration, many plants add a final pH correction, again with lime, soda ash or liquid caustic soda, to make the water less corrosive to pipes before it enters the distribution network.

Wastewater

Aluminum Sulfate for Phosphorus Removal in Wastewater

Phosphorus in treated effluent feeds algae in rivers and lakes, so many discharge permits set strict limits. Aluminium ions react with dissolved phosphate to form insoluble aluminium phosphate, which settles with the sludge. Alum can be dosed in the primary clarifier, the aeration basin or ahead of tertiary filters.

The theoretical ratio is 1 mol of aluminium per mol of phosphorus, but competing reactions mean plants need more in practice. Typical molar ratios are:

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Based on solid aluminum sulfate 14-hydrate (about 17% Al₂O₃, 297 g per mol Al). Confirm the ratio by jar test or plant trial, because pH, mixing point and competing reactions change the real demand.

Coagulant choice

Alum vs PAC vs Ferric Chloride: Choosing a Coagulant

Aluminum sulfate is not the only coagulant. The right choice depends on raw water, plant design and cost per cubic metre treated, not cost per tonne of chemical.

Swipe the table sideways to compare.

Many plants keep alum as their base coagulant and add a polymer coagulant aid to strengthen the floc, rather than switching chemicals.

Technical data

Aluminum Sulfate for Water Treatment: Lot Analysis and Specifications

These are the limits we supply to and a typical lot analysis of our solid aluminum sulfate, Al₂(SO₄)₃·xH₂O. Every shipment comes with its own batch COA.

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What each value means for your plant

• Al₂O₃ 17.68%: the active aluminium content. Dose calculations on this page assume 17%, so this lot gives a small safety margin.
• Fe₂O₃ 0.02%: low iron, so the coagulant adds no visible colour to drinking water or paper.
• Insolubles 0.08%: very little residue in dissolving tanks, dosing pumps and lines.
• Free H₂SO₄ 0.00%: no free acid, so the product is fully reacted and less aggressive to handle and store.
• pH 3.24: normal for a fully reacted aluminum sulfate solution.

How our grade compares with a typical drinking water tender

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If your tender sets a tighter limit, send it with your enquiry and we will confirm the matching lot before you order.

Physical data

Liquid alum is typically 7.5–8.4% Al₂O₃, so one tonne of solid carries roughly the aluminium of two tonnes of liquid. That is why solid alum is the usual choice for export shipments. Alum is made by reacting aluminium hydroxide or bauxite with sulfuric acid.

Standards buyers often reference

• AWWA B403: aluminum sulfate for water supply service (USA)
• EN 878: aluminium sulfate for treatment of water intended for human consumption (Europe)
• GOST 12966-85: purified technical aluminium sulfate (Russia and CIS)
• NSF/ANSI/CAN 60: drinking water treatment chemicals and health effects

Compliance with a named standard or certification is confirmed per producer and shipment. Full product data is on our aluminum sulfate supplier page.

Health and safety

Residual Aluminium, Drinking Water Limits and Safe Handling

Almost all of the aluminium dosed leaves the plant in the sludge. A small residual can pass the filters if the pH, dose or mixing is wrong. Regulators therefore control residual aluminium in treated water:

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To keep residuals low, WHO points to operating at the optimum pH, avoiding excessive dosage, good mixing at the dosing point, and effective flocculation and filtration. Aluminium is least soluble near pH 6 at 25 °C, and the minimum-solubility pH rises to about 6.5–7 in cold water.

Procurement

Bulk Aluminum Sulfate for Water Treatment Plants and Distributors

Water utilities, treatment contractors and chemical distributors buy alum on annual contracts or tenders. We supply solid, low-iron aluminum sulfate in these formats:

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MOQ: one full container load (1 FCL, 20ft or 40ft). Loading: FOB Mersin (Türkiye) or FOB Jebel Ali (UAE), with CFR and CIF on request. Lead time: depends on the destination and is confirmed with each quotation. Payment: T/T or L/C at sight.

Water plants usually need more than a coagulant. We also supply calcium hypochlorite and sodium hypochlorite for disinfection, caustic soda, soda ash and lime for pH correction, and sulfuric acid for pH reduction, so a plant can consolidate its chemicals on one contract.

Sources

Standards and References Used in This Guide

• Australian Drinking Water Guidelines (NHMRC), Part 5: Aluminium sulfate (alum): dose range, optimum pH and forms supplied
• World Health Organization, Aluminium chemical fact sheet: practicable levels of 0.1 mg/L and 0.2 mg/L
• Directive (EU) 2020/2184 on the quality of water intended for human consumption: aluminium indicator value
• US EPA National Secondary Drinking Water Regulations: aluminium 0.05–0.2 mg/L
• US EPA, Aluminum Sulfate Supply Chain Profile (2022): about 45% of US consumption goes to water and wastewater treatment
• UNICEF Supply Catalogue, aluminium sulphate granules for drinking water treatment: specification
• TU Delft OpenCourseWare, Drinking and wastewater treatment: Al:P molar ratios for phosphorus removal
• AWWA B403 and EN 878 product standards for aluminium sulfate in water treatment
• Product data: SUHA International aluminum sulfate 17% specification and typical lot analysis. Stoichiometric figures calculated from molar masses

Supplier

Your Main Supplier of Aluminum Sulfate for Water Treatment, with Offices in Türkiye and Dubai

SUHA International Trading supplies aluminum sulfate for water treatment to utilities, contractors and distributors across Türkiye, the Middle East, Africa, the Balkans and Central Asia. Aluminum sulfate is a core product for us, not a side line: we keep a consistent 17% low-iron grade, support public tenders with documents and inspection, and plan container schedules around your plant's consumption. We work from two offices: our head office in Business Bay, Dubai, which serves the UAE and Gulf, and our Ankara office, which serves Türkiye and exports through Mersin. More about SUHA International

Meetings at either office are by appointment. WhatsApp is monitored seven days a week, and enquiries are answered within one business day.

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