If you buy water treatment chemicals for a municipal plant, an effluent treatment plant or a mine, the coagulant is usually your largest chemical cost. Three products cover most applications: poly aluminium chloride (PAC), aluminium sulphate (alum) and ferric chloride. India manufactures all three at scale, which makes it a practical sourcing base for buyers in Africa, the Middle East and South-East Asia.
What a coagulant does
Raw water and wastewater carry tiny suspended particles with a negative surface charge. Because they repel each other, they stay suspended and make the water cloudy. A coagulant adds positively charged metal ions that neutralise this charge, so the particles collide and form small clumps called micro-flocs. A flocculant such as polyacrylamide then binds these into larger flocs that settle or float off.
Poly aluminium chloride (PAC)
PAC is a pre-polymerised aluminium salt. Because part of the chemistry has already happened in the factory, it forms flocs faster and works over a wider pH range than alum, roughly pH 5 to 9. In many plants it needs a lower dose, consumes less alkalinity and produces less sludge.
- Best for: drinking water, cold or low-turbidity water, and effluents with changing quality.
- Forms: yellow or white powder (commonly around 28–31% Al₂O₃) and liquid.
- Watch for: basicity and Al₂O₃ content. Ask for both on the certificate of analysis.
Aluminium sulphate (alum)
Alum is the traditional, lowest-cost coagulant and is still widely used. It performs best in a narrower pH band and lowers pH as it reacts, so plants often dose lime alongside it.
- Best for: large plants with stable raw water and tight budgets.
- Grades: non-ferric for drinking water and ferric (iron-bearing) for effluent and paper.
Ferric chloride
Ferric chloride is an iron-based coagulant supplied as a dark brown liquid, usually around 40%. It forms heavy, fast-settling flocs, works across a broad pH range and is very effective at removing phosphorus, which is why many sewage plants use it.
- Best for: sewage and industrial effluent, phosphate removal and sludge conditioning.
- Watch for: it is corrosive, so storage tanks, pumps and transport need suitable materials.
Quick comparison
| PAC | Alum | Ferric chloride | |
|---|---|---|---|
| Effective pH range | Wide | Narrow | Wide |
| Floc formation | Fast | Moderate | Fast, heavy flocs |
| Sludge volume | Lower | Higher | Moderate |
| Typical use | Drinking water, ETP | Large municipal plants | Sewage, phosphate removal |
Run a jar test first
The right coagulant depends on your water. Before placing a large order, run a jar test with samples of each product at several doses and compare turbidity, floc size and settling time. A good supplier will send samples for this.
What to ask a water treatment chemicals exporter in India
- The exact grade and the key specifications, such as Al₂O₃ content and basicity for PAC, or iron content for ferric chloride.
- A technical data sheet, a certificate of analysis for your lot, and the safety data sheet.
- Packing details: bag or drum weight, liners, palletisation and how many fit in a 20-foot container.
- Whether drinking-water use needs a specific certification in your country.
- FOB or CIF pricing and the lead time to your port.
Rudra International exports PAC, alum, ferric chloride, calcium hypochlorite, TCCA, polyacrylamide and hydrated lime from India. See the full water treatment chemicals range or send us your specification for a written quotation.