Water Treatment Chemicals: Coagulants, Flocculants and Disinfection

Water Treatment Chemicals: How the Pieces Fit Together

Water and wastewater treatment is a sequence of chemical steps, and buying it product-by-product leads to mismatched doses, incompatible grades and missed savings. This page is the overview of the water-treatment chemicals we supply, why each is used, and how they work together – from coagulation and flocculation through disinfection, dechlorination, corrosion and scale control. Use it to find the right product, then follow the links for the detail.

1. The treatment sequence

Stage	What it does	Typical chemicals we supply
Coagulation	Destabilises suspended particles so they can stick together	Polyaluminium chloride (PAC), aluminium sulfate, ferric sulphate
Flocculation	Bridges the particles into large, settleable flocs	PolyDADMAC, polyamine, polyacrylamide (PAM)
Clarification / dewatering	Separates sludge from water	PAM, polyamine, polyDADMAC
Disinfection	Kills pathogens	Chlorine, glutaraldehyde, DDAC, 5,5-dimethylhydantoin
Dechlorination	Removes residual chlorine before discharge or downstream processes	Sodium metabisulfite
Corrosion / scale control	Protects boilers, cooling and RO systems	Morpholine, sulfamic acid (descaling)
pH adjustment	Sets the pH each stage needs	Potassium hydroxide (KOH), sulfuric acid

2. Coagulants (inorganic)

Coagulants neutralise the surface charge on suspended particles so they can be collected. The choice depends on the water, the target and the sludge you can handle.

Polyaluminium chloride (PAC, CAS 1327-41-9) – a pre-hydrolysed coagulant that works across a wide pH range and is widely used for drinking water and wastewater. Efficiency generally depends on the Al₂O₃ content and basicity of the grade.
Aluminium sulfate – the classic, low-cost coagulant for drinking water and general clarification.
Ferric sulphate (CAS 10028-22-5) – a strong coagulant for wastewater and phosphorus removal (see ferric sulphate for phosphorus removal).

Comparing ferric and ferrous salts? See Ferric vs Ferrous Sulphate in Water Treatment.

3. Flocculants (organic polymers)

Organic flocculants build the coagulated particles into flocs that settle, float or dewater well. They are usually selected by charge type (cationic, anionic, nonionic) and molecular weight.

PolyDADMAC (CAS 26062-79-3) – a high-charge cationic polymer whose charge is essentially pH-independent; used for drinking water (NSF standards), papermaking and industrial clarification.
Polyamine (CAS 42751-79-1) – a cationic coagulant/flocculant for wastewater, sludge dewatering, oil-water separation and papermaking.
Polyacrylamide (PAM) – the workhorse flocculant, available as anionic, cationic and nonionic grades for clarification, sludge dewatering, mining and agriculture.

Choosing between them? See the comparison Polyamine vs PAM vs PolyDADMAC, and for PAM grades Anionic vs Cationic vs Nonionic PAM.

4. Dechlorination and reducing agents

Sodium metabisulfite (CAS 7681-57-4) reduces free chlorine and chloramine to chloride – the standard reagent for removing residual chlorine from drinking water, wastewater and RO feed, and for Cr(VI) reduction. See dechlorination and RO protection.

5. Corrosion, scale and descaling

Morpholine (CAS 110-91-8) – a volatile amine used in boiler-water treatment to raise condensate pH and control corrosion (see corrosion inhibition).
Sulfamic acid (CAS 5329-14-6) – a safe, easy-to-handle descaler for boilers, heat exchangers and RO membranes (see descaling).

6. Biocides

For microbial control in cooling water, oilfield and process water:

Glutaraldehyde (CAS 111-30-8) – a broad-spectrum biocide (water treatment and oilfield).
DDAC (CAS 7173-51-5) – a quaternary ammonium biocide/surfactant (DDAC vs benzalkonium chloride).
5,5-Dimethylhydantoin (CAS 77-71-4) – a precursor to halogenated hydantoin biocides (see the biocide route).

7. pH adjustment and natural polymers

Potassium hydroxide (KOH, CAS 1310-58-3) – a strong base for pH adjustment and neutralisation.
Chitosan (CAS 9012-76-4) – a bio-based flocculant for drinking water and wastewater (chitosan in water treatment).
Polyaspartic acid – a biodegradable chelant for scale and metal control.

8. Supplying water treatment chemicals to African projects

Africa’s growth in municipal supply, seawater and brackish-water RO, and mine water treatment is driving demand for exactly these products. We supply the range from China to African ports with the packaging and documentation projects require – 25 kg bags and 1000 kg jumbo bags or IBCs, per-batch COA and SDS, third-party inspection (SGS/BV) on request, and FOB or CIF terms to Durban, Mombasa, Dar es Salaam, Tema/Takoradi, Lagos/Apapa, Beira and Walvis Bay. See water treatment in Africa for a worked example.

9. How to specify and buy

What to confirm	Why
Active content / grade	PAC by Al₂O₃ and basicity; PAM by charge and molecular weight; coagulants by assay
Application grade	Drinking-water use needs the right approvals (for example NSF-listed PolyDADMAC)
Form and packaging	Solid vs liquid, bag or IBC or bulk; storage and dosing method
COA and SDS per batch	Traceability and compliance
Delivery terms	FOB or CIF, port of discharge, annual or quarterly volume

Frequently Asked Questions

Which coagulant should I use, PAC or aluminium sulfate?

PAC works across a wider pH range and is common for drinking water and wastewater; aluminium sulfate is the classic low-cost option. The right choice depends on your water and sludge handling – test both on your water.

What is the difference between a coagulant and a flocculant?

Coagulants (PAC, alum, ferric sulphate) destabilise particles; flocculants (PolyDADMAC, polyamine, PAM) build them into large flocs that settle or dewater.

Do you supply for drinking water?

Yes – including PolyDADMAC for drinking-water coagulation (check the relevant approvals) and sodium metabisulfite for dechlorination.

Can you supply to African ports?

Yes, FOB or CIF to Durban, Mombasa, Dar es Salaam, Tema/Takoradi, Lagos/Apapa, Beira, Walvis Bay and others.