Coagulation is the first major step in most effluent and drinking-water treatment plants: a coagulant neutralises the charge on suspended colloidal particles so they can clump together (flocculate) and settle or filter out. Picking the wrong coagulant doesn't just waste money on dosing — it can mean more sludge to dispose of, poor removal on cold or high-colour water, or a treated effluent that fails discharge norms. The three coagulants below cover the vast majority of Indian ETP and water-treatment applications.
Aluminium Sulphate (Non-Ferric Alum)
Alum is the most widely used and most economical coagulant, with decades of operating history in Indian municipal and industrial plants. It performs best in a fairly narrow pH window — roughly pH 6.5 to 7.5 — outside of which coagulation efficiency drops off quickly, so plants running alum need reasonably consistent influent pH or a pH-correction step ahead of dosing. It also tends to produce a larger sludge volume than PAC for the same turbidity load, and floc formation slows noticeably in cold water.
See our Aluminium Sulphate (Non-Ferric Alum) product page for characteristics and packaging.
Poly Aluminium Chloride (PAC)
PAC is a pre-hydrolysed aluminium coagulant, which is why it generally needs a lower dose than alum to hit the same turbidity-removal target. It works across a wider pH range (roughly pH 5–9), performs noticeably better in cold water, and produces less sludge — all of which is why it has largely replaced alum in newer municipal and industrial plants. It's available as a liquid or as a powder grade, and dosing/handling equipment differs slightly between the two.
We stock both Poly Aluminium Chloride (PAC) liquid and the Poly Aluminium Chloride Powder (AC100S) — the powder grade carries NSF/ANSI/CAN 60 certification for potable water dosing. A Vikram-brand liquid range is also available: Poly Aluminium Chloride — Vikram Brand Liquid Grades.
Ferric Chloride
Ferric chloride is the coagulant of choice for high-turbidity or strongly coloured water, and it's particularly effective for phosphate removal in effluent treatment — a requirement many ETPs now have to meet. It works over a broader pH range than alum, but it's also the most corrosive of the three: dosing systems and storage need acid-resistant (HDPE/FRP-lined) construction, and overdosing can leave a slight iron colour in the treated water.
Available as liquid or anhydrous: Ferric Chloride Liquid and Ferric Chloride Anhydrous.
Which One Should You Choose?
As a rough starting point: choose alum if cost per kg is the priority and your plant has spare sludge-handling capacity; choose PAC if you're dealing with cold water, want a lower sludge footprint, or need consistent performance across a variable pH influent; choose ferric chloride if your effluent is highly turbid or coloured, or if phosphate removal is a discharge requirement.
Every effluent stream behaves a little differently, so the standard practice before committing at plant scale is a simple jar test comparing 2–3 candidate coagulants and doses side by side. We're happy to send samples for exactly this purpose.