Choosing the right coagulant comes down to matching your water chemistry and treatment goals to the strengths of three main candidates: ferric chloride, polyaluminum chloride (PAC), and aluminum sulfate (alum). No coagulant wins everywhere — the correct comparison is performance and total cost per volume of water treated, confirmed by a jar test on your actual water. The factors below tell you which candidates deserve a place on the shortlist; the linked guide and a jar test then finish the job.
The Decision Factors in Brief
- Target contaminant — ferric chloride is typically the first candidate for phosphorus removal, hydrogen sulfide control, and strong color; PAC and alum center on turbidity and general clarification.
- pH and alkalinity — iron coagulants tolerate a wide pH range; alum needs a narrower window and healthy alkalinity; pre-hydrolyzed PAC consumes the least alkalinity of the three.
- Temperature — PAC keeps working in cold water where alum slows markedly.
- Sludge — PAC typically produces less sludge than alum; ferric produces dense sludge that dewaters well.
- Economics — compare on dose-adjusted cost per treated cubic metre, never on price per ton.
Read the Full Comparison
This page is only the map. The full engineering comparison — dosing chemistry, alkalinity consumption, sludge mathematics, temperature effects, and worked selection scenarios for municipal and industrial water — lives in our in-depth guide, Ferric Chloride vs PAC vs Alum: How to Choose a Coagulant, in the Insights section at /insights/coagulant-selection-ferric-pac-alum. If you are shortlisting a coagulant, start there.
Then Let the Jar Test Decide
Shortlists end at the bench. A structured jar test comparing your two or three candidates on fresh raw water settles the question in an afternoon — see our jar testing best-practices article for the procedure. CHIMI ART supplies ferric chloride, liquid and powder PAC, ferrous coagulants, and polyacrylamide flocculants from one source, and our technical team can provide samples and dosing support for the comparison. Contact us to set it up.