Last reviewed: September 2026
Aluminum sulfate, commonly called alum, is an inorganic coagulant used in drinking water, wastewater, and industrial water treatment. Aluminum species formed during hydrolysis help destabilize particles and create aluminum hydroxide floc for sedimentation and filtration.
Aluminum Sulfate
Aluminum Sulfate (Alum) in Coagulation
Common applications
- Coagulation and floc formation in drinking water treatment
- Turbidity and suspended-solids removal
- Clarification programs in wastewater and industrial systems
Process and handling considerations
Alum performance depends on raw-water chemistry, pH, alkalinity, temperature, mixing energy, settling, and downstream filtration. Alum addition can consume alkalinity and shift pH, and the process produces residual solids that must be managed. Jar testing and routine plant monitoring should guide chemical selection and feed-rate adjustments.
Compare aluminum sulfate and ferric sulfate for coagulation.
Contact WSU about aluminum sulfate availability and delivery.
Source: U.S. EPA guidance on conventional water treatment and inorganic coagulants.
