Alum and polyelectrolytes can be used to remove algae from water:

 Alum and polyelectrolytes can be used to remove algae from water: 

Alum: A chemical coagulant that can be used to remove algae from water. The effectiveness of alum depends on the amount of alum added, the initial concentration of algae, and the type of algae. 

Polyaluminum chloride (PAC): A coagulant that can be used with alum to remove algae from water. 

Acid alum: A formulation of aluminum sulfate with 1–15% free sulfuric acid. 

Cationic polyelectrolyte: A coagulant aid that can be used with alum to remove algae from water. 

Other methods for removing algae include:

Flotation: A technique that uses dissolved air flotation (DAF) or dispersed air flotation (DiAF). 

Ultrasound: Ultrasonic sound waves can damage algae, causing them to sink and die. 

Copper sulfate: A chemical that can be used as an algaecide, fungicide, root killer, and antimicrobial.