Final answer:
Coagulants such as alum and lime can be used to neutralize the electrical charge of colloidal particles and enable them to flocculate, increasing in size so they settle out.
Step-by-step explanation:
Coagulants can be used to neutralize the electrical charge of colloidal particles and enable them to flocculate, increasing in size so they settle out. Flocculants are chemicals that are added to the water to cause the colloidal particles to stick together and form larger particles called floc. Examples of coagulants that can be used include alum (aluminum potassium sulfate) and lime (calcium hydroxide).