What are the most commonly used coagulants in water treatment processes and how do they help in removing impurities from water?

The most commonly used coagulants in water treatment processes are aluminum sulfate (alum) and ferric chloride. These coagulants help in removing impurities from water by attracting and binding together particles in the water, forming larger clumps called flocs. These flocs then settle to the bottom of the water, carrying impurities with them, making it easier to filter them out.