What is the main purpose of using a coagulant such as aluminum in water treatment?

The primary purpose of using a coagulant like aluminum in water treatment is to promote flocculation. Coagulation is a process where particles in the water that are too small to settle out on their own are agglomerated into larger particles, known as floc. This occurs when the coagulant is added to the water, destabilizing the fine particles by neutralizing their negative charges. Once these particles are neutralized, they attract each other and form larger aggregates that settle out of the water more easily.

This process is essential in treating drinking water as it helps remove suspended solids, bacteria, and other contaminants effectively. By promoting flocculation, coagulants enhance the overall water clarity and quality, making it safer for consumption. Other options like decreasing pH, increasing water temperature, or softening water do not directly relate to the primary role of coagulants in the treatment process.