What substance is commonly added to municipal water supply to enhance its clarity?

Alum, or aluminum sulfate, is frequently added to municipal water supplies as a coagulant in the water treatment process. Its primary function is to improve water clarity by causing small particles and impurities in the water to clump together. This process, known as coagulation, facilitates the removal of these particles during subsequent filtration, resulting in clearer and cleaner water. Through this mechanism, alum significantly enhances the aesthetic quality of drinking water by removing turbidity caused by suspended particles.

The other substances mentioned have different purposes in water treatment. Chlorine, for instance, is primarily used as a disinfectant to kill harmful bacteria and viruses in the water but does not directly work to clear the water of suspended particles. Fluoride is added to promote dental health but, like chlorine, does not play a role in improving water clarity. Sodium bicarbonate is often used to adjust the pH level of water, which is important for maintaining water quality but does not contribute to enhancing clarity.