Which chemical is commonly used to improve water clarity?

Alum is commonly used to enhance water clarity, particularly in water treatment processes. It acts as a coagulant, meaning it helps to bind together small particles suspended in water, forming larger aggregates that can then be more easily removed through sedimentation or filtration. This process is essential in both drinking water treatment and in swimming pool maintenance, as it reduces turbidity and improves the visual quality of the water.

The other chemicals listed have different primary applications that do not focus on improving clarity. Muriatic acid is primarily used to lower pH levels, while hydrogen chloride is an industrial chemical that has various uses but is not typically associated with water treatment for clarity. Sodium carbonate, on the other hand, is often used to raise pH or soften water but does not directly contribute to increasing clarity in the same way alum does.