What is the function of coagulants like alum in water treatment?

Coagulants like alum play a crucial role in water treatment processes by helping to clarify water. When added to water, alum reacts to form flocs—larger aggregates of particles that can trap impurities and suspended solids. The coagulation process essentially facilitates the removal of these particles, which can include dirt, organic material, and microorganisms, thereby drastically reducing the turbidity of the water.

This clarification process is vital for producing clean, safe drinking water and improving water quality in treatment facilities. It is essential to understand that the effectiveness of coagulants hinges on their ability to cause fine particles to agglomerate into larger clumps (flocs), which can then be removed in subsequent steps, such as sedimentation and filtration.

In contrast, coagulants do not promote bacterial growth, which is why options relating to increasing bacterial levels or merely improving turbidity without addressing clarity aren't accurate. They also do not primarily serve the purpose of adding essential minerals to the water; their function is more focused on the physical removal of impurities. Therefore, the primary and correct function of coagulants like alum is indeed to clarify water by facilitating the removal of suspended solids.