What is commonly used as a chemical coagulant in water treatment?

Alum is a widely recognized chemical coagulant used in water treatment processes. It functions by destabilizing suspended particles in water, causing them to clump together, or agglomerate, into larger particles that can then be easily removed through sedimentation or filtration. The mechanism behind this process involves the positive charge of the aluminum ions in alum, which neutralizes the negative charges on the particles in the water, allowing them to bond and settle out.

In many water treatment facilities, alum is preferred for its effectiveness and relatively low cost. It is particularly useful in treating water that contains high levels of turbidity, as it enhances the clarity of the final product by removing particulates, organic matter, and some pathogens.

While other substances like iron, chlorine, and lime are indeed used in water treatment, they serve different purposes. Iron salts can also function as coagulants, but alum is more commonly utilized. Chlorine is primarily a disinfectant used to kill bacteria and viruses, and lime is used to adjust pH levels and soften water, rather than serving as a coagulant. Understanding these distinctions is crucial for recognizing the specific roles various chemicals play in the water treatment process.