What type of contaminants are removed by the filtration stage in water treatment?

The filtration stage in water treatment is primarily designed to remove smaller insoluble particles. During this phase, water passes through filters that typically consist of layers of sand, gravel, and sometimes activated charcoal. These materials trap particulates, such as silt, clay, and other fine debris, that may be present in the water.

This process is essential for improving the clarity and quality of the water before it undergoes further purification steps, such as disinfection. While some larger solids may be caught during filtration, the main focus is on the finer particles that are not easily removed just by sedimentation.

Other contaminants, like microorganisms, might be reduced in number due to physical entrapment, but filtration is not primarily aimed at removing bacteria or viruses, which are better addressed through disinfection methods. Chemical impurities, on the other hand, require different treatment processes, as filtration does not remove dissolved substances but rather targets particulate matter. Thus, the filtration stage's primary purpose is the effective removal of smaller insoluble particles from the water.