Which is NOT a filter removal mechanism?

Coagulation is a process that involves the addition of chemicals to water that help to aggregate small particles into larger flocs, which can then be removed from the water through sedimentation or filtration. This process is primarily a pre-treatment stage that prepares the water for subsequent filtration, rather than a direct removal mechanism utilized by filters themselves.

Filters rely on physical and biological mechanisms to remove particles after the coagulation process, such as sedimentation on media, which allows particles to settle out; absorption, where particles adhere to the surface of the filter media; and biological action, which involves microorganisms breaking down or utilizing particles as food. Each of these mechanisms directly contributes to the filtration process, making coagulation distinct as a preparatory treatment rather than an active filter mechanism.