Which of the following is NOT a filtration mechanism?

Evaporation is correctly identified as not a filtration mechanism. Filtration processes focus on removing particles and contaminants from water through various physical or chemical means, while evaporation is a phase change that involves the transition of water from a liquid to a vapor state. This process is related to the concentration of dissolved substances rather than the removal of particulates or impurities.

In contrast, the other options describe actual mechanisms used in water treatment. Sedimentation on media involves the settling of heavier particles as water flows through a filter medium, allowing lighter particles to pass through. Adsorption refers to the process where contaminants adhere to the surface of filter materials, effectively removing them from the water. Straining occurs when particles larger than the openings in the filter media are retained while water passes through, effectively clearing the water of larger debris.

Understanding these filtration mechanisms is crucial for water treatment operators, as they form the basis for designing and managing effective filtration systems.