Which of the following does NOT enhance the longevity of a carbon contactor?

• A. Regular backwashing
• B. Increase in flow rate
• C. Replacement of media when exhausted
• D. Stable influent quality

Answer: (B)

Longevity of a carbon contactor hinges on maintaining effective adsorption and preventing bed fouling. Regular backwashing keeps the bed loose and porous, preventing compaction and blocking of flow paths, which helps the media continue adsorbing efficiently. Replacing media when it’s exhausted restores the bed’s adsorption capacity, so the system can keep treating water at the intended performance level. Stable influent quality minimizes shock loads and abrupt fouling or breakthrough, allowing the bed to reach its designed lifespan.

Increasing flow rate, on the other hand, reduces contact time between the water and the carbon, which lowers adsorption efficiency and can cause preferential flow paths or channeling. This speeds up saturation and reduces the effective life of the bed, so it does not enhance longevity.