Which type of filter commonly requires backwashing to restore flow capacity?

• A. Media Filter
• B. Screen Filter
• C. Disc Filter
• D. UV Filter

Answer: (A)

Backwashing reverses flow through a filter to flush out accumulated solids and restore porosity. In a media filter, filtration occurs throughout the depth of the granular bed, so particles clog many pores as water passes through. Over time this reduces flow capacity and increases head loss. By backwashing, the bed is lifted and fluidized, loosening and carrying out the trapped material, which reopens the pores and returns the filter to its original flow capacity. Other filters clean differently: surface-trapping screens and discs are typically cleaned by surface-clearing methods, and UV filters don’t rely on a porous bed and thus don’t require backwashing for flow restoration.