What does backwashing achieve in water filtration?

Backwashing is an essential process in water filtration systems, particularly for sand or multimedia filters. The purpose of backwashing is to reverse the flow of water through the filter to dislodge and remove accumulated dirt, debris, and other contaminants that have been trapped in the media. This action not only cleans the filter but also helps to restore its efficiency and flow rate.

During backwashing, water is pushed in the opposite direction, which lifts the filtering media and allows the trapped particles to be washed away. This process is vital for maintaining the operability of the filtration system, ensuring that it continues to provide clean and safe water.

Other options do not accurately describe the backwashing process. For example, backwashing does not entirely remove all chemicals from the water, nor does it fully sterilize the filter. It also does not replace water in the system but rather cleans the existing filter media to enhance its performance.