What is one significant purpose of filter underdrains in the filtration process?

A significant purpose of filter underdrains in the filtration process is to deliver backwash water uniformly underneath the filter media. This function is crucial for effective cleaning of the filter during the backwashing process. When the filter media becomes clogged with contaminants, backwashing is implemented to reverse the flow of water and flush out impurities. Underdrains facilitate this action by ensuring that water is distributed evenly across the entire bottom surface of the filter media. This uniformity helps to dislodge trapped particles and supports the thorough cleaning of the filtration system, thus maintaining its efficiency and effectiveness in treating water.