An Enhanced Backwashing Technique for Improved Filter Ripening

The increased passage of particles through granular media filters immediately following backwashing is commonly known as the filter‐ripening period, and several strategies have been developed through the years to reduce the effect of this vulnerable period of the filtration cycle on finished water quality. A new filter‐backwashing strategy aimed at reducing particle passage into the effluent water—the extended terminal subfluidization wash—has been developed and evaluated on both pilot‐ and full‐scale filters at a direct biological filtration plant. The filter‐ripening sequence (FRS) is described with new clarity based on the interpretation of experimental results. The numerous mechanisms and stages of the FRS are described in detail and may benefit future attempts to model the entire filtration cycle from a fundamental perspective.