APPARATUS AND METHOD FOR IMPROVING GAS BACKWASH IN LATERAL UNDERDRAINS

摘要

An apparatus (10) and method for gas backwashing a granular media (14) supported upon a lateral underdrain (12) is disclosed. The lateral underdrain (12) includes a plurality of dispersion apertures (40) therethrough and at least one liquid return conduit (36) extending to a discharge (20) at a level below the dispersion apertures (40). The present invention provides for equal distribution of backwash gas across the entire lateral underdrain (12) by directing backwash gas through the dispersion apertures (40) into the granular media (4) and directing liquid from the granular media (14) through the liquid return conduit without obstructing backwash gas flow through said apertures (40) from a gas pocket (50) formed underneath said apertures (40).