Filtering apparatus having positively buoyant and negatively buoyant particulate

摘要

An apparatus for filtering contaminated fluids is provided. In a filtering mode, contaminated fluid is introduced into a vessel housing a bed of positively buoyant particulate material and a bed of negatively buoyant particulate material in a spaced apart relationship. The contaminated fluid is passed through the bed of negatively buoyant particulate and through the bed of positively buoyant particulate. In a backwashing mode, a backwashing fluid is passed through the bed of positively buoyant particulate to flush particulate contaminants therefrom. The backwashing fluid is discharged from the vessel at a location between the bed of negatively buoyant particulate and the bed of positively buoyant particulate.