Tapered bed filtration apparatus

A filter apparatus comprising:

• an upright casing defining an inlet and an outlet, and having upper and lower ends and a peripheral wall extending between the inlet and outlet, the peripheral wall defining a filtration chamber having a longitudinal axis and a transverse cross-sectional area which increases between the inlet and the outlet;
• a bed of particulate filtering media within the chamber and including at least one layer of media having a specified, common density, the media within said at least one layer ranging in size between relatively large particles and relatively small particles, the media within said at least one layer being distributed by particle size within the chamber, with the large particles being disposed closer to said inlet and with smaller particles being disposed closer to the outlet so that the particle size of the media of said at least one layer in the chamber decreases from the inlet toward the outlet while the transverse cross-sectional area of the chamber increases;
• and
• fluid delivery means operably coupled with said casing for delivery of unfiltered fluid to said inlet for passage of unfiltered fluid from the inlet to the outlet through said chamber in order to filter the initially unfiltered fluid, and for alternate delivery of backwashing fluid to the lower end of said chamber for passage of backwashing fluid upwardly through the chamber in order to fluidize the bed of particulate filtering media for cleaning thereof.