Filter Underdrain with Internal Air Scour Laterals
AssigneeOvivo Inc.
InventorsGary D. Haggard, SR., Brendan Kelly
Life of this patent
Estimating the term…
Abstract
Underdrain units in a sand medium or dual medium filtration system include efficient air, water and combined air/water cleaning. Air, water or both are delivered in backflow direction from a very low position on the underdrain unit, as well as water from a higher position, so as to effectively remove blocking contaminants on the outside the underdrain unit and in the surrounding filter media.
Claims7
An underdrain filtration system having a series of longitudinal underdrain units for collection of filtrate passing down through a filter medium and through perforations in the walls of the units, the filtrate flowing into an internal plenum of each unit, with an efficient air and water backflow cleaning system for removing filter cake and contaminants surrounding the underdrain units, each underdrain unit comprising:
- an elongated metal shell having two sides and a top, and having said perforations formed directly in the metal shell, and the underdrain unit having a floor such that the shell with the floor define the internal filtrate-collecting plenum,
- the perforations in sides of the underdrain unit including perforations at least as low as two inches above the bottom of the underdrain unit,
- each underdrain unit being positioned over floor inlets for delivering water and air into the plenum, with the air being directed from one or more of said floor inlets into side ducts formed in the lower part of the plenum of the unit and extending longitudinally through the unit near the bottom of both sides, for distribution of air to lower perforations throughout the length of the underdrain unit,
- the floor inlets for each unit including water inlets separated from the one or more air inlets and positioned to deliver water into an upper part of the plenum which is isolated from the side ducts, so that water from the water inlets is delivered through perforations in said upper part of the plenum,
- whereby air alone can be directed into the underdrain unit for delivery through lower perforations via the side ducts in both sides of the unit, including perforations at least as low as about two inches above the bottom of the unit so as to clean clogging particulate matter along the entire outside of the unit;
- air and water can be delivered together to and through the lower perforations at both sides, and water can be delivered at the same time via other floor inlets to and through remaining perforations in said upper part of the plenum;
- and water alone can be delivered through all perforations of the underdrain unit, thus providing thorough scouring and cleaning and removal of particulate material from the exterior of the underdrain unit and the surrounding filter medium.
A method for cleaning underdrain units and surrounding filter medium and an underdrain filtration system that has a series of such longitudinal underdrain units for collection of filtrate passing down through a filter medium or media and through perforations in the walls of the underdrain units, by air and water backflow cleaning to remove filter cake and contaminants surrounding the underdrain units, comprising:
- an underdrain unit comprising an elongated metal shell having two sides and a top, and having perforations formed directly in the metal shell, and the underdrain unit having a floor such that the shell with the floor define an internal filtrate-collecting plenum, the perforations in sides of the underdrain unit including perforations at least as low as two inches above the bottom of the underdrain unit,
- in a second cleaning step, directing pressurized air into side ducts formed in the lower part of the plenum of the unit and extending longitudinally through the unit near the bottom of both sides, to distribute air to lower perforations throughout the length of the underdrain unit to exit the low perforations and to effect a scrubbing action that detaches trapped particles from grains of filter medium outside the unit;
- then delivering both air and water simultaneously under pressure, into the side ducts to exit through the lower underdrain perforations;
- and
- in a third cleaning step, delivering water alone under pressure into the side ducts and the remainder of the plenum so as to flush water through all perforations of the underdrain unit, thereby flushing substantially all detached particles from the filter medium bed.
Dependencies are inferred from the claim text.