Abstract: A granular media filter including a settler assembly for reducing media loss during high-turbulence washing of media in the granular media filter. The settler assembly is comprised of plates, tubes, or other porous materials placed between a system of baffles and a conventional backwash trough. The settler assembly reduces turbulence near the overflow weir edge of the backwash trough, thereby reducing media carry over with the backwash water into the backwash trough. The trough baffle settler assembly will allow higher backwash rates per backwash with the same or lower media losses than experienced with previous trough-baffle designs, thereby reducing costs of construction and operation of granular media filter systems. The settler assembly is particularly adapted for use with granular media filters employing simultaneous application of air and water to produce a high turbulence backwash.

Abstract: A method is described in which two or more granular filter media are used in combination in such a manner that the filter bed is backwashed using air and water simultaneously. The media size gradation and density are selected so that, although the media may be mixed during backwash, the media are separated into layers according to their density and/or size following termination of the simultaneous air-water wash and prior to returning the filter to the filtration mode. The simultaneous air-water wash step can be carried out without media loss by use of an appropriate media retaining procedure.

Abstract: A baffle and wash trough assembly is provided for reducing media loss during high-turbulence washing of granular-media filters. The assembly includes a water collection trough having an overflow weir on at least one side thereof and a lower portion with downwardly and inwardly converging sides, and a baffle supported adjacent one side of the trough; the baffle having an upwardly concave arcuate portion in opposed relation to the trough lower portion, and defining a restricted flow channel for the wash water to the trough. There may also be provided a second baffle supported adjacent the other side of the trough and having an upwardly concave arcuate portion in opposed relation to the other side of the trough lower portion. The lower end of the second baffle preferably terminates above and inwardly of the lower end of the first baffle, thereby defining a second channel for removal of backwash water.