Abstract: A cleaning device for a water treatment sedimentation tank and characterized by the highly efficient removal of the sediment from the bottom of the tank and without requiring the draining thereof, and which comprises a cleaning assembly positioned within the tank and adapted to reciprocate along the floor to move the sediment into one or more gutters. The cleaning assembly is supported upon rails mounted along the lower portion of the side walls of the tank, and it is driven by a direct drive system which includes a rack carried by each rail, a submersible electric motor carried by the cleaning assembly, and a drive shaft rotatably mounted on the assembly and having a pinion at each end which operatively engages the adjacent rack.

Abstract: An underdrain is provided in a water filtration system beneath a bed of filter media and comprises a plurality of elongate hollow underdrain units defining respective elongate substantially horizontal fluid passageways therein with the hollow underdrain units being arranged with the elongate fluid passageways thereof in fluid communication with each other and forming a network of fluid passageways beneath the bed of filter media. Each underdrain unit is provided with a plurality of nozzles in the upper wall thereof communicating with the interior of the hollow underdrain unit and with at least some of the nozzles in each underdrain unit cooperating with each other and being arranged in spaced groups. The cooperating nozzles in each group are so oriented as to direct streams of wash water issuing therefrom during backwashing into impingement with each other outside the filter underdrain unit for dispersing the streams of wash water and reducing the velocity thereof.