Abstract: A travelling bridge filtration unit includes a tank having a bottom wall, a pair of side walls and a pair of end walls arranged to provide a rectangular tank with an open top. An interior partition in the tank extends lengthwise between the pair of end walls forms a filtrate channel between the interior partition and one of the side walls, and a filter basin between the interior partition and the other of the pair of side walls, with a bed of filter media located in the filter basin. A travelling bridge is mounted on the tank for movement therealong in a lengthwise direction, the travelling bridge supporting a backwash pump and a backwash hood for movement across the filter basin in close proximity to the filter bed. A plurality of structural underdrain headers extend between the interior partition and the other of the pair of side walls, the headers having closed ends adjacent one of the side walls, and open ends extending through the interior partition in communication with the filtrate channel.

Abstract: In a travelling bridge filtration system including a tank divided into a plurality of adjacent filter cells, each of the cells containing filter media, a travelling bridge carriage located above the tank and movable along the tank, the carriage supporting a backwash hood engageable with each of the filter cells, the improvement comprising a liquid backwash pump for causing backwash liquid to flow through the cell in a first backwash direction counter to a second filtration direction, and for causing backwash air to be drawn into the cell and to flow in the first direction with the backwash liquid.