Abstract: A cap for filter underdrain blocks is provided, wherein the cap has a porous body with a top surface, a bottom surface and downwardly extending flanges. The cap is installed on a filter block having a plurality of orifices in a top wall of the filter block for channelling fluids to and from an overlying filter media. The bottom surface of the cap along with the flanges define a distribution chamber above the orifices, and the cap has a porosity such that a fine grain filter media may be placed directly on the top surface of the cap without media penetrating therethrough and clogging the underdrain blocks. The distribution chamber enhances distribution of backwash fluids throughout the filter media, and the cap eliminates the need for a separate gravel support layer to be installed between the fine grain filter media and the underdrain blocks.

Abstract: A cap for filter underdrain blocks is provided, wherein the cap has a porous body with a top surface, a bottom surface and downwardly extending flanges. The cap is installed on a filter block having a plurality of orifices in a top wall of the filter block for channelling fluids to and from an overyling filter media. The bottom surface of the cap along with the flanges define a distribution chamber above the orifices, and the cap has a porosity such that a fine grain filter media may be placed directly on the top surface of the cap without media penetrating therethrough and clogging the underdrain blocks. The distribution chamber enhances distribution of backwash fluids throughout the filter media, and the cap eliminates the need for a separate gravel support layer to be installed between the fine grain filter media and the underdrain blocks.

Abstract: A filter block having a plurality of exterior and interior walls defining a plurality of interior chambers, said chambers including at least a first and second conduits parallel to the longitudinal axis of said block, one disposed above the other, with a third conduit provided to supply gas under pressure to the upper conduit; a top exterior wall of the block having a plurality of apertures distributed thereover. The interior chambers comprise separate conduits for both gas and liquid backwash flows. The interior walls defining the conduits are disposed to provide even distribution of the backwashing gas and to provide bearing support for the top wall of the block.

Abstract: A beach for the scum trough of a sewage settling tank or the like is biased to an upright position by a weighted member or the like so as to prevent the flow of liquid over the beach and into the scum trough. The construction of the beach allows it to be rotated against this bias to a second position below the level of liquid in the settling tank, so as to permit scum and other floating materials accumulated adjacent the beach to flow over the beach and into the scum trough.