Apparatus and method of filtering solids from a liquid effluent

Abstract

There is provided an improvement in a waste effluent filter of the type including a tank, a generally flat fine mesh screen over the lower portion of the tank to define an underdrain cavity below the screen and a filter bed of particulate material having an upper surface and a lower general surface adjacent the underdrain cavity. The particle size of the particulate material being greater than the size of the apertures in the fine mesh screen. The filter improvement includes a jet creating grid for creating a plurality of upwardly directed hydraulic jets evenly distributed throughout the filter bed during the filtering of the effluent through the bed wherein the jet creating grid includes a plurality of nozzles in the bed itself substantially below the upper surface of the bed and above the fine mesh screen a selected distance to retain the lower layer of the bed undisturbed. As a further improvement a plurality of horizontal liquid jets are created as a network over the upper surface of the sand bed to scour the media surface during filtering. A further improvement in the filter is the creation of a plurality of hydraulic cleaning jets usable during backwashing along with a vertical flushing action through the screen from the underdrain cavity. Yet a further improvement in the filter is the provision of a chemical cleaning feature utilizing two separate and distinct chemicals injected into the bed for cleaning the filter bed. Preferably, the chemical injection uses the two sets of vertically displaced jets.