Abstract: Air grid systems for distributing a gas within treatment systems such as underdrain filters and contact clarifiers is disclosed. The air grid is supported from above so that it can be lowered into position and thus modified or repaired. Additionally, this feature permits retrofitting an air grid into an existing system, such as an underdrain filter, in which the bed of media overlying the underdrain is not upset by the installation. Thus, methods of installing or retrofitting air grid systems are also disclosed. In another aspect of the present invention, the air grid is comprised of an air manifold connected to air laterals by a spreader conduit that is inserted through a smooth bore in the walls of the manifold, thereby providing a simple and easy to manufacture structure that avoids problems found in prior art components.

Abstract: A system for distributing both gas and liquid in separate conduits within an underdrain filtration system is disclosed. A tubular liquid conducting conduit also contains a separate air conduit. Extending from each conduit are, respectively, liquid conducting laterals and air laterals. The system is placed within a bed of gravel at the bottom of a filter bed and acts as conventional underdrain blocks and air grids. In a downflow mode, effluent is filtered as it passes through the filter media and filtered water is collected through orifices in the liquid conducting laterals, which in turn feed into the liquid conducting conduit to form a filtrate stream. In a backwash mode, backwash liquid flows through the liquid conducting conduit, out the laterals and up through the filter bed. During backwash, air may be introduced through the air conduit and laterals and rise through the filter media to enhance the effectiveness of the backwash operation.

Abstract: A method of washing an upflow filter between service runs employs a filter bed having a non-buoyant particulate filter layer through which influent to be filtered is directed in an upward direction, and through which liquid employed in the washing operation is directed in an upflow direction. A two-stage washing operation includes the steps of first directing a combination of air and liquid in an upflow direction through the filter layer with the velocity of the liquid being less than the minimum fluidization velocity of the filter layer, for disrupting only some floc retained in the filter layer during a previous service run, and thereafter directing only liquid in an upflow direction through the filter layer at a velocity less than the minimum fluidization velocity of the filter layer for removing disrupted floc from the filter layer while leaving some floc attached to said particulate media of the filter layer.

Abstract: A method of washing an upflow filter between service runs employs a filter bed having a non-buoyant particulate filter layer through which influent to be filtered is directed in an upward direction, and through which liquid employed in the washing operation is directed in an upflow direction. A two-stage washing operation includes the steps of first directing a combination of air and liquid in an upflow direction through the filter layer with the velocity of the liquid being less than the minimum fluidization velocity of the filter layer, for disrupting only some floc retained in the filter layer during a previous service run, and thereafter directing only liquid in an upflow direction through the filter layer at a velocity less than the minimum fluidization velocity of the filter layer for removing disrupted floc from the filter layer while leaving some floc attached to said particulate media of the filter layer.

Abstract: Nozzles for use on a rotary agitator of a water and/or waste water filter system have an outer housing including a rear section through which the nozzle is connectable to the rotary agitator, and a forward wall including a plurality of ports therethrough. Fluid passage means extend from the rear connecting means to the ports for transmitting fluid from the agitator through the ports.

Abstract: A method of washing an upflow filter between service runs employs a filter bed having a non-buoyant particulate filter layer through which influent to be filtered is directed in an upward direction, and through which liquid employed in the washing operation is directed in an upflow direction. A two-stage washing operation includes the steps of first directing a combination of air and liquid in an upflow direction through the filter layer with the velocity of the liquid being less than the minimum fluidization velocity of the filter layer, for disrupting only some floc retained in the filter layer during a previous service run, and thereafter directing only liquid in an upflow direction through the filter layer at a velocity less than the minimum fluidization velocity of the filter layer for removing disrupted floc from the filter layer while leaving some floc attached to said particulate media of the filter layer.

Abstract: A rotary agitator for use in filter systems has a horizontal arm formed of a single, elongate, hollow tubular section. An opening through the peripheral wall of the tubular section at substantially the midpoint thereof communicates with the hollow interior of the tubular section. An external rotor section of a central bearing assembly is secured directly to the hollow tubular section in a region overlying the opening through the peripheral wall of the tubular section. The external rotor section has a passageway therethrough communicating with the opening through the peripheral wall of the tubular section. The central bearing assembly further includes an elongate stator positioned interiorly of the external rotor section. The passage through the elongate stator is aligned with and in communication with the opening through the peripheral wall of the tubular section.