Abstract: A grit removal device, as may be used in a water or wastewater treatment plant, has a vortex grit collector and a mechanical conveyor for removing the grit from the collector. The grit collector includes a tank having an influent channel and an effluent channel, and a stirrer or other mechanism for inducing vortex flow within the tank. The tank has a sump located beneath it, wherein grit settles. A mechanical conveyor, such as a rotating screw, removes and dewaters grit from the sump to an exterior location. The conveyor is preferably offset from the horizontal. The invention also includes a method of grit removal employing the device.

Abstract: A screening device useful in water and waste water treatment plants separates fluid flow into two streams. The screening device is perforated so that solids having a predetermined cross-section will be maintained within a first fluid stream, and a portion of the fluid flow that has been screened of solids will flow into a second split-off fluid flow. The streams may go to different locations; only the first stream need be processed for the solids. The screening device is preferably cylindrical or another surface of rotation or a section of such a surface, and rotates. These features help maintain the screening device free of solids, and supplemental cleaning devices may also be used.

Abstract: A device for cleaning a bar rack of the type used as a screen to remove solid objects from the inlet of a water or waste treatment plant. Such devices typically have rake and a motor to drive the rake up and down the screen; the motor being connected to the rake via a rake arm. The disclosed rake arm has a variable length in response to contact between the rake arm or the rake with an object fixed to the screen or resting on the channel floor. This variable length allows the motor to drive the rake without interruption to its normal operation. Such device has particular utility in a front cleaned rack.

Abstract: A method and apparatus for controlling the fluid flow through a waste fluid inlet channel, such as for a sewage treatment plant, includes a weir that may be inserted into the channel. The weir may be one or more plates that serve to reduce the effective cross section of the channel. The plates may be shaped so that the channel is more restricted at greater depths, or may be combined to form such other shape, in order to provide desirable flow patterns. Plates may be added, removed, or exchanged with different sized plates, to accommodate a range of fluid volume at a desired flow rate. The plates may combine with a bar rack, and will not interfere with the cleaning thereof. The plates may be positioned to allow grit to flow through without impediment.

Abstract: A grit chamber for removing grit and other dense inorganic materials from a waste water stream in a waste water treatment facility. The grit chamber includes an upper settling chamber and a lower grit collection chamber, separated by a divider with one or more holes therethrough near the center portion to allow grit to pass. The settling chamber is substantially cylindrical, but with a transition curve connecting the inlet to the cylindrical portion, to assist in the production of a forced vortex with a minimum of turbulence.

Abstract: A settling tank for settling inorganic matter such as sand, grit and plastic from a fluid stream such as a waste water stream entering a waste water treatment facility. A set of mechanical mixers directing energy into the fluid stream so as to cause spiraling flow parallel to a substantially horizontal axis. The mixer shaft is rotated by a motorized drive, the speed of which is adjustable to account for variations in fluid flow rate so that an optimal balance is achieved between the settling of inorganic solids and continuing suspension and resuspension of organic solids for subsequent treatment.