Abstract:
A grit removal unit for a wastewater system including a grit removal chamber with a substantially annular vertical wall. A horizontal annular ring above the chamber bottom extends inwardly from the annular vertical wall, with an influent channel extending into the chamber beneath the ring and an effluent channel above the rim and extending out of the chamber. The influent and effluent channels both have inner side walls with a curved portion, with both curved portions extending through an arc of at least 90 degrees within the chamber annular vertical wall.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This is a non-provisional application claiming priority to U.S. Provisional Application Ser. No. 62/035,594, entitled “Ring Grit Remover” and filed Aug. 11, 2014. 
     
    
     FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
       [0002]    Not Applicable. 
       MICROFICHE/COPYRIGHT REFERENCE 
       [0003]    Not Applicable. 
       FIELD OF THE INVENTION 
       [0004]    The present invention relates to a grit selector or trap for selectively removing sand and grit from a flowing stream of fluid. 
       BACKGROUND OF THE INVENTION 
       [0005]    Grit is one of the most unpredictable and difficult materials a sewage treatment plant must handle, Grit can be defined as the heavy mineral matter present in sewage. It is principally made up of sand, gravel, and inorganic material which reaches a sewage disposal plant. It is desirous to remove this material as it cannot be treated, reduced in size, or eliminated by biological treatment methods. It presents a problem to waste treatment as it is hard and abrasive. It wears pumps and other mechanical devices. It is heavy and accumulates in clarifiers, treatment basins, digesters, etc., where it must sometimes be removed by manually. 
         [0006]    Grit removal devices of various designs have been proposed to remove grit from a flowing stream of water. Several such devices are shown, for example, in U.S. Pat. Nos. 3,941,698, 4,107,038, 4,519,907, 6,811,697, 6,881,350, and 8,906,233. 
         [0007]    U.S. Pat. No. 3,941,698 includes an upper settling chamber and a lower grit storage chamber. The settling chamber, being of large diameter, communicates with the storage chamber through a relatively small opening in a substantially flat transition surface therebetween. Rotating paddles positioned within the settling chamber, a short distance above the transition surface, can enhance the natural rotational flow of liquid entering the settling chamber adjacent the outer periphery to rotate about the chamber as a forced vortex resulting in an upward spiral flow which urges the settled particles across the transition surface towards the opening. The heavier settled particles fall through the opening into the storage chamber and the lighter organic particles rise in the spiral flow. The contents in the storage chamber are lightly air scoured prior to removal to cause any organics therein to be lifted out of the storage chamber and returned to the settling chamber. 
         [0008]    A similar type of grit removal device is disclosed in U.S. Pat. No. 4,107,038, in which a ramp is in communication with the flume portion of the inlet trough to cause grit to follow the ramp down towards the transition surface. A baffle is also positioned in the settling chamber against which the rotating liquid impinges to deflect the liquid downwardly into a generally toroidal flow pattern that spirals around the periphery of the settling chamber. The toroidal motion of the liquid moves the grit on the transition surface towards the center opening. 
         [0009]    The above-described prior art devices operate on the forced vortex principle. In these devices the head at the periphery of the settling chamber is higher than at the center of the settling chamber. This causes liquid to flow down the wall of the settling chamber to the bottom thereof and across the bottom to the point of lower head at the center thereof. It is this transverse circulatory flow pattern which permits the device to work. The particulate matter in suspension must follow this path to reach the bottom of the settling chamber and be carried to the center of the transition surface to the storage chamber. This takes some time and some of the particulate matter may not travel the full circuit before it is caught in the flow passing out the effluent, which results in a lowering of grit removal efficiency. 
         [0010]    In still other grit removal devices such as shown in U.S. Pat. Nos. 4,767,532, 6,811,697, and 8,906,233 flow toward the center of a chamber is facilitated by a rotating propeller or paddle. U.S. Pat. No. 8,906,233 also includes a ring around the interior periphery of the settling chamber blocking fluid flowing around the outside of the chamber from rising up to the level of the chamber outlet. 
         [0011]    Grit removal devices as described above, whether operating by settling or vortex action, require a relatively large footprint, presenting space problems in designing overall treatment facilities in which the grit removal devices are only a part, Of course, larger devices are inherently more costly, and can use more energy. Further, such devices are not as well adapted as might be desired to operate efficiently in environments in which the flow rate varies widely. Still further, the ability of the devices to efficiently remove grit can always be improved. 
         [0012]    The present invention is directed toward, inter alia, one or more of the problems set forth above. 
       SUMMARY OF THE INVENTION 
       [0013]    In one aspect of the present invention, a grit removal unit for a wastewater system is provided, including a round grit removal chamber defined by a bottom surface and a substantially annular vertical wall extending up from the bottom surface, a substantially horizontal annular ring spaced above the chamber bottom surface and extending inwardly from the chamber annular vertical wall to an inner edge, and an enclosed influent channel extending into the chamber beneath the ring. The influent channel has an outer side wall with a planar portion tangent to the chamber vertical wall and an inner side wall with a planar portion and a curved portion extending through an arc of at least about 90 degrees within the chamber annular vertical wall. 
         [0014]    In one form of this aspect of the invention, the inner side wall is a J-shaped baffle having a leg with a curved portion extending at least 90 degrees and concentric with the chamber annular vertical wall, the curved portion secured around the inner diameter of the ring. In an alternate form, the inner side wall curved portion spirals from a proximate end adjacent the baffle leg to a distal end spaced from the baffle leg, the spiral having a radius at the distal end which is less than the radius at the proximate end. 
         [0015]    In another form of this aspect of the invention, the enclosed influent channel inner side wall curved portion extends through an arc of between about 90 degrees to about 270 degrees within the chamber annular wall. 
         [0016]    In another aspect of the present invention, a grit removal unit for a wastewater system is provided, including a round grit removal chamber defined by a bottom surface and a substantially annular vertical wall extending up from the bottom surface, a substantially horizontal annular ring spaced above the chamber bottom surface and extending inwardly from the chamber annular vertical wall to an inner edge, an enclosed influent channel extending into the chamber beneath the ring, and an effluent channel above the rim and extending out of the chamber. The influent channel has an outer side wall with a planar portion tangent to the chamber vertical wall and an inner side wall with a planar portion and a curved portion extending through an arc of at least 90 degrees within the chamber annular vertical wall. The effluent channel has an outer side wall with a planar portion tangent to the chamber vertical wall and an inner side wall with a planar portion and a curved portion extending through an arc of at least 90 degrees within the chamber annular vertical wall. 
         [0017]    In one form of this aspect of the invention, the influent channel has an outlet substantially aligned with an inlet to the effluent channel so as to substantially prevent influent from the influent channel outlet from exiting to the effluent channel input without first entirely circling the chamber. 
         [0018]    In another form of this aspect of the invention, the influent channel outlet is substantially aligned with and below the effluent channel inlet. 
         [0019]    In still another form of this aspect of the invention, the enclosed influent channel inner side wall curved portion and the effluent channel inner side wall both extend through an arc of between about 90 degrees to about 270 degrees within the chamber annular wall. 
         [0020]    In yet another form of this aspect of the invention, the enclosed influent channel inner side wall curved portion and the effluent channel inner side wall curved portion both extend through an arc of about 180 degrees. 
         [0021]    In another form of this aspect of the invention, the radially inner sides of the influent and effluent channels are defined by J-shaped baffles with curved portions substantially concentric with the chamber annular vertical wall. 
         [0022]    In still another form of this aspect of the invention, the inner side wall curved portion spirals from a proximate end adjacent the baffle leg to a distal end spaced from the baffle leg. In a further form, the spiral has a radius at the distal end which is less than the radius at the proximate end. 
         [0023]    In still another aspect of the present invention, a grit removal unit for a wastewater system is provided, including a round grit removal chamber defined by a bottom surface and a substantially annular vertical wall extending up from the bottom surface, a substantially horizontal annular ring extending inwardly from the chamber annular vertical wall to an inner edge having a radius the ring being spaced above the chamber bottom surface, an influent channel through an opening in the chamber vertical wall beneath the ring, and an effluent channel through an opening in the chamber vertical wall above the ring. The influent channel has one influent side wall substantially tangential to the chamber vertical wall at the influent channel opening in the chamber vertical wall, and a influent inner side wall having a substantially flat portion parallel to the one influent side wall and a curved portion extending between the chamber bottom surface and the ring, the influent inner side wall curved portion having a radius R i  and extending through an arc of at least 90 degrees, the influent channel having its outlet at the end of the influent inner side wall curved portion. The effluent channel has one effluent side wall substantially tangential to the chamber vertical wall at the effluent channel opening in the chamber vertical wall, and an effluent inner side wall having a substantially flat portion parallel to the one effluent side wall and a curved portion extending upwardly from the ring, the effluent inner side wall curved portion having a radius R i  and extending through an arc of at least 90 degrees, the effluent channel having its inlet at the end of the effluent inner side wall curved portion. 
         [0024]    In one form of this aspect of the invention, the influent channel outlet and the effluent channel inlet are aligned so as to substantially prevent influent from the influent channel from exiting to the effluent channel input without first entirely circling the chamber. 
         [0025]    In another form of this aspect of the invention, the end of the influent inner side wall curved portion is substantially aligned with and below the end of the effluent inner side wall curved portion. 
         [0026]    In still another form of this aspect of the invention, the influent inner side wall curved portion and the effluent inner side wall curved portion both extend through an arc of between about 90 degrees and about 270 degrees within the chamber annular wall. 
         [0027]    In yet another form of this aspect of the invention, the inner side wall is a J-shaped baffle having a leg with a curved portion extending through an angle at least 90 degrees and concentric with the chamber annular vertical wall, the curved portion secured around the inner diameter of the ring. In a further form, the inner side wall curved portion spirals from a proximate end adjacent the baffle leg to a distal end spaced from the baffle leg, the spiral having a radius at the distal end which is less than the radius at the proximate end. 
         [0028]    In still another aspect of the present invention, a grit removal unit for a wastewater system is provided, including a round grit removal chamber defined by a bottom surface and a vertical wall substantially annular vertical wall about a center and extending up from the bottom surface, a substantially horizontal annular ring extending inwardly a radial distance R d  from the chamber annular vertical wall, the ring being above the chamber bottom surface, an influent channel through an opening in the chamber vertical wall and beneath the ring, and an effluent channel through an opening in the chamber vertical wall and above the ring. The chamber vertical wall has a radius of R vw  around a chamber center. The influent channel has one influent side wall substantially tangential to the chamber vertical wall at the influent channel opening in the chamber vertical wall, a second influent side wall substantially parallel to the one influent side wall and spaced from the one influent side wall by the distance R d , and a curved extension of the second influent side wall within the chamber, where the curved extension has a radius of R ex  and R ex =R vw −R d . The second influent side wall and curved extension extend from the chamber bottom surface to the ring so that the influent channel is defined between the first and second influent side walls, the curved extension, the ring, and the chamber bottom surface. The effluent channel has one effluent side wall substantially tangential to the chamber vertical wall at the effluent channel opening in the chamber vertical wall, a second effluent side wall substantially parallel to the one effluent side wall, and a curved extension of the second effluent side wall within the chamber. The effluent curved extension has a radius of R ex , wherein the second effluent side wall and curved extension extend upwardly from the ring so that the effluent channel is defined above the ring between the first and second effluent side walls and the curved extension. The curved, extensions of the influent and effluent channel second side walls extend through an arc of at least about 90 degrees around the center. 
         [0029]    In one form of this aspect of the present invention, the output from the influent channel and the input to the effluent channel are aligned so as to substantially prevent influent from the influent channel from exiting directly to the effluent channel input without first substantially entirely circling the chamber. 
         [0030]    In another form of this aspect of the invention, the end of the curved extension of the second influent side wall is substantially aligned with the end of the curved extension of the second effluent side wall. 
         [0031]    In still another form of this aspect of the invention, the influent curved extension and the effluent curved extension both extend through an arc of about 90 degrees to about 270 degrees around the chamber center and within the chamber annular wall. 
         [0032]    Other objects, features, and advantages of the invention will become apparent from a review of the entire specification, including the appended claims and drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0033]      FIG. 1  is a perspective view of a grit removal apparatus having at least one of the advantageous new features of the present invention; 
           [0034]      FIG. 2  is a partial cut away view of the apparatus of  FIG. 1 ; 
           [0035]      FIG. 3  is a second perspective view of the apparatus of  FIG. 1 ; 
           [0036]      FIG. 4  is a third perspective view of the apparatus of  FIG. 1 ; 
           [0037]      FIG. 5  is a perspective view of baffles which may advantageously define the inner walls of the influent and influent channels according to the present invention; and 
           [0038]      FIGS. 6 and 7  are perspective views of grit removal apparatuses having different orientations of the influent and effluent channels than the orientation of the  FIGS. 1-4 . 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0039]    The Figures show an apparatus  10  for separating grit from incoming liquid sewage (influent) in accordance with the present invention. A circular cylindrical separation chamber or basin  12  having an annular vertical side wall  13  is disposed immediately above and concentric with a cylindrical grit storage chamber  14  (see  FIG. 2 ) of a lesser diameter. 
         [0040]    A substantially flat transition bottom surface or floor  16  including a removable plate  18  centered in the separation chamber  12  separates the storage and separation chambers  14 ,  12 . Suitable openings  19  through the plate  18  permit communication between the chambers  12 ,  14 . 
         [0041]    A multi-bladed propeller  20  may be mounted on a cylindrical shaft  24  for rotation, with the upper portion of the shaft  24  connected, for example, to a suitable drive  30  for rotating the propeller  20 . Such configurations are shown, for example, in U.S. Pat. Nos. 4,107,038, 4,767,532 and 8,906,233, the disclosures of which are hereby incorporated by reference. Still other propeller and storage chamber constructions may also be used within the scope of some aspects of the present invention as described herein. 
         [0042]    An influent channel or inlet trough  40  has a covered downwardly extending influent flume portion  42  to introduce an influent liquid stream directly into a lower portion (i.e., the bottom) of the separation chamber  12  through an opening at the bottom of the separation chamber annular side wall  13 . The flume portion  42  includes a ramp at its bottom which may be advantageously sloped at, for example, about 20 degrees, with the ramp and the ceiling of the flume portion  42  being substantially parallel. 
         [0043]    The influent channel  40  also has an outer side wall  46  which is substantially tangential to the separation chamber annular side wall  13  on one side of the bottom chamber opening and an inner side wall or baffle  48  described in greater detail hereafter. 
         [0044]    An annular, ring-shaped flange or ring  50  is secured or married around the separation chamber annular side wall  13  at a height above the chamber floor  16  which is substantially equal to the vertical height at the bottom end of the flume portion  42  and the vertical height of the bottom of an effluent channel or outlet trough  60  through an opening at the top of the separation chamber annular side wall  13 . The ring  50  thus has an outer diameter equal to the radius of the vertical wall of the separation chamber  12  (R vw ) and a radial dimension (R d ), and an inner edge having an inner radius (R i ), where R vw −R d =R i . The ring  50  may advantageously extend around the entirety of the separation chamber  12 , although it should be appreciated that a ring  50  of less than 360 degrees could also be advantageously used in some aspects of the present invention. 
         [0045]    It should be noted that the annular components as described herein are curved around a center  62  which is generally aligned with the cylindrical shaft  24  of the propeller  20 . 
         [0046]    The effluent channel  60  allows fluid to flow out of the separation chamber  12  through an opening at the top of the separation chamber annular side wall  13 . The effluent channel  60  also has an outer side wall  64  which is substantially tangential to the separation chamber annular side wall  13  on one side of the top chamber opening and an inner side wall or baffle  68  described in greater detail hereafter. 
         [0047]    Specifically, the inner side walls  48 ,  68  may be advantageously defined by bottom and top J-shaped vertical baffles  70 ,  72  secured to the ring  50 , wherein each includes a straight portion  80 ,  82  and a curved portion  90 ,  92 , wherein the curved portion  90 ,  92  may advantageously be secured to the inner edge of the ring  50 . In one aspect of the present invention, the straight portions  80 ,  82  are substantially parallel to the respective outer side walls  46 ,  64 , spaced therefrom by a distance of about R d . The curved portions  90 ,  92  may be substantially concentric with the cylindrical separation chamber outer wall  13 , with a diameter less than the chamber outer wall  13  of about R d . 
         [0048]    It should be understood, however, that the curved portions  90 ,  92  may alternatively not be substantially concentric with the cylindrical separation chamber outer wall  13 , with the radius at a given point on an arc (R A ) being a function of the arcuate position (θ) at that point, or R A =ƒ(θ). For example, the curve of the curved portions  90 ,  92  could spiral in the direction of flow with the radius of curvature decreasing in the direction of flow. 
         [0049]    The bottom J-shaped baffle  70  extends up from the chamber floor  16  to the ring  50 , so that the influent channel  40  is enclosed on top and bottom by the ring  50  and floor  16  and on opposite sides by the outer side wall  46  and inner side wall (baffle)  48 . The top J-shaped baffle  72  extends up from the ring  50 , so that the effluent channel  60  is on top of the ring  50  and between the chamber outer side wall  46  and inner side wall (baffle)  68 . 
         [0050]    Advantageously the curved portions  90 ,  92  of the J-shaped baffles  70 ,  72  extend through an arc of at least about 90 degrees and up to about 270 degrees (i.e., plus or minus 10 degrees). 
         [0051]    It should be appreciated that extending the bottom baffle  70  through an arc inside the separation chamber  12  will ensure that the influent will all flow through at least that arc without exiting into the chamber  12 , and without entering the effluent channel  60 . Moreover, when the curved portion  90  of the bottom J-shaped baffle  70  extends through an arc of, for example, 180 degrees, it should be recognized that as flow of that influent continues around the chamber  12 , it will after exiting the influent channel  40  continue around 180 degrees inside of the bottom J-shaped baffle  70  (see arrow  100  in  FIGS. 1 and 3 ), plus an arc in which the inner radius transitions with the baffle straight portion  80 . Thus the grit within the fluid will be forced toward the center and the storage chamber  14 , with the maximum radial distance for the grit to travel to the storage chamber  14  reduced by R d  (i.e., from inside the J-shaped baffle  70  rather than from the storage chamber outer wall). 
         [0052]    It should also be appreciated that the combination of both J-shaped baffles  70 ,  72  with the ring  50  can further ensure that fluid entering the separation chamber  12  will travel around the chamber  12  at least once to provide efficient separation. This is particularly so in configurations in which the baffle curved portions  90 ,  92  extend far enough so that their ends  110 ,  112  distal from the straight portions  80 ,  82  are substantially aligned or overlap such as best illustrated in  FIGS. 2 and 3  (e.g., the exit from the influent channel  40  may advantageously be beneath or beyond the entrance to the effluent channel  60 . It should be appreciated that the exit from the influent channel  40  into the separation chamber  12  is substantially aligned beneath the effluent channel  60  such that any influent would have to flow essentially at least 360 degrees around the chamber before being able to enter the effluent channel  60 . 
         [0053]    It should be understood also that the straight portions  80 ,  82  could be oriented in different relative positions than illustrated in  FIGS. 1-3  (wherein they are substantially in line with one another). For example, baffle(s) according to at least one aspect of the present invention could be used if the environment of the apparatus  10 ′ requires that the effluent flow back in the direction from which the influent came as shown in  FIG. 6 , or the apparatus  10 ″ requires influent and effluent flow at right angles as shown in  FIG. 7 . As with the  FIGS. 1-4  embodiment, the ends of the baffles could also he aligned, or overlap, or fall short of each other (i.e., the exit from the influent channel  40  could end beneath the ring  50  before the entrance to the effluent channel  60  above the ring  50 , where the ring  50  is sufficient to block flow from occurring straight from the influent channel outlet into the effluent channel inlet), depending on the choice of arc from 90 to 270 degrees of the baffle curved portions  90 ,  92 . In such configurations the baffle(s) may similarly advantageously improve efficiency by reducing the maximum radial distance grit may be required to be separated into the storage chamber  14 , and may further advantageously assist in preventing any influent from immediately and undesirably entering the effluent channel  60  without flowing around entirely around the inside of the chamber at least once. 
         [0054]    Still other aspects and advantages of the present invention may be obtained from a study of the disclosure herein.