Abstract:
An aerator for a water treatment plant or water conditioning application, includes a draft tube for vertical positioning within a volume of water and an outlet structure overlying a top open end of the draft tube. Water is lifted or pumped through the draft tube out of the top open end. The outlet structure includes a stepped splash plate which deflects the water flowing out of the top open end in a cascading fashion which increases the oxygenation efficiency and spray pattern of the thus aerated water. Additionally, a blinder bracket is applied to the outlet structure to reduce flow from the outlet structure at a particular preselected arc. The draft tube and outlet structure can be molded as a unitary plastic piece, and flow windows and openings can be cut into the piece.

Description:
TECHNICAL FIELD OF THE INVENTION 
     The present invention relates to aerators for treating water. Particularly the present invention relates to a splash plate structure which overlies an open top end of a draft tube of the aerator. 
     BACKGROUND OF THE INVENTION 
     Aerators are known which are utilized to increase the oxygen content of water, i.e., to “oxygenate” water, within a body of water. Aerators placed into a body of waste water have heretofore incorporated a draft tube having an open bottom end located at a depth of the waste water to be aerated, and an open top end extending near to the surface of the waste water. The aerator includes a mechanism for drawing water through the open bottom end and displacing the water vertically to mix with air as the water exits the open top end. In some apparatus, the mechanism is a rotary device such as a pump or an impeller while in other apparatus the device is a conduit for injecting pressurized air into the draft tube. The latter device is referred to as an “airlift”. 
     Aerators of both types are disclosed in U.S. Pat. Nos. 3,466,608; 3,972,965; and 3,966,599. 
     Airlifts operate on the principal of using air to displace water to cause a pumping action of the water. Airlifts have been used to transfer water from one treatment zone to another and have been used in different types of water treatment systems. Airlifts also enhance mixing and oxygen transfer into a waste water stream to aid in the treatment of water and wastewater in aerobic water/waste water treatment processes. 
     It would be desirable to provide an apparatus which would increase the oxygenation and the oxygen transfer efficiency of an aerator useful in water treatment applications, particularly in waste water treatment processes. 
     Traditional airlifts, due to their configuration, also tend to allow a certain amount of water to escape the treatment zone without being fully treated. It would be desirable to provide an apparatus which would reduce this tendency. 
     SUMMARY OF THE INVENTION 
     The invention is directed to an aeration device for placing in a body of water which utilizes a draft tube with an open top end wherein a splash plate is elevated from, and overlies the open top end. The device directs water through the open top end and against the splash plate to deflect the water radially outwardly onto a surface of the body of water. The splash plate includes a stepped surface which is stepped upwardly and radially outwardly with horizontal surfaces of increasing horizontal dimensions. The stepped surface of the splash plate causes a cascading of water that is splashed against the splash plate and a resulting increased oxygenation effect. The splash plate of the invention improves the oxygen transfer efficiency of the aerator and improves the spray pattern of the water deflected off the splash plate while utilizing the same size treatment aeration zone within the body of water. 
     The splash plate of the invention can be incorporated into varying types of water pumping or water lifting devices. The invention is particularly adapted to an airlift type aerator having an air injection tube extending axially into the draft tube to supply a bottom region of the draft tube with a source of pressurized air. The air tube is supported on a top surface of the splash plate. The splash plate is mounted to the draft tube by a plurality of bars or brackets extending from a top end of the draft tube upwardly to the splash plate. 
     As an additional aspect of the invention, a blinder bracket or bar of preselected width, is arranged between the splash plate and a top end of the draft tube. The blinder bracket is sized and located to block and prevent a direct flow path between the draft tube and an outlet of the surrounding aeration vessel. Thus, flow from the draft tube can be selectively limited to certain arcs around a top end of the draft tube. The blinder bracket can be made as wide as desired to block flow out of a corresponding arc. 
     Advantageously, the aerator of the present invention is composed of plastic. The support structure between the draft tube and the splash plate can be configured as a hollow cone and preselected windows can be cut from the cone to form flow areas and intermittent support brackets and one or more blinder brackets. Advantageously, the draft tube and the hollow cone can be rotationally molded as a single hollow plastic piece. The windows and the open bottom end of the draft tube can be cut from the hollow plastic piece. 
     Numerous other advantages and features of the present invention will become readily apparent from the following detailed description of the invention and the embodiments thereof, from the claims and from the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a fragmentary, schematic sectional view of a waste water treatment basin incorporating an aerator of the present invention; 
     FIG. 2 is an enlarged, elevational view of the aerator shown in FIG. 1; 
     FIG. 3 is a top view of the aerator shown in FIG. 2; 
     FIG. 4 is a sectional view taken generally along line  4 — 4  of FIG.  2 . 
     FIG. 5 is an enlarged elevational view of an alternate embodiment aerator; and 
     FIG. 6 is a sectional view taken generally along line  6 — 6  of FIG.  5 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     While this invention is susceptible of embodiment in many different forms, there are shown in the drawing and will be described herein in detail specific embodiments thereof with the understanding that the present disclosure is to be considered as an exemplification of the principles of the invention and is not intended to limit the invention to the specific embodiments illustrated. 
     FIG. 1 illustrates one example of a waste water treatment plant  10  which incorporates an aeration unit or aerator  20  of the present invention. The treatment plant includes a basin  22  having a waste water inlet, indicated by the arrow  24 , and a waste water outlet  25 . A shell  26  is held within the basin  22 . The outlet  25  is connected into the shell  26 . The tank shell  26  has an opening  34  through a bottom thereof. A filter media or other treatment media  38  is contained within the shell  26  and surrounds the aeration unit  20 . 
     Waste water contained within the basin  22  is drawn into a bottom open end  44  of the aeration unit  20  and pumped through an open top end  46  of the aeration unit  20  to be distributed onto a top surface  48  of the media  38 . The water passes through the media  38  to be drawn once again through the aeration unit  20 . Aerated water passes through a surface outlet  49  and/or a submerged outlet  50  to travel out of the basin  22  through the basin outlet  25 . 
     The aeration unit  20  can be of a type referred to as an “airlift”. In this type of aeration unit, pressurized air is supplied via tube  56  into the aeration unit  20 . 
     FIG. 2 illustrates the aeration unit  20  including a draft tube  66  having a support flange  68  which (as shown in FIG. 1) supports the aeration unit  20  on top of the media  38  (or other support structure). The draft tube  66  defines an open bottom end  44  and the open top end  46 . Mounted to the draft tube  66  at the open top end  46  is an outlet structure  70 . The outlet structure  70  includes a splash plate  74 . The splash plate  74  is supported by four, evenly spaced brackets  76  extending from the draft tube  66 . The support brackets  76  define windows  78  between adjacent support brackets  76 . The windows  78  can be trapezoidally shaped. The support brackets  76  are preferably arranged at 90° points around the circumference of the draft tube  66 . The support brackets  76  include longitudinally oriented, indented ribs  77  which stiffen the brackets  76 . 
     As shown in FIGS. 3 and 4, the splash plate  74  is preferably circularly-shaped overall, and has a stepped bottom surface  80 . The stepped bottom surface  80  includes a circular first surface  82  having a first outside diameter d1, an annular second surface  84  having a larger outer diameter d2, and an annular third surface  86  having a still larger outer diameter d3. The surfaces  82 ,  84 ,  86  are arranged coaxially about a centerline  90  of the draft tube  66 . The surfaces  82 ,  84  are vertically spaced from each other by the dimension a, and the surfaces  84 ,  86  are spaced from each other by the dimension b. 
     The first surface  82  is connected continuously to the second surface  84  by a first annular edge wall  83 . The second surface  84  is continuously connected to the third surface  86  by a second annular edge wall  85 . The edge walls  83 ,  85  are arranged parallel to the centerline or axis  90  of the draft tube  66 , i.e., perpendicular to the surfaces  82 ,  84 ,  86 . 
     Although according to the preferred embodiment, the splash plate  74  and surfaces  82 ,  84 ,  86  have circular perimeters, other shapes, such as irregularly shaped, oblong or rectangular, are encompassed by the invention. 
     A mechanism for pumping water from the bottom open end  44  through the top open end  46  and against the splash plate  74  can be a rotary element such as an impeller for pumping water through the draft tube  66  or can be a source of pressurized air to hydraulically lift the water from the bottom open end  44  through the top open end  46  and against the splash plate  74 . According to the latter example, a tube  100  penetrates the splash plate  74  through the surface  82  along the centerline  90  and extends down through the draft tube to within a short distance c from the bottom open end  44 . The tube  100  is supported on the splash plate  74  by a coupling  101  which also serves to connect the tube  100  to a source of pressurized air  102  (shown schematically). 
     Referring back to FIG. 2, in a further aspect of the invention, a blinder bracket  120  is mounted within a window  78  to reduce the flow area of the window at a specific location. Particularly, the window  78  is reduced to block a direct radial flow route of water from the aerator  20 , through the window  78 , toward the outlets  49 ,  50  (shown in FIG.  1 ). By locating one or more blinder brackets of preselected width and location around the circumference of the outlet structure  70 , water flow can be directed or limited in a preselected fashion for process reasons. 
     The blinder bracket prevents waste water (which may contain solids) from exiting the treatment zone prematurely, via a direct or shortened route, to the waste water outlet  25 , thus preventing water that has not been completely treated from escaping the treatment zone as effluent. The blinder bracket interrupts the spray pattern along a direction that is toward where the treatment zone outlet(s), such as the outlets  49 ,  50 , is (are) located. The blinder bracket can have as an additional function, the adding of structural stability to the splash plate along with the four regular brackets  76 . 
     The splash plate  74  works as a reverse cascading aerator. Operation of the airlift occurs when water rises up the center flume of the draft tube and comes in contact with the multiple surfaces  82 ,  84 ,  86 . 
     As a result, water splashes off the first horizontal surface  82 , and then continues upwardly cascading to the second horizontal surface  84 , and then cascading to the third horizontal surface  86 , before eventually being dispersed downwardly and outwardly into the water treatment zone. This additional cascading process allows for additional oxygenation (mixing of air and water) for aerobic waste water treatment as well as improving the spray pattern over the entire water treatment zone. The improvement of the spray patters helps to improve the oxygen transfer efficiency (the amount of energy required to put air into the water) so that less energy is required to conduct oxygenation. 
     According to the preferred embodiment of the invention, the splash plate  74  is a stepped, single thickness molded plastic piece. A stacking of solid plates, for example, to arrive at the stepped configuration of the splash plate is also encompassed by the invention. 
     The outlet structure  70  can also be molded as a single, conically shaped plastic piece and the windows  78  can be removed as desired from the single conically shaped plastic piece. The draft tube  66  can be molded together with the flange  68  as a single thickness piece. Plural pieces that can be pre-molded and attached together, or the support flange  68  can be an annular piece fastened around a separate tube. 
     According to one exemplary embodiment of the present invention, the inside diameter of the draft tube d4 is 4 inches, the diameter d1 is 2⅜ inches, the diameter d2 is 4¾ inches, the diameter d3 is 8½ inches and the tube  100  is a 1½ inch, schedule  40  pipe. The distance between the splash plate and the bottom open end is approximately 30½ inches and the distance between the bottom open end and the top open end is approximately 27 inches. The dimension a is between {fraction (3/8+L )} and {fraction (1/2+L )} inch and the dimension b is {fraction (3/8+L )} inch. 
     Advantageously, the ratio of d1 to d4 can be about 0.6 to 1; the ratio of d2 to d4 can be about 1.2 to 1; and the ratio of d3 to d4 can be about 2.1 to 1. Preferably, the ratio of d2 to d4 is at least about 1 to 1 and the ratio of d3 to d4 is at least about 2 to 1. The diameter d2 is preferably greater than d4 so that all of the water passing through the draft tube splashes against the surfaces  82 ,  84  initially. 
     An alternate embodiment aerator  124  is illustrated in FIGS. 5 and 6. According to this embodiment, support brackets  176  support a splash plate  174  above the draft tube. The brackets  176  include longitudinally extending, outwardly formed ribs  178  for effecting stiffening of the brackets  176 . Two annular surfaces  184 ,  186  are provided on the splash plate  174 . An outer annular surface  187  having a width  187   a  of about 0.5 inch surrounds the second annular surface  186 . The surfaces  184 ,  186  are continuously connected by an oblique wall  185  to create a smooth transition between the two surfaces  184 ,  186 . An opening  190  for receiving the air tube  100  is reinforced by an integral sleeve  192 . The tube  100  includes the coupling  101  which sets onto the plate  174  to support the tube  100 . The coupling is shown slightly elevated from the plate  174  only for simplicity of description. The tube  100  can be secured to the plate  174  by gravity, or by an adhesive, or by the use of opposed threaded couplings (not shown) which capture the plate  174  therebetween. 
     According to the second embodiment, the dimension d4 is about 6″, the dimension d2 is about 6¾″, and the dimension d3 is about 12½. The tube  100  is preferably a 2″ schedule  40  plastic pipe. Advantageously, the ratio of d2 to d4 can be about 1.1 to 1; the ratio of d3 to d4 can be about 2.1 to 1. The dimension d2 is slightly larger than the dimension d4 to ensure the water passing up vertically through the tube  66  strikes the surface  184 . Preferably, the ratio of d2 to d4 is at least about 1 to 1 and the ratio of d3 to d4 is at least about 2 to 1. The dimension a can be approximately {fraction (3/16+L )} inch. The dimension b can be approximately {fraction (3/8+L )} inch. A window dimension e can be approximately 3½ inches. A dimension f can be about 27 inches. 
     The outlet section  70 , the support flange  68  and the draft tube  66  are advantageously molded as a unitary plastic piece in a rotary mold which uses centrifugal force to mold the hollow piece against an inside surface of the mold volume. After molding, the openings  190 ,  44  and  78  are cut into the piece. By molding the entire aerator  124  (except for the air tube  100 ) of one plastic piece, a significant cost savings results due to reduced assembly labor and parts costs. The embodiment of FIGS. 2 and 4 can be similarly manufactured. 
     From the foregoing, it will be observed that numerous variations and modifications may be effected without departing from the spirit and scope of the invention. It is to be understood that no limitation with respect to the specific apparatus illustrated herein is intended or should be inferred. It is, of course, intended to cover by the appended claims all such modifications as fall within the scope of the claims.