Patent Publication Number: US-2022234926-A1

Title: System for microorganism based treatment of wastewater

Description:
BACKGROUND 
     Wastewater treatment facilities, such as municipal, agricultural or industrial wastewater treatment facilities, commonly utilize aeration techniques in order to treat the wastewater. Aeration of the wastewater has been found to reduce or eliminate contaminants found in the wastewater by increasing the oxygen available to microorganisms which break down contaminants during a biological process. 
     An example of wastewater treatment is disclosed in U.S. Pat. No. 6,231,766. U.S. Pat. No. 6,231,766 discloses disposing a plurality of bio-suspension elements within an enclosure which is at least partially submerged in a body of water, wherein a screen is disposed within the enclosure, wherein the bio-suspension elements provide surfaces for supporting the growth of at least five different biological microorganisms, and wherein the bio-suspension elements are disposed above the screen, introducing the at least five different biological microorganisms into the enclosure along with the water continuously agitating, aerating, and feeding the water into the enclosure, (d) forcing air through the screen, whereby treated water is produced, and continuously removing the treated water from the enclosure. The entire content of U.S. Pat. No. 6,231,766 is hereby incorporated by reference. 
     Another example of wastewater treatment is disclosed in U.S. Pat. No. 7,101,483. U.S. Pat. No. 7,101,483 discloses a process for treating a body of water in which a bioreactor located in a body of water. Water is passed through the bioreactor that contains a plurality of bio-suspension elements within an enclosure located above a screen. The entire content of U.S. Pat. No. 7,101,483 is hereby incorporated by reference. 
     A third example of wastewater treatment is disclosed in U.S. Pat. No. 8,372,285. U.S. Pat. No. 8,372,285 discloses a reactor that contains a perforated chimney through which air can flow and optimize dissolving oxygen into the aqueous environment of the various bio-remediation stages. The entire content of U.S. Pat. No. 8,372,285 is hereby incorporated by reference. 
     In the various conventional wastewater treatment systems described above, the microorganisms used to treat the wastewater are lost during the discharge of the treated water. Moreover, the wastewater treatment process requires a constant seeding of microorganisms that may not be mature enough to effectively process the wastewater. 
     Therefore, it is desirable to provide a wastewater treatment system that minimizes the loss of mature microorganisms during discharge. 
     Moreover, it is desirable to provide a wastewater treatment system that reduces the seeding of microorganisms in the treatment process. 
     In addition, it is desirable to provide a wastewater treatment system that recycles microorganisms in a discharge container back to a first treatment chamber. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The drawings are only for purposes of illustrating various embodiments and are not to be construed as limiting, wherein: 
         FIG. 1  shows an example of a conventional treatment reactor for treating wastewater; 
         FIG. 2  shows a treatment bio-reactor for treating wastewater; 
         FIG. 3  illustrates a system of multiple treatment bio-reactors for treating wastewater; 
         FIG. 4  shows a diversion member for diverting fluid to an outer edge of a non-round treatment bio-reactor container; 
         FIG. 5  shows a side view of the diversion member of  FIG. 4 ; 
         FIG. 6  shows a cross section of the diversion member of  FIG. 4 ; and 
         FIG. 7  shows a diversion member for diverting fluid in a rotational manner along an outer edge of a round treatment bio-reactor container. 
     
    
    
     DETAILED DESCRIPTION 
     For a general understanding, reference is made to the drawings. In the drawings, like references have been used throughout to designate identical or equivalent elements. It is also noted that the drawings may not have been drawn to scale and that certain regions may have been purposely drawn disproportionately so that the features and concepts may be properly illustrated. 
     A conventional treatment reactor for treating wastewater is illustrated in  FIG. 1 . As illustrated in  FIG. 1 , a reactor R contains solid outer walls  11 . The reactor R generally has a bottom chamber  18  that receives air or oxygen-containing gas under a slight pressure. Air is admitted to the reactor R via an air pump, not shown, that supplies air through air supply pipe or conduit  1  and into the top of the reactor through reactor air inlet pipe  5 . Air inlet pipe  5  is solid except at the bottom portion thereof that has openings or perforations  24  that admits the pressurized air into air pressure chamber  18 . Air inlet pipe  5  is connected to reactor bottom plate  19  through connection  20 . 
     Since the air flowing into chamber  18  is under pressure, the air is forced through micro-porous diffuser  16  that has tiny openings so that the air is admitted into aqueous waste composition chamber  17  in the form of tiny (fine) bubbles  10 . 
     The aqueous waste composition is added to the reactor R through wastewater inlet  21  that can be in the shape of an elbow having an opening at the other end thereof. When placed in a tank containing an aqueous waste composition therein, the aqueous waste composition will flow into aqueous waste composition chamber  17  where it is mixed with air bubbles  10 . 
     The aqueous waste composition will be caused to flow upward through the reactor R via drag forces due to forced air flow through the perforated air carrier pipe, chimney  9 . 
     In other words, the reactor R is a bottom input of air as well as the aqueous waste composition that is then caused to flow upward through various perforated separators  15 A,  15 B,  15 C,  15 D, and  15 E, which have perforations  13  therein. The size of the various perforated openings in the separators is sufficient to allow air and water to flow therethrough but generally and desirably does not permit the packing substrates  30 , to pass therethrough. 
     Perforated separator  15 A is a diffuser that allows bubbles  10  of air in aqueous waste composition  17  to flow upward therethrough (flow arrows  25 ) thus providing an additional mixing of the aqueous waste composition and the air bubbles so that some of the oxygen in the air is dissolved into the water. 
     The area formed between perforated separators  15 A,  15 B,  15 C,  15 D, and  15 E, identified as chamber  15 AA,  15 BB,  15 CC,  15 DD, and  15 EE. The chambers  15 AA,  15 BB,  15 CC,  15 DD, and  15 EE are filled with packing substrate  30 . 
     For example, chamber  15 AA contains packing substrate  30 A that is efficient in mixing the air bubbles and water to dissolve the oxygen within the water. Packing substrate  30 A has a high surface area and a high amount of pores. 
     Located within packing substrate  30 A are microorganisms. Microorganisms are utilized so that the reactor R is efficient with regard to eradicating, detoxifying, complexing, or otherwise treating the various different types of waste contained with the aqueous waste composition. 
     Since bubbles  10  are lighter than the water, the bubbles  10  flow upward through chamber  15 AA and cause the aqueous waste composition to flow upward so that continuous mixing of the air and the waste composition occurs, thereby continuously causing dissolving of some of the oxygen into the water. 
     The upward flow of the aqueous waste composition through the packing substrates  30 A causes the dissolved molecular components of the waste composition to eventually contact microorganisms contained within the pores of the substrate whereby the waste composition molecule is bio-remediated. Thus, upon reaching perforated top plate  6  only purified water is discharged. 
     The reactor R also contains a chimney pipe  9  that has perforations  12  therein. Chimney pipe  9  is located generally in the center of the reactor R such as adjacent to input air pipe  5 . As illustrated in  FIG. 1 , there are two chimney pipes  9  located on either side of air pipe  5  with the chimney pipes  9  being perforated  36  at the bottom thereof and also being perforated  36  at the top thereof at perforated top plate  6 . 
     Accordingly, air bubbles  10  and the aqueous waste composition can enter the bottom of chimney pipe  9  and flow upward through the pipe  9 . 
     As illustrated in  FIG. 2 , a treatment bio-reactor for treating wastewater effluent includes a tank  100  that utilizes microorganisms to treat the wastewater. The tank  100  includes a packed media bed  150 . The packed media bed  150  is composed of small components, which provide a large surface area for the microorganisms to interact with the wastewater effluent being treated. 
     The microorganisms can be introduced at an upper volume  105  of the tank  100  through an opening  130 . Moreover, fresh wastewater effluent  125  can be introduced in upper volume  105  of the tank  100  via an inlet pump and/or valve  120 . 
     A first air pump  110  provides air to a central volume  170  of the tank  100  so as to introduce bubbles into the wastewater effluent within the central volume  170  of the tank  100 . 
     The central volume  170  of the tank  100  is formed by a non-porous barrier(s) that forms a channel between the upper volume  105  of the tank  100  and a lower volume  164  of the tank  100 . The barrier(s) holds the packed media bed  150  of small components in place and channels the wastewater effluent towards the lower volume  164  of the tank  100 . The central volume  170  of the tank  100  is open at either end so that wastewater effluent is received at one end and wastewater effluent is discharged at the other end. The central volume  170  and the packed media bed  150  make up a middle volume  155  of the tank  100 . 
     The air from the first air pump  110  may be is forced through a diffuser (not shown) that has openings so that the air is admitted into wastewater effluent within central volume  170  of the tank  100  in the form of bubbles. 
     The bubbles can be further reduced in size by a propeller device  175  which pushes the wastewater effluent within the central volume  170  of the tank  100  downward into a lower volume  164  of the tank  100 . 
     With respect to the air being pumped by the first air pump  110 , the propeller device  175  can also function as an aerator to aerate the wastewater effluent within the central volume  170  of the tank  100  with the air being introduced into the central volume  170  of the tank  100  by the first air pump  110 . 
     The wastewater effluent within the central volume  170  of the tank  100  flows downward into a lower volume  164  of the tank  100  and back up through the packed media bed  150  of small components to create a flow of the wastewater effluent from the upper volume  105  of the tank  100 , down through the central volume  170  of the tank  100 , into a lower volume  164  of the tank  100 , and upward through the packed media bed  150  of small components towards the upper volume  105  of the tank  100 . 
     A second air supply  160  pumps air into the lower volume  164  of the tank  100  via an air inlet  167  and diffusers  165 . The diffusers  165  create bubbles to assist in moving the wastewater effluent upward through the packed media bed  150  of small components towards the upper volume  105  of the tank  100 . 
     It is noted that the diffusers  165  may be angled towards the outer wall of the lower volume  164  of the tank  100  to create a flow near the outer wall to prevent or reduce pooling of the wastewater effluent near the outer wall. 
     In the lower volume  164 , a portion of the wastewater effluent can be drained off and pumped by pump  180  to a second tank (not shown). 
     In addition to the introduction of fresh wastewater effluent  125  into the upper volume  105  of the tank  100 , recycled wastewater effluent from another tank is introduced in the upper volume  105  of the tank  100  via a recycled wastewater effluent inlet  140 . The recycled wastewater effluent is wastewater effluent which has been processed in another tank having the components discussed above with respect to the tank  100 . 
       FIG. 3  illustrates a system of multiple treatment bio-reactors for treating wastewater effluent. As illustrated in  FIG. 3 , a first bio-reactor tank  100  treats wastewater effluent utilizing microorganisms in the same manner as the tank illustrated in  FIG. 2 . 
     The first bio-reactor tank  100  includes a packed media bed of small components. The small components provide a large surface area for the microorganisms to interact with the wastewater effluent being treated. 
     The microorganisms can be introduced at an upper volume of the first bio-reactor tank  100  through an opening. Moreover, fresh wastewater effluent can be introduced in upper volume of the first bio-reactor tank  100  via an inlet pump and/or valve. 
     An air pump provides air to a central volume of the first bio-reactor tank  100  so as to introduce bubbles into the wastewater effluent within the central volume of the first bio-reactor tank  100 . 
     The air from the air pump may be is forced through a diffuser (not shown) that has openings so that the air is admitted into wastewater effluent within the central volume of the first bio-reactor tank  100  in the form of bubbles. 
     The bubbles can be further reduced in size by a propeller device which pushes the wastewater effluent within the central volume of the first bio-reactor tank  100  downward into a lower volume of the first bio-reactor tank  100 . 
     With respect to the air being pumped by the air pump, the propeller device can also function as an aerator to aerate the wastewater effluent within the central volume of the first bio-reactor tank  100  with the air being introduced into the central volume of the first bio-reactor tank  100  by the first air pump. 
     The wastewater effluent within the central volume of the first bio-reactor tank  100  flows downward into a lower volume of the tank  100  and back up through the packed media bed of small components to create a flow of the wastewater effluent from the upper volume of the first bio-reactor tank  100 , down through the central volume of the first bio-reactor tank  100 , into a lower volume of the tank  100 , and upward through the packed media bed of small components towards the upper volume of the first bio-reactor tank  100 . 
     An air supply pump  500  pumps air into the lower volume of the first bio-reactor tank  100  via an air inlet and diffusers. The diffusers create bubbles to assist in moving the wastewater effluent upward through the packed media bed of small components towards the upper volume of the first bio-reactor tank  100 . 
     It is noted that the diffusers may be angled towards the outer wall of the lower volume of the first bio-reactor tank  100  to create a flow near the outer wall to prevent or reduce pooling of the wastewater effluent near the outer wall. 
     In the lower volume, a portion of the wastewater effluent can be drained off and pumped by pump  180  to a second bio-reactor tank  200 . The portion of the wastewater effluent drained off from the first bio-reactor tank  100  is introduced to an upper volume of the second bio-reactor tank  200 . 
     In addition to the introduction of fresh wastewater effluent into the upper volume of the tank  100 , recycled wastewater effluent from another tank is introduced in the upper volume of the tank  100  via a recycled wastewater effluent inlet. The recycled wastewater effluent, as illustrated, is effluent from a clarifier tank  300 . 
     The second bio-reactor tank  200  includes a packed media bed of small components. The small components provide a large area for the microorganisms to interact with the wastewater effluent being treated. 
     An air pump provides air to a central volume of the second bio-reactor tank  200  so as to introduce bubbles into the wastewater effluent within the central volume of the tank  100 . 
     The air from the air pump may be is forced through a diffuser (not shown) that has openings so that the air is admitted into wastewater effluent within the central volume of the second bio-reactor tank  200  in the form of bubbles. 
     The bubbles can be further reduced in size by a propeller device which pushes the wastewater effluent within the central volume of the second bio-reactor tank  200  downward into a lower volume of the second bio-reactor tank  200 . 
     The bubbles can be further reduced in size by a propeller device which pushes the wastewater effluent within the central volume of the second bio-reactor tank  200  downward into a lower volume of the second bio-reactor tank  200 . 
     The wastewater effluent within the central volume of the second bio-reactor tank  200  flows downward into a lower volume of the second bio-reactor tank  200  and back up through the packed media bed of small components to create a flow of the wastewater effluent from the upper volume of the second bio-reactor tank  200 , down through the central volume of the second bio-reactor tank  200 , into a lower volume of the second bio-reactor tank  200 , and upward through the packed media bed of small components towards the upper volume of the second bio-reactor tank  200 . 
     The air supply pump  500  pumps air into the lower volume of the second bio-reactor tank  200  via an air inlet and diffusers. The diffusers create bubbles to assist in moving the wastewater effluent upward through the packed media bed of small components towards the upper volume of the second bio-reactor tank  200 . 
     It is noted that the diffusers may be angled towards the outer wall of the lower volume of the second bio-reactor tank  200  to create a flow near the outer wall to prevent or reduce pooling of the wastewater effluent near the outer wall. 
     In the lower volume, a portion of the wastewater effluent can be drained off and pumped by pump  280  to a third clarifier tank  300 . The portion of the wastewater effluent drained off from the second bio-reactor tank  200  is introduced to an upper volume of the third clarifier tank  300 . 
     Optionally, fresh wastewater effluent can be introduced into the upper volume of the second bio-reactor tank  200 , as well as, microorganisms can be introduced into the upper volume of the second bio-reactor tank  200 . 
     The third tank  300  is a clarifier tank that allows sloughed-off-sludge (biofilm) to settle out of the treated effluent so that a portion of the treated effluent can be discharged. The sloughed-off-sludge (biofilm) is recycled, via pump  380 , back to the first tank  100  for further treatment. 
     By recycling the biofilm and some of the treated effluent, all or a significant portion of the microorganisms are not lost in the discharge process. This reduces the need to introduce new microorganisms into the first bio-reactor tank  100 , as seed microorganism. 
     Moreover, the microorganism being recycled to the first bio-reactor tank  100  are mature, and thus, the microorganisms can process the wastewater effluent more effectively. 
     As illustrated in  FIG. 3 , the wastewater effluent passes through the first bio-reactor tank  100 , the second bio-reactor tank  200 , and the clarifier tank  300  before being discharged as treated effluent. Accumulated sloughed-off-sludge (biofilm) from the clarifier tank  300  is recycled back to the first bio-reactor tank  100  to enable further digesting of the remaining particles. 
     Carbon compounds in the wastewater effluent are digested by the microorganism and converted to carbon dioxide and water. Any remaining solids can be eventually removed through sludge drain  400  for additional processing or other uses. 
     Although  FIG. 3  shows two bio-reactor tanks for microorganism digestion and a clarifier, the system may contain more than two bio-reactor tanks for microorganism digestion, wherein each bio-reactor tank is connected in a similar manner. 
       FIG. 4  shows a diversion member for diverting fluid to an outer edge of a non-round bio-reactor container. As illustrated in  FIG. 4 , a diversion member  1000  is located beneath the central volume of the bio-reactor tank so as to divert the downward flowing effluent towards the outer edges (walls) of the bio-reactor tank. 
     The diversion member  1000  includes a central peak  1100 . The diversion member  1000  further includes projecting edges  1300  that extend from the central peak  1100  towards the outer edges (walls) of the bio-reactor tank. The projecting edges  1300  extend in a downward manner from the central peak  1100  to a floor of the bio-reactor tank. 
     The diversion member  1000  includes planar surfaces  1200 , each having an edge which coincides with a projecting edge  1300 . The planar surfaces  1200  slope downwardly from the projecting edge  1300  to a floor edge  1350 . 
     As illustrated in  FIG. 4 , two planar surfaces  1200  are located between adjacent projecting edges  1300 . The adjacent projecting edges  1300  may be orthogonal thereto. 
     The two planar surfaces  1200  located between adjacent projecting edges  1300  share a common edge  1400 . The common edge  1400  slopes downwardly from the central peak  1100  to a floor. 
     As effluent encounters the diversion member  1000 , the effluent flows down ( 1500 ) the planar surfaces  1200  and outwardly ( 1600 ) towards the outer edges (walls) of the bio-reactor tank. 
       FIG. 5  shows a side view of the diversion member of  FIG. 4 . The diversion member  1000  includes planar surfaces  1200 , each having an edge which coincides with a projecting edge  1300 . The planar surfaces  1200  slope downwardly from the projecting edge  1300  a floor edge  1350  that meets a floor  1700 . 
     As illustrated in  FIG. 5 , two planar surfaces  1200  located between adjacent projecting edges  1300  share a common edge  1400 . The common edge  1400  slopes downwardly from the central peak  1100  to a floor  1700 . 
       FIG. 6  shows a cross section of the diversion member of  FIG. 4 . The diversion member  1000  includes a central peak  1100  and planar surfaces  1200 . The planar surfaces  1200  slope downwardly from the central peak  1100  to a floor edge  1350  that meets a floor  1700 . 
     The diversion member  1000  of  FIGS. 4-6  divert a portion of the effluent towards the outer edges of the bio-reactor tank to prevent sediment from collecting along the walls of the tank. Specifically, the diversion member  1000  of  FIGS. 4-6  can be configured to divert a portion of the effluent towards the corners of a non-round bio-reactor tank to prevent sediment from collecting in the corners of a non-round bio-reactor tank. 
       FIG. 7  shows a diversion member  2000  for diverting fluid in a rotational manner along an outer edge of a round bio-reactor container. As illustrated in  FIG. 7 , the diversion member  2000  may be a tube that is coiled so that the effluent is influenced to flow in a rotational manner so that as the effluent exits the diversion member  2000 , the effluent flows along a wall of a round bio-reactor tank to prevent sediment from collecting along the walls of a round bio-reactor tank. 
     It is noted that although the diversion member is described as being located on or near the floor of a bio-reactor tank, the diversion member may be located anywhere in the effluent&#39;s flow path as the effluent leaves the central volume to enter the lower volume so long as the diversion member diverts a portion of the effluent towards the outer walls and/or corners of the bio-reactor tank to prevent build-up of sediment or particulate along the outer walls and/or in the corners of the bio-reactor tank. 
     As discussed above, the bio-reactor includes two distinct introductions of bubbles into the bio-reactor tank to provide oxygen to the microorganisms as well as to provide a force to cause the effluent to circulate within the bio-reactor tank. Bubbles are introduced within a central volume of the bio-reactor tank and propelled downward with effluent by a propeller mechanism to a lower volume of the bio-reactor tank. In the lower volume, additional bubbles are introduced to the “bubbled” effluent causing the bubbled effluent to flow upward through the packed media (housing the microorganism), before the effluent reaches an upper volume of the bio-reactor tank, where it cascades over the edge of the central volume and flows back towards the lower volume, completing the circulation path. 
     A portion of the effluent is “drained” off from the lower volume of the bio-reactor tank and pumped to an upper volume of a second bio-reactor tank. The second bio-reactor tank includes essentially the same components as the first bio-reactor tank. 
     A portion of the effluent in the second bio-reactor tank is “drained” off from the lower volume of the second bio-reactor tank and can be pumped to an upper volume of a clarifier tank for settling and discharge. The non-discharged effluent and remaining non-digested particulates in the clarifier tank are recycled back to the first bio-reactor tank and introduced into the upper volume of the first bio-reactor tank. 
     It is noted that more than two bio-reactor tanks can be chained together before the effluent is pumped into a clarifier tank for settling and discharge, wherein a portion of the effluent is drained off from a lower volume of a bio-reactor tank and pumped into an upper volume of the next bio-reactor tank. 
     As disclosed above, a bio-reactor for treating wastewater effluent using microorganisms, comprises a tank having a first volume, a second volume, and a third volume, each volume having an outer wall; an inlet in the first volume to introduce wastewater effluent; a central channel located within the second volume; a first air supply to introduce air into wastewater effluent located in the central channel within the second volume; a packed media bed of small components, the packed media bed being located in the second volume; a second air supply to introduce air into wastewater effluent located in the third volume to assist movement of wastewater effluent upward from the third volume, through the packed media bed, to the first volume; and an outlet in the third volume to drain a portion of the wastewater effluent. 
     The second air supply may include second air supply diffusers to introduce air bubbles into wastewater effluent located in the third volume. The first air supply may include first air supply diffusers to introduce air bubbles into wastewater effluent located in the central channel. 
     The bio-reactor may include a propulsion device in the central channel to propel wastewater effluent located in the central channel into the third volume. The propulsion device may reduce a size of the air bubbles in the wastewater effluent located in the central channel. The propulsion device may aerate the wastewater effluent located in the central channel. 
     The second air supply diffusers may be directed at the outer wall of the third volume to create wastewater effluent flow near the outer wall of the third volume to prevent or reduce pooling of wastewater effluent near the outer wall of the third volume. 
     The bio-reactor may include a diverter, located in the third volume to divert a portion of wastewater effluent flowing into the third volume from the central channel to the outer wall of the third volume to prevent build-up of particulate along the outer wall of the third volume. 
     A system for treating wastewater effluent using microorganisms, comprises a first bio-reactor; the first bio-reactor including, a tank having a first volume, a second volume, and a third volume, each volume having an outer wall, an inlet in the first volume to introduce wastewater effluent, a central channel located within the second volume, a first air supply to introduce air into wastewater effluent located in the central channel within the second volume, a packed media bed of small components, the packed media bed being located in the second volume, a second air supply to introduce air into wastewater effluent located in the third volume to assist movement of wastewater effluent upward from the third volume, through the packed media bed, to the first volume, and an outlet in the third volume to drain a portion of the wastewater effluent; and a second bio-reactor; the second bio-reactor including, a tank having a first volume, a second volume, and a third volume, each volume having an outer wall, an inlet in the first volume to introduce wastewater effluent, a central channel located within the second volume, a first air supply to introduce air into wastewater effluent located in the central channel within the second volume, a packed media bed of small components, the packed media bed being located in the second volume, a second air supply to introduce air into wastewater effluent located in the third volume to assist movement of wastewater effluent upward from the third volume, through the packed media bed, to the first volume, and an outlet in the third volume to drain a portion of the wastewater effluent; the outlet of the first bio-reactor being operatively connected to the inlet of the second bio-reactor. 
     The second air supply may include second air supply diffusers to introduce air bubbles into wastewater effluent located in the third volume. The first air supply may include first air supply diffusers to introduce air bubbles into wastewater effluent located in the central channel. 
     The bio-reactor may include a propulsion device in the central channel to propel wastewater effluent located in the central channel into the third volume. The propulsion device may aerate the wastewater effluent located in the central channel. 
     The second air supply diffusers may be directed at the outer wall of the third volume to create wastewater effluent flow near the outer wall of the third volume to prevent or reduce pooling of wastewater effluent near the outer wall of the third volume. 
     A diversion member for a bio-reactor for treating wastewater effluent using microorganisms, comprises a central peak; projecting edges extending from the central peak in a downward manner from the central peak; and planar surfaces sloping downwardly from the projecting edges, each planar surface having an edge coinciding with a projecting edge. 
     Two planar surfaces may be located between adjacent projecting edges. Adjacent projecting edges may be orthogonal. 
     The two planar surfaces may share a common edge, the common edge sloping downwardly from the central peak. 
     It will be appreciated that several of the above-disclosed embodiments and other features and functions, or alternatives thereof, may be desirably combined into many other different systems or applications. Also, various presently unforeseen or unanticipated alternatives, modifications, variations, or improvements therein may be subsequently made by those skilled in the art which are also intended to be encompassed by the description above and the following claims.