Abstract:
A system, apparatus, and method for treating wastewater having bio-solids therein. The system includes a tank, a wastewater inlet line, an effluent discharge outlet line, and an aeration source. The tank has an upper aeration chamber and a lower clarification chamber separated by a common inclined partition having an opening defined therein. The inclined partition opens into the lower clarification chamber near a bottom of the tank which allows fluid communication between the upper aeration chamber and the lower clarification chamber. The bottom of the tank has a bio-sludge outlet for removal of settled bio-solids. The wastewater inlet line opens into the aeration chamber and an intake end of the effluent discharge outlet line is positioned within the clarification chamber. The aeration source is positioned within the aeration chamber to supply air to the wastewater within the aeration chamber. It is emphasized that this abstract is provided to comply with the rules requiring an abstract which will allow a searcher or other reader to quickly ascertain the subject matter of the technical disclosure. It is submitted with the understanding that is will not be used to interpret or limit the scope or meaning of the claims. 37 C.F.R. §1.72(b).

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    This invention relates, generally, to systems and methods for treatment of wastewater and, more particularly, to systems and methods for continuous treatment of influent wastewater in a single tank.  
           [0003]    2. Prior Art  
           [0004]    Numerous devices are known in the art for the treatment of wastewater. Most treatment systems have at least two separate tanks: a treatment tank for aeration of the wastewater, and a settling tank for removing bio-solids. An inlet in communication with the treatment tank, an outlet in communication with the settling tank, and a conduit in communication with the treatment tank and the settling tank are normally provided in the wastewater systems. Influent is fed to the treatment tank via the inlet and treated wastewater is removed from the treatment system via the outlet.  
           [0005]    In the treatment tank, oxygen is typically provided to the microbes to aerobically oxidize the organic pollutants in the wastewater. Typically, air may be injected into the treatment tank at various locations via an aeration source, such as an aerator, so that a sufficient amount of oxygen is transferred and distributed throughout the treatment tank to support the aerobic bio-activity. Typically, the aeratol is a conventional design, such as, for example, a fine bubble diffuser, a coarse bubble diffuser, a jet aerator, an inductor aerator, a low speed mechanical aerator, a high speed aerator, and the like. The treatment tank tends to be a fairly high energy environment to keep microbial solids suspended (i.e., mixed) and to supply the mixture with the appropriate level of oxygen.  
           [0006]    The aerobically treated wastewater is generally delivered to the settling tank via at least one conduit extending therebetween. Typically, a gravity flow conduit or a pressurized conduit delivers the aerobically treated wastewater to the settling tank. To allow the bio-solids present in the wastewater to settle, the settling tank typically is designed as a generally low energy, quiescent, environment. Treated wastewater is removed from the settling tank through the outlet.  
           [0007]    As noted above, the general state of the art is to employ a separate tank for each sequential phase of the treatment cycle. That is, to use at least one treatment tank for aerobic bio-treatment, and to use at least one settling tank for settling of bio-solids. The disadvantages to the use of separate tanks include the greater use of land and the additional cost of building two tanks and the plumbing to connect the two tanks. Various designs of single tank wastewater treatment systems have been proposed to overcome the noted disadvantages.  
           [0008]    One common type of a single tank wastewater treatment system incorporates both a clarifier chamber and treatment chamber into a single tank. A partition is typically provided within the tank to create the two chambers, a lower aeration chamber and an upper clarification chamber. The partition does not extend to the floor of the tank and defines an opening so that the two chambers can be in fluid communication. Examples of such wastewater treatment systems are shown in U.S. Pat. No. 6,096,203 to Drewery, U.S. Pat. No. 5,785,854 to McKinney, U.S. Pat. No. 5,549,818 to McGrew, U.S. Pat. No. 5,490,935 to Guy, U.S. Pat. No. 5,221,470 to McKinney, and U.S. Pat. No. 4,983,285 to Nolen. The wastewater treatment systems described in the exemplary patents can adequately be characterized as aerated septic tanks and are generally small, with a capacity typically less than 2500 gallons. Such aerated septic tank systems are suitable for only very low volumes of wastewater, with flow rates ranging from only 500 to 1,500 gallons per day.  
           [0009]    An alternative example of a single tank wastewater system is demonstrated in sequencing batch reactor (SBR) wastewater treatment systems. SBR wastewater treatment systems typically use only one tank in which aeration and clarification are achieved by alternatively aerating a batch of wastewater in the tank, during a reaction phase, then turning off the aerator to allow the bio-solids to settle, in a clarifying phase, so that clear, treated effluent forms above the bio-sludge blanket formed by the settled bio-solids. During the clarifying phase no liquids enter or leave the tank to avoid the introduction of turbulence in the supernatant. After settling, in a decanting phase, treated effluent is withdrawn from below the surface of the mixed liquor to avoid disturbing the settled bio-sludge. The tank is then refilled and the reaction phase is reinitiated. By definition, SBRs process intermittently so they are only suitable for very low volumes of wastewater. To overcome the low volume limitation, SBRs often use two tanks so that one tank is being aerated while the other is settling. To function properly, SBRs require the use of programmed timers and pumps to properly control the sequential processes that take place in the single tank, and, if used, to alternate the processes between the two tanks.  
         SUMMARY  
         [0010]    The present invention overcomes the prior art limitations by providing a system and method which is highly reliable, relatively economical in manufacture, cost effective in installation, and allows for relatively high flow rates of treated wastewater.  
           [0011]    In one exemplary embodiment, the wastewater treatment system includes a treatment tank having an internal partition, a wastewater inlet line, an effluent discharge outlet line, and an aeration source. The partition is connected to a side wall of the tank intermediate the bottom and the top of the treatment tank and divides the tank into an upper aeration chamber and a lower clarification chamber. The partition defines an opening that is spaced from the bottom of the treatment tank which allows for fluid communication between the upper aeration chamber and the lower clarification chamber. In one example, the partition may have, in portion, an inverted frustoconical shape.  
           [0012]    The wastewater inlet line opens into and is in fluid communication with the aeration chamber of the treatment tank. The effluent discharge outlet line is in fluid communication with the clarification chamber for communication of treated wastewater away from the treatment tank. The aeration source is positioned within the aeration chamber to supply oxygen to the wastewater in the aeration chamber. The aeration source in the aeration chamber provides mixing of the wastewater within the aeration chamber and supplies oxygen to the mixed liquor in the aeration chamber for efficient removal of organic pollutants.  
           [0013]    The treatment tank may also include a second partition that is connected to portions of the side wall of the treatment tank. In position, a top edge of the second partition is proximate the peripheral edge of the treatment tank and a bottom edge is spaced from an upper surface of the partition that divides the treatment tank into the upper aeration chamber and the lower clarification chamber. The second partition forms a separate anoxic chamber within the aeration chamber of the treatment tank. In one example, the wastewater inlet line opens into the anoxic chamber of the treatment tank. The tank may also include a bio-sludge recirculation conduit in communication with a bio-sludge outlet in the bottom of the treatment tank and in communication with the anoxic chamber for supplying bio-sludge from the clarification chamber to the anoxic chamber of the tank. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]    The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate several embodiments of the invention and together with the description, serve to explain the principals of the invention.  
         [0015]    [0015]FIG. 1 is a cut-away perspective view of an embodiment of the wastewater treatment system;  
         [0016]    [0016]FIG. 2 is a sectional view of the invention shown in FIG. 1 taken in a vertical plane which bisects the exemplified embodiment of the wastewater treatment system;  
         [0017]    [0017]FIG. 3 is a cut-away perspective view of an alternate embodiment of the wastewater treatment system; and  
         [0018]    [0018]FIG. 4 is a sectional view of the invention shown in FIG. 3 taken in a vertical plane which bisects the exemplified embodiment of the wastewater treatment system.  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0019]    The present invention is more particularly described in the following examples that are intended to be illustrative only since numerous modifications and variations therein will be apparent to those skilled in the art. As used in the specification and in the claims, the singular form “a,” “an” and “the” include plural referents unless the context clearly dictates otherwise.  
         [0020]    Referring to the figures, the wastewater treatment system  10  of the present invention may include a tank  20 , a wastewater inlet line  40 , an effluent discharge outlet line  60 , and an aeration source  80 . The tank  20  has a bottom  22 , an open top  24 , an upper aeration chamber  26 , and a lower clarification chamber  28 . The bottom  22  of the tank  20  has a bio-sludge outlet  23  and the top  24  has a peripheral edge  25  extending along the periphery of the tank  20 . The tank  20  may, for example, have a cylindrical shape.  
         [0021]    A common partition  30  is connected to a continuous side wall  21  of the tank intermediate the bottom  22  and the top  24  of the tank  20  and divides the tank  20  into the upper aeration chamber  26  and the lower clarification chamber  28 . The partition  30  has an upper surface  31 , a lower surface  32 , and defines an opening  34  extending through the partition  30 . The partition  30  is spaced from the bottom  22  of the tank  20 . As one would appreciate, the opening  34  in the common partition  30  is also spaced from the bottom  22  of the tank  20  and allows for fluid communication between the upper aeration chamber  26  and the lower clarification chamber  28 . Preferably, at least a portion of the common partition  30  is inclined toward the bottom  22  of the tank  20  so that the opening  34  in the common partition  30  opens into the lower clarification chamber  28  near the bottom  22  of the tank  20 . In one example, the common partition  30  has, at least in portion, an inverted frustoconical shape and the opening  34  in the partition is typically defined at the apex of the frustoconical shape.  
         [0022]    It is preferred that the bio-sludge outlet  23  be proximate a center of the bottom  22  of the treatment tank  20 . The bottom  22  of the tank  20  may have, at least in portion, an inverted frustoconical shape. In this example, the bio-sludge outlet  23  is preferably positioned proximate the apex of the frustoconical shape of the bottom  22  so that, in operation, bio-sludge, formed on the bottom  22  of the tank  20  by the bio-solids settling out of the wastewater within the clarification chamber  28  will tend to migrate toward the bio-sludge outlet  23  of the tank  20  under the influence of gravity.  
         [0023]    The wastewater inlet line  40  opens into, and is in fluid communication with, the aeration chamber  26  of the treatment tank  20 . The effluent discharge outlet line  60  is in fluid communication with the clarification chamber  28 . In one example, an inlet end  62  of the effluent discharge outlet line  60  is positioned within the clarification chamber  28  and an outlet end  64  of the effluent discharge outlet line  60  is positioned external of the interior of the tank  20 . In one example, the intake end  62  of the effluent discharge outlet line  60  extends through the side wall  21  of the tank  20  and is positioned proximate to and below the lower surface  32  of the common partition  30 . Thus, the intake end  62  of the discharge outlet line  60  is positioned relative to the bottom  22  of the tank  20  so that the intake end  62  is spaced from the bio-sludge blanket formed from the settled bio-solids deposited on the bottom  22  of the tank  20 . With the intake end  64  in this preferred position, bio-sludge is prevented from being drawn into the intake end  64  of the effluent discharge outlet line  60  as treated wastewater is withdrawn from the clarification chamber  28 .  
         [0024]    The aeration source  80  is positioned within the aeration chamber  26  to supply oxygen to the wastewater held therein. The aeration source supplies oxygen to the mixed liquor in the aeration chamber, which, because of the increase in the oxygenation level, provides an environment conducive for aerobic treatment of the wastewater. In operation, the aeration chamber  26  is a generally high energy environment so that the wastewater within the aeration chamber  26  is adequately mixed by the turbulence supplied by the aeration source  80  and the mixed liquor is exposed to adequate levels of oxygen to effect removal of organic pollutants.  
         [0025]    As one skilled in the art will appreciate, the aeration source  80  is typically an aerator  82 . Many examples of conventional aerators are known that can be positioned in the aeration chamber  26  to provide the desired levels of mixing and oxygen dissolution. These examples include, but are not limited to, a fine bubble diffuser, a course bubble diffuser, a jet aerator, an inductor aerator, a low speed mechanical aerator, and a high speed mechanical aerator.  
         [0026]    Referring to FIGS. 1 and 2, an example of the present invention is shown with an exemplified course bubble diffuser  84  positioned in the aeration chamber  26  of the tank  20 . The diffuser  84  preferably has at least one air outlet pipe  86  connected to an external compressed oxygenation gas source, such as, for example, an air blower. In this example, a portion of the air outlet pipe  86  extends from the exterior of the tank  20  into the aeration chamber  26  and is positioned so that at least a portion of the air outlet pipe  86  is spaced from the upper surface  31  of the common partition  30 . As one skilled in the art will appreciate, the end of the air outlet pipe  86  may be open or closed. A portion of the air outlet pipe defines a plurality of openings  88 , such as slots or holes, which run up the side of the air outlet pipe  86  near the end of the air outlet pipe  86 . The purpose of the openings  88  is to allow for uniform aeration and mixing of the aeration chamber  26 . The release of air into the aeration chamber  26  via the openings  88  in the air outlet pipe  86  introduces a turbulent current in the aeration chamber  26  for mixing while providing a sufficient supply of oxygen for the growth of the aerobic bacteria.  
         [0027]    In another example of the invention as shown in FIGS. 3 and 4, a mechanical aerator  90  is in communication with the wastewater of the aeration chamber  26 . In this example, the mechanical aerator  90  has at least one blade  92  coupled to, and extending generally radially from, a drive shaft  94 . As one would appreciate, the drive shaft  94  is driven by a conventional drive assembly that is disposed with respect to the open top  24  of the treatment tank  20 . In operation, the rotation of the blade  92  of the mechanical aerator  90  within the aeration chamber  26  induces the desired turbulence in the mixed liquor for mixing and transfers oxygen into the aeration chamber  26 .  
         [0028]    To include the capability for denitrification in the wastewater treatment system of the present invention, the system may also include an anoxic chamber  110  defined within the aeration chamber  26  of the tank  20  by a second common partition  112 . The second common partition  112  has a top edge  114 , a spaced bottom edge  116 , and a pair of opposing side edges  118  that extend from the top edge  114  to the bottom edge  116  of the second common partition  1112 . In one example, the side edges  118  of the second common partition  112  are connected to portions of the side walls  21  of the tank  20  so that the top edge  114  of the second common partition  112  is proximate the peripheral edge  25  of the tank  20  and the bottom edge  116  of the second common partition  112  is spaced from the upper surface  31  of the common partition  30  separating the upper aeration chamber  26  and the lower clarification chamber  28 . The second common partition  112  is preferably substantially upright.  
         [0029]    As one will appreciate, since the anoxic chamber  110  is positioned within the aeration chamber  26  of the tank  20 , the anoxic chamber  110  and the aeration chamber  26  are in fluid communication with each other. However, unlike the relatively high energy environment of the aeration chamber  26 , the second common partition  112  forms a barrier that generally shields the anoxic chamber  110  from the turbulence and oxygenation effects of the aeration source  80 . Thus, the anoxic chamber  110  forms a zone that tends to be oxygen deficient, which promotes anoxic degradation of nitrates in the wastewater. During the denitrification process, anoxic degradation of nitrates results in the generation of nitrogen gas. Anoxic treatment in a wastewater treatment system is desirable, as it assists in promoting a more complete biological degradation.  
         [0030]    To aid in minimizing the effects of the aeration source  80  on the anoxic chamber  110 , the bottom edge  116  of the second common partition  112  is preferably spaced from the upper surface  31  of the common partition  30  a first distance d, and the aeration source  80  is spaced from the upper surface  31  of the common partition  30  a second distance d 2 . The second distance d 2  is preferably greater than the first distance d 1  so that the bottom edge  116  of the second common partition  112  extends generally below the aeration source  80 .  
         [0031]    In one example, the wastewater inlet line  40  may open into the anoxic chamber  110  so that the wastewater is first subjected to anoxic treatment in the anoxic chamber  110  prior to passing into the aeration chamber  26 . Referring to FIGS. 1 and 2, the system  10  may also include a bio-sludge recirculation line  120 . The bio-sludge recirculation line  120  has a first end  122  in fluid communication with the bio-sludge outlet  23  and a second end  124  in fluid Communication with the anoxic chamber  110 . A pump  126 , for example, an air lift pump, is operably Coupled to the bio-sludge recirculation line  120  so that bio-sludge removed from the clarification chamber  28  of the tank  20  via the bio-sludge outlet  23  may be metered though the bio-sludge recirculation line  120  and into the anoxic chamber  110  of the tank  20 .  
         [0032]    In another example, shown in FIGS. 3 and 4, the second end  124  of the bio-sludge recirculation conduit  120  may be connected to the wastewater inlet line  40  at a juncture removed from the outlet of the wastewater inlet line  40 . In this example, the wastewater inlet line  40  is positioned so that it opens into the anoxic chamber of the tank  20 .  
         [0033]    In yet another example, the portion of the wastewater inlet line  40  extending from the juncture of the bio-sludge recirculation line  120  to the outlet of the wastewater inlet line  40  is sized to act as a relatively low energy anoxic treatment chamber. Thus, in this alternate example, the wastewater exiting the outlet of the wastewater inlet line  40  undergoes anoxic treatment in a portion of the wastewater inlet line  40  proximate the outlet and may be deposited directly into the aeration chamber  26 . As one will appreciate, the second common partition  112  which defines the anoxic chamber  110  within the aeration chamber  26  is not needed in this example.  
         [0034]    The wastewater treatment system may also include a mixer  160  positioned so that a portion is disposed in the anoxic chamber in contact with the materials contained therein. The mixer generally operates at a speed sufficient to provide a gentle mixing action and assure contact between the influent wastewater and the recycled bio-solids from the bio-sludge recirculation line 120 .  
         [0035]    The present invention may also include a bio-sludge removal subsystem  140  for removing accumulating bio-sludge from the bottom  22  of the treatment tank  20 . As one skilled in the art will appreciate, the bio-sludge removal subsystem  140  is entirely optional as the exemplified wastewater treatment system can utilize gravity as the motivating force for urging the bio-sludge toward the bio-sludge outlet  23 . For example, the bio-sludge removal system  140  may include a bridge member  142 , a conventional drive mechanism  144 , and a driven assembly  150 . The bridge member  142  is disposed on portions of the peripheral edge  25  of the tank  20  so that the bridge member  142  spans the open top  24  of the tank  20 . The bridge member  142  preferably is positioned so that it substantially bisects the open top  24  to the tank  20 . Thus, a portion of the bridge member  142  may extend over the proximate center of the open top  24 . The drive mechanism  144  is supported by and is coupled to the bridge member  142  proximate the center of the top  24  of the tank  20 .  
         [0036]    The driven assembly  150  is operatively coupled to the drive mechanism  144  and will typically include a downwardly extending shaft  152 , at least one rake arm  154 , and at least one scraper blade  156 . In the present invention, the shaft  152  extends through the opening  34  in the common partition  30  so that a distal end  153  of the shaft  152  is spaced from the bottom  22  of the tank  20 . The rake arm  154  is connected to the shaft  152  near the distal end  153  of the shaft  152  and extends generally radially from the shaft  152 . The rake arm  154  is spaced from the bottom  22  of the tank  20 . At least one scraper blade  156  is connected to and depends from the rake arm  154  for close sliding contact with at least a portion of the bottom  22  of the tank  20 . In operation, the rotation of the shaft  152  causes the scraper blade  156  to urge accumulated bio-sludge from the bottom  22  of the tank  20  toward the bio-sludge outlet  23  in the bottom  22  of the tank  20 . As one will appreciate, if a mechanical aerator is used in the system  10 , the drive shaft  94  and the shaft  152  for the bio-sludge removal subsystem may be the same shaft.  
         [0037]    In operation, wastewater is supplied to the aeration chamber  26  via the wastewater inlet line  40 . An oxygen bearing gas, such as air, is supplied to the aeration chamber  26  via the aeration source  80  so that the oxygen content of the wastewater in the aeration chamber  26  is increased and the suspended bio-solids in the wastewater are adequately mixed to effect efficient removal of organic pollutants in the aeration chamber  26 . The aerobically treated wastewater passes through the opening  34  in the common partition  30  and into the clarification chamber  28 . In the clarification chamber  28 , bio-solids in the wastewater settle onto the bottom  22  of the tank  20  to form a bio-sludge layer. The treated wastewater is removed from the clarification chamber  28  via the effluent discharge line without disturbing the bio-sludge layer. Finally, the bio-sludge is removed from the tank  20  via the bio-sludge outlet  23  in the bottom  22  of the tank  20 . As one will appreciate, the tank  20  is capable of processing a continual flow of wastewater, and can thus process high flow rates of wastewater. For example, a tank  20  having a diameter of approximately 50 feet may be able to process in excess of 1,000,000 GPD. The larger the tank, the larger the treatable flow rate.  
         [0038]    Further, if the tank  20  includes the anoxic chamber  110 , the wastewater is preferably initially supplied to the anoxic chamber  110  for anoxic treatment of the wastewater prior to the introduction of the wastewater into the aeration chamber  26 . Bio-sludge removed from the clarification chamber  28  of the tank  20  may be pumped into the anoxic chamber  110  along with the supplied wastewater.  
         [0039]    The invention has been described herein in detail, in order to comply with the Patent Statutes and to provide those skilled in the art with information needed to apply the novel principles, and to construct and use such specialized components as are required. However, it is to be understood, by those skilled in the art, that the invention can be carried out by specifically different equipment and devices, and that various modifications, both as to equipment details and operating procedures can be affected without departing from the scope of the invention itself. Further, it should be understood that, although the present invention has been described with reference to specific details of certain embodiments thereof, it is not intended that such details should be regarded as limitations upon the scope of the invention except as and to the extent that they are included in the accompanying claims.