Abstract:
A wastewater treatment system is disclosed whereby trickling filters remove a high proportion of biochemical oxygen demand, total suspended solids, and nutrients from wastewater using, in one embodiment, a pressurized media container. The system accomplishes this in an improved way by combining venturies or blowers to aerate the wastewater, and recirculating the wastewater and air down through the treatment media, improving the overall efficiency of the system and reducing its size. A screen at the base of the pressurized media container supports the media and allows the wastewater to exit the pressurized media container. The system also includes a low pressure nozzle that aids in the proper distribution of the wastewater.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]    This application is related to and claims the benefit of Provisional U.S. Patent Application No. 60/206,784 entitled Trickling Filter Pressurized Canister Wastewater Treatment, filed by the Assignee of the present invention, and incorporated herein by reference. 
     
    
     
       TECHNICAL FIELD  
         [0002]     The present invention relates to systems for treating wastewater, and more particularly, relates to wastewater treatment systems including biological media.  
         BACKGROUND IN FORMAT ION  
         [0003]    The object of wastewater treatment is to reduce the total suspended solids (TSS), biochemical oxygen demand (BOD), nitrogen compounds,  E-coli,  phosphorous, and virtually any other bacteria from the wastewater, so as to minimize the quantity of such undesirables outputted by the treatment system. Various well known means have been devised for achieving such goals, with varying degrees of success and efficiency. An overriding general problem, for the most part, with such prior systems has been the scale of operation required to effectively treat the wastewater to achieve a high-quality water output at a reasonable expense. That is, for the volumes of water to be treated, the sizes of these systems are correspondingly large. This may be particularly true for relatively small-scale systems, such as single-family residences and small groupings of homes and/or buildings, where coupling to a municipal treatment system may be unsuitable or unavailable.  
           [0004]    The use of biological treatments to accelerate the breakdown of solids and the various contaminants associated with wastewater is also well known. The biological treatment usually involves the use of microbes having an affinity for the pollutants contained in the water. That is, rather than simply permit solids to slowly decant from the wastewater, and then apply a hazardous chemical treatment designed to destroy the pollutants, along with virtually everything else in the water, these microbes are permitted to act upon the wastewater. In relative terms, they act to remove the pollutants faster than if nothing were used, and do so without the hazardous and difficulties associated with chemical treatment.  
           [0005]    The microbes must, however, be permitted to reside in some type of holding tank in order to multiply and feed on the contaminants. Upon completion of their ingestion of the pollutants, the microbes simply die and are removed. The treated water then passes to the next stage, which may simply be some form of a leach bed, or it may be a more complex system, including, but not limited to, an ultraviolet disinfection means for subsequent transport to a body of water, or for recycling in non-critical uses, such as horticulture.  
           [0006]    Unfortunately, while biological treatment has significant advantages, use of the microbes requires a sufficient “dwell time” for the microbes to “eat” enough of the pollutants so that the wastewater is rendered satisfactorily contaminant-free. Of course, the extent to which contaminant removal is satisfactory is a function of governmental regulation. In any case, the volume of water that must be treated can often lead to the need for a rather large-scale treatment unit for a relatively small waste-water-generating facility. This is particularly true for small scale (i.e., single or small groups of individual housing) were any economies of scale are impossible. As a result, wastewater treatment is particularly expensive for individuals. Furthermore, treatment for larger groups can be expensive as well due to the even larger scale necessary to meet the government requirements.  
           [0007]    Another problem associated with many of the prior systems results from “plugging” of the system. The plugging can result from either the solids entrapped in the effluent stream or from biological build-up. As the microbes live and die, their mass can build up and reduce the efficiency of the system by blocking the access of the living microbes to the pollutants or by simply plugging the system altogether.  
           [0008]    A further problem associated with many of the prior systems is their inability to effectively oxygenate the wastewater. Without the necessary oxygen, many of the microbes will not be able to sustain life. The ability of a system to introduce oxygen is a factor in overall size of the system, i.e. the amount of oxygen per square foot is proportionate to the amount of microbes in the system per square foot.  
           [0009]    Several prior wastewater treatment systems have been described. These systems have apparently been designed for large- and/or small-scale treatment using biological media to accelerate contaminant reduction. For the most part, they include biological treatment as well as mechanisms designed to enhance the effectiveness of the microbial action. However, each in turn suffers from one or more deficiencies that significantly affect the ability to provide the most effective and relatively inexpensive waste treatment system.  
           [0010]    Therefore, what is needed is a media containment apparatus and that takes advantage of the useful characteristics of biological treatment in an effective manner. What is also needed is such an apparatus and process that maximizes the contact between contaminants from the wastewater and the microbes without the need for a relatively large processing tank or unit. Further, what is needed is an apparatus and process that operates economically and without the need to periodic maintenance.  
         SUMMARY  
         [0011]    According to one embodiment of the present invention, there is provided a wastewater treatment system including at least one recirculation tank for containment of wastewater to be treated, and at least one low pressure helical spray nozzle. Optionally, the wastewater treatment system may include at least one pressurized media canisters in fluid communication with the recirculation tank and containing the treatment media.  
           [0012]    In another embodiment, a wastewater treatment system includes at least one recirculation tank, at least one wastewater treatment region, and at least one venturi. The treatment region may contain a treatment medium in fluid communication with the recirculation tank for treating the wastewater. The venturi inputs at least 2000 cubic feet of air per pound of biochemical oxygen demand into the wastewater to be treated. Optionally, the system may include at least one low pressure nozzle.  
           [0013]    In yet another embodiment, the wastewater treatment system comprises a recirculation tank for containment of the wastewater, at least one treatment region, and a recirculation system for circulating the wastewater from the recirculation tank to the treatment region. The recirculation system comprises piping means for fluidly connecting the recirculation tank to the treatment region, at least one pump, at least one venturi for inputting air into the wastewater, and at least one low pressure helical nozzle for dispersing the wastewater within the treatment region.  
           [0014]    In any one of the above embodiments, the treatment medium may comprise a fixed bed of hydrophobic particles sized to create interstices therebetween and surface area sufficient for microbes to grow and for dead microbes and treated waste water to pass therethrough. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0015]    These and other features and advantages of the present invention will be better understood by reading the following detailed description, taken together with the drawings wherein:  
         [0016]    [0016]FIG. 1 is a cross sectional view of an embodiment of the present invention;  
         [0017]    [0017]FIG. 2 is a schematic flow diagram of an embodiment of the present invention;  
         [0018]    [0018]FIG. 3 is a cross sectional view of one embodiment of the pressurized canister of the present invention;  
         [0019]    [0019]FIG. 4 is an expanded view the media according to one embodiment of the present invention; and  
         [0020]    [0020]FIG. 5 is a side plain view of the low-pressure spiral nozzle according to one embodiment of the present invention.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0021]    One embodiment of the wastewater treatment system  10 , FIG. 1, according to the present invention, is generally housed in a concrete or plastic recirculation tank  11 , though other materials such as metal are also envisioned. At least one cover  12  allows access to the system  10 . The size of the system  10 , including at least one pressurized media container  14 , is determined by the amount of wastewater to be treated and is well within the knowledge of one of ordinary skill in the art.  
         [0022]    In a preferred embodiment, a twenty-four inch diameter pressurized media container  14  can treat about 150 gallons per day. The recirculation tank  11  and associated number of pressurized media containers  14  and recirculation pump  16  are proportioned larger or smaller to treat various quantities of water. For example, recirculation spray pump  16 , sized to achieve a maximum of 2 gpm/sqft of media area is located approximately ⅓ down between the water level  18  and the  20  floor of tank  11 . This pump  16  is preferably a submerged sump type pump generally of the kind used to pump diluted effluent.  
         [0023]    A decant zone  22  preferably has a projected top surface area sized generally at a minimum of about one square foot per 500 gallons of wastewater treated per day. The projected top surface area is sized to allow for sufficient time of any residual solids to settle. In a preferred embodiment, the system  10  has at least the following inputs/outputs: input wastewater  24 , input air  26 , treated water discharge  30 , and sludge reject  32 .  
         [0024]    Effluent flows into tank  11  via gravity or a pump from a septic tank (not shown) or other containment vessel that substantially filters out the larger solids. Pump  16  then delivers a large quantity of water efficiently, but at low pressures to the pressurized media container  14 . A simple cycle timer relay (not shown) with individually adjusted on and off cycles operates pump  16 . The pump  16  would see at least 50% duty cycle and the shortest on-time limited to about ten minutes. More on-time as opposed to off-time will enable more water to be treated or less water treated to a higher degree.  
         [0025]    Three pressurized media containers  14  are shown, but more or less can be utilized depending upon the amount of input wastewater  24  to be treated. Also, the pressurized media containers  14  are shown within the tank  11 , but may also be contained outside of the tank  11 . The pressurized media containers  14  are preferably pressurized with air  26  introduced by the venturies  28  brought in through tank openings  27 . Air  26  is distributed from the venturies  28  through a pipe header system, not shown. In an alternative embodiment, the pressurized media containers  14  can be pressurized using a blower (not shown) or any other means of increasing air pressure. The pressurized media containers  14  require about 2000 cubic feet of air per pound of BOD treated from the venturies  28  or blower.  
         [0026]    Excess air  44  not absorbed by the treatment process exits the canister  14  through media support screen  46  and exits the tank  11  preferably through the input  24  void space  48  enabling excess air  44  to pass through the septic tank (not shown) and up through the house&#39;s vent stack or stink pipe (not shown). Recirculated water  50  trickles down through the media  52  held within the pressurized media containers  14  and out screens  46  to the recirculated water volume  54 , which is constantly being drawn back to pump  16 .  
         [0027]    In a preferred embodiment, the pressurized media containers  14  are supported by 2-inch diameter PVC joists  56  spaced two per canister. Joists  56  are supported by at least two equally spaced 3-inch diameter PVC pipe beams  58  ninety degrees apposed from joists  56 . Other support structures are envisioned, and the system is not limited in any way to the above described support structure.  
         [0028]    Solids  60  generally settle under pump  16 , but some may travel into the decant zone  22  and settle out there. These solids  60  are removed periodically by pump  62  preferably located near the input floor area of the tank  11 , and the solids  60  are rejected back to the septic tank (not shown). Control of pump  62  is preferably by a simple cycle timer relay (not shown) with individually adjusted on and off cycles set to limit the flow of this pump  62  to a maximum of one tenth of the input flow daily with pump on-time dependent on the size of the pump and its installed head losses. Other systems for controlling the pump are envisioned including such as height control devices, weight control devices, etc.  
         [0029]    A pipe  64  connected to sump pump  62  traverses along the base of tank  11  and through tank partition  66  that creates a decant zone  22 . In another embodiment, the decant zone  22  is separate from the tank  11 . Pipe  64  preferably has holes  66  drilled about every foot along its length. This pipe  64  may also pass through the water-proof wall partition  66  into the decant zone  22  through a water-proof bulkhead ring  68  and preferably has a flapper check valve  70  to prevent water from short circuiting through holes  66  into the bottom of the decant zone  22 . Treated water preferably flows through a gravity inverted siphon  72  from the recirculation water volume  54  to the decant zone  22 . This water  50  can be discharged through opening  74  by gravity or under pressure by pump  76 .  
         [0030]    [0030]FIG. 2 is an isometric plumbing arrangement of one embodiment of the present invention although a specific embodiment is described, the exact arrangement and specific elements utilized are purely for illustrative purposes only. A multitude of modifications are envisioned, and are well within the ordinary skill of the plumbing arts. In order for multiple media canisters  14  to operate properly from a single pump  16  and three venturies  28 , it is preferable to introduce a certain amount of randomness, chaos, or turbulences into the flow header design by using tee&#39;s at the ends instead of smooth elbows in the heeders. This minimizes pressure differences feeding the venturies resulting in nearly identical performance between venturies.  
         [0031]    Pump  16  pressurizes riser  34  through tee  80  located mid way to the first two venturies  28  on venturi feed header  36 . As noted above, uniform water distribution is accomplished for each venturi  28  by chaos caused by tees  82  and  82 ′ on each end, and with extension pipes  84  and  84 ′ respectively inducing additional chaos. Caps  86  and  86 ′ seal each end of the venturies&#39; feed header  36 . Branch headers  38  that follow the venturies  28  feed mid way to the final distribution headers  40  through elbows  88  and tees  90 . The extension pipes  38  create more chaos between induced air and the water and enhance venturi  28  operation by pulling in more air per unit volume of water than otherwise would occur before making a right angle turn to feed the air and water mix to final distribution headers  40 . This is also aided by introducing the flow into the headers  40  near the center through tees  90 .  
         [0032]    Headers  40  are can be comprised of vertical distribution tee&#39;s  92  center, and tee&#39;s  94  and  96  and caps  98  and  100  respectively at the ends of distribution pipes  40 . It is preferred, though not required, that tee&#39;s  94  and  96  are not ninety-degree elbows. The use of tee&#39;s  94  and  96  at the ends of header pipes  40  add additional chaos to evenly distribute the flow to the respective media canisters  14 . It should be stressed that the above description is only one embodiment of the present invention. The exact layout of the system  1  will depend on a multitude of variables such as, but not limited to, the amount of BOD to be treated, the location parameters, etc. These variable are common to all wastewater treatment systems, and modifications to the above described embodiment are well within the ordinary skill of one in the art.  
         [0033]    [0033]FIG. 3 is a cross sectional view of one embodiment of the pressurized media canister  14  containing media  52 . In a preferred embodiment, the pressurized media canister  14  contains at least one low-pressure nozzle  42  and contains media  52  preferably having a depth of about twenty-four inches and an overall height of about thirty-six inches. Wastewater is preferably fed down into the pressurized media container  14  through an airtight threaded bulkhead fitting  102 .  
         [0034]    In a preferred embodiment, an airtight cap  104  is preferably about one half inch thick polyethylene. The airtight cap  104  retains the excess air  26  forcing it down through the media  52 , along with the wastewater. The pressurized media canister  14  is preferably maintained airtight with slot  106  filled with silicon. Caps  104  are retained to the pressurized media canister  14  preferably using #8 stainless self-tapping screws  108 . Testing has shown that only enough screws  108  are required to retain a pressure of about one inch of water pressure, or about twenty pounds of force up against a twenty-four inch inside diameter for caps  104 .  
         [0035]    The high surface area media  52 , about one hundred eighty square feet per cubic foot, retains the microbial biomass that lives within the media. Media  52  is preferably hydrophobic so it won&#39;t plug, yet it should be light and inexpensive so that canisters  14  supports  58  do not have to be excessive. The preferred media  52  is “A” type polystyrene beads, but other media  52  such as, but not limited to, polyethylene, polypropylene, ABS, or any molded plastic can also be used.  
         [0036]    To live and reproduce more rapidly, microbes need oxygen. Pressurizing the media containers  14  increases the time for the air  26  to be absorbed by the wastewater as it slowly passes through the media  52 . It takes far longer, for example, for air to pass down through the media than it does water, over a hundred times longer.  
         [0037]    Thus, pressurization of air  26  over the media  52  greatly improves the efficiency of air utilization. Screens  46  are preferably attached to the bottom of the pressurized containers  14  are preferably an extruded polyethylene screen with openings smaller than the “A” sized bead media  52  an allow dead microbes to trickle out with the water. Screen  46  is preferably wrapped up around the bottom outside of canisters  14 , and retained with a one inch wide by one eighth inch thick polyethylene band that is secured with #8 stainless self-tapping screws  110 .  
         [0038]    In one embodiment, the media  52 , FIG. 4, is preferably a set of small-sized spheres or beads  120  that may be hollow, but that are preferably solid. The beads  120  are much smaller than buoyant balls yet large enough to create interstices  122  through which the wastewater, as well as air  26  for the aerobic process, can pass. The interstices  122  create significant surface area in a relatively small unit, surface area upon which the microbes can reside for interaction with the passing wastewater. Further, the interstices  122  provided by the bead  120  arrangement of the present invention are big enough to allow dead microbes to pass therethrough upon completion of their task. The net result is a continual sloughing off of dead microbes that have ingested more than their weight in contaminants. The quantity and size of the interstices  122  created greatly increases the effective space for biological action to occur without the need for a very large treatment tank or unit. The beads  120  are preferably substantially hydrophobic so that they are not detrimentally altered—whether by swelling or deterioration—by substantially continuous contact with wastewater. Of course, it is necessary that there is some surface roughness or other means for retaining microbes on suitable dwelling sites on the beads  120  surfaces. It has been determined that non-metallic materials, such as plastic beads, and polystyrene beads in particular, are suitable for use in the present invention. The media  52  may also be contained in mesh bags  118  as described in U.S. Pat. No. 6,187,183 assigned to the assignees of the present application, and incorporated fully herein be reference.  
         [0039]    Through the use of the bead medium  120 , the pressurized media containers  14  of the present invention used to hold the porous medium, can be relatively small in relation to the quantity of wastewater to be treated. Moreover, it can be larger in its horizontal dimension than its vertical, such that it can be unobtrusively low to the ground. For the most part, prior devices were made of relatively great height so that waste water had to move a considerable downward distance to reach the output point. That was the way in which dwell time could be increased. Of course, it also increased the space and cost associated with such systems. The creation of pressurized media container  14  eliminates the need for large, deep treatment units, especially when combined with the above-described media  52 .  
         [0040]    In another embodiment, the pressurized media container  14  may also have one or more low-pressure spray nozzles  42 . It is important to achieve even water distribution over the area of the media  52  in order to ensure maximum efficiency. The low-pressure spray nozzles  42  should preferably work with only about fifty inches of water pressure or about two psi, and must accommodate both high water flow and air simultaneously. For a typical twenty-four inch diameter pressurized media container  14 , this is accomplished by opening up the low-pressure spray nozzle  42  to accommodate a one-inch pipe diameter for both wastewater and air  26  feed to each pressurized media container  14 . Larger pressurized media containers  14  would require proportionally larger low-pressure spray nozzles  42 .  
         [0041]    In one embodiment, the low-pressure spray nozzles  42 , FIG. 5, are helical and have a one-inch male pipe thread  112  and hex nut  114 . The helical low-pressure spray nozzles  42  preferably have at least two rotations of the open helix with three-eighths inch wide openings  116  and  116 ′ for wastewater to pass, and a tapered body  118  of about one eighth inch thickness minimum. The overall body length is about three inches. In operation, the helix fills with the air and wastewater mixture and sprays most of the air wastewater mixture from the top or first helical opening  116 , which reaches out to the furthest diameter. It sprays proportionally less water from the lower helical opening  116 ′ spraying to a lesser diameter than the first helix. The helical low-pressure spray nozzles can be used with the wastewater treatment system described above, or with any other type such as, but not limited to, systems utilizing activated carbon, ultraviolet disinfection, or any other biological filtration such as the wastewater treatment system described in U.S. Pat. No. 6,187,183, issued to the assignee of the present invention, and fully incorporate herein by reference.  
         [0042]    Modifications and substitutions by one of ordinary skill in the art are considered to be within the scope of the present invention, which is not to be limited except by the following claims.