Abstract:
A system and method for processing wastewater into usable water is provided. The method comprises: receiving a supply of wastewater; passing the wastewater into a refractory vessel having a heat generator associated therewith; increasing the temperature of the wastewater to a predetermined temperature using the heat generator for a predetermined amount of time to produce heated exhaust gases containing at least one product gas and water vapor; separating the at least one product gas and water vapor; and condensing the water vapor to produce usable water. The system comprises a refractory vessel defining a heat processing zone, a heat generator that is used to increase the temperature of the wastewater to produce a heated exhaust gas containing at least one product gas and water vapor, a scrubber to separate the product gases and the water vapor, and a condenser to condense the water vapor into usable water.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. Provisional Patent Application No. 60/965,391, filed on Aug. 20, 2007, which is incorporated herein by reference in its entirety. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present patent application is directed to a system and method for processing wastewater. More particularly, the present patent application relates to the processing of wastewater using a heat generator, such as a plasma generator, to produce a supply of usable water. 
       BACKGROUND OF THE INVENTION 
       [0003]    Wastewater has a high pure water content, but requires substantial processing before it can be usable water because it typically contains human waste and other harmful contaminants, such as, for example, hazardous heavy metals, organic poisons, microbiological infective organisms, pharmaceuticals, medications and hormones. Currently, there are a variety of systems used in the treatment of wastewater. Some large municipal applications provide an integrated process of filters, oxygenators, settling tanks, clarifying tanks and digesters. In addition, some processes use ultraviolet (UV) light for destroying estrogens and hair products, chemical additives, carbon filtration to control odor, micropore filters with multiple barriers to decrease the dangers of infection, and ozone for color removal to achieve pureness and to add clarity to the water. These treatment processes generally comprise a biological format, using microorganisms contained in an active biomass for the removal of biological oxygen demand (bod, organic carbon compounds) and chemical oxygen demand (cod), phosphorous and or nitrogen from wastewater. 
         [0004]    Furthermore, current wastewater systems may use multiple levels of treatment incorporating the processes described above, including, for example, preliminary treatment, primary treatment, and secondary treatment processes. While the existing treatment systems may produce usable water, it can be a long and rather complicated process for purifying a supply of wastewater. One of the major issues that has to be dealt with in wastewater treatment is the public discomfort of turning wastewater into drinking water. 
         [0005]    The use of heat to achieve gasification of solid waste materials has been used for many years. Many sources of heat have been used, including fossil fuels, optic treatment of solar energy, electric energy and plasma generators. The use of a plasma generator for the disposal of municipal solid waste (refuse, garbage and, although there is no data available, it has been suggested that in Japan, solid waste residual) has been accomplished. Currently there are two successful plants operating in Japan, and construction of new plants in Canada and St. Lucie, Fla. are underway. Several other plants are under discussion in the United States. Generally speaking, municipal solid waste systems are comprised of a plasma generator as the gasification tool and a myriad of processes to achieve the disposal, including: the feed of solid waste, maintenance of waste temperature (e.g., Joule Bath), the removal of gases from the volatile materials, as well as the reduction of non-combustibles (e.g., glass and metal) to inert slag which is drained and disposed of. The resultant hot gases may then drive appropriate energy conversion means such as a turbine generator and may be scrubbed or otherwise purified before being allocated for further use or released to the atmosphere. Some patents refer to the introduction of liquid waste in the system. This generally refers to specific waste associated with carbon fuels, or other hazardous liquid manufactured products. 
         [0006]    The disposal of waste materials, especially toxic wastes, with plasma generators is known. In such a process, a plasma generator transfers electrical energy through a stream of ionized gases so that the gases become an electrical conductor. A plasma generator disposal reactor raises the temperature of waste materials, including toxic waste materials, to such high levels that such materials break down chemically and decompose. This breakdown can be enhanced by maintaining an atmosphere of additive products in the processing chamber. As a result, the residues are usually harmless gases and solids which are suitably removed from the processing chamber. While the use of plasma generators for disposing of municipal solid waste is known, the use of plasma generators to process wastewater into usable water in the manner disclosed herein is not disclosed in the existing art. 
         [0007]    The hallmark of the wastewater treatment using biological/mechanical processes is that they generally are very complex and require a lot of time and energy to isolate usable water from the contents of the wastewater. 
         [0008]    Therefore, what is needed is a simplified and efficient system and method for producing usable water from wastewater that simplify the complex systems currently being used to process wastewater. The present invention meets this need as well as other needs. 
       SUMMARY OF THE INVENTION 
       [0009]    In order to address the need for efficiently providing usable water and to address the drawbacks of the existing methods for the treatment of wastewater, a method and system for processing wastewater from an available source is provided. 
         [0010]    According to a first aspect of the present invention, a system and method for generating a supply of usable water is disclosed. In particular, the method comprises the steps of: a) receiving a supply of wastewater; b) passing the wastewater into a heat processing zone defined in a refractory vessel, wherein the refractory vessel has a heat generator, such as a plasma generator, associated therewith; c) increasing the temperature of the wastewater to a predetermined temperature using the heat generator for a predetermined amount of time to produce heated exhaust gases, wherein the heated exhaust gases includes at least one product gas and water vapor; d) separating the at least one product gas and water vapor; and e) condensing the water vapor to produce usable water. It will be understood that the method may include treating all or a portion of the wastewater in at least one of a pretreatment phase and a primary treatment phase to produce an effluent, wherein the effluent is processed into usable water using steps b) through e) recited above. 
         [0011]    The method may also include mixing the wastewater upon entering the refractory vessel and keeping the wastewater in motion as the heat generator increases the temperature of the wastewater to the predetermined temperature. Further, a secondary treatment phase may include aeration and clarification of wastewater fed from the primary treatment phase, or, in the alternative, passing the wastewater from the primary treatment phase through a membrane bioreactor. The municipal solid waste produced in the membrane bioreactor may be processed in a solid waste plasma generator and/or an independent plasma generator refractory vessel. 
         [0012]    Other aspects of the method recited above are also provided. For example, the method may include the steps of providing a gas turbine downstream of the refractory vessel and passing the heated exhaust gases through the gas turbine to produce electricity. The method may also comprise the steps of providing a steam turbine, creating heat with the separated at least one product gas, using the heat to generate steam from the usable water, and passing the steam through the steam turbine to produce electricity. The steam exhausted from the steam turbine may be used to preheat the wastewater passing into the refractory vessel. 
         [0013]    A further aspect of the method recited above may include the steps of providing a heat exchanger downstream of the refractory vessel, wherein the heat exchanger includes a first side and a second side, providing a steam turbine, passing the heated exhaust gas through the first side of the heat exchanger, passing the usable water through the second side of the heat exchanger, wherein sufficient heat is transferred from the heated exhaust gas to the useable water in the heat exchanger to convert the usable water to steam, and passing the steam through the steam turbine to produce electricity. The steam exhausted from the steam turbine may be used to preheat the wastewater passing into the refractory vessel. 
         [0014]    The system for processing wastewater into usable water disclosed herein includes a refractory vessel, a heat generator, a scrubber, and a condenser. The refractory vessel includes a heat processing zone therein for receiving a supply of wastewater. The heat generator, such as a plasma generator, is associated with the refractory vessel to increase the temperature of the wastewater within the heat processing zone to a predetermined temperature for a predetermined amount of time to produce a heated exhaust gas, wherein the heated exhaust gas includes at least one product gas and water vapor. The scrubber is used to separate the at least one product gas and the water vapor, and the condenser operates to condense the water vapor into usable water. The system may further include at least one of a pretreatment phase and a primary treatment phase, wherein all or a portion of the wastewater is fed through at least one of the phases to produce an effluent, wherein the effluent is fed to the refractory vessel to produce usable water. 
         [0015]    The system may also include at least one mixer for mixing the effluent upon entering the refractory vessel, and including at least one mixing apparatus, for example, at least one paddle, for keeping the effluent in motion as the heat generator increases the temperature of the effluent to the predetermined temperature. A secondary treatment phase may include an aerator and a clarification tank, or, in the alternative, a membrane bioreactor to produce a secondary effluent. In the instance that the secondary treatment phase utilizes a membrane bioreactor, the municipal solid waste that is produced by the membrane bioreactor may be fed to a solid waste plasma generator and/or an independent plasma generator refractory vessel. 
         [0016]    In another aspect of the system set forth above, the system may include a gas turbine disposed downstream of the refractory vessel, wherein the heated exhaust gas is passed through the gas turbine to produce electricity. 
         [0017]    In yet another aspect of the system set forth above, the system may include a steam turbine and a gas flame heater, wherein the separated at least one product gas is burned in the gas flame heater to produce heat, the usable water is fed into the gas flame heater to generate steam, and wherein the steam is fed through the steam turbine to produce electricity. 
         [0018]    In a further aspect, the system may include a heat exchanger disposed downstream of the refractory vessel, and a steam turbine. The heat exchanger includes a first side and a second side. The heated exhaust gas is passed through the first side of the heat exchanger and the usable water is passed through the second side of the heat exchanger, wherein sufficient heat is transferred from the heated exhaust gas to the useable water to convert the usable water to steam. The steam is then passed through the steam turbine to produce electricity. 
         [0019]    In yet another aspect of the present invention, there may be great advantage to the co-utilization of a municipal solid waste plasma furnace or independent plasma generator refractory vessel for the gasification of waste (primary sludge) from a primary treatment phase or secondary treatment phase. In addition, the fats, oil and grease (FOG) resulting from the primary treatment can be used as fuel for further reclamation of energy. 
         [0020]    As mentioned above, wastewater can contain human waste and other harmful contaminants. Current techniques use a multiplicity of systems and methods to get usable water from this array of contaminants. The method and system presented herein provides the ultimate desired result of usable water, free of these contaminants, in an efficient manner using only plasma processing, a scrubber and a condenser. In addition, it provides the possibility of recovering some of the energy required to process the wastewater. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0021]    The above-mentioned and other features and advantages of this invention, and the manner of attaining them, will become apparent and be better understood by reference to the following description of the aspects of the invention in conjunction with the accompanying drawings, wherein: 
           [0022]      FIG. 1  is a schematic drawing of a wastewater treatment system including a refractory vessel in accordance with a first aspect of the present invention; 
           [0023]      FIG. 2  is a schematic drawing of the refractory vessel shown in  FIG. 1 ; 
           [0024]      FIG. 3  is a schematic drawing of other aspects of the present invention; and 
           [0025]      FIG. 4  is a schematic drawing of another version of the wastewater treatment system shown in  FIG. 1 . 
       
    
    
       [0026]    Additional aspects, advantages, and novel features in the invention will be set forth in part in the description that follows, and in part will become apparent to those in the practice area of the invention. 
       DETAILED DESCRIPTION OF THE INVENTION 
       [0027]    Referring to the drawings in detail, and particularly  FIG. 1 , a wastewater treatment system in accordance with a first aspect of the present invention is shown generally as reference numeral  10 . In general, wastewater treatment system  10  in accordance with the present invention includes a refractory vessel  12  containing a heat generator  14 , such as, for example, a plasma generator, that operates to increase the temperature of a supply of wastewater, or an effluent derived from the supply of wastewater, to a predetermined temperature for a predetermined amount of time to provide water that is usable for human consumption, agricultural and industrial use. The details of wastewater treatment system  10  are set forth below. 
         [0028]    In the water treatment system  10  set forth in  FIG. 1 , the effluents  16   a,    18   a  that may be fed to refractory vessel  12  are derived from wastewater that is processed in at least one of a pretreatment phase  16  and a primary treatment phase  18 . In operation, the supply of wastewater  24  that is fed to the wastewater treatment system  10  may first enter pretreatment phase  16 , wherein solid inorganic materials are removed from the wastewater using bar screens and sedimentation tanks  26  to capture sand, silt and other gritty solids. The pretreated effluent  16 a produced from pretreatment phase  16  may include organic matter, including human waste, fats, oils, etc. with a dehydration process may be fed to refractory vessel  12 . 
         [0029]    In the primary treatment phase  18 , approximately 85 percent of organic and inorganic suspended solids may be removed from pretreated effluent  16   a  to meet the requirement for obtaining National Pollutant Discharge Elimination System (NPDES) discharge permits. The suspended solids are precipitated out of pretreated effluent  16   a  using coagulants and about 1-2 hours of sedimentation. The solids  26  (i.e., primary sludge) settle to the bottom of the tanks and the fats, oil and grease (FOG) float to the surface and are skimmed off the top of the wastewater. The primary sludge  26  may then be pumped to a solid waste residual handling unit  27 , including one or more anaerobic digesters, for further processing. The dehydrated solid waste residual can then be treated with either a municipal solid waste plasma generator or an independent plasma generator refractory vessel. The remaining water, which is referred to as primary effluent  18 a with a dehydration process, may be fed to refractory vessel  12  and/or to secondary treatment phase  20  for further treatment. 
         [0030]    The secondary treatment phase  18  typically involves the use of living microorganisms, referred to as activated sludge, to remove remaining nutrients or non-settling suspended and soluble organics from primary effluent  18   a.  Initially, activated sludge may be mixed with primary effluent  18   a,  and then the mixture is fed into an aeration tank  28 . After sufficient retention time in aeration tank  28 , the mixture of primary effluent  18   a  and activated sludge is introduced into a clarifying or settling tank  30  wherein the biomass separates as settled activated sludge  32  from the primary effluent  18   a  to produce secondary effluent  20   a.  This process may take hours and results in the removal of about 90 to 95 percent of the solids in the primary effluent  18   a.  All or a part of activated sludge  32   a  may then be mixed with the primary effluent  18   a  prior to being introduced into aeration tank  28  (i.e., return activated sludge) or be fed to solid handling unit  27  for further processing, which is represented by reference numeral  32   b.  After the completion of secondary treatment phase  20 , secondary effluent  20   a  may be fed to a disbursement system  34  wherein secondary effluent  20   a  is pumped out to sea or stored in large underground storage areas, and/or fed to a reclamation system  36  with further treatment to be used for municipal purposes, such as watering golf courses, parks and vehicle washing, or industrial purposes. 
         [0031]    The primary sludge  26  and activated sludge  32   b  (collectively referred to herein as solid waste residuals) referred to above may be fed to solids handling unit  27 , wherein the solid waste residuals are handled in digesters to harvest methane gas and in centrifuges to yield biosolids that can be used for agricultural purposes. Furthermore, the solid waste residuals may also be redistributed through a return feed  38  and mixed with pretreated effluent  16   a  prior to entering the primary treatment phase  18  or after a digestion/dehydration process solid waste residual ( 27 ) may be treated in a municipal solid waste plasma generator or an independent plasma generator refractory vessel. 
         [0032]    In accordance with one aspect of the present invention, the supply of raw wastewater (sewage)  24  and/or one or more of the effluents  16   a,    18   a  may be controllably fed to refractory vessel  12  to produce usable water. The conduits that direct the incoming wastewater and/or one or more of the effluents  16   a,    18   a  into refractory vessel may have a regulating device  40  associated therewith to controllably regulate the flow of wastewater and/or effluent into a plasma processing zone  26  ( FIG. 2 ) contained within refractory vessel  12 . Instead of including separate regulating devices for each effluent feed, it will be understood that there may be a single effluent feed into the refractory vessel  12  that is downstream from feeds  16   a,    18   a  to allow for a single regulating device that controls the effluent entering refractory vessel  12 . It will also be understood that if effluent feed to the refractory vessel  12  is derived from raw wastewater  24 , some initial screening, filtration steps, and dehydration steps may be required. 
         [0033]    One example of refractory-lined vessel  12  that may be used in wastewater system  10  described herein is shown in  FIG. 2 . Refractory vessel  12  includes an intake port  42  for feeding wastewater  24  and/or effluent  16   a,    18   a  (collectively referred to herein as refractory intake effluent  43 ) to a high temperature plasma processing zone  44  (i.e., heat processing zone) that is defined within a chamber  45  of refractory vessel  12 . Upon flowing through intake port  42 , refractory intake effluent  43  may flow into one or more mixers  46 . The mixers  46  are used to achieve a homogeneous fluid, to add steam heat  47  or other additives, as needed and assist in maintaining a constant flow of effluent through intake port  42  to plasma processing zone  44 . Further, the refractory intake effluent  43  is modulated by at least one mixing apparatus  48  to keep refractory intake effluent  43  in motion for an even exposure to the plasma processing zone  44 , thereby forming a layer of refractory intake effluent  43  with a relatively large surface area that can be quickly heated to the desired high temperature. One aspect of this wastewater system  10  contemplates a flow regulating device (not shown) to assure that all refractory intake effluent  43  reaches a sufficiently high predetermined temperature, for a sufficient predetermined amount of time, to fully process refractory intake effluent  43  to fundamental atoms and molecules in a gas form. 
         [0034]    Further, the refractory vessel  12  includes at least one heat generator  50 , such as a cost effective AC plasma generator, fossil fuels, optic treatment of solar energy and electric energy, that operates to raise and maintain the temperature within plasma processing zone  44  at very high temperatures in thousands of degrees centigrade. The energy source to drive the plasma generators is derived from an electrical source. It will also be understood that refractory vessel  12  may include inlet ports (not shown) for feeding air and/or additive agents to the high temperature plasma processing zone  44 . Upon heating refractory intake effluent  43  within plasma processing zone  44  within a predetermined temperature range for a predetermined amount of time, heated exhaust gases  54  are produced that fill chamber  45  and escape through a narrowing outlet  56  of refractory vessel  12 . The heated exhaust gases  54  may include a mixture of one or more product gases and water vapor. It should be understood that the contents of the heated exhaust gases will vary according to the effluent and additives introduced into refractory vessel  12 . 
         [0035]    As best seen in  FIG. 1 , after the heated exhaust gases  54  are emitted from outlet  56  of refractor vessel  12 , they are introduced to a scrubber  58  that operates to separate heated exhaust gases  54  into water vapor  60  and one or more product gases  62 . The water vapor  60  is then fed to a condenser  64  that operates to condense the water vapor to usable water  66  for at least one of human consumption, agricultural use and industrial use. In addition, any sludge that is contained within wastewater  24  and/or one or more of the effluents  16   a,    18   a  that is fed to refractory vessel  12  will be treated by refractory vessel  12  and thereby eliminate a substantial portion of the sludge that is collected and processed by solids handling unit  27 . 
         [0036]    It should be understood that the plasma generator may have different requirements for processing the intake effluent into usable water depending on the type of effluent is fed to the plasma generator. For example, primary treatment phase operates to isolate fats, oils and grease (FOG) from the water and precipitated or settled material. The precipitated or settled material (i.e., primary sludge) with a dehydration process may also be treated by the plasma generator, eliminating the arduous tasks of sludge treatment using, grinders, compactors, driers, and digesters. Further, the primary effluent may go on to the secondary treatment phase where, rather than have activated microorganisms digest the residual organic material, the primary effluent feed with a dehydration process may go to the plasma generator that gasifies the primary effluent, the resultant heated exhaust gas is scrubbed removing the specialized product gases and releasing the water to be condensed. 
         [0037]    A second aspect of the present invention relates to a wastewater processing system  10 ′ shown in  FIG. 3 , which operates to generate electricity using the heated exhaust gases  54  emitted from refractory vessel  12 , the usable water condensed in the condenser  64 , and the specialized product gases  62  separated by scrubber  58 . The components described with respect to wastewater processing system  10  also is applicable to the system  10 ′ shown in  FIG. 3 . However, the wastewater system  10 ′ shown and described in  FIG. 3  includes additional components that were not included in system  10 . In particular, the heated exhaust gases  54  that are emitted from outlet  56  of refractory vessel  12  may pass through a first side of a heat exchanger  68  and then through a gas turbine  70  to generate electricity. The exhaust gas  54  coming out of gas turbine  70  is passed through scrubber  58 , wherein the resultant products are separated into specialized product gases  62  and water vapor  60 . The water vapor  60  coming out of scrubber  58  is sent to condenser  64  for the distillation of usable water  66 . Some of specialized products  62  may be able to be modified to have a flammable quality. The flammable specialized products  62   a  can be used in a gas flame heater  72  to bring water  66   a  that was distilled from condenser  64  to a superheated state, which expands through a steam turbine  74  to produce electric energy. As best seen in  FIG. 3 , the exhaust  76  of the steam turbine  74  can be mixed with refractory intake effluent  43  entering the refractory vessel  12 , which could make up all or part of the supply of steam  47  shown in  FIG. 2 . In the alternative, the specialized products  62   b  can be stored for further treatment and sales. 
         [0038]    In a third aspect of the wastewater processing system  10 ′, as best seen in  FIG. 3 , heated exhaust gases  54  passing through the first side of heat exchanger  68  may be used in a steam cycle to produce electrical energy using steam turbine  74 . In particular, the heated exhaust gases  54  passing through the first side of heat exchanger  68  operate to transfer heat to water  66   b  passing through a second side of heat exchanger  68  that is pumped from the usable water  66  distilled from condenser  64 . The water  66   b  gains a sufficient amount of heat from exhaust gas  54  to convert water  66   b  to steam to drive steam turbine  74  and thereby generate electricity. 
         [0039]    A fourth embodiment (not shown) considers the possibility of other architectural and engineering possibilities for the design of refractory vessel. The refractory vessel may appear to be but not limited to a tube-like structure, curved at one end and a narrowed outlet at the other. A wastewater feed is located at the curved end of the device. This feed has a regulating device that controls the flow of wastewater into the plasma processing zone. The wastewater cascades down over the surface of a series of steps allowing its exposure to the plasma processing zone. The plasma processing zone has very high temperatures that can be thousands of degrees centigrade produced by the plasma generator. The wastewater is processed in the plasma processing zone. The resultant heated gas escapes through the narrowing in the far end of the refractory vessel. 
         [0040]    As best seen in  FIG. 4 , a fifth aspect of the wastewater treatment system is provided and is generally indicated with reference numeral  10 ″. The wastewater treatment system  10 ″ is similar in many respects to the system  10  shown in  FIG. 1 , except the aeration tank  28  and clarifying tank  30  are replaced with a membrane bioreactor (MBR)  78  that combines primary effluent with a membrane liquid-solid separation process. The membrane component uses low pressure microfiltration or ultrafiltration membranes may eliminate the need for clarification and tertiary filtration. However, secondary effluent  20   a  may still contain organisms, dissolved particles causing decreased clarity, pharmaceuticals, etc. and, if that is the case, these residuals may be handled using chlorine, ultraviolet (UV) light, ozone, carbon filters and other known treatment methods. Further, the mixed liquor or sludge  80  left over from the membrane bioreactor process may be disposed of with a dehydration process and a subsequent refractory vessel  82  either a municipal solid waste (MSW) plasma generator or an independent plasma generator refractory vessel thereby eliminating the need for the solids handling  27  (solid waste residual) shown in  FIG. 1 . 
         [0041]    While the invention has been described by reference to various specific aspects, it should be understood that numerous changes may be made within the spirit and scope of the inventive concepts described. Accordingly, it is intended that the invention not be limited to the described aspects, but will have full scope defined by the language of the following claims.