Abstract:
A valveless siphon decanter for processing fluid within a tank having a siphon tube external to the tank, the siphon tube having an output, a boom extending substantially transversely from the siphon tube, the boom providing a path for the communication of fluid from within the tank into the siphon tube, a vacuum head in association with the boom, the vacuum head having at least one orifice disposable within the tank for receiving the fluid, a vacuum source for creating a vacuum within the siphon tube and the boom to draw the fluid in through the at least one orifice of the vacuum head into the boom and into the siphon tube thereafter, a vacuum break for breaking the vacuum within the boom and the siphon tube; and wherein the siphon tube and the boom are disposed outside of the tank.

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
     This application is a continuation of U.S. patent application Ser. No. 12/754,315, filed Apr. 5, 2010, now U.S. Pat. No. 8,871,086 entitled “VALVELESS SIPHON DECANTER AND METHODS OF USE,” which claims the priority benefit of U.S. Provisional Application Ser. No. 61/234,337 filed Aug. 17, 2009, entitled “VALVELESS SIPHON DECANTER AND METHODS OF USE,” all of which are hereby incorporated herein by reference their entireties, including all references cited therein. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates in general to a wastewater decanter and, more particularly, but not by way of limitation, to a valveless siphon decanter which can substantially exclude solids and can be retrofit into existing sequencing batch reactor systems to replace current wastewater decanters. 
     2. Background Art 
     The treatment of wastewater is well known in the art. Commonly, sequencing batch reactors or SBRs are used to process wastewater and can include two or more processing tanks. SBRs treat wastewater such as sewage or output from anaerobic digesters or mechanical biological treatment facilities in batches. The tanks have a “flow through” system, with raw wastewater (influent) entering through an inlet and treated fluid (effluent) flowing out the other. While one tank is in settle/decant mode the other may be aerating and filling. At the inlet is a section of the tank known as the bio-selector. This consists of a series of walls or baffles which direct the flow either from side to side of the tank or under and over consecutive baffles. The walls or baffles help to mix the incoming influent and any returned activated sludge, beginning the biological digestion process before the wastewater enters the main part of the first tank. 
     Typically, there are five stages in the treatment of wastewater including filling the tank, reacting the wastewater with biological agents, allowing the solids to settle from the wastewater, drawing the treated fluid from the first tank and idling the removed fluid in a second tank. Aeration of the mixed wastewater is performed during the first two stages by the use of fixed or floating mechanical pumps or by blowing it into finely perforated membranes fixed to the floor of the tank. During this period the inlet valve to the tank is open and a returned activated sludge pump takes mixed liquid and solids (mixed liquor) from the outlet end of the tank to the inlet to “seed” the incoming sewage with live bacteria. 
     After the step of settling, the wastewater is stratified such that the solids are disposed at the bottom of the tank, a mixture of solids and biological agents are disposed above the solids, and a level of cleaner fluid is disposed at the surface of the tank. Currently, the step of drawing the cleaner fluid from the first tank is facilitated by the use of something such as a floating decanter. While wastewater decanters are well known, they suffer from common drawbacks including, but not limited to, portions of the decanter being disposed underneath the fluid leading to unnecessary and costly maintenance thereof and unwanted removal of solids from the reactor which can cause fouling of the decanter and thus increased maintenance. Common decanters include a gravity inlet orifice supported above or below the fluid by a flotation device. The gravity inlet orifice is connected to a tubular boom or outlet pipe that extends from near the bottom of the tank and angles upwardly towards the cleaner fluid such that the gravity inlet orifice is disposed just below the surface of the fluid. 
     Therefore the need exists for a valveless siphon decanter for use in wastewater reactors that substantially excludes solids during operation thereof, and furthermore to a valveless siphon decanter which can be installed through or over the tank in such a way that none of the parts of the decanter are submerged under the wastewater contained within the reactor. 
     SUMMARY OF THE INVENTION 
     In one embodiment, the present invention is directed to a valveless siphon decanter for processing fluid within a tank, comprising: (a) a siphon tube external to the tank, the siphon tube having an output; (b) a boom extending substantially transversely from the siphon tube, the boom providing a path for the communication of fluid from within the tank into the siphon tube; (c) a vacuum head in association with the boom, the vacuum head having at least one orifice disposable within the tank for receiving the fluid; (d) a vacuum source for creating a vacuum within at least one of the siphon tube and the boom to draw the fluid in through the at least one orifice of the vacuum head into the boom and into the siphon tube thereafter; (e) a vacuum break for breaking the vacuum within at least one of the boom and the siphon tube; and (f) wherein the siphon tube and the boom are disposed outside of the tank. 
     In another embodiment, the siphon tube includes a flexible section of pipe located below the intersection point between the boom and the siphon tube to allow the boom and the first portion of the siphon tube to pivot about the second portion of the siphon tube. 
     In an additional embodiment, the decanter further comprises at least one stabilizer bar connected to the first portion and the second portion, above and below the flexible section of pipe to support the flexible section of pipe. 
     In yet another embodiment, the boom intersects the siphon tube to bifurcate the siphon tube into a first portion and a second portion. 
     In accordance with the present invention, the boom is pivotally connected to a sidewall of the tank. 
     In an additional embodiment, the vacuum break includes a sensor that senses the level of fluid within the siphon tube and a control system monitoring output of the sensor, wherein the control system controls the operation of the vacuum source based upon output received from the sensor. 
     In one embodiment, the vacuum break includes a pipe connected to the siphon tube proximate the first portion of the siphon tube, the pipe having a terminal end disposed within the tank, wherein when the level of fluid within the tank goes below the terminal end of the pipe, the vacuum drawing fluid into the boom and siphon tube is broken causing a cessation of fluid flow. 
     In an additional embodiment, the pipe is selectively adjustable to raise or lower the terminal end of the pipe within the tank. 
     In another embodiment, the vacuum head includes an elongated tubular member having a center, opposing ends, and plurality of orifices spaced apart from one another. 
     In yet another embodiment, the diameter of the orifices increases from the center of the elongated tubular member outwardly towards the ends of the elongated tubular member. 
     In accordance with the present invention, the decanter further comprises at least one pontoon associated with the elongated tubular member for floatably supporting the elongated tubular member on the surface of the fluid within the tank. 
     In one embodiment, the decanter further comprises a buoyancy system for adjusting the buoyancy of the at least one pontoon. 
     In accordance with the present disclosure, the buoyancy system includes: (i) a fluid source in communication with the at least one pontoon via a pump capable of bidirectional fluid flow for introducing or removing fluid into the at least one pontoon; (ii) means for determining the buoyancy of the at least one pontoon; and (iii) a control system in communication with the means for determining the buoyancy of the at least one pontoon and controlling the operation of the pump. 
     In one embodiment, the decanter further comprises two elongated pontoons and a central pontoon, one of the elongated pontoons disposed along a front surface of the elongated tubular member and the other elongated pontoon disposed along a rear surface of the elongated tubular member, the central pontoon disposed between the two elongated pontoons and below the center of the elongated tubular member. 
     In yet another embodiment, the decanter further comprises a plurality of baffles extending between the two elongated pontoons, the baffles extending through a centerline of the orifices and at each of the opposing ends of the elongated tubular member. 
     In an alternative embodiment, the baffles include mesh screens to further prevent debris from entering the orifices. 
     In accordance with the present disclosure, the decanter further comprises support legs extending downwardly from the vacuum head, the support legs contacting a bottom portion of the tank when the vacuum head has translated downwardly a predetermined distance into the tank. 
     In one embodiment, the vacuum head is connected to the boom via a flexible hose. 
     In another embodiment, the present invention is directed to a sequencing batch reactor for processing wastewater, comprising: (a) a tank for retaining and stratifying the wastewater to produce at least a substantially clear layer of water disposed below a debris layer; (b) a siphon tube external to the tank, the siphon tube having an output; (c) a boom extending substantially transversely from the siphon tube, the boom providing a path for the communication of water from within the tank into the siphon tube; (d) a vacuum head in association with the boom, the vacuum head having at least one orifice disposed within the tank for receiving the water; (e) means for positioning the at least one orifice of the vacuum head in the clear layer of water below the debris layer; (f) a vacuum source for creating a vacuum within at least one of the siphon tube and the boom to draw the clear water in through the at least one orifice of the vacuum head into the boom and into the siphon tube thereafter; (g) a vacuum break for breaking the vacuum within at least one of the boom and the siphon tube; and (h) wherein the siphon tube and the boom are disposed outside of the tank. 
     In an additional embodiment, the at least one orifice includes at least one pontoon associated with the elongated tubular member. 
     In yet another embodiment, the decanter further comprises a buoyancy system for adjusting the buoyancy of the at least one pontoon. 
     In one embodiment, the buoyancy system includes: (i) a fluid source in communication with the at least one pontoon via a pump capable of bidirectional fluid flow for introducing or removing fluid into the at least one pontoon; (ii) means for determining the buoyancy of the at least one pontoon; and (iii) a control system in communication with the means for determining the buoyancy of the at least one pontoon and controlling the operation of the pump. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Certain embodiments of the present invention are illustrated by the accompanying figures. It will be understood that the figures are not necessarily to scale and that details not necessary for an understanding of the invention or that render other details difficult to perceive may be omitted. It will be understood that the invention is not necessarily limited to the particular embodiments illustrated herein. 
       The invention will now be described with reference to the drawings wherein: 
         FIG. 1  of the drawings is a perspective view of a valveless siphon decanter for use in a wastewater reactor, constructed in accordance with the present invention; 
         FIG. 2  of the drawings is a perspective view of the valveless siphon decanter of  FIG. 1 ; 
         FIG. 3  of the drawings is a fragmented, perspective view of the bottom side of the valveless siphon decanter of  FIGS. 1 and 2 ; 
         FIG. 4  of the drawings is a fragmented, front elevation view of the valveless siphon decanter of  FIGS. 1-3 ; 
         FIG. 5  of the drawings is a fragmented, side plan view of the valveless siphon decanter of  FIGS. 1-4 ; 
         FIG. 6  of the drawings is a perspective view of an alternative embodiment of a valveless siphon decanter; 
         FIG. 7  of the drawings is a side plan view of the decanter sub-assembly of  FIG. 6 ; 
         FIG. 8  of the drawings is a front view of the decanter sub-assembly of  FIGS. 6 and 7 ; 
         FIG. 9  of the drawings is a bottom plan view of the decanter sub-assembly of  FIGS. 7-8 ; and 
         FIG. 10  of the drawings is a side elevation view of an alternative valveless siphon decanter. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     While this invention is susceptible of embodiment in many different forms, there is shown in the drawings and will herein be described in detail several specific embodiments with the understanding that the present disclosure is to be considered as an exemplification of the principles of the invention and is not intended to limit the invention to the embodiments illustrated. 
     It will be understood that like or analogous elements and/or components, referred to herein, may be identified throughout the drawings with like reference characters. 
     Referring now to the drawings, and in particular to  FIGS. 1-5  collectively, shown therein is one embodiment of a valveless siphon decanter, hereinafter referred to as the decanter  10  for use with a wastewater reactor. The reactor system includes one or more tanks  12  with an inlet providing wastewater communicated from a wastewater source (not shown) into the tank  12 . The tank  12  receives and holds wastewater allowing the wastewater to stratify into separate levels including a solids level located at the bottom of the tank  12 , an intermediate level that includes small particulate matter suspended in the fluid, and a layer of substantially clear fluid disposed near the top of the tank  12 . The clear fluid is preferably removed via the decanter  10  in accordance with the present invention. 
     The decanter  10  preferably includes a boom  14  that extends from at least the edge of the tank  12  and extends at least partially into the tank  12 . The boom  14  is preferably positioned above the top of the wastewater as will be discussed in greater detail infra. 
     In one embodiment, the boom  14  is preferably an elongated tubular member providing fluid communication between the tank  12  of the boom  14  and a siphon tube  16  which preferably includes an outlet for discharging processed water to a secondary tank  18 , also known as an equalization and/or chlorine contact tank. The boom  14  is preferably pivotally connected to a top edge  20  of the tank  12  via a cradle  22 , although it will be understood that the boom  14  may include any number of different means for pivotally connecting the boom  14  to the top edge  20  of the tank  12  that would be known to one of ordinary skill in the art with the present disclosure before them. 
     The boom  14  preferably extends transversely from and bifurcates the siphon tube  16  into first and second portions  24  and  26 . The first portion  24  of the siphon tube  16  extends above the boom  14  and the second portion  26  of the tube extends at least partially below the boom  14 . 
     In one embodiment, a vacuum pump  28  is disposed towards the top of the first portion  24  of the siphon tube  16 . The vacuum pump  28  creates a vacuum within the system that draws fluid into the boom  14  via a vacuum head  30  as will be discussed in greater detail infra. 
     Fluid communicating through the boom  14  travels downwardly through the siphon tube  16  into the second portion  26  of the siphon tube  16  until the second portion  26  is filled. When the second portion  26  of the siphon tube  16  is filled with fluid, the vacuum created by the vacuum pump  28  will begin to draw fluid upwardly into the first portion  24  of the siphon tube  16 . A sensor  32  associated with the decanter  10  senses the level of the fluid within the siphon tube  16  and outputs a signal indicative of the level of fluid within the siphon tube  16 . A control system  34  automatically and continuously, or periodically, monitors the output of the sensor  32  and communicates with the vacuum pump  28  to control the operation of the vacuum pump  28 . As such, the control system  34  is capable of maintaining the fluid level within the siphon tube  16  (and therefore the flow rate) at a predetermined level. It will further be understood that because the decanter  10  utilizes a vacuum pump  28  to draw fluids into the decanter  10 , atmospheric air drawn into the decanter  10  contemporaneously with the fluids can be metered, thus allowing for the decanter  10  to be operated at high discharge flow rates. In other words, the utilization of vacuum pressure within the decanter  10  allows for high flow rate discharge during high flow rate input into the tank  12 . 
     Additionally, a liquid or gas disinfectant compounds commonly utilized in reactors may be drafted into the decanter  10  along with the fluid rather than mixed in a separate process. The disinfectant compound may float along the top of the fluid or may be at least partially mixed with the fluid. When the vacuum pump  28  draws the disinfectant compound and fluid into the decanter  10  together, the disinfectant and fluid are mixed thoroughly within at least a portion of the decanter  10 . The act of mixing a disinfectant compound and fluid within the decanter  10  substantially eliminates the need for a secondary equalization tank and further processing via a disinfection system, which is required with typical single batch reactors. 
     In an additional embodiment, the decanter  10  may also include a vacuum break  36  which allows for a controlled flow of fluids through the decanter  10 . Stated otherwise, the addition of the vacuum break  36  allows for automatic decanter level control. The vacuum break  36  may include a check valve in combination with a pipe  38 . In one embodiment, the pipe  38  is connected to the first portion  24  of the siphon tube  16 . A terminal end of the pipe  38  is disposed a predetermined distance down into the fluid within the tank  12 . The location of the terminal end of the pipe  38  is selectively adjustable such that the vacuum break level for the system may be varied in the field. In operation, when the level of fluid within the tank  12  falls below the terminal end of the pipe  38 , air flows into the pipe  38  breaking the vacuum within the system and therefore interrupting the flow of fluid through the boom  14 . 
     It will be understood that the use of a vacuum break  36  allows the system to run without constant operation of the vacuum pump  28 , significantly increasing the energy efficiency of the decanter  10 . That is, once the vacuum pump  28  causes a predetermined amount of fluid to be drawn into the siphon tube  16 , hydrostatic pressure within the decanter  10  maintains the flow of fluid from the tank  12  through the siphon tube  16  until the fluid level in the tank falls below the terminal end of the pipe  38  breaking the vacuum within the decanter  10 . 
     As stated previously, the siphon tube  16  is an elongated tubular member fabricated from a strong and resilient material that is bifurcated into first and second portions  24  and  26  via the boom  14 . In one embodiment, the first portion  24  of the siphon tube  16  is connected to the second portion  26  via a flexible tubular member  40 . The flexible tubular member  40  is connected to the bottom of the first portion  24  of the siphon tube  16  and the top end of the second portion  26  of the siphon tube  16 . The flexible tubular member  40  may be fabricated from any number of flexible and/or resilient materials such as a plastic or polymer, or a rubber. Additionally, the flexible tubular member  40  may also be fabricated from a metal or other rigid or partially rigid material constructed to flex or bend. It will be understood that the flexible tubular member  40  may be fabricated from a variety of materials having varying physical properties so long as the flexible tubular member  40  allows the first portion  24  of the siphon tube  16  to pivot about the second portion  26  of the siphon tube  16  while maintaining a path for fluid communication therethrough. 
     The flexible tubular member  40  may include a support member  42  for supporting the first and second portions  24  and  26  of the siphon tube  16  in a spaced apart relationship. In one embodiment, the support member  42  may include a rigid and/or semi rigid dowel, for example, a section of all-thread. 
     In an additional embodiment, the vacuum head  30  preferably includes an elongated tubular member  44  that floats above the top of the wastewater via one or more pontoons  46 . The elongated tubular member  44  includes a plurality of apertures or orifices  48  disposed along the bottom of the elongated tubular member  44 . The orifices  48  may have any number of shapes and/or sizes that can vary according to design requirements including, but not limited to flow rate, vacuum pressure, and the like. The orifices  48  may be substantially equally or unequally spaced along the bottom of the elongated tubular member  44  and are adapted to provide a path for communication of fluids between the tank  12  and the boom  14 . In one embodiment, the diameter of the orifices  48  increases with the distance that the orifices  48  are spaced from a center point  50  of the elongated tubular member  44 . 
     In one embodiment, the one or more pontoons  46  include four elongated pontoons  52  and a central pontoon  54 . The elongated pontoons  52  extend along the elongated tubular member  44  and each elongated pontoon  52  includes a length  56 , a width  58  and a height  60 . The elongated pontoons  52  are connected to the elongated tubular member  44  in pairs such that one of the elongated pontoons  52  is disposed frontwardly of the elongated tubular member  44  and one is disposed rearwardly. 
     Each of the elongated pontoons  52  is preferably fabricated as a hollow enclosure filled with air, or a buoyant material such that the elongated pontoon  52  may float on top of the fluid within the tank  12 . In accordance with the present disclosure, the elongated pontoons  52  extend a predetermined distance below the bottom of the elongated tubular member  44 . It will be understood that the widths  58  of the elongated pontoons  52  are sized such that they substantially preclude solids floating on the surface of the fluid from traveling under the elongated pontoons  52  and up through the orifices  48 . Moreover, as the width  58  of the elongated pontoons  52  increases, the likelihood of solids traveling underneath the elongated pontoons  52  decreases. 
     Each of the pairs of elongated pontoons  52  on either side of the elongated tubular member  44  are connected together via a sidewall  62  and one or more baffles  64  extending between the elongated pontoons  52 . The sidewalls  62  and baffles  64  cooperate to define enclosures  66 . In one embodiment, the baffles  64  are oriented along the midline of each of the orifices  48 . In other embodiments, the baffles  64  may be disposed between each of the orifices  48 . Furthermore, the baffles  64  may include one or more apertures or filters, which provide paths of fluid communication between the enclosures  66 . 
     In accordance with the present invention the central pontoon  54  is a sealed container filled with a fluid such as air and is positioned substantially below the intersection of the boom  14  and elongated tubular member  44 . 
     In one embodiment, the decanter  10  also includes one or more support legs  68  that support the elongated support member  44  above the bottom of the tank  12 . More specifically, the support legs  68  are fixedly connected to at least one of the boom  14 , center pontoon  54 , and the elongated tubular member  44 . The support legs  68  may contact the bottom of the tank  12  acting as a stop to prevent excessive downward movement of the elongated tubular member  44 . It will be understood that the length of the support legs  68  may vary according to design requirements. Furthermore, it will be understood that the support legs  68  may be selectively adjustable to vary the vertical translation of the elongated tubular member  44 . 
     In operation, the vacuum pump  28  of the decanter  10  is activated creating a vacuum within the decanter  10  that causes the fluid in the tank  12  to be drawn into the enclosures  66  of the elongated pontoons  52 . The fluid drawn into the enclosures  66  is directed into the plurality of orifices  48  and then into the boom  14  via the elongated tubular member  44 . Hydrostatic pressure drives the fluid through the boom  14  and into the siphon tube  16 . When the fluid reaches a predetermined level within the siphon tube  16 , for example, when the fluid level begins the reach into the first portion  24  of the siphon tube  16 , the sensor  32  outputs a signal indicative of the fluid level to the control system  34 . When the control system  34  that receives data from the sensor  32  receives a signal indicative of the water level being within a predetermined level, the control system  34  causes the vacuum pump  28  to cease operation breaking the vacuum within the decanter  10 . 
     It will be understood that as fluid is being drawn from the tank  12 , decreasing the level of fluid therein, the elongated tubular member  44  floating on the surface of the fluid moves downwardly in the tank  12  until the support legs  68  contact the bottom of the tank  12 . 
     To install, the cradle  22  is secured to the top edge  20  of a wall of the tank  12 . Next, the boom  14  is secured to the cradle  22  such that the boom  14  may pivot about the cradle  22  and vacuum head  30  of the decanter  10  is disposed in the tank  12 . It will be understood that the second portion  26  of the siphon tube  16  is associated with the secondary tank  18 . It will be further understood that a tank  12  with an existing decanter may be retrofit with the decanter  10  of the present invention without need for removing the old decanter. Furthermore, the decanter  10  is installed such that all parts of the decanter  10 , with the exception of the support legs  68  are not submerged in the fluid. Therefore, the parts of the decanter  10  are not subjected to corrosive and/or other types of damage due to contact with the wastewater contained in the tank  12 . 
     Referring now to  FIGS. 6-9  collectively, shown therein is another embodiment of a decanter  110  for use in accordance with the present invention. More specifically, the decanter  110  may be used in “through the wall” applications where at least a portion of the decanter  110  extends through the sidewall of the tank  112  rather than “over the wall.” 
     The decanter  110  is constructed similarly to the decanter  10  described above with the exception that the decanter  110  includes only two elongated pontoons  152  connected to the elongated tubular member  144 . Two rectangular enclosures  128  are disposed below two sections of the elongated tubular member  144  and are provided to receive fluid from the tank. In one embodiment, the rectangular enclosures  128  include one or more baffles  164  extending between the elongated pontoons  152  for subdividing the rectangular enclosures  128  into a plurality of enclosures  166 . 
     As this embodiment can be used in a “through the wall” application, the boom  114  includes a pivot joint  170  that allows the boom  114  to pivot upwardly and downwardly relative to the sidewall of the tank  112 . It will be understood that because the boom  114  pivots via the pivot joint  170 , the siphon tube  216  does not have to include a flexible tubular member, although the inclusion of a flexible tubular member is permissible. Although not shown, the discharge end of the siphon tube  216  is disposed within a secondary tank similarly to the siphon tube  16  described above. 
     Referring now to  FIG. 10 , shown therein is an alternative embodiment of decanter  10 , hereinafter referred to as decanter  200 . As stated previously, in any wastewater stratification process a thin layer of debris  300  is commonly found along the surface of the fluid within the tank  212 . It is desirable to prevent the communication of the debris  300  from the tank  212  through decanter  200 . Therefore, it is advantageous to dispose the orifices  248  of the elongated tubular member  244  below the debris  300  during the decanting process to prevent debris from entering the decanter  200 . 
     To these ends, decanter  200  is designed similarly to decanter  10  with the exception that the elongated tubular member  244  is flexibly connected to the boom  214 . Furthermore, the decanter  200  is provided with only a center pontoon  254  that is designed to be selectively adjusted within the tank  212  by varying the overall buoyancy of the elongated tubular member  244  and the center pontoon  254  in combination. 
     The elongated tubular member  244  is flexibly connected to the boom  214  by a flexible hose  278 . The flexible hose  278  allows the elongated tubular member  244  to translate substantially vertically downwardly into the fluid contained within the tank  212 , rather than downwardly and arcuately based upon the pivoting of the boom  214  alone. 
     The center pontoon  254  is disposed proximate the elongated tubular member  244  and can act as both a pontoon and ballast. That is, the center pontoon  254  is operatively connected to a buoyancy control system  280  that includes a fluid source  282  connected to the center pontoon  254  via a fluid path  284  such as a hose or pipe. Between fluid source  282  and center pontoon  254  is a pump  286  capable of facilitating bidirectional fluid flow between fluid source  282  and center pontoon  254 . It will be understood that the center pontoon  254  floats when it is mostly filled with air, allowing the elongated tubular member  244  to float on the surface of the liquid in the tank  212 . In contrast, as the center pontoon  254  is filled with a liquid it begins to sink. The operation of pump  286  is controlled by control system  234  that also controls the vacuum break  236  that is constructed similarly to the vacuum break  36  of decanter  10 . The functional and operational details of the control system  234  will be readily understood by one of ordinary skill in the art and will not be discussed in any further detail. 
     In accordance with the present invention, the buoyancy control system  280  preferably includes a sensor (not shown) which measures the buoyancy of the center pontoon  254 . The control system  234  automatically and continuously monitors the output of the sensor to determine if the buoyancy of the center pontoon  254  is within a predetermined range of values. 
     In one embodiment, the fluid within the buoyancy control system  280  is preferably a mixture of water and ethylene glycol in percentages of 40% and 60%, respectively, although it will be understood that the percentages may vary according to operational requirements. 
     The foregoing description merely explains and illustrates the invention and the invention is not limited thereto, as those skilled in the art who have the disclosure before them will be able to make modifications without departing from the scope of the invention.