Abstract:
A mobile wastewater separator and recover unit and method for the separation and disposal/recovery of waste water for example in the oil and gas industry. It is fully self-contained and maintains the ability to separate heavy solids, floating contaminants, and water for recovery and reuse or disposal as required. Main components of the system are a large wastewater holding capacity implementing various compartments &amp; separator/recovery mechanisms, evaporation compartments that are interchangeable for efficiency in both warm &amp; extreme cold temperature operations, and finally a condensation recovery system and clean water holding compartment.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority under 35 U.S.C. 119(e) from U.S. Provisional Application No. 60/794,645 filed on Apr. 25, 2006 and is a continuation of U.S. patent application Ser. No. 11/627,310 filed Jan. 25, 2007. 
     
    
     BACKGROUND 
       [0002]    Containment, transportation, and disposal of drilling waste is expensive. Spills are a common occurrence in operations and are not only very expensive for the operator in lost product but are detrimental to the environment. Various systems have been proposed for waste water treatment, for example at well drilling sites, but there is room for improvement on them. 
       SUMMARY 
       [0003]    There is provided an apparatus for waste water treatment. In one embodiment, the waste water treatment apparatus comprises a platform, such as a skid, a phase separation tank, an evaporation tank with condenser and clean water recovery tank mounted together on the platform with fluid transfer mechanisms interconnecting the tanks. The phase separation tank may provide three phase separation into solids, water and an oil fraction. The evaporation portion of the apparatus may be provided by interchangeable summer and winter evaporation tanks. The evaporation tanks may be provided with a steam hood. Fluid transfer between the separation and evaporation tank may pass through a transitional tank such as a floe tank. A method for the seasonal treatment of waste water is also provided. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0004]    There will now be described embodiments of a waste water treatment apparatus by way of illustration, with reference to the drawings, in which like reference characters denote like elements, and in which: 
           [0005]      FIG. 1  is a top view of a waste water treatment apparatus; 
           [0006]      FIG. 2  is side view of a summer evaporator for use with the apparatus of  FIG. 1 ; 
           [0007]      FIG. 3  is a top view of a winter evaporator for use with the apparatus of  FIG. 2 ; 
           [0008]      FIG. 4  is a side view of a winter evaporator for use with the apparatus of  FIG. 2 ; and 
           [0009]      FIG. 5  is a perspective view of a steam hood with condenser jacket for use with the apparatus of  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION 
       [0010]    In  FIG. 1  an apparatus  10  for waste water treatment includes a supporting platform  12 , which could be a skid, and a phase separation tank  14 , transitional tank  16 , evaporation tank  18  and clean water recovery tank  20  mounted together on the platform  12 . By using a skid for mounting the tanks  14 ,  16 ,  18  and  20 , the apparatus  10  is made mobile. The phase separation tank  14  is used as an entry point for waste water, such as drilling waste and spillage fluids. For remote locations, a fuel tank and generator may also be mounted on the platform  12  to provide necessary power. 
         [0011]    The phase separation tank  14  may provide for solids separation by using a series of graduated plates. Solids may include heavy solids such as sand, sawdust, clay and gravel. The incoming waste water is delivered to compartment  14 A of phase separation tank  14 . The waste water passes from compartment  14 A to compartment  14 B over a floor plate  22  that catches larger solids. The waste water then passes over a second floor plate  24  into compartment  14 C and then over a third floor plate  26  into compartment  14 D. The floor plates  22 ,  24 ,  26  together comprise a series of graduated floor plates that catch solids on the floor of the tank  14 . For example, plate  22  may be a 6 inch floor plate extending across the tank bottom, and plates  24  and  26  may be 12 inch floor plates. 
         [0012]    A skimmer plate  28  is provided in an upper portion of the tank  14  to contain floating contaminants such as oils, solvents, detergents, and oil based drilling fluids, and a skimmer  30 , such as a Maxi-Skimmer™ is provided on the tank  14  to collect and recover the floating contaminants. A flow line  32 , for example piping, with a ball valve  34 , leads from tank  14  to tank  16 . The flow line  32  may be at a relatively high level for flow of fluids under gravity from tank  14  to tank  16 , but may also be operated at a relatively low level, but above the plate  26 , and used in cooperation with a high flow line  35  that extends from tank  14  to tank  16 . Filters may be provided in each of flow line  32  and flow line  35 . In normal operation, fluid drains by gravity from tank  14  to tank  16 . For this reason, a relatively high flow line should be used to ensure that tank  16  fills. But in order to drain tank  14  for subsequent removal from a remote site, tank  14  should also be provided with a low flow line, that is normally closed, but may be opened, such as by using ball valve  34  to drain tank  14 . The low flow line  32  may be for example 12 inches off the floor of the tank  14 , and the high flow line  35  may be for example four feet off the floor of the tank  14 . The plates  22 ,  24 ,  26  help keep solids away from the flow lines  32 ,  35 . Various filters may be used instead of plates  22 ,  24  or  26 . At the conclusion of use at a remote site, the solids in the tank  14  may be removed using for example a vacuum truck. 
         [0013]    The flow lines  32  and  35  thus transfer fluids, for example by gravity, from tank  14  to tank  16 . The tank  16  may be operated as a floe tank, to which a chemical flocculant may be added if required for further clarification of fluid. However, the tank  16  may simply be used for additional settling of solids, or omitted if solids separation and filtering in the tank  14  is sufficient to produce clarified fluid for the evaporation tank  18 . 
         [0014]    A conduit system  36 , which may be provided with a feed pump such as an electric pump, leads clarified fluids from the tank  16  to tank  18  through evaporation tank supply line  37 . The supply line  37  constitutes a fitting provided on the platform  12  for supplying waste water to the tank  18 . Tank  18  is installed at location  19  on the platform and may be one of two inter-changeable evaporation tanks. A summer boil-off tank insert is shown in  FIG. 1 . Control of the supply of waste water to tank  18  from tank  16  is provided by a float operated switch  38  located inside tank  16  and float operated switch  40  located outside tank  18  in a float box  41 . The conduit system  36  includes valves (not shown) that are responsive to the float operated switches  38  and  40  to manipulate the source water from tank  16 . The float operated switch in tank  16  operates in a low level detection mode. When fluid in the tank  16  is below a set level, the apparatus  10  is turned off, with no evaporation, and no pumping of fluids. When fluid in the tank  16  is above a set level, the conduit system  36  and its feed pump are turned on to supply fluid to tank  18 . When fluid in the tank  18  reaches a set low level, the level is detected by a float operated switch  40  and the feed pump  36  for tank  18  is turned on. When fluid in the tank  18  reaches a set high level, the float inside the float box  40  detects this high level and turns off fluid transfer into the tank  18 . An additional float (not shown) is also in the float box  40  which signals the burner to fire when its low water level is reached. The burner will continue to fire as long as the float in tank  16  is above its low water level and the low level switch for the burner in the float box  40  is above its low water level. This additional float offers another safety mechanism to signal the burner to shut down due to low water and thus saving damage to the piping and combustion chamber. The flow lines  32 ,  35 , transitional tank  16  and conduit system  36  together constitute a fluid transfer system for moving fluid from separation tank  14  to tank  18 . Other methods for providing clarified fluid to the evaporation tank  18  may be used. 
         [0015]    Tank  18  may be one of two interchangeable evaporation tanks, one of which is illustrated in  FIG. 2 .  FIG. 2  shows a warm temperature/summer time tank  42 , which is preferably an insulated boil-off tank. A burner chamber  44  is provided inside the tank  42  that is supported off the floor of tank  42  by burner legs  45 . Hot exhaust gases are provided from the burner  54  through exhaust piping  46 ,  48  which make multiple passes through the tank  42  and reconnects at an exhaust manifold  50 . Exhaust air may be blown across the surface of the boiling water from the exhaust manifold  50  as illustrated by exhaust outlet  52 . The heat source is a burner  54  mounted on the exterior of the summer tank  42 . Fuel for the burner  54  may include but is not exclusive to available sources such as diesel, natural gas, or propane. 
         [0016]    Tank  42  may be interchanged with a winter evaporation tank  56  illustrated in  FIGS. 3 and 4  and connected to the supply line  70  from tank  16  ( FIG. 1 ). Again, the tank  56  is preferably an insulated boil-off tank installed at location  19 , and includes a series of steam lines  58  that run through the inside of the tank  56  between a series of steam manifolds  60 ,  62  and  64 . Manifold  62  is a steam injection manifold supplied from steam inlet  66 . Manifold  64  collects the steam from steam lines  58  and supplies it to outlet  68 . 
         [0017]    Steam is supplied to steam inlet  66  through supply line  70  that runs through tanks  14  and  16  for pre-heating of fluids. When the tank  56  is installed in the apparatus  10 , the inlet  66  is connected to the supply line  70 . However, when the summer evaporator  42  is installed in apparatus  10 , the line  70  is disconnected. When tank  56  is installed in the apparatus  10 , the steam outlet  68  is connected to line  72 , which continues through clean water tank  20  to help prevent freezing of clean water in tank  56  Float operated switches  40  are used in each of the tanks  42  and  56  to control conduit system  36 , which includes a feed pump, to ensure that water is kept near a pre-determined level  74 ,  76  in tanks  42 ,  56  respectively. Since the tanks  42 ,  56  are used to boil water, it is necessary to include suitable safety measures such as a safety gate  90  hinged to the tank  16  at hinge  92  to help prevent personnel or objects coming too close or falling against the tanks  42 ,  56 . For interchange of the tanks  42 ,  56 , the gate  90  may be opened, and one or the tanks  42 ,  56  removed and exchanged for the other. The tanks  42 ,  56  may be secured on the skid  12  by any suitable means such as bolts. 
         [0018]    Evaporated water from evaporation tanks  42 ,  56  may be provided through condenser  78 . The condenser  78  may comprise a peaked steam hood placed above the evaporation tank  42 ,  56 , whichever is used, at locations  86 ,  88  respectively, leaving an air space to avoid pressurization. The hood of the condenser  78  has a handle  80  and is hinged on one side with hinges  81  that allow the hood to be fully opened if steam recovery is not desired. A condensation tube  82  runs from the condenser  78  to clean water recovery tank  20 , and is provided with an electric fan  84  that may be automatically controlled to be powered when the hood is lowered and the boil-off tank burner float low water level has been reached, according to the position of the float of float operated switch  40 . The operation of the burner float operated switch  40  signals the fan  84  in the condenser  78  as the case may be, to be powered. The condensing tube  82  is preferably connected to and runs the length of the exterior of the hood of the condenser  78  to drain condensed water into the clean water tank  20 . The tank  20  is used to collect and hold clean water readily available for reuse. 
         [0019]    Apparatus  10  is provided with tanks large enough to handle the volumes of waste from for example a drilling rig, while still being deliverable and functional in isolation to any site including remotes. The tank  14  functions as both a containment tank and starting point of the separation process, where solids separation begins. Wastewater in the drilling sector varies greatly from traditionally defined wastewater in that it contains many heavy solids that would not normally be present in other situations where water treatment is desired. These heavy solids include such materials as sand, sawdust, clay and gravel. The graduated bottom plates  22 ,  24  and  26  cause heavy solids to settle out and be contained in tank  14 . These heavy solids are dealt with at the end of the application by traditional disposal methods. 
         [0020]    The apparatus also removes floating contaminants such as oil and diesel in the tank  14  while settling out solids and recovers these floating contaminants for re-use or traditional disposal methods. Transitional fluids (fluids that are lighter than settled solids but heavier than any remaining floating contaminants) are delivered to the tank  16  through piping  32 . Tank  16  may be operated as a floe compartment in which a flocculant may or may not be added depending on the initial constituents of the wastewater being treated. Clarified water from the tank  16  is then transferred by way of feed pump in conduit system  36  to tank  18 . When tank  18  is provided for summer operation, exhaust gases from a burner are used to boil water and are exhausted to the atmosphere. For winter operation, i.e. extreme cold temperature operation, a tank such as tank  56  is provided, in which a series of steam lines  58  pass directly through the fluid. The steam supply  70  is initially run through the tanks  14  and  16  for pre-heating of fluids and after running through the tank  18  continues through the water recovery tank  20  to keep recovered water from freezing. 
         [0021]    Tanks  42  and  56  are interchangeable in apparatus  10  to allow for fuel efficiency and temperature requirements depending on the operator&#39;s situation. Both tanks  42  and  56  may be fitted with condenser  78  for recovery of clean water if desired, which is delivered to clean water recovery and holding tank  20 . 
         [0022]    Apparatus  10  reduces on-site volume of waste and recovers components of the waste. With an on-site system spill sites can be cleaned up and material recovered immediately, minimizing both loss of product and damage to the environment. In addition, waste water may be treated seasonally, by providing the apparatus  10  with one of a warm weather evaporation tank and a cold weather evaporation tank; and interchanging the warm weather evaporation tank with the cold weather evaporation tank when desirable due to weather conditions. The terms “warm” and “cold” are defined relative to each other, that is, the summer tank is intended for warmer conditions than the winter tank. 
         [0023]    In the claims, the word “comprising” is used in its inclusive sense and does not exclude other elements being present. The indefinite article “a” before a claim feature does not exclude more than one of the feature being present. 
         [0024]    Immaterial modifications may be made to the embodiments described here without departing from what is covered by the claims.