Abstract:
A compact, self-contained apparatus for treating wastewater containing as impurities and pollutants various non-volatile (at water boiling points) fluids such as greases, oils and soaps, a vessel for collecting the wastewater, a heating chamber including electric heating elements and a heat transfer liquid such as mineral oil to heat the wastewater admixture to boil off the water and to reduce the volume of liquid for disposal, and a wastewater supply tank positioned under the apparatus. The apparatus may further include a disposable liner to isolate the wastewater from the vessel itself and facilitate rapid and clean removal and disposal of waste material after evaporation of the water, and thermally-activated sensors to maintain a desired temperature differential between the heating elements and the heat transfer liquid contained in the apparatus.

Description:
PRIOR APPLICATIONS 
   This application is based on and claims the benefit of the filing dates of U.S. Provisional Patent Applications Ser. No. 60/147,736, filed Aug. 6, 1999, and Ser. No. 60/159,664, filed Oct. 15, 1999, both entitled  Compact Wastewater Cleaning Apparatus  (“the co-pending provisional applications”), the entire disclosures of which are incorporated by reference into this application. 

   FIELD OF INVENTION 
   This application relates to apparatus for the treatment of wastewater resulting from cleaning of, for example, buildings, vehicles and machinery by reducing the volume of wastewater required for disposal by an efficient water evaporation. 
   BACKGROUND OF INVENTION 
   As explained in my U.S. Pat. No. 5,582,680, and in my U.S. Pat. No. 6,200,428, filed Mar. 31, 1998, the entire disclosures of which are incorporated by reference into this application, good manufacturing processes, concern for the environment, and changes in environmental practices and regulations all have created additional needs in handling waste fluids after manufacturing and cleaning operations, especially in disposing of water based mixtures containing pollutants such as greases, oils, soaps, heavy metals, road film and carcinogens. Whereas in the past it was acceptable merely to dump such waste liquids in the ground or in sewer systems, current good practices and environmental laws and regulations now severely discourage and/or prohibit such practices. Although very laudable in intent, the result can be very costly, especially to businesses who must use substantial quantities of water in their operations, as for example to clean buildings, vehicles and other machines, which will result in wastewater containing greases, oils, minute metallic and other particles, and detergents. Each of the aforementioned patent and co-pending application describes and claims an apparatus operated on the evaporation principle and which is relatively inexpensive to manufacture, simple and safe to operate, and relatively more efficient in the active removal of non-volatile fluids and contaminants from wastewater. I now have invented an improvement to such apparatus which is compact and especially useful in the treatment and reduction of wash and rinse water resulting from the cleaning and or mopping of buildings, vehicles and machinery, including especially the large amounts of wastewater generated by cleaning large areas of high trafficked floors in commercial and industrial facilities using power scrubbing equipment. 
   The apparatus is compact and easily moved within a facility, and it uses an environmentally safe heat transfer fluid and an optional disposable liner to contain the wastes remaining after evaporation. 
   SUMMARY OF THE INVENTION 
   In accordance with this invention, there is provided a novel wastewater treatment apparatus that treats wastewater containing, as impurities and pollutants, various non-volatile (at water boiling points) fluids such as greases, oils, carcinogens and detergents, by vaporizing the water, using electrical heating elements and a heat transferring mineral oil by which heat transfer is effected and in which the outer surfaces of the apparatus remain essentially cool to the touch even while in operation. 
   Further features of the invention include a special liner in the wastewater receiving vessel of the apparatus to isolate the wastewater from the vessel itself and facilitate rapid and clean removal and disposal of waste material after evaporation of the water, and paired thermally-activated sensors or temperature probes to control the electrical current to the heating elements, one of which probes measures and responds to the temperature of the heat transferring mineral oil and the other of which measures and responds to the surface temperature of the electrical heating elements. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will be more fully understood by reference to the following detailed description of a preferred embodiment and the attached drawings, in which like reference numerals refer to like elements, and wherein: 
       FIG. 1  is a partial isometric view of the preferred embodiment of this invention, taken on line  1 — 1  of FIG.  2  and showing the essential structure of a wastewater treatment apparatus according to the invention; 
       FIG. 2  is a side view of the preferred embodiment of the apparatus as shown in  FIG. 1 , with the wastewater tray shown in partial cross section; 
       FIG. 3  is a top view of the embodiment of  FIGS. 1 and 2 ; 
       FIG. 4  is a cross sectional view taken on line  4 — 4  of  FIG. 2 ; 
       FIG. 5  illustrates the liner of the present invention; 
       FIG. 6  is a partial isometric view of the wastewater treatment apparatus, in cross-section, with the liner of the present invention shown in working position in the fluid receiving vessel; 
       FIG. 7  shows a cross-sectional view of the apparatus, illustrating the relative positions in the heating vessel of the oil temperature sensor and the heating element temperature sensor, and 
       FIG. 8  shows an exemplary diagram of an electrical circuit to detect and react appropriately to the varying differences in temperature between the heating elements and the heating fluid in which they are immersed. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Referring to  FIG. 1 , a preferred embodiment of the present invention comprises a wastewater treatment apparatus  10  and an optional separate wastewater receiving tank  12 . Apparatus  10  includes an external jacket  14  substantially cubic in shape. Contained inside and spaced from jacket  14  is an interior heat generating chamber  16  (e.g., 4 inches wide at its four sides and 6 inches at its bottom) which is defined at its outside by a heating vessel  18  (e.g., 10 gauge steel) having side walls and a bottom wall as shown, and on the inside by a fluid (e.g., wastewater) receiving vessel  20  preferably of titanium or stainless steel (e.g., about 24 inches in all three dimensions and 15½ gauge). Heating vessel  18  in turn is spaced from outer jacket  14  by an air space  22  (e.g., about 2 inches in width on all four sides and at its top and bottom) to insulate jacket  14 . Although not shown, heating vessel  18  may be supported at its bottom by jacket  14  using vertical posts or the like. The bottom of jacket  14  also contains a number of spaced vent holes  15  to admit ambient air into air space  22  both to keep jacket  14  cool to touch and to create air flow to facilitate vapor exhaust. 
   Fluid receiving vessel  20  as shown includes side walls, a bottom wall and at least a partially open top. Fluid vessel  20  in turn is supported by heating vessel  18  by outwardly extending (e.g., 4 inch) flanges  24  at the top of all four sides sitting atop similar, inwardly extending flanges  26  at the top of all four sides of heating vessel  18 . As thus shown in  FIGS. 1 and 4 , heating chamber  16  extends across the bottom wall and the height of the side walls of fluid vessel  20 . Vessels  18  and  20  may be welded together by their respective flanges, but preferably are held together by detachable means such as stainless steel bolts to enable vessel  20  to be readily removed for maintenance of heating chamber  16  and the heating elements to be described. 
   Within heating chamber  16  and below vessel  20  as shown in  FIG. 4  are a 10 kilowatt array of preferably three serpentine electric heating elements  30  (e.g., flat bar stock with 8 watts per square on 5½ inch centers between bars), the electrical power to which is provided by leads  33  as shown in  FIG. 4  to a control panel  28 . In addition, heating chamber  16  is substantially filled (e.g., about one half the depth of chamber  16 ) with about 50 gallons of a non-toxic, heat transfer liquid mineral oil  32  such as PARATHERM NF Heat Transfer Fluid supplied by Paratherm Corporation of Conshocken, Pa., to evenly distribute to vessel  20  the heat generated by heating elements  30  and causing the wastewater contained in the fluid vessel to boil and evaporate while enabling the contaminates in the wastewater to settle in vessel  20  in concentrated form for later disposal. Also as shown in  FIGS. 1 and 4 , heat transfer oil  32  fills at least the entire bottom and a substantial portion of the sides of heating chamber  16 . Such a mineral oil can be heated up to 600° F., which on being so heated begins to circulate convectively to carry the heat to the fluid receiving vessel. 
   The wastewater is delivered to vessel  20  by an inlet  34  connected by a pipeline or flexible hose  35  and self priming pump means  36  to a suitable supply tank such as tank  12  as shown. Water vapor as it is generated escapes from vessel  20  in the apparatus with an air flow from space  22  by exhaust pipe  40  which preferably includes an exhaust blower fan  42  to facilitate the air flow and exhaust. There also is preferably provided a removable access cover  44  that may be lifted off by handles  45  as shown to expose the inside of vessel  20  through at least a partially open top for inspection and routine maintenance, and may also be available for hand filling of wastewater from pails and the like. At the rear of vessel  20  is an access pipe  46  extending through both jacket  14  and vessel  18  and opening into vessel  20  to enable the insertion of a hose to pump out any contaminate concentrated water remaining in the apparatus for suitable disposal. Pipe  46 , which may include a removable cap on its outer side, preferably is angled, for example at 45 degrees, to enable the inserted hose to be extended to the bottom of vessel  20 . 
   Power to operate apparatus  10  is supplied to the control panel  28  mounted at the side of jacket  14  as shown, with the electrical power delivered through a suitable 3-prong plug from any 220 volt receptacle. The control features may include those described in my patent, but may also simply comprise a “dead man” switch  52  to power supply pump  36  only while switch  52  is actively held in its closed position by the operator, a combined start-stop 24-hour timer control  54  to start and shut off the electrical power at selectable times, and a “HI-LO” switch  56  to select alternative high and low heat settings of, for example, 350° F. and 150° F., respectively. 
   Further as shown, apparatus  10  is supported by suitable legs  59 , which preferably are adjustable in height and may include lockable casters for easy movement. 
   The removable wastewater supply tank  12  (e.g., about 24 inches wide and 4 inches high to enable a direct fill from the drain of a power scrubber preferably extends beyond apparatus  10  (say 10 inches at each end) and is mounted on casters  60  to enable the tank  12  to be moved out from under apparatus  10 . The top wall  62  of tank  12  includes an access opening through which wastewater is dumped into a removable filter tray  65  placed in tank  12 , and supply pump  36  which is mounted on a bracket detachable from top wall  62  (to enable pump  36  to be used with other wastewater supply means) connected by the flexible, detachable hose  35  to inlet  34 . The example size of tank  12  is sufficient to hold wastewater from a 50 gallon power scrubber. The power cord  57  for pump  36  may conveniently be plugged into a twist lock receptacle  58  in control panel  28  to operate the pump from the control panel. Filter tray  65  is removable and disposable filter bag into which the waste water is poured to filter out larger particles in the wastewater. Filter tray  65  may be made of any suitable close mesh material such as a polyester which when full can be removed and incinerated or otherwise properly disposed along with its filtered contents. 
   Pump  36  may alternatively be mounted directly on the back wall of jacket  14 . If desired, or if necessary because of local environmental regulations, the evaporating discharge pipe  40  can be connected to a conventional water condenser coil (not shown) to collect distilled water for reclaiming and reuse as washwater. 
   In operation, the apparatus is first filled with wastewater generated by a floor scrubber of the like, either by hand or through supply tank  12  by holding pump switch  52  closed until vessel  20  is filled to an appropriate level. The preferred heating level is then set on HI-LO switch  56  and the timer control  54  then set both to close the heating circuit for the selected time and to actuate blower fan  42  causing the wastewater to reach its boiling temperature, evaporate the water and expel the water vapor from the apparatus. When the water is substantially evaporated, the remaining waste is then removed from vessel  20  through pipe  46  or cover  44 . 
   Referring now to  FIGS. 5 and 6 , an alternate embodiment of the present invention comprises a disposable liner  75 , made of a material which is waterproof and both nonporous and impervious with respect to the expected content of contaminants in the wastewater, and which is further capable of withstanding heat up to about 450° F., for example a 32 oz. silicone rubber coated, fiberglass woven fabric identified as G32SIL and manufactured by Amatex Corporation of Norristown, Pa. 
   Liner  75  is fabricated so as to prevent the through-passage of water and waste, the sides and bottom of liner  75  conforming in its outer shape to the contours of the fluid receiving vessel  20  of the wastewater treating apparatus. Liner  75  has at least one closeable opening  76  at its top to admit unprocessed wastewater from any source and vent evaporating water during operation to reduce the nonvolatile contaminates to their dry state. Liner  75  is formed of sufficient material at its top to be capable of being sealed shut and removed from fluid receiving vessel  10  and disposed, for example by incineration, along with the residue. The closure may consist of draw string  78  as shown or other suitable means such as adhesive tape. 
   If the temperature difference between the heating elements and the oil exceeds certain limits, the efficiency of the heat transfer from heating elements to oil is reduced, due in part to radiative and conductive cooling through the external walls of the heating chamber containing the oil and the heating elements, and due in part to variations in convective behavior of the oil at different temperature ranges and viscosities. Consequently, a means is described whereby the relative difference between the oil temperature and the heating element temperature may be held within such limits as will promote a maximally efficient transfer of heat to the oil and energy savings. This means also contributes to the useful life of the heating elements and the heat transfer fluid. 
   To accomplish the foregoing, an alternate embodiment of the invention includes the incorporation of a pair of thermally-activated sensors, one immersed in the oil in the heating vessel and not touching other surfaces or substances, and the other also immersed in the oil but attached directly to the surface of at least one heating element. The sensors are interconnected in the electrical circuit so that when the temperature difference between the oil and the heating element exceeds a certain preset limit electrical current, the heating element is turned off. 
   To control the heating circuit as described and as shown in  FIG. 7 , a pair of thermally-activated sensors or thermocouples  80  and  82 , for example sensor type Rapidship MI manufactured by Watlow-Gordon of Richmond, Ill. connected to the heating element power circuit  85 , the thermal sensor element  81  of sensor  80  suspended in oil  32  in heating vessel  18 , and the thermal sensor element  83  of sensor  82  mounted against the surface of a heating element  30  in heating vessel  18 . 
   Thermally-activated sensors  80  and  82  are connected to heating control circuit  85  of any type, an example of which is shown in  FIG. 8 , which detects a difference in temperature between the two sensors and changes the state of a power-circuit switching means depending on the relationship between that difference and a set value, e.g.: 
   
     
       
             
             
           
         
             
                 
             
             
               Condition 
               Action 
             
             
                 
             
           
           
             
               Difference less than set value 
               Close switching means to heat elements 30 
             
             
               Difference exceeds set value 
               Open switching means to open circuit to 
             
             
                 
               heating elements 30 
             
             
                 
             
           
        
       
     
   
   A suitable preset value may be about 30° F. such that the switching means is closed if the temperature difference is less than that amount and open if more than that amount. Heating elements  32  in heating vessel  18  are supplied power through a power-circuit switching means as described above and illustrated in FIG.  8 . When the starter button of apparatus  10  is first closed, the switching means is closed to begin heating the heating elements  30  and raise the temperature of the heat transfer fluid  32  sufficient to cause wastewater in vessel  20  to be evaporated. However, as the transfer fluid  32  is being heated, the temperature of the heating elements  30  will continue to rise even faster and cause temperature gradients to occur within the transfer fluid  50 . The temperature probes  80 ,  82  are provided to limit the temperature differential. Consequently, when a difference in temperature between thermally-activated sensors  81  and  83  exceeds a set value, the heating circuit  85  will cut off power to heating elements  30  until the temperature of heating elements  30  drops to a level at which the temperature differential is less than the set value. At that time, the difference in temperature between thermally-activated sensors  81  and  82  which does not exceed the set value will allow power to flow to heating elements  30  and cause the switching means to close and to continue heating the heat transfer fluid  32 . This more energy efficient cycle continues until the heat transfer fluid  32  reaches and is maintained at its preset operating temperature to cause evaporation of the wastewater. The operation may continue by adding more wastewater as desired. When a sufficient amount of contaminants has been collected, the apparatus  10  preferably is operated until all of the remaining wastewater is evaporated leaving a dry residue of the contaminants in liner  75  for disposal by an environmentally safe means. 
   From the description above, it should be clear that the present invention offers significant savings in labor, reduction of contamination risk, and energy savings. For example, an apparatus according to the invention may only need about 10-12 amps to operate as opposed to about 40-41 amps. The use of a removable liner which may either be cleaned or disposed of substantially reduces the cleaning effort required for the apparatus. The use of the described temperature-difference control for the heating vessel reduces the waste of energy used in heating, and further adds to the useful life of the heat transfer fluid  32  and heating elements  30 . It also may provide a degree of safety in case of heating vessel leakage or other abnormal condition. 
   It is to be understood that the aforementioned description is illustrative only and that changes can be made in the apparatus, in its components and their functions, without departing from the scope of the invention as defined in the following claims.