Abstract:
A filtration system is provided for removing oil and/or hydrocarbons from blige water that collects in the blige of a marine vessel to ensure discharge of oil-free water into the surrounding waters of the vessel. The filtering medium of the system is composed of a mixture of peat, anthracite and bentonite resulting in a composition that is hydrophobic and olephilic. Due to the chemical composition of the medium, it burns efficiently and can be disposed of in the onboard incinerators of the vessel producing over 17,000 BTU&#39;s per pound. Also, the filtration system employs full backwash capability for filtering liquids combined with particulates.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to an oil removal filtration system for removing oil and hydrocarbons from water. More particularly, the present invention is directed to a filtration system which removes all oil and hydrocarbons from the bilge water that collects in the bilge of a marine vessel to ensure discharge of oil-free water into to the surrounding waters. 
     For purposes of the present invention, the term “oil” is intended to include a wide variety of petroleum products such as engine oil, lubricating oil, diesel fuel, gasoline, etc. Also, for the purposes of the present invention, the term “hydrocarbon” will be used interchangeably with the term “oil”. In the operation of virtually all engine powered marine vessels having inboard engines, a wide variety of petroleum products are utilized in conjunction with engine operation. During operation of the engine or engines, a certain quantity of engine oil can be lost through engine seals and into the bilge of the vessel. Regardless of how clean and how well cared for is the engine system of the vessel, it is virtually always the case that at least a small amount of engine oil is lost into the bilge. This engine oil tends to coat all of the exposed surfaces in the bilge and can combine with other contaminants, such as dust and certain marine life, to develop a coating or buildup of oily residue in the bilge. Also, during operation of the engine and during servicing of the engine, small amounts of lubricating oil are frequently lost into the bilge due to minute leakage thereof during prolonged engine operation. 
     Inboard engines, especially in larger marine vessels typically have power output drive shafts that extend through seals in wall surfaces of the vessel, especially the bottom and transom surfaces. There rotary shaft seals are almost always subject to a small volume of water leakage as the shafts are rotated during vessel operation. This water leakage will build up in the bilge of the vessel; consequently it must be periodically removed from the bilge and pumped overboard by means of bilge water discharge lines having orifice openings externally of the vessel&#39;s hull. For the reason that leaked oil continuously collects in the bilge and leaked water through the shaft seals also collects in the bilge, the bilge water in marine vessels is virtually always contaminated with oil that it picks up from bilge deposits. In the past, bilge water pumping systems have been provided which operate automatically or by manual selection and which function to pump bilge water, even though contaminated with oil, out of the bilge of the vessel and into the surrounding water. 
     The Federal Water Pollution Control Act (FWPCA) prohibits the discharge of oil or hazardous substances in to the waters of the United States. To comply with this act, large marine vessels have employed oil-water separators to remove the oil from the bilge water before discharging it into the surrounding waters. Conventional oil-water separators separate oil from water by a mechanical means which does not efficiently remove small oil particles. In enforcing the FWPCA, the Coast Guard requires any bilge water that is to be discharge overboard into the surrounding waters must contain less than fifteen parts per million (PPM) of oil, or else it cannot be discharged. If the vessel&#39;s oil-water separators cannot maintain the required PPM levels, the vessel must contain the water and discharge it while they are in port at a cost per gallon. Theoretically, if the water is continuously recirculated through the oil water separator, the oil PPM levels may fall below the allowable discharge level. But due to the large volume of water that needs to be treated within a limited period of time as these ships are traveling from port to port, the conventional oil-water separator cannot obtain the maximum PPM levels by the recirculation method alone. 
     It is an object of the subject invention to provide an oil removal filtration system for removing all oil and hydrocarbons from water. 
     It is another object of the subject invention to provide an oil removal system for bilge water of a marine vessel. 
     It is another object of the subject invention to provide an oil removal system which accepts an oily effluent from an oil-water separator and completely removes any oil and/or hydrocarbons to a level of zero PPM. 
     It is of further object of the subject invention to provide an oil removal system where the charge of the filter can be easily disposed of onboard the vessel. 
     SUMMARY OF THE INVENTION 
     The above stated objects are met by a new and improved oil removal filtration system for bilge water of marine vessels. The subject oil filtration system comprises a generally cylindrical, upright housing including an upper and lower end. The lower end of the housing is closed off by a first, circular end cap which includes a circular aperture adapted for a threaded coupling. The threaded coupling is connected to an inlet pipe which introduces an oily effluent into the filtration system. The upper end of the cylindrical housing is closed off by a second end cap similar to the first end cap. The second end cap comprises an aperture for coupling the system to an outlet pipe to discharge the oil-free water. The cylindrical housing defines an interior chamber which houses an oil/hydrocarbon removal filtering charge. The filter charge and system are manufactured under the trademark NOMIS by the assignee of this application. 
     The multi-component charge is assembled away from the filter housing and is inserted into the housing as one unit. The charge comprises a center tube which runs the length of the charge and is as long as the upright housing of the filter. The tube includes two ends: a first end adapted to couple to the aperture of the lower, first end cap of the filter housing and a second end which likewise is adapted to couple to the aperture of the upper, second end cap of the housing. The center tube includes a series of vertical slots placed circumferentially around the tube. A sleeve formed from an extruded polypropylene mesh is slid over the center tube to prevent particulate from entering the center tube. A micron-rated polypropylene fabric surrounds the sleeve and prevents the filtering medium from entering the center tube and being discharged. Additional fabric is then stitched into a cylindrical form with one end being secured to the lower, first end of the center tube. The area between the two polypropylene fabrics into then filled with the filtering medium. 
     The filtering medium consists of three parts: peat moss, anthracite and bentonite. The peat is an engineered material and has the characteristics of being hydrophobic and oleophilic, that is, has the ability to resist water while attracting oil or hydrocarbons. The engineered peat has a weight-absorption ratio of 8-to-1. Since peat is compressible, the anthracite and bentonite are added to the medium composition to create voids in it so that the peat does not become fully compressed and unable to pass water. While the carbon granules of the anthracite and the clay-like bentonite prevent the peat medium from being compressed, they are also oil absorbent and contribute to the oil/hydrocarbon removal of the filtering system. 
     Once the filtering medium is placed in the charge, the top of the outer polypropylene fabric is secured to a retaining disk to completely retain the filtering medium within the charge. The charge, which is substantially cylindrical when assembled, is placed in the interior chamber of the housing. A horizontal partitioning disk is positioned above the retaining disk to come into contact with the wall of the cylindrical housing to separate the interior chamber into a lower and upper chamber. The partitioning disk is formed to accept an O-ring to insure liquid-tight separation between the lower and upper chambers. The upper, second end cap is then secured in place by retaining elements to complete the filtering assembly. 
     In normal usage, effluent from the oil-water separators is pumped to the filtering system through the inlet pipe located at the bottom of the upright, cylindrical housing. The liquid fills the lower, interior chamber, and being pressurized, is forced through the filter medium and inner sleeves toward the center tube. As the liquid passes through the outer polypropylene fabric, particulate matter is caught in the fabric and prevented from entering the medium. As particulate-free liquid is forced through the medium, oil/hydrocarbons are absorbed and oil-free water flows to the upper chamber and out the upper, second end cap through the outlet pipe. The oil-free water can now be discharged into the surrounding waters without any environmental impact. 
     The output of the system will be continuously monitored to ensure the hydrocarbon levels are below 15 PPM. As the charge becomes spent or filled with oil/hydrocarbons, the output level will begin to rise indicating the charge needs to be replaced. The differential pressure across the filter will also be monitored. An increase in differential pressure will indicate the filter is becoming clogged or blocked. This blockage usually results from particulate matter loading on the outer surface of the polypropylene fabric. To resolve the particulate loading, especially when the charge is not spent, the new and improved filtering system has backwashing capabilities. In backwashing mode, air and water are introduced in the opposite direction from the normal flow path. While this process disposes of the particulate filtered by the system, the filtering medium will retain the oil/hydrocarbons. 
     Another advantage of the filtering system of the subject invention is in the disposal of the filtering charge. First, since the medium of the charge is organic, it is biodegradable. If the charge was buried in a landfill, it would retain the oil without leaching it into the ground water. Once the oil degrades, the medium would also biodegrade naturally. Secondly, because of the oil and chemistry of the medium, the charge will maintain a very high BTU value, about 17,000 per pound, when burned. Therefore, the charges can be incinerated onboard of a vessel and used as fuel by the vessel&#39;s incinerator. 
     These and other features of the present invention will become apparent from the following detailed description considered in connection with the accompanying drawings. It should be understood, however, that the drawings are designed for the purpose of illustration only and not as a definition of the limits of the invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a cross-sectional view of the oil/hydrocarbon removal filtration system of the subject invention. 
     FIG. 2 is a cross-sectional view of the charge of the oil/hydrocarbon removal filtration system of the subject invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to FIG. 1, the oil removal filtration system of the present invention is generally indicated by the reference numeral  10 . The subject oil filtration system comprises a generally cylindrical, upright housing  12  including a lower end  14  and an upper end  16 . The lower end  14  of the housing  12  is closed off by a first circular end cap  18  which includes a circular aperture  20  adapted for a threaded coupling  22 . The threaded coupling  22  is connected to an inlet pipe  24  which introduces an oily effluent from a conventional oil-water separator. The upper end  16  of the cylindrical housing  12  is closed off by a second end cap  26  similar to the first end cap  18 . The second end cap  26  comprises an aperture for coupling the system to outlet pipe  30  to discharge the oil-free water from the oil removal filtration system  10 . The cylindrical housing  12  defines an interior chamber  32  which houses an oil/hydrocarbon removal filtering charge  100 , which will now be describe in more detail. 
     Referring to FIG. 2, the multi-component charge  100  is assembled away from the filter housing  12  and is inserted into the housing  12  as one unit. The charge  100  comprises a center tube  102  which runs the length of the charge  100  and is as long as the upright housing  12  of the filter. The center tube  102  is composed of polyvinyl chloride (PVC) or chlorinated polyvinyl chloride (CPVC), as are the housing  12  and end caps  18 , 26  mentioned above. The center tube  102  includes a first end  104  which is adapted to couple to the aperture  20  of the lower, first end cap  18  of the filter housing  12  and a second end  106  which likewise is adapted to couple to the aperture  28  of the upper, second end cap  26  of the housing  12 . The center tube  102  includes a series of vertical slots  108  placed circumferentially around the tube  102 . As will be shown below, in normal use, water flowing through the filtration system  10  will exit the housing  12  through the center tube  102  after passing through the filtering medium. The large vertical slots  108  are position on the center tube  102  to allow ample open area for the fluid to exit the housing  12  resulting in the least amount of differential pressure across the charge  100 . To prevent the filtering medium from passing though the large vertical slots  108  of the center tube  102 , a sleeve  110  form from an extruded polypropylene mesh is slid over the center tube  102 . The sleeve  110  has perforations which are about an eighth of an inch in size, which is still large enough to allow the filtering medium to pass. A micron-rated polypropylene fabric  112  surrounds the sleeve  110  and prevents the filtering medium from entering the center tube  102  and being discharged. The fabric  112  is a  300  micron-rated monofilament polypropylene fabric which is in direct contact with the filtering medium. An additional polypropylene fabric  114  is then stitched into a cylindrical form with a diameter slightly smaller than a diameter of the cylindrical housing  12 . One end of the cylindrical fabric  114  is secured to a first disc  116  which is located at the lower end  104  of the center tube  102 . The fabric  114  is secured to the disc  116  with a standard heavy-duty cable tie. The area between the first polypropylene fabric  112  and the cylindrical fabric  114  defines an annular cavity  118  which holds and retains the filtering medium  120 . 
     The filtering medium  120  consist of three parts: peat, anthracite and bentonite. The peat is an engineered material and has the characteristics of being hydrophobic and oleophilic, that is, it has the ability to resist water while attracting oil or hydrocarbons. The engineered peat has a weight-absorption ratio of 8-to-1, meaning that for every pound or given volume of peat, it can remove eight times that weight in oil. Since the peat is compressible, the anthracite and bentonite are added to the medium composition to create voids  128  in it so that the peat does not become fully compressed and unable to pass water. Anthracite is a hard natural coal that burns slowly and gives off intense heat. Anthracite is not compressible and facilitates the flow of water through the peat. Bentonite is an absorbent aluminum silicate clay formed from volcanic ash. While the bentonite also facilitates the flow of water through the peat, it also has hydrocarbon absorbent properties. Although mixture of the three components of the medium can be custom blend depending of the application, the preferred mixture will be 50% peat by weight, 25% anthracite by weight and 25% bentonite by weight. 
     Once the filtering medium  120  is placed in the charge  100 , the top of the cylindrical fabric  114  is secured to a second disc  122  to completely retain the filtering medium  120  within the charge  100 . The charge  100 , which is substantially cylindrical when assembled, is placed in the interior chamber  32  of the housing  12 . A horizontal partitioning disc  124  is positioned above the second disc  122  to come into contact with the wall of the cylindrical housing  12 . The partitioning disc  124  divides the interior chamber  32  of the housing  12  into a lower chamber  36  and an upper chamber  38 . The partitioning disc  124  is formed to accept an O-ring  126  to ensure a liquid-tight separation between the lower  36  and upper  38  chambers. The upper, second end cap  26  is then secured in place by retaining elements  40  to complete the filtering assembly  10 . 
     In normal usage, a fluid from the oil-water separators is pump to the filtering system  10  through the inlet pipe  24  located at lower end  14  of the cylindrical housing  12 . The liquid fills the lower, interior chamber  36  and becomes pressurized by the partitioning disc  124 . The liquid is then forced through the filtering medium  120  and the inner sleeve  110  toward the center tube  102 . As the liquid passes through the outer polypropylene fabric  114 , particulate matter is caught in the fabric and is prevented from entering the medium  120 . As particulate-free liquid is forced through the medium  120 , oil/hydrocarbons are absorbed and oil-free water flows to the upper chamber  38  and out the upper, second end cap  26  through the outlet pipe  30 . The oil-free water can now be discharged into the surrounding waters without any environmental impact. 
     Although the focus is oil, the filtering medium  120  will absorb any type of hydrocarbon due to the oleophilic nature of the medium  120 . The medium  120  encapsulates hydrocarbons virtually instantaneously requiring no prolonged contact time. Once encapsulated, the hydrocarbons will not leach back from the medium  120 . A typical listing of liquid hydrocarbons which can be removed from contaminated water in accordance with the present invention includes gasoline, motor oil, diesel oil, benzene, alkyl benzene such as ethyl benzene, o-, m-, and p-xylene, chlorinated solvents, polychlorinated bisphenols, mixtures thereof, etc. It is also important to note that the filtering system  10  of the present invention can also remove emulsified oil, that is, oil that is in solution as opposed to separated from water. So when an oil-water separator can only separate oil if it is not emulsified because it has to allow mechanical separation, the filtering medium  120  of the subject invention will absorb emulsified oil in addition to pure hydrocarbons. 
     To illustrate the effectiveness of its oil/hydrocarbon removal capability, the following non-limiting working example is now presented. 
     Assume for the purposes of this example that a flow rate of 44gallons per minute of bilge water contains 100 PPM of oil or hydrocarbons. Given the above flow rate and oil content, 2.2 pounds of oil per hour would flow though the filtering system. A typical filtering system for large marine vessels would be configured with 8 filters piped in parallel, with each filter holding 12 pounds of filtering medium, therefore, a total system would comprise 96 pounds of filtering medium. Using a mixture of 50% peat by weight, 25% anthracite by weight and 25% bentonite by weight, the filtering medium will have an absorption rate of 4× its weight or approximately 384 pounds of oil. Given the fact that oil weighs approximately 8 pounds, 48 gallons of oil will be removed by the filtering system. At 2.2 pounds of oil per hour in the flow stream, the 8 filtering changes would run for 174.5 hours before the system reaches a saturation point of 384 pounds of oil where the charge would have to be replaced. During this time period, 1,745 tons or 460,680 gallons of water can be treated resulting in a discharge water containing 0 PPM of oil/hydrocarbons. 
     The output of the system will be continuously monitored to ensure the hydrocarbon levels are below 15 PPM. As the charge  100  becomes spent or filled with oil/hydrocarbons, the output level will begin to rise indicating the charge needs to be replaced. The differential pressure across the filter  10  will also be monitored. An increase in differential pressure will indicate the filter  10  is becoming clogged or blocked. This blockage usually results from particulate matter loading on the outer surface of the polypropylene fabric  114 . To resolve the particulate loading, especially when the charge is not spent, the new and improved filtering system has backwashing capabilities. In backwashing mode, air and water are introduced in the opposite direction from the normal flow path. While this process disposes of the particulate filtered by the system, the filtering medium  120  will retain the oil/hydrocarbons. 
     The charge  100  of the filtering system  10  of the subject invention can be disposed in two ways without any environmental impact. First, since the medium  120  of the charge  100  is organic, it is biodegradable. If the charge  100  was buried in a landfill, it would retain the oil without leaching it into the ground water. Once the oil degrades, the medium  120  would also biodegrade naturally. Secondly, because of the oil and chemistry of the medium, the charge  100  will maintain a very high BTU value, about 17,000 per pound, when burned. Therefore, the charges  100  can be incinerated onboard of a vessel and used as fuel by the vessel&#39;s incinerator. Also, due to the composition of the medium  120 , the charge  100  will burn cleanly resulting in ash of only 2% of the total weight of the charge  100 . 
     As it readily apparent numerous modifications and changes may readily accurate to those skill in the art, and hence, it is not desire to limit the invention to the exact construction and operation as shown and described, and accordingly, all suitable modification equivalent may be resorted to form within the scope of the invention as claimed.