Abstract:
An apparatus for applying a dilute antimicrobial solution to workpieces, such as raw poultry, includes a housing and a sprayer positioned to direct a first volume of dilute antimicrobial solution onto workpieces conveyed through a passage of the housing. A portion of the first volume that does not adhere to the workpieces is collected at a lower portion of the housing and passed to a recycle tank. Solution is transported between the recycle tank and sprayer and includes a supply segment to receive solution from the recycle tank, an application segment to receive the first volume from the supply segment for passage to the sprayer, and a bypass segment, separate from the application segment, to receive a second volume of the solution from the supply segment for return passage to the recycle tank without passage through the sprayer.

Description:
[0001]    This application is a continuation of co-pending U.S. patent application Ser. No. 14/790,246, filed Jul. 2, 2015; which is a continuation of U.S. patent application Ser. No. 14/471,846, filed Aug. 28, 2014, issued as U.S. Pat. No. 9,185,929 on Nov. 17, 2015; which is a continuation of U.S. patent application Ser. No. 10/535,030, filed Oct. 10, 2008, issued as U.S. Pat. No. 9,072,315 on Jul. 7, 2015; which is the 371 National Stage entry of PCT/US2003/035933, filed Nov. 12, 2003; which claims the benefit of U.S. Provisional Application Ser. No. 60/425,679, filed on Nov. 12, 2002, the disclosures of which are incorporated herein by reference in their entirety. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    This invention relates to an antimicrobial application system, and more particularly to an antimicrobial application system with recycle features for use in connection with food products and surfaces and other items associated with food processing. 
         [0003]    Antimicrobial application systems, including spray cabinets are known in the art. U.S. patent application Ser. No. 10/001,896, filed on Nov. 19, 2002 by Gary Nolen, discusses a number of such systems and highlights a number of the advantages and disadvantages of these systems. The disclosure of U.S. patent application Ser. No. 10/001,896 (Nolen) is incorporated herein by reference. The spray application systems disclosed in that application offer a number of advantages over earlier systems, as discussed in more detail in that application. Still, the present inventors have further refined and built upon those systems to offer alternate embodiments offering additional flexibility. For example, it may be desirable to recycle the antimicrobial that is applied to the workpieces. Adding equipment and steps to allow for recycling adds to the cost and complexity of a system, so it will not always be preferred. Still, using recycling reduces consumption of the antimicrobial and water and reduces the amount of waste material in need of disposal. This may be desirable for any number of reasons such as environmental concerns, raw material costs, raw material storage limitations, disposal costs, and regulatory issues involving disposal of wastewater and some antimicrobials. Accordingly, under  many circumstances, it will be desirable to recycle the antimicrobial for multiple applications to workpieces to be treated. 
         [0004]    Recycling of liquids applied to some types of workpieces in a process line is generally known in the art. Still, recycling liquids in connection with food processing and items associated with food processing presents a number of special issues and concerns, particularly concerning adulteration, contamination, and cross-contamination. These concerns typically argue against recycling or lead to the use of slow, cumbersome, undesirable extra steps and extra equipment that add to the cost and complexity of a system. One such complex system is disclosed in U.S. Pat. No. 6,348,227, issued to Caracciolo, Jr. in 2002, the disclosure of which is incorporated herein by reference. 
       SUMMARY OF THE INVENTION 
       [0005]    It is therefore an object of the present invention to provide an antimicrobial application system that provides for the safe, effective, and cost efficient recycling of antimicrobial in connection with food processing and items associated with food processing. 
         [0006]    It is a further object of the present invention to provide a system of the above type that reduces raw material consumption without sacrificing safety. 
         [0007]    It is a still further object of the present invention to provide a system of the above type that provides for periodic, batch style separation and disposal of spent antimicrobial. 
         [0008]    It is a still further object of the present invention to provide a system of the above type which automatically monitors and maintains a desired composition of the antimicrobial composition to be recycled. 
         [0009]    It is a still further object of the present invention to provide a system of the above type which provides for improved recapture and return of an antimicrobial composition applied to workpieces.  
         [0010]    It is a still further object of the present invention to provide a system of the above type which automatically compensates for additional liquids passing from wetted workpieces to the recycled antimicrobial composition. 
         [0011]    It is a still further object of the present invention to provide a system of the above type which is capable of providing continuous, real-time monitoring and control of the composition of an antimicrobial composition. 
         [0012]    It is a still further object of the present invention to provide a system of the above type which reduces waste leaving the system and waste disposal costs associated therewith. 
         [0013]    It is a still further object of the present invention to provide a system of the above type which provides a safe waste stream that may be safely drained into a wastewater system. 
         [0014]    It is a still further object of the present invention to provide a system of the above type that increases the flexibility and advantages of the spray application systems and spray cabinets disclosed in U.S. patent application Ser. No. 10/001,896 (Nolen). 
         [0015]    It is a still further object of the present invention to provide a system of the above type that provides a simple, reliable method of monitoring and controlling the composition of a composition to be recycled. 
         [0016]    Toward the fulfillment of these and other objects and advantages, the antimicrobial application system of the present invention comprises an antimicrobial application unit and a recycle unit. An initial, dilute antimicrobial composition is prepared with automatically controlled concentration composition of the antimicrobial solution. The composition is provided to the antimicrobial application unit and applied to workpieces, such as raw poultry. After application to the workpieces, the composition is returned to the recycle tank of the recycle unit. The concentration of the antimicrobial in the recycle tank is monitored, and additional antimicrobial is automatically added if the concentration of the antimicrobial in the composition  falls below a desired amount. The composition is periodically diverted to a capture tank, and the antimicrobial is selectively removed from the composition. The removed antimicrobial and remaining composition are then disposed of in appropriate manners. The antimicrobial is preferably a quaternary ammonium compound, is more preferably an alkylpyridinium chloride, and is most preferably cetylpyridinium chloride. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0017]    The above brief description, as well as further objects, features and advantages of the present invention will be more fully appreciated by reference to the following detailed description of the presently preferred but nonetheless illustrative embodiments in accordance with the present invention when taken in conjunction with the accompanying drawing, wherein: 
           [0018]      FIG. 1  is a schematic view of an antimicrobial application system of the present invention; 
           [0019]      FIG. 2  is a side elevation view of a portion of a recycle unit of the present invention; and 
           [0020]      FIG. 3  is a schematic view of an alternate embodiment of an antimicrobial application system of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0021]    Referring to  FIG. 1 , the reference numeral  10  refers in general to an antimicrobial application system of the present invention. The antimicrobial application system  10  of the present invention generally comprises an antimicrobial application unit  12  and a recycle unit  14 , and may include a capture unit  15 . 
         [0022]    The antimicrobial application unit  12  may take any number of configurations. In the preferred embodiment, the antimicrobial application unit  12  takes the general form of one of the embodiments of a spray application system as disclosed in U.S. patent application Ser. No.  10/001,896 (Nolen). One possible exception is that the liquid barriers described in U.S. patent application Ser. No. 10/001,896 are not used in the preferred embodiment of the present invention. A conveyor  16  passes through a housing  18  for moving workpieces  20 , such as raw poultry, through the housing  18 . As described in more detail below, a drip tray or pan  22  extends downstream of the housing  18 , disposed below the conveyor  16  and the workpieces  20  carried thereby. Examples of spray application systems that might be used in connection with the present invention are discussed in detail in U.S. patent application Ser. No. 10/001,896 (Nolen) and will not be discussed in more detail here. It is of course understood that the antimicrobial application unit  12  is not limited to those embodiments or to spray application systems in general. The antimicrobial application unit  12  may apply a composition such as an antimicrobial composition to any number of different kinds and types of workpieces  20  in any number of different ways. Methods of application used by such an application unit  12  may include but are not limited to spraying, misting, fogging, immersing, pouring, dripping, and combinations thereof. It is understood that the system  10  may be used to treat a wide variety of different workpieces  20 , including but not limited to meat, poultry, fish, fresh and salt water seafood, fruits, vegetables, other foodstuffs, animals, food packaging, and items and surfaces related to food or food processing. It is also understood that the workpieces  20  may be live, dead, raw, hide-on, carcass, pieces, cooked, prepared, processed, partially processed, ready to eat, or ready to cook. It is further understood that the system  10  may be used to treat workpieces  20  completely unrelated to food or food processing items. 
         [0023]    A rigid member  24 , such as stainless steel tubing, is affixed to the housing  18 , preferably at a downstream end of the housing  18 . As best seen in  FIG. 3 , the rigid member  24  has parallel arms  26  that are aligned on opposite sides of the conveyor line  16 . A series of matching openings  28  are provided in each arm  26  for housing counters or sensors. Protective lenses  30  provide watertight seals, preferably NEMA 4 seals, to protect the counters from damage that might otherwise occur under the harsh washdown conditions to which the systems  10  are routinely subjected. Three counters are preferably provided in series. As best seen in  FIG. 1 , the arms  26  are disposed so that the counters are aligned to detect the presence or absence of workpieces  20 . The use of three counters provides redundancy and increases accuracy. In that regard, the counters are operably connected to a controller such as a central control unit  32  or  164 , and the counts taken by the three counters are continuously compared. If one counter provides a reading or count that differs from that provided by the other two, the central control unit  32  or  164  will typically be programmed to disregard the reading of the inconsistent counter and rely instead upon the readings of the other two counters. The logic and interpretation of the different readings may of course be modified in any number of ways. 
         [0024]    The recycle unit  14  dilutes a concentrated antimicrobial composition or solution to obtain a dilute antimicrobial composition or solution and provides the dilute antimicrobial solution to the antimicrobial application unit  12 . An antimicrobial source, such as a supply tank  34 , is connected to the housing  18  via antimicrobial supply line or conduit  36 . A chemical feed pump  38  is disposed in antimicrobial supply line  36 . The pump  38  is operably connected to a controller  40  for reasons to be described below. The antimicrobial preferably comprises a quaternary ammonium compound, more preferably comprises an alkylpyridinium chloride, and most preferably comprises cetylpyridinium chloride. More particularly, the concentrated antimicrobial solution preferably comprises a concentrated solution of a quaternary ammonium compound as described in U.S. patent application Ser. No. 09/494,374, filed on Jan. 31, 2000 by Compadre et al. The disclosure of U.S. patent application Ser. No. 09/494,374 (Compadre et al.) is incorporated herein by reference. The concentrated solution preferably comprises an antimicrobial and a solubility enhancing agent, and the solubility enhancing agent preferably comprises propylene glycol. The quaternary ammonium compound is preferably present in the concentrated solution in a weight percent of approximately 40%, and the solubility enhancing agent is preferably present in the concentrated solution in a weight percent of approximately 60%. It is of course understood that any number of different antimicrobials and solubility enhancing agents may be used, and the concentrated and dilute solutions may have any number of different components and compositions, including but not limited to the components and compositions of the concentrated and dilute solutions disclosed in U.S. patent application Ser. No. 09/494,374 (Compadre et al.). Concerns of adulteration, contamination, or cross-contamination are eliminated or alleviated because of the broad-spectrum efficacy of the preferred antimicrobial solutions and because of the filtration and automatic concentration measures.  
         [0025]    One or more recycle tanks  42  are provided. A return line or conduit  44  extends between the housing  18  and the recycle tank  42  for passing liquid from the housing  18  to the tank  42 . Multiple return lines  44  may be used to connect multiple antimicrobial application units  12  to the recycle tanks  42 . A filter  46  is disposed in the housing  18  or in the return line  44 . The filter  46  is preferably a wire mesh filter, such as a 100 mesh filter, sized to capture visible particulate matter in the effluent from the antimicrobial application unit  12 . Visible particulate matter in the effluent will typically be minimal because of upstream washing that will typically be performed on the workpieces  20 . First and second filters  48  and  50  are associated with each tank  42  and are disposed between the tank  42  and a system pump  52  to provide for parallel flow between the tank  42  and the system pump  52 . Valves  54  or other means are provided for selectively directing liquid passing from the tank  42  to the system pump  52  through either the first filter  48  or the second filter  50 . This allows the system  10  to continue operating while one of the filters  48  or  50  is being cleaned, replaced, or repaired. A three-way valve  56  is disposed in conduit  58  for reasons to be discussed below. A purge or capture line  60  passes from the valve  56  to the capture tank  62 . A capture pump  64  is disposed in capture line  60 . Although the recycle tank  42  may include an impeller or some other stirring or agitation means, no such stirring or agitation means is used in the preferred embodiment. A feed line  66  passes from the system pump  52  to the housing  18  and is connected to one or more sprayers  68 . Multiple feed lines  66  may be used, or the feed line  66  may be branched or divided, if desired, to connect the recycle tank  42  to multiple antimicrobial application units  12 . A bypass conduit  70  having a relief valve  72  is disposed in the feed line  66 . A diverting line  74  is also disposed in the feed line  66 . The diverting line  74  is connected to a dilution pump  78  and has a pressure regulator  80  disposed therein. 
         [0026]    A source of potable water  82 , such as tap water, is connected to the recycle tank  42  via water supply line or conduit  84 . A diverting line  86  is also disposed in water supply line  84 . The diverting line  86  is connected to a dilution pump  88  and has a pressure regulator  90  disposed therein. The pressure regulators  80  and  90  preferably regulate the pressure in lines  74  and  86  to a pressure lower than the pressures in lines  66  and  84  and preferably regulate the pressure in lines  74  and  86  down to approximately  15  psig. The dilution pumps  78  and  88  are electrically interlocked to provide for matched, stroke for stroke pumping action. The dilution pumps  78  and  88  are also sized to provide for a desired, fixed dilution ratio. The dilution ratio is preferably less  than or equal to approximately 1 part dilute composition to 1 part water, is more preferably less than or equal to approximately 1 part dilute composition to 30 parts water, and is most preferably less than or equal to approximately 1 part dilute composition to 60 parts water. Conduits  92  and  94  exit the dilution pumps  78  and  88  and are disposed to route liquids from the dilution pumps  78  and  88  to a static mixer  96 . The static mixer is preferably an inline, auger style static mixer. 
         [0027]    A sensor  98  is disposed at the discharge end of the static mixer  96 . In the preferred embodiment, the sensor  98  is an ultraviolet light spectrophotometer or UV spec sensor. Of course it is understood that any number of different types of sensors  98  may be used, including but not limited to infrared, visible light, or ultraviolet sensors. The sensor  98  is capable of detecting the concentration of the antimicrobial in the solution exiting the static mixer  96 . The controller  40  operably connects the sensor  98  to the chemical feed pump  38 . The controller  40  is capable of receiving a signal from the sensor  98  and sending a corresponding on/off signal to the chemical feed pump  38 . A discharge line  100  passes from the sensor  98  to the capture or purge tank  62 . 
         [0028]    A siphon  102  is disposed in the capture tank  62  and is connected to a drain line  104 . The drain line  104  passes from the capture tank  62  to an antimicrobial separation unit  106 . The antimicrobial separation unit  106  preferably comprises one or more filters  108 , such as disposable carbon filters, that selectively remove the antimicrobial from the composition. A disposal line  110  exits the antimicrobial separation unit  106  for disposing of water and any other components remaining after the antimicrobial is selectively removed. It is understood that a separation unit  106  may or may not be used and that any number of different separation methods may be used. It is also understood that filters  108  may be disposable or reusable. The central control unit  32  is used to control the entire system  10 . 
         [0029]    In operation, a dilute antimicrobial solution will typically be prepared and used for one spray cycle that will typically last for one day. The dilute antimicrobial solution will then be discarded, disposed of, or removed from the system  10  for further processing. It is of course understood that the spray cycle may be of any number of different durations. It is also understood that the system  10  may be operated in batch mode, in steady-state mode, or in any  number of different types or combinations of modes of operation. A new spray cycle will typically begin each morning with an empty and clean recycle tank  42  and an empty and clean capture tank  62 . Before the antimicrobial application unit  12  is activated, and before the system pump  52  is turned on, the dilute antimicrobial solution is prepared. In that regard, a desired amount of tap water is fed to the recycle tank  42 . The recycle tank  42  is preferably filled to approximately one third to approximately one half of its capacity with potable water. The concentration pump  38  is activated to feed the concentrated antimicrobial composition to the housing  18 , where it drains through return conduit  44 , and to the recycle tank  42 , until a predetermined amount of the concentrate composition is provided. The concentrate composition combines with the water in the recycle tank  42  to form a dilute solution of the desired concentration. The desired ranges of the concentration of antimicrobial in dilute solution include but are not limited to the concentration ranges of the antimicrobial in the dilute solutions disclosed in U.S. patent application Ser. No. 09/494,374 (Compadre et al.). 
         [0030]    Once the desired concentration is obtained in the recycle tank  42 , the system pump  52  is activated, and the dilute solution is supplied to the antimicrobial application unit  12 . The dilute solution provided to the antimicrobial application unit  12  is not potable. Still, contamination or cross-contamination of the workpieces  20  is not a concern because of the safety and broad spectrum efficacy of the dilute antimicrobial solution used. The recycle unit  14  supplies the dilute antimicrobial solution to the antimicrobial application unit or units  12  at any number of different flow rates and pressures. These flow rates and pressures may include, but are not limited to, the flow rates and pressures discussed in U.S. patent application Ser. No. 10/001,896 (Nolen). The bypass conduit  70  and relief valve  72  route a portion of the dilute composition to a lower portion of the housing  18  so that it does not pass through the sprayers  68  and is not applied to the workpieces  20 . The ratio of dilute composition passing through the bypass conduit  70  versus passing to the sprayers  68  will typically be greater than or equal to approximately 1:1 and will more typically be greater than or equal to approximately 2:1. The dilute composition passing through the bypass conduit  70  provides for improved mixing of the captured composition and any concentrate composition that might be added. The use of the bypass conduit  70  and relief valve  72  provides greater flexibility in providing dilute composition to sprayers  68  at or within desired pressure ranges. The use of the bypass conduit  70  and relief valve  72  also makes it easier  to continue to provide dilute composition to the sprayers  68  at consistent pressure as additional spray application units  12  are brought online or taken offline and regardless of the number of spray application units  12  that are online. 
         [0031]    Once the recycle unit  14  is supplying the dilute antimicrobial solution to the antimicrobial application unit  12 , the workpieces  20  to be processed, such as raw poultry, are moved by the conveyor  16 , through the housing  18 , and the dilute antimicrobial solution is applied to the workpieces  20 , such as by spraying. The portion of the dilute antimicrobial solution that does not adhere to the workpieces  20  collects in a drain and is returned via return line  44 , through filter  46 , and to the recycling tank  42  for reuse. The length of the drip tray  22  is selected so that it will catch drops from workpieces  20  exiting the housing  18  for approximately 1 minute after the workpieces  20  exit the housing  18 . This enhances the recovery of the dilute antimicrobial solution and reduces downstream losses. Although not preferred, liquid barriers such as water spray curtains may be used in the housing  18 . Also, the workpieces  20  may be wet from upstream washing, so additional water may enter the recycle tank  42 , decreasing the concentration of the antimicrobial in the dilute solution. 
         [0032]    It is desirable to avoid concentration spikes in the dilute composition, particularly in the dilute composition exiting the sprayers  68  and passing through the diverting line  74  for routing to sensor  98 . Accordingly, steps are taken to insure thorough mixing of the dilute composition being recycled between the recycle unit  14  and the antimicrobial application unit  12 . This is one reason why the concentrate supply line  36  routes the concentrated antimicrobial solution to the housing  18  rather than directly to the recycle tank  42 . By the time the concentrate composition mixes with dilute compositions from the sprayers  68  and from the bypass line  70 , passes through return line  44 , filter  44 , recycle tank  42 , filter  48  or  50 , and system pump  52 , the resultant liquid is thoroughly mixed and has a relatively uniform composition. 
         [0033]    A preferred sensor  98 , such as a spectrophotometer, is typically used to measure very low concentrations of a component in a composition. It is therefore important to provide a liquid that has not only has a relatively uniform composition but also a very low concentration of the antimicrobial or component to be measured. Often, it will not be practical or feasible to obtain accurate, reliable readings for the antimicrobial at the concentration ranges typically found in the recycle tank  42 . Diluting the composition before taking a concentration reading will offer greater flexibility in the selection of a sensor  98  for monitoring the concentration of the antimicrobial. Samples of the composition exiting the recycle tank  42  are therefore taken and further diluted, to yield further diluted compositions in which the antimicrobial is present within a concentration range that is readily and accurately measured by the sensor  98 . The dilution ratio of the dilution pumps  78  and  88  is selected to provide the desired degree of dilution, such as within the ranges discussed above. The pumps  78  and  88  are set on a timer to take samples at a set interval, each sample being taken for a set duration of time. It is understood that the concentration may be monitored at any number of different intervals and for any number of different durations and that the concentration may be continuously monitored. The electrically interlocked pumps  78  and  88  provide the dilute composition and water in the desired fixed ratio to further dilute the dilute composition. Using electrically interlocked pumps at a desired, fixed dilution ratio simplifies controls needed to operate the system  10 . It is of course understood that the pumps need not be interlocked, the dilution ratio need not be fixed, and any number of different methods may be used to select, control, and adjust the dilution ratio as desired. 
         [0034]    The dilute composition and water are combined and passed through the static mixer  96  to provide for thorough mixing, further reducing the risk of concentration spikes as the liquid passes the spectrophotometer  98 . The spectrophotometer  98  senses the concentration of the antimicrobial in the passing liquid. The sensor  98  is operably connected to the controller  40 . Accordingly, if the sensor  98  detects that the concentration of antimicrobial falls below a desired amount, the controller  40  activates the chemical feed pump  38  to add more of the concentrated antimicrobial solution into the housing  18  and to bring the concentration of the antimicrobial in the dilute antimicrobial solution back up to the desired level. The system  10  can be configured to allow the potable water to be controlled in this fashion as well, but it is unlikely that there will be a need to add make-up water. 
         [0035]    It is undesirable to route the highly diluted liquid that passes the sensor  98  back into the recycle tank  42 , so it is routed to the capture tank  62 . The siphon  102  in the capture tank  62  allows the liquid to collect in the capture tank  62 , until the liquid reaches a desired level. When the liquid in the capture tank  62  reaches the desired level, the siphon  102  empties the capture tank  62 , passing the liquid through conduit  104  and to the disposable carbon filters  108  of the antimicrobial separation unit  106 . The disposable filters  108  capture the antimicrobial to selectively remove the antimicrobial from the solution. Using the siphon  102  reduces or eliminates channeling problems that might otherwise arise if the liquid were allowed to continuously drip from the capture tank  62  onto the carbon filters  108 . 
         [0036]    At the end of the spray cycle, such as at the end of a shift or a day or other chosen period of time, the valve  56  is actuated to divert the dilute antimicrobial solution received from the recycle tank  42  to the capture pump  64 . The capture pump  64  empties the recycle tank  42  and passes the dilute antimicrobial solution to the capture tank  62 . When the liquid reaches a desired level in the capture tank  62 , the siphon  102  routes the liquid through conduit  104  and to the disposable carbon filters  108  of the antimicrobial separation unit  106 . The disposable filters  108  capture the antimicrobial to selectively remove the antimicrobial from the solution. When the antimicrobial impregnated disposable filters  108  are spent, they are then disposed of in an appropriate manner, such as by incineration or disposal at an approved landfill. The remaining, relatively antimicrobial-free liquid is then disposed of in an appropriate manner, such as by being drained into a wastewater system of a plant. The frequency with which the system  10  will need to be purged will depend upon any number of factors, such as the number of workpieces  20  to be processed by the antimicrobial application unit  12  and the volume of the dilute antimicrobial solution required to charge the system  10  at the beginning of a spray cycle. A periodic purge of the system  10  will typically be used. 
         [0037]    An alternate embodiment of the antimicrobial application system  10  is disclosed in  FIG. 3 . The antimicrobial application system  10  of the alternate embodiment also generally comprises an antimicrobial application unit  112  and a recycle unit  114  and will typically include a capture unit  115 . 
         [0038]    The antimicrobial application unit  112  may take any number of configurations. For example, the antimicrobial application unit  112  may take the general form of one of the embodiments of a spray application system as disclosed in U.S. patent application Ser. No. 10/001,896 (Nolen). In the preferred embodiment, spray containment barriers are not used. A conveyor  116  passes through a housing  118  for moving workpieces  120 , such as raw poultry, through the housing  118 . As described in more detail below, a drip tray or pan  122  extends downstream of the housing  118 , disposed below the conveyor  116  and the workpieces  120  carried thereby. The spray application systems are discussed in detail in U.S. patent application Ser. No. 10/001,896 (Nolen) and will not be discussed in more detail here. It is of course understood that the antimicrobial application unit  112  is not limited to those embodiments or to spray application systems in general. The antimicrobial application unit  112  may apply an antimicrobial to any number of different types of workpieces  120  in any number of different conventional ways. Methods of application used by such an antimicrobial application unit  112  may include but are not limited to spraying, misting, fogging, immersing, pouring, dripping, and combinations thereof It is understood that the system  10  may be used to treat a wide variety of different workpieces  120 , including but not limited to meat, poultry, fish, fruits, vegetables, other foodstuffs, animals, food packaging, and items and surfaces related to food or food processing. It is also understood that the workpieces  120  may be live, dead, raw, cooked, prepared, processed, partially processed, or ready to eat. It is also understood that the system  10  may be used to treat workpieces  120  completely unrelated to food or food processing items. 
         [0039]    The recycle unit  114  dilutes a concentrated antimicrobial composition to obtain a dilute antimicrobial composition and provides the dilute antimicrobial composition to the antimicrobial application unit  112 . A recycle tank  124  is provided. The recycle tank  124  may include an impeller or some other stirring or agitation means. A source of potable water  126 , such as tap water, is connected to the recycle tank  124  via water supply line  128 . Similarly, an antimicrobial source, such as a supply tank  130 , is connected to the recycle tank  124  via antimicrobial supply line  132 . The antimicrobial preferably comprises a quaternary ammonium compound, more preferably comprises an alkylpyridinium chloride, and most preferably comprises cetylpyridinium chloride. More particularly, the concentrated antimicrobial composition preferably comprises a concentrated composition of a quaternary ammonium compound as described in U.S. patent application Ser. No. 09/494,374, filed on Jan. 31, 2000 by Compadre et al. The disclosure of U.S. patent application Ser. No. 09/494,374 (Compadre et al.) is incorporated herein by reference. The concentrated composition preferably comprises an antimicrobial and a solubility enhancing agent, and the solubility enhancing agent preferably comprises propylene glycol. The quaternary ammonium compound is preferably present in the concentrated composition in a weight percent of approximately 40%, and the solubility enhancing agent is preferably present in the concentrated composition in a weight percent of approximately 60%. It is of course understood that any number of different antimicrobials and solubility enhancing agents may be used, and the concentrated and dilute compositions may have any number of different components and compositions, including but not limited to the components and compositions of the concentrated and dilute compositions disclosed in U.S. patent application Ser. No. 09/494,374 (Compadre et al.). Concerns of contamination or cross-contamination are eliminated or alleviated because of the broad spectrum efficacy of the preferred antimicrobial compositions. 
         [0040]    A chemical feed pump  134  is disposed in antimicrobial supply line  132 . A sensor  136  is connected to the recycle tank  124  via lines  138  and  140 . In the preferred embodiment, the sensor is an ultraviolet light photospectrometer or UV spec sensor. It is of course understood that any number of different sensors and any number of different light sensors may be used. For example, the light sensor may use light having wavelengths that fall in any number of different ranges, including but not limited to ultraviolet light, visible light, infrared light, and combinations thereof Of course it is understood that any number of different types of sensors  136  may be used, including but not limited to infrared, visible light, or ultraviolet sensors. The sensor  136  is capable of detecting the concentration of the antimicrobial in the composition in the recycle tank  124 . A controller  142  operably connects the sensor  136  to the chemical feed pump  134 . The controller  142  is capable of receiving a signal from the sensor  136  and sending a corresponding on/off signal to the chemical feed pump  134 . A feed line  144  exits the recycle tank  124 , passes through the system pump  146 , through a valve  148 , and connects to the antimicrobial application unit  112 . Multiple feed lines may be used, or the feed line  144  may be branched or divided, if desired, to connect the recycle tank  124  to multiple antimicrobial application units. The valve  148  is preferably a three-way valve. A return line  150  exits the antimicrobial application unit  112 , passes through a filter  152 , and connects to the recycle tank  124 . Multiple return lines may be used to connect multiple antimicrobial application units to the recycle tank  124 . The filter  152  is preferably a wire mesh filter sized to capture visible particulates in the effluent from the antimicrobial application unit  112 . Visible particulates in the effluent will typically be minimal because of upstream washing that will typically be performed on the workpieces  120 . A capture line  154  passes from the valve  148  to a capture tank  156 . A drain line  158  passes from the capture tank  156  to an antimicrobial separation unit  160 . The antimicrobial separation unit  160  preferably comprises one or more disposable filters selected to separate the antimicrobial from water. A disposal line  162  exits the antimicrobial separation unit  160  for disposing of water after the antimicrobial is removed. A central control unit  164  is used to control the entire system  10 . 
         [0041]    In operation, a dilute antimicrobial composition will typically be prepared and used for one spray cycle that will typically last for one day. The dilute antimicrobial composition will then discarded, disposed of, or removed from the system  10  for further processing. Accordingly, each spray cycle, typically beginning each morning, begins with an empty and clean recycle tank  124  and an empty and clean purge or capture tank  156 . Before the antimicrobial application unit  112  is activated, and before the system pump  146  is turned on, the dilute antimicrobial composition is prepared. In that regard, a desired amount of tap water is fed to the recycle tank  124 . The recycle tank  124  is preferably filled to approximately one third to approximately one half of its capacity with potable water. The central control unit  164  activates the sensor  136  so that liquid from the recycle tank  124  passes through the sensor  136 . The sensor  136  initially detects the absence of antimicrobial (no absorbance at 260 nm), so the controller  142  activates the chemical feed pump  134  to begin metering the concentrated antimicrobial composition into the recycle tank  124 . When the concentration of the antimicrobial in the dilute composition in the recycle tank  124  reaches a desired level, the sensor  136  and, in turn, the controller  142  turn off the chemical feed pump  134 . The desired ranges of the concentration of antimicrobial in dilute composition include but are not limited to the concentration ranges of the antimicrobial in the dilute compositions disclosed in U.S. patent application Ser. No. 09/494,374 (Compadre et al.). Once the desired concentration is obtained in the recycle tank  124 , the system pump  146  is activated, and the dilute composition is supplied to the antimicrobial application unit  112 . The dilute composition provided to the antimicrobial application unit  112  is not potable. Still, contamination or cross-contamination of the workpieces  120  is not a concern because of the safety and broad spectrum efficacy of the dilute antimicrobial composition used. The recycle unit  114  supplies the dilute antimicrobial composition to the antimicrobial application unit or units  112  at any number of different flow rates and pressures. These flow rates and pressures may include, but are not limited to, the flow rates and pressures discussed in U.S. patent application Ser. No. 10/001,896 (Nolen). 
         [0042]    Once the recycle unit  114  is supplying the dilute antimicrobial composition to the antimicrobial application unit  112 , the workpieces  120  to be processed, such as raw poultry, are moved by the conveyor  116 , through the housing  118 , and the dilute antimicrobial composition is applied to the workpieces  120 , such as by spraying. The portion of the dilute antimicrobial composition that does not adhere to the workpieces  120  collects in a drain and is returned via return line  150 , through filter  152 , and to the recycling tank for reuse. The length of the drip tray  122  is selected so that it will catch drops from workpieces  120  exiting the housing  118  for approximately 1 minute after the workpieces  120  exit the housing  118 . This enhances the recovery of the dilute antimicrobial composition and reduces downstream losses. Water spray curtains may be used in the application chamber, and the workpieces  120  may be wet from upstream washing, so additional water will typically enter the recycle tank  124 . 
         [0043]    The sensor  136  continuously monitors the concentration of the antimicrobial in composition in the recycling tank. If the concentration falls below a desired amount, the sensor  136  activates the chemical feed pump  134  to add more of the concentrated antimicrobial composition and to bring the concentration of the antimicrobial in the dilute antimicrobial composition back up to the desired level. The system  10  can be configured to allow the tap water to be controlled in this fashion as well, but it is unlikely that there will be a need to add water. The dilute antimicrobial composition is thereby used repeatedly to treat any number of units of the workpieces  120  being processed. 
         [0044]    At the end of the spray cycle, such as at the end of a shift or a day or other chosen period of time, the valve  148  is actuated to divert the dilute antimicrobial composition received from the system pump  146  through capture line  154  to the purge tank  156 . The liquid in the purge tank  156  is gravity fed through the drain line  158  to the disposable filters of the antimicrobial separation unit  160 . The disposable filters capture the antimicrobial to separate the antimicrobial from the composition. The antimicrobial impregnated filters are then disposed of in an appropriate manner, such as by incineration or disposal at an approved landfill. The remaining, relatively antimicrobial-free liquid is then disposed of in an appropriate manner, such as by being drained into a wastewater system of a plant. The frequency with which the system  10  will need to be purged will depend upon any number of factors, such as the number of workpieces  120  to be processed by the antimicrobial application unit  112  and the volume of the dilute antimicrobial composition required to charge the system  10  at the beginning of a spray cycle. A periodic purge of the system  10  will be used. 
         [0045]    Other modifications, changes and substitutions are intended in the foregoing, and in some instances, some features of the invention will be employed without a corresponding use of other features. For example, the different features of the alternate embodiments may be merged or combined in any number of different combinations. Also, the antimicrobial application unit  12  may take any number of forms, shapes, and sizes and need not be one of the spray cabinet embodiments disclosed in U.S. patent application Ser. No. 10/001,896 (Nolen). Similarly, any number of different compositions may be used in any number of different concentrations, and the compositions may or may not include one or more antimicrobials. Further, any number of different separation techniques may be used in the antimicrobial separation unit  106 , and the antimicrobial separation unit  106  may be used with or without a corresponding use of a capture tank  62 . Further still, additional pumps, filters, and similar components may be incorporated into the system  10 . Also, any number of different methods may be used to monitor the composition of the composition in the recycle tank  24 . Similarly, the composition may be monitored constantly or at desired intervals. Further still, the drip tray  22  may not be used and may be any number of different lengths. Of course, quantitative information is included by way of example only and is not intended as a limitation as to the scope of the invention. Accordingly, it is appropriate that the invention be construed broadly and in a manner consistent with the scope of the invention disclosed.