Patent Publication Number: US-2011049048-A1

Title: Water purification system

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is entitled to the benefit of Provisional Patent Application Ser. No. 61/239,611 filed Sep. 3, 2009, and titled COMBINATION OF UF AND RO MEMBRANES ON A SINGLE SKID; and Provisional Patent Application Ser. No. 61/239,596 filed Sep. 3, 2009, and titled USE OF SINGLE TANK FOR UF CIP, UF BACKWASH, UF PERMEATE TANK, RO CIP TANK VERSUS THE CONVENTION USE OF FOUR SEPARATE TANKS. Both of the above listed applications are herein incorporated by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to a water purification system. In particular, it relates to a water purification system having a tank. 
     2. Description of Related Art 
     Traditionally, ultrafiltration and reverse osmosis water purification systems employ multiple tanks, such as an ultrafiltration clean-in-place tank, an ultrafiltration backwash tank, an ultrafiltration permeate break tank, and a reverse osmosis clean-in-place tank. Accordingly, a need exists to reduce the number of tanks required by a water purification system. 
     SUMMARY OF THE INVENTION 
     The present invention concerns a water purification system comprising an ultrafiltration unit, a reverse osmosis unit, and a tank. The ultrafiltration unit is upstream of the tank on an operation conduit and the tank is upstream of the reverse osmosis unit on a reverse osmosis conduit. A backwash conduit is situation between said tank and said ultrafiltration unit. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and other aspects of the invention will be understood from the description and claims herein, taken together with the drawings showing details of construction and illustrative embodiments, wherein: 
         FIG. 1  schematically illustrates a water purification system operating in an ultrafiltration/reverse osmosis production mode in accordance with one embodiment of the present invention; 
         FIG. 2  schematically illustrates a water purification system operating in an ultrafiltration backwash/reverse osmosis production mode in accordance with one embodiment of the present invention; 
         FIG. 3  schematically illustrates a water purification system operating in an ultrafiltration daily maintenance cleaning mode in accordance with one embodiment of the present invention; 
         FIG. 4  schematically illustrates a water purification system operating in an ultrafiltration daily maintenance rinsing mode in accordance with one embodiment of the present invention; 
         FIG. 5  schematically illustrates a water purification system operating in an ultrafiltration monthly recovery clean recirculation and soak mode in accordance with one embodiment of the present invention; 
         FIG. 6  schematically illustrates a water purification system operating in an ultrafiltration monthly recovery clean rinse mode in accordance with one embodiment of the present invention; 
         FIG. 7  schematically illustrates a water purification system operating in an reverse osmosis quarterly clean mode in accordance with one embodiment of the present invention; and 
         FIG. 8  schematically illustrates a water purification system operating in an reverse osmosis quarterly rinse mode in accordance with one embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     Approximating language, as used herein throughout the specification and claims, may be applied to modify any quantitative representation that could permissibly vary without resulting in a change in the basic function to which it is related. Accordingly, a value modified by a term or terms, such as “about”, is not limited to the precise value specified. In at least some instances, the approximating language may correspond to the precision of an instrument for measuring the value. Range limitations may be combined and/or interchanged, and such ranges are identified and include all the sub-ranges stated herein unless context or language indicates otherwise. Other than in the operating examples or where otherwise indicated, all numbers or expressions referring to quantities of ingredients, reaction conditions and the like, used in the specification and the claims, are to be understood as modified in all instances by the term “about”. 
     “Optional” or “optionally” means that the subsequently described event or circumstance may or may not occur, or that the subsequently identified material may or may not be present, and that the description includes instances where the event or circumstance occurs or where the material is present, and instances where the event or circumstance does not occur or the material is not present. 
     As used herein, the terms “comprises”, “comprising”, “includes”, “including”, “has”, “having”, or any other variation thereof, are intended to cover a non-exclusive inclusion. For example, a process, method, article or apparatus that comprises a list of elements is not necessarily limited to only those elements, but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. 
     The singular forms “a”, “an”, and “the” include plural referents unless the context clearly dictates otherwise. 
     The water purification system  200  depicted in Modes  1 - 5  of  FIGS. 1-8  comprises an ultrafiltration membrane (“UF”) unit  201 , a backwash/clean in place (“CIP”) pump  215 , a booster/clean in place (“CIP”) pump  214 , an Reverse Osmosis (“RO”) high pressure pump  219 , an RO unit  202 , a tank  203 , and a tank level control  218  (“LC”). The UF unit  201  is sized to provide continuous flow through the RO unit  202 . Optionally, the system can include a UF feed pump  217 , a pre-filter  216 , and a RO recovery unit  222 . The tank  203  receives inflows from the RO unit  202 , the RO recovery unit  222 , and the UF unit  201 . Further, the tank  203  is multifunctional in that it acts as a UF permeate break tank and as a source for the backwash/CIP pump  215  and booster/CIP pump  214 . LC  218  is used in each mode to monitor and control the fluid level in tank  203 . In  FIGS. 1-8 , the conduits that are used in the mode depicted in each drawing are bold, the active components are shaded, and the dormant components are hatched. 
     As can be seen in  FIGS. 1-8 , both the UF unit  201  and tank  203  have individual drains  221  and  223 . Normally, the contents of the UF unit  201 , tank  203 , RO unit  202 , and RO recovery unit  222  can be drained into gray water drains However, if the contents include acid or other substances that cannot be disposed in the same manner as gray water, the contents are drained into a neutralization tank. Further, it is contemplated that in some embodiments, the RO unit permeate, RO unit concentrate, RO recovery unit permeate, and RO recovery unit concentrate have separate drain lines. It is contemplated that some embodiments of water purification system  200  can process about 100 gpm to about 300 gpm of water. Further, it is contemplated that other embodiments of water purification system  200  can process about 50 gpm to about 500 gpm of water. 
     Turning to  FIG. 1 , which depicts Mode  1 , UF/RO production mode, the UF feed pump  217  directs source  220  water through the pre-filter  216  and UF unit  201 . An operation conduit  204  conducts UF permeate to the tank  203 . An RO conduit  210  conducts UF permeate from the tank  203  to the booster/CIP pump  214 , RO high pressure pump  219 , and RO unit  202 . Permeate exits the RO unit  202  as product, and the RO unit concentrate passes into an optional RO recovery unit  222 . The RO recovery unit permeate is returned to the tank  203  via RO recovery conduit  206 , and the RO recovery unit concentrate is directed into the RO/RO recovery drain  224 . 
     Additionally, the optional RO recovery unit  222  can be bypassed by directing the RO unit concentrate into the RO/RO recovery drain  224 . If a system does not contain the optional RO recovery unit  222 , the RO unit concentrate is directed into the RO/RO recovery drain  224 . 
     Turning to  FIG. 2 , which depicts Mode  2 , UF unit backwash and RO unit production mode, the system uses the contents of the tank  203  to simultaneously operate in a backwash mode of operation and produce product with the RO unit  202 . Accordingly, the tank  203  is sized for continuous RO operation during backwash mode. In backwash mode, the backwash/CIP pump  215  conducts UF permeate from the tank  203 , through the backwash conduit  205 , and backward through the UF unit  201 . The UF permeate then exits the UF unit  201  and is directed to the UF unit drain  221 . 
     Further, in Mode  2 , an RO conduit  210  conducts fluid from the tank  203 , through the booster/CIP pump  214  and RO high pressure pump  219 , and to the RO unit  202 . The RO unit permeate exits as product, and the RO unit concentrate passes to the RO recovery unit  222 . The RO recovery unit permeate is returned to the tank  203  via the RO recovery conduit  206 , and the RO recovery unit concentrate is directed to the RO/RO recovery drain  224 . If a system does not contain the optional RO recovery unit  222 , the RO unit concentrate is directed to the RO/RO recovery drain  224 . 
     In the preferred embodiment, the system enters Mode  2  approximately every 30 minutes, based on recovery and feed water. The duration of Mode  2  is approximately 120 seconds, including pre-aeration, backwash/CIP pump  215  ramp up and ramp down, UF feed pump  217  ramp up and rinse. Below is a chart detailing one possible Mode  2  backwash process, of which there are alternatives. This chart discusses the use of aeration equipment, such as a UF unit scour blower, which is contemplated to be included in some embodiments. 
     
       
         
           
               
               
               
               
             
               
                   
               
               
                   
                   
                 Duration, 
                 Total elapsed 
               
               
                 Process Step 
                 Description 
                 (seconds) 
                 time (seconds) 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
            
               
                 UF Feed pump 
                 UF Feed pump ramp- 
                 10 
                 10 
               
               
                 ramp-down 
                 down and valve rotation 
                   
                   
               
               
                 Backwash/CIP 
                 Aeration and ramp-up 
                 5 
                 15 
               
               
                 pump ramp-up 
                 Backwash/CIP pump 
                   
                   
               
               
                 Backwash 
                 Aeration and backwash 
                 60 
                 75 
               
               
                 Backwash/CIP 
                 Backwash/CIP pump  
                 10 
                 85 
               
               
                 pump ramp-down 
                 ramp-down and valve  
                   
                   
               
               
                   
                 rotation + aeration off 
                   
                   
               
               
                 UF Feed pump 
                 UF Feed pump ramp-up  
                 5 
                 90 
               
               
                 ramp-up (feed flush) 
                 for feed flush 
                   
                   
               
               
                 UF Feed flush 
                 UF Feed flush 
                 30 
                 120 
               
               
                 Production 
                 Valve rotation for 
                   
                   
               
               
                   
                 production 
               
               
                   
               
            
           
         
       
     
     Turning to  FIG. 3 , which depicts Mode  3   a , the system is placed in a UF daily maintenance cleaning mode. In the UF daily maintenance cleaning mode, a cleaning fluid is prepared in the tank  203  by adding chemicals to the contents of the tank  203  through chemical feed line  208 . Such chemicals can include citric acid or phosphoric acid to help control inorganic fouling, and hypochlorite to help control organic fouling. The backwash/CIP pump  215  conducts fluid from the tank  203  to the UF cleaning conduit  207 , which directs the fluid along an upstream to downstream direction through the UF unit  201 , before returning the fluid back to the tank  203 . The RO unit  202  is usually shut down during the daily maintenance cleaning mode. 
     Following Mode  3   a , the system is placed in Mode  3   b , which is depicted in  FIG. 4 , a daily maintenance rinse mode. In the daily maintenance rinse mode, the UF feed pump  217  sends source  220  water through a UF rinsing conduit  212 , which directs source  220  water from an upstream to downstream direction through the pre-filter  216 , the UF unit  201 , and into the tank  203 . Rinsing fluid used during the daily maintenance rinse mode is drained via UF unit drain  221  and tank drain  223 . Additionally, the RO unit  202  is normally shut down during this rinse mode. 
     The daily maintenance cleaning prolongs the life of the UF membranes. In the preferred embodiment, the duration of Mode  3   a - b  is approximately 27 minutes, which includes the UF drain, CIP content transfer, recirculation, draining the CIP solution, and chemical flush. Below is a chart detailing one possible Mode  3   a - b  daily maintenance clean and rinse process, of which there are alternatives. 
     
       
         
           
               
               
               
               
             
               
                   
               
               
                   
                   
                   
                 Total elapsed 
               
               
                   
                   
                 Duration, 
                 time 
               
               
                 Process Step 
                 Description 
                 (minutes) 
                 (minutes) 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
            
               
                 Fill tank with 
                 Tank filled with permeate, 
                   
                   
               
               
                 chemical solution 
                 (optional heating), 
                   
                   
               
               
                   
                 Chemicals mixed 
                   
                   
               
               
                 Stop System 
                   
                 0 
                 0 
               
               
                 Drain UF Unit 
                 Drain unit using UF feed 
                 2 
                 2 
               
               
                   
                 pump 
                   
                   
               
               
                 Transfer Tank 
                 Pump chemical from  
                 3 
                 5 
               
               
                 Contents Using 
                 tank to the UF modules 
                   
                   
               
               
                 Backwash/CIP pump 
                   
                   
                   
               
               
                 Recirculate 
                 Recirculate CIP solution 
                 15 
                 20 
               
               
                   
                 using Backwash/CIP 
                   
                   
               
               
                   
                 pump 
                   
                   
               
               
                 Drain CIP Solution 
                 Drain CIP solution to tank 
                 2 
                 22 
               
               
                 Chemical Flush 
                 Fill UF unit with feed and 
                 5 
                 27 
               
               
                   
                 direct permeate to 
                   
                   
               
               
                   
                 neutralization drain 
                   
                   
               
               
                 Start system 
               
               
                   
               
            
           
         
       
     
     Turing to  FIG. 5 , which depicts Mode  4   a , the system is placed in a UF monthly recovery clean recirculation and soak mode. In this mode, a cleaning fluid is prepared in the tank  203  by adding chemicals to the contents of the tank  203  through chemical feed line  208  and heating the fluid using heater  209 . Such chemicals can include sodium hypochlorite to help control organic fouling, and citric acid or phosphoric acid to help control inorganic fouling. The backwash/CIP pump  215  conducts fluid from the tank  203  to the UF cleaning conduit  207 , which directs the fluid along an upstream to downstream direction through the UF unit  201 , before returning the fluid back to the tank  203 . Bisulfite is added at the end of this mode to remove any chlorine. The tank  203  and heater  209  are sized such that the contents of the tank  203  can be heated to 40° C. (104° F.) in four hours. The RO unit  202  is usually shut down during this mode. Mode  4   a  cleaning is more extensive than Mode  3   a.    
     Following Mode  4   a , the system is placed in Mode  4   b , which is depicted in  FIG. 6 , a UF monthly recovery clean rinse. In this mode, the UF feed pump  217  sends source  220  water through a UF rinsing conduit  212 , which directs source  220  water from an upstream to downstream direction through the pre-filter  216 , the UF unit  201 , and into the tank  203 . The UF unit  201  and tank  203  both include a drain  221  and  223  for draining the rinsing fluid during the UF monthly recovery clean rinse mode. Additionally, the RO unit  202  is normally shut down during this rinse mode. 
     In the preferred embodiment, the duration of Mode  4   a - b  is approximately 317 minutes, which includes the UF drain, CIP content transfer, recirculation and soak, draining the CIP solution, and chemical flush. Below is a chart detailing one possible Mode  4   a - b  monthly recovery clean recirculation, soak, and rinse, of which there are alternatives. 
     
       
         
           
               
               
               
               
             
               
                   
               
               
                   
                   
                   
                 Total elapsed 
               
               
                   
                   
                 Duration, 
                 time, 
               
               
                 Process Step 
                 Description 
                 (minutes) 
                 (minutes) 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
            
               
                 Fill tank with 
                 Tank filled with permeate, 
                 ( ~240) 
                   
               
               
                 chemical 
                 heated, Chemicals mixed 
                   
                   
               
               
                 solution 
                   
                   
                   
               
               
                 Stop system 
                   
                 0 
                 0 
               
               
                 Drain rack 
                 Drain rack using UF feed pump 
                 2 
                 2 
               
               
                 Transfer CIP 
                 Pump chemical from tank  
                 3 
                 5 
               
               
                 Content 
                 to the UF modules 
                   
                   
               
               
                 Recirculate and 
                 Recirculate tank solution for 
                 300 
                 305 
               
               
                 Soak 
                 5 min and soak for 25 min;  
                   
                   
               
               
                   
                 repeat this cycle 10 times 
                   
                   
               
               
                 Drain CIP 
                 Drain CIP solution to 
                 2 
                 307 
               
               
                 Solution 
                 neutralization drain 
                   
                   
               
               
                 Chemical Flush 
                 Fill rack and rinse to 
                 5 
                 312 
               
               
                   
                 neutralization drain 
                   
                   
               
               
                 Start system 
               
               
                   
               
            
           
         
       
     
     Turning to  FIG. 7 , in Mode  5   a , the system is placed in a RO cleaning mode. Here, the operation, backwash, cleaning, and rinsing conduits are closed. In this mode, a cleaning fluid is prepared in the tank  203  by adding chemicals to the contents of the tank  203  through the chemical feed line  208  and heating the fluid with the tank immersion heater  209 . A booster/CIP pump  214  conducts fluid from the tank  203  to the RO conduit  210 , which directs the fluid through the RO high pressure pump  219  and into the RO unit  202 . The RO unit permeate is returned to the tank  203  through a recycle conduit  211  and the concentrate is directed to the RO recovery unit  222 . The permeate and concentrate from the RO recovery unit  222  are both returned to the tank  203  through a RO recovery conduit  206 . 
     Alternatively, in Mode  5   a , the RO unit  202  can be bypassed by shutting down the RO high pressure pump  219  and utilizing only the booster/CIP pump  214  to conduct fluid from the tank  203  to the RO recovery unit  222  via the RO recovery bypass conduit  225 . The permeate and concentrate from the RO recovery unit  222  are both returned to the tank  203  through a recovery recycle conduit  211 . 
     Following Mode  5   a , the system is placed in Mode  5   b , as depicted in  FIG. 8 , a RO clean rinse mode. Here, source  220  water is pumped by the UF feed pump  217  through the pre-filter  216  and UF unit  201  along the operation conduit  204  and into the tank  203 . A booster/CIP pump  214  conducts UF permeate from the tank  203  to the RO high pressure pump  219 , which directs UF permeate along the RO conduit  210  into the RO unit  202 . The RO unit permeate is directed to the RO/RO recovery drain  224  and the RO unit concentrate is directed to the RO recovery unit  222 . The RO recovery unit permeate and concentrate are directed to the RO/RO recovery drain  224 . 
     Alternatively, in Mode  5   b , the RO unit  202  can be bypassed by shutting down the RO high pressure pump  219  and utilizing only the booster/CIP pump  214  to conduct fluid from the tank  203  to the RO recovery unit  222  via the RO recovery bypass conduit  225 . The RO recovery unit permeate and concentrate are directed to the RO/RO recovery drain  224 . In one embodiment, RO cleaning mode depicted in  5   a  and  5   b  are carried out about once a quarter. 
     Stated alternatively, in a water purification system  200  of the type in which influent water flows along an upstream to downstream direction, through an upstream UF unit  201  and through a downstream RO unit  202 , a tank  203  is located intermediate said UF unit  201  and said RO unit  202 . An operation conduit  204  is provided to conduct UF permeate to the tank  203 . An RO conduit  210  is provided to conduct UF permeate from the tank  203  to the RO unit  202  in a purification operational mode. Additionally, a backwash conduit  205  is provided between the tank  203  and the UF unit  201  for directing a backward or countercurrent fluid flow from the tank  203  in a downstream to upstream direction through the UF unit  201  in a UF backwash mode of operation. During the backwashing mode, permeate feed from the tank  203  through the RO unit  202  via the RO conduit  210  may proceed, if desired. 
     In a daily maintenance cleaning mode of operation, a UF cleaning conduit  207  is provided between the tank  203  and the UF unit  201  for directing cleaning fluid flow from the tank  203  and then along an upstream to downstream direction through the UF unit  201 . A chemical feed line  208  in operational communication with the tank  203  is used to feed chemicals to the tank  203  for this cleaning function. For example, sodium hypochlorite may be fed through one chemical feed line so as to help control organic fouling with citric acid or phosphoric acid fed to the tank  203  through a second chemical feed line to help reduce inorganic fouling, if needed. During the daily UF cleaning cycle, the RO unit  202  is usually shut down. In the cleaning cycle, the UF cleaning conduit  207  may also be used to recirculate cleaning fluid from the tank  203  to the UF unit  201 . 
     A UF rinsing conduit  212  is also provided for directing rinsing fluid flow from an upstream to a downstream direction through the UF unit  201  then into the tank  203  in a UF rinsing mode of operation. The tank  203  further includes a drain means  221  for draining rinsing fluid therefrom during the UF rinsing mode of operation. Additionally, the RO unit  202  is normally shut down during this rinsing mode. It is contemplated that in some embodiments, operation conduit  204  can be used as rinsing conduit  212 . 
     In another mode of operation, the RO unit  202  is cleaned. Here, the operation, backwash, cleaning and rinsing conduits are closed. The RO conduit  210  is provided to supply cleaning chemical to the RO unit  202 . A recycle conduit  211  extends from the downstream product exit  226  of the RO unit  202  to the tank  203  to recycle the RO cleaning fluid to the tank  203 . Additionally, a RO recovery conduit  206  extends from the concentrate exit  213  from the RO and returns the cleaning fluid to the tank  203 . In embodiments using an optional RO recovery unit  222 , permeate and concentrate from the RO recovery unit  222  are returned to the tank  203  via RO recovery conduit  206 . Acid cleaning is usually the first cleaning treatment employed, followed by caustic recirculation through the tank  203 , RO unit  202  and optional RO recovery unit  222 . 
     Typically, on a periodic basis, such RO unit  202  is rinsed. Here, source  220  or influent water is pumped through the UF unit  201  to the tank  203  where the UF permeate flows through a RO conduit  210  from the tank  203  by employment of a RO high pressure pump  219  into the RO unit  202 . This rinsing fluid is then drained via the RO/RO recovery drain  224  after it has rinsed the RO unit  202 . 
     While this invention has been described in conjunction with the specific embodiments described above, it is evident that many alternatives, combinations, modifications and variations are apparent to those skilled in the art. Accordingly, the preferred embodiments of this invention, as set forth above are intended to be illustrative only, and not in a limiting sense. Various changes can be made without departing from the spirit and scope of this invention. Therefore, the technical scope of the present invention encompasses not only those embodiments described above, but also all that fall within the scope of the appended claims. 
     This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated processes. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. These other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal language of the claims.