Abstract:
In a reverse osmosis fluid purification system, an input fluid is received at an input of the purification system, and a fluid purification run cycle is performed on the input fluid. The fluid purification cycle includes pumping the input fluid through a membrane with a pump at a first pressure and first flow rate to generate product fluid and waste fluid. The product fluid is provided to an external system and the waste fluid is provided to a drain port. The membrane is then rinsed after performing the fluid purification run cycle by providing the input fluid to the pump and pumping the input fluid through the membrane at a second pressure less than the first pressure and a second flow rate greater than the first flow rate for a predetermined period of time.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority to U.S. Provisional Application No. 61/732,034, filed on Nov. 30, 2012, and entitled “Portable Reverse Osmosis Water Purification System,” the disclosure of which is incorporated by reference. 
     
    
     TECHNICAL FIELD 
       [0002]    The present disclosure relates to water purification systems. More specifically, the present disclosure relates to a portable reverse osmosis water purification system. 
       BACKGROUND 
       [0003]    Reverse osmosis is a filtration method that removes many types of large molecules and ions from solutions by applying pressure to the solution when it is on one side of a selective membrane. More formally, reverse osmosis is the process of forcing a solvent from a region of high solute concentration through a semipermeable membrane to a region of low solute concentration by applying a pressure in excess of the osmotic pressure. The result is that the solute is retained on the pressurized side of the membrane and the pure solvent is allowed to pass to the other side. The membrane is selective in that large molecules or ions are not allowed through the pores in the membrane, but allows smaller components of the solution (such as the solvent) to pass freely. Reverse osmosis filtration has various applications, including drinking water purification, wastewater purification, food industry uses (e.g., for concentrating food liquid), and health care uses (e.g., electrodialysis systems). 
       SUMMARY 
       [0004]    In one aspect of the present disclosure, a method for operating a reverse osmosis fluid purification system includes receiving an input fluid at an input of the purification system, and performing a fluid purification run cycle on the input fluid. The fluid purification cycle includes pumping the input fluid through a membrane with a pump at a first pressure and first flow rate to generate product fluid and waste fluid. The product fluid is provided to an external system and the waste fluid is provided to a drain port. The membrane is then rinsed after performing the fluid purification run cycle by providing the input fluid to the pump and pumping the input fluid through the membrane at a second pressure less than the first pressure and a second flow rate greater than the first flow rate for a predetermined period of time. 
         [0005]    In another aspect, a method for operating a reverse osmosis fluid purification system includes initiating a disinfection cycle and draining an internal tank to a minimum level. Input fluid is pumped from a fluid source through a membrane to generate product fluid and waste fluid. The flow of the input fluid from the fluid source is then terminated. The product fluid is directed to the internal tank until the internal tank is filled to a maximum level. The flow of the input fluid from the fluid source is then terminated. An amount of the product fluid is pumped from the internal tank through the membrane until the product fluid in the internal tank is at an intermediate level between the minimum and maximum levels. The amount of product fluid pumped from the internal tank forces fluid residing in the fluid path from the pump through the membrane and to the drain port. 
         [0006]    In a further aspect, a method for operating a reverse osmosis fluid purification system includes disconnecting the fluid purification system from a fluid source and waste port, transporting the fluid purification system to a storage location, and connecting the fluid purification system to an electrical source at the storage location. A storage heat cycling mode is then performed in which the product fluid in the internal tank and system is repeatedly heated and circulated through portions the reverse osmosis fluid purification system. 
         [0007]    While multiple embodiments are disclosed, still other embodiments of the present invention will become apparent to those skilled in the art from the following detailed description, which shows and describes illustrative embodiments of the invention. Accordingly, the drawings and detailed description are to be regarded as illustrative in nature and not restrictive. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]      FIG. 1  is a schematic view of an embodiment of a reverse osmosis water purification system illustrating water flow during a water purification cycle with varying fluid pressures. 
           [0009]      FIG. 2  is a schematic view of the reverse osmosis water purification system illustrating water flow during a shut down flush after the water purification cycle. 
           [0010]      FIG. 3  is a schematic view of the reverse osmosis water purification system illustrating water flow during steps of a pure water storage and purge of the reverse osmosis membrane. 
           [0011]      FIG. 4  is a schematic view of the reverse osmosis water purification system illustrating water flow during a recurring heat mode after disconnecting the system from water feed and waste lines. 
       
    
    
       [0012]    While the invention is amenable to various modifications and alternative forms, specific embodiments have been shown by way of example in the drawings and are described in detail below. The intention, however, is not to limit the invention to the particular embodiments described. On the contrary, the invention is intended to cover all modifications, equivalents, and alternatives falling within the scope of the invention as defined by the appended claims. 
       DETAILED DESCRIPTION 
       [0013]      FIG. 1  is a schematic view of an embodiment of a reverse osmosis water purification system  10  according to the present disclosure. The system  10  purifies a given feed water (by way of reverse osmosis) for use in various applications, such as hemodialysis. The system  10  possesses monitoring for feed water pressure, feed water quality, feed water temperature, pump outlet pressure, product water pressure, product water temperature, product water quality, and membrane performance (percent rejection). A pump provides the pressure required to push water through the reverse osmosis membrane and against a fixed orifice. Fluid controls provide a means of managing flow rates and pressures. 
         [0014]    The system  10  includes a pressure sensor  11 , a reverse osmosis membrane  12 , a valve body  14  including an orifice  16  and solenoid valve  18 , a valve body  20 , check valves  22  and  24 , a valve body  26 , a check valve  28 , a pump  29 , a valve body  30 , a pressure sensor  31 , solenoid valves  32  and  34 , a valve body  36 , a quality sensor  38 , a valve body  40 , a pressure sensor  42 , a quality sensor  44 , a check valve  46 , a tank vent valve  48 , a valve body  50 , an internal tank  52 , a thermal switch  54 , level sensors  56 ,  58 , and  60 , a heater  62 , check valves  64  and  65 , solenoid valves  66  and  68 , a check valve  70 , and an external connection  72 . The system  10  also includes a product water output  80 , a return input  82 , an overpressure output  84 , a drain output  86 , and a feed water input  88 . The valve bodies  14 ,  20 ,  26 ,  30 ,  36 ,  40 , and  50  are configured to control flow rates and pressures in the system  10 . The operation of the system  10  is controlled by a controller (not shown) that is programmed to operate the components of the system  10  to provide various functionalities (e.g., water purification, sanitization, etc.). 
         [0015]    The membrane  12  is connected to the pump  29  at the input of the membrane  12 . The pump  29  controls the fluid pressure through the system  10 . The pump  29  controls water pressure input to the membrane  12 . In some embodiments, the pump  29  includes a variable frequency drive. In some embodiments, the pump  29  has a pump pressure of about 160-200 pounds per square inch (psi) (1.10-1.24 MPa). The pressure sensor  11  measures the pressure of the fluid provided to the input of the membrane  12 . In some embodiments, the output of the pressure sensor  11  is used to control the operation of the pump  29 . For example, the pressure sensor  11  may be configured to shut down the system  10  if the sensor  11  detects an overpressure condition. 
         [0016]    In some embodiments, the membrane  12  is a single membrane comprised of a polymeric material. The membrane  12  may include a dense layer in a polymer matrix, such as the skin of an asymmetric membrane or an interfacially polymerized layer within a thin-film-composite membrane, where the separation of the product water from the waste water occurs. The membrane  12  may have a variety of configurations including, for example, spiral wound or hollow fiber configurations. 
         [0017]    The outputs of the membrane  12  are connected to the valve body  14  (via a waste output) and valve body  40  (via a product output). The solenoid valve  18  of the valve body  14  remains closed during normal operation, such that drain water from the output of the membrane  12  passes through the orifice  16 . During a heat sanitization process, the solenoid valve  18  opens to help maintain the system  10  at a predetermined pressure during the sanitization process. 
         [0018]    The output of the valve body  14  is provided to the check valve  22  via the valve body  20 . The check valve  22  is controlled in some embodiments to reduce flow and maintain a minimum pressure in the fluid path. The output of the check valve  22  is in fluid communication with the check valve  24  via the valve body  26 . In some embodiments, the check valve  24  is controlled in some embodiments to maintain a minimum pressure sufficient to block flow to the drain output  86 . The output of the check valve  24  is connected to the drain output  86  via the valve body  20 . The drain output  86  may be connected to a receptacle or other system for proper disposal of the drain fluid. 
         [0019]    An output of the valve body  26  is also connected to the inlet of the check valve  28 , which located between the feed water fluid path from the input  88  and the fluid path of the drain output  86  and, in some embodiments, is configured to allow waste fluid flow to supply the pump  29  with water, such as during low pressure operation conditions. The output of the check valve  28  is connected to the solenoid valve  34  via the valve body  30 . During a normal water purification cycle, as illustrated in  FIG. 1 , the solenoid valve  34  cycles with depending on the level of water in the tank  52 . During heating and chemical sanitization modes of operation, described in more detail below, the solenoid valve  34  operates to isolate the pump  29 . 
         [0020]    The solenoid valve  32  is connected between the feed water input  88  and the valve body  30 . The feed water input  88  may be connected to any pre-filtered fluid source that provides untreated water to the system  10  for purification. The solenoid valve  32  is configured to control the flow of feed water into the system  10  from the feed water input  88 . The pressure sensor  31  monitors the fluid pressure in valve body  30  and in some embodiments is configured to shut down the system  10  if the feed water from the feed water input  88  falls below a threshold pressure. 
         [0021]    The product water output of the membrane  12  is connected to the solenoid valve  66  via the valve body  40 . The solenoid valve  66  is configured to divert product water away from the product water output  80  during certain operations of the system  10 . For example, during system run startup flush, the solenoid valve  66  is closed until the system  10  is producing product water below a water quality set point (e.g., as measured in μS). During heat sanitization and chemical modes, the solenoid valve  66  cycles to direct fluid throughout the system  10  to ensure proper cleaning and disinfection. During normal operation, illustrated in  FIG. 1 , the solenoid valve  66  is open to allow product water to be provided to the external connection  72  via the product water output  80 . The external connection  72  may be coupled to a system that uses the product water, such as a hemodialysis machine. 
         [0022]    The pressure sensor  43  is connected between the membrane  12  and the solenoid valve  66  and is configured to monitor the pressure of the product water provided from the membrane  12 . If an overpressure condition is detected by the pressure sensor  43 , the system  10  may respond to reduce the pressure and may be shut down. 
         [0023]    The quality sensor  44  monitors the quality and temperature of the product water after it exits the membrane  12 . The product water quality measured by the quality sensor  44  can be reviewed (e.g., on a screen associated with the system  10 ) during normal operation. An additional display for review is a system calculated percent rejection comparison between the unpurified water flowing in valve body  36  and the purified product water flowing in valve body  40 . 
         [0024]    The input of the check valve  46  is connected between the output of the membrane  12  via the valve body  40 , and the output of the check valve  46  is connected to the input of the internal tank  52  via the valve body  50 . The check valve  46  is controllable to prevent backflow of water in the internal tank  52  into the product water provided to the product water output  80 . The check valve  46  also provides a pressure regulation for the line from the membrane  12  to the product water output  80 . 
         [0025]    The solenoid valve  68  provides fluid flow resistance during normal operation to the unused product water returning from the external connection  72 . In some embodiments, the solenoid valve  68  provides a backpressure to maintain the product water at a pressure of approximately 35 psi (0.241 MPa). During heating operation, the solenoid valve  68  is opened and provides full free flow. 
         [0026]    The return input  82  provides an input to return product fluid via the external connection  72  to the system  10 . For example, in a hemodialysis application, the return input  82  allows fluid not used during dialysis to be returned to the system  10  for re-purification. The return input  82  may also be used to return fluid to the system  10  during heat and chemical cleaning modes of the system  10 . 
         [0027]    The internal tank  52  receives water from the check valve  46  and/or the return input  82 . The vent valve  48  is configured to allow airflow to and from the tank  52 , but not water from the tank  52 . The temperature of the water in the internal tank  52  is monitored by the thermal switch  54 . If the water in the tank  52  exceeds a fixed threshold temperature, the thermal switch  54  provides an indication to the system controller and also removes the control signal from the heater  62  power supply circuit. The level of the fluid in the internal tank  52  is measured by the level sensors  56 ,  58 , and  60 . The level sensor  56  is triggered when water in the tank  52  is at or above a maximum water level, the level sensor  58  is triggered when water in the tank  52  is at or below an intermediate water level, and the level sensor  60  is triggered when the water in the tank  52  is at or below a minimum water level. The heater  62  is operable to heat the water in the tank  52 . The check valve  64  is at the outlet of the tank  52  and prevents pump  29  feed water from being fed back into the tank  52 . 
         [0028]    The check valve  65  is connected between the tank  52  and the overpressure output  84  and is configured to prevent the tank  52  from over-pressurizing. The check valve  70  is connected between the drain output  86  and the overpressure output  84  and is configured to relieve pressure in the drain line when the drain output  86  is not connected or not functional. 
         [0029]      FIG. 1  illustrates the water flow during a water purification cycle, in conjunction with water quality monitoring and run flush activities, in which the system  10  purifies feed water supplied at the feed input  88  and provides product water at the external connection  72  via the product water output  80 . In this process, the solenoid valves  18  and  68  and check valves  65  and  70  are closed, while the solenoid valves  32 ,  34 , and  66  and check valves  22 , and  24  are open. In some embodiments with lower feed water pressure at input  88 , check valves  28  and  64  open and allow water flow to support the supply to pump  29 . The water from the feed water input  88  is fed through solenoids  32  and  34  via valve bodies  36  and  30  to the pump  29  and forced through the membrane  12  at a pressure controlled using pressure sensor  11  and the pump  29 . In some embodiments, the pressure of the feed water at the input side of the membrane  12  is about 160-180 psi. The product water from the membrane  12  is then provided to the product water output  80 , and the non-recirculating waste or drain water flows through the check valves  22  and  24  to the drain output  86 . 
         [0030]      FIG. 2  is a schematic view of the reverse osmosis water purification system  10  illustrating water flow during a shut down flush after the water purification cycle according to an embodiment of the present disclosure. During the shutdown flush, the membrane  12  is rinsed to clear the membrane surface of high concentration feed water. In some embodiments, the shut down flush is performed automatically and cannot be overridden by the operator of the system  10 . 
         [0031]    In the shut down flush mode, the solenoid valves  18 ,  32 , and  34  are open, while the solenoid valves  65 ,  66  ,  68 , and  70  are closed. Additionally, the check valves  22 ,  24 ,  28 ,  46 , and  64  are open. Thus, the flow path from the membrane to the product water output  80  is closed to divert the product water to the tank  52 . The speed of the pump  29  is controlled to supply the feed water applied by the pump  29  at a pressure less than the pressure during the normal water purification cycle. This allows low pressure, high flow rate water to rush across the outer surface of the membrane  12 . The flushing water flows through the membrane  12 , out the waste output of the membrane, to the drain output  88 . In some embodiments, the shut down flush is performed on the membrane  12  for a programmed period of time. For example, in one implementation, the shut down flush is performed for at least about one minute. 
         [0032]      FIG. 3  is a schematic view of the reverse osmosis water purification system  10  illustrating various water flow paths during a pure water purge, heat sanitization, and or chemical induction of the reverse osmosis water purification system  10 , according to embodiments of the present disclosure. Specifically during the pure water purge step, a contained amount of pure product water is produced and captured. A portion of this captured pure water is then used to force or purge out the high concentration water from the membrane  12  and the waste fluid flow paths to the drain port  86 . The remaining volume of pure water is used for recirculation during heating or chemical induction modes of operation. Specifically, in the chemical mode of operation, a container of chemical sterilant is connected between external connection  72  and the product output  80  for chemical induction by the system  10 . In this induction process the solenoid valves  34 ,  66  and  68  are opened, and the solenoid valves  18  and  32  are closed. Additionally, the check valves  22 ,  28 ,  46  and  64  are opened, and the check valves  24 ,  65 , and  70  are closed. This arrangement allows chemical to be circulated through the system  10 . Specifically in the heat recirculation mode of operation, the solenoid valves  66 ,  68  and  34  are opened, and the solenoid valves  18  and  32  are closed. Additionally, the check valves  64 ,  28 ,  22  and  46  are opened, and the check valves  24 ,  65 , and  70  are closed. In some embodiments, the chemical is heated to provide increase the efficacy of the sterilant (e.g., at least about 70° F.). 
         [0033]    Upon selecting the chemical or heat mode of operation, standing water in the internal tank  52  is provided to the drain output  86  until the level of water in the tank  52  is at a minimum level. For example, the internal tank  52  will be drained until the level sensor  60  no longer senses water in the tank  52 . The solenoid valves  32  and  34  are then opened to allow the feed water from the feed water input  88  to be provided to the pump  29 , and the system  10  is operated in a normal water purification mode as described previously, but the product water is diverted to the internal tank  52  to refill the tank  52  to a maximum level. For example, product water will be diverted into the internal tank  52  until the level sensor  56  senses water. The solenoid valve  32  is then closed, and the system  10  is operated to again consume the water in the tank  52  down to an intermediate level between the maximum level and the minimum level. For example, product water in the tank  52  is provided to the pump  29  to be forced through the membrane  12  until the water in the tank  52  drops until the level sensor  58  no longer senses water in the tank  52 . In some embodiments, the amount of water consumed in from the tank  52  to reach the intermediate level is sufficient to displace the water in the flow path between the tank  52  and the drain output  86 . 
         [0034]      FIG. 4  is a fluid flow schematic view of the reverse osmosis water purification system  10  illustrating water flow specifically during a recurring heat mode after the purge step and after disconnecting tubing lines from water feed  88  and waste line  86 , according to an embodiment of the present disclosure. When the water purification system  10  is going to be stored for an extended period of time, it is important to maintain the system  10  in a sanitized state such that the system  10  is ready for use when needed. In the recurring heat mode, the solenoid valves  68  and  34  are opened, solenoid valve  18  is closed, and solenoid valve  66  is alternatingly opened and closed in predetermined intervals to allow fluid flow and even heating in the flow paths between membrane  12  product output and system  10  product output  80 , past the product supply port  72 , and on to return port  82 . And alternately the product divert path through check valve  48  and valve body  50 , with both flows returning to tank  52  for re-heating. Additionally check valve  48  allows the tank  52  to breath or exchange air as needed during the heating process. 
         [0035]    The operator of the system  10  can initiate a recurring heat mode when the system  10  is ready to be transported to a storage location. In some embodiments, when the recurring heat mode is initiated, the system  10  may execute a pure water purging step as described above with regard to  FIG. 3 . This puts product water into the tank  52  for the recurring heat mode. A display (not shown) associated with the system  10  may then provide the operator with instructions for relocating the system  10  to a storage location to initiate the recurring heat mode. The operator disconnects the feed water line from the feed water input  88  and the drain connection from the drain output  86 , and the system  10  from an electrical source that powers the system controller and other system components. The system  10  is then transported to the storage location and re-connected to an electrical source. The operator can then complete the steps to cause the system  10  to operate in the recurring heat mode while being stored with no ties to feed water or waste connections. 
         [0036]    When started, the recurring heat mode begins by operating pump  29  and the heater  62  to circulate and heat the water in the system  10  to a predetermined temperature. In some embodiments, the predetermined temperature is at least about 176° F. When the system  10  reaches the predetermined temperature, the system  10  cycles the heater  62  to maintain the water at the predetermined temperature for a predetermined period of time. In some embodiments, this predetermined period of time is at least about 30 minutes. After this time, the system  10  allows the water to cool by halting the heating process and continuing to circulate the water through the system  10 . The system may then initiate another heat cycle to heat the water to the predetermined temperature, regardless of the standing system temperature. The system  10  may be programmed by the operator to set the frequency at which the recurring heat cycle is run. In some embodiments, in the event of a failure of the power source while the system  10  is in the recurring heat mode, or resting, waiting for the next recurring heat mode trigger, the system  10  will automatically re-initiate the recurring heat mode upon the return of power, starting with circulation and heating of the water in the system  10 . 
         [0037]    When the system  10  is to be used, the operator can cancel or abort the recurring heat mode. When canceled, the system  10  will exit from the recurring heat mode. If the water in the system  10  is above a programmed temperature (e.g., 105° F.) when the recurring heat mode is canceled, the system  10  enters a cool down mode until the water in the system is below the programmed temperature. The system  10  can then be run by the operator for a period of time (e.g., ten minutes), after which time the system  10  is ready for dialysis use. 
         [0038]    Attached to this application as Appendix A is a document entitled “Mar Cor Purification, Millenium HX Reverse Osmosis Unit, Operation and Maintenance Manual,” which describes aspects of the system  10  and processes described herein, as well as the user interface, housing, and other features of the system  10 . The information in Appendix A supplements the information discussed herein. 
         [0039]    Various modifications and additions can be made to the exemplary embodiments discussed without departing from the scope of the present invention. For example, while the embodiments described above refer to particular features, the scope of this invention also includes embodiments having different combinations of features and embodiments that do not include all of the described features. Accordingly, the scope of the present invention is intended to embrace all such alternatives, modifications, and variations as fall within the scope of the claims, together with all equivalents thereof