Abstract:
Systems and methods for treating water as well as maintaining water treatment systems are disclosed. The systems and methods include circulating influent water in a recirculation loop. In addition, a contaminate level may be monitored by sensors. When the contaminate level exceeds a set contaminate level, contaminates may be bleed from the systems.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     The present application is a Continuation-In-Part of U.S. patent application having Ser. No. 10/982,731 filed Nov. 5, 2004 which is hereby incorporated by reference in its entirety. 
     
    
     FIELD OF INVENTION  
       [0002]     Embodiments of the present invention relate to water treatment. More specifically, embodiments of the present invention relate to systems and methods for water treatment and maintaining the membranes of a reverse osmosis water treatment system.  
       BACKGROUND  
       [0003]     Pressurized reverse osmosis water treatment systems which incorporate a recirculation loop to improve efficiency are sensitive to membrane degradation and excessive contaminates in permeate (treated) water. Influent water contaminate levels can vary widely. Currently, pressurized reverse osmosis water treatment systems utilizing a recirculation loop have a fixed bleed system which sets system water efficiency. The bleed rate may be set at the factory or set in the field by a technician. The bleed rate may be based on the influent water contaminate levels at the time of installation. If the influent water chemistry changes over time, or the bleed rate is set incorrectly, the permeate water quality may be inconsistent. Moreover, improperly set bleed rates may also lead to shortened system life.  
         [0004]     Currently systems require that a customer pay a technician to monitor and maintain their systems on a regular basis. These maintenance contracts can be costly, time consuming, and inadequate to facilitate proper system maintenance. Setting a cleaning cycle for a fixed time may result in poor system water treatment and may shorten system component life. Furthermore, if the time between the maintenance inspections is too great, contamination levels may rise without notice and may lead to premature system malfunction. There exists a need for systems and methods to combat the aforementioned problems.  
       BRIEF DESCRIPTION OF THE INVENTION  
       [0005]     In one aspect, embodiments of the present invention include a system and method of treating water is disclosed. The method includes circulating influent water in a recirculation loop. A portion of the influent water passes through at least one membrane. In one embodiment, a sensor may monitor a recirculation contaminate level in the recirculation loop. When the recirculation contaminate level exceeds a maximum contaminate level, contaminates may be bled from the recirculation loop.  
         [0006]     In another embodiment, a sensor may monitor a permeate contaminate level after the permeate has exited the recirculation loop. When the permeate contaminate level exceeds a maximum permeate contaminate level, contaminates may be bled from the recirculation loop.  
         [0007]     In another embodiment, the system includes a recirculation loop configured to allow a portion of influent water to pass through at least one membrane. A sensor may be configured to monitor a contaminate level within the system. Upon receiving an indication from the sensor, contaminates may be bled from the system. 
     
    
     BRIEF DESCRIPTION OF THE FIGURES  
       [0008]     Non-limiting and non-exhaustive embodiments are described with reference to the following figures, wherein like reference numerals refer to like parts throughout the various views unless otherwise specified.  
         [0009]      FIG. 1  depicts a water conditioning system;  
         [0010]      FIG. 2  depicts the water conditioning system of  FIG. 1  configured to cleanse membranes;  
         [0011]      FIG. 3  depicts a softening membrane in a system for conditioning water; and  
         [0012]      FIG. 4  is another embodiment showing a softening membrane in a system for conditioning water. 
     
    
     GENERAL DESCRIPTION  
       [0013]     Embodiments of the present invention utilize a sensor to monitor contaminate levels in a recirculation loop and/or permeate water. Upon receiving an indication from the sensor that contaminate levels have exceeded and/or are approaching a maximum contaminate level, contaminates in the recirculation loop may be bled from the system.  
         [0014]     Other aspects of the invention include having the sensor monitor a cleaning cycle. The cleaning cycle includes recirculating permeate water across the membranes of a reverse osmosis water treatment system. Upon commencement of the cleaning cycle the sensor may monitor the contaminate level of the recirculation loop and/or the permeate water to determine a cleaning cycle operating time.  
       DETAILED DESCRIPTION  
       [0015]     Referring now to the figures,  FIG. 1  depicts a water treatment system  100 . Influent water enters the system  100  at a point of entry  102 . Upon entering the system  100  the influent water may bypass the treatment components of the system  100  if a bypass valve  104  is so configured. Check valve  105  acts to prevent “back flow.” When the bypass valve  104  is closed, the influent water flows through check valve  105  and may pass through filter  106 . Filters  106  may be used to “prefilter” the influent water. This prefiltering stage may remove precipitants and/or other solids from the influent water.  
         [0016]     Valve  108  may be a flush valve used to purge the system  100  upon performing maintenance on filters  106 . For example, after replacing filters  106  valve  110  may be closed to restrict water from continued flow through the system  100 . Valve  108  may be opened to allow flushed water to be diverted to drain  112 . The flushed water may be diverted to a municipal drain or reintroduced to the system  100  at some point before filters  106  for treatment. While three prefilter filters  106  are shown, it is contemplated that any number of prefiltering filters  106 , including zero, may be implemented.  
         [0017]     As symbolized by the “X”, valve  110  is configured to allow water from filters  106  to enter pump  114 . As seen in  FIG. 2 , value  110 , as symbolized by the “X”, may be configured to block water from filters  106  from entering pump  114 . The “X” in  FIGS. 1 and 2  symbolizes that water will not flow in the pipe section where the “X” is located.  
         [0018]     Pump  114  boosts the pressure of the influent water as necessary for system operations. For example, if the inlet pressure is 1.00 ATM (14.7 psi) pump  114  may boost the pressure to 10.89 ATM (160 psi). Valve  116  is a pressure control valve. In various embodiments valve  116  may be a differential pressure control valve. Current pressurized reverse osmosis systems utilize pumps with variable speed motors and/or staged pumping systems, both of which are expensive. Valve  116  may enable pump  114  to be a fixed boost (e.g. a rotary vane pump) and become a variable boost pump by causing pump  114  to enter a race state. The race state comprises diverting a portion of the influent water from the exit of pump  114  back to the inlet of pump  114 . Valve  116  creates a head loss so that the portion of the flow diverted back to the inlet has a pressure approximately equal to that of the flow exiting valve  110 . While  FIG. 1  shows a fixed boost pump and a pressure control valve to control the boost pressure, it is contemplated that a variable boost may be used with or without a pressure control valve.  
         [0019]     Water leaving pump  114  enters recirculation loop  118 . The direction of flow within the recirculation loop is controlled by check valve  124 . While within the recirculation loop  118  pump  122  causes the water to circulate through membranes  120 . While two membranes are shown in  FIG. 1 , it is contemplated that a single membrane or more than two membranes may be implemented within the recirculation loop  118 .  
         [0020]     In an embodiment of the present invention, sensor  126  may be located within recirculation loop  118 . By placing sensor  126  in the recirculation loop  118 , the contaminate level (i.e. contaminate concentration) may be monitored. Upon detecting that the contaminate level has reached a maximum contaminate level, sensor  126  may cause valve  128  to open and bleed contaminates from the recirculation loop  118 . By way of example and not limitation, sensor  126  may be a total dissolved solids sensor or any other sensor able to measure contaminate levels. When the contaminate level reaches and/or goes below a minimum contaminate level, sensor  126  may partially or completely close valve  128  so as to retard or halt bleeding of contaminates from the recirculation loop  118  to drain  112 . Similarly, valve  128  may be a variable flow valve that may be used in conjunction with sensor  126  to continuously bleed contaminates from the system  100 . For example, valve  128  may open and close to continuously adjust the bleed rate in an attempt to maintain contaminates levels at a fixed value or within a range of values. In addition, a series of valves may also be used to reduce or increase the amount of bleed water and regulate the level of contaminates in the recirculation loop  118 .  
         [0021]     For example, a maximum contaminate level within the recirculation loop  118  of 1,500 ppm (parts per million) may be established. During operation of the system  100  valve  128  may close and the recirculation loop  118  may have a contaminate level of 1,290 ppm. As the system  100  operates the contaminate level may rise as influent water is treated. When the contaminate level within the recirculation loop reaches 1,500 ppm or some other preset level, valve  128  may open and contaminates are bled from the system. When the contaminate level drops below a previously defined threshold level, sensor  126  may signal valve  128  to partially or completely close, retarding and/or halting the bleeding of contaminates.  
         [0022]     The system includes a valve  130  to allow for a membrane flush. A membrane flush may occur after or during maintenance of the recirculation loop  118  and comprises flushing large quantities of water or other cleaner(s) through the recirculation loop  118 . For example, after replacement and/or cleaning of membranes  120 , a membrane flush may be performed to remove solids or other contaminates that may have been introduced to the system  100 . In addition, valve  130  may be controlled by sensor  126  to assist with contaminate bleeding.  
         [0023]     For example, valve  128  may be sized so that the maximum flow achievable is 0.45 lpm (liters per minute) (0.1 gallons per minute) and valve  130  may have a maximum flow rate of 45.46 lpm (10.0 gpm). Should the influent water have high contaminate levels, a 0.45 lpm flush may not be enough to bring the contaminate levels within the recirculation loop  118  to within allowable tolerances. In this instance, valve  130  may be used instead of or in conjunction with valve  128  to achieve a necessary bleed rate.  
         [0024]     Water exits the recirculation loop  118  through valve  132 . Valve  132  may be a check valve or other form of back flow prevention. Valve  132  inhibits permeate water from being reintroduced into the recirculation loop  118 . After exiting the recirculation loop  118 , a portion of the permeate water may be stored in a storage tank  134 . The stored permeate water may be used in a cleaning cycle, as described with reference to  FIG. 2 . Before entering the storage tank  134 , a permeate water contaminate level may be monitored by sensor  136 . Consistent with embodiments of the present invention, other fluids may be circulated through recirculation loop  118  to clean the membranes  120 . By way of example and not limitation, the cleaning fluid may be water, a water/detergent solution, an alcohol based solution, or any other suitable solution.  
         [0025]     Similar in concept to the monitoring contaminate levels in the recirculation loop  118 , by placing sensor  136  in the flow of permeate water, the contaminate level (i.e. contaminate concentration) may be monitored. Upon detecting that the contaminate levels within the permeate water has reached a maximum level, sensor  136  may control valve  128  to bleed contaminates from the recirculation loop  118 . By way of example and not limitation, sensor  136  may be a total dissolved solid sensor or any other sensor able to measure contaminate levels. When the contaminate level reaches or goes below a minimum contaminate level, sensor  136  may partially or completely close valve  128  so as to retard and/or halt bleeding of contaminates from the recirculation loop  118  to drain  112 . Similarly, valve  128  may be a variable flow valve used in conjunction with sensor  136 .  
         [0026]     For example, a maximum contaminate level within the permeate water of  120  ppm may be established. During operation of the system  100  valve  128  may be closed and the permeate water may have a contaminate level of 82 ppm. As the system  100  operates the contaminate levels may rise as influent water is treated. When the contaminate level within the permeate water reaches 120 ppm or some other preset value, valve  128  may open to allow contaminates to be bled from the system. When the contaminate level of the permeate water drops below a previously defined threshold level, sensor  136  may send a signal to valve  128 . Valve  128  may partially or completely close, retarding and/or halting the bleeding of contaminates.  
         [0027]     Sensors  126  and  136  may be used separately or in combination with one another. For example, in embodiments of the invention, the contaminate levels of the recirculation loop  118  alone may be monitored. Also consistent with embodiments of the invention, the contaminate levels of the permeate water alone may be monitored. Still consistent with embodiments of the invention, both the contaminate levels of the recirculation loop  118  and the permeate water may be monitored.  
         [0028]     For example, permeate water with too low a contaminate level can be corrosive to pipes. If the contaminate level in the permeate water is below an acceptable level, sensor  136  may instruct valve  128  to partially and/or completely close, retarding and/or halting the bleeding of contaminates.  
         [0029]     As a safety precaution, the system  100  may also include a pressure control valve  138 . Should the pressure within the system  100  become too great, valve  138  would reduce pressure by discharging water to a drain. Consistent with embodiments of the invention, multiple pressure control valves may be placed throughout the system for safety.  
         [0030]     The system  100  may also include various other sensors, metering devices, or safety devices including but not limited to a flow meter  140 , differential pressure switches  142 , and filter  144 . After treatment, the permeate water exits the system  100  at a point of exit  146 .  
         [0031]     During the water treatment cycle, contaminates can precipitate out of the influent water on the membrane surface.  FIG. 2  depicts an embodiment of the present invention configured to clean the membranes  120 . As symbolized by the “X”, valve  110  is configured to hinder and/or prohibit water from filter  106  entering pump  114 . Instead, permeate water from storage tank  134  enters pump  114 . Permeate water then enters the recirculation loop  118 . As with the treatment cycle, the direction of flow within the recirculation loop  118  is controlled by check valve  124 . While within the recirculation loop  118  pump  122  causes the water to circulate through membranes  120 .  
         [0032]     In an embodiment of the present invention, sensor  126  may be located within recirculation loop  118 . By placing sensor  126  in the recirculation loop  118 , the contaminate level may be monitored. Permeate water introduced into the recirculation loop  118  acts to clean the membranes and remove precipitate material or other solids from the system  100 . As the permeate water circulates within the recirculation loop  118 , the contaminate level may rise. Upon detection that the contaminate level has reached a maximum, sensor  126  may open valve  128  to begin flushing contaminates from the recirculation loop  118  and/or the system  100 .  
         [0033]     During cleaning of the membranes  120 , permeate water may continue to be introduced and circulated within the recirculation loop  118 . Sensor  126  may monitor contaminate levels within the recirculation loop  118 . After a certain amount of time and/or when sensor  126  detects that the contaminate level has reached a minimum contaminate level, sensor  126  may close valve  128  to retard and/or stop the bleeding of contaminates.  
         [0034]     During treatment of influent water, it is contemplated that sensor  126  and/or  136  may detect that the system  100  has attained a maximum contaminate level within the permeate water and/or the recirculation loop  118 . Either sensor  126  and/or  136  may be configured to alter the state of valve  110  from the state shown in  FIG. 1  to the state shown in  FIG. 2 . Permeate water may be introduced into the recirculation loop  118  from the storage tank  134 . The permeate water may circulate for a predetermined time or until sensor  126  detects the contaminate level has reached a constant or has reached a maximum contaminate level. Upon reaching a maximum contaminate level, sensor  126  may open valve  128  to begin flushing contaminates from the recirculation loop  118 .  
         [0035]     This cycle of introducing and recirculating permeate water and flushing the permeate water when a certain contaminate level is reached may be repeated until the sustained contaminate level is at or below a preset contamination level. For example, if the minimum sustained contaminate level is 1,000 ppm, the introduction of permeate water and flushing of contaminates may repeat until the sustained contaminate level in the recirculation loop  118  is at or below 1,000 ppm. After which, sensors  126  and/or  136  may alter the configuration of valve  110  to allow influent water into the system  100  and halt introduction of permeate water.  
         [0036]      FIG. 3  shows a softening membrane in a system  24  for conditioning water according to embodiments of the present invention. In addition to the softening membrane  10 , the water conditioning system  24  comprises a purification device  26  connected in series to the softening membrane  10 . The purification device  26  may be configured to remove additional impurities from a portion of the output flow of softened permeate water generated from the softening membrane  10 . As used herein, impurities removed by the purification device  26  may include minerals, contaminants (e.g., radon, radium, arsenic, chloramine, dissolve iron, metals, sodium), additional hardness, and bacteria (e.g. viruses, giardia, crypotosporidium). The purification device  26  may also be configured to discharge an output flow of second concentrate water. Consistent with embodiments of the present invention, the purification device  26  may comprise a membrane such as a demineralizing membrane like a “tight” reverse osmosis membrane or a loose reverse osmosis membrane. A “tight” reverse osmosis membrane differs from the loose reverse osmosis in that it may reject monovalent ionic contaminants to a higher degree. The tight reverse osmosis membrane may result in demineralized water while the loose reverse osmosis membrane may result in partially demineralized water. In addition, the purification device  26  may comprise a filter such as an activated carbon filter for the removal of chlorine, sulfides, and other taste and odor sources.  
         [0037]     Regardless of whether a tight or loose reverse osmosis membrane is selected, the purification device may operate by taking the softened water from the softening membrane at the existing pressure and purifying it further to become purer water at the point of use, such as the refrigerator ice water dispenser, the kitchen sink or the bathroom sink, places where lower flow rates are typically needed. The rejected concentrated stream may be sent directly to the nearby drain or sewer line.  
         [0038]     Although  FIG. 3  shows that the softening membrane  10  and the purification device  26  as separate elements, it is contemplated that one membrane can perform both softening and purification functions. A high flux, chlorine resistant loose reverse osmosis membrane is one example of a membrane that can perform both softening and purification. The loose reverse osmosis membrane may perform both softening and purification by removing hardness ions as well as reducing bacteria, sodium, fluoride, arsenic, lead and other metal ions that are potentially toxic in higher concentrations.  
         [0039]     Also, it is further contemplated that there are other possible configurations for the system shown in  FIG. 3 . For instance, it may be desirable to have the softening membrane  10  and the purification device  26  aligned in parallel as opposed to a serial connection so that not all the water flow has to be conditioned to the same extent and blending streams of different water qualities is desirable. Also, module size and shape could be different between the softening membrane  10  and the purification device  26 .  
         [0040]      FIG. 3  also shows that the water conditioning system  24  further comprises a prefilter  28  that filters particulates of a specified diameter from the feed water. Examples of particulates that the prefilter  28  may remove comprise elements such as bacteria, protozoa, and other microorganisms. In addition, the prefilter may remove sediments of a specified diameter and other items such as iron and chlorine. In embodiments of the invention, the prefilter  24  may comprise a carbon filter, ceramic filter, or a UV disinfecting device.  FIG. 3  shows the water conditioning system  24  only with one prefilter, however, it is contemplated that more than one prefilters may be used. For example, one or more filters can act as a prefilter and one or more other filters can acts as a polishing filter.  
         [0041]     A pump  30  may receive the filtered water and may boost the pressure. The amount of pressure boost may depend on whether the source of the feed water is a pressurized municipal supply, groundwater or well water. Typically, water pressure from one of these sources will be in the range of about 20 to about 120 pounds per square inch. The pump  30  may then boost the water pressure to a pressure that is greater than 20 pounds per square inch in order to maintain optimal performance of the softening membrane  10  and purification device  26 .  
         [0042]      FIG. 3  shows that a portion of the concentrate water generated from the softening membrane  10  is recycled back through the membrane. In particular, this portion of concentrate water may pass through a filter  32  which may capture any incipient scale produced during idle, maintenance or cleaning periods or bacterial film which may keep the softening membrane cleaner. Although  FIG. 3  shows only one filter  32 , the water conditioning system  24  may have more than one filter. In this embodiment, the filter  32  may comprise filters such as ceramic filters and strainers.  
         [0043]     The water conditioning system  24  in  FIG. 3  may operate by receiving the feed water provided from a water source. The prefilter  28  may filter particulates from the feed water such as bacteria, protozoa, and other microorganisms, as well as other items such as sediments (e.g., total suspended solids), iron and chlorine. The pump  30  may receive the filtered water and may boost the pressure of the water to a pressure that is greater than 20 pounds per square inch. The feed water may enter the softening membrane  10 , where it may be exposed to the surface of the membrane elements. A portion may be caused to pass through the membranes and into the permeate collection material. The retained uncharged components, divalent and multivalent ions may be removed from the membrane as concentrate flow. A portion of the softened permeate water may be ready for use and consumption, while another portion of permeate may enter the purification device  26  for additional removal of impurities. The purification device  26  may generate softened and purified permeate water and may discharge an output flow of concentrate water. A portion of the concentrate from the softening membrane  10  may be recycled back to the membrane through the filter  32  and pump  30 . The rest of the concentrate water from the softening membrane  10  and purification deice  26  may be discharged into a sewer along with the concentrate from the purification device  26 .  
         [0044]      FIG. 4  is another embodiment showing the softening membrane  10  in a second system  34  for conditioning water. The second water conditioning system  34  may be similar to the one shown in  FIG. 3 , except that the system  34  may include a conditioning agent dosing unit  36  configured to supply at least one conditioning agent to the feed water in order to prevent membrane fouling. Antiscalants may be used to prevent scale formation in industrial systems or processes when hard water is concentrated. EDTA (ehtylenediaminetetracetic acid) and its derivatives is one type of antiscalant that has been used in these industrial applications.  
         [0045]     Consistent with embodiments of the present invention, the at least one conditioning agent may comprise one of a scale inhibitor, an antiscalant, a biofoulant suppressant, a pH adjustment chemical additive or combinations thereof. The at least one conditioning agent may also comprise a membrane cleansing agent. All of these conditioning agents may be approved by the National Sanitation Foundation (NSF) and may be suitable for drinking and cooking.  
         [0046]     The scale inhibitor agent, antiscalant (chelating) agent, pH adjustment chemical additive and membrane cleansing agent that may be provided by the conditioning agent dosing unit  36  may be suitable for preventing scale formation and the need for cleaning of the softening membrane  10 . These agents may be useful because at some point the solubility limit of the softening membrane  10  is exceeded, causing salts to precipitate in the membrane elements. The precipitation of salts deposits or adheres to the membrane elements as a scale causing them to eventually clog. An illustrative but non-exhaustive list of scale inhibitor agents, antiscalant agents and membrane cleansing agents may include calcium carbonate antiscalants, phosphonates, biocarbonate, barium sulphate, hydrochloric acid, sulphuric acid and biostatic agents such as benzoic acids, to prevent chlorine degradation.  
         [0047]     The biofoulant suppressants that may be provided by the conditioning agent dosing unit  36  may be suitable for reducing membrane fouling that generally arises from the formation of bacteria such as planktonic and sessile bacteria. An illustrative but non-exhaustive list of biofoulant suppressants may include biocides such as sodium metabisulfite (“sulfites”), and benzoates.  
         [0048]     The water conditioning agents may work in the softening membrane  10  by dissolving, flushing or displacing the feed/concentrate in the lumens of the membrane elements until a substantial part of the volume of the lumens of the elements are clean. With clean membrane elements, high water fluxes across the softening membrane may be maintained. Effluent of this operation may be removed from the softening membrane  10  as concentrate and may be sent to the sewer.  
         [0049]     Consistent with aspects of the invention, the conditioning agent dosing unit  36  may comprise a container or containers that store the conditioning agents and a device to supply the conditioning agents to the feed water such as a valve like a solenoid valve. Other configurations may include a mechanical feeder that doses a desired amount of the agent(s) to the feed water through a valve. A micro fluidic module such as a MEMS type dispenser in cooperation with a meter may supply the conditioning agent(s) to the feed water. These examples are illustrative of only few types of devices that can serve as the conditioning agent dosing unit, it is contemplated that other configurations exist.  
         [0050]     Referring back to  FIG. 4 , the water conditioning system  34  may also comprises a water quality monitoring unit  38  configured to monitor the water quality of the output flow of softened permeate water. In particular, the water quality monitoring unit  38  may monitor the softened permeate water via measurements of turbidity, refractive index, conductivity, pressure, flow and the like. These measurements are illustrative of some measurements that the water quality monitoring unit  38  may take and is not exhaustive. For example, it is contemplated that the water quality monitoring unit may take measurements such as −pH, turbidity, hardness, total dissolved solids (TDS), chlorine and sulfides. Consistent with aspects of the invention, the water quality monitoring unit  38  may comprise devices such as a turbidity meter, an ion selective probe and a conductivity meter.  
         [0051]     The water conditioning system in  FIG. 4  may also include another water quality monitoring unit  38  configured to monitor the water quality of the portion of concentrate water recycled back through the softening membrane  10 . The water quality monitoring unit  38  may monitor the concentrate for fouling, scaling and incipient nucleation of crystals that form scaling. The water quality monitoring unit  38  may comprise a control unit configured to control the supply of the at least one conditioning agent to the input flow of water in accordance with the monitored water quality. The water quality monitoring unit  38  is not limited to this configuration and as an alternative that unit may include an in-situ monitoring device that may be placed near the membrane  10  so that it may track scale formation right at the membrane surface.  
         [0052]     The water conditioning system  34  in  FIG. 4  may operate by receiving the feed water provided from a water source. The prefilter  28  may filter particulates from the feed water such as bacteria, protozoa, and other microorganisms, as well as other items such as sediments, iron and chlorine. The pump  30  may receive the filtered water and may boost the pressure of the water to a pressure that is greater than 20 pounds per square inch. The feed water may enter the softening membrane  10 , where it may be exposed to the surface of the membrane elements. A portion may be caused to pass through the membranes and into the permeate collection material. The retained uncharged components, divalent and multivalent ions may be removed from the membrane as concentrate flow. A portion of the concentrate from the softening membrane  10  may be recycled back to the membrane through the filter  32  and pump  30 . As the water may be recycled back, the water quality monitoring unit  38  may monitor the water for fouling, scaling and incipient nucleation of crystals that form scaling. The water quality monitoring unit  38  may provide a signal to control of supply conditioning agent(s) by the conditioning agent dosing unit  36  in accordance with the monitored water quality. The conditioning agent dosing unit  36  may then supply the conditioning agent(s) to the water which may flow back into the softening membrane  10 . During normal operation, the conditioning agent dosing unit  36  may supply the conditioning agent(s) continuously or periodically to maintain proper operation of the membrane (e.g., prevent scale formation). During idle or off-line time, the conditioning agent dosing unit  36  may supply the conditioning agent to dissolve, flush, rinse or dislodge any deposits that have accumulated on the membrane. Concentrate water that is not recycled backed to the softening membrane  10  may be discharged into the sewer.  
         [0053]     A portion of the softened permeate water may be ready for use and consumption, while another portion of permeate may enter the purification device  26  for removal of impurities. As the water enters the purification device  26 , the water quality monitoring unit  38  may monitor the water quality of the output flow of softened permeate water. In particular, the water quality monitoring unit  38  may monitor the softened permeate water via measurements of turbidity, refractive index, conductivity, pressure, flow and the like. The purification device  26  may then generate softened and purified permeate water and may discharge an output flow of concentrate water, which may be discharged into the sewer.  
         [0054]     Although the water conditioning systems shown in  FIGS. 3-4  may be point-of-entry systems, it is possible to configure them as point-of-use systems. For example, the softening membrane  10 , possibly located in bathrooms, may be configured to prevent residue build-up around sinks and tubs and near dishwashers to prevent build-up on dishes and utensils. Also, the softening membrane  10 , possibly located near a washing machine, may be configured to prevent water deposits from forming on clothing. The purification device may then be located in the kitchen and it may be used for drinking and culinary applications.  
         [0055]     It may be desirable to run feed water or even softened water through the membrane for a few seconds or a minute longer at prevailing (low pressure) city water pressure to displace the high concentration concentrate stream from the membrane lumens. Generally, when a demand for water has ended in a house, it is typical for the membrane module to be left with high hardness concentrate water on the concentrate side of the membrane. Under these circumstances, where the concentrate hardness may be above the saturation limit of the salts present in the water, it is likely that the hardness salts may precipitate onto the membrane causing it to foul and form scale. To help avoid the precipitation of hardness salts over time, it would be desirable to run feed water or softened water through the membrane for a few seconds or a minute longer at prevailing (low pressure) city water pressure to displace the high concentration concentrate stream from the membrane lumens and aid further in the dissolution of any previous hardness scale that might have previously formed or break ion concentration polarization or other contaminants that accumulate within the lumens.  
         [0056]     This flushing process may be done automatically at the end of every water demand cycle, or periodically after a few hours of idle time. In this way, scale may be prevented from forming and clogging the membrane over time during idle operation. The flushing water may be sent to the drain or sewer or to the discharge location for the concentrate. Furthermore, since most feed city waters are below their saturation level with respect to hardness, this state of flushing the membrane may foster the dissolution of any scale that might have formed and lodged within the membrane and may help restore some of the initial higher flux. Additional benefits of this flushing method include breaking the ion concentration polarization, dislodging bacteria or debris, or other ions present.  
         [0057]     This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to make and use the invention. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such 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.