Abstract:
Water purifier using membranes, ion exchange resins and electricity to remove ionic, organic and suspended impurities from water to produce high quality, pure water. Supply water is pre-treated by directing it first into a sediment pre-filter module, a softener module and a sediment removal and dechlorination module. The pre-treated water is supplied to a reverse osmosis module which separates the water into two streams (a purified water stream and a concentrate stream) by collecting fluids from both sides of pressurized membranes. The purified water is passed to an electrodeionization module which further purifies the water and directs the water to an ultraviolet sterilization module. The concentrate stream is divided into a recycle stream which is passed to the inlet of the reverse osmosis module and a waste concentrate stream which flows to an outlet of the machine. A control method for the water purifier is also disclosed.

Description:
FIELD OF THE INVENTION 
     The present invention relates to a water purifier which delivers a high quality, pure stream of water. 
     The present invention also relates to a method for controlling a water purifier to optimize the production of pure water by the water purifier. 
     BACKGROUND OF THE INVENTION 
     The need for water purifiers is expanding as water purifiers are needed for the electronic, pharmaceutical and power industries and purified water is needed for the food, beverage and chemical industries. Pure water is also needed for research purposes, pilot facilities and laboratories. 
     Generally, water purifiers include one or more filtering components and means for directing water through the filtering component(s) so that impurities in the water are removed during passage of the water through the water purifier. Raw, impure water is directed into the water purifier through an inlet and a pure stream of water is obtained from an outlet of the water purifier. The time in which the water remains in each filtering component is often regulated to ensure adequate purification of the water. 
     In the prior art, there are numerous patents and publications directed to water purifiers. In particular, reference is made to the following U.S. patents: 
     U.S. Pat. No. 6,086,754 (Watanabe) describes a water purifier including a timer which controls valves to provide for proper sterilization of the water. The valves are associated with components such as a purification unit, a filter and electrodes. For example, the timer controls the energizing period of the electrodes to ensure that water is heated sufficiently to sterilize it. 
     Also, U.S. Pat. No. 6,080,313 (Kelada) describes a water purifier with several purification and filtration units in a common housing (see FIG.  1 ). A flowboard serves as a base of the water purifier and has several mounting assemblies designed to receive different cartridges. Each cartridges has a different function, for example, an activated carbon filter cartridge and a disinfection cartridge. The type of cartridge and the order of the cartridges can be varied to provide for any number of different flow arrangements. A circuit may be included to shut the unit down if the concentration of dissolved solids exceeds a preset limit, e.g., when the water purifier is not providing sufficiently pure water. 
     U.S. Pat. No. 5,741,416 (Tempest, Jr.) describes a water purifier in which the quality of the water at the outflow is determined by measuring its electrical potential and if the electrical potential indicates that the water is not sufficiently pure, then the water is diverted through a feedback loop to pass through for additional purification treatment. 
     U.S. Pat. No. 5,698,091 (Kuennen et al.) describes a water purifier with a carbon block filter. A flow regulator is provided to ensure that the system operates at an adequate pressure and provides for an adequate exposure time. Specifically, the flow of water through the filter is measured and if it falls below a preset limit, indicative of blockage in the filter, an audio and/or visual indication is provided indicating that the filter needs to be changed. 
     U.S. Pat. No. 5,547,584 (Capchart) describes a self-contained water purifier (which presumably means that the components are situated in a common housing) including filter components and pumps which control flow of the water through the purifier. A programmable logic controller is associated with the pumps and pressure switches to control operation of the system and shut the system down when an indication of a malfunction is detected. 
     U.S. Pat. No. 5,126,050 (Irvine et al.) describes a water treatment apparatus including a microprocessor which controls pumps and valves to provide for desired flows through the apparatus. 
     The water purifiers described in these patents do not include a particular combination of purification and filtering components as in the invention nor do these patents describe a method for controlling a water purifier to optimize the production of pure water as in the invention. 
     OBJECTS OF THE INVENTION 
     It is an object of the present invention to provide a new and improved water purifier. 
     It is another object of the present invention to provide a new and improved water purifier which produces a high quality, pure water stream. 
     It is yet another object of the present invention to provide a new and improved water purifier including several purification/filtration modules which are controlled to achieve overall optimum performance of the water purifier. 
     It is still another object of the present invention to provide a new and improved water purifier including several purification/filtration modules whose operation is monitored and adjusted if necessary to achieve overall optimum performance of the water purifier. 
     It is yet another object of the present invention to provide a new and improved method for controlling components in a water purifier with a view toward optimizing and/or maximizing the purification of water, and/or achieving optimum overall performance. 
     SUMMARY OF THE INVENTION 
     In order to achieve one or more of the objects set forth above, a general embodiment of a water purifier in accordance with the invention has a novel combination of purification and/or filtration components. Further, the water purifier including the purification and/or filtration components is controlled by controlling the individual components in a specific manner. 
     The water purifier uses membranes, ion exchange resins and electricity to remove ionic, organic and suspended impurities from water, producing a high quality, pure water stream. In the water purifier, raw or supply water is pretreated by directing it first into a sediment pre-filter module, then into a softener module and then into a sediment removal and dechlorination module. The pre-treated water is then supplied in a controlled manner to a reverse osmosis module which separates the water into two streams (a purified water stream and a concentrate stream) by collecting fluids from both sides of pressurized membranes in the reverse osmosis module. The purified water stream is passed to an electrodeionization module which further purifies the water and directs the water to an ultraviolet sterilization module from which pure water is obtained. The concentrate stream is divided into a recycle stream which is passed to the inlet of the reverse osmosis module and a waste concentrate stream which flows to an outlet of the machine. 
     An important feature of the invention is the presence of a central microprocessor which utilizes a proprietary program to control the modules, valves and pumps to ensure satisfactory water quality and operation of the machine. The microprocessor is coupled to various monitors and sensors associated with the modules and determines the necessary or allowable operation of the valves and pumps. If the valves or pumps deviate from the necessary or allowable operation, the control system is programmed to either automatically correct the deviation or to notify the operator that manual correction is necessary. In this manner, the water purifier will not operate is the conditions for generating pure water are not proper. 
     One exemplifying embodiment of the water purifier in accordance with the invention comprises a softener module arranged to receive the supply water and remove metallic ions from the water, a de-chlorination module arranged to receive water from the softener module and remove oxidizing and organic compounds from the water, a control valve arranged downstream of the de-chlorination module for regulating flow of water from the de-chlorination module, a reverse osmosis module arranged downstream of the control valve and comprising reverse osmosis membranes which purify the water upon flow of water through the membranes, a pump arranged between the control valve and the reverse osmosis module for pump water at a high pressure through the reverse osmosis module, an electrodeionization module arranged to receive water from the reverse osmosis module and remove ions from the water to provide a stream of pure water, and a control system for controlling operation of the softener module, the de-chlorination module, the control valve, the reverse osmosis module, the pump, the electrodeionization module and the ultraviolet sterilization module to optimize purification of the supply water. 
     The control valve, pump and modules mentioned above may be arranged in connection with a frame forming a self-contained unit, e.g., arranged in an interior space defined by the frame. 
     The control system is coupled to various monitors associated with the modules including a flow monitor associated with the softener module for measuring rate of flow of water into the softener module. The control system determines processing capacity of the softener module based on the measured flow rate and initiates regeneration of the softener module, e.g., regeneration of sodium ion resins in a tank, based on analysis of the determined processing capacity of the softener module and a pre-determined capacity of the sodium ion resins. 
     Another flow monitor is associated with the de-chlorination module for measuring rate of flow of water into the de-chlorination module. An indicator visible from exterior of the water purifier is preferably provided. The control system determines processing capacity of carbon elements of the de-chlorination module and controls the indicator to provide an indication when replacement of the carbon elements is required. 
     Other monitors include a water quality monitor for measuring ionic concentration in the water, a temperature monitor for measuring temperature of the water, and a pressure monitor for measuring pressure of the water. The control system is preferably designed to activate an indicator or alarm when the measured ionic concentration, temperature or pressure of the water is outside of an operational range and/or user pre-set value. 
     Another monitor is a water quality monitor for measuring ionic concentration in pure water outlet from the electrodeionization module. The control system calculates electrical voltage and current required by the electrodeionization module and automatically adjusts each to achieve optimum outlet water quality, if such adjustment is necessary. 
     An optional sediment pre-filter module may be arranged before the softener module and removes particles from the supply water. Pressure sensors measures pressure of ceramic elements of the sediment pre-filter module at an inlet end of the module and at an outlet end of the module. The control system analyzes the pressure readings and determines when the sediment pre-filter module is performing below a threshold satisfaction level indicative of the need to clean the ceramic elements. 
     Another optional module is an ultraviolet sterilization module arranged after the electrodeionization module and is constructed to eliminate bacteria from the water such that the pure water stream is provided from the ultraviolet sterilization module. 
     A method for controlling a water purifier including in sequence a softener module, a de-chlorination module, a pump, a reverse osmosis module and an electrodeionization module, entails controlling the softener module, de-chlorination module, reverse osmosis module and the electrodeionization module. Control of the softener module may entail measuring flow rate of water into the softener module, determining whether the processed volume of water by the softener module exceeds the volumetric softening capacity of the softener module, and directing regeneration of the softener module when the processed volume of water exceeds the volumetric softening capacity. Control of the de-chlorination module may entail measuring flow rate of water into the de-chlorination module, determining whether the processed volume of water by the de-chlorination module exceeds the processing capacity of the de-chlorination module, and directing replacement of the de-chlorination module when the processed volume of water exceeds the processing capacity. Control of the reverse osmosis module may entail measuring the flow rate and pressure of an RO permeate stream and an RO concentrate stream generated by the reverse osmosis module, determining whether the flow rates and pressure of the RO permeate stream and RO concentrate stream are within allowable operating margins or non-optimal, and adjusting valves to change at least one of the flow rate and pressure of the RO permeate stream and RO concentrate stream when the flow rates and pressure of the RO permeate stream and RO concentrate stream are determined to be outside of allowable operating margins or non-optimal. Control of the electrodeionization module may entail measuring the flow rate and pressure of an EDI process stream, an EDI electrode stream and an EDI concentrate stream which pass separately through the electrodeionization module, determining whether the flow rates and/or pressure of the EDI process stream, EDI electrode stream and EDI concentrate stream are within allowable operating margins and/or non-optimal, and adjusting valves to change the flow rate and/or pressure of the RO permeate stream and/or RO concentrate stream when the flow rates and/or pressure of the RO permeate stream and/or RO concentrate stream are determined to be outside of allowable operating margins or non-optimal. 
     The method may also include measuring ionic concentration in the water at a location in the water purifier which is indicative of the quality of the water, determining whether the measured ionic concentration is within allowable margins and optimal, and adjusting the electrodeionization module when the measured ionic concentration is determined to be outside of the allowable margins or non-optimal. Instead of or in addition to adjusting the electrodeionization module, an indicator or warning device may be activated. 
     The temperature of the water can be measured at a location in the water purifier, a determination is made if the temperature of the water is outside of allowable margins and if so, an indicator or warning device is activated. 
     Other enhancements of the method include measuring pressure of the water at the softener module, determining if the pressure of the water is outside of allowable margins, and activating an indicator or warning device when the pressure is determined to be outside of allowable margins. Another enhancement is to monitor time of operation of the pump and activate an indicator or warning device when maintenance of the pump is required as determined by elapsed time of operation of the pump. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention, together with further objects and advantages thereof, may best be understood by reference to the following description taken in conjunction with the accompanying drawings, wherein like reference numerals identify like elements, and wherein: 
     FIG. 1 is a flow diagram of the water purification process in a water purifier in accordance with the invention; 
     FIG. 2 is a front view of one embodiment of a water purifier in accordance with the invention; 
     FIG. 2A is a top view of the embodiment of the water purifier shown in FIG. 2; 
     FIG. 3 is a schematic of a water purifier in accordance with the invention; 
     FIGS. 4-11 are flow charts of the operation of a water purifier in accordance with the invention; and 
     FIG. 12 is a diagram showing the connection of various components of a water purifier in accordance with the invention to the control system. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to the accompanying drawings wherein like reference numerals refer to the same or similar elements, the water purification process will first be described with reference to FIG.  1 . 
     As an initial step, supply water, i.e., the water to be purified, is directed into and through a series of pre-treatment or pre-conditioning modules designed to condition the supply water prior to primary and secondary processing operations. 
     The first pre-treatment module is a sediment pre-filter module  10 . Sediment pre-filter module  10  includes tubular ceramic elements with a specific pore size (filter rating) designed to trap particles on the surface of the ceramic elements and enable the removal of the suspended particles from the surface of the ceramic elements. It has been found that an effective pore size of 10 microns is particularly useful for optimum practice of the invention but the invention is not limited to ceramic elements having such a pore size. 
     In a proposed commercial embodiment, the sediment pre-filter module  10  includes stainless steel or polypropylene tubular element housings and the ceramic elements are placed in the housings and have a diameter substantially equal to the diameter of the tubular element housings. For example, the tubular element housings and ceramic elements may both have a diameter of about 2½″. The tubular element housings are arranged such that the supply water flows from the exterior of the module  10  through the tubular element housings, and thus into contact with the ceramic element(s) therein, and into the interior of the module  10 . 
     The sediment pre-filter module  10  incorporates an automated cleaning (backwash) feature to flush the ceramic elements in order to remove accumulated particles from the surfaces of the ceramic elements. Flushing of the ceramic elements is performed at predetermined intervals, either selected by the user or programmed by the manufacturer or user, and entails the passage of a flow of a high velocity water stream from a pure water reservoir  12  in a direction opposite to the direction of the flow of supply water through the tubular element housings. Flushing of the ceramic elements is shown in the operating sequence in FIGS. 4-11 with reference to, e.g., elements  126 - 130  (the sediment pre-filter module being “module 1” in FIGS.  4 - 11 ). Other systems for flushing ceramic elements known to those skilled in the art could also be used in conjunction with the sediment pre-filter module  10 . 
     The sediment pre-filter module  10  also incorporates pressure sensors  14 , 16  for measuring the pressure of the water at the inlet and outlet ends of the module  10 , respectively. The pressure readings are directed to a control system which determines the frequency at which the module should be cleaned as well as considers whether the pressure readings are indicative of a problem with the water purification process. In the latter case, the pressure readings might reveal that there is an inadequate amount of supply water for proper operation of the water purifier. As such, a control valve situated after the pre-treatment modules could be closed to prevent flow of water to components downstream, such as a pump, which would be detrimentally affected by inadequate water flow. 
     Sediment pre-filter module  10  is an optional module and is not required to enable practice of the invention, although it is present in a preferred embodiment. If a sediment pre-filter module is not used, then the supply water should be filtered to 10-microns and be free of suspended solids and materials, which might precipitate on concentration. Further, ideally, the feed water should be chlorinated continuously at no less than 0.2 ppm free chlorine or the water purifier flushed with biocide periodically. 
     After particles are removed from the supply water in the sediment pre-filter module  10 , the water is directed through a conduit  18  to a softener module  20 . Softener module  20  “softens” the water by removing hard minerals such as calcium and magnesium. In the event that the sediment pre-filter module  10  is not present, then the feed water would pass directly into the softener module  20 . 
     In a proposed commercial embodiment, softener module  20  utilizes sodium form ion exchange resins to remove calcium and magnesium ions (hereinafter referred to as hardness ions) from the supply water. The ion exchange resins are stored in one or more vertically oriented fiberglass or epoxy-coated steel tanks. The supply water is directed into each tank at its top and flows to the bottom of the tank by gravitational force while an exchange of hardness ions for sodium ions on the resins occurs. 
     Other means for removing hard minerals from the supply water known to those skilled in the art could also be used in the invention instead of or in addition to the softener module  20  described above. 
     Once the sodium ions in the tank(s) are exhausted, the resins must be regenerated. One manner to regenerate the sodium ions is to inject a brine solution from a brine reservoir  22  into the resin tank(s), although other ways to regenerate the sodium ions known to those skilled in the art can also be used in the invention. 
     A flow monitor  24  is associated with the softener module  20  to measure the flow rate of supply water into the softener module  20 . The flow monitor  24  provides the measured flow rate of supply water into the softener module  20  to the control system. Based thereon, the control system is able to determine the processing capacity of the softener module  20  (using a localized hardness concentration value input by the operator) and totals the processed volume and compares the processed volume to the calculated volumetric capacity of the resins in the tank. 
     The hardness concentration value is preferably adjusted to reflect the current operating conditions since it often changes in light of seasonal variations in the supply water. An inaccurate hardness concentration value would result in non-optimal operation of the water purifier and may in fact actually damage the water purifier. Further, the free chlorine levels often vary seasonally along with the hardness concentration value and the machine should be adjusted accordingly. The free chlorine level and hardness concentration value of the supply water are thus periodically measured and entered into the control system of the water purifier so that the control system can take into account variations in these parameters and adjust the operation of the water purifier accordingly. 
     When the total flow into the softener module  20  is greater than the volumetric capacity of the tank(s) thereof, regeneration is initiated (automatically). This can take the form of enabling of a regeneration bit, as described below in the operating sequence (with reference to elements  156 - 162  and  238 - 244 , the softener module  20  being “module 2”). A flag will be created in the control software or a register thereof, which may result in a notification to the operator on the control panel that regeneration is necessary, and when it is possible to perform the regeneration procedure, the control system can automatically initiate its performance. 
     Thus, the control system automatically determines when regeneration of the resins is required and is coupled to the brine reservoir  22  and associated injection pump (not shown) to cause injection of brine into the resin tank(s) in the softener module  20 . To this end, the brine reservoir  22  should be continually maintained with a sufficient amount of salt. 
     From the softener module  20 , water is directed through a conduit  26  to a de-chlorination module  28 . De-chlorination module  28  involves the application of two pre-treatment processes, an ultraviolet sterilization and total organic carbon (TOC) reduction stage  28   a  and a sediment removal and de-chlorination stage  28   b . The ultraviolet sterilization and TOC reduction stage  28   a  is optional and not required in the practice of the invention, although it is present in a preferred embodiment. 
     For the sediment removal and de-chlorination stage  28   b , stainless steel or polypropylene tubular housings are provided and solid block, activated carbon elements are situated in the tubular housings. The carbon elements preferably have the same diameter as the tubular housings, e.g.,  2½″, and are tubular, solid and acid washed. When the water passes through the carbon elements, oxidizing (chlorine) compounds are removed. In addition, organic compounds are removed. The carbon elements are preferably encased in a polypropylene membrane which prevents sediments (including carbon fragments) from migrating downstream of the elements.    
     The carbon elements are in the form of a replaceable cartridge, as is known in the art, in order to enable replacement once the effectiveness of the carbon elements has been rendered null. 
     For the optional ultraviolet sterilization portion of stage  28   a , ultraviolet lamps (254 nm wavelength) are suspended down through the center of the tubular housings to reduce microbial growth, which may occur on the interior carbon surfaces. The lamps are placed in the housings and surround by the membrane containing the carbon. 
     The de-chlorination module  28  includes a flow monitor  30  at an inlet end that measures the flow rate of supply water into the de-chlorination module  28 . The flow monitor  30  provides the measured flow rate of supply water into the de-chlorination module  28  to the control system. Based thereon, the control system is able to automatically calculate the processing capacity of the carbon elements (using a localized oxidizing concentration value input by the operator) and alerts the operator when replacement of the carbon elements is required. This is determined by totaling the volume of water processed by the de-chlorination module  28 , and comparing the processed volume to the calculated volumetric capacity of the carbon elements. The replacement function is described in the flow chart of FIGS. 4-11 with reference to elements  164 - 170 . 
     Replacement of the carbon elements, i.e., the cartridge, can also be determined when the pressure drop increases by 8-10 psid over the pressure differential of a clean cartridge. The pressure differential can be determined by arranging pressure monitors before and after the carbon elements (e.g., monitors  30 ,  30   a ), connecting the pressure monitors to the control system and programming the control system to calculate the pressure differential and compare it to a pre-determined pressure differential of a clean cartridge. The water purifier is thus designed to allow access to the carbon elements and to enable replacement of the carbon elements. 
     The water flowing from the de-chlorination module  28  has completed the pre-treatment or pre-conditioning stages and is now ready for the primary purification stage. Such water is now referred to as feed water. 
     The feed water flows from the de-chlorination module  28  through a conduit  32  having an inlet control valve  34  arranged in connection therewith. Control valve  34  is controlled by the control system and is usually opened when the water purifier is turned on allowing feed water to flow to a pressurization pump module  36  including a pump  38 . When the water purifier is turned off (or the flow of water into the water purifier as measured by flow monitor  14  is less than a required minimum), the control valve  34  closes thereby preventing the flow of feed water through the remainder of the water purifier, and more specifically through the pump  38  which is susceptible to damage in the presence of an insufficient water flow. 
     In a proposed commercial embodiment, pump  38  is a multi-stage, stainless steel centrifugal design and generates the high pressures (200-600 PSIG) required for proper operation of the water purifier. Other pumps can also be used in the invention without deviating from the scope and spirit thereof. 
     The pump module  36  also includes a feed water quality monitor  40  that continuously measures the ionic concentration in the feed water and provides the concentration value to the control system. The pump module  36  also includes temperature monitors  42  and pressure monitors  44  that provide measured values to the control system. Monitors  40 , 42 , 44  are shown associated with the conduit  32  in that portion between the control valve  34  and the pump  38 . Monitors  40 , 42 , 44  can be located at other locations such as after the pump  38 . 
     The control system monitors these parameters and alerts the user when any value falls outside of the correct machine operating requirements. The control system also monitors the operating hours for the pump  36  and notifies the user when periodic maintenance of the pump is required or when the pump has malfunctioned. 
     The high-pressure pump  38  provides a pressurized water supply to a reverse osmosis module  46  including one or more element housings containing semi-permeable reverse osmosis membranes configured in series or parallel, depending upon the design flow rates for the water purifier. In each element housing, purified water is collected within a central tube (permeate tube). The semi-permeable reverse osmosis membranes, under sufficient effective pressure, allow passage of purified water while rejecting and concentrating dissolved and suspended solids. The feed water is thus separated by the membranes and leaves the module  46  in two streams, as purified water supply (RO permeate) through a conduit  48  and concentrated wastewater (RO concentrate) through a conduit  50 . 
     The RO permeate from each membrane is collected in a central manifold, where a check valve prevents reverse flow into the membranes, and from the central manifold, the RO permeate is directed into an inlet of the secondary processing module, discussed below. 
     The RO concentrate leaving each housing, is collected in a concentrate manifold and flows to a concentrate header assembly. This concentrated water is divided into a recycle stream and a waste stream. The recycle stream is directed back through a conduit  41  to the inlet of the primary processing module where it is blended with the feed water, i.e., into conduit  32  in that portion between the control valve  34  and the pump  38 . This allows higher machine recovery while maintaining adequate cross flow through the membranes. 
     Flow monitor  43  is associated with conduit  41  and measures the flow of the recycle stream. Flow monitor  45  is associated with the waste stream and measures the flow of the waste stream. 
     The waste stream is directed to a central wastewater manifold used for collection of all waste streams from the water purifier. The wastewater manifold directs all waste flows to the local waste system. Incorporated in the waste stream manifold is a control valve  52  coupled to the control system. Control valve  52  is periodically opened at predetermined intervals to allow a high velocity flow of water to purge the membrane surfaces and prevent bacteria growth within the reverse osmosis module  46 . 
     The reverse osmosis module  46  includes flow and pressure monitors in each process stream that measure the flow and pressure of the fluid and provide the measured flow rate per minute of processing time and instantaneous process pressures to the control system. Flow monitor  47  is associated with conduit  48  and measures the flow of the RO permeate. Further, a control valve  51  is associated with conduit  48  to enable the removal or draining of the RO permeate. The measurements provided by flow monitors  43 , 45  provide the total flow of the RO concentrate. 
     The control system calculates the optimum required flow rates and pressures for each process stream and adjusts control valves  51 , 52  to achieve these parameters. The control system also monitors each process parameter and notifies or alerts the user when any value falls outside of the correct machine operating requirements. For example, the control system monitors the operation of the reverse osmosis module  46  and alerts the user when periodic maintenance or cleaning of the module is required. 
     The reverse osmosis module  46  is the primary processing unit in the illustrated embodiment of the invention. From the reverse osmosis module  46 , the purified water is directed to a secondary processing stage. 
     The first component in the secondary processing stage is an electrodeionization (EDI) module  54 . The purified water from the reverse osmosis module  46 , i.e., the RO permeate collected in the central manifold, is separated into three distinct processing streams prior to entering the electrodeionization module  54 : a product stream in conduit  58  (which is destined to be purified by the EDI module  54 , then directed to an outlet post-treatment module); a concentrate stream  60  and an electrode stream  62 . 
     The EDI module  54  uses hydrogen form cation and hydroxide form anion ion exchange resins, ion selective membranes and electricity to remove remaining ions in the pure water stream. Pure water processed through the EDI module  54  is directed through a conduit  64  to a post-treatment sterilization module  56 . 
     The concentrate and electrode streams are directed through the EDI module  54  and then to the central wastewater manifold or a unit drain connection  96  (see FIGS.  2  and  2 A). The EDI module  54  includes a pure water quality monitor  66  that continuously measures the ionic concentration in the outlet pure water and provides the concentration value to the control system. The control system calculates the required electrical voltage and current required by the EDI module  54  and automatically adjusts each to achieve optimum outlet water quality. 
     The EDI module  54  also includes flow monitors  68 , 70 , 72  for each process stream (the product stream, concentrate stream and electrode stream, respectively) that measure the flow rate of the associated stream and provide the measured flow rate per minute of processing time and instantaneous process pressures to the control system. Based thereon, the control system calculates the optimum required flow rates for each process stream and adjusts unit control valves  69 , 71 , 73  to achieve these parameters, if such adjustment is necessary. The control system also monitors each process parameter and notifies or alerts the user when any value falls outside of the correct machine operating requirements. 
     Instead of or in addition to providing independent flow monitors  70 , 72  for the concentrate stream  60  and the electrode stream  62 , it is also possible to provide flow orifices. 
     The control system also monitors the operation of the EDI module  54  and notifies or alerts the user when periodic maintenance or cleaning of the module is required. 
     Product (pure) water leaving the EDI module  54  passes through a final post-treatment conditioning module  56  designed to insure product water quality prior leaving the unit. The post-treatment conditioning module is in the illustrated embodiment, a UV sterilization module  56  which uses 254 nm wavelength ultraviolet lamps to effectively destroy (sterilize) any residual organisms (bacteria) that may be present in the pure water steam exiting the EDI module  54 . The intensity of the ultraviolet light provided by the lamps is measure by a measurement device  74 , which is connected to the control system so that the control system continually monitors the intensity of the ultraviolet light and notifies or alerts the operator when replacement of the lamps is required. Purified water is thus obtained at the outlet of the sterilization module  56 . 
     The UV sterilization module  56  is an optional feature and is not required for the practice of the invention. 
     The modules, pumps, valves and monitors described above are preferably arranged in a frame with access to certain replaceable components easily provided, e.g., the carbon elements of the de-chlorination module. The compact design of the water purifier thereby provides several significant advantages most notably the need for minimal floor space. The water purifier is a compact self-contained unit requiring only a connection to an inlet water supply and the input of several operating parameters in order to commence operation. 
     The various monitors described above generally are designed to provide a signal to the control system relating to the physical quantity the monitor is designed to measure. For example, a flow monitor would provide a signal whenever a specific volume of water is measured. Thus, the control system can determined the total amount of water based on the number of signals received. 
     With respect to the control system, the control system is a novel in that it integrates and controls the operation of each process module in the invention in order to achieve optimum overall performance. The operation of the modules is coordinated by the control system to provide for optimum overall performance. 
     The control system uses a central microprocessor and operator interface device to integrate and control the operation of each module. The central program controls each vital operating parameter of the water purifier as described above, continually monitoring the performance of individual modules and adjusting the module if necessary to achieve overall optimum unit performance. The control program thus monitors the operation of each module by receiving and processing data from monitors associated with each module and notifies or alerts the operator when component maintenance or operational repairs are required. 
     For example, an alarm, or other oral and/or visual indicator designed to attract the attention of the operator, will be activated in the event of high inlet water temperature, low inlet pressure, high permeate pressure, pressure pump failure and poor outlet water quality. If any alarm condition exists and shuts down the water purifier, the water purifier can only be re-started by first pushing an alarm reset button and then reinitializing the operating status of the water purifier. 
     The water purifier uses the computer operator interface (a control panel discussed below) to display operational parameters of the machine, to indicate alarms and to indicate required external operator maintenance, and allows customization of operational parameters and constraints used by the control system to calculate required operational performance conditions. 
     Exemplifying operational functions that the microprocessor controls include: 
     1. Unit operational sequences including preflush, purge and production. 
     2. Unit production performance including individual component production performance. 
     3. Unit operational parameters including temperature, inlet/outlet pressures, product flow, waste flow, inlet/outlet quality. 
     4. Individual component maintenance requirements. 
     5. Unit alarms including loss of utility services (feed water, compressed air, electricity) and unit malfunction. 
     FIG. 2 is a front view of an exemplifying commercial embodiment of a water purifier in accordance with the invention and FIG. 2A is a top view thereof. The water purifier is contained entirely within a frame or outer housing  76 . An inlet connection  78  for the water supply is arranged on the housing  76 . A control panel  80  is arranged on a front panel  82  of the housing  76 . Control panel  80  includes a display screen (LED, LCD and the like) and input buttons or function keys. 
     System indicators are also arranged on the front panel  82  and include a system pressure indicator  84 , a permeate flow rate indicator  86 , an EDI concentrate flow rate indicator  88  and a RO concentrate flow rate indicator  90 . 
     The permeate flow indicator  86  displays an indication of the flow of RO permeate obtained from the flow monitor  47  associated with the RO permeate stream. The EDI concentrate flow rate indicator  88  displays an indication of the flow of EDI concentrate obtained from the flow monitor  70 . The RO concentrate flow rate indicator  90  displays an indication of the flow of RO concentrate obtained from the flow monitors  43 , 45 . 
     An RO recycle valve  92  and an RO concentrate valve  94  are also arranged in connection with the front panel  82 . These valves enable manual adjustment of the recycle stream from the reverse osmosis module  54  and the concentrate stream from the reverse osmosis module  54 , respectively. 
     The water purifier is designed to operate at a specified pressure. To ensure proper and optimal operation of the water purifier, the RO recycle valve  92  and RO concentrate valve  94  might require adjustment such that the proper recovery is set (the ratio of permeate flow to the feed water flow). The flow rates are shown on the indicators  88 , 90 . For example, a 75% recovery system will have 25% of feed water as concentrate. If the concentrate rate is higher or lower as seen by the indicators  88 , 90 , manual adjustment of the RO recycle valve  92  and/or RO concentrate valve  94  will bring the recovery rate to the designed rate at which the system will perform optimally. 
     It can be seen from FIGS. 2 and 2A that the reverse osmosis module  54  include four element housings which are arranged in series so that feed water passes through all four element housings. The number and size of the element housings is variable so that if a smaller number of element housings were desired to be used, the element housings might be designed to be larger to enable the same flow rate of water to be processed. 
     FIGS. 2 and 2A also show a drain  96  from the EDI module  54 , from both the concentrate and electrode streams, or a manifold in which the two streams are combined, and another drain  98  from a central wastewater manifold. 
     FIG. 3 shows another schematic diagram of the water purification process in accordance with the invention. Included in FIG. 3 are several valves denoted CIP or CIP connection valves. These valves are used to clean and/or flush the different components of the water purifier. 
     The reverse osmosis module  46  and the EDI module  54  are cleaned separately, or in some situations can even be cleaned together. To clean the reverse osmosis module, a CIP valve  300  is opened while the supply water inlet valve is closed. Water during the cleaning cycle is directed through the system to the CIP outlet valve  302 . Valve  308  is closed to prevent water passing through to the EDI module  54 . 
     The EDI module  54  is cleaned by opening a CIP valve  304 . Water is directed through the EDI module  54  to a CIP outlet valve  306 . 
     Referring now to FIGS. 4-11, a flow chart of the operating sequence of a water purifier in accordance with the invention will now be described. 
     The operation of the water purifier starts at circle  100  and proceeds to a determination of the operating mode of the unit at  102 . For the following discussion and in FIGS. 4-11, the water purifier is referred to as the unit. 
     The unit has three operating modes, service (in which water is purified), clean (in which the unit is cleaned) and rinse (in which the unit is rinsed). 
     In the clean mode, operation proceeds to a determination as to whether an indicator for the start of the clean cycle is engaged at  104 . If not, the sequence waits until such time as the indicator for the start of the clean cycle is engaged. Once the indicator for the start of the clean cycle is engaged, the clean cycle commences at  106 . Engagement of the indicator for the start of the clean cycle can be performed by entering appropriate commands via the control panel  80 . 
     The operation proceeds to a determination whether module 4 cleaning alert bit is engaged at  108 . Module 4 is the reverse osmosis module. Engagement of the cleaning alert can be performed automatically by the water purifier when certain operating parameters are not satisfied. These operating parameters can be set based on the measured flow and pressure of the RO concentrate stream and RO process stream by monitors  43 , 45 , 47 . 
     If the module 4 cleaning alert bit is not engaged, a clean cycle timer is engaged at  110 . A determination is then made at  112  if the clean cycle time is greater than a preset value which is the pre-set time for the duration of the clean cycle. If not, the clean cycle continues. Once the clean cycle time is greater than the pre-set value, the operator indicator is cleared at  114 . A determination is made whether the clean cycle is engaged at  116  (see FIG.  5 ). If so, the clean cycle commences again at  106 . If not, the operating mode of the unit is again checked at  102  to determine whether the operating mode of the unit is service, rinse or clean. 
     If module 4 cleaning alert bit is not engaged, then a determination is made whether the clean cycle is engaged at  116 . If so, the clean cycle commences at  106 . If not, the operating mode of the unit is again checked at  102  to determine whether the operating mode of the unit is service, rinse or clean. 
     In the service mode, a determination is made whether the unit is in a manual service mode or an automatic service mode at  118  (see FIG.  6 ). Placement of the unit in the manual or automatic service mode is performed via the control panel  80 . If the unit is in the automatic service mode, a determination is made whether the level interlock is engaged at  120 . If so, the unit proceed as if it is in the manual service mode. If not, the automatic service mode continues by engaging a standby timer at  122 . A determination is then made whether the value of the standby timer is equal to a value preset by the user at  124 . 
     If the standby timer value does not equal the user preset value, then a determination is made whether the module 1 clean cycle bit is engaged at  126 . Module 1 is the sediment pre-filter module  10 . If so, the module 1 clean cycle is engaged at  128 , a determination is then made periodically whether the cycle is complete at  130  and once the cycle is complete, a determination is made whether the module 2 regeneration bit is engaged at  132  (see FIG.  7 ). Module 2 is the softener module  20  and engagement of the regeneration bit may be accomplished automatically when the calculated volumetric flow into the softener module  20  exceeds the volumetric capacity of the tank. If in this case, regeneration of the softener module  20  is required and the regeneration cycle is commenced at  134  and a determination is periodically made as to whether the cycle is complete at  136 . The module 2 regeneration is the regeneration of the sodium ions in the tank(s) of the softener module  20  which is achieved by directing brine from the brine reservoir into the softener module  20 . 
     Once the regeneration cycle is complete, or if the module 2 regeneration bit is not engaged, a determination is made whether the module 3 replacement bit is engaged at  138 . Module 3 is the de-chlorination module  28 . Engagement of the module 3 replacement bit is an indication that one or more of the elements of the de-chlorination module requires replacement, e.g., the cartridge requires replacement. Thus, when the module 3 replacement bit is engaged, an operator indicator is enabled at  140  and a determination is periodically made as to whether the cartridge has been replaced at  142 . 
     Once it has been determined that the element or elements have been replaced, or if the module 3 replacement bit is not engaged, the operator indicator is cleared at  144  and the sequence returns to determine again whether the level interlock is engaged at  120 . 
     Referring back to FIG. 6, when the standby timer value equals the user pre-set value, operation of the unit is engaged at  144 . Unit operation is also engaged when the service mode is set to manual or when the level interlock is engaged. 
     Engagement of the unit operation initially entails determining whether the module 1 dP value is greater than a user pre-set value at  146 . This is performed by the control system. If so, module 1 clean bit cycle is engaged at  148 . The module 1 dP value is a value obtained by the difference between the outlet pressure of the water from the sediment pre-filter module  10 , as obtained by pressure monitor  16 , and the inlet pressure of the water into the sediment pore-filter module  10 , as obtained by pressure monitor  14 . If this difference is above a certain predetermined value, it would be indicative of build-up of sediments on the ceramic elements in the sediment pre-filter module  20 . The user pre-set value is determined based on the maximum allowable difference in pressure which would provide adequate sediment removal without unduly impending the flow of water. Once the build-up of sediments is excessive to the point where it would interfere with the operation of the water purifier, then the clean cycle bit is engaged to cause cleaning or flushing of the ceramic elements. 
     After the module 1 clean bit cycle is engaged, or if the module 1 dP value is not greater than the user pre-set value, a determination is made whether the module 1 inlet pressure value is less than a user pre-set value at  150  (see FIG.  7 ). The inlet pressure of module 1 (the sediment pre-filter module  10 ) is determined by pressure monitor  14 . The control system assesses the relation between the pressure measured by monitor  14  and the user pre-set value. The user pre-set value is determined based on what the minimum possible water pressure into the sediment pre-filter module  20  is required to ensure adequate operation of the water purifier. 
     If so, a service alarm is sound at  152 . After the alarm sounds, a determination is made whether the alarm reset is engaged at  154 , i.e., a response to the alarm was effected. If not, the alarm continues to sound. Instead of an alarm, any type of warning device, oral and/or visual, can be used. After the alarm reset is engaged, the operating sequence returns to again check the unit&#39;s operating mode at  102 . 
     If the module 1 inlet pressure value is not less than the user pre-set value, the module 2 total flow is measured at  156  and the allowable total flow for module 2 is calculated at  158 . A determination is made whether the module 2 total flow is greater than the calculated allowable flow at  160  and if so, then the module 2 regeneration bit is enabled at  162 . Module 2 is the softener module  20  including a tank of sodium ion resins which require regeneration after a certain volume of water is passed through the tank. Measurement of the total flow into softener module  20  is obtained by flow monitor  24 . 
     When the module 2 total flow is not greater than the calculated allowable flow, or after the module 2 regeneration bit is enabled, the module 3 total flow is measured at  164  and the allowable total flow for module 3 is calculated at  166 . Measurement of the flow into module 2 is performed by flow monitor  24  with the total flow being determined in the control system. 
     A determination is made whether the module 3 total flow is greater than the calculated allowable flow at  168 , and if so, then the module 3 replacement bit is enabled at  170 . Module 3 is the de-chlorination module  28  and the measurement of the total flow into module 3 is obtained by the flow monitor  30 . Calculation of the allowable total flow for module 3 is performed in the control system as well as the relative analysis of the calculated allowable total flow to the measured total flow. 
     When the module 3 total flow is not greater than the calculated allowable flow, or after the module 3 replacement bit is enabled, a determination is made whether the module 4 temperature value is greater than a user pre-set value at  172  (see FIG.  8 ). If so, a service alarm is sound at  174 . After the alarm sounds, a determination is made whether the alarm reset is engaged at  176 , i.e., a response to the alarm was effected. If not, the alarm continues to sound. Instead of an alarm, any type of warning device, oral and/or visual, can be used. After the alarm reset is engaged, the operating sequence returns to again check the unit&#39;s operating mode at  102 . 
     The module 4 temperature value is determined by temperature monitor  42  which is positioned to measure the temperature of the feed water proximate the RO module  46  in the illustrated embodiment. Temperature monitor  42  can be situated at other locations in the process. 
     When the module 4 temperature value is not greater than the user pre-set value, a determination is made whether the module 4 flow rates equal the required flow rates at  178 . If not, the module 4 control valves are adjusted at  180 , and it is again considered whether the module 4 flow rates equal the required flow rates. Thus, when needed, the module 4 control valves will be continually adjusted until the measured module 4 flow rates equal the required flow rates. 
     Once the module 4 flow rates equal the required flow rates, a determination is made whether module 4 pressures equal the required pressures at  182 . If not, the module 4 control valves are adjusted at  184 , and it is again considered whether the module 4 pressures equal the required pressures. Thus, when needed, the module 4 control valves will be continually adjusted until the measured module 4 pressures equal the required pressures. 
     The module 4 pressure is determined by pressure monitor  44  which is positioned to measure the pressure of the feed water proximate the RO module  46  in the illustrated embodiment. Pressure monitor  44  can be situated at other locations in the process. 
     Once the module 4 pressures equal the required pressures, the module 4 total operation hours is measured at  186 . A determination is made whether the module 4 total flow is greater than a user pre-set value at  188  and if so, the module 4 cleaning alert bit is enabled at  190  and an operator indicator is enabled at  192 . 
     If the module 4 total flow is not greater than the user pre-set value, or after the operator indicator is enabled, a determination is made whether the module 5 flow rates equal the required flow rates at  194  (see FIG.  9 ). Module 5 is the EDI module  54  and the measurement of the flow rates is obtained by flow monitors  68 , 70 , 72 . If not, the module 5 control valves are adjusted at  196 , and it is again considered whether the module 5 flow rates equal the required flow rates. Thus, when needed, the module 5 control valves will be continually adjusted until the measured module 5 flow rates equal the required flow rates. 
     Once the module 5 flow rates equal the required flow rates, a determination is made whether module 5 pressures equal the required pressures at  198 . If not, the module 5 control valves are adjusted at  200 , and it is again considered whether the module 5 pressures equal the required pressures. Thus, when needed, the module 5 control valves will be continually adjusted until the measured module 5 pressures equal the required pressures. 
     To this end, flow monitors  68 , 70 , 72  can represent monitors which measure the flow of liquid in the associated stream, or monitors which measure the pressure of the liquid or monitor which measure both the flow and pressure of the liquid. 
     After the measured module 5 pressures equal the required pressures, a determination is made whether the module 5 quality is greater than the calculated allowable minimum at  202 . The quality of the water is measured by monitor  66 . If the water quality is not greater than the allowable minium quality, then the module 5 power supply is adjusted at  204  and it is again considered whether the module 5 quality is greater than the calculated allowable minium. Thus, when needed, the module 5 power supply will be continually adjusted until the module 5 quality (the quality of the feed water after passage through the EDI module  54 ) is greater than the calculated allowable minimum. 
     Once the measured module 5 quality is greater than the calculated allowable minimum, a determination is made whether the module 5 quality value is less than a user pre-set value at  206  (the user being able to set a desired quality above the allowable minimum). If so, a service alarm is sound at  208 . After the alarm sounds, a determination is made whether the alarm reset is engaged at  210 , i.e., a response to the alarm was effected. If not, the alarm continues to sound. Instead of an alarm, any type of warning device, oral and/or visual, can be used. After the alarm reset is engaged, the operating sequence returns to again check the unit&#39;s operating mode at  102 . 
     If the measured module 5 quality value is not less than the user pre-set value, the pure water outlet valve is opened at  212  and provides a stream of purifier water. 
     A determination is continuously made whether the level interlock is engaged at  214 . Once the level interlock is not engaged, the operating sequence returns to check the service mode at  118 . 
     Referring back to FIG. 4, in the rinse mode, initially a determination is made to the service mode at  216 , i.e., the unit is designed to enable multiple rinse cycles, in the exemplifying embodiment, two. If the first rinse cycle is selected, then a timer is engaged at  218 , the cycle is commenced at  220  and the rinse valves are opened at  222 . Periodically, a determination is made whether the timer value is equal to a user pre-set value at  224 , i.e., the duration of the rinse cycle is predetermined by the user and when the timer indicates that the elapsed cycle time is equal to the predetermined time, the service mode is again checked at  216 . 
     The second rinse cycle is a more detailed cycle and in this rinse cycle, the unit operation is engaged at  226 . Engagement of the unit operation initially entails determining whether the module 1 dP value is greater than a user pre-set value at  228 . If so, module 1 clean bit cycle is enabled at  230 . 
     After the module 1 clean bit cycle is enabled, or if the module 1 dP value is not greater than the user pre-set value, a determination is made whether the module 1 inlet pressure value is less than a user pre-set value at  232 . If so, a service alarm is sound at  234 . After the alarm sounds, a determination is made whether the alarm reset is engaged at  236 , i.e., a response to the alarm was effected. If not, the alarm continues to sound. Instead of an alarm, any type of warning device, oral and/or visual, can be used. After the alarm reset is engaged, the operating sequence returns to again check the service mode at  216 . 
     If the module 1 inlet pressure value is not less than the user pre-set value, the module 2 total flow is measured at  238  and the allowable total flow for module 2 is calculated at  240  (see FIG.  5 ). A determination is made whether the module 2 total flow is greater than the calculated allowable flow at  242  and if so, then the module 2 regeneration bit is enabled at  244 . 
     When the module 2 total flow is not greater than the calculated allowable flow, or after the module 2 regeneration bit is enabled, the module 3 total flow is measured at  246  and the allowable total flow for module 3 is calculated at  248 . A determination is made whether the module 3 total flow is greater than the calculated allowable flow at  250 , and if so, then the module 3 replacement bit is enabled at  252 . 
     When the module 3 total flow is not greater than the calculated allowable flow, or after the module 3 replacement bit is enabled, a determination is made whether the module 4 temperature value is greater than a user pre-set value at  254 . If so, a service alarm is sound at  256 . After the alarm sounds, a determination is made whether the alarm reset is engaged at  258 , i.e., a response to the alarm was effected. If not, the alarm continues to sound. Instead of an alarm, any type of warning device, oral and/or visual, can be used. After the alarm reset is engaged, the operating sequence returns to again check the service mode at  216 . 
     When the module 4 temperature value is not greater than the user pre-set value, a determination is made whether the module 4 flow rates equal the required flow rates at  260  (see FIG.  10 ). If not, the module 4 control valves are adjusted at  262 , and it is again considered whether the module 4 flow rates equal the required flow rates. Thus, when needed, the module 4 control valves will be continually adjusted until the measured module 4 flow rates equal the required flow rates. 
     Once the module 4 flow rates equal the required flow rates, a determination is made whether module 4 pressures equal the required pressures at  264 . If not, the module 4 control valves are adjusted at  266 , and it is again considered whether the module 4 pressures equal the required pressures. Thus, when needed, the module 4 control valves will be continually adjusted until the measured module 4 pressures equal the required pressures. 
     Once the module 4 pressures equal the required pressures, the module 4 total operation hours is measured at  268 . A determination is made whether the module 4 total flow is greater than a user pre-set value at  270  and if so, the module 4 cleaning alert bit is enabled at  272 . 
     If the module 4 total flow is not greater than the user pre-set value, or after the operator indicator is enabled, a determination is made whether the module 5 flow rates equal the required flow rates at  274 . If not, the module 5 control valves are adjusted at  276 , and it is again considered whether the module 5 flow rates equal the required flow rates. Thus, when needed, the module 5 control valves will be continually adjusted until the measured module 5 flow rates equal the required flow rates. 
     Once the module 5 flow rates equal the required flow rates, a determination is made whether module 5 pressures equal the required pressures at  278  (see FIG.  11 ). If not, the module 5 control valves are adjusted at  280 , and it is again considered whether the module 5 pressures equal the required pressures. Thus, when needed, the module 5 control valves will be continually adjusted until the measured module 5 pressures equal the required pressures. 
     After the measured module 5 pressures equal the required pressures, a determination is made whether the module 5 quality is greater than the calculated allowable minimum at  282 . If not, the module 5 power supply is adjusted at  284  and it is again considered whether the module 5 quality is greater than the calculated allowable minium. Thus, when needed, the module 5 power supply will be continually adjusted until the module 5 quality is greater than the calculated allowable minimum. 
     Once the measured module 5 quality is greater than the calculated allowable minimum, a determination is made whether the module 5 quality value is less than a user pre-set value at  286 . If so, a service alarm is sound at  288 . After the alarm sounds, a determination is made whether the alarm reset is engaged at  290 , i.e., a response to the alarm was effected. If not, the alarm continues to sound. Instead of an alarm, any type of warning device, oral and/or visual, can be used. After the alarm reset is engaged, the operating sequence returns to again check the service mode at  216 . 
     If the measured module 5 quality value is not less than the user pre-set value, a divert outlet valve is opened at  292  and provides a stream of purifier water through the divert outlet valve. 
     A determination is periodically made whether the second rinse mode is engaged at  294 , i.e., whether the rinse cycle is still desired. Once the rinse mode is no longer engaged, the operating sequence returns to check the service mode at  216 . 
     Water purifiers in accordance with the invention can be constructed to provide variable output flow rates. In practice, water purifiers have been designed to provide output flow rates from about 0.5 gallons per minute to about 50 gallons per minute. The significant difference between the different models of the water purifier is the size of the components, with the type and function of components being substantially the same for all of the different models. 
     While a particular embodiment of the invention has been shown and described, it will be obvious to those skilled in the art that changes and modifications may be made without departing from the invention in its broader aspects, and, therefore, the aim in the appended claims is to cover all such changes and modifications as fall within the true spirit and scope of the invention.