LIQUID MANAGEMENT DEVICE, METHOD AND SYSTEM
BACKGROUND
Technical Field
[0001] Embodiments of the invention relate to the field of desalination of liquids Embodiments of the invention relate to a desalination device and a method of using the desalination device
Discussion of Related Art
[0002] Less than one percent of water on the earth's surface is suitable for direct consumption in domestic or industrial applications With the limited sources of natural drinking water, de-ionization of seawater or brackish water, commonly known as desalination, is a way to produce fresh water There are a number of desalination techniques that are currently employed to de-ionize or desalt a water source
[0003] Capacitive deionization is an electrostatic process that operates at a low voltage (about 1 volt) and low pressure (15 psi) When the brackish water is pumped through a high-surface-area electrode assembly, ions in the water—such as dissolved salts, metals, and some organics—are attracted to oppositely charged electrodes This concentrates the ions at the electrodes and reduces the concentration of the ions in the water When the electrode capacity is exhausted, the water flow has to be stopped to discharge the capacitor, with the ions rejected back into a now-concentrated solution
[0004] It may be desirable to have a device or system for desalination that differs from those devices or systems that are currently available It may be desirable to have a method of making or using a device or system for desalination that differs from those methods that are currently available
BRIEF DESCRIPTION
[0005] In accordance with and embodiment, a method is provided that includes discharging a solute from a solute-bearing electrode into a discharge liquid stream, wherein the discharge liquid stream has a relatively higher concentration of solute than a feed stream from which the solute-bearing electrode gained the solute
[0006] In one embodiment, a desalination system is provided that includes a first subsystem, and a second sub-system in fluid communication with the first sub-system The second sub-system includes a means for discharging a solute from a solute-bearing electrode into a discharge liquid stream, wherein the discharge liquid stream has a relatively higher concentration of solute than a solute-bearing feed stream from which the solute-beanng electrode gained the solute
[0007] According to one aspect, a desalination system having the first sub-system receives a fluid supply and produces first and second out-flowing fluid streams The first out-flowing fluid stream has a solute concentration that is relatively less than the solute concentration of the fluid supply The second out-flowing fluid stream has a solute concentration that is relatively more than the solute concentration of the fluid supply
[0008] In one embodiment, a treatment system is provided that includes a first subsystem, a second sub-system in fluid communication with the first sub-system, and a controller in communication with the second sub-system In response to a signal from the controller, the second sub-system discharges a solute from a solute-beanng electrode mto a discharge liquid stream The discharge liquid stream has a relatively higher concentration of solute than a solute-beanng feed stream from which the solute-beanng electrode gained the solute
[0009] According to one aspect, the first sub-system receives a liquid supply and outputs a first stream and a second stream Relative to the liquid supply, the first stream has a lower solute content and the second stream has a higher solute content The second stream flows to the second sub-system as the solute-beanng feed stream
BRIEF DESCRIPTION OF THE DRAWING FIGURES
[0010] Like numbers represent substantially the same parts from figure to figure
[0011] FIG 1 is a schematic diagram of a device comprising an embodiment of the invention
[0012] FIG 2 is an exploded perspective diagram of a portion of the stack of FIG 1
[0013] FIG 3 is a schematic diagram of another device comprising an embodiment of the invention
[0014] FIG 4 is a perspective diagram of a supercapacitor desalination cell during a charging state of operation according to certain embodiments of the invention
[0015] FIG 5 is a perspective view of a supercapacitor desalination cell during a discharging state of operation according to certain embodiments of the invention
[0016] FIG. 6 is a block diagram of a desalination system according to certain embodiments of the mvention
[0017] FIG 7 is a block diagram of a test setup in accordance with embodiments of the present invention
[0018] FIGS 8-10 are graphical representations of test results obtained during a first exemplary experiment of the test setup in FIG 7
[0019] FIGS 11 and 12 are graphical representations of test results obtained a second exemplary experiment of the test setup in FIG 7
[0020] FIG 13 is a block diagram of a desalination system for management of wastewater
[0021] FIG 14 is a block diagram of an alternate embodiment of a desalination system for management of wastewater
[0022] FIG 15 is a block diagram of an alternate embodiment of a desalination system for management of wastewater
DETAILED DESCRIPTION
[0023] Embodiments of the invention relate to the field of desalination of liquids Embodiments of the invention relate to a method of using a desalination device
[0024] A supercapacitor desalination (SCD) cell according to an embodiment of the invention may be employed for desalination of seawater or de-ionization of other brackish waters to reduce the amount of salt to a permissible level for domestic and industrial use Such SCD cells may remove or reduce other charged or ionic impurities from a liquid
[0025] Approximating language, as used herein throughout the specification and claims, may be applied to modify any quantitative representation that could permissibly vary without resulting in a change in the basic function to which it is related Accordingly, a value modified by a term or terms, such as "about", are not to be limited to the precise value specified In some instances, the approximating language may correspond to the precision of an instrument for measuring the value
[0026] Supercapacitor is an electrochemical capacitor that has a relatively higher energy density when compared to a common capacitor As used herein, supercapacitor is inclusive of other high performance capacitors, such as ultracapacitors A capacitor is an electrical device that can store energy in the electric field between a pair of "closely spaced-conductors (called 'plates') When voltage is applied to the capacitor, electric charges of equal magnitude, but opposite polarity, build up on each plate Saturated water refers to the water that is saturated with at least one kind of solute or salt at a given temperature As used herein, supersaturated water refers to water that contains an amount of at least one kind of solute or salt that is greater man the solubility limit of that solute or salt at a given temperature Scaling refers to build-up of concentrate or precipitate of otherwise dissolved salts or solutes on a sidewall in contact "with a salt or solute-bearing liquid
[0027] FIG 1 is a diagrammatic view of an exemplary supercapacitor desalination device 10 having a controller (not shown) and employing a desalination vessel 12 The desalination vessel has an inner surface that defines a volume Within the volume the desalination vessel houses a supercapacitor desalination stack 14 The desalination stack includes a plurality of supercapacitor desalination cells 16 Each of the plurality of cells 16 includes a pair of electrodes, an insulating spacer and a pair of current collectors Further, the desalination vessel includes at least one inlet 18 from which a feed liquid enters the desalination vessel, and an outlet 20 from which the liquid exits the desalination vessel after contact with the supercapacitor desalination cells The liquid may be guided inside the desalination vessel by using external forces Suitable external forces may include gravity, suction, and pumping
[0028] The salinity of the liquid exiting the desalination vessel through outlet will differ from the salinity of the feed liquid entering the desalination vessel through the inlet The difference in salinity can be higher or lower depending on whether the cells are in a charging mode of operation (which will remove salt or other impurities from the liquid feed stream) or a discharging mode of operation (which will add salt or other impurities to the liquid feed stream) The controller may communicate with and control appropriate valves, sensors, switches and the like such that the mode of operation can reversibly switch from a charging mode to a discharging mode in response to defined criteria Such criteria can include elapsed time, saturation, conductivity, resistivity, and the like
[0029] During a charging phase, the feed liquid may be passed through the stack one timenior more than one time That is, "more than one iteration may be required to de-lonize the liquid to a defined level of charged species as measured by an appropriately located sensor in communication with the controller In certain embodiments, a plurality of such cells may be arranged within the desalination vessel such mat the output of one cell may be treated as a feed liquid for the other cell This way, the liquid may be allowed to pass through the de-ionization cells several times before exiting through the outlet
[0030] The desalination vessel may be made of suitable desalination vessel materials Suitable desalination vessel materials may include one or more material selected from metal or plastic Suitable metals include noble metals and ferrous-based alloys, such as stainless steel Suitable plastics may include thermosets, such as acrylics, urethanes, epoxies, and the like, and thermoplastics, such as polycarbonates, polyvinyl chloride (PVC), and polyolefins Suitable polyolefins may include polyethylene or polypropylene As will be appreciated, the selection of materials for the desalination vessel is such that the material of the desalination vessel should not contribute to the impurities of the liquid that is to be de-ionized or desalinated The desalination vessel may be cylindrical in shape Further, the desalination vessel may be shaped such that it converges at the inlets and outlets, as illustrated in FIG 1 Other shapes and sizes may be employed for the desalination vessel
[0031] With reference to FIG 2, an arrangement of the various elements employed in a supercapacitor desalination stack, such as the stack 14 of FIG 1, is illustrated In the illustrated embodiment, the supercapacitor desalination stack includes a plurality of supercapacitor desalination cells and a plurality of current collectors
[0032] The supercapacitor desalination cells include at least one pair of electrodes Each electrode pair includes a first electrode, a second electrode, and an electrically insulating spacers disposed therebetween In certain embodiments, in the charging mode of operation of the stack, the first and second electrodes can adsorb ions from the liquid that is to be de-ionized In the charging mode of operation, the surfaces of the first and second electrodes can each accumulate an electric charge or polarized electnc potential The potential of the first electrode can differ from the potential of the second electrode Subsequently, when the liquid is flowed through these electrodes, the electnc charges accumulated on the electrodes attract oppositely charged ions from the liquid, and these charged ions are then adsorbed on the surface of the electrodes After the electrode surface is saturated with the adsorbed charged ions, die mode of operation of the stack may be switched from a charging mode of operation to a discharging mode of operation
[0033] The charged ions may be removed or desorbed from the surface of the electrodes by discharging the cell In the discharging mode of operation, the adsorbed ions dissociate from the surface of the first and second electrode surfaces and may combine with the liquid flowing through the cell during the discharging mode of operation In some embodiments, during the discharging mode of operation of the cell, the polarities of the electrodes may be reversed In other embodiments, during the discharging mode of operation of the cell, the polarities of the first and second electrodes may be the same as each other The charging and discharging of the cell will be described and illustrated in more detail with reference to FIGS 4 and 5
[0034) In certain embodiments, each of the first electrodes may include a first conducting matenal and each of the second electrodes may include a different, second conducting matenal As used herein the term conducting material refers to materials that are electrically conducting without regard to the thermal conductivity In these embodiments, the first conducting matenal and the second conducting material may mclude an electrically conducting material, for example, a conducting polymer composite In some embodiments, the first conducting matenal and the second conducting matenal may have particles with smaller sizes and large surface areas Due to large surface areas such conducting materials may result in high adsorption capacity, high energy density and high capacitance of the cell The capacitance of the stack may be greater than about 10 Farad per gram In one embodiment, the stack capacitance may be in a range of from about 10 Farad per gram to about 50 Farad per gram, from about 50 Farad per gram to about 75 Farad per gram, from about 75 Farad per gram to about 100 Farad per gram, from about 100 Farad per gram to about 150 Farad per gram, from about 150 Farad per gram to about 250 Farad per gram, from about 250 Farad per gram to about 400 Farad per gram, from about 400 Farad per gram to about 500 Farad per gram, from about 500 Farad per gram to about 750 Farad per gram, from about 750 Farad per gram to about 800 Farad per gram, or greater than about 80 Farad per gram
[0035] Suitable first "conducting material and second conducting material may be formed as particles- having an average size that is less than about 500 micrometers Further, the particles may be present in a mono-modal particle distribution of about 1
In other embodiments, the particle size distribution may be multi-modal, such as bi-modal The use of multi-modal particle size distributions may allow for control of packing, and, ultimately, flow rate and surface area through the particle bed Naturally, the first conducting material and the second conducting material may differ from each other in terms of surface area, configuration, porosity, and composition In exemplary embodiments, the particle size of the first conducting material and the second conducting material may be in a range from about 5 micrometers to about 10 micrometers, from about 10 micrometers to about 30 micrometers, from about 30 micrometers to about 60 micrometers, or from about 60 micrometers to about 100 micrometers
[0036] Further, the first conducting material and the second conducting material may have high porosity In one embodiment, the porosity of the first and/or second materials may be in a range from about 10 percent to about 95 percent of the theoretical density Each electrode may have a relatively high Brunauer-Emmet-Teller (BET) surface area A relatively high BET surface area may be in a range of from about 2 0 to about 5 5 x 106 ftz lb"1 or about 400 to 1100 square meters per gram (m2g1) In one embodiment, the electrode surface area may be in a range of up to about 1 3 x 107 ftz lb"1 or about 2600 m2g-' Each electrode may have a relatively low electrical resistivity (e g , <40 mS2cm) In one embodiment, additional material may be deposited on the surfaces of the first and second electrodes where such additional materials include catalysts, anti-foulants, surface energy modifiers, and the like
[0037] Further, the first conducting material and the second conducting material may include organic or inorganic materials, for example, these conducting materials may include polymers, or may include inorganic composites which are conductive In another exemplary embodiment, the inorganic conducting material may include carbon, metal or metal oxide Further, the first and second electrodes may be formed from, contain, or include the same materials as each other Alternatively, the first and second conductive electrodes may employ different materials from each other, or the placement or amounts of the same materials may differ Additionally, in some embodiments, die first conducting material and the second conducting material may be reversibly doped In these embodiments, the first and second materials may or
may not be the same In an exemplary embodiment, the dopants may include either anions or cations Non-limiting examples of cations may include Li+, Na+, K*, NH/, Mg2+, Ca2+, Zn2+, Fe2+, Al3+, or combinations thereof Non-limiting examples of suitable anions may include CI", NO3", S042", and P043
[0038] Suitable conducting polymers may include one or more of polypyrrole, polythiophene, or polyanihne In some embodiments, the conducting polymers may include sulfonic, chloride, fluoride, alkyl, or phenyl denvates of polypyrrole, polythiophene, or polyanihne In one embodiment, the conducting material may include carbon, or carbon based materials Suitable carbon-based matenals may include activated carbon particles, porous carbon particles, carbon fibers, carbon nanotubes, and carbon aerogel Suitable matenals for use in the first conducting composite and second conducting composite may include carbides of titanium, zirconium, vanadium, tantalum, tungsten, and niobium Other suitable materials for use in the first conducting composite and second conducting composite may include oxides of manganese and iron In an exemplary embodiment, the conducting material may include powders that have particle sizes in the nanoscale Suitable nanoscale powders can include fernte-based materials
[0039] Additionally, electrically conducting fillers may also be used along with the conducting materials Also, suitable adhesives, hardeners, or catalysts may also be employed with the conducting materials Filler matenals or additives may affect one or more attributes of the conducting matenals, such as minimum width, viscosity, cure profile, adhesion, electncal properties, chemical resistance (e g, moisture resistance, solvent resistance), glass transition, thermal conductivity, heat distortion temperature, and the like
[0040] The filler may have an average particle diameter of less than about 500 micrometers In one embodiment, the filler may have an average particle diameter in a range of from about 1 nanometer to about 5 nanometers, from about 5 nanometers to about 10 nanometers, jrom about 10 nanometers to about 50 nanometers, from about 50 nanometers to about 100 nanometers, from about 100 nanometers to about 1000 nanometers, from about 1 micrometer to about 50 micrometers, from about 50
micrometers to about 100 micrometers, from about 100 micrometers to about 250 micrometers, from about 250 micrometers to about 500 micrometers, or greater than about 500 nanometers
[0041] In certain embodiments, filler particles may have shapes and sizes that may be selected based on application specific cntena Suitable shapes may include one or more of sphencal particles, semi-sphencal particles, rods, fibers, geometric shapes, and the like The particles may be hollow or solid-cored, or may be porous Long particles, such as rods and fibers may have a length that differs from a width
[0042] In embodiments where an electrically conducting polymer is employed as a conducting material, the capacitance of the cell may be enhanced due to the reversible Faradic mechanism or the electron transfer mechanism of the polymer In an exemplary embodiment, the capacitance of the cell may be increased by about 3 to about 5 times Such capacitance values are higher than the capacitance values of a cell, such as cell, employing active carbon materials In some embodiments, the capacitance of the cell employing conducting polymer composites may be in a range from about 100 Farad per gram to about 800 Farad per gram Due to the high values of capacitance, the first electrode and the second electrode each may adsorb a considerable amount of ions on their respective surfaces without requiring high operational pressure or electrochemical reactions, thereby resultmg in relatively less energy consumption as compared to systems employing other desalination techniques
[0043] A high surface area of the conducting polymers may facilitate the deposition of relatively higher amounts of ions so that a device with a similar efficiency may a relatively smaller footprint or size As used herein, "footprint" refers to the number of supercapacitor desalination cells employed in a given stack, or a number of supercapacitor desalination stacks employed in a design in order to achieve a predetermined productivity In certain embodiments, the footprint of a supercapacitor desalination device having 200 stacks may be greater than 1 supercapacitor desalination cell In one embodiment, the footprint of a supercapacitor desalination device having 200 stacks may be less than 1000 supercapacitor desalination cells In one embodiment, the footprint may be in a range of from about 1 supercapacitor
desalination cell to about 10 supercapacitor desalination cells, from about 10 supercapacitor desalination cells to about 100 supercapacitor desalination cells, or from about 100 supercapacitor desalination cells to about 500 supercapacitor desalination cells
[0044] Although in the illustrated embodiment, the first and second electrodes are shaped as plates that are disposed parallel to each other to form a stacked structure, in other embodiments, the first and second electrodes may have different shapes Such other shapes may include rugate and nested bowl configurations In one embodiment, the first and second electrodes may be disposed concentrically relative to each other in a roll-type arrangement
[0045] Suitable electrically insulating spacers may include electrically insulative polymers Suitable electrically insulative polymers may include an olefin-based material Suitable olefin-based material can include polyethylene and polypropylene, which can be halogenated Other suitable electrically insulative polymers can include, for example, poly vinyl chloride, polytetrafloroethylene, polysulfone, polyarylene ether, and nylon Further, the insulating spacer may have a thickness in a range from about 0 0000010 centimeters to about 1 centimeter In one embodiment, the thickness may be in a range of from about 0 0000010 centimeters to about 0 00010 centimeters, from about 0 00010 centimeters to about 0 010 centimeter, from about 0 0010 centimeters to about 0 1 centimeter, or from about 0 10 centimeters to about 1 centimeter The electrically insulating spacer may be ra the form of a membrane, a mesh, a mat, a sheet, a film, or a weave To allow fluid communication, the electrically insulating spacer may be porous, perforated, or have fluid channels that extend from one major surface to another The fluid channels, pores and perforates may have an average diameter that is less than 5 millimeters, and may be configured to increase turbulence of a through-flowing liquid In one embodiment, the average diameter is in a range of from about 5 millimeters to about 4 millimeters, from about 4 millimeters to about 3 millimeters, from about 3 millimeters to about 2 millimeters, from about 2 milhmeters to about 1 millimeter, from about 1 millimeter to about 0 5 millimeters, or less than about 0 5 millimeters Such increased turbulence may positively affect the performance of the proximate electrode In one embodiment, a
mesh is used that has overlapping threads that are not coplanar The out-of-plane threads may increase turbulence of the through-flowing liquid
[0046] Further, as illustrated, each of the cells may include current collectors 30, which are coupled to the first and second electrodes The current collectors conduct electrons The selection of current collector materials and operating parameters may affect the power consumption and lifetime of the cell For example, a high contact resistance between one of the electrodes and the corresponding current collector may result in high power consumption In certain embodiments, the conducting material of the first and second electrodes of the cell may be deposited on the corresponding current collectors In such embodiments, the electrode conducting materials may be deposited on the current collector surface by one or more deposition techniques Suitable deposition techniques may include sputtering, spraymg, spin-coating, pnnting, dipping, or otherwise coating
[0047] A suitable current collector may be formed as a foil or as a mesh The current collector may include an electncally conducting material Suitable electrically conducting matenal may include one or more of aluminum, copper, nickel, titanium, platmum, and palladium Other suitable electncally conducting material may include one or both of iridium or rhodium, or an indium alloy or a rhodium alloy In one embodiment, the current collector may be titanium mesh In one embodiment, the current collector may have a core metal with another metal disposed on a surface thereof In another embodiment, the current collector may include a carbon paper/felt or a conductive carbon composite
[0048] The stack further may include support plates 32 to provide mechanical stability to the structure Suitable support plates may include one or more material selected from metal or plastic Suitable metals include noble metals and ferrous-based alloys, such as stainless steel Suitable plastics may include thermosets, such as acrylics, urethanes, epoxies, and the like, and thermoplastics, such as polycarbonates, polyvinyl chloride (PVC), and polyolefins Suitable polyolefins may include polyethylene or polypropylene
[0049] The support plates may act as electrical contacts for the stack to provide electrical communication between the stack and a power supply or the" energy recovery converter In the illustrated embodiment, the support plates, the electrodes, and the current collectors may define apertures or holes 21 to direct the flow of liquid and to define a hydraulic flow path between the pair of electrodes As illustrated, the liquid is directed inside the cell from the direction mdicated by the directional arrow labeled with reference number 22 After entering the cell, the liquid is directed such that it contacts, and flows through, the surface of the corresponding electrodes as indicated by the hydraulic flow path indicated by the directional arrow labeled with reference number 23 The liquids may flow such that the liquid traverses through the maximum portion of the surface of the corresponding electrode More dwell time, or contact time between the liquids and the electrode surface, may result in more adsorption of the charged species or ions from the liquid onto the electrode surface That is, more contact time between the liquids and the surface of the electrodes may result in a lesser number of iterations required to reduce the concentration of the charged species in the liquid to a predetermined value Subsequently, the liquid exits the cell as indicated by the directional arrow labeled with reference number 25
[0050] While the stack of FIG 2 is described with reference to its incorporation into a desalination vessel, in an alternative embodiment, the stack may also be employed without use of the desalination vessel For instance, as illustrated in FIG 3, the stack, including the cells, may be sandwiched between the support plates, without using a desalination vessel Applying mechanical forces to the support plates may hold the stack together As previously described, each cell includes electrodes separated by an . insulating spacer Further, current collectors are coupled to the first and second electrodes In accordance with the embodiment of FIG 3, the inlet and the outlet align with openings in the support plates to allow liquid to flow through the stack, as described with reference to FIG 2
[0051] As a comparative example, a conventional SCD system operates by alternating charging and discharging steps In the conventional system, the feed water at the charging and discharging step are delivered from the same water source During the charging mode of operation, the feed water is fed into the SCD system to remove salt
or other impurities from the feed stream Accordingly, the product of the SCD system during the charging mode of operation (1 e , the "dilute stream") is less saline than the feed stream During the discharging mode of operation when the SCD cells are purged of salt or other impurities, salt and impurities are released from the SCD cells into the incoming feed stream and thus, the product during the discharge mode of operation (e g, the "concentrate stream") is more saline than the feed stream Because the concentrate stream is more saline than the feed stream, it may be considered wastewater to be disposed
[0052J Embodiments of the invention operate in contrast to the comparison example, above A Zero Liquid Discharge (ZLD) SCD system is provided having defined modes of operation A principle of a disclosed ZLD-SCD is illustrated with regard to FIGS 4 and 5 In accordance with embodiments of the invention, saturated or supersaturated water is fed to the supercapacitor desalination device during the dischargmg step while normal feed water is fed mto the supercapacitor desalination device during the charging step Besides this salt, the water may or may not contain other salts that may or may not be saturated or supersaturated Besides this salt, the water may or may not contain other salts that may or may not be saturated or supersaturated
[0053] In certain embodiments, the saturated or supersaturated water (concentrate stream) is continuously circulated and reused for the discharge steps Accordingly, the supersaturation degree of the concentrate stream continually increases as the discharge contmues As a result, the saturation degree will increase to a point where precipitation begins to take place When the precipitation rate in the discharge step equals to the salt removal rate at the charge step, the supersaturation degree of the concentrate stream will not increase any more and equilibrium will be established Advantageously, in accordance with the described system, the volume of discharge water does not increase with the number of cycles, and thus, the liquid discharge of the system is zero or nearly zero The ZLD-SCD system advantageously reduces or eliminates the amount of liquid waste, thereby providing advantages over typical water treatment systems
[0054] Referring briefly to FIG 4, an exemplary SCD cell 16 is illustrated in the charging mode of operation As previously described, the SCD cell 16 typically includes electrodes 24 and 26 The electrodes 24 and 26 are electrically coupled to a power supply (not shown), and oppositely charged The power supply may either act as an energy recovery converter or may be in operative association with the energy converter Accordingly, during the charging mode of operation, the cell 16 stores energy In the illustrated embodiment, the electrode 24 is coupled to the negative terminal of the power supply and acts as a negative electrode Similarly, the electrode 26 is coupled to the positive terminal of the power supply and acts as a positive electrode As previously described and illustrated with reference to FIG 2, an insulating spacer may also be disposed between two oppositely charged electrodes During the charging mode of operation, a feed stream 34 having charged species is fed into the SCD cell When the feed stream 34 passes between the electrodes, the charged species or ions from the liquid feed stream accumulate at the electrodes As illustrated, cations 36 move towards the negative electrode and the anions 38 move towards the positive electrode As a result of this charge accumulation inside the cell, a dilute stream 40 (the output liquid) coming out of the cell has a lower concentration of charged species as compared to the liquid feed stream into the cell
[0055] As noted above, in certain embodiments, the dilute stream again may be subjected to de-iomzation by feeding it through another cell similar to cell or by feeding it back to the cell as a feed stream In some embodiments, a plurality of such cells may be employed in a stack, as previously described The system may also include several stacks Alternatively,, the dilute stream then may be fed to another type of desalination device, such as a reverse osmosis unit (not shown), for further treatment
[0056] As described and illustrated with regard to FIG 4, during charging of the SCD cell, the charged species (anions and cations) from the feed stream are accumulated on the surface of the corresponding oppositely charged electrodes The accumulation of charged species on *tie electrodes continues until the cell is discharged, a saturation limit is reached, or the resistivity of the ion layer is about the same as the voltage potential of the electrode
[0057] FIG 5 illustrates the cell during the discharging mode of operation Dunng the discharging mode of operation, the cell releases the stored energy captured dunng the charging mode of operation The charged species are desorbed from the electrode surfaces And, rather than using the same feed stream during the charging and discharging modes of operation, a different feed stream may be fed from a different source into the cell during the discharging mode of operation, thereby reducing the amount of liquid discharge that must be eliminated Specifically, a saturated feed stream 42 is fed into the cell during the discharging mode of operation Thus, in the illustrated embodiment, in the discharging mode of operation of the cell, the cations and anions desorb from the electrode surfaces and move out of the cell along with the saturated feed stream, thereby producing a discharge stream 44 that may then be recycled and regenerated repeatedly for each discharge mode of operation During the discharging mode of operation, the liquid coming out of the supercapacitor desalination cell (discharge stream 44) will be higher in ionic concentration as compared to the saturated feed stream 42 that is fed into the supercapacitor desalination cell The discharge stream 44 may be more saturated than the saturated feed stream, and may supersaturate
[0058] As noted above, when the mode of operation of the supercapacitor desalination is transferred from a charging mode of operation to a discharging mode of operation, there is an energy release in the system, similar to the energy release when a battery goes from a fully charged mode of operation to a discharged mode of operation In certain embodiments, it may be desirable to harvest this energy for use The desalination system may include an energy recovery device, such as a converter (not shown) Thus, the cell also may be in communication with the energy recovery device
[0059] In the chargmg mode of operation, the converter directs the supplied power from a power source, such as a battery (not shown) or from an electrical grid to the cell Conversely, in the dischargmg mode of operation, the converter re-directs or recovers the electrical energy released by the cell This re-directed or recovered energy may be at least partially transferred to the energy storage device, such as a battery or to the gnd For example, this recovered energy from the cell may be used
at a later stage while charging the cell, a different cell from a stack of cells, or by cells in a different stack The energy recovery converter may be referred to as bidirectional converter as there are two directions of energy flow through the converter For example, the energy may either flow from the stack to a grid or bus, or from the grid or bus to the stack In certain embodiments, the converter may recover the energy of the discharging cell in DC form in the discharging mode of operation and later transfer it to the cell in the DC form to charge the cell to convert it from a discharged state to a charged state
[0060] Referring again to FIG 5, the saturated feed stream may be fed to the cell from a regeneration source, such as a regeneration tank 46 As illustrated, during the discharge mode of operation, the regeneration tank can define a feedback loop The feedback loop can provide the saturated feed stream to the cell and receive the discharge stream from the cell Because the same stream recirculates through the cell during each discharge step, the feed stream and the discharge stream become increasingly saturated as the discharge steps continue Eventually, the recirculated liquid, also referred to herein as the "regeneration water" or "regeneration liquid," will become so saturated that precipitation begins to take place and a solid precipitate 48 begins to form The precipitate can be filtered such that it remains in the regeneration tank The precipitate can be removed from the regeneration tank when the cell is not being discharged For instance, to remove the precipitate, the system may also include a crystal separation unit Suitable separation units may include a centrifuge, a filtration membrane, a bleed-off valve, a skimmer, a filtration unit, or an evaporation unit By this method of removing solids or semi-solid slurry, there may be zero, or nearly zero, liquid waste in the disclosed system When the precipitation rate in the discharge step equals the salt removal rate at the charge step, the supersaturation degree of the concentrate stream will not increase and equilibrium can be established In accordance with a described system, the volume of discharge water may not increase with the number of cycles, and thus, the liquid discharge of the system is zero or nearly zero As the precipitation takes place in the discharge regeneration tank, the cell employed in the SCD system may operate in combination
with a crystalhzer or a container functioning as a crystalhzer to enhance crystallization due to the supersaturation, as will be described further below
[0061] The described system may operate using the same regenerated water indefinitely during discharge cycles, such that no liquid waste ever needs to be discarded But when the flow shifts from the regeneration water-(discharging mode of operation) to normal feed water (charging mode of operation), some of the regeneration water retained in the SCD cells during the discharging mode of operation may mix mto the feed stream during the charging mode of operation This effect may have an adverse effect on the desalination The magnitude of this adverse "mixing effect" depends on the concentration difference between the regeneration water and the feed stream, as well as the volume of regeneration water retained in the cells Thus, if the feed stream contains sparingly soluble salts, the concentration of the dissolved salts in the regeneration water may not be high (m a range of from about 0 1 ppm to about 10,000 ppm) due to the continuous precipitation In this case, the possible reuse time of the regeneration water may have no limits However, when the feed stream contains highly soluble salts, for example sodium chlonde, the concentration of the dissolved salts in the regeneration water can go very high (in a range of about 20,000 ppm to about 200,000 ppm) where the penalty of the mixing effect on the desalting process may be considerable In this case, if the regeneration water is continually reused cycle by cycle, the concentration of the regeneration water may increase to a pomt where the penalty of the mixing effect equals to the desalting capability in the charging step, which reduces or eliminates net desaltmg capability in subsequent charging cycles
[0062] To eliminate or reduce the penalty of the mixing effect, several approaches may be applied One approach is to use a phased or sequential flow shift to shift the flow of liquid into the supercapacitor desalination device a certain time interval (e g, 10-30 seconds) ahead of the shifting of the flow out from the supercapacitor desalination device This approach allows a portion of the regeneration water retained in the cells at the end of the discharging step to be pushed out to the regeneration tank, which will reduce the penalty associated with the mixing effect Another approach to reducing the mixing effect is to pump air or other gas mto the supercapacitor
desahnation device and push the retained water out as much as possible before the feed stream is reintroduced to the supercapacitor desahnation device ^hiring the charging mode of operation This approach may also reduce the penalty associated with the mixing effect Yet another approach is to use feed water flushing For example, at the end of the discharge step, a certain amount of feed stream may be used to flush the supercapacitor desalination device before the outlet of the supercapacitor desahnation device is shifting to deposit the output of the liquid output during charge mode of operation to its intended target (e g, a dilute tank for desahnated/iseable water storage) The water used to flush the supercapacitor desahnation device may be directed instead to the regeneration tank or to a separate container If this approach is utilized, some regeneration water may need to be removed from the regeneration tank to maintain a fixed volume of regeneration water for use during discharge A tradeoff to this flushing approach between cycles may be that some water recovery loss may occur Further, any of these approaches may be employed in a combination For example, flushing with some feed water followed by an air-flushing step could be utilized
[0063[ One further consideration of the disclosed system involves "scaling " The high concentration of salt or solute dissolved in the regeneration liquid (eg, the saturated feed stream and the discharge stream) may increase the scaling potential In one embodiment, a supercapacitor desahnation device is charged and discharged alternately, and the supercapacitor desahnation device (and thus the individual cells) is exposed to both the normal feed stream and to the high concentration saturated feed stream, alternately Compared with RO systems, in which the concentrate stream always flows through a concentrate spacer during operation, the reduced intermittent exposure of the supercapacitor desalination device to the saturated feed stream reduces the scaling potential, as compared to the scaling potential in RO systems
[0064] The described SCD system may provide reduced scaling when compared with EDR systems, as well As with the SCD desahnation process, EDR chambers are also exposed with dilute and concentrate alternately However, it is well known that one of the major causes for scaling in EDR systems is the local pH change due to polarization at dilute chambers and the fact that the resulting OH" migrates through
the anion membrane to the concentrate chamber, where the concentrations of both the anions and the cations are very high and precipitates takes place first- at certain conditions As will be appreciated, in the SCD process there is neither polarization nor local pH change takes place during discharge steps, and thus, the risk of scaling is decreased
[0065] The supercapacitor desalination device may have dilute and concentrate tanks exist alternately to each other The concentration of dilute water limits the operating current during operation in an EDR system, in contrast to the concentration of dilute water only limiting the operating current in the supercapacitor desalination device during charging steps This feature makes the operation of the supercapacitor desalination device relatively more flexible than EDR systems For example, lower operating currents'wifh longer charging times may be employed during charging steps in the supercapacitor desalination device to avoid polarization, while higher operating currents are employed during the shorter discharging steps This relationship may be employed while maintaining the same output during one cycle, which may reduce the scaling nsk through Jess polarization and less exposure time to the high concentration liquids,
[0066] Referring now to FIG 6, a block diagram of an SCD system 50 in accordance with an exemplary embodiment of the present invention is illustrated As descnbed above, the SCD system 50 includes an SCD unit 52, which includes one or more SCD cells arranged in a stacked configuration During the charging mode of operation, a feed stream 54 is directed to the inlet 56 of the SCD unit 52 through a valve 58 As descnbed above, the feed stream 54 passes through the SCD unit 52 for deiom^tion The deionized dilute stream 60 is directed through an outlet 62 of the SCD unit 52, through a valve 64 and to an intended target For instance, the dilute stream 60 may be directed to a dilute tank (not shown) for use Alternatively, the dilute stream may be redirected into the SCD system as the feed stream for further processing, and, the dilute stream may be directed to a different desalination system, such as an RO system, for further processing As descnbed above, the dilute stream is less saline than the feed stream
[0067] During the discharging mode of operation, a saturated feed stream 66 is directed to the inlet 56 of the SCD unit 52 The saturated feed stream 66 rs provided by a regeneration tank 68 through the valve 70 and the valve 58 As discussed above, the regeneration tank 68 includes saturated or supersaturated liquid for use during the discharge mode of operation The saturated feed stream 66 is directed through the SCD unit 52 to the outlet 62, where it is fed back to the regeneration tank 68 as a discharge stream 72, through the valve 64 As described above, the discharge stream is more saline than the saturated feed stream When the precipitation rate in the discharge step equals the salt removal rate at the charge step, the supersaturation degree of the concentrate stream circulating between the regeneration tank and the SCD unit will not increase any more and equilibrium will be established The volume of discharge water need not increase with the number of cycles, and thus, the liquid discharge of the system can be zero or nearly zero Regardless, the majority of waste will be solid waste that may be removed through a waste outlet 74 in the regeneration tank
[0068] While the system described above may be sufficient in most applications, the system may optionally include an evaporator 78 and/or a crystallizer 80 to provide 100 percent water recovery The evaporator 78 and crystallizer 80 may both be employed, as illustrated in FIG 6, or only one may be employed, or they might both be combined into a single evaporation and thermal crystallization system In accordance with the illustrated embodiment, at the end of each discharge cycle, a certain amount feed stream is fed into the into the SCD unit through the valve The output stream is directed through the outlet and into the regeneration tank through the valve To maintain a constant volume in die regeneration tank, a corresponding amount of liquid in the regeneration tank may be fed into the evaporator through the valve and the flow path This liquid may be highly concentrated (e g , 10-30% wt) after the evaporation in the evaporator, which then may be fed to the crystallizer via the flow path The crystallizer may be a thermal crystallizer, such as a dryer, for instance The crystallizer produces solid waste 84 that may be disposed of by conventional means
[0069] The control of each of the valves 58, 64 and 70 may be preset and/or controlled by an external controller (not shown) to provide the proper functionality of the system to control the flow of liquid through the system Further, tn an alternate embodiment, multiple inlets and outlets may be provided at the SCD unit such that each source of liquid that flows mto the SCD unit has a respective mlet path and that each destination of liquid that flows out of the SCD unit has a respective outlet path Further, while not illustrated, other mechanisms, such as pumps may be used to draw water through the SCD unit or to/from other components in the system
[0070] The following examples are included to provide additional guidance to those of ordinary skill in the art in practicing the claimed invention Accordingly, these examples do not limit the invention as defined in the appended claims
EXAMPLE 1
[0071] A test system 86 as show in FIG 7 is employed The system 86 includes an SCD unit 88, a dilute tank 90 and a regeneration tank 92 The dilute tank 90 is employed to provide a liquid feed stream to the SCD unit 88 during the charging mode of operation A pump 94 is employed to pump the liquid feed through the SCD unit 88 during the charging mode of operation The regeneration tank 92 is- used to provide a liquid feed stream to the SCD unit 88 during the discharging mode of operation A pump 96 is employed to pump the liquid feed through the SCD unit 88 during the discharging mode of operation
[0072] A first experiment is performed using CaSC>4 water Because CaSCvj is regarded as the most notable inorganic salt whose precipitation is the major obstacle to membrane process operating at higher recoveries (e g, RO systems), a nearly saturated CaS04 solution (2025 ppm, 96 3% saturation) is employed for both the charging mode of operation (feed stream) and the discharging mode of operation (saturated feed stream) The volume of the charging water is 2000 ml while that of the regeneration water is 250 ml The process is operated under a batch mode (l e ,
both charging and regeneration water are circulated and reused in successive cycles, with the flow rate of about 100 ml/min)
[0073] An SCD unit (88) with a single cell is used to conduct the experiments The electrodes, with an effective area of 16cm by 32cm, consisted of activated carbon and titanium mesh as the active material and current collector, respectively A plastic mesh spacer with a thickness of 0 95mm is placed between the two electrodes To block the counter ions and increase the current efficiency, an anion exchange membrane and a cation membrane are placed between the electrodes and on either side of the spacer An electrochemical instrument, here a battery testing system is connected to the two electrodes of the cell, with the anion membrane side as the positive pole and the cation membrane side as the negative pole A suitable battery testing systems is commercially available from Kingnuo Electronic, mc (Wuhan, China)
[0074] As illustrated in FIG 7, shows the flow diagram of the experiments, four ball valves 98, 100, 102 and 104 are installed at the inlet and outlet of the SCD unit 88, to control the flow into and out from the SCD unit 88 Needle valves 106 and 108 are also employed to more precisely control the flow of liquid from through the system 86 The electrical charge and discharge timing is controlled by the electrochemical instrument In the described experiments, each cycle included a 10-minute. constant current (600mA) charging step, followed by a 1-minute rest step After the 1-minute rest step, the cycle continued with a 10-mmute constant current (-600mA) discharging step, followed by another 1-minute rest step The cycle is then repeated
[0075] In the charging steps, the charging water in the dilute tank 90 is circulated through the SCD unit 88 by opening ball valve 98 and ball valve 102 and closing ball valve 100 and ball valve 104 In the discharging steps, the open/close states of the ball valves 98, 100, 102 and 104 are reversed, such that ball valves 98 and 102 are closed and ball valves 100 and 104 are opened to allow the regeneration water in the regeneration tank 92 to circulate through the SCD unit 88 In order to minimize the undesired mixing of chargmg and regeneration water during the flow shifts between charging and discharging steps, air is pumped into the SCD unit 88 at each rest step to
minimize the retaining water in the cell from previous step As descnbed above, each cycle took about 22 minutes (10-minute charge step, 10-minute discharge step and two 1-minute rest steps) More than 30 cycles are conducted continuously to investigate the desalting of the charging water and the conductivity evolution for the regeneration water, as well as the crystallization and mixing effects
[0076] During the presently descnbed experiment, the conductivity of charging water is monitored at the end of each charging step FIG 8 illustrates the concentration evolution in the chargmg water for 30 cycles The resulting salt concentration in part per million (ppm) is indicated along the axis 110, versus cycle, indicated along the axis 112 As indicated in the salt concentration tracking curve 114, the concentration of the charging water decreased with each cycle, resulting in a reduction in concentration from 2000 ppm to about 500 ppm after 30 cycles As also indicated along the axis 116, the net salt removal in grams (g) at each cycle is also tracked As indicated in the best-fit salt removal curve 118, the amount of the salt removed in each cycle is distributed over a relatively narrow range (between approximately 0 07 g and 0 16 g), especially at the latter part of the experimental runs Therefore, the salt removal capacity of the SCD unit 88 showed no degradation over the conducted 30 cycles
[0077] The conductivity evolution in the regeneration water for 30 cycles is illustrated in FIG 9 The graph illustrates the measured conductivity (mS/cm), indicated by the axis 120, the calculated saturation percentage, indicated by the axis 122, at each cycle, indicated by the axis 124 As will be appreciated, conductivity is a measure of the amount of dissolved salt in the water, from which the percentage of supersaturation of the regeneration water can be calculated As illustrated by the conductivity plot 126, the conductivity of the regeneration water increased quickly over the first few cycles, while the supersaturation level of the regeneration water is relatively low, as indicated by the saturation plot 128 However, as the supersaturation level increases, the rate of increase of the conductivity decreases due to the increased salt precipitation rate at higher supersaturation while the same amount of dissolved salt is released to the concentrate stream at each discharge step
[0078] As illustrated in FIG 9 two sudden drops for the conductivity of the discharging step at the end of the 10th cycle and 30th cycle are noted, which represented two long rest steps during the experimentation (about 12 hours over night and 64 hours over a weekend, respectively) As indicated, a considerate amount of salt crystallized and precipitated out from the supersaturated water during the long rest duration resulting in concentration drop of the dissolved salts The crystallization will be discussed in more detail in the following section However, it is notable that even dunng a short period, e g a charge step time, when the regeneration water is at rest, the conductivity of the regeneration water slowly decreases In one example, the conductivity of the regeneration water decreased from 7 69 to 7 67 mS/cm after an 8-minute quiet rest This indicates that the precipitation is taking place all the time, including charging, discharging and rest steps
[0079J As discussed above, the supersaturation of the regeneration water increased as the number of cycles increased At the end of the 10th cycle, some particles are observed at the bottom of the regeneration tank 92 After 2 hours of rest, the precipitation at the hottom of the regeneration tank 92 increased significantly After a 12-hour (overnight) rest, the amount of the precipitates further increased while the conductivity of the regeneration water decreased A Scanning Electro Microscopy (SEM) result is used to analyze the volume of the precipitates, which proved to be CaSC>4 when analyzed by X-ray diffraction method
[0080] Another interesting phenomenon that is noted is that the material employed to construct the regeneration tank 92 appeared to have an effect on the crystallization process Two cylindrical columns define the regeneration tank 92 and hold the regeneration water in the experiments The first column is a 250ml glass cylinder, which is used for the 30-cycle test discussed above After 30 cycles, the regeneration water is transferred into another column made of a polymeric material (PMMA) Another 10 cycles are circulated with the same regeneration water in the polymer column FIG 10 illustrates a graph that compares the conductivity evolution of the regeneration water in glass column with that in polymer column dunng successive cycles The conductivity (mS/cm) is indicated along the y-axis 132 and the number of cycles is indicated along the x-axis 134 As illustrated, the conductivity of the
regeneration water in polymer column increases more rapidly relative to the glass column This is indicated by the conductivity plot 136 (organic glass) compared with the conductivity plot 130 (glass) Crystallization may be difficult in the polymer column, and use of that material type in the regeneration tank construction may affect the system efficiency The glass surface may higher polarity than polymer surfaces, which is favorable for the nucleation of inorganic salts
[0081] Different materials are used within the regeneration tank 92 and tubing In one embodiment, the regeneration tank 92 may be elongate, having first and second ends, and each end may be constructed of a differ material During use, the first end may be up or top relative to the second end, which may be down or bottom A first type of material is used at the first end portion of the regeneration tank 92 Another type of material is used at the second end portion of the regeneration tank 92
[0082] The crystallizing zone of the regeneration water tank is the lower area of the regeneration tank where crystallized particles gather and settle Suitable construction materials may include, for example, inorganic compositions as the structure or as a coating that lines an inner surface of the regeneration water tank Suitable construction materials may include ceramic, metal, and glass The polymer material could be used as the material for the container's clarifying zone where clear saturated or supersaturated water is fed to the SCD unit Suitable polymer material can be engineering plastic The use of a coating or liner may allow for construction of the regeneration water tank using a single material, with an after treatment on an inner surface of another material
EXAMPLE 2
[0083] As noted, supersaturation of the regeneration water can be as high as about 600 percent (see FIG 9) Though the SCD process exhibits good tolerance on supersaturation for the regeneration water, a lower saturation level may be beneficial and may exhibit a lower mixing penalty and less scaling risk To demonstrate, sand is placed in a regeneration tank The height of the sand in the regeneration column is about 25 centimeters (cm) The sand is sieved to have a granularity in a range of
about 1 millimeter (mm) to about 3 mm The sieved sands are washed with de-lonized water several times before being placed into the column During discharge steps, the discharge water is pumped out from the bottom of the column and pumped to the inlet of the SCD unit The regeneration stream from the outlet of the SCD unit is looped back to the top of the regeneration tank
[0084] FIG 11 illustrates the conductivity (y-axis 140) versus the cycle (x-axis 142) profiles of both the dilute stream 144 from the charging cycle and the concentrate stream 146 during the discharging cycle FIG 11 illustrates the conductivity of the dilute stream 144 decreases over cycles, except for the jump at the end of cycle 20, where the onginal charge water is replaced by another fresh tank The conductivity of the concentrate stream 146 demonstrates a relatively rapid mcrease in the first several cycles while it tends to be constant during subsequent cycles The two drops (at cycle 10 and cycle 16) are due to long rest steps The first drop is due to a 45-minute rest step, while the second drop is due to a 12-hour rest step These trends are very similar to the trends observable in experiments without sand bed Precipitates are observable on the top of the sand bed in the regeneration column
[0085] When comparing the supersaturation of the regeneration waters with sand and without sand in the regeneration column, as illustrated in FIG 12, the difference can be significant FIG 12 illustrates the conductivity (y-axis 148) versus the cycle (x-axis 150) of the concentrate stream with and without sand in the regeneration tank Though in both cases the conductivity of the regeneration waters tends to be constant as the number of cycles increased, the absolute supersaturation of regeneration waters in these two cases (with and without sand) differs Specifically, a much lower equilibrium conductivity is observable when the sand is present in the regeneration tank, as illustrated by plot 154, than when no sand is placed in the regeneration tank, as indicated by the plot 152 The mechanism behind this phenomenon may be that the sand provides many seeding sites The seeding sites enhanced the precipitation in the regeneration water Another function of the sand bed is that it works as a filtration layer for the regeneration water Due to the high supersaturation, there may be many small crystals suspended in the regeneration water, which is filtrated by the sand before it entering into the SCD unit during discharge steps Aside from the sand bed,
other crystallization enhancement technologies may include forced precipitation, seed crystals enhancement, magnetic field enhancement, chemical precipitation, pH control, anti-sealant control, and the like
EXAMPLE 3
[0086] The previously described expenments (EXAMPLES 1 and 2) are conducted with CaSC>4 water In Example 3, synthetic water with a concentration of 2 times that of Los Angeles city water is produced and tested The composition of this synthetic water is shown in Table 1
Table 1 Synthetic water composition
(Table Removed)
[0087] The water used in EXAMPLE 3 is hard and can be viewed as the concentrate from ah RO plant treating LA water with 50 percent water recovery, for example Before the experiments, an automated test system with solenoid valves for automated switching is built During the experiments, the volumes of charging water and regeneration water are 4500 milliliters (ml) and 200 ml, respectively The test results are similar to the results of the previously descnbed expenments in terms of conductivity profiles for the charge water and regeneration water Small precipitation particles are observable in the sand bed A difference is the conductivity of the regeneration water continues to mcrease to as much as about 16 milhSiemens per centimeter (mS/cm), while the expenments using calcium sulfate water level off at less than about 10 mS/cm This effect can be due to the presence of the highly soluble salts such as sodium chlonde Sometimes, the presence of the highly soluble salts is less desirable for the process due to the mixing effect, which demonstrates a gradually declining desalting, capability over cycles
[0088] Referring to FIG 13, a desalination system 160 includes a first sub-system 162 and a second sub-system 164 Each of the sub-systems can be a water treatment system The first sub-system 162 may be a reverse osmosis system, and the second sub-system may be a supercapacitor desalination system In one embodiment, the second sub-system may be a ZLD-SCD system Further, the first sub-system may be located in a treatment plant, while the second sub-system may be located remotely from the treatment plant
[0089] The first sub-system receives a feed stream 166 (in-flow) to be desalinated or treated and outflows two streams The first sub-system produces a first, dilute stream 168 that has relatively lower dissolved or suspended solids than the feed stream The - dilute stream may be used for human consumption, for example The first sub-system produces a second, concentrate stream 170 that has relatively more dissolved or suspended solids (more saline) than the feed stream The concentrate stream is referred to as an output stream or wastewater If the first sub-system 162 is in a treatment plant, and the second sub-system 164 is located remotely, the second subsystem may treat what would otherwise be considered wastewater (needing disposal) from the treatment plant
[0090] The second sub-system 164 receives the concentrate stream out flowing from the first sub-system, and may desalinate or otherwise treat that concentrate- stream The second sub-system 164 may include an SCD or ZLD-SCD system The second sub-system 164 produces two out-flowing streams a dilute stream 172 that has a relatively lower concentration of dissolved or suspended solids (less salme) than the concentrate stream The dilute stream may be available for human consumption, for example The second sub-system also produces waste stream or discharge stream 174 The discharge stream may be liquid waste, such as a concentrate stream having a higher salinity than the concentrate stream Alternatively, in the case of a ZLD-SCD system the discharge stream may be a slurry, a semi-solid, or a solid waste or mostly solid waste For instance, the second sub-system may have a relative volume that is less than-.10% of the concentrate stream volume (about 90 percent of the concentrate stream is desalinated and converted to the dilute stream) Still, the second sub-system may waste less than 1 percent of the concentrate stream (99 percent of the
concentrate stream is desalinated and converted to the dilute stream) Some or all of the dilute stream may be looped back to the first sub-system via a feedback path 176, for further processing
[0091] Referring now to FIG 14, a desalination system 160 is provided that includes a first sub-system 162 and a second sub-system 164 In the illustrated embodiment, the first sub-system includes a two-pass brackish water reverse osmosis (RO) system having a first RO unit 178 and a second RO unit 180 The first and second RO units together define the RO system of a desalination plant An inflowing feed stream 166 to the first RO unit 178 produces two outflowing streams a clean dilute stream 168 and a concentrate sub-stream 182 The dilute stream 168 may be consumed or used in a clean water end-use application The concentrate sub-stream 182 may be directed to the second RO unit 180 a&an inflowing stream for further desalination As with the first RO unit 178, the second RO unit 180 produces two outflowing streams a clean dilute stream (also indicated by reference number 168), which may be routed for consumption or use in clean water applications, and a concentrate stream (also indicated by reference number 170) In some treatment plants or treatment systems, the concentrate stream 170 is wastewater that must be further treated
[0092J The first sub-system may be a two-pass RO system and can be combined with the second sub-system 164 in series to receive the concentrate stream 170 from a treatment plant In the illustrated embodiment, the second sub-system 164 includes a zero liquid discharge-supercapacitor desalination (ZLD-SCD) system The ZLD-SCD system includes an SCD unit 184 and a regeneration tank 186 which may be employed to manage the concentrate stream 170 The SCD unit and the regeneration unit are arranged in a feedback configuration such that a discharge stream (either in concentrate or superconcentrate form) circulates between the SCD unit and the regeneration tank when the SCD unit is in a discharging mode of operation The second sub-system mcludes the SCD unit without the regeneration tank In this alternate embodiment, the waste 174 may include relatively more liquid than if the regeneration tank reemployed
[0093] In the desalination system 160 of FIG 14, the water recovery mcreases beyond that of a system incorporating only a two-pass RO system For example, an RO plant incorporatmg a two-pass RO system with 75 percent water recovery plus a concentrate management SCD unit with 90 percent water recovery will produce 1 -(L-0 75)*(l-0 90) = 97 5 percent water recovery for the whole system The relatively increased water recovery may be beneficial to the operation of a desalination plant In accordance with one embodiment, the RO units may be part of a desalination plant or of a separate system, wherein the wastewater output of the RO unit (concentrate stream 170) is delivered to the second sub-system comprising an SCD unit or a ZLD-SCD unit Thus, the ZLD-SCD unit of the second sub-system may be employed to manage the wastewater from an established treatment plant
[0094J In the illustrated desalination system, the RO concentrate is partially recovered as product water (a dilute stream), the flow rate of the feed stream 166 can be decreased accordingly Due to the decrease in flow rate of the feed stream, the actual concentrate water that is treated by the second sub-system 164 (concentrate stream 170) is also decreased Compared to the original two-pass RO system, there may be an economic benefit of the RO system assuming that the capital cost is proportional to the flow rate of the feed stream
[0095] In an alternate embodiment illustrated in FIG 15, the dilute stream 172 of the second sub-system 164 15 fed back to the first sub-system 162 for further desalination That is, rather than directing the dilute stream 172 for clean water use or consumption, the dilute stream 172 may receive further desalination treatment at the first subsystem 162 The dilute stream produced from the SCD unit when the SCD unit is in a charging mode of operation is directed back to the input of the second RO unit 180 This embodiment allows for further treatment of the dilute stream Further, this embodiment reduces the need for cleanwater storage or disposal at the second subsystem This operational configuration may be useful where the first sub-system is a water treatment and clean water production plant, while the second sub-system treats and manages concentrate water, rather than having to manage clean water (dilute stream) that may be produced After treatment at the first sub-system, the second
dilute stream 172 may be routed for cleanwater use along with the first dilute stream 168
[00961 The embodiments described herein are examples of compositions, structures, systems, and methods having elements corresponding to the elements of the invention recited in the claims This written description may enable those of ordinary skill in the art to make and use embodiments having alternative elements that likewise correspond to the elements of the invention recited in the claims The scope of the invention thus includes compositions, structures, systems and methods that do not differ from the literal language of the claims, and further includes other structures, systems and methods with insubstantial differences from the literal language of the claims While only certain features and embodiments have been illustrated and described herein, many modifications and changes may occur to one of ordinary skill in the relevant art The appended claims cover all such modifications and changes

WE CLAIMS:
1. A method, comprising:
discharging a solute from a solute-bearing electrode into a discharge iiquid stream, wherein the discharge liquid stream has a relatively higher concentration of solute than a feed stream from which the solute-bearing electrode gained the solute.
2. The method as defined in claim 1, wherein the electrode is a supercapacitor electrode, and further comprising absorbing the solute from the feed stream onto the electrode to form the solute-bearing electrode and an output stream, wherein the output stream has a solute concentration that is relatively lower than the feed stream.
3. The method as defined in claim 1 , further comprising looping the discharge liquid stream so that the stream flows across the electrode more than once before exiting a housing containing the electrode.
4. The method, as defined in claim 1, further comprising storing energy at the electrode in a first mode of operation, and recovering energy from the electrode in a second mode of operation.
5. The. method as defined in claim 1, wherein the electrode is a positively charged electrode, and the solute, is negatively charged.
i t
6. The method as defined in claim 1, wherein the discharging comprises supersaturating the discharge liquid stream.
7. The method as defined in claim 1, further comprising reducing a water content of the discharge liquid stream.
8. A desalination system, comprising:
a first sub-system, and
a second sub-system in fluid communication with the first sub-system, wherein the second sub-system comprises a means for discharging a solute from a solute-bearing electrode into a discharge liquid stream, wherein the discharge liquid stream has a relatively higher concentration of solute than a solute-bearing feed stream from which the solute-bearing electrode gained the solute.
9. A treatment system, comprising:
a first sub- system;
a second sub-system in fluid communication with the first sub-system; and a controller in. communication with the second sub-system, wherein in response to a signal from the controller the second sub-system discharges a solute from a solute-bearing electrode into a-discharge liquid stream, wherein the discharge liquid stream has a relatively higher concentration of solute than a solute-bearing feed stream from which the solute-bearing electrode gained the solute.
10. A desalination system, comprising:

a supercapacitor desalination unit that is operable in a charging mode of operation and a discharging mode of operation;
a feed source configured to provide a feed stream to the supercapacitor desalination unit when the supercapacitor desalination unit is in the charging mode of operation; and
a regeneration source configured to provide a saturated feed stream or a supersaturated feed stream to the supercapacitor desalination unit when the supercapacitor desalination unit is in the discharging mode of operation.
11. A desalination system, comprising:
a supercapacitor desalination unit;
a first liquid flow path comprising a first feedback loop configured to guide liquid through the supercapacitor desalination unit when the system is in a first mode of operation; and
a second liquid flow path comprising a second feedback loop configured to guide liquid through the supercapacitor desalination unit when the system is in a second mode 'of operation.
12. A method of treating liquid, comprising:
feeding a first liquid stream from a first source through a supercapactive desalination unit during a charging mode of operation for a first period of time; and
feeding a second liquid stream from a second source through the supercapacitor desalination unit during a discharging mode of operation for a second period of time.