Device and method for providing mineralized drinking water

Abstract

The present invention relates to a method for providing purified and mineralized drinking water from polluted fresh or brackish water. It also relates to a water treatment device for providing purified and mineralized drinking water from polluted fresh or brackish water.

Description

Technical Field

[0001] The present invention relates to a method for providing purified and mineralized drinking water from contaminated fresh water. The present invention also relates to an apparatus for providing purified and mineralized drinking water from contaminated fresh water. Background Art

[0002] Reverse osmosis is one of the most widely used processes for preparing drinking water from seawater, considering its use for treating contaminated surface water or groundwater. Reverse osmosis is known to produce water characterized by a very low mineral content, called "osmotic water". The water is corrosive and erosive, thus causing damage to pipes and pipelines. In addition, the weakly mineralized water is not suitable for drinking and has an unpleasant taste.

[0003] Several methods of remineralizing water obtained by reverse osmosis treatment are known and used. Most commonly, the water obtained downstream of the reverse osmosis treatment is contacted with a filter containing limestone media. The limestone gradually dissolves in the water. As a result, the mineral content of the water gradually stabilizes. This process requires the presence of solid matter, the source of which may be far from the water treatment facility, and the remineralization process therefore generates additional operating costs for water treatment.

[0004] Remineralized water can also be obtained by adding lime to water with a low mineral content and injecting CO2. However, this process produces some turbidity. In addition, the production of lime from lime milk is complicated. Therefore, this process has never been used in practice as a final step in the production of drinking water.

[0005] Other possible methods of remineralizing waters with low mineral content include the injection of calcium chloride (CaCl2) or calcium bicarbonate (Ca(HCO3)2) solutions. In practice, said solutions are not easy to produce and are therefore not used in water treatment facilities.

[0006] The presence of micropollutants and various organic substances, including dissolved organic carbon, in freshwater is a growing public health concern, influenced by population, agricultural and industrial growth. Advances in laboratory testing highlight their growing presence in the aquatic environment and their toxic effects, even at very low concentrations.

[0007] Therefore, there is a need for a process capable of producing drinking water from contaminated fresh water, wherein the drinking water is purified and exhibits a mineral content suitable for human and animal consumption; in particular, the mineralized water is characterized by acceptable total dissolved solids (TDS), conductivity and hardness.

[0008] Electrodialysis is commonly used to remove minerals from brackish water or seawater. Desalination processes are known in which reverse electrodialysis is applied to seawater prior to a reverse osmosis process. CN20443440 discloses a water circulation system in which a reverse electrodialysis system is located upstream of a reverse osmosis system, which first reduces the salt content of the water to be treated by a reverse osmosis unit.

[0009] WO 2019 / 197505 discloses a method for storing energy and generating electrical energy, wherein a water treatment device such as a reverse osmosis device is used to produce a distillate and a concentrate. The distillate and the concentrate are stored in a distillate storage tank and a concentrate storage tank, respectively. When needed, the stored distillate and concentrate are used to feed a RED device.

[0010] Also known are processes comprising the sequential steps of reverse osmosis and electrodialysis metathesis (EDM), wherein a feed water source is sent to a reverse osmosis treatment, concentrated salts rejected by the reverse osmosis are fed to an electrodialysis metathesis and sodium chloride solution is injected into the electrodialysis metathesis unit. In the process, metathesis consists of a conversion coordination between ions from the reverse osmosis brine and the sodium chloride feed stream, ultimately producing mixed sodium salts and mixed chloride salts. Alternatively, sodium chloride and sodium sulfate are injected into the electrodialysis metathesis, ultimately producing mixed sodium salts and mixed chloride salts.

[0011] A process for removing micropollutants from urine and comprising the successive steps of microfiltration, electrodialysis and ozonation is disclosed (“Lutte à la source pour la rétention de micropolluants dans les eaux”, L. Rossi et al., TSM N° 4, 2009). Summary of the invention

[0012] The inventors have now developed a water treatment device for providing mineralized and purified drinking water from fresh water that may contain undesirable substances such as organic matter and micropollutants, the water treatment device comprising at least one reverse osmosis (RO) unit and one reverse electrodialysis (RED) unit, wherein the at least one reverse osmosis unit is installed upstream of the at least one reverse electrodialysis unit.

[0013] The inventors have also developed a process comprising at least one reverse osmosis step and at least one reverse electrodialysis step, wherein the at least one reverse osmosis step is followed by the at least one reverse electrodialysis step.

[0014] The present invention thus provides a water treatment device and a method for remineralizing low-mineral water produced by reverse osmosis treatment of fresh water, wherein any potentially undesirable substances are eliminated from the fresh water. The water treatment device and method of the present invention allow the desired minerals, including monovalent and divalent ions, in particular calcium (Ca 2+ ), magnesium (Mg 2+ ), bicarbonate (HCO3 - ) and carbonate (CO3 2- ) back to acceptable levels in the permeate water produced by the reverse osmosis unit without any recontamination of the water.

[0015] The water treatment device and method according to the invention are simple and reliable, they do not require the addition of any external solid media or solutions, thus limiting the costs and disadvantages associated with these additional media and / or solutions. The water treatment device and method according to the invention produce drinking mineralized water which exhibits acceptable ion levels, in particular acceptable Ca 2+ Mg 2+ 、HCO3 - and CO3 2- level.

[0016] In a first aspect, the invention relates to a water treatment device for providing mineralized and purified drinking water, said device comprising at least:

[0017] - A first reverse osmosis unit comprising at least:

[0018] o a first inlet for introducing fresh water containing ions and potential micropollutants,

[0019] o First outlet for the first permeate,

[0020] o a second outlet for the first retentate,

[0021] - a reverse electrodialysis unit comprising at least:

[0022] o a second inlet connected to the first outlet,

[0023] o a third inlet connected to the second outlet,

[0024] o a third outlet for a first effluent, said first effluent comprising at least a portion of said first permeate and at least a portion of the ions from said first retentate,

[0025] o a fourth outlet for a second effluent, said second effluent comprising at least a portion of said potential micropollutants and a portion of said first retentate.

[0026] According to non-limiting embodiments, the water treatment device of the present invention may also include one or more of the following additional features:

[0027] - the reverse electrodialysis unit is a short-circuit reverse electrodialysis unit or an auxiliary reverse electrodialysis unit;

[0028] - The device further comprises a second reverse osmosis unit, the second reverse osmosis unit comprising at least:

[0029] o a fourth inlet connected to the second outlet,

[0030] o a fifth outlet for a second permeate connected to said second inlet,

[0031] o a sixth outlet for the second retentate, which is connected to the third inlet or the sixth inlet,

[0032] - the device further comprises at least one further reverse electrodialysis unit, said at least one reverse electrodialysis unit being connected in series with the other RED units,

[0033] a filtration unit, preferably a microfiltration, ultrafiltration or nanofiltration unit, connected to the first inlet, wherein the filtration unit removes particles from the water to be treated by reverse osmosis, the person skilled in the art being able to choose between microfiltration, ultrafiltration and nanofiltration depending on the size of the particles to be removed,

[0034] a filtration unit, preferably a microfiltration, ultrafiltration or nanofiltration unit, connected to the third outlet,

[0035] a filtration unit, preferably a microfiltration, ultrafiltration or nanofiltration unit, connected to the fourth outlet,

[0036] a separation unit connected to said second outlet for said first retentate, said separation unit providing a chemical, physical or gravity separation for said first retentate and thus improving the quality of the final effluent from the device according to the invention, said separation unit being preferably a microfiltration, ultrafiltration or nanofiltration unit,

[0037] - A bypass unit comprising at least:

[0038] o a fifth inlet connected to the first outlet and / or the fifth outlet,

[0039] o a seventh outlet, which is connected to the third outlet,

[0040] The bypass unit can be implemented in one of the following ways:

[0041] ■ A first mode, wherein the first outlet and / or the fifth outlet is connected to the second inlet,

[0042] ■ A second mode, wherein the first outlet and / or the fifth outlet is connected to the fifth inlet, and the seventh outlet is connected to the third outlet,

[0043] - a recirculation loop between said fourth outlet and said third inlet which results in at least one further reverse electrodialysis treatment of the effluent of the first compartment of said reverse electrodialysis,

[0044] - a recirculation loop between said third outlet and said second inlet, wherein the two recirculation loops increase the actual residence time of the solution inside the RED unit, maintaining optimal hydrodynamic conditions and resulting, at least in part, in at least one additional reverse electrodialysis treatment of the effluent of the connected compartment of said reverse electrodialysis,

[0045] - an electrodialysis metathesis unit comprising at least:

[0046] o a sixth inlet connected to the second outlet or the sixth outlet,

[0047] o an eighth outlet connected to the third inlet, and

[0048] oExit 9.

[0049] - a control circuit comprising at least one sensor of a physical or chemical parameter of the first effluent of said third outlet, in order to better control the process and quality of said first effluent, in particular the ion and micropollutant concentrations, said sensor being connected to said third outlet.

[0050] According to the present invention, "drinking water" means water that can be drunk without causing any danger to humans and animals and therefore complies with official requirements regarding its mineral concentration and the presence of potential pollutants or harmful components. In France, the mineral concentration requirements are quoted as follows: 11 janvier 2007 relatif aux limites et références dequalité des eaux brutes et des eaux destinées à la consommation humainementnées aux articles R.1321-2,R.1321-3,R.1321-7 et R.1321-38 du code dela santépublique》.

[0051] For example, according to the French standardized values, mineralized drinking water is characterized as follows:

[0052] - TDS (Total Dissolved Solids) measures the dissolved combined content of all inorganic and organic substances present in water in the form of suspension of molecules, ions or particles (colloidal sols),

[0053] Conductivity at -25°C: 2μS / cm to 1100μS / cm

[0054] -Hardness: in French degrees (f or f H ) indicates that 1 French degree is defined as the hardness of a CaCO3 solution having a concentration of 10 mg / ml or 0.0001 mol / LCaCO3; (f) is better than 7°f

[0055] -pH: 6.5 to 9.

[0056] More specifically, acceptable mineral levels in drinking water may be defined as follows:

[0057] Acceptable level chloride <250mg / L Sulfate <250mg / L sodium <200mg / L Nitrates <50mg / L Nitrite <0.5mg / L

[0058] For the purposes of this invention, "fresh or brackish water" refers to water characterized by less than 30,000 parts per million (ppm) of dissolved salts. Fresh water is characterized by a salinity below 500 ppm, while brackish water is characterized by a salinity between 500 and 30,000 ppm. Seawater has a salinity above 30,000 ppm and contains a high proportion of sodium chloride.

[0059] “Fresh or brackish water” means surface water, such as water from rivers, lakes and dams, groundwater, and any effluent from a plant or facility, such as wastewater.

[0060] "Micropollutants" are any organic substances or minerals that have the potential to have a negative impact on the natural environment and / or organisms. Mineral micropollutants include metals, metalloids and radioactive elements such as lead, cadmium, mercury, arsenic, antimony, radon and uranium. Organic micropollutants include pesticides, hydrocarbons, solvents, detergents, cosmetics and pharmaceutical substances. These pollutants are present in very low concentrations in water (micrograms or nanograms per liter).

[0061] "Reverse Osmosis" refers to a process or unit using a partially permeable membrane in which pressure is applied to overcome the osmotic pressure. Reverse osmosis uses a semipermeable membrane and high pressure to produce a clean permeate, which consists of softened or low-mineralized water, and a retentate containing salts and ions (including heavy metals) and potential pollutants and micropollutants, which is retained on the pressurized side of the membrane. The reverse osmosis membrane is selected so that its cut-off threshold is appropriate for the size and weight of the compound to be captured.

[0062] "Reverse electrodialysis" refers to a process or unit in which the concentration gradient between two solutions is used to move ionized salts through an ion exchange membrane. When auxiliary, the process is regulated jointly by the power applied to enhance the passage of ions. In a specific embodiment, reverse electrodialysis is a continuous reverse electrodialysis. Salt solution and softened water or low mineralized water pass through a stack of alternating cation and anion exchange membranes. Those skilled in the art can easily select cation and anion exchange membranes for use in devices according to the present invention according to the water to be treated and according to the electrochemical and physical properties of known membranes, particularly their known selectivity to monovalent and divalent anions and cations and micropollutants."Reverse electrodialysis" refers to simple reverse electrodialysis, which is carried out without any added ions and without any conversion ion step as in reverse electrodialysis metathesis.

[0063] According to the present invention, “short-circuit reverse electrodialysis” refers to a specific operating condition in a RED unit in which the applied external voltage is zero, which is also called “short circuit” or “short-circuited” RED (La Cerva et al., Desalination, 467, 175-195, 2019).

[0064] According to the present invention, “assisted reverse electrodialysis” refers to a specific operating condition in a RED unit where an additional external voltage is applied to increase the stack current (and therefore the salt flux from seawater to the downwelling flow) above short-circuit conditions (La Cerva et al., Desalination, 467, 175-195, 2019).

[0065] In a second aspect, the present invention relates to a method for providing mineralized and purified drinking water, the method comprising:

[0066] -i) in a first step, providing fresh or brackish water containing ions and possibly micropollutants,

[0067] -ii) a second step of treating said fresh or brackish water by reverse osmosis to obtain a retentate and a permeate, wherein said retentate is enriched in ions and said potential micropollutants, and in said permeate the ion concentration is reduced and micropollutants are absent or present in very low concentrations, which are acceptable for drinking water,

[0068] -iii) a third step of treating the retentate and the permeate of the second step by reverse electrodialysis, wherein at least a portion of the ions are extracted from the retentate and transferred to the permeate, and

[0069] -iv) a fourth step of recovering the mineralized water from said third step.

[0070] According to a non-limiting embodiment, the method according to the invention may also include one or more of the following additional features:

[0071] - reverse electrodialysis is short-circuit reverse electrodialysis or assisted reverse electrodialysis,

[0072] - the reverse electrodialysis is an auxiliary reverse electrodialysis, and the method further comprises applying a voltage higher than a predetermined level to the auxiliary reverse electrodialysis unit,

[0073] - the second step comprises a single reverse osmosis treatment, or main reverse osmosis treatment, followed by a further reverse osmosis treatment of the retentate of said main reverse osmosis treatment, wherein the presence of said further reverse osmosis treatment results in a higher amount of permeate consisting of softened water and / or decontaminated water, the higher ion concentration in the retentate contributing to an increase in the efficiency of the electrodialysis step and possibly allowing a smaller size of the device according to the invention,

[0074] - The third step comprises:

[0075] o injecting the reverse osmosis retentate of the second step ii) into the first compartment of the reverse electrodialysis unit, wherein the retentate is the retentate of a single reverse osmosis or the retentate of an additional reverse osmosis,

[0076] o injecting the reverse osmosis permeate of the second step ii) into the second compartment of the reverse electrodialysis unit, wherein the permeate is the permeate of a single reverse osmosis or the permeate of an additional reverse osmosis,

[0077] o wherein the retentate and the permeate are injected into the reverse electrodialysis unit as parallel flows and wherein the pressure applied to the first compartment is lower than the pressure applied to the second compartment,

[0078] - a filtration step of the fresh or brackish water upstream of the single or main reverse osmosis treatment, preferably microfiltration, ultrafiltration or nanofiltration,

[0079] - a filtration step of the mineralized water of the first effluent (E1) recovered from said fourth step iv), preferably microfiltration, ultrafiltration or nanofiltration, and / or comprising

[0080] - a filtration step, preferably a microfiltration, ultrafiltration or nanofiltration step, of the second effluent (E2) recovered from said fourth step iv) which may contain micropollutants,

[0081] a separation step of the retentate recovered from said reverse osmosis step of step ii), said retentate coming from said single reverse osmosis step or from said further reverse osmosis step, said separation step providing a chemical, physical or gravity separation of said first retentate and thus improving the quality of the final effluent of the device according to the invention, said separation step being preferably a microfiltration, ultrafiltration or nanofiltration step,

[0082] - a bypass step of the reverse electrodialysis step, in which at least part of the permeate of the reverse osmosis step is added to the effluent of the reverse electrodialysis step; the presence of the bypass unit allows diverting at least part of the permeate, so that the diverted part of the permeate is not treated by electrodialysis and is therefore not remineralized; depending on the concentration of the retentate passing the reverse electrodialysis unit, in the method according to the invention it may be faster and cheaper to divert high concentration salts in the permeate and then dilute the permeate with part of the permeate passing the bypass unit,

[0083] - a recycling step, in which the effluent of the first compartment of said reverse electrodialysis is subjected to at least one further treatment by electrodialysis,

[0084] - a recycling step, in which the effluent from the second compartment of said reverse electrodialysis is subjected to at least one further treatment by electrodialysis,

[0085] - an electrodialytic metathesis step of the retentate of the reverse osmosis of the second step ii), wherein the retentate is the retentate of the single reverse osmosis or the retentate of the further reverse osmosis; the electrodialytic metathesis step is an electrodialytic step carried out on an electrodialytic unit comprising a specific membrane configuration exhibiting a specific ion selectivity, the presence of the electrodialytic metathesis step enhancing the recovery process of the reverse osmosis and thus allowing to obtain a retentate exhibiting a higher ion concentration and therefore a higher permeate volume, finally the presence of the electrodialytic metathesis leads to a higher efficiency of the method and the device according to the invention,

[0086] - a step of monitoring the physicochemical properties and the presence of potential organic substances or micropollutants of the mineralized water recovered from said third outlet in said step iv) by using at least one suitable sensor, preferably chosen from: conductivity meter, spectrophotometer, pH meter, thermometer and / or flow meter, the presence of which allows controlling the remineralization of the permeate and determining the organic and micropollutant elements that may be present in said mineralized water recovered from step iv), it also allows determining the mineralization of said water.

[0087] Features, advantages and utilities of the subject matter of the invention are described in more detail below in an illustrative and non-limiting manner.Disclosure of a range expressed as "... to ..." means, when present, that the limits are included in the stated range.

[0088] The following embodiments of the water treatment device and method according to the invention comprise several different elements that can be combined with one another, provided that, according to a person skilled in the art, there are no technical incompatibilities between the combined elements. Figure 2 and 3 Any elements may be combined in the water treatment device and method according to the present invention.

[0089] Figure 1 is a schematic diagram of a first embodiment of a water treatment device according to the present invention, which represents a simpler embodiment of the device.

[0090] Figure 2 is a schematic diagram of a second embodiment of the device according to the invention.

[0091] Figure 3 is a schematic diagram of a third embodiment of a device according to the invention.

[0092] Figure 4 is a schematic diagram of an implementation scheme of a device according to Example 2. DETAILED DESCRIPTION

[0093] In a first aspect, the invention relates to a water treatment device for providing mineralized and purified drinking water, said device comprising at least:

[0094] - A first reverse osmosis unit (1), comprising at least:

[0095] o a first inlet (11) for introducing fresh or brackish water containing ions and potential micropollutants,

[0096] o a first outlet (12) for a first permeate (P1),

[0097] o a second outlet (13) for the first retentate (R1),

[0098] - a reverse electrodialysis unit (2), comprising at least:

[0099] o a second inlet (21), which is connected to the first outlet (12),

[0100] o a third inlet (22) connected to the second outlet (13),

[0101] o a third outlet (23) for an effluent (E1), said effluent comprising at least a portion of said first permeate (P1) and at least a portion of the ions from said first retentate (R1),

[0102] o a fourth outlet (24) for a second effluent (E2) comprising at least a portion of said potential micropollutants and a portion of said first retentate (R1).

[0103] Figure 1 A first embodiment of the device according to the invention is illustrated, wherein the device comprises a single reverse osmosis unit (1) and a reverse electrodialysis unit (2).

[0104] In a specific embodiment, the water treatment device of the present invention comprises a short-circuit reverse electrodialysis unit. In another specific embodiment, the water treatment device of the present invention comprises an auxiliary reverse electrodialysis unit.

[0105] In a second embodiment, the water treatment device according to the present invention comprises a first reverse osmosis unit (1) and a second reverse osmosis unit (3), and a reverse electrodialysis unit (2), such as Figure 2 As shown, the second reverse osmosis unit at least includes:

[0106] o a fourth inlet (31), which is connected to the second outlet (13),

[0107] o a fifth outlet (32) for the second permeate, which is connected to the second inlet (21),

[0108] o A sixth outlet (33) for the second retentate (R2), which is connected to the third inlet (22) or the sixth inlet (51).

[0109] The presence of a second reverse osmosis unit increases the mineral concentration of the retentate to be treated by the reverse electrodialysis unit, thus resulting in a better efficiency of said reverse electrodialysis unit.Thus, the presence of more than one reverse osmosis unit allows the production of higher levels of mineralized drinking water.

[0110] In a third embodiment of the invention, the device comprises means for removing suspended matter and / or for adding a chelating agent, provided that the chelating agent is an uncharged chelating agent before the water comes into contact with the reverse osmosis membrane.

[0111] In another embodiment, Figure 3 As shown, the water treatment device according to the present invention comprises:

[0112] - a first filtration unit (6), preferably a microfiltration, ultrafiltration or nanofiltration unit, connected to the first inlet (11), and / or

[0113] and / or

[0114] - a second filtration unit (7), preferably a microfiltration, ultrafiltration or nanofiltration unit, connected to the third outlet (23) to increase the purity of the mineralized drinking water produced by the water treatment device.

[0115] a third filtration unit (8), preferably a microfiltration, ultrafiltration or nanofiltration unit, connected to the fourth outlet (24), the presence of which is intended to protect the environment from micropollutants that may be present in the corresponding compartment of the electrodialysis unit.

[0116] In another embodiment of the present invention, Figure 3As shown, the water treatment device comprises a separation unit (9), which provides physical, chemical or gravity separation and preferably comprises a microfiltration, ultrafiltration or nanofiltration unit, which is connected to the second outlet (13).

[0117] In another specific embodiment, the water treatment device according to the invention comprises a bypass unit (4), such as Figure 2 As shown, it at least includes:

[0118] o a fifth inlet (41), which is connected to the first outlet (12) and / or the fifth outlet (32),

[0119] o a seventh outlet (42), which is connected to the third outlet (23),

[0120] The bypass unit can be implemented in one of the following ways:

[0121] o A first mode, wherein the first outlet (12) and / or the fifth outlet (32) is connected to the second inlet (21),

[0122] o A second mode, wherein the first outlet (12) and / or the fifth outlet (32) is connected to the fifth inlet (41), and the seventh outlet (42) is connected to the third outlet (23).

[0123] The presence of the bypass unit (4) diverts at least a portion of the permeate produced by the first reverse osmosis unit (1) or the second reverse osmosis unit (3) away from the electrodialysis unit, so that the portion of the permeate is not remineralized in the reverse electrodialysis unit.

[0124] The presence of the bypass unit (4) allows treating a permeate of a smaller flow rate in the RED unit while achieving an outlet permeate conductivity higher than the desired conductivity. Thus, after the combined addition of the bypass permeate and the remineralized permeate, the mixed permeate has the target mineral content. Thus, the presence of the bypass unit firstly allows reducing the flow to be treated in the RED unit, thereby increasing the desalination capacity of the overall solution or reducing the specific costs of the RED unit, and also allows reducing the difference between the flow rates of the inlet permeate and the retentate, thereby reducing the pressure difference and the risk of internal leakage.

[0125] Depending on the concentration of the mineral of interest in the permeate and / or retentate produced by reverse osmosis, a person skilled in the art of providing drinking water determines which part of the permeate, if any, should be diverted from the reverse electrodialysis unit so that the mineralized water in the effluent (E1) presents an acceptable mineral concentration. Thus, the presence of a bypass unit allows the device and the method to be adapted to the water to be treated and results in a faster and cheaper water treatment process.

[0126] In another specific embodiment, the water treatment device according to the invention comprises an electrodialysis metathesis unit (5), such as Figure 2 As shown, it at least includes:

[0127] o a sixth inlet (51), the sixth inlet (51) being connected to the second outlet (13) or the sixth outlet (33),

[0128] o an eighth outlet (52), the eighth outlet (52) being connected to the third inlet (22), and

[0129] oExit 9 (53).

[0130] A reverse electrodialysis metathesis unit (5) is defined as a reverse electrodialysis unit comprising a specific combination of ion-selective membranes which, when compared to a "classical" reverse electrodialysis unit, leads to the recovery of a more concentrated retentate and a higher amount of permeate and thus to a better yield of the water treatment plant.

[0131] In a third embodiment, if Figure 3 As shown, the water treatment device according to the invention comprises a connection between the fourth outlet (24) and the third inlet (22) to allow the recirculation of the RED effluent of the reverse electrodialysis first compartment and at least one further electrodialysis treatment of the RED effluent. Such recirculation allows increasing the flow rate of the retentate flowing within the RED unit, thereby ensuring similar flow rates in the permeate and retentate compartments, aiming to maintain similar pressure drops, thereby minimizing the risk of internal leaks. Retentate recirculation is required when the brine flow rate available in the RO unit is much lower than the permeate flow rate.

[0132] In another embodiment, Figure 3 As shown, the water treatment device according to the present invention comprises a connection between the third outlet (23) and the second inlet (21) to allow the recirculation of the RED effluent of the reverse electrodialysis second compartment. And at least one further electrodialysis treatment of the RED effluent. This recirculation allows increasing the conductivity of the flux entering the RED second inlet (21). This recirculation of permeate is required when the conductivity of the permeate P1 is below a predetermined threshold. The system may include a conductivity probe for measuring whether the conductivity of the permeate P1 is below / above a predetermined threshold and initiating the recirculation of the permeate from the third outlet (23) to the second inlet (21).

[0133] In another embodiment, Figure 3As shown, the water treatment device according to the present invention comprises at least one sensor (10) connected to the third outlet (23) in order to determine physicochemical parameters and detect organic components of the effluent (E1) that may be present. In the water treatment device according to the present invention, the at least one sensor is selected from: a conductivity meter, a spectrophotometer, a pH meter, a thermometer and / or a flow meter. In a specific embodiment, the ultraviolet absorbance is measured; an increase in ultraviolet absorbance at a predetermined level indicates that the membrane needs to be cleaned. In another specific embodiment, the conductivity is monitored; depending on the level of the conductivity, the potential applied to the reverse electrodialysis is adjusted to achieve the desired properties of the effluent (E1).

[0134] In a second aspect, the present invention relates to a method for providing mineralization and purification of drinking water, the method comprising:

[0135] -i) in a first step, providing fresh or brackish water containing ions and possibly micropollutants,

[0136] -ii) a second step of treating said fresh or brackish water by reverse osmosis to obtain a retentate and a permeate, wherein said retentate is enriched in ions and said potential micropollutants,

[0137] -iii) a third step of treating the retentate and the permeate of the second step by reverse electrodialysis, wherein at least a portion of the ions are extracted from the retentate and transferred to the permeate, and

[0138] -iv) a fourth step of recovering the mineralized water from said third step.

[0139] In the reverse electrodialysis step of the process according to the invention, the water flow rate is between 1 and 20 liters / hour.

[0140] In a particular embodiment of the process according to the invention, at least a portion of the ions in the retentate from the reverse osmosis step is extracted and transferred to the permeate, wherein another portion of the ions from the retentate is used for treatment. A person skilled in the art will determine the fraction of ions from the retentate to be transferred to the permeate according to the salinity of the fresh or brackish water to be treated, the salinity of the mineralized water to be generated and the efficiency of the process according to the invention.

[0141] In a particular embodiment of the process according to the invention, all ions in the retentate from the reverse osmosis step are extracted and transferred to the permeate.

[0142] In a particular embodiment, the process of the invention comprises a reverse electrodialysis step which is a short-circuit reverse electrodialysis.

[0143] In another specific embodiment, method of the present invention comprises reverse electrodialysis step, and it is auxiliary reverse electrodialysis.More specifically, method of the present invention comprises auxiliary reverse electrodialysis, wherein voltage is applied on the direction of natural salinity gradient, increases ion transport rate.In specific embodiments according to the method of the present invention, voltage higher than predetermined level is applied to reverse electrodialysis unit.The level of described voltage is to 0V to 8V for each membrane, and the quantity to which the membrane in the reverse electrodialysis unit is 5 to 1000 according to unit size.

[0144] In certain embodiments, the methods of the present invention include a reverse osmosis treatment step, including a single reverse osmosis treatment to produce a permeate and a retentate.

[0145] In another particular embodiment, the reverse osmosis step comprises a main reverse osmosis treatment and an additional reverse osmosis treatment of the retentate of the main reverse osmosis treatment.

[0146] In certain embodiments, the methods of the present invention comprise:

[0147] - injecting the retentate of the reverse osmosis of the second step ii) into the first compartment of the reverse electrodialysis unit, wherein the retentate is the retentate of a single reverse osmosis or the retentate of an additional reverse osmosis, and

[0148] - injecting the reverse osmosis permeate of the second step ii) into the second compartment of the reverse electrodialysis unit, wherein the permeate is the permeate of a single reverse osmosis or the permeate of a further reverse osmosis,

[0149] wherein the retentate and the permeate are injected into the reverse electrodialysis unit as parallel streams, and wherein the pressure applied to the first compartment is lower than the pressure applied to the second compartment.

[0150] In a particular embodiment, the method of the present invention further comprises a filtration step of the fresh or brackish water upstream of the reverse osmosis treatment, preferably microfiltration, ultrafiltration or nanofiltration, the reverse osmosis treatment being a single reverse osmosis treatment or a main reverse osmosis treatment. The filtration step upstream of the reverse osmosis is intended to remove suspended solid matter that may be present in the fresh or brackish water. Filtration can be performed by any means known to those skilled in the art, such as a multi-media filter, activated carbon, a bag filter and / or a cartridge filter.

[0151] In a particular embodiment, the process of the invention further comprises a filtration step, preferably microfiltration, ultrafiltration or nanofiltration, of the mineralized water recovered in said fourth step iv).

[0152] In a particular embodiment, the method of the present invention further comprises a filtration step of the second effluent (E2) from the fourth outlet (24), preferably microfiltration, ultrafiltration or nanofiltration, wherein the second effluent (E2) comprises at least a portion of the potential micropollutants and at least a portion of the first retentate (R1).

[0153] In a more specific embodiment, the method of the present invention further comprises:

[0154] - a filtration step of the fresh or brackish water upstream of the reverse osmosis step, preferably microfiltration, ultrafiltration or nanofiltration, and / or

[0155] - a filtration step, preferably microfiltration, ultrafiltration or nanofiltration, of the mineralized water of said first effluent (E1) recovered from said step iv), and / or

[0156] - a filtration step, preferably microfiltration, ultrafiltration or nanofiltration, of said second effluent (E2) recovered from said step iv).

[0157] In another specific embodiment, the method of the present invention further comprises a physical, chemical or gravity separation step of the effluent recovered from the second outlet (13) of the first reverse osmosis unit or from the sixth outlet (33) of the second reverse osmosis unit, preferably a filtration step, more preferably a microfiltration, ultrafiltration or nanofiltration step.

[0158] In another particular embodiment, the method of the invention further comprises a step of reversing the polarity of the reverse electrodialysis unit in order to minimize the risk of fouling the membrane with colloidal particles that may be present in the water to be treated and / or to help clean the membrane.

[0159] In an advantageous embodiment of the process of the invention, the process comprises a step of removing suspended matter, a step of adding a chelating agent, before the water is brought into contact with the reverse osmosis membrane, with the proviso that the chelating agent is an uncharged chelating agent.

[0160] In another specific embodiment, the process of the present invention comprises a step of bypassing the electrodialysis, wherein at least a portion of the permeate of the reverse osmosis step is added directly to the effluent of the reverse electrodialysis step, wherein the reverse osmosis is a single reverse osmosis, a main reverse osmosis and / or an additional reverse osmosis.

[0161] In another specific embodiment, the method of the invention further comprises at least one additional treatment by electrodialysis of the effluent of the first compartment of said reverse electrodialysis.According to this embodiment, the RED effluent containing salts and potential micropollutants is recycled and subjected to an additional reverse electrodialysis treatment.

[0162] In another particular embodiment, the method of the invention further comprises at least one further treatment by electrodialysis of the effluent of the second compartment of said reverse electrodialysis.According to this embodiment, the RED effluent comprising mineralized water is recycled and subjected to a further reverse electrodialysis treatment.

[0163] In another specific embodiment, the method of the present invention further comprises a step of subjecting the retentate of the reverse osmosis of step ii) to an electrodialysis metathesis treatment, wherein the retentate of the reverse osmosis is the retentate of a single reverse osmosis or the retentate of another reverse osmosis. The electrodialysis metathesis treatment allows, for example, the conversion of ions present in the retentate of the RO treatment with sodium and / or chloride, and comprises the addition of an external NaCl solution.

[0164] In another specific embodiment, the method of the present invention further comprises a step of monitoring the physicochemical properties of the resulting mineralized water of the first effluent of the third outlet and the level of any potential micropollutants and / or organic matter in the mineralized water. The monitoring or controlling step is performed by a control loop comprising at least one sensor of a physical or chemical parameter of the water.

[0165] The following examples illustrate but do not limit the water treatment apparatus and method according to the present invention.

[0166] Example:

[0167] Example 1: Treatment of artificially spiked brine by the method according to the invention

[0168] This example demonstrates the feasibility of the method and water treatment device according to the present invention for treating fresh water and brackish water (which may be artificially adulterated with micropollutants).

[0169] The saline was artificially spiked with the following micropollutants: isoproturon, carbamazepine, diuron, metoprolol, atenolol, PFOS, PFOA, sulfamethoxazole The salt water was treated by the method according to the present invention, and the mineralization degree of the obtained mineralized water and the concentration of each of the micropollutants were tested.

[0170] Saline and saline artificially spiked with micropollutants were treated by the method according to the invention, wherein the reverse electrodialysis step was carried out for 10 hours, with an applied current of 10 V (2 V per membrane pair) and a flow rate of 3 to 4 liters / hour / membrane pair. Mineralized water was obtained and characterized.

[0171] The resulting mineralized water was tested for concentrations of bicarbonate, calcium, potassium, magnesium, sodium, chloride, nitrate and sulfate. The hardness and electrical conductivity of the water were determined. The experimental results showed that the water had good mineral quality and its hardness was comparable to that of known bottled water.

[0172] The determination of the presence of micropollutants in the mineralized water obtained by the method of the invention shows that for any spiked micropollutant, 90% to 100% of said micropollutant is not present in the mineralized water. From these experimental results obtained with spiked brines, the predicted concentration of any tested micropollutant in mineralized water obtained from "real" brines is in compliance with any standard regulations.

[0173] Example 2: Experimental conditions of test configuration

[0174] according to Figure 4 A water treatment device is provided, the device comprising:

[0175] Two stacks in series, with the same voltage applied

[0176] Number of membrane pairs per stack, N cp =150

[0177] Channel geometry is 22cm x 50cm

[0178] Gasket thickness, δ = 760 μm

[0179] The configuration includes recycling the retentate and permeate streams exiting the second RED stack to the inlet of the first RED stack. This example illustrates that, by recycling, the conductivity of the permeate increases from 0.074 mS / cm to 0.1 mS / cm after recycling.

Claims

1. A water treatment device for providing mineralized and purified drinking water, the device comprising at least: - A first reverse osmosis unit (1), comprising at least: o a first inlet (11) for introducing fresh or brackish water containing ions and potential micropollutants, o a first outlet (12) for a first permeate (P1), o a second outlet (13) for the first retentate (R1), - a reverse electrodialysis unit (2), comprising at least: o a second inlet (21), which is connected to the first outlet (12), o a third inlet (22) connected to the second outlet (13), o a third outlet (23) for a first effluent (E1), said first effluent comprising at least a portion of said first permeate (P1) and at least a portion of the ions from said first retentate (R1), o a fourth outlet (24) for a second effluent (E2) comprising at least a portion of said potential micropollutants and at least a portion of said first retentate (R1), The reverse electrodialysis unit is an auxiliary reverse electrodialysis unit.

2. The water treatment device according to claim 1, comprising a second reverse osmosis unit (3), wherein the second reverse osmosis unit comprises at least: o a fourth inlet (31), which is connected to the second outlet (13), o a fifth outlet (32) for the second permeate, which is connected to the second inlet (21), o A sixth outlet (33) for the second retentate (R2), which is connected to the third inlet (22) or the sixth inlet (51).

3. The water treatment device according to claim 1 or 2, comprising: o a first filter unit (6) connected to the first inlet (11), and / or o a second filter unit (7), which is connected to the fourth outlet (24), and / or o A third filter unit (8), which is connected to the third outlet (23).

4. The water treatment device according to claim 2, comprising a bypass unit (4), wherein the bypass unit (4) comprises at least: o a fifth inlet (41), which is connected to the first outlet (12) and / or the fifth outlet (32), o a seventh outlet (42), which is connected to the third outlet (23), The bypass unit can be implemented in one of the following ways: o A first mode, wherein the first outlet (12) and / or the fifth outlet (32) is connected to the second inlet (21), o A second mode, wherein the first outlet (12) and / or the fifth outlet (32) is connected to the fifth inlet (41), and the seventh outlet (42) is connected to the third outlet (23).

5. The water treatment device according to claim 1, comprising a recirculation loop connecting the fourth outlet (24) and the third inlet (22) and / or a recirculation loop connecting the third outlet (23) and the second inlet (21).

6. The water treatment device according to claim 2, comprising an electrodialysis metathesis unit (5), which comprises at least: o a sixth inlet (51), which is connected to the second outlet (13) or the sixth outlet (33), o an eighth outlet (52) connected to the third inlet (22), and oExit 9 (53).

7. A water treatment device according to claim 1, comprising at least one sensor of a physicochemical parameter of the first effluent (E1), said sensor being connected to said third outlet (23).

8. A method for providing mineralized and purified drinking water, the method comprising: -i) in a first step, providing fresh or brackish water containing ions and potential micropollutants, -ii) a second step of treating said fresh or brackish water by reverse osmosis to obtain a retentate and a permeate, wherein said retentate is enriched in ions and said potential micropollutants, -iii) a third step of treating the retentate and the permeate of the second step by reverse electrodialysis, wherein at least a portion of the ions are extracted from the retentate and transferred to the permeate, so as to obtain a first effluent (E1) and a second effluent (E2), and -iv) a fourth step of recovering mineralized water from said first effluent (E1) of said third step.

9. The method according to claim 8, wherein the reverse electrodialysis is short-circuit reverse electrodialysis or assisted reverse electrodialysis.

10. The method according to claim 9, wherein the reverse electrodialysis is an auxiliary reverse electrodialysis, and the method further comprises applying a voltage higher than a predetermined level to the auxiliary reverse electrodialysis unit.

11. The method according to claim 8, wherein the second step comprises: a) a single reverse osmosis treatment or b) a main reverse osmosis treatment and a further reverse osmosis treatment of the retentate of said main reverse osmosis treatment.

12. The method according to claim 8, wherein the third step comprises: - injecting the retentate of the reverse osmosis of the second step into the first compartment of the reverse electrodialysis unit, wherein the retentate is the retentate of a single reverse osmosis or the retentate of a further reverse osmosis, - injecting the permeate of the reverse osmosis of the second step into the second compartment of the reverse electrodialysis unit, wherein the permeate is the permeate of a single reverse osmosis or the permeate of a further reverse osmosis, wherein the retentate and the permeate are injected into the reverse electrodialysis unit as parallel streams, and wherein the pressure applied to the first compartment is lower than the pressure applied to the second compartment.

13. The method according to claim 11, further comprising a filtration step of the fresh water or brackish water upstream of the single reverse osmosis or main reverse osmosis treatment, and / or further comprising a filtration step of the second effluent (E2), and / or further comprising a filtration step of the mineralized water recovered by the fourth step.

14. The method according to claim 8, further comprising a bypass step of the electrodialysis step, wherein at least part of the permeate of the reverse osmosis step is added to the first effluent (E1) of the reverse electrodialysis step.

15. The method according to claim 8 further comprises the step of performing at least one additional treatment of the second effluent (E2) of the reverse electrodialysis step by performing reverse electrodialysis, wherein the second effluent (E2) is recycled through the reverse electrodialysis unit, and / or further comprises the step of performing at least one additional treatment of the first effluent (E1) of the reverse electrodialysis step by performing reverse electrodialysis, wherein the first effluent (E1) is recycled through the reverse electrodialysis unit.

16. The method according to claim 11, further comprising the step of subjecting the reverse osmosis retentate of the second step to electrodialysis metathesis treatment, wherein the retentate is the single reverse osmosis retentate or the additional reverse osmosis retentate.

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