Description:FIELD OF THE INVENTION
[0001] Embodiments of the present disclosure relate to a system and method for remediating water from impurities with no waste being released to the environment, and more specifically to a system and method for remediating water from impurities such as metals, metalloids and fluorides, thereby providing purified drinking water and zero waste being disposed to the environment.

BACKGROUND OF THE INVENTION
[0002] Groundwater sources in several locations are contaminated with metals and/or metalloids and/or fluorides, and consuming water with these elements may result in causing harm to humans and animals, such as causing cancer, reproductive disorders, disorders of the blood vessels, bone disorders etc., which may even form permanent disabilities and genetic disorders, that pass on to the next generations. It is therefore imperative that these elements should be removed from groundwater or reduced to levels acceptable by health standards, such as those laid out by WHO before the water is consumed by humans and/or animals.
[0003] Several existing techniques, such as adsorption, ion exchange, precipitation/coagulation, and reverse osmosis are being used for removing impurities such as metal and/or metalloids and/or fluoride from groundwater to obtain purified water. However, these technologies often generate sludge or waste that is rich in impurities, which pose further disposal problems when the waste needs to be disposed. For example, adsorption is an efficient method for removing metalloids from groundwater; however, the disposal of metalloids-laden adsorbent or the metalloid-rich stream after desorption in case of regeneration of adsorbent becomes a significant environmental concern, due to the waste metalloids being disposed or dispersed into the environment. Reverse osmosis an efficient method for the removal of impurities such as metalloids, but the main disadvantage of reverse osmosis is that it produces a highly concentrated impure stream and results in a lot of water wastage.
[0004] There is, therefore, a need to develop an alternative method where there is zero waste generation at the end of the water purification process with minimal wastage of water, as well as the purified water still being purified of metals and metalloids with zero waste being generated.

SUMMARY OF THE INVENTION
[0005] Embodiments of the present disclosure relate to a method and system remediating contaminated water, for example groundwater from certain impurities, which include metals, metalloids and fluorides. In an embodiment, the system includes at least a water purifying unit, wherein the water purifying unit has a plurality of units (sub-units), which may also generally be referred to as adsorption-desorption beds. In a further embodiment, the plurality of units may be divided into two sets, one set of units being used to clean water, while the other set of units which are contaminated with the metals and/or metalloids and/or fluoride during the purification of water that need to be cleansed for reuse, wherein both the water purification units and the contaminated units are operating simultaneously.
[0006] In an embodiment, considering a simplistic purification unit containing two units, contaminated water is circulated through a first unit, wherein the first unit is configured to adsorb the metals and/or metalloids and/or fluoride present in the contaminated water, and purified water is collected from the output of the first unit. In an embodiment, when the first unit is saturated with the impurity, i.e., metals and/or metalloids and/or fluoride during the purification processes, the water to be purified is switched to a second unit for purification, where while the water is now being purified by the second unit, the first unit is simultaneously cleaned of the impurities by washing the first unit with a high acidic or alkaline solution depending on the impurity removed thereby regenerating the first unit and keeping it ready for use.
[0007] In an embodiment, one method to detect the saturation of the first unit is by detecting a breakthrough of the impurity (metal or metalloid or fluoride) passing out of the outlet of the first unit. In an embodiment, on detection of the saturation, the flow of water is switched from the first unit to the second unit. In an embodiment, the switching between the first unit and the second unit may be performed either manually or automatically. In an embodiment, on switching the water to the second unit after detecting that the first unit has attained saturation, the first unit having the contaminant (hereinafter also referred to as adsorbent in this disclosure or may be referred to as adsorbent material in this disclosure, which essentially is the metal or metalloid or fluoride) is treated with either one of a highly alkaline solution or highly acidic solution depending on the impurity present in the contaminant. In an embodiment, the contaminant of the first unit is washed with the alkaline solution or acidic solution, and the solution with the impurity (also referred to as a contaminant) is sent to a separation chamber. In an embodiment, the separation chamber is provided with a pH tolerant membrane which allows passage of the acidic/alkalinity-causing species along with a major portion of water while at the same time preventing the impurity from passing through the membrane. In an embodiment, the residual matter (impurity or contaminant) collected in the separation chamber can then be flushed to an isolation chamber where the impurity may be properly converted to a useful form for use by humans and/or animals or the impurity may be made into a less harmful form before disposing to the environment. Other embodiments are also disclosed.

BRIEF DESCRIPTION OF THE DRAWINGS
[0008] The detailed description is provided with reference to the accompanying figures. Features, aspects, and advantages of the subject matter of the present disclosure will be better understood with regard to the following description and the accompanying drawings. The figures are intended to be illustrative, not limiting, and are generally described in context of the embodiments, and it should be understood that it is not intended to limit the scope of the disclosure to these particular embodiments. In the figures, the same numbers may be used throughout the drawings to reference features and components. In order that the present disclosure may be readily understood and put into practical effect, reference will now be made to exemplary embodiments as illustrated with reference to the accompanying figures. The figures together with detailed description below, are incorporated in and form part of the specification, and serve to further illustrate the embodiments and explain various principles and advantages.
[0009] Figure 1 is an exemplary illustration of a water purifying system in accordance with an embodiment of the present disclosure.
[0010] Figure 2 is an exemplary illustration of a process for processing the solution post desorption of the purifying unit for remediation of a specific metalloid, such as arsenic, from contaminated water in accordance with an embodiment of the present disclosure.
[0011] Figure 3A is an exemplary illustration of a method for purifying water using the purifying system of Figure 1 in accordance with an embodiment of the present disclosure.
[0012] Figure 3B is an exemplary illustration of a method for switching the units for purifying water of the purification system of Figure 1 in accordance with an embodiment of the present disclosure.
[0013] Figure 3C is an exemplary illustration of a method for regenerating the contaminated unit while purifying water of the purification system of Figure 1 in accordance with an embodiment of the present disclosure.
[0014] Figure 4 is an exemplary illustration of a specific embodiment of arsenic rejection at different pHs at varying transmembrane pressure in accordance with an embodiment of the present disclosure.
[0015] Figure 5 is an exemplary illustration of a specific embodiment of NaOH rejection at pH concentration of 11 for different transmembrane pressure in accordance with an embodiment of the present disclosure.
[0016] Throughout the drawings, identical reference numbers designate similar, but not necessarily identical elements. The figures as disclosed herein are not necessarily to scale, and the size of some parts may be exaggerated to more clearly illustrate the example shown. Moreover, the drawings are meant to only be provided as examples and/or implementations consistent with the description, and the description may not be limited to the examples and/or implementations provided in the drawings.

DETAILED DESCRIPTION
[0017] The following describes technical solutions in exemplary embodiments of the subject matter of the present disclosure with reference to the accompanying drawings. In this application as disclosed herein, "at least one" means one or more, and "a plurality of" means two or more. The term "and/or" describes an association relationship for describing associated objects and represents that three relationships may exist. For example, A and/or B may represent the following cases: Only A exists, both A and B exist, and only B exists, where A and B may be singular or plural. The character "/" usually indicates an "or" relationship between the associated objects. "At least one item (piece) of the following" or a similar expression thereof means any combination of the items, including any combination of singular items (piece) or plural items (pieces). For example, at least one item (piece) of a, b, or c may represent a, b, c, a and b, a and c, b and c, or a, b, and c, where a, b, and c each may be singular or plural.
[0018] It should be noted that in this application articles “a”, “an” and “the” are used to refer to one or to more than one (i.e., to at least one) of the grammatical object of the article. The terms “comprise” and “comprising” are used in the inclusive, open sense, meaning that additional elements may be included. It is not intended to be construed as “consists of only”. Throughout this specification defined above, unless the context requires otherwise the word “comprise”, and variations such as “comprises” and “comprising”, will be understood to imply the inclusion of a stated element or step or group of elements or steps but not the exclusion of any other element or step or group of elements or steps. The term “including” is used to mean “including but not limited to”. “Including” and “including but not limited to” are used interchangeably. In the structural formulae given herein and throughout the present disclosure, the following terms have been indicated meaning, unless specifically stated otherwise.
[0019] Unless otherwise defined, all terms used in the disclosure, including technical and scientific terms, have meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. By means of further guidance, term definitions are included for better understanding of the present disclosure. The term ‘about’ as used herein when referring to a measurable value such as a parameter, an amount, a temporal duration, and the like, is meant to encompass variations of ±10% or less, preferably ±5% or less, more preferably ±1% or less and still more preferably ±0.1% or less of and from the specified value, insofar such variations are appropriate to perform the present disclosure. It is to be understood that the value to which the modifier ‘about’ refers is itself also specifically, and preferably disclosed.
[0020] It should be noted that in this application, the term such as "example" or "for example" or “exemplary” is used to represent giving an example, an illustration, or descriptions. Any embodiment or design scheme described as an "example" or "for example" in this application should not be explained as being more preferable or having more advantages than another embodiment or design scheme. Exactly, use of the word such as "example" or "for example" is intended to present a related concept in only a specific manner.
[0021] It should be understood that in the embodiments of the present subject matter that "B corresponding to A" indicates that B is associated with A, and B can be determined based on A. However, it should be further understood that determining B based on A does not mean that B is determined based on only A. B may alternatively be determined based on A and/or other information. Descriptions such as "first", "second" in the embodiments of this application are merely used for indicating and distinguishing between described objects, do not show a sequence, do not indicate a specific limitation on a quantity of devices in the embodiments of this application, and do not constitute any limitation on the embodiments of this application.
[0022] Exemplary embodiments of the present disclosure relate to a method and system for remediating contaminated water, for example groundwater from certain elements, which include impurities such as metals, metalloids or fluorides. In an embodiment, the system includes a purifying or purification unit (this may also be referred to as a adsorption-desorption unit in the present disclosure). In an embodiment, the purifying unit has a plurality of units (which may also be referred to as beds or adsorption beds or adsorption-desorption beds). In an embodiment, the plurality of units is filled with a substance or material (also referred to as adsorbent or adsorbent material), wherein the substance in the plurality of units depends on the impurity that needs to be filtered from the contaminated water source. In a further embodiment, within the purifying unit, the plurality of units may be divided into two sets. In an embodiment, a first set of the plurality of units may be used to clean the contaminated water from the impurity such as metals and/or metalloids and/or fluoride. In an embodiment, a second set of the plurality of units, in which the substance become contaminated with the impurity during the purification of the contaminated water, need to be cleansed for reuse while the first set of the plurality of units is purifying the contaminated water. It should be obvious to a person of ordinary skill in the art that embodiments of the present disclosure do not relate to removal of particulate matter or suspended matter or colloidal matter, which need to have been removed before the use of the current scheme to remove impurities such as metals and/or metalloids and/or fluorides. In an example case water obtained from a groundwater source or water obtained from industrial use that is free of suspended and/or settleable and/or colloidal particles.
[0023] In an embodiment, considering a simple purifying unit, which contains two units, and each of the two units is initially filled with the substance, wherein the substance is to adsorb the impurity in the water. In an embodiment, contaminated water is circulated through a first unit, wherein the first unit is configured to adsorb the impurity present in the contaminated water. In an embodiment, after the contaminated water has passed through the first unit, water that is free from the impurity, i.e., purified water may be collected from an output of the first unit.
[0024] In an embodiment, as the first unit purifies the contaminated water, the first unit is saturated with the impurity and the flow of water is switched to a second unit, wherein the second unit begins purifying the water. In an embodiment, when the switching of water for purification happens from the first unit to the second unit, the first unit will be cleaned of the impurity simultaneously, such that both units are operational, one purifying water and the other being cleansed of the impurity. In an embodiment, cleaning of the substance in the first unit is performed by washing the first unit with a highly acidic or highly alkaline solution, wherein the solution for cleaning the substance depends on the type of impurity to be removed from the substance since its interaction with the adsorbed impurity determines the efficiency of desorption, and further the cleaning solution imparts a charge to the membrane thereby effecting the removal efficiency of the impurity by the membrane. In an embodiment, after cleaning the impurity from the substance, the first unit is regenerated and ready for use. In an embodiment, the first unit which has been regenerated and ready to be used may be swapped with the second unit when the second unit attains saturation, which ensures continuity in the process of purifying the water.
[0025] In an embodiment, saturation of the first unit is detected when there is a breakthrough of the impurity (metal or metalloid or fluoride) passing out of the outlet of the first unit along with the water. In an embodiment, on detection of the breakthrough of the impurity, the flow of water is switched from the first unit to the second unit. In an embodiment, switching between the first unit and the second unit may be performed either manually or automatically. In an embodiment, washing the substance implies washing away the impurities present in the substance. It should be obvious to a person of ordinary skill in the art that various methods may be used to detect the breakthrough of impurity at the outlet of the unit purifying the water or saturation of the substance purifying the water, and all such methods employed to detect the breakthrough of impurity or saturation of the substance of the unit fall within the scope of the present disclosure.
[0026] In an embodiment, the substance of the first unit is washed with the alkaline solution or acidic solution, and the alkaline solution or acidic solution with the impurity, i.e., metals and/or metalloid and/or fluoride (hereinafter referred to broadly as impurity in the present disclosure) is sent to a separation chamber. In an embodiment a small motor or pump may be provided to send the solution with the impurity to the separation chamber. In an embodiment, the separation chamber is provided with a pH tolerant membrane which allows passage of the pH-imparting species (alkaline or acidic) along with a major part of the water, while at the same time preventing the impurity from passing through because a size difference of the species and a charge that is developed on the membrane, which repels the impurity of similar charge, specifically the ions of the metals and/or metalloids and/or fluoride. In an embodiment, the residual matter (impurity) collected in the separation chamber from the adsorbent, can then be flushed to an isolation unit where the impurity, is properly converted to a useful form for human and/or animal use, or made into a form that is less harmful before disposing to the environment. In an embodiment, the membrane in the separation chamber develops a negative charge at high pH (when basic solutions are used). In an embodiment, the membrane develops a positive charge at low pH (when acidic solutions are used). In an embodiment, the membrane allows ions from the strong basic species added to impart alkaline nature or strong acidic species added to impart acidic nature to permeate through and retain the ions of the impurity. In an embodiment, the isolation unit is a bio-reactor or a precipitator. In an embodiment, size based and charge based exclusion of the membrane is used to separate the impurity. Various other techniques may be used to separate the impurity at the separation unit and all such methods fall within the scope of the present disclosure.
[0027] In an exemplary case, the substance may be a bio-adsorbent, such that no toxic ingredients are used, or no toxic waste is generated during its preparation. In a specific exemplary embodiment, for removal of arsenic as an impurity from water, the bio-adsorbent (substance) comprises magnetic beads prepared with a mixture of FeCl3.6H20 and FeCl2.4H20 in a chitosan substrate. In an embodiment, the substance removes the impurity from the contaminated water provided as input to the purifying unit. In the exemplary embodiment, NaOH is used to wash the substance, and NaOH creates a strong negative charge on the membrane in the separation unit, allowing the NaOH to pass through with a major portion of water and retaining the As(oxyanions), which may then be flushed to the isolation unit.
[0028] Reference is now made to Figure 1, which is an illustration of an exemplary case of a purifying system (also referred to as a purification system) in accordance with an embodiment of the present disclosure, wherein the purifying system illustrates the purifying unit, a separation unit and an isolation unit for cleaning contaminated water. Figure 1 illustrates is an exemplary set up of purifying system 100 containing purifying unit 110, separation unit 130 and isolation unit 140 in accordance with the present disclosure. In an example case, the purifying system may simply consist of purifying unit 110 and isolation unit 140, without separation unit 130. It should be obvious to a person of ordinary skill in the art that different variation of the purifying system may be possible, and all such variations fall within the scope of the present disclosure. Purifying unit 110 may contain a plurality of units, where a first set of units from the plurality of units may be used for adsorption of impurities present in the water and a second set of units from the plurality of units may be used for desorption, while the first set of units are operational cleaning water. In an embodiment, the adsorption-desorption process occurs simultaneously. In an exemplary set-up there may be three sets of units, where a first set unit are cleaning the water, a second set of units are on stand-by to switch from the first set of units to the second set units when the first set of units needs to be cleaned and the third set of units which may be in the cleaning process and once cleaned will be the stand-by set. It should be obvious to a person of ordinary skill in the art that various other combination may be possible, and all such combination fall within the scope of the present disclosure.
[0029] In exemplary purifying unit 110 as illustrated in Figure 1, specifically for purpose of illustration only two units are shown to clearly illustrate the working principles of purifying unit 110. Purifying unit 110 has first unit 112 and second unit 122. Water 105, from a contaminated water source, containing impurities such as metals and/or metalloids and/or fluorides, which are generally free of suspended particles or colloidal particles is provided as input to first unit 112 of purifying unit 110. At the same instant of time, if purifying unit 110 has been in use, second unit 122 will be purified/cleaned to remove impurities that have been collected therein and prepare to keep in stand-by mode, such that when first unit 112 reaches saturation of impurities, water 105 is switched from first unit 112 to second unit 122.
[0030] First unit 112 and second unit 122 have a substance, wherein the substance adsorbs the impurities present in water 105 being provided as input to purifying unit 110. As illustrated in exemplary Figure 1, water 105 is provided to first unit 112, wherein impurities from the water 105 are adsorbed by the substance in first unit 112, and clean or purified water 115 is collected as output after purification of the contaminated water 105. First unit 112 has first valve 114 and second valve 116, where first valve 114 controls the flow of water into first unit 112 and second valve 116 controls the flow of purified water from first unit 112. First valve 114 and second valve 116 is a two-way valve. As the water 105 coming to first unit 112 is purified, the output water at second valve 116 is monitored for breakthrough, which implies that first unit 112 has reached saturation and can no longer purify the contaminated water 105. On reaching saturation, first unit 112 is shut, by reversing the direction of flow of first valve 114 and second valve 116, and water is switched to second unit 122. On reversing the direction of flow of first valve 114 and second valve 116, the substance in first unit 112 is set to be cleaned from the impurities.
[0031] Flow of water 105 is switched to second unit 122, wherein the inflow of water 105 is now controlled and third valve 124 and the outflow of water from the second unit 122 is controlled by fourth valve 126. Operation of second unit 122 is similar to operation of first unit 112 as mentioned previously, wherein on attaining saturation flow of water is switched to first unit 112 and third valve 124 and fourth valve 126 are reversed flow such that substance in second unit washed and cleaned of the impurity. While second unit 122 is operational in purifying water, first unit 112 which is contaminated with impurities is washed, cleaned, and regenerated to be in stand-by for use while the second unit 122 is getting saturated with the impurities. Advantageously switching between first unit 112 and second unit 122 ensure continuous purification of contaminated water without any break in the purification cycle. Further, switching between first unit 112 and second unit 122 may be performed manually or automatically on detection of saturation of impurities in the unit which is purifying the water. Advantageously, purified water 125 obtained using the methodology as described by the present disclosure is practically free from impurities such as metals and/or metalloids and/or fluorides and is deemed fit to be consumed by humans and animals.
[0032] As illustrated in Figure 1, assuming that second unit 122 was being used to purify contaminated water 105 from impurities and second unit 122 has reached saturation, i.e., breakthrough in impurities has been detected at fourth valve 126. Third valve 124 is reversed which prevents the inflow of water to second unit 122 and fourth valve 126 is reversed which prevents the outflow of water from second unit 122. Flow of water 105 is now through first unit 112, wherein first unit 112 is purifying the contaminated water. The substance of second unit 122 which is contaminated with the impurities and will now be cleaned and regenerated and the wash can continue as the direction of the valves in the second unit is reversed.
[0033] Second unit 122 which has the substance with the impurities is washed with a highly acidic solution or a highly basic solution, depending on the nature of impurity that is being removed from water 105. A source of the acidic solution or basic solution is provided to second unit 122, and the acidic solution or basic solution carries the impurities to separation chamber 130, where separation chamber is connected to purifying unit 110. Preferably the acidic solution or basic solution has a pH that is close to the extreme ranges of 0 and 14 while not damaging either the substance or membrane material. It should be obvious to a person skilled in the art that other ranges of pH may be covered for the solution being acidic or basic, including negative pH ranges, with the caveat that such an solution does not cause damage to the substance or membrane material. Again, depending on the impurity being removed from substance, which was present in the water, membrane 135 used in separation unit 130 to separate the impurities from either the acidic- or basic- pH imparting species should permeate the membrane along with a major part of the water. Membrane 135 is a pH tolerant membrane, which depends on the pH of solution being used in the cleaning process. At the same time, an additional make-up feed 137 of the acidic solution or the basic solution is provided to second unit 122 during the cleaning process to ensure that the cleaning process of removing impurities from the substance is unaffected. Depending on the solution used for cleaning the impurities from the substance, membrane 135 develops a charge and species imparting the acidic or basic nature to the solution are allowed to pass through membrane along with the majority of water, while ions of the impurity are retained in separation unit 130. Impurities are then sent to isolation unit 140, where the impurities are either converted to a less toxic species or isolated for human use. In an exemplary case, impurities may be either isolated by precipitation for further use or bio-digested and disposed safely. In an exemplary case, isolation unit 140 may be a bioreactor. As described previously, purifying unit 110 may not be provided with a separation unit and the impurity may be directly fed to the isolation unit 140.
[0034] In an exemplary case, when groundwater is contaminated with impurity Arsenic (As) and second unit 122 has been used to clean the contaminated groundwater. In the exemplary case, magnetic chitosan beads may be used as the substance i.e., the adsorbent material, which is filled in first unit 112 and second unit 122. In the exemplary case, impurity As is adsorbed by the adsorbent in second unit 122, and when the switch has happened to first unit 112 being in operation to purify the water from impurities, second unit 122 is regenerated. Second unit 122 is washed with a strong basic solution such as aqueous NaOH, which desorbs the As from the adsorbent and carries it to separation chamber 130. Membrane 135 develops a high negative charge and allows passage of the Na+ and OH- ions with the water, and the As species are retained in separation chamber 130. The As species are flushed to isolation unit 140, which in this specific exemplary case is a bioreactor. The As species are mixed with dung in the bioreactor and then disposed in a non-toxic form. In an exemplary case, animal dung may be used in the bioreactor. It should be obvious to a person of ordinary skill in the art that various other techniques may be used to dispose the impurity depending on the type of impurity and all such techniques fall within the scope of the present disclosure. In an exemplary case, if the impurities are precipitated, they may be used for other purposes.
[0035] In an exemplary case, the solution with the impurity may be sent to separation chamber/unit 130 by pump or motor 150 attached between to purifying unit 110 and separation unit 130. Pump 150 sends the solution with impurity at a constant pressure from the purifying unit 110 to the separation chamber 130. In an exemplary case, pump 150 may be configured to simply send the solution with impurity to the isolation unit 140 in the absence of the separation chamber 130. Pump 150 is only illustrative in nature and there may be several other techniques and methods employed to feed the solution containing impurities to the separation chamber 130 or isolation unit 140, which should be obvious to a person of ordinary skill in the art and all such methods and techniques fall within the scope of the present disclosure.
[0036] Reference is now made to Figure 2, which is an exemplary illustration of a process for processing the solution with impurities post desorption of the purifying unit for remediation of a specific metalloid in the separation chamber/unit, such as arsenic, from contaminated water in accordance with an embodiment of the present disclosure. As illustrated, the membrane system of the separation unit of the purifying system for remediation of a specific metalloid from contaminated water is disclosed. The exemplary case disclosed in Figure 2 is for removal of an impurity such as arsenic from groundwater source, and cleaning the substance from As collected as an impurity from the water, and it should be obvious that the same technique may be used to remove other impurities and depending on the impurity an appropriate cleaning agent may be used, and all such variation fall within the scope of the present disclosure. In an exemplary case to remove Nickle (Ni) as an impurity, a highly acidic solution may be used as a cleaning agent to clean the adsorbent. In the exemplary case, the substance/material in the purifying unit for removing Ni as an impurity may be different from the substance/material used to clean As which may be found as an impurity in water, and it should be obvious to a person of ordinary skill in the art that all such variations fall within the scope of the present disclosure, provided the methodology used for purifying water is in accordance with the embodiments of the present disclosure.
[0037] To illustrate the purification process and disposal of the impurities, a specific case of groundwater contaminated with Arsenic is illustrated in Figure 2. In the exemplary case, unit 210 (which can either be the first unit or the second unit as disclosed in Figure 1) is used to purify groundwater contaminated with impurities, where substance 220 in unit 210 adsorbs the impurities from the groundwater while the groundwater is passing through unit 210. For purpose of illustration only one unit is shown in Figure 2. In an exemplary case, considering one of the units, unit 210, to be filled with the impurity i.e., As, during the purification process, unit 210 having the impurities is provided with an aqueous NaOH stream (hereinafter also referred to as NaOH stream in the present disclosure) to wash the impurity collected by substance 220 in unit 210, wherein the impurities were collected by substance 220 while the water is flowing through unit 210. Additionally, a make up NaOH solution is also supplied separately to unit 210 to compensate for loss of NaOH during the separation process, in separation chamber 230, and the remaining NaOH is fed back to unit 210. The stream of NaOH (illustrated as NaOH rich stream) washes the impurities from substance 220 and the NaOH stream along with the impurity is sent to separation unit 230. The NaOH solution which is provided as input to unit 210 washes the impurities from substance 220 and the solution post desorption is provided to separation unit 230.
[0038] Separation unit 230 is provided with membrane 235, which as disclosed previously as a pH-tolerant membrane and membrane 235 is selected based on the impurity to be isolated from the groundwater and disposed.. In the illustrated exemplary example, NaOH solution with the impurity that is flushed from unit 210 is sent to separation unit 230, and makeup NaOH is being continuously supplied to unit 210, which should remove the impurities from substance 220. In a specific embodiment pump/motor 250 is used to send the feed of NaOH solution with the impurities into separation chamber 230. This pressurized NaOH solution with impurities to separation unit 230 creates a pressure gradient across membrane 235. In the exemplary case, because As is being removed from the groundwater source, the species of As is negatively charged, and a high negative charge is developed/induced across membrane 235 due to the high pH of the solution, which in this case is NaOH. The negative charge developed/induced on membrane 235 repels the As oxyanions that are coming into separation unit 230 along with the NaOH and allows passage of water and NaOH across membrane 235. NaOH that passed out from separation unit 230 is recycled and supplied back to unit 210 to remove impurities from substance 220, and as disclosed previously in accordance with the embodiments of the present disclosure, make up NaOH solution is also provided with the recycled NaOH.
[0039] In this exemplary case, the stokes radius for the As oxyanions is around 0.28 nm, while the stokes radius for the OH- ions is around 0.046 nm. Considering the size of the radius of the impurity, it should be obvious to a person of ordinary skill in the art that in the exemplary case, membrane 235 may be chosen such that membrane 235 has pore size such that the arsenic oxyanions are removed by size-based effects, as the size of arsenic oxyanions is larger than the pore size of the membrane, and the size of the basic species used is smaller than the pore size of membrane 235, thereby allowing the smaller Na+ and OH? ions to permeate through the membrane . It should also be obvious to a person of ordinary skill in the art that various other techniques may also be used to separate the As impurity from the NaOH stream and all such techniques fall within the scope of the present disclosure. It should also be obvious to a person of ordinary skill in the art that various techniques may be used to create a charge effect that allows for separation of the impurity ions, As ions, from the species ions, Na+ and OH- ions, and all such techniques fall within the scope of the present disclosure. In an exemplary case a magnetic field or a laser may be employed to separate the larger charged ions from the species ions and it should be obvious to a person of ordinary skill in the art that such techniques also fall within the scope of the present disclosure.
[0040] The retained As (reference to As oxyanions) in separation unit 230 which is in a concentrated form is subsequently diverted/sent to isolation unit 240, which in this specific case was a bioreactor. The As supplied from isolation unit 240 is either precipitated or disposed by other means, for example mixing it with animal dung. In this specific exemplary case, the concentrated As stream is treated with animal dung that may be readily available. In a bioreactor interaction of animal dung and concentrated arsenic stream will result in the formation of a non-toxic sludge which is then be easily disposed, thereby preventing any harm to be caused to the environment, plants, humans and/or animals.
[0041] The exemplary case of Figure 2 only illustrates a specific case of removing As found as an impurity from groundwater source. It should be obvious to a person of ordinary skill in the art that the same methodology may be used to remove other metals and/or metalloids and/or fluorides by changing the substance, changing the washing solution, which can be either a basic solution or an acidic solution depending on the impurity to be removed, providing an extra feed (make-up) of the washing solution, selecting an appropriate membrane that can repel the impurity and collect the impurity in an isolation unit to be properly disposed or converted to a useful form that is non-toxic to the environment, and all such variations of the methodology illustrated above fall within the scope of the present disclosure.
[0042] Figure 3A is an exemplary illustration of a method for purifying water using the purifying system of Figure 1 in accordance with an embodiment of the present disclosure. In step 310, contaminated water is received at a purifying unit. The water is generally groundwater that has impurities such as metals and/or metalloids and/or fluoride. The purifying unit has a plurality of units, the plurality of units may be divided into two or three sets or more sets as described with respect to Figure 1. In an exemplary case considering two units in the purifying unit, the first unit and the second unit comprise a substance (an adsorbent material). In step 312, contaminated water is provided as a feed to a first unit, wherein the first unit removes the impurities from the water and provides clean water as output from the first unit. In step 314 the impurities are adsorbed by the substance in the first unit, and in Step 316, purified water, i.e., water that has been cleaned of the impurity is collected, which can be consumed by humans and animals. During purification of the contaminated water in step 314, as per step 318, the first unit is continuously monitored to detect that the first unit has reached saturation, wherein saturation is determined by a breakthrough of impurities in the water coming from the outlet of the first unit, wherein a detailed description of the working of the embodiments of the present disclosure is provided with reference to Figure1 and Figure 2.
[0043] Figure 3B is an exemplary illustration of a method for switching the units purifying water of the purifying system of Figure 1 in accordance with an embodiment of the present disclosure. In step 320, the first unit is being monitored for a breakthrough of impurities at the outlet of the first unit. In step 322, once breakthrough is determined at the first unit, the flow of water is switched from the first unit to the second unit. In an exemplary case, monitoring the breakthrough at the outlet may be continuous or based on specific time intervals. In an exemplary case, to remove arsenic from water it may take about 4-6 days for the first unit to get saturated, therefore a timer may be set to either manually or automatically switch the flow of water from the first unit to a second unit of the purifying unit. In an exemplary case of As removal with chitosan beads, the breakthrough is observed in about 5 days. It should be obvious to a person of ordinary skill in the art that depending on the impurity the time range for detecting the breakthrough may be pre-determined and these techniques fall within the scope of the present disclosure. It should also be obvious that if a different material is used, substance, the time for saturation may vary and such variations fall within the scope of the present disclosure. If should also be obvious to a person of ordinary skill in the art that the time for detecting a breakthrough of impurity also depends on the size of the units used for purifying water, and the time for breakthrough detection may vary, which also fall within the scope of the embodiments of the present disclosure. Further, a detailed description of the working of the embodiments of the present disclosure is provided with reference to Figure1 and Figure 2.
[0044] Figure 3C is an exemplary illustration of a method for regenerating the unit contaminated with impurities while purifying water of the purifying system of Figure 1 in accordance with an embodiment of the present disclosure. In step 330, once the first unit is saturated with the impurity the flow of water is switched to the second unit, and the first unit where the substance is now adsorbed the impurity, the substance needs to be washed and regenerated such that the first unit is made ready and kept in standby, such that when the second unit which is purifying water is saturated with the impurity, the water flow is switched from the second unit to the first unit. This ensures non-stop and continuous purification of the water. To cleanse the substance a strong acidic solution or a strong basic solution is selected depending on the type of impurity that needs to be washed from the substance. In step 332, the impurity collected from the substance by the acidic or basic solution is sent to a separation unit. The separation unit has a membrane which is selected to isolate the impurity and let the species imparting acidic or basic nature to pass through it along with a majority of water. The membrane develops a charge that will repel the impurity ions and let the ions imparting acidic or basic nature to pass through along with a majority of water. In step 334, the impurity that is separated at the separation unit is sent to an isolation unit where the impurity may be properly disposed after conversion to a low-toxicity form or isolated for further use by precipitation or any other methods like ultrasound, laser etc. For example, the impurity may be precipitated or disposed via a bioreactor by creating a sludge which is free of toxic species, wherein a detailed description of the working of the embodiments of the present disclosure is provided with reference to Figure1 and Figure 2.
[0045] Reference is now made to Figure 4, which is an exemplary illustration of a specific embodiment of arsenic species (arsenate and arsenite) rejection at different pHs at varying transmembrane pressures, in accordance with an embodiment of the present disclosure. In an exemplary case, groundwater contaminated with arsenic was studied as a specific embodiment. It should be obvious to a person of ordinary skill in the art that other metals and/or metalloids and/or fluoride may also be considered and fall within the scope of the methodology of the present disclosure, but have not been discussed in the present disclosure. In an exemplary case to show enablement of the present disclosure, groundwater contaminated with arsenic was chosen as a sample.
[0046] The plot illustrates arsenic rejection in terms of percentage against the transmembrane pressure measured in bar. For a solution with pH 6.9, the As(III) rejection (shown as diamonds in the graph) at a pressure of 10 bar was about 45-47% whereas at a pressure of about 30 bar the rejection was around 69-71%. For a solution with pH 11, the As(III) rejection (shown as square in the graph) at a pressure of 10 bar was about 57-59% whereas at a pressure of about 30 bar the rejection rate was around 75-77%. For a solution with pH 6.9, the As(V) rejection (shown as triangle in the graph) at a pressure of 10 bar was about 51-54% whereas at a pressure of about 30 bar the rejection was around 66-68%. For a solution with pH 11, the As(V) rejection (shown as cross (x) in the graph) at a pressure of 10 bar was about 69-72% whereas at a pressure of about 30 bar the rejection rate was above 80%, around 82-84%. The plot only indicates an exemplary case, and it should be obvious that different metals and/or metalloids and/or fluorides will have different rejections for different pHs and transmembrane pressures.
[0047] Reference is now made to Figure 5, which is an exemplary illustration of a specific embodiment of NaOH rejection at pH of 11 for different transmembrane pressures in accordance with an embodiment of the present disclosure. Again, as illustrated previously, the enablement of this exemplary case was for removal of arsenic from groundwater, where a strong basic solution of NaOH was used to clean the adsorbent. The graph shows NaOH rejection in percentage as a function of transmembrane pressure in bar, wherein the aqueous NaOH solution had a pH of 11, the NaOH rejection at a pressure of about 10 bar is around 50% and the rejection at a pressure of about 30 bar is found to be around 20%.
[0048] Although the present disclosure has been described with reference to several preferred embodiments, it should be understood that the present disclosure is not limited to the preferred embodiments disclosed here. Embodiments of the present disclosure are intended to cover various modifications and equivalent arrangements within the spirit and scope of the appended claims. Although the foregoing disclosure has been described in some detail for purposes of clarity of understanding, it will be apparent that certain changes and modifications may be practised within the scope of the appended claims. Examples of the present disclosure have been described in language specific to structural features and/or methods. It should be noted that there are many alternative ways of implementing both the process and apparatus of the present invention. Accordingly, embodiments of the present disclosure are to be considered illustrative and not restrictive, and the invention is not to be limited to the details given herein but may be modified within the scope and equivalents of the appended claims. It should be understood that the appended claims are not necessarily limited to the specific features or methods described. Rather, the specific features and methods are disclosed and explained as examples of the present disclosure.

, Claims:We Claim:
1. A system 100 for remediating impurities from contaminated water 105, the system comprising:
- a purifying unit 110, the purifying unit 110 comprising:
- a plurality of units, wherein the plurality of unit comprises:
- a first unit 112 and a second unit 122, the first unit 112 and the second unit 122 comprises:
- a substance 220, the substance 220 configured to adsorb impurities from contaminated water 105 and provide purified water 115;
- contaminated water 105 being routed via the first unit 112;
- on detection of the first unit 112 reaching saturation, routing the contaminated water 105 via the second unit 122 by switching a flow of the contaminated water 105 from the first unit 112 to the second unit 122;
- a separation unit 130, the separation unit 130 configured to receive an impure solution flushed from the first unit 112, wherein the impure solution flushed comprises a first solution along with the impurities from the substance 220, and the solution configured to regenerate the substance of the first unit 112 while the second unit 122 is cleaning the contaminated water 105;
- the separation unit 130 further configured to separate the impurities from the impure solution flushed from the first unit 112; and
- an isolation unit 140, wherein the isolation unit 140 receives a concentrated feed of the impurities from the separation unit 130 to be disposed.

2. The system as claimed in claim 1, wherein the first solution is a highly alkaline solution or a highly acidic solution, and wherein the impurities in the substance are washed away by the highly alkaline solution or the highly acidic solution.

3. The system as claimed in claim 1, wherein the valve 116 of the first unit 112 is monitored for a breakthrough of the impurities, wherein detection of the breakthrough at the valve 116 implies saturation of the first unit 112.

4. The system as claimed in claim 1, wherein a pre-defined time is set for saturation, wherein on reaching the pre-defined time, the flow of contaminated water 105 is switched from the first unit 112 to the second unit 122.

5. The system as claimed in claims 3 or 4, wherein switching between the first unit 112 and the second unit 122 is performed either manually or automatically on detection of the saturation.

6. The system as claimed in claim 1, wherein the separation unit 130 comprises a membrane 135.

7. The system as claimed in claim 6, wherein the membrane 135 is configured to retain the impurity from the impure solution flushed and allow a species imparting an acidic nature or a basic nature to the first solution pass through along with a majority of the water.

8. The system as claimed in claim 6, wherein the membrane is pH tolerant membrane.

9. The system as claimed in claim 6, wherein the membrane 135
- develops a negative charge for a solution with high pH, or
- develops a positive charge for a solution with low pH.

10. The system as claimed in claim 9, wherein the membrane 135 is configured to allow ions of
- a strong basic species added to impart alkaline nature or
- a strong acid species added to impart acidic nature,
to permeate through along with majority of water, while retaining ions of the impurities.

11. The system as claimed in claim 1, wherein the substance is a solid material, wherein the solid material adsorbs impurities from the contaminated water 105.

12. The system as claimed in claim 1, wherein the impurities comprise at least one of a metal and/or a metalloid and/or a fluoride.

13. A method for remediating impurities from contaminated water 105, the method comprising:
- providing contaminated water 105 as a feed to a purifying unit110, wherein the contaminated water provided as feed is free from colloidal and suspended impurities, and wherein the purifying unit 110 comprises at least a first unit 112 and a second unit 122, and wherein the first unit 112 and the second unit 122 comprise a substance;
- receiving contaminated water 105 at the first unit 112;
- removing the impurities from the contaminated water 105, wherein the substance adsorbs the impurities from the contaminated water 105;
- providing clean water 115 at an outlet 116.

14. The method as claimed in claim 13, the method comprising:
- detecting occurrence of saturation at the first unit 112;
- switching a flow of contaminated water 105 from the first unit 112 to the second unit 122 on detection of saturation of the first unit 112.

15. The method as claimed in claim 12, the method comprising:
- treating the substance with a first solution, wherein the first solution is a highly alkaline solution or a highly acidic solution, wherein the impurities in the substance are washed away by the highly alkaline solution or the highly acidic solution; and
- collecting an impure solution flushed from the first unit 112 at a separation unit 130, wherein the impure solution flushed comprises the first solution along with the impurities.

16. The method as claimed in claim 13, the method comprising:
- separating the impurities from the impure solution flushed using a membrane 135, wherein the membrane is pH tolerant; and
- providing a concentrate feed of impurities separated to an isolation unit 140, wherein the impurities are disposed via the isolation unit.

17. The method as claimed in claim 16, wherein the membrane 135
- develops a negative charge for a solution with high pH, or
- develops a positive charge for a solution with low pH.

18. The method as claimed in claim 17, wherein the membrane 135 is configured for:
- allowing ions of
- a strong basic species added to impart alkaline nature or
- a strong acid species added to impart acidic nature,
to permeate through the membrane 135 along with a majority of water and retain ions of the impurities, wherein the retained ions of the impurities are sent to the isolation unit 140.

19. The method as claimed in claim 13, wherein the impurities comprise at least one of a metal and/or a metalloid and/or a fluoride.

20. The method as claimed in claims 14, wherein switching between the first unit 112 and the second unit 122 is performed either manually or automatically on detection of the saturation.

Dated this 13th day of February 2024
Indian Institute of Science
By their Agent & Attorney

(Dr. Eric W B Dias)
of Khaitan & Co
Reg No IN/PA-1058