Methods for removing a dissolved contaminant from wastewater using zero valent iron

Abstract

Methods for removing a dissolved contaminant from wastewater are provided. The methods include providing wastewater to a reactor containing a zero valent iron media, a surface of the zero valent iron comprising rust following addition of the wastewater to the reactor; and contacting the wastewater and the zero valent iron media to adsorb the dissolved contaminant on the surface of the zero valent iron media as a contaminant-iron complex, thereby removing the dissolved contaminant from the wastewater and forming cleaned water, wherein contact between the zero valent iron media removes the contaminant-iron complex from the surface of the zero valent iron media as a precipitate.

Description

METHODS FOR REMOVING A DISSOLVED CONTAMINANT FROM WASTEWATER USING ZERO VALENT IRONFIELD OF INVENTION

[0001] The present invention relates to methods for removing one or more dissolved contaminants from wastewater. More specifically, the present invention relates to methods for removing one or more dissolved contaminants from wastewater in a reactor comprising zero valent iron media.BACKGROUND

[0002] Wastewater from various sources, such as industrial facilities, may contain a significant concentration of dissolved contaminants which pose significant environmental and health risks, as the dissolved contaminants present in the wastewater are generally above concentrations deemed as safe by most regulatory bodies. The removal of many dissolved contaminants from wastewater is complex and expensive due to the stringent discharge limits for such contaminants and the equipment and processes required for removal of such contaminants. Moreover, the use of wet scrubbing processes in industrial settings further increases the quantity of wastewater containing undesired dissolved contaminants and, furthermore, provides such dissolved contaminants at high concentrations that are difficult to cost-effectively remove using current techniques.

[0003] There are a number of technologies for the removal of dissolved contaminants, such as metals, from wastewater, including, the use of iron, and in particular, zero valent iron (ZVI). When iron meets water or atmospheric oxygen, it undergoes a process known as corrosion, leading to the formation of a layer of rust on the surface of the iron. This rust comprises iron oxides and hydroxides, and the entire process is an electrochemical reaction, where iron is oxidized while oxygen or water is reduced.

[0004] Rust, particularly iron hydroxides and oxides, acts as an efficient adsorbent for various dissolved metals and contaminants present in water. Iron rust can effectively trap and remove these harmful substances in wastewater, making it valuable for water purification purposes.

[0005] ZVI systems are known to be effective for reducing the concentration of contaminants in wastewater in which the iron corrosion process is exploited to transform and immobilize dissolved contaminants present in wastewater. In particular, ZVI is known for itscapabilities in the removal of dissolved metals, such as selenium. Utilizing ZVI for removal of dissolved metals offers several advantages. Iron is relatively inexpensive and readily available, making it a cost-effective option for water treatment processes. The treatment procedure for removal of dissolved metals, such as selenium, using ZVI is relatively simple, involving the placement of ZVI media in columns through which a wastewater containing the dissolved metal is pumped.

[0006] However, the efficiency of ZVI treatment diminishes over time regardless of the geometry of the ZVI used (powder, rod, wool, scrap iron) because, after the formation of the initial layers of rust on the surface of the iron, further direct contact between the iron and the wastewater is limited. Consequently, the formation of additional rust slows down significantly, hampering the overall dissolved contaminant removal process and leaving the majority of the ZVI unutilized.

[0007] Current ZVI treatment systems for removal of dissolved contaminants are mainly limited to passive treatment systems or applications where only a small amount of contaminant removal is required. In more extensive water treatment scenarios, the decline in efficiency becomes a significant drawback for ZVI. Despite this drawback, ZVI treatment systems remain relevant and cost-effective but only for situations that demand limited contaminant removal such as passive treatment systems. To address more substantial water treatment challenges in dissolved contaminant removal, innovative methodologies are essential to capitalize on the unique adsorbent properties of iron rust while addressing the limitations of ZVI-based treatments, including various pre-treatment and post-treatment steps.

[0008] ZVI systems are limited by a diminishing efficiency for removal of dissolved contaminants over time due to surface passivation, making them unsuitable for active continuous water treatment, such as those required in many industrial settings. Currently, the regeneration of ZVI requires the extraction of media from the reactor and / or the inclusion of additional chemicals, which may be costly and / or impractical to employ in methods for removal of dissolved contaminants from wastewater.

[0009] Thus, there remains a need for methods for removal of dissolved contaminants with ZVI providing high rates of dissolved contaminant removal from wastewater without the need to extract ZVI containing media from a reactor and / or provide additional chemicals.SUMMARY OF THE INVENTION

[0010] The present disclosure provides methods for removing a dissolved contaminant from wastewater. The method may offer the following improved features when compared with known methods comprising ZVI for the removal of a dissolved contaminant, including, but not limited to: in-situ Z\ / \ media regeneration, low-cost and robust operation, no additional chemicals for ZVI regeneration, improved removal rates over current technologies, improved concentrations of a dissolved contaminant in the clean water produced over current technologies, and a streamlined treatment process.

[0011] In one aspect of the disclosure, there is provided herein a method for removing a dissolved contaminant from wastewater, the method comprising providing the wastewater to a reactor, wherein the reactor contains a zero valent iron media, a surface of the zero valent iron comprising rust following addition of the wastewater to the reactor; and contacting the wastewater and the zero valent iron media to adsorb the dissolved contaminant on the surface of the zero valent iron media as a contaminant-iron complex, thereby removing the dissolved contaminant from the wastewater and forming cleaned water, wherein contact between the zero valent iron media removes the contaminant-iron complex from the surface of the zero valent iron media as a precipitate.

[0012] In various embodiments, the method may further comprise (c) removing the cleaned water from the reactor.

[0013] In various embodiments, the dissolved contaminant comprises a metal. In various embodiments, the dissolved contaminant may comprise antimony, arsenic, boron, cadmium, chromium, copper, lead, molybdenum, nickel, selenium, silver, zinc or any combination thereof. In various embodiments, the dissolved contaminant may comprise selenium.

[0014] In various embodiments, removal of the contaminant-iron complex from the surface of the zero valent iron media may regenerate the surface of the zero valent iron media to form rust and adsorb further dissolved contaminant from the wastewater.

[0015] In various embodiments, the method may be a batch process.

[0016] In various embodiments, the method may be a continuous process.

[0017] In various embodiments, the rust is green rust.

[0018] In various embodiments, formation of the contaminant-iron complex may comprise a redox reaction between the contaminant and iron of the rust.

[0019] In various embodiments, the adsorption and the redox reaction occur in situ in the reactor.

[0020] In various embodiments, the zero valent iron media may be balls, rods, pebbles, wool, iron pieces or a combination thereof.

[0021] In various embodiments, the zero valent iron media further comprises an additive. For example, the additive may be harder than zero valent iron. For example, the additive may be sand.

[0022] In various embodiments, the method does not comprise a filtration step prior to step (a).

[0023] In various embodiments, the method may further comprise adjusting a pH of the wastewater prior to step (a).

[0024] In various embodiments, a rate of removal of the dissolved contaminant from the wastewater may be about 15 mg / L / h to about 35 mg / L / h.

[0025] In various embodiments, a concentration of the contaminant in the clean water may be less than about 1 mg / L. For example, the concentration of the contaminant in the clean water may be less than 20 pg / L. For example, the concentration of the contaminant in the clean water may be less than 2 pg / L.

[0026] In various embodiments, a concentration of the dissolved contaminant in the wastewater may be greater than about 0.1 mg / L, 0.2 mg / L, 0.3mg / L, 0.4mg / L or 0.5mg / L.

[0027] In various embodiments, a concentration of the dissolved contaminant in the wastewater may be 1 mg / L to 100 mg / L.

[0028] In various embodiments, the wastewater may comprise an industrial wastewater, a surface water, or a ground water.

[0029] In various embodiments, the industrial wastewater may comprise wastewater from a metal-processing facility.

[0030] In various embodiments, the wastewater from the metal-processing facility may be a wastewater from a gold-processing facility.

[0031] In various embodiments, the dissolved contaminant may be selenate (SeO42-) and / or selenite (SeOs2')-

[0032] Other aspects and features of the present disclosure will become apparent to those of ordinary skill in the art upon review of the following description of specific embodiments of the disclosure in conjunction with the accompanying claims.BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In drawings which illustrates embodiments of the disclosure,

[0034] Figure 1 shows selenium concentration in water (mg / L) as a function of reaction time for a batch treatment of scrubber solution according to an embodiment of a method as described herein;

[0035] Figure 2 shows selenium removal from a solution with 100 mg / L selenium in a batch demonstration. Figure 2A provides a linear scale of selenium concentration and Figure 2B provides a logarithmic scale of selenium concentration according to an embodiment of the disclosure;

[0036] Figure 3 shows average selenium concentration in water (mg / L) as a function of time for a continuous treatment of scrubber solution using a 3-hour HRT according to an embodiment of a method as described herein;

[0037] Figure 4 shows average boron concentration in water (mg / L) as a function of time for a continuous treatment of scrubber solution using a 3-hour HRT according to an embodiment of a method as described herein;

[0038] Figure 5 shows average selenium concentration in water (pg / L) as a function of time for a continuous treatment of mine impacted water using a 10-minute HRT according to an embodiment of a method as described herein; and

[0039] Figure 6 shows selenium concentration in water (mg / L) as a function of reaction time for a batch treatment of retentate from reverse osmosis treatment of mine impacted water according to an embodiment of a method as described herein.DETAILED DESCRIPTION

[0040] In the context of the present disclosure, various terms are used in accordance with what is understood to be the ordinary meaning of those terms.

[0041] Described herein are methods for removing a dissolved contaminant from wastewater. It will be appreciated that embodiments and examples are provided herein for illustrative purposes intended for those skilled in the art, and are not meant to be limiting in any way.

[0042] As used herein, the term “about” refers to an approximately + / -10 % variation from a given value. It is to be understood that such a variation is always included in any given value provided herein, whether or not it is specifically referred to.

[0043] As used herein, the term “substantially” refers to an approximately + / -5 % variation from a given value. If a value is not used, then substantially means almost completely, but perhaps with some variation, contamination and / or additional component. In some embodiments, “substantially” may include completely.

[0044] As used herein, the term “dissolved contaminant” refers to one or more contaminants which may be present in the wastewater and can include both inorganic and organic compounds. In various embodiments, the dissolved contaminant which is removed from the wastewater is an element or metal ion, such as Lithium (Li), Beryllium (Be), Boron (B), Sodium (Na), Magnesium (Mg), Aluminum (Al), Silicon (Si), Potassium (K), Calcium (Ca), Scandium (Sc), Titanium (Ti), Vanadium (V), Chromium (Cr), Manganese (Mn), Iron (Fe), Cobalt (Co), Nickel (Ni), Copper (Cu), Zinc (Zn), Gallium (Ga), Germanium (Ge), Arsenic (As), Rubidium (Rb), Strontium (Sr), Ytterbium (Yb), Zirconium (Zr), Niobium (Nb), Molybdenum (Mo), Technetium (Tc), Ruthenium (Ru), Rhodium (Rh), Palladium (Pd), Silver (Ag), Cadmium (Cd), Indium (In), Tin (Sn), Antimony (Sb), Tellurium (Te), Cesium (Cs), Barium (Ba), Lanthanum (La), Hafnium (Hf), Tantalum (Ta), Wolfram or tungsten (W), Rhenium (Re), Osmium (Os), Iridium (Ir), Platinum (Pt), Gold (Au), Mercury (Hg), Thallium (TI), Lead (Pb), Bismouth (Bi), Polonium (Po), Francium (Fr), Radium (Ra), Actinium (Ac), Rutherfordium (Rf), Dubnium (Db), Seaborgium (Sg), Bohrium (Bh), Hassium (Hs), Meitnerium (Mt), Darmstadtium (Ds), Roentgenium (Rg), Copernicium (Cn), Cerium (Ce), Praseodymium (Pr), Neodymium (Nd), Promethium (Pm), Samarium (Sm), Europium (Eu), Gadolinium (Gd), Terbium (Tb), Dysprosium (Dy), Holmium (Ho), Erbium (Er), Thulium (Tm), Ytterbium (Yb), Lutetium (Lu), Thorium (Th), Protactinium (Pa), Uranium (U),Neptunium (Np), Plutonium (Pu), Americium (Am), Curium (Cm), Berkelium (Bk), Californium (Cf), Einsteinium (Es), Fermium (Fm), Mendelevium (Md), Nobelium (No), and Lawrencium (Lr). In various embodiments, the contaminant may be dissolved in the wastewater. In certain embodiments, the one or more dissolved contaminant incorporated into a liquid may form a solution. In certain embodiments, the liquid incorporating the one or more dissolved contaminant is a water or a wastewater. In certain embodiments, the dissolved contaminant may comprise antimony, arsenic, boron, cadmium, chromium, copper, lead, molybdenum, nickel, selenium, silver, zinc or any combination thereof. In certain embodiments, the dissolved contaminant comprises boron. In certain embodiments, the dissolved contaminant comprises selenium. In certain embodiments, the selenium may comprise selenate (SeC>42') and / or selenite (SeOs2-)-

[0045] As used herein, the term “wastewater” refers to any water generated after the use of a substantially clean water, such as fresh water, drinking water or purified water. In certain embodiments, wastewater may comprise one or more of industrial wastewater, cooling water, leachate, return flow, surface runoff, urban runoff or agricultural wastewater. In certain embodiments, the wastewater may comprise one or more dissolved contaminant.

[0046] As used herein, the term “zero valent iron” or “ZVI” refers to iron that is substantially in a Fe° state. In certain embodiments, the “zero valent iron” may be metallic iron. In certain embodiments, the zero valent iron may be a reducing agent. In certain embodiments, the zero valent iron may be capable of adsorbing, binding, degrading, and / or sequestering one or more dissolved contaminant.

[0047] As used herein, the term “adsorb” or “adsorption” refers to an ability of a solid to bind a molecule, such as a dissolved metal, present in a gas or liquid, as a layer on a surface of the solid.Methods for removing a dissolved contaminant from a wastewater

[0048] In various embodiments, there is provided herein a method for removing a dissolved contaminant from wastewater, the method comprising: providing the wastewater to a reactor, wherein the reactor contains a zero valent iron media, a surface of the zero valent iron media comprising rust following addition of the wastewater to the reactor; and contacting the wastewater and the zero valent iron media to adsorb the dissolved contaminant on the surface of the zero valent iron media as a contaminant-iron complex, thereby removing the dissolved contaminant from the wastewater and forming cleaned water, wherein contact between the zerovalent iron media removes the contaminant-iron complex from the surface of the zero valent iron media as a precipitate.

[0049] In certain embodiments, the method comprises providing wastewater to a reactor. In certain embodiments, the step of contacting comprises contact in the reactor such that the contaminant-iron complex from the surface of the ZVI media is removed as a precipitate. As used herein, the term “contact” or “contacting” refers to the movement, such as the movement of a wastewater containing zero valent iron media, to mix, stir, or disturb the liquid. Contact also includes contact between different particles of the media. In certain embodiments, the reactor may operate in a batch mode or a continuous mode. In certain embodiments, the reactor may be a reactor capable of providing a rate of 25mL / h to 50mL / h in a continuous mode.

[0050] In certain embodiments, the reactor may be a mill. In certain embodiments, the reactor may be an attritor mill, a rod mill, a jet mill, a ball mill, a hammer mill, a vibratory mill, a disperser mill, a pebble mill, a bead mill or a colloid mill. In certain embodiments, the reactor may be any reactor capable of contacting the ZVI media such that the contaminant-iron complex from the surface of the ZVI media is removed as a precipitate due to contact between the media in the reactor. To aid this contact, the zero valent iron media may comprise one or more additives in order to remove the contaminant-iron complex from the surface of the zero valent iron media. For example, the additives may be balls, such as stainless steel balls or zirconia balls, amongst other materials.

[0051] In certain embodiments, the zero valent iron media may comprise ZVI media of varying particle sizes. In certain embodiments, the zero valent iron media may comprise ZVI media of about 0.2 mm to about 2 mm particle size. In certain embodiments, the zero valent iron media may be balls, rods, pebbles, wool, iron pieces or a combination thereof. In certain embodiments, the zero valent iron media may be any geometry or shape that, following contact between the media, removes the contaminant-iron complex from the surface of the zero valent iron media as a precipitate. In certain embodiments, the zero valent iron media may further comprise silica as the additive, such as a silica sand or a washed silica sand. In certain embodiments, zero valent iron media and silica sand may be added to the reactor while performing the method. In certain embodiments, zero valent iron media and silica sand may be added to the reactor daily or every approximately 24 hours. In certain embodiments, zero valent iron media may be added one or more times while performing the method.

[0052] A surface of the zero valent iron comprises rust following addition of the wastewater to the reactor. In certain embodiments, the rust may comprise an iron oxide and / or an iron hydroxide. In various embodiments, the rust may comprise green rust. In certain embodiments, the surface of the zero valent iron may comprise rust following addition of the wastewater to the reactor, in which iron oxide and / or iron hydroxide is produced by the reaction of iron and oxygen in the presence of water. The dissolved contaminant adsorbs on the surface of the zero valent iron media as a contaminant-iron complex. In certain embodiments, a contaminant-iron complex is a complex between one or more dissolved contaminant and the ZVI. In certain embodiments, the contaminant-iron complex is on the surface of the ZVI media and the contaminant-iron complex comprises one or more dissolved contaminant in complex with the ZVI.

[0053] The method comprises removing the dissolved contaminant from the wastewater and forming a cleaned water. As used herein, the term “clean water” or “cleaned water” refers to a wastewater, wherein one or more dissolved contaminants has been removed. In certain embodiments, the one or more dissolved contaminants may be substantially absent in the clean water. In certain embodiments, the one or more dissolved contaminants may be at or below a level acceptable or required by a governing body or act, such as, for example, the Canadian Environmental Protection Act (CEPA) or the U.S Environmental Protection Agency (US EPA) in the cleaned water. In certain embodiments, the cleaned water may be safe for human consumption.

[0054] The method comprises contact between the zero valent iron media and / or between the zero valent iron media and the additive, thereby removing the contaminant-iron complex from the surface of the zero valent iron media as a precipitate. As used herein, the term “precipitate” refers to a substance separated from a solution, such as, for example, a solid formed from the solution. In certain embodiments, the collisions between the zero valent iron media may remove the contaminant-iron complex from the surface of the zero valent iron media as a precipitate, wherein contact removes the contaminant-iron complex from the surface of the zero valent iron media. The contact between the zero valent iron media that removes the contaminant-iron complex from the surface of the zero valent iron media as a precipitate regenerates a surface of the zero valent iron media capable of adsorbing one or more dissolved contaminants from the wastewater. In certain embodiments, the removal of the contaminant-iron complex from the surface of the zero valent iron media may regenerate the surface of the zero valent iron media to form rust and adsorb further dissolved contaminant from the wastewater. In certain embodiments,the regenerated surface of the zero valent iron media adsorbs the dissolved contaminant on the surface of the zero valent iron media as a contaminant-iron complex.

[0055] The method may further comprise, after the step of contacting, a step comprising removing the cleaned water from the reactor.

[0056] In certain embodiments, the cleaned water from the reactor may be treated with a flocculant. In certain embodiments, the flocculant may comprise Nalco 9907 flocculant or other high molecular weight cationic polymeric flocculants. In certain embodiments, after a step of flocculation, the wastewater may be clarified for separation of solids from liquids therein. In certain embodiments, clarified wastewater may be filtered using, for example, media filtration, to produce a cleaned water with substantially no dissolved contaminant, such as selenium, and / or no solids therein.

[0057] In certain embodiments, the method may be a batch process. In certain embodiments, a batch process or method, may comprise a process or method wherein once the process or method has completed, a new process or method is performed to generate a new batch. In certain embodiments, a batch process may provide a defined start point, a defined end point or both.

[0058] In certain embodiments, the method may be a continuous process. In certain embodiments, a continuous process or method, may comprise a process or method that runs substantially constantly with no or limited interruption, to produce the cleaned water. In certain embodiments, the continuous process or method may not have a defined start point, end point, or both.

[0059] The formation of the contaminant-iron complexes comprises a redox reaction between the contaminant and iron of the rust. In certain embodiments, the formation of the contaminant-iron complex may comprise a reaction between the dissolved contaminant and iron of the rust, in which the reaction transfers electrons from one species to another. In certain embodiments, the formation of the contaminant-iron complex may comprise one or both of the following reactions when the contaminant is selenium:2Fe + Na2SeO4+ 2HCI + 2H2O 2Fe(OH)3+ Se° + 2NaCI (Reaction 1)2Fe + Na2SeO3+ 3H2O 2Fe(OH)2+ Se° + 2NaOH (Reaction 2)

[0060] In certain embodiments, a rate of removal of the dissolved contaminant from the wastewater may be about 15 mg / L / h to about 35 mg / L / h. In certain embodiments, a rate of removal of the dissolved contaminant from the wastewater may be 15 mg / L / h, 15.5 mg / L / h, 16 mg / L / h, 16.5 mg / L / h, 17 mg / L / h, 17.5 mg / L / h, 18 mg / L / h, 18.5 mg / L / h, 19 mg / L / h, 19.5 mg / L / h, 20 mg / L / h, 20.5 mg / L / h, 21 mg / L / h, 21.5 mg / L / h, 22 mg / L / h, 22.5 mg / L / h, 23 mg / L / h, 23.5 mg / L / h,24 mg / L / h, 24.5 mg / L / h, 25 mg / L / h, 25.5 mg / L / h, 26 mg / L / h, 26.5 mg / L / h, 27 mg / L / h, 27.5 mg / L / h,28 mg / L / h, 28.5 mg / L / h, 29 mg / L / h, 29.5 mg / L / h, 30 mg / L / h, 30.5 mg / L / h, 31 mg / L / h, 31.5 mg / L / h,32 mg / L / h, 32.5 mg / L / h, 33 mg / L / h, 33.5 mg / L / h, 34 mg / L / h, 34.5 mg / L / h, or 35 mg / L / h. In certain embodiments, a rate of removal of the dissolved contaminant from the wastewater may be any rate that achieves a desired concentration of one or more dissolved contaminant in a cleaned water produced by the method. In certain embodiments, a rate of removal of the dissolved contaminant from the wastewater may be any rate that provides a concentration of one or more dissolved contaminant in a cleaned water produced by the method that achieves regulatory approval in the jurisdiction performing the method, such as for example, the Canadian Environmental Protection Act in Canada or the U.S Environmental Protection Agency in the United States of America.

[0061] In certain embodiments, the clean water has less than 20 pg / L of the dissolved contaminant. In certain embodiments, the clean water has less than 2 pg / L of the dissolved contaminant. In certain embodiments, the clean water has less than 20 mg / L, less than 19.5 mg / L, less than 19 mg / L, less than 18.5 mg / L, less than 18 mg / L, less than 17.5 mg / L, less than 17 mg / L, less than 16.5 mg / L, less than 16 mg / L, less than 15.5 mg / L, less than 15 mg / L, less than 14.5 mg / L, less than 14 mg / L, less than 13.5 mg / L, less than 13 mg / L, less than 12.5 mg / L, less than 12 mg / L, less than 11.5 mg / L, less than 11 mg / L, less than 10.5 mg / L, less than 10 mg / L, less than 9.5 mg / L, less than 9 mg / L, less than 8.5 mg / L, less than 8 mg / L, less than 7.5 mg / L, less than 7 mg / L, less than 6.5 mg / L, less than 6 mg / L, less than 5.5 mg / L, less than 5 mg / L, less than 4.5 mg / L, less than 4 mg / L, less than 3.5 mg / L, less than 3 mg / L, less than 2.5 mg / L, less than 2 mg / L, less than 1.5 mg / L, less than 1.4 mg / L, less than 1.3 mg / L, less than 1.2 mg / L, less than 1.1 mg / L, less than 1 mg / L, less than 0.9 mg / L, less than 0.8 mg / L, less than 0.7 mg / L, less than 0.6 mg / L, less than 0.5 mg / L, less than 0.4 mg / L, less than 0.3 mg / L, less than 0.2 mg / L, or less than 0.1 mg / L, of the dissolved contaminant. In certain embodiments, the clean water has a concentration of one or more dissolved contaminant that achieves local regulatory approval in the jurisdiction wherein the method is performed, such as, for example, the Canadian EnvironmentalProtection Act in Canada or the U.S Environmental Protection Agency in the United States of America.

[0062] In certain embodiments, a hydraulic retention time in the reactor may be adjusted to achieve a desired cleaned water or to achieve desired operating parameters, such as for example, a desired duration of the method or a desired quantity of wastewater processed by the method. As used herein, the phrase “hydraulic retention time” may refer to a time interval in which a substrate, such as a wastewater, is kept inside a reactor.

[0063] In certain embodiments, the dissolved contaminant may have a concentration in the wastewater at greater than about 0.1 mg / L, 0.2 mg / L, 0.3 mg / L, 0.4 mg / L or 0.5 mg / L. In certain embodiments, the dissolved contaminant in the wastewater may have a concentration of 1 mg / L to 100 mg / L. In certain embodiments, wherein the dissolved contaminant comprises a plurality of dissolved contaminants, each dissolved contaminant may independently have a concentration greater than about 0.1 mg / L, 0.2 mg / L, 0.3 mg / L, 0.4 mg / L or 0.5 mg / L in the wastewater. In certain embodiments, wherein the dissolved contaminant comprises a plurality of dissolved contaminants, each dissolved contaminant may independently have a concentration of 1 mg / L to 100 mg / L. In certain embodiments, the dissolved contaminant, or each of the plurality of dissolved contaminants, may have a concentration of 0.1 mg / L, 0.5 mg / L, 1 mg / L, 1.5 mg / L, 2 mg / L, 2.5 mg / L, 3 mg / L, 3.5 mg / L, 4 mg / L, 4.5 mg / L, 5 mg / L, 5.5 mg / L, 6 mg / L, 6.5 mg / L, 7 mg / L,7.5 mg / L, 8 mg / L, 8.5 mg / L, 9 mg / L, 9.5 mg / L, 10 mg / L, 10.5 mg / L, 11 mg / L, 11.5 mg / L, 12 mg / L,12.5 mg / L, 13 mg / L, 13.5 mg / L, 14 mg / L, 14.5 mg / L, 15 mg / L, 15.5 mg / L, 16 mg / L, 16.5 mg / L, 17 mg / L, 17.5 mg / L, 18 mg / L, 18.5 mg / L, 19 mg / L, 19.5 mg / L, 20 mg / L, 20.5 mg / L, 21 mg / L, 21.5 mg / L, 22 mg / L, 22.5 mg / L, 23 mg / L, 23.5 mg / L, 24 mg / L, 24.5 mg / L, 25 mg / L, 25.5 mg / L, 26 mg / L,26.5 mg / L, 27 mg / L, 27.5 mg / L, 28 mg / L, 28.5 mg / L, 29 mg / L, 29.5 mg / L, 30 mg / L, 30.5 mg / L, 31 mg / L, 31.5 mg / L, 32 mg / L, 32.5 mg / L, 33 mg / L, 33.5 mg / L, 34 mg / L, 34.5 mg / L, 35 mg / L, 35.5 mg / L, 36 mg / L, 36.5 mg / L, 37 mg / L, 37.5 mg / L, 38 mg / L, 38.5 mg / L, 39 mg / L, 39.5 mg / L, 40 mg / L,40.5 mg / L, 41 mg / L, 41.5 mg / L, 42 mg / L, 42.5 mg / L, 43 mg / L, 43.5 mg / L, 44 mg / L, 44.5 mg / L, 45 mg / L, 45.5 mg / L, 46 mg / L, 46.5 mg / L, 47 mg / L, 47.5 mg / L, 48 mg / L, 48.5 mg / L, 49 mg / L, 49.5 mg / L, 50 mg / L, 50.5 mg / L, 51 mg / L, 51.5 mg / L, 52 mg / L, 52.5 mg / L, 53 mg / L, 53.5 mg / L, 54 mg / L,54.5 mg / L, 55 mg / L, 55.5 mg / L, 56 mg / L, 56.5 mg / L, 57 mg / L, 57.5 mg / L, 58 mg / L, 58.5 mg / L, 59 mg / L, 59.5 mg / L, 60 mg / L, 60.5 mg / L, 61 mg / L, 61.5 mg / L, 62 mg / L, 62.5 mg / L, 63 mg / L, 63.5 mg / L, 64 mg / L, 64.5 mg / L, 65 mg / L, 65.5 mg / L, 66 mg / L, 66.5 mg / L, 67 mg / L, 67.5 mg / L, 68 mg / L,68.5 mg / L, 69 mg / L, 69.5 mg / L, 70 mg / L, 70.5 mg / L, 71 mg / L, 71.5 mg / L, 72 mg / L, 72.5 mg / L, 73 mg / L, 73.5 mg / L, 74 mg / L, 74.5 mg / L, 75 mg / L, 75.5 mg / L, 76 mg / L, 76.5 mg / L, 77 mg / L, 77.5mg / L, 78 mg / L, 78.5 mg / L, 79 mg / L, 79.5 mg / L, 80 mg / L, 80.5 mg / L, 81 mg / L, 81 .5 mg / L, 82 mg / L,82.5 mg / L, 83 mg / L, 83.5 mg / L, 84 mg / L, 84.5 mg / L, 85 mg / L, 85.5 mg / L, 86 mg / L, 86.5 mg / L, 87 mg / L, 87.5 mg / L, 88 mg / L, 88.5 mg / L, 89 mg / L, 89.5 mg / L, 90 mg / L, 90.5 mg / L, 91 mg / L, 91.5 mg / L, 92 mg / L, 92.5 mg / L, 93 mg / L, 93.5 mg / L, 94 mg / L, 94.5 mg / L, 95 mg / L, 95.5 mg / L, 96 mg / L,96.5 mg / L, 97 mg / L, 97.5 mg / L, 98 mg / L, 98.5 mg / L, 99 mg / L, 99.5 mg / L, or 100 mg / L.

[0064] In certain embodiments, the wastewater may comprise an industrial wastewater, a surface water or a ground water. As used herein, an “industrial wastewater” may refer to any water produced after the use of a substantially clean water, such as fresh water, drinking water or purified water, in an industrial setting or facility. An industrial setting, as would be known to the person of skill, in light of the teachings herein, may refer to a combination of machines, apparatuses, appliances, equipment, instruments and / or materials which together make up a stationary unit for producing goods or providing services. In certain embodiments, the industrial facility may produce the wastewater by processes or methods known to the skilled person, such as, for example, wet scrubbing or any process or method known to the skilled person to create a wastewater comprising a dissolved contaminant. As used herein, a “scrubbing solution” may be a solution produced by wet scrubbing. In certain embodiments, a scrubbing solution may comprise one or more dissolved metal. In certain embodiments, the industrial facility may comprise a metalprocessing facility. In certain embodiments, the industrial facility may comprise a gold processing plant or facility. In certain embodiments, the wastewater may comprise any wastewater wherein it is desirous to remove one or more dissolved metal therefrom.

[0065] In certain embodiments, the pH of the wastewater may have a pH from about 4.0 to about 10.0. In certain embodiments, the pH of the wastewater may be 4, 4.1 , 4.2, 4.3, 4.4, 4.5,4.6, 4.7, 4.8, 4.9, 5, 5.1 , 5.2, 5.3, 5.4, 5.5, 5.6, 5.7, 5.8, 5.9, 6, 6.1 , 6.2, 6.3, 6.4, 6.5, 6.6, 6.7, 6.8,6.9, 7, 7.1 , 7.2, 7.3, 7.4, 7.5, 7.6, 7.7, 7.8, 7.9, 8, 8.1 , 8.2, 8.3, 8.4, 8.5, 8.6, 8.7, 8.8, 8.9, 9, 9.1 ,9.2, 9.3, 9.4, 9.5, 9.6, 9.7, 9.8, 9.9, or 10. In certain embodiments, the pH of the wastewater may be adjusted to obtain a desired pH. In certain embodiments, the pH of the wastewater may be adjusted with HCI. In certain embodiments, the pH of the wastewater may be adjusted before the step of providing the wastewater to the reactor. In certain embodiments, the pH of the wastewater provided to the reactor may be 4, 4.1 , 4.2, 4.3, 4.4, 4.5, 4.6, 4.7, 4.8, 4.9, 5, 5.1 , 5.2, 5.3, 5.4, 5.5,5.6, 5.7, 5.8, 5.9, 6, 6.1 , 6.2, 6.3, 6.4, 6.5, 6.6, 6.7, 6.8, 6.9, 7, 7.1 , 7.2, 7.3, 7.4, 7.5, 7.6, 7.7, 7.8,7.9, 8, 8.1 , 8.2, 8.3, 8.4, 8.5, 8.6, 8.7, 8.8, 8.9, 9, 9.1 , 9.2, 9.3, 9.4, 9.5, 9.6, 9.7, 9.8, 9.9, or 10. In certain embodiments, the pH of the wastewater may be adjusted in the reactor to maintain a desired pH. In certain embodiments, the pH of the wastewater in the reactor may be maintainedbetween about 4 and about 10. Furthermore, concentrations of additional anionic species, such as nitrate, which may be in the wastewater in addition to the contaminant, may require adjustment before the step of providing the wastewater to the reactor.ExamplesWastewater characterization

[0066] T able 1 presents an exemplary composition of a scrubber solution sample received for performing a method as disclosed herein. Table 1 also includes the wastewater chemistry and the scrubber solution spiked with sodium selenate to a concentration of 100 mg / L and the composition of an exemplary solution following treatment according to a batch process as described herein.Table 1 Scrubber solution chemistry and wastewater chemistry used for preliminary assessment.

[0067] The scrubber solution was primarily composed of sodium, chloride, and carbonate / bicarbonate alkalinity (HCO37CC>32')- In addition, it contained heavy metals and other oxyanions like molybdenum and antimony. An analysis on selenium speciation conducted on samples of the scrubber solution provided that selenium is predominantly present in the form of selenate.

[0068] The high alkalinity in the scrubber solution necessitated the implementation of a pre-treatment step, involving the removal of alkalinity from the scrubber solution through acidification with HCI before proceeding with the subsequent treatment for removal of dissolved contaminants, such as selenium and boron.

[0069] The scrubber solution sample already contained the maximum expected concentrations of selenium and boron at approximately 20 mg / L. However, the scrubber solution was spiked with sodium selenate to a concentration of 100 mg / L for testing.Reactor Setup

[0070] The reactor used for both batch and continuous demonstrations was constructed from stainless steel and had a volume of 47 L. The reactor was filled with a mix of ZVI (0.2 - 3 mm particle size) and washed silica sand. In the continuous demonstration, the system started by operating in a batch mode for 3 hours. Subsequently, the reactor was continuously fed at a rate of 40 mL / min, which resulted in a hydraulic retention time (HRT) of 3 hours. To maintain consistent testing conditions in continuous testing, approximately 100 grams of a mixture containing ZVI was added to the reactor daily. The reactor was temporarily shut down overnight and then restarted in the morning for continuous demonstration tests, employing a 3-hour hydraulic retention time (HRT).

[0071] As shown in reactions 2 and 3, the removal of selenium from either selenate or selenite forms consumes acidity.2Fe + Na2SeO4+ 2HCI + 2H2O 2Fe(OH)3+ Se° + 2NaCI (Reaction 1)2Fe + Na2SeO3+ 3H2O 2Fe(OH)2+ Se° + 2NaOH (Reaction 2)

[0072] Therefore, the addition of acid may be used for some embodiments to maintain the solution's pH during treatment. A pH range of 8-9 was maintained during testing using HCI.Batch Tests1. Selenium removal

[0073] Figure 1 displays the results of an exemplary batch test conducted using a scrubber solution containing 100 mg / mL selenium. As illustrated, the selenium concentration decreased from 100 mg / L to 0.1 mg / L after 3 hours of treatment, and further reduced to <0.002 mg / L after 4 hours of treatment in the reactor, using methods as disclosed herein.

[0074] For some applications, the treatment objectives may also require the removal of alkalinity from the water. This step may be performed upstream of the selenium removal process. Alkalinity removal was achieved by adding HCI to the solution, adjusting the pH to 4.5, and allowing the alkalinity to volatilize as CO2gas. As a result of this treatment, the chloride concentration in the solution increased from 14,800 mg / L to 23,500 mg / L prior to the batch treatment for selenium removal, as shown in Table 1.

[0075] Figures 2A and Figure 2B present the outcomes of batch tests conducted using scrubber solution spiked with sodium selenate to achieve a selenium concentration of 100 mg / L. Figure 2B provides a logarithmic scale to depict the lowest achieved concentrations during batch treatment. For batches 1 and 2, adjustments were made to the reactor conditions to expedite selenium removal by adjusting the amount of sand in the zero valent iron media. These modifications led to almost complete selenium removal in both batches 1 and 2, with concentrations dropping below the inductively coupled plasma mass spectrometry (ICP-MS) detection limits. Due to differing dilutions, the detection limit for batch 1 was set at 0.025 mg / L, while batch 2 samples had a detection limit of 0.002 mg / L.Continuous Demonstration1. Selenium removal

[0076] Figure 3 presents the results of continuous demonstration testing over 5 consecutive days, using an 3-hour HRT. The selenium concentration consistently decreased from 100 mg / L to about 0.10 mg / L, confirming the ability of the method to meet a treatment target.2. Boron removal

[0077] Figure 4 displays the results of boron removal throughout the 5 days of continuous demonstration testing with an 3-hour HRT. At 3 hours of HRT treatment, the system achieved a boron concentration of approximately 12.8 mg / L in the treated solution, representing around a 40% removal rate.3. Removal of other elements

[0078] Table 2 shows the chemical composition of the treated scrubber solution in comparison to the untreated scrubber solution of an exemplary embodiment of the methods as disclosed herein. The results highlight that, in addition to removing selenium and boron, the treatment process resulted in near-complete removal of other heavy metals and oxyanions in the scrubber solution, contributing to overall effluent quality improvement.Table 2 Performance of a continuous method as disclosed herein for the removal of dissolved metals.Treatment Residue Stability

[0079] Approximately 0.1 m3of sludge at 15 wt.% solids density is expected to be generated for treatment of every cubic meter of the scrubber solution with 100 mg / L selenium, which is predominantly comprised of iron and contains contaminants removed from the scrubber solution. Table 3 shows the results of Toxicity Characteristic Leaching Procedure (TCLP) analysis using a sample of solid residue cake from filtration, washed with tap water. The solids obtained from the method showed no release of their contents beyond the specified TCLP limits, indicating they are suitable for disposal as non-hazardous waste.Table 3 TCLP results of treatment by-product.Design parameters

[0080] Table 4 provides exemplary design parameters and process consumables identified through testing.Table 4 Design parameters and process consumables.Reagents and Analytical Methods

[0081] Table 5 provides an overview of the reagents used in the testing process.Table 5 Reagents used for testing.

[0082] Samples comprising dissolved metals were directly drawn from the reactor, filtered using a 0.45-micrometer filter, and preserved in nitric acid, pre-filled in sample containers received. Owing to the small solution volumes used in testing, samples of 5 mL were collected and subsequently diluted 5-10 times using de-ionized water.

[0083] Table 6 outlines exemplary analytical methods applied throughout the program, ensuring the accurate assessment of various parameters.Table 6 Analytical methods used during test program.Treatment of Mine Impacted Water By Continuous Method

[0084] T able 7 present the water chemistry of mine impacted water that was then treated in a reactor using a hydraulic retention time (HRT) of 10 minutes. The results are also shown in Figure 5 as a function of time. The water was saturated with respect to gypsum. The treatment flow rate corresponding to the 10-minute HRT was 700 mL / min, or 42 L / h. The system was operated for 8 hours per day over a period of three days of continuous demonstration, with shutdowns overnight and restarts the following morning. As indicated in Figure 5, the selenium concentration was consistently reduced from 53 pg / L to 6 pg / L in the treated water.Table 7 Composition of mine impacted water prior to treatmentTreatment of Retentate from Reverse Osmosis Treatment of Mine Impacted Water By Batch Method

[0085] Table 8 presents the retentate chemistry from reverse osmosis (RO) treatment of mine impacted water. Samples of the solution were synthetically prepared in the lab and used for batch testing. The RO retentate from treatment of this mine-impacted water was also saturated with respect to gypsum and contained 250 mg / L of nitrate. As shown in Figure 6, the selenium concentration in the RO retentate was reduced from 3.17 mg / L to 0.261 mg / L after 80 minutes of treatment, and further reduced to 0.1 mg / L after only 100 minutes of treatment in the reactor.Table 8 Composition of retentate from RO treatment of mine impacted water prior to treatment

[0086] In the present disclosure, all terms referred to in singular form are meant to encompass plural forms of the same. Likewise, all terms referred to in plural form are meant to encompass singular forms of the same. In addition, the use of “or” means “and / or” unless otherwise stated. The term “plurality” as used herein means more than one, for example, two or more, three or more, four or more, and the like. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure pertains.

[0087] It should be understood that the methods are described in terms of "comprising," "containing," or "including" various components or steps, the methods can also "consist essentially of” or "consist of” the various components and steps. Moreover, the indefinite articles "a" or "an”, as used in the claims, are defined herein to mean one or more than one of the element that it introduces.

[0088] For the sake of brevity, only certain ranges are explicitly disclosed herein. However, ranges from any lower limit may be combined with any upper limit to recite a range not explicitly recited, as well as, ranges from any lower limit may be combined with any other lower limit to recite a range not explicitly recited, in the same way, ranges from any upper limit may be combined with any other upper limit to recite a range not explicitly recited. Additionally, whenever a numerical range with a lower limit and an upper limit is disclosed, any number and any included range falling within the range are specifically disclosed. In particular, every range of values (of the form, "from about a to about b," or, equivalently, "from approximately a to b," or, equivalently, "from approximately a-b", or equivalent, “from a-b”) disclosed herein is to be understood to set forth every number and range encompassed within the broader range of values even if not explicitly recited. Thus, every point or individual value may serve as its own lower or upper limit combined with any other point or individual value or any other lower or upper limit, to recite a range not explicitly recited.

[0089] Therefore, the present disclosure is well adapted to attain the ends and advantages mentioned as well as those that are inherent therein. The particular embodiments disclosed above are illustrative only, as the present disclosure may be modified and practiced in different but equivalent manners apparent to those skilled in the art having the benefit of the teachings herein. Although individual embodiments are discussed, the disclosure covers all combinations of all those embodiments. Furthermore, no limitations are intended to the details of construction or design herein shown, other than as described in the claims below. Also, the terms in the claims have their plain, ordinary meaning unless otherwise explicitly and clearly defined by the patentee. It is therefore evident that the particular illustrative embodiments disclosed above may be altered or modified and all such variations are considered within the scope and spirit of the present disclosure. If there is any conflict in the usages of a word or term in this specification and one or more patent(s) or other documents that may be incorporated herein by reference, the definitions that are consistent with this specification should be adopted.

[0090] Many obvious variations of the embodiments set out herein will suggest themselves to those skilled in the art in light of the present disclosure. Such obvious variations are within the full intended scope of the appended claims.

Claims

CLAIMSWhat is claimed is:

1. A method for removing a dissolved contaminant from wastewater, the method comprising:(a) providing the wastewater to a reactor, wherein the reactor contains a zero valent iron media, a surface of the zero valent iron comprising rust following addition of the wastewater to the reactor; and(b) contacting the wastewater and the zero valent iron media to adsorb the dissolved contaminant on the surface of the zero valent iron media as a contaminant-iron complex, thereby removing the dissolved contaminant from the wastewater and forming cleaned water, wherein contact between the zero valent iron media removes the contaminant-iron complex from the surface of the zero valent iron media as a precipitate.

2. The method of claim 1 , further comprising (c) removing the cleaned water from the reactor.

3. The method of claim 1 or 2, wherein the dissolved contaminant comprises antimony, arsenic, boron, cadmium, chromium, copper, lead, molybdenum, nickel, selenium, silver, zinc or any combination thereof.

4. The method of claim 1 , 2 or 3, wherein the dissolved contaminant comprises selenate (SeCU2') and / or selenite (SeOs2-)-5. The method of any one of claims 1 to 4, wherein removal of the contaminant-iron complex from the surface of the zero valent iron media regenerates the surface of the zero valent iron media to form rust and adsorb further dissolved contaminant from the wastewater.

6. The method of any one of claims 1 to 5, wherein the rust is green rust.

7. The method of any one of claims 1 to 6, wherein the method is a batch process.

8. The method of any one of claims 1 to 6, wherein the method is a continuous process.

9. The method of any one of claims 1 to 8, wherein formation of the contaminant-iron complex comprises a redox reaction between the contaminant and iron of the rust.

10. The method of claim 9, wherein adsorption and the redox reaction occur in situ in the reactor.

11. The method of any one of claims 1 to 10, wherein the zero valent iron media comprises balls, rods, pebbles, wool, iron pieces or a combination thereof.

12. The method of any one of claims 1 to 11, wherein the zero valent iron media comprises an additive.

13. The method of claim 12, wherein the additive is sand.

14. The method of any one of claims 1 to 13, wherein the method does not comprise a filtration step prior to step (a).

15. The method of any one of claims 1 to 14, further comprising adjusting a pH of the wastewater prior to step (a).

16. The method of any one of claims 1 to 15, wherein a rate of removal of the dissolved contaminant from the wastewater is about 15 mg / L / h to about 35 mg / L / h.

17. The method of any one of claims 1 to 16, wherein a concentration of the contaminant in the clean water is less than about 1 mg / L.

18. The method of any one of claims 1 to 16, wherein a concentration of the contaminant in the clean water is less than 20 pg / L.

19. The method of any one of claims 1 to 18, wherein a concentration of the dissolved contaminant in the wastewater is greater than about 0.1 mg / L, about 0.2 mg / L, about 0.3 mg / L, about 0.4mg / L or about 0.5 mg / L.

20. The method of any one of claims 1 to 18, wherein a concentration of the dissolved contaminant in the wastewater is about 1 mg / L to about 100 mg / L.

21. The method of any one of claims 1 to 20, wherein the wastewater comprises an industrial wastewater, a surface water, or a ground water.

Images