The present invention generally relates to filtration systems. More specifically, the present invention generally relates to a chemical-aided filtration system for, and method of, removing per-and polyfluorinated alkyl substances from a contaminated aqueous stream.
The present invention also generally relates to sustainable water management for aqueous streams, water-reserves, and aquifers. These “waters” may be associated with industrial or consumer-good manufacturing processes, or the waters may be independent from industrial or consumer manufacturing processes (i.e., the waters may be natural but contaminated water-reservoirs or aquifers, or may be contaminated municipal or agricultural water bodies or streams, for example), all together referred to herein as “aqueous streams”. The sustainable water management realized by the present invention also may encompass open water treatments and treatment systems for, but not limited to, lakes, reservoirs, rivers, ponds, and streams.
The present invention also generally relates to a system for and method of producing or reducing the inputs, especially harsh inputs, necessary for aqueous stream processing. These inputs may be (1) energy, (2) fresh water, or (3) the active ingredients necessary for adequate processing, for example. The present invention also generally relates to reducing the non-useful, or potentially toxic, outputs from the aqueous stream processing. These outputs may be residues laden with unrecovered or unrecycled per-and polyfluorinated alkyl substances that are usually too difficult to capture.
Per-and polyfluorinated alkyl substance (PFAS) contaminated fluid streams primarily are generated from two main sources: firefighting foam and industrial discharges. For example, for decades, the United States (U.S.) Department of Defense (DoD) contracted for the Military to use firefighting foam containing PFASs to fight fuel-fires in training exercises at bases around the country. U.S. commercial airports also used PFAS-containing foam or aqueous-film forming foam (AFFF). AFFF is intended to be directly discharged into the environment, where it is used to fight fires, such as at an airfield training exercise. PFASs also are found in countless consumer products like non-stick pans (e.g., pans with TEFLON-like coatings or polytetrafluoroethylene, PTFE or PTFT), food packing, waterproof liners and fabrics, textile coatings and sprays for water, grease, and stain resistance or repellence, in personal care products like waterproof mascaras, eyeliners, and sunscreen, in shampoos and shaving creams, and in the associated industrial processes for the production of these products.
Consequently, PFASs represent an interesting, growing, increasingly diverse inventory of chemicals for the general public, scientific researchers, and regulatory agencies world-wide. Precise knowledge of the presence, concentration, interactions, and effects of all PFASs in a given contaminated unit is difficult if not impossible due to a lack of consensus definitions in the field and due to the miniscule scales at which PFAS exist. Data-gathering, testing, and environmental monitoring exercises have led to the publication and sharing of various lists of PFASs, some exceeding several thousand substances in length. For example, the U.S. Environmental Protection Agency (EPA) National Center for Computational Toxicology has curated a list of PFASs based on environmental occurrence (through literature reports and analytical detection, for example,) and manufacturing process data, as well as lists of PFAS chemicals procured for testing within EPA research programs. The consolidated list contains about 6,330 PFAS Chemical Abstracts Services (CAS) named substances, with about 5,264 represented with a defined chemical structure. There is no precisely clear definition of what constitutes a PFAS substance, given the inclusion of partially fluorinated substances, polymers, and ill-defined reaction products; hence, the following serves as a non-limiting representative grouping of substances spanning and bounded by the below representative lists, defining a practical boundary for the PFAS chemical space at the time of this disclosure:
https://comptox.epa.gov/dashboard/chemical_lists/EPAPFASRL is a manually curated cross-agency research list of mainly straight-chain and branched PFASs compiled from various internal, literature, and public sources by EPA researchers and program office representatives (note that this list includes a number of parent, salt and anionic forms of PFAS, the latter being the form detected by mass spectroscopic methods), and that these different forms are assigned unique DTXSIDs, with a unique structure, CAS (if available) and name, but will collapse to a single form in a structural representation observed using high resolution mass spectrometry (HRMS) (MS-ready structure representations) or in a structure representation observed using quantitative-structure-activity-relationship (or QSAR-ready);
https://comptox.epa.gov/dashboard/chemical_lists/EPAPFASINV is a PFAS list of the EPA's ToxCast chemical inventory, and consists of chemicals successfully procured from commercial suppliers (with a small number provided by National Toxicology Program partners) and deemed suitable for testing (i.e., solubilized in DMSO above 5 millimolar and not gaseous or highly reactive), with all or a portion of this inventory being made available to EPA researchers and collaborators to be analyzed and tested in various high-throughput screening (HTS) and high-throughput toxicity (HTT) assays;
https://comptox.epa.gov/dashboard/chemical_lists/EPAPFAS75S1 list is a PFAS list corresponding to seventy-four (74) unique substances (DTXSID3037709, Potassium perfluorohexanesulfonate duplicated in set, procured from two different suppliers) selected based on a prioritization scheme that considered EPA Agency priorities, exposure/occurrence considerations, availability of animal or in vitro toxicity data, and ability to procure in non-gaseous form and solubilize samples in dimethyl sulfoxide;
https://comptox.epa.gov/dashboard/chemical_lists/EPAPFASINSOL is an expanded PFAS list of the EPA's ToxCast chemical inventory, and consists of chemicals that are determined to be insoluble in DMSO above about 5 mM, wherein said chemicals were procured from commercial suppliers (with a small number provided by National Toxicology Program partners) and were deemed unsuitable for testing due to limited DMSO solubility;
https://comptox.epa.gov/dashboard/chemical_lists/PFASOECD is a new comprehensive global database list of PFASs compiled from the Organization for Economic Co-operation and Development (OECD) listing more than four-thousand seven-hundred (4700) new PFASs, including several new groups of PFASs that fulfill the common definition of PFASs (i.e., they contain at least one perfluoroalkyl moiety) but have not yet been commonly regarded as PFASs;
https://comptox.epa.gov/dashboard/chemical_lists/PFASKEMI is a PFAS list of the KEMI Swedish Chemicals Agency Report 7/15 (provided by Stellan Fischer), and consists of highly fluorinated substances and alternatives (2015);
https://comptox.epa.gov/dashboard/chemical_lists/PFASTRIER is an international community public list of PFASs compiled by a community effort including Xenia Trier, David Lunderberg, Graham Peaslee, Zhanyun Wang and colleagues, EPA's Dashboard team, the NORMAN Suspect List Exchange in 2015;
https://comptox.epa.gov/dashboard/chemical_lists/EPAPFASCAT is a list of registered DSSTox “category substances” representing PFAS categories created using ChemAxon's Markush structure-based query representations, wherein the markush categories can be broad and inclusive of more specific categories or can represent a unique category not overlapping with other registered categories, and wherein for each PFAS category registered with a unique DTXSID considered a generalized substance or “parent ID” that can be associated with one or many “child IDs” (i.e. many parent-child mappings) within the full DSSTox database; and
https://comptox.epa.gov/dashboard/chemical_lists/PFASSTRUCT is a list of all PFAS structures containing a defined substructure of RCF2CFR′R″ (R cannot be H).
Generally, PFASs, also known as per-and polyfluoroalkyl substances, are synthetic organofluorine or perfluorinated chemical compounds that have multiple fluorine atoms attached to an alkyl chain. As such, the average member of the group contains at least one perfluoroalkyl moiety, —CnF2n—. A subgroup of PFASs—the fluorosurfactants or fluorinated surfactants-are a group of surfactants having a fluorinated “tail” and a hydrophilic “head”. The subgroup includes the perfluorosulfonic acids such as the perfluorooctane sulfonate (PFOS) and the perfluorocarboxylic acids such as the perfluorooctanoic acid (PFOA). PFOS and PFOA were the most highly used and most highly distributed PFASs in the U.S until recently.
A number of environmental studies have been conducted or are being conducted into the effects of PFAS contaminated fluid streams. The concluded studies tend to indicate that about 95% of the U.S. population has PFASs in their body, with further study recommended. The concluded studies also indicate that PFASs have contaminated tap water for at least about 16 million people in about 33 states and Puerto Rico, and has contaminated groundwater in at least about 38 states.
There are no known studies to show that swimming or bathing in water containing PFOS or PFOA, for example, can be harmful to human health. Further, PFOS and PFOA are not easily absorbed through the skin, and accidentally swallowing contaminated water while bathing or swimming will not result in a significant exposure. However, due to their persistence, possible toxicity, risk of bio-accumulation, and widespread occurrence in the bodies of the general population and wildlife at large, fluorosurfactant PFASs such as PFOS, PFOA, and perfluorononanoic acid (PFNA) already have caught the attention of regulatory agencies across the globe.
There are two dominant attributes of PFASs that make the class of chemicals especially concerning: 1) PFASs are characterized by a carbon-fluorine (C—F) backbone; and 2) the carbon fluorine bond is one of the most stable bonds in organic chemistry, giving PFASs a relatively long environmental half-life. PFASs do not rapidly break down in water or soil and readily are carried over great distances by wind and water currents. Humans are readily exposed to PFASs in the air, in indoor dust, food, and water; and in some consumer products. The main source of human exposure to PFASs usually is from eating food and drinking water that has been contaminated.
As a result of this concern, the production of certain PFASs are regulated by various governments across the world, or have been unilaterally phased-out by international manufacturers like 3M, DuPont, Daikin, and Miteni in the US, Japan, and Europe. For example, 3M already has replaced PFOS and PFOA with short-chain PFASs like perfluorohexanoic acid (PFHxA), perfluorobutanesulfonic acid, and perfluorobutane sulfonate (PFBS). Although short-chain fluorosurfactant PFASs may be less prone to bio-accumulation, concerns remain that short-chain PFASs may be harmful to both humans and the environment at large.
Several technologies currently are available for remediating PFASs in aqueous streams. These technologies are applicable to drinking-water supplies, groundwater, industrial wastewater, surface water, and other miscellaneous applications (such as landfill leachate processing). Influent concentrations of PFASs may vary by orders of magnitude over time for specific media or applications, and these variable influent concentrations, along with other general water quality parameters (e.g., pH) may influence the performance and operating costs for each specific treatment technology.
One technology commonly used for the removal of various PFASs from an aqueous stream is activated carbon adsorption. Activated carbon treatment or adsorption is used to adsorb natural organic compounds, taste and odor compounds, and synthetic organic chemicals in drinking-water supplies, for example. PFAS adsorption occurs at the interface between the liquid and solid phase. Activated carbon is an effective solid adsorbent, as it is a highly porous material and provides a large surface area upon which contaminants may be adhered. Activated carbon usually is made from organic materials with high carbon contents such as wood, lignite, and coal, and often is used in a granular form called granular activated carbon (GAC), powdered activated carbon, or biochar.
A person having ordinary skill in the art understands that the cost of activated carbon treatment, including the cost of handling the spent activated carbon waste, is high due to the high amounts of activated carbon needed for filtration and the high amounts of waste generated from the spent carbon after exhaustion and disposal of the hazardous waste. The footprint per flow of the average activated carbon treatment facility also is high due to the carbon filtration needing a contact time of about five to seven minutes, which result in large size unit or volume of vessels for required flow. For example, a 100 gallon per minute system needs about a 500 gallon to a 700 gallon filtration vessel capacity.
Another technology commonly used for the removal of various PFASs from an aqueous stream is ion exchange or resin exchange. Ion exchange resins are made up of highly porous, polymeric material(s) that is/are acid, base, or water insoluble. The tiny beads that make up the resin often times are made up of hydrocarbons. There are two broad categories of ion exchange resins: cationic and anionic. The negatively charged cationic exchange resins (CER) are effective at removing positively-charged contaminants, and the positively charged anion exchange resins (AER) are effective at removing negatively-charged contaminants, like PFASs. Ion exchange resins are characterized as tiny and powerful magnets that attract and hold the target contaminant material from passing with the aqueous stream. In practice, the negatively charged PFAS ions are attracted to the positively charged anion resins. AER has shown to have a high capacity for many PFAS; however, it is typically more expensive than GAC at an equally large footprint per flow. Once exhausted, the ion exchange beds typically are regenerated with caustic or alkaline liquid solutions, which generate alkaline PFAS contaminated waste streams that must be processed at high risk and cost.
Another technology commonly used for the removal of various PFASs from an aqueous stream is membrane filtration. High-pressure membranes, such as nanofiltration membranes or reverse osmosis membranes, for example, are effective at removing PFASs. Reverse osmosis membranes are more selective than nanofiltration membranes; therefore, membrane filtration technology depends on membrane permeability characteristics and selectivity. A standard difference between nanofiltration and reverse osmosis technology is that a nanofiltration membrane will reject hardness to a high degree (i.e., will soften by removing polyvalent cations), but will pass sodium chloride, for example. A reverse osmosis membrane, on the other hand, will reject all salts to a high degree. Consequently, nanofiltration membranes may remove particles and particulates while retaining minerals, which reverse osmosis membranes would likely capture.
Research shows that high-pressure membranes typically are more than about 90% effective at removing a wide range of PFASs, including short-chain PFASs. Despite the high-pressure membrane's effectiveness at removing PFASs, approximately 20% of the feedwater-the water coming into the high-pressure membrane system-is retained as a concentrated waste that must be handled, processed, and ultimately disposed of. A person having ordinary skill in the art understands that a concentrated waste stream at 20 percent of the feedwater is difficult and costly to handle especially when the concentrated waste is loaded in PFASs. For example, the associated operating costs are an order of magnitude greater than that of GAC or ion exchange systems.
It is, therefore, desirable to overcome the deficiencies of, and provide for improvements to, the state of the prior art. Thus, there is a need in the art for a system and method for removing PFASs from a contaminated aqueous stream that provides a more efficient and effective system for solving the problems in the art and improving the state of the art.
Accordingly, there is now provided within this disclosure a system and method of use for overcoming the aforementioned difficulties and longstanding problems inherent in the art. A better understanding of the principles and details of the present invention will be evident from the following detailed description.
Exemplary embodiments are directed to a system for removing per-and polyfluorinated alkyl substances from a contaminated aqueous stream. In one exemplary embodiment, the system comprises an agitation and flocculation system and a particulate filter capture system.
Optionally, the system may comprise a feedback system configured to consider the concentration of at least one of a group consisting of perfluoroalkylcarboxylic acids, perfluoroalkyl sulfonates, perfluoroalkyl-sulfonic acids, and perfluorosulfonamidoacetic acids in the aqueous stream, and the concentration of at least one of the group consisting of perfluoroalkylcarboxylic acids, perfluoroalkyl sulfonates, perfluoroalkyl-sulfonic acids, and perfluorosulfonamidoacetic acids in the decontaminated aqueous stream exiting the system-to make efficient use of the anhydrite quantity introduced into and used by the system. As another option, the system also may comprise a water softening system for softening the decontaminated aqueous stream exiting the system.
The agitation and flocculation system is configured to receive an aqueous stream contaminated with contaminants, and configured to receive an anhydrite quantity as a primary flocculant. In certain exemplary embodiments, the anhydrite quantity comprises solid anhydrite particles or granules—either pre-hydrated or dry or a combination thereof. In other exemplary embodiments, the anhydrite quantity is introduced into the aqueous stream via a liquid carrier.
The agitation and flocculation system comprises a means for agitating the aqueous stream and a means for mixing the aqueous stream with the anhydrite, such that effectively positively charged calcium ions hydrate from the anhydrite and interact with the negatively charged contaminants to form a precipitate of calcium sulfate hydrate +contaminant complexes in the aqueous stream. The agitation and flocculation system also is configured to cease agitating and mixing the aqueous stream such that a portion of the calcium sulfate hydrate+contaminant complexes settle or are redirected under the influence of gravity, and such that a portion of the calcium sulfate hydrate+contaminant complexes resist the influence of gravity and remain suspended in a partially decontaminated aqueous stream. In certain exemplary embodiments, the agitation and flocculation system comprises at least one from a group consisting of stirring blades, baffles, vortex generators, liquid flow devices, and gas or air pumps for bubbles or microbubble generation, to increase the kinetics between the aqueous stream and the anhydrite quantity.
In another exemplary embodiment, the system comprises a fixed-bed type cross-flow system and a particulate filter capture system. The fixed-bed type cross-flow system may be configured as a fixed-bed type cross-flow filter system comprising a cartridge-type filter media comprising the anhydrite quantity. The fixed-bed type cross-flow system also may be configured and structured to have the agitation and flocculation system downstream of the fixed-bed type cross-flow system and upstream of the particulate filter capture system.
To go along with the illustrative and exemplary systems, exemplary embodiments of the present invention are directed to a method of removing per-and polyfluorinated alkyl substances from a contaminated aqueous stream. In one exemplary embodiment, the method comprises the acts of: providing an anhydrite quantity; contacting the anhydrite quantity with an aqueous stream contaminated with contaminants; increasing the kinetics of the anhydrite quantity in contact with the aqueous stream such that effectively positively charged calcium ions hydrate from the anhydrite and interact with the negatively charged contaminants to form a precipitate of calcium sulfate hydrate+contaminant complexes in the aqueous stream; and collecting the precipitate of calcium sulfate hydrate+contaminant complexes from the aqueous stream.
In certain exemplary embodiments, the collecting act comprises capturing the calcium sulfate hydrate+contaminant complexes in the aqueous stream via a particulate filter capture system comprising filter media. Further, the collecting act may comprise drying the captured calcium sulfate hydrate+contaminant complexes, or processing the dried captured calcium sulfate hydrate+contaminant complexes via techniques like, but not limited to, milling, grinding, and pulverizing the dried captured calcium sulfate hydrate+contaminant complexes.
In one aspect, a system for removal of contaminants from a contaminated aqueous stream is disclosed. The system comprises (1) an agitation and flocculation system, and (2) a particulate filter capture system. The agitation and flocculation system is configured to receive an aqueous stream contaminated with contaminants, and configured to receive an anhydrite quantity as a primary flocculant. The agitation and flocculation system comprises an agitation and mixing subsystem for agitating the aqueous stream and mixing the aqueous stream with the anhydrite quantity such that the anhydrite quantity interacts with negatively charged contaminants to form a precipitate of calcium+contaminant complexes in the aqueous stream. The agitation and flocculation system is also configured to cease agitating and mixing the aqueous stream such that a portion of the calcium+contaminant complexes settle or are redirected under the influence of gravity, and such that a portion of the calcium+contaminant complexes resist the influence of gravity and remain suspended in a partially decontaminated aqueous stream. The particulate filter and capture system comprises filter media, and is configured to receive the partially decontaminated aqueous stream and to capture, via the filter media, the calcium+contaminant complexes that resist the influence of gravity and remain suspended in the partially decontaminated aqueous stream.
In some embodiments, the anhydrite quantity comprises solid anhydrite particles or granules, either pre-moistened or dry, or a combination thereof.
In some embodiments, the anhydrite quantity is introduced into the aqueous stream via a liquid carrier.
In some further embodiments, the system for removal of contaminants from a contaminated aqueous stream additionally comprises a water softening system for softening the decontaminated aqueous stream.
In some further embodiments, the system for removal of contaminants additionally comprises a feedback system configured to react to the concentration of at least one of a group consisting of perfluoroalkylcarboxylic acids, perfluoroalkyl sulfonates, perfluoroalkyl-sulfonic acids, and perfluorosulfonamidoacetic acids in the aqueous stream, and the concentration of at least one of the group consisting of perfluoroalkylcarboxylic acids, perfluoroalkyl sulfonates, perfluoroalkyl-sulfonic acids, and perfluorosulfonamidoacetic acids in the aqueous stream.
In some further embodiments, the system for removal of contaminants additionally comprises an ion exchange resin system downstream of the agitation and flocculation system and the particulate filter capture system.
In another aspect, a system for removal of contaminants from a contaminated aqueous stream is disclosed. The system comprises at least the following: (1) a fixed-bed cross-flow system configured to receive an aqueous stream contaminated with contaminants, and configured to hold an anhydrite quantity as a primary flocculant, the fixed-bed cross-flow system configured to bring into contact the aqueous stream with the anhydrite quantity such that the anhydrite quantity interacts with negatively charged contaminants to form a precipitate of calcium+contaminant complexes in the aqueous stream; and (2) a particulate filter capture system comprising filter media, and configured to receive the aqueous stream and to capture, via the filter media, the calcium+contaminant complexes suspended in the aqueous stream.
In some embodiments, the anhydrite quantity comprises solid anhydrite particles or granules, either pre-moistened or dry, or a combination thereof.
In some embodiments, the fixed-bed cross-flow filter system comprises a cartridge filter media comprising the anhydrite quantity.
In some further embodiments, the system for removal of contaminants from a contaminated aqueous stream additionally comprises a feedback system configured to react to the concentration of at least one of a group consisting of perfluoroalkylcarboxylic acids, perfluoroalkyl sulfonates, perfluoroalkyl-sulfonic acids, and perfluorosulfonamidoacetic acids in the aqueous stream, and the concentration of at least one of the group consisting of perfluoroalkylcarboxylic acids, perfluoroalkyl sulfonates, perfluoroalkyl-sulfonic acids, and perfluorosulfonamidoacetic acids in the aqueous stream.
In some further embodiments, the system for removal of contaminants from a contaminated aqueous stream additionally comprises a water softening system for softening the decontaminated aqueous stream.
In some further embodiments, the system for removal of contaminants from a contaminated aqueous stream additionally comprises an agitation and flocculation system downstream of the fixed-bed cross-flow system and upstream of the particulate filter capture system. The agitation and flocculation system may comprise at least one from a group consisting of stirring blades, baffles, vortex generators, liquid flow devices, and gas or air pumps for bubbles or microbubble generation, to increase the kinetics between the aqueous stream and the anhydrite quantity.
In some further embodiments, the system for removal of contaminants from a contaminated aqueous stream additionally comprises an ion exchange resin system downstream of the fixed-bed cross-flow system and the particulate filter capture system.
In another aspect, a method of removing contaminants from a contaminated aqueous stream is disclosed. The method comprises at least the following steps: (1) providing an anhydrite quantity within a fixed-bed cross flow system; (2) channeling an aqueous stream contaminated with contaminants to the anhydrite quantity within the fixed-bed cross flow system such that the anhydrite quantity interacts with negatively charged contaminants to form a precipitate of calcium+contaminant complexes in the aqueous stream; and (3) collecting the precipitate of calcium+contaminant complexes from the aqueous stream.
The collecting step may comprise capturing the calcium+contaminant complexes in the aqueous stream via a particulate filter capture system comprising filter media. In other embodiments, the collecting step may further comprise drying the captured calcium+contaminant complexes. In still further embodiments, the collecting step may comprise processing the dried captured calcium+contaminant complexes. Processing the dried captured calcium+contaminant complexes may comprise at least one from a group consisting of milling, grinding, and pulverizing the dried captured calcium+contaminant complexes.
In some embodiments, the method for removing contaminants from a contaminated aqueous stream additionally comprises providing an ion exchange resin and contacting the aqueous stream with the ion exchange resin after the collecting step.
In another aspect, another system for removing contaminants from a contaminated aqueous stream is described. The system comprises an agitation and flocculation system configured to receive an aqueous stream contaminated with contaminants, and configured to receive an anhydrite quantity as a primary flocculant. The agitation and flocculation system comprises at least the following: (1) an agitation and mixing subsystem, the agitation and mixing subsystem configured to agitate the aqueous stream and mix the aqueous stream with the anhydrite quantity such that the anhydrite quantity interacts with negatively charged contaminants to form one or more precipitate complexes, which comprise a calcium cation and a negatively charged contaminant, in the aqueous stream; and (2) an electro-coagulation and/or electro-oxidation subsystem configured to receive the aqueous stream comprising the one or more precipitate complexes, the electro-coagulation and/or electro-oxidation subsystem comprising aluminum-containing or titanium-containing electrodes that are configured, when electrified, to yield hydroxyl ions in the aqueous stream comprising the one or more precipitate complexes.
In some embodiments, the agitation and flocculation system comprises: (1) an agitation and mixing subsystem, and (2) an electro-coagulation subsystem. The electro-coagulation subsystem is configured to receive the aqueous stream comprising the one or more precipitate complexes, and comprises an aluminum-containing anode and an aluminum-containing cathode that are configured, when a voltage is applied, to yield aluminum ions, hydroxyl ions, and aluminum hydroxide in the aqueous stream that interact with the one or more precipitate complexes in the aqueous stream to form one or more heavier precipitate complexes in the aqueous stream. At least one of the aluminum-containing anode and the aluminum-containing cathode may comprise aluminum only or aluminum and one or more selected from the following: iron, milled steel, copper, and zinc. In some embodiments, at least one of the aluminum-containing anode and the aluminum-containing cathode are coated.
In embodiments including an electro-coagulation subsystem, the system may further comprise a particulate filter capture system configured to receive the aqueous stream comprising the heavier precipitate complexes, and to capture and remove the heavier precipitate complexes from the aqueous stream comprising the heavier precipitate complexes.
In embodiments including an electro-coagulation subsystem, the system may be configured to cease any agitating and mixing of the aqueous stream so that a portion of the heavier complexes settle out of the aqueous stream and a portion of the heavier complexes remain suspended in the aqueous stream.
In some embodiments, the agitation and flocculation system comprises: (1) an agitation and mixing subsystem, and (2) an electro-oxidation subsystem. The electro-oxidation subsystem may be configured to receive the aqueous stream comprising the one or more precipitate complexes, and may comprise a titanium-containing cathode and a titanium-containing anode that are configured, when electrified, to yield hydroxyl ions in the aqueous stream comprising the one or more precipitate complexes. The hydroxyl ions interact with the one or more precipitate-complexes forming heavier precipitate complexes.
In some embodiments, at least one of the titanium-containing anode and the titanium-containing cathode is coated. The coating may be a platinum coating, boron-doped diamond coating or a mixed metal oxide (MMO) coating.
In embodiments including an electro-oxidation subsystem, the system may further comprise a particulate filter capture system configured to receive the aqueous stream comprising the heavier precipitate complexes, and to capture and remove the heavier precipitate complexes from the aqueous stream comprising the heavier precipitate complexes.
In another aspect, yet another system for removal of contaminants from a contaminated aqueous stream is disclosed. The system comprises at least the following: (1) a fixed-bed cross-flow subsystem; and (2) an electro-coagulation and/or electro-oxidation subsystem.
The fixed-bed cross-flow subsystem may be configured to receive an aqueous stream contaminated with contaminants, and configured to hold an anhydrite quantity as a primary flocculant. The fixed-bed cross-flow system may also be configured to bring into contact the aqueous stream with the anhydrite quantity such that the anhydrite quantity interacts with negatively charged contaminants to form one or more precipitates, which comprise a calcium cation and a negatively charged contaminant, in the aqueous stream.
The electro-coagulation and/or electro-oxidation subsystem is, in some embodiments, configured to receive the aqueous stream comprising the one or more precipitate complexes. The electro-coagulation or electro-oxidation subsystem may comprise aluminum-containing or titanium-containing electrodes that are configured, when a voltage is applied, to yield hydroxyl ions in the aqueous stream comprising the one or more precipitate complexes.
In some embodiments, the system comprises: (1) a fixed-bed cross-flow subsystem; and (2) an electro-coagulation subsystem. The electro-coagulation subsystem may be configured to receive the aqueous stream comprising the one or more precipitate complexes. The electro-coagulation subsystem may comprise an aluminum-containing anode and an aluminum-containing cathode that are configured, when a voltage is applied, to yield aluminum ions, hydroxyl ions, and aluminum hydroxide in the aqueous stream that interact with the one or more precipitate complexes in the aqueous stream to form one or more heavier precipitate complexes in the aqueous stream.
In some embodiments, at least one of the aluminum-containing anode and the aluminum-containing cathode may comprise, in some embodiments, aluminum only, or aluminum and one or more selected from the following iron, milled steel, copper, and zinc. In some embodiments, at least one of the aluminum-containing anode and the aluminum-containing cathode are coated.
In embodiments including an electro-coagulation subsystem, the system may further comprise a particulate filter capture system configured to receive the aqueous stream comprising the heavier precipitate complexes, and to capture and remove the heavier precipitate complexes from the aqueous stream comprising the heavier precipitate complexes.
In embodiments including an electro-coagulation subsystem, the system may be configured to cease any agitating and mixing of the aqueous stream so that a portion of the heavier complexes settle out of the aqueous stream and a portion of the heavier complexes remain suspended in the aqueous stream.
In some embodiments, the system comprises: (1) a fixed-bed cross-flow subsystem; and (2) an electro-oxidation subsystem. The electro-oxidation subsystem being configured to receive the aqueous stream comprising the one or more precipitate complexes. The electro-oxidation subsystem may comprise a titanium-containing cathode and a titanium-containing anode that are configured, when a voltage is applied, to yield hydroxyl ions in the aqueous stream comprising the one or more precipitate complexes. The hydroxyl ions may interact with the one or more precipitate-complexes forming heavier precipitate complexes.
In some embodiments, at least one of the titanium-containing anode and the titanium-containing cathode is coated. The coating may be a platinum coating, a boron-doped diamond coating, or a mixed metal oxide (MMO) coating.
In one other aspect, another method for removing contaminants from a contaminated aqueous stream is disclosed. The method may comprise at least the following steps: (1) contacting an anhydrite quantity and the contaminated aqueous stream, resulting in the formation of one or more precipitate complexes, which comprise a calcium cation and a negatively charged contaminant, in the contaminated aqueous stream; and (2) generating hydroxyl ions in the aqueous stream comprising the one or more precipitate complexes by applying a voltage to aluminum-containing or titanium-containing electrodes. The hydroxyl ions interact with the one or more precipitate
In the figures, like reference numbers refer to like parts throughout the various views unless otherwise indicated. For reference numbers with letter character designations such as “102A” or “102B”, the letter character designations may differentiate two like parts or elements present in the same figure. Letter character designations for reference numbers may be omitted when it is intended that a reference numeral to encompass all parts having the same reference number in all figures.
For a further understanding of the nature, function, and objects of the present invention, reference should now be made to the following detailed description taken in conjunction with the accompanying drawings. While detailed descriptions of the preferred embodiments are provided herein, as well as the best mode of carrying out and employing the present invention, it is to be understood that the present invention may be embodied in various forms. Therefore, specific details disclosed herein are not to be interpreted as limiting, but rather as a basis for the claims and as a representative basis for teaching one skilled in the art to employ the present invention in virtually any appropriately detailed system, structure, or manner. The practice of the present invention is illustrated by the included Example, which is deemed illustrative of both the process taught by the present invention and of the results yielded in accordance with the present invention.
As used herein, the word “exemplary” or “illustrative” means “serving as an example, instance, or illustration.” Any implementation described herein as “exemplary” or “illustrative” is not necessarily to be construed as preferred or advantageous over other implementations.
Embodiments and aspects of the present invention provide an efficient, effective, and economical filtration system for removing PFASs from contaminated aqueous streams. The inventive concepts described herein also provide a solution that is not susceptible to the limitations and deficiencies of the prior art. The inventive concepts described herein lessen the operating-costs, capital expenditures, and/or infrastructure associated with the removal of PFASs from contaminated aqueous streams.
A first exemplary embodiment of the present invention provides a system for and a method of removing PFASs from PFAS contaminated aqueous streams via chemical aided capture and filtration. The system and method is configured to process PFAS contaminated aqueous streams without need for activated carbon filters or equivalent. The system and method also is configured to reduce operating costs, between about 30% to about 40% when compared to activated carbon filtration systems and ion exchange resin systems, and between about 50% to about 70% when compared to other prior art treatment processes such as reverse osmosis.
In particular, the system and method reduces the non-useful, or potentially toxic, outputs from PFAS processing. The system and method also efficiently and effectively treats and decontaminates aqueous streams, with limited bi-products and/or residues that cannot be captured, filtered, and/or reused, recycled, or safely disposed of, and with limited quantities of new or fresh waste materials or reagents. Further, the system and method also efficiently and effectively treats and decontaminates the aqueous stream without need for any secondary pH adjustment pre-treatment steps.
Specifically, prior art carbon filtration, membrane filtration, or ion exchange methods are very susceptible to fluctuations in pH, temperature, salinity, and/or the presence of any other type of organics in addition to PFAS/PFOS. The system and method of the present disclosure-unlike carbon filtration or membrane filtration or ion exchange-works on a wide range of pH values for the aqueous stream, between about 4 to about 11, and a wide range of temperatures from between about 32 degrees Fahrenheit (F) to about 90 degrees F., and wide range of salinity levels of up to about 32,000 parts per million (ppm), and are not affected by the presence of organics. Outside of these ranges, the system and method 100 may operate with known modifications and/or pre-conditioning and/or post-conditioning steps for the stream.
A second exemplary embodiment of the present invention provides a transportable and/or stand-alone system, and associated method, that can be deployed on an emergency or quick response basis to purify PFAS contaminated aqueous streams emitted from chemical processing and/or manufacturing facilities, or emitted as chemical runoff and/or leachate. The system and method is configured to substantially purify, or nearly-completely purify, PFAS contaminated aqueous streams laden with, amongst others, PFOS, PFOA, and any combinations thereof. The PFAS contaminated aqueous stream may be laden with various PFAS-types of measurable and unmeasurable quantities—due to the current state of deployable technology and/or the sometimes extreme dilution of the contaminated stream—and other similarly structured and charged contaminants. Yet the system and method is proven to capture commonly measurable PFAS-types (perfluoroalkyl carboxylic acids, perfluoroalkyl sulfonates, perfluoroalkyl sulfonic acids, and perfluorosulfonamidoacetic acids, for example) that directly facilitate capture of the—usually unmeasurable—other PFAS-types commonly associated with the contaminated stream and other similarly structured and charged contaminants.
A third exemplary embodiment of the present invention provides a transportable, stand-alone system, and associated method, configured to be mounted on a trailer or skids that can be deployed on an emergency or quick response basis, to purify PFAS contaminated fluid streams. The system and method allows chemical processing and manufacturing facilities, having internal cleanup issues, for example, to quickly purify or nearly-completely purify FPAS contaminated aqueous streams. The system and method also allows municipalities, governments, and localities, as well as private consumers to purify or nearly-completely purify PFAS contaminated aqueous streams. Once the issues in the facility or locality are fixed, the system and method may be remobilized and removed from the site in a short period of time. The system also easily may be remobilized or ramped up within a short period of time, as needed.
A fourth exemplary embodiment of the present invention provides a chemical aided capture and filtration system and method-involving the use of anhydrous calcium sulfate or anhydrite (Drierite™®, for example) as a flocculant or precipitation and agglomeration agent—for the removal of PFASs from a PFAS contaminated aqueous stream. PFASs tend to have negatively charged functional groups, while the anhydrite in the aqueous stream yields positively charged calcium ions. The anhydrite generally exhibits limited solubility in water and exhibits retrograde solubility, i.e., the solubility decreases as temperature increase.
As such, the positively charged calcium ions from the hydrated anhydrite interacts with at least some of the negatively charged groups PFASs-such that the buoyancy/weight of these PFASs in the aqueous stream is affected—which causes the calcium sulfate hydrate+PFAS complexes to precipitate. The insoluble calcium sulfate hydrate+PFAS complexes also will begin to agglomerate, which directly facilitates substantial capture of the other PFASs in the contaminated stream that may be of a type that do not interact with the positively charged calcium ions but would, nonetheless, still be bound-up by the calcium sulfate hydrate+PFAS complexes as they precipitate and/or agglomerate.
In this way, the system and method leverages flocculation, sedimentation, and/or filtration to purify the PFAS contaminated aqueous stream. In particular, the system and method may leverage flocculation and sedimentation-through gravity-induced settling of the calcium sulfate hydrate+PFAS insoluble precipitate complexes. In certain embodiments, the system and method then leverage filtration to filter out from the aqueous stream any un-sedimented or un-precipitated agglomerated calcium sulfate hydrate+PFAS complexes along with their bound-up or captured secondary PFASs—which secondarily flock onto the agglomerated calcium sulfate hydrate+PFAS complexes. As such, the system and method is configured to process PFAS contaminated aqueous streams without need for activated carbon filters, ion exchange systems, reverse osmosis systems, membrane systems, or equivalent—although further processing of the aqueous stream would yield further purification and decontamination without the limitations reported in the prior art.
Accordingly, further downstream processing under similar principles as explained herein-using other hydrated forms of calcium sulfate like CaSO4·2H2O or gypsum and selenite (a mineral dihydrate of calcium sulfate), CaSO4·½H2O or basanite (a hemihydrate, also known as plaster of Paris, either a-hemihydrate and β-hemihydrate of calcium sulfate), bauxite, alumina, and/or alum, etc .-would yield further purification and decontamination without the limitations reported in the prior art. Further, the system and method result in a captured solid waste that more easily can be processed, transported, and disposed of than the activated-chemical, liquid, or wet-waste of the prior art.
With the above context in mind, embodiments and aspects of the present invention become apparent from the drawings and the following detailed description.
For example, in comparison to an activated carbon system used for PFAS removal, for 1 pound of PFAS compounds removed from the aqueous stream, the estimated cost of activated carbon is about $450 U.S. dollars including cost of new activated carbon, replacement of spent carbon, and waste disposal of the spent carbon. This generates about 101 pounds of waste to be disposed of. In stark contrast, the system 100, for the same 1 pound of PFAS compounds removed from the aqueous stream, the estimated cost is around $100 U.S. dollars including consumables and disposal. This is about 75% reduction in estimated operating costs. The system 100 also generates less than about 7 pounds of waste, which is more than about 90% waste reduction. Further, the footprint of the system 100 is about 50% smaller than activated the carbon system, to achieve the same performance.
For purposes of the system 100 and the associated method, the PFAS contaminated feedwater 6 is fed initially into a primary agitation and flocculation tank 1. The feedwater 6 is fed via a pump, by gravity flow, by any other equivalent, or by any other method known to a person having ordinary skill in the art. Although the primary agitation and flocculation tank 1 is shown as a single tank, it is envisioned that the agitation and flocculation may occur along a series of interconnected and interrelated tanks, or any other system known to a person having ordinary skill in the art for inducing mixing, agitation, aggregation, precipitation, agglomeration as between the contaminated feedwater 6 and the flocculant, and/or any other common additive, to be introduced into the system 100.
In particular, the primary agitation and flocculation tank 1 is configured to receive the PFAS contaminated feedwater 6 and a quantity of anhydrite 7 as the primary flocculant. The quantity of anhydrite 7 may be introduced into the feedwater 6 as solid particles or granules, either hydrated or dry, as a liquid mixture, or as a fixed bed of material within the tank(s) (see
Further, the primary agitation and flocculation tank 1 is configured, and has the necessary structure(s), for mixing and agitating the feedwater 6 with the added quantity of anhydrite 7 as flocculant. The tank 1 may have stirring blades, baffles, or equivalent structures, may rely on vortex generators or liquid flow devices to increase the kinetics between the PFAS contaminated feedwater 6 and the anhydrite 7 mixture, or may rely on pumps introducing gas or air into the mixture within the tank 1. The tank 1, specifically, is configured to receive compressed or uncompressed gas or air, and to form gas bubbles or microbubbles 8 in the feedwater 6 and the anhydrite 7 mixture.
With the feedwater 6 and the anhydrite 7 mixed and agitated in the primary agitation and flocculation tank 1, the generally insoluble anhydrite begins to hydrate and release the positively charged calcium ions in the PFAS contaminated feedwater 6. The negative charge of the PFASs interacts with the effectively positively charged and hydrated anhydrite to form calcium sulfate hydrate+PFAS complexes in the feedwater 6 within the tank 1. As the insoluble calcium sulfate hydrate+PFAS complexes begin to agglomerate, they also begin to precipitate. Together, this directly facilitates substantial capture of the other PFASs in the feedwater 6 that may be of a type that do not/are not known to/have not been evidenced yet to interact with the positively charged calcium ions but would, nonetheless, still be bound-up by the calcium sulfate hydrate+PFAS complexes as they precipitate and/or agglomerate.
Upon cessation of the mixing and agitation of the feedwater 6 and the anhydrite 7 mixture in the tank 1, the calcium sulfate hydrate+PFAS complexes begin to settle under the influences of gravity, along with their bound-up or captured secondary PFASs (which secondarily flock onto the agglomerated calcium sulfate hydrate+PFAS complexes, as explained in detail herein). The calcium sulfate hydrate+PFAS complex(es), having a greater weight and different structure than the component parts, begin to either precipitate or aggregate and form a solid deposit. As the barriers to aggregation are reduced by the nature of calcium sulfate hydrate+PFAS complex, the calcium sulfate hydrate+PFAS complexes begin to agglomerate to form floc or flakes which further precipitate. Some complexes resist precipitation and remain suspended in the feedwater 6. Those calcium sulfate hydrate+PFAS complexes 9 that do precipitate are then separated from the remainder of the liquid phase in the tank 1, for further processing and drying, and for collection and disposal. The calcium sulfate hydrate+PFAS complexes 9 are characterized as a generally insoluble calcium salt.
Despite the chemical-aided capture of the majority of the PFASs in the feedwater 6, the remainder of the liquid phase in the tank 1, after collection of the precipitant 9, likely contains trace amounts of unprecipitated calcium sulfate hydrate+PFAS complexes. The residual calcium sulfate hydrate+PFAS complexes, nonetheless, are larger in size than the component parts, which makes them easier to capture physically or mechanically, e.g., makes them easier to simply filter-capture in a particulate filter without need for activated carbon filter systems or adsorbent beds, etc. The system 100 and the entire method from start to finish including precipitation and physical/mechanical capture removes upwards of 99.9 percent of the PFASs in the liquid phase.
More specifically, the remainder of the liquid phase in the tank 1, after collection of the precipitate 9, and containing trace amounts of unprecipitated calcium sulfate hydrate+PFAS complexes, is passed into 2 a cross-flow filter system 3. The cross-flow filter system 3 of system 100 comprises filter media 4 defining an interior 5. The filter media 4 comprises hydrophobic materials, e.g., melt blown polypropylene, spiral wound cellulose, nylon, glass, and/or can be selectively electrically charged, and may take various forms such as a cylindrical filter cartridge, for example. The flow rate of the filter media 4, in certain exemplary embodiments, may range from between about 0.25 liters per minute to about 20.0 liters per minute per 10 inch length and 2.5 inch diameter of filter and contact time of less than about 1 minute. Instead of a cross-flow filter system 3, a fixed bed of filter media also may be used; however, a cross-flow system with a radial flow design, for example, ensures high surface area and hence high flow and a small footprint when compared to a fixed-bed filter configuration.
In exemplary embodiments with cartridge configurations, the dimensions of each filter cartridge may be in the range of between about 5 inches to about 60 inches in length and between about 2.5 inches to about 6 inches in diameter. In exemplary embodiments with fixed-bed filter configurations, the flow rate may be in the range of between about 0.25 liters per minute to about 4 liters per min per 2.5 inch diameter. These dimensions may be significantly scaled up or down depending on the specific need, e.g., for industrial fixed installations. In other exemplary embodiments, other types of particulate filter capture systems are envisioned such as depth filters, multimedia filter systems, or sand-bed filters with flow from top to bottom or bottom to top. For a depth filter-like system, for example, the contact time may be between about 1 second to about 1 minute.
Returning to system 100, as the remainder of the liquid phase in the tank 1 is passed over 2 the filter media 4, the filter media 4 can capture all of the trace amounts of unprecipitated calcium sulfate hydrate+PFAS complex(es)-so long as the surface area and flow rates are managed-and the filter media 4 is maintained or replaced as needed. As the name implies, this is a cross-flow filter system wherein the liquid phase travels tangentially across the surface of the filter media 4, rather than into/through the filter media 4. The principal advantage of this arrangement is that filter cake-which can blind the filter-substantially is washed away during the filtration process, which increases the length of time that the filter media 4 can be effectively used. In this way, system 100 can operate as a continuous process, unlike batch-wise dead-end filtration systems. The resulting outlet liquid 10 coming out of the filter media 4 is the final treated aqueous stream, which has been substantially decontaminated of PFASs, and which can now exit the system 100.
As the aqueous stream has been hardened by the introduction of calcium ions via the anhydrite treatment, it is envisioned that the system 100 may additionally comprise a water softening subsystem for the final outlet treated aqueous stream 10. It also is envisioned that, once differential pressure in the filter media 4 has reached a predetermined stage, caused by the amount of unprecipitated calcium sulfate hydrate+PFAS complexes captured, the filter media 4 may be backwashed, reused, or disposed of. Other techniques that may be employed include alternating tangential flow, clean-in-place techniques, diafiltration, and/or process flow disruption.
For example, in comparison to an activated carbon system used for PFAS removal, for 1 pound of PFAS compounds removed from the aqueous stream, the estimated cost of activated carbon is about $450 U.S. dollars including cost of new activated carbon, replacement of spent carbon, and waste disposal of the spent carbon. This generates about 101 pounds of waste to be disposed of. In stark contrast, the system 100, for the same 1 pound of PFAS compounds removed from the aqueous stream, the estimated cost is around $100 U.S. dollars including consumables and disposal. This is about 75% reduction in estimated operating costs. The system 100 also generates less than about 7 pounds of waste, which is more than about 90% waste reduction. Further, the footprint of the system 100 is about 50% smaller than activated the carbon system, to achieve the same performance.
For purposes of the system 200 and the associated method, the PFAS contaminated feedwater 6 is processed via a fixed-bed type structure 11 configured to hold the flocculant. Like the system 100 structure, the feedwater 6 is fed via a pump, by gravity flow, by any other equivalent, or by any other method known to a person having ordinary skill in the art. The fixed-bed type structure 11 is configured as a cross-flow system but may be configured as a depth system or any other equivalent; however, regardless of the embodiment discussed, the anhydrite is held as part of the media, multi-media, cassette, and/or cartridge, etc. The anhydrite may be in the form of solid particles or granules, either hydrated or dry until the system is introduced to the feedwater 6. Flocculation begins to occur within the anhydrite media of the fixed-bed type structure 11, and downstream therefrom, via the positively charged calcium ions hydrated from the anhydrite media.
In exemplary embodiments with a depth configuration for the fixed-bed type structure 11, multiple porous layers of filter-like media are used to make contact with the PFAS contaminated feedwater 6. Due to the tortuous and channel-like nature of the filtration media, the feedwater 6 enters and interacts with the anhydrite within its structure, as opposed to substantially on or near the surface. A depth filter configuration provides the added advantage of attaining a high separation efficiency, and having the ability to be used with substantially higher flow rates. A depth filter configuration may comprise cassettes (pads or panels), cartridges, deep-beds such as sand filters, and lenticulars.
Returning to system 200, although the fixed-bed type structure 11 is illustrated in
The fixed-bed type structure 11 of system 200 receives a quantity of anhydrite and holds it as the primary flocculant. Like system 100, the quantity of anhydrite to be maintained or replenished in the fixed-bed type structure 11 of system 200 may be determined by a feedback system that takes into consideration of a least one of the measurable PFASs in the feedwater 6 (perfluoroalkylcarboxylic acids, perfluoroalkyl sulfonates, perfluoroalkyl sulfonic acids, and/or perfluorosulfonamido-acetic acids, for example), the initial and current quantity of anhydrite in the fixed-bed type structure 11, the measurable concentration of a least one of the measurable PFASs in the final outlet treated aqueous stream 10, etc.—to make most efficient use of the quantity of anhydrite introduced into and used by the system 200.
Again, as the insoluble calcium sulfate hydrate+PFAS complexes begin to agglomerate, they also begin to precipitate. Together, this directly facilitates substantial capture of the other PFASs in the feedwater 6 that may be of a type that do not/are not known to/have not been evidenced yet to interact with the positively charged calcium ions but would, nonetheless, still be bound-up by the calcium sulfate hydrate+PFAS complexes as they precipitate and/or agglomerate.
In the cross-flow configuration, the fixed-bed type structure 11 includes a filter-type media 13 comprising anhydrite granules and/or powder 15. In other exemplary embodiments, the filter-type media 13 essentially comprises anhydrite granules and/or powder. The cross-flow system 11 may take various forms such as that of planar filter(s) for a vessel or cylindrical filter cartridge(s) for a canister. In exemplary embodiments with cartridge configurations, the dimensions of each cartridge may be in the range of between about 5 inches to about 60 inches in length and between about 2.5 inches to about 6 inches in diameter. These dimensions may be significantly scaled up or down depending on the specific need, e.g., for industrial fixed installations.
Returning to the system 200, the contact time and the amount of anhydrite granules and/or powder 15 in the filter-like media 13 is adjusted based on the expected or anticipated PFAS concentration in the feedwater 6 and the flow rate of the feedwater 6—whether or not actively controlled. The contact time between the PFASs in the feedwater 6 and the anhydrite granules and/or powder 15 is between about 1 second to about 1 minute. With the feedwater 6 and the anhydrite granules and/or powder 15 in contact within the fixed-bed type structure 11, the generally insoluble anhydrite begins to hydrate and release positively charged calcium ions into the feedwater 6. The negative charge of the PFASs interact with the effectively positively charged and hydrated anhydrite to form calcium sulfate hydrate+PFAS complexes in the feedwater 6 within in the filter-like media 13 and downstream of the filter-like media 13.
From within, and upon exiting the fixed-bed type structure 11—as the barriers to aggregation are reduced by the nature of the calcium sulfate hydrate+PFAS complex-the calcium sulfate hydrate+PFAS complexes begin to agglomerate and to form floc; however, due to the force of the flow coming out of the fixed-bed type structure 11, none of the agglomerates or floc settle. Like system 100 of
Next, as flocculation begins to occur within the anhydrite fixed filter-like media 13 of the fixed-bed type structure 11 and downstream therefrom, the calcium sulfate hydrate+PFAS complexes are separated from the liquid phase exiting the fixed-bed type structure 11. Specifically, the liquid phase is passed over 2 an actually cross-flow filter 17 differently configured from the fixed-bed type cross-flow system 11. The cross-flow filter 17 is substantially identical to the cross-flow filter except for the difference described herein. Instead of a cross-flow filter system 17, a fixed bed of filter media also may be used; however, a cross-flow system with a radial flow design, for example, ensures high surface area and hence high flow and a small footprint when compared to a fixed-bed filter configuration.
Regardless of the specific configuration used, the cross-flow filter 17 can capture all of the unprecipitated calcium sulfate hydrate+PFAS complexes-so long as the filter media 19 cartridge, multimedia, sand bed, etc. and flow 2 are managed-and the encapsulating calcium sulfate hydrate+PFAS complexes 21 are removed, managed, and/or processed as needed. This may require removal and replacement of the filter media 19 and/or removal and processing of the encapsulating calcium sulfate hydrate+PFAS complexes 21. The flow rate of the filter media 4, in certain exemplary embodiments, may range from between about 0.25 liters per minute to about 20.0 liters per minute per 10 inch length and 2.5 inch diameter of filter and contact time of less than about 1 minute.
In exemplary embodiments with cartridge configurations, the dimensions of each filter cartridge may be in the range of between about 5 inches to about 60 inches in length and between about 2.5 inches to about 6 inches in diameter. In exemplary embodiments with simplified fixed-bed filter configurations, the flow rate may be in the range of between about 0.25 liters per minute to about 4 liters per min per 2.5 inch diameter. These dimensions may be significantly scaled up or down depending on the specific need, e.g., for industrial fixed installations. In one exemplary embodiment, other types of particulate filter capture systems are envisioned such as depth filters, multimedia filter systems, or sand-bed filters with flow from top to bottom or bottom to top. In another embodiment, the filter(s) may be installed as a single or multiround configuration holding multiple filters in one vessel depending on the flow capacity and pressure drop requirements.
In this way, the resulting outlet liquid stream 23 coming out of the filter media 19 of the cross-flow filter 17 is the final treated aqueous stream, which has been substantially decontaminated of PFASs, and which can now exit the system 200. As the aqueous stream has been hardened by the introduction of anhydrite, it is envisioned that the system 200 may additionally comprise a water softening subsystem for the final outlet liquid stream 23. It also is envisioned that, once differential pressure in the filter media 19 has reached a predetermined stage, caused by the amount of unprecipitated calcium sulfate hydrate+PFAS complexes captured, the filter media 19 may be backwashed, reused, or disposed of. Other techniques that may be employed include alternating tangential flow, clean-in-place techniques, diafiltration, and/or process flow disruption.
The following is a non-limiting illustrative example of the present invention when applied under experimental conditions, for a PFAS contaminated aqueous stream, and the experimental results thereof, based on the system and method of
The system used has an about 1 liter per minute feedwater intake containing about 1 ppm of PFASs (each; see Table 1). The primary agitation and flocculation tank has a capacity of about 10 liters. A quantity of anhydrite granules of about 2.0 milligrams (mg) is introduced into the feedwater. The feedwater functions as the inlet feed liquid for the 2.0 mg of anhydrite. The ratio of flocculant to expected quantity of PFASs in the tank ranges between about 0.3 to about 1000.
The primary agitation and flocculation tank mixes and agitates the feedwater with the anhydrite as flocculant. The tank forms gas bubbles or microbubbles in the feedwater and the anhydrite mixture. With the feedwater and the anhydrite mixed and agitated in the tank, the generally insoluble anhydrite begins to hydrate and interact with the PFASs to form calcium sulfate hydrate+PFAS complexes in the feedwater within the tank.
Upon cessation of the mixing and agitation of the feedwater and the anhydrite mixture in the tank, the calcium sulfate hydrate+PFAS complexes begin to either precipitate or aggregate. Some complexes resist precipitation and remain suspended in the feedwater. The tank has a residence time of about 5 minutes or greater to yield the majority of the precipitate product, which contains from between about 95% to about 99.9% of the PFASs that are in feedwater intake.
The precipitate is then separated from the remainder of the liquid phase in the tank, for further processing and drying, and for collection and weighing. The remainder of the liquid phase in the tank, after collection of the precipitate, contains the remaining about 0.05 mg to about 0.0001 mg of trace unprecipitated calcium sulfate hydrate+PFAS complexes.
Specifically, the liquid phase is passed into a cross-flow filter system comprising cylindrical filter media cartridge defining an interior outlet. As the remainder of the liquid phase in the tank is passed over the filter media, the filter media captures all or nearly all of the about 0.05 mg to about 0.0001 mg trace unprecipitated calcium sulfate hydrate+PFAS complexes. The resulting outlet liquid coming out of the filter media interior is substantially decontaminated of PFASs.
This is confirmed by the following experimental results presented as Table 1—
Turning now to
In some exemplary embodiments, the 1008 step may alternatively consist of collecting the precipitate of calcium sulfate hydrate+contaminant complexes in the aqueous stream that has settled out of solution or suspension. The collected product may take the form of a hard cement-like product when taken out of aqueous stream and dried. The collected product encapsulates the PFAS contaminants and exhibits insignificant leaching of the contaminant back into the environment when left exposed to nature.
Additional systems and methods described herein, include systems and methods for removing contaminants from an aqueous stream where anhydrite is used as a primary flocculant, but additional or secondary flocculation, agglomeration, coagulation, settling, deposition, and/or the like also occurs.
Systems and methods using anhydrite as a primary or as the only flocculant are described in detail herein, e.g., “agitation and flocculation” systems and methods, and “fixed-bed cross flow” systems and methods described hereinabove. In each, one or more precipitate complexes, which comprise a calcium cation from anhydrite and a negatively charged contaminant from a contaminated aqueous stream, are formed. For example, in some embodiments, the anionic or negatively charged contaminants are PFAS/PFOS contaminants. The anionic or negatively charged PFAS/PFOS contaminants react with calcium in the calcium sulfate anhydrite and form insoluble precipitate complexes comprising calcium ions complexed with negatively charged PFAS/PFOS and some soluble calcium hydroxide ions. This insoluble complex may be separated by gravity. However, typically 30 minutes of gravity settling time is needed to separate a majority of the insoluble precipitate complexes as a sludge. This gravity settling time presumes no mixing or agitation. Any mixing or agitation will result in slower settling times. As a result, in the methods described hereinabove, most of the insoluble precipitate complexes are carried over and captured by the particulate filter. This results in a need to continually replace or clean the filters, which is undesirable particularly in situations where the filters are difficult to access. Remaining calcium ions may be removed by ion exchange resins.
To reduce the 30-minute settling time, to remove a majority of insoluble precipitate complexes, and to reduce extent of carryover to particulate filters and subsequent consummation of the filters, an electrocoagulation process utilizing sacrificial aluminum electrodes (anode and cathode) is utilized. An aqueous stream comprising the insoluble precipitate complexes (e.g., Ca+-PFAS/PFOS-) flows into a vessel comprising aluminum electrodes (anode and cathode). The anode and cathode are supplied with DC power through a rectifier. When voltage is supplied across the aluminum anodes and cathodes, aluminum ions, hydroxyl ions, and aluminum hydroxide (generated by the combination of the aluminum ions and hydroxyl ions) are generated. These interact with the insoluble precipitate complexes (e.g., Ca+-PFAS/PFOS-) to form heavier precipitate complexes (e.g., calcium aluminate complexes-Ca+-PFOS/PFAS-Al(OH)3). Gravity settling times for these heavier precipitate complexes are only 5-10 minutes, compared to 30 minutes for the Ca+-PFAS/PFOS-complexes. These heavier precipitate complexes settle faster, resulting in less work for the filter. Separation occurs more efficiently before the aqueous stream makes its way to the particulate filter. This can enable smaller size of the system. This also allows the particulate filter to have a much longer life and reduced consumption. Also the electrocoagulation is known to reduce calcium hardness in the water which means it also separates and removes the soluble calcium ions in the water. This can reduce the usage of ion exchange resin to remove the Calcium hardness. Ion exchange resins may be used in these processes to remove aluminum ions generated in the electrocoagulation process.
An example of a system or method for removing contaminants from an aqueous stream that uses anhydrite as a primary flocculant is shown in
In the agitation and flocculation subsystem, a contaminated aqueous stream enters a vessel of the subsystem and comes into contact with anhydrite granules or powder. This may occur under mixing and/or agitation conditions.
The aqueous stream comprising the precipitate complexes, e.g., Ca+-PFAS, may then enter a vessel where an electrocoagulation process can occur. Alternatively, the electrocoagulation process may occur in the same vessel where the one or more precipitate complexes were formed. This electrocoagulation process results in the formation of heavier precipitate complexes that settle more easily than, for example, the Ca+-PFAS-complexes. The vessel comprises two aluminum-containing electrodes (an anode and a cathode). The anode and cathode are supplied with DC power through a rectifier. When voltage is supplied across the aluminum-containing anode and cathode, aluminum ions, hydroxyl ions, and aluminum hydroxide (generated by the combination of the aluminum ions and hydroxyl ions) are generated. These interact with the insoluble precipitate complexes (e.g., Ca+-PFAS/PFOS-) to form heavier precipitate complexes (e.g., calcium aluminate complexes-Ca+-PFOS/PFAS-Al(OH)3). See
One or both of the aluminum-containing electrodes may comprise, consist of, or consist essentially of aluminum alone, or aluminum and one or more selected from iron, milled steel, copper, or zinc. In some embodiments, one or both of the aluminum-containing electrodes may be coated.
As a result of this electrocoagulation process, the aqueous stream that enters the particulate filter of the particulate filter capture system is less contaminated than a stream resulting when no electrocoagulation process is used. This results in less need to replace and/or clean the particulate filter. The useful life of the particulate filter is lengthened.
An aqueous stream emerging from the particulate filter of the particulate filter capture system still may contain calcium ions (from the anhydrite) and/or aluminum ions (generated by the aluminum-containing electrodes). Ion exchange resins may be used to remove these ions, which are regulated and cannot be released into the environment unchecked.
Another example of a system or method for removing contaminants from an aqueous stream that uses anhydrite as a primary flocculant is shown in
In the fixed-bed cross-flow subsystem, a contaminated aqueous stream enters the subsystem and comes into contact with anhydrite granules or powder. When the aqueous stream contacts the anhydrite, one or more precipitate complexes form via an interaction with the calcium cations from anhydrite and negatively charged contaminants in the contaminated aqueous stream, e.g., PFAS/PFOS. See
The aqueous stream comprising the precipitate complexes, e.g., Ca+-PFAS, then enters a vessel where an electrocoagulation process can occur. Alternatively, the electrocoagulation process may occur in the same vessel where the one or more precipitate complexes were formed. This electrocoagulation process results in heavier precipitate complexes that settle more easily. The vessel comprises two aluminum-containing electrodes (an anode and a cathode). The anode and cathode are supplied with DC power through a rectifier. When voltage is supplied across the aluminum-containing anode and cathode, aluminum ions, hydroxyl ions, and aluminum hydroxide (generated by the combination of the aluminum ions and hydroxyl ions) are generated. These interact with the insoluble precipitate complexes (e.g., Ca+-PFAS/PFOS-) to form heavier precipitate complexes (e.g., calcium aluminate complexes-Ca+-PFOS/PFAS-Al(OH)3). See
One or both of the aluminum-containing electrodes may comprise, consist of, or consist essentially of aluminum alone, or aluminum and one or more selected from iron, milled steel, copper, or zinc. In some embodiments, one or both of the aluminum—containing electrodes may be coated.
As a result of this electrocoagulation process, the aqueous stream that enters the particulate filter of the particulate filter capture system is less contaminated than a stream resulting when no electrocoagulation process is used. This results in less need to replace and/or clean the particulate filter. The useful life of the particulate filter is lengthened.
An aqueous stream emerging from the particulate filter of the particulate filter capture system still may contain calcium ions (from the anhydrite) and/or aluminum ions (generated by the aluminum-containing electrodes). Ion exchange resins may be used to remove these ions, which are regulated and cannot be released into the environment unchecked.
Yet another example of a system or method for removing contaminants from an aqueous stream that uses anhydrite as a primary flocculant is described herein. This system or method comprises, consists of, or consists essentially of, at least the following: (1) an agitation and flocculation subsystem, and (2) an electro-oxidation subsystem. The system or method may further comprise, consist of, or consist essentially of the following: (3) a particulate filter capture system comprising a particulate filter and/or (4) an ion exchange resin system.
In the agitation and flocculation subsystem, a contaminated aqueous stream enters a vessel of the subsystem and comes into contact with anhydrite granules or powder. This may occur under mixing and/or agitation conditions. For example, stirring blades, gas bubbles, and the like may be used to mix and/or agitate. When the anhydrite contacts the contaminated aqueous stream, one or more precipitate complexes form via an interaction with the calcium cations from anhydrite and negatively charged contaminants in the contaminated aqueous stream, e.g., PFAS/PFOS contaminants. Exemplary precipitate complexes are, for example, Ca+-PFAS or Ca+-PFOS. Some of these precipitate complexes will settle and can be collected, but many remain in the aqueous stream.
The aqueous stream comprising the precipitate complexes, e.g., Ca+-PFAS, then enters a vessel where an electro-oxidation process can occur. Alternatively, the electro-oxidation process may occur in the same vessel where the one or more precipitate complexes were formed. This electro-oxidation process results in heavier precipitate complexes that settle more easily. The vessel comprises two titanium-containing electrodes (an anode and a cathode). The anode and cathode are supplied with DC power through a rectifier. When voltage is supplied across the titanium-containing anode and cathode, hydroxyl ions are generated. See
As a result of this electro-oxidation process, the aqueous stream that enters the particulate filter of the particulate filter capture system is less contaminated than a stream resulting when no electro-oxidation process is used. This results in less need to replace and/or clean the particulate filter. The useful life of the particulate filter is lengthened.
An aqueous stream emerging from the particulate filter of the particulate filter capture system still may contain calcium ions (from the anhydrite). Ion exchange resins may be used to remove these ions, which are regulated and cannot be released into the environment unchecked.
In some embodiments, the titanium-containing electrodes of the electro-oxidation process may be the same or different. Preferably, at least one titanium-containing electrode must be a coated electrode. Having at least one of the titanium-containing electrodes be a coated electrode allows for the production of a proper level of hydroxyl ion production. The coated titanium-containing electrode may be a titanium electrode coated with at least one of a platinum coating, a mixed metal oxide (MMO) coating, and a boron-doped diamond coating. The MMO coating may comprise two or more oxides selected from iridium oxide, ruthenium oxide, and tantalum oxide.
A benefit of having both titanium-containing electrodes be coated electrodes also exists. Specifically, if both titanium-containing electrodes are coated, e.g., both are coated with an MMO coating, un-fouling of the electrodes without requiring removal and cleaning or replacement of the electrodes. During the electro-oxidation process, the anode fouls. If both electrodes are coated, polarity can be reversed, i.e., the cathode becomes the anode and the fouled anode becomes the cathode. This results in electrode de-fouling.
Applied voltage in the electro-oxidation process is not so limited, and may depend on characteristics of the aqueous stream, e.g., its salinity. In some embodiments an appropriate applied voltage may be from 0.1 V to 30 V, from 0.5 V to 25 V, from 1 V to 20 V, from 3 V to 15 V, or from 3V to 12 V.
With regard to the applied voltage, an applied voltage resulting in a current density of 10-70 mA/cm2 may be desirable. A resulting current density greater than 70 mA/cm2 may result in generation of H2 gas, Cl2 gas, and/or Br2 gas, which in some instances may be undesirable. Generation of such gases could, in some situations be a desirable side effect, but this is less typical. In some embodiments, an applied voltage of 5-10 V may result in a current density of 25 mA/cm2. In some embodiments, an applied voltage of 3V may result in a current density of 15 mA/cm2.
The distance or gap between the electrodes in the electro-oxidation process are not so limited, and may be from 2 mm to 60 mm, from 2 mm to 50 mm, from 2 mm to 400 mm, from 2 mm to 30 mm, from 2 mm to 20 mm, from 2 mm to 10 mm, from 2 mm to 9 mm, from 2 mm to 8 mm, from 2 mm to 6 mm, from 2 mm to 4 mm, from 4 mm to 10 mm, from 4 mm to 8 mm, or from 4 mm to 6 mm.
Residence time for the electro-oxidation process is not so limited, and may vary based on how contaminated the aqueous stream is. In some embodiments, the residence time may be from 0.5 minutes to 30 minutes, from 0.5 minutes to 25 minutes, from 0.5 minutes to 20 minutes, from 0.5 minutes to 15 minutes, from 0.5 minutes to 10 minutes, from 0.5 minutes to 10 minutes, from 0.5 minutes to 9 minutes, from 0.5 minutes to 8 minutes, from 0.5 minutes to 7 minutes, from 0.5 minutes to 6 minutes, from 0.5 minutes to 5 minutes, from 0.5 minutes to 4 minutes, from 0.5 minutes to 3 minutes, from 0.5 minutes to 2 minutes, or from 0.5 minutes to 1 minute.
Throughput of the electro-oxidation process is not so limited, and may also vary based on how contaminated the aqueous stream is. In some embodiments, the throughput is from 0.1 L/min to 10,000 L/min, from 0.1 L/min to 5,000 L/min, from 0.1 L/min to 1,000 L/min, from 0.1 L/min to 500 L/min, from 0.1 L/min to 100 L/min, or from 0.1 L/min to 10 L/min.
A penultimate example of a system or method for removing contaminants from an aqueous stream that uses anhydrite as a primary flocculant is disclosed herein. This system or method comprises, consists of, or consists essentially of, at least the following: (1) a fixed-bed cross-flow subsystem, and (2) an electro-oxidation subsystem. The system or method may further comprise, consist of, or consist essentially of the following: (3) a particulate filter capture system comprising a particulate filter and/or (4) an ion exchange resin system.
In the fixed-bed cross-flow subsystem, a contaminated aqueous stream enters the subsystem and comes into contact with anhydrite granules or powder. When the aqueous stream contacts the anhydrite, one or more precipitate complexes form via an interaction with the calcium cations from anhydrite and negatively charged contaminants in the contaminated aqueous stream, e.g., PFAS/PFOS. Exemplary precipitate complexes that are formed are, for example, Ca+-PFAS or Ca+-PFOS. Some of these precipitate complexes settle out, but some remain suspended in the aqueous stream.
The aqueous stream comprising the precipitate complexes, e.g., Ca+-PFAS, then enters a vessel where an electro-oxidation process can occur. Alternatively, the electro-oxidation process may occur in the same vessel where the one or more precipitate complexes were formed. This electro-oxidation process results in heavier precipitate complexes that settle more easily. The vessel comprises two titanium-containing electrodes (an anode and a cathode). The anode and cathode are supplied with DC power through a rectifier. When voltage is supplied across the titanium-containing anode and cathode, hydroxyl ions are generated. These interact with the insoluble precipitate complexes (e.g., Ca+-PFAS/PFOS-) to form heavier precipitate complexes. These heavier precipitate complexes settle more quickly, and can be collected from the bottom of the vessel after draining the same.
As a result of this electro-oxidation process, the aqueous stream that enters the particulate filter of the particulate filter capture system is less contaminated than a stream resulting when no electro-oxidation process is used. This results in less need to replace and/or clean the particulate filter. The useful life of the particulate filter is lengthened.
An aqueous stream emerging from the particulate filter of the particulate filter capture system still may contain calcium ions (from the anhydrite). Ion exchange resins may be used to remove these ions, which are regulated and cannot be released into the environment unchecked.
In some embodiments, the titanium-containing electrodes of the electro-oxidation process may be the same or different. Preferably, at least one titanium-containing electrode must be a coated electrode. Having at least one of the titanium-containing electrodes be a coated electrode allows for the production of a proper level of hydroxyl ion production. The coated titanium-containing electrode may be a titanium electrode coated with at least one of a platinum coating, a mixed metal oxide (MMO) coating, and a boron-doped diamond coating. The MMO coating may comprise two or more oxides selected from iridium oxide, ruthenium oxide, and tantalum oxide.
A benefit of having both titanium-containing electrodes be coated electrodes also exists. Specifically, if both titanium-containing electrodes are coated, e.g., both are coated with an MMO coating, un-fouling of the electrodes without requiring removal and cleaning or replacement of the electrodes. During the electro-oxidation process, the anode fouls. If both electrodes are coated, polarity can be reversed, i.e., the cathode becomes the anode and the fouled anode becomes the cathode. This results in electrode de-fouling.
Applied voltage in the electro-oxidation process is not so limited, and may depend on characteristics of the aqueous stream, e.g., its salinity. In some embodiments an appropriate applied voltage may be from 0.1 V to 30 V, from 0.5 V to 25 V, from 1 V to 20 V, from 3 V to 15 V, or from 3V to 12 V.
With regard to the applied voltage, an applied voltage resulting in a current density of 10-70 mA/cm2 may be desirable. A resulting current density greater than 70 mA/cm2 may result in generation of H2 gas, Cl2 gas, and/or Br2 gas, which in some instances may be undesirable. Generation of such gases could, in some situations be a desirable side effect, but this is less typical. In some embodiments, an applied voltage of 5-10 V may result in a current density of 25 mA/cm2. In some embodiments, an applied voltage of 3V may result in a current density of 15 mA/cm2.
The distance or gap between the electrodes in the electro-oxidation process are not so limited, and may be from 2 mm to 60 mm, from 2 mm to 50 mm, from 2 mm to 400 mm, from 2 mm to 30 mm, from 2 mm to 20 mm, from 2 mm to 10 mm, from 2 mm to 9 mm, from 2 mm to 8 mm, from 2 mm to 6 mm, from 2 mm to 4 mm, from 4 mm to 10 mm, from 4 mm to 8 mm, or from 4 mm to 6 mm.
Residence time for the electro-oxidation process is not so limited, and may vary based on how contaminated the aqueous stream is. In some embodiments, the residence time may be from 0.5 minutes to 30 minutes, from 0.5 minutes to 25 minutes, from 0.5 minutes to 20 minutes, from 0.5 minutes to 15 minutes, from 0.5 minutes to 10 minutes, from 0.5 minutes to 10 minutes, from 0.5 minutes to 9 minutes, from 0.5 minutes to 8 minutes, from 0.5 minutes to 7 minutes, from 0.5 minutes to 6 minutes, from 0.5 minutes to 5 minutes, from 0.5 minutes to 4 minutes, from 0.5 minutes to 3 minutes, from 0.5 minutes to 2 minutes, or from 0.5 minutes to 1 minute.
Throughput of the electro-oxidation process is not so limited, and may also vary based on how contaminated the aqueous stream is. In some embodiments, the throughput is from 0.1 L/min to 10,000 L/min, from 0.1 L/min to 5,000 L/min, from 0.1 L/min to 1,000 L/min, from 0.1 L/min to 500 L/min, from 0.1 L/min to 100 L/min, or from 0.1 L/min to 10 L/min.
As final examples of a systems or method for removing contaminants from an aqueous stream, systems or methods as disclosed herein above that include both an electro-oxidation subsystem and an electro-coagulation subsystem are disclosed. In such embodiments, an aqueous stream comprising the one or more precipitates disclosed hereinabove (e.g., Ca+-PFAS) may enter a vessel comprising two titanium-containing electrodes as described hereinabove and chunks, particles, or a bed of aluminum-containing material. In such embodiments, the titanium-containing electrodes should be adjacent to or touching the aluminum-containing material.
The various embodiments are provided by way of example and are not intended to limit the scope of the disclosure. The described embodiments comprise different features, not all of which are required in all embodiments of the disclosure. Some embodiments of the present disclosure utilize only some of the features or possible combinations of the features. Variations of embodiments of the present disclosure that are described, and embodiments of the present disclosure comprising different combinations of features as noted in the described embodiments, will occur to persons with ordinary skill in the art. It will be appreciated by persons with ordinary skill in the art that the present disclosure is not limited by what has been particularly shown and described herein above.
Certain implementations of systems and methods consistent with the present disclosure are provided as follows:
Clause 1. A system removing contaminants from a contaminated aqueous stream, the system comprising an agitation and flocculation system configured to receive an aqueous stream contaminated with contaminants, and configured to receive an anhydrite quantity as a primary flocculant, the agitation and flocculation system comprising: an agitation and mixing subsystem, the agitation and mixing subsystem configured to agitate the aqueous stream and mix the aqueous stream with the anhydrite quantity such that the anhydrite quantity interacts with negatively charged contaminants to form one or more precipitate complexes, which comprise a calcium cation and a negatively charged contaminant, in the aqueous stream; and an electro-coagulation and/or electro-oxidation subsystem configured to receive the aqueous stream comprising the one or more precipitate complexes, the electro-coagulation and/or electro-oxidation subsystem comprising aluminum-containing or titanium-containing electrodes that are configured, when a voltage is applied, to yield hydroxyl ions in the aqueous stream comprising the one or more precipitate complexes.
Clause 2. The system of clause 1, comprising an electro-coagulation subsystem, the electro-coagulation subsystem being configured to receive the aqueous stream comprising the one or more precipitate complexes and comprising an aluminum-containing anode and an aluminum-containing cathode that are configured, when electrified, to yield aluminum ions, hydroxyl ions, and aluminum hydroxide in the aqueous stream that interact with the one or more precipitate complexes in the aqueous stream to form heavier precipitate complexes in the aqueous stream.
Clause 3. The system of clause 2, wherein at least one of the aluminum-containing anode and the aluminum-containing cathode comprises aluminum only or aluminum and one or more selected from the following: iron, milled steel, copper, and zinc.
Clause 4. The system of clause 3, wherein at least one of the aluminum-containing anode and the aluminum-containing cathode are coated.
Clause 5. The system of clause 2, further comprising a particulate filter capture system configured to receive the aqueous stream comprising the heavier precipitate complexes, and to capture and remove the heavier precipitate complexes from the aqueous stream comprising the heavier precipitate complexes.
Clause 6. The system of clause 2, configured to cease any agitating and mixing of the aqueous stream so that a portion of the heavier precipitate complexes settle out of the aqueous stream and a portion of the heavier precipitate complexes remain suspended in the aqueous stream.
Clause 7. The system of clause 1, comprising an electro-oxidation subsystem, the electro-oxidation subsystem being configured to receive the aqueous stream comprising the one or more precipitate complexes and comprising a titanium-containing cathode and a titanium-containing anode that are configured, when a voltage is applied, to yield hydroxyl ions in the aqueous stream comprising the one or more precipitate complexes, wherein the hydroxyl ions interact with the one or more precipitate complexes forming heavier precipitate complexes.
Clause 8. The system of clause 7, wherein at least one of the titanium-containing anode and the titanium-containing cathode comprises a coating and the coating is a platinum coating, a mixed metal oxide (MMO) coating, or a boron-doped diamond coating.
Clause 9. The system of clause 7, further comprising a particulate filter capture system, configured to receive the aqueous stream comprising the heavier precipitate complexes, and to capture and remove the heavier precipitate complexes from the aqueous stream comprising the heavier precipitate complexes.
Clause 10. A system for removal of contaminants from a contaminated aqueous stream, the system comprising: a fixed-bed cross-flow subsystem configured to receive an aqueous stream contaminated with contaminants, and configured to hold an anhydrite quantity as a primary flocculant, the fixed-bed cross-flow subsystem configured to bring into contact the aqueous stream with the anhydrite quantity such that the anhydrite quantity interacts with negatively charged contaminants to form one or more precipitate complexes, which comprise a calcium cation and a negatively charged contaminant, in the aqueous stream; and an electro-coagulation and/or electro-oxidation subsystem configured to receive the aqueous stream comprising the one or more precipitate complexes, the electro-coagulation and/or electro-oxidation subsystem comprising aluminum-containing or titanium-containing electrodes that are configured, when electrified, to yield hydroxyl ions in the aqueous stream comprising the one or more precipitate complexes.
Clause 11. The system of clause 10, comprising an electro-coagulation subsystem, the electro-coagulation subsystem being configured to receive the aqueous stream comprising the one or more precipitate complexes and comprising an aluminum-containing anode and an aluminum-containing cathode that are configured, when electrified, to yield aluminum ions, hydroxyl ions, and aluminum hydroxide in the aqueous stream that interact with the one or more precipitate complexes in the aqueous stream to form heavier precipitate complexes in the aqueous stream.
Clause 12. The system of clause 11, wherein at least one of the aluminum-containing anode and the aluminum-containing cathode comprises aluminum only or aluminum and one or more selected from the following: iron, milled steel, copper, and zinc.
Clause 13. The system of clause 12, wherein at least one of the aluminum-containing anode and the aluminum-containing cathode are coated.
Clause 14. The system of clause 11, further comprising a particulate filter capture system configured to receive the aqueous stream comprising the heavier precipitate complexes, and to capture and remove the heavier precipitate complexes from the aqueous stream comprising the heavier precipitate complexes.
Clause 15. The system of clause 11, configured to cease any agitating and mixing of the aqueous stream so that a portion of the heavier precipitate complexes settle out of the aqueous stream and a portion of the heavier precipitate complexes remain suspended in the aqueous stream.
Clause 16. The system of clause 10, comprising an electro-oxidation subsystem, the electro-oxidation subsystem being configured to receive the aqueous stream comprising the one or more precipitate complexes and comprising a titanium-containing cathode and a titanium-containing anode that are configured, when a voltage is applied, to yield hydroxyl ions in the aqueous stream comprising the one or more precipitate complexes, wherein the hydroxyl ions interact with the one or more precipitate complexes forming heavier precipitate complexes.
Clause 17. The system of clause 16, wherein at least one of the titanium-containing anode and the titanium-containing cathode comprises a coating, and the coating is a platinum coating, a mixed metal oxide (MMO) coating, or a boron-doped diamond coating.
Clause 18. The system of clause 16, further comprising a particulate filter capture system, configured to receive the aqueous stream comprising the heavier precipitate complexes, and to capture and remove the heavier precipitate complexes from the aqueous stream comprising the heavier precipitate complexes.
Clause 19. A method for removing contaminants from a contaminated aqueous stream comprising: contacting an anhydrite quantity and the contaminated aqueous stream, resulting in the formation of one or more precipitate complexes, which comprise a calcium cation and a negatively charged contaminant, in the contaminated aqueous stream; and then generating hydroxyl ions in the contaminated aqueous stream comprising the one or more precipitate complexes by applying a voltage to aluminum-containing and/or titanium-containing electrodes.
Clause 20. The method of clause 19, wherein hydroxyl ions, aluminum ions, and aluminum hydroxide are generated by applying a voltage to aluminum-containing electrodes.
Clause 21. The method of clause 19, wherein hydroxyl ions are generated by applying a voltage to titanium-containing electrodes.
This application is a continuation-in-part of U.S. Non-Provisional patent application Ser. No. 18/136, 158 filed on Apr. 18, 2023, which is a continuation of U.S. Non-Provisional patent application Ser. No. 17/183,333 filed on Feb. 23, 2021, which claims the priority and benefit of U.S. Provisional Patent Application No. 63/041,099 filed on Jun. 18, 2020, the contents of each of which are herein incorporated by reference in their entirety.
Number | Date | Country | |
---|---|---|---|
63041099 | Jun 2020 | US |
Number | Date | Country | |
---|---|---|---|
Parent | 17183333 | Feb 2021 | US |
Child | 18136158 | US |
Number | Date | Country | |
---|---|---|---|
Parent | 18136158 | Apr 2023 | US |
Child | 18648139 | US |