System and method for removing hardly removable organic compounds from water

Abstract

To provide a system and a method for increasing a removal of PFAS and other persistent organic compound contaminants from water, particularly groundwater and drinking water, using submicron powdered activated carbon.SOLUTION: The method includes the steps of: 1) adding submicron powdered activated carbon (SPAC) 12 to treated water; 2) combining the SPAC with the treated water; 3) introducing the mixture of SPAC and the treated water into an adsorption reactor 20; 4) allowing the adsorption reactor to have a residence time of 30-60 minutes at an influent flow rate (Qi) to hold the mixture in the adsorption reactor long enough for the SPAC to adsorb contaminants in the treated water; and 5) transferring the mixture from the adsorption reactor to a high rate ceramic membrane filter unit 30, where the treated water is released as permeate in the high rate ceramic membrane filter unit and the SPAC is returned to the adsorption reactor as a holding solution.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to systems and methods for removing recalcitrant organic compounds including perfluoroalkyl and polyfluoroalkyl substances from water. In particular, the present invention relates to systems and methods for removing such contaminants from water using submicron powdered activated carbon in combination with ceramic membrane filtration. The present invention also relates to systems and methods for the concentration and removal of spent carbon.

Background Art

[0002] Per- and polyfluoroalkyl substances ("PFAS"), such as perfluorooctane sulfonic acid ("PFOS") and perfluorooctanoic acid ("PFOA"), including their precursors and those within the relevant scope, are compounds that are resistant to water and oil. They are artificial compounds used in a variety of industries, such as textiles, interior decorations, and fire-fighting foams. However, such compounds are bioaccumulative and known carcinogens, and removing them from water, particularly groundwater and drinking water, is an important environmental issue. Due to the strong fluorine-carbon bond, PFAS compounds are resistant to common treatment methods, including biological and chemical oxidation.

[0003] One of the more common methods for removing PFAS from water is a granular activated carbon ("GAC") or powdered activated carbon ("PAC") treatment system. As the name indicates, GAC uses granular activated carbon to remove various contaminants, including organic recalcitrant compounds such as PFAS. In a typical GAC system, a tank contains granular activated carbon, and the tank is sized to hold the flow of water to be treated for a time sufficient for the contaminants to react with the GAC. During the reaction, PFAS and other organic compounds adhere to the surface of the granular activated carbon, i.e., they are adsorbed by the granular activated carbon.

[0004] After use, the adsorption of organic contaminant compounds decreases until the system ceases to function. In other words, breakthrough is said to occur when the amount of contaminants adsorbed becomes less than the required treatment requirements. At that point, a typical system must be shut down, the granular activated carbon removed, and appropriately restored. Depending on the filtered contaminants, spent GAC, especially that which has adsorbed PFAS, must be withdrawn and incinerated. Further, due to the rapid breakthrough of GAC systems as well as the frequent need for GAC regeneration and treatment, the operating costs of GAC treatment are relatively high. A relatively large plant footprint is also required for GAC treatment systems.

[0005] The ability of GAC to adsorb contaminants and the typical breakthrough time are related to the average particle diameter (“MPD”) of the carbon. In conventional GAC systems, the MPD is approximately 1,600 microns. In systems using PAC, the MPD of the PAC is 45 microns or greater. In both GAC and PAC, the adsorption of PFAS is facilitated by the porous structure of the carbon, including macropores, micropores, and mesopores. The main adsorption mechanism depends on the size of the contaminant, and it has been found that macropores and mesopores are most important for the removal of PFAS. For both GAC and PAC, using those with a larger MPD can result in breakthrough occurring even though the surface area available for adsorption deep within the carbon particles due to restricted access to the internal pores. As shown, as the MPD increases, the breakthrough time decreases, and the carbon removal and disposal costs increase. Further, typical GAC systems do not effectively remove PFAS compounds with short chain lengths (i.e., 4, 6, and 7 carbon chain lengths).

[0006] Therefore, there is a need to increase the removal of PFAS and other recalcitrant organic compound contaminants from water, particularly groundwater and drinking water. There is also a need to increase the breakthrough time of typical GAC filtration systems and reduce the burden and cost of disposal of used materials. In the present invention, it has been found that the use of submicron powdered activated carbon ("SPAC") and its smaller particle size provide a larger surface area and an increased amount of mesopores, resulting in a lower usage rate and faster adsorption, and requiring a smaller volume. SPAC is also effective in removing short-chain PFAS that is ineffective with known treatment methods. The larger surface area and improved access to mesopores and macropores provided by SPAC and the present invention have been shown to increase PFAS adsorption by more than 500 times that of GAC on a per-carbon basis. Further, the present invention results in thickening or concentration of used SPAC, reducing disposal costs.

Summary of the Invention

[0007] Therefore, the present invention retains the advantages of known PFAS removal systems and methods and further provides novel features and advantages.

[0008] An object of the present invention is to use submicron powdered activated carbon ("SPAC") to remove recalcitrant organic compound contaminants from water, which contaminants include PFAS, 1,4-dioxane, BTEX, and many others.

[0009] Another object of the present invention is to provide an adsorption reactor, preferably a pressure adsorption reactor, to provide a residence time of the slurry of SPAC and water sufficient for the SPAC to adsorb contaminants from the influent water to be treated.

[0010] An additional object of the present invention is to use a ceramic membrane filter, preferably a high-speed cross-flow ceramic membrane filter, to separate the filtered water from the SPAC that has adsorbed contaminants and return a portion of the bulk liquid to the adsorption reactor.

[0011] A further object of the present invention is to increase the recovery rate and concentration of the SPAC and reduce the removal and disposal of used SPAC.

[0012] A further additional object of the present invention is to keep the SPAC in a closed-loop system when the treated water is separated from the SPAC using a high-intensity, high-speed cross-flow ceramic membrane filter and a feed-and-bleed type SPAC storage and recovery system.

[0013] Yet another object of the present invention is to wash away and clean the fouling of the membrane of the ceramic membrane filtration system while filtering the treated water from the SPAC and its adsorbed contaminants.

[0014] A still further object of the present invention is to use a ceramic membrane filter to hold the SPAC within the system, thereby enabling the SPAC to continue to remove soluble and difficult-to-remove organic compounds including PFAS.

[0015] Yet another object of the present invention is to reduce the backwash frequency and backwash waste using a high-speed cross-flow ceramic membrane filter.

[0016] Another further object of the present invention is to maximize the pollutant adsorption amount and reduce the used rate and disposal of the SPAC.

[0017] Another further another object of the present invention is to concentrate the used SPAC and reduce the frequency and amount of removal and / or disposal.

[0018] In accordance with the object of the present invention, a method for removing contaminants from water is provided. The process includes the following steps: adding submicron granular activated carbon (SPAC) to the influent liquid stream of the water to be treated; combining the SPAC with the water to be treated; introducing the mixture or slurry of the SPAC and water into an adsorption reactor for treatment; enabling the mixture to be held in the adsorption reactor for a residence time sufficient for the SPAC to adsorb the contaminants in the water; and transferring the mixture or slurry from the adsorption reactor to a high-speed ceramic membrane filter unit operating in cross-flow filtration using a recycle pump, wherein in the high-speed ceramic membrane filter unit, the treated water is discharged as the permeate and the SPAC slurry is returned to the adsorption reactor as the retentate. This method may also include the following steps: after the SPAC reaches breakthrough, removing the concentrate of the SPAC and the adsorbed contaminants from the ceramic membrane filter via a concentrate line; and adding fresh SPAC to the influent liquid stream of the water to continue the removal of contaminants. Further, in a preferred method, the SPAC and the adsorbed contaminants are thickened for removal by stopping the influent liquid stream to the adsorption reactor and continuing the operation of the recycle pump until the retentate is thickened and then removed via a concentrate line for disposal. The membrane of the ceramic membrane filter has a nominal pore size barrier of approximately 0.1 micron. In a preferred method, the flow rate of the influent liquid stream is 1Qi, and the mixture of the SPAC and the influent liquid is pumped from the adsorption reactor to the ceramic membrane filter at a flow rate 10 times that of the influent liquid (10Qi). Also, preferably, the permeate is discharged from the ceramic membrane filter at a flow rate 1 times that of the influent liquid stream (1Qi), and the retentate is returned to the adsorption reactor at a flow rate of Qr, where Qr is preferably 9 times the flow rate of the influent liquid (9Qi). Preferably, the SPAC has an average particle diameter of less than approximately 1 micron.

[0019] Also provided is a system for removing contaminants containing PFAS from water.This system includes: a pressurized adsorption reactor fluidly connected to an influent line; a SPAC supply line connected to the influent line for adding SPAC to the influent; an adsorption reactor that receives an influent stream of water to be treated and sub-micron powdered activated carbon (“SPAC”), the adsorption reactor having the ability to hold the influent and the SPAC slurry for a sufficient retention time such that contaminants to be removed are adsorbed by the SPAC in the slurry; a slurry effluent line connected to the discharge outlet of the adsorption reactor and a recycle pump in the slurry effluent line; a cross-flow ceramic membrane filter fluidly connected to the slurry effluent line of the adsorption reactor; a recycle pump that transfers the SPAC adsorbed with contaminants to the ceramic membrane filter unit at a high flow rate, the ceramic membrane filter unit separating the treated water from the SPAC adsorbed with contaminants as the permeate; a pressurized adsorption reactor fluidly connected to the influent line; a SPAC supply line connected to the influent line for adding SPAC to the influent; an adsorption reactor that receives an influent stream of water to be treated and sub-micron powdered activated carbon (“SPAC”), the adsorption reactor having the ability to hold the influent and the SPAC slurry for a sufficient retention time such that contaminants to be removed are adsorbed by the SPAC in the slurry; a slurry effluent line connected to the discharge outlet of the adsorption reactor and a recycle pump in the slurry effluent line; a cross-flow ceramic membrane filter fluidly connected to the slurry effluent line of the adsorption reactor; a recycle pump that transfers the SPAC adsorbed with contaminants to the ceramic membrane filter unit at a high flow rate, the ceramic membrane filter unit separating the treated water from the SPAC adsorbed with contaminants as the permeate; a permeate line fluidly connected to the ceramic membrane filter for removing the treated water as the permeate; a hold-up line fluidly connected to the ceramic membrane filter and the adsorption reactor for returning the SPAC slurry to the influent line; and a concentrate line for removing the SPAC after breakthrough.A preferred system uses a SPAC having an average particle size of less than approximately 1 micron, in which case the ceramic membrane filter has a nominal pore size barrier of approximately 0.1 micron. In one embodiment of this system, a SPAC supply system fluidly connected to the influent line may be included. Definition of the Inventor's Terms

[0020] The following terms that may be used in various claims and / or the specification of this patent application are intended to have their broadest meanings consistent with legal requirements:

[0021] As used herein, "influent" or "influent flow" (also referred to as Qi) refers to the liquid (water or wastewater) to be treated that is introduced into the contaminant removal system.

[0022] As used herein, "permeate" or "filtrate" shall refer to the treated fluid or fluid flow after treatment by the contaminant removal system and separation from the SPAC and the contaminants adsorbed thereon.

[0023] As used herein, "retentate" or "retentate flow (Qr)" refers to the bulk liquid or slurry containing the SPAC from which the "permeate" or "filtrate" has been removed.

[0024] As used herein, "SPAC" refers to submicron or ultrafine powdered activated carbon, preferably wood-based, and preferably having an average particle size of less than approximately 1 micron.

[0025] As used herein, "PFAS" refers to a wide range of per- or polyfluoroalkyl substances, including, for example, perfluorooctanesulfonic acid (PFOS) and perfluorooctanoic acid (PFOA), along with short-chain polyfluoroalkyl acids (PFAA) and their precursors. PFAS as used herein may also generally refer to other persistent organic compounds.

[0026] As used herein, "breakthrough" refers to a SPAC that can no longer adsorb contaminants at a level sufficient for the desired effective treatment.

[0027] Where alternative meanings are possible, the broadest meaning consistent with the understanding of those skilled in the art is intended in this specification or the claims. All words used in the claims are intended to be used in their grammatical, commercial, and ordinary customary usage in the English language.

Brief Description of the Drawings

[0028] The described and un-described objects, features, and advantages of the present invention (which may be used in the singular but do not exclude the plural) will become apparent from the description and drawings shown below. In that case, like reference numerals represent like elements in the various drawings.

[0029]

Figure 1

[0030]

Figure 2

Modes for Carrying Out the Invention

[0031] What is described below is a description of what is currently considered to be the preferred embodiments or best representative examples of the claimed invention. Future and current alternatives and embodiments to these embodiments and preferred embodiments are contemplated. Any alternatives or variations that make non-substantial changes in function, purpose, structure, or result are intended to be covered by the claims of this patent application.

[0032] A preferred PFAS removal system and method of the present invention are shown in its basic form in Figure 1. The system includes an influent line 11, which introduces an influent flow (Qi) of water to be treated into the system. The SPAC 12 is typically added to the influent (Qi) via a SPAC supply line 13 using a carbon supply system or other means as described below. An optional mixer 14 may be included to facilitate mixing of the influent water and the SPAC 12 to form a large volume of liquid or slurry to be treated. The slurry of the SPAC 12 and the influent is then transported by a supply pump 16 through a slurry supply line 15 to an adsorption reactor 20. The supply pump 16 is sized to transport the influent flow and the SPAC slurry at a design flow rate (Qi). The supply pump 16 transports the influent at Qi together with the SPAC slurry through the slurry supply line 15 to the adsorption reactor 20.

[0033] In a preferred embodiment, the system and method use a wood-based SPAC 12 having an average particle diameter (MPD) of less than about 1 micron. The use of submicron powder particles provides a larger external surface area per unit mass and an increase in the amount of mesopores contained in the particles and access thereto, enabling faster and more effective adsorption of contaminants. The use of submicron powder particles also allows for greater contact with contaminants and a lower used rate. As a result, it has been found to be effective, inter alia, in the removal of short-chain PFAS.

[0034] Since the current demand for SPAC12 is relatively low, it is not currently considered to be a material with abundant inventory and easy availability. However, it can be easily manufactured from GAC and / or PAC, and for GAC and / or PAC, as those skilled in the art understand, many manufacturers are known. Some well-known GAC / PAC manufacturers include Asbury Carbons, Nalco Waters, and Calgon Carbons. These and other GAC / PAC manufacturers also have a grinding process available for manufacturing SPAC. For example, Asbury Carbons owns an easily available grinding process that can produce SPAC from GAC or PAC with a very short lead time. Thus, the source of the SPAC of the present invention is easily available to those skilled in the art.

[0035] In a preferred embodiment, the SPAC12 will be manufactured as a liquid slurry for ease of handling and end use and shipped to the treatment site. For example, it has been found desirable to use a 10% slurry of 1 micron SPAC and water (100 grams of carbon / liter) in the present invention. As described below, the initial SPAC12 slurry is further diluted to the working concentration by the influent water to be treated and transferred to the adsorption reactor 20. In a preferred embodiment where the SPAC slurry is 100 grams of carbon / liter, the slurry is diluted to approximately 0.5 - 2 grams of carbon / liter in the adsorption reactor 20. These concentrations are merely illustrative and not limiting.

[0036] The adsorption reactor 20 is a container in which the water to be treated is in contact with the SPAC12 or SPAC slurry for a sufficient time so that PFAS can be adsorbed by the SPAC12 within the container. The adsorption tank 20 serves as a reaction chamber for the SPAC12 and the water to be treated such that PFAS and other contaminants are adsorbed by the SPAC12 within the adsorption tank 20. The adsorption reactor 20 provides the desired and / or designed residence time of the SPAC / influent slurry so that PFAS and other contaminants can be sufficiently adsorbed by the SPAC12.

[0037] In a preferred embodiment, the adsorption reactor 20 is sized to accommodate at least 10 times (10Qi) the influent flow rate as described below. It will also be understood by those skilled in the art that the adsorption reactor 20 is sized to provide the desired residence time to facilitate the adsorption of PFAS and other contaminants by the SPAC. The larger the adsorption reactor 20 at a given flow rate, the longer the residence time it can provide. In a preferred embodiment, a residence time of 30 to 60 minutes at the influent flow rate (Qi) has been determined to be sufficient for the reaction between the SPAC and PFAS in the influent having a typical influent of 100 gallons (379 liters) / minute (Qi). Other residence times may be sufficient depending on the desired treatment parameters and influent flow. Thus, in a system where Qi is 100 gallons (379 liters) / minute and the residence time in the adsorption reactor 20 is 1 hour, the adsorption reactor 20 must accommodate at least 6,000 gallons (22.7 kiloliters).

[0038] The preferred adsorption reactor 20 of the present invention is a pressurized tank closed from the atmosphere. A baffle 21 (see FIG. 2) may be provided within the adsorption reactor 20 to prevent short-circuiting. It will be understood by those skilled in the art that a non-pressurized tank may be used. However, such a tank would have to be relatively tall and / or would require a substantially greater energy requirement.

[0039] The SPAC adsorbs PFAS and other contaminants within the adsorption reactor 20. After sufficient residence time within the adsorption reactor 20, the slurry in which the SPAC has reacted with the bulk liquid is then transported via the slurry effluent line 22 to the ceramic membrane filter unit 30 using the recycle pump 26. In a preferred embodiment, the recycle pump 26 is sized to transport ten times (10Qi) the influent flow to the ceramic membrane filter 30 through the slurry effluent line 22.

[0040] The ceramic membrane filter unit 30 provides an important unique function of the present invention. First, the ceramic membrane filter 30 separates the SPAC and the adsorbed contaminants from the treated liquid, which is discharged as clean permeate via the permeate line 32. The ceramic membrane filter also returns the SPAC slurry back to the adsorption reactor 20 for further treatment of the influent, which reduces the consumption of the SPAC. Third, the ceramic membrane filter 30 also serves to concentrate and thicken the SPAC 12 after breakthrough or exhaustion, facilitating the disposal of the SPAC 12 without the need for complex additional equipment.

[0041] In a preferred embodiment, the ceramic membrane filter 30 has a nominal pore size barrier of 0.1 micron. This small pore size results in high permeability and reduced pressure loss when passing through each membrane of the ceramic membrane filter 30. As will be understood by those skilled in the art, suitable ceramic membrane filters 30 are available from a number of manufacturers, including Aqua-Aerobic Systems, Inc. (see www.aqua-aerobic.com).

[0042] In a preferred embodiment, the ceramic membrane filter 30 is operated in a cross-flow filtration mode. Preferably, the recycle pump 26 sends the SPAC / liquid slurry via the slurry effluent line 22 to the ceramic membrane filter 30 at 10 times the influent flow rate, i.e., 10Qi. The membrane of the ceramic membrane filter 30 separates the treated liquid from the slurry of SPAC and liquid. The treated water is preferably discharged as permeate via the permeate line 32 at a flow rate approximately the same as the initial influent flow rate Qi. The SPAC and bulk liquid not discharged as permeate are discharged from the ceramic membrane filter 30 as the retentate (Qr) via the retentate line 36, preferably at 9 times the initial flow rate, i.e., 9Qi. The retentate is returned either upstream of the adsorption reactor 20 to the slurry supply line 15 or directly to the adsorption reactor 20. In particular, returning the retentate slurry containing SPAC increases the concentration of SPAC 12 in the adsorption reactor 20, thereby reducing the amount of unused SPAC 12 that needs to be added to the system. This also promotes PFAS adsorption enhanced by SPAC 12. The ceramic membrane filter 30 also comprises a concentrate outlet 37, which is in fluid connection with a concentrate extraction line 38 to remove the spent SPAC 12 after breakthrough.

[0043] Importantly, pumping the high-speed slurry at 10Qi into the ceramic membrane filter 30 while removing only 1Qi as the permeate flushes the dirt on the membrane 31 inside the ceramic membrane filter 30. This results in a clean membrane 31 and the maintenance of the high permeability of the membrane 31. This also reduces the frequency of the need for backwashing. Passing through the ceramic membrane filter 30 at a high speed further reduces the opportunity for biological growth, which helps maintain the filtration efficiency and reduces the need for frequent backwashing or chemical adjustment. In a preferred embodiment, when 10Q is sent to the ceramic membrane filter 30 by the pump 26, 1Qi is removed as the permeate via the permeate line 32. As a result, 9Q (9Qr) is returned to the adsorption reactor 20 via the retention line 36 as the retention liquid. These flow rates are exemplary and / or preferred, and it will be understood by those skilled in the art that other flow rates may be used in consistency with the present invention.

[0044] What has been described above is the basic system and method for removing PFAS using the SPAC, adsorption reactor 20, and ceramic membrane filter 30 of the present invention. Further, a more comprehensive system of the present invention is described herein by referring to FIG. 2. The system and method for thickening and removing the SPAC are also described by referring to FIG. 2. However, thickening and removing are also part of the basic system shown in FIG. 1.

[0045] As shown in FIG. 2, the SPAC supply system 40 is provided as an alternative to the direct supply to the influent line 11 of the SPAC 12 and the use of an optional mixer 14. The SPAC supply system 40 includes a tank 41 and a mixer 42, and the mixer 42 mixes the SPAC slurry for use in this system. Specifically, in a preferred embodiment, a 10% SPAC slurry (e.g., 100 grams of carbon per liter) is added to the tank 41 and mixed by the mixer 42. The SPAC slurry is sent from the tank 41 through the SPAC supply line 13 to the influent line 11 using the SPAC supply pump 43. The mixture or slurry is then sent to the adsorption reactor 20 via the slurry supply line 15 using the supply pump 16, preferably at a flow rate of Qi. In a preferred embodiment, the 10% SPAC concentration is diluted to approximately 0.5 to 2 grams of carbon per liter in the adsorption reactor 20. As shown in the schematic diagram, the preferred adsorption reactor 20 is provided with one or more baffles 21 to help prevent short-circuiting. After a sufficient residence time for the SPAC 12 to adsorb the contaminants, the bulk liquid is sent to the ceramic membrane filter 30 via the slurry effluent line 22 and the recycle pump 26. Again, the preferred pump throughput is to pump at 10Qi into the ceramic membrane filter 30 and the recycle pump 26 of corresponding size.

[0046] Similar to the embodiment of FIG. 1, the ceramic membrane filter 30 separates the permeate from the SPAC 12 and the contaminants adsorbed thereon. The permeate is removed from the ceramic membrane filter 30 via the permeate line 32 at a flow rate of 1Qi. However, in this embodiment, a permeate tank 50 fluidly connected to the permeate line 32 is provided. The permeate from the ceramic membrane filter 30 is sent to the permeate tank 50 and removed as treated effluent via the permeate drain line 52, or may be stored for use in backwashing as described previously.

[0047] In the embodiment of FIG. 2, the backflow line 62 is fluidly connected to the permeate tank 50 for extracting the permeate for use in backwashing. A backwashing pump 61 is also provided in the backflow line 62. The backflow line 62 is fluidly connected to the backwashing tank 70. The backwashing tank 70 is then fluidly connected to the permeate line 32 of the ceramic filter membrane unit 30. When backwashing is desirable or required, the permeate is sent from the permeate tank 50 to the backwashing tank 70 by the backwashing pump 61. The permeate from the backwashing tank 70 flows from the backwashing line 62 into the permeate line 32, and the permeate line 32 is fluidly connected to the ceramic membrane filter 30. This backwashes the membrane 31 by reversing the flow through the ceramic membrane filter 30, as described below.

[0048] An optional chemical tank 60 may also be provided. The chemical tank 60 is fluidly connected to a chemical supply line 65, and the chemical supply line 65 includes a chemical supply pump 64. The chemical supply line 65 is also fluidly connected to the backflow line 62 in the following order. The chemical tank 60 holds a solution of chemicals that may be used when backwashing the membrane of the ceramic membrane filter 30. Such chemicals may include NaOCl and citric acid to facilitate cleaning the membrane. As will be understood by those skilled in the art, other chemicals may be used. Thus, when chemicals are desired for use in backwashing, the chemical solution is pumped by the chemical supply pump 64 through the chemical supply line 65 and into the permeate flow in the backflow line 62.

[0049] Furthermore, an optional air supplier 80 may be provided. The air supplier 80 is fluidly connected to an air supply line 81. The air supply line 81 is fluidly connected to a backwash tank 70 and a holding liquid line 36. The air supplier 80 may be provided with a specific stem for use in backwashing. When backwashing is desired, the air supplier 80 pressurizes the backwash tank 70 via the air supply line 81 until a pressure set value is reached, and then the air supply valve 83 closes. Then, after that, the backwash valve 63 is opened, and the pressurized permeate is discharged from the backwash tank 70 through the membrane filter 30, helping to clean the membrane 31.

[0050] An important aspect of the present invention is the thickening, dewatering, and removal of spent SPAC 12. Preferred systems and methods are described by referring to FIG. 2. For the removal of PFAS and other organic contaminants, the influent stream at a flow rate of Qi is introduced in the influent line 11 (for example, 100 gallons (379 liters) / minute). Using the SPAC supply pump 43, a SPAC solution (for example, 100 grams of carbon / liter) is sent from the SPAC tank 41 through the SPAC supply line 13 through the opened SPAC supply valve 18. The slurry of the influent and SPAC is sent to the adsorption tank 20 via the slurry supply line 15 by the supply pump 16. This slurry is fed into the adsorption reactor 20 at a flow rate of Qi. The slurry of this SPAC 12 and the influent is retained in the adsorption reactor 20 for a desired residence time, whereby PFAS and other contaminants are adsorbed into the SPAC 12. The concentration of the SPAC 12 slurry in the adsorption reactor 20 may typically be 0.5 to 2 grams of carbon / liter.

[0051] The slurry of SPAC adsorbed with contaminants and a large amount of liquid is transferred from the adsorption reactor 20 to the ceramic membrane filter 30 for filtration. Specifically, the slurry is fed into the ceramic membrane filter 30 through the slurry effluent line 22, through the opened recycle valve 27, using the recycle pump 26. As discussed previously, the recycle pump 26 is sized to feed a flow rate 10 times that of the influent flow (10Qi) into the ceramic membrane filter 30. The membrane of the ceramic membrane filter 30 separates the permeate from the SPAC / influent slurry.

[0052] The permeate is sent out from the ceramic membrane filter 30 via the permeate line 32, put into the permeate tank 50, where the permeate may be removed via the permeate removal line 52. The retentate is sent out from the ceramic membrane filter 30 through the retentate line 36 and the opened retentate valve 34 and returned to the adsorption reactor 20. The retentate is returned to the adsorption reactor 20 at a flow rate of Qr, which is 9 times the influent flow rate, i.e., 9Qi. During typical filtration operation, the backwash pump 61 is stopped, the backwash valve 66 is closed, and also the air supply valves 83 and 84 are closed.

[0053] As shown, an important aspect of the present invention is the dehydration, thickening, and removal of the used SPAC 12 (and the contaminants adsorbed thereon). When the SPAC reaches breakthrough, the influent flow to the system is stopped, the supply pump 16 is stopped, and also the SPAC supply valve 18 is closed. The recycle pump 26 continues to operate and sends out the slurry from the adsorption reactor 20 at a flow rate of 10Qi. During the dehydration process, the ceramic membrane filter 30 continues to send out the permeate at a flow rate of 1Qi, and the retentate continues to be returned to the adsorption reactor 20 at a flow rate of 9Qi. After a certain time based on the size (retention time) of the adsorption reactor 20, the used SPAC is dehydrated and concentrated to a sufficient extent to be removed for disposal. The desired concentration of the SPAC 12 slurry when removed is, for example, 10 grams of carbon per liter. If the concentration is too high, it is difficult to remove from the system.

[0054] After the inflow liquid flow Qi to the adsorption reactor 20 is stopped, when concentrating the holding liquid for removal, it should also be noted that, in fact, the permeate is typically not removed at a flow rate of 1Q sufficient for the entire process. Instead, the permeate is reduced to less than 1Q at a constant ratio so that the holding liquid is not thickened or concentrated too much for effective removal from this system.

[0055] When backwashing of the membrane of the ceramic membrane filter 30 is required, the above-mentioned inflow liquid flow for dehydration is stopped. The recycle pump 26 is closed and the drain valve 59 is opened. The permeate valve 33 is closed and the backwashing valves 63 and 66 are opened. The backwashing pump 61 is started and the permeate is pumped out from the permeate tank 50. The permeate flows through the backwashing line 62 to the backwashing tank 70. If desired, chemicals may be added to the permeate through the chemical line 65 and through the backwashing line 62. The permeate or chemically enhanced permeate flows into the permeate line 32 from the backwashing line 62 in a direction opposite to the permeate. The backwashed permeate passes through the ceramic membrane filter 30 in a direction opposite to filtration. The backwashing liquid flows back to the slurry effluent line 22 and is removed through the opened drain valve 59.

[0056] The foregoing description is not intended to limit the meaning of the words used therein or the scope of the following claims that define the invention. More precisely, it is contemplated that there may be structural, functional or result modifications that are not substantial changes, and that all such non-substantial changes in the claimed invention are intended to be covered by the claims. Accordingly, although preferred embodiments of the invention have been illustrated and described, it will be understood that changes and modifications can be made without departing from the claimed invention. Further, although the term "claimed invention" or "the invention" may be used herein in the singular, it will be understood that there are multiple inventions described and claimed.

[0057] The various features of the invention are set forth in the following claims.

Claims

1. A method for removing PFAS from water, comprising the following steps: 1) adding submicron powdered activated carbon (SPAC) to the influent liquid stream of the water to be treated; 2) combining said SPAC with said water to be treated; 3) introducing the mixture of said SPAC and water into an adsorption reactor for treatment; 4) having a residence time of 30 to 60 minutes in said adsorption reactor to allow said mixture to be held in said adsorption reactor for a time sufficient for said SPAC to adsorb PFAS in said water, with a SPAC concentration of 0.5 to 2 grams of carbon per liter; 5) transferring said mixture from said adsorption reactor to a high-speed ceramic membrane filter unit operating by cross-flow filtration using a recycle pump, wherein in said high-speed ceramic membrane filter unit the treated water is discharged as permeate, and said SPAC is returned to said adsorption reactor as a retained liquid, and the flow rate of the influent liquid stream of said water through the slurry supply line is 1Q, and the mixture of said SPAC and the influent liquid is sent by said recycle pump from said adsorption reactor through the slurry effluent line to said high-speed ceramic membrane filter unit at a flow rate 10 times that of the influent liquid (10Q); and 6) periodically backwashing said high-speed ceramic membrane filter unit using a backwashing line fluidly connected to a backwashing pump and a permeate line; comprising, wherein said step of backwashing comprises the addition of chemicals from a chemical tank and a chemical supply pump fluidly connected to said backwashing line as well as the addition of air from an air supply connected to an air supply line fluidly connected to said backwashing tank and a retained liquid line, wherein said air supply pressurizes said backwashing tank by connection to said air supply line and the backwashing valve is opened, the addition of air comprising, a method.

2. The method according to claim 1, comprising the following steps: 1) after said SPAC reaches breakthrough, removing the concentrate of said SPAC and adsorbed PFAS from said high-speed ceramic membrane filter unit via a concentrate line; and 2) adding fresh SPAC to the influent liquid stream of said water to continue the removal of PFAS.

3. The method according to claim 1, wherein the permeate is discharged from the high-speed ceramic membrane filter unit at a flow rate 1 time that of the influent liquid flow, and the retention liquid is returned to the adsorption reactor at a flow rate 9 times that of the influent liquid flow (9Q).

4. The method according to claim 3, wherein the SPAC has an average particle diameter of less than 0.1 micron.

5. The method according to claim 2, wherein the SPAC and the adsorbed PFAS are thickened by stopping the influent liquid flow to the adsorption reactor and continuing the operation of the recycle pump until the retention liquid is thickened and then removed via the concentrate line for disposal.

6. The method according to claim 4, wherein the high-speed ceramic membrane filter unit has a nominal pore size of 0.1 micron.

7. A system for removing PFAS from water, the system comprising: 1) A pressurized adsorption reactor fluidly connected to an influent line, a SPAC supply line connected to the influent line for adding SPAC to the influent, and an adsorption reactor for receiving an influent liquid flow of water to be treated and submicron powdered activated carbon (SPAC), wherein the adsorption reactor retains the influent and the SPAC slurry for a sufficient residence time such that the PFAS to be removed is adsorbed by the SPAC in the slurry, and the adsorption reactor is retained in the adsorption reactor for 30 to 60 minutes, and the SPAC has a concentration of 0.5 to 2 grams of carbon / liter; 2) A slurry effluent line connected to the discharge port of the adsorption reactor and a recycle pump in the slurry effluent line; 3) A cross-flow ceramic membrane filter unit fluidly connected to the slurry effluent line of the adsorption reactor, wherein the recycle pump transfers the SPA that has adsorbed PFAS to the cross-flow ceramic membrane filter unit at a high flow rate, and the cross-flow ceramic membrane filter unit separates the treated water from the SPA that has adsorbed PFAS as a permeate, the flow rate of the influent flow of the water through the slurry supply line being 1Q, and the mixture of the SPA and the influent being sent by the recycle pump from the adsorption reactor through the slurry effluent line to the cross-flow ceramic membrane filter unit at a flow rate 10 times that of the influent (10Q); the cross-flow ceramic membrane filter unit; 4) A permeate line fluidly connected to the cross-flow ceramic membrane filter unit for removing the treated water as a permeate; 5) A holding liquid line fluidly connected to the cross-flow ceramic membrane filter unit and the adsorption reactor for returning the SPA slurry from which the permeate has been removed to the influent line; 6) A concentrate line for removing SPA after breakthrough; 7) A backwash pump, a backwash tank, and a backwash line fluidly connected to the permeate line for backwashing the cross-flow ceramic membrane filter unit; and 8) A chemical tank and a chemical supply pump fluidly connected to the backwash line; and an air supply device fluidly connected to an air supply line fluidly connected to the backwash tank and the holding liquid line, the air supply device pressurizing the backwash tank by connection to the air supply line and opening a backwash valve.

8. The system according to claim 7, wherein the SPA has an average particle size of less than 0.1 micron.

9. The system according to claim 8, wherein the cross-flow ceramic membrane filter unit has a nominal pore size of 0.1 micron.

10. The system according to claim 9, comprising a SPA supply system fluidly connected to the influent line.

11. The system according to claim 7, wherein the PFAS to be removed includes perfluoroalkyl and polyfluoroalkyl substances.

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