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US-20260125290-A1 - Methods and Systems of Nitrate Removal in Aqueous Systems for Improved PFAS Destruction

US20260125290A1US 20260125290 A1US20260125290 A1US 20260125290A1US-20260125290-A1

Abstract

Methods and systems of PFAS destruction in water containing nitrate. The methods and systems include filtering water containing PFAS and nitrate through a membrane selective for PFAS to obtain a membrane reject containing PFAS and nitrate and a filtrate containing nitrate, forming a treatment solution using the membrane reject including diluting the membrane reject and combining the membrane reject with a photosensitizer, a sulfite salt, and a sufficient amount of base such that the treatment solution has a pH of about 10 or more, and irradiating the treatment solution with UV light in a photoreactor to destroy a portion of the PFAS. Before dilution, a concentration of PFAS in the membrane reject may be between about 3 times and about 20 times greater than before the filtering step. Dilution of the membrane reject may include between about a 3 and about a 20 times dilution.

Inventors

  • Zekun Liu
  • Terrance P. Smith
  • Adam Michael Hilbrands
  • Nathan Ernst Kamm
  • Joseph Reuel Levine Tirado
  • Sonja Elise Moons
  • John Wilfrid Brockgreitens
  • Andrew Thomas Healy

Assignees

  • CLAROS TECHNOLOGIES INC.

Dates

Publication Date
20260507
Application Date
20251229

Claims (20)

  1. 1 . A system for the destruction of PFAS in water, the system comprising: a nitrate removal system configured to remove nitrate from water containing PFAS and nitrate, the nitrate removal system comprising: a membrane selective for PFAS which produces a membrane reject; a source of water configured to dilute the membrane reject; a photoreactor comprising: a reactor vessel; an influent port configured to direct the membrane reject into the reactor vessel; and a source of ultraviolet light source positioned to direct light onto the diluted membrane reject within the reactor vessel; wherein the system is configured to mix water with the membrane reject before entry into the photoreactor or within the photoreactor.
  2. 2 . The system of claim 1 further comprising a tank configured to receive the membrane reject, to receive water from the water source, to mix the membrane reject with the water, and to supply the diluted membrane reject to the photoreactor.
  3. 3 . The system of claim 1 further comprising a pipe configured to convey membrane reject from the nitrate removal system to the photoreactor, wherein the water supply is configured to provide water to the pipe, and wherein the system is configured to dilute the membrane reject by mixing with water within the pipe.
  4. 4 . The system of claim 1 wherein the supply of water is configured to supply water to the photoreactor to dilute the membrane reject by mixing with water within the photoreactor.
  5. 5 . The system of claim 1 wherein the membrane selective for PFAS comprises a membrane having a MWCO of between about 150 and about 300 Da.
  6. 6 . The system of claim 1 wherein the membrane is negatively charged.
  7. 7 . The system of claim 1 where the membrane is in a cross flow configuration.
  8. 8 . The system of claim 1 wherein the UV light source emits at a peak wavelength between 185 and 254 nm.
  9. 9 . The system of claim 1 wherein the UV light source emits at a peak wavelength of 222 nm.
  10. 10 . The system of claim 1 wherein the UV light source is a low pressure mercury lamp, medium pressure mercury lamp, or excimer lamp.
  11. 11 . A continuous system for PFAS destruction comprising: a continuous photoreactor comprising: a reactor vessel configured to receive water containing PFAS; and a UV light source configured to direct UV light onto water containing PFAS within the reactor vessel; a selective membrane in fluid communication with, and downstream of, the continuous photoreactor, the selective membrane selective for greater than 99% of PFAS present in the water containing PFAS after photolysis in the photoreactor; and means for fluid transport of membrane reject formed by the selective membrane to a location upstream of the continuous photoreactor for further transport into the continuous photoreactor or directly into the continuous photoreactor.
  12. 12 . The system of claim 11 further comprising a tank configured to receive the membrane reject, to receive water from the water source, to mix the membrane reject with the water, and to supply the diluted membrane reject to the photoreactor.
  13. 13 . The system of claim 11 further comprising a pipe configured to convey membrane reject from the nitrate removal system to the photoreactor, wherein the water supply is configured to provide water to the pipe, and wherein the system is configured to dilute the membrane reject by mixing with water within the pipe.
  14. 14 . The system of claim 11 wherein the supply of water is configured to supply water to the photoreactor to dilute the membrane reject by mixing with water within the photoreactor.
  15. 15 . The system of claim 11 wherein the membrane selective for PFAS comprises a membrane having a MWCO of between about 150 and about 300 Da.
  16. 16 . The system of claim 11 wherein the UV light source emits at a peak wavelength between 185 and 254 nm.
  17. 17 . The system of claim 11 wherein the UV light source emits at a peak wavelength of 222 nm.
  18. 18 . The system of claim 11 wherein the UV light source is a low pressure mercury lamp, medium pressure mercury lamp, or excimer lamp.
  19. 19 . The system of claim 11 wherein the membrane is negatively charged.
  20. 20 . The system of claim 11 where the membrane is in a cross flow configuration.

Description

CROSS REFERENCE TO RELATED APPLICATIONS This application is a continuation of U.S. application Ser. No. 19/015,905 filed Jan. 10, 2025 titled “METHODS AND SYSTEMS OF NITRATE REMOVAL IN AQUEOUS SYSTEMS FOR IMPROVED PFAS DESTRUCTION,” which is a continuation-in-part of U.S. application Ser. No. 18/771,292 filed Jul. 12, 2024 titled “Methods and Systems of Nitrate Removal in Aqueous Systems for Improved PFAS Destruction,” which claims priority to U.S. Provisional Application No. 63/513,782 filed Jul. 14, 2023 titled “PROCESSES FOR EFFICIENT PHOTOCHEMICAL DESTRUCTION OF PFAS FROM WASTE STREAMS”; U.S. Provisional Application No. 63/591,040 filed Oct. 17, 2023 titled “SYSTEMS AND METHODS OF PFAS DESTRUCTION”; and U.S. Provisional Application No. 63/635,938 filed Apr. 18, 2024 titled “PRETREATMENT OF PFAS CONTAMINATED WATER PRIOR TO PHOTOREDUCTION,” disclosures of all of which are hereby incorporated by reference. BACKGROUND Per- and polyfluoroalkyl substances (PFASs) are a class of synthetically prepared compounds that have been used for decades in numerous consumer and industrial applications. PFASs have some unique surface properties and can also be both hydrophobic and oleophobic. As a result, PFASs are used as coating aids, lubricants, foaming aids and various surface treatments. They have proven especially useful as flame retardants in the form of aqueous film-forming foams (AFFF). Also, some PFASs are known to bio-accumulate in plants and animals. There is a growing body of evidence that exposure to PFASs can also cause a variety of health problems. Owing to these concerns, various world-wide regulatory agencies have started to establish strict limits to the presence of PFAS in food and water. PFASs are a class of chemicals that contain perfluoroalkyl or polyfluoroalkyl groups. The definition and classification of PFASs has changed over time. PFASs are fluorinated substances that contain at least one fully fluorinated methyl or methylene carbon atom (without any H/Cl/Br/I atom attached to it), i.e. with a few noted exceptions, any chemical with at least a perfluorinated methyl group (—CF3) or a perfluorinated methylene group (—CF2-) is a PFAS. Some of the most important examples of PFASs include the perfluorosulfonic acids (PFSAs), such as perfluorooctanesulfonic acid (PFOS) and the perfluorocarboxylic acids (PFCAs) like perfluorooctanecarboxylic acid (PFOA). Fluorotelomers are fluorocarbon-based oligomers, or telomers, synthesized by telomerization. Some fluorotelomers and fluorotelomer-based compounds are a source of environmentally persistent perfluorinated carboxylic acids such as PFOA. The persistence of PFASs, the health issues, and the regulatory landscape have prompted a great deal of research effort to reduce their presence in the environment. Much of the early work was focused on capture, for example from drinking water. However, more recently, there has been a stronger effort on the destruction of these materials. One of the attributes of PFASs is their resistance towards breaking down in the environment. PFASs are not easily metabolized by organisms, and do not decompose by exposure to visible light or longer wavelength UV irradiation typically found under terrestrial conditions. Some of the methods that have proven effective for breaking down PFASs are supercritical water oxidation (SCWO) and treatment of PFASs in an aprotic polar solvent. SCWO works by heating water to 374° C. under high pressure (over 3000 psi). Therefore, SCWO is quite energy intensive and can suffer from clogging issues. The use of SCWO often requires wastes containing high solids because it relies on the heat capacity (btu) generated from this waste to make the process cost effective. An advantage of SCWO is its short residence time to be effective, on the order of 30 seconds to minutes. The use of basic aprotic media to destroy PFASs suffers from the fact that most waste streams are water-based and therefore not readily transferred to aprotic media that requires minimum water levels. In other cases, generating subcritical water conditions in alkaline environments has also been shown to destroy PFAS compounds. This process, referred to as hydrothermal alkaline treatment (HALT), operates at temperatures around 350° C. and pressures around 2400 psi. Other processes for destroying PFASs involve the use of electrochemistry. Electrochemical destruction can destroy long chain PFASs (for example, PFOS and PFOA), however, shorter chain PFASs are less prone to destruction. It is speculated that the longer chained PFASs readily assemble on the electrodes and therefore can be readily oxidized or reduced. Other work has shown that sonication can result in PFAS destruction. Improved processes are needed to efficiently and effectively destroy PFAS, particularly PFAS in water. SUMMARY Various embodiments include systems and methods for nitrate reduction for improved PFAS destruction. In some embodiments, the methods and systems include f