Method for removing per- and polyfluoroalkyl substances (PFAS) from an aqueous stream, device, and system for removing said pfas

Abstract

The present invention relates to a method for removing per- and polyfluoroalkyl substances (PFAS) from an aqueous stream, a device for removing per- and polyfluoroalkyl substances (PFAS) from an aqueous stream, a system for removing per- and polyfluoroalkyl substances (PFAS) from an aqueous stream, a computing for removing per- and polyfluoroalkyl substances (PFAS) from an aqueous stream, and an aqueous stream obtainable by said method.

Description

[0001] METHOD FOR REMOVING PER- AND POLYFLUOROALKYL SUBSTANCES (PFAS) FROM AN AQUEOUS STREAM, DEVICE, AND SYSTEM FOR REMOVING SAID PFAS

[0002] The present invention relates to a method for removing per- and polyfluoroalkyl substances (PFAS) from an aqueous stream, a device for removing per- and polyfluoroalkyl substances (PFAS) from an aqueous stream, a system for removing per- and polyfluoroalkyl substances (PFAS) from an aqueous stream, a computing for removing per- and polyfluoroalkyl substances (PFAS) from an aqueous stream, and an aqueous stream obtainable by said method.

[0003] Per- and Polyfluorinated substances (PFAS) are a group of man-made chemicals that persist in the environment. These chemicals have been used for decades in consumer products to make them non-stick and water resistant. They are also found in firefighting foams and are applied in many industrial processes. Unfortunately, the characteristics that make them useful are the reason they persist in the environment and can bioaccumulate, or build up, in our bodies and the bodies of animals.

[0004] PFAS also dissolve in water, and combined with their chemical properties mean traditional (drinking) water treatment technologies are not able to remove them.

[0005] Conventional techniques to remove PFAS from drinking water, especially perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS), include activated carbon adsorption, ion exchange resins, and high-pressure and / or reversed osmosis membranes. Filters containing activated carbon and / or reverse osmosis membranes have been shown to remove PFAS from water supplies. Unfortunately, said techniques require severe maintenance to work properly. Water treatment systems that are not properly maintained will lose their effectiveness over time.

[0006] Furthermore, said techniques works well on longer-chain PFAS like PFOA and PFOS, but shorter chain PFAS like perfluorobutanesulfonic acid (PFBS) and perfluorobutyrate (PFBA) do not adsorb as well.

[0007] Therefore, there is a long felt need for an efficient and effective method to remove PFAS from water, in particular when water needs to be treated at a large scale such as contaminated (waste) water.

[0008] The present invention aims at obviating or at least reducing the aforementioned problems and to enable efficient and effective removal of per- and polyfluoroalkyl substances (PFAS) from an aqueous stream.

[0009] This objective is achieved with the method for removing per- and polyfluoroalkyl substances (PFAS) from an aqueous stream, comprising the steps of:

[0010] - providing an aqueous stream comprising PFAS;

[0011] - moving the aqueous stream through one or more subsequent treatment stages;

[0012] - mixing the aqueous stream in each treatment stage; - providing, in each treatment stage, an additive to the stream;

[0013] - reacting the PFAS with the additive to form a precipitate;

[0014] - separating, in each treatment stage, the aqueous stream and the precipitate; and

[0015] - measuring at least the quantity of PFAS in the aqueous stream at an outlet of at least one of the one or more subsequent treatment stages.

[0016] The method may start with the step of providing an aqueous stream comprising PFAS and followed by the step of moving the aqueous stream through one or more subsequent treatment stages. The aqueous stream is mixed in each treatment stage by the step of mixing the aqueous stream in each treatment stage.

[0017] It is noted that the step of mixing may be performed passively and / or actively, wherein passive mixing occurs when two or more streams are combined or when one of the streams provides a flow within a treatment stage.

[0018] It is also noted that throughout this application the precipitate may comprise PFAS and / or PFAS residues, wherein PFAS residues refer to (smaller) molecules originating from PFAS after reacting with the additive.

[0019] In addition, the method according to the invention includes the step of providing, in each treatment stage, an additive to the stream. Furthermore, the method according to the invention includes the step of reacting the PFAS with the additive to form a precipitate and is followed by the step of separating, in each treatment stage, the aqueous stream and the precipitate, and the step of measuring at least the quantity of PFAS in the aqueous stream at an outlet of at least one of the one or more subsequent treatment stages.

[0020] It is noted that moving the aqueous stream through one or more subsequent treatment stages enables a cascade of treatment stages, wherein said subsequent treatment stages are in series.

[0021] An advantage of the method according to the invention is that the concentration of carcinogenic and mutagenic substances (such as PFAS) in an aqueous stream are lowered. Thus, the concentration of harmful chemicals such as PFAS is reduced. As a result, the aqueous stream may be released to surface water and / or used to produce drinking water.

[0022] A further advantage of the method according to the invention is that the selection of additive enables a cost efficient and effective method. As a result, the PFAS may be bound and / or react with the additive and precipitate. Said precipitate is efficiently and effectively removed from the aqueous stream.

[0023] In addition, the step of reacting the PFAS with the additive to form a precipitate may enable to breakdown the PFAS, forming a residue. Said residue may be due to the pH and / or the additive coagulate and / or precipitate.

[0024] The reaction of the PFAS with the additive may involve oxidation of the PFAS. For example, the method according to the invention is more cost efficient compared to conventional techniques based on incineration for the removal of PFAS.

[0025] Furthermore, the method according to the invention enables to coagulate and / or trap the PFAS. Therefore, PFAS may be removed from an aqueous stream in a solid form, wherein said solid form comprises one or more of the additives and the PFAS. As a result, the solids comprising the PFAS may be processed efficiently and effectively.

[0026] It was found that the method according to the invention enables a high throughput. Therefore, contaminated industrial waste streams as well as water from lakes and / or rivers can be treated with the method according to the invention.

[0027] It was also found that the method according to the invention at least enables to remove the following group of PFAS molecules: perfluoro-n-butane acid (PFBA), perfluoropentane acid (PFPeA), perfluorohexane acid (PFHxA), perfluoroheptane acid (PFHpA), perfluorononanoic acid (PFNA), perfluorodecanoic acid (PFDA), perfluoroundecanoic acid (PFUnDA), perfluordodecanoic acid (PFDoDA), perfluorotridecanoic acid (PFTrDA), perfluorotetradecanoic acid (PFTeDA), perfluorohexadecanoic acid (PFHxDA), perfluoro-n-octadecanoic acid (PFODA), perfluoro-1- butanesulfonic acid (Lineair) (L_PFBS), perfluoropentane-1 -sulfonic acid (PFPeS), perfluoro- 1- hexanesulfonic acid (Lineair) (L_PFHxS), perfluoro- 1 -heptanesulfonic acid (Lineair) (L_PFHpS), perfluoro- 1 -decanesulfonic acid (Lineair) (L_PFDS), 4:2 fluorotelomer sulfonic acid (4:2 FTS), 6:2 fluorotelomer sulfonic acid (6:2 FTS), 8:2 fluorotelomer sulfonic acid (8:2 FTS), 10:2 fluorotelomer sulfonic acid (10:2 FTS), perfluoro-n-octane sulfonic amide (PFOSA), N- methylperfluoro-n-octane sulfonic amide (NMeFOSA), A-methylperfluoro-n-octane sulfonic amide acetic acid (n-MeFOSAA), A-ethylperfluoro-n-octane sulfonic amide acetic acid (EtFOSAA), 8:2 polyfluorodecylphosphate (8:2 diPAP), perfluoro-n-octane acid (linear) (L_PFOA), perfluoro-n-octane acid (branched) (B_PFOA), perfluoro-n-octane acid (PFOA), perfluoro-n-octane sulfonic acid lineair (L_PFOS), perfluoro-n-octane sulfonic acid (branched) (B- PFOS), perfluoro-n-octane sulfonic acid (PFOS), 2,3,3,3-tetrafluor-2- (heptafluoropropoxy)propionic acid (HFPODA) [GENX].

[0028] In a preferred embodiment, the step of measuring at least the quantity of PFAS in the aqueous stream at an outlet of at least one of the one or more subsequent treatment stages comprises the step of measuring at least the quantity of PFAS in the aqueous stream at an outlet of each stage.

[0029] In a presently preferred embodiment according to the invention, the method further comprises the step of:

[0030] - discharging the aqueous stream to an outlet if the aqueous stream at the outlet comprises at most 300 ppb of PFAS; or - moving the aqueous stream to a subsequent treatment step if the aqueous stream at the outlet comprises more than 300 ppb of PFAS.

[0031] It was found that the method according to the invention enables to reduce the PFAS concentration to an amount of less than 300 ppb. Said PFAS concentration of less than 300 ppb may be determined using liquid chromatography-mass spectrometry. Furthermore, the PFAS concentration may be determined using ASTM D7979-20, ASTM D8421-22, and / or NEN-ISO 21675:2019.

[0032] It is noted that a subsequent treatment step includes the steps of providing, in each treatment stage, an additive to the stream, reacting the PFAS with the additive to form an oxidated PFAS, and / or a coagulation, and / or a precipitate, separating, in each treatment stage, the aqueous stream and the oxidated PFAS and / or the coagulated PFAS and / or the precipitate, and measuring at least the quantity of PFAS in the aqueous stream at an outlet of each stage.

[0033] An advantage of providing, in each treatment stage, an additive to the stream is that the PFAS in each treatment stage may react with the additive, such that the PFAS molecules are degraded to smaller molecules (PFAS residues). Said molecules may coagulate and / or flocculate , and preferably form a precipitate.

[0034] Moving the aqueous stream to a subsequent treatment step if the aqueous stream at the outlet comprises more than 300 ppb of PFAS enables to perform different treatments and optimize the treatment, such that the time of treatment is reduced to the necessary time.

[0035] Furthermore, the step of discharging the aqueous stream to an outlet if the aqueous stream at the outlet comprises at most 300 ppb of PFAS may be performed instead of the step of moving the aqueous stream to a subsequent treatment step if the aqueous stream at the outlet comprises more than 300 ppb of PFAS. Said moving step may therefore be performed several times, until the PFAS concentration is at most 300 ppb. When the PFAS concentration is at most 300 ppb the aqueous stream may be discharged.

[0036] An advantage of determining the PFAS concentration before discharging the aqueous stream is that an aqueous stream is discharged comprising PFAS below the undesired amount.

[0037] In a preferred embodiment according to the invention, the method according to the invention for removing per- and polyfluoroalkyl substances (PFAS) from an aqueous stream, comprising the steps of:

[0038] - providing an aqueous stream comprising PFAS;

[0039] - moving the aqueous stream through one or more subsequent treatment stages;

[0040] - mixing the aqueous stream in each treatment stage;

[0041] - providing, in each treatment stage, an additive to the stream;

[0042] - reacting the PFAS with the additive to form a precipitate;

[0043] - separating, in each treatment stage, the aqueous stream and the precipitate; - measuring at least the quantity of PFAS in the aqueous stream at an outlet of each stage; and

[0044] - discharging the aqueous stream to an outlet if the aqueous stream at the outlet comprises at most 300 ppb of PFAS; or

[0045] - moving the aqueous stream to a subsequent treatment step if the aqueous stream at the outlet comprises more than 300 ppb of PFAS.

[0046] In a further presently preferred embodiment according to the invention, the additive may be one or more selected from the group of oxidant agent, coagulant agent, and flocculant agent.

[0047] Providing, in each of the treatment stage, an additive reduces the total amount of sludge, as the total amount of additive may be dosed sufficiently and effectively. In addition, it was found that adding the additive in each stage enables a sufficient reaction of the PFAS with the additive.

[0048] It is noted that reacting the PFAS with the additive may including oxidation, breaking down of PFAS (forming PFAS residues), coagulation, flocculation, binding, and the like, such that the PFAS is no longer dissolved (thus precipitates) in the aqueous stream.

[0049] An advantage of the additive is that the PFAS may react with said additive, such that PFAS residues are formed. In other words, the additive, such as ferrate VI, may react with PFAS forming PFAS residues / breaking down PFAS to PFAS residues.

[0050] A further advantage of the additive being one or more selected from the group of oxidant agent, coagulant agent, and flocculant agent is that the PFAS (and / or PFAS residues) may precipitate, and thus easily removed from the aqueous stream.

[0051] In a further presently preferred embodiment according to the invention, the oxidant agent may be one or more selected from the group of ozone, hydrogen peroxide, sodium hypochlorite, chlorine dioxide, chlorine gas, peracetic acid, ferrate.

[0052] It was found that an oxidant agent being one or more selected from the group of ozone, hydrogen peroxide, sodium hypochlorite, chlorine dioxide, chlorine gas, peracetic acid, ferrate enables an efficient and effective oxidation of the PFAS.

[0053] In a further presently preferred embodiment according to the invention, the coagulant agent may be one or more selected from the group of ferrate, aluminium sulphate (A^SO^s), aluminium chloride (AICI3), sodium aluminate (NaAlCh), iron(II) sulphate (FeSCH), iron(III) sulphate (Fe2(SC>4)3), iron(III) chloride (FeCh), iron(III) chloride sulphate (FeCISCH), calcium hydroxide (Ca(OH)2), magnesium carbonate (MgCCh), preferably the coagulant agent is ferrate and iron(III) chloride.

[0054] An advantage of one or more of said coagulants is that the PFAS may coagulate with the additive. Therefore, precipitation of the PFAS (and / or PFAS residues) is enhanced.

[0055] In a preferred embodiment, iron(III) chloride is provided to at least one of the two first stages. In a further presently preferred embodiment according to the invention, the oxidant agent and / or coagulant agent comprises ferrate, wherein the ferrate is ferrate (VI) ([FeO4]2-), preferably wherein the ferrate (VI) is one or more selected from the group of sodium ferrate, potassium ferrate, potassium-sodium ferrate, calcium ferrate, barium ferrate.

[0056] An advantage of ferrate, preferably ferrate (VI), is that said compound is an oxidant and coagulant agent. As a result, ferrate, preferably ferrate (VI), may perform a dual functionality.

[0057] In addition, it was found that a combination of ferrate, preferably ferrate (VI) and iron(III) chloride as coagulant agent increases the coagulation of PFAS.

[0058] In a further presently preferred embodiment according to the invention, the flocculant agent is a polyelectrolyte, preferably wherein the polyelectrolyte is an anionic polyelectrolyte. Preferably the polyelectrolyte comprises a polyacrylic amide.

[0059] It is noted that polyelectrolytes are defined as a macromolecular material with repeated units that have the ability to dissociate in ionizing solvents (e.g., water), yielding a highly charged polymeric chain with either positively or negatively charged units.

[0060] An advantage of one or more of said flocculants is that the PFAS may flocculate with said flocculant in an efficient and effective manner. Therefore, precipitation of the PFAS (and / or PFAS residues) is enhanced.

[0061] In a further presently preferred embodiment according to the invention, the flocculant is provided to at least the last stage of the one or more subsequent treatment stages.

[0062] It was found that the flocculant, preferably in combination with the coagulant agent and oxidant, enables to precipitate the PFAS (and / or PFAS residues) efficiently and effectively when the concentration of the PFAS is decreasing. For example decreasing below a value of 1000 ppb.

[0063] In a further presently preferred embodiment according to the invention, the step of discharging the aqueous stream to an outlet comprises discharging the aqueous stream to an outlet if the aqueous stream at the outlet comprises at most 200 ppb of PFAS and wherein the step of moving the aqueous stream to a subsequent treatment step comprises moving the aqueous stream to a subsequent treatment step if the aqueous stream at the outlet comprises more than 200 ppb of PFAS, preferably wherein the step of discharging the aqueous stream to an outlet comprises discharging the aqueous stream to an outlet if the aqueous stream at the outlet comprises at most 100 ppb of PFAS and wherein the step of moving the aqueous stream to a subsequent treatment step comprises moving the aqueous stream to a subsequent treatment step if the aqueous stream at the outlet comprises more than 100 ppb of PFAS.

[0064] It was found that the method according to the invention enables to reduce the PFAS concentration to an amount of less than 200 ppb, or even less than 100 ppb. Said PFAS concentration of less than 200 ppb or even less than 100 ppb, may be determined using liquid chromatography-mass spectrometry. Furthermore, the PFAS concentration may be determined using ASTM D7979-20, ASTM D8421-22, and / or NEN-ISO 21675:2019.

[0065] An advantage of the method according to the invention is that a low concentration of PFAS, or PFAS free, aqueous stream is achieved. As a result, the appearance of carcinogenic and mutagenic substances in the water is reduced or even prevented.

[0066] In a further presently preferred embodiment according to the invention, the step of discharging the aqueous stream to an outlet comprises discharging the aqueous stream to an outlet if the aqueous stream at the outlet comprises at most 50 ppb of PFAS and wherein the step of moving the aqueous stream to a subsequent treatment step comprises moving the aqueous stream to a subsequent treatment step if the aqueous stream at the outlet comprises more than 50 ppb of PFAS, preferably wherein the step of discharging the aqueous stream to an outlet comprises discharging the aqueous stream to an outlet if the aqueous stream at the outlet comprises at most 25 ppb of PFAS and wherein the step of moving the aqueous stream to a subsequent treatment step comprises moving the aqueous stream to a subsequent treatment step if the aqueous stream at the outlet comprises more than 25 ppb of PFAS.

[0067] It was found that the method according to the invention enables to reduce the PFAS concentration to an amount of less than 50 ppb, or even less than 25 ppb. Said PFAS concentration of less than 50 ppb or even less than 25 ppb, may be determined using liquid chromatography-mass spectrometry. Furthermore, the PFAS concentration may be determined using ASTM D7979-20, ASTM D8421-22, and / or NEN-ISO 21675:2019.

[0068] It is believed that the method according to the invention enables an aqueous stream which is substantially free from PFAS.

[0069] In a further presently preferred embodiment according to the invention, the method according to the invention further comprises the step of measuring the pH of the aqueous stream in at least one of the one or more stages, and, optionally comprising adjusting the pH of the aqueous stream in at least one of the one or more stages using an acid.

[0070] Measuring the pH in at least one of the one or more stages enables to adjust the pH if necessary. Adjusting the pH enables to modify the reaction accordingly as a low pH at the start of the method according to the invention is preferred.

[0071] In a further presently preferred embodiment according to the invention, the method according to the invention further comprises the step of acidifying the aqueous stream in at least one of the one or more stages to a pH below 3.5, preferably to a pH below 3.0, more preferably to a pH below 2.8.

[0072] It was found that acidifying the aqueous stream in at least one of the one or more stages, preferably the first stage, to a pH below 3.5, preferably to a pH below 3.0, more preferably to a pH below 2.8 enables to precipitate the PFAS (and / or PFAS residues) and results in a efficient and effective removal of the PFAS from the aqueous stream.

[0073] In a further presently preferred embodiment according to the invention, the step of acidifying is performed in the first stage, and wherein the pH in the first stage is below 3.0.

[0074] It was found that the removal of PFAS is particularly efficient and effective when the aqueous stream provided to the first of the one or more subsequent treatment stages has a pH below 3.0.

[0075] In a further presently preferred embodiment according to the invention, the acid is one or more selected from the group of hydrochloric acid, sulphuric acid, nitric acid, sulphurous acid, phosphoric acid, nitrous acid, organic acid, preferably the acid is sulphuric acid. Preferably, the acid is sulphuric acid.

[0076] The organic acid may for example be one or more selected from the group of oxalic acid, citric acid, acetic acid, formic acid, carboxylic acid.

[0077] One or more acids selected from the group of hydrochloric acid, sulphuric acid, nitric acid, sulphurous acid, phosphoric acid, nitrous acid, organic acid provide a sufficient pH such that the removal of the PFAS from an aqueous stream is efficient and effective.

[0078] In a preferred embodiment, the acid is one or more selected from the group of hydrochloric acid, sulphuric acid, nitric acid, sulphurous acid, phosphoric acid, nitrous acid. Preferably, the acid is one or more selected from the group of sulphuric acid, nitric acid, sulphurous acid, phosphoric acid, nitrous acid, more preferably the acid is sulphuric acid.

[0079] Said acids are free of organic material. Therefore, the exposure of the environment to additional organic material is reduced. As a result, the use of an acid such as sulphuric acid is more environmental friendly compared to organic acids.

[0080] In a preferred embodiment, the additive comprises an oxidant agent, a coagulant agent, and a flocculant agent, wherein said oxidant agent is ferrate, preferably ferrate (VI), said coagulant agent is iron(III) chloride and / or ferrate, wherein the ferrate is preferably ferrate (VI), and said flocculant is a polyelectrolyte, and the aqueous stream is initially acidified using sulphuric acid.

[0081] In a further presently preferred embodiment according to the invention, the pH in the final stage is in the range of 2.6 to 14, preferably in the range of 4.5 to 14, more preferably in the range of 6 to 13.

[0082] In a preferred embodiment according to the invention, the pH in the final stage is in the range of 9 to 14, more preferably in the range of 11 to 14.

[0083] It was found that an increase of the pH over the one or more subsequent treatment stages results in an efficient and effective removal of PFAS.

[0084] In a further presently preferred embodiment according to the invention, the acid is provided to at least one of the one or more subsequent treatment stages in an amount in the range of 0.1 mol per cubic metre aqueous stream to 5 mol per cubic metre aqueous stream, preferably 0.2 mol per cubic metre aqueous stream to 4 mol per cubic metre aqueous stream, more preferably 0.3 mol per cubic metre aqueous stream to 3 mol per cubic metre aqueous stream.

[0085] It is noted that said amount refer to each of the individual treatment stages.

[0086] In a further presently preferred embodiment according to the invention, the additive is provided to at least one of the one or more subsequent treatment stages in an amount in the range of 0.01 mmol per cubic metre aqueous stream to 10 mmol per cubic metre aqueous stream, preferably 0.05 mmol per cubic metre aqueous stream to 7.5 mmol per cubic metre aqueous stream, more preferably 0.1 mmol per cubic metre aqueous stream to 5 mmol per cubic metre aqueous stream.

[0087] It is noted that said amount refer to each of the individual treatment stages.

[0088] In a further presently preferred embodiment according to the invention, the method according to the invention further comprises the step of neutralising the aqueous stream of the discharging step to a pH in the range of 6.8 to 7.5.

[0089] The step of neutralising the aqueous stream before said stream is discharged to a pH in the range of 6.8 to 7.5 reduces the effect of the discharged aqueous stream in the environment.

[0090] In a preferred embodiment each of the one or more subsequent treatment stages includes a reactor vessel in the range of 0.5 m3to 10 m3, preferably in the range of 0.5 m3to 8 m3. for example, said reactor vessel may comprise the dimensions of 100 cm to 200 cm by 100 cm to 200 cm by 150 cm to 250 cm.

[0091] In a further presently preferred embodiment according to the invention, the mixing for each stage is individually within the range of 100 rpm to 500 rpm, preferably in the range of 150 rpm to 400 rpm, more preferably in the range of 200 rpm to 300 rpm, most preferably about 250 rpm.

[0092] It was found that the mixing of each individual stage with a rotational speed in the range of 100 rpm to 500 rpm enables a sufficient reaction of the PFAS with the additive.

[0093] In a further presently preferred embodiment according to the invention, the residence time of the aqueous stream in each individual stage is in the range of 2 minutes to 10 minutes, preferably in the range of 2 minutes to 8 minutes, more preferably in the range of 2 minutes to 6 minutes.

[0094] In a further presently preferred embodiment according to the invention, the residence time of the aqueous stream in a device configured for removing per- and polyfluoroalkyl substances (PFAS) from an aqueous stream is at most 120 minutes, preferably at most 100 minutes, more preferably at most 80 minutes, most preferably at most 60 minutes.

[0095] The invention also relates to a device for removing per- and polyfluoroalkyl substances (PFAS) from an aqueous stream, comprising:

[0096] - an inlet configured for providing an aqueous stream; - one or more reaction chambers, wherein the one or more reaction chambers are fluidly coupled to each other to form a flow path through the device;

[0097] - an outlet configured for discharging the aqueous stream from the device;

[0098] - at least one additive supply unit that is configured to supply an additive to one or more of the one or more reactions chambers;

[0099] - at least one acid supply unit that is configured for providing an acid to one or more of the one or more reactions chambers; and

[0100] - one or more separating means that are configured to separate a precipitate and the aqueous stream, wherein each of the one or more reaction chambers is provided with a mixing unit configured for mixing the aqueous stream.

[0101] The device for removing per- and polyfluoroalkyl substances (PFAS) according to the invention provides the same effects and advantages as those described for the method for removing per- and polyfluoroalkyl substances (PFAS) from an aqueous stream according to the invention.

[0102] In a presently preferred embodiment according to the invention, the device comprises at least 6 reaction chambers, preferably at least 8 reaction chambers, more preferably at least 10 reaction chambers, even more preferably at least 12 reaction chambers.

[0103] It was found that a device comprising at least 12 reaction chambers, enabling at least 12 subsequent treatment stages, provides an aqueous stream comprising at most 300 ppb, preferably at most 100 ppb, more preferably at most 50 ppb.

[0104] In a further presently preferred embodiment according to the invention, the volume of each reaction chamber is in the range of 0.5 m3to 10 m3, preferably in the range of 0.5 m3to 8 m3, more preferably in the range of 0.5 m3to 5 m3, even more preferably in the range of 1 m3to 3 m3.

[0105] In a further presently preferred embodiment according to the invention, each reaction chamber comprises a reaction chamber inlet and a reaction chamber outlet that form part of the flow path, wherein each reaction chamber outlet is connected, via a switching unit, to a subsequent reaction chamber inlet and to a discharge outlet, and wherein the switching unit is switchable between a discharge mode in which the aqueous stream is discharged through the discharge outlet, and a treatment mode in which the aqueous stream is provided to a subsequent reaction chamber for further treatment.

[0106] An advantage of said switching unit is that the aqueous stream may be provided to a further subsequent treatment stage when the concentration of the PFAS in the aqueous stream has not reached the desired amount.

[0107] In a further presently preferred embodiment according to the invention, each reaction chamber, and preferably a flow inlet and / or flow outlet thereof, is at least provided with a PFAS sensor that is configured to measure a concentration of PFAS in the aqueous stream. An advantage of said sensor is that the PFAS concentration may be measured on demand, and that the PFAS concentration of the aqueous stream released from the device according to the invention is determined. Therefore, the environmental impact of said aqueous stream may be monitored.

[0108] In a further presently preferred embodiment according to the invention, the device further comprises at least one sensor, wherein the at least one sensor is configured for measuring one or more of pH, additive concentration, infrared.

[0109] In a further presently preferred embodiment according to the invention, the device according to the invention further comprises a control unit that is configured to control one or more of pH in the reaction chamber, the additive supply unit, the acid supply unit, a mixing speed of the mixing unit, a flow speed of the aqueous stream and / or a residence time of the aqueous stream in each reaction chamber.

[0110] The control unit according to the invention enables to tune the reaction such that an efficient and effective removal of the PFAS from the aqueous stream is achieved. In addition, said control unit enables an optimal use of the resources such as the additive and the acid.

[0111] In a further presently preferred embodiment according to the invention, the control unit is configured to control the switching unit based on a measured quantity of PFAS in the aqueous stream by the PFAS sensor, wherein the control unit is configured to:

[0112] - switch the switching unit to the discharge mode if the aqueous stream at the outlet comprises at most 300 ppb of PFAS; or

[0113] - switch the switching unit to the treatment mode if the aqueous stream at the outlet comprises more than 300 ppb of PFAS.

[0114] In a further presently preferred embodiment according to the invention, each reaction chamber is provided with individual additive supply means and / or wherein each reaction chamber is provided with individual acid supply means.

[0115] In a further presently preferred embodiment according to the invention, the control unit is configured to, preferably based on measurement data by a pH sensor, regulate an amount of acid dispensed by each individual acid supply unit; and / or wherein the control unit is configured to, preferably based on measurement data by an additive concentration sensor, regulate an amount of additive dispensed by each individual additive supply unit.

[0116] The invention also relates to a system for removing per- and polyfluoroalkyl substances (PFAS) from an aqueous stream, comprising:

[0117] - at least one device according to the invention and a clarifier container; and

[0118] - a collection tank that is positioned downstream of the at least one device and that is configured to collect the aqueous discharge stream from each of the reaction chambers. The system for removing per- and polyfluoroalkyl substances (PFAS) according to the invention provides the same effects and advantages as those described for the method for removing per- and polyfluoroalkyl substances (PFAS) from an aqueous stream according to the invention, and device for removing per- and polyfluoroalkyl substances (PFAS) according to the invention.

[0119] In a presently preferred embodiment according to the invention, the system may comprise multiple devices, wherein said multiple devices are preferably coupled in parallel.

[0120] In a further presently preferred embodiment according to the invention, the collection tank comprises a sewage discharge outlet that is operatively connected to a sewage treatment plant, and a post-processing outlet that is connected to a precipitation tank, and wherein the system further comprises a control unit configured to, based on an amount of particles in the aqueous discharge stream, discharge the aqueous stream to one of the sewage discharge outlet and the post-processing outlet.

[0121] The invention also relates to a computing device configured to cooperate with a device according to the invention, wherein the computing device is configured for performing one or more of the steps of:

[0122] - measuring and / or collecting the measuring data from one or more sensors.

[0123] - controlling the acid supply and / or the additive supply; and

[0124] - controlling the residence time of the aqueous stream in the one or more reaction chambers.

[0125] The computing device according to the invention provides the same effects and advantages as those described for the method for removing per- and polyfluoroalkyl substances (PFAS) from an aqueous stream according to the invention, device for removing per- and polyfluoroalkyl substances (PFAS) according to the invention, and system for removing per- and polyfluoroalkyl substances (PFAS) according to the invention.

[0126] The invention also relates to an aqueous stream obtainable by the method according to the invention comprising at most 300 ppb PFAS according to ASTM D7979-20, ASTM D8421-22, and / or NEN-ISO 21675:2019.

[0127] The aqueous stream obtainable by the method according to the invention provides the same effects and advantages as those described for the method for removing per- and polyfluoroalkyl substances (PFAS) from an aqueous stream according to the invention, device for removing per- and polyfluoroalkyl substances (PFAS) according to the invention, system for removing per- and polyfluoroalkyl substances (PFAS) according to the invention, and computing device according to the invention.

[0128] Further advantages, features and details of the invention are elucidated on the basis of preferred embodiments thereof, wherein reference is made to the accompanying drawings, in which: - Figure 1 : shows a schematic overview of the method according to the invention.

[0129] Method 10 for removing per- and polyfluoroalkyl substances (PFAS) from an aqueous stream follows a sequence of different steps.

[0130] In the illustrated embodiment method 10 may start with step 12 of providing an aqueous stream comprising PFAS, and followed by step 14 of moving the aqueous stream through one or more subsequent treatment stages. The aqueous stream is mixed in each treatment stage by step 16 of mixing the aqueous stream in each treatment stage.

[0131] In addition, method 10 according to the invention comprises step 18 of providing, in each treatment stage, an additive to the stream. Furthermore, method 10 according to the invention comprises step 20 of reacting the PFAS with the additive to form a precipitate and may be followed by step 22 of separating, in each treatment stage, the aqueous stream and the precipitate, and step 24 of measuring at least the quantity of PFAS in the aqueous stream at an outlet at least one of the one or more subsequent treatment stages.

[0132] Furthermore, method 10 comprises in a preferred embodiment step 26 of discharging the aqueous stream to an outlet if the aqueous stream at the outlet comprises at most 300 ppb of PFAS, and step 28 of moving the aqueous stream to a subsequent treatment step if the aqueous stream at the outlet comprises more than 300 ppb of PFAS.

[0133] It is noted that depending on the concentration of PFAS present in the aqueous stream step 26 or step 28 is selected.

[0134] In addition, method 10 may comprise step 30 of measuring the pH of the aqueous stream in at least one of the one or more stages, and, optionally step 30 may comprise step 32 of adjusting the pH of the aqueous stream in at least one of the one or more stages using an acid. Step 30 may be followed by step 34 of acidifying the aqueous stream in at least one of the one or more stages to a pH below 3.5, preferably to a pH below 3.0, more preferably to a pH below 2.8.

[0135] In a preferred embodiment of method 10 according to the invention, step 26 of discharging the aqueous stream to an outlet if the aqueous stream at the outlet comprises at most 300 ppb of PFAS may be followed by step 36 of neutralising the aqueous stream of the discharging step to a pH in the range of 6.8 to 7.5.

[0136] In an experiment, the method according to the invention was used to remove PFAS from an aqueous stream (see Table 1). The method included nine subsequent treatment stages. Table 1: Removal of PF AS using the method according to the invention. In a further experiment, the pH of the aqueous stream in the first treatment stage was lowered to a pH below 3 (pH of about 2.8) using sulphuric acid. In a second stage iron(III) chloride is added to the aqueous stream in an amount of 1 mmol per cubic metre aqueous stream. In addition, the aqueous stream was provided to six consecutive treatment stages. In each of said consecutive treatment stages 0.3 mmol per cubic metre aqueous stream of ferrate (VI) (preferably sodium ferrate) was added. During the last stage an anionic polyelectrolyte, such as SUPERFLOC A- 100 or SUPERFLOC A- 150 from Kemira, was added in an amount of about 2 mmol per cubic metre aqueous stream.

[0137] All stages were mixed using an overhead stirred with a rotation speed of about 250 rpm, and the residence time of the aqueous stream in each individual stage was about 5 minutes.

[0138] It is noted that each stage of the method according to the invention was about three cubic metre.

[0139] The aqueous stream used in the abovementioned experiment, comprised an initial amount of about 140,000 ng L1of PFOS. It was found that after nine treatment stages the PFOS concentration was lower than 20 ng L1(0.02 ppb) according to ASTM D7979-20, ASTM D8421- 22, and / or NEN-ISO 21675:2019.

[0140] The present invention is by no means limited to the above described preferred embodiments and / or experiments thereof. The rights sought are defined by the following claims within the scope of which many modifications can be envisaged.

Claims

CLAIMS1. Method for removing per- and polyfluoroalkyl substances (PFAS) from an aqueous stream, comprising the steps of: providing an aqueous stream comprising PFAS; moving the aqueous stream through one or more subsequent treatment stages; mixing the aqueous stream in each treatment stage; providing, in each treatment stage, an additive to the stream; reacting the PFAS with the additive to form a precipitate; separating, in each treatment stage, the aqueous stream and the precipitate; and measuring at least the quantity of PFAS in the aqueous stream at an outlet of at least one of the one or more subsequent treatment stages.

2. Method according to claim 1, further comprising the step of: discharging the aqueous stream to an outlet if the aqueous stream at the outlet comprises at most 300 ppb of PFAS; or moving the aqueous stream to a subsequent treatment step if the aqueous stream at the outlet comprises more than 300 ppb of PFAS.

3. Method according to any one of the preceding claims, wherein the additive is one or more selected from the group of oxidant agent, coagulant agent, and flocculant agent.

4. Method according to claim 3, wherein the oxidant agent is one or more selected from the group of ozone, hydrogen peroxide, sodium hypochlorite, chlorine dioxide, chlorine gas, peracetic acid, ferrate.

5. Method according to claim 3 or 4, wherein the coagulant agent is one or more selected from the group of ferrate, aluminium sulphate, aluminium chloride, sodium aluminate, iron(II) sulphate, iron(III) sulphate, iron(III) chloride, iron(III) chloride sulphate, calcium hydroxide, magnesium carbonate.

6. Method according to any one of the claims 3 to 5, wherein the oxidant agent and / or coagulant agent comprises ferrate, wherein the ferrate is ferrate (VI), preferably wherein the ferrate (VI) is one or more selected from the group of sodium ferrate, potassium ferrate, potassium-sodium ferrate, calcium ferrate, barium ferrate.

7. Method according to any one of the claims 3 to 6, wherein the flocculant agent is a poly electrolyte, preferably wherein the poly electrolyte is an anionic poly electrolyte.

8. Method according to any one of the claims 3 to 7, wherein the flocculant is provided to at least the last stage of the one or more subsequent treatment stages.

9. Method according to any one of the preceding claims, when dependent on claim 2, wherein the step of discharging the aqueous stream to an outlet comprises discharging the aqueous stream to an outlet if the aqueous stream at the outlet comprises at most 200 ppb of PFAS and wherein the step of moving the aqueous stream to a subsequent treatment step comprises moving the aqueous stream to a subsequent treatment step if the aqueous stream at the outlet comprises more than 200 ppb of PFAS, preferably wherein the step of discharging the aqueous stream to an outlet comprises discharging the aqueous stream to an outlet if the aqueous stream at the outlet comprises at most 100 ppb of PFAS and wherein the step of moving the aqueous stream to a subsequent treatment step comprises moving the aqueous stream to a subsequent treatment step if the aqueous stream at the outlet comprises more than 100 ppb of PFAS.

10. Method according to any one of the preceding claims, when dependent on claim 2, wherein the step of discharging the aqueous stream to an outlet comprises discharging the aqueous stream to an outlet if the aqueous stream at the outlet comprises at most 50 ppb of PFAS and wherein the step of moving the aqueous stream to a subsequent treatment step comprises moving the aqueous stream to a subsequent treatment step if the aqueous stream at the outlet comprises more than 50 ppb of PFAS, preferably wherein the step of discharging the aqueous stream to an outlet comprises discharging the aqueous stream to an outlet if the aqueous stream at the outlet comprises at most 25 ppb of PFAS and wherein the step of moving the aqueous stream to a subsequent treatment step comprises moving the aqueous stream to a subsequent treatment step if the aqueous stream at the outlet comprises more than 25 ppb of PFAS.

11. Method according to any one of the preceding claims, further comprising the step of measuring the pH of the aqueous stream in at least one of the one or more stages, and, optionally comprising adjusting the pH of the aqueous stream in at least one of the one or more stages using an acid.

12. Method according to claim 11, further comprising the step of acidifying the aqueous stream in at least one of the one or more stages to a pH below 3.5, preferably to a pH below 3.0, more preferably to a pH below 2.8.

13. Method according to claim 12, wherein the step of acidifying is performed in the first stage, and wherein the pH in the first stage is below 3.0.

14. Method according to any one of the claims 11 to 13, wherein the acid is one or more selected from the group of hydrochloric acid, sulphuric acid, nitric acid, sulphurous acid, phosphoric acid, nitrous acid, organic acid, preferably the acid is sulphuric acid.

15. Method according to any one of the claims 11 to 14, wherein the pH in the final stage is in the range of 2.6 to 14, preferably in the range of 4.5 to 14, more preferably in the range of 6 to 13.

16. Method according to any one of the claims 11 to 15, wherein the acid is provided to at least one of the one or more subsequent treatment stages in an amount in the range of 0.1 mol per cubic metre aqueous stream to 5 mol per cubic metre aqueous stream, preferably 0.2 mol per cubic metre aqueous stream to 4 mol per cubic metre aqueous stream, more preferably 0.3 mol per cubic metre aqueous stream to 3 mol per cubic metre aqueous stream.

17. Method according to any one of the preceding claims, wherein the additive is provided to at least one of the one or more subsequent treatment stages in an amount in the range of 0.01 mmol per cubic metre aqueous stream to 10 mmol per cubic metre aqueous stream, preferably 0.05 mmol per cubic metre aqueous stream to 7.5 mmol per cubic metre aqueous stream, more preferably 0.1 mmol per cubic metre aqueous stream to 5 mmol per cubic metre aqueous stream.

18. Method according to any one of the preceding claims, when dependent on cause 2, further comprising the step of neutralising the aqueous stream of the discharging step to a pH in the range of 6.8 to 7.5.

19. Method according to any one of the preceding claims, wherein the mixing for each stage is individually within the range of 100 rpm to 500 rpm, preferably in the range of 150 rpm to 400 rpm, more preferably in the range of 200 rpm to 300 rpm, most preferably about 250 rpm.

20. Method according to any one of the preceding claims, wherein the residence time of the aqueous stream in each individual stage is in the range of 2 minutes to 10 minutes, preferably in the range of 2 minutes to 8 minutes, more preferably in the range of 2 minutes to 6 minutes.

21. Method according to any one of the preceding claims, wherein the residence time of the aqueous stream in a device configured for removing per- and polyfluoroalkyl substances (PFAS) from an aqueous stream is at most 120 minutes, preferably at most 100 minutes, more preferably at most 80 minutes, most preferably at most 60 minutes.

22. Device for removing per- and polyfluoroalkyl substances (PFAS) from an aqueous stream, comprising: an inlet configured for providing an aqueous stream; one or more reaction chambers, wherein the one or more reaction chambers are fluidly coupled to each other to form a flow path through the device; an outlet configured for discharging the aqueous stream from the device; at least one additive supply unit that is configured to supply an additive to one or more of the one or more reactions chambers; at least one acid supply unit that is configured for providing an acid to one or more of the one or more reactions chambers; and one or more separating means that are configured to separate a precipitate and the aqueous stream, wherein each of the one or more reaction chambers is provided with a mixing unit configured for mixing the aqueous stream.

23. Device according to claim 22, wherein the device comprises at least 6 reaction chambers, preferably at least 8 reaction chambers, more preferably at least 10 reaction chambers, even more preferably at least 12 reaction chambers.

24. Device according to any one of the claims 22 or 23, wherein the volume of each reaction chamber is in the range of 0.5 m3to 10 m3, preferably in the range of 0.5 m3to 8 m3, more preferably in the range of 0.5 m3to 5 m3, even more preferably in the range of 1 m3to 3 m3.

25. Device according to any one of the claims 22 to 24, wherein each reaction chamber comprises a reaction chamber inlet and a reaction chamber outlet that form part of the flow path, wherein each reaction chamber outlet is connected, via a switching unit, to a subsequent reaction chamber inlet and to a discharge outlet, and wherein the switching unit is switchable between a discharge mode in which the aqueous stream is discharged through the discharge outlet, and a treatment mode in which the aqueous stream is provided to a subsequent reaction chamber for further treatment.

26. Device according to any one of the claims 22 to 25, wherein each reaction chamber, and preferably a flow inlet and / or flow outlet thereof, is at least provided with a PFAS sensor that is configured to measure a concentration of PFAS in the aqueous stream.

27. Device according to any one of the claims 22 to 26, wherein the device further comprises at least one sensor, wherein the at least one sensor is configured for measuring one or more of pH, additive concentration, infrared.

28. Device according to any one of the claims 22 to 27, further comprising a control unit that is configured to control one or more of pH in the reaction chamber, the additive supply unit, the acid supply unit, a mixing speed of the mixing unit, a flow speed of the aqueous stream and / or a residence time of the aqueous stream in each reaction chamber.

29. Device according to claim 28, when dependent on claim 25, wherein the control unit is configured to control the switching unit based on a measured quantity of PFAS in the aqueous stream by the PFAS sensor, wherein the control unit is configured to: switch the switching unit to the discharge mode if the aqueous stream at the outlet comprises at most 300 ppb of PFAS; or switch the switching unit to the treatment mode if the aqueous stream at the outlet comprises more than 300 ppb of PFAS.

30. Device according to any one of the claims 22 to 29, wherein each reaction chamber is provided with individual additive supply means and / or wherein each reaction chamber is provided with individual acid supply means.

31. Device according to claims 30, when dependent on claim 28, wherein the control unit is configured to, preferably based on measurement data by a pH sensor, regulate an amount of acid dispensed by each individual acid supply unit; and / or wherein the control unit is configured to, preferably based on measurement data by an additive concentration sensor, regulate an amount of additive dispensed by each individual additive supply unit.

32. System for removing per- and polyfluoroalkyl substances (PFAS) from an aqueous stream, comprising: at least one device according to any one of the claims 22 to 31 and a clarifier container; and a collection tank that is positioned downstream of the at least one device and that is configured to collect the aqueous discharge stream from each of the reaction chambers.

33. Computing device configured to be with a device according to any one of the claims 22 to 31, wherein the computing device is configured for performing one or more of the steps of: measuring and / or collecting the measuring data from one or more sensors. controlling the acid supply and / or the additive supply; and controlling the residence time of the aqueous stream in the one or more reaction chambers.

34. Aqueous stream obtainable by the method according to any one of the claims 1 to 21 comprising at most 300 ppb PFAS according to ASTM D7979-20, ASTM D8421-22, and / or NEN- ISO 21675:2019, preferably the PFAS is one or more selected from the group of perfluoro-n- butane acid (PFBA), perfluoropentane acid (PFPeA), perfluorohexane acid (PFHxA), perfluoroheptane acid (PFHpA), perfluorononanoic acid (PFNA), perfluorodecanoic acid (PFDA), perfluoroundecanoic acid (PFUnDA), perfluordodecanoic acid (PFDoDA), perfluorotridecanoic acid (PFTrDA), perfluorotetradecanoic acid (PFTeDA), perfluorohexadecanoic acid (PFHxDA), perfluoro-n-octadecanoic acid (PFODA), perfluoro- 1 -butanesulfonic acid (Eineair) (L_PFBS), perfluoropentane- 1 -sulfonic acid (PFPeS), perfluoro- 1 -hexanesulfonic acid (Lineair) (L_PFHxS), perfluoro- 1 -heptanesulfonic acid (Lineair) (L_PFHpS), perfluoro- 1 -decanesulfonic acid (Lineair) (L_PFDS), 4:2 fluorotelomer sulfonic acid (4:2 FTS), 6:2 fluorotelomer sulfonic acid (6:2 FTS), 8:2 fluorotelomer sulfonic acid (8:2 FTS), 10:2 fluorotelomer sulfonic acid (10:2 FTS), perfluoro- n-octane sulfonic amide (PFOSA), A-methylperfluoro-n-octane sulfonic amide (NMeFOSA), N- methylperfluoro-n-octane sulfonic amide acetic acid (n-MeFOSAA), A-ethylperfluoro-n-octane sulfonic amide acetic acid (EtFOSAA), 8:2 polyfluorodecylphosphate (8:2 diPAP), perfluoro-n- octane acid (linear) (L_PFOA), perfluoro-n-octane acid (branched) (B_PFOA), perfluoro-n-octane acid (PFOA), perfluoro-n-octane sulfonic acid lineair (L_PFOS), perfluoro-n-octane sulfonic acid (branched) (B-PFOS), perfluoro-n-octane sulfonic acid (PFOS), 2,3,3,3-tetrafluor-2- (heptafluoropropoxy)propionic acid (HFPODA) [GENX].

Images