Process and system for recovering fatty acids and / or nutrients from a feed stream

Abstract

The invention relates to a process for recovering fatty acids and / or nutrients from a feed using a system comprising an electrodialysis bipolar membrane (EDBPM) system, an electrodialysis system (ED) system, and a membrane contactor (MC). The process utilizes an EDBPM system to generate an acidic flow and an alkaline flow. The acidic flow is pumped directly to the feed side of the MC. The ED system is utilized to isolate the hydroxide ions generated by the bipolar membrane of the EDBPM system. The isolated OH- stream is pumped directly to the permeate side of the MC. The invention further relates to a system for recovering fatty acids and / or nutrients from a feed.

Description

Process and system for recovering fatty acids and / or nutrients from a feed streamField of the invention

[0001] The present invention relates to a process and to a system for recovering fatty acids, in particular volatile fatty acids, and / or nutrients from a feed stream, for example, a (bio)waste feed stream. In particular, the present invention relates to a process and to a system for simultaneously recovering fatty acids, in particular volatile fatty acids, and / or nutrients from a feed stream.Background art

[0002] Fatty acids, and in particular volatile fatty acids (VFAs), are widely used chemicals. They are, for example, used as precursors for fuels and high-value chemical products, such as polymers, biofuels, pH adjusters, and preservatives, in the pharmaceutical, chemical, food, and textile industries. Most of the world's demand for VFAs is met by VFAs produced by petrochemical routes. However, petroleum-based routes are considered unsustainable.

[0003] Therefore, in recent years, extensive research has been directed towards the development of processes to convert waste streams such as biowaste streams into a variety of chemicals and products, e.g., volatile fatty acids (VFAs) and nutrients such as K+, NH4+, Ca2+, Mg2+, NOs-, SO42-, and PO43-.

[0004] The production of bio-based fertilizers and volatile fatty acids (VFAs) from waste streams such as food waste has become one of the approaches to valorize the 1.3 billion tonnes of food waste generated annually worldwide.

[0005] However, food waste is a complex system that requires processing to effectively utilize the constituent nutrients and to convert the organic matter into VFAs. As the mineral nutrient concentrations in waste streams are typically very low (20-1100 mg / L), the recovery of nutrients for bio-based fertilizers is usually inefficient. In addition, the mineral nutrient concentrations, such as nitrate, phosphate, and / or sulphate concentrations are usually not balanced relative to, for example, potassium and / or ammonium concentrations.

[0006] Separation processes such as chemical precipitation, adsorption, membrane filtration (e.g., reverse osmosis and nanofiltration), chemical extraction, and electrodialysis have been used to recover either nutrients or VFAs from various streams.

[0007] Techniques such as chemical precipitation, adsorption, and chemical extraction have the disadvantage of requiring the addition of large amounts of chemicals with significant post-treatment to remove excess chemicals.

[0008] Membrane filtration, such as reverse osmosis (RO) and nanofiltration (NF) requires fewer chemicals than precipitation, adsorption, and chemical extraction but is less selective for nutrients and VFAs than, for example, electrodialysis (ED).

[0009] Membrane contactor (MC) processes typically require an acidified feed and a basic permeate to achieve higher, more selective VFA transport. This can be achieved by chemical acidification of the feed with sulfuric acid, nitric acid, or hydrochloric acid, coupled with the direct addition of NaOH or Ca(OH)2 to the permeate. Direct chemical acidification involves protonating VFAs with hydroxonium ions to enhance VFAs sorption, diffusive transport, and recovery. Direct addition of NaOH or Ca(OH)2 is used to promote an in situ reaction of hydroxide with the permeating VFAs to increase VFAs desorption and overall mass transfer coefficient.

[0010] Because electrodialysis (ED) can simultaneously, rapidly, and efficiently separate and concentrate mixed nutrients and dissociated VFAs from most uncharged compounds, it is a preferred technique for recovering VFAs and nutrients. Its combined lower applied pressure with a higher ion selectivity is rather difficult to achieve in other commercially available technologies, especially reverse osmosis (RO) and nanofiltration (NF). Nonetheless, ED is inefficient for selectively separating nutrients from dissociated VFAs since they are both charged species and, therefore, produce nutrients and VFAs of low purity.

[0011] Kotoka, F., Gutierrez, L., Verliefde, A., & Cornelissen, E. (2024). Journal of Environmental Management, 354, 120290. https: / / doi.org / 10.1016 / jjenvman.2024.12029, describes the separation of nutrients and VFAs from food waste using an electrodialysis system and a membrane contactor. As such a system requires high energy consumption and may suffer from fouling, which affects operation and possible selectivity, there is a need for alternative methods to recover acids and / or nutrients from a feed stream.Summary of the invention

[0012] It is an object of the present invention to provide a process for recovering fatty acids, in particular VFAs, and / or nutrients from a feed stream, for example, a (bio)waste stream, thereby avoiding the problems of the prior art.

[0013] It is another object of the present invention to provide a process for simultaneously and selectively recovering fatty acids, in particular VFAs, and nutrients from a feed stream, for example, a (bio)waste stream.

[0014] It is a further object of the present invention to provide a process for recovering fatty acids, in particular VFAs, and / or nutrients from a feed stream not requiring chemical addition of, for example, acids (for example, sulfuric acid or hydrochloric acid) or bases (for example, NaOH or Ca(OH)2).

[0015] It is also an object of the present invention to provide a process for selective nutrient recovery from fatty acids, in particular VFAs, or for selective VFA recovery from nutrients, for example, in fermentation media and liquid solutions.

[0016] It is a further object of the present invention to provide a process for the recovery of nutrients, allowing the adjustment of the nutrient ratios of, for example, nitrate, sulphate, phosphate, potassium, ammonium, magnesium, and calcium.

[0017] Furthermore, it is an object of the present invention to provide a system for recovering fatty acids, in particular VFAs and / or nutrients from a feed stream.

[0018] According to a first aspect of the present invention, a process for recovering fatty acids, in particular volatile fatty acids (VFAs), and / or nutrients from a feed stream using a system comprising an electrodialysis bipolar membrane (EDBPM) system, an electrodialysis system (ED) system, and a membrane contactor (MC) is provided.EDBPM system

[0019] The EDBPM system comprises a cathode, a first bipolar membrane (BPM1), at least one cation exchange membrane (CEM), at least one anion exchange membrane (AEM), a second bipolar membrane (BPM2), and an anode.The first bipolar membrane is positioned at the cathode side, and the second bipolar membrane is positioned at the anode side. The at least one cation exchange membrane is positioned at the OFT producing side of the first bipolar membrane, and the at least one anion exchange membrane is positioned at the H+producing side of the second bipolar membrane.The EDBPM system thereby defines a cathode chamber positioned at the cathode side and bound by the H+producing side of the first bipolar membrane; a base receiver chamber bound by the OH- producing side of the first bipolar membrane and the at least one cation exchange membrane, a feed chamber bound by the at least one cation exchange membrane and the at least one anion exchange membrane, an acid receiver chamber defined by the at least one anion exchange membrane and the H+producing side of the second bipolar membrane, and an anode chamber positioned at the anode side and bound by the OH- producing side of a bipolar membrane, for example, the second bipolar membrane.

[0020] The feed chamber preferably has at least one inlet configured to receive a feed. In particular embodiments, the feed chamber has more than one inlet, for example, two or three inlets, configured to receive a feed.

[0021] In a preferred embodiment, the EDBPM system consists of a cathode, a first bipolar membrane (BPM1), a cation exchange membrane (CEM), an anion exchange membrane (AEM), a second bipolar membrane (BPM2), and an anode.The first bipolar membrane is positioned at the cathode side, and the second bipolar membrane is positioned at the anode side. The cation exchange membrane is positioned at the OH- producing side of the first bipolar membrane, and the anion exchange membrane is positioned at the H+producing side of the second bipolar membrane.In such embodiment, the EDBPM system consists ofa cathode chamber positioned at the cathode side and bound by the H+producing side of the first bipolar membrane; a base receiver chamber bound by the OH- producing side of the first bipolar membrane and the cation exchange membrane; a feed chamber bound by the cation exchange membrane and the at anion exchange membrane; an acid receiver chamber defined by the at least one anion exchange membrane and the H+producing side of the second bipolar membrane; and an anode chamber positioned at the anode side and bound by the OH- producing side of the second bipolar membrane.

[0022] In alternative embodiments, the EDBPM system further comprises at least one additional pair of a cation exchange membrane and an anion exchange membrane, and at least one additional bipolar membrane. In a particular preferred embodiment, the EDBPM system comprises more than one additional pair of a cation exchange membrane and an anion exchange membrane, for example, 2 additional pairs or 3 additional pairs.

[0023] In such embodiments, the at least one additional pair of a cation exchange membrane and an anion exchange membrane, and the at least one additional bipolar membrane are positioned between the second bipolar membrane and the anode.

[0024] In case the EDBPM comprises more than one additional pair of a cation exchange membrane and an anion exchange membrane, the additional pairs are positioned in such a way that the cation exchange membranes and the anion exchange membranes are positioned in alternating positions.

[0025] The at least one additional bipolar membrane is preferably positioned close to the anode, i.e., between the anion exchange membrane of the additional pair of a cation exchange membrane and an anion exchange membrane closest to the anode and the anode.

[0026] An EDBPM system comprising one or more additional pairs of a cation exchange membrane and an anion exchange membrane, and at least one additional bipolar membrane, allows for concentrating and separating (fatty) acids, in particular VFAs, and nutrients, as well as balancing nutrients.

[0027] In embodiments of an EDBPM system comprising at least one or more additional pairs of an anion exchange membrane and a cation exchange membrane and at least one additional bipolar membrane, the EDBPM system comprises one or more additional feed chambers bound by the cation exchange membrane and the anion exchange membrane of a pair of a cation exchange membrane and an anion exchange membrane.

[0028] Furthermore, such embodiments have one or more additional acid receiver chambers. Such additional acid receiver chamber is defined by an anion exchange membrane and a cation exchange membrane of two subsequent pairs of a cation exchange membrane. An additional acid receiver chamber is defined by the H+producing side of the additional bipolar membrane (positionednext to the anode) and the anion exchange membrane positioned next to the at least one additional bipolar membrane.

[0029] Additionally, in such embodiments, an additional base receiver chamber is present. Such additional base receiver chamber is defined between the second bipolar membrane and the cathode exchange membrane of the additional pair of a cation exchange membrane and an anode exchange membrane.ED system

[0030] The ED system comprises a cathode, at least one cation exchange membrane (CEM), at least one anion exchange membrane (AEM), and an anode. The cation exchange membrane and the anion exchange membrane are positioned next to each other, thereby creating an intermediate chamber between the cation exchange membrane and the anion exchange membrane. The ED system thus defines a cathode chamber positioned at the cathode side; an intermediate chamber defined by at least one cation exchange membrane and the at least one anion exchange membrane; an anode chamber positioned at the anode side.

[0031] The ED system may further comprise one or more additional cation exchange membranes and / or one or more additional anion exchange membranes and / or one or more additional pairs of alternating cation exchange membranes and cation exchange membranes and / or one or more bipolar membranes.

[0032] In a particularly preferred embodiment, the ED system comprises subsequently a bipolar membrane (positioned at the cathode side), an anion exchange membrane, a cation exchange membrane, and a cation / anion exchange membrane (positioned at the anode side). Such ED system thereby defines respectively a cathode chamber, a first intermediate chamber, a second intermediate chamber, a third intermediate chamber, and an anode chamber.Membrane contactor

[0033] The membrane contactor (MC) comprises at least one selective membrane defining a feed side and a permeate side. The selective membrane creates two chambers: a feed chamber on the feed side of the selective membrane and a permeate chamber on the permeate side of the selective membrane.

[0034] The process, according to the present invention, comprises the steps of introducing a feed into the feed chamber of the EDBPM system, preferably through the at least one inlet of the feed chamber; applying a voltage or electric current between the cathode and the anode of the EDBPM system, thereby providing an acidic flow and an alkaline flow from the EDBPM system;applying a voltage or electric current between the cathode and the anode of the ED system, thereby providing / isolating an OH- stream from the ED system; introducing the acidic flow from the EDBPM system to the feed side of the MC; introducing the alkaline flow from the EDBPM system to the ED system; introducing the isolated OH- stream from the ED system to the permeate side of the MC.

[0035] In the method according to the present invention, (pure) VFAs are produced at the permeate side of the MC by introducing the isolated OH- stream to the permeate side of the MC,

[0036] The process according to the present invention utilizes an electrodialysis bipolar membrane system to (simultaneously) generate an acidic flow and an alkaline (basic) flow from the feed stream to promote the transport of acids, in particular of (volatile) fatty acids. The acidic flow is pumped directly to the feed side of a membrane contactor for selective recovery of fatty acids, in particular, volatile fatty acids from nutrients. Preferably, the acidic flow is pumped from the acid receiver chamber of the EDBPM system to the feed side of the membrane contactor.In addition, conventional electrodialysis is utilized to isolate the hydroxide ions (OH- stream) generated by the bipolar membrane of the EDBPM system. The isolated OH- stream is pumped directly to the permeate side of the membrane contactor for in-situ reaction with the permeating (fatty) acids, in particular volatile fatty acids (VFAs deprotonation).

[0037] The feed stream introduced in the electrodialysis bipolar membrane system comprises an aqueous solution, for example, water, in particular (bio)waste water, anaerobic digestates, fermentation broths, for example, fermentation broths for the production of organic acids, solvents, and biofuels, and gut microbiomes.Preferred feed streams comprise anaerobic digestates, for example, anaerobic digestates from agricultural residues, animal manure, food waste, sewage sludge, energy crops, organic industrial waste, municipal solid waste, and algal biomass.

[0038] Preferably but not necessarily, the voltage or electric current between the cathode and the anode of the EDBPM system and the voltage or electric current between the cathode and the anode of the ED system are applied simultaneously or substantially simultaneously.

[0039] An alkaline flow is provided from the EDBPM system and introduced into the ED system.

[0040] The alkaline flow is, for example, provided from the basic chamber of the EDBPM system or from the cathode chamber of the EDBPM system and is introduced to an intermediate chamber of the ED system or to the cathode chamber of the ED system.

[0041] In a preferred embodiment an alkaline flow is provided from the basic chamber of the EDBPM system and introduced from the basic chamber of the EDBPM system to an intermediate chamber of the ED system.

[0042] In another preferred embodiment, an alkaline flow is provided from the basic chamber of the EDBPM system and is introduced to the cathode chamber of the ED system.

[0043] In an alternative embodiment, an alkaline flow is provided from the cathode chamber of the EDBPM system and introduced from the cathode chamber to an intermediate chamber of the ED system.

[0044] In such embodiment, it can be preferred to circulate an alkaline flow from the base receiver chamber to the anode chamber of the EDBPM system, thereby reducing the pH and avoiding scaling. Furthermore, in such embodiment, it can be preferred to circulate a flow of VFA in the ED system to the cathode chamber of the ED system to further receive OH- ions generated by the cathode.

[0045] As mentioned above, an isolated OH- stream from the ED system is introduced to the permeate side of the MC system.

[0046] In particular embodiments, an OH- stream is isolated from the at least one intermediate chamber of the ED system and introduced to the permeate side of the MC system.

[0047] In alternative embodiments, an OH- stream is isolated from the cathode chamber of the ED system to the permeate side of the MC system.

[0048] It can be preferred to circulate a flow of VFA in the ED system to the cathode chamber of the ED system to further receive OH- ions generated by the cathode.

[0049] In some embodiments, an additional, external alkaline flow, for example NaOH or Ca(OH)2, is introduced to the ED system (in addition to the alkaline flow introduced from the EDBPM system to the ED system).

[0050] According to a second aspect of the present invention, a system for the recovery of fatty acids, in particular volatile fatty acids and / or nutrients from a feed stream, is provided. The system comprises an electrodialysis bipolar membrane (EDBPM) system, an electrodialysis system (ED) system, and a membrane contactor (MC).

[0051] The EDBPM system comprises a cathode, a first bipolar membrane (BPM1), at least one cation exchange membrane (CEM), at least one anion exchange membrane (AEM), a second bipolar membrane (BPM2), and an anode.The first bipolar membrane is positioned at the cathode side, and the second bipolar membrane is positioned at the anode side. The at least one cation exchange membrane is positioned at the OH- producing side of the first bipolar membrane, and the at least one anion exchange membrane is positioned at the H+producing side of the second bipolar membrane.The EDBPM system thereby defines a cathode chamber positioned at the cathode side and bound by the H+producing side of the first bipolar membrane;a base receiver chamber bound by the OH- producing side of the first bipolar membrane and the at least one cation exchange membrane, a feed chamber bound by the at least one cation exchange membrane and the at least one anion exchange membrane, an acid receiver chamber defined by the at least one anion exchange membrane and the H+producing side of the second bipolar membrane, and an anode chamber positioned at the anode side and bound by the OH- producing side of a second bipolar membrane, for example, the second bipolar membrane.

[0052] The EDBPM system, preferably the feed chamber of the EDBPM system, comprises at least one inlet configured to receive a feed. In particular embodiments, the EDBPM system, preferably the feed chamber of the EDBPM system, comprises more than one inlet, for example, 2 or 3 inlets configured to receive a feed.

[0053] The EDBPM system is configured to provide an acidic flow and an alkaline flow from the EDBPM system by applying a voltage or electric current between the cathode and the anode of the EDBPM system.

[0054] In a preferred embodiment, the EDBPM system consists of a cathode, a first bipolar membrane a first bipolar membrane (BPM1), a cation exchange membrane (CEM), an anion exchange membrane (AEM), a second bipolar membrane (BPM2), and an anode.The first bipolar membrane is positioned at the cathode side, and the second bipolar membrane is positioned at the anode side. The cation exchange membrane is positioned at the OH- producing side of the first bipolar membrane, and the anion exchange membrane is positioned at the H+producing side of the second bipolar membrane.In such embodiment, the EDBPM system consists of a cathode chamber positioned at the cathode side and bound by the H+producing side of the first bipolar membrane; a base receiver chamber bound by the OH- producing side of the first bipolar membrane and the cation exchange membrane, a feed chamber bound by the cation exchange membrane and the at anion exchange membrane, an acid receiver chamber defined by the at least one anion exchange membrane and the H+producing side of the second bipolar membrane, and an anode chamber positioned at the anode side and bound by the OH- producing side of the second bipolar membrane.

[0055] In alternative embodiments, the EDBPM system further comprises one or more additional pairs of a cation exchange membrane and an anion exchange membrane, and at least one additional bipolar membrane.

[0056] The one or more additional pairs of a cation exchange membrane and an anion exchange membrane, and the at least one additional bipolar membrane are positioned between the second bipolar membrane and the anode.

[0057] In case the EDBPM comprises more than one additional pair of a cation exchange membrane and an anion exchange membrane, the additional pairs are positioned in such a way that the cation exchange membranes and the anion exchange membranes are positioned in alternating positions.

[0058] The at least one additional bipolar membrane is positioned close to the anode, i.e., between the anion exchange membrane of the additional pair of a cation exchange membrane and anion exchange membrane closest to the anode.

[0059] An EDBPM system comprising one or more additional pairs of a cation exchange membrane and an anion exchange membrane allows for concentrating and separating VFAs and nutrients, as well as balancing nutrients.

[0060] In embodiments comprising one or more additional pairs of an anion exchange membrane and a cation exchange membrane, and at least one additional bipolar membrane, the EDBPM system comprises one or more additional feed chambers bound by the cation exchange membrane and the anion exchange membrane of an additional pair of a cation exchange membrane, and an anion exchange membrane.

[0061] Furthermore, such embodiments have one or more additional acid receiver chambers. Such additional acid receiver chamber is defined by an anion exchange membrane and a cation exchange membrane of two subsequent pairs of a cation exchange membrane. An additional acid receiver chamber is defined by the H+producing side of the additional bipolar membrane (positioned next to the anode) and the anion exchange membrane positioned next to the at least one additional bipolar membrane.

[0062] Additionally, in such embodiments an additional base receiver chamber is present. Such additional base receiver chamber is defined between the second bipolar membrane and the cation exchange membrane of the additional pair of a cation exchange membrane and an anion exchange membrane.

[0063] The ED system comprises a cathode, at least one cation exchange membrane (CEM), at least one anion exchange membrane (AEM), and an anode. The cation exchange membrane and the anion exchange membrane are positioned next to each other, thereby creating an intermediate chamber between the cation exchange membrane and the anion exchange membrane. The ED system may further comprise one or more additional pairs of alternating cation exchange membranes and cation exchange membranes and / or one or more bipolar membranes. The ED system thus defines a cathode chamber positioned at the cathode side; an intermediate chamber defined by at least one cation exchange membrane and the at least one anion exchange membrane;an anode chamber positioned at the anode side.

[0064] The ED system is configured to provide / isolate an OFT stream by applying a voltage or electric current between the cathode and the anode of the ED system.

[0065] The membrane contactor (MC) comprises at least one selective membrane defining a feed side and a permeate side. The selective membrane creates two chambers: a feed chamber at the feed side of the selective membrane and a permeate chamber at the permeate side of the selective membrane.

[0066] Preferably, the system further comprises means configured to discharge the acidic flow provided from the EDBPM system and to introduce the acidic flow to the feed side of the MC; means configured to discharge the alkaline flow provided from the EDBPM system and to introduce the alkaline flow to the ED system; and means configured to discharge the OH- stream provided / isolated from the ED system and to introduce the OH- stream to the permeate side of the MC.Brief description of the drawings

[0067] The present invention will be discussed in more detail below, with reference to the attached drawings, in which:Figure 1 a to Figure 5a show flow diagrams of different embodiments of systems according to the present invention;Figure 1 b to Figure 5b show the nomenclature of the membranes used in the stacks shown respectively in Figure 1 a to Figure 5b, as well as the nomenclature of the flow streams shown respectively in Figure 1 a to Figure 5b;Figure 6 and Figure 7 show schematic illustrations of embodiments of systems for the recovery of fatty acids, such as volatile fatty acids and nutrients, according to the present invention.Description of embodiments

[0068] The present invention will be described with respect to particular embodiments and with reference to certain drawings, but the invention is not limited thereto but only by the claims. The drawings are only schematic and are non-limiting. The size of some of the elements in the drawing may be exaggerated and not drawn on scale for illustrative purposes. The dimensions and the relative dimensions do not correspond to actual reductions to practice of the invention.

[0069] When referring to the endpoints of a range, the endpoint values of the range are included.

[0070] When describing the invention, the terms used are construed in accordance with the following definitions, unless indicated otherwise.

[0071] The term ‘and / or’ when listing two or more items, means that any one of the listed items can by employed by itself or that any combination of two or more of the listed items can be employed.

[0072] The terms first, second, third, and the like are used to distinguish between like elements and not necessarily to describe a sequential or chronological order. The terms are interchangeable under appropriate circumstances, and the embodiments of the invention may be used in sequences other than those described or illustrated herein.

[0073] The term ‘fatty acids’ refers to carboxylic acids having an aliphatic chain, which can be saturated or unsaturated, unbranched or branched.

[0074] The term ‘volatile fatty acids’ or ‘VFAs’ (also known as low molecular weight organic acids) comprises aliphatic monocarboxylic acids having a maximum of eight carbon atoms (C1 to C8) and preferably having two to eight carbon atoms (C2 to C8). The most common VFAs are acetic acid (C2), propionic acid (C3), and butyric acid (C4) (iso-butyric acid, n-butyric acid). Other VFAs comprise formic acid (C1), valeric acid (C5) (iso-valeric acid, n-valeric acid), caproic acid (C6) (isocaproic acid, n-caproic acid), and caprylic acid (octanoic acid) (C8).

[0075] The term ‘nutrients’ refers to any substance that a living organism needs in order to live and grow. Nutrients comprise chemical compounds in an aqueous solution, for example, in (waste) water. Nutrients include for example Na+, K+, NH4+, Ca2+, Mg2+, Cl", NOs-, SO42-and PO43-.

[0076] Electrodialysis refers to a process for the separation of an electrolyte from a solvent, typically water, using a direct electrical current or voltage to transport ions through ion-exchange membranes. An electrodialysis process is operated in a unit having at least one cation exchange membrane and at least one anion exchange membrane positioned next to each other, thereby creating a chamber (the intermediate chamber) between the cation exchange membrane and the anion exchange membrane. The unit further comprises two terminal chambers housing a cathode and an anode. A potential difference is applied between the anode and the cathode to drive the ions through the electrolyte solutions and the membranes.

[0077] It is clear that the ED system may comprise a plurality of pairs of alternating anion and cation exchange membranes.

[0078] Typical anion exchange membranes comprise membranes comprising a polymer matrix having a fixed amount of cation charged groups such as but not limited to NH4+, NRs+, NR2H+, NHR2+. Examples of anion exchange membranes are membranes sold under the tradenames Fujifim AEM, and Neosepta AMX.

[0079] Typical cation exchange membranes comprise membranes comprising a polymer matrix having a fixed amount of anion charged groups such as but not limited to -SOs", -COO", -POs2",-PHO2-. Examples of cation exchange membranes are membranes sold under the tradenames Fujifilm CEM, Neosepta CMX, and Ralex.

[0080] The ED system used in the process according to the present invention may further comprise one or more bipolar membranes.

[0081] Preferably, the cathode chamber and the anode chamber of the ED system are rinsed during the process, preferably by using water or by using an electrolyte (electrically conductive solution) as a rinse solution. Examples of rinse solutions comprise Na2SO4, KNO3, NaOH, KOH, KCI, H2SO4, NaCI, HCI, HNO3 or NaNOs. In alternative embodiments, the cathode and anode chambers may comprise electrically conductive or capacitive electrodes.

[0082] An electrodialysis bipolar membrane (EDBPM) system integrates bipolar membranes with traditional electrodialysis and is capable of producing an acidic and an alkaline flow.

[0083] A ‘bipolar membrane’ refers to a membrane comprising an anion exchange membrane and a cation exchange membrane. When used in conjunction with an electrical field, a bipolar membrane can efficiently dissociate a water molecule into a proton and a hydroxyl ion.

[0084] The EDBPM system comprises at least one repetitive unit comprising an anion exchange membrane, a cation exchange membrane, and comprises one or more bipolar membranes.

[0085] The EDBPM system has two terminal chambers housing a cathode and an anode. A potential difference or electric current is applied between the anode and the cathode to drive the ions through the electrolyte solutions and the membranes.

[0086] Typical anion exchange membranes comprise membranes comprising a polymer or inorganic matrix having a fixed amount of cation charged groups, such as but not limited to NH4+, NR3+, NR2H+, NHR2+. Examples of anion exchange membranes are membranes sold under the tradenames Fujjifim AEM, and Neosepta AMX.

[0087] Typical cation exchange membranes comprise membranes comprising a polymer or inorganic matrix having a fixed amount of anion charged groups, such as but not limited to -SOs-, -COO-, — PO32-, -PHO2-. Examples of cation exchange membranes are membranes sold under the tradenames Fujifilm CEM, Neosepta CMX, and Ralex AMH.

[0088] Typical bipolar membranes comprise a cation exchange membrane or layer and an anion exchange membrane or layer fixed together. Examples of bipolar membranes are membranes sold under the tradename Pccell bp (Germany), and Fumasep FBM.Preferably, the cathode chamber and the anode chamber of the EDBPM system are rinsed during the process, preferably by using water or by using an electrolyte (electrically conductive solution) as rinse solution.

[0089] In alternative embodiments, the cathode and / or anode chamber may comprise electrically conductive or capacitive electrodes.

[0090] A membrane contactor (MC) is a device used in various separation processes. It consists of a membrane that allows the selective transfer of components between two phases, typically gas and liquid, while preventing the mixing of the phases themselves. The basic principle involves onephase being brought into contact with one side of the membrane (the feed side), while the other phase flows on the opposite side (permeate side) of the membrane. The membrane selectively allows certain components to pass through based on their permeability, size, or chemical properties. This selective transfer enables the separation or extraction of specific components from one phase to another.

[0091] Typical selective membranes comprise a polymer material, preferably a selective polymer material, such as but not limited to polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), polypropylene (PP), silicone, polysulfone (PS), polyethersulfone (PES), polystyrene (PSE), polydimethylsiloxane (PDMS), polyethylene (PE), polyvinylchloride (PVC), polyesters, polyurethanes (PU). Alternatively, selective membranes may comprise ceramic or inorganic materials, preferably selective ceramic and inorganic materials such as but not limited to alkylsilane and (coated) oxides, for example, coated AI2O3 or TiO2.

[0092] A flow diagram of a first embodiment of a process for recovering fatty acids, in particular volatile fatty acids, and nutrients from a feed stream, is given in Figure 1a. The nomenclature of the membranes used in the stacks, as well as the nomenclature of the flow streams, is given in Figure 1 b.

[0093] The system comprises an electrodialysis bipolar membrane (EDBPM) system 1 , an electrodialysis (ED) system 2, and a membrane contactor (MC) 3.

[0094] The EDBPM system 1 has a cathode and an anode and comprises, subsequently from the cathode to the anode, a first bipolar membrane, a cathode exchange membrane, an anion exchange membrane, and a second bipolar membrane, defining respectively a cathode chamber, a base receiver chamber, a feed chamber, an acid receiver chamber, and an anode chamber.

[0095] The ED system 2 has a cathode and an anode and comprises, subsequently from the cathode to the anode, a cation exchange membrane, an anion exchange membrane, and a cation / anion exchange membrane, defining a cathode chamber, a first intermediate chamber, a second intermediate chamber, and an anode chamber.

[0096] The membrane contactor system comprises a selective membrane, thereby defining a feed side and a permeate side.

[0097] The EDBPM system 1 generates an acidic flow and an alkaline (basic) flow. The acidic flow is pumped from the acid receiver chamber from the EDBPM to the feed side of the MC 3 for selective VFAs recovery from nutrients. The alkaline flow is pumped from the EDBPM system 1 to the ED system 2, in particular from the base receive chamber of the EDBPM system 1 to the first intermediate chamber of the ED system 2.

[0098] The ED system 2 is utilized to isolate the hydroxide ions (OH- stream) generated by the bipolar membrane. The isolated OFT stream is then pumped from the ED system 2, in particular from the second intermediate chamber of the ED system 2, to the permeate side of the MC 3 for in- situ reaction with the permeating VFAs (VFAs deprotonation).

[0099] The flow stream shown in Figure 1 clearly indicates the VFAs and nutrient feed stream, the base receiver stream, the acid receiver stream, the membrane contactor permeate stream, the electrode rinse stream at the cathode and at the anode of the ED system 2, and the ER stream at the cathode and the anode of the EDBPM system 1 .

[0100] The flow stream of a second embodiment of a process according to the present invention is illustrated in Figure 2a. The nomenclature of the membranes used in the stacks, as well as the nomenclature of the flow streams, is given in Figure 2b.

[0101] The system comprises an EDBPM system 1 , an ED system 2, and an MC 3. The EDBPM system 1 and the MC 3 correspond with the EDBPM system 1 and the MC 3 shown in Figure 1 .

[0102] The ED system 2 has a cathode and an anode and comprises subsequently from the cathode to the anode a BPM, an anion exchange membrane, a cation exchange membrane, an anion exchange membrane and a cation / anion exchange membrane, defining a cathode chamber, a first intermediate chamber, a second intermediate chamber, a third intermediate chamber, a fourth intermediate chamber and an anode chamber.

[0103] The EDBPM system 1 generates an acidic flow and an alkaline (basic) flow. The acidic flow is pumped from the acid receiver chamber of the EDBPM system to the feed side of the MC 3 for selective VFAs recovery from nutrients. The alkaline flow is pumped from the cathode chamber of the EDBPM system 1 to the ED system 2 (in particular to the third intermediate chamber of the ED system 2).

[0104] An alkaline flow is circulated from the base receiver chamber to the anode chamber of the EDBPM system 1 , thereby reducing the pH and avoiding scaling. Furthermore, a flow of VFA is created in the ED system 2 so that the VFA flow further receives OH- ions generated by the cathode. (VFA alkalization by the ED cathode).

[0105] An OH- stream is isolated from the ED system 2 and pumped from the ED system, in particular from the cathode chamber of the ED system 2, to the permeate side of the MC 3 for in- situ reaction with the permeating VFAs (VFAs deprotonation).

[0106] The flow stream shown in Figure 2a clearly indicates the VFAs and nutrient feed stream, the base receiver stream, the acid receiver stream, the membrane contactor permeate stream, the electrode rinse stream at the cathode and at the anode of the ED system 2, the ER stream at the cathode and the anode of the EDBPM system 1 as well as a buffer stream.

[0107] The flow stream of a third embodiment of a process according to the present invention is illustrated in Figure 3a. The nomenclature of the membranes used in the stacks, as well as the nomenclature of the flow streams, is given in Figure 3b.

[0108] The system comprises an EDBPM system 1 , an ED system 2, and an MC 3. The EDBPM system 1 and the MC 3 correspond with the EDBPM system 1 and MC 3 shown in Figure 1 .

[0109] The ED system 2 corresponds with the ED system 2 of Figure 2a.

[0110] The EDBPM system 1 generates an acidic flow and an alkaline (basic) flow. The acidic flow is pumped from the acid receiver chamber of the EDBPM system 1 to the feed side of the MC 3 forselective VFAs recovery from nutrients. The alkaline flow is pumped from the base receive chamber of the EDBPM system 1 to the ED system 2 (to the third intermediate chamber of the ED system 2).[00111JVFA alkalinization occurs at the cathode of the ED system 2.

[0112] The ED system 2 is utilized to isolate an OFT stream. The isolated OFT stream is then pumped from the ED system 2, i.e., from the cathode chamber of the ED system 2, to the permeate side of the MC 3 for in-situ reaction with the permeating VFAs (VFAs deprotonation).

[0113] The flow stream shown in Figure 3a clearly indicates the VFAs and nutrient feed stream, the base receiver stream, the acid receiver stream, the membrane contactor permeate stream, the electrode rinse stream at the cathode and at the anode of the ED system 2 and the ER stream at the cathode and the anode of the EDBPM system 1 as well as a buffer stream.

[0114] The flow stream of a fourth embodiment of a process according to the present invention is illustrated in Figure 4a. The nomenclature of the membranes used in the stacks, as well as the nomenclature of the flow streams, is given in Figure 4b.

[0115] The system comprises an EDBPM system 1 , an ED system 2, and an MC 3. The EDBPM system 1 and the MC 3 correspond with the EDBPM system 1 and the MC 3 shown in Figure 1 .

[0116] The ED system 2 has a cathode and an anode and comprises, subsequently from the cathode to the anode, an anion exchange membrane, a cation exchange membrane, an anion exchange membrane, and a cation / anion exchange membrane, defining a cathode chamber, a first intermediate chamber, a second intermediate chamber, a third intermediate chamber, and an anode chamber.

[0117] The EDBPM system 1 generates an acidic flow and an alkaline (basic) flow. The acidic flow is pumped from the acid receiver chamber from the EDBPM to the feed side of the MC 3 for selective VFAs recovery from nutrients. The alkaline flow is pumped from the base receive chamber of the EDBPM system 1 to the ED system 2 (in particular to the cathode chamber of the ED system 2).

[0118] An additional base, ZOH, for example, NaOH, Ca(OH)2, Mg(OH)2, NH4OH, is introduced to the ED system 2, for example, to the second intermediate chamber of the ED system 2.

[0119] An OH- stream is isolated from the ED system 2 and pumped from the ED system 2, i.e., from the third intermediate chamber of the ED system 2 to the to the permeate side of the MC 3 for in-situ reaction with the permeating VFAs (VFAs deprotonation).

[0120] An additional base, ZOH, for example, NaOH, Ca(OH)2, Mg(OH)2, NH4OH, is introduced to the ED system, for example, to the second intermediate chamber of the ED system 2. The flow induced by the additional base ZOH referred to as ZOH stream is indicated in Figure 4a.

[0121] The flow stream shown in Figure 4a clearly indicates the VFAs and nutrient feed stream, the base receiver stream, the acid receiver stream, the membrane contactor permeate stream, the electrode rinse stream at the cathode and at the anode of the ED system and the ER stream at the cathode and the anode of the EDBPM system 1 as well as the ZOH stream.

[0122] The flow stream of a fifth embodiment of a process according to the present invention is illustrated in Figure 5a. The nomenclature of the membranes used in the stacks, as well as the nomenclature of the flow streams, is given in Figure 5b.

[0123] The system comprises an EDBPM system 1 , an ED system 2, and an MC 3. The EDBPM system 1 and the MC 3 correspond with the EDBPM system 1 and the MC 3 shown in Figure 1 . The ED system 2 corresponds with the ED system 2 shown in Figure 4a.

[0124] The EDBPM system 1 generates an acidic flow and an alkaline (basic) flow. The acidic flow is pumped from the acid receiver chamber from the EDBPM to the feed side of the MC 3 for selective VFAs recovery from nutrients. The alkaline flow is pumped from the base receive chamber of the EDBPM system 1 to the ED system 2 (in particular to the cathode chamber of the ED system 2).

[0125] Similar to the flow diagram shown in Figure 4a, an additional base, ZOH, for example, NaOH, Ca(OH)2, Mg(OH)2, NF OH, is introduced to the ED system 2, for example, to the second intermediate chamber of the ED system 2.

[0126] An alkaline flow is circulated from the base receiver chamber to the anode chamber of the EDBPM system 1 , thereby reducing the pH and avoiding scaling.

[0127] An OH- stream is isolated from the ED system 2 and pumped from the ED system 2, i.e, from the third intermediate chamber of the ED system 2 to the permeate side of the membrane contactor for in-situ reaction with the permeating VFAs (VFAs deprotonation).

[0128] An additional base, ZOH, for example, NaOH, Ca(OH)2, Mg(OH)2, NH4OH, is introduced to the ED system 2, for example, to the second intermediate chamber of the ED system 2. The flow induced by the additional base ZOH, referred to as the ZOH stream, is indicated in Figure 4a.

[0129] The flow stream shown in Figure 5a clearly indicates the VFAs and nutrient feed stream, the base receiver stream, the acid receiver stream, the membrane contactor permeate stream, the electrode rinse stream at the cathode and at the anode of the ED system 2 and the ER stream at the cathode and the anode of the EDBPM system 1 , the base regulation stream as well as the ZOH stream.

[0130] Figure 6 shows a schematic illustration of an embodiment of a system for the recovery of fatty acids, in particular volatile fatty acids and nutrients according to the present invention, whereby the EDBPM system consists of a cathode, a first bipolar membrane (BPM1), a cation exchange membrane (OEM), an anion exchange membrane (AEM), a second bipolar membrane (BPM2) and an anode.The first bipolar membrane is positioned at the cathode side, and the second bipolar membrane is positioned at the anode side. The cation exchange membrane is positioned at the OH- producing side of the first bipolar membrane, and the anion exchange membrane is positioned at the H+producing side of the second bipolar membrane.The EDBPM system thereby defines a cathode chamber positioned at the cathode side and bound by the H+producing side of the first bipolar membrane;a base receiver chamber bound by the OH- producing side of the first bipolar membrane and the cation exchange membrane, a feed chamber bound by the cation exchange membrane and the at anion exchange membrane, an acid receiver chamber defined by the at least one anion exchange membrane and the H+producing side of the second bipolar membrane, and an anode chamber positioned at the anode side and bound by the OH- producing side of the second bipolar membrane;

[0131] The system shown in Figure 6 allows to concentrate and separate VFAs and nutrients.

[0132] Figure 7 shows a schematic illustration of a further embodiment of a system for the recovery of fatty acids, in particular volatile fatty acids and nutrients according to the present invention, whereby the EDBPM system comprises a cathode, a first bipolar membrane (BPM1), a cation exchange membrane (CEM), an anion exchange membrane (AEM), a second bipolar membrane (BPM2) and an anode similar to the system shown in Figure 6. Furthermore, the EDBPM system comprises two additional pairs of a cation exchange membrane and an anion exchange membrane, and an additional bipolar membrane. The additional two pairs of a cation exchange membrane and an anion exchange membrane, and the at least one additional bipolar membrane are positioned between the second bipolar membrane and the anode.

[0133] The system shown in Figure 7 allows to concentrate and separate VFAs and nutrients and to simultaneously balance nutrient ratios.

Claims

Claims1. A process for recovering volatile fatty acids and / or nutrients from a feed using a system comprising an electrodialysis bipolar membrane (EDBPM) system, an electrodialysis system (ED) system, and a membrane contactor (MC) with the EDBPM system comprising a cathode, a first bipolar membrane (BPM1), at least one cation exchange membrane (CEM), at least one anion exchange membrane (AEM), a second bipolar membrane (BPM2), and an anode, with the first bipolar membrane being positioned at the cathode side and the second bipolar membrane being positioned at the anode side, and with the at least one cation exchange membrane being positioned at the OH- producing side of the first bipolar membrane and with the at least one anion exchange membrane being positioned at the H+producing side of the second bipolar membrane, the EDBPM system defining a cathode chamber positioned at the cathode side; a base receiver chamber bound by the OH- producing side of the first bipolar membrane and the at least one cation exchange membrane, a feed chamber bound by the at least one cation exchange membrane and the at least one anion exchange membrane, an acid receiver chamber defined by the at least one anion exchange membrane and the H+producing side of the second bipolar membrane, and an anode chamber positioned at the anode side and bound by the OH- producing side of the second bipolar membrane; the ED system comprising a cathode, at least one cation exchange membrane (CEM), at least one anion exchange membrane (AEM) and an anode defining a cathode chamber, at least one intermediate chamber bound by the at least one cation exchange membrane and the at least one anion exchange membrane and an anode chamber; the MC comprising at least one selective membrane defining a feed side and a permeate side; the method comprising the steps of introducing a feed into the feed chamber of the EDBPM system; applying a voltage or electric current between the cathode and the anode of the EDBPM system, thereby providing an acidic flow and an alkaline flow from the EDBPM system; applying a voltage or electric current between the cathode and the anode of the ED system, thereby providing / isolating an OH- stream from the ED system; introducing the acidic flow from the EDBPM system to the feed side of the MC; introducing the alkaline flow from the EDBPM system to the ED system; isolating an OH- stream from the ED system and introducing the isolated OH- stream from the ED system to the permeate side of the MC.

2. The process according to claim 1 , wherein the fatty acids comprise volatile fatty acids.

3. The process according to claim 1 or claim 2, wherein the EDBPM further comprises at least one pair of a cation exchange membrane and an anion exchange membrane and at least one additional bipolar membrane, with the at least one pair of a cation exchange membrane and an anion exchange membrane and the at least one additional bipolar membrane being positioned between the second bipolar membrane and the anode.

4. The process according to any one of the preceding claims, wherein the acidic flow is provided from the acidic chamber of the EDBPM system.

5. The process according to any one of the preceding claims, wherein the alkaline flow is provided from the base receiver chamber of the EDBPM system, and wherein the alkaline flow is introduced from the base receiver chamber of the EDBPM system to the ED system.

6. The process according to any one of the preceding claims, wherein the isolated OH- stream from the ED chamber is provided from the at least one intermediate chamber of the ED system and introduced to the permeate side of the MC.

7. The process according to claims 1 to 3, wherein the isolated OFT stream from the ED chamber is provided from the cathode chamber of the ED system and introduced to the permeate side of the MC.

8. The process according to any one of the preceding claims, wherein the feed comprises an aqueous solution, (bio)waste water, anaerobic digestates, fermentation broths, gut microbiomes, or combinations thereof.

9. A system for the recovery of fatty acids and / or nutrients from a feed, the system comprising an electrodialysis bipolar membrane (EDBPM) system, an electrodialysis system (ED) system, and a membrane contactor (MC) with the EDBPM system comprising a cathode, a first bipolar membrane (BPM1), at least one cation exchange membrane (CEM), at least one anion exchange membrane (AEM), a second bipolar membrane (BPM2), and an anode, with the first bipolar membrane being positioned at the cathode side and the second bipolar membrane being positioned at the anode side, and with the at least one cation exchange membrane being positioned at the OH- producing side of the first bipolar membrane and with the at least one anion exchange membrane being positioned at the H+producing side of the second bipolar membrane,the EDBPM system defining a cathode chamber positioned at the cathode side and bound by the H+producing side of the first bipolar membrane; a base receiver chamber bound by the OH- producing side of the first bipolar membrane and the at least one cation exchange membrane, a feed chamber bound by the at least one cation exchange membrane and the at least one anion exchange membrane, an acid receiver chamber defined by the at least one anion exchange membrane and the H+producing side of the second bipolar membrane, and an anode chamber positioned at the anode side and bound by the OH- producing side of the second bipolar membrane, the EDBPM system comprising at least one inlet configured to receive a feed, the EDBPM system being configured to provide an acidic flow and an alkaline flow from the EDBPM system by applying a voltage or electric current between the cathode and the anode of the EDBPM system; the ED system comprising a cathode, at least one cation exchange membrane (CEM), at least one anion exchange membrane (AEM), and an anode defining a cathode chamber, at least one intermediate chamber bound by the at least one cation exchange membrane and the at least one anion exchange membrane, and an anode chamber, the ED system being configured to provide / isolate an OH- stream from the ED system by applying a voltage or electric current between the cathode and the anode of the ED system; the MC comprising at least one selective membrane defining a feed side and a permeate side; the system further comprising means configured to discharge the acidic flow provided from EDBPM system and to introduce the acidic flow to the feed side of the MC; means configured to discharge the alkaline flow provided from the EDBPM system and to introduce the alkaline flow to the ED system; and means configured to discharge the OH- stream provided / isolated from the ED system and to introduce the OH- stream to the permeate side of the MC.

10. The system according to claim 9, wherein the fatty acids comprise volatile fatty acids.

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