Device and method for extracting ammonium ions from a digestate

Abstract

The invention relates to a device for extracting ammonium ions (8) from a digestate resulting from a treatment of an enrichment liquid with biodegradable material and comprising: - A bioelectrochemical treatment unit (12) receiving a first volume of digestate and a second volume of enrichment liquid, - A member (40) for acquiring a value of at least one parameter representative of a value of at least one quality parameter of the digestate, and a value of at least one quality parameter of the enrichment liquid, - A member (44) for determining a value of a ratio of a mixture representative of a quantity of biodegradable organic material relative to a quantity of ammonium ions, - A member (48) for determining a ratio of the mixture of digestate and enrichment liquid as a function of the value of the characteristic ratio of a mixture, - A control member (52) configured to obtain the. Figure for abstract: Figure 1

Description

Title of the invention: Device and method for extracting ammonium ions from a digestate

[0001] The invention relates to the field of effluent treatment by anaerobic digestion, and in particular the coupling of a digester with a bioelectrochemical system allowing the intensification of the operation of the digester and the recovery of the ammoniacal nitrogen contained in the digestate produced during anaerobic digestion.

[0002] Anaerobic digestion is a cascade of biochemical reactions that convert the organic matter present in the digester into biogas, which is mainly a mixture of carbon dioxide and methane. The remaining materials are called digestate.

[0003] Most anaerobic digestion processes have as their main objective the production of energy in the form of biogas. However, the recovery of nutrients from digestates is increasingly being studied due to the increase in the price of inorganic fertilizers, particularly nitrogen fertilizers, and the scarcity of resources, particularly phosphorus. There are several recovery approaches.

[0004] A first approach to recovery consists of direct spreading of the digestate from anaerobic digestion. This method corresponds to the classic practice implemented in most anaerobic digesters for the recovery of digestate in agronomic applications. The digester is sized to express the vast majority of the methanogenic power of the input(s), then the digestate is then used to make nitrogen and phosphorus inputs directly in the field. However, this approach constrains the sizing of the digester so that it can express the majority of the methanogenic potential of the substrates (i.e. large reactors must be developed). In addition, numerous regulatory constraints weigh on the quality of the digestate for its return to the soil, in particular the nitrogen flow but also the content of pathogens or heavy metals.Finally, the transport of digestate containing a significant fraction of water represents a significant cost, limiting this solution to decentralized methanization plants.

[0005] A second approach consists of valorizing the solid fraction of the digestate. The digester is sized to express the vast majority of the methanogenic power of the input(s). The digestate can then be dehydrated to obtain a liquid fraction and a solid fraction. The solid fraction can then be composted or dried and then transported at lower costs than the raw digestate (because it contains less water). Depending on local constraints, the liquid fraction can also be spread directly, concentrated and often treated as water. used to reduce its COD (chemical oxygen demand), nitrogen and phosphorus content. However, the liquid fraction of the digestate contains the majority of the ammonia nitrogen flow (75 to 80%), which is then not recovered. In addition, its treatment requires significant infrastructure (e.g., nitrification / denitrification, anaerobic oxidation of ammonium) and induces significant operating costs.

[0006] A third approach consists of nitrogen recovery by struvite production. The digester is sized to express the vast majority of methanogenic power of the input(s). After digestion, phase separation makes it possible to produce a liquid fraction concentrated in ammonium and phosphates (particularly in the digestion of wastewater treatment plant sludge). Struvite (NH4 MgPO4-6H2O) can thus be precipitated, which requires in particular pH adjustments and a magnesium supply and a controlled crystallization process. Several variants exist. For example, if the digestate is rich in potassium, the nitrogen from the digestate can be stripped for subsequent recovery of K-struvite (MgKPO4-6H2O). However, struvite precipitation requires a large consumption of chemical reagents.Additionally, several ionic forms present in the digestate compete with struvite and result in lower value salts, including calcium / iron / aluminum salts and phosphates. In the case of organic waste digestates, quality variations can make the process difficult to control and dissolved organic matter can impact the quality of the precipitation.

[0007] A fourth approach consists of conventional nitrogen stripping. The digester is sized to express the vast majority of methanogenic power of the input(s). The digestate is then treated, with or without solid / liquid separation, by stripping the NH3. The NH4+ / NH3 balance is shifted towards NH3 by adjusting the temperature and / or pH, then a gas flow in a stripping tower (for example: air, biogas, N2) is imposed on the digestate in order to extract the NH3. Then, the NH3 is recovered by absorption in an acid washing tower, conventionally in a sulfuric acid solution. The resulting solution of ammonium sulfate (or its crystals) can then be marketed. In another possible configuration, ammonia water is produced by evaporation of the digestate and condensation of the vapors. The ammonia water is then sent to stripping and washing towers as described previously.According to such an approach, the stripping efficiency increases with the concentration of total ammonia nitrogen in the digestate. However, the presence of high ammonia nitrogen concentration in the digester (and therefore in the digestate) can cause inhibition of the process and limit methane production, which limits the techno-economic performance of stripping. In both configurations described, whether in the case of direct stripping or during the evaporation phase, . Clogging of columns or heat exchangers due to the presence of suspended matter and / or salt deposits is a well-known operational problem. In addition, the control of these physicochemical processes can be difficult given the variability in digestate quality.

[0008] A fifth approach consists of nitrogen recovery by electrochemical process. The digester is sized to express the vast majority of methanogenic power of the input(s). The ammoniacal nitrogen contained in the digestate can then be recovered by ionic migration in an electrochemical process, either by electrodialysis or by migration from an anode compartment to a cathode compartment. The electrochemical system can be positioned on a recirculation loop of the digester for in-line extraction, or downstream of the digester. The concentrated ammoniacal nitrogen flow can then be recovered by stripping and absorption. However, the electrochemical process requires a significant potential difference to operate, resulting in significant electrical energy consumption.

[0009] A sixth approach consists of nitrogen recovery by bioelectrochemical process. The digester is sized to express the vast majority of methanogenic power of the input(s). The process is coupled with a bioelectrochemical process in which at least one of the redox reactions is catalyzed by electroactive microorganisms. These systems can exploit the chemical energy contained in organic molecules in order to move electrons in an electrical circuit. The positioning of the bioelectrochemical system is similar to that of the purely electrochemical system (i.e. without electroactive microorganisms), but requires less energy, or even no energy at all depending on the reactions catalyzed by the microorganisms. The concentrated ammoniacal nitrogen stream can then be recovered by stripping and absorption.However, online nitrogen extraction by bioelectrochemical systems requires the consumption of organic matter by the electroactive microorganisms present in the anode compartment. When positioned downstream of the methanizer, the bioelectrochemical process is limited by the amount of biodegradable material, the vast majority having been converted into methane during the anaerobic digestion step.

[0010] The invention aims in particular to provide a device for extracting ammonium ions from a digestate resulting from a treatment by anaerobic digestion of an input comprising carbonaceous material and nitrogen compounds, for example from sewage treatment plant sludge, making it possible to optimize the recovery of nitrogenous nutrients contained in a digestate resulting from an anaerobic digestion process and this at a lower cost.

[0011] For this purpose, the invention relates to a method for extracting ammonium ions from a digestate or a fraction of a digestate, resulting from a treatment of an input comprising carbonaceous material and nitrogen compounds by anaerobic digestion, by means of an ammonium ion extraction device comprising a bioelectrochemical treatment unit configured to receive a first volume of digestate, or a liquid fraction of the digestate, and a second volume of liquid for enriching with biodegradable material, the bioelectrochemical treatment unit comprising electroactive microorganisms and at least one separator capable of allowing ammonium ions to pass in the presence of a potential difference, the method comprising the following steps: - a step of acquiring a value of at least one parameter representative of the capacity of the bioelectrochemical treatment unit to separate the ammonium ions, a value of at least one quality parameter of the digestate or its liquid fraction brought to the bioelectrochemical treatment unit, representative of a quantity of ammonium ions relative to a total quantity of cations and a concentration of ammonium ions in the digestate or in its liquid fraction and a concentration of ammonium ions in the digestate or in its liquid fraction, and a value of at least one quality parameter of the biodegradable material enrichment liquid, representative of a concentration of biodegradable material in the biodegradable material enrichment liquid brought to the bioelectrochemical treatment unit, - a step of determining a value of a characteristic ratio of a mixture of digestate, or of the liquid fraction of digestate, and of liquid enrichment in biodegradable matter, representative of a quantity of biodegradable organic matter relative to a quantity of ammonium ions, as a function of a target yield of ammonium ions extracted from the bioelectrochemical treatment unit or of a target concentration of separated ammonium ions present in the bioelectrochemical treatment unit, and of the values ​​determined during the acquisition step, - a step of determining a ratio of a mixture of digestate, or of a liquid fraction of the digestate, and of liquid enrichment in biodegradable material as a function of the value of the characteristic ratio of a mixture of the digestate, or of the liquid fraction of the digestate, and of liquid enrichment in biodegradable material, - a step of mixing digestate, or liquid fraction of digestate, and biodegradable material enrichment liquid to obtain the ratio of the mixture of digestate, or of a liquid fraction of the digestate, and of liquid enrichment in biodegradable material, and - a step of bioelectrochemical treatment of the mixture of digestate, or liquid fraction of digestate, and liquid enrichment in biodegradable material.

[0012] Thus, an enrichment liquid is used to enrich the digestate, or its liquid fraction, with biodegradable organic matter that can be consumed by the electroactive microorganisms to provide the bioelectrochemical treatment unit with the energy necessary for the extraction of ammonium ions. This enrichment makes it possible to compensate for the consumption of biodegradable matter by a digester, which is sized to satisfactorily express the methanogenic potential of the substrates. This implies that the digestate or the liquid fraction of the digestate contains only a small amount of biodegradable matter, which would limit the recovery of nitrogen in the bioelectrochemical system due to a deficit in energy production.

[0013] In practice, the recovery of ammonium by electrodialysis is competed with by the migration of other cations such as Na+, K+, or Ca2+ which are present in significant quantities in wastewater. Indeed, most cation exchange membranes are not specific to one cationic species or another. One solution consists of feeding the bioelectrochemical cell with a mixture of biodegradable material enrichment liquid and digestate or liquid fraction of digestate in order to find a compromise between concentration of biodegradable material and ammonium migration efficiency. The cationic composition of digestates or liquid fractions of digestate is very largely dominated by ammonium.In addition, the ammonium concentrations of these matrices are high compared to a biodegradable matter enrichment liquid such as wastewater (for example, sludge digestate from urban wastewater treatment with a concentration typically greater than 500 mgN / L). Thus, it is possible to find a mixture of the two effluents that can significantly increase the ammonium concentration as well as the share of ammonium compared to other cations, while maintaining a BOD5 / N ratio favorable to the recovery of ammonium by electrodylysis. In addition, and in the case of using wastewater in a treatment plant as a source of biodegradable matter, the coupling also makes it possible to treat part of the BOD5 of the treatment plant, thus reducing the energy costs related to the aeration of the wastewater as well as the production of biological sludge.

[0014] The extraction method according to the invention may further comprise at least one of the following optional characteristics: - the value of a characteristic ratio of the mixture of digestate, or of the liquid fraction of digestate, and of the liquid enrichment in biodegradable material is between 0.25 elO gDCO / gN, - the step of acquiring a value of at least one quality parameter of the enrichment liquid in biodegradable material comprises the acquisition of at least one of the following parameters: the biological oxygen demand, the biological oxygen demand measured after 5 days, the soluble chemical oxygen demand, the total chemical oxygen demand, the total organic carbon, - the step of determining a ratio of a mixture of digestate, or of a liquid fraction of the digestate, and of liquid for enriching with biodegradable material as a function of the value of the characteristic ratio of a mixture of the digestate, or of the liquid fraction of the digestate, and of liquid for enriching with biodegradable material comprises a determination of the ratio of the mixture as a function of an ammonium recovery rate, the ammonium recovery rate being determined from the determination of a migration flow of ammonium ions by electrodialysis and a diffusion flow of the ions through the separator, and - the bioelectrochemical treatment step further comprises the implementation of a reaction chosen from a reaction for reducing dioxygen or nitrate and a reaction for producing dihydrogen or organic molecules of interest chosen from organic acids, alcohols, methane.

[0015] The invention also relates to a method for the biological treatment of an input containing carbonaceous material and nitrogen compounds to produce biogas and recover ammonium ions via a biological treatment installation comprising: - a digester adapted to produce biogas and digestate by anaerobic digestion, - a source of enrichment liquid in biodegradable material, - an ammonium ion extraction device comprising a bioelectrochemical treatment unit configured to receive a first volume of digestate, or a liquid fraction of the digestate, and a second volume of liquid for enrichment with biodegradable material, the bioelectrochemical treatment unit comprising electroactive microorganisms and at least one separator capable of allowing ammonium ions to pass in the presence of a potential difference, the method comprising the following steps: - an anaerobic digestion step producing biogas and digestate, and - the ammonium ion extraction process according to the invention.

[0016] Advantageously, the biological treatment method according to the invention further comprises at least one step of recovering the ammonium ions contained in an effluent enriched in ammonium ions at the outlet of the bioelectrochemical treatment unit, the step of recovering the ammonium ions being chosen from a stripping step followed by a step of absorbing nitrogen, a step of precipitating the ammonium ions in the form of struvite.

[0017] The invention also relates to a device for extracting ammonium ions from a digestate or a liquid fraction of a digestate, resulting from a treatment of an input containing carbonaceous material and nitrogen compounds and obtained by anaerobic digestion, the device comprising: - At least one bioelectrochemical treatment unit configured to receive a first volume of digestate, or a liquid fraction of the digestate, and a second volume of a liquid for enriching with biodegradable material, the bioelectrochemical treatment unit comprising electroactive microorganisms and at least one separator configured to allow ammonium ions to pass in the presence of a potential difference, - at least one acquisition device for a value of at least one parameter representative of the capacity of the bioelectrochemical treatment unit to separate ammonium ions, a value of at least one quality parameter of the digestate, or of its liquid fraction, brought to the bioelectrochemical treatment unit, representative of a quantity of ammonium ions relative to a total quantity of cations and a concentration of ammonium ions in the digestate or in its liquid fraction, and a value of at least one quality parameter of the biodegradable matter enrichment liquid, representative of a concentration of biodegradable matter in the wastewater brought to the bioelectrochemical treatment unit, - at least one device for determining a value of a characteristic ratio of a mixture of digestate, or of the liquid fraction of digestate, and of liquid enrichment in biodegradable matter, representative of a quantity of biodegradable organic matter relative to a quantity of ammonium ions, as a function of a target yield of ammonium ions extracted from the bioelectrochemical treatment unit or of a target concentration of separated ammonium ions present in the bioelectrochemical treatment unit, and of the values ​​received by the acquisition device, - at least one organ for determining a ratio of a mixture of digestate, or of a liquid fraction of the digestate, and of enrichment liquid in biodegradable material depending on the value of the characteristic ratio of a mixture of digestate, or of the liquid fraction of digestate, and of liquid enrichment in biodegradable material, - at least one member for controlling the quantity of digestate, or of a liquid fraction of the digestate, and of liquid for enriching with biodegradable material to be brought to the bioelectrochemical treatment unit and configured to obtain the ratio of the mixture of digestate, or of a liquid fraction of the digestate, and of liquid for enriching with biodegradable material.

[0018] The extraction device according to the invention may further comprise at least one of the following optional characteristics: - the value of a characteristic ratio of the mixture of digestate, or of the liquid fraction of digestate, and of the liquid enrichment in biodegradable material is between 0.25 and 10 gDCO / gN, - the parameter representative of the concentration of biodegradable matter in the biodegradable matter enrichment liquid is chosen from at least one of the following parameters: biological oxygen demand, biological oxygen demand measured after 5 days, soluble chemical oxygen demand, total chemical oxygen demand, total organic carbon, and - the member for determining a ratio of a mixture of digestate, or of a liquid fraction of the digestate, and of liquid for enriching with biodegradable material as a function of the value of the characteristic ratio of a mixture of the digestate, or of the liquid fraction of the digestate, and of liquid for enriching with biodegradable material is configured to determine the ratio of a mixture as a function of an ammonium recovery rate, the ammonium recovery rate being determined from the determination of a migration flow of ammonium ions by electrodialysis and a diffusion flow of ions through the separator.

[0019] The invention also relates to an installation for the biological treatment of an input containing carbonaceous material and nitrogen compounds to produce biogas and recover ammonium ions, the installation comprising: - a digester adapted to produce biogas and digestate by anaerobic digestion, - a source of enrichment liquid in biodegradable material, - an ammonium ion extraction device according to the invention, - at least one conduit for supplying digestate, or the liquid fraction of the digestate, from the digester to the ammonium ion extraction device, and - at least one conduit for supplying the biodegradable material enrichment liquid from the source of biodegradable material enrichment liquid to the ammonium ion extraction device,

[0020] The biological treatment installation according to the invention may further comprise at least one of the following optional characteristics: - The biological treatment installation forms a wastewater treatment plant, in which the conduit for supplying the digestate, or the liquid fraction of the digestate, from the digester to the ammonium ion extraction device is a digestate return conduit upstream of the biological treatment installation, for example upstream of a primary settling device, and - The biological treatment installation forms a wastewater treatment plant, the biodegradable material enrichment liquid being formed by wastewater, in which the source of wastewater is for example formed by the wastewater leaving a primary settling device. Brief description of the figures

[0021] The invention will be better understood on reading the following description given solely by way of example and with reference to the appended drawings in which:

[0022] [Fig. 1] is a representation of a biological treatment installation according to the invention,

[0023] [Fig.2] is a representation of an ammonium ion extraction device according to the invention,

[0024] [Fig.3] is a flowchart of an extraction method according to the invention,

[0025] [Fig.4] is a flowchart of a biological treatment method according to the invention, And

[0026] [Fig.5] is a representative graph of an ammonium ion recovery rate as a function of a percentage of wastewater in a mixture of digestate, or liquid fraction of digestate, and wastewater. Detailed description

[0027] This patent application incorporates the following definitions: - Electroactive microorganisms are microorganisms capable of exchanging electrons with solid and conductive surfaces. - Biodegradable matter enrichment liquid means any liquid that increases the ratio of biodegradable matter to the ammoniacal nitrogen concentration in a mixture between the latter and the digestate (or its liquid fraction). The examples below relate to urban wastewater used as a source of biodegradable matter. However, any effluent containing carbonaceous organic matter (agricultural wastewater, water industrial waste, leachate, biowaste or hydrolyzed sludge) can be used as a biodegradable material enrichment liquid. - BOD: Biological Oxygen Demand (quantity of oxygen required to oxidize all organic (biodegradable) matter biologically) - DBO5: Biological oxygen demand measured after 5 days - COD or DCOtot: Chemical oxygen demand (measurement of the totality of oxidizable substances, whether biodegradable or not). COD can be measured according to the NFT 90-101-February 2001 or ISO 6060-1989 standard. - gDCO / gN: quantity of chemical oxygen demand relative to the quantity of nitrogen compounds.

[0028] The present invention relates to an installation 2 ([Fig.l]) and a method 4 ([Fig.4]) for the biological treatment of an input containing carbonaceous material and nitrogen compounds, for example wastewater treatment plant sludge, in order to produce biogas, and in particular methane, while recovering the nitrogen present in the wastewater in order to recover it. The examples below describe a wastewater treatment plant as an installation for treating an input, sludge from wastewater treatment as an input and urban wastewater as a liquid for enriching biodegradable material. Urban wastewater is of interest as a liquid for enriching biodegradable material because it generally contains between 100 and 300 mg BOD5 / L and 20 to 85 mgN / L. This BOD5 / N ratio is sufficient to ensure the recovery of ammoniacal nitrogen from wastewater by a bioelectrochemical system.The use of another input and / or another liquid for enriching with biodegradable material will lead to obtaining measured values ​​(parameters, ratios, etc.) etc. different from the example described, due to the change in nature of the latter, without however departing from the invention.

[0029] The treated input may contain any carbonaceous material suitable for reactions fermentation, including, but not limited to, mining, agricultural, industrial or domestic derived materials, including virgin products or waste from any process producing carbonaceous material, including the organic fraction of municipal solid waste and sewage sludge.

[0030] The input containing carbonaceous materials may be, but is not limited to, a sludge produced in a liquid treatment line in a sewage treatment plant or any other sludge.

[0031] Such sludge may be, but is not limited to, primary sludge from the discharge of a primary clarification process, or biological sludge from a secondary biological process in wastewater treatment, such as, but not limited to, waste activated sludge, or a combination of primary sludge and biological sludge.

[0032] The primary sludge may have been previously thickened, for example to achieve a dry matter content of 2 to 15% by mass.

[0033] The input used in the present invention may have been previously subjected to one or more sub-steps chosen from a thickening step, a filtration step ("screening"), a dehydration step, a heat treatment step and a dilution step.

[0034] This heat treatment step may comprise a thermal hydrolysis process (THP) and / or a hydrothermal carbonization process (HTC). In a THP process, the sludge, the dry matter content of which is generally between 12% and 25% by mass, is maintained at a temperature between 140°C and 170°C, generally for 30 to 60 minutes. The HTC process generally operates at temperatures between 180°C and 280°C for a period of several minutes to several hours in a non-oxidizing atmosphere.

[0035] The input used in the present invention may have a dry matter content of 1 to 50% by mass, preferably 1 to 40% by mass or 1 to 35% by mass, for example 2 to 15% by mass or 15 to 30% by mass, or 17 to 25% by mass, or in any interval defined by two of these limits. The dry matter content may be determined gravimetrically, for example following the protocol proposed in the following report: Standard Methods for the Examination of Water and Wastewater American Public Health Association, Washington, DC (2005).

[0036] The input also contains water. Any presence of water sufficient for the implementation of biological reactions within the digester is considered suitable.

[0037] For this purpose, the invention uses an ammonium ion extraction device 8 ([Fig.2]) from the biological treatment installation 2 and a method for extracting said ammonium ions 6, the biological treatment installation 2 comprising at least one digester 10 and a bioelectrochemical treatment unit 12 coupled to the digester 10, directly or via a phase separation system and / or an impurity removal system. In particular, the extraction device 8 and the extraction method 6 make it possible to determine at least one operating parameter of the bioelectrochemical treatment unit 12, at least one parameter representative of the quality of the digestate and at least one parameter representative of the quality of wastewater intended to be mixed with the digestate, and this before determining ratios of digestate and wastewater in a digestate / wastewater mixture. Biological treatment plant

[0038] The biological treatment installation 2 comprises: - a digester 10 adapted to produce biogas and digestate by anaerobic digestion, and - a bioelectrochemical treatment unit 12 receiving the digestate, or a liquid fraction of the digestate, this bioelectrochemical treatment unit 12 comprising electroactive microorganisms and at least one separator 14 capable of allowing ammonium ions to pass in the presence of a potential difference, to be applied (“electrolyzer” configuration) or present naturally (“battery” configuration).

[0039] The bioelectrochemical treatment unit 12 is in particular adapted to treat the mixture of digestate or a liquid fraction thereof and wastewater. Thus, the electroactive microorganisms are selected from microorganisms capable of oxidizing the biodegradable organic matter of the digestate or its liquid fraction. This selection may be a selection of a pure strain added voluntarily to the bioelectrochemical treatment unit 12 or a selection by a biological process from a mixed microbial culture.

[0040] The ammonium ions separated during the application or in the presence of a potential difference can typically be extracted from the bioelectrochemical treatment unit, for example by an extraction system 30. This extraction system 30 comprises for example a pipe connected to a pump or any other device allowing the withdrawal of a fluid or a precipitate.

[0041] Typically, the bioelectrochemical treatment unit 12 may comprise at least one recovery compartment 16 equipped with the extraction system 30, and electroactive microorganisms separated from the recovery compartment 16 by the separator 14 so that, under the application or presence of a potential difference, the ammonium ions contained in the digestate or its liquid fraction migrate through the separator 14 towards the recovery compartment 16.

[0042] An example of an embodiment of this installation is described below with reference to [Fig.l].

[0043] In the example shown [Fig.l], the treatment installation 2 comprises a digester 10, adapted to produce biogas and digestate by anaerobic digestion and a bioelectrochemical treatment unit 12 adapted to treat the digestate or a liquid fraction thereof.

[0044] The digester 10 typically has an inlet 10' through which an input to be treated enters (in [Fig.l] sludge from a primary settling unit 18 and sludge from an activated sludge biological treatment unit 20), a first outlet 10” for evacuating the biogas produced and an outlet 10”' for evacuating the digestate produced.

[0045] The digester 10 may comprise one or more bioreactors mounted in parallel or in series adapted for carrying out anaerobic digestion in the presence of suitable microorganisms. These may be bioreactors with continuous, semi-continuous or discontinuous feed ("batch"). For example, a sequential reactor also called an SBR reactor (Sequential Batch Reactor), a mixed culture reactor with continuous feed, a fixed or free culture reactor, etc. may be used.

[0046] The digestate can then enter a dewatering unit 22 in order to separate the digestate into a solid fraction and a liquid fraction. Generally, the installation 2 can comprise one or more optional digestate treatment systems, configured to separate the liquid fraction of the digestate before its treatment in the bioelectrochemical treatment unit and / or to remove impurities from the digestate before its entry into the latter. The optional treatment system can thus be a phase separation system typically comprising one or more decanters or clarifiers or filters. The optional treatment system can also be a system for removing impurities, for example by screening.

[0047] In the above case (separation of solid fraction / liquid fraction of the digestate), the liquid fraction of the digestate (otherwise the digestate leaving the digester via the second outlet 10”' in a case without a dehydration unit) then enters, via a digestate or liquid fraction supply pipe 13 and a first inlet 12', into the bioelectrochemical treatment unit 12. The latter also comprises a first outlet 12” for discharging the treated digestate and a second outlet 12”' for discharging an effluent enriched in ammonium ions.

[0048] The digestate supply conduit 13, or the liquid fraction of the digestate, from the digester 10 to the bioelectrochemical treatment unit 12 is advantageously a digestate return conduit upstream of the biological treatment installation 2, for example upstream of a primary settling member 18 and downstream of a pretreatment member 19. This is also referred to as a “head return”.

[0049] The bioelectrochemical treatment unit 12 comprises at least one separator 14 capable of allowing ammonium ions to pass through. In the example of [Fig.2], it further comprises at least one recovery compartment 16 equipped with an extraction system (comprising for example a pipe connected to a pump), and electroactive microorganisms capable of oxidizing the biodegradable organic matter of the digestate mixture or its liquid / wastewater fraction by releasing electrons and separated from the recovery compartment 16 by the separator 14 so that, under the application or presence of a potential difference, the ammonium ions contained in the digestate or its liquid fraction migrate through the separator 14 to the recovery compartment 16. Alternatively to the example of [Fig.2], it is possible to dispense with the recovery compartment 16 in order to separate only a anode compartment 24 and a cathode compartment 26 by the separator 14, the ammonium ions being recovered in the cathode compartment 26.

[0050] Generally, the recovery compartment 16 allows the passage of ions (cations or anions) between the anode 24 and cathode 26 compartments. It comprises several separators 14 comprising ion exchange membranes, a porous ceramic material allowing the passage of ions, or other. When it has two ion exchange membranes, it can also comprise an intermembrane compartment 28.

[0051] Whatever the embodiment, the recovery compartment 16 may comprise a cation exchange membrane and an anion exchange membrane separated from each other by the intermembrane compartment 28 comprising the extraction system 30 (typically soluble molecules) present within the intermembrane compartment 28. The intermembrane compartment 28 is thus capable of collecting the ions or molecules produced in the anodic and / or cathodic compartments. The molecules recovered at this intermembrane compartment 28 comprise, for example, ammonium salts, and, depending on the composition of the digestate, other salts such as phosphate salts or others.

[0052] When such an intermembrane compartment 28 is present, the membranes may be positioned so that the anode compartment 24 is separated from the cathode compartment 26 by, going from the anode compartment 24 to the cathode compartment 26, a cation exchange membrane and an anion exchange membrane. For example, it is then possible to recover carboxylic acids synthesized at the cathode compartment, as well as cations (eg NH4+) from the anode compartment.

[0053] The bioelectrochemical treatment unit 12 therefore typically comprises at least one anode compartment 24 coupled to the digester 10 so as to receive the digestate or a liquid fraction thereof and in which there are electroactive microorganisms capable of oxidizing the organic matter of the digestate and its liquid fraction, at least one cathode compartment 26, at least one extraction system 30 for ammonium ions, and optionally at least one intermediate compartment (for example the recovery compartment 16), these different compartments being separated by separators 14. In addition, in a usual manner, it typically comprises at least one electrode 32 in each of the anode 24 and cathode 26 compartments as well as, and if necessary, means 34 for applying a potential difference between the anodes and cathodes.

[0054] The bioelectrochemical treatment unit 12 further comprises a second inlet 12”” connected to a wastewater supply conduit 15 and allowing the entry of wastewater for the purpose of supplying the bioelectrochemical treatment unit 12 with a source comprising biodegradable material in order to enrich the digestate, or its liquid fraction, rich in ammonium ions but poorer in biodegradable carbon material, in order to supply the electroactive microorganisms with biodegradable material. In the example in [Fig.l], the wastewater source is wastewater that has undergone pretreatment and primary settling. This source could be different, as long as it allows the supply of wastewater rich in biodegradable matter.

[0055] Whatever the embodiment, the bioelectrochemical treatment unit 12 may comprise at least one bioelectrochemical reactor - in particular a microbial electrolysis or electrosynthesis reactor.

[0056] A reactor in which only the anode compartment comprises electroactive microorganisms may be used, in particular in an abiotic bio-anode / cathode configuration, to couple the treatment of organic matter from the digestate in the anode compartment (by bioelectrochemical oxidation of the COD), either with the production of H2 from H2O in the cathode compartment in the case of a microbial electrolysis process, or with a reduction of O2 in the cathode compartment for a microbial cell.

[0057] Alternatively, a reactor may be used whose anode and cathode compartments contain electroactive microorganisms. By operating as a microbial electrolyser, this type of reactor can be used in bio-electrosynthesis processes coupling a treatment of the digestate in the anode compartment and the synthesis of carbon molecules in the cathode compartment. By operating as a microbial cell, this type of reactor can be used to couple a treatment of the digestate in the anode compartment with a denitrification treatment in the cathode compartment of an effluent containing it.

[0058] In one embodiment, the bioelectrochemical treatment unit 12 can thus be used as a microbial fuel cell to produce electric current. In another embodiment, the bioelectrochemical treatment unit 12 can be used as an electrolysis system or a microbial electrosynthesis system. It can then be used to produce dihydrogen (H2) or chemical molecules of interest (methane, organic acids, alcohol, etc.). When methane is produced, the total quantity of methane produced by the installation according to the invention can be increased. In this case, the at least one cathode compartment comprising electroactive microorganisms can comprise at least one inlet for a carbon source, typically injected in the form of gas, such as CO2, biogas, or syngas and / or introduced in the form of mineral carbon, in particular a bicarbonate.

[0059] In general, electroactive microorganisms are present in the form of a biofilm on the surface of the electrode. The latter may be flat, brush-shaped or in granular form, in a fixed or fluidized bed. Examples of reactors that can be used are described in documents FR3123347A1 and WO2020 / 053529A1.

[0060] The bioelectrochemical treatment unit 12 may comprise a multistack type structure, with a (horizontal) succession of an anode compartment 24, a first recovery compartment 16, a cathode compartment 26, a second recovery compartment 16, etc., it being understood that the two ends of this succession are anode or cathode compartments.

[0061] The biological treatment installation 2 according to the invention may further comprise one or more systems for treating the effluent rich in ammonium ions leaving the bioelectrochemical treatment unit 12, making it possible in particular to separate and purify the nitrogen contained in the effluent. This system may comprise one or more columns adapted to carry out stripping of the nitrogen followed by absorption, or one or more reactors adapted to precipitate the ammonium ions in the form of struvite.

[0062] According to the invention, the installation 2 comprises a system for determining operating parameters configured to implement the extraction method 6 according to the invention and comprising members for determining different parameters and members for applying such parameters to the bioelectrochemical treatment unit 12, or even to the digester 10.

[0063] This determination system is described in detail below. It typically comprises one or more processors, for example microprocessors or microcontrollers. The processor(s) may have storage means which may be random access memory (RAM), electrically erasable programmable read-only memory (EEPROM), flash memory, external memory or other. These storage means may, among other things, store received data, a control model and one or more computer programs. The determination system also comprises communication means, optionally bidirectional, between the determination system and / or with sensors and / or measuring and / or determination means.

[0064] The determination system may further comprise, typically, means for adjusting the operating parameters of the installation, for example of the digester 10, for example a flow rate sensor for the flows entering and leaving the digester making it possible to measure and control the flow of digestate.

[0065] Method and device for extracting ammonium ions

[0066] As shown schematically in Figures 2 and 3, the extraction method 6 and the extraction device 8 comprise: - At least one acquisition member 40 of a value of at least one, preferably at least two, parameter representative of the capacity of the bioelectrochemical treatment unit 12 to separate the ammonium ions, of a value of at least one quality parameter of the digestate, or of its liquid fraction, brought to the bioelectrochemical treatment unit 12 and representative of a quantity of ammonium ions relative to a total quantity of cations and of a concentration of ammonium ions in the digestate or its liquid fraction, and of a value of at least one parameter representative of the quality of the wastewater brought to the bioelectrochemical treatment unit 12, representative of a concentration of biodegradable material in the wastewater. The extraction method 6 comprises a step 42 of acquiring the aforementioned parameters. - at least one member 44 for determining a value of a characteristic ratio of a mixture of the digestate, or of the liquid fraction of the digestate, and of wastewater, representative of a quantity of biodegradable organic matter relative to a quantity of ammonium ions, as a function of a target yield of ammonium ions extracted from the bioelectrochemical treatment unit 12 or of a target concentration of separated ammonium ions present in the bioelectrochemical treatment unit 12, and of the values ​​received by the acquisition member 40. The extraction method 6 comprises a step 46 of determining the aforementioned value. - at least one member 48 for determining a ratio of a mixture of digestate, or of a liquid fraction of the digestate, and of wastewater as a function of the value of the characteristic ratio of a mixture of the digestate, or of the liquid fraction of the digestate, and of wastewater. The extraction method 6 comprises a step 50 of determining the aforementioned ratio. - at least one control member 52 of the quantity of digestate, or of a liquid fraction of the digestate, and of wastewater to be brought to the bioelectrochemical treatment unit 12 configured to obtain the ratio of the mixture of digestate, or of a liquid fraction of the digestate, and of wastewater determined by the determination member 48 of the ratio of the mixture of digestate (or liquid fraction of the digestate) / wastewater. The extraction method 6 comprises a step 54 of mixing digestate, or of the liquid fraction of the digestate, and of wastewater to obtain the ratio of the mixture of digestate, or of a liquid fraction of the digestate, and of wastewater.

[0067] The acquisition member 40 (and the acquisition step 42) is used to acquire, by measurement, modeling or empirically, the values ​​of at least one parameter representative of the capacity of the bioelectrochemical treatment unit 12 to separate the ammonium ions and at least one quality parameter of the digestate or its liquid fraction.

[0068] The at least one parameter representative of the capacity of the bioelectrochemical treatment unit 12 to separate the ammonium ions may in particular comprise at least one parameter representative of the capacity of the at least one separator 14 to allow the ammonium ions to pass, and a parameter representative of a concentration gradient of the ammonium ions on either side of the at least one separator 14.

[0069] The parameter representative of the capacity of the at least one separator 14 to allow ammonium ions to pass typically depends on the intrinsic properties of the separator 14. It is in particular typically linked to the diffusion coefficient of the separator 14 and to its thickness. The value of this parameter can be determined, in particular calculated, from diffusion coefficient values ​​and the dimensions of the separator 14, or else be estimated empirically or by means of a model, for example based on Fick's law. When it is estimated, it could for example be a loss parameter expressed as a percentage and representing a rate of ammonium ions which can pass through the separator.

[0070] The parameter representative of a concentration gradient of ammonium ions on either side of the at least one separator 14 capable of allowing ammonium ions to pass during the application or the presence of a potential difference depends on the flows entering and leaving the bioelectrochemical treatment unit 12. The value of this parameter can thus be estimated from a model or empirically, or determined, in particular by calculation, for example as a function of a rate of extraction of ammonium ions (or of the effluent enriched in ammonium ions) from the bioelectrochemical treatment unit 12, of the residence time of the digestate mixture (or of its liquid fraction) / wastewater inside the bioelectrochemical treatment unit 12.

[0071] The at least one quality parameter of the digestate or its liquid fraction is a parameter representative of a quantity of ammonium ions relative to a total quantity of cations. The value of this parameter may be estimated, in particular by means of a model or empirically, or measured as a function of the concentration of ammonium ions in the digestate or its liquid fraction, and of its conductivity or its total concentration of cations. For example, the ratio of its concentration of ammonium ions to its conductivity or the ratio of its concentration of ammonium ions to its total concentration of cations, measured for example by ion chromatography, may be used as a parameter. When estimated, this parameter may be a safety coefficient taking into account the non-specificity of ion migration within the system, the value of which is for example between 0 and 1, in particular between 0.2 and 1.

[0072] The at least one parameter representative of the quality of the wastewater brought to the bioelectrochemical treatment unit 12, representative of a concentration of biodegradable matter in the wastewater, may be chosen from at least one of the following parameters: the biological oxygen demand of the wastewater brought to the bioelectrochemical treatment unit 12, the biological oxygen demand measured after 5 days, the soluble chemical oxygen demand, the total chemical oxygen demand, the total organic carbon. The total chemical oxygen demand generally varies between 200 and 600 mg / L in the context of urban wastewater.

[0073] Thus, the acquisition step 42 can comprise a step of receiving parameter values, and optionally a step of determining parameter values.

[0074] During the acquisition step, other operating parameters of the bioelectrochemical treatment unit 12 may also be acquired, such as a potential difference applied or applicable to the bioelectrochemical treatment unit 12, and / or the residence time of the digestate (or its liquid fraction) / wastewater mixture in the bioelectrochemical treatment unit 12, and / or the flow rate of effluent enriched in ammonium ions extracted from the bioelectrochemical treatment unit 12. It is then possible to carry out this determination as a function of a particular bioelectrochemical treatment unit that it is desired to use, and in particular of its dimensions and the operating parameter ranges used for this particular unit.In this case, it is not necessary to control the operating parameters of the bioelectrochemical treatment unit 12 to allow the desired recovery of the quantity of ammonium ions during the bioelectrochemical treatment step, because the ratio determined during this step is applicable to the different possible operating conditions of the particular bioelectrochemical treatment system.

[0075] During the acquisition step 42, other quality parameters of the digestate or its liquid fraction may also be optionally acquired, such as its temperature and the fraction of non-hydrolyzed methanization substrate. The temperature will have a direct effect on the microbial kinetics of the anodic biofilm while the fraction of non-hydrolyzed methanization substrate corresponds to a potential biodegradable substrate for the bioelectrochemical treatment unit 12.

[0076] The acquisition member 40 may comprise one or more processors and memories, in particular for storing values ​​and models, and / or means of communication, in particular with sensors and / or means of measuring and / or determining values ​​of the aforementioned parameters.

[0077] The member 44 for determining a value of a characteristic ratio of a mixture (and the associated step 46) makes it possible to determine the value of a characteristic ratio of a mixture of the digestate, or of the liquid fraction of the digestate, and of waste water, representative of a quantity of biodegradable organic matter relative to a quantity of ammonium ions, depending on a target yield of ammonium ions extracted from the bioelectrochemical treatment unit 12 or a target concentration of separated ammonium ions present in the bioelectrochemical treatment unit 12, and the values ​​received by the acquisition member 40. During the step of determining a value of a ratio 46, it is a matter of determining the quantity of biodegradable material that the microorganisms of the bioelectrochemical treatment unit 12 must degrade to release enough electrons to ensure the passage of a target quantity of ammonium ions to the other side of the separator. This quantity of biodegradable material can for example be estimated by material balance or determined by a kinetic model taking into account the phenomena of ion migration and diffusion within the bioelectrochemical treatment unit 12, these methods being well known in bioelectrochemistry.From this requested quantity can be derived the characteristic ratio of the digestate mixture (or its liquid fraction) / waste water in order to obtain a mixture having an optimal concentration of biodegradable material in said mixture.

[0078] This ratio can for example be chosen from the C / N ratio of the quantity of carbon to the quantity of nitrogen, the COD / NH4+ ratio of the chemical oxygen demand to the concentration of ammonium ions, the AGV / NH4+ ratio of a concentration of volatile fatty acids to the concentration of ammonium ions and the DBO5 / NH4+ ratio of the biological oxygen demand at 5 days to the concentration of ammonium ions. The concentrations of AGVs and NH4+ can be determined by conventional acid-base titrations.

[0079] For example, the COD / NH4+ ratio can be from 0.25 to 10 gCOD / gN.

[0080] The target yield of extracted ammonium ions or the target concentration of separated ammonium ions can be determined as a function of the desired quality of effluent enriched in ammonium ions and / or as a function of the desired quality for the digestate, or its liquid fraction, and the wastewater, for example if it is desired that the nitrogen content be below a threshold.

[0081] The target yield of extracted ammonium ions or the target concentration of separated ammonium ions may also be determined as a function of a subsequent treatment of an effluent containing the extracted ammonium ions from the bioelectrochemical treatment unit 12, and in particular of a treatment such as struvite precipitation, or stripping. Those skilled in the art will be able to determine these thresholds as a function of the technology used.

[0082] The step 46 of determining a value of a characteristic ratio of a mixture can be implemented by the member 44 for determining this value adapted to determine the value of a characteristic ratio of the aforementioned mixture. This member can optionally also be adapted, in particular programmed, to implement implements the different embodiments of the step 46 of determining a value of a characteristic ratio of the mixture. It may comprise one or more processors and one or more memories for storing the determined values, and optionally models.

[0083] The member 48 for determining a ratio of a mixture of digestate, or of a liquid fraction of the digestate, and of wastewater as a function of the value of the characteristic ratio of a mixture of the digestate, or of the liquid fraction of the digestate, and of wastewater (and the associated step 50) makes it possible to determine a value of a mixture making it possible to obtain the characteristic value of the ratio determined previously.

[0084] The table below represents an example of different quality parameters of a liquid fraction of digestate (intended for return to the head in this example) and of wastewater (at the outlet of the primary decanter):

[0085] [Tables 1] Parameter Unit Wastewater outlet decanter w primary Return esi head (liquid fraction digestate) Total COD mgO2 L4 300 ±23 363 ±13 Soluble COD mgO2 U'5 131 ± 22 196 ± 15 D8Q5 mgÜ2 L4 190 ±10 120 + 6 pH - 7.86 ± 0.2 6.19 + 0.03 4H2 - N mgU L4 57 ± 7 800 ±24 Gond activity PS OT1 1450 ± 56 7950+:62 COD / NHC-N ratio gO2gU4 5.26 0.45 BOD / NHf-N ratio gO2gL ' 3.33 Q 1b

[0086] Two mixtures were made from these two liquids: - A first ratio equal to 3.17 DBO5 / NH4+-N obtained from a mixture of 90% wastewater and 10% liquid digestate fraction (90 / 10 mixture). - A second ratio equal to 3.01 gO2gN 1 obtained from a mixture of 95% wastewater and 5% liquid digestate fraction (95 / 5 mixture).

[0087] The table below illustrates the COD reduction rate and the NH4+ recovery rate at the bioelectrochemical treatment unit 12 for the wastewater alone, for the liquid fraction of the digestate alone, for the 90 / 10 mixture and for the 95 / 5 mixture. The experiments were carried out in batch. Taking into account the dimensions of the process according to this example, a natural recovery of 30% of the ammonium ions by diffusion phenomenon is achieved.

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[0089] An improvement in the COD reduction rate of the two mixtures is observed, corresponding to a doubling of this rate compared to the liquid digestate fraction alone. Concerning the NH4+ recovery rate, the latter is slightly improved for the 95 / 5 mixture and significantly improved for the 90 / 10 mixture.

[0090] Advantageously, the member 48 for determining a ratio of a mixture of digestate, or of a liquid fraction of the digestate, and of wastewater as a function of the value of the characteristic ratio of a mixture of the digestate, or of the liquid fraction of the digestate, and of wastewater is configured to determine the ratio of a mixture as a function of an ammonium recovery rate, the ammonium recovery rate being determined from the determination of a migration flow of the ammonium ions by electrodialysis and a diffusion flow of the ions through the separator.

[0091] This is illustrated in [Fig.5]. This example makes it possible to determine the optimal ratio for a wastewater / digestate mixture (or liquid fraction of the digestate) to maximize ammonium recovery by electrodialysis in a bioelectrochemical process.

[0092] To calculate this NH4+ recovery rate, it is necessary to determine three flows: - The migration flux of NH4+ by electrodialysis, directly linked to the intensity of the current and therefore to the quantity of BOD reduced by the electroactive microorganisms. - The diffusion flux between the recovery compartment 16 and the anode compartment 24. It can therefore be calculated by taking into account the difference in NH4+ concentration between the two compartments as well as the characteristics of the membrane. - The apparent migration flux corresponding to the sum of the migration and diffusion fluxes, which therefore corresponds to the variation in NH4+ concentration in the recovery compartment 16 over time.

[0093] Depending on the ratio of the mixture between wastewater / digestate (or liquid fraction), its characteristics must first be determined (BOD, NH4+, number of ions). Its characteristics therefore depend on those of the wastewater and the digestate.

[0094] In the example of [Fig.5], the BOD reduction is set at 90%. First, the BOD reduction flow is calculated by taking into account the BOD feed flow and its reduction. It is then possible to convert this reduction flow into current intensity. Indeed, when one mole of BOD is oxidized, four moles of electrons are transferred in the electrical circuit. Finally, when an electron is transferred from the anode compartment to the cathode compartment, a positive charge migrates from the anode compartment to the cathode compartment. By taking into account the number of ammonium ions (which is a characteristic of the mixture), it is possible to reduce the current intensity to an ammonium migration flow.

[0095] To determine the diffusion flux, the characteristics of the membrane must first be determined as described above. Its thickness is known, while its diffusion coefficient must be estimated by modeling a Fick law. In the present example, the concentration in the recovery compartment 16 is set at 1.5 gN / L. By taking into account the difference in concentrations between the two compartments and the characteristics of the membrane, the diffusion flux can be estimated.

[0096] Regarding the calculation of the ammonium recovery rate, the apparent migration flux must first be estimated by adding the diffusion and migration fluxes. By taking into account the ammonium feed flux and this recovery flux, it is possible to calculate the NH4+ recovery rate.

[0097] In the example, the ammonium recovery rate was calculated for different ratios between wastewater and digestate (the BOD reduction rate was set at 90%). An optimum ammonium recovery is observed for a 90 / 10 ratio (90% wastewater and 10% digestate (or its liquid fraction), the curve 49 of the ammonium recovery rate reaching a peak equal to a recovery rate of 80% at around this 90 / 10 ratio. It is notable that it is also possible to set the ammonium recovery rate and calculate the BOD reduction rate as a function of the wastewater / digestate ratio (or its liquid fraction).

[0098] Advantageously, the ratio of the wastewater / digestate mixture (liquid fraction of the digestate) is, in the case of a digestate from sewage treatment plant sludge mixed with urban wastewater, advantageously between 50 / 50 and 95 / 5. Biological treatment process

[0099] The biological treatment method 4 makes it possible to produce biogas (during anaerobic digestion), and in particular methane, while recovering nitrogen, during the bioelectrochemical treatment of the digestate (or its liquid fraction) / wastewater mixture, in order to recover it. The biological treatment method according to the invention can be implemented by means of a biological treatment installation 2 previously described.

[0100] The method 4 and the biological treatment installation 2 according to the invention are suitable for treating wastewater treatment plant sludge containing carbonaceous matter and nitrogen compounds. The carbonaceous matter may be in dissolved, colloidal or particulate form.

[0101] The anaerobic digestion step 38 of the biological treatment method 4 may be carried out in a digester as previously described. This anaerobic digestion step 38 may be carried out under mesophilic or thermophilic temperature conditions. The hydraulic residence time and the solids residence time may be from 5 to 100 days.

[0102] The digestate produced during the anaerobic digestion step 38 can be sent directly to the bioelectrochemical treatment unit 12 to carry out the ammonium ion extraction method according to the invention or can be sent to a liquid-solid separation step of the digestate making it possible to separate the digestate into a solid fraction and a liquid fraction, such as for example a centrifugation step or even a filtration step. The liquid fraction of the digestate is then sent to the bioelectrochemical treatment unit 12 described above.

[0103] In one embodiment, the digestate, or its liquid fraction, may in particular have a COD / Ammoniacal Nitrogen ratio of 0.25 to 10 gCOD / gN. In particular, this ratio may correspond to the ratio of the concentration of VFAs to the concentration of ammonium ions (VFA / Ammoniacal Nitrogen).

[0104] Alternatively or in combination, the digestate, or its liquid fraction, may thus have one or more of the following characteristics: - a total ammoniacal nitrogen concentration of 0.5 to 7gN / L or 0.5 to 5gN / L, or in any interval defined by two of these limits, - a conductivity of 10 to 150 mS / cm or 10 to 75 mS / cm or in any interval defined by two of these limits, - a molar ratio of the ammonium ion concentration to the total cation concentration (total NH47cations) of 0.25 to 1 mol / mol or 0.75 to 1 mol / mol or in any interval defined by two of these limits.

[0105] The concentration of total ammoniacal nitrogen can be measured by colorimetric method, by acid-base dosage, or by ion chromatography. The conductivity can be measured according to standard NF EN 27888-January 1994 or ISO 7888:1985. Such characteristics of the digestate or its liquid fraction can improve the operation of the bioelectrochemical treatment unit 12.

[0106] The bioelectrochemical treatment step 56 is implemented in a bioelectrochemical treatment unit 12, in particular of the type previously described with reference to the biological treatment installation 2.

[0107] In one embodiment, the bioelectrochemical treatment step 56 may comprise the implementation of a reaction chosen from a reaction for reducing dioxygen or nitrate and a reaction for producing dihydrogen or organic molecules of interest chosen from organic acids, alcohols, methane. This may make it possible to improve the recovery of the digestate or its liquid fraction treated. Thus, in a preferred embodiment, the bioelectrochemical treatment step 56 comprises a step for producing methane. The bioelectrochemical treatment unit 12 may thus operate as a microbial fuel cell or an electrolyzer.

[0108] Whatever the embodiment, the method according to the invention may further comprise at least one step of recovering the ammonium ions 58 contained in said effluent enriched in ammonium ions chosen from a stripping step followed by a step of absorbing nitrogen, a step of precipitating the ammonium ions in the form of struvite (NH4MgPO4 • 6 H2O).

[0109] The stripping step can typically be carried out in at least one column in which the effluent circulates countercurrent to a gas which can be air, or in a column containing a membrane (membrane stripping). This stripping step makes it possible to shift the chemical equilibrium of the effluent towards the gas phase (NH3 gas). The adsorption step can typically be carried out in at least one column in which the gas phase leaving the stripping step is brought into contact with an absorbent, for example a sulfuric acid solution. The succession of stripping and absorption makes it possible to concentrate the nitrogen, for example in the form of ammonium sulfate in the case of washing with sulfuric acid.

[0110] The step of precipitation of ammonium ions in the form of struvite can typically be carried out in a reactor in which a source of magnesium and / or phosphorus is generally added to the effluent, for example as described in the publication: Desmidt E, Ghyselbrecht K, Zhang Y, et al. Global phosphorus scarcity and full-scale p-recovery techniques: a review. Crit Rev Env Sci Technol. (2015). List of references

[0111] 2: biological treatment installation

[0112] 4: biological treatment process

[0113] 6: ammonium ion extraction process

[0114] 8: ammonium ion extraction device

[0115] 10: digester

[0116] 10': digester entrance

[0117] 10”: first exit from the digester

[0118] 10”': second digester outlet

[0119] 12 bioelectrochemical treatment unit

[0120] 12': first inlet of the bioelectrochemical treatment unit

[0121] 12': first outlet of the bioelectrochemical treatment unit

[0122] 12' ”: second outlet of the bioelectrochemical treatment unit

[0123] 12' '”: second inlet of the bioelectrochemical treatment unit

[0124] 13 digestate supply pipe

[0125] 14 separators

[0126] 15 wastewater supply pipe

[0127] 16 recovery compartment

[0128] 18 primary settling unit

[0129] 20 activated sludge treatment unit

[0130] 22 dehydration unit

[0131] 24 anode compartment

[0132] 26 cathode compartment

[0133] 28 intermembrane compartment

[0134] 30 ammonium ion extraction system

[0135] 32 electrodes

[0136] 34 means for applying a potential difference

[0137] 38 anaerobic digestion step

[0138] 40 acquisition member

[0139] 42 acquisition step

[0140] 44 member for determining a value of a ratio

[0141] 46 step of determining a value of a ratio

[0142] 48 member for determining a mixing ratio

[0143] 49 curve of the ammonium recovery rate

[0144] 50 step of determining a mixing ratio

[0145] 52 control member

[0146] 54 mixing step

[0147] 56 step of bioelectrochemical treatment

[0148] 58 step of recovering ammonium ions

Claims

1. Claims Method for extracting ammonium ions (6) from a digestate or a fraction of a digestate, resulting from a treatment of an input comprising carbonaceous material and nitrogen compounds by anaerobic digestion, by means of an ammonium ion extraction device (8) comprising a bioelectrochemical treatment unit (12) configured to receive a first volume of digestate, or a liquid fraction of the digestate, and a second volume of liquid for enriching with biodegradable material, the bioelectrochemical treatment unit (12) comprising electroactive microorganisms and at least one separator capable of allowing ammonium ions to pass in the presence of a potential difference, the method comprising the following steps: - a step (42) of acquiring a value of at least one parameter representative of the capacity of the bioelectrochemical treatment unit (12) to separate the ammonium ions, a value of at least one quality parameter of the digestate or of its liquid fraction brought to the bioelectrochemical treatment unit (12), representative of a quantity of ammonium ions relative to a total quantity of cations and of a concentration of ammonium ions in the digestate or in its liquid fraction, and a value of at least one quality parameter of the biodegradable material enrichment liquid, representative of a concentration of biodegradable material in the biodegradable material enrichment liquid brought to the bioelectrochemical treatment unit (12), - a step of determining (46) a value of a characteristic ratio of a mixture of the digestate, or of the liquid fraction of the digestate, and of the liquid for enriching with biodegradable material, representative of a quantity of biodegradable organic material relative to a quantity of ammonium ions, as a function of a target yield of ammonium ions extracted from the bioelectrochemical treatment unit (12) or of a target concentration of separated ammonium ions present in the treatment unit bioelectrochemical (12), and values ​​determined during the acquisition step (42), - a step of determining (50) a ratio of a mixture of digestate, or of a liquid fraction of the digestate, and of liquid enrichment in biodegradable material as a function of the value of the characteristic ratio of a mixture of digestate, or of the liquid fraction of the digestate, and of liquid enrichment in biodegradable material, - a step of mixing (54) digestate, or of liquid fraction of the digestate, and of liquid enrichment in biodegradable material to obtain the ratio of the mixture of digestate, or of a liquid fraction of the digestate, and of liquid enrichment in biodegradable material, and - a step of bioelectrochemical treatment (56) of the mixture of digestate, or of liquid fraction of the digestate, and of liquid enrichment in biodegradable material.

2. Extraction method (6) according to the preceding claim, in which the value of a characteristic ratio of the mixture of digestate, or of the liquid fraction of the digestate, and of liquid enrichment in biodegradable material is between 0.25 elO gDCO / gN.

3. Extraction method (6) according to any one of claims 1 or 2, wherein the step of acquiring (42) a value of at least one quality parameter of the biodegradable material enrichment liquid comprises acquiring at least one of the following parameters: biological oxygen demand, biological oxygen demand measured after 5 days, soluble chemical oxygen demand, total chemical oxygen demand, total organic carbon.

4. Extraction method (6) according to any one of claims 1 to 3, wherein the step of determining (50) a ratio of a mixture of digestate, or of a liquid fraction of the digestate, and of biodegradable material enrichment liquid as a function of the value of the characteristic ratio of a mixture of the digestate, or of the liquid fraction of the digestate, and of biodegradable material enrichment liquid comprises a determination of the ratio of the mixture as a function of an ammonium recovery rate, the ammonium recovery rate being determined from of the determination of a migration flow of ammonium ions by electrodialysis and of a diffusion flow of ions through the separator.

5. Extraction method (6) according to any one of claims 1 to 4, in which the bioelectrochemical treatment step (56) further comprises carrying out a reaction chosen from a reaction for reducing dioxygen or nitrate and a reaction for producing dihydrogen or organic molecules of interest chosen from organic acids, alcohols, methane.

6. Method for biological treatment (4) of an input containing carbonaceous matter and nitrogen compounds to produce biogas and recover ammonium ions via a biological treatment installation comprising: - a digester (10) adapted to produce biogas and digestate by anaerobic digestion, - a source of liquid for enriching with biodegradable material, - an ammonium ion extraction device (8) comprising a bioelectrochemical treatment unit (12) configured to receive a first volume of digestate, or a liquid fraction of the digestate, and a second volume of liquid for enriching with biodegradable material, the bioelectrochemical treatment unit (12) comprising electroactive microorganisms and at least one separator capable of allowing ammonium ions to pass through in the presence of a potential difference,the method comprising the following steps: - an anaerobic digestion step (38) producing biogas and digestate, and - the method for extracting ammonium ions according to any one of claims 1 to 5.,

7. Biological treatment method (4) according to claim 6, further comprising at least one step of recovering ammonium ions (58) contained in an effluent enriched in ammonium ions at the outlet of the bioelectrochemical treatment unit, the step of recovering ammonium ions (58) being chosen from a step

8. stripping followed by a nitrogen absorption step, a precipitation step in the form of struvite of ammonium ions. Device for extracting ammonium ions (8) from a digestate or a liquid fraction of a digestate, resulting from the treatment of an input containing carbonaceous material and nitrogen compounds, and obtained by anaerobic digestion, the device comprising: - At least one bioelectrochemical treatment unit (12) configured to receive a first volume of digestate, or a liquid fraction of the digestate, and a second volume of a liquid for enriching with biodegradable material, the bioelectrochemical treatment unit (12) comprising electroactive microorganisms and at least one separator (14) configured to allow ammonium ions to pass in the presence of a potential difference, - at least one acquisition member (40) of a value of at least one parameter representative of the capacity of the bioelectrochemical treatment unit (12) to separate the ammonium ions, of a value of at least one quality parameter of the digestate, or of its liquid fraction, brought to the bioelectrochemical treatment unit (12), representative of a quantity of ammonium ions relative to a total quantity of cations and of a concentration of ammonium ions in the digestate or in its liquid fraction, and of a value of at least one quality parameter of the biodegradable material enrichment liquid, representative of a concentration of biodegradable material in the wastewater brought to the bioelectrochemical treatment unit (12), - at least one determining member (44) of a value of a characteristic ratio of a mixture of the digestate, or of the liquid fraction of the digestate, and of liquid enrichment in biodegradable material, representative of a quantity of biodegradable organic material relative to a quantity of ammonium ions, as a function of a target yield of ammonium ions extracted from the bioelectrochemical treatment unit (12) or of a target concentration in separated ammonium ions present in the bioelectrochemical treatment unit (12), and values ​​received by the acquisition member (40), - at least one member for determining (48) a ratio of a mixture of digestate, or of a liquid fraction of the digestate, and of liquid for enriching with biodegradable material as a function of the value of the characteristic ratio of a mixture of the digestate, or of the liquid fraction of the digestate, and of liquid for enriching with biodegradable material, - at least one member for controlling (52) the quantity of digestate, or of a liquid fraction of the digestate, and of liquid for enriching with biodegradable material to be brought to the bioelectrochemical treatment unit (12) and configured to obtain the ratio of the mixture of digestate, or of a liquid fraction of the digestate, and of liquid for enriching with biodegradable material.

9. Extraction device (8) according to claim 8, in which the value of a characteristic ratio of the mixture of digestate, or of the liquid fraction of the digestate, and of liquid enrichment in biodegradable material is between 0.25 and 10 gDCO / gN.

10. Extraction device (8) according to any one of claims 8 or 9, in which the parameter representative of the concentration of biodegradable material in the biodegradable material enrichment liquid is chosen from at least one of the following parameters: biological oxygen demand, biological oxygen demand measured after 5 days, soluble chemical oxygen demand, total chemical oxygen demand, total organic carbon.

11. Extraction device (8) according to any one of claims 8 to 10, in which the member (48) for determining a ratio of a mixture of digestate, or of a liquid fraction of the digestate, and of liquid for enriching with biodegradable material as a function of the value of the characteristic ratio of a mixture of the digestate, or of the liquid fraction of the digestate, and of liquid for enriching with biodegradable material is configured to determine the ratio of a mixture as a function of an ammonium recovery rate, the ammonium recovery rate being determined from of the determination of a migration flow of ammonium ions by electrodialysis and of a diffusion flow of ions through the separator (14).

12. Biological treatment plant (2) for an input containing carbonaceous material and nitrogen compounds to produce biogas and recover ammonium ions, the plant comprising: - a digester (10) adapted to produce biogas and a digestate by anaerobic digestion, - a source of biodegradable material enrichment liquid, - an ammonium ion extraction device (8) according to any one of claims 8 to 11, - at least one conduit for supplying the digestate (13), or the liquid fraction of the digestate, from the digester (10) to the ammonium ion extraction device (8), and - at least one conduit for supplying the biodegradable material enrichment liquid (15) from the source of biodegradable material enrichment liquid to the ammonium ion extraction device (8).

13. Biological treatment installation (2) according to claim 12, forming a wastewater treatment station, in which the conduit for supplying the digestate (13), or the liquid fraction of the digestate, from the digester (10) to the ammonium ion extraction device (8) is a digestate return conduit upstream of the biological treatment installation (2), for example upstream of a primary settling member (18).

14. Biological treatment installation (2) according to any one of claims 12 or 13, forming a wastewater treatment station, the biodegradable material enrichment liquid being formed by wastewater, in which the source of wastewater is for example formed by the wastewater leaving a primary settling member (18).

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