System and method for electro-ozonation of an effluent

Abstract

The invention relates to a system (100) for the electro-ozonation of an effluent (1, 3) comprising a polluting material, the system (100) being configured to receive the effluent (1, 3), to generate a direct current with a current density of between 1.4 A / m² and 7.5 A / m² and to carry out electro-ozonation on the received effluent (1, 3) using ozone partially decomposed with the generated direct current, thus obtaining an electro-ozonated effluent (9).

Description

Description Title of the invention: System and method for electrozonation of an effluent Technical field

[0001] The present invention relates to the field of treatment of an effluent comprising polluting material and more particularly concerns a system and a method for electrozonation of an effluent comprising polluting material. Prior art

[0002] It is known to remove polluting matter from an effluent by membrane separation, evaporation-concentration or physicochemical treatment processes. These processes are separation processes and not treatment processes. Their operating costs are very high. They also generate a large quantity of sludge, which is very bulky to store and harmful to the environment because it must be treated.

[0003] Conventional treatment methods also exist. These conventional methods include, for example, flotation, dissolved air or ozone flotation, electrolysis, electrocoagulation, electrozonation or ozoflotation. However, these conventional methods have disadvantages.

[0004] Flotation, dissolved air flotation, and dissolved ozone flotation require the addition of chemicals (coagulants and flocculants) to increase their effectiveness. Dissolved ozone flotation also requires special equipment, and the contact time of dissolved ozone with the material must be perfectly controlled for this process to be effective.

[0005] Electrolysis has the disadvantages of high power consumption, fragile electrodes, the problem of electrode clogging due to the formation of scale (limescale and metal oxides) and frequent replacement. The generation of by-products such as hydrogen and chlorine and low efficiency also pose problems.

[0006] Electrocoagulation uses the same principle as electrolysis with the addition of coagulant. In addition to the problems of electrolysis, the addition of coagulant increases the volume of sludge generated and involves additional costs.

[0007] The treatment efficiency of electrozonation is satisfactory. However, it has the same disadvantages as electrolysis.

[0008] Ozoflotation is a less efficient process than the conventional treatment processes mentioned above.

[0009] These conventional processes also require a pre-treatment step that is difficult to optimize and control, especially in the case of effluent to be treated with variable quality and containing hydrocarbons and / or detergents.

[0010] Another effluent treatment process is described in CN 108 423 893. In this process, the effluent to be treated and the ozone are brought into contact between electrodes, which promotes the oxidation of the effluent to be treated by the ozone and the coagulation of the ozone to eliminate the polluting material from the effluent. Unlike electrolysis, the process described in CN 108 423 893 uses low currents because the current density is 19 mA / cm 2 , or 190 A / m 2. However, the process described in CN 108 423 893 has the disadvantages related to the electrolysis electrodes, i.e. fragility of the electrodes, clogging of the electrodes due to the formation of scale and frequent replacement. In addition, the process described in CN 108 423 893 is not very efficient. Indeed, the chemical oxygen demand (COD) is only reduced by 48%. Document US5972196A describes a method for sterilizing tools and medical waste by high current density catalysis between 0.1 A / cm 2 and 2.5 A / cm 2 , or between 1000 A / m 2 and 25000 A / m 2 , which requires a large expenditure of electrical energy and is therefore not satisfactory in its application to the treatment of effluents, particularly urban and industrial.

[0011] There is therefore a need for a simple and effective solution to at least partially overcome these drawbacks. Statement of the invention

[0012] For this purpose, the invention firstly relates to a system for electrozoning an effluent comprising a polluting material, said system being configured to receive said effluent, to generate a direct current whose current density is between 1.4 A / m 2 and 7.5 A / m 2 and to carry out electrozonation of the received effluent by partially decomposed ozone with the direct current generated and thus obtain an electrozoned effluent.

[0013] Preferably, the generated direct current has a current density of between 1.7 A / m 2 and 5.5 A / m 2 , preferably still between 1.75 A / m 2 and 1.8 A / m 2 .

[0014] The limited value range [1.4 A / m 2 ; 7.5 A / m 2 ] selected is narrow compared to the known range of values ​​and is sufficiently far from any specific example disclosed in the prior art.

[0015] Advantageously, the treatment method of the invention is particularly effective. Indeed, the electrozonation step makes it possible to reduce the chemical oxygen demand (COD) by more than 90%.

[0016] Without wishing to be bound by any theory, the inventor is of the opinion that the high efficiency of the electrozonation step is due to the combination:

[0017] - the oxidizing power of ozone which allows part of the matter to be eliminated polluting the effluent by oxidation, and

[0018] - the coagulating criterion of ozone which allows ozone to fragment another part of the polluting material in the effluent while electrically charging it in order to promote the coagulation, then the flocculation, of the fragmented particles of the polluting material.

[0019] Advantageously, the coagulating criterion of ozone is promoted and increased by the direct current density within the ranges indicated above and by the partially decomposed ozone used in the electrozonation step.

[0020] The use of the limited value range [1.4 A / m 2 ; 7.5 A / m 2 ] selected therefore confers singular technical effects. Furthermore, the person skilled in the art would not have seriously considered working in the limited range of values ​​[1.4 A / m 2 ; 7.5 A / m 2 ] selected because it is unusual and the usual beaches are very different.

[0021] Furthermore, by promoting and increasing the coagulating criterion of ozone, the system of the invention also generates less sludge than conventional processes.

[0022] The system according to the invention is also economical in electricity because the direct current density implemented during the electrozonation step is low, in particular lower than for electrolysis.

[0023] For the purposes of the present invention, the term "effluent" means a flow, preferably liquid, comprising polluting material. Typically, the effluent may have a chemical oxygen demand (COD) of between 200 mg / L and 13,500 mg / L.

[0024] The effluent used in the treatment process of the invention may be an industrial effluent, an urban effluent, a medical effluent, a pharmaceutical effluent, an agri-food effluent, non-potable water or mixtures thereof, in particular an industrial effluent.

[0025] Advantageously, treating non-potable water using the method of the invention makes it possible to make this water potable.

[0026] Typically, the industrial effluent may be wastewater from a vehicle wash station, effluent from a laundry, a distillate, for example a distillate from an evaporator-concentrator, leachate from a waste disposal site, effluent from a hydroseparator, effluent from a dye works, effluent from a paper mill, effluent from an oil platform, effluent from an oil refinery, effluent from a surface treatment plant, effluent from a metal processing plant, effluent from a chemical manufacturing plant, effluent from a perfumery or mixtures thereof.

[0027] Typically, urban effluent may include urban wastewater (i.e. black water, grey water or their mixture), excess rainwater, parasitic water (i.e. groundwater entering non-maintained networks). waterproof) or their mixtures.

[0028] Typically, medical effluent may be effluent from a hospital, a nursing home, or mixtures thereof.

[0029] Typically, pharmaceutical effluent may be effluent from a pharmaceutical laboratory, a drug destruction plant, a chemical destruction plant or their mixtures.

[0030] Typically, agri-food effluent can be an effluent from a dairy, a fruit and / or vegetable processing plant, a slaughterhouse, an oil mill, or mixtures thereof. A vegetable water is an example of effluent from an oil mill.

[0031] In particular embodiments, the effluent may be wastewater from a vehicle wash station, a distillate from an evaporator-concentrator, a leachate from a waste disposal site, an effluent from a hydro-separator or mixtures thereof.

[0032] Depending on the effluent, the pollutant may include foams, large particles of pollutant, oils, plastics, paints and / or materials that can trap ozone. Examples of materials that can trap ozone include carbonates, particularly calcium carbonate.

[0033] In one embodiment, the effluent is of any type except an urban effluent, an industrial effluent, a mixture of urban and industrial effluents, an effluent from an oil platform or an effluent from a vehicle wash station, in other words the effluent is neither an urban effluent, nor an industrial effluent, nor a mixture of urban and industrial effluents, nor an effluent from an oil platform, nor an effluent from a vehicle wash station.

[0034] According to one aspect of the invention, the system comprises a reactor, said reactor comprising a side wall having a cylindrical shape along a vertical axis of revolution and a bottom delimiting a reaction space, an ozone injection port and an effluent injection port or a port for injecting a mixture of ozone and effluent, and at least two electrodes, an anode and a cathode, in the reaction space.

[0035] In one embodiment, the reactor comprises a side wall having a cylindrical shape along a vertical axis of revolution and a bottom delimiting a reaction space.

[0036] Advantageously, the reactor comprises a porous membrane positioned in the reaction space.

[0037] Advantageously, the reactor comprises at least two electrodes, including at least one anode and at least one cathode, for example exactly two electrodes: one anode and one cathode.

[0038] Preferably, the electrodes have a tubular circular cylindrical shape.

[0039] Preferably, the electrodes are made of aluminum.

[0040] Advantageously, the electrodes are positioned in the reaction space, upstream of the porous membrane in the direction of an ozone flow and concentrically with respect to each other and, possibly with respect to the side wall.

[0041] Advantageously, the reactor comprises a port for injecting a mixture of ozone and effluent located at the bottom of the reactor, preferably positioned upstream of the porous membrane positioned in the reaction space.

[0042] In one embodiment, the system comprises a porous membrane, said membrane comprising a support and a metal oxide on the surface of the support, the support being selected from an oxidized ceramic, a metal alloy, a chromium compound and mixtures thereof, and the metal oxide being selected from titanium dioxide, manganese oxide, cerium oxide, iron oxide, copper oxide, aluminum oxide and mixtures thereof, wherein partially decomposed ozone is obtained by passing a stream of ozone through said porous membrane.

[0043] Preferably, the partially decomposed ozone comprises between 1% by mass and 99.9% by mass of ozone.

[0044] In one embodiment, the system is configured to perform catalytic ozonation of the electrozoned effluent to obtain a treated effluent. Thus, while the electrozonation step had reduced the chemical oxygen demand (COD) by more than 90%, the catalytic ozonation of the electrozoned effluent then reduces the chemical oxygen demand to almost 0 ppm. This is referred to as hybrid ozonation.

[0045] Advantageously, the system comprises a catalyst for implementing catalytic ozonation, said catalyst comprising a support chosen from an activated alumina, a clay, an activated carbon, an oxidized ceramic and their mixtures, and an active phase on the surface of the support and chosen from palladium, a metal alloy, manganese oxide, cerium oxide, titanium dioxide, iron oxide, copper oxide, aluminum oxide and their mixtures.

[0046] Advantageously, the system is configured to pretreat the received effluent by dissolved air flotation in order to obtain a pretreated effluent, this pretreated effluent then being used in electrozonation to obtain a flotelectrozoned effluent. This is then referred to as flotelectrozonation.

[0047] Advantageously, the system is configured to carry out an evapo-concentration of the effluent making it possible to obtain a concentrated effluent, this concentrated effluent then being used in electrozonation or in pretreatment by dissolved air flotation.

[0048] Besides the electrozoned effluent, a residue can be obtained as a result of electrozonation of the received effluent by partially decomposed ozone with direct current generated.

[0049] Advantageously, the system is configured to recycle the residue obtained during electrozonation in the unit / stage of pretreatment of the effluent by dissolved air flotation.

[0050] Advantageously, the system is configured to treat the electrozoned effluent by low pressure dissolved air flotation in order to obtain a treated flotelectrozoned effluent, this treated flotelectrozoned effluent then undergoing the catalytic ozonation step.

[0051] The invention also relates to a method for electrozoning an effluent comprising a polluting material, said method comprising a step of electrozoning the effluent with partially decomposed ozone to obtain an electrozoned effluent, the electrozoning being carried out with a direct current density of between 1.4 A / m 2 and 7.5 A / m 2 , especially between 1.7 A / m 2 and 5.5 A / m 2 , especially between 1.75 A / m 2and 1.8 A / m 2 .

[0052] Advantageously, the partially decomposed ozone comprises between 1% by mass and 99.9% by mass of ozone.

[0053] Advantageously, the partially decomposed ozone is obtained by passing a stream of ozone through a porous membrane comprising a support and a metal oxide on the surface of the support, the support being selected from an oxidized ceramic, a metal alloy, a chromium compound and mixtures thereof, and the metal oxide being selected from titanium dioxide, manganese oxide, cerium oxide, iron oxide, copper oxide, aluminum oxide and mixtures thereof.

[0054] In a preferred embodiment, ozone and effluent are injected into the reaction space and passed through the porous membrane to produce partially decomposed ozone, to destabilize foams, and to settle large particles from the effluent. Then, between the two electrodes, the pollutant material in the effluent is treated with the partially decomposed ozone. The residue can then be easily separated from the electrozoned effluent on top of the reactor.

[0055] Advantageously, the method further comprises, before the electrozonation step, a pretreatment step by dissolved air flotation making it possible to obtain a pretreated effluent, this pretreated effluent then being used in the electrozonation step to obtain a flotelectrozoned effluent. This is then referred to as flotelectrozonation.

[0056] Advantageously, the method further comprises, before the electrozonation step or before the dissolved air flotation pretreatment step, a step of evaporation-concentration of the effluent making it possible to obtain a concentrated effluent, this concentrated effluent then being used in the electrozonation step or in the dissolved air flotation pretreatment step.

[0057] Advantageously, a residue being obtained as a result of the electrozonation, the method comprises a step of recycling at least part of the residue obtained in the unit of pretreatment by dissolved air flotation.

[0058] In one embodiment, the method further comprises a step of catalytic ozonation of the electrozoned effluent to obtain a treated effluent.

[0059] Advantageously, the method further comprises, between the electrozonation step and the catalytic ozonation step, a step of treatment by low-pressure dissolved air flotation of the electrozoned effluent obtained during the electrozonation step to obtain a treated flotelectrozoned effluent, this treated flotelectrozoned effluent then undergoing the catalytic ozonation step.

[0060] Advantageously, the catalytic ozonation step of the effluent is carried out by a catalyst comprising: a support chosen from an activated alumina, a clay, an activated carbon, an oxidized ceramic and their mixtures, and an active phase chosen from palladium, a metal alloy, manganese oxide, cerium oxide, titanium dioxide, iron oxide, copper oxide, aluminum oxide and their mixtures.

[0061] According to another aspect, the catalytic ozonation step of the effluent is carried out in a catalyst comprising: a support chosen from an activated alumina, a clay, an activated carbon, an oxidized ceramic and their mixtures, in particular from activated alumina, clay, activated carbon and their mixtures, in particular being activated alumina or activated carbon, and an active phase chosen from palladium, a metal alloy, manganese oxide, cerium oxide, titanium dioxide, iron oxide, copper oxide, aluminum oxide and their mixtures, in particular palladium, the metal alloy, manganese oxide, cerium oxide and their mixtures, in particular being a mixture of palladium and the metal alloy, a mixture of palladium and manganese oxide or a mixture of palladium, manganese oxide and cerium oxide.

[0062] Advantageously, the method further comprises, after the catalytic ozonation step, a step of disinfecting a mixture comprising the treated effluent and ozone by passing this mixture through a porous membrane to obtain a disinfected effluent. Brief description of the drawings

[0063] Other characteristics and advantages of the invention will become apparent from reading the description which follows. This description is purely illustrative and must be read in conjunction with the appended drawings in which:

[0064] [Fig.l] [Fig.l] schematically illustrates an embodiment of the system according to the invention.

[0065] [Fig.2] [Fig.2] schematically illustrates an embodiment of the method according to the invention. Description of the embodiments

[0066] [Fig. 1] illustrates an example of a system 100 according to the invention for treating an effluent 1.

[0067] System 100

[0068] With reference to [Fig. 1], the system 100 comprises a pretreatment unit 2, an anti-scale treatment unit 4, a reactor 6 and a catalytic ozonation unit 10.

[0069] Pretreatment Unit 2

[0070] The pretreatment unit 2 is configured to carry out a pretreatment by dissolved air flotation of the effluent 1 in order to obtain a pretreated effluent 3. The effluent 1 may undergo pre-ozonation before its admission into the pretreatment unit 2, in a manner known per se.

[0071] Anti-limescale treatment unit 4

[0072] The anti-scale treatment unit 4 is configured to carry out an anti-scale treatment of the pre-treated effluent 3 before being mixed with ozone 5.

[0073] Reactor 6

[0074] The reactor 6 comprises a porous membrane 7 and electrodes 8 and defines a reaction space.

[0075] According to a particular embodiment, the reactor 6 comprises: a side wall having a cylindrical shape along a vertical axis of revolution and a bottom delimiting a reaction space, an ozone injection port and an effluent injection port or a port for injecting a mixture of ozone and effluent (not shown for the sake of clarity), and at least two electrodes 8, an anode and a cathode, in the reaction space.

[0076] For the purposes of the present invention, the term "wall having a cylindrical shape" means a wall in the general shape of a cylinder, a cylinder being a surface generated by a straight line which moves parallel to the vertical axis of revolution, resting on two fixed planes. Typically, the cylinder may be a prism with a polygonal base such as a prism with a triangular base, a square base or a rectangular base. The cylinder may also be a circular cylinder, in particular a right circular cylinder characterized by a radius r and a height h. According to a specific embodiment, the cylinder is a circular cylinder so that the side wall has a right circular cylindrical shape.

[0077] For the purposes of the present invention, the term "reaction space" means the internal part of the reactor, i.e. the volume between the side wall and the bottom, the reactor being open at the top and possibly having no cover to facilitate the recovery of the residue and the preozonated effluent obtained during electrozonation.

[0078] For the purposes of the present invention, "ozone injection port" means any element adapted to introduce a flow of ozone or partially decomposed ozone into the reaction space of the reactor. Typically the ozone injection port is adapted to be connected to a gas line. For example, the ozone injection port may be a gas fitting.

[0079] For the purposes of the present invention, "effluent injection port" means any element adapted to introduce a flow of the effluent intended to undergo electrozonation into the reaction space of the reactor. Typically, the effluent injection port is adapted to be connected to a liquid line. For example, the effluent injection port may be a liquid connection.

[0080] For the purposes of the present invention, the term "injection port for a mixture of ozone and effluent" means any element adapted to introduce a flow of mixture of ozone and effluent intended to undergo electrozonation in the reaction space of the reactor. Typically, this effluent injection port is adapted to be connected to a pipe containing a gas / liquid mixture.

[0081] The ozone injection port, the effluent injection port, the injection port for a mixture of ozone and effluent may be located at a lower part of the reactor, preferably at the bottom of the reactor. This configuration is suitable for operation of the reactor in co-current mode.

[0082] For the purposes of the present invention, the terms "bottom", "low", "top", "above" and "vertical" are used to designate elements of the reactor 6 implementing the electrozonation of the process of the invention and must therefore be considered when the reactor 6 is in its normal position of use.

[0083] Membrane 7

[0084] The porous membrane 7 is configured to partially decompose the ozone 5, to destabilize the foams and settle the large particles of the pretreated effluent 3. The porous membrane 7 is also configured to destabilize the calcium ions of the pretreated effluent 3, thus protecting the electrodes 8 from possible limescale deposits and consequently promoting the coagulating criterion of the ozone which allows the ozone to fragment a portion of the polluting material of the pretreated effluent 3 while electrically charging it in order to promote the coagulation, then the flocculation, of the fragmented particles of the polluting material.

[0085] For the purposes of the present invention, "partially decomposed ozone" means a mixture of ozone and compounds resulting from the decomposition of ozone such as hydroxyl radicals "OH" and singlet oxygens.

[0086] Typically, the partially decomposed ozone may comprise between 1% by mass and 99.9% by mass, in particular between 5% by mass and 90% by mass, most particularly between 10% by mass and 50% by mass of ozone. In the present application, these mass percentages are defined relative to the total mass of the ozone par- partially decomposed.

[0087] According to one embodiment, the partially decomposed ozone is obtained by passing, preferably at a constant flow rate, a stream of ozone through the porous membrane 7. For this purpose, the porous membrane 7 comprises a support and a metal oxide on the surface of the support. The passage of the stream of ozone through the porous membrane 7 can be done at the temperature of the effluent.

[0088] Typically, the porous membrane 7 may have a porosity of between 5 and 80, in particular between 15 and 50, especially between 21 and 27. The porosity can be determined according to standard NF ISO 5017 (May 2013).

[0089] The porous membrane 7 can be obtained by one of the methods of synthesis of porous membranes known to those skilled in the art.

[0090] The support of the porous membrane 7 can be chosen from an oxidized ceramic, a metal alloy, a chrome compound and their mixtures, in particular from the oxidized ceramic and a mixture of the metal alloy and the chrome compound.

[0091] For the purposes of the present invention, "oxide ceramic" means a ceramic consisting mainly of one or more metal oxides such as aluminum oxide, zirconium dioxide, titanium dioxide and mixtures thereof, in particular a mixture of aluminum oxide, zirconium dioxide and titanium dioxide.

[0092] Typically, the oxidized ceramic may comprise: between 80% by mass and 99% by mass, in particular between 90% by mass and 95% by mass, especially between 92% by mass and 94% by mass of aluminum oxide, 10% by mass or less, in particular between 2% by mass and 9% by mass, especially between 4.5% by mass and 5.5% by mass of titanium dioxide, and 10% by mass or less, in particular between 1% by mass and 3% by mass, especially between 1.5% by mass and 2.5% by mass of zirconium dioxide. In the present application, these mass percentages are defined relative to the total mass of the oxidized ceramic.

[0093] Typically, the metal alloy may include iron, chromium, nickel, carbon, molybdenum, or mixtures thereof.

[0094] According to one embodiment, the metal alloy may comprise: at least 10% by mass, in particular between 15% by mass and 25% by mass, very particularly between 16% by mass and 19% by mass of chromium, at least 5% by mass, in particular between 7% by mass and 15% by mass, very particularly between 8% by mass and 13% by mass of nickel, 2% by mass or less, in particular 1% by mass or less, very particularly between 0.01% by mass and 0.1% by mass of carbon, optionally 10% by mass or less, in particular between 0.5% by mass and 5% by mass, very particularly between 1% by mass and 3% by mass of molybdenum, the remainder being iron. In the present application, these mass percentages are defined relative to the total mass of the metal alloy. For the purposes of the present invention, "the remainder being iron" means iron and unavoidable impurities.

[0095] According to a particular embodiment, the metal alloy may comprise: between 16% by mass and 19% by mass of chromium, between 8% by mass and 13% by mass of nickel, between 0.01% by mass and 0.1% by mass of carbon, the remainder being iron.

[0096] According to another particular embodiment, the metal alloy may comprise: between 16% by mass and 19% by mass of chromium, between 8% by mass and 13% by mass of nickel, between 0.01% by mass and 0.1% by mass of carbon, between 1% by mass and 3% by mass of molybdenum, the remainder being iron.

[0097] The chrome compound is a metal alloy which may comprise: between 0.1% by mass and 20% by mass, in particular between 16.5% by mass and 18% by mass of chromium, between 4% by mass and 25% by mass, in particular between 10% by mass and 13% by mass of nickel, 0.06% by mass or less, in particular 0.03% by mass or less of carbon, between 1% by mass and 3% by mass, in particular between 2% by mass and 2.5% by mass of molybdenum, the remainder being iron. In the present application, these mass percentages are defined relative to the total mass of chrome compound.

[0098] According to a particular embodiment, the mixture of the metal alloy and the chrome compound may comprise more than 50% by mass of iron, between 0.07% by mass and 0.3% by mass of carbon, between 10.5% by mass and 26% by mass of chromium and between 9% by mass and 21% by mass of nickel. In the present application, these mass percentages are defined relative to the total mass of the mixture of the metal alloy and the chrome compound.

[0099] According to another particular embodiment, the mixture of the metal alloy and the chrome compound may comprise more than 50% by mass of iron, between 0.07% by mass and 0.3% by mass of carbon, between 16% by mass and 26% by mass of chromium, between 1.5% by mass and 21% by mass of nickel and between 1% by mass and 3% by mass of molybdenum.

[0100] The metal oxide of the porous membrane may, for example, be chosen from titanium dioxide, manganese oxide, cerium oxide, iron oxide, copper oxide, aluminum oxide and mixtures thereof, in particular from titanium dioxide, iron oxide, aluminum oxide and mixtures thereof, more particularly be titanium dioxide.

[0101] The support and the metal oxide of the porous membrane 7 are chosen independently of each other by a person skilled in the art.

[0102] However, a person skilled in the art will avoid choosing the same metal oxide as a support (if the support is an oxidized ceramic) and as a metal oxide. For example, a person skilled in the art will avoid choosing aluminum oxide, or carbon dioxide. titanium, as a support and as a metal oxide.

[0103] A person skilled in the art may nevertheless choose an oxide ceramic comprising a mixture of metal oxides as a support and a metal oxide from this mixture as a metal oxide. For example, a person skilled in the art may choose an oxide ceramic comprising a mixture of aluminum oxide, titanium dioxide and zirconium dioxide as a support and titanium dioxide as a metal oxide.

[0104] The porous membrane 7 may comprise less than 50% by mass, in particular between 0.1% by mass and 30% by mass, especially between 1% by mass and 5% by mass of metal oxide. In the present application, these mass percentages are defined relative to the total mass of the porous membrane 7.

[0105] The porous membrane 7 may comprise 50% by mass or more, in particular between 70% by mass and 99.9% by mass, especially between 95% by mass and 99% by mass of support. In the present application, these mass percentages are defined relative to the total mass of the porous membrane 7.

[0106] Typically, in the porous membrane 7, the mass content of metal oxide represents between 1% and 99%, in particular between 1% and 30%, especially between 1% and 5.5% of the mass content of support.

[0107] According to a particular embodiment, the porous membrane 7 may have a porosity of between 21 and 27, and comprise: between 1% by mass and 5% by mass of titanium dioxide as metal oxide, and between 95% by mass and 99% by mass of the mixture of the metal alloy and the chrome compound as support, said mixture of the metal alloy and the chrome compound comprising between 0.07% by mass and 0.3% by mass of carbon, between 16% by mass and 26% by mass of chromium and between 1.5% by mass and 21% by mass of nickel.

[0108] According to a particular embodiment, the porous membrane 7 may have a porosity of between 21 and 27, and comprise: between 3% by mass and 7% by mass of titanium dioxide as metal oxide, and between 93% by mass and 97% by mass of an oxidized ceramic as support, said oxidized ceramic comprising between 92% by mass and 94% by mass of aluminum oxide, between 4.5% by mass and 5.5% by mass of titanium dioxide, and between 1.5% by mass and 2.5% by mass of zirconium dioxide.

[0109] According to one embodiment, the effluent can also pass through the porous membrane 7. Advantageously, this can make it possible to destabilize the foams and to settle the bulky particles of the effluent and therefore to increase the efficiency of T electrozonation. This also makes it possible to destabilize the calcium ions possibly present in the effluent, thus protecting the electrodes used during the electrozonation from a possible deposit of limestone and therefore from clogging. This method of This implementation advantageously allows the time between two replacements of the electrodes used in electrozonation to be spaced.

[0110] The reactor 6 preferably comprises the porous membrane 7 in the reaction space at the outlet of the ozone injection port and possibly the effluent injection port, or the port for injecting a mixture of ozone and effluent. This configuration allows the ozone injected into the reaction space to pass through the porous membrane 7 to be partially decomposed and that, possibly, the effluent injected into the reaction space also passes through the porous membrane 7. [OR I] Electrodes 8

[0112] The reactor 6 comprises at least two electrodes 8, an anode and a cathode, for carrying out the electrozonation. Typically, the anode may be made of titanium, iron, aluminum or mixtures thereof, in particular iron, aluminum or mixtures thereof, especially aluminum. The cathode may, for example, be made of titanium, iron, aluminum or mixtures thereof, in particular iron, aluminum or mixtures thereof, especially aluminum.

[0113] Each of the electrodes 8 implemented in the electrozonation may have a plate shape, a solid cylindrical shape or a tubular cylindrical shape. When the electrode 8 has a solid cylindrical shape then it may have a solid circular cylindrical shape. When the electrode 8 has a tubular cylindrical shape then it may have a tubular circular cylindrical shape.

[0114] Preferably, the electrodes are positioned concentrically with respect to each other, and optionally with respect to the side wall of the reactor.

[0115] The reactor 6 may also comprise a system for cleaning the electrodes 8. This system may, for example, be a scraper, a rotating brush or both.

[0116] Catalytic ozonation unit 10

[0117] With reference to [Eig.1], the catalytic ozonation unit 10 is configured to receive the electrozoned effluent 9 comprising residual polluting material and concentrated ozone and to remove said residual polluting material. The residue 11 from the reactor 6 is preferably recycled into the pretreatment unit 2.

[0118] In order to carry out the catalytic ozonation of the electrozoned effluent, the catalytic ozonation unit 10 comprises a catalyst. Said catalyst typically comprises a support and an active phase on the surface of the support.

[0119] The catalyst support may be selected from activated alumina, clay, activated carbon, oxidized ceramic and mixtures thereof, in particular from activated alumina, clay, activated carbon and mixtures thereof, in particular being activated alumina or activated carbon.

[0120] Advantageously, these supports can absorb part of the residual polluting material and therefore increase the efficiency of catalytic ozonation.

[0121] For the purposes of the present invention, the term "activated alumina" means a porous aluminum oxide with a high specific surface area, i.e. a specific surface area of, for example, between 200 m 2 / g and 350 m 2 / g Typically the high specific surface area can be determined by the method based on the Brunauer, Emmett and Teller theory (BET method) according to ISO 9277:2010.

[0122] For example, the clay can be kaolinite, especially Kaolinite KGa-2. The oxidized ceramic of the catalyst support is the same as that of the porous membrane support described above.

[0123] The active phase of the catalyst may be chosen from palladium, a metal alloy, manganese oxide, cerium oxide, titanium dioxide, iron oxide, copper oxide, aluminum oxide and mixtures thereof, in particular palladium, the metal alloy, manganese oxide, cerium oxide and mixtures thereof, in particular being a mixture of palladium and the metal alloy, a mixture of palladium and manganese oxide or a mixture of palladium, manganese oxide and cerium oxide.

[0124] Advantageously, catalytic ozonation is very efficient with such an active phase.

[0125] The metal alloy of the active phase of the catalyst is the same as that of the support of the porous membrane described above.

[0126] The support and the active phase of the catalyst are chosen independently of each other by the skilled person. However, the skilled person will avoid choosing the same metal oxide as the support (if the support is an oxide ceramic or an activated alumina) and as the active phase. For example, the skilled person will avoid choosing aluminum oxide, or titanium dioxide, as the support and as the active phase. The skilled person may nevertheless choose an oxide ceramic comprising a mixture of metal oxides as the support and a metal oxide from this mixture as the active phase. For example, the skilled person may choose an oxide ceramic comprising a mixture of aluminum oxide, titanium dioxide and zirconium dioxide as the support and titanium dioxide as the active phase.

[0127] The catalyst may comprise less than 50% by mass, in particular between 0.1% by mass and 30% by mass, especially between 1% by mass and 5% by mass of active phase. In the present application, these mass percentages are defined relative to the total mass of the catalyst.

[0128] The catalyst may comprise 50% by mass or more, in particular between 70% by mass and 99.9% by mass, especially between 95% by mass and 99% by mass of support. In the present application, these mass percentages are defined relative to the total mass of the catalyst.

[0129] Typically, in the catalyst, the mass content of active phase represents between 1% and 99%, in particular between 1% and 30%, especially between 1% and 5.5% of the mass content of support.

[0130] According to one embodiment, the catalyst may comprise: a support chosen from an activated alumina, a clay, an activated carbon, an oxidized ceramic and their mixtures, in particular from activated alumina, clay, activated carbon and their mixtures, in particular being activated alumina or activated carbon, and an active phase chosen from palladium, metal alloy, manganese oxide, cerium oxide, titanium dioxide, iron oxide, copper oxide, aluminum oxide and their mixtures, in particular palladium, metal alloy, manganese oxide, cerium oxide and their mixtures, in particular being a mixture of palladium and the metal alloy, a mixture of palladium and manganese oxide or a mixture of palladium, manganese oxide and cerium oxide.

[0131] According to a first preferred embodiment: the catalyst support is activated carbon, the support content being between 90% by mass and 99% by mass, in particular between 93% by mass and 95% by mass, most particularly being 94% by mass, and the active phase is a mixture comprising palladium and the metal alloy, the palladium content being between 0.5% by mass and 1.5% by mass relative to the total mass of the catalyst, the metal alloy content being between 4.5% by mass and 5.5% by mass relative to the total mass of the catalyst, and the metal alloy comprising: between 16% by mass and 19% by mass of chromium, between 8% by mass and 13% by mass of nickel, between 0.01% by mass and 0.1% by mass of carbon, the remainder being iron, or ... and 13% by mass of nickel, between 0.01% by mass and 0.1% by mass of carbon, between 1% by mass and 3% by mass of molybdenum,the rest being iron.,

[0132] According to a second preferred embodiment: the catalyst support is activated alumina, the content of the support being between 90% by mass and 99% by mass, in particular between 93% by mass and 95% by mass, most particularly being 94% by mass, and the active phase is a mixture comprising palladium and manganese oxide, the palladium content being between 0.5% by mass and 1.5% by mass relative to the total mass of the catalyst and the manganese oxide content being between 4% by mass and 6% by mass relative to the total mass of the catalyst.

[0133] According to a third preferred embodiment: the catalyst support is clay, the content of the support being between 90% by mass and 99% by mass, in particular between 92% by mass and 95% by mass, most particularly being 93% by mass, and the active phase is a mixture comprising palladium, metal alloy- metal and cerium oxide, the palladium content being between 0.5% by mass and 1.5% by mass relative to the total mass of the catalyst, the manganese oxide content being between 4% by mass and 6% by mass relative to the total mass of the catalyst and the cerium oxide content being between 0.5% by mass and 1.5% by mass relative to the total mass of the catalyst.

[0134] Advantageously, the catalysts of these preferred embodiments make it possible to obtain an ozonation rate of between 0.2 and 0.4 g of ozone / g of COD. This ozonation rate is much lower than the theoretical rate of 1 g of ozone / g of COD. The catalytic ozonation step of the process of the invention using these catalysts therefore requires little ozone to be effective.

[0135] The catalyst can be obtained by one of the catalyst synthesis methods known to those skilled in the art.

[0136] Example of implementation

[0137] The process comprises several steps E1 ...E8 including an electrozonation step E6 and a catalytic ozonation step E7.

[0138] In step El, effluent 1 undergoes preozonation (optional) before its admission into unit 2.

[0139] Since oils and materials that can trap ozone can reduce the efficiency of the electrozonation step E6, the effluent 1 undergoes a pretreatment step by dissolved air flotation in the pretreatment unit 2 in a step E2, in order to obtain a pretreated effluent 3. The contents of oils and materials that can trap ozone in the pretreated effluent are lower than the contents of oils and materials that can trap ozone in the effluent, in particular these contents can advantageously be thousands. The pretreatment step E2 by dissolved air flotation is a conventional step for those skilled in the art who will know how to implement it.

[0140] Then, preferably, in a step E3, the pretreated effluent 3 undergoes an anti-scale treatment by passing through the anti-scale treatment unit 4 before being mixed with ozone 5 in a step E4.

[0141] This mixture is then injected into the bottom of the reactor 6 and passes through the porous membrane 7 in a step E5 before undergoing electrozonation by the electrodes 8 in a step E6.

[0142] The porous membrane 7 allows the partial decomposition of the ozone 5, the destabilization of the foams and the decantation of large particles from the pretreated effluent 3. The porous membrane 7 also allows the destabilization of the calcium ions of the pretreated effluent 3, thus protecting the electrodes 8 from possible limescale deposits and consequently promoting the coagulating criterion of the ozone which allows the ozone to fragment part of the polluting material of the pretreated effluent 3 while electrically charging it in order to promote the coagulation, then the flocculation, of the particles fragmented from the polluting material.

[0143] Electrozonation E6 of effluent 1 by partially decomposed ozone is carried out with a direct current density of between 1.4 A / m 2 and 7.5 A / m 2 , especially between 1.7 A / m 2 and 5.5 A / m 2 , especially between 1.75 A / m 2 and 1.8 A / m 2 .

[0144] During the electrozonation step E6, the effluent 1 undergoes the combined treatment of oxidation by ozone and coagulation of the partially decomposed ozone to obtain on the one hand a residue and on the other hand an electrozoned effluent. In fact, part of the polluting material in the effluent is eliminated by oxidation with ozone.

[0145] In parallel, under the effect of the electric field generated by the electrodes implemented in the electrozonation step E6, fine ozone bubbles obtained by deformation of ozone bubbles fragment another part of the polluting material of the effluent to obtain fragmented particles of polluting material. The coagulating criterion of ozone charges these fragmented particles of polluting material which facilitates their coagulation and the formation of flocs. The flocs formed are stabilized thanks to the ions generated by the electrodes under the effect of the direct current density. The residue obtained during the electrozonation step E6 can comprise the stabilized flocs and the fragmented particles of coagulated but not flocculated polluting material.

[0146] Typically, the ozone concentration during the electrozonation step E6 may be between 0.1 ppm and 12 ppm, in particular between 0.5 ppm and 5 ppm, more particularly between 1 ppm and 2 ppm.

[0147] Typically, the contact time between the effluent and the partially decomposed ozone may be less than 2 hours, in particular between 15 minutes and 1.5 hours, more particularly between 30 minutes and 1 hour.

[0148] Electrozonation step E6 may not remove all polluting material from the effluent. Thus, the electrozoned effluent may include residual polluting material.

[0149] The electrozoned effluent is also concentrated in ozone because it includes the ozone that has not reacted during the electrozonation step E6. To remove the residual pollutant, the electrozoned effluent undergoes the catalytic ozonation step E7. More specifically, the electrozoned effluent 9 comprising residual pollutant and concentrated ozone is sent to the catalytic ozonation unit 10 in order to remove the residual pollutant.

[0150] Catalytic ozonation step E7 uses the catalyst described above. Catalytic ozonation step E7 can be carried out with the ozone included in the electrozoned effluent. Thus, advantageously, the treatment method of the invention is ozone-efficient because catalytic ozonation step E7 can be carried out without additional ozone addition.

[0151] The method may further comprise, between step E6 and step E7, a step E6-7 of treatment by low-pressure dissolved air flotation of the electrozoned effluent obtained during step E6 to obtain a treated electrozoned effluent, this treated electrozoned effluent then undergoing the catalytic ozonation step E7. Advantageously, this treatment step E6-7 makes it possible to increase the efficiency of the method of the invention by treating part of the residual polluting material from the electrozoned effluent.

[0152] The method may also comprise, at the end of the electrozonation step E6, in a step E65, the recycling of the residue 11 from the reactor 6 in the pretreatment unit 2 by dissolved air flotation in a step E8.

[0153] In other words, recycling the residue 11 in the pretreatment unit 2 makes it possible to increase the efficiency of the pretreatment without adding an external chemical coagulant, in particular to achieve contents of oils and materials which can trap almost 1000 ozone. Indeed, the inventor has found that the residue 11, which can comprise stabilized flocs and particles of coagulated but not flocculated polluting materials, can replace an external chemical coagulant conventionally used to increase the efficiency of dissolved air flotation. Examples

[0154] Example 1: Electrozonation Step E6

[0155] The electrozonation step E6 of the process of the invention is tested on a pilot scale with the following parameters: the porous membrane is composed of:

[0156] - 94% by mass of an oxidized ceramic as a support, the oxidized ceramic comprising 93% by mass of aluminum oxide, 5% by mass of titanium dioxide and 2% by mass of zirconium dioxide, and

[0157] - 6% by mass of titanium dioxide as metal oxide,

[0158] - porosity of the porous membrane: 22

[0159] - ozone flow rate: 20 L / min,

[0160] - direct current density of 1.78 A / m 2 ,

[0161] - ozone concentration of 1 to 2 ppm,

[0162] - aluminum anode and aluminum cathode,

[0163] - maximum effluent flow rate of 5000 liters per hour,

[0164] - 1 hour contact time.

[0165] The chemical oxygen demand (COD) of four different effluents is measured before and after the electrozonation step E6. The COD removal rate (reduction) expressed in (%) was determined for each effluent (Table 1 below).

[0166] [Tables 1]

[0167] These results demonstrate that the electrozonation step E6 of the process of the invention makes it possible to reduce COD by more than 90%.

[0168] Example 2: Step E7 of catalytic ozonation

[0169] Step E7 of catalytic ozonation of the process of the invention is tested on a pilot scale with the following parameters:

[0170] - Flow rate of effluent to be treated: 250 L / h,

[0171] - Ozone flow rate: 20 g / h,

[0172] - Contact time: 30 min,

[0173] - Initial COD: 205 ppm and

[0174] - Final COD: 0 ppm.

[0175] The ozonation rate of three different catalysts is measured and presented in Table 2 below. The metal alloy comprises 73.95% by mass of iron, 0.05% by mass of carbon, 17% by mass of chromium and 9% by mass of nickel. The clay is Kaolinite KGa-2.

[0176] [Paintings!]

[0177] These mass percentages are defined in relation to the total mass of the catalyst.

[0178] These results show that the ozonation rate is between 0.2 and 0.4 g of ozone / g of COD. It is therefore significantly lower than the theoretical rate of 1 g of ozone / g of COD.

Claims

Claims

1. System (100) for electrozoning an effluent (1, 3) comprising a polluting material, said system (100) being configured to receive said effluent (1, 3), to generate a direct current whose current density is between 1.4 A / m 2 and 7.5 A / m 2 , especially between 1.7 A / m 2 and 5.5 A / m 2 , especially between 1.75 A / m 2 and 1.8 A / m 2 , and to carry out electrozonation of the effluent (1, 3) received by partially decomposed ozone with the direct current generated and thus obtain an electrozoned effluent (9).

2. System (100) according to claim 1, said system (100) comprising a reactor (6) for carrying out electrozonation of the effluent (1, 3) received, said reactor (6) comprising a side wall having a cylindrical shape along a vertical axis of revolution and a bottom delimiting a reaction space, an ozone injection port and an effluent injection port or a port for injecting a mixture of ozone and effluent, and at least two electrodes, an anode and a cathode, in the reaction space.

3. A system (100) according to any preceding claim, said system (100) comprising a porous membrane (7) configured to provide partially decomposed ozone by filtering a received ozone stream, said membrane (7) comprising a support and a metal oxide on the surface of the support, the support being selected from an oxidized ceramic, a metal alloy, a chromium compound and mixtures thereof, and the metal oxide being selected from titanium dioxide, manganese oxide, cerium oxide, iron oxide, copper oxide, aluminum oxide and mixtures thereof, the partially decomposed ozone being obtained by passing a stream of ozone through said porous membrane.

4. System (100) according to any one of the preceding claims, said system (100) being configured to carry out catalytic ozonation of the electrozoned effluent (9) in order to obtain a treated effluent.

5. Method for electrozoning an effluent comprising a polluting material, said method comprising a step of electrozoning (E6) the effluent (1, 3) by partially decomposed ozone to obtain an electrozoned effluent (9), electrozonation (E6) being carried out with a direct current density of between 1.4 A / m 2 and 7.5 A / m 2 , especially between 1.7 A / m 2 and 5.5 A / m 2 , especially between 1.75 A / m 2 and 1.8 A / m 2 .

6. A method according to the preceding claim, wherein the partially decomposed ozone comprises between 1% by mass and 99.9% by mass of ozone.

7. A method according to any one of claims 5 or 6, wherein the effluent (1) is an industrial effluent, an urban effluent, a medical effluent, a pharmaceutical effluent, an agri-food effluent, non-potable water or mixtures thereof.

8. A method according to any one of claims 5 to 7, wherein the partially decomposed ozone is obtained by passing a stream of ozone through a porous membrane comprising a support and a metal oxide on the surface of the support, the support being selected from an oxidized ceramic, a metal alloy, a chromium compound and mixtures thereof, and the metal oxide being selected from titanium dioxide, manganese oxide, cerium oxide, iron oxide, copper oxide, aluminum oxide and mixtures thereof.

9. A method according to any one of claims 5 to 8, wherein, a residue being obtained as a result of electrozonation (E6), the method comprises a step of recycling at least a portion of the residue obtained in the dissolved air flotation pretreatment unit.

10. Method according to any one of claims 5 to 9, said method comprising a step (E7) of catalytic ozonation of the electrozoned effluent (9) in order to obtain a treated effluent.

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