Water treatment process by adsorption on micro-granular activated carbon incorporating microwave regeneration of the activated carbon.

Abstract

A water treatment process for reducing dissolved organic pollution and micropollutants, comprising contacting water with activated carbon in a single contactor, extracting treated water from the contactor, extracting, dehumidifying, and drying the spent activated carbon, and desorbing the pollution adsorbed onto the activated carbon by microwaves without interrupting the contact of water with the activated carbon, and recycling the regenerated activated carbon back into the contactor, the entire process being carried out in a single installation, characterized in that: the activated carbon is self-draining micro-granular activated carbon with an iodine value between 900 and 1000 mg / g, a particle size between 300 μm and 1000 μm, an average particle size (D50) between 500 μm and 600 μm, and a proportion strictly less than 5% by weight of grains with a size less than 400 μm;The extraction, dehumidification, drying, desorption, and recycling of the activated carbon into micro-granules are carried out without equipment causing significant agitation of the activated carbon; dehumidification includes simple draining of the activated carbon; drying is carried out by microwaves, with drying and desorption conducted in the same microwave equipment operating according to a drying cycle to obtain dried activated carbon with a residual moisture content of less than 5% by weight, followed by a desorption cycle; microwave drying and microwave desorption are carried out under a controlled atmosphere; and in that it includes the destruction of volatile organic compounds emitted during microwave desorption. Figure for the abstract: [Fig. 1];

Description

Title of the invention: Water treatment process by adsorption on micro-granular activated carbon incorporating microwave regeneration of the activated carbon. technical field

[0001] The present invention relates to the field of water treatment. More specifically, the invention relates to a water treatment process for reducing its organic matter content, including, where appropriate, the content of micropollutants (pesticides and their metabolites, endocrine disruptors, drug residues, industrial product residues...). The process according to the invention falls within the framework of water treatment processes using a granular material enabling the adsorption of organic matter and micropollutants it contains. The process according to the invention finds its application particularly in the field of drinking water treatment, in the field of tertiary wastewater treatment and in the field of industrial water treatment for discharge into the natural environment or for reuse. Previous art

[0002] Various water treatment processes using adsorbent materials to remove organic matter and, where appropriate, micropollutants, contained in water are known in the prior art.

[0003] Among these adsorbent materials, activated carbon is a preferred material due to its very high specific surface area, which is proportional to its adsorption capacity.

[0004] It is thus known to use powdered activated carbon (PAC) in the context of water treatment. According to those skilled in the art of water treatment, powdered activated carbon consists of particles having an average size of between 5 µm and 50 µm, preferably between 15 µm and 25 µm.

[0005] These techniques employ reactors containing activated carbon (AC) in which the water to be treated is brought into contact with the AC for a sufficiently long time to allow for the proper adsorption onto the AC of the materials to be removed. This contact can be carried out on a fluidized bed of AC or by injecting AC into a reactor. In the latter case, after the contact step, the water-AC mixture undergoes a separation step leading, on the one hand, to the production of powdered activated carbon loaded with adsorbed materials and, on the other hand, clarified water. This separation step can be carried out in various ways, primarily by sedimentation or by membrane or mechanical filtration, or even by fluidization (hydraulic speed change). While it can be recycled a number of times, CAP loses its adsorptive capacity fairly quickly, and it is necessary to regularly replace some of the CAP used in the reactor with fresh CAP. Therefore, quantities of new CAP must be regularly injected into the reactor to compensate for the loss of adsorption from the used CAP.

[0006] Although this type of process allows the replacement of part of the used CAP with new CAP without having to shut down the installations that implement it, it also presents other disadvantages. Specifically, used CAP cannot be regenerated because no cost-effective treatment is known to restore its original or near-original adsorption capacity. This results in the production of CAP sludge, which must be removed from the plant, dewatered, and then transported, increasing the costs associated with landfilling or incineration.

[0007] Since CAP is an expensive material, its use in water treatment is therefore hampered by economic imperatives, as the techniques implementing it have the disadvantage of consequently involving high operating costs.

[0008] Other processes use activated carbon not in powder form but in granular form. According to those skilled in water treatment, granular activated carbon (GAC) consists of carbon grains much larger than powdered activated carbon particles, generally ranging in size from 1000 µm to 3000 µm. In recent years, a new type of activated carbon has also been used in water treatment. This activated carbon does not correspond to the classic definition of powdered activated carbon (PAC) or the classic definition of granular activated carbon (GAC). It consists of micro-grains with a particle size smaller than that of GAC and much larger than that of PAC, generally ranging from 300 µm to 1000 µm. Furthermore, they have specific surface areas of the same order as those of PAC.This micro-granular activated carbon (“CApG”) allows for excellent adsorption of organic matter and micropollutants.

[0009] Granular or micro-granular activated carbons have the advantage of exhibiting excellent adsorption qualities.

[0010] However, they have the disadvantage of becoming saturated relatively quickly by the materials adsorbed onto them. When saturated, the objectives of treating and removing organic matter and micropollutants can no longer be met. Furthermore, when granular or micro-granular activated carbon is saturated, a release of the organic substances adsorbed into the water being treated can occur. Such a release can have negative consequences on the final quality of the treated water. To avoid such release, the activated carbon in granular or micro-granular form must be renewed frequently.

[0011] The drawback of granular and micro-granular activated carbon, namely their relatively rapid saturation, is offset by their regeneration potential. Regeneration, also called reactivation, involves subjecting these materials to appropriate treatment to restore their original adsorption capacities or capacities close to them. The most common method used for this is thermal regeneration, carried out in a furnace where a high temperature (around 800 °C) is maintained, allowing the adsorbed molecules to be desorbed and / or destroyed by the heat. Steam can be used to complete this regeneration, enabling the granular or micro-granular activated carbon to regain a structure very close to its initial structure, free of any pollutants.Activated carbon in granules or micro-granules can also be regenerated by acid or alkaline washing, although this generally does not restore all of its initial performance.

[0012] Activated carbon regeneration operations are generally not carried out on-site. Granular activated carbon extracted from the facilities is, in practice, stored and, when the stored quantity is sufficient, loaded, transported, and unloaded at a plant where it can undergo a regeneration process. These various storage and transport operations considerably lengthen and complicate the time and logistics required to obtain regenerated activated carbon. Furthermore, regeneration is only implemented on large quantities of spent activated carbon, which does not adequately meet the frequent need for small quantities of regenerated activated carbon.

[0013] A problem arising from these storage, transport, and regeneration operations, which has been poorly documented until now, is that they cause an increase in the proportion of fine particles in the regenerated activated carbon compared to the new activated carbon. In practice, all granular or microgranular activated carbons available on the market contain a small proportion of fine particles. The main drawback of the presence of these particles is that, due to their fineness, they can end up in the treated water and thus degrade the quality of the treatment. Good quality new granular or microgranular activated carbons have a low level of such fine particles. However, when they return from the regeneration processes, granular or microgranular activated carbons have higher levels of such fine particles.The abrasion of granular or micro-granular activated carbons, a source of loss of adsorbent materials, comes largely from the multiple handling (loading, unloading, transferring, shoveling, etc.) that the activated carbon undergoes during its transport to these channels and during its use. The treatment process in these materials, particularly when it involves heat treatment in rotary kilns, results in significant agitation of the activated carbon. This agitation causes abrasion of the activated carbon grains, leading to the formation of fine particles.

[0014] It should also be noted that, in many prior art installations, the renewal of the granular or microgranular activated carbon they use—that is, the replacement of saturated activated carbon with new or regenerated activated carbon—cannot be carried out without stopping their operation. This results in all the disadvantages associated with such an interruption, and primarily the loss of productivity of the installations.

[0015] To address this problem, water treatment systems have been proposed in the prior art. These systems include a contactor in which granular or microgranular activated carbon is brought into contact with the water to be treated. The systems are equipped with means by which used activated carbon can be gradually extracted from the contactor, roughly cleaned (for example, by hydrocycloning), and then returned to the contactor via a recycling pipe. A purge allows for the regular removal of saturated or partially saturated activated carbon, and means are provided for supplying new or regenerated activated carbon to the contactor to compensate for the purged carbon. This makes it possible to extend the residence time of the activated carbon in the system and to gradually replace it without necessarily interrupting its operation.Such installations are marketed under the names FILTRAFLO®CARB and OPACARB®FL.

[0016] One drawback of cleaning activated carbon for recycling is that such cleaning produces sludge, which constitutes an effluent that must itself be treated to reduce its pollutant content. Furthermore, cleaning activated carbon within the installation does not constitute regeneration of the activated carbon, in that it only restores a small proportion of the adsorption capacity of the used activated carbon.

[0017] Prior art has also proposed water treatment installations using adsorption on activated carbon in which the activated carbon is regenerated within the installation itself, thus without the need to extract it. In this regard, CN1260138C describes a technique in which a contactor containing activated carbon is sometimes subjected to adsorption cycles during which water to be treated flows through the contactor, and sometimes subjected to microwave activated carbon regeneration cycles during which no fluid flows through the contactor. Such a contactor must therefore be equipped with means enabling The device must produce microwaves internally and be made of materials that allow microwave action. Furthermore, the adsorption and regeneration stages are linked by the same contactor geometry, according to this technique. Finally, the water treatment process must be interrupted to regenerate the activated carbon. In practice, the use of such a technique is therefore limited to the laboratory scale and is not economically feasible on an industrial scale.

[0018] US7303684B2 also discloses an installation combining two contactors mounted in parallel for water treatment by adsorption onto activated carbon. The flow of the fluid to be treated can be interrupted alternately in each of the two contactors to allow for microwave regeneration of the activated carbon it contains, while adsorption continues in the other contactor. In addition to the drawbacks of the technique mentioned in the preceding paragraph, such an installation also has the disadvantage of requiring two contactors instead of one. Objectives of the invention

[0019] An objective of the present invention is to propose a water treatment process to reduce the content of dissolved organic pollution and micropollutants in this water by adsorption on an activated carbon, in which the activated carbon used can be regenerated, and which allows minimizing the release, by the regenerated activated carbon, of polluting substances and fine particles of carbon into the treated water.

[0020] Another objective of the present invention is to describe such a process which significantly reduces the requirements for loading, unloading, transporting activated carbon to carry out its regeneration.

[0021] Yet another objective of the present invention is to disclose such a process which makes it possible, in at least some of its embodiments, to increase the quality of regenerated activated carbon, by maximizing the restoration of its original adsorption properties.

[0022] Yet another objective of the present invention is to describe such a process which, in at least some of its embodiments, leads to minimizing the quantities of new activated carbon that need to be used.

[0023] Another objective of the present invention is to propose such a process which allows, in at least some of its embodiments, the regeneration of small quantities of activated carbon and thus to adapt continuously and in a synchronized manner to the operation of the water treatment plant implementing such a process under economically acceptable conditions.

[0024] Finally, an objective of the present invention is to disclose such a process which can operate without the use of chemicals and without the production of sludge or other solid residues. Description of the invention

[0025] These various objectives, or at least some of them, are achieved by means of the invention which relates to a water treatment process for reducing its dissolved organic pollution and micropollutant content, comprising a step of contacting said water with activated carbon in a single contactor, a step of extracting treated water from said contactor, a step of extracting used activated carbon from said contactor, a step of dehumidifying said used activated carbon extracted from said contactor, a step of drying the dehumidified used activated carbon, a step of microwave desorption of the pollution adsorbed on said dehumidified and dried activated carbon, and a step of recycling the activated carbon thus regenerated in said contactor, said extraction, dehumidification,drying and desorption of activated carbon being carried out without stopping said step of bringing said water into contact with said activated carbon, and the entire process being carried out in the same installation,

[0026] characterized in that:

[0027] said activated carbon is self-draining micro-granular activated carbon (CAqG) having an iodine value between 900 and 1000 mg / g, a particle size between 300 µm and 1000 µm, an average particle size (D50) between 500 µm and 600 µm and a proportion strictly less than 5% by weight of grains having a size less than 400 µm,

[0028] said extraction, dehumidification, drying, desorption and recycling steps of activated carbon into micro-grains are carried out without equipment causing significant stirring of the activated carbon, said dehumidification step comprising a simple draining of the activated carbon extracted from the contactor;

[0029] said drying step is a microwave drying step, said microwave drying step and said microwave desorption step being carried out in the same microwave emitting equipment operating according to a drying cycle in order to obtain dried activated carbon having a residual moisture content of less than 5% by weight followed by a desorption cycle;

[0030] said microwave drying step and said microwave desorption step are carried out under a controlled atmosphere;

[0031] and in that it includes a step of destruction of volatile organic compounds emitted during said microwave desorption step.

[0032] The process according to the invention makes it possible to minimize the release by regenerated micro-grain activated carbon of polluting substances and fine particles of carbon into the treated water.

[0033] Such a process has the advantage of using regenerated activated carbon, of which The particle size and adsorption characteristics are essentially the same as those of the original activated carbon. Thus, the process of the invention can greatly minimize the quantities of new activated carbon required during its implementation, or even eliminate it entirely over relatively long periods of time, up to several months.

[0034] Indeed, the various characteristics of the process according to the invention contribute on the one hand to limiting the abrasion of the micro-grained activated carbon during its extraction from the contactor and the steps allowing its regeneration and on the other hand to allowing the obtaining of a regenerated micro-grained activated carbon which has recovered most of its adsorption capacities and is free of all the polluting material which had been adsorbed into it.

[0035] Firstly, the micro-grain activated carbon used is very specific and was chosen after numerous tests for its cumulative ability to be little abraded and to have excellent adsorption qualities of organic matter and in particular of micropollutants contained in the water to be treated.

[0036] Secondly, although the recommended micro-granular activated carbon already exhibits very high abrasion resistance, any significant agitation of the carbon during its extraction from the contactor, its dehumidification, its drying, and the desorption of the pollutants adsorbed upon it, is prohibited according to the present invention. To the inventors' knowledge, it had never been considered that such significant agitation could contribute to the technical problem resulting from the abrasion of the activated carbon, namely the appearance of fine particles in the regenerated activated carbon that could pass into the treated water and degrade the quality of the treatment.It is emphasized that prior art, for these stages, advocated indiscriminately the use of equipment that caused such significant mixing, such as, in particular, pipes equipped with pumps to extract the activated carbon from the contactors and fluidized bed dryers or rotary kilns to dry it and desorb pollutants, as well as other equipment that did not. It is clear from this prior art that the problem posed by the significant mixing of activated carbon during its extraction and during the various stages leading to its regeneration had, until now, been completely neglected in practice. Contrary to the preconceived notion that such significant mixing had no impact on the quality of granular activated carbon, the inventors were able to demonstrate the opposite.

[0037] Consequently, according to the invention, the dehumidification of the microgranular activated carbon extracted from the contactor is carried out simply by draining it. Such draining does not cause any significant disturbance of the material. This method of dehumidification is possible only because the microgranules of activated carbon referred to in the present invention are self-draining. In practice, this means by Self-draining means that, when placed on a sieve with a mesh that retains the grains while allowing water to pass through, some of the water mixed with them can drain away by gravity. Thus, simple draining dehumidifies them. This is a property found in only a few commercially available granular activated carbons.

[0038] Thirdly, the drying and desorption steps of the microgranular activated carbon are both carried out in the same microwave-emitting equipment. Thus, no transfer operation, and therefore no significant mixing of the material, occurs between these two steps.

[0039] Fourthly, the step of desorption of pollutants adsorbed on micro-grained activated carbon being carried out by means of microwave action, taking care to destroy the volatile compounds thus desorbed, the process according to the invention makes it possible to restore the adsorption capacities of the micro-grained activated carbon and to avoid any subsequent release of pollutants into the water treated by this activated carbon thus regenerated.

[0040] It should be noted that the use of microwaves has already been considered in the prior art for the purpose of regenerating activated carbon used in water treatment processes. Microwaves have the advantage of being able to heat this type of material uniformly and to desorb the substances that have become adsorbed onto it. The present invention proposes to implement these microwaves under a controlled atmosphere, that is to say, one low in oxygen, in order to prevent any combustion of the activated carbon and to complement this implementation by destroying the volatile compounds resulting from the application of the microwaves. Thus, it is possible to regenerate the activated carbon into micro-grains and to prevent any subsequent release of pollutants into the treated water.

[0041] According to a preferred embodiment of the process, a temperature between 90°C and 150°C is uniformly maintained within the micro-grained activated carbon for a period of between 2 min and 30 min thanks to said microwave emitting equipment during said drying cycle.

[0042] Also preferably, a temperature between 600°C and 900°C is uniformly maintained within the micro-grained activated carbon for a period of between 1 min and 20 min thanks to said microwave emitting equipment during said desorption step.

[0043] Advantageously, said step of extraction of used micro-grained activated carbon from said contactor consists of transferring said micro-grained activated carbon from said contactor directly into a filtering structure.

[0044] Also advantageously, the process includes a step of filtering the treated water from said treated water extraction step of said contactor.

[0045] According to one variant, during said step of bringing the water to be treated into contact with said micro-granular activated carbon in said contactor, said micro-granular activated carbon is in the form of a fixed bed.

[0046] According to another variant, during said step of bringing the water to be treated into contact with said micro-grained activated carbon in said contactor, said micro-grained activated carbon is in the form of a fluidized or semi-fluidized bed.

[0047] Also according to one variant, said step of extraction of used micro-grain activated carbon from said contactor is carried out in an essentially continuous manner.

[0048] Preferably, the process includes a step of bringing the activated carbon from said desorption step to room temperature.

[0049] The energy emitted by said micro-grained activated carbon during said stage of bringing it to room temperature is then advantageously used to implement a pre-drying stage of the micro-grains of activated carbon provided just before said drying stage of these micro-grains.

[0050] Preferably, said pre-drying step is implemented in said microwave emitting equipment.

[0051] Optionally, the process also includes a step of injecting steam or CO2 into the micro-granular activated carbon after the microwave desorption step. This injection, which may be intermittent, aims to reactivate the micro-granular activated carbon, i.e., to restore its adsorption capacity. This injection may preferably be carried out either at the microwave oven or directly at its outlet using a contactor. It will be performed before the step of bringing the activated carbon to room temperature when such a step is implemented. Brief description of the figures

[0052] [Fig.1] : [Fig.1] schematically represents an installation enabling the implementation of the process according to the invention. Detailed description of the invention

[0053] The invention will now be described in more detail by means of the following description of a non-limiting embodiment thereof given with reference to the single figure.

[0054] The installation shown includes a contactor 1 provided with means for supplying 2 water to be treated containing pollutants, including a supply pipe, and means for evacuating treated water no longer containing pollutants, including an evacuation pipe.

[0055] The contactor 1 contains, in addition to the water to be treated, micro-granular activated carbon onto which the pollutants contained in the water can be adsorbed. As As indicated above, this micro-grain activated carbon may, within the framework of the invention, be present in the contactor in the form of a fixed bed or in the form of a fluidized or semi-fluidized bed.

[0056] In the context of this embodiment, micro-grain activated carbon marketed by Chemviron Carbon under the trade name MICROSORB(™) 400 R was used.

[0057] In accordance with the provisions of the present invention, this activated carbon consists of micro-grains which, in particular, have the characteristic of being self-draining. This micro-grained activated carbon also has an iodine value of between 900 and 1000 mg / g. The constituent micro-grains have a particle size predominantly (D50) between 500 µm and 600 µm, with a proportion strictly less than 5% by weight of particles smaller than 400 µm. Its specific surface area is 900 m² / g (BET method).

[0058] The contactor 1 is also provided in its lower part with a conduit 4 for the extraction of used micro-granular activated carbon, i.e., micro-granular activated carbon whose adsorption capacity is no longer sufficient to continue adsorbing the pollutants present in the water to be treated. As already mentioned, the extraction of this used activated carbon can be carried out continuously, for example when the contactor 1 is a contactor of the type used in the FILTRAFLO®CARB technique, or discontinuously, for example when the contactor 1 is a contactor of the type used in the OPACARB®FL technique.

[0059] Filter bags 5 are also provided to receive the used microgranular activated carbon extracted from the contactor 1 via the pipe 4. These filter bags have openings with a size of 100 sq m allowing the activated carbon to drain, i.e., allowing some of the liquid present in the mixture of water and microgranules to escape. Thus, to dehumidify this used activated carbon, it is sufficient to leave it in these filter bags for a sufficient period. It should be noted that, according to the present invention, the transfer of the used activated carbon from the contactor 1 to the filter bags 5 is carried out without causing significant agitation, i.e., without the need, for example, for a pipe equipped with a pump. In the present embodiment, the used micro-granular activated carbon is thus collected by a hydro-ejector system from the outlet of the pipe 4 equipping the contactor 1.

[0060] The installation also includes means 6, including a microwave oven, for drying and desorbing the materials adsorbed onto the used activated carbon. This microwave oven can operate at different power levels according to different programs. It is equipped with means (not shown) for maintaining an oxygen-poor atmosphere within its enclosure.

[0061] In the context of this embodiment, the microwave oven used allows the emission of microwaves with frequencies ranging from 300 MHz to 300 GHz.

[0062] The enclosure of this microwave oven communicates with means 7 consisting of thermal oxidation means possibly supplemented by adsorption means and aimed at destroying certain organic compounds such as halide gases like hydrogen chloride or hydrogen fluoride and / or sulfur oxides from this enclosure.

[0063] The installation is also equipped with means 12 for injecting steam (or CO2) into the activated carbon from the microwave oven in order to perform, after the thermal desorption step, a reactivation step of the activated carbon by gasification. This gasification step may only be carried out intermittently; it is not necessary for each regeneration cycle. It allows the elimination of any carbon residues formed during desorption that could clog some of the pores of the activated carbon.

[0064] In the process according to the invention, the dehumidified activated carbon from the filter bags 5 is extracted from these filter bags and transferred by a conveyor belt into the chamber of a microwave oven. Again, no significant mixing of the activated carbon occurs during the transfer of the activated carbon from the filter bags to the chamber.

[0065] The microwave oven enclosure is first used to pre-dry the activated carbon by bringing hot air with a temperature of approximately 100 to 150°C into it without using microwaves and to keep this hot air in contact with the activated carbon for a sufficient time to lower its moisture content to 5 to 10% by weight.

[0066] At the end of this pre-drying stage, the air present in the oven enclosure is extracted so as to create an oxygen-poor atmosphere in said enclosure.

[0067] The microwave oven is then operated by emitting microwaves into the chamber, according to a first cycle in which microwaves are applied to completely dry the micro-granular activated carbon. In this embodiment, this first cycle consists of applying sufficient energy to the micro-granular activated carbon inside the oven chamber using microwaves to raise its temperature uniformly to 150°C for 10 minutes. At the end of this first cycle, the used activated carbon has a moisture content of less than 5% by weight.

[0068] The microwave oven is then operated according to a second cycle that desorbs the pollutants adsorbed onto the micro-granular activated carbon and thus restores its adsorption capacity. In the present embodiment, this second cycle consists of distributing the micro-granular activated carbon present in The furnace chamber is heated by microwaves, providing sufficient energy to raise its temperature uniformly to approximately 850°C for 10 minutes. Thanks to the oxygen-poor atmosphere inside the furnace, combustion of the micro-granular activated carbon is prevented. During this second cycle, some of the pollutants are vaporized by the heat. These volatile substances are extracted from the furnace (6) and then destroyed by means of (7), thus preventing them from redepositing on the activated carbon and subsequently being released into the contactor (1).

[0069] Upon exiting the microwave oven, water vapor (or CO2) is injected by means 12 into the activated carbon in order, as indicated above, to eliminate any carbonaceous residues still present in part of the pores of the activated carbon.

[0070] After these steps, the micro-granular activated carbon exhibits adsorption capacities corresponding to approximately 90% of these original adsorption capacities.

[0071] This regenerated activated carbon is then conveyed via means 8 such as a belt conveyor to a storage tank 10 in order to be subsequently redistributed into the contactor 1.

[0072] In this storage tank 10, the activated carbon is brought back to ambient temperature. The heat emitted can then be transferred, via a heat exchanger 13, to heat an air stream. The air thus heated can be conveyed into the chamber of the microwave oven 6 to be used in the pre-drying step described above.

[0073] A new activated carbon storage tank 11 is also provided to supply new activated carbon to the contactor 1 as needed via a pipeline 9.

[0074] Thanks to the invention, the regenerated activated carbon arriving at the contactor 1 has a fine particle content that is virtually no higher than that of virgin activated carbon. Furthermore, the mass loss of activated carbon is minimal throughout the entire process, including activated carbon extraction, pre-drying, drying, regeneration, and the return of the regenerated activated carbon to the contactor 1. Thus, the supply of virgin micro-granular activated carbon via the pipeline 9 is minimized. The installation costs are therefore reduced.

[0075] The present installation was used to implement the process according to the invention at the Applicant's Gahard (France) site in order to treat catchment water taken from this site over a period of one year.

[0076] Thanks to the process according to the invention, it has been possible to consistently obtain good quality treated water by regenerating the micro-granular activated carbon used in the installation six times, thus drastically reducing, in practice by 90%, the input of new activated carbon. Considering that activated carbon represents 75% of the considering the cost of implementing such an installation, the savings on this cost thanks to the invention have been estimated at 50% taking into account the cost of microwave desorption.

Claims

1. Demands A water treatment process for reducing dissolved organic pollution and micropollutants, comprising a step of contacting said water with activated carbon in a single contactor, a step of extracting treated water from said contactor, a step of extracting used activated carbon from said contactor, a step of dehumidifying said used activated carbon extracted from said contactor, a step of drying the dehumidified used activated carbon, a step of desorbing the pollution adsorbed on said dehumidified and dried activated carbon by microwaves, and a step of recycling the regenerated activated carbon back into said contactor, said extraction, dehumidification, drying and desorption steps of activated carbon being carried out without stopping said step of contacting said water with said activated carbon, and the entire process being carried out in the same installation, characterized in that: said activated carbon is self-draining micro-granular activated carbon having an iodine value between 900 and 1000 mg / g, a particle size between 300 µm and 1000 µm, an average particle size (D50) between 500 µm and 600 µm and a proportion strictly less than 5% by weight of grains having a size less than 400 µm, said extraction, dehumidification, drying, desorption and recycling steps of micro-granular activated carbon are carried out without equipment causing significant mixing of the activated carbon, said dehumidification step comprising a simple draining of the activated carbon extracted from the contactor; said drying step is a microwave drying step, said microwave drying step and said microwave desorption step being carried out in the same microwave emitting equipment operating according to a drying cycle in order to obtain dried activated carbon having a residual moisture content of less than 5% by weight followed by a desorption cycle; said microwave drying step and said microwave desorption step are carried out under a controlled atmosphere; and in that it includes a step of destruction of the volatile organic compounds emitted during said desorption step by micro- waves.

2. The method according to claim 1 characterized in that during said drying cycle a temperature between 90°C and 150°C is uniformly maintained within the micro-grained activated carbon for a period between 2 min and 30 min thanks to said microwave emitting equipment.

3. A method according to claim 1 or 2 characterized in that during said desorption cycle, a temperature between 600°C and 900°C is uniformly maintained within the micro-granular activated carbon for a period of between 1 min and 20 min thanks to said microwave emitting equipment.

4. A method according to any one of claims 1 to 3 characterized in that said step of extraction of used micro-granular activated carbon from said contactor consists of transferring said granular activated carbon from said contactor directly into a filtering structure.

5. A method according to any one of claims 1 to 4 characterized in that it comprises a step of filtering the treated water from said treated water extraction step of said contactor.

6. A method according to any one of claims 1 to 5 characterized in that during said step of bringing the water to be treated into contact with said micro-granular activated carbon in said contactor, said micro-granular activated carbon is in the form of a fixed bed.

7. A method according to any one of claims 1 to 5 characterized in that during said step of bringing the water to be treated into contact with said micro-granular activated carbon in said contactor, said micro-granular activated carbon is in the form of a fluidized or semi-fluidized bed.

8. A method according to any one of claims 1 to 7 characterized in that said step of extraction of used micro-grain activated carbon from said contactor is carried out in an essentially continuous manner.

9. A process according to any one of claims 1 to 8 characterized in that it comprises a step of bringing the activated carbon from said desorption step to room temperature.

10. The process according to claim 9 characterized in that the energy emitted by said micro-granular activated carbon during said stage of bringing it to room temperature is used to carry out a pre-drying step provided just before said drying step.

11. The method according to claim 10, characterized in that said pre-drying step is carried out in said micro-emitting equipment

12. waves. A method according to any one of claims 1 to 11 characterized in that it comprises a step of injecting water vapor or CO2 into the micro-granular activated carbon carried out after said microwave desorption step.

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