Method for treating water by activated carbon adsorption combined with ozone addition and apparatus implementing this method

Abstract

This invention relates to a water treatment method, comprising the steps of injecting ozone into water to be treated via the Venturi effect, followed by saturating the water with ozone, supplying the ozonated water to a reactor comprising a fluidized bed of activated carbon particles, contacting the ozonated water with the activated carbon particles via an upward flow in the reactor, and discharging the treated water. The invention also relates to an apparatus comprising an activated carbon reactor, a means for supplying water to the reactor, a means for discharging treated water, a means for injecting ozone into the water via the Venturi effect, and a means for saturating the water with ozone, said means being directly installed on the means for supplying water to the reactor, or installed as a bypass to the means for supplying water to the reactor.

Description

Technical Field

[0001] Technical Field of the Invention

[0002] This invention relates to the field of water treatment technology, and more particularly to methods for obtaining drinking water and purifying wastewater. More specifically, this invention relates to methods for treating water to remove dissolved organic pollutants by means of an upflow in a reactor containing activated carbon used in conjunction with ozone addition, and to apparatus that enables the implementation of such methods. Background Technology

[0003] Existing technology

[0004] There are various types of methods that enable the removal of organic pollutants dissolved in aqueous effluents. The main methods used in drinking water production systems for treating municipal wastewater and residual effluents are biological processes, coagulation / flocculation / sedimentation, oxidation, and adsorption.

[0005] Biological and coagulation / flocculation / sedimentation processes have the disadvantage of producing sludge, which is increasingly problematic and costly to manage. Coagulation / flocculation / sedimentation also suffers from the drawback of relying on the supply and consumption of chemical products (coagulants, flocculants) that cannot be extracted from the resulting sludge and therefore cannot be reused at the starting point of this same process. Oxidation processes inherently suffer from the production of oxidation byproducts (partial oxidation of dissolved organic compounds fails to achieve their final complete mineralization), which may possess toxicity and / or ecotoxicity levels comparable to the initial organic compounds. Furthermore, some of these oxidation processes are based on homogeneous catalytic mechanisms (e.g., the Fenton reaction), which in turn leads to sludge production.

[0006] Adsorption technology (especially adsorption on activated carbon) is a known technique and is commonly used to remove dissolved organic pollutants (pesticides, industrial residues, pharmaceutical residues, etc.) in drinking water production systems and for treating municipal and industrial wastewater. However, a drawback of this technique is the generation of large quantities of used activated carbon, which must be extracted from the reactor and replaced with the same amount of fresh activated carbon.

[0007] The combined use of ozonation and activated carbon adsorption steps in drinking water treatment systems is also known. The benefits of this technology lie not only in the combined strong oxidizing power of ozone and the large adsorption capacity of activated carbon, but also in the fact that activated carbon accelerates the decomposition of ozone into hydroxyl radicals. These two steps are performed sequentially, each in its own dedicated compartment; that is, the water-ozone contact step is performed first, followed by the adsorption step, which can be carried out in a granular activated carbon filter. Ozone injection is typically carried out via a porous diffuser installed in the ozonation reactor, with a contact time of approximately 20 minutes. However, because the transfer of ozone into the water is incomplete, ozone may remain in the gas space within the ozonation reactor. To protect operator health, it is therefore necessary to cover the ozonation reactor and add ozone depletion devices to the vents. Furthermore, to reduce residual ozone molecules in the water leaving the ozonation reactor, a reducing agent such as sodium bisulfite must be added. Another drawback of this technology is that the physical separation of the ozonation and adsorption steps, with their long contact times between the treated water and ozone, creates conditions conducive to the formation of ozonation byproducts, such as bromate, which begins to form 2-3 minutes after contact, and byproducts derived from organic matter present in the water, such as N-nitrosodimethylamine (NDMA). These byproducts are not always adsorbed onto the activated carbon particles and can accumulate in the water leaving the adsorption step. Therefore, it is important to avoid their formation. Summary of the Invention

[0008] The purpose of this invention

[0009] One object of the present invention is to provide a water treatment technology that does not result in the formation of byproducts or solid residues.

[0010] Another object of the present invention is to provide a water treatment technology that does not result in the formation of bubbles and / or gas clouds above the compartment where adsorption occurs, thereby avoiding or at least limiting the use of chemical products such as reducing agents. This technology also involves reducing operator health risks.

[0011] Another object of the present invention is to provide a technique for treating water by adsorption on activated carbon, which allows the activated carbon to become saturated more slowly or even to be regenerated in situ, thereby reducing the amount of fresh adsorbent introduced as a replacement for the used adsorbent.

[0012] Another object of the present invention is to provide a water treatment technology that consumes less ozone compared to existing advanced oxidation methods.

[0013] Another object of the present invention is to provide a technique that enables these objectives to be achieved while reducing the contact time between ozone and the water to be treated.

[0014] Another object of the present invention is to provide a water treatment technology that enables the removal of bacteria and viruses present in water to be treated without requiring special steps for this purpose.

[0015] Overview of the Invention

[0016] These objectives, and others that will become apparent below, are achieved by virtue of the present invention.

[0017] The first objective of the present invention relates to a water treatment method. Specifically, the method according to the present invention comprises:

[0018] - The step of injecting ozone into the water to be treated.

[0019] - The step of feeding the ozonated water to be treated into a reactor containing a fluidized bed of activated carbon particles.

[0020] -The process involves contacting the ozonated water with activated carbon particles via an upward water flow in the reactor.

[0021] - The steps to drain the water that has been treated in this way

[0022] The step of injecting ozone into the water to be treated is carried out through the Venturi effect, and the step of saturating the water to be treated with ozone immediately follows the injection step.

[0023] This method allows ozone to be added to water and then dissolved to remove bubbles while regenerating activated carbon particles present in the reactor. Due to this method, and as will be disclosed in the examples, compared to existing methods, the amount of ozone used and the amount of fresh activated carbon introduced as a replacement for used activated carbon can be reduced, while maintaining good water treatment performance.

[0024] Alternatively, the amounts of ozone and activated carbon can be equal to those used in existing methods, and the water treatment performance is then improved relative to that obtained by these existing methods.

[0025] According to a preferred embodiment, the step of saturating water with ozone is carried out by means of a saturation cone (…). This can be done through desaturation or a degassing tower.

[0026] The use of a saturation cone is advantageous because it is a simple, effective, and quick-to-install device, and its footprint can be selected based on the equipment configuration and desired performance. Therefore, the saturation cone can be easily integrated into existing equipment containing reactors with fluidized beds of activated carbon granules to improve their performance or reduce the consumption of replenished fresh activated carbon. Saturation can also be carried out in a degassing tower.

[0027] According to a preferred embodiment, the injection step and the step of saturating water with ozone have a total duration of less than 1 minute, preferably 10-30 seconds.

[0028] The method according to the invention effectively enables improvements in water treatment performance or reduces the consumption of ozone and fresh activated carbon without slowing down the water treatment process. The injection of ozone and its dissolution in the water take only a few seconds, which is particularly interesting in the context of retrofitting existing equipment.

[0029] According to one particular embodiment, the ozone injection step and the ozone saturation step are carried out in a device for supplying the water to be treated to the reactor. Alternatively, these steps can be carried out as a bypass in a conduit installed on the device for supplying the water to be treated to the reactor.

[0030] This configuration option allows the method to be adapted as cleverly as possible to existing equipment, especially based on the available floor space.

[0031] According to one embodiment, the activated carbon particles used in this method are agglomerates with a particle size of 300μm-1500μm, preferably 400μm-800μm, and a true density greater than 0.45.

[0032] Agglomerates of activated carbon that meet these characteristics are particularly advantageous because they enable optimal expansion of the fluidized bed of activated carbon particles, which improves the adsorption capacity of pollutants on it.

[0033] According to one embodiment, the fluidized bed reactor according to the method is equipped with at least one water deflector disposed at the top. This deflector is designed to reduce the velocity of the upward flow of water to create a tranquil zone above the activated carbon particle bed. This tranquil zone is a low-hydrodynamic turbulence zone, which allows for the prevention of activated carbon particles, especially the finest particles, from being carried away by the upward flow of water and from escaping from the reactor (which would increase the consumption of replenished fresh activated carbon). This is particularly advantageous where ozone coalescence on the surface of the activated carbon particles would lead to bubble emission and carbon loss.

[0034] According to one variation, the at least one deflection device consists of a set of blades that are inclined relative to the vertical direction and parallel to each other, the blades being inclined at an angle θ of 50° to 60°, preferably close to 60°, relative to the vertical direction.

[0035] According to one embodiment, when at least one deflection device is present in the reactor, the reactor further includes a water recovery device disposed downstream of the calm zone. This recovery device preferably consists of a prismatic trough with sides forming an angle α of 45° to 70° relative to the horizontal direction, and each side is provided with a first fluid overflow outlet and a deflector that acts as a baffle for the deflection device.

[0036] According to one embodiment, the upward flow of water in the fluidized bed reactor has a velocity of 8 m / h to 50 m / h, preferably 20 m / h to 40 m / h.

[0037] Because air bubbles are incompatible with the operation of fluidized bed reactors (as they cause hydraulic disturbances), it is essential that there are no air bubbles (in this case, ozone) in the ozonated water. This is achieved by the ozone dissolving in the water within the saturated cone before entering the activated carbon reactor. The absence of ozone bubbles in the water reduces turbulence in the activated carbon granular bed. This has the effect of further reducing the amount of activated carbon that tends to escape from the reactor.

[0038] Another object of the invention relates to apparatus for treating water according to the method of the invention.

[0039] Specifically, the device according to the invention includes:

[0040] - An activated carbon reactor, comprising a fluidized bed of activated carbon particles.

[0041] -A device for supplying the water to be treated to the reactor.

[0042] - A device for discharging treated water.

[0043] It also includes a device for injecting ozone into water via the Venturi effect and a device for saturating water with ozone, the devices being directly installed on the device that supplies water to the reactor, or installed on a pipe that is installed as a bypass to the device that supplies water to be treated to the reactor.

[0044] The advantage of this device is that it does not significantly increase the footprint of existing structures and can easily be modified to integrate the supplementary technical features according to the present invention.

[0045] According to a preferred embodiment, the activated carbon particles in the device are agglomerates with a particle size of 300μm-1500μm, preferably 400μm-800μm, and a true density greater than 0.45.

[0046] These activated carbon agglomerates are particularly suitable for the equipment according to the invention. Their special properties enable optimal activated carbon bed expansion, even when applying increased velocities to upwelling water.

[0047] According to one particular embodiment, the reactor of the device is equipped with at least one deflection device disposed at the top of the reactor.

[0048] This device allows for the creation of a calm zone at the top of the reactor, which prevents leakage of activated carbon particles, especially the finest particles.

[0049] According to one variation, the at least one deflection device comprises a set of blades that are inclined relative to the vertical direction and parallel to each other, the blades being inclined at an angle θ of 50° to 60°, preferably close to 60°, relative to the vertical direction.

[0050] According to one embodiment, and when the reactor includes a deflection device, the reactor also includes a water recovery device disposed downstream of the calm zone, the recovery device preferably consisting of prism-shaped chute having sides forming an angle α of 45° to 70° with respect to the horizontal direction and each having a first fluid overflow outlet and a deflector that acts as a baffle as the deflection device. Attached Figure Description

[0051] Brief description of the attached figures

[0052] [ Figure 1 ]: Figure 1 A schematic diagram of the equipment is shown, in which the Chinese Churi system and the device for saturating water with ozone are installed on the pipeline that supplies water to the reactor.

[0053] [ Figure 2 ]: Figure 2 A schematic diagram of the device according to the invention is shown, in which the Churi system and the device for saturating water with ozone are installed on a pipeline that serves as a bypass to the pipeline supplying the water to be treated to the reactor.

[0054] [ Figure 3 ]: Figure 3 The figure shows the activated carbon particles (10 g / m³) in the presence or absence of ozone. 3 Percentage removal of various micropollutant compounds in an activated carbon granular bed reactor. White: ozone absent; Black: 2 g / m³ 3 Ozone. A list of compounds is shown in Table 2. Detailed Implementation

[0055] Detailed Description of the Invention

[0056] This invention aims to improve existing water treatment methods and equipment. In particular, it aims to improve technologies for treating wastewater and / or drinking water. This is because these types of water are particularly suitable for treatment by ozonation and activated carbon adsorption. Therefore, the technology according to this invention is particularly effective for treating this type of water.

[0057] The method and apparatus according to the invention involve, in an original manner, the combination of a device for injecting ozone via the Venturi effect upstream of a reactor specifically designed for adsorbing pollutants passing through a fluidized bed of activated carbon particles with a device for saturating water with ozone.

[0058] Within the meaning of this invention, "polluting substances" refers to organic and chemical substances that are harmful to water quality, including those present at very low concentrations (micropollutants).

[0059] In the first step of the method according to the invention, ozone is injected into the water to be treated. The ozonated water is then directed to a reactor comprising a fluidized bed of activated carbon particles. As it evolves through the activated carbon particle bed in an upflow manner, pollutants in the water are adsorbed onto the activated carbon particles, and then the treated water is discharged from the reactor.

[0060] Ozone injection is achieved through suction generated by the Venturi effect, which has the advantage of preventing any ozone leakage into the atmosphere and allowing it to mix with water. The Venturi effect is a suction effect produced by fluid moving under negative pressure. Therefore, through the Venturi effect, the water to be treated is subjected to negative pressure, which allows ozone to be drawn into the water. Due to this technique, all injected ozone is incorporated and mixed into the water to be treated. Therefore, a reduced amount of ozone can be used compared to techniques known in the prior art. Preferably, the amount of ozone injected into the water is 0.5-3.0 mg per liter of water to be treated. The Venturi effect is achieved by any means known in the art. In particular, it is achieved through a Venturi system.

[0061] The water to be treated, mixed with ozone, immediately undergoes an ozone saturation step. Ozone molecules dissolve in the water, significantly preventing the formation of ozone bubbles. In fact, such bubbles promote turbulence within the activated carbon particle bed and thus facilitate their exit from the reactor. Furthermore, ozone in bubble form is less likely to be captured on the surface of the activated carbon particles, which are capable of reducing ozone molecules. Therefore, the reduced ability of the activated carbon particles to capture ozone contributes to the formation of a harmful gaseous space above the reactor. Finally, the very short time of ozone injection and saturation of the water to be treated (a few seconds) also has the advantage of avoiding the formation of byproducts through the reaction of ozone with substances contained in the water. Water ozone saturation is achieved by any known method. In particular, it is achieved using a saturation cone, which allows for a transfer efficiency of approximately 95-99%. Alternatively, the water ozone saturation step can be achieved using a degassing tower. Such towers have the advantage of simple construction, but their large height may hinder their implementation in existing operations.

[0062] Without wishing to associate it with any theory, it is believed that the improvement obtained by the method of the present invention is partly based on the ability of dissolved ozone molecules to react at the surface of activated carbon particles to generate new surface functional groups. In fact, activated carbon captures pollutant molecules due to the presence of adsorption sites and also due to the presence of functional groups capable of binding with pollutants (especially organic pollutants). Ozone, due to its strong oxidizing power, enables the generation of new functional groups at the surface of activated carbon particles. The adsorption capacity of activated carbon particles is thus significantly improved, particularly for organic pollutants such as pesticides, drug residues, and natural organic matter. Therefore, for the same amount of activated carbon used, water treatment performance is significantly improved. Up to 10 g / m³ has been observed. 3 The reduction in carbon renewal in the treated water is associated with a 25% increase in the adsorption capacity for pollutants. Alternatively, the method according to the invention can maintain the same performance while significantly reducing the amount of activated carbon required for water treatment. Furthermore, the reaction of ozone on the activated carbon surface advantageously enables ozone reduction, and thus avoids the presence of ozone in the treated water and / or in the gas space above the reactor.

[0063] As shown in the experimental section, the method according to the invention enables the absence of byproducts such as bromate, even in the presence of high concentrations of bromide in the water to be treated. Furthermore, the method according to the invention enables the reduction of the vast majority of micro-contaminants by a rate greater than 90%. Finally, the invention enables better water cleaning, particularly by reducing bacteria and viruses in the water through the action of ozone.

[0064] Another advantage of the method according to the invention is that the total duration of the steps of ozone injection and ozone saturation of the water to be treated is very short. According to a particular embodiment, the total duration of the ozone injection step and the ozone saturation step is less than 60 seconds, preferably less than 30 seconds, more preferably 10-20 seconds. Ozone saturation of the water to be treated requires only a few seconds, thus significantly improving water treatment performance, or significantly reducing the amount of activated carbon particles to be replaced for the same performance. Reducing the contact time advantageously makes it possible to avoid or at least reduce the formation of byproducts.

[0065] According to one embodiment, the steps of injecting ozone and saturating water with ozone are carried out in a device for supplying the water to be treated to the reactor, such as a pipeline. In practice, the method according to the invention yields better results when these two steps are performed near a reactor containing a fluidized bed of activated carbon particles. Increasing the supply time of ozone-saturated water promotes the formation of byproducts such as bromate.

[0066] However, the method according to the invention also makes it possible to perform these injection and saturation steps at other levels, which makes it possible to adapt it to various configurations of water treatment equipment.

[0067] Therefore, according to another embodiment, these steps are performed at the level of a pipe installed as a bypass for supplying the water to be treated to the reactor. Thus, a preliminary step of supplying the water to be treated to the bypass pipe as a main pipe can be added, wherein steps of injecting ozone and saturating the water with ozone are performed. An additional step of supplying the ozone-saturated water to the main pipe can then be provided.

[0068] Once the water to be treated is saturated with ozone, it is supplied to a reactor containing a fluidized bed of activated carbon particles. This step is carried out via a device (e.g., a main pipeline) for supplying the water to the reactor, optionally preceded by a step where the ozone-saturated water is carried out from a pipeline installed as a bypass to the device for supplying the water to the reactor.

[0069] In the reactor, ozone-saturated water flows upward through a fluidized bed of activated carbon particles. As previously mentioned, the ozone in the water allows new functional groups to form on the surface of the activated carbon particles. Pollutants in the water are thus adsorbed by both the adsorption sites on the activated carbon particles and the functional groups formed on their surface. Simultaneously, the reaction of ozone on the surface of the activated carbon particles leads to its reduction, resulting in virtually no ozone or very little ozone in the interstitial water.

[0070] In a preferred embodiment, the step of contacting the ozone-saturated water to be treated is carried out on activated carbon particles in the form of agglomerates. Agglomerates of activated carbon particles differ from powdered activated carbon, particularly in their particle size, their specific surface area, and their density.

[0071] Preferably, the agglomerates of activated carbon particles are in the form of micrograins. The activated carbon micrograins implemented in the method according to the invention have an average particle size of 300 μm-1500 μm, preferably 400 μm-800 μm, and the proportion of particles smaller than 400 μm is strictly less than 5%. It should be noted that powdered activated carbon has a significantly lower particle size, typically 5 μm-50 μm, particularly 10 μm-25 μm.

[0072] According to one embodiment, the density of activated carbon microparticles is greater than 0.45, preferably greater than 0.5 (dry product).

[0073] According to one embodiment, the concentration of activated carbon particles in the reactor is between 100 g / L and 400 g / L, preferably between 150 g / L and 300 g / L.

[0074] The upflow velocity of the water applied to the reactor is adjusted according to the particle size of the activated carbon particles in the granular bed. This is because it should not cause the granular bed to expand to be too small or too large. When the bed expands too small, the carbon particles cannot completely separate from each other, which reduces the adsorption performance of the granular bed. Conversely, when the expansion is too large, the activated carbon particles are further at risk of being carried away by the upflow of water and leaving the reactor, thus increasing the amount of fresh activated carbon that needs to be added to compensate for these losses. In practice, the upflow velocity can therefore be preferably selected to form an expansion zone of the activated carbon granular bed and a transition zone above it, where the particle concentration density is lower than in the expansion zone.

[0075] According to one embodiment, the upward flow velocity of water in the reactor is between 8 m / h and 50 m / h, preferably between 20 m / h and 40 m / h.

[0076] This implementation is particularly suitable when the activated carbon particles forming the reactor bed are microparticles as described above.

[0077] According to one particular embodiment, a water deflector is positioned at the top of the reactor. Such deflectors are described, for example, in International Patent Application No. WO2019224258A1. They help to create a calm zone at the top of the reactor.

[0078] This allows for the use of high-speed upflow of the water to be treated while preventing any leakage of activated carbon particles. This further enables the elimination of the need for ballast polymers, even at relatively high upflow velocities of the water to be treated.

[0079] Preferably, the deflection device comprises a set of blades that are inclined relative to the vertical and parallel to each other. Preferably, these blades are inclined at an angle θ of 50° to 60° relative to the vertical. Advantageously, the blades are inclined at an angle θ close to 60° relative to the vertical.

[0080] The blades can be spaced 25mm-100mm apart. More specifically, they can be spaced 36mm-42mm apart. This spacing is particularly suitable for adsorbent media particles, especially activated carbon particles or microparticles with a particle size of 300μm-1500μm. When water passes through the deflector, its velocity decreases within the blades, creating a calm zone where particles can settle.

[0081] According to a particular embodiment, when a deflection device is present, the reactor of the apparatus further includes a water recovery device located downstream of the calm zone. This recovery device, for example, consists of prismatic chute-shaped flanks having sides forming an angle α of 45° to 70° relative to the horizontal direction, each side having a first fluid overflow outlet and a deflector acting as a baffle in the deflection device. The angle α can particularly have a value close to 60°. Such a chute has been described in patent application published under FR2694209A1.

[0082] The present invention also relates to apparatus for treating water, particularly wastewater or drinking water, which is suitable for carrying out the aforementioned method according to the invention. Reference now is made to... Figure 1 and 2 Describe the device. Figure 1 and 2 This is for illustrative purposes only and does not constitute a limitation on the detailed description below.

[0083] The device 10 according to the present invention includes:

[0084] - Activated carbon reactor 1, which includes an activated carbon granular fluidized bed 2

[0085] -The device 3 that supplies the water to be treated to the reactor 1

[0086] - The treated water discharge device 7,

[0087] - and the device for injecting ozone into the water to be treated by means of the Venturi effect, here being the Venturi system 4, and the device for saturating the water with ozone, here being the saturation cone 5, which is located directly on the device 3, or on the device 3' which is installed as a bypass of the device 3.

[0088] The reactor 1 suitable for the method of the present invention includes an activated carbon granular fluidized bed 2. The reactor can be cylindrical or square. Preferably, the reactor has a height of 3m-10m. It is equipped with an injection and distribution device for the water to be treated at the bottom of the reactor to create an upward flow of water within the reactor.

[0089] The activated carbon particles constituting the bed 2 of reactor 1 are as described above. The activated carbon particle bed in the reactor preferably has a height of 1.5m to 3m when at rest and a height of 2m to 5m when expanded.

[0090] The water supply device 3 and its optional bypass device 3' can be pipes. When the bypass device 3' is used, devices 3 and 3' are interconnected by a known device such as a tee. In a variation of this particular embodiment, a supply device 6 for the water to be treated can be provided to direct a portion of the water from device 3 to device 3'. This may specifically involve a pump, preferably an accelerator pump.

[0091] The suitable Venturi system 4 within the scope of this invention can be any known Venturi system. Venturi syringes or equivalent products sold under the Stübbe brand may be specifically mentioned.

[0092] The saturation cone used in this invention can be selected from known cones suitable for saturating water with ozone. It can also be selected based on various criteria, particularly the space occupied and the flow rate of the water to be treated. For example, saturation cones or equivalents sold by Pentair or Linde-Gas are known. Of course, other devices for saturating water with ozone, such as degassing towers, can also be used.

[0093] According to a particular embodiment, the reactor of the device according to the invention is equipped with a deflection device (not shown). The deflection devices suitable for the device of the invention are those described above. Their implementation in the device advantageously allows for an increase in reactor height without having to avoid loss of activated carbon particles, thus enabling a more compact device. Advantageously, this deflection device is achieved via a water recovery device as described above.

[0094] Advantageously, the device includes a treated water discharge device 7, such as a pipe, to direct the treated water to a collection tank or additional treatment reactor.

[0095] Example

[0096] Other features and advantages of the invention will become more apparent from the following embodiments, which are given for illustrative and non-limiting purposes.

[0097] Example 1: Formation of functional groups on activated carbon particles

[0098] Laboratory experiments were conducted to verify the effect of ozonation on the activation of surface functional groups in powdered and particulate activated carbon. It is known that when the pH is above the "zero charge point" pH (pH... PZC When the pH is below a certain level, the surface of activated carbon carries a negative charge, while when the pH is below a certain level... PZC In this case, the surface of activated carbon is positively charged. In the latter case, activated carbon has a strong affinity for anionic compounds.

[0099] In these tests, the pH of the water containing the tested activated carbon was between 7.4 and 7.9. This activated carbon is therefore suitable for negatively charged organic matter. The injected ozone concentration was 2 g / m³. 3 The water to be treated is either zero or neutral. Activated carbon granules are present at a concentration of 1.2 g / L. The test is conducted for 10 minutes.

[0100] Surface functional groups were identified using the Boehm method. Iodine values ​​were obtained according to ASTM D4607-94 (2006). pH PZC The zero charge point was obtained according to the Noh and Schwarz method (1989).

[0101] Table 1 presents the results obtained.

[0102] [Table 1]

[0103]

[0104] pH of water containing activated carbon PZC The value was 8.05 in the absence of ozone and 8.28 after ozonation for 10 minutes (degassing of CO2 present in the sample). In-situ ozonation of activated carbon particles directly acts on the surface of the material by generating or increasing surface functional groups. Therefore, an increase in surface functional groups was observed.

[0105] Activated carbon exhibits highly acid-base properties on its surface, and these properties appear to outweigh its porosity when adsorbing organic compounds in an aqueous phase. The surface chemistry of carbon is caused by the presence of heteroatoms such as oxygen, nitrogen, hydrogen, chlorine, sulfur, and phosphorus. These heteroatoms form organic functional groups (side functional groups), such as ketones (Group I), ethers (Group II), amines (Group III), and phosphate esters (Group IV), which are located on the periphery of the carbon microcrystals. Their content depends on the source of carbon and its activation method, and determines the acidity or basicity of the material. Their presence has a non-negligible effect on the adsorption of polar molecules.

[0106] The results show that Group I, from 2.58 meq / g to 4.30 meq / g, represents a significant increase in strong carboxyl functional groups; Group III, from 2.36 meq / g to 0 meq / g, is explained by the oxidation of hydroxyl and phenolic groups to carbonyl and carboxyl groups; and Group IV, from 3.24 meq / g to 9.28 meq / g. This is of particular interest because Groups I and IV involve the adsorption of organic matter, especially through CO and OH interactions (organic matter-surface functional groups).

[0107] The iodine value increased from 910 to 930 mg / g. This increase in iodine value, along with the overall increase in surface functional groups, indicates an optimization of the adsorption performance of the activated carbon that has been subjected to ozone.

[0108] Example 2: In-situ Removal of Pollutants

[0109] An existing activated carbon microparticle fluidized bed reactor with a activated carbon concentration of 100-300 g / L was modified to allow ozone injection and ozone saturation of the water before it entered the reactor. The water used came from two plants, one producing drinking water and the other treating tertiary wastewater.

[0110] For each of these factories, the amount of ozone injected is 1 g / m³. 3 -2.5g / m 3 The activated carbon microparticle replacement rate is 10 mg / L-20 mg / L. The upward flow velocity of the water in the reactor is 20 m / h-40 m / h. The contact time of the ozone-saturated water to be treated in the fluidized reactor is approximately 10 minutes.

[0111] The amounts of the various compounds listed in Table 2 below were measured to evaluate their effectiveness depending on the percentage of removal by the treatment.

[0112] [Table 2]

[0113]

[0114] The results obtained are Figure 3 It is displayed in the middle.

[0115] They confirmed that the method according to the invention leads to a significant improvement in water treatment quality. At one site, a 20%-25% gain in average performance for removing various micropollutants was recorded, resulting in a removal efficiency of 85%-92%. At another site, all molecules except benzotriazole (77.6%) were removed with a rate exceeding 80%, including carbamazepine (compound 1), diclofenac (compound 7), hydrochlorothiazide (compound 13), and sulfamethoxazole. The removal efficiency of azole (compound 5, removed at 98%) reached 99%.

[0116] Example 3: Formation of Byproducts

[0117] In existing technologies, the ozone concentration used is 8-10 g / m³. 3 Such concentrations and long water / ozone contact times are known to favor the oxidation of pollutants by ozone, resulting in byproducts. In particular, it is well known that the ozonation of bromide-containing water leads to the formation of bromates.

[0118] Experiments were conducted to examine whether the low-dose ozone used as implemented due to this invention also led to the harmful formation of byproducts. These experiments used tertiary wastewater containing approximately 6.5-7 mg / L bromide. The injected ozone concentration was approximately 2 g / m³. 3 The concentration of activated carbon particles in the fluidized bed reactor was 100-300 g / L. The contact time in the fluidized bed was greater than 8 minutes. The results were compared with those obtained by ozonation in different compartments, for example, using methods known from the prior art, with a contact time of 3 minutes and an ozone injection rate of 3 g / m³. 3 They were also compared with results obtained in a fluidized bed reactor without ozone injection.

[0119] Table 3 shows the results of bromate concentration in water.

[0120] [Table 3]

[0121]

[0122] Less than 3g / m 3 The injected ozone concentration is too low to oxidize pollutants, especially micropollutants. This allows for the production of no byproducts in the water.

[0123] Furthermore, due to the method of this invention, ozone is injected almost directly into the reactor containing activated carbon. This results in a direct reaction between the oxidant (ozone) and the reducing agent (activated carbon), which is much faster than the reaction between ozone and pollutants (such as organic matter and micropollutants). This is why the ozonation reaction does not alter the micropollutants. Additionally, the interstitial water does not contain residual ozone.

[0124] Example 4: Bactericidal effect

[0125] E. coli in the raw water to be treated was counted, and then E. coli in the water leaving the reactor containing activated carbon was also counted. A reduction of approximately one to two logarithms in the total E. coli count was observed. These results confirm the bactericidal effect of ozone.

[0126] Since ozone is also known for its antiviral properties, similar results can be expected in the presence of viruses in the water to be treated.

[0127] References

[0128] Joong S Noh,James A Schwarz,1989.Estimation of the point of zerocharge of simple oxides by mass titration.Journal of Colloid and InterfaceScience 130(1):157-164.ISSN 0021-9797,https: / / doi.org / 10.1016 / 0021-9797(89)90086-6。

Claims

1. Water treatment methods, including: - The step of injecting ozone into the water to be treated. - The step of feeding the ozonated water to be treated into a reactor containing a fluidized bed of activated carbon particles. - Following the steps of bringing the ozonated water to be treated into contact with activated carbon particles via an upward flow of water in the reactor. - The steps for draining this treated water, Its features - The step of injecting ozone into the water to be treated is carried out through the Venturi effect. - This injection step is immediately followed by a step of saturating the water to be treated with ozone, and The steps of ozone injection and ozone saturation of water are carried out in a device for supplying the water to be treated to the reactor or in a pipeline installed as a bypass in the device for supplying the water to be treated to the reactor.

2. The method according to claim 1, characterized in that, The saturation step is carried out using a saturation cone or a degassing tower.

3. The method according to claim 1 or 2, characterized in that, The injection step and the step of saturating the water with ozone have a total duration of less than 1 minute.

4. The method according to claim 1 or 2, characterized in that, The activated carbon particles are agglomerates with a particle size of 300-1500µm and a true density greater than 0.

45.

5. The method according to claim 1 or 2, characterized in that, The reactor is equipped with at least one water deflector located at the top, which is designed to reduce the velocity of the upward flow of water in order to create a calm zone above the activated carbon granule bed.

6. The method according to claim 5, characterized in that, The at least one deflection device consists of a set of blades that are inclined relative to the vertical and parallel to each other, the blades being inclined at 50 degrees relative to the vertical. o Up to 60 o The angle θ is tilted.

7. The method according to claim 5, characterized in that, The reactor also includes a water recovery device located downstream of the calm zone, which consists of prismatic inclined troughs with sides forming a 45° angle with respect to the horizontal direction. o Up to 70 o Each of them has an angle α and a first fluid overflow port and a deflector that acts as a baffle as a deflection device.

8. The method according to claim 1 or 2, characterized in that, The upwelling speed of the water is 8-50 m / h.

9. An apparatus (10) for carrying out the method according to any one of the preceding claims, comprising: - Activated carbon reactor (1), which includes a fluidized bed of activated carbon particles (2). - The device (3) that supplies the water to be treated to the reactor. - Discharge device for treated water (7). The device (10) is characterized in that it further includes a device (4) for injecting ozone into water by means of the Venturi effect and a device (5) for saturating water with ozone, the devices being directly installed on the device (3) for supplying the water to be treated to the reactor, or installed on a pipe (3') installed as a bypass on the device (3) for supplying the water to be treated to the reactor.

10. The device (10) according to claim 9, characterized in that, The activated carbon particles are agglomerates with a particle size of 300-1500µm and a true density greater than 0.

45.

11. The device (10) according to claim 9 or 10, characterized in that, The reactor (1) is equipped with at least one deflection device disposed at the top of the reactor.

12. The device (10) according to claim 11, characterized in that, The at least one deflection device consists of a set of blades that are inclined relative to the vertical and parallel to each other, the blades being inclined at 50 degrees relative to the vertical. o Up to 60 o The angle θ is tilted.

13. The device (10) according to claim 11, characterized in that, The reactor also includes a water recovery device located downstream of the calm zone, which consists of prismatic inclined troughs with sides forming a 45° angle with respect to the horizontal direction. o Up to 70 o Each of them has an angle α and a first fluid overflow port and a deflector that acts as a baffle as a deflection device.

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