SEQUENTIAL BIOLOGICAL REACTOR AND METHOD IMPLEMENTING THE REACTOR

Abstract

The present invention relates to a sequential biological reactor for treating, by settling, liquid effluent (0) containing sludge (25). This reactor comprises at least a first tank (1a) suitable for receiving liquid effluent (0) to be treated by settling, a means (2) for admitting the liquid effluent (0) into the first tank (1a), suitable for introducing the liquid effluent (0) at one or more points (3) located in the vicinity of the bottom of the first tank (1a), a collection means (4) suitable for extracting, in the vicinity of the surface (5) of the liquid effluent (0), at least one portion of the clarified liquid effluent in a layer (6) clarified by the settling of the sludge (25). The invention also relates to a method of using the reactor.

Description

Sequential biological reactor and process implementing the reactor The present invention relates to the field of liquid effluent treatment and more particularly to a sequential batch reactor (SBR). Wastewater treatment is an important aspect of environmental protection. Wastewater is generally treated in wastewater treatment plants. Several treatment processes are implemented in these plants, including aerobic activated sludge systems such as Selective Batch Reactor (SBR). The SBR process is characterized by its sequential treatment stages occurring within a single basin. SBR processes offer several advantages, including a smaller footprint, better integration into the landscape, reduced treatment times, and lower construction costs. The stages of an SBR process typically consist of: a liquid intake stage, an aeration stage, a settling stage, and a discharge stage.However, although the SBR process requires only one basin for treating liquid effluents, another buffer basin is necessary when large volumes of liquid effluents need to be treated. Often, it is also essential to have two or three basins operating the process in parallel to be able to treat large volumes of liquid effluents quickly enough. The present invention aims to overcome one or more drawbacks of the prior art, and in particular to provide a sequential biological reactor and a method for implementing the sequential biological reactor, enabling the continuous treatment of large volumes of liquid effluents in a single basin. This objective is achieved by means of a sequential biological reactor for treating liquid effluents containing sludge, characterized in that it comprises at least: - a first basin suitable for receiving liquid effluents to be treated by contact of the latter with a bacterial mass, - a means of admitting liquid effluents into the first basin, capable of introducing the liquid effluents at one or more points located near the bottom of the first basin, - a means of capture capable of extracting, near the surface of the liquid effluents, at least a part of the liquid effluents clarified in a layer clarified by the settling of the sludge. According to another feature, the admission means includes at least one siphon wall capable of forcing the passage of liquid effluents entering the first basin between the bottom of the first basin and the lower part of the siphon wall. According to another peculiarity, the distance between the bottom of the first basin (and the lower part of the siphon wall) is between 0.1 m and 1 m, preferably 0.5 m. According to another feature, the inlet means is suitable for introducing liquid effluents into the first basin in such a way that the rate of rise of the level of liquid effluents in the first basin is less than the rate of settling of the sludge contained in the liquid effluents. According to another feature, the collection means is capable of simultaneously extracting clarified liquid effluents at several points on the same plane near the surface of the liquid effluents, the plane being substantially parallel to the surface of the liquid effluents. According to another feature, the inlet means and the collection means are arranged at opposite locations within the first basin. According to another feature, the capture means includes a siphon system capable of preventing the extraction of clarified liquid effluents when the pressure of a gas in the siphon system is greater than atmospheric pressure, the siphon system being capable of triggering the extraction of clarified liquid effluents when the pressure of the gas in the siphon system is less than or equal to atmospheric pressure. According to another feature, the siphon system includes at least a first substantially vertical pipe, the lower free end of which is suitable for extracting liquid effluents, the other upper end being connected to a second substantially horizontal pipe, one end of the second pipe being connected to a collector, the collector being connected to the first descending leg of a third U-shaped pipe, the free end of the first leg having an opening controlled by a valve, the second ascending leg of the third U-shaped pipe including a fourth discharge pipe, the free end of the second leg of the U including an opening communicating with the ambient air. According to another feature, the first pipe(s) include inside each a plate placed perpendicular to the first pipe and pierced with a hole, the area of ​​the hole increasing progressively between, on the one hand, the first pipe whose junction with the second pipe is closest to the collector and, on the other hand, the first pipe whose junction with the second pipe is furthest from the collector. According to another feature, at the junction between the second pipe(s) and the collector, the second pipe(s) include inside each one a plate placed perpendicular to the second pipe and pierced with a hole, the area of ​​the hole increasing progressively between, on the one hand, the second pipe whose junction with the collector is closest to the third pipe and, on the other hand, the second pipe whose junction with the collector is furthest from the third pipe. According to another feature, the reactor includes means for aerating liquid effluents to promote an aerobic reaction with said bacterial mass before settling, the aeration means being capable of bubbling oxygen into the liquid effluents. According to another feature, the reactor is suitable for integration into a container in which at least the first basin, the admission means and the capture means are provided. According to another distinctive feature, the reactor also includes a means of evacuating sludge deposited by settling at the bottom of the first basin. According to another feature, the reactor includes a second basin in fluidic communication with the first basin in such a way that the level of liquid effluents in the first basin is the same as the level of liquid effluents in the second basin, the second basin being upstream of the first basin in the direction of circulation of the liquid effluents, the second basin including a means of aerating the liquid effluents capable of bubbling oxygen into the liquid effluents. According to another feature, the first basin and / or the second basin also includes at least one means for measuring oxygen concentration and / or a means for measuring redox potential. According to another characteristic, the first basin and / or the second basin include at least one means of measuring the level of liquid effluents in the first basin and / or the second basin. According to another feature, the reactor includes a control means, the control means comprising a processor and a memory, the control means being capable of monitoring the level of the liquid effluents contained in the basin(s) from signals representative of the level of the liquid effluents sent by the liquid effluent level measurement means, the control means being capable of sending an opening or closing signal of at least one valve, according to the levels measured by the level measurement means, to open or close the valve(s) according to the levels controlled. According to another feature, the control means is capable of sending a start or stop signal to the liquid effluent aeration means according to the oxygen aeration measured by the oxygen aeration measurement means. According to another feature, the reactor also includes an ultraviolet treatment means located downstream of the capture means in the direction of flow of the liquid effluents, the treatment means being capable of treating the liquid effluents extracted by the capture means. According to another feature, the reactor further comprises a means for dewatering the sludge discharged by the discharge means, the dewatering means being located downstream of the discharge means in the direction of sludge flow. The invention also relates to a method for implementing a sequential biological reactor according to the invention, characterized in that it comprises at least the following steps: - introduction of liquid effluents (0) containing sludge near the bottom of the first basin by means of inlet, - aeration of liquid effluents by means of aeration, - settling of the sludge contained in the basin, - evacuation of sludge from the first basin by means of sludge evacuation, the introduction stage being implemented continuously during the implementation of the aeration, decantation and evacuation stages, the aeration, decantation and evacuation stages being repeated cyclically. Another distinctive feature is that the steps are repeated without interruption during the decantation stage. The invention, with its features and advantages, will become clearer upon reading the description provided with reference to the attached drawings, in which: - Figure 1 shows a cross-section of the siphon system at a single stage at the beginning of the process cycle, - Figure 2 shows a cross-section of the single-stage siphon system following the stage in Figure 1, - Figure 3 shows a cross-section of the single-stage siphon system following the stage shown in Figure 2, - Figure 4 shows a cross-section of the one-stage siphon system following the stage in Figure 3 according to one embodiment, - Figure 5 shows a cross-section of the single-stage siphon system following the stage shown in Figure 3 or Figure 4, - Figure 6 shows a cross-section of the single-stage siphon system following the stage shown in Figure 5, - Figure 7 shows a top view of the first basin, - Figure 8 shows a profile section of the first basin, - Figure 9 represents the reactor according to an embodiment in which it includes a second basin. The invention will be described with reference to the figures previously cited. The invention relates to a sequential biological reactor (SBR) for treating liquid effluents (0) containing sludge (25) after contact with a bacterial mass, in particular by sedimentation of the sludge (or decantation) and evacuation of a clarified layer. In the following description, the term "liquid effluents" will refer to the liquid effluents admitted into the reactor. It can also define all the sludge and clarified liquids before the sludge is removed and before the clarified portion of the liquid effluents is extracted. The SBR includes a first basin (1 a) suitable for receiving liquid effluents (0) to be treated by settling. The first basin (1 a) is a sequential aeration basin. The first basin (1a) is sized according to the mass loading and the upward velocity of the liquid effluents (0) in the basin. The mass loading is the ratio between the weight of BOD5 (biochemical oxygen demand over five days) removed daily in an aeration basin and the weight of microorganisms contained in that basin. The upward velocity is for example between 0.25 m / h and 0.5 m / h depending on the capacity of the mud (25) to settle. The volume of the first basin (1a) is calculated relative to the average level of the liquid effluent (0) in the basin: Nmoy = (Nh / Nb) / 2, where Nmoy is the average level (5) of the effluent, Nh is the highest level the effluent can reach in the basin relative to the bottom of the basin, this level being defined by the position of the overflow of the siphon system described below, and Nb is the lowest level the effluent can reach in the basin relative to the bottom of the basin, this level being defined by the position of the lower threshold level. In the remainder of this text, we will refer to N1 as the highest threshold level and N0 as the lowest threshold level. The choice of upward velocity, ranging from 0.1 m / h to 1 m / h, preferably from 0.25 m / h to 0.5 m / h, is linked to the sedimentation rate of the sludge (25). Indeed, sludge with a low sedimentation capacity will settle at a rate of 0.5 m / h to 1 m / h, for example. For example, the first basin (1 a) has a rectangular shape. For example, the first basin (1 a) has a usable volume of 43.8 m3, i.e., for example, a width of 2.25 m, a length of 9.5 m and a water height of 2.05 m. The liquid effluents (0) may be wastewater from domestic, agricultural, or industrial uses, or runoff, etc. The SBR further includes a means (2) for admitting the liquid effluents (0) into the basin. This admission means (2) is characterized by introducing the liquid effluents (0) at one or more points located near the bottom of the first basin (1a). The admission means (2) is, for example, a lift pump (28). The fact that the liquid effluents (0) are introduced at one or more points (3) located near the bottom of the first basin (1a) allows for the continuous admission of the liquid effluents (0) into this first basin (1a). This is an advantage compared to prior art SBRs in which admission is discontinuous to allow time for the sludge (25) to settle in the basin. The admission means (2) may include a screening device (27) for retaining bulky materials or waste in liquid effluents (0). The SBR also includes a collection means (4) capable of extracting, near the surface of the liquid effluent (0), at least a portion of the clarified liquid effluent (6) from a layer clarified by the settling of the sludge (25). The clarified layer (6) is located immediately below the surface (5) of the liquid effluent (0). Thus, the collection of the clarified layer (6) is carried out at a level below the surface of the liquid effluent (0). In this clarified layer (6), the sludge (25), which tends to settle to the bottom of the basin due to gravity, is no longer present following its settling. According to one embodiment, the admission means (2) includes at least one siphon wall (7) capable of forcing the passage of the liquid effluents (0) entering the first basin (1 a) between the bottom of the first basin (1 a) and the lower part of the siphon wall (7). The siphon wall (7) serves to prevent hydraulic short circuits and to avoid disrupting the settling process. This siphon wall (7) can be made of concrete, stainless steel, composite, or any other material suitable for use as a siphon wall (7). The siphon wall (7) thus delimits a buffer compartment within the basin (1a, 1b) of the SBR, which regulates the inflow of liquid effluents (0). The cross-section of this buffer compartment, delimited by the siphon wall (7), can have different shapes. The cross-section can be triangular, trapezoidal, or any other shape suitable for the use of the siphon wall (7). In some embodiments, the SBR provides for a continuous admission of effluent to accelerate treatment. In these embodiments, the volume of this buffer compartment, delimited by the siphon wall (7), and the cross-sectional area for the liquid effluent (0) passing under the siphon wall (7) define a geometry that must be configured to optimize the treatment of the liquid effluent (0) with its continuous admission into the basin. This geometry is determined by the retention time of the liquid effluent (0) before entering the first basin (1a), by the inflow velocity of the liquid effluent (0) at the bottom of the first basin (1a), and by the difference between the maximum threshold level (N1) and the minimum threshold level (N0) of the liquid effluent (0) that can be contained in the basin to ensure that the SBR implementation process remains feasible.Indeed, this minimum threshold level (N0) corresponds to a height slightly above the level of the lower part of the extraction means (4), below which the extraction of the clarified layer is stopped to prevent the introduction of sludge (or floating objects) into the extraction means during the subsequent backflow of the water. This stoppage is achieved by a control means that detects the level in the basin or the elapsed time and controls the extraction means (4), for example, via the valve controlling the siphon. Similarly, the maximum threshold level (N1) corresponds to the maximum height reached by the effluent (0) before the discharge / extraction phase is triggered or the time after which discharge / extraction will be triggered. In some embodiments, the SBR therefore includes a control means that regulates the various parameters of the SBR, and in particular the effluent levels or the times that trigger discharge / extraction.Indeed, the regular repetition of cycles over time improves settling capacity, meaning it facilitates the settling of liquid effluents (0) during the various cycles. Thus, in some embodiments, the control means imposes a regular minimum number of cycles per determined time period by regulating intake and discharge. The retention time of the liquid effluents (0) is controlled by the volume of the buffer compartment defined by the siphon wall (7). Thus, the retention time is defined by the height of the siphon wall (7) and by the dimensions of the buffer compartment, as well as by the dimensions of the cross-section through which the liquid effluents (0) pass under the siphon wall (7). The speed of entry of the liquid effluents (0) at the bottom of the first basin (1 a) is dependent on the height of the siphon wall (7). The minimum threshold level (N0) of the liquid effluents (0) is dependent on the distance between the bottom of the first basin (1 a) and the lower part of the siphon wall (7). For example, the distance between the bottom of the first basin (1 a) and the lower part of the siphon wall (7) is between 0.1 m and 1.5 m, preferably between 0.1 m and 1 m, preferably 0.5 m. For example, the geometry of the siphon wall (7) is designed so that the retention time is greater than 30 min and the inflow velocity of the liquid effluents (0) is less than 0.1 m / s. Preferably, the inlet means (2) is configured to introduce the liquid effluents (0) into the first basin (1a) such that the rate of rise of the liquid effluents (0) level in the first basin (1a) is less than the settling rate of the sludge (25) contained in the liquid effluents (0). Indeed, the treatment area in the basin and the maximum inlet flow rate are preferably sized so that the upward velocity of the effluents is less than the settling rate of the sludge. In some embodiments, the control means regulates the inlet flow rate based on the treatment area in the basin, preferably taking into account the parameters relating to the siphon baffle (buffer compartment volume, baffle height, and flow cross-section). In other embodiments, the basin area is determined based on the maximum inlet flow rate so that the upward velocity of the effluent never exceeds the sludge settling velocity. In such embodiments, the dimensions of the various components of the SBR are such that it is no longer necessary to control the inlet flow rate by the control means, which then regulates the SBR by controlling the levels reached and / or the durations of the treatment stages. Thus, the sludge (25) contained in the liquid effluents (0) does not reach the layers near the surface of the liquid effluents (0). The collection means (4) can then extract the liquid effluents (0) from a clarified layer (6) near the surface (5) of the liquid effluents (0). According to one embodiment, the collection means (4) can extract the clarified liquid effluents (6) simultaneously at several points (10) on the same plane (11) near the surface (5) of the liquid effluents (0). The plane (11) is substantially parallel to the surface (5) of the liquid effluents (0). Thus, the means (4) of capture can extract large volumes of water from the layer (6) clarified by the settling of the sludge (25) without disturbing the bed (25) of sludge formed at the bottom of the first basin (1 a) by the settling of the sludge (25) of the liquid effluents (0). According to one embodiment, the inlet means (2) and the collection means (4) are arranged at opposite locations in the first basin (1a). This embodiment ensures that the clarified layer (6) of the liquid effluents (0) is less disturbed by the sludge (25) than in the vicinity of the inlet means (2). Preferably, the collection means allows for gravity extraction of the clarified liquid effluents. In one embodiment, the collection means (4) includes a siphon system arranged to prevent the extraction of the clarified liquid effluents (6) when the pressure of a gas in the siphon system exceeds atmospheric pressure. However, when the gas pressure in the siphon system is less than or equal to atmospheric pressure, the siphon system is arranged to initiate the extraction of the clarified liquid effluents (6). The siphon system thus allows for gravity extraction of the clarified liquid effluents. In one embodiment, the siphon system comprises at least one first substantially vertical pipe (12), the lower free end of which is adapted to extract liquid effluents (0). The other upper end is connected to a second substantially horizontal pipe (13). One end of the second pipe (13) is connected to a manifold (14). The manifold (14) is connected to the first descending leg (15) of a third U-shaped pipe (16). The free end of the first leg (15) has an opening controlled by a valve (26). The second ascending leg (17) of the third U-shaped pipe (16) comprises a fourth discharge pipe (18) disposed approximately at mid-height of the second leg (17), at least below the lower threshold level (NO). The free end (19) of the second leg (17) of the U comprises an opening communicating with the ambient air to act as an overflow.The valve (26) is, for example, a solenoid valve. In some embodiments, as mentioned above, extraction is carried out at several points (10). For example, the siphon system performs extraction through a plurality of first pipes (12) which are spaced far apart and distributed over a defined area of ​​the basin, preferably opposite the inlet, so as to extend the extraction area by drawing water from multiple points, in order to limit the turbulence generated by the extraction at each drawing point. Furthermore, in some of these embodiments, in order to optimize extraction and limit turbulence, the extraction provides for an equal distribution of flow rates at each extraction point (10).Thus, in the case of gravity extraction, the diameter of the pipes (12, 13) at a given point is proportional to the distance between that point and the outlet of the SBR (the collector (14), for example), so that the flow rate is substantially the same from one draw-off point to another. For example, in one embodiment, the first pipe(s) (12) each include a plate or diaphragm positioned perpendicular to the first pipe (12) and pierced with a hole, for example, a circular one. The area of ​​the hole increases progressively between, on the one hand, the first pipe (12) whose junction with the second pipe (13) is closest to the collector (14) and, on the other hand, the first pipe (12) whose junction with the second pipe (13) is furthest from the collector (14). The diaphragms are used to compensate for the pressure losses induced by the distance of the first pipes from the collector (14).Similarly, for example, in one embodiment, at the junction between the second pipe(s) and the collector (14), the second pipe(s) each include a plate or diaphragm positioned perpendicular to the second pipe (13) and pierced with a hole, for example, a circular one. The area of ​​the hole increases progressively between, on the one hand, the second pipe (13) whose junction with the collector (14) is closest to the third pipe (16) and, on the other hand, the second pipe (13) whose junction with the collector (14) is furthest from the third pipe (16). The diaphragms are used to compensate for the pressure losses induced by the distance of the arms from the third discharge pipe (16). For example, and without limitation, the siphon structure is as follows. The siphon comprises two horizontal manifolds (14) connected opposite each other in a T-junction to the first descending leg (15) of the third U-shaped pipe (16). The free end of the first leg (15) has an opening controlled by a valve. The second ascending leg (17) of the third U-shaped pipe (16) includes a fourth drain pipe (18). The free end of the second leg (17) of the U includes an opening communicating with the ambient air. Each manifold (14) is connected to several horizontal second pipes, also called arms. The arms are connected in pairs opposite each other to the horizontal manifold (14). Each arm is connected to several vertical first pipes (12), also called nozzles. The siphon comprises 2 manifolds (14), 6 arms per manifold (14), and 4 nozzles per arm. The nozzles are spaced 0.8 m apart.The inside diameter of the third pipe (16) is 250 mm. The inside diameter of the manifolds (14) is 200 mm. The inside diameter of the arms is 100 mm. For a flow rate of 1 L / s per nozzle, the diameter of the circular diaphragm holes for two opposing arms, from upstream to downstream, is 91 mm, 72 mm, and 61 mm, respectively. The diameter of the circular diaphragm holes for each nozzle, from upstream to downstream, is 88 mm, 64 mm, 55 mm, and 48 mm, respectively. This siphon system allows for the evacuation of large volumes of water from the clarified layer of liquid effluent (0) between floating elements on the surface of the liquid effluent (0) and the sludge bed (25) deposited at the bottom of the first basin (1a) by settling, without disturbing the sludge bed (25). Furthermore, no moving parts or parts requiring maintenance are immersed in the liquid effluent (0). It is a reliable, automated system requiring minimal maintenance. The siphon system is sized to prevent any lifting of the sludge bed (25) when operating with the sludge bed (25) at a height of 200 mm from the nozzles. Thus, the siphon system is dimensioned in a non-limiting way with an extraction speed ranging from 1.5 m / s to 2 m / s and a hydraulic load at the level of these nozzles ranging in a non-limiting way from 5 m3 / h / m to 15 m3 / h / m. Depending on the capacity of the sludge (25) to settle, the height of the tidal change of the liquid effluent in the first basin (1 a) will be adapted in a non-limiting manner from 0.5 m to 1 m. The valve which controls the opening of the first leg (15) can be controlled by a control means. The control means includes a processor and memory. The control means enables, at a minimum, monitoring of the level of the liquid effluents (0) contained in the basin(s) based on signals representing the level of the liquid effluents (0) sent by the liquid effluent level measurement means (23). The level measurement means are, for example, level sensors. This control means can be connected to at least one level sensor for the liquid effluent (0) contained in the first basin (1a). The control means thus receives signals from the level sensor(s) (23). Depending on the level detected by the level sensor(s) (23), the control means can send a signal to open or close the valve. The valve (26) is, for example, a solenoid valve or a solenoid valve. The SBR further includes means (20) for aerating the liquid effluents (0) to promote an aerobic reaction with said bacterial mass before settling. The aeration means (20) can introduce oxygen into the liquid effluents (0). The aeration means (20) allow the liquid effluents (0) to be brought into aerobic conditions. For example, means (20) of aeration are a hydro-ejector, a submerged turbine, a fine bubble aeration system or any other system allowing the aeration of liquid effluents. In one embodiment, the SBR comprises a container in which at least the first basin (1a), the inlet means (2), and the collection means (4) are provided. This container allows the SBR to be transported to hard-to-reach locations with a single vehicle without having to transport several components, which would require the use of multiple vehicles. To remove the sludge (25) that has settled at the bottom of the first basin (1a), the reactor includes a means (21) for removing the sludge (25) deposited by settling at the bottom of the first basin (1a). In one embodiment, at least one SBR is supplemented by at least one second basin (1b) in fluidic communication with the first basin (1a) to form a reactor system. The second basin (1b) is a semi-continuous aeration basin. This second basin (1b) is located upstream of the first basin (1a) in the direction of flow of the liquid effluents (0). Fluid communication can be achieved by means of a pipe (29). This pipe is, for example, sized so that the flow entering the second basin (1 b) can be transferred to the first basin (1 a) without the velocity of the effluent at any point in the pipe exceeding 1 m / s. The fluid communication is arranged such that the liquid level in the first basin (1a) is the same as the liquid level in the second basin (1b). Furthermore, the treated liquid effluents in the second basin (1b) enter the first basin (1a) through the siphon wall (7). The advantage of the second basin (1b) is the possibility of increasing the contact time between the liquid effluents (0) and oxygen, which will enhance the oxidation of organic matter and nitrification. It also helps to protect the biomass from shocks or variations in load, avoids the need for oversized treatment plants that are difficult and costly to manage, allows for advanced nitrogen treatment, provides oxygen on demand, and prevents the risk of hydraulic short circuits. The second basin (1 b) can be based, for example, on the Moving Bed Bio Reactor (MBBR) process. This process uses bacteria grouped in a biofilm grown on moving supports, for example spherical supports, having a density equal to or less than the density of water. The second basin (1b) includes a means (20) for aerating the liquid effluents (0) in order to introduce oxygen into the liquid effluents (0) and thus place them under aerobic conditions. The aeration means (20) also allow the supports on which the biofilms are grown to remain suspended in the liquid effluents (0). In the two-basin embodiment, the reactor may include a sludge recirculation means (30), for example, a recirculation pump, which allows some of the sludge (25) that has settled at the bottom of the first basin (1a) to pass into the second basin (1b). According to one embodiment, the first basin (1a) and / or the second basin (1b) further include at least one means (22) for measuring the oxygen aeration of the basin, which measures the oxygen concentration in the basin. The measuring means (22) may be connected to the control means, which is connected to the aeration means (20). Thus, the control means receives signals from the aeration measuring means (22). Depending on the measurement of the oxygen concentration of the basin(s) (1 a, 1 b) detected by the aeration measurement means (22), the control means can send a signal commanding the start-up or stop-down of the aeration means (20).For example, a low oxygen concentration setpoint conditions the start of aeration by the means (20) of aeration and a high oxygen concentration setpoint conditions the stop of aeration by the means (20) of aeration. In another embodiment, the first basin (1a) and / or the second basin (1b) further comprise at least one means (31) for measuring the redox potential. The measuring means (31) may be connected to the control means, which is connected to the aeration means (20). Thus, the control means receives signals from the redox potential measuring means. Depending on the redox potential measurement of the basin(s) detected by the redox potential measuring means (31), the control means may send a signal to start or stop the aeration means (20). For example, a low redox potential setpoint triggers the start of aeration by the aeration means (20), and a high redox potential setpoint triggers the stop of aeration by the aeration means (20). The oxygen aeration measurement means (22) and the redox potential measurement means (31) can operate together. The regulation achieved by the oxygen aeration measurement means (22) and the redox potential measurement means (31) can be supplemented by the implementation of a timer. According to one embodiment, oxygen aeration can be regulated based on a target value for oxygen concentration or redox indicator. In this case, the aeration means (20) modulates the oxygen supply to the basin(s) in order to approach the target value. According to one embodiment, the regulation of oxygen aeration can be achieved by controlling the aeration means (20) by only a time delay for stopping the aeration means (20) and a time delay for operating the aeration means (20). The first basin (1 a) and / or the second basin (1 b) include at least one means (23) for measuring the level of liquid effluents (0) in the first basin (1 a) and / or the second basin sending by means of control signals representative of the levels of liquid effluents (0) in the basin(s). The control means can send an open or close signal to at least one valve (26), according to the levels measured by the level measurement means (23), to open or close the valve(s) (26) according to the levels controlled. In one embodiment, the SBR further includes an ultraviolet treatment means (24) disposed downstream of the intake means (4) in the direction of flow of the liquid effluents (0). The treatment means (24) treats the liquid effluents (0) extracted by the intake means (4). This treatment means (24) ensures compliance with the physicochemical standards for discharge into the natural environment. However, due to the discharge of treated water into the sea and potentially into bathing waters, it may be necessary to reduce the concentration of microorganisms. For example, the ultraviolet treatment means (24) uses high-intensity, low-pressure amalgam lamps emitting, for example, at an optimal wavelength of 253.7 nm for good energy efficiency. The compact structure of the SBR minimizes bulk and pressure loss while ensuring that maintenance operations, such as lamp replacements, can be carried out quickly and safely. The SBR further includes a means for dewatering the sludge (25) discharged by the discharge means (21). The dewatering means is located downstream of the discharge means (21) in the direction of sludge (25) flow. The dewatering method is, for example, drying beds. Generally, the drying bed technique is carried out in the open air on liquid sludge (25). It combines natural evaporation and the drainage of free water through a filtering layer of sand and gravel. Drying beds may consist of a layer of sand placed on a support layer of gravel. Drains may be placed within the gravel support layer to collect runoff. This runoff can then be returned to the head of the SBR (Sequencing Batch Reactor) via a wastewater treatment plant for further treatment. The layer of mud spread over the beds is, but not limited to, 30 cm. In one configuration, the dehydration unit comprises 4 beds, for a total area of ​​36 m2 with a bed width of 2 m and a length of 4.5 m to produce 5.25 t / year of dry matter. The SBR implementation process includes at least the following steps: - introduction near the bottom of the first basin (1 a) of liquid effluents (0) containing sludge (25) by means of inlet, - aeration of liquid effluents (0) by means of aeration (20), - settling of the sludge (25) contained in the basin, - extraction, by means of capture, near the surface of liquid effluents, of at least a portion of the liquid effluents clarified in a layer clarified by sludge settling, - sludge removal (25) from the first basin (1 a) by means of sludge removal (25). The introduction step is carried out continuously during the implementation of the aeration, settling, and removal steps. The aeration, settling, and removal steps are repeated cyclically. The process operates continuously. It is designed to maintain a significant margin of aeration capacity to accommodate potential pollution spikes. This helps prevent odor nuisances and considerably reduces sludge production (25) by allowing for endogenous respiration periods. Each operating cycle comprises several phases. The management of the various means used is done by the control system. We first describe an embodiment with the first sequential aeration basin (1 a). At the end of a cycle (Figure 1), the level in the first basin (1a) is at the lower threshold level (NO). New liquid effluent (0) is introduced near the bottom of the first basin (1a) by the inlet means (2) comprising at least one feed pump (28). The intake means (4) and the sludge removal means (21) are stopped. The aeration system (20) then activates to aerate the liquid effluents (0). During this aeration stage, several reactions occur. An anabolic reaction takes place in which organic pollution is transformed into biomass in the presence of microorganisms in a bacterial mass. An endogenous respiration reaction occurs in which the biomass is mineralized into carbon dioxide, ammonia, and water. A nitrification reaction also occurs to produce NH4+, then NO2+, and finally NO3+ from the nitrogen compounds contained in the liquid effluents. Without limitation, aeration can be carried out continuously or sequentially throughout this aeration stage. Due to the admission of the liquid effluents to be treated, the level rises between the lower threshold level (NO) and an upper threshold level (N1) at which point the settling phase is triggered. During the settling stage, which can last, for example, 1 hour: The admission means (2) continues to introduce new effluents. (0) liquids. The means (4) of capture is stopped. The means (20) of aeration which have operated until the high threshold level (N1) triggering the settling phase is reached (Figure 2) are then stopped. The means (21) for evacuating the sludge (25) is stopped. With aeration stopped, the liquid effluents (0) and the bacterial mass contained in the first basin (1 a) are in anaerobic conditions and a denitrification reaction occurs in the liquid effluents (0) to produce NO3" and then N2 in gaseous form. Decantation allows the sludge (25) to fall to the bottom of the first basin (1 a) under the effect of gravity. After a certain programmable time delay, controlled by the device, the settling stage is complete and the discharge stage can begin: The inlet means (2) continues to introduce new liquid effluent (0). The intake means (4) is then primed. For example, the intake means (4) is primed by opening the valve controlling the free end of the first leg (15) of the third U-shaped pipe (16). This causes the level of the liquid effluent (0) to begin to drop (Figures 3, 4, 5, 6). The aeration means (20) remain off. The sludge removal means (21) is activated for a time delay programmed in the control means to initiate the sludge removal step (25) from the first basin (1a) by the sludge removal means (25). The time delay can be between 4 and 10 minutes depending on the size of the intake means (4).In one embodiment, the control means includes a safety module that automatically closes the valve (26) when the level of the liquid effluent (0) reaches a safety threshold (N2) or when the level of the liquid effluent (0) drops, even if the time delay has not yet expired (Figure 4). This prevents the intake means (4) from losing prime, even at low flow rates. This level is detected by the device's level sensor. The safety threshold is lower than the upper threshold level (N1). Once the lower threshold level (N0) is reached by the liquid effluents (0), the cycle starts again from the beginning (Figure 1). We first describe an embodiment with the first basin (1 a) of sequential aeration and the second basin (1 b) of semi-continuous aeration. Before the start of a cycle, the treated sludge (25) is discharged and the level of the liquid effluent (0) falls in the first basin (1 a) and the second basin (1 b), which are in fluidic communication, until they reach a low threshold level (N0). New liquid effluent (0) is introduced into the second basin (1b) via the inlet (2), which includes, for example, at least one feed pump (28). Simultaneously, by fluidic communication, the same volume from the second basin (1b) is introduced by gravity near the bottom of the first basin (1a) via the inlet (2), which includes a siphon wall. The intake (4) and sludge (25) removal means (21) are stopped. The recirculation means (30) starts. The aeration means (20) for the second basin (1b) are stopped or in operation depending on the control mode, which is determined by the quantity and quality of the liquid effluent (0) to be treated. The aeration means (20) for the first basin (1a) are then activated to aerate the liquid effluents (0) from the first basin (1a). During this aeration stage, several reactions occur. An anabolic reaction takes place in which organic pollution is transformed into biomass in the presence of microorganisms, including bacterial biomass. An endogenous respiration reaction occurs in which the biomass is mineralized into carbon dioxide, ammonia, and water. A nitrification reaction also occurs to produce NO2 and NO3 from the nitrogen compounds contained in the liquid effluents. The same reactions occur in the second basin (1b) when the aeration means (20) for the second basin (1b) are activated. Without limitation, aeration can be carried out continuously or sequentially throughout this aeration stage. Due to the admission of liquid effluents to be treated, the level in the basins rises between the lower threshold level (N0) and an upper threshold level (N1) at which point the settling phase is triggered. During the settling phase, which can last, for example, 1 hour: The admission means (2) continues to introduce new liquid effluents (0). The means (4) of capture is stopped. The means (20) of aeration of the first basin (1 a) which operated until the high threshold level (N1) triggering the settling phase was reached (Figure 2) are then stopped. The means (21) for evacuating the sludge (25) is stopped. The recirculation means (30) continues to operate. The aeration means (20) of the second basin (1 b) are either stopped or in operation depending on the evolution of the control mode. With aeration stopped, the liquid effluents (0) and the bacterial mass contained in the first basin (1 a) are in anaerobic conditions and a denitrification reaction occurs in the liquid effluents (0) to produce NO3" and N2 in the gaseous state. Decantation allows the sludge (25) to fall to the bottom of the first basin (1 a) under the effect of gravity. After a certain programmable time delay, controlled by the device, the settling stage is complete and the discharge stage can begin: The intake means (2) continues to introduce new liquid effluents (0) into the first basin (1a). The intake means (4) is then primed. For example, the intake means (4) is primed by opening the valve controlling the free end of the first leg (15) of the third U-shaped pipe (16). This causes the level of the liquid effluents (0) to begin to drop. The aeration means (20) remain off. The sludge removal means (21) is activated for a time delay programmed in the control means to initiate the sludge removal step (25) from the first basin (1a) by the sludge removal means (25). The time delay can be between 4 and 10 minutes depending on the size of the intake means (4). The recirculation means (30) is still out of service.The means (20) of aeration of the second basin (1 b) are either stopped or in operation depending on the evolution of the regulation mode. Once the lower threshold level (N0) is reached by the liquid effluent (0), the cycle restarts from the beginning. Sludge recirculation (25) maintains an equivalent biomass concentration in the second basin (1b) and the first basin (1a). At peak flow rates, the aeration time can sometimes represent only 1 / 3 of the total cycle time. However, sludge recirculation (25) only occurs during the aeration phase. Therefore, the maximum capacity of the effluent recirculation pumps is equivalent to, for example, 3 times the maximum incoming flow rate: Qiec = 3 x galim, where Qiec is the recirculation flow rate between the second basin (1b) and the first basin (1a), and galim is the maximum incoming flow rate to the reactor. In one embodiment, the control means may include a safety module that automatically closes the valve when the level of the liquid effluent (O) reaches a safety threshold level (N2), even if the time delay has not yet expired. This prevents the intake means (4) from losing prime, even at low flow rates. This level is detected by the device's level sensor. The safety threshold is lower than the upper threshold level (N1). With regard to the siphon system, the size of the siphon is directly related to the volume of liquid effluents (0) to be treated per cycle. The tidal height h is linked to the volume of effluents to be treated by the formula: V = S h where V is the volume of liquid effluents (0) to be treated, S is the surface area of ​​the basin(s) and h is the tidal height between the upper threshold (N1) and the lower threshold (N0). In a reactor comprising a first basin (1 a), only the surface area of ​​the first basin (1 a) is taken into account. In a reactor comprising a first and a second basin (1b), the surface area of ​​both basins is taken into account. During operation, when the level of the liquid effluent (0) in the basin increases from the lower threshold level (NO) to the upper threshold level (N1) during the aeration phase of the cycle, the air trapped in the horizontal arms (13) and the extraction nozzles (12) is compressed, and the water level in the vertical nozzles (12) rises. When the level of the liquid effluent (0) increases, the relative pressure displayed by a pressure sensor is greater than 0 mbar. Simultaneously, the trapped gas pushes the level of the liquid effluent (0) downwards in the first descending leg (15) of the siphon. The trapped gas is pressurized by the difference in height of the water column in the two legs (15, 17) of the U-shaped pipe (16). This pressure increase raises the water level well above the collectors (14) of the extraction pipes, while the water level in the extraction nozzles rises only slightly. Water cannot escape from the basin until the air trapped between the basin effluent and the treated water plug is released into the atmosphere by opening the valves (26) for a short time. The opening of the valves (26), triggered by the end of the time delay T1, is responsible for the discharge period at the end of the sedimentation period. At this stage, the relative pressure displayed by the pressure transmitter drops to 0 mbar. This discharge period is divided into two parts: - A discharge occurs by the force of gravity exerted on the liquid when the level of the liquid effluents (0) in the first basin (1 a) is greater than the level of the horizontal arms. - Discharge occurs by siphoning when the level of the liquid effluent (0) is below the level of the horizontal extraction arms (13) and above the lower threshold (N0) in the first basin (1a). The transition from gravity discharge to siphon discharge is achieved by closing the valves (26). This valve closure occurs either upon the end of the time delay T2 or upon reaching a threshold level (N2). At the end of the discharge period, the valves (26) are opened for a certain time to allow the gas to be drawn in until it occupies all the space in the siphon except for the treated water plug in the U-shaped pipe (16) and a certain height, for example 70 mm, from the bottom of the extraction nozzles (12). The relative pressure displayed by the pressure sensor is equal to 0 mbar. It should be obvious to those skilled in the art that the present invention allows for embodiments in many other specific forms without departing from the scope of the invention as claimed. Therefore, the present embodiments should be considered illustrative, but may be modified within the scope defined by the attached claims, and the invention should not be limited to the details given above.

Claims

DEMANDS 1. Sequential biological reactor for treating liquid effluents (0) containing sludge (25) by settling, characterized in that it comprises at least: - a first basin (1 a) suitable for receiving liquid effluents (0) to be treated by contact of the latter with a bacterial mass, - a means (2) for admitting liquid effluents (0) into the first basin (1 a), suitable for introducing liquid effluents (0) at one or more points (3) located near the bottom of the first basin (1 a), - a means (4) of capture suitable for extracting, near the surface (5) of liquid effluents (0), at least a part of the liquid effluents clarified in a layer (6) clarified by the settling of sludge (25).

2. Reactor according to claim 1, characterized in that the inlet means (2) comprises at least one siphon wall (7) capable of forcing the passage of the liquid effluents (0) entering the first basin (1 a) between the bottom (8) of the first basin (1 a) and the lower part (9) of the siphon wall (7).

3. Reactor according to claim 2, characterized in that the distance between the bottom (8) of the first basin (1a) and the lower part (9) of the wall (7) siphon is between 0.1 m and 1 m, preferably 0.5 m.

4. Reactor according to at least one of claims 1 to 3, characterized in that the admission means (2) is suitable for introducing the liquid effluents (0) into the first basin (1 a) in such a way that the rate of rise of the level of the liquid effluents (0) in the first basin (1 a) is less than the rate of settling of the sludge (25) contained in the liquid effluents (0).

5. Reactor according to claim 1, characterized in that the capture means (4) is capable of extracting the clarified liquid effluents (6) simultaneously at several points (10) of the same plane (11) near the surface (5) of the liquid effluents (0), the plane (11) being substantially parallel to the surface (5) of the liquid effluents (0).

6. Reactor according to at least one of claims 1 to 5, characterized in that the admission means (2) and the capture means (4) are arranged at opposite locations in the first basin (1 a).

7. Reactor according to at least one of claims 1 to 6, characterized in that the capture means (4) comprises a siphon system capable of preventing the extraction of the clarified liquid effluents (0) when the pressure of a gas in the siphon system is greater than atmospheric pressure, the siphon system being capable of triggering the extraction of the clarified liquid effluents (0) when the pressure of the gas in the siphon system is less than or equal to atmospheric pressure.

8. Reactor according to at least one of claims 1 to 7, characterized in that the siphon system comprises at least a first substantially vertical pipe (12) having a lower free end adapted to extract liquid effluents (0), the other upper end being connected to a second substantially horizontal pipe (13), one end of the second pipe (13) being connected to a collector (14), the collector (14) being connected to the first descending leg (15) of a third U-shaped pipe (16), the free end of the first leg (15) having an opening controlled by a valve (26), the second ascending leg (17) of the third U-shaped pipe (16) comprising a fourth discharge pipe (18), the free end of the second leg (17) of the U comprising an opening communicating with the ambient air.

9. Reactor according to claim 8, characterized in that the first pipe or pipes (12) comprise within each a plate placed perpendicular to the first pipe (12) and pierced with a hole, the area of ​​the hole increasing progressively between, on the one hand, the first pipe (12) whose junction with the second pipe (13) is closest to the collector (14) and, on the other hand, the first pipe (12) whose junction with the second pipe (13) is furthest from the collector (14).

10. Reactor according to claim 8, characterized in that, at the junction between the second pipe(s) and the collector (14), the second pipe(s) comprise within each a plate placed perpendicular to the second pipe (13) and pierced with a hole, the area of ​​the hole increasing progressively between, on the one hand, the second pipe (13) whose junction with the collector (14) is closest to the third pipe (16) and, on the other hand, the second pipe (13) whose junction with the collector (14) is furthest from the third pipe (16). 1 1. Reactor according to at least one of claims 1 to 10, characterized in that the reactor comprises means (20) for aerating the liquid effluents (0) to promote an aerobic reaction with said bacterial mass before settling, the means (20) for aeration being capable of bubbling oxygen into the liquid effluents (0).

12. Reactor according to one of claims 1 to 11, characterized in that the reactor is suitable for integration into a container in which at least the first basin (1a), the admission means (2) and the capture means (4) are provided.

13. A reactor according to at least one of claims 1 to 12, characterized in that the reactor further comprises a means (21) for removing sludge (25) deposited by settling at the bottom of the first basin (1a).

14. Reactors according to at least one of claims 1 to 13, characterized in that it comprises a second basin (1b) in fluidic communication with the first basin (1a) such that the level of the liquid effluents in the first basin (1a) is the same as the level of the liquid effluents in the second basin (1b), the second basin (1b) being upstream of the first basin (1a) in the direction of flow of the liquid effluents, the second basin (1b) comprising a means (20) for aerating the liquid effluents capable of bubbling oxygen into the liquid effluents.

15. Reactor according to at least one of claims 1 to 14, characterized in that the first basin (1 a) and / or the second basin (1 b) further comprises at least one means for measuring oxygen concentration and / or a means for measuring redox potential.

16. Reactor according to at least one of claims 1 to 14, characterized in that the first basin (1 a) and / or the second basin (1 b) comprise at least one means for measuring the level of liquid effluents (0) in the first basin (1 a) and / or the second basin.

17. Reactor according to at least one of claims 1 to 15, characterized in that the reactor comprises a control means, the control means comprising a processor and a memory, the control means being capable of monitoring the level of the liquid effluents (0) contained in the basin(s) from signals representative of the level of the liquid effluents (0) sent by the liquid effluent level measurement means (0), the control means being capable of sending an opening or closing signal of at least one valve, according to the levels measured by the level measurement means (0), to open or close the valve(s) according to the levels monitored.

18. Reactor according to at least one of claims 1 to 16, characterized in that the control means is capable of sending a start or stop signal of the means (20) for aerating liquid effluents (0) according to the oxygen aeration measured by the oxygen aeration measurement means (20).

19. Reactor according to at least one of claims 1 to 17, characterized in that the reactor further comprises an ultraviolet treatment means disposed downstream of the capture means (4) in the direction of flow of the liquid effluents (0), the treatment means being capable of treating the liquid effluents (0) extracted by the capture means (4).

20. Reactor according to at least one of claims 1 to 18, characterized in that the reactor further comprises a means for dewatering the sludge (25) discharged by the discharge means (21), the dewatering means being disposed downstream of the discharge means (21) in the direction of sludge (25) flow.

21. A method for implementing a sequential biological reactor according to claim 1, characterized in that it comprises at least the following steps: - introduction near the bottom of the first basin (1 a) of liquid effluents (0) containing sludge (25) by means of inlet, - aeration of liquid effluents (0) by means of aeration (20), - settling of the sludge (25) contained in the basin, - evacuation of sludge (25) from the first basin (1 a) by means of sludge evacuation (25), The introduction step is carried out continuously during the aeration, settling, and removal steps, with the aeration, settling, and removal steps repeating cyclically.

22. A method according to claim 23, characterized in that the steps repeat without interruption during the settling step.