Method for treating a wastewater effluent in a sequencing batch reactor (SBR) having a constant level and controlled recovery

Abstract

The invention relates to a facility for treating a wastewater effluent in a constant-level sequencing batch reactor (SBR), said SBR comprising: - a chamber (11) that is suitable for containing a sludge-wastewater mixture (12) and comprises different levels, each level being defined by a sludge concentration and / or density; - a sludge bed (13) located at the bottom of the chamber (11); - a device for supplying the SBR with a volume of effluent to be treated in the sludge bed (13) near the bottom of the chamber (11), preferably via a distribution network (21) covering the bottom of the chamber; - recovery means (200) for drawing off a clarified fraction of the content (12) of the chamber (11), the SBR (10) being suitable for carrying out a treatment process comprising a reaction sequence (102) including at least one aeration step (105) consisting in aerating the contents of the chamber (11), during which the level of the surface (24) of the mixture (12) rises, a decanting step (106) during which sludge is deposited at the bottom of the chamber (11) and the contents of the chamber (11) are clarified in the vicinity of the surface thereof (24), a recovery step (107) of drawing off the clarified fraction (22) of the contents of the chamber (11), the recovery (107) and supply (101) steps taking place simultaneously, so as to maintain the level of the contents of the chamber (11) substantially constant during said recovery (107) and supply (101) steps, the facility further comprising control means (210) for controlling the recovery means (200).

Description

METHOD FOR TREATING A WASTEWATER EFFLUENT IN A CONSTANT-LEVEL AND CONTROLLED REBOOT BATCH SEQUENCE REACTOR (SBR)

[0001] The invention lies in the technical field of biological treatment of municipal and industrial wastewater and more specifically the technology known as Sequencing Batch Reactor (also known by its Anglo-Saxon acronym SBR).

[0002] An SBR operates in a sequential manner with different treatment stages, including a settling phase which allows the so-called "activated" sludge to be separated from the treated water.

[0003] An activated sludge process uses biological treatment for wastewater. It is a treatment method based on free-floating cultures. The principle is to have organic matter, suspended or dissolved in the wastewater, broken down by bacteria. A good level of biodegradation is achieved through homogenization of the medium, allowing bacteria access to the particles, and good aeration. The sludge then settles to the bottom of the reactor during the sedimentation phase.

[0004] An activated sludge process can aim to remove carbonaceous and nitrogenous pollution, and to remove or recover phosphorus contained in phosphorus pollution.

[0005] Regardless of the treatment technology used, SBR technology is limited in its sizing by the settling capacity of the sludge. Indeed, one of the factors limiting the concentration of activated sludge in an SBR, which itself represents the treatment potential of a pollutant load, is the sludge's settling capacity, generally expressed by the Mohlman index. The Mohlman index is the index of the sludge's settling capacity. This index defines the volume of activated sludge that settles in half an hour relative to the mass of dry residue (or the suspended solids concentration, also denoted TSS) of that sludge: the lower the index, the better the sludge's settling capacity.

[0006] The denser the sludge, the faster the settling phase and the shorter the overall duration of the treatment cycle, which makes it possible to treat more pollution in a single day by carrying out a higher number of cycles.

[0007] Denser sludge allows working with higher concentrations while allowing good settling (index) and therefore treating more pollution in the same volume of structure.

[0008] An early design of a sequenced reactor (SBR) used two separate volumes that were alternately used for reaction and settling, with water being transferred from the reaction compartment to the settling compartment (Seghers' Unitank process). However, this type of SBR has been improved, and most current sequenced biological reactors (SBRs) are designed with a single volume in which the different treatment stages take place sequentially. These reactors are generally variable-level: the raw water feed phase and the treated water return phase are separated in time, so that when the treated water is returned, the water level in the reactor drops.

[0009] Constant-level SBR reactors are also known, which reduce the time of each treatment sequence while maintaining treatment efficiency. Such a reactor is described, for example, in document WO2016020805.

[0010] Constant level SBR operation involves the simultaneous supply of raw water and the return of treated water at the same rate to maintain the constant level: if the equipment allowing the return of treated water is immersed without special precautions, it will be contaminated by TSS (suspended solids) during the reaction phase (reaction sequence) and more specifically during the aeration phase during which the entire volume of the biological reactor will be at an average sludge concentration of several grams per liter.

[0011] The SBR process described in application W02004 / 024638 operates on the basis of a semi-submerged chute within the SBR chamber. This operation requires a lowering of the liquid level during the cycle to to avoid the sludge being carried into the chute during the reaction phase due in particular to the rise in water level linked to gas retention.

[0012] This lowering of the level leads to a number of problems that the proposed invention seeks to solve: - increasing the reactor height by using a hydraulic volume for the feeding stage, - Increased cycle time to incorporate the level drop time and then the refill time. - the need to recycle the volume corresponding to the drop in level at the head of the treatment process via intermediate storage and pumps, - Increased instantaneous feed rate to incorporate the processing of this recycled volume, - the water located in the volume corresponding to the lowering of the level is potentially rich in nitrates which will prove harmful to the release of phosphates during the resumption of the feeding phase.

[0013] US patent 2018 / 0043286 describes a method for draining water from a tank based on a drain pipe located entirely within the tank. Water from the tank enters the drain pipe through permanently submerged orifices. Compressed air is introduced into the drain pipe to force the water through the pipe to a collector. Compressed air is then released from the drain pipe to refill it with water. In this solution, the drain pipe has simple orifices through which water and sludge enter directly. Specifically, during the aeration phase, the expansion height of the water volume within the tank varies due to the regulation of the amount of air injected. This results in a pressure variation within the pipe. The water and sludge present in the tank then accumulate inside the pipe.Sludge accumulates in the pipe during the aeration phase and is partially carried along with the treated water, compromising its quality and failing to meet discharge standards. This solution is therefore incompatible with a wastewater treatment process that includes aeration and sludge settling stages in the tank.

[0014] US patent 6884354 is also known, describing a constant-level sequenced batch reactor (SBR) that includes a clarifier (or recirculation device) as described in US patent 4596658. This clarifier is arranged horizontally near a wall of the reactor. The clarifier in US patent 4596658 includes a laminar opening in the form of an elongated slot to collect the clarified water. Such a device is likely to create turbulence during the intake of clarified water, which can impair the quality of the recirculated clarified water.

[0015] The invention aims to overcome all or part of the problems mentioned above by proposing a process for treating wastewater effluent in a constant-level sequenced batch reactor (SBR) in which the treated water is returned through an air-locked return line. The invention is based on a control step for the SBR return line, during which, just before the SBR aeration is activated, the return line is filled with air until it is completely emptied of the water it contains. The invention ensures that the treated water return line is not contaminated by activated sludge during aeration by means of controlled air filling of the return line according to the treatment process steps.

[0016] To this end, the invention relates to a method for treating wastewater effluent in a sequenced batch reactor (SBR), said SBR comprising: - an enclosure suitable for containing a wastewater-sludge mixture comprising different levels, each level being defined by a concentration and / or density of sludge, - a bed of mud located at the bottom of the enclosure, - means for recovering a clarified fraction of the contents of the enclosure, comprising: o a recovery duct extending below the surface of the mixture in the enclosure, between the inside and outside of the enclosure, comprising: ■ a plurality of channels hydraulically connecting the contents of the containment building and the return duct, ■ a plurality of return ports through which the clarified fraction of the contents of the enclosure is intended to be drained, an air duct hydraulically or aerodically connecting the return duct to the atmosphere, o an air exhaust valve on the air duct, capable of assuming an open or closed position, o an air / water blocking device on the return duct, capable of blocking air in the return duct upstream of the air / water blocking device and blocking water downstream of the blocking device, o an air injector connected to the return duct and intended to supply the return duct with pressurized and / or compressed air, said method comprising: - a feeding stage for the SBR, during which a volume of effluent to be treated is introduced near the bottom of the enclosure, into the sludge bed, preferably via a distribution network covering the bottom of the enclosure, - a biological treatment reaction sequence comprising at least: o an aeration step of the container contents, during which the surface level of the mixture rises, - a settling stage, during which sludge settles at the bottom of the enclosure and the contents of the enclosure become clear near its surface, - a step of recovering the clarified fraction of the contents of the enclosure, said recovery and feeding steps taking place simultaneously, so as to maintain the level of the contents of the enclosure substantially constant during the recovery and feeding steps, said process being characterized in that it comprises: - a piloting step of the recovery means during which: o the recovery duct is filled with air until the recovery duct is completely emptied of the clarified fraction contained in the recovery duct, and o the recovery duct is kept filled with air during the reaction sequence and preferably until the end of the decantation step, - a step of expelling the air contained in the return duct by the clarified fraction just before the feed and return stages, - after the SBR fuel supply stage, an air filling stage of the intake manifold by air injection, with the exhaust valve closed and the air / water blocking device said to be closed, during the aeration stage, - a step of maintaining the filling of the return duct with air without injection of air, the exhaust valve being closed and the air / water blocking device being said to be closed, during the aeration and decantation steps.

[0017] Advantageously, during the air filling stage of the return duct, the exhaust valve is in the closed position, and the air / water blocking device blocks the air in the return duct by creating a hydraulic discontinuity between the upstream and downstream of the air / water blocking device.

[0018] Advantageously, during the air expulsion stage of the return line, the exhaust valve is in the open position so as to allow the air to be evacuated simultaneously with the entry of clarified water into the return line.

[0019] Advantageously, during the air expulsion stage of the return duct, after the air has been evacuated, the air / water blocking device takes the so-called open position so as to allow the clarified fraction to exit through the return orifices.

[0020] The invention also relates to a wastewater effluent treatment installation in a sequenced batch reactor (SBR), said SBR comprising: - an enclosure suitable for containing a wastewater-sludge mixture comprising different levels, each level being defined by a concentration and / or density of sludge, - a bed of mud located at the bottom of the enclosure, - a system for supplying the SBR with a volume of effluent to be treated near the bottom of the enclosure, in the sludge bed, preferably via a distribution network covering the bottom of the enclosure, - means for recovering a clarified fraction of the contents of the enclosure, comprising: o a recovery duct extending below the surface of the contents of the enclosure, between the inside and outside of the enclosure, comprising: ■ a plurality of channels hydraulically connecting the contents of the containment building and the return duct, ■ a plurality of return ports through which the clarified fraction of the contents of the enclosure is intended to be drained, ■ an air duct hydraulically or aeraulically connecting the return duct to the atmosphere, o an air exhaust valve on the air duct, capable of assuming an open or closed position, o an air / water blocking device on the return duct, each of the two valves being capable of blocking air in the return duct or allowing it to pass through, o an air injector connected to the return duct and intended to supply the return duct with pressurized and / or compressed air, the SBR being capable of implementing a treatment process comprising a biological treatment reaction sequence including at least one aeration stage of the contents of the vessel, during which the surface level of the mixture rises, a settling stage, during which sludge settles to the bottom of the vessel and the contents of the vessel become clear near its surface, a recovery stage of the clarified fraction of the contents of the vessel,said recovery and feeding stages taking place simultaneously, so as to maintain the level of the contents of the containment substantially constant during the recovery and feeding stages, the installation further comprising means for controlling the recovery means so as to fill the recovery duct with air until the recovery duct is completely emptied of the clarified fraction contained in the recovery duct, to keep the recovery duct filled with air during the aeration stage, and to expel the air contained in the recovery duct with clarified fraction just before the feeding and recovery stages, to fill the recovery duct with air by injecting air during the aeration stage, and to maintain the filling of the recovery duct with air without injecting air during the aeration and settling stages.

[0021] In one embodiment, the blocking device includes a U-shaped siphon between the air duct and the return air ports.

[0022] In another embodiment, the return air ports are positioned above the level of the return duct, and the return duct includes an air exhaust duct.

[0023] In another embodiment, the return orifices are positioned below the level of the return duct, and the return duct includes an air exhaust duct.

[0024] In another embodiment, the blocking device includes a regulating valve positioned at the return ports.

[0025] The invention will be better understood and other advantages will become apparent upon reading the detailed description of an embodiment given by way of example, a description illustrated by the accompanying drawing in which:

[0026] Figure 1 schematically represents an example of a sequenced batch reactor adapted to the implementation of the treatment process of the invention;

[0027] Figure 2 schematically represents the SBR enclosure and the recovery means;

[0028] Figure 3 represents a flowchart of the steps in the process of treating a wastewater effluent according to the invention;

[0029] Figures 4, 5, 6, 7, 8 and 9 schematically represent the characteristics of the means of recovery of the SBR at different phases of operation according to the invention;

[0030] Figures 10, 11 and 12 schematically represent variant embodiments of the means for resuming the SBR according to the invention;

[0031] Figure 13 represents a flowchart of the steps of a variant of the wastewater effluent treatment process according to the invention in an SBR;

[0032] Figure 14 schematically represents variants of the means of recovery of the SBR.

[0033] For the sake of clarity, the scales in these figures are not to scale. Furthermore, the same elements will have the same reference points in the different figures.

[0034] Figure 1 schematically represents an example of a sequenced batch reactor 10 adapted for implementing the treatment process of the invention. The invention relates to a wastewater effluent treatment installation in a sequenced batch reactor 10 (SBR). According to the invention, the SBR 10 comprises: - an enclosure 11 suitable for containing a mixture 12 of water (wastewater or treated) and sludge comprising different levels, each level being defined by a concentration and / or density of sludge, - a bed of mud 13 located at the bottom of enclosure 11, - a device for supplying the SBR with a volume of effluent to be treated 20 near the bottom of the enclosure 11, in the sludge bed 13, preferably via a distribution network 21 covering the bottom of the enclosure, - means for recovering 200 a clarified fraction of the contents 12 of the containment 11, the SBR 10 being capable of implementing a treatment process comprising a biological treatment reaction sequence 102 including at least one step 105 of aerating the contents of the containment 11, during which the level of the surface 24 of the mixture 12 rises, and optionally a settling step 106, during which sludge settles at the bottom of the containment 11 and the contents of the containment 11 become clear near its surface 24, a step 107 of recovering the clarified fraction 22 of the contents of the containment 11, said recovery steps 107 and feeding steps 101 taking place simultaneously, so as to maintain the level of the contents of the containment 11 substantially constant during the recovery steps 107 and feeding steps 101, the installation including in addition control means 210 recovery means 200 allowing the clarified fraction of the enclosure to be recovered.In what follows, the term reprise / reprendre is to be understood as evacuation / evacuate and / or drainage / draining. The contents of the enclosure are ventilated with air 8 through a distribution network 27, preferably covering the bottom of the enclosure 11.

[0035] Figure 2 schematically represents the containment 11 of the SBR 10 and the recovery means 200. The recovery means 200 for the clarified fraction of the contents 12 of containment 11 include: - a return duct 201 extending below the surface 24 of the contents 12 of the enclosure 11, between the inside 25 and the outside 26 of the enclosure, comprising: o a plurality of channels 202 hydraulically connecting the contents 12 of the enclosure 11 and the return duct 201, o a plurality of return orifices 203 through which the clarified fraction of the contents 12 of the enclosure 11 is intended to be drained, o an air duct 204 hydraulically or aeraulically connecting the return duct 201 with the atmosphere, - an air exhaust valve 205 on the air duct 204, capable of assuming an open or closed position, through which the air trapped in the return duct can be vented to the atmosphere, - an air / water blocking device 216 on the return duct 201, capable of switching from a so-called closed state to a so-called open state, and vice versa, so as to block air in the return duct 201 upstream of the air / water blocking device 216 and capable of blocking water downstream of the air / water blocking device 216, - an air injector 207 connected to the return duct 201 and intended to supply the return duct 201 with pressurized and / or compressed air.

[0036] For better visibility of the figures, two channels 202 are shown. However, it should be understood that the return duct may include several other channels 202, arranged in a particular way: the channels 202 are distributed so as to cover the surface and form a network of channels and sampling orifices. In other words, the channels 202 are arranged along the duct 201. The plurality of channels constitutes a plurality of entry points for the clarified water into the duct 201. For a given volume of liquid to be discharged through the duct 201, this results in a lower flow rate per channel. Unlike a device with a single water inlet channel, this arrangement of the invention prevents the creation of currents likely to create surface turbulence, which would be detrimental to the quality of the intake water.

[0037] The 203 water sampling orifices can be in the form of elongated or circular slits.

[0038] The air / water blocking device 216 will be detailed below with two embodiment examples. This device can be a valve, preferably motorized, that can be in the open or closed position, or a U-shaped siphon that can be primed or unprimed. In the following, the air / water blocking device 216 is said to be open if the valve is in the open position or the siphon is primed, and closed if the valve is closed or the siphon is unprimed.

[0039] The return air means 200 may include an air injector 207 connected to the air duct 204 between the exhaust valve 205 and the air / water blocking device 216, and may be used to supply the return air duct 201 with pressurized / compressed air. The air used to block the return air duct may alternatively come from the air source used in the treatment process. More specifically, the air injector 207 may be dedicated to air / water blocking. In this case, it includes a check valve. The air injector 207 may also be not dedicated to air / water blocking; that is, the air injector may come from the chamber's air supply. In this case, the return air means 200 further include a blocking valve 206 to perform the blocking function. Air injector 207 is not necessarily connected to air duct 204 but it is systematically connected to intake duct 101 to block it in air / water.

[0040] The air injector 207 can operate intermittently during the aeration stage 105 or continuously.

[0041] The exhaust valve 205 corresponds to an atmospheric venting valve.

[0042] The control means 210 of the recovery means 200 are intended to fill the return duct 201 with air until the return duct 201 is completely emptied of the clarified fraction contained in the return duct 201, to maintain the return duct 201 filled with air during the aeration step 105 and during the settling step 106, and to evacuate the air contained in the return duct 201 by the clarified fraction 22 during the feeding step 101 and the step 107 of return. More specifically, the control means 210 are configured to actuate the valve 205 and the blocking device 216 as needed so that the return line empties of the clarified fraction present in the return line 201 and maintains the return line 201 filled with air during the aeration and settling phases. The air can be supplied continuously. It can also come from an external air source, i.e., not dedicated to air / water blocking, and intended for venting the chamber. In the case of an external air source, an isolation valve 206 is required. If the return means 200 include an air injector 207 dedicated to air / water blocking, this injector can inject pressurized and / or compressed air into the return line 201. Note that this dedicated 207 air injector has a non-return valve (not shown in the figures).In other words, the return duct 201 is then blocked by air: it is filled with air that cannot escape due to the closure of the air / water blocking device 216 and the exhaust valve 205. During the aeration phase, the level of the contents of the chamber rises due to the introduction of air into the chamber. However, since the return duct is filled with air, this air cannot enter the duct.This has the advantages of avoiding sludge loss from the system (the presence of sludge being important for densification), and of avoiding contamination of the return line and of the clarified water coming out of the orifices 203 (this is important with regard to the tertiary treatment which would have to be implemented downstream, and / or with regard to discharge standards), the channels 202 make it possible to compensate for the gaseous retention raising the water level of the reactor in aeration, they also compensate for an imperfect horizontality of the piping.

[0043] The contents rise in the channels 202 in the case of discontinuous air injection, but cannot enter the return duct 201. This configuration guarantees, through the control of the return means, that only clarified fraction enters the return duct, without any risk of contents containing sludge entering it.

[0044] It is important to emphasize that the return duct extends below the surface 24 of the container's contents. It is therefore permanently immersed in the container's contents. The channels 202, which are tubes with inlet ports, are permanently immersed and filled with the container's contents (water). The clarified fraction is fed into the recirculating chamber (during the feed / recirculation and anaerobic phases) or into air (during the reaction phase, including the aeration and settling phases). In other words, the contents of the channels vary depending on the current sequence. Channels 202 have a dual role: they provide access for the clarified fraction to the recirculation duct 201 during the feed / recirculation phase, and they form a buffer volume, without access to the recirculation duct 201, which contains the chamber's contents when the chamber's level rises due to aeration. The transition from providing access to the recirculation duct to acting as a buffer volume occurs as the treatment process progresses, through the injection / exhaust of pressurized and / or compressed air and the opening / closing of the blocking device and the exhaust valve.The injection / exhaust of supercharged and / or compressed air and the opening / closing of the blocking device and the exhaust valve are controlled by the control means 210 of the recovery means 200.

[0045] In one embodiment, the air / water blocking device 216 includes a U-shaped siphon 208 between the air duct 204 and the return orifices 203. When air is injected, the clarified water contained in the siphon and the return duct is replaced by air up to a height equivalent to the end(s) of the channel(s). By this means, the siphon aims to hydraulically disconnect the contents of the chamber from the clarified water outside the chamber, thereby de-priming it. By extending the height of the siphon, it is also possible to compensate for the rise in the level of the surface 24 during the aeration step. The presence of a siphon is not mandatory, and other embodiments are possible and will be described below.The siphon can be associated with a blocking valve 206, which is also controlled by the control means 210, if the air used to fill the return line comes from the air used for treatment (air injector 207 not dedicated to air blocking). A return port 203 is an opening through which the treated water is discharged.

[0046] The return air ports 203 are advantageously positioned above the level of the return air duct 201. Advantageously, the return air duct 201 includes an air exhaust duct 211. Again, other embodiments are possible and will be presented below.

[0047] Figure 3 shows a flowchart of the steps in the wastewater treatment process according to the invention in an SBR 10. As explained previously, the SBR 10 comprises: - an enclosure 11 suitable for containing a wastewater-sludge mixture 12 comprising different levels, each level being defined by a concentration and / or a sludge density, - a bed of mud 13 located at the bottom of enclosure 11, - a device for supplying the SBR with a volume of effluent to be treated near the bottom of the enclosure 11, in the sludge bed 13, preferably via a distribution network 21 covering the bottom of the enclosure, - means of recovery 200 of a clarified fraction of the contents 12 of the enclosure 11, and means of control 210 of the means of recovery.

[0048] The means of recovery 200 were described on the basis of Figure 2.

[0049] The process for treating wastewater effluent in a sequenced batch reactor (SBR) 10 according to the invention comprises: - a step 101 of feeding the SBR 10, during which a volume of effluent to be treated 20 is introduced near the bottom of the enclosure 11, into the sludge bed 13, preferably by a distribution network 21 covering the bottom of the enclosure 11, - a biological treatment reaction sequence 102 comprising at least one step 105 of aeration of the contents of the enclosure, during which the level of the surface 24 of the mixture 12 rises. Air injection can be done by a non-dedicated air distribution system with an isolation valve 206 such as an air distribution device, for the aeration stage 105, or can also be done by a dedicated distribution system (a compressor or a blower for example) advantageously including a non-return valve.

[0050] The method of the invention also includes: - a settling stage 106, during which sludge settles at the bottom of enclosure 11 and the contents of enclosure 11 become clear near its surface 24, - a step 107 of retrieval of the clarified fraction 22 of the contents of the enclosure 11, said retrieval steps 107 and feeding steps 101 taking place simultaneously, so as to maintain the level of the contents of the enclosure 11 substantially constant during the retrieval steps 107 and feeding steps 101.

[0051] The process according to the invention may also include a waiting phase 116 coupled with the feeding, decantation or anaerobic steps.

[0052] According to the invention, the treatment process comprises: - a piloting step 120 of the recovery means 200 during which the recovery duct 201 is filled with air until the recovery duct 201 is completely emptied of the clarified fraction 22 contained in the recovery duct 201, and the recovery duct 201 is kept filled with air during the reaction sequence 102 and preferably also during the settling step 106, and optionally during the waiting step, and - a step 123 of expulsion of the air contained in the return duct 201 by the clarified fraction 22 during the feed step 101 and the return step 107.

[0053] After step 120 and before step 123, the process may include a step 121 of filling, at least partially, the channels 202 with the contents 12 of the enclosure 11 during the aeration step 105, if the air injection is not continuous during the air injection steps.

[0054] Furthermore, the treatment process includes, between steps 120 and 123, two additional steps for maintaining the air supply to the return duct. As mentioned previously, step 120, which involves filling the return duct 201 with air, is achieved by simultaneously injecting air and draining clarified water. With valve 205 closed and the air / water blocking device 216 closed, the air injection device (air injector 207) is operational at the beginning of the first aeration step 105.

[0055] Next, the process includes a step 122 of maintaining the air supply to the return duct 201 by air injection. The valve 205 is closed and the air / water blocking device 216 is said to be closed, the air injection device 207 is in operation, during the aeration step 105.

[0056] Next, the process includes a step 122bis of maintaining the air supply to the return duct without air injection. The valve 205 is closed and the air / water blocking device 216 is said to be closed, the air injection device 207 is stopped, during the aeration 105 and settling 106 steps.

[0057] Next comes step 123, which involves expelling the air contained in the return line and simultaneously filling it with clarified water. Valve 205 is open and blocking device 216 is said to be open, while air injection device 207 is off, during the supply 101, return 107, and anaerobic 103 steps.

[0058] And, if the air injection is not continuous during the aeration step 105, particularly to save energy, a step 121 of at least partially filling the channels 202 with the contents 12 of the enclosure 11 during the aeration step 105 may occur (although this step is not intended). In this case, it is possible to reinject air to refill the return duct 201; this is step 122. This can be done intermittently by setting a frequency and duration of air injection, or more precisely by integrating a level sensor that detects when air reinjection is necessary and triggers step 122 during the aeration step 105.

[0059] The return line is kept filled with air during the reaction sequence, including the aeration step. Preferably, it is also kept filled with air during the settling step. Indeed, if the return line were no longer filled with air at the beginning of settling, the sludge film would not have enough time to descend below the inlet ports of the channels 202, resulting in contamination of the return line by the sludge.

[0060] The distinctive feature of the invention lies in the positioning of the return duct 201 below the surface 24 of the container's contents, meaning it is always submerged. However, its contents are controlled by the piloting steps (120, 122, 122bis, 123) of the return means 200 according to the treatment process stages. As a result, only treated water can enter the The return duct is shown to be essentially horizontal, i.e., parallel to the surface 24 of the containment's contents, but it could also be inclined and extend along an axis intersecting the plane in which surface 24 lies. The primary advantage is that it does not limit the containment's volume, since it is not necessary to lower the water level below the return duct to prevent the entry of untreated water and sludge during the aeration step 105. Thanks to the control of the return system, the return duct is filled with air just before the reactor's aeration step 105. In other words, the return duct is filled with air, meaning it is blocked by air and thus rendered inaccessible to the containment's contents during phases where the containment's contents near the duct are not solely treated water.Another distinctive feature is the channels 202, which hydraulically connect the contents of the containment chamber 11 to the return duct 201. They are shown perpendicular to the surface 24, but can also be inclined downwards. The channels 202 play a crucial role: while ensuring the hydraulic connection between the clarified fraction and the return duct to allow for the recovery of the clarified fraction, they also help to control the rise in the level of the containment's contents during the aeration stage. Each channel 202 has two ends (visible in Figure 4): a first end 221 and a second end 222 in direct contact with the return duct 201, allowing flow between the return duct 201 and the channel 202. Each channel 202 can have any cross-section: circular, rectangular, polygonal, etc., as can the return duct 201.

[0061] The aeration step 105 causes a variation in the level of the enclosure contents due to the injection of air into the enclosure. During the aeration step 105, the channels 202 fill at least partially with the enclosure contents. This is the specific case of step 121, for a process in which the air injection into the return duct is not continuous. The filling height of the channels 202 corresponds to the height of the enclosure contents' elevation. Since the channels 202 are sized to be sufficiently tall to accommodate the specific case of step 121, the contents 12 do not reach the second end 222 of the channels 202. The return duct 201, however, remains filled with air. During the aeration step 105, the enclosure contents are homogeneous, even at the level of the Surface 24. Thanks to the channels 202, this homogeneous sludge-containing content does not enter the return line 201. The channels 202 form a transition zone between the air-locked return line and the contents of the containment chamber. The ends 221 of the channels 202 can be in contact with both water and sludge. The ends 222 of the channels 202 never come into contact with sludge. Thus, it is guaranteed that the return line, depending on the phase, contains either air or treated water, but never sludge.

[0062] The return line 201 is kept filled with air during the reaction sequence 102 and preferably the settling step 106, and optionally the holding phase 116. This is step 122bis. At the end of settling, the sludge present in the chamber has settled to the bottom of the chamber 11, and the contents of the chamber 11 become clear near its surface 24. The process then includes a step 123 for expelling Pair from the return line 201. The valve 205 is in the open position, and clarified water enters the return line, allowing the air trapped in the return line to be expelled by the valve 205 and the vent line. There is no longer any trapped air in the return line.

[0063] Subsequently, the air / water blocking device 216 moves to the open position and a new cycle begins: the feed step 101 occurs simultaneously with the recirculation step 107. By introducing a volume of effluent into the chamber, the same volume is drained to maintain a substantially constant level. Since the recirculation line is no longer airtight, the recirculation line 201 and the channels 202 fill with this volume of the contents 12 of the chamber 11 located at the surface 24. This is the clarified fraction that is to be recirculated.

[0064] The controlled filling of the return duct with air (step 120) and the blocking of air in the return duct (step 122bis, possibly supplemented by step 122 if the air injection is not continuous) results in precise control of the timing at which contents are introduced into the return duct. The return duct is accessible to the contents of the containment when the contents of the containment are clarified at its surface. Conversely, during the aeration step, when the contents are homogeneous—that is, when the contents of the containment are not clarified at the return duct—the return duct is not accessible to these contents. In other words, the process according to the invention allows precise control of what enters the return duct. Depending on the wastewater treatment steps, There is a succession of phases of air blockage of the return duct and phases of free hydraulic connection during which the contents of the enclosure can circulate in the return duct.

[0065] Figures 4 to 9 schematically represent the characteristics of the SBR recovery means at different operating phases according to the invention. In Figure 2, the return duct 201 is filled with clarified fraction. Just before the end of the feeding and recovery stages and before the aeration stage (or the air injection stage 110), the return duct is not blocked with air. At this point, just before the aeration stage, the level of the clarified fraction stabilizes at a reference level indicated Q=0 m³ / h in Figure 4 within the return duct, assuming the return orifices 203 are positioned above the level of the return duct.

[0066] Between the representations in Figures 2 and 4, air injection begins. The clarified fraction exits through the return inlets 203. The exhaust valve 205 is in the closed position. Air cannot escape; it remains in the return line. Once the return line is full of air and all the clarified fraction has left the return line, only a supply of air is needed to regulate the quantity of air throughout the aeration stage. This is stage 122. The return line is thus filled with air on one side, and the clarified fraction is retained in the downstream part of the siphon on the other. The aeration stage then begins. Air is introduced into the chamber by an external air injector (i.e., one not dedicated to blocking the return line with air) to aerate the chamber contents.Additional air may be added to the return duct during aeration to compensate for pressure variations in the return duct that will be linked to changes in water level during aeration. This is step 122.

[0067] In Figure 5, biomass aeration has begun. The level of the contents of the chamber has increased due to the air injection for the aeration step 105 (for example, by approximately 30 cm, symbolized by level Q'). There is a slight increase in pressure in the return duct due to the increased level of the chamber contents. When using a siphon as an air / water blocking device 216, chamber contents enter the channels 202, and the level of the clarified fraction changes in the siphon (see the arrows in Figure 5). The channels 202 must be sufficiently high to stabilize the contents level at the inside of the channels (and so that this content does not reach the inside of the return duct) at the time when the level of the contents of the enclosure is at its highest (i.e. during the aeration stage).

[0068] In Figure 6, the aeration stage ends and the settling stage begins. Because the air injection for aeration has stopped, the surface level returns to the reference level, denoted Q=0. Air remains trapped in the return line to ensure that the unsettled sludge stays within the chamber. The air / water blocking device 216 is shown in the closed position, and valve 205 is closed, thus blocking air from the return line 201 upstream of the blocking device 216.

[0069] Figure 7 represents the settling stage. Sludge can be extracted from the containment. The level of the containment level decreases slightly (by a few centimeters). The level decreased by the sludge extraction is represented by Q”.

[0070] At the end of the settling step 106 and / or at the beginning of the feeding steps 101 and 107 of retrieval, when the surface 24 of the enclosure is clarified, and all the sludge has settled and is disposed of at the bottom of the enclosure, the air exhaust valve 205 is put in the open position and the air / water blocking device 216 goes into the open position (i.e. the device 216 opens in the case of a motorized valve, or it primes in the case of the siphon) to allow the clarified water to pass through. Some of the clarified fraction enters the return line and is discharged through the return ports 203 while air is expelled through the valve 205 and the vent line 204. This step is shown in Figure 8. At the end of the settling stage, the sludge is located far from the return line and the channels 202. There is no longer any risk of sludge entering the return line.The air is released: valve 206 is closed in the case of an air injector not dedicated to air blocking, and exhaust valve 205 is open (as well as the air / water blocking device 216), just before the supply and return stages. Advantageously, air injector 207 does not operate during the settling stage 106: it operates only during the aeration or air injection stages into the chamber.

[0071] Figure 9 illustrates the simultaneous feeding and return stages. By feeding the containment with wastewater from the bottom, the level of the contents increases according to the pressure losses generated by the return means 200. The fraction of these contents located at the surface 24 is clarified (because it is just after the settling stage); this fraction enters the return conduit and is discharged through the return ports 203. A new cycle can then begin, resuming the control of the return means, as explained in Figure 2.

[0072] In addition to managing the air injection to fill the return line, the control means for the return line also manage the opening and closing of the exhaust valve 205 and the air / water blocking device 216. During step 122, when the air injector fills the return line 201 with air, the exhaust valve 205 is in the closed position, and the air / water blocking device 216 is in the closed position (i.e., device 216 is closed in the case of a motorized valve, or it loses its prime in the case of a siphon). The air / water blocking device 216 blocks the air in the return line 201 by creating a hydraulic discontinuity between the upstream and downstream sides of the device.Before the feeding step 101, during the air expulsion step 123 from the conduit, the exhaust valve 205 is in the open position so as to allow the air to be evacuated simultaneously with the entry of clarified water into the return conduit, then the air / water blocking device 216 takes the so-called open position so as to allow the clarified fraction 22 to exit through the return orifices 203.

[0073] Figures 10 to 12 schematically represent variant embodiments of the SBR recovery means according to the invention.

[0074] In the embodiment shown in Figure 10, the return ports 203 are positioned below the level of the return duct 201, and the return duct 201 includes an air exhaust duct 211 to ensure proper air evacuation.

[0075] In the embodiment shown in Figure 11, the return air ports 203 are positioned below the level of the return air duct 201, and the air / water blocking device 216 includes a control valve 212 (advantageously motorized, in particular a motorized valve coupled to a control device of the flow rate) positioned upstream of the intake ports 203. The control valve 212 aims to hydraulically disconnect the water in the containment from the water outside the containment and to block the air upstream of the device 216, it also makes it possible to maintain a constant level of the surface of the reactor during the feeding stage 101 and the recovery stage 107 by limiting the generation of hydraulic shocks downstream of the intake ports 203. The control valve 212 is then closed during the disconnection after the feeding stage 101 and the recovery stage 107 and before the aeration stage 105 (or the air injection stage 110). The regulating valve is opened during step 123 of air expulsion to then allow the clarified fraction to pass through the return orifices 203. Note that for the blocking function, the valve 212 is not necessarily a regulating valve (a simple opening / closing valve is sufficient).

[0076] Finally, as shown in Figure 12, the invention also relates to a return duct in which the return orifices 203 are positioned substantially at the same level as the return duct. In this case, the return means 200 also include a control valve 212 positioned upstream of the return orifices 203.

[0077] Figure 13 represents a flowchart of the steps of a variant of the wastewater effluent treatment process according to the invention in an SBR 10. The SBR 10 reactor according to this variant of the invention allows for the selective extraction of the sludge least suited to settling which is found in the mixture 12.

[0078] In this embodiment, the SBR 10, visible in Figure 1, includes extraction means 19 adapted to extract sludge 23 (shown schematically for clarity) at varying levels between the minimum extraction level 17 and the maximum extraction level 18 (arrow B represents the sludge outlet). By way of example and without limitation, the extraction means 19 may include an extractor 191 comprising at least a first part having at least one opening 191a inside the enclosure 11 and a second part 191b adapted to discharge the sludge outside said enclosure. The extraction means 19 may include variation means 192 adapted to vary the position of the opening 191a of said extractor 191, in particular the level of said opening between the minimum extraction level 17 and The maximum extraction level 18. The extractor 191 advantageously includes a (suction) pump or a gravity valve (not shown) for sludge extraction. Advantageously, the extractor 191 may include a set of tubes arranged at different levels within the enclosure 11, each tube having a first end with an opening inside the enclosure 11 and a second end connected to the second part 91b of the extractor 191, the adjustment means 192 comprising a set of valves suitable for opening or closing said tubes. The extraction means thus allow sludge to be extracted at one or more variable levels. For better readability of the figure, the extraction means 19 are shown on the left side of the SBR, but the second part 191b for the sludge outlet is to be connected to the extracted sludge 23.

[0079] The means 16 for determining the minimum level 17 and the maximum level 18 for sludge extraction 23 in the containment 11 may include measuring means 161 suitable for measuring the concentration at different levels of a wastewater-sludge mixture. For example, a sludge blanket probe measures the surface area of ​​the sludge bed. A suspended solids (SS) probe measures the sludge concentration. Several probes may be arranged along the height of the containment to measure the suspended solids concentration at different levels. These measurements are used to determine levels 17 and 18. The means 16 may include selection means 162 suitable for selecting a maximum sludge concentration value and a minimum sludge concentration value, as well as a volume of sludge to be extracted. The selection may be made by an operator or based on a calculation related to the sludge age.The means 16 may include means 163 of deduction capable of deducing a minimum level of extraction corresponding to the selected maximum concentration value and a maximum level of extraction corresponding to the selected minimum concentration value.

[0080] The measuring means 161 may include, for example, a measuring probe. This measuring probe allows the concentration of sludge in the mixture to be measured. The measuring probe 161 is immersed in the mixture as illustrated. It may be at a fixed or variable immersion depth depending on the type of probe chosen. Or, as mentioned above, there may be several measuring probes along the height of the chamber. The measuring probe 161 is connected to the selection means. 162, which allow verification of whether the measurement corresponds to sludge to be extracted or not, and to the deduction means 163 which allow the measurement to be linked to the corresponding extraction level. These determination means 16 are linked to sludge extraction means 19, more particularly to the means 192 for varying the extraction level, primarily for selecting the extraction level. The variation means 192 vary the level of the opening 191a of the extractor 191, or extraction can be selectively performed at fixed extraction levels and at variable times depending on the evolution of the contents, for example during the settling stage, the waiting period, feeding / resumption, anaerobic extraction following the measurement of the sludge blanket, or even non-selectively during the aeration stage.

[0081] For example, and without limitation, the measuring means 161 of the determining means 16 include an ultrasonic sensor immersed below the surface of the wastewater-sludge mixture. The ultrasonic sensor transmits an ultrasonic wave into the mixture (it then functions as a transmitter) and receives a returning ultrasonic wave after traveling a given distance through the wastewater-sludge mixture (it then functions as a receiver). The sensor is connected to the selection means 162 and the deduction means 163.

[0082] Figure 13 shows the flowchart of the steps in the variant of the wastewater effluent treatment process according to the invention. In this variant, the treatment process according to the invention comprises: - a step 101 of feeding the SBR 10, during which a volume of effluent to be treated 20 is introduced near the bottom of the enclosure 11, into the sludge bed 13, preferably by a distribution network 21 covering the bottom of the enclosure 11, - a reaction sequence 102 comprising: o at least a first anaerobic step 103, during which the PAO 14 capture carbon pollution and release phosphorus compounds, o optionally, a second denitrification step 104, under anoxia, this step being implemented only in the event of a NOx concentration exceeding a predetermined threshold, o a third stage 105 of aeration, allowing the dephosphatation of the effluent by the PAO 14 to be carried out, the aeration being controlled so as to simultaneously carry out either nitrification (partial or total), or nitritation (partial or total), - a settling stage 106, during which sludge settles at the bottom of enclosure 11 and the contents of enclosure 11 become clear near its surface 24, - a recovery step 107, during which a clarified fraction 22 of the contents of the enclosure is removed, said recovery steps 107 and feeding steps 101 taking place simultaneously, so as to maintain the level of the contents of the enclosure 11 substantially constant during the recovery steps 107 and feeding steps 101, and - a step 108 of extraction of at least part of the light sludge 23 to a predefined level between the minimum extraction level 17 and the maximum extraction level 18, preferably near the sludge cover 15.

[0083] Typically, feeding step 101 is carried out anaerobically or anobically. In the latter case, step 101 under anoxia allows for denitrification. Anaerobic step 103 is carried out anaerobically, aeration step 105 is carried out aerobically, and settling step 106 is carried out aerobically followed by anoxically.

[0084] The second step 104 can be linked to a step 117 of measuring the concentration of NOx in the enclosure.

[0085] The treatment process according to the invention may optionally include a fourth step 111, an anoxic denitrification, denitrification, or deammonification step. More specifically, three main variants are considered: according to the first variant, the third step 105 includes total or partial nitrification, and the anoxic step 111 is denitrification (post-denitrification process); according to a second variant, the third step 105 includes total or partial nitritation, and the anoxic step 111 is denitrification (post-denitrification process); finally, according to a third variant, the third step 105 includes partial nitritation, and the anoxic step 111 is deammonification (the so-called "ANAMMOX" process). The fourth step 111 may be linked to a step 117bis for measuring the NOx concentration in the chamber.

[0086] Step 101, feeding through the sludge bed, allows the sludge to come into contact with the raw water to be treated. The volume of wastewater to be treated, 20, is introduced through the sludge bed containing the PAO (polycyclic aromatic hydrocarbons). This makes the particles and the soluble fraction of the introduced volume accessible to the bacteria. In the anaerobic step 103, the PAO capture carbonaceous pollution and release phosphate compounds. The aeration step 105 allows the PAO to remove phosphorus from the contents of the containment vessel. The reaction sequence 102 contributes to the development of PAO, which exhibits good settleability. During the settling step 106, the sludge settles by gravity to the bottom of the containment vessel. Heavy sludge and PAO settle more quickly than light sludge. They contribute to the sludge bed. Light sludge has lower settleability. They remain suspended longer in the contents of the enclosure, above the bed of mud.

[0087] Step 108, which involves extracting at least a portion of the light sludge, allows for the removal of the least settleable sludge during each cycle. However, extraction is not necessarily linked to each cycle, depending on operational constraints. For example, it is possible to avoid extraction on weekends. Consequently, only sludge with good settleability remains in the SBR tank. In addition to treating the pollution present in the incoming effluent, the combined action of the PAOs (Processing Active Oils), which produce denser sludge, and the extraction of light sludge densifies the sludge present in the tank. As a result, the process of the invention, known as the densified sludge process, achieves high sludge settling rates, regardless of the nature of the sludge present in the SBR tank.

[0088] During reaction sequence 102, when it includes a second step 104, there may be a step 110 of air injection into the chamber 11. It is also during this step 110 that air may be simultaneously injected into the return duct to achieve the airlock following step 120. The injection of air into the chamber before step 104 allows the biomass to be suspended for better mixing with the supernatant rich in oxidized nitrogen (nitrate NO3 and nitrite NO2), which improves the denitrification yield of the feeding step 104, and also the yield of the first anaerobic step 103. It can be noted that this step 110 is optional, if the second optional step 104 is activated, depending on the NOx concentration measurement.

[0089] Step 106, the settling step, can be preceded by step 112, which involves injecting air into the chamber 11. It is also during this step 112 that air can be simultaneously injected into the return line to achieve the airlock required in step 122. Injecting air into the chamber before the settling step allows for homogenization of the chamber contents and contact between the sludge and the oxidized nitrogen species. Furthermore, the air injection also allows for the degassing of nitrogen.

[0090] Furthermore, the treatment process according to the invention may include a sludge densification step 113 using a densification device 30 located inside or outside the enclosure 11. The densification device 30 may be a suitably sized sieve positioned upstream of the sludge extraction means to retain the largest flocs and thus improve the selection, i.e., their retention within the enclosure, of the particles that settle most easily. Alternatively or in addition, the sludge densification step may consist of adding ballast (such as zeolites).

[0091] Advantageously, the treatment process according to the invention includes a step 114 for controlling the duration of the third aeration step 105 based on the pollution level of the wastewater effluent 20, specifically based on the concentration of NH4 and / or NO2' and / or NO3' in the contents of the containment. More precisely, the pollution of the raw water is indirectly measured as soon as the contents of the containment are aerated at least once.

[0092] This variant of the process is called the "densified sludge" treatment variant, which allows for high sludge settling rates regardless of the sludge type (granular or non-granular), and advantageously with non-granular sludge. In this variant, sludge densification is achieved in a constant-level SBR by optimizing the production of easily settleable microorganisms. This is accomplished through a combination of factors, including a sludge extraction strategy that retains the sludge with the highest settleability in the reactor, while removing the least settleable sludge at each cycle.

[0093] Figure 14 schematically represents variants A, B, C, and D of the SBR return air means. In variants A and C, the air injector 207 is dedicated to blocking air / water. In this case, it includes a non-return valve 2071. In variants B and D, the air injector 207 is not dedicated to blocking air / water; that is, the air injector 2071 also serves to supply air to the chamber. In this case, the return air means 200 further include a blocking valve 206 to perform the blocking function. The air injector 207 can be connected to the air duct 204 (variant C), but this is not mandatory. However, the air injector 207 must be connected to the return duct 101 to block air / water.

[0094] It will be more generally apparent to a person skilled in the art that various modifications can be made to the embodiments described above, in light of the teaching that has just been disclosed to them. In the claims that follow, the terms used shall not be interpreted as limiting the claims to the embodiments set forth in this description, but shall be interpreted to include all equivalents that the claims aim to cover by virtue of their formulation and whose prediction is within the grasp of a person skilled in the art based on their general knowledge.

Claims

DEMANDS 1. A process for treating wastewater effluent in a sequenced batch reactor (SBR), said SBR (10) comprising: - an enclosure (11) suitable for containing a wastewater-sludge mixture (12) comprising different levels, each level being defined by a concentration and / or a sludge density, - a bed of mud (13) located at the bottom of the enclosure (11), - means for recovering (200) a clarified fraction (22) of the contents of the enclosure (11), comprising: o a recovery duct (201) extending below the surface (24) of the mixture (12) of the enclosure (11), between the inside (25) and the outside (26) of the enclosure (11), comprising: ■ a plurality of channels (202) hydraulically connecting the contents of the enclosure (12) and the return conduit (201), ■ a plurality of return ports (203) through which the clarified fraction (22) of the contents of the enclosure is intended to be drained, ■ an air duct (204) hydraulically or aerodically connecting the return duct (201) to the atmosphere, o an air exhaust valve (205) on the air duct (204), capable of assuming an open or closed position, o an air / water blocking device (216) on the return duct (201), capable of switching from a closed state to an open state, and vice versa, so as to block air in the return duct (201) upstream of the air / water blocking device (216) and to block water downstream of the blocking device (216), o an air injector (207) connected to the return duct (201) and intended to supply the return duct (201) with pressurized and / or compressed air, said method comprising: - a step (101) of feeding the SBR (10), during which a volume of effluent to be treated (20) is introduced near the bottom of the enclosure (11), into the sludge bed (13), preferably by a distribution network (21) covering the bottom of the enclosure (11), - a biological treatment reaction sequence (102) comprising at least: o a step (105) of aerating the contents of the enclosure, during which the level of the surface (24) of the mixture (12) rises, - a settling stage (106), during which sludge settles at the bottom of the enclosure (11) and the contents of the enclosure (11) become clear near its surface (24), - a step (107) of retrieving the clarified fraction (22) of the contents of the enclosure (11), said retrieval (107) and feeding (101) steps taking place simultaneously, so as to maintain the level of the contents of the enclosure (11) substantially constant during the retrieval (107) and feeding (101) steps, said process being characterized in that it comprises: - a piloting step (120) of the recovery means (200) during which: o the recovery duct (201) is filled with air until the recovery duct (201) is completely emptied of the clarified fraction (22) contained in the recovery duct (201), and o the recovery duct (201) is kept filled with air during the reaction sequence (102) and preferably until the end of the settling step (106), - a step (123) of expelling the air contained in the return duct (201) by the clarified fraction (22) just before the feed step (101) and the return step (107), - after the SBR supply step (101), a step (122) of filling the return duct (201) with air by air injection, the exhaust valve (205) being closed and the air / water blocking device (216) being said to be closed, during the aeration step (105), - a step (122bis) of maintaining the air supply to the intake duct (201) without air injection, the exhaust valve (205) being closed and the air / water blocking device (216) being said to be closed, during the aeration (105) and decantation (106) stages.

2. A treatment method according to claim 1, wherein during the step (122) air filling of the return duct (201), the exhaust valve (205) is in the closed position, and the air / water blocking device (216) blocks the air in the return duct (201) by creating a hydraulic discontinuity between the upstream and downstream of the air / water blocking device (216).

3. A treatment method according to any one of claims 1 or 2, wherein during the step (123) of expelling air from the return line, the exhaust valve (205) is in the open position so as to allow the air to be evacuated simultaneously with the inlet of clarified water into the return line.

4. A treatment method according to claim 3, wherein during the step (123) of expulsion of air from the return duct (201), after the evacuation of the air, the air / water blocking device (216) takes the so-called open position so as to allow the clarified fraction (22) to exit through the return orifices (203).

5. Installation for the treatment of wastewater effluent in a sequenced batch reactor (SBR), said SBR comprising: - an enclosure (11) suitable for containing a wastewater-sludge mixture (12) comprising different levels, each level being defined by a concentration and / or a sludge density, - a bed of mud (13) located at the bottom of the enclosure (11), - a device for supplying the SBR with a volume of effluent to be treated near the bottom of the enclosure (11), in the sludge bed (13), preferably via a distribution network (21) covering the bottom of the enclosure, - means for recovering (200) a clarified fraction of the contents (12) of the enclosure (11), comprising: o a recovery conduit (201) extending below the surface (24) of the contents (12) of the enclosure (11), between the inside (25) and the outside (26) of the enclosure, comprising: a plurality of channels (202) hydraulically connecting the contents (12) of the enclosure (11) and the recovery conduit (201), ■ a plurality of return ports (203) through which the clarified fraction of the contents (12) of the enclosure (11) is intended to be drained, ■ an air duct (204) hydraulically or aerodically connecting the return duct (201) to the atmosphere, o an air exhaust valve (205) on the air duct (204), capable of assuming an open or closed position, o an air / water blocking device (216) on the return duct (201), the exhaust valve (205) being capable of blocking air in the return duct (201) or allowing it to pass through, o an air injector (207) connected to the return duct (201) and intended to supply the return duct (201) with pressurized and / or compressed air, the SBR (10) being capable of implementing a treatment process comprising a biological treatment reaction sequence (102) including at least one step (105) of aerating the contents of the enclosure (11), during which the surface level (24) of the mixture (12) rises, a settling step (106),during which sludge settles at the bottom of the enclosure (11) and the contents of the enclosure (11) become clear near its surface (24), a step (107) of retrieving the clarified fraction (22) from the contents of the enclosure (11), said retrieval (107) and feeding (101) steps taking place simultaneously, so as to maintain the level of the contents of the enclosure (11) substantially constant during the retrieval (107) and feeding (101) steps, the installation further comprising control means (210) of the retrieval means (200) so as to fill the retrieval duct (201) with air until the retrieval duct (201) is completely emptied of the clarified fraction contained in the retrieval duct (201), to maintain the retrieval duct (201) filled with air during the aeration step (105),and to expel the air contained in the return duct (201) by means of the clarified fraction (22) just before the feeding step (101) and the return step (107), to fill the return duct (201) with air by injecting air during the aeration step (105), to maintain the filling of the return duct (201) with air without injecting air during the aeration (105) and settling (106) steps.

6. Processing installation according to claim 5, wherein the blocking device (206) comprises a U-shaped siphon between the air duct (204) and the return ports (203).

7. Processing installation according to any one of claims 5 or 6, wherein the return ports (203) are positioned above the level of the return duct (201), and the return duct (201) includes an air exhaust duct (211).

8. Processing installation according to claim 5 or 6, wherein the return ports (203) are positioned below the level of the return duct (201), and the return duct (201) includes an air exhaust duct (211).

9. Processing installation according to claim 5 or 6, wherein the blocking device (206) comprises a regulating valve (212) positioned at the return ports (203).

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