A method for treating wastewater effluent in a sequencing batch reactor (SBR) with constant level and controlled recovery.

Abstract

The present invention relates to an installation for treating wastewater effluent in a constant level sequential batch reactor (SBR), said SBR comprising: - a chamber (11) capable of containing a mixture (12) of wastewater and sludge with different liquid levels, each liquid level being determined by the concentration and / or density of the sludge; - a sludge bed (13) located at the bottom of said chamber (11); - a device for supplying the SBR with the amount of effluent to be treated near the bottom of the chamber (11) within the sludge bed (13), preferably via a distribution network (21) covering the bottom of the chamber; - means (200) for recovering a clarified fraction of the contents (12) of the chamber (11); The SBR (10) is capable of carrying out a treatment method comprising a biological treatment reaction sequence (102) including at least a step (105) of aerating the contents of the chamber (11), during which the level of the surface (24) of the mixture (12) rises; a settling step (106) in which sludge is deposited at the bottom of the chamber (11) and the contents of the chamber (11) are clarified near its surface (24); and a step (107) of recovering the clarified fraction (22) of the contents of the chamber (11), wherein the recovery step (107) and the feeding step (101) are carried out simultaneously, thereby maintaining a substantially constant level of the contents of the chamber (11) during the recovery step (107) and the feeding step (101), The installation also comprises a control means (210) and a recovery means (200).

Description

[Technical Field]

[0001] The present invention is in the field of biological treatment of municipal and industrial wastewater, and more particularly in what is known as a sequencing batch reactor (SBR). [Background technology]

[0002] SBRs operate in a continuous manner with different treatment steps, in particular a decanting stage which makes it possible to separate the so-called "activated" sludge from the treated water.

[0003] The so-called "activated sludge" process uses biological purification to treat wastewater. It is a purification method using free culture. Its principle is to decompose suspended or dissolved organic matter in the wastewater by bacteria. A good level of biodegradation is achieved by homogenizing the medium and by good aeration, which allows the bacteria access to the particles. The sludge then settles to the bottom of the reactor during a settling stage.

[0004] Activated sludge processes may be aimed at removing carbon-based and nitrogen-based pollutants and removing or recovering phosphorus contained in phosphorus-based pollutants.

[0005] Regardless of the treatment technology used, SBR technology is limited in its sizing by the sludge's settleability. Specifically, one of the factors limiting the concentration of activated sludge in an SBR, which itself represents the potential for pollution load treatment, is the sludge's settleability, commonly expressed as the Mohlman index. The Mohlman index is an index that indicates the settleability of sludge. This index defines the volume of activated sludge that settles in 30 minutes relative to the mass of dry residue (or the concentration of suspended matter, also known as SM) in the sludge. The lower the index, the better the sludge settleability.

[0006] The denser the sludge, the faster the settling stage and the shorter the overall treatment cycle time, so more pollutants can be treated per day by running more cycles.

[0007] The denser the sludge, the higher the concentration it can operate at while allowing for good settling properties (index), and therefore the more pollutants can be treated in a single structure volume.

[0008] The first designs of what are called continuous biological reactors (SBRs) used two different volumes alternately used for reaction and settling, with water being transferred from the reaction section to the settling section (Seghers Unitank process). However, this type of SBR has been improved, and most continuous-type biological reactors (SBRs) are now designed to carry out the different treatment steps successively in a single volume. These reactors are generally variable-level reactors, i.e., the raw water feed and treated water recovery stages are separated in time, and the water level in the reactor drops during the recovery of treated water.

[0009] Constant-level SBRs are also known, which allow for a shorter duration of each treatment sequence while maintaining the same treatment efficiency. Such reactors are described, for example, in WO 2016020805.

[0010] The operation of a constant level SBR involves the simultaneous supply of raw water and the withdrawal of treated water at the same flow rate in order to maintain a constant level, and if the treated water recovery device is immersed without special care, it will become contaminated with SM (suspended solids) during the reaction phase (reaction sequence), and more specifically during the aeration phase, when the entire volume of the biological reactor reaches an average sludge concentration of several grams per liter.

[0011] The SBR process described in WO 2004 / 024638 operates on the basis of the operation of semi-submerged pipes in the chamber of the SBR, which require the liquid level to be lowered during the cycle in order to avoid sludge being entrained in the pipes during the reaction phase, in particular due to the rise in the water level associated with gas retention.

[0012] This drop in liquid level poses certain problems which the proposed invention attempts to solve: - Increase in reactor height by the hydraulic volume required for the feed step, - Increasing the cycle time to include the drawdown time and subsequent fill time; - the need for intermediate storage and recirculation of the volume corresponding to the drop in liquid level at the start of treatment via pumps; - an increase in the instantaneous feed flow rate to incorporate the treatment of this recirculation volume; - The water located in the volume corresponding to the drop in liquid level is potentially rich in nitrates, which has proven to have a negative effect on the extraction of phosphates during the feed recovery phase.

[0013] U.S. Patent Application Publication No. 2018 / 0043286 describes a method for draining water from a reservoir based on a drain pipe positioned entirely within the reservoir. Water from the reservoir enters the drain pipe through a permanently submerged orifice. Compressed air is introduced into the drain pipe to expel water from the pipe into a collector. The compressed air is then discharged from the drain pipe to fill the drain pipe with water. In this solution, the drain pipe has a simple orifice through which water and sludge enter directly into the pipe. More specifically, during the aeration phase, the amount of air injected changes the expansion height of the water volume in the chamber, which changes the pressure inside the pipe. The water and sludge in the chamber then accumulate in the pipe. The sludge accumulates in the pipe during the aeration phase and is partially flushed away along with the treated water, adversely affecting water quality and compliance with discharge standards. Therefore, this solution is not suitable for water treatment involving aeration and sludge settling steps within the reservoir.

[0014] Also known is U.S. Pat. No. 6,884,354, which describes a constant level continuous batch reactor (SBR) including a clarifier (or recovery device) like that described in U.S. Pat. No. 4,596,658, which is horizontally positioned near the reactor wall. The clarifier in U.S. Pat. No. 4,596,658 has layered openings in the form of elongated slots for collecting clarified water. Such devices are prone to turbulence when drawing in clarified water, which can have a negative impact on the quality of the recovered clarified water. [Prior art documents] [Patent documents]

[0015] [Patent Document 1] International Publication No. 2016020805 Brochure [Patent Document 2] International Publication No. 2004 / 024638 Pamphlet [Patent Document 3] US Patent Application Publication No. 2018 / 0043286 [Patent Document 4] U.S. Patent No. 6,884,354 [Patent Document 5] U.S. Patent No. 4,596,658 Summary of the Invention [Problem to be solved by the invention]

[0016] The present invention aims to alleviate all or part of the above problems by proposing a method for treating wastewater effluent in a constant level continuous batch reactor (SBR) in which the treated water is recovered by a recovery duct that is blocked with air. The invention is based on a step of controlling the recovery means of the chamber of the SBR, during which, just before aeration in the SBR begins, the recovery duct is filled with air until the duct is completely emptied of the water it contains. The invention relies on a step of the treatment method in which the controlled air filling of the recovery duct ensures that the recovery duct of the treated water is not contaminated with activated sludge during aeration. [Means for solving the problem]

[0017] To this end, the subject of the present invention is a method for treating a wastewater effluent in a sequential batch reactor (SBR), said SBR comprising: - a chamber capable of containing a mixture of wastewater and sludge with different liquid levels, each liquid level being determined by the concentration and / or density of the sludge; - a sludge bed located at the bottom of the chamber, and - means for recovering a clarified fraction of the contents of the chamber, a collection duct extending below the surface of the mixture in the chamber between the inside and outside of the chamber, several channels hydraulically connecting the chamber contents with the recovery duct; a plurality of collection orifices through which the clarified fraction of the contents of the chamber is intended to be drained; and an air duct hydraulically or pneumatically connecting the recovery duct to the atmosphere; a recovery duct comprising: an exhaust valve in the air duct that can be in an open or closed position; an air / water shutoff device provided in the recovery duct, the air / water shutoff device being capable of shutting off the air in the recovery duct upstream of the air / water shutoff device and shutting off the water downstream of the shutoff device; an air injector connected to the recovery duct, the air injector intended to supply pressurized and / or compressed air to the recovery duct; a means for Equipped with The method comprises: - feeding the SBR, during which the amount of effluent to be treated near the bottom of the chamber is introduced in a sludge bed, preferably via a distribution network covering the bottom of the chamber; a biological treatment reaction sequence comprising at least: aeration of the contents of the chamber, during which the liquid level at the surface of the mixture rises; a biological treatment reaction sequence including: a settling step in which the sludge is deposited at the bottom of the chamber and the contents of the chamber are clarified near its surface; - recovering a clarified fraction of the contents of the chamber, said recovering and dispensing steps being performed simultaneously, thereby maintaining a substantially constant liquid level of the contents of the chamber during the recovering and dispensing steps; Including, The method comprises: - controlling the recovery means during which: Filling the collection duct with air until it is completely empty of the clarified fraction contained therein, the collection duct is kept filled with air throughout the reaction sequence, preferably until the end of the settling step; controlling; - immediately before the feeding step and the recovery step, displacing the air contained in the recovery duct by the clarified fraction; - after the step of feeding the SBR, filling the recovery duct with air by air injection, during the aeration step the exhaust valve is closed and the air / water shutoff device is said to be closed; - maintaining the collection duct filled with air without air injection, the exhaust valve being closed and the air / water shutoff device being said to be closed during the aeration and settling steps; The method is characterized by comprising:

[0018] Advantageously, during the step of filling the recovery duct with air, the exhaust valve is in a closed position and the air / water shut-off device shuts off the air in the recovery duct by creating a hydraulic discontinuity between upstream and downstream of the air / water shut-off device.

[0019] Advantageously, during the step of expelling air from the collection duct, the exhaust valve is in an open position to allow the evacuation of air simultaneously with the entry of clarified water into the collection duct.

[0020] Advantageously, during the step of expelling air from the recovery duct, after the air has been expelled, the air / water shutoff device assumes a position referred to as open so as to allow the clarified fraction to exit through the recovery orifice.

[0021] The present invention also provides an installation for treating wastewater effluent in a sequencing batch reactor (SBR), said SBR comprising: - a chamber capable of containing a mixture of wastewater and sludge with different liquid levels, each liquid level being determined by the concentration and / or density of the sludge; - a sludge bed located at the bottom of the chamber; - a device for feeding the amount of effluent to be treated near the bottom of the chamber to the SBR within the sludge bed, preferably via a distribution network covering the bottom of the chamber, and - means for recovering a clarified fraction of the contents of the chamber, a collection duct extending below the surface of the contents in the chamber between the inside and outside of the chamber, several channels hydraulically connecting the chamber contents with the recovery duct; a plurality of collection orifices through which the clarified fraction of the contents of the chamber is intended to be drained; and air ducts hydraulically or pneumatically connecting the recovery ducts to the atmosphere; a recovery duct comprising: an exhaust valve in the air duct that can be in an open or closed position; an air / water shut-off device in the recovery duct, with two valves each capable of shutting off air in the recovery duct or allowing air to pass through; an air injector connected to the recovery duct, the air injector intended to supply pressurized and / or compressed air to the recovery duct; a means for Equipped with the SBR is capable of carrying out a treatment method comprising a biological treatment reaction sequence including at least a step of aerating the contents of the chamber, during which a liquid level at the surface of the mixture rises; a settling step, during which sludge is deposited at the bottom of the chamber and the contents of the chamber are clarified near the surface; and a step of recovering the clarified fraction of the contents of the chamber, said recovery step and feeding step being carried out simultaneously, thereby maintaining a substantially constant liquid level of the contents of the chamber during the recovery step and the feeding step; The installation also comprises means for controlling the collection means to fill the collection duct with air until it is completely emptied of the clarified fraction contained therein, to maintain the collection duct in an air-filled state during the aeration step, to displace the air contained in the collection duct with the clarified fraction immediately before the feeding step and the collection step, to fill the collection duct with air by air injection during the aeration step, and to maintain the collection duct in an air-filled state without air injection during the aeration step and the settling step.

[0022] In one embodiment, the shutoff device comprises a U-shaped siphon between the air duct and the collection orifice.

[0023] In another embodiment, the recovery orifice is positioned above the level of the recovery duct, the recovery duct comprising the exhaust duct.

[0024] In another embodiment, the recovery orifice is positioned below the level of the recovery duct, the recovery duct comprising the exhaust duct.

[0025] In another embodiment, the shutoff device comprises a control valve positioned at the collection orifice.

[0026] The invention will be better understood and further advantages will become apparent on reading the detailed description of embodiments given by way of example, such description being illustrated by the accompanying drawings, in which: [Brief explanation of the drawings]

[0027] [Figure 1] 1 shows a schematic diagram of an example of a continuous batch reactor suitable for carrying out the processing method according to the present invention. [Figure 2] 1 shows a schematic representation of the chamber and collection means of an SBR. [Figure 3] 1 shows a flow chart of steps in a method for treating wastewater effluent according to the present invention. [Figure 4] 2 shows a schematic representation of the recovery means features of an SBR according to the present invention at different stages of operation. [Figure 5] 2 shows a schematic representation of the recovery means features of an SBR according to the present invention at different stages of operation. [Figure 6] 2 shows a schematic representation of the recovery means features of an SBR according to the present invention at different stages of operation. [Figure 7] 2 shows a schematic representation of the recovery means features of an SBR according to the present invention at different stages of operation. [Figure 8] 2 shows a schematic representation of the recovery means features of an SBR according to the present invention at different stages of operation. [Figure 9] 2 shows a schematic representation of the recovery means features of an SBR according to the present invention at different stages of operation. [Figure 10]2 shows a schematic representation of a variant embodiment of the recovery means of the SBR according to the invention; [Figure 11] 2 shows a schematic representation of a variant embodiment of the recovery means of the SBR according to the invention; [Figure 12] 2 shows a schematic representation of a variant embodiment of the recovery means of the SBR according to the invention; [Figure 13] 3 shows a flow chart of the steps of a variant of the method for treating wastewater effluent in an SBR according to the present invention. [Figure 14] 1 shows a schematic diagram of a variation of the recovery means for an SBR. DETAILED DESCRIPTION OF THE INVENTION

[0028] For clarity, the figures are not drawn to scale. Furthermore, identical elements are provided with the same reference numerals in the various figures.

[0029] Figure 1 shows a schematic representation of an example of a sequential batch reactor 10 suitable for carrying out the treatment method according to the invention. The invention relates to an installation for treating wastewater effluent in a sequential batch reactor 10 (SBR). According to the invention, the SBR 10 comprises: a chamber 11 capable of containing a mixture 12 of wastewater or treated water and sludge with different liquid levels, each liquid level being determined by the concentration and / or density of the sludge; - a sludge bed 13 located at the bottom of the chamber 11; - a device for supplying the SBR with the amount of effluent 20 to be treated, near the bottom of the chamber 11, in the sludge bed 13, preferably via a distribution network 21 covering the bottom of the chamber; - means 200 for recovering the clarified fraction of the contents 12 of the chamber 11; Equipped with The SBR 10 is capable of carrying out a treatment method comprising a biological treatment reaction sequence 102 including at least a step 105 of aerating the contents of the chamber 11 while the level of the surface 24 of the mixture 12 rises, optionally a settling step 106 in which sludge accumulates at the bottom of the chamber 11 and the contents of the chamber 11 become clarified near its surface 24, and a step 107 of recovering the clarified fraction 22 of the contents of the chamber 11, said recovery step 107 and feeding step 101 being carried out simultaneously so as to maintain a substantially constant level of the contents of the chamber 11 during the recovery step 107 and the feeding step 101, and the installation also comprising means 210 for controlling the recovery means 200 for recovering the clarified fraction from the chamber. In the following text, the term recover / recover should be understood to mean discharge / discharge and / or drain / drain. Aeration of the contents of the chamber is preferably carried out with air 8 via a distribution network 27 covering the bottom of the chamber 11.

[0030] 2 shows a schematic representation of the chamber 11 of the SBR 10 and a collection means 200. The means 200 for collecting the clarified fraction of the contents 12 of the chamber 11 comprises: a recovery duct 201 extending below the surface 24 of the contents 12 of the chamber 11 between the inside 25 and the outside 26 of the chamber 11, a number of channels 202 hydraulically connecting the contents 12 of the chamber 11 with the collection duct 201; a plurality of collection orifices 203 through which the clarified fraction of the contents 12 of the chamber 11 is intended to be drained, an air duct 204 hydraulically or pneumatically connecting the recovery duct 201 with the atmosphere; a recovery duct 201 comprising: an exhaust valve 205 in the air duct 204, which can be in an open or closed position and which allows the air trapped in the recovery duct to be exhausted to the atmosphere; an air / water shut-off device 216 provided in the recovery duct 201, which can be moved from a state called closed to a state called open, and vice versa, so as to shut off the air in the recovery duct 201 upstream of the air / water shut-off device 216 and to shut off the water downstream of the air / water shut-off device 216; an air injector 207 connected to the recovery duct 201 and intended to supply it with pressurized and / or compressed air;

[0031] For clarity of illustration, two channels 202 are shown. However, it should be understood that the collection duct may comprise several other channels 202 in a particular arrangement, with the channels 202 distributed to cover the surface and form a network of channels and collection orifices. In other words, the channels 202 are arranged along the duct 201. Multiple channels form multiple entry points for the clarified water into the duct 201. This reduces the flow rate per channel relative to the amount of liquid discharged from the duct 201. Unlike devices with a single water inlet channel, this arrangement of the present invention avoids the generation of currents that are likely to cause surface turbulence that may be detrimental to the quality of the collected water.

[0032] The water collection orifice 203 may be in the form of an elongated or circular slot.

[0033] The air / water shutoff device 216 is described in detail below in the form of two exemplary embodiments. This device can be a valve, preferably an electrically operated valve, that can be in an open or closed position, or a U-shaped siphon that can be primed or unprimed. In the following text, the air / water shutoff device 216 is referred to as open when the valve is in the open position or the siphon is primed, and is referred to as closed when the valve is closed or the siphon is unprimed.

[0034] The recovery means 200 may comprise an air injector 207 connected to the air duct 204 between the exhaust valve 205 and the air / water shutoff device 216, and may be intended to supply pressurized / compressed air to the recovery duct 201. Alternatively, the air for shutting off the recovery duct 201 may originate from the air source used in the present treatment method. More specifically, the air injector 207 may be dedicated to air / water shutoff. In this case, it comprises a check valve. Alternatively, the air injector 207 may not be dedicated to air / water shutoff, i.e., the air injector may originate from the source of air supply to the chamber. In this case, the recovery means 200 further comprises a shutoff valve 206 to provide the shutoff function. The air injector 207 does not necessarily have to be connected to the air duct 204, but may be systematically connected to the recovery duct 101 to shut it off with air / water.

[0035] The air injector 207 may operate intermittently or continuously during the aeration step 105.

[0036] The exhaust valve 205 corresponds to a vent valve.

[0037] The control means 210 of the collection means 200 is intended to fill the collection duct 201 with air until it is completely emptied of the clarified fraction contained therein, to keep the collection duct 201 filled with air during the aeration step 105 and the settling step 106, and to expel the air contained in the collection duct 201 with the clarified fraction 22 during the supply step 101 and the collection step 107. More specifically, the control means 210 is configured to operate the valve 205 and the shutoff device 216 as needed to empty the collection duct 201 of the clarified fraction present in the collection duct 201 and to keep the collection duct 201 filled with air during the aeration and settling steps. Air can be supplied continuously. It can also come from an external air source, i.e., one not dedicated to the air / water shutoff but provided for aeration of the chamber. In the case of an external air source, an isolation valve 206 is required. If the recovery means 200 comprises an air injector 207 dedicated to the air / water shutoff, this may inject pressurized and / or compressed air into the recovery duct 201. Note that this dedicated air injector 207 is equipped with a non-return valve (not shown). In other words, the recovery duct 201 is then sealed with air and filled with air that cannot be expelled due to the closure of the air / water shutoff device 216 and the exhaust valve 205. During the aeration phase, the introduction of air into the chamber increases the liquid level of the contents of the chamber, causing the liquid level of the contents to rise. However, since the recovery duct is filled with air, these contents cannot enter the duct. This has the advantage that it avoids the loss of sludge from the system (the presence of sludge is important for densification), it avoids contamination of the clarified water leaving the recovery duct and orifice 203 (which is important with regard to tertiary treatment that may have to be carried out downstream and / or with regard to wastewater standards), the channels 202 make it possible to compensate for gas retention that raises the water level in the reactor during aeration, and they also compensate for imperfections in the horizontality of the pipes.

[0038] If the air injection is discontinuous, the contents will rise in the channel 202 but will not be able to enter the recovery duct 201. This configuration ensures that the control of the recovery means ensures that only the clarified fraction enters the recovery duct without the risk of sludge-containing contents entering.

[0039] It is important to emphasize that the recovery duct extends below the surface 24 of the chamber contents. It is therefore permanently immersed in the chamber contents. The channel 202, a tube with an inlet orifice, is permanently immersed and filled with the chamber contents (either with clarified water (during the feed / withdrawal and anaerobic steps) or with air (during the reaction steps, and therefore the aeration and sedimentation steps)). In other words, the channel contents change depending on the ongoing sequence. The channel 202 has a dual role: it provides access for the clarified fraction to the recovery duct 201 during the feed / withdrawal steps, and also forms a buffer volume containing the chamber contents without access to the recovery duct 201 when the level of the chamber contents rises due to aeration. The transition from the role of allowing access to the recovery duct to the role of buffer volume occurs by the injection / exhaust of pressurized and / or compressed air and the opening and closing of the shut-off device and exhaust valve, depending on the progress of the treatment method. The injection / exhaust of pressurized and / or compressed air and the opening and closing of the shut-off devices and exhaust valves are controlled by means 210 for controlling the recovery means 200 .

[0040] In one embodiment, the air / water shutoff device 216 comprises a U-shaped siphon 208 between the air duct 204 and the recovery orifice 203. When air is injected, the clarified water in the siphon and in the recovery duct is replaced with air up to a height corresponding to the end of one or more channels. By this means, the siphon aims to hydraulically separate the contents of the chamber from the clarified water outside the chamber, thus inactivating it. By extending the height of the siphon, it is also possible to compensate for the rise in the liquid level on the surface 24 during the aeration step. The presence of a siphon is not absolutely necessary; other embodiments are possible and are presented below. The siphon may also be associated with a shutoff valve 206 controlled by the control means 210 if the air for filling the recovery duct comes from the process air (the air injector 207 is not dedicated to air shutoff). The recovery orifice 203 is the orifice through which the treated water is discharged.

[0041] The recovery orifice 203 is advantageously positioned above the level of the recovery duct 201, which in turn advantageously comprises an exhaust duct 211. Again, other embodiments are possible and are presented below.

[0042] 3 shows a flow chart of the steps of a method for treating wastewater effluent in accordance with the present invention in an SBR 10. As previously described, the SBR 10 comprises: a chamber 11 capable of containing a mixture 12 of wastewater and sludge with different liquid levels, each liquid level being determined by the concentration and / or density of the sludge; - a sludge bed 13 located at the bottom of the chamber 11; - a device for supplying the SBR with the amount of effluent to be treated near the bottom of the chamber 11, in the sludge bed 13, preferably via a distribution network 21 covering the bottom of the chamber; means 200 for recovering the clarified fraction of the contents 12 of the chamber 11, and means 210 for controlling the recovery means; Equipped with.

[0043] The collection means 200 has been described based on FIG.

[0044] The method for treating wastewater effluent in a sequential batch reactor (SBR) 10 according to the present invention comprises: a step 101 of feeding the SBR 10, during which the amount of effluent 20 to be treated near the bottom of the chamber 11 is introduced into the sludge bed 13, preferably via a distribution network 21 covering the bottom of the chamber 11; a biological treatment reaction sequence 102 including at least a step 105 of aeration of the contents of the chamber, during which the level of the surface 24 of the mixture 12 rises; Includes.

[0045] The injection of air can be done by a non-dedicated air distribution system with an isolation valve 206, such as an air distribution device, for the aeration step 105, or it can be done by a dedicated distribution system (e.g., a compressor or booster) that advantageously includes an anti-return valve.

[0046] The method of the present invention also includes: a settling step 106 during which the sludge settles at the bottom of the chamber 11 and the contents of the chamber 11 are clarified near its surface 24; - a step 107 of recovering the clarified fraction 22 of the contents of chamber 11, said recovery step 107 and supply step 101 being carried out simultaneously so as to maintain a substantially constant liquid level of the contents of chamber 11 during the recovery step 107 and the supply step 101.

[0047] The method according to the invention may also include a waiting stage 116 coupled to the feeding step, the settling step or the anaerobic step.

[0048] According to the present invention, the treatment method comprises: a step 120 of controlling the recovery means 200, during which the recovery duct 201 is filled with air until it is completely empty of the clarified fraction 22 contained therein, and which continues to be filled with air during the reaction sequence 102, preferably during the settling step 106 and, optionally, during the waiting step; and a step 123 of expelling the air contained in the recovery duct 201 by the clarified fraction 22 during the supply step 101 and the recovery step 107 .

[0049] After step 120 and before step 123, the method may include step 121 of at least partially filling channel 202 with contents 12 of chamber 11 during aeration step 105 if the injection of air is not continuous during the air injection step.

[0050] Furthermore, the treatment method includes two other steps between steps 120 and 123 that keep the collection duct filled with air. As mentioned above, step 120 of filling the collection duct 201 with air is performed by simultaneously injecting air and draining the clarified water. Valve 205 is closed, air / water shutoff device 216 is said to be closed, and the air injection device (air injector 207) is activated at the start of the first aeration step 105.

[0051] The method then includes a step 122 of keeping the recovery duct 201 filled with air by injecting air: the valve 205 is closed, the air / water shutoff device 216 is said to be closed, and the air injection device 207 is active during the aeration step 105.

[0052] The method then includes a step 122bis of keeping the collection duct filled with air without air injection: valve 205 is closed, air / water shutoff device 216 is said to be closed, and air injection device 207 is turned off during aeration step 105 and settling step 106.

[0053] Next comes step 123, in which the air contained in the recovery duct is expelled and simultaneously filled with clarified water. Valve 205 is opened, shut-off device 216 is said to be open, and air injection device 207 is turned off during feed step 101, recovery step 107 and anaerobic step 103.

[0054] And finally, if the injection of air is not continuous during the aeration step 105, particularly in order to save energy, a step 121 can be performed (although this step is somewhat undesirable) of at least partially filling the channel 202 with the contents 12 of the chamber 11 during the aeration step 105. In this case, it is possible to re-inject air to refill the recovery duct 201, this being step 122. This can be done synchronously by adjusting the frequency and time of the air injection, or more precisely by incorporating a level measurement probe that makes it possible to detect if re-injection of air is necessary and to trigger step 122 during the aeration step 105.

[0055] The collection duct is maintained in an air-filled state during the reaction sequence, including the aeration step, and preferably during the settling step as well. Specifically, if the collection duct were no longer air-filled at the start of settling, the sludge veil would not have enough time to descend below the inlet orifice of channel 202, resulting in contamination of the collection duct with sludge.

[0056] A special feature of the present invention is that the recovery duct 201 is positioned below the surface 24 of the chamber contents, i.e., it is always submerged. Nevertheless, the contents are controlled by steps (120, 122, 122bis, 123) of controlling the recovery means 200 depending on the treatment method step. As a result, only treated water can penetrate the recovery duct to be recovered. The recovery duct is depicted substantially horizontally, i.e., parallel to the surface 24 of the chamber contents, but it can also be inclined and extend along an axis intersecting the plane in which the surface 24 lies. A first advantage is that the chamber volume is not limited, since it is not necessary to lower the water level below the recovery duct to avoid the intrusion of untreated water and sludge during the aeration step 105. By controlling the recovery means, the recovery duct is filled with air just before the aeration step 105 of the reactor. In other words, the collection ducts are filled with air, i.e., blocked with air, thus making the contents of the chamber inaccessible during stages when the contents of the chamber near the duct are not solely treated water. Another special feature results from the channels 202 hydraulically connecting the contents of chamber 11 to collection duct 201. They are depicted perpendicular to surface 24, but they can also be inclined downward. Channels 202 play an important role: they ensure a hydraulic connection between the clarified fraction and the collection duct, allowing the collection of the clarified fraction, while also allowing the elevation of the chamber contents during the aeration step. Each channel 202 has two ends (visible in FIG. 4): a first end 221 and a second end 222, which are in direct contact with collection duct 201, allowing flow between said collection duct 201 and said channel 202. Like collection duct 201, each channel 202 can have any cross-section, be it circular, rectangular, polygonal, or any other shape.

[0057] The aeration step 105 involves the injection of air into the chamber, causing the liquid level of the chamber contents to fluctuate. During the aeration step 105, the channel 202 is at least partially filled with the chamber contents. This is a specific case of step 121, where the injection of air into the collection duct is not continuous. The filling height of the channel 202 corresponds to the height to which the chamber contents rise. Because the channel 202 is designed to be tall enough to accommodate the specific case of step 121, the contents 12 do not reach the second end 222 of the channel 202. For its part, the collection duct 201 remains filled with air. During the aeration step 105, the chamber contents are homogenous, even at its surface 24. Thanks to the channel 202, these homogenous contents, including sludge, do not enter the collection duct 201. The channel 202 forms a transition zone between the collection duct, which is filled with air, and the chamber contents. End 221 of channel 202 may come into contact with water and sludge. End 222 of channel 202 does not come into contact with sludge. This therefore ensures that the recovery duct contains either air or treated water, depending on the stage, but never sludge.

[0058] The recovery duct 201 is kept filled with air during the reaction sequence 102, preferably the settling step 106, and optionally the waiting phase 116. This is step 122bis. At the end of settling, the sludge present in the chamber settles to the bottom of the chamber 11, and the contents of the chamber 11 are clarified near its surface 24. The method then includes a step 123 of expelling air from the recovery duct 201. The valve 205 is in the open position, and clarified water enters the recovery duct, forcing the air trapped in the recovery duct out through the valve 205 and through the ventilation duct. There is no longer any trapped air in the recovery duct.

[0059] The air / water shutoff device 216 then moves to what is referred to as the open position, and a new cycle begins: the feed step 101 is performed simultaneously with the recovery step 107. When a volume of effluent is introduced into the chamber, an equal volume is drained to maintain a substantially constant liquid level. As the recovery duct is no longer blocked with air, the recovery duct 201 and channel 202 are filled with this volume of the contents 12 of chamber 11 located at surface 24. This is the clarified fraction intended to be recovered.

[0060] By controlling the filling of the collection duct with air (step 120) and the blocking of the air in the collection duct (step 122bis, optionally supplemented by step 122 if the air injection is not continuous), the time at which the contents are transferred to the collection duct is precisely controlled. The collection duct has access to the contents of the chamber when they are clarified on its surface. In contrast, during the aeration step when the contents are homogenous, i.e. when the contents of the chamber are not clarified at the liquid level in the collection duct, the collection duct does not have access to these contents. In other words, the method according to the invention makes it possible to precisely control what enters the collection duct. According to the wastewater treatment step, there is a succession of stages: sealing the collection duct with air and a stage of free hydraulic connection, during which the contents of the chamber can circulate in the collection duct.

[0061] Figures 4 to 9 show diagrammatically the characteristics of the SBR recovery means according to the invention at different stages of operation. According to the representation in Figure 2, the recovery duct 201 is filled with the clarified fraction. Just before the end of the feeding and recovery steps and before the aeration step (or air injection step 110), the recovery duct is not blocked with air. At this point, just before the aeration step, if the recovery orifice 203 is positioned above the level of the recovery duct, the level of the clarified fraction stabilizes in the recovery duct at a reference level, shown in Figure 4 as Q = 0 m3 / h.

[0062] Between the representations of Figures 2 and 4, the injection of air begins. The clarified fraction exits through the collection orifice 203. The exhaust valve 205 is in the closed position. The air cannot escape and remains in the collection duct. As soon as the collection duct is filled with air and the entire clarified fraction leaves it, only additional air is needed to adjust the air volume for the entire aeration step. This is step 122. Thus, the collection duct is filled with air on the one hand, and the clarified fraction is maintained downstream of the siphon on the other. The aeration step then begins. Air is introduced into the chamber by an external air injector (i.e., one not dedicated to blocking the collection duct with air) to aerate the contents of the chamber. Air can also be added to the collection duct during aeration to compensate for pressure fluctuations in the collection duct related to fluctuations in the water height during aeration. This is step 122.

[0063] In Figure 5, aeration of the biomass is initiated. The injection of air for the aeration step 105 causes the level of the chamber contents to rise (e.g., approximately 30 cm, represented by level Q'). The rise in the chamber contents level causes a slight increase in pressure in the collection duct. If a siphon is used as the air / water shutoff device 216, the chamber contents enter channel 202, and the level of the clarified fraction changes within the siphon (see arrows in Figure 5). Channel 202 must be high enough to stabilize the level of the contents within the channel (and prevent the contents from migrating into the collection duct) when the chamber contents level is at its highest (i.e., during the aeration step).

[0064] In Figure 6, the aeration step ends and the settling step begins. With the cessation of air injection for aeration, the surface liquid level returns to the reference level marked Q=0. Air is still blocked in the recovery duct so that unsettled sludge remains in the chamber. The air / water shut-off device 216 is said to be in the closed position and the valve 205 is closed, ensuring that air is blocked in the recovery duct 201 upstream of the shut-off device 216.

[0065] Figure 7 shows the settling step. Sludge may be extracted from the chamber. The level of the chamber contents decreases slightly (by a few centimeters). The level decreased by the extraction of sludge is represented by Q''.

[0066] At the end of the settling step 106 and / or at the start of the feeding step 101 and the recovery step 107, the chamber surface 24 is clarified, and once all the sludge has settled and is located at the bottom of the chamber, the exhaust valve 205 is moved to the open position and the air / water shutoff device 216 is moved to the open position (i.e., the device 216 is open in the case of an electric valve or primed in the case of a siphon) to allow the clarified water to pass through. The clarified fraction enters the recovery duct and is drained through the recovery orifice 203, while the air flows out through the valve 205 and the ventilation duct 204. This step is shown in FIG. 8. At the end of the settling step, the sludge is far away from the recovery duct and the channel 202. There is no longer any risk of sludge entering the recovery duct. The air is not shut off: in the case of an air injector that is not dedicated to air shutoff, the valve 206 is closed and the exhaust valve 205 (as well as the air / water shutoff device 216) is opened just before the feeding and recovery steps. Advantageously, the air injector 207 is not activated during the settling step 106: it is activated only during the aeration step or step of injecting air into the chamber.

[0067] Figure 9 shows the simultaneous steps of feeding and recovery. By feeding wastewater into the chamber via its bottom, the level of the contents rises according to the pressure drop caused by the recovery means 200. The fraction of this content located at the surface 24 is clarified (because it has just undergone a settling step) and moves to the recovery duct, and it is this fraction that is discharged via the recovery orifice 203. A new cycle can be started by repeating the control of the recovery means as explained in Figure 2.

[0068] In addition to managing the air injection to fill the collection duct with air, the means for controlling the collection means also manages the opening and closing of the exhaust valve 205 and the air / water shutoff device 216. During step 122 of filling the collection duct 201 with air by the air injector, the exhaust valve 205 is in a closed position and the air / water shutoff device 216 is in a closed position (i.e., device 216 is closed in the case of an electric valve or unprimed in the case of a siphon). The air / water shutoff device 216 shuts off the air in the collection duct 201 by creating a hydraulic discontinuity between upstream and downstream of the air / water shutoff device 216. Before the supply step 101, during step 123 of expelling air from the duct, the exhaust valve 205 is in an open position to exhaust air simultaneously with the entry of clarified water into the collection duct, after which the air / water shutoff device 216 assumes a position referred to as open so that the clarified fraction 22 exits through the collection orifice 203.

[0069] 10 to 12 show schematic diagrams of modified embodiments of the recovery means for an SBR according to the present invention.

[0070] In the embodiment presented in FIG. 10, the recovery orifice 203 is positioned below the level of the recovery duct 201, which is provided with an exhaust duct 211 to ensure proper air evacuation.

[0071] 11, the collection orifice 203 is positioned below the level of the collection duct 201, and the air / water shutoff device 216 comprises a control valve 212 (advantageously electrically operated, in particular an electrically operated valve coupled to a flow control device) positioned upstream of the collection orifice 203. The control valve 212 is intended to hydraulically separate the water in the chamber from the water outside the chamber and to shut off the air upstream of the device 216, which also limits the occurrence of hydraulic jerks downstream of the collection orifice 203, thereby allowing the liquid level on the surface of the reactor to remain constant during the feeding step 101 and the collection step 107. The control valve 212 is then closed during the isolation after the feeding step 101 and the collection step 107 and before the aeration step 105 (or the air injection step 110). The control valve is opened during the air release step 123, allowing the clarified fraction to pass through the collection orifice 203. Regarding the shutoff function, the valve 212 is not necessarily a control valve (a simple on-off valve is sufficient).

[0072] Finally, the invention also relates to a recovery duct in which the recovery orifice 203 is positioned substantially at the same level as the recovery duct, as shown in Figure 12. In this case, the recovery means 200 also comprises a control valve 212 positioned upstream of the recovery orifice 203.

[0073] 13 shows a flow chart of the steps of a variant of the method for treating wastewater effluent according to the invention with an SBR 10. The SBR 10 according to this variant of the invention makes it possible to selectively extract the sludge that is least settleable and is located in the mixture 12.

[0074] In this embodiment, the SBR 10 that can be seen in Figure 1 comprises extraction means 19 that are able to extract sludge 23 (represented diagrammatically for ease of understanding) at a variable level between a minimum extraction level 17 and a maximum extraction level 18 (arrow B represents the sludge outlet). By way of non-limiting example, the extraction means 19 may comprise an extractor 191 that comprises at least a first part having at least one opening 191a inside the chamber 11 and a second part 191b through which the sludge can leave said chamber. The extraction means 19 may comprise variation means 192 that are able 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. Advantageously, the extractor 191 comprises a (suction) pump or a gravity valve (not shown) for extracting the sludge. Advantageously, the extractor 191 may comprise a set of tubes arranged at different levels in the chamber 11, each tube having a first end with an opening inside the chamber 11 and a second end connected to the second part 191b of the extractor 191, the varying means 192 comprising a set of valves capable of opening and closing said tubes. In this way, the extraction means makes it possible to extract sludge at one level or at variable levels. For the sake of clarity, the extraction means 19 is shown in the left part of the SBR, while the second part 191b for the sludge outlet is intended to be connected to the extracted sludge 23.

[0075] The means 16 for determining the minimum and maximum levels 17 and 18 of the extraction of sludge 23 from the chamber 11 may comprise measuring means 161 capable of measuring concentrations at different levels of the wastewater-sludge mixture. For example, a sludge bale probe makes it possible to measure the surface of the sludge bed. A SM (suspended solids) probe makes it possible to measure the concentration of the sludge. By placing several probes along the height of the chamber, it is possible to measure the concentration of suspended solids at different levels. These measurements are used to determine the levels 17, 18. The means 16 may comprise selection means 162 capable of selecting a maximum and a minimum sludge concentration value, as well as the amount of sludge to be extracted. This selection may be made by an operator or based on a calculation linked to the age of the sludge. The means 16 may comprise deduction means 163 capable of deducing the minimum extraction level corresponding to the selected maximum concentration value and the maximum extraction level corresponding to the selected minimum concentration value.

[0076] The measuring means 161 may comprise, for example, a measuring probe, which allows the concentration of sludge in the mixture to be measured. As shown, the measuring probe 161 is immersed in the mixture. Depending on the type of probe selected, it may have a fixed or variable immersion depth. Alternatively, as mentioned above, there may be several measuring probes over the height of the chamber. The measuring probe 161 is connected to a selection means 162, which allows verifying whether the measured value corresponds to the sludge to be extracted, and to a deduction means 163, which allows relating the measured value to the corresponding extraction level. These determination means 16 are connected to the sludge extraction means 19, more specifically to a means 192 for varying the extraction level, primarily for selecting the extraction level. The variation means 192 allows varying the level of the opening 191a of the extractor 19, or to extract at a fixed extraction level, for a variable time depending on the evolution of the contents, for example during settling, waiting, feeding / recovery, or anaerobic steps, or non-selectively during the aeration step, depending on the sludge bale measurements.

[0077] As a non-limiting example, the measuring means 161 of the determining means 16 comprises an ultrasonic sensor immersed below the surface of the wastewater and sludge mixture. The ultrasonic sensor is capable of transmitting ultrasonic waves into the mixture (thus acting as a transmitter) and receiving the returning ultrasonic waves (thus acting as a receiver) after traveling a given distance in the wastewater and sludge mixture. The sensor is connected to the selecting means 162 and the deductive means 163.

[0078] 13 shows a flow chart of the steps of a modified method for treating wastewater effluent according to the present invention. In this modification, the treatment method according to the present invention comprises: a step 101 of feeding the SBR 10, during which the amount of effluent 20 to be treated near the bottom of the chamber 11 is introduced into the sludge bed 13, preferably via a distribution network 21 covering the bottom of the chamber 11; a reaction sequence 102 comprising: o at least a first anaerobic step 103, during which the PAO 14 captures carbon-based contaminants and extracts phosphorus-based compounds; Optionally, a second anaerobic denitration step 104, which is performed only if the NOx concentration exceeds a predetermined threshold; a third aeration step 105, allowing the dephosphorization of the effluent by the PAO 14, the aeration being controlled so as to simultaneously carry out (partial or total) nitrification or (partial or total) nitritation, a reaction sequence 102 comprising: a settling step 106, during which the sludge settles at the bottom of the chamber 11 and the contents of the chamber 11 are clarified near its surface 24; a collection step 107 during which the clarified fraction 22 of the contents of the chamber is discharged, said collection step 107 and the supply step 101 being carried out simultaneously so as to keep the liquid level of the contents of the chamber 11 substantially constant during the collection step 107 and the supply step 101; and A step 108 of extracting at least a portion of the light sludge 23 at a predetermined level between the minimum extraction level 17 and the maximum extraction level 18, preferably in the vicinity of the sludge bale 15.

[0079] Typically, the feed step 101 is performed under anaerobic or anoxic conditions. In the latter case, the anoxic step 101 allows for denitrification. The anaerobic step 103 is performed under anerobic conditions, and the aeration step 105 is performed under aerobic conditions. The settling step 106 is performed under anaerobic and then anoxic conditions.

[0080] The second step 104 may be coupled with a step 117 for measuring the NOx concentration in the chamber.

[0081] The treatment method according to the invention may also optionally include a fourth anaerobic denitration, denitritation or deammoniation step 111. More specifically, essentially three variants are considered: according to a first variant, the third step 105 comprises total or partial nitritation and the anaerobic step 111 is denitration (post-denitritation method); according to a second variant, the third step 105 comprises total or partial nitritation and the anaerobic step 111 is denitritation (post-denitritation step); and finally, according to a third variant, the third step 105 comprises partial nitritation and the anaerobic step 111 is deammoniation (method referred to as "ANAMMOX"). The fourth step 111 may be coupled to a step 117bis of measuring the NOx concentration in the chamber.

[0082] The feeding step 101 through the sludge bed allows the sludge to come into contact with the raw water to be treated. A volume of wastewater to be treated 20 is introduced through the sludge bed where the PAO is located. Thus, the particulate and soluble fractions of the introduced volume are made accessible to the bacteria. Thanks to the anaerobic step 103, the PAO captures carbon-based contaminants and extracts phosphate-based compounds. The aeration step 105 allows the PAO to dephosphorylate the chamber contents. The reaction sequence 102 contributes to the development of PAOs that exhibit good settling properties. During the settling step 106, the sludge settles to the bottom of the chamber by gravity. Heavy sludge and PAO settle faster than light sludge, contributing to the sludge bed. Light sludge exhibits lower settling properties and remains suspended longer in the chamber contents above the sludge bed.

[0083] The step 108 of extracting at least a portion of the light sludge allows the least settleable sludge to be extracted in each cycle. However, due to operational constraints, extraction is not necessarily tied to each cycle. For example, extraction may not be performed on weekends. As a result, only sludge with good settling properties remains in the SBR chamber. In addition to treating the contaminants present in the incoming effluent, the sludge present in the chamber is densified by the combined action of the PAO, which produces a denser sludge, and the extraction of the light sludge. As a result, the method of the present invention, referred to as the densified sludge method, is capable of achieving high sludge settling rates regardless of the nature of the sludge present in the SBR chamber.

[0084] During the reaction sequence 102, if the latter includes a second step 104, there can be a step 110 of injecting air into the chamber 11. Also, during this step 110, air can be simultaneously injected into the recovery duct in order to achieve an air cut according to step 120. Injecting air into the chamber before step 104 allows the biomass to be suspended for better mixing with the supernatant liquid rich in nitrogen oxides (nitrates NO3 and NO2), thereby improving the denitrification performance of the feeding step 104 and also the performance of the first anaerobic step 103. It should be noted that this step 110 is optional depending on the NOx concentration measurement if the second optional step 104 is performed.

[0085] The settling step 106 can be preceded by a step 112 of injecting air into the chamber 11. During this step 112, air can also be injected simultaneously into the recovery duct to achieve an air barrier according to step 122. Injecting air into the chamber before settling allows the chamber contents to be homogenized and the sludge to be exposed to oxidized nitrogen species. Furthermore, the injection of air also allows the degassing of dinitrogen.

[0086] Furthermore, the treatment method according to the invention may comprise a step 113 of densifying the sludge using a densifier 30 inside or outside the chamber 11. The densifier 30 may be a suitably sized sieve placed upstream of the sludge extraction means to retain the largest agglomerates and thus improve the selection of the most easily settling particles, i.e., retention within the chamber. Alternatively or additionally, the sludge densification step may involve the addition of ballast material (such as zeolite).

[0087] Advantageously, the treatment method according to the invention is carried out by reducing the NH4 and / or NO2 content of the chamber depending on the level of contamination of the wastewater effluent 20. - and / or NO3 -The method includes a step 114 of feedback controlling the duration of the third aeration step 105 depending on the concentration of . More specifically, it is the degree of contamination of the raw water that is indirectly measured as soon as the contents of the chamber have been aerated at least once.

[0088] This method variant, termed the "densified sludge" treatment variant, makes it possible to achieve high sludge settling rates regardless of the nature of the sludge (granular or not), and advantageously with non-granular sludge. In this variant, sludge densification is achieved in a constant level SBR by a combination of several factors, in particular by a sludge extraction strategy that makes it possible to retain the most easily settled sludge in the reactor by extracting the least easily settled sludge in each cycle, thereby optimizing the production of easily settled microorganisms.

[0089] 14 shows diagrammatically variants A, B, C, and D of the recovery means of the SBR. In variants A and C, the air injector 207 is dedicated to the air / water barrier. In this case, it comprises a non-return valve 2071. In variants B and D, the air injector 207 is not dedicated to the air / water barrier, i.e., the air injector 2071 is also intended to supply air to the chamber. In this case, the recovery means 200 further comprises a shut-off valve 206 to provide the barrier function. The air injector 207 can be connected to the air duct 204 (variant C), but this is not required. In contrast, the air injector 207 must be connected to the recovery duct 101 for the air / water barrier.

[0090] It will be more generally apparent to those skilled in the art that various modifications can be made to the above-described embodiments in light of the teachings just disclosed. In the following claims, the terms used should not be construed as limiting the scope of the claims to the embodiments set forth in this description, but rather as including all equivalents that the claims are intended to cover by their language and that can be anticipated by those skilled in the art based on common general knowledge.

Claims

1. 1. A method for treating wastewater effluent in a sequential batch reactor (SBR), comprising: a chamber (11) capable of containing a mixture of wastewater and sludge (12) with different liquid levels, each liquid level being determined by the concentration and / or density of the sludge; a sludge bed (13) located at the bottom of said chamber (11), and - means (200) for recovering the clarified fraction (22) of the contents of said chamber (11), a recovery duct (201) extending between the inside (25) and the outside (26) of said chamber (11) below the surface (24) of said mixture (12) in said chamber (11), a plurality of channels (202) connecting said chamber (12) and said recovery duct (201); a plurality of collection orifices (203) through which the clarified fraction (22) of the contents of the chamber is intended to be drained; and an air duct (204) connecting said recovery duct (201) to the atmosphere; a collection duct (201) comprising: an exhaust valve (205) in said air duct (204) that can be in an open or closed position; an air / water shut-off device (216) provided in the recovery duct (201), which can be moved from a state called closed to a state called open and vice versa, so as to shut off the air in the recovery duct (201) upstream of the air / water shut-off device (216) and to shut off the water downstream of the shut-off device (216); an air injector (207) connected to said recovery duct (201), intended to supply pressurized and / or compressed air to said recovery duct (201); a means (200) comprising: Equipped with The method comprises: a step (101) of feeding the SBR (10) during which the amount of effluent (20) to be treated is introduced near the bottom of the chamber (11) into the sludge bed (13); a biological treatment reaction sequence (102) comprising at least: a step (105) of aerating the contents of the chamber, during which the level of the surface (24) of the mixture (12) rises; a biological treatment reaction sequence (102) including: a settling step (106) in which sludge is deposited at the bottom of the chamber (11) and the contents of the chamber (11) are clarified near its surface (24); a step (107) of recovering the clarified fraction (22) of the contents of the chamber (11), the recovery step (107) and the supply step (101) being carried out simultaneously, thereby maintaining a constant liquid level of the contents of the chamber (11) during the recovery step (107) and the supply step (101); Including, The method comprises: a step (120) of controlling said recovery means (200), during which: filling the collection duct (201) with air until it is completely empty of the clarified fraction (22) contained in the collection duct (201); the collection duct (201) remains filled with air throughout the reaction sequence (102) until the end of the settling step (106); a controlling step (120); a step (123) of expelling the air contained in the recovery duct (201) by means of the clarified fraction (22) immediately before the feeding step (101) and the recovery step (107); - after the step (101) of feeding the SBR, a step (122) of filling the recovery duct (201) with air by air injection, during the aeration step (105) the exhaust valve (205) is closed and the air / water shut-off device (216) is said to be closed; a step (122bis) of maintaining the collection duct (201) filled with air without air injection, during the aeration step (105) and the settling step (106), the exhaust valve (205) is closed and the air / water shut-off device (216) is said to be closed; A method comprising:

2. 2. The method of claim 1, wherein during the step of expelling air from the collection duct (123), the exhaust valve (205) is in an open position to allow the exhaust of air simultaneously with the entry of the clarified water into the collection duct.

3. 3. The method of claim 2, wherein, during the step (123) of expelling air from the recovery duct (201), after the air has been expelled, the air / water shutoff device (216) assumes a position referred to as open so as to allow the clarified fraction (22) to exit through the recovery orifice (203).

4. 1. An installation for treating wastewater effluent in a sequential batch reactor (SBR), comprising: a chamber (11) capable of containing a mixture of wastewater and sludge (12) with different liquid levels, each liquid level being determined by the concentration and / or density of the sludge; a sludge bed (13) located at the bottom of said chamber (11), - a device for feeding the SBR, in the sludge bed (13), the amount of effluent to be treated near the bottom of the chamber (11); - means (200) for recovering the clarified fraction of the contents (12) of said chamber (11), a recovery duct (201) extending below the surface (24) of the contents (12) of the chamber (11) between the inside (25) and the outside (26) of the chamber (11), a plurality of channels (202) connecting said chamber (11) and said recovery duct (201); a plurality of collection orifices (203) intended to allow the clarified fraction of the contents (12) of the chamber (11) to be drained; and an air duct (204) connecting said recovery duct (201) to the atmosphere; a collection duct (201) comprising: an exhaust valve (205) in said air duct (204) that can be in an open or closed position; an air / water shut-off device (216) in the recovery duct (201), which allows the exhaust valve (205) to shut off the air in the recovery duct (201) or to allow air to pass through; an air injector (207) connected to said recovery duct (201), intended to supply pressurized and / or compressed air to said recovery duct (201); a means (200) comprising: Equipped with The SBR (10) is capable of carrying out a treatment method comprising a biological treatment reaction sequence (102) including at least a step (105) of aerating the contents of the chamber (11), during which the liquid level at the surface (24) of the mixture (12) rises (105); a settling step (106) in which sludge is deposited at the bottom of the chamber (11) and the contents of the chamber (11) are clarified near its surface (24); and a step (107) of recovering the clarified fraction (22) of the contents of the chamber (11), wherein the recovery step (107) and the feeding step (101) are carried out simultaneously, thereby maintaining a constant liquid level of the contents of the chamber (11) during the recovery step (107) and the feeding step (101), The installation also comprises means (210) for controlling the recovery means (200) to fill the recovery duct (201) with air until it is completely emptied of the clarified fraction contained therein, to maintain the recovery duct (201) in an air-filled state during the aeration step (105), to expel the air contained in the recovery duct (201) by the clarified fraction (22) immediately before the feeding step (101) and the recovery step (107), to fill the recovery duct (201) with air by air injection during the aeration step (105), and to maintain the recovery duct (201) in an air-filled state without air injection during the aeration step (105) and the settling step (106).

5. 5. The treatment facility of claim 4, wherein the air / water shutoff device (216) comprises a U-shaped siphon between the air duct (204) and the collection orifice (203).

6. 6. A treatment installation according to claim 4 or 5, wherein the recovery orifice (203) is positioned above the level of the recovery duct (201), the recovery duct (201) comprising an exhaust duct (211).

7. 6. A treatment installation according to claim 4 or 5, wherein the recovery orifice (203) is positioned below the level of the recovery duct (201), the recovery duct (201) comprising an exhaust duct (211).

8. 6. The treatment facility of claim 4 or 5, wherein the air / water shutoff device (216) comprises a control valve (212) positioned at the collection orifice (203).

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