Aeration Device, Membrane Bioreactor, and Method

Technical Field

The present invention concerns an aeration device for a membrane bioreactor, a membrane bioreactor with such an aeration device, and a method for operating such an aeration device.

Prior Art

Membrane bioreactors are used primarily in industrial and communal wastewater treatment and permit a water purification process with comparatively few method steps, which constitutes a significant simplification compared to typical clarification processes. Such membrane bioreactors comprise, according to in-house knowledge, a purification tank to which wastewater is supplied. A plurality of membrane bodies is immersed in the purification tank, each comprising an interior that is separated in regard to fluid flow from an interior of the purification tank by a filtration membrane in the form of a selective membrane layer. In operation of the membrane bioreactor, the membrane bodies are subjected to a relative vacuum so that the purified wastewater can be removed through the filtration membrane as permeate via a permeate connector provided at the membrane body.

In order to achieve a regular cleaning of surfaces of the membrane body in operation of the membrane bioreactor, below the membrane body an aeration device can be arranged by means of which air bubbles are generated in the purification tank which rise to the top and remove dirt adhering to the surfaces of the membrane bodies which then, for example, sinks to the bottom of the purification tank. However, this is not mandatorily required. Due to the aeration, in particular a cover layer adhering to the membrane body is minimized and the dirt is transported away from the membrane body back into the wastewater.

Such aeration devices can be embodied as so-called siphon aerators that enable a particularly effective cleaning. In this context, supplied air is retained for a while in a siphon of the siphon aerator until a liquid level of the wastewater in the siphon has dropped to a level of a riser pipe immersed in the siphon. As a result, the air escapes suddenly through the riser pipe with a good cleaning effect. Filling with wastewater and the escape of air are continuously performed in alternation. After a certain operating time, a sediment layer can form in the siphon which, in the worst case, leads to blocking of the riser pipe and a limited cleaning performance of the membrane body. For this reason, known siphon aerators must be disassembled and manually cleaned in regular intervals. This is laborious and reduces the availability of the membrane bioreactor.

Summary of the Invention

In view of this background, the present invention has the object to provide an improved aeration device for a membrane bioreactor.

Accordingly, an aeration device for a membrane bioreactor is proposed. The aeration device comprises an air collection chamber closed at least partially at the top for collecting air that is supplied to the aeration device, wherein the air is configured to displace wastewater contained in the air collection chamber out of the aeration device in an aerating state, and with a siphon open at the top which is in fluid connection with the air collection chamber, and with a riser pipe that is immersed in the siphon, wherein, in the aerating state, the supplied air is capable of escaping suddenly from the riser pipe as soon as a liquid level of the wastewater displaced by the air has reached a bottom edge of the riser pipe, and with a cleaning nozzle, to which a cleaning medium can be supplied, for in-situ cleaning of the siphon.

Because the cleaning nozzle is provided, it is possible to clean off sediment deposits from the siphon in operation of the aeration device. Stopping the operation and disassembling the aeration device can thus be dispensed with.

The aeration device can be referred to as an aerator or siphon aerator. The air collection chamber is preferably enclosed by a housing of the aeration device. The air collection chamber can be referred to also as air collection space. The aeration device or the housing is immersed in the wastewater so that the wastewater fills the air collection chamber. As soon as air is supplied to the air collection chamber, it displaces at least partially the wastewater out of the air collection chamber. In particular, the air displaces the wastewater out of the siphon. In this context, the wastewater is forced out via the riser duct from the siphon. However, the wastewater can be discharged also downwardly out of the air collection chamber. The cleaning medium can be air, water, or a water-air mixture. As soon as so much air has been received in the air collecting chamber and in the siphon that the liquid level of the wastewater has reached the bottom edge of the riser pipe, the air suddenly escapes via the riser pipe out of the aeration device and wastewater flows into the siphon. A discontinuous discharge of the air is thus realized by the aeration device. Due to the discontinuous discharge of the air, a surge of air bubbles can be produced which rise along the membrane bodies of the aeration device. In this way, aerating and cleaning of the membrane bodies is achieved.

That the siphon is in “fluid connection” with the air collection chamber means presently in particular that wastewater and/or air can pass from the air collection chamber into the siphon. The siphon is in particular configured to have rotational symmetry in relation to a symmetry axis or center axis. The siphon comprises a conical shape with a spherically shaped bottom. The cleaning nozzle is in particular oriented toward the bottom. The cleaning nozzle can be integrated, for example, into the housing of the aeration device.

In embodiments, the cleaning nozzle is arranged at a top edge of the riser pipe. In particular, the cleaning nozzle is arranged in a region of the top edge of the riser pipe. In relation to a direction of force of gravity, the top edge of the riser pipe is arranged above the bottom edge thereof. The top edge and the bottom edge are provided at the ends of the riser pipe, respectively.

In embodiments, the cleaning nozzle is arranged eccentrically in relation to a center axis of the siphon. In particular, the cleaning nozzle is configured to have rotational symmetry in relation to a further symmetry axis or center axis. The center axis of the cleaning nozzle is however arranged at a distance from the center axis of the siphon. This means that the center axis of the cleaning nozzle and the center axis of the siphon do not coincide with each other. However, the cleaning nozzle can also be arranged centrally or centered.

In embodiments, the cleaning nozzle is arranged such that a cleaning medium jet which is exiting from the cleaning nozzle impacts eccentrically on a bottom of the siphon. As mentioned before, the bottom is in particular spherically shaped. This means that the bottom in sections has a spherical geometry. Because the cleaning medium jet impacts eccentrically on the bottom, a circular flow of the cleaning medium is achieved. This improves the cleaning performance. The cleaning medium jet can impact, for example, at a slant or perpendicularly on the bottom. Presently, “eccentrically” means in particular that the center axis of the cleaning nozzle does not coincide with the center axis of the siphon. The cleaning medium jet can be produced, for example, by means of fresh water. Moreover, the cleaning medium jet can also be generated by means of the permeate removed from the membrane bodies. As mentioned before, the cleaning medium however can also be air or a water-air mixture.

In embodiments, the bottom edge of the riser pipe is arranged at a distance from the bottom of the siphon. The distance can amount to a few millimeters. The bottom edge of the riser pipe preferably does not contact the bottom of the siphon.

In embodiments, the siphon is in fluid connection with the air collection chamber through an opening provided at the top of the siphon. The opening can be of any suitable geometry. Presently, “at the top” means facing away from the bottom of the siphon. Air and wastewater can pass through the opening into the siphon.

In embodiments, the aeration device moreover comprises a housing that encloses the air collection chamber wherein the housing at the top comprises a cover that closes off the housing at the top, and wherein the housing is open at the bottom. Presently, “at the top” and “at the bottom" are to be understood in relation to the direction of force of gravity. This means in particular that the cover is arranged above the bottom opening of the housing. Since the housing is open at the bottom, the wastewater can enter the housing. At the cover, the air collects prior to passing through the opening into the siphon. The housing is preferably a plastic component, in particular an injection-molded plastic component.

In embodiments, the aeration device comprises moreover an air distributor in which the cleaning nozzle is integrated and which is connected to the housing. Preferably, the air distributor is a plastic component, in particular an injection-molded plastic component.

In embodiments, the siphon is part of a siphon cup wherein engagement sections of the siphon cup are extended through the cover of the housing and wherein the engagement sections engage with form fit in counter engagement sections of the air distributor in order to connect the air distributor to the housing. A form-fit connection is produced by the mutual engagement or engagement from behind of at least two connection partners. For example, the engagement sections and the counter engagement sections are locked or snapped to each other. In this way, a simple mounting of the aeration device is possible. Preferably, the siphon cup comprises, in addition to the siphon, two fastening arms which are laterally projecting away from the siphon at which the engagement sections are provided. The siphon cup is preferably also a plastic component, in particular an injection- molded plastic component.

In embodiments, the air distributor comprises a plurality of air outlet channels for uniform distribution of the air, wherein the air outlet channels in particular point radially away from the cleaning nozzle. Preferably, at least three air outlet channels are provided. Particularly preferred, precisely four air outlet channels are provided in order to ensure a uniform air distribution. However, also six air outlet channels can be provided. The air outlet channels extending “radially” away from the cleaning nozzle means presently in particular that the air outlet channels in relation to the center axis of the cleaning nozzle extend away from the latter. The air outlet channels can be arranged concentrically to the cleaning nozzle.

In embodiments, the air outlet channels each comprise air guiding ribs that in particular point radially away from the cleaning nozzle. Preferably, each air outlet channel has two such air guiding ribs correlated therewith. The air outlet channels and the guiding ribs ensure a uniform distribution of the exiting air.

In embodiments, the riser pipe at its top edge is in fluid connection with an air inlet of the air distributor. This means that the air can enter the air inlet of the air distributor across the top edge of the riser pipe and is distributed from there to the air outlet channels.

In embodiments, the air distributor comprises at the top side, which is facing away from the cleaning nozzle, a cleaning medium connector that is in fluid connection with the cleaning nozzle. By means of the cleaning medium connector, the cleaning nozzle can be supplied with the cleaning medium, in particular with fresh water or permeate. For this purpose, for example a supply pressure of 4 bar can be provided.

Moreover, a membrane bioreactor with a plurality of membrane bodies and a plurality of such aeration devices for aerating the membrane bodies is proposed. The membrane bioreactor comprises preferably a purification tank filled with wastewater in which the membrane bodies and the aeration devices are arranged. The membrane bodies are plate-shaped in this context. In relation to the direction of force of gravity, the aeration devices are arranged below the membrane bodies so that air bubbles rising from the aeration devices rise along the membrane bodies to the top and aerate and clean them. In embodiments, the membrane bioreactor comprises moreover an air distribution pipe with air outlet openings for distributing the air to the aeration devices. Preferably, each aeration device has correlated therewith at least one air outlet opening. The air outlet openings point preferably to a bottom of the purification tank. In this way, it is reliably ensured that sediment which has deposited in the air distribution pipe can be discharged again. In this way, an accumulation of the sediment is avoided.

In embodiments, the aeration devices are arranged parallel to each other wherein housings of the aeration devices are connected to each other, in particular with form fit. The number of parallel arranged aeration devices is arbitrary. By means of the aforementioned air distribution pipe, all aeration devices can be supplied with air simultaneously. For connecting the housings of the aeration devices with form fit to each other, the housings can comprise corresponding engagement sections and counter engagement sections. The cleaning nozzles of the aeration devices are supplied with the cleaning medium, in particular fresh water or permeate, via a common cleaning medium supply.

Moreover, a method for operating such an aeration device for a membrane bioreactor is proposed. The method comprises the following steps: a) collecting air supplied to the aeration device in an air collection chamber closed at least partially at the top; b) transferring the aeration device into an aerating state, wherein, in the aerating state, wastewater contained in the air collection chamber is displaced by the air out of the air collection chamber into a siphon open at the top which is in fluid connection with the air collection chamber and in which a riser pipe is immersed, wherein, in the aerating state, the supplied air escapes suddenly from the riser pipe as soon as a liquid level of the wastewater displaced by the air has reached a bottom edge of the riser pipe; and c) in situ cleaning of the siphon by means of a cleaning medium.

The in-situ cleaning is realized preferably by means of the cleaning nozzle. The term “in- situ” cleaning is presently understood as a cleaning action during the operation of the aeration device or of the membrane bioreactor. This means the operation must not be interrupted for cleaning.

Brief Description of the Drawings It is shown in this context in: Fig. 1 a schematic view of an embodiment of a membrane bioreactor;

Fig. 2 a schematic view of an embodiment of an aeration arrangement for the membrane bioreactor according to Fig. 1;

Fig. 3 a schematic section view of an embodiment of an aeration device for the aeration arrangement according to Fig. 2;

Fig. 4 a schematic perspective view of an embodiment of an air distributor for the aeration device according to Fig. 3;

Fig. 5 a further schematic section view of the aeration device according to Fig. 3;

Fig. 6 a schematic view of an embodiment of a membrane bioreactor arrangement with a membrane bioreactor according to Fig. 1; and

Fig. 7 a schematic block diagram of an embodiment of a method for operating the aeration device according to Fig. 3.

In the Figures, same or functionally the same elements are provided with the same reference characters, if nothing to the contrary is indicated.

Embodiment(s) of the Invention

Fig. 1 shows a schematic view of an embodiment of a membrane bioreactor (MBR) 1. Such membrane bioreactors 1 are, for example, used in industrial and communal wastewater treatment and permit a water purification process with comparatively few method steps, which represents a significant simplification compared to typical clarification processes. The membrane bioreactor 1 comprises a clarification tank or purification tank 2 which is supplied with wastewater 3. The purification tank 2 encloses an interior 4.

The membrane bioreactor 1 has correlated therewith a coordinate system with a width direction or x direction x, a vertical direction or y direction y, and a depth direction or z direction z. The directions x, y, z are oriented perpendicularly to each other. A direction of force of gravity g is oriented parallel to and opposite to the y direction y. In the purification tank 2, a plurality of membrane bodies 5 are immersed of which in Fig.

1 only one is provided with a reference character. The membrane bodies 5 can be plate shaped with an edge length of more than 0.75 m. The membrane bodies 5 can have a thickness of approximately 2 mm. The membrane bodies 5 can be configured as flat membranes or as hollow fiber membranes. The membrane bodies 5 can comprise, for example, plastic materials and/or ceramic materials.

The membrane bodies 5 each can comprise an interior 7 which is separated in respect to fluid flow by a filtration membrane 6 from the interior 4 of the purification tank 2. The filtration membrane 6 can comprise, for example, a polymer and comprises a predetermined porosity so that, depending on the pore size, a micro filtration or nano filtration can be achieved.

The membrane bodies 5 are subjected to a relative vacuum in operation of the membrane bioreactor 1 so that the purified wastewater 3 can be removed as permeate 8 through a permeate connector which is provided at the membrane bodies 5. The membrane bodies 5 can be assembled from flat membrane sections wherein the interior 7 of the membrane bodies 5 is supported in particular by suitable spacers against the pressure action of the wastewater 3.

In order to achieve a regular cleaning of surfaces of the membrane bodies 5 in operation of the membrane bioreactor 1 , below the membrane bodies 5 an aeration arrangement 9 is arranged by means of which air bubbles 10 are produced in the purification tank 2 which rise opposite to the direction of force of gravity g to the top and remove dirt adhering to the surfaces of the membrane bodies 5 which then sinks to a bottom 11 of the purification tank 2. As already mentioned before, the deposits do not mandatorily sink to the bottom 11 but are transported by the flow and generated turbulences into the wastewater 3 and away from the membrane body 5.

The aeration arrangement 9 has correlated therewith an air supply 12, for example, in the form of a pipe or hose, through which the aeration arrangement 9 can be supplied with air for forming the air bubbles 10. The aeration arrangement 9 has correlated therewith furthermore a cleaning medium supply 13, for example, in the form of a hose or pipe, by means of which the aeration arrangement 9 can be supplied with a cleaning medium. The cleaning medium can be fresh water or permeate 8. However, the cleaning medium can also be air or a water-air mixture. The aeration arrangement 9 comprises a plurality of aeration devices 14. The aeration devices 14 are of a cuboid shape, respectively. The aeration devices 14 are arranged above the bottom 11 so that a gap 15 is provided between the bottom 11 and the aeration arrangement 9. The aeration devices 14 are arranged adjacent to each other. In this context, a plurality of, for example, four, aeration devices 14 can be connected in a row or in series. This means that the aeration devices 14, viewed along the x direction x, are arranged one after another.

A plurality of such aeration arrangements 9, each comprising a plurality of aeration devices 14, are positioned, viewed along the z direction z, adjacent to each other so that the aeration devices 14 of all aeration arrangements 9 are placed matrix-like or pattern like below the membrane bodies 5. In this context, “matrix-like” or “pattern-like” means that the aeration devices 14 are arranged in the manner of rows and columns.

Fig. 2 shows a schematic plan view of an aeration arrangement 9 as mentioned before with four aeration devices 14. Each aeration device 14 comprises a cuboid housing 16. The housing 16 can be a plastic component, in particular an injection-molded plastic component. For example, polypropylene (PP), polyethylene (PE), polyoxymethylene (POM), acrylonitrile butadiene styrene (ABS) or other arbitrary plastic materials can be used as suitable plastic materials.

The housing 16 of the aeration device 14, which in the orientation of Fig. 2 is arranged farthest downwardly, comprises an air connector 17 to which the air supply 12 is connected. The air connector 17 can be a component that is separate from the housing 16 that is, for example, locked or snapped to the housing 16. The air connector 17 can however also be of a one-piece, in particular monolithic one-part, configuration together with the housing 16. In this context, “one-piece” or “one-part” means that the housing 16 and the air connector 17 form a common component and are not assembled of different components. Presently, “monolithic one-part” means that the housing 16 and the air connector 17 are manufactured continuously of the same material.

The housings 16 of neighboring aeration devices 14 are connected to each other with form fit. A form fit connection is produced by the mutual engagement or engagement from behind of at least two connecting partners. Presently, each housing 16 comprises two rail-shaped engagement sections 18, 19 which are provided at the ends at the housing 16 as well as two counter engagement sections 20, 21 which are facing away from the engagement sections 18, 19. The engagement sections 18, 19 and the counter engagement sections 20, 21 can be inserted into each other along the y direction y so that neighboring housings 16 are connected to each other.

Fig. 3 shows a schematic section view of an embodiment of an aeration device 14 as mentioned before. The aeration device 14 is configured as a so-called siphon aerator that enables a particularly effective cleaning and aerating of the membrane bodies 5. The housing 16 of the aeration device 14 encloses an air collection space or air collection chamber 22 that is filled with wastewater 3. In the orientation of Fig. 3 in downward direction, the housing 16 is open so that the wastewater 3 can flow from below into the housing 16.

At the housing 16, the air connector 17 is integrally formed that receives an air distribution pipe 23. The air distribution pipe 23 extends completely through the housing 16 and serves for distributing air 24 that is supplied to the air connector 17 via the air supply 12 to all aeration devices 14 of the aeration arrangement 9. The air 24 is illustrated in Fig. 3 by means of thick arrows. The air distribution pipe 23 comprises at the bottom, i.e., facing the bottom 11 , air outlet openings 25 from which the air 24 can exit from the air distribution pipe 23 and can collect in the air collection chamber 22 of the housing 16. The air outlet openings 25 are arranged at the bottom so that entrained sediment can be simply discharged again by the flow of the air 24. In case of standstill of the aeration device 14, the air distribution pipe 23 can fill completely with wastewater 3.

The aeration device 14 comprises a siphon cup 26 which is arranged within the air collecting chamber 22. The siphon cup 26 is a plastic component, in particular an injection-molded plastic component. The siphon cup 26 comprises a truncated cone- shaped siphon 27 with a bottom 28 which in sections is spherically shaped and is facing the air distribution pipe 23. The siphon 27 is substantially configured to have rotational symmetry in relation to a symmetry axis or center axis 29. The siphon 27 in the orientation of Fig. 3 is open in upward direction. The siphon 27 comprises an opening 30 by means of which an interior 31 of the siphon 27 is in fluid connection with the air collecting chamber 22. The siphon 27 is filled with wastewater 3.

The siphon cup 26 comprises, in addition to the siphon 27, two fastening arms 32, 33 by means of which the siphon cup 26 is fastened to the cover 34 of the housing 16. The fastening arms 32, 33 extend laterally away from the siphon cup 26. The fastening arms 32, 33 can be arranged displaced by 180° relative to each other. Each fastening arm 32, 33 comprises an engagement section 35, 36. The engagement sections are extended through corresponding bores through the cover 34.

At the cover 34, a riser pipe 37 is integrally formed that is open at both sides. The riser pipe 37 projects into the siphon 27 and ends with a bottom edge 38 in front of the bottom 28. The riser pipe 37 is of a one-piece configuration, in particular of a monolithic one-part configuration, together with the cover 34. The riser pipe 37 comprises a top edge 39 provided at the cover 34. At the top edge 39, the riser pipe 37 penetrates the cover 34. The riser pipe 37 is conical and tapers, beginning at the cover 34, in the direction toward the bottom 28. The riser pipe 37 is substantially configured to have rotational symmetry in relation to a symmetry axis or center axis 40. The center axis 40 does not coincide with the center axis 29. Instead, the center axis 29, viewed along the x direction x, is displaced relative to the center axis 40.

The aeration device 14 comprises moreover an air distributor 41 which is illustrated in Fig. 4 in a schematic perspective view. The air distributor 41 is a plastic component, in particular an injection-molded plastic component. The air distributor 41 comprises a base section 42 at which centrally and at the front a cleaning medium connector 43 is integrally formed. The cleaning medium supply 13 is connected to the cleaning medium connector 43. The cleaning medium connector 43 is configured to have rotational symmetry in relation to a symmetry axis or center axis 44 which coincides with the center axis 40 of the riser pipe 37.

To the rear, this means facing away from the cleaning medium connector 43, the air distributor 41 comprises a cleaning nozzle 45 integrally formed at the base section 42 which is configured to have rotational symmetry in relation to the center axis 44. The cleaning nozzle 45 is thus placed centrally in the riser pipe 37. The cleaning nozzle 45 is in fluid connection with the cleaning medium connector 43 so that the cleaning medium, in particular fresh water or permeate 8, can be supplied to the cleaning nozzle 45 by means of the cleaning medium connector 43. The cleaning nozzle 45 can comprise, for example, a nozzle diameter of 1 to 2 mm.

The air distributor 41 comprises two fastening arms 46, 47 which extend laterally away from the base section 42. The fastening arms 46, 47 are positioned displaced by 180° relative to each other. Each fastening arm 46, 47 comprises a counter engagement section 48, 49. The engagement sections 35, 36 of the siphon cup 26 can engage with form fit in the counter engagement sections 48, 49 so that the housing 16, the siphon cup 26, and the air distributor 41 can be connected with form fit to each other. For example, the engagement sections 35, 36 lock at or snap into the counter engagement sections 48, 49.

The air distributor 41 comprises a plurality of air outlet channels 50 to 55. For example, six air outlet channels 50 to 55 are provided. Each air outlet channel 50 to 55 comprises air guiding ribs 56, 57 wherein in Fig. 4 only the air guiding ribs 56, 57 of the air outlet channel 51 are provided with reference characters. The air distributor 41 comprises an air inlet 58 which is in fluid connection with the riser pipe 37.

The functionality of the aeration device 14 will be explained in the following. By means of the air distribution pipe 23 and the air outlet opening 25, air 24 is blown into the air collecting chamber 22 of the housing 16 filled with wastewater 3. The air 24 rises in form of air bubbles 59 to the top in the direction of the cover 34. The air 24 collects at the cover 34 and passes through the opening 30 into the interior 31 of the siphon 27. Here, the air 24 displaces the wastewater 3 out of the siphon 27 in the riser pipe 37.

The supplied air 24 is retained in the siphon 27 for a while until a liquid level of the wastewater 3 in the siphon 27 has dropped to the level of the bottom edge 38 of the riser pipe 37, whereupon the air 24 suddenly with good cleaning effect escapes through the riser pipe 37 and rises as air bubbles 10 along the membrane bodies 5 to the top in order to aerate and clean the latter. In order to aerate a plurality of membrane bodies 5 as uniformly as possible, the air distributor 41 comprises, as mentioned before, a plurality of air outlet channels 50 to 55 which are designed to correspond with an arrangement and dimensions of the membrane bodies 5.

Fig. 5 shows a further schematic section view of the aeration device 14. The air 24 which is flowing into the air collecting chamber 22 is not illustrated in Fig. 5. The cleaning process of the siphon 27 explained in the following can however also be performed during inflow of the air 24. Alternatively, the cleaning process can also be performed when the air supply 12 is switched off.

As can be seen in Fig. 5, after a certain operating duration of the aeration device 14, a sediment layer 60 can form in the siphon 27 which, in the worst case, namely when the sediment layer 60 reaches the bottom edge 38 of the riser pipe 37, can lead to blocking of the riser pipe 37. For this reason, known systems with siphon aerators must be disassembled and manually cleaned in regular intervals. This is laborious and reduces the availability of the device.

By providing the cleaning nozzle 45, it is possible to remove the sediment layer 60 in an automatic fashion. For this purpose, the cleaning nozzle 45 is loaded with cleaning medium, in particular with fresh water or permeate 8, that is supplied to the cleaning nozzle 45, for example, at a pressure of 4 bar, through the cleaning medium supply 13. In this way, a sharp cleaning medium jet 61 is produced which impacts off-center on the bottom 28 of the siphon 27. The sediment layer 60 can thus be removed in-situ in the siphon 27, in operation and without the aeration device 14 having to be disassembled. Since the cleaning nozzle 45 is arranged off-center in relation to the siphon 27, the cleaning medium jet 61 also impacts off-center on the spherically shaped bottom 28 of the siphon 27 whereby a circular flow is produced. This improves the cleaning action.

Fig. 6 shows a schematic view of an embodiment of a membrane bioreactor arrangement

62 with a membrane bioreactor 1 as explained before. In addition to the membrane bioreactor 1, the membrane bioreactor arrangement 62 comprises an air supply device

63 that supplies the aeration arrangement 9 by means of air supply 12 with air 24. The air supply device 63 can be a blower, a compressor or a compressed air bottle. Downstream of the air supply device 63, a valve 64 is provided by means of which the supply of air to the aeration arrangement 9 can be controlled.

By means of a permeate conduit 65, the permeate 8 can be removed from the membrane bodies 5 and supplied to a venting tank 66. Upstream of the venting tank 66, a valve 67 is provided in order to be able to interrupt removal of the permeate 8. A venting valve 68 for venting the venting tank 66 is provided at the venting tank 66.

By means of a further permeate conduit 69 and a permeate pump 70, the permeate 8 is pumped out of the venting tank 66 into a permeate tank 71. From the permeate tank 71, the permeate 8 can be removed via an outlet 72. Optionally, the permeate 8 can also be used for cleaning the aeration devices 14 of the aeration arrangement 9. For this purpose, the cleaning medium, presently permeate 8, is pumped by means of a cleaning pump 73 into the cleaning medium supply 13. Alternatively, also fresh water, air or a water-air mixture can be used. The cleaning medium supply 13 comprises a cleaning valve 74 that can be opened for cleaning the aeration devices 14 by means of cleaning medium, presently the permeate 8.

Fig. 7 shows a schematic block diagram of an embodiment of a method for operating the aeration device 14. In a step S1, air 24 which is supplied from the aeration device 14 is collected in the air collection chamber 22 that is at least partially closed at the top.

In a step S2, the aeration device 14 is transferred into an aerating state wherein, in the aerating state, the wastewater 3 contained in the air collection chamber 22 is displaced by the air 24 out of the air collection chamber 22 into the siphon 27 open at the top, which is in fluid connection with the air collection chamber 22 and in which the riser pipe 37 is immersed, wherein, in the aerating state, the supplied air 24 escapes suddenly from the riser pipe 37 as soon as a liquid level of the wastewater 3 displaced by the air 24 has reached the bottom edge 38 of the riser pipe 37.

In a step S3, an in-situ cleaning action S3 of the siphon 27 by means of the cleaning medium is performed. In this context, “in-situ” means during the operation of the aeration device 14. The cleaning medium is injected in this context by means of the cleaning nozzle 45 into the siphon 27.

Employed Reference Characters:

1 membrane bioreactor

2 purification tank

3 wastewater

4 interior

5 membrane body

6 filtration membrane

7 interior

8 permeate

9 aeration arrangement

10 air bubble

11 bottom

12 air supply

13 cleaning medium supply

14 aeration device

15 gap

16 housing

17 air connector

18 engagement section

19 engagement section

20 counter engagement section

21 counter engagement section

22 air collection chamber

23 air distribution pipe

24 air

25 air outlet opening

26 siphon cup

27 siphon

28 bottom

29 center axis

30 opening

31 interior

32 fastening arm

33 fastening arm

34 cover 35 engagement section

36 engagement section

37 riser pipe

38 bottom edge

39 top edge

40 center axis

41 air distributor

42 base section

43 cleaning medium connector

44 center axis

45 cleaning nozzle

46 fastening arm

47 fastening arm

48 counter engagement section

49 counter engagement section

50 air outlet channel

51 air outlet channel

52 air outlet channel

53 air outlet channel

54 air outlet channel

55 air outlet channel

56 air guiding rib

57 air guiding rib

58 air inlet

59 air bubble

60 sediment layer

61 cleaning medium jet

62 membrane bioreactor arrangement

63 air supply device

64 valve

65 permeate conduit

66 venting tank

67 valve

68 venting valve

69 permeate conduit

70 permeate pump 71 permeate tank

72 outlet

73 cleaning pump

74 cleaning valve g direction of force of gravity

51 step

52 step

53 step x x direction y y direction z z direction