DE2800035A1 - METHOD AND DEVICE FOR WASTE WATER PURIFICATION - Google Patents

Description

The invention relates to a method for wastewater purification in which pure oxygen or oxygen enriched Air supplied to a water surface and by generating a movement of the water surface through it is absorbed by the wastewater.

By using pure oxygen or oxygen-enriched air instead of conventional aeration, a considerable increase in efficiency can be achieved in wastewater treatment according to the activated sludge process, which, however, is associated with considerable costs for the provision of oxygen. There are numerous different methods and systems for acid off be gassing known (cf. "Korrespondenz Abwasser", 1975, pages 278 to 287). In this, the oxygen is corresponds

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ORIGINAL INSPECTED

neither fine-bubble in the bottom area of gas-tight covered or open basins, or the oxygen is introduced fed to a gas space formed by a cover over the sewage and od by agitators, surface aerators. Like. Entered into the wastewater.

In the method with oxygen supply into the gas space under a cover, from which the present invention is based, an overpressure of 30 to 50 mm water column is generally maintained and the excess gas is drawn off again from the cover. Depending on the amount and nature of the wastewater to be treated and thus the oxygen demand, this exhaust gas can still contain considerable proportions of unused oxygen. On the other hand, the optimal biological cleaning conditions cannot be established in the wastewater, since the gaseous metabolic products that occur, in particular COp, cannot or only incompletely escape. It is known that this CO _{2 can be} expelled from the wastewater in a downstream stripping stage, which, however, means additional effort and also does not create optimal conditions, since oxygen is also lost here and the CO remaining in the wastewater until expulsion enables an optimal biological balance to be established impaired. These disadvantages, in particular the loss of oxygen in the exhaust gas, which is difficult to control, are particularly evident in the event of major deviations (from the normal values of the waste water volume and pollution for which the system is designed

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from these normal values down to unnecessarily high oxygen concentrations in the wastewater itself as well as in the exhaust gas or in the case of deviations upwards to an insufficient reduction of the Pollutants come.

The object of the invention is to provide / create a method of the type mentioned at the outset which, with particularly economical use of the oxygen enables an optimal cleaning effect and an adaptability to changing operating conditions.

This object wi i inventively achieved in that one circulates the water in horizontal circuit and exposing it to its cycle of supplying oxygen or oxygen-enriched air is only on one or more sections, while it on the other part of its circuit the free atmosphere suspends.

This has the advantage that the wastewater (which usually always includes a mixture of wastewater and activated sludge is to be understood) repeatedly runs through a reaction section consisting of a gas supply section with oxygen input and an open part on which the carbon dioxide can escape from the water. There can then be a reaction equilibrium with optimal cleaning conditions for upright sharks set a relatively low oxygen concentration in the wastewater. Relatively large amounts can get into the sewage system the amount of oxygen introduced is optimally

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280003S

can be used without excessive, uneconomical oxygen concentrations being formed in the water. Another The particular advantage of the process is its great flexibility and adaptability to changing feed quantities and degrees of pollution of the wastewater to be treated.

Further advantageous features of the method according to the invention emerge from the subclaims. You concern in particular a bubble-free and thus energy-saving circulation of the wastewater, and on the other hand a process management, which are switched depending on the amount and nature of the wastewater to be treated can choose between an oxygen gassing at atmospheric pressure and oxygen gassing at overpressure and / or conventional surface aeration without oxygen gassing. Within each of these operating modes, the oxygen supply or ventilation output can be regulated in such a way that that the oxygen concentration in the wastewater is kept within an economically optimal range, and both the Switching as well as the regulation can be dependent on limit values of the oxygen concentration in the wastewater and / or the oxygen content in the gas space under the cover.

The invention also relates to a device for carrying out the specified method, with a basin, a cover covering the water surface in the basin in a gas-tight manner and a device for supplying pure or enriched oxygen under the cover, with the

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direction according to the invention is characterized in that an annular basin with rolling devices for generating a horizontal Circuit of the wastewater either has a covered by the cover section or to that with the Cover provided basin is connected by means of supply and discharge lines for a partial flow of the circulated wastewater.

Further advantageous features of the device emerge from the subclaims.

Embodiments of the invention are explained in more detail with reference to the drawings.

Fig. 1 shows schematically a plan view of a device for carrying out the invention Method according to one embodiment.

Fig. 2 shows the device of FIG. 1 in section according to the line II-II with an additional scheme

the regulation and control device.

Fig. 3 shows schematically a longitudinal section through a

Gas basin with a bubble-free advance device.

4 show a top view of ring basins with other outlets and 5

guide forms for bubble-free jacking devices.

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6 shows the flow diagram schematically in plan view

a modified embodiment of the method according to the invention.

Fig. 7 shows in longitudinal section a gassing basin with a cover according to another embodiment

form of invention.

FIG. 8 shows a further embodiment in a representation similar to FIG. 3.

The device shown in Fig. 1 and 2 for performing the method consists essentially of an annular basin 1 with middle wall 3 in the manner of the usual activation or oxidation ditches. There are two horizontal axes in the basin Ventilation rotors 5, 7 are arranged, which generate a horizontal circulation in the basin according to the arrows 9. The inlet of the wastewater to be treated is not shown, the drain is located at 11 and is with a height-adjustable weir 13, so that the height of the water level in the basin 1 and thus the immersion depth of the Ventilation rotors 5, 7 can be regulated.

The surface of the water is on part of the route that the wastewater travels when it circulates through the basin 1 gas-tight covered by a cover 15, which with its longitudinal edges on the pool wall or the middle

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Partition 3 is seated and has movable flaps 17 on their transverse edges, which are immersed in the sewage. These Flaps 17 can have sealing lips or the like at their ends. for a gas-tight system on the pool walls. the Flaps 17 can be brought into a position either by hand or by a drive (not shown) which do not immerse them in the water and thus allow air to enter under the cover 15. In this case it will the surface aerator 5 located under the cover 15 perform surface aeration with ambient air, just like the surface aerator 7 located outside the cover. The. ^. appen can also be used as rigid transverse walls be designed in which closable access openings for ambient air are provided by doors or hatches.

Aich a subdivision of the transverse walls into rigid parts and foldable sections are possible.

From a container 19 for pure oxygen leads a line 20 with flow meter 22 and valves 24, 26, 28 in the space under the cover 15 to this pure oxygen feed, which can be entered through the surface aerator 5 in the water. This in the form of gas bubbles Oxygen introduced will partly dissolve, and partly the gas bubbles will re-establish after a certain length of time get to the surface. The cover 15 extends from the surface aerator 5 in the direction of this generated flow (arrow 30) preferably at least so

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far than the length of time the gas bubbles remain in the water. A discharge duct 32 with a shut-off valve 34 extends from the cover 15 to release excess gas into the atmosphere.

A measuring probe arranged in the water for the oxygen content is via a measuring signal amplifier 38 with a after Type of a two-position controller operating threshold level 40 connected, which compares the measured value delivered by the measuring probe with adjustable upper and lower limit values and to a central regulating and control unit 42 different Emits signals depending on whether the oxygen content in the water exceeds the upper limit value or falls below the lower limit value. There is also a measuring probe 44 for the oxygen content or partial pressure which is arranged in the gas space under the cover 15 Via a measuring signal amplifier 46 to a type of two-point controller working threshold stage 48 connected, which the central control and regulating unit different Provides signals, depending on the oxygen content in the gas space under the cover 15 falls below a lower limit value or exceeds an upper limit value. In the gas space under the Cover 15 is also a pressure measuring probe 45 is arranged, which controls the valve 26 so that the oxygen over the line 20 is fed with the valves 24, 28 open at constant pressure.

From the central control and regulation unit 42, control lines go to the valves 24, 28, 34, to a display

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unit 50, which dictates the position of the movable flaps 17, as well as to an adjusting motor 52 for the weir 13.

The operation of this device is described using the following example method.

Example 1. Surface ventilation with ambient air

It is initially assumed that the wastewater to be treated is relatively little polluted, ie has a low chemical and / or biological oxygen demand (COD ₁ - or BOD ₅ ). In this case, the flaps 17 of the

Cover 15 is open (e.g. when a green Lamp on the display unit 50 can be displayed to the operator), and the valve 24 is in the oxygen line closed. The wastewater is cleaned by surface ventilation with ambient air, the measuring probe 36 via the Two-point controller 40, the central control unit 42 and the motor 52 determine the position of the weir 13 and thus the immersion depth the surface aerator 5, 7 controls such that an oxygen content in the waste water e.g. between 1.8 mg / l and 2.2 mg / l is observed.

2. Oxygen gassing without excess pressure

If during surface ventilation with ambient air, even with the greatest immersion depth of the ventilation rotors, the og-

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remains less than e.g. 1.8 mg / 1 in the waste water for 15 minutes, for example, the probe 36, the two-point controller 40 and the control unit 42 controls the display unit 50 so that a second, e.g. indicates that the flaps 17 are to be closed. Of course, the control unit 42 can also use it instead an automatic closing of the flaps 17 can be effected. In addition, the control unit 42 in this case the initiated the following processes:

a) setting the weir 13 by means of the drive 52 to an optimal height for oxygen gassing;

b) opening the oxygen shut-off valve 24;

c) opening the exhaust valve 34;

d) regulating, i.e. opening and closing, the oxygen valve 28 as a function of that from the probe 36 measured oxygen content in the wastewater in such a way that this oxygen content e.g. between 1.8 and 2.2 mg / l is held.

In order to maintain these oxygen concentrations in the waste water, larger or smaller values of the oxygen concentration in the gas space under the cover 15 are required, depending on the degree of pollution of the waste water. If the probe 44 indicates that the necessary oxygen input is already taking place at an oxygen content of 21% or less, then under Ab-

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blocking the oxygen supply and opening the flaps 17 switched back to surface ventilation with ambient air will.

3. Oxygen gassing with positive pressure

If, on the other hand, the probe 44 indicates that to maintain the desired oxygen concentration in the water, an oxygen content or partial pressure in the gas space under the cover 15 is necessary which is higher than, for example, 35%, then so much oxygen would escape through the exhaust pipe 32 that this would happen would be unlikely. Therefore, if the oxygen content in the gas space under the cover 15 is longer than, for example, 15 minutes, e.g. over 35 % , a signal is sent to the control unit 42 via the probe 44 and the two-point controller 48, so that it closes the exhaust valve 34 and the oxygen valve 28 opens continuously (the valve 24 is also open). Oxygen now flows under the cover 15 'until the pressure set on the pressure control valve 26 and measured by the pressure measuring probe 45 is reached and the oxygen supply then stops. All of the supplied oxygen is then absorbed by the wastewater. Even in this operating mode, however, the oxygen content in the waste water is regulated via the probe 36 such that the two-point controller 40 controls the exhaust valve 34 via the control unit 42 in such a way that it is opened when the Op content in the waste water is below 1.8, for example mg / l drops, and closes if it rises above 2.2 mg / l, for example.

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4. Return to oxygen gassing without excess pressure

If the degree of pollution of the wastewater decreases again in such a way that the oxygen gassing with excess pressure If the oxygen concentration in the water is longer than, for example, 15 minutes, e.g. above 2.2 mg / 1, the control unit operates 42 a return to oxygen gassing without excess pressure by the exhaust valve 34 is now constantly open and the oxygen supply valve 28 is opened or in the sense of a two-point control closed in order to bring the oxygen content in the wastewater back between the two limit values (e.g. 1.8 and 2.2 mg / 1) keep.

5. Return to surface ventilation with ambient air

If the pollution of the waste water continues to decrease, as already mentioned above, by switching off the oxygen supply and opening the flaps 17 can be switched back to surface ventilation with ambient air, which then is regulated by raising and lowering the weir 13.

Of course, the invention is not restricted to the details of the exemplary embodiment. In particular the relevant limit values for the control and switching can be set in the wastewater or in the gas space, depending on the circumstances can also be changed, and / or other criteria can also be used, such as the inflow amount of wastewater, the return sludge ratio, or e.g. also external conditions, such as

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Time of year, time of day, temperature, etc., are included in the changeover and control.

In Fig. 3, 60 denotes the bottom of an annular basin, which is partially covered by a cover 15 with an oxygen supply line 20 and gas discharge line 32 is provided. There is no surface aerator or other gas inlet element under the cover 15, but the uptake of the oxygen at the water surface 61 should only be sufficient rapid and turbulent movement of this surface can be achieved. To do this, the water in the ring basin must be included be circulated at a speed that is significantly higher than the usual, only to prevent sludge sedimentation required speeds. The flow velocity is in particular greater than 1 m / sec. and amounts to preferably about 2 m / sec.

To generate the flow and circulation of the wastewater, it is advantageous if the propulsion is carried out by a device which works in a medium that is as free of gas bubbles as possible, as a medium that is free of gas bubbles and uses less energy can be circulated as a vesiculate. For this purpose, a propulsion device operating entirely under water is shown in FIG. 3 shown, which consists of a number of paddle surfaces 63, which extend over substantially the entire width of the Extend basin and are pivotably articulated at one end to a bracket 65, which by means of a not shown

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provided drive is constantly moved up and down according to the double arrow 67. Stops provided on the bracket 65 69 ensure that the paddle surfaces 63 when the holder 65 is moved downwards into the drawn in solid line, adjust upward position 63, while the dashed line during the upward movement of the holder 65 Assume drawn, downward position 63 '. As a result, the paddle surfaces have the effect of and downward movement in the manner of fish fins a completely bubble-free propulsion according to the arrows 71, so that the waste water is passed under the cover at sufficient speed.

To increase the speed in the area under the cover, cross-section narrowing can be used in this arm of the ring trench Built-in components may be provided, e.g. as a (dot-dashed line) elevation 60 'of the floor 60 and / or are designed as projections extending from the side walls. Instead of this or in addition, in the area of the surface Disruptive bodies to be arranged to generate turbulence. For example, the lower edge 62 of the front bulkhead of the Cover 15 as a comb or the like. be formed, or such combs or other disruptive bodies can be found elsewhere the cover may be provided.

Other possibilities, the water with propulsion devices working completely under water essentially bubble-free

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η. 280003S

4 and 5. According to FIG. 4, an annular basin 70 is divided into two straight sections by a partition 72 divided, and at the turn of the basin a rotor 73 is arranged, which consists essentially of a single There is a vertical paddle surface, which essentially completely fills the cross section of the pool and around the vertical Acke 75 is rotatable. The partition 72 extends up to the circumference of the outer edge of the paddle surface 73 described circle 77. As a result, the circulation movement generated by the paddle surface 73 (arrow 79) in a rectilinear movement (arrows 81) converted along the ring basin. Of course, the rotor can also have several paddle surfaces 73. These paddle areas can also be used as be formed vertically extending narrow strips which are arranged at regular intervals on a circumference. In order to improve their effectiveness, the paddle surfaces can be rotated about a vertical longitudinal axis on a support cage attached and movable via steering levers and control cams so that they measure during each revolution in the 180 ° Circular arc section of the trench are aligned radially and in the two remaining quadrants transversely to the longitudinal flow. As a result, they are always effective with their full, and not just with their projected area. It is essential that the Rotor is arranged under water and therefore only as a propulsion organ and does not work as a surface aerator.

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The same effect is achieved according to FIG. 5 with a rotor 83 which is rotatable around the axis 85 from a center mounted and driven paddle surface, which is arranged in a gap in the partition wall 72 of the ring basin 70 is, revolves in the direction of arrow 87 and also generates a circulation flow. One more way to intensify and equalize the circulation flow consists in using the ones close to the rotor To bend or kink the end portion of the partition wall 72 so that the partition wall is approximately tangential to the circumference of the rotor ends, preferably in the opposite direction to the direction of rotation of the rotor, i.e. on its downstream side.

In the device shown schematically in FIG. 6, the sewage-activated sludge mixture is in an annular basin 70 with a partition 72 guided in a horizontal cycle, whereby the propulsion equipment required for this is not presented

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may be of the construction shown in Figures 3 to 5, for example. Of course, other propulsion organs also come, such as surface aerators, propellers or the like., in question. From the annular basin 70 is by means of a line 89 with a pump 91 branched off a partial flow of the wastewater and fed to a gassing basin 93, in which through a line 95 purer Oxygen is supplied, which is introduced into the wastewater, e.g. by means of an agitator 97. If in the gas space of the If a sufficiently high partial pressure of oxygen is maintained in the basin, oxygen concentrations can be found in the wastewater of about 50 mg / l. This wastewater, which is highly saturated with oxygen, becomes the ring basin through line 99 70 fed back in and mixed with the wastewater circulated there. The ratio of the branched Partial flow to the total circulated amount of wastewater is selected so that in the annular basin 70 the for economical cleaning sets the optimum oxygen concentration, which is approx. 2 mg / l. This embodiment of the method has the advantage that completely bubble-free wastewater is circulated in the ring basin 70, which saves energy, and that the Compliance with the desired oxygen concentration in the ring basin is very simple by regulating the branched off via line 89 Waste water, in particular by regulating the flow rate of the pump 91 ^ can be done.

Fig. 7 shows how a gas-tight cover of the water surface is realized with particularly simple and inexpensive means

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$ 280003

extending a sufficiently long distance from a surface aerator. With this arrangement, which largely corresponds to that of FIG. 2, the rigid cover 15 extends only over one relatively short distance above the surface aerator 5, which the oxygen supplied through the line 20 in the Wastewater enters. The wastewater is circulated in the direction of the arrows 16. At the front end, the cover 15 has an in the water-submerging flap 17, while at the downstream end of the cover 15 a flexible film 100, e.g. Rubber mat, is connected, which rests directly on the water surface and the water surface via a Covers route that corresponds to the length of time the gas bubbles in the wastewater calculated by the surface aerator 5. the lateral edges of the film or rubber mat 100 can by means of suitable devices, flaps, strips or the like. into the sewage immerse. The rubber mat 100 can float 102 or just by the underneath the film from the Water escaping and gas accumulating are kept floating. A suspension of the rubber mat 100 at 104 prevents that the mat sinks when the device is at a standstill. At the end of the film or rubber mat 100 is a collecting chamber 106 for collecting the non-dissolved oxygen escaping from the wastewater, which is passed through a return line 108 is connected to the gas space under the cover 15.

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In Fig. 8, similar to Fig. 3, the bottom 60 of an annular basin is shown, in which the sewage through (not shown) propulsion means is circulated according to the arrows 71. The cover 16 with supply line 20 and discharge line 32 is arranged here as a diving bell under the water surface 61, and by the excess pressure of the supplied Gas, a free surface 61 'is maintained below it. Because of the higher pressure, the oxygen is absorbed more intensively or even at a lower flow velocity and turbulence than on surface 61.

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L e r s e i t e

Claims (27)

Patent application back 1.) Process for wastewater purification, in which a pure Oxygen or oxygen-enriched air existing gas supplied to a water surface and generated by a Movement of the water surface through it is absorbed by the wastewater, characterized in that that the wastewater is circulated in a horizontal cycle and it only on one or more sections of his The circuit is exposed to the supply of gas, while the rest of the circuit is exposed to the free atmosphere suspends. 2. The method according to claim 1, characterized in that one of substantially the free The main wastewater cycle exposed to the atmosphere is branched off a partial flow and only this partial flow of the oxygen 909827/0527 28ÜÜÜ3S exposed to fumigation and then added to the main circuit again. 3. The method according to claim 1, characterized in that g e k e η η - ζ indicates that the wastewater is circulated in an annular basin that is only partially covered by a cover and its dwell time in the ring basin is dimensioned in such a way that each partial volume of the sewage passes under the cover several times . 4. The method according to claim 1, characterized in that g e k e η η that one is arranged as a diving bell under the water surface by supplying the gas under pressure Covering under this creates a free surface of the sewage for the uptake of the oxygen. 5. The method according to claim 4, characterized in that the wastewater at a flow rate which is several times the speed required to prevent sludge settling, below the cover can flow through, so that the oxygen uptake is effected only by this flow movement. 6. The method according to claim 5, characterized in that the flow rate is more than 1 m / sec. and preferably about 2 m / sec. amounts to. -Z- 909827/0527 7. The method according to any one of claims 1 Ms 6, characterized in that the wastewater for his Circulation moved by propulsion means working exclusively under water, essentially without the entry of gas bubbles. 8. The method according to claim 3, characterized in that the oxygen uptake on the water surface caused by a surface aerator arranged under the cover. 9. The method according to claim 3, characterized in that the oxygen gassing under the Cover is carried out either at atmospheric pressure or with overpressure and between these two modes of operation as a function switches on the amount and / or nature of the wastewater. 10. The method according to claim 1 or 3, characterized in that the oxygen gassing is temporarily carried out and instead perform surface ventilation with ambient air, with between surface ventilation and the oxygen gassing switches over depending on the amount and / or nature of the wastewater. 11. Wastewater purification device for performing the method according to one of claims 1 to 10, with a - 3 90982 7/0527 28Ü0Q35 Pool, a water surface in the tank gas-tight covering cover and a means for supplying pure or enriched oxygen to the cover, characterized in that an annular tank (1, 70) with circulating means (5, 63, 73, 83) for generating a horizontal Circulation of the wastewater either has a section covered by the cover (15, 16) or is connected to a basin (93) provided with the cover by means of inlet and outlet lines (89, 99) for a partial flow of the circulated wastewater. 12. The device according to claim 11, characterized in that the circulating device is one or more has conveying elements (63, 73, 83) which operate completely under water and are essentially bubble-free. 13. Apparatus according to claim 12, characterized in that a vertical axis is used as the conveyor member Rotor with one or more completely submerged paddle surfaces (73, 83) is provided, wherein a partition wall (72) of the ring basin (70) extends to close to the circumference of the rotor. 14. The device according to claim 12, characterized in that a number of paddle surfaces as a conveyor member (63) are provided, which can be moved vertically or horizontally to and fro in the wastewater and for the back and forth - 4 90982 7/0527 -ί> · 280003b movement with opposite inclination to the direction of flow are adjustable. 15. Device according to one of claims 11 to 14, characterized in that in the area of the cover cross-section narrowing and / or turbulence generating internals (6O ^! ) Or disruptive bodies (62) are provided. 16. Device according to one of claims 11 to 15, characterized in that the cover (15) is designed as a diving bell and one located below the surface of the water due to the pressure of the supplied gas upright maintained free surface (61 ') of the sewage covered. 17. Device according to one of claims 11 to 15, characterized characterized in that under the cover (15) at least one surface aerator (5) for entering the Oxygen is placed in the water. 18. The device according to claim 17, characterized in that the cover (15) extends into one such distance extends from the surface aerator (5) than is the dwell distance of the surface aerator into the water corresponds to registered gas bubbles. 19. Device according to one of claims 11 to 15 and 17, 18, characterized in that the - 5 90982 7/0527 Cover (15) moving parts (17) for releasing air access having under the cover. 20. Device according to one of claims 11 to 15 and 17 to 19, characterized in that the cover (15) or parts (100) thereof are supported in a floating manner on the water surface. 21. The device according to claim 20, characterized in that the cover consists of a rigid part (15) and an adjoining part of a flexible one
Foil formed part (100) is made, which rests floating on the water surface and / or is carried by swimmers (102). 22. Apparatus according to claim 18 or 21, characterized in that the cover (15, 100) in one distance corresponding to the dwell distance of the gas bubbles from the surface aerator (5) has a collecting pocket (106) for gas bubbles escaping from the wastewater. 23. The device according to claim 22, characterized by a return line (108) from the collecting pocket (1O6) into the space under the cover (15). 24. The device according to claim 17, characterized in that the surface aerator (5) at the same time Funding organ for circulating the wastewater in the circuit is. - 6 - 909827/0527 ORIGINAL INSPECTED 25. Device according to one of claims 17 to 23, characterized characterized in that the surface aerator (5) is a horizontal axis ventilation rotor. 26. Device according to one of claims 11 to 25, characterized characterized in that at least one surface aerator (7) is arranged outside the cover (15) is. 27. Device according to one of claims 11 to 26, characterized by sensors (36, 44) for the oxygen content in the wastewater and for the oxygen content in the gas space under the cover (15), and through of the signals the sensor-controlled regulating and / or switching devices (42) for the oxygen supply to the cover (15), for the gas vent from the cover, for the surface aerator (5) and / or for the moving parts (17) of the cover. - 7 90982 7/0527