Clearwater exhaust device (decanter) for a wastewater treatment plant

Description

[0001] The invention relates to a clear water extraction device (decanter) for a sewage treatment plant according to the preamble of claim 1.

[0002] In biological wastewater treatment, pollutants contained in the wastewater are removed with the help of microorganisms, known as activated sludge, to obtain largely unpolluted clear water. The separation of the activated sludge from the clear water typically occurs through sedimentation, either in so-called "secondary clarifiers" or in mixing reactors. In these reactors, after the inlet is shut off and the mixing and aeration systems are switched off, the activated sludge settles at the bottom of the tank below the clear water.

[0003] After a sedimentation period of, for example, about one hour, the clear water zone forms above the settled activated sludge, whereby the clear water can be extracted from the settling tank or mixing reactor - among other technologies - by means of a clear water extraction device or a clear water extraction system, which is also referred to as a clear water decanter or simply decanter.

[0004] Such decanters typically feature a horizontally oriented inlet pipe as their central component. A T-shaped outlet pipe connects to this inlet pipe, which is pivotally mounted around an underwater swivel joint within the settling tank or mixing reactor. A winch or similar mechanism allows the inlet pipe to be moved vertically between a parking position, which it occupies between mixing and sedimentation processes, and at least one extraction position, where the clarified water can be drawn off. Typically, a controlled winch or similar mechanism is used to follow the falling water level resulting from the clear water extraction, thus lowering the inlet pipe progressively as the clear water level drops.For the purpose of extracting or drawing off the clear water, one or more inlet openings are provided within the drain pipe, which penetrate the inlet pipe and through which clear water can be drawn off from the settling tank and discharged into the drain pipe.

[0005] A problem with the operation of such lowering clear water decanters is that, after sedimentation is complete, so-called "floating sludge" forms on the surface or horizon of the clear water. This sludge consists, for example, of a mixture of activated sludge, fats, and light solids. This "floating sludge" must not, under any circumstances, enter the inlet pipe and subsequently the outlet pipe via the inlet openings, as this would lead to undesirable (or even unacceptable) contamination of the discharged clear water. For this reason, it is already state of the art to use a cover element in the form of a baffle or similar device, which serves to displace the "floating sludge" when it enters the water horizon. This cover element or baffle is fixed to the inlet pipe at a distance from and overlapping with the respective inlet opening.However, especially with a considerable layer thickness of "floating sludge," unwanted ingress of "floating sludge" into the extracted clear water can occur through the gap or space between the cover element / valve and the inlet pipe. DE 10 2011 087966 and DE 10 2006 036591 are examples of such systems.

[0006] The object of the present invention is therefore to provide a decanter of the type mentioned above, by means of which contamination of the clear water can be avoided particularly effectively. This object is achieved according to the invention by a decanter with the features of claim 1. Advantageous embodiments with expedient further developments of the invention are the subject of the dependent claims.

[0007] To create a clear water decanter that prevents "floating sludge" accumulating on the water surface above the clear water from entering the decanter's inlet pipe and subsequently the outlet via the at least one inlet opening when the decanter is inserted into the settling tank or mixing reactor, a displacement device is provided according to the invention. This device allows the cover element to be moved between a closed position and an inlet position. The displacement device comprises at least one buoyancy element, which, as a result of the buoyancy element being immersed, for example, in the water horizon of the clear water and thus below the floating sludge layer, moves the cover element into its inlet position.The displacement device is designed, for example, geometrically and in terms of weight, such that the cover element is in the closed position due to gravity before being immersed in the settling tank. When the buoyancy element then reaches the water level or the surface of the clear water, it is displaced relative to the inlet pipe by the buoyancy force as the decanter and inlet pipe continue to descend. This displacement, facilitated by the displacement device, moves the cover element from the gravity-induced closed position to the inlet position, in which the clear water can be drawn off through the inlet openings. At the moment the cover element is moved into the inlet position, the inlet pipe and its inlet openings are already below the floating sludge in the clear water layer.

[0008] In other words, the displacement device, and in particular its buoyancy element, ensures that when the inlet pipe is immersed in the water horizon of the "floating sludge", the cover element is in its closed position, closing the respective inlet openings of the inlet pipe, in order to prevent "floating sludge" from entering the inlet pipe.During the further lowering movement, the cover element is then moved into the inflow position by means of the buoyancy force when the buoyancy element hits the horizon or the water surface, at a time when the inflow openings of the inlet pipe are already below the surface of the clear water layer. The particular advantage of the buoyancy element is that a displacement movement of the displacement device is initiated solely due to physical forces, namely as a result of the corresponding water displacement, by means of which the cover element is forcibly moved into its open position.

[0009] Alternatively, in an unclaimed but nevertheless part of the invention, it is also conceivable to move the cover element from the inlet position to the closed position – and back – by means of an actuator or similar drive. This movement could, for example, be effected by a proximity sensor when the inlet pipe encounters the floating sludge. However, this embodiment is technically more complex.

[0010] The displacement device according to the invention and claimed has the significant advantage that it is actuated solely by the buoyancy force of the buoyancy element upon immersion in the water horizon or "floating sludge," thereby displacing the cover element. In the present case, the cover element is initially held in the closed position by the gravity of the displacement device's components before immersion in the settling tank. In this position, the at least one inlet opening is protected from the inflow of "floating sludge." Then, upon immersion of the inlet pipe or the displacement device with the buoyancy element into the clear water layer, the cover element is moved into the open position.The components of the displacement device and the inlet pipe are geometrically coordinated such that the cover element is only moved into its inflow position, and consequently opens at least one inflow opening, once the outlet pipe and its inflow opening have penetrated the floating sludge and reached the clear water layer in the settling tank. Thus, it is possible for the inlet pipe with the cover element closed to penetrate the floating sludge, and only subsequently—due to the geometric design of the displacement device with the buoyancy element relative to the inlet pipe—does the cover element move into the inflow position after penetrating the floating sludge and reaching the clear water layer. The buoyancy element, which in the meantime reaches the floating sludge, then initiates an adjustment of the cover element due to the buoyancy force acting upon it.

[0011] In a further embodiment of the invention, it has proven advantageous if the at least one cover element is arranged below the at least one inlet opening of the inlet pipe. An arrangement of the cover element on the underside relative to the inlet pipe has the particular advantage that the inlet openings provided in the inlet pipe can also be arranged on the underside of the inlet pipe. This, in turn, has the advantage that, on the one hand, clear water can be drawn off down to near the sediment layer, while on the other hand, the cover element ensures that no sediment or activated sludge enters the inlet pipe.

[0012] Furthermore, it has proven advantageous if the at least one cover element, in its inlet position, forms an inlet channel that runs at least substantially horizontally with the underside of the inlet pipe in its outlet position. This horizontal inlet channel, or the cover element positioned on the underside of the at least one inlet opening, ensures that clear water can only reach the respective inlet opening quasi-horizontally, and not vertically, since the respective cover element is located below and overlapping the inlet opening in its inlet position. This has the significant advantage that, in particular, clear water cannot be drawn in vertically below the inlet openings due to a suction effect, but rather that the cover element is positioned directly below the respective inlet opening.Therefore, the clear water must flow in via the horizontally running inlet channel, which in turn prevents any corresponding vortices or similar suction effects below the respective inlet opening from leading to the intake of sediments or activated sludge.

[0013] In a further embodiment of the invention, the at least one cover element, in its closed position, seals the at least one inlet opening at least substantially tightly. This tightness can be achieved, for example, by adapting the geometric shape of the cover element to that of the outer contour of the drain pipe. A corresponding flat contact of the cover element with the inlet pipe in its closed position thus already provides sufficient sealing or closure of the respective inlet opening for the clear water, in order to prevent, for example, the ingress of floating sludge. In an alternative embodiment, a corresponding seal can also be provided between the cover element and the inlet pipe, which surrounds the respective inlet opening on its outer circumference.

[0014] In a further advantageous embodiment of the invention, the displacement device comprises lever arms mounted on an end face of the inlet pipe, on which at least one buoyancy element and at least one cover element are arranged. This creates a particularly simple and reliable displacement device, whereby forces acting on the buoyancy element during entry into and exit from the settling tank reliably and safely result in a corresponding displacement of the cover element between the closed position and the inlet position.On the other hand, the positioning of the buoyancy body and the lever arms relative to the inlet pipe can be used to geometrically determine in a simple way when the cover element should be moved from its closed position to its inflow position, for example when the inlet pipe with the buoyancy body is immersed in the settling tank.

[0015] In this context, it has proven further advantageous if the lever arms each have a cam guide for an associated guide element located on the end face of the inlet pipe. Such a cam guide, in conjunction with the guide element located on the side of the inlet pipe, allows for a simple and reliable movement of the cover element between the closed and open positions. Furthermore, the respective ends of the cam guide can also serve as end stops, defining the respective closed and open positions of the cover element.

[0016] It has also proven advantageous in this context if the lever arms are arranged on the inlet pipe via an adjustable pivot bearing, allowing the relative position and tightness of the cover element in its closed position relative to the inlet pipe to be adjusted. By making the bearing point of the respective lever arms adjustable, corresponding adjustments to the closed position and the inlet position of the cover element can thus be easily achieved.

[0017] In a further embodiment of the invention, at least one buoyancy element is designed as a hollow body filled with a gas, particularly air. This allows for a particularly simple design of the buoyancy element. Alternatively, however, other buoyancy bodies, for example made of a plastic foam, another plastic material, or the like, would also be conceivable.

[0018] In a further advantageous embodiment of the invention, the cover element and / or the components of the displacement device are made of a steel material, in particular a stainless steel material or a coated steel material, and / or of a plastic or a hybrid construction of these materials. By selecting the appropriately described materials for the respective components of the displacement device and the cover element, it is ensured that, even during years of operation, no corrosion, abrasion, or the like occurs as a result of the permanent displacement of the buoyancy element or the cover element between its closed position and its inflow position between the respective adjacent components. Finally, it has proven advantageous if the inlet pipe is permeated with a plurality of inflow openings arranged in a row.This results in a particularly effective clear water drainage.

[0019] Further features of the invention will become apparent from the claims, the figures, and the description of the figures. The features and combinations of features mentioned above in the description, as well as the features and combinations of features mentioned below in the description of the figures and / or shown in the figures alone, are not only usable in the combinations specified, but also in other combinations or on their own.

[0020] The invention will now be explained in more detail with reference to a preferred embodiment and the drawings. The drawings show: Figs. 1a and 1b each show a perspective view of a decanter according to the invention for a wastewater treatment plant, comprising an inlet pipe and a T-shaped outlet pipe arranged thereto, at the end of which the decanter is pivotally mounted on a basin edge of the treatment basin and a displacement device associated with the inlet pipe, which includes a buoyancy element pivotally mounted via respective lever arms mounted on the end face of the inlet pipe and by means of which, for closing at least one inlet opening passing through the underside of the inlet pipe, between a Fig. 1a shown closing position and one in Fig. 1b The inlet opening shown is relocatable when the decanter is immersed in the settling tank and the buoyancy element and, by means of this, the cover element are relocated; Fig. 2a, 2b respective partial perspective views of the relocation device mounted on the inlet pipe with the respective lever arms arranged on the end face of the inlet pipe, on which, on the one hand, the buoyancy element and, on the other hand, the cover element are provided for closing or opening the at least one inlet opening passing through the inlet pipe, wherein Fig. 2a in the closed position of the cover element, in which it closes the respective inlet openings located on the underside of the inlet pipe, and Fig. 2b The displacement device is shown along respective cam guides arranged in the lever arm in the form of arcuate elongated slots, which are displaced accordingly during immersion due to the buoyancy force acting by the buoyancy element, so that the cover element is in its inlet position; Fig. 3a, 3b respective partial perspective views of the inlet tube of the decanter with the displacement device, where also here Fig. 3a the relocation device with the cover element in its closed position and Fig. 3b Fig. 4 shows the inlet pipe with the displacement device and the cover element in its inlet position; Fig. 4 shows a perspective view of the decanter according to the invention, mounted on the edge of a settling tank filled with wastewater, wherein the inlet pipe and the associated displacement device are initially located above a "sludge layer" of the wastewater, and the cover element, due to the gravity of the displacement device, is in its closed position, closing the respective inlet openings on the underside of the inlet pipe; Fig. 5 shows another perspective view of the decanter analogous to Fig. 4 In the further course of the lowering movement, it can be seen that the inlet pipe has already penetrated the "floating sludge zone" on the surface of a clear water layer, or rather, has entered the clear water zone, and that the buoyancy element of the lowering movement's displacement device is resting on the surface of the clear water at this point, due to the continuing force of gravity on the displacement device, the cover element is still in its closed position; and Fig. 6 shows another perspective view of the decanter during the further lowering movement, analogous to the Fig. 4 und 5 , whereby it can be seen that, as a result of the buoyancy force acting on the buoyancy element by the water horizon of the clear water, the cover element has been moved into the inlet position by means of the displacement device, in which it releases a plurality of inlet openings visible on the underside of the inlet pipe, so that clear water can enter the inlet pipe.

[0021] In the Fig. 1a und 1b In each perspective view, a decanter 10 for a wastewater treatment plant is visible. This decanter 10 is – as can be seen in conjunction with the Fig. 4, 5 and 6 The respective perspective views also show the arrangement within a settling tank 12, in particular a mixing reactor of the wastewater treatment plant. More precisely, the decanter 10 is pivotably fixed to a basin edge 16 of the settling tank 12 by means of a bearing bracket 14.

[0022] The decanter 10 is essentially T-shaped and comprises an inlet pipe 18, through which clear water can be drawn off from the settling tank or mixing reactor 12 and discharged into an outlet pipe 20, which is connected to the centrally tapered inlet pipe 18 via flange connections 22, as described in more detail below. The clear water can then be fed into the further process of biological wastewater treatment via the outlet pipe 20. It is also considered to be within the scope of the invention that several outlet pipes 20 can be provided. The inlet pipe 18 is supported by the outlet pipe 20 and pivotally mounted in the area of ​​the bearing bracket 14.The decanter 10 can, for example, be raised or lowered at a point of application far from the bearing console 14 by means of a winch or similar lifting and lowering device, which is not shown here, as can be seen in conjunction with the . Fig. 4, 5 and 6 This will be explained in more detail below. Lowering or raising the decanter 10 is therefore achieved by shifting it about its pivot axis in the area of ​​the bearing bracket 14.

[0023] As seen in the overall view of the Fig. 1a und 1b with the further Fig. 2a bis 3b , which each show a partial and enlarged perspective view of the decanter 10 in the area of ​​the inlet pipe 18, a displacement device 24 is also provided on the inlet pipe 18, by means of which a cover element 26 in the form of a trough or the like, which will be explained in more detail below, is moved between a in the respective Fig. 1a , 2a and 3ashown closing position into a respective one, into the Fig. 1b , 2b and 3b The inlet position shown can be moved, in which the cover element 26 has a plurality of in Fig. 6 recognizable inlet openings 28, which penetrate the inlet pipe 18 and through which clear water from the settling tank can enter the inlet pipe 18 and subsequently be extracted via the outlet pipe 20.

[0024] The displacement device 24 has lever arms 32 mounted on a corresponding end face 30 of the inlet pipe 18, on which a buoyancy body 34 and a cover element 26 are held. These lever arms 32 are, for example, designed as flat plate elements or the like. Other designs would, of course, also be conceivable.

[0025] The lever arms 32 are mounted on the corresponding end face 36 of the inlet pipe 18 in the area of ​​a bearing point formed by a screw 38, about which the two lever arms 32 can pivot relative to the inlet pipe 18 and the respective end face 36, respectively. Each of the two lever arms 32 also has a cam guide 40 in the form of an arc-shaped elongated slot, which has the screw 38 at its center, and into which an associated guide element 42, projecting from the end face 36 of the inlet pipe 18, engages. The pivoting movement of the two lever arms 32 about the pivot axis formed by the screws 38 is thus limited by the cam guide 40 and by respective end stops 44, 46.

[0026] The buoyancy element 34 is designed as a tubular or hollow body, adapted to the length of the inlet pipe 18. The buoyancy element 34 is filled with a gas, in particular air. Likewise, any other buoyancy element made of a different material and in a different shape would also be conceivable. Alternatives are familiar to those skilled in the art. Furthermore, the buoyancy element 34 is firmly connected to the respective lever arm 32 by means of two screws 48.

[0027] On the side opposite the screws 38 forming the pivot axis of the lever arms 32, the cover element 26 is attached to the underside of the lever arms 32. The cover element 26 can be attached to the respective lever arm 32 by means of a screw 50 and, if necessary, adjusted. For example, this makes it possible to adjust the position of the cover element 26 relative to the inlet pipe 18 via the screw 50 in order to achieve sufficient closure of the inlet openings 28 or sufficient tightness between the cover element 26 and the inlet pipe 18 in the closed position of the cover element 26, which will be explained in more detail later. Alternatively or additionally, it would also be conceivable that the lever arms 32 are arranged on the inlet pipe 18 via an adjustable pivot bearing (screw 38), thereby allowing the relative position and tightness of the cover element 26 in its closed position relative to the inlet pipe to be adjusted.

[0028] The cover element 24 and / or the components of the displacement device 24 are preferably made of a steel material, in particular a stainless steel material or a coated steel material, and / or of a plastic or in a hybrid construction of these materials. By selecting the materials described above for the respective components of the displacement device 24 and the cover element 24, it is ensured that, even during continuous operation, no corrosion, abrasion, or the like occurs as a result of the permanent displacement of the buoyancy element 34 or the cover element 26 between its closed position and its inflow position between the respective adjacent components.

[0029] Based on the Fig. 4 bis 6 Finally, the functioning of the decanter 10 and the transfer device 24 with the cover element 26 and the buoyancy element 34 will be explained in more detail: For this purpose, the Fig. 4 bis 6 In a respective perspective view, the decanter 10, stored at the edge of basin 16 of the wastewater-filled settling basin 12 or mixing reactor, is shown during a lowering into the settling basin 12 between a parking position and a respective extraction position. Fig. 4 It can be seen that both the inlet pipe 18 and the displacement device 24 with the cover element 26 are still located above the floating sludge S, which rises to the top of the clear water layer K. The displacement device 24 is designed, for example, geometrically and in terms of weight, such that the cover element 26 is in the closed position due to gravity before being immersed in the settling tank. In this case, this is achieved in particular by the design of the lever arms 32 and the weight of the buoyancy body 34. In the closed position, the respective guide element 42 is at the lower end stop 44 of the respective guide rail. The inlet openings 28 of the inlet pipe 18 are thus closed against the ingress of floating sludge S.

[0030] In the further course of the lowering movement of decanter 10 according to fig. 5 The inlet pipe 18 then first passes through the "floating sludge" S and subsequently enters the clear water layer K. Thus, the inlet openings 28, which are located on the underside of the inlet pipe 18, are already within the clear water layer K.

[0031] However, due to the geometric design of the displacement device 24, the cover element 26 is still in the closed position, since the buoyancy element 34 according to Fig. 5 during the lowering movement, it has just penetrated the "layer of mud" (which at least does not generate any significant buoyancy) and is only now coming into contact with the surface of the clear water K.

[0032] Only through the impact and immersion of the buoyancy element 34 on or into the clear water layer K according to Fig. 6During the further course of the decanter's downward movement, a sufficient buoyancy force is generated, acting on the buoyancy element 34. This force causes the cover element 26 to be moved into the inlet position by means of the lever arms 34 of the displacement device 24. In this position, clear water K can flow in and be drawn out through the now exposed and visible inlet openings. In this inlet position, the cover element 26 is arranged in overlap with at least one inlet opening 28.

[0033] Subsequently, the decanter 10 is lowered further as the clear water layer descends. Towards the end of the lowering movement, the inlet pipe 18, due to its displacement within the bearing bracket 14, is positioned so close to the sediment layer or the activated sludge that has settled below the clear water layer K that the cover element 26 is located below the inlet openings 28 on the underside of the outlet pipe 18. This underside arrangement of the cover element 26 relative to the inlet pipe has the particular advantage that the inlet openings 28 provided in the inlet pipe 18 can also be located on the underside of the inlet pipe 18. This, in turn, has the advantage that, on the one hand, clear water K can be drawn off down to near the sediment layer, while on the other hand, the cover element 26 ensures that no sediment or activated sludge enters the inlet pipe 18.

[0034] Furthermore, at least in this lowest dispensing position of the decanter 10, an inlet channel is formed that runs at least substantially horizontally. The horizontal inlet channel, or rather the cover element 26 arranged on the underside of the at least one inlet opening 28, ensures that clear water K can only reach the respective inlet opening 28 quasi-horizontally, and not vertically, since the respective cover element 26 is located below and overlapping the inlet opening 28 in its inlet position. This has the significant advantage that, in particular, clear water cannot be drawn in vertically below the inlet openings 28 due to a suction effect, but rather that the cover element 26 is arranged directly below the respective inlet opening 28.Thus, the clear water K must flow in via the horizontally running inlet channel, which in turn ensures that no corresponding vortices or similar suction effects below the respective inlet opening28 can lead to the suction of sediments or activated sludge. Reference symbol list

[0035] 10 Decanter 12 Settling tank 14 Bearing bracket 16 Basin edge 18 Inlet pipe 20 Outlet pipe 22 Flange connections 24 Displacement device 26 Cover element 28 Inlet opening 30 Front side 32 Lever arm 34 Buoyancy element 36 Front side 38 Screws 40 Slide guide 42 Guide element 44 End stop 46 End stop 48 Screws 50 Screw Clear water layer, mud layer

Claims

1. A decanter (10) for a clarification facility, comprising an inlet pipe (18), which can be moved between a parked position and a removal position and which is penetrated by at least one inflow opening (28), via which clarified water below a floating sludge layer can be withdrawn from a clarification tank (12) and can be conducted into an outlet pipe (20), and comprising at least one cover element (26), which, in an inflow position, is arranged below and so as to overlap with the at least one inflow opening (28) penetrating the inlet pipe (18) on the underside and releases said opening, characterized in that the cover element (26) can be moved between a closed position that closes the at least one inflow opening (28) and the inflow position by means of a movement device (24), which comprises at least one buoyancy element (34), by means of which the cover element (26) can be moved into the closed position as a result of immersing the buoyancy element (34) in the wastewater, with the cover element (26) being in the closed position before being immersed in the clarification tank (12) and passing through the floating sludge layer, and being moved into the inflow position by the buoyancy element (34) meeting and being immersed in the clarified water layer (K).

2. The decanter (10) according to claim 1, characterized in that the at least one cover element (26) is arranged below the at least one inflow opening (28) in the inlet pipe (18).

3. The decanter (10) according to claim 1 or 2, characterized in that the at least one cover element (26) forms, in the inflow position, an at least substantially horizontally extending inflow duct together with an underside of the inlet pipe (18) in its removal position.

4. The decanter (10) according to any of the preceding claims, characterized in that the at least one cover element (26) at least substantially tightly closes the at least one inflow opening (28) in the closed position.

5. The decanter (10) according to any of the preceding claims, characterized in that the movement device (24) comprises respective lever arms (32), which are mounted on an end face of the inlet pipe (18) and on which both the at least one buoyancy body (34) and the at least one cover element (26) are arranged.

6. The decanter (10) according to claim 5, characterized in that the lever arms (32) comprise a relevant link guide (40) for an associated guide element (42) arranged on the end face (36) of the inlet pipe (18).

7. The decanter (10) according to any of claims 5 or 6, characterized in that the lever arms (32) are arranged on the inlet pipe (18) by means of a relevant adjustable pivot bearing and / or in that the cover element (26) can be adjusted on and fastened to the relevant lever arm (32), as a result of which the relative position and tightness of the cover element (26) in its closed position is adjustable relative to the inlet pipe (18).

8. The decanter (10) according to any of the preceding claims, characterized in that the at least one buoyancy element (34) is configured as a hollow body filled with a gas, in particular with air.

9. The decanter (10) according to any of the preceding claims, characterized in that the cover element (26) and / or the components (32, 34) of the movement device (24) are made of a steel material, in particular a stainless steel material or a coated steel material, and / or are made of a plastics material or have a hybrid construction of these materials.

10. The decanter according to any of the preceding claims, characterized in that the inlet pipe (18) is penetrated by a plurality of inflow openings (28) arranged in a row.