CN112062321A

CN112062321A - Separating device with sensor-controlled dosing device

Info

Publication number: CN112062321A
Application number: CN202010506144.XA
Authority: CN
Inventors: 贝恩哈尔·科塞尔
Original assignee: Kessel AG
Current assignee: Kessel AG
Priority date: 2019-06-11
Filing date: 2020-06-05
Publication date: 2020-12-11
Also published as: DE102019118314A1

Abstract

The invention relates to a separation device (1) for pre-purifying waste water (6) on the building side before introduction into a public pipeline system, comprising: a grease separator (2); an extraction tank (3) which is arranged downstream of the grease separator (2) in the direction of throughflow of the waste water (6) and from which purified waste water (7) can be extracted for introduction into a public pipe system; a return line (9) for returning a portion of the waste water (7) from the extraction tank (3) to the grease separator (2); and a dosing device (12) for feeding the recirculated wastewater (10) with an agent (11) for sedimentation and/or flocculation. The invention is characterized in that the separating device (1) comprises at least one sensor (13) for determining the volume flow (V) of the waste water (6) flowing from the fat separator (2) into the extraction tank (3) and/or the pH value of the waste water (6), and in that the separating device (1) comprises a control unit (14) which is designed in such a way that the dosing of the agent (11) discharged by the dosing device (12) is controlled as a function of the determined volume flow (V) and/or pH value. The invention also relates to a method for operating a separation device (1) for pre-purifying waste water (6) on the building side before introduction into a public pipeline system.

Description

Separating device with sensor-controlled dosing device

Technical Field

The invention relates to a separating device, in particular for food processing companies, for the preliminary purification of waste water on the building side before introduction into a public pipe system, comprising: a grease separator; an extraction tank arranged downstream of the grease separator in the direction of throughflow of the waste water, from which tank purified waste water can be extracted for introduction into a public pipe system; a return line for returning a portion of the wastewater from the extraction tank to the grease separator; and a dosing device for delivering an agent for sedimentation and/or flocculation to the recirculated wastewater.

Background

DE 102004014517 a1 discloses a gravity separator with an inlet opening for the waste water to be treated and a waste water outlet opening. The wastewater enters the extraction tank from the pretreatment tank in a free-fall motion. The wastewater is conveyed to the flotation plant under level control by means of a sewage pump. The precipitant and flocculant are added by means of a dosing device to the transfer line to the flotation plant. This separates out the emulsified lipophilic substances. These large flocs are then floated out in a flotation unit by the input of fine bubbles. The flotation sludge is conducted away through the flotater line and re-conveyed to the gravity separator. The clarified aqueous phase flowing off at the bottom is led from the flotation plant in a purified manner into a public pipe network. The disadvantage of this solution is the high consumption of precipitant and flocculant in the apparatus. And the running cost of the equipment is very high. Furthermore, the equipment is very expensive, since additional flotation equipment is required.

Disclosure of Invention

It is therefore an object of the present invention to provide a separating apparatus which is characterized by a reduced acquisition and/or operating cost.

The solution of the invention for achieving the object is a separating device for pre-cleaning waste water on the building side before introduction into a public line system, in particular for food processing plants, and a method for operating such a separating device, having the features of the independent claims.

A separating device is proposed for pre-purifying waste water on the building side before introduction into a public pipeline system, in particular for food processing companies. The separating device has a grease separator. In this grease trap, grease is separated from the incoming waste water for subsequent removal. The separating device also comprises an extraction tank arranged at the downstream of the grease separator along the through-flow direction of the waste water. From this extraction tank, the purified waste water is extracted for introduction into a public pipe system. The separation device also has a return line for returning a portion of the waste water from the extraction tank to the grease separator. The return line preferably extends from the extraction tank back to the grease separator. The separation device further comprises a dosing device. By means of the dosing device, agents for sedimentation and/or flocculation can be supplied to the recirculated waste water. The separating device comprises at least one sensor for determining the volume flow of the waste water flowing from the fat separator into the extraction tank and/or the PH value of the waste water, in particular of the waste water flowing into the extraction tank and/or of the waste water present in the extraction tank. In this case, the volume flow and/or in particular the PH of the waste water supplied to and/or in the extraction tank can preferably be detected directly by the sensor, but can also be calculated indirectly by the control unit from the measured values detected by the sensor. The term "direct" is understood to mean that the sensor is designed to directly measure or detect the volume flow and/or the pH value. The term "indirect" means that the sensor is not designed to measure the volume flow and/or the PH value, but to measure a further measured value, by means of which the volume flow and/or the PH value can be calculated. In the case of a volume flow, this can be, for example, a sensorically detected hydrostatic pressure or a liquid level. In addition to the at least one sensor, the separating device comprises a control unit for controlling the dosing device. For this purpose, the control unit is designed such that it controls the amount of reagent released by the dosing device as a function of the determined volume flow and/or PH value, wherein the volume flow and/or PH value is preferably detected directly or indirectly by a sensor. This advantageously reduces the consumption of precipitant and flocculant and thus also reduces the operating costs of the separation apparatus.

Preferably, the separating device comprises a waste water inlet for conveying raw waste water to the separating device and/or a clean water outlet for conveying waste water purified by the separating device to the public pipe system.

Also preferably, the cleaning water outlet of the separating device is formed by an extraction tank outlet of the extraction tank. This makes it possible to construct the separating device particularly simply and inexpensively.

It is also preferred that the sensor is arranged in a region of the separating device downstream of the grease separator in the throughflow direction of the waste water. This makes it possible to sense, in particular directly or indirectly, the volume flow and/or the PH value from the fat separator to the extraction tank.

In a particularly preferred manner, the sensor is arranged in the region of the grease trap outlet, the extraction groove inlet and/or a connecting tube connecting the grease trap to the extraction groove, in particular in or on the assembly. This allows very accurate and rapid measurement of the volume flow and/or the PH value.

Also preferably, the sensor is disposed in the lumen of the extraction slot. This allows sensing to be performed in a very cost-effective manner.

Preferably, the inner space of the extraction tank is divided by a wall into an inlet chamber, into which waste water from the grease separator can be fed via an inlet of the extraction tank, and an extraction chamber, from which waste water can be discharged via an outlet of the extraction tank.

Furthermore, the wall preferably has, in particular in its lower region, a connection opening between the inlet chamber and the extraction chamber.

Particularly preferably, the connection opening is designed as a throttle valve, so that the inlet chamber level of the waste water can be raised as a function of the volume flow compared to the extraction chamber level of the waste water.

Further preferably, the sensor is disposed in the access chamber and/or the extraction chamber. At least one sensor may also be provided in the access chamber and the extraction chamber, respectively. This advantageously allows the level of wastewater to be sensed both in the inlet chamber and in the extraction chamber. Therefore, the liquid level difference can be calculated by settlement, and the volume flow rate can be calculated from the liquid level difference.

Preferably, the sensor and/or the control unit are configured such that the volume flow and/or the PH value can be measured directly by the sensor or can be determined indirectly by the control unit from the sensor value transmitted by the sensor.

It is also preferred that the sensors are volume flow sensors, level sensors, in particular immersion tubes and/or level probes for hydrostatic pressure measurement, and/or PH sensors.

Furthermore, the separating device preferably has a return pump, which is arranged in particular in the extraction tank, for pumping the waste water from the extraction tank into the return line. This advantageously allows the recirculated wastewater to be pumped under pressure through the recirculation line, thereby improving mixing with the reagent and/or improving air accumulation. In the event of a partial pressure drop, bound oxygen is released in the recirculated wastewater, which in turn leads to improved flocculation in the grease trap.

Wherein the feedback pump is also controllable by the control unit. For example, the control unit may control the return pump in dependence on the volume flow and/or the PH value. Additionally or alternatively, the control unit may also control the return pump in dependence on the extraction chamber level in the extraction chamber. For example, if the extraction chamber level rises, the control unit increases the power of the feedback pump so that the extraction chamber level at least remains constant or even falls.

Preferably, the control unit is configured as follows: this control unit switches the dosing device and/or the return pump on if a first sensor threshold value, in particular a sensor value of the volume flow and/or the PH value, is exceeded and switches these devices off if a second sensor threshold value is undershot, wherein the second sensor threshold value is smaller than the first sensor threshold value.

It is also preferred that the pump volume flow of the return pump is stored in the control unit. In addition or alternatively, the control unit is preferably configured as follows: the control unit subtracts the stored pump volume flow from the sensorially detected volume flow after the first sensor threshold is exceeded. The required volume flow can thereby be calculated. This is equal to the volume flow into the separation device. The control unit is preferably configured as follows: the control unit delays the implementation of the above-mentioned compensation step only after a time that is predefined and/or stored in the control unit.

The control unit is preferably configured as follows: the control unit activates the return pump and/or the dosing device if the PH value is less than 7 and/or if the volume flow exceeds a first sensor threshold. The control unit is preferably configured as follows: the control unit increases the dosage of the dosing device in the case of an increase in the volume flow and/or a decrease in the pH value.

The separation device is preferably constructed in such a way that flocculation takes place in the grease separator, not in the return line and/or in the swirl chamber.

Particularly preferably, the return line is an inlet pipe connected to the extraction chamber and/or to the waste water inlet and/or the grease separator.

Further preferably, the separation device has a swirl chamber provided in the return line. Whereby the mixing and the release of oxygen can be further improved.

The dosing device is preferably designed in such a way that it introduces the agent into the return line, in particular into a section located upstream of the swirl chamber in the flow direction, or into the swirl chamber.

Also preferably, the swirl chamber has a larger diameter than the return line. Turbulence can thereby be induced, which contributes to good mixing.

The separating device preferably has a flow constriction in the return line and/or in the swirl chamber, by means of which a swirl flow can be generated for mixing the reagent with the returned waste water. Preferably, a flow widening is provided downstream of the flow constriction in the flow direction. The flow constriction is designed as a baffle or as a venturi nozzle.

Furthermore, it is preferred that the return line and/or the swirl chamber have an intermediate wall which contains such a flow constriction. Whereby also the mixing can be improved.

A method for operating a separation device, in particular for food processing systems, for the preliminary purification of waste water on the building side before introduction into a public pipeline system is proposed. In the method, the waste water is conducted to a grease separator, in which grease on the water surface is separated from the waste water. The waste water is then conducted into an extraction tank arranged downstream of the grease separator in the throughflow direction of the waste water. In this extraction tank the wastewater is left to stand so that a sediment can be deposited on the bottom of the extraction tank. The purified waste water is then led from the extraction tank to a public pipe system. In a parallel treatment step to this step, a portion of the waste water is returned from the extraction tank to the fat separator via a return line. In this case, the recirculated wastewater is mixed and/or fed with reagents for sedimentation and/or flocculation by means of a dosing device. The method is carried out with the aid of a separation device according to the preceding description, wherein the method features mentioned are carried out individually or in any combination.

Drawings

Further advantages of the invention are described in the following description of the embodiments. Wherein:

FIG. 1 is a schematic view of a separation apparatus.

Detailed Description

The separation device 1 is used for pre-purification of wastewater 6 at the building level. Especially in the case of food processing enterprises, such as the catering or meat processing industry, it is necessary to pre-clean, in particular, the fat 8 before the waste water is conducted to the public pipe system. Fig. 1 schematically shows such a separating apparatus 1.

The separating device 1 comprises a grease separator 2 and an extraction tank 3 arranged downstream of the grease separator 2 in the throughflow direction of the waste water 6. Dirty waste water 6 is conveyed to the separation device 1 through the waste water inlet 4. The waste water 6 flows first through the grease separator 2 and then through the extraction tank 3. The purified waste water 7 is conveyed via the clean water outlet 5 of the separating device 1 to a pipe system not shown here. The cleaning water outlet 5 of the separating device 1 constitutes an extraction tank outlet 28 of the extraction tank 3. Thus, the dirty waste water 6 flows into the grease separator 2, where it is partly stripped of grease 8 deposited on the pre-water surface, then into the extraction tank 3, where the sludge is deposited on the bottom, and then leaves the separation device 1 as purified waste water 7 through the clean water outlet 5, which is here formed by the extraction tank outlet 28.

As shown in fig. 1, the separation device 1 further comprises a return line 9. A return line 9 is connected to the extraction tank 3. A part of the waste water 7, which has been partly degreased 8 by the grease trap 2 and/or partly freed of settled sludge via the extraction tank 3, can be conducted back out of the extraction tank 3 via a return line 9 and returned to the grease trap 2. For this purpose, the return line 9 can be connected to the waste water inlet 4 and/or to the inlet line 29 of the grease separator 2. In the return process, the returned waste water 10 is supplied with an agent 11 for sedimentation and/or flocculation. For this purpose, the separating device 1 has a dosing device 12.

In order to deliver the correct dosage of reagent 11 as appropriate to the specific situation, the separating device 1 comprises at least one sensor 13 and a control unit 14. The control unit 14 is connected to the at least one sensor 13 and to the dosing device 12, in particular electrically, hydraulically and/or mechanically. The volume flow V of the pre-purified waste water 7 from the fat separator 2 to the extraction tank 3 and/or the PH value of the pre-purified waste water 7, in particular the PH value of the pre-purified waste water 7 flowing from the fat separator 2 into the extraction tank 3 and/or in the extraction tank 3, can be determined by means of the sensor 13.

The control unit 14 is configured as follows: which controls the dosing device 12 in dependence on the measured volume flow V and/or PH value such that a sufficient amount of reagent 11 is always delivered to the recirculated wastewater 10. For this purpose, a table, in particular empirically determined beforehand, can be stored in the control unit 14, which reflects the correlation between the volume flow V and/or the PH value and the quantity of reagent 11 to be discharged. From this list, the control unit 14 can determine the required addition amount of reagent 11, depending on the measured volume flow V and/or PH value. Alternatively or additionally, a mathematical model can be stored in the memory unit 14, by means of which the required quantity of reagent 11 is calculated from the detected volume flow V and/or PH value. By adding reagent 11 so controlled, excessive consumption of expensive reagent 11 can be avoided. This reduces the operating costs of the separating apparatus 1.

As shown in fig. 1, the at least one sensor 13 is arranged in the region of the separating device 1 downstream of the grease separator 2 in the direction of flow of the waste water 4. By means of the first sensor 13a, the second sensor 13b and the third sensor 13c, three different positions in the separating device 1 are shown, at least one sensor 13 being provided at least one of these positions, in particular for indirectly and/or directly determining the volume flow V and/or the PH value. The sensor 13 can also be designed to measure both the volume flow V and the PH. The separating apparatus 1 can have one or several sensors 13. Furthermore, at least one sensor 13 can be provided at one or several positions of the separating device 1, which are indicated by

reference numerals

13a, 13b, 13c, in particular for indirectly and/or directly determining the volume flow V and/or the PH value. The

different positions

13a, 13b, 13c will also be explained in detail below.

The grease separator 2 and the extraction tank 3 are connected by a connecting pipe 15. According to the position 13c shown, the sensor 13 can be arranged in the region of this connecting tube 15. Thus, the sensor 13 may be arranged, for example, in or on the grease separator outlet 16, in or on the extraction groove inlet 17, but also in the connecting pipe 15 itself.

In addition or as an alternative, a sensor 13 can also be provided at least at one of the

subsequent positions

13a, 13b of the separating device 1, i.e. in particular in the interior 18 of the extraction tank 3.

According to the present embodiment, the inner cavity 18 of the extraction groove 3 is divided by a wall 19 into an inlet cavity 20 and an extraction cavity 21. The wall 19 may be configured as a submerged wall as shown, or as an immersed tube. According to this embodiment, the wall 19 comprises a bottom. This bottom extends between the submerged wall and the inner wall of the extraction tank 3. The access chamber 20 is closed off in particular by the bottom and the submerged wall.

The wall 19 has a connection opening 22 between the access chamber 20 and the extraction chamber 21. The connection port 22 serves as a throttle valve 23 or is configured as a throttle valve. Thus, waste water 6 from the grease separator 2 flows into the inlet chamber 20 through the extraction tank inlet 17. The inlet chamber level of the waste water 6 can be increased by the volume flow V compared to the extraction chamber level of the waste water 6 in the extraction chamber 21 via the connection opening 22. The corresponding level change can be detected sensorically by the sensor 13 provided at the position 13b in the inlet chamber 20 and/or by the sensor 13 provided at the position 13a in the extraction chamber 21. This level change can be used (in particular by the control unit 14) for determining, in particular calculating, the volume flow V.

As previously mentioned, the sensor 13 and/or the control unit 14 may be configured as follows: so that the volume flow V and/or the PH value can be measured directly by the sensor 13 or can be determined indirectly by the control unit 14 on the basis of the sensor values transmitted by the at least one sensor 13.

For the direct detection of the volume flow V, the sensor 13 is preferably a volume flow sensor. In this case, the sensor is preferably positioned in the region of the position indicated by reference numeral 13c, i.e. in particular in the region of the connecting tube 15, preferably in or on the grease separator outlet 16, in or on the extraction groove inlet 17 and/or in or on the connecting tube 15.

In particular in the case of a sensor 13 which cannot directly detect the volume flow V and/or PH value, but measures another value, this sensor is preferably arranged in the interior 18 of the extraction tank 3. To this end, at least one sensor 13 is positioned in at least one of the positions indicated with

reference numerals

13a, 13 b. Such a sensor is preferably a level sensor. The level sensor may in particular be an immersion tube and/or a level probe for hydrostatic pressure measurement.

In order to ensure good mixing of the wastewater 10 recirculated via the recirculation line 9 with the reagent 11 and/or in order to be able to release oxygen from the recirculated wastewater 10, the separation device 1 preferably has a flow constriction 27 in the region of the recirculation line 9. The flow constriction 27 can be formed by a baffle or a venturi nozzle. According to an exemplary embodiment, which is not shown here, the flow constriction 27 can be formed directly in the return line 9, in particular inserted into it.

Additionally or alternatively, the separation device 1 may have a swirl chamber 24. A swirl chamber 24 is provided in the return line 9. Thus, the return line 9 is connected to the swirl chamber 24 via an inlet and an outlet. The swirl chamber 24 has only an outlet formed by this outlet which leads back into the return line 9. The recirculated wastewater 10 cannot be discharged from the vortex chamber 24 into the common piping system.

The dosing device 12 is connected to the return line 9 in the return direction upstream of the flow constriction 27 and/or, according to the exemplary embodiment shown in fig. 1, upstream of the swirl chamber 24. Alternatively, however, the dosing device 12 can also be connected directly to the swirling chamber 24, so that the reagent 11 is introduced directly into the swirling chamber 24.

The separation device 1 further comprises a return pump 25 connected to the return line 9. By means of this return pump, the returned waste water 10 can be pumped under pressure through the return line 9 and/or into the swirl chamber 24.

The return pump 25 is also connected to the control unit 14, so that it can be controlled by the control unit 14. The return pump 25 can be controlled, for example, by the control unit 14 as a function of the volume flow V and/or the PH value. The control unit 14 can control the power, in particular the pump power, of the return pump 25 in such a way that the pumping capacity of the return pump 25 is approximately equal to the volume flow V. In addition or as an alternative, the return pump 25 can also be controlled by the control unit 14 as a function of the extraction chamber level. If the liquid level in the extraction chamber 3 rises, the return pump 25 can be controlled with a higher power.

In order to achieve good mixing and/or air accumulation, the swirl chamber 24 has a larger cross section than the return line 9. This produces turbulence in the recirculated waste water 10 entering the swirl chamber 24 under pressure, which ensures good mixing. In the case of a swirl chamber having an intermediate wall 26 with a flow constriction 27 as shown in fig. 1, mixing and/or air accumulation can be further improved. Alternatively, a venturi nozzle can also be provided in the swirl chamber 24 and/or directly in the return line 9.

The invention is not limited to the embodiments disclosed and described. The embodiments may also vary within the scope of the claims, e.g. combining features, even if these features are disclosed and described in different embodiments.

List of reference numerals

1 separating device

2 grease separator

3 extraction tank

4 waste water inlet

5 clean water outlet

6 waste water

7 purified waste water

8 oil and fat

9 feedback pipeline

10 recycled waste water

11 reagent

12 quantitative feeding device

13 sensor

14 control unit

15 connecting pipe

16 oil separator outlet

17 extraction tank inlet

18 inner cavity

19 wall part

20 into the cavity

21 extraction chamber

22 connecting port

23 throttle valve

24 vortex chamber

25 feedback pump

26 intermediate wall

27 flow constriction

28 draw tank outlet

29 entry tube

V volume flow from the grease separator to the extraction tank

Claims

1. A separation device (1) for pre-purification of waste water (6) on the building side before introduction into a public pipe system

Comprises a grease separator (2),

having an extraction tank (3) arranged downstream of the fat separator (2) in the direction of throughflow of the waste water (6), from which extraction tank (3) purified waste water (7) can be extracted for introduction into a public pipe system,

having a return line (9) for returning a portion of the waste water (7) from the extraction tank (3) to the fat separator (2), and having a dosing device (12), the dosing device (12) being used to supply the returned waste water (10) with an agent (11) for sedimentation and/or flocculation,

it is characterized in that the preparation method is characterized in that,

the separating device (1) comprises at least one sensor (13), the at least one sensor (13) being used to determine the volume flow (V) of the waste water (6) flowing from the fat separator (2) into the extraction tank (3) and/or the pH value of the waste water (6), and the separating device (1) comprises a control unit (14),

the control unit is designed to control the amount of reagent (11) dispensed by the dosing device (12) as a function of the measured volume flow (V) and/or pH value.

2. The separating device according to the preceding claim, characterized in that the separating device (1) comprises a waste water inlet (4) for conveying raw waste water (6) to the separating device (1) and/or

For conveying the waste water (7) purified by the separating device (1) to a clean water outlet (5) of a public pipe system.

3. The separating device according to one or more of the preceding claims, characterized in that the clean water outlet (5) of the separating device is formed by an extraction tank outlet (28) of the extraction tank (3).

4. The separating device according to one or more of the preceding claims, characterized in that the sensor (13) is arranged in the region of the separating device (1) downstream of the grease separator (2) in the throughflow direction of the waste water (6), in particular in the region of the grease separator outlet (16), in the region of the extraction sump inlet (17) and/or in the region of a connecting pipe (15) connecting the grease separator (2) to the extraction sump (3).

5. The separation device according to one or more of the preceding claims, characterized in that said sensor (13) is arranged in an inner cavity (18) of said extraction tank (3).

6. Separating device according to one or more of the preceding claims, characterized in that the inner chamber (18) of the extraction tank (3) is divided by a wall (19) into an inlet chamber (20) and an extraction chamber (21), into which inlet chamber (20) waste water (6) from the fat separator (2) can be fed through the extraction tank inlet (17), and from which extraction chamber (21) purified waste water (7) can be discharged through the extraction tank outlet (28).

7. Separating device according to one or more of the preceding claims, characterized in that the wall (19) has a connection opening (22) between the inlet chamber (20) and the extraction chamber (21), in particular in the lower region of the wall (19).

8. The separation device according to one or more of the preceding claims, characterized in that the connection port (22) is configured as a throttle valve (23) so that the intake chamber level of the waste water (6) can be raised according to the volume flow (V) compared to the extraction chamber level of the waste water (6).

9. Separating device according to one or more of the preceding claims, characterized in that the sensor (13) is arranged in the inlet chamber (20) and/or the extraction chamber (21).

10. The separation device according to one or more of the preceding claims, characterized in that the sensor (13) and/or the control unit (14) are configured such that the volume flow (V) and/or the pH value can be measured directly by the sensor (13), or

Can be indirectly measured by the control unit (14) on the basis of the sensor values transmitted by the sensor (13).

11. The separation device according to one or more of the preceding claims, characterized in that the separation device (1) has a return pump (25), which return pump (25) is used for pumping waste water (7) from the extraction tank (3) into the return line (9), wherein the return pump (25) is preferably controllable by the control unit (14), in particular as a function of the volume flow (V), the PH value and/or the extraction chamber liquid level in the extraction tank (3).

12. The separation device according to one or more of the preceding claims, characterized in that said control unit (14) is configured such that it (14) switches said dosing device (12) and/or said return pump (25) on in case of exceeding a first sensor threshold and switches it off in case of falling below a second sensor threshold, wherein said second sensor threshold is smaller than said first sensor threshold.

13. The separation device according to one or more of the preceding claims, characterized in that the pump volume flow of the return pump (25) and/or the pump volume flow of the return pump (25) are stored in the control unit (14)_，

The control unit (14) is designed in such a way that, after exceeding a first sensor threshold, it subtracts the stored pump volume flow from the sensorically detected volume flow (V) for determining the purified volume flow.

14. The separation device according to one or more of the preceding claims, characterized in that said separation device (1) has a swirl chamber (24) provided in said return line (9).

15. The separation device according to one or more of the preceding claims, characterized in that said dosing device (12) is configured in such a way as to introduce a reagent (11) into said return line (9) or into said swirling chamber (24).

16. The separation device according to one or more of the preceding claims, characterized in that the separation device (1) has a through-flow constriction (27) provided in the return line (9) and/or in the swirl chamber (24), by means of which constriction (27) a vortex flow can be generated for mixing the reagent (11) with the returned waste water (10).

17. A method for operating a separation device (1) for pre-purifying waste water (6) on the building side before introduction into a public pipe system,

wherein the waste water (6) is conducted to a grease separator (2),

introducing the waste water (6) into an extraction tank (3) arranged downstream of the grease separator (2) in the direction of throughflow of the waste water (6), and

directing the purified wastewater (7) from the extraction tank (3) into a common piping system,

wherein a portion of the purified waste water (7) is returned from the extraction tank (3) to the fat separator (2) via a return line, and

wherein the recirculated wastewater (10) is supplied with a reagent (11) for sedimentation and/or flocculation by means of a dosing device (12),

it is characterized in that the preparation method is characterized in that,

the method is carried out by means of a separation device (1) according to one or more of the preceding claims.