METHOD FOR TREATING FAT-CONTAINING WASTEWATER

Description

[0001] The present invention relates to a method for treating fatty wastewater in a separator tank.

[0002] In order to reduce the environmental impact of wastewater as well as the mechanical and chemical / biological impact on public wastewater networks, it is advisable to treat wastewater before it is discharged into the public wastewater systems and, in particular, to remove certain substances or types of substances from the wastewater and, if necessary, to dispose of them separately.

[0003] Especially with regard to kitchen wastewater, it is often necessary to separate fats and oils, which are typically present in relatively large quantities in kitchen wastewater. Especially for commercial and professional kitchens, such as those in restaurants and canteens, the separation of fats before discharging the wastewater into the sewer system is often advisable and is usually required by law.

[0004] A common, state-of-the-art method for separating fats is based on the density difference between water and fat and the poor miscibility of water and fat, which generally leads to the fat and water separating and the fat floating due to gravity. The water layer that forms beneath the floating fat contains a significantly lower fat content than the total fat-water mixture.

[0005] A second approach to fat reduction is based on the use of active ingredients that convert or break down the fat in chemical, biological, or chemical-biological processes. Bacteria and / or enzymes are introduced into a fat-water mixture and, as part of their own metabolism, convert or break down the fat components primarily into water and carbon dioxide, or break it down into its components. Many of these active ingredients require oxygen to be active; some bacteria and enzymes are also capable of anaerobically converting fats and therefore do not necessarily require an oxygen supply. In particular, those fat components that form an emulsion with the wastewater and are therefore very difficult to separate from the water by gravity can be separated from the water using bacteria and enzymes.

[0006] EP 1 614 662 A1 describes a generic method and an associated device for the post-treatment of fatty wastewater. In this method, the wastewater passes through a post-treatment section with a total of four tanks connected in series, in which various mechanical and chemical / biological processes take place to reduce the fat content in the wastewater to be treated. The wastewater is first fed via the inlet into a gravity separator, where flow movement is kept to a minimum, so that a large portion of the fat is separated from the water. The water is then fed into a lamella separator, where further mechanical separation takes place, and then into a bioreactor, where microorganisms and enzymes break down the fat as described above.Compressed air is fed into the bioreactor from below, supplying the bacteria and enzymes with oxygen, while simultaneously mixing the wastewater and the bacteria and enzymes it contains through the resulting rising air bubbles. The final stage in the post-treatment section is a post-treatment stage, where settled sludge sinks to the bottom of the post-treatment section. This settled sludge can be recirculated via guide pipes to other sections of the post-treatment section.

[0007] In conventional post-treatment systems, the wastewater is discharged and the grease is separated continuously during normal operation. The feed into the open system requires a roughly simultaneous or staggered discharge of the treated wastewater, so that the total volume of wastewater in the post-treatment system remains roughly constant during normal operation. As the wastewater passes through the gravity separator, a continuously thickening layer of grease grows on the liquid surface, which must be broken up, removed, and disposed of at regular intervals as part of a cleaning routine (disposal). For disposal, the normal operation of the separation system is interrupted, so that no wastewater is discharged or treated during this time, and in particular, no treated wastewater flows out.

[0008] To carry out the cleaning routine, a discharge line with a pump is provided on the gravity grease separator. Using a multi-way valve, a portion of the water in the gravity grease separator can first be pumped out. After activating the multi-way valve, the remaining water can be pumped through the circuit to loosen the grease and then pump out the mixed contents of the gravity grease separator. At the end of the cleaning routine, the tank used for gravity-driven separation should be as empty as possible, i.e., contain no wastewater or only the smallest possible residual amount of wastewater. Before returning to normal operation, the tank is refilled with fresh water.

[0009] The frequency of these cleaning processes or the time interval between two cleaning processes depends on the flow rate of the wastewater, the extent of the fat content of the wastewater and the volume of the gravity grease separator and represents a significant cost factor for the operation of the wastewater treatment plant. In order to keep costs and downtimes as low as possible, the duration of the mixing and pumping must be short.

[0010] JP 2014 226615 A ​​describes a wastewater treatment process in a grease trap. The process is carried out in a phase-based batch operation, in which the process steps are carried out sequentially at separate time intervals.

[0011] The present invention is based on the object of proposing a process corresponding to the above-mentioned type, which can separate large quantities of fat from fatty wastewater with the smallest possible space requirement and can be operated cost-efficiently.

[0012] This object is achieved according to the invention by a method according to claim 1. By carrying out various process phases, the gravity-driven separation and the biological-chemical degradation of fats by bacteria and enzymes can be carried out effectively in a separation tank. By homogenizing the contents of the separation tank, previously formed fat agglomerates can be broken up and reduced in size, and the surface area of ​​fat particles in the wastewater can be increased in order to provide a larger attack surface for bacteria and / or enzymes. Bacteria and enzymes can also be evenly distributed in the water. By homogenizing above all water, fat and any bacteria / enzymes, the effectiveness of fat degradation can be increased. The degradation of the fat distributed in the wastewater takes place particularly during a settling phase.The homogenization and settling phases can also overlap in some areas, especially with regard to the activity of bacteria and enzymes. Overall, the amount of grease accumulating in the separator tank can be reduced, so that grease removal and cleaning can be performed less frequently, assuming otherwise identical input parameters.

[0013] During the settling phase, the homogenized wastewater can settle to allow for effective gravity-driven separation of the grease in the subsequent discharge phase. These two phases can also overlap, resulting in gravity-driven separation during the settling phase.

[0014] The process is not restricted to a specific sequence of phases. For example, the induction phase can be followed by a homogenization phase and then a settling phase, with the same sequence being repeated. Alternatively, after completing an induction phase, the homogenization phase and the settling phase can be performed alternately in multiple sequences before another induction phase is performed.

[0015] The induction phase, homogenization phase and settling phase can take place within an uninterrupted normal operation and can be understood as parts of the normal operation.

[0016] In one embodiment of the invention, no significant inflow can occur into the separator tank during the homogenization phase and / or the settling phase. This prevents wastewater with a high fat content from being discharged into downstream tanks or the sewage system, ensuring that as much fat as possible is retained in the separator tank.

[0017] According to a further alternative, the homogenized contents of the separator tank can remain in the separator tank between the homogenization phase and the settling phase. This allows the bacteria and / or enzymes to act on all the grease and wastewater contained in the separator tank.

[0018] Advantageously, the homogenization phase and / or the settling phase can be carried out separately from the discharge phase. For example, the homogenization and settling phases can be carried out without a significant inflow of untreated, greasy wastewater. This allows the contents of the separator tank to be limited during the homogenization and settling phases. This can, for example, result in better settling. In particular, at least one of these phases can take place at times when no or only a small amount of wastewater is scheduled to be discharged into the separator tank, for example, at night or during periods of downtime.

[0019] According to one variant, wastewater removed from the separation tank can be fed directly or indirectly into at least one post-treatment tank, whereby wastewater or components separated from the wastewater from the post-treatment tank can be introduced into the separation tank during and / or at the beginning of the homogenization phase. Components separated in the post-treatment tank can primarily contain sinking or rising components, such as sludge, grease and bacteria or enzymes. By recirculating the wastewater, the concentration of bacteria and enzymes in the separation tank can be increased and, at the same time, a cleaning effect can be achieved in the post-treatment tank. By selecting the right time for the introduction, the mixing of grease, water and the largest possible quantity of bacteria and / or enzymes can promote the degradation of grease during the homogenization phase and in a subsequent settling phase.

[0020] It may be possible to introduce an oxygen-containing gas or gas mixture into the separation tank during the homogenization and / or settling phases. Depending on the type of bacteria and enzymes, their activity may be enhanced by the addition of oxygen.

[0021] According to a further development of the invention, bacteria and / or enzymes can be stored in a container and fed into at least the separation container and / or a post-treatment container. This allows a desired amount of bacteria and / or enzymes to be quickly adjusted in the separation container and post-treatment container, since they are readily available in the container. For example, a change in the amount of bacteria and / or enzymes in the separation container or post-treatment container can be quickly responded to, and this amount can be adjusted.

[0022] In a favorable embodiment, the homogenization phase within a process cycle can last at least 10 seconds and in particular at least 5 minutes, and / or no more than 1 hour or 3 hours. By selecting a favorable period for homogenization, a high degree of mixing can be achieved in the separation vessel. In particular, it has been shown that a favorable homogenization state can be achieved after one minute, and especially after 5 to 10 minutes, whereas continuous homogenization results in smaller increases in the mixing effect.

[0023] In another suitable embodiment, the settling phase within a process cycle can last at least one hour, in particular at least two hours, and / or no more than nine or 12 hours. Sufficient settling time allows gravity-induced stratification of fat and water to develop, so that wastewater is introduced in a subsequent discharge phase and discharged again with a reduced fat content. It has been shown that such a favorable settling state can be achieved after one and, in particular, after two hours.

[0024] In the following, the invention will be explained using several exemplary embodiments.

[0025] They show: Figure 1 is a schematic representation of a first embodiment of a grease separator without a post-treatment tank, Figure 2 is a schematic representation of a second embodiment with a post-treatment tank, and Figure 3 is a schematic representation of a third embodiment with a post-treatment tank and a biology tank.

[0026] Identical reference numerals are used for identical or corresponding elements in the various figures and embodiments. Elements will not be discussed again if they have already been explained with reference to another figure or embodiment. By referring to the identical reference numerals, explanations once given for one figure or embodiment also apply to all subsequent figures and embodiments.

[0027] In Figure 1a grease separator tank 1 is shown, to which wastewater can be fed from the outside via an inlet 2 and from which wastewater can be discharged through an outlet 3. The outlet 3 can, for example, be connected directly to the sewer system or, for example, to a collection container or subsequent wastewater treatment facility. To calm the flow, i.e. to reduce liquid movement within the grease separator tank, the inlet 2 is connected to an inflow channel 4 and the outlet is connected to an outflow channel 5. The lower openings of the inflow channel 4 and the outflow channel 5 are below the water surface 6, which can change its water level between a minimum water level 7 (shown here in dashed lines) and a maximum water level 8.

[0028] Inlet 2 and outlet 3 can each be equipped with valves, flaps, or dedicated pumps to block them as needed or to specifically control the inflow and outflow of wastewater. In the example shown, inlet 2 is directly connected to a kitchen wastewater drain and positioned at a low geodetic level, allowing kitchen wastewater to be fed directly into grease separator tank 1 by gravity. This inflow raises the liquid level in grease separator tank 1 until the wastewater flows out of the grease separator tank via outlet 3.

[0029] A circulation line 9 is located in the bottom area of ​​the grease separator tank 1, through which liquid is pumped to a pump-out valve 11, which is designed here as a three-way valve, by means of a homogenization pump 10. The contents of the grease separator tank 1 can be drained out of the system via the pump-out valve 11 in the direction of a pump-out line 12, for example, to empty or clean the grease separator tank 1. Via a second outlet, the pump-out valve 11 is connected to a homogenization nozzle 13, through which liquid removed from the grease separator tank 1 can be returned under pressure to the grease separator tank 1. By feeding the liquid under pressure, solid fat components that can harden on the wastewater surface and form a shell can be broken up.

[0030] Biologically and chemically active components 15, such as bacteria and / or enzymes, are stored in a container 14. These components can be fed to the grease separator tank 1 via a supply line 16 using a dosing pump 17. The active components can be fed, for example, directly into the inlet 2 or into the inlet channel 4.

[0031] A common control unit 18 is connected to the homogenization pump 10, the pump-out valve and the dosing pump 17.

[0032] The operation of the grease separation system can be advantageously adapted to typical operating cycles of a canteen or restaurant and can be largely automated using a programmable controller 18. During the day, when there is a steady inflow of untreated wastewater from the kitchen, the grease separation tank 1 is operated in the discharge phase, so that the grease in the wastewater floats to the surface due to its lower density. It remains there while the wastewater, now with a significantly lower fat content, is discharged through outlet 3. Bacteria and enzymes located in the grease separation tank can actively degrade grease. Flow movements in the grease separation tank 1 should be minimized as much as possible, causing the grease to agglomerate on the surface, and bacteria and enzymes, along with other, heavier components of the wastewater, tend to sink to the bottom.

[0033] After the kitchen closes, for example, in the evening, when there is virtually no inflow of fatty wastewater overnight until operations resume the following day, the homogenization and settling phases are carried out. Effective homogenization with the desired increase in fat degradation can be achieved after a homogenization phase of approximately 5 to 10 minutes. A homogenization time of at least 15 minutes, and especially 30 minutes, is more favorable. Long homogenization achieves the finest possible breakdown of previously agglomerated fats and an even distribution of water, fats, and active ingredients.

[0034] The homogenization phase can also be carried out in a similar manner as part of a cleaning routine described above during regular operation. In the exemplary embodiment, the homogenization phase is part of regular operation. After the homogenization phase within regular operation, the homogenized contents of the separator tank can remain in the separator tank to transition to the settling phase without interrupting regular operation. The settling phase of the homogenized contents is carried out separately from the cleaning phase / routine. In principle, the settling phase and the homogenization phase with the fatty wastewater can be carried out in the same separator tank. This saves space. In the present embodiments, the fatty wastewater is also fed into this tank, where biological and / or chemical degradation takes place.

[0035] By the time the kitchen is operational again, a stable phase stratification of fat and water should be re-established. To this end, the homogenization phase should be terminated in good time before the next wastewater discharge, and the settling phase should begin. During this phase, fats are broken down in the homogenized wastewater while the water and fat gradually separate. When the discharge phase begins again, new, untreated water can be discharged, and wastewater with a lower fat content due to gravity separation can be removed from grease separator tank 1. A favorable duration for the settling phase is at least one hour, and in particular at least two hours.

[0036] A cleaning routine can be carried out as described above with reference to the state of the art.

[0037] Active ingredients 15 can be added from the container 14 to the grease separator tank 1 to ensure continuous fat degradation. The addition can be made regularly during each homogenization, at specific time intervals, or whenever an optional sensor detects an excessively low concentration of active ingredients 15 in the grease separator tank 1. The amount of active ingredients 15 in the grease separator tank 1 can increase or decrease depending on the amount of nutrients necessary for the active ingredients in the wastewater. Furthermore, active ingredients 15 can be carried out of the grease separator tank 1 through the outlet along with the wastewater.

[0038] In order to maintain particularly good homogenization over a long period of time, a new homogenization phase followed by a settling phase can take place at the end of a settling phase in which the components of the wastewater separate.

[0039] Carrying out an induction phase as described above leads to a steady growth of fat on the surface, which is regularly removed from the grease separator tank 1 when a system-dependent maximum amount is reached. By effectively implementing homogenization and settling in conjunction with the active ingredients, it is possible to significantly reduce the amount of fat accumulating in the grease separator tank 1, thus allowing more time to pass between two cleaning or emptying processes. Tests of the invention suggest that a reduction in the growth of the fat layer by up to 90% is possible. The circulation line and homogenization pump are also used to clean and remove the fat accumulated in the grease separator tank in order to break up fat agglomerations and make them pumpable. The contents are then pumped out of the grease separator tank via the pumping line.

[0040] The discharge phase, homogenization phase, and settling phase occur within uninterrupted regular operation and are considered parts of regular operation. During regular operation, a producer of greasy wastewater, such as a kitchen, continues to operate unhindered, regardless of its working and rest periods—whether the kitchen is in operation or when it is closed or not in operation at night, for example. The producer therefore hardly has to take into account the degradation of grease taking place within the separator tank. This facilitates continuous kitchen operation.

[0041] Classic maintenance work can be distinguished from regular operation, where certain tasks must be performed separately and impact the operation of the generator. While cleaning routines and wastewater treatment measures in the prior art often impact the operation of the generator and are performed as separate maintenance, the cleaning routine of the present invention can be integrated into regular operation. This applies in particular to the homogenization according to the invention during operation.

[0042] In contrast, homogenization measures, for example, are part of the current state of the art maintenance, which requires interrupting the generator's operation. The first embodiment, with only one separator tank and no post-treatment tank, could be suitable for wastewater with a low fat content, such as wastewater from a dining room without a kitchen and / or wastewater from a dishwasher.

[0043] In Figure 2In addition to the grease separator tank 1, a post-treatment tank 19 is provided, with a post-treatment inlet 20 directly coupled to the outlet 3 of the grease separator tank 1, so that wastewater leaving the grease separator tank 1 is fed into the post-treatment tank 19. Furthermore, the post-treatment tank has a post-treatment outlet 21, which is connected, for example, to the sewer system. A post-treatment outlet channel 22 is coupled to the post-treatment outlet 21.

[0044] In the post-treatment tank 19, similar to the grease separator tank 1, a particularly low liquid movement is aimed for, so that heavier components and, if possible, enzymes and bacteria still present in the wastewater sink to the bottom and form a kind of sediment 23, so that as few active components 15 as possible leave the system.

[0045] The sediment 23 forming in the lower area of ​​the post-treatment tank 19 can be pumped back into the inlet 2 of the grease separator tank by means of a return pump 25 through a return line 24 located at the bottom of the post-treatment tank 19. This both cleans the post-treatment tank 19 and prevents excessive buildup of sediment, while simultaneously supplying the grease separator tank with active components 15 that would have been flushed from the system without the use of the post-treatment tank 19.

[0046] The post-treatment tank can also be used for the biological-chemical degradation of fats in the wastewater, especially those that form an emulsion with the water. For this purpose, the post-treatment tank is connected to the supply line 16 for active ingredients from tank 14.

[0047] In Figure 3A biology tank 26 is interposed between the post-treatment tank 19 and the grease separator tank 1, wherein the outlet 3 of the grease separator tank 1 is coupled to a biology inlet 27 of the biology tank 26 and the post-treatment inlet 20 is coupled to a biology outlet 28 of the biology tank 26. A flow channel 29, 30 is arranged at the biology inlet 27 and at the biology outlet 28 to calm the flow.

[0048] The biological tank 26 is designed primarily to promote the biological-chemical degradation of fat. Filler elements can be inserted to which bacteria and enzymes can adhere, thus ensuring they remain in the biological tank more effectively.

[0049] By means of compressors (one or more) 33, oxygen-containing compressed air is introduced through aeration candles 31 into the biological tank 26, which can be used by some enzymes and bacteria for aerobic fat degradation and contributes to the swirling and mixing of the wastewater components.

[0050] In a similar way, as shown in the third embodiment, air can also be introduced into the grease separator tank 1 via additional compressors 34 and, for example, aerator candles 35.

[0051] Compared to the first embodiment ( Fig. 1 ) in the second ( Fig. 2 ) and third ( Fig. 3The additional tanks provided are designed to treat larger volumes of wastewater or more heavily contaminated wastewater while using a system that is as space-saving as possible. Accordingly, the second embodiment could be used for a small restaurant kitchen, and the third for a commercial kitchen.

[0052] The use of the present invention in the field of kitchen wastewater treatment is to be understood as exemplary, so the described method is applicable to the treatment of other types of wastewater and oils and fats. In this sense, fat can also be understood as oils or other light liquids to be treated.

Claims

1. Method for treating fatty wastewater in a separation tank (1), wherein in an inlet phase, fatty wastewater is fed into a separation tank (1) while fat-reduced wastewater is discharged from the separation tank (1), wherein in the separation tank (1) a gravity-driven separation of fat takes place, and in a homogenization phase, homogenization of the wastewater in the separation tank (1) and the fat separated therein takes place, wherein, in the homogenization phase, liquid is removed from the bottom region of the separation tank (1) and fed back under pressure via a homogenization nozzle (13) to the wastewater surface in the separation tank (1), characterized in that in a settling phase, and optionally in an inlet phase, the contents of the separation tank (1) homogenized in the homogenization phase undergo biological and / or chemical degradation of fats, in particular by means of bacteria and / or enzymes.

2. Method according to one of the previous claims, characterized in that during the homogenization phase and / or the settling phase, no significant inflow into the separation tank (1) takes place.

3. Method according to one of the previous claims, characterized in that the homogenized contents of the separation tank (1) remain in the separation tank between the homogenization phase and the settling phase.

4. Method according to one of the previous claims, characterized in that the homogenization phase and / or the settling phase takes place separately from the introduction phase.

5. Method according to one of the previous claims, characterized in that wastewater removed from the separation tank (1) is fed directly or indirectly into at least one post-treatment tank (19, 26), wherein wastewater or components separated from the wastewater are introduced from the post-treatment tank (19, 26) into the separation tank (1) during and / or at the beginning of the homogenization phase.

6. Method according to one of the previous claims, characterized in that during the homogenization phase and / or the settling phase, an oxygen-containing gas or gas mixture is introduced into the separation tank (1) or into the post-treatment tank (19, 26).

7. Method according to one of the previous claims, characterized in that bacteria and / or enzymes are stored in a container (14) and are fed at least into the separation container (1) and / or a post-treatment container (19, 26).

8. Method according to one of the previous claims, characterized in that within a process cycle, the homogenization phase lasts at least 10 seconds and in particular at least 5 minutes and / or no more than 1 or 3 hours.

9. Method according to one of the previous claims, characterized in that within a process cycle, the settling phase lasts at least one hour and in particular at least 2 hours and / or no more than 9 or 12 hours.