AU2008271639A1

AU2008271639A1 - Apparatus and method for the purification of grey water

Info

Publication number: AU2008271639A1
Application number: AU2008271639A
Authority: AU
Inventors: Oliver Ringelstein
Original assignee: INTEWA GmbH
Current assignee: INTEWA GmbH
Priority date: 2007-07-03
Filing date: 2008-06-20
Publication date: 2009-01-08
Also published as: DE102007030938A1; WO2009003603A8; WO2009003603A4; WO2009003603A2; WO2009003603A3; EP2165021A2

Description

Apparatus and method for the purification of grey water This present invention concerns an apparatus and a method for the purification of grey water with the features of the generic part of claims 1 and 10. 5 State-of-the-art Every household produces a quantity of slightly soiled waste water, the so called grey water. Especially in areas of water shortage should this slightly soiled water purified and reused, instead of conveying it to the sewer system. 10 Numerous methods and apparatuses for the use of grey water are known. EP 07 32 457 B1, for example, describes a method and an apparatus for the purification of grey water. The apparatus comprises three grey water tanks, through which the grey water is successively conveyed. The purification of the grey water is 15 carried out in this case by successive settling of the dirt particles. EP 08 55 473 B1 describes a method and an apparatus for the use of grey water, wherein a control device monitors the operating conditions and, if required, triggers certain functions and in addition checks the quality of the purified waste 20 water. EP 08 94 904 B1 shows an apparatus for the reuse of grey water for applications wherein the water quality is of lesser importance. This apparatus can be directly built into the household, so that the grey water is directly used from the bathtub 25 and/or shower for flushing the toilets. EP 10 36 888 A2 describes a system, wherein the slightly soiled grey water from the rinsing cycle of the washing machine is to be used and reused, for example, in the first washing cycles in the washing machine. 30 DE 197 40 642 B4 describes an apparatus, wherein the grey water is forcibly conveyed through a sterilising device. The sterilising device contains an annular channel, in which the grey water is irradiated by a radiation source along the entire length of the annular channel and thus is sterilised.

2 DE 101 56 253 Al shows a plant for the reuse of waste water, wherein not only is the waste water itself reused, but the heat stored in it is also made use of with the aid of a heat exchanger. For this purpose a heat exchanger is provided in the 5 waste water tank, that has a smooth flat exchange surface. The warm waste water is circulated past this heat exchanger surface. In the case of the above described methods the grey water passes through certain purification stages and at the end is stored in a storage tank. The dwell 10 time of the water in this last storage tank depends on the quantity of purified grey water removed. If the requirement is very low, it may happen that the purified water has to be left relatively long in the storage tank, resulting in turn in a deterioration of the water quality. 15 Furthermore, DE 42 28 804 Al describes a waste water plant to supply flushing water for toilets in buildings. This plant comprises a flushing cistern that can be charged with flushing water via a pipeline and can be discharged into an associated toilet, as well as a small treatment tank that on the inlet side has a settling tank charged via a course filter by waste water from bathtubs, showers, 20 wash basins and/or washing machines and a clear water tank, connected with the settling tank via a fine filter. A pipeline, containing a water pump and leading to the flushing cistern, is connected to the clear water tank. From DE 203 16 374 U1 a treatment plant, used on a ship, is known, that has a 25 container, divided into a plurality of chambers. To carry out the treatment, the material to be treated passes through a first and then a second chamber, while there are at least three treatment chambers. The treated mass can be conveyed from the second chamber back into the first one by a pump. 30 DE 195 09 531 Al discloses a method and an apparatus for the reuse of grey water. The apparatus comprises at least two grey water tanks positioned one behind another in such a manner, that the grey water can flow to the second tank only after a certain dwell time in the first tank. Both tanks have funnel-like bottoms with an outlet where the dirt particles can settle and accumulate. In the grey water 3 tanks floating bodies, inoculated with bacteria cultures, are disposed in the grey water. By producing a flow within the water a circulation of the water and of the floating bodies takes place. The flow is so managed that no turbulences will be produced which would prevent the sinking and settling of particles. The possibility 5 of providing three tanks behind one another is also disclosed, whereby the grey water will be increasingly purer in each following tank. The grey water then can be removed from the last grey water container as water ready for use. Finally, from DE 37 12 421 Al an apparatus to substitute potable water for toilet 10 flushing is known. To an enclosed collecting tank, that in its bottom part has a sludge collecting funnel, grey water is conveyed through a pressurised vertical pipe in the tank, said pipe terminating above the funnel. In its top region the tank has an overflow, that can be connected via a pipeline to a waste water pipe of a household. A sludge removing pipeline is connected on the one hand with the 15 sludge collecting funnel and on the other is guided outside of the collecting tank, parallel with it, upwards up to a height that corresponds to the normal filling level in the collecting tank, and terminates in the overflow pipe or in the outlet pipe. One end of a discharge pipe terminates above the sludge collecting tank in the tank, whereas its other end can be connected to the toilet flushing. 20 Description The object of invention is to produce a compact apparatus for the purification of grey water to be reused as potable or process water, whereby the water is continuously subjected to multiple biological purification to achieve an as high as 25 possible degree of purification. A further aspect of the invention concerns a method for the continuous purification of grey water. This objective of the invention is achieved by the subject matter of the independent claim. Features of advantageous configurations of the invention 30 become obvious from the dependent claims. The apparatus according to the invention is used for the purification of grey water, preferably from the bathtub, shower or of other slightly soiled waste water.

4 The apparatus for reusing grey water comprises at least two storage tanks for grey water, each of them having a sludge outlet in the bottom region. The grey water is directly conveyed to the first storage tank. According to a 5 further embodiment the grey water can be initially conveyed through a pre-filter, connected upstream. The purpose of this pre-filter is the removal of course dirt particles and it can be automatically back-washed at an appropriate pressure using the operational water pump. 10 The bottom region of the storage tank is preferably funnel-shaped, so that the settled dirt particles move downward and due to the slight turbulence and the low flow velocity accumulate in this region at the deepest position. At this position a sludge discharge can be provided. 15 The first grey water tank is divided at least into two chambers. In a first chamber it has a bioreactor and in a second chamber it may have an inclined clarifier. This two-chamber division is analogous to the two-step method for the purification in a first grey water storage tank. 20 The first storage tank is relatively large. It has a capacity, for example, of 400 L. Therefore when soiled grey water is fed to the system, first a mixing process takes place, by virtue of which the quality of the water will be immediately improved. 25 In a first step of the method the grey water is first conveyed through the bioreactor and biologically purified therein before in a second step of the method it can flow through the inclined clarifier in a upflow method. Due to this the sedimentation behaviour of the of the solid dirt particles is further optimised and they are guided to the funnel-shaped depression. Furthermore, additional steps of 30 the method, for example a mixing process, may be provided. According to a preferred version the bioreactor comprises a scrubbing body or trickle filter in which a biological purification of the grey water takes place. In this case one deals with a biochemical waste water purification, since in addition to 5 the biological decomposition process parallel chemical reactions of the contaminants also take place. The organic compounds, contained in the grey water, are subjected during the biological waste water purification to a decomposition process. The decomposition is essentially carried out by 5 microorganisms in conjunction with released oxygen. During this by virtue of metabolic processes inorganic compounds and biomasses are produced. In the trickle filter aerobic microorganisms, decomposing the dirt, are settled on solid material (growth body). The colony of microorganisms is also described as 10 biological turf. The growth body may be made from different materials which preferably offer a large surface to be colonised by the microorganisms. Natural stones (e.g. volcanic slag), for example, or synthetic filler bodies, may be used. Above the bioreactor a perforated sheet metal or a construction with a 15 corresponding function may be provided. The grey water is conveyed to the bioreactor through this perforated sheet metal. The grey water is distributed by the perforated sheet metal or the corresponding construction over the entire upper absorbing surface of the bioreactor. An automatic aeration of the grey water is carried out simultaneously, without the necessity of additional aerating 20 devices. According to a further embodiment a rotating sprinkler is provided above the bioreactor, through which the grey water evenly flows and is distributed. 25 At least one of the storage tanks, but preferably both, have a syphon to remove the sludge. For this purpose the syphon is attached to the sludge outlet and mostly serves the purpose of removal of the settled dirt material. The sludge is syphoned off into the overflow. 30 At specified intervals the syphon syphons the dirt and sludge accumulated on the bottom of the first storage tank. The syphoning is limited by an outflow limiter via an air valve. This is connected with the syphon and the first tank.

6 The use of the syphon can be the result of a particularly great inflow. Alternatively, a regulation of the supply of potable water at defined intervals, for example every x days, may increase the supply so that to activate the syphon. Furthermore, as an alternative, every x days for a certain time, e.g. for 6 hours, 5 the supply pump to fill the clear water tank can be switched off until the syphon starts again. The method is characterised in that the grey water passes through the bioreactor several times. The grey water, pre-purified, for example, by means of the trickle 10 filter and the inclined clarifier, is returned to the bioreactor via a circulating or charging pump, that can be provided, for example, above the inclined clarifier or in another position, and passes repeatedly through the bioreactor. By virtue of this a continuous improvement of the water quality is achieved due to multiple biological purification and sedimentation. 15 According to a preferred embodiment the grey water passes through the biological purification cycle in the first storage tank several times within a specified time. 20 After the expiration of the preset/specified time the water, purified several times, is conveyed to the second storage tank. The purification cycle can be set, for example, for 5 hours; afterwards the water is conveyed to the clear water tank that is preferably situated above the first storage 25 tank. The cycle of filling the clear water may last one hour. In this conjunction provision may be made that the water passes through a disinfecting device, that is situated between the first and the second storage tanks. According to a preferred embodiment in the case of the disinfecting device 30 one deals with a UV lamp. The microorganisms possibly contained in the water are destroyed by the UV radiation. The advantage of the conveying of the grey water, purified several times, from the first to the second storage tank after a specified period is that the UV lamp 7 has to be switched on only for a few hours per day. This controlled operating period prolongs the service life of such a UV lamp. A further advantage of this system is that only one valve is required in the supply 5 line to the first chamber (= bioreactor) of the first storage tank. When the valve is opened, the pump conveys the water again to the bioreactor, since the water column to the clear water automatically prevents an inflow to this tank. If, according to a preferred embodiment, only little water is supplied to the first 10 storage tank, upon reaching a minimum water level in this first storage tank the conveying pump returns the water back only to this tank and no longer to the clear water tank. This means that the conveying cycle is automatically switched off when there is only a little grey water in the first storage tank. This will ensure that the water still passes through the biological purification several times and will 15 have the necessary purity and will trigger the syphon when reaching the maximum water level. The second storage tank is also described as the clear water tank, since in this only water, purified several times, is present. This tank may also have a funnel 20 shaped depression with sludge discharge, in the outlet of which sediments, still present, may be deposited. In turn the outlet is connected to a syphon, that again has an air throttle connected to the clear water tank. Should the water level exceed a specified level in the second storage tank, a 25 portion of the water will be discharged via the syphon. The excess water is conveyed from the second storage tank via the bioreactor to the first storage tank. By virtue of this a further improvement of the water quality is achieved in the first storage tank. 30 Thus when the clear water tank is full, water, already disinfected, can return to the first storage tank, leading to a further improvement of the water quality.

8 A particular advantage is that in the case of longer shutdown periods a continuous water circulation takes place, in particular that of the clear water, preventing germination and deterioration of the water quality. 5 The equipment operates according to the principle of continuous circulation. This also corresponds to the principle of natural purification of water, for example, in a brook. The water to be purified is continuously moving in the equipment, i.e. it is continuously aerated and further purified. A minimum cycle period and a minimum tank capacity ensure a minimal water quality. 10 The less water is removed later during the operation, the better the water quality will be. If a lot of water is removed, the water quality of the freshly incoming water after the minimal purification phase is still adequate for the consumers who are connected to the purification circulation. 15 The time periods can be set differently and adapted to suit depending on the requirement placed on the water quality, the quantity of the incoming grey water and the demand for waste water. 20 By virtue of the free flow of water on the trickle filter it will be continuously supplied with oxygen. Thus a further advantage of the equipment is that no aeration with associated accessories and problems is necessary. A further configuration of the equipment is based on the fact, that a further 25 purification stage takes place between the clear water tank and the first storage tank. This stage can look the same as the first storage tank and comprise a trickle filter, inclined clarifier, syphon as well as a conveying pump and a valve. This stage can be additionally installed if a further improvement of the water 30 quality is required. The removal of waste water can be affected by an underwater pump, positioned in the clear water tank. The advantage of this is that no further space for installation is required and the noise of the pump is minimised due to the 9 arrangement of the tank. However, the water can be also evacuated from the tank by using a conventional suction pump. According to a further variant the water can be fed by gravity to the pipeline system of the consumer. This could be the case, for example, when the system is installed in the roof. 5 The follow-up supply can be carried out via a mechanical floating valve, that directly supplies potable water into the clear water tank via a free inlet. The valve has in this case an extended lifting arm that is immersed into the water, so that when the water level falls below a minimum, a small quantity of potable water will 10 be supplied. Alternatively, the follow-up supply can be carried out via an electronic magnetic switch, that opens and closes an electric valve depending on the water level. 15 The modus operandi of the equipment according to the method according to the invention is now illustrated based on a numerical example. According to a variant of the configuration a gradual grey water supply of 40-160 L may be provided for. The inflow to the first chamber of the first storage tank is 20 carried out, for example, with a flow rate of 20 L grey water per minute. This grey water is mixed with the water already in the tank and is integrated with it during the continuous purification process. 25 When the water capacity is established at 350 L ± a buffer capacity of 150 L, a maximum of 500 L, for example, has to be circulated. When using an aquarium pump with a circulating capacity of 5 /min, the total water capacity would have been circulated once after 100 minutes. 30 In the case of a preset purification period of 5 h within the first storage tank, the water (depending on the volume) would have been circulated at least three times and consequently has passed through the biological purification and sedimentation at least three times.

10 After five hours the aquarium pump is reset to fill the clear water tank. In this conjunction approx. 200 L water, for example, several times purified, is transferred to the clear water tank. The filling process lasts approx. 40 minutes. 5 At the same time the water passes through a disinfecting device, for example a UV lamp. This UV lamp has to be switched on only for that 40 minutes while the filling process of the clear water tank is carried out. If in the meantime no clear water is removed from the second storage tank, the 10 excess clear water flows over a skimmer pipe again back to the first storage tank. According to a preferred embodiment the method for the reuse of grey water comprises at least three different steps of the method. The steps of the method that can be combined are (a) aeration of the grey water, (b) mixing of the grey 15 water with already pre-purified grey water, (c) biological purification, (d) sedimentation of existing dirt particles and/or of activated sludge, (e) removal of the settled dirt particles and/or of settled activated sludge by means of a syphon, and (f) sterilisation of the grey water by means of the disinfecting device. 20 According to a particularly preferred embodiment the method comprises all the above mentioned steps of the method in the sequence stated. In the case of the disinfecting device one could use, for example, a UV lamp to kill the remaining germs in the grey water. 25 According to a further embodiment after passing through the trickle filter the grey water can be aerated again. Due to this additional oxygen is supplied to the biologically pre-purified grey water. This is of particular importance when this biologically pre-purified grey water is to be conveyed again through the trickle filter. The microorganisms present in the trickle filter need the oxygen to enable 30 an effective biological purification. According to a further preferred embodiment a separation step can be provided in the trickle filter. The two-chamber first storage tank contains the bioreactor in the first chamber. There is a separating wall disposed between the two chambers, 11 while the first chamber has an opening at the lower region, through which it is hydraulically connected with the second chamber. This means that the grey water first has to flow through the bioreactor before it reaches the second chamber. 5 The separation step provides that contaminants, in particular fats and oils, that have a lesser density than grey water and consequently swim on top of the grey water, remain in the trickle filter and are not conveyed to the second chamber. To achieve this, the minimum water level must not sink below the separating wall. 10 By virtue of this the fats and oils remain in the trickle filter and consequently are disintegrated by the microorganisms. For the person skilled in the art it is obvious that the return of the purified water to the reactor and/or to one of the tanks of the arrangement according to the 15 invention can be carried out by means of a hydraulic pump or another suitable conveying device. When one talks about pumps in this context, generally all possible types of conveying devices to convey fluids are understood and included. The same is valid, for example, for the term syphon, used in the application. Instead of such a syphon a pump or another suitable conveying 20 device could also be used. Description of the figures Further features, aims and advantages of this present invention become obvious from the following detailed description of a preferred embodiment of the invention, 25 that is not to be used as a limiting example and refers to the attached drawings. At the same time the same components have basically the same reference numerals and partly will not be explained on every occasion. Fig.1 shows a schematic front view of an apparatus for the purification of grey 30 water, Figs.2 and 3 show side views of this apparatus.

12 A possible configuration of a grey water purification apparatus 10 with the first storage tank constructed according to the invention is illustrated based on Fig. 1. The grey water, preferably from the bathtub or the shower or other slightly soiled 5 water, is conveyed via the grey water inlet 22 into the bioreactor 24 that is situated in the first storage tank 20. An embodiment of the apparatus 10 may have such a design that the uncleaned water first is conveyed through a pre-filter. This pre-filter can be automatically 10 backwashed by the operational water pump at an appropriate pressure. The first storage tank 20 has a two-chamber construction. The bioreactor 24 is disposed in the first chamber. Between the first and second chambers 24, 25 there is a separating wall 23. The separating wall has such a design that an 15 opening is present between the first and second chambers 24, 25 in the lower region of the first storage tank 20, so that the two chambers 24, 25 are hydraulically connected. As the result of this the water level is always the same in both chambers 24, 25 of 20 the first storage tank 20. There is a bioreactor 24 disposed in the first storage tank 20, said bioreactor partially operating as a trickle filter immersed in the water. It comprises an embankment of growth bodies with a possibly large surface, on which bacteria 25 settle, assuming biological purification of the soiled grey water. Above the bioreactor 24 a perforated sheet or another construction may be provided, that ensures that the water flows evenly distributed into the bioreactor 24 and retains coarse dirt particles. In addition, the inflow carries oxygen into the 30 bioreactor 24. The first storage tank 20 is relatively large, so that as the soiled grey water flows into the system first a mixing process takes place that directly improves the water quality.

13 The first storage tank 20 has a funnel-shaped lower region 21. Due to the low turbulence and low flow velocities in the system solid dirt accumulates on the bottom, in particular in the funnel 21. To further optimise the sedimentation behaviour, an inclined clarifier 26 can be integrated in the first storage tank 20. 5 The water passes through this inclined clarifier 26 in an upward flow, resulting in that further solid dirt particles will settle and slide into the funnel-shaped depression. At the bottom funnel-shaped depression 21 a syphon 28 is attached. This syphon 10 28 draws at determined intervals from the tank 20 the dirt and sludge accumulated at its bottom to the overflow. The suction is limited via an outflow limiter by an air valve. It is connected to the syphon and the tank 20. If the syphon 28 is positioned in the interior of the tank 20, the air valve can be a small opening in the syphon 28. In this case the syphon 28 is operated at a specified water level 15 in the tank 20. If this water level is not achieved due to the removal of a large quantity of grey water, then by controlling the cyclical pumping in the second storage tank/clear water tank 40 it can be interrupted until this predetermined water level is reliably achieved, so that the syphon 20 commences to operate. 20 A recirculating/charging pump 30 disposed in the tank 20, said pump returning the pre-purified water first to the bioreactor 24. As described, the water circulates here again over the trickle filter and so on. Therefore the water is continuously circulated and this continuously improves the water quality due to biological purification and sedimentation. To reduce the electricity consumption, this return 25 conveying can be switched on periodically by means of a circuitry. After a certain purification cycle. e.g. a 5 h cycle, the water can be conveyed to the clear water tank 40, that is preferably provided above the first storage tank 20. The cycle of filling of the clear water tank 40 can take, for example, 1 h. While 30 the pre-purified water flows into the clean water tank via the water inlet 34, the water can pass through a disinfecting device 42. In the case of the disinfecting device 42 one can deal, for example, with a UV lamp. The advantage of this is that a UV lamp 42 has to be switched on only for a few hours each day and 14 operates only for a few hours each day. This results in a very long service life of the UV lamp 42. An advantage is that only one valve 32 is required for the return from the tank 20 5 to the bioreactor 24. When the valve 32 is closed the circulating/charging pump 30 conveys the water to the clear water tank 40. In the case of an open valve 32 the geodetic pressure differential prevents an inflow into the clear water tank 40. The clear water tank 40 also has a funnel-shaped bottom 41, in the outlet of 10 which sediments, still present, can settle. The outlet in turn is connected to a syphon 44, that too is fitted with an air valve connected to the clear water tank 40. When the water level rises in the clear water tank 40 above a certain level, a portion of the water is discharged via the syphon 44. The water is then returned 15 to the tank 20 via the bioreactor 24. Accordingly, in the case of a full clear water tank 40 already disinfected water can also return to the first storage tank 20, further improving the water quality. A particular advantage is also that even in the case of longer shutdown periods a 20 continuous circulation of the clear water is carried out, preventing germination and deterioration of the water quality. Furthermore, the apparatus additionally comprises at least two emergency overflow devices 36 and 46, while each emergency overflow device 36, 46 is 25 assigned to one of the storage tanks 20, 40. The emergency overflow devices 36, 46 should prevent an overfilling of the storage tanks. When only a little clear water is removed, a portion of the water, subjected to multiple purification and pumped from the storage tank 20 into the clear water 30 tank 40, flows via the bioreactor 24 back into the tank 20. By virtue of this the volume of water in the tank 20 is reduced by less than the quantity of water pumped upward. However, if more grey water flows in through the grey water inlet 22, the capacity of the first storage tank 20 could be fast used up and this may lead to the bursting of the tank 20. For this reason the container 20 has an 15 emergency overflow 36 through which the grey water can flow out from the first storage tank 20 when the water level exceeds in this tank 20 a certain level. The same is valid for the emergency overflow 46 of the upper clear water tank 40. 5 Furthermore, a potable water supply valve 50 is allocated to the upper clear water tank 40. If a lot of clear water is removed from the upper clear water tank 40 while only a little grey water flows in via the grey water inlet 24, potable water may be supplied to the clear water tank 40 via the potable water supply valve 50, thus 10 maintaining the continuous circulation. The invention is not limited to the above embodiments. A plurality of variants and deviations are conceivable which make use of the concept of the invention and consequently also fall into the scope of protection.

16 List of reference numerals 10 Grey water purification plant 20 First storage tank 21 Funnel-shaped lower region 22 Grey water inlet 23 Separating wall 24 Bioreactor (first chamber in the first storage tank) 25 Second chamber in the first storage tank 26 Inclined clarifier 28 Syphon 30 Circulating/charging pump 32 Valve 34 Water inlet of the first storage tank 36 Emergency overflow of the first storage tank 40 Second storage tank/Clear water tank 41 Funnel-shaped bottom 42 Disinfecting device 44 Syphon 46 Emergency overflow of the second storage tank

Claims

1. A method to reuse grey water by means of passing it through at least two storage tanks (20; 40) for grey water, each of which has a sludge outlet 5 provided in the bottom region, characterised by the following steps: a. treatment of the grey water in a first storage tank (20), wherein the treatment comprises at least a biological purification in a bioreactor (24), 10 b. transfer of the purified grey water from the first storage tank (20) to the second storage tank (40), and c. return of the purified grey water from the second storage tank (40) to the first storage tank (20). 15

2. A method according to claim 1, characterised in that water is conveyed from the second storage tank (40) to the first storage tank (20) via the bioreactor (24) when the water level exceeds a certain level in the second storage tank (40). 20

3. A method according to claim 1, characterised in that the treatment of the grey water in a first grey water tank (20) comprises at least a biological purification in a bioreactor (24) and that the water, biologically pre-purified, is returned via a circulating/charging pump (30) to the bioreactor (24) and repeatedly passes 25 through it.

4. A method according to claim 1 or 2, characterised in that the treatment of the grey water in a first grey water tank (20) comprises a biological purification in a bioreactor (24) and a mechanical purification in an inclined clarifier (26) and 30 that the water, pre-purified by means of the bioreactor (24) and the inclined clarifier (26), is returned by a circulating/charging pump (30) to the bioreactor (24) and repeatedly passes through it. 18

5. A method according to any one of the preceding claims, characterised in that this cycle is repeated several times within a set time.

6. A method according to any one of the preceding claims, characterised in that 5 after the expiry of the set time the water, purified several times, is conveyed to a second storage tank (40).

7. A method according to any one of the preceding claims, characterised in that the water, purified several times, during its conveying to the second storage 10 tank (40) passes through a disinfecting device (42).

8. A method according to any one of the preceding claims, characterised in that the water, purified several times, during its conveying to the second storage tank (40) is irradiated by means of UV. 15

9. A method according to any one of the preceding claims, characterised in that residual sediments settle in the funnel-shaped depression (41) of the second storage tank (40) and are removed by suction to the overflow by means of a syphon (44). 20

10. A method according to any one of the preceding claims, characterised in that in a further step of the method grey water is mixed with already purified grey water. 25

11. A method according to any one of the preceding claims, characterised in that in the bioreactor (24) the grey water is conveyed through a trickle filter.

12. A method according to any one of the preceding claims, characterised in that after passing through the trickle filter (24) the grey water will be repeatedly 30 aerated.

13. A method according to any one of the preceding claims, characterised in that the grey water is conveyed above the bioreactor (24) through a perforated sheet metal. 19

14. A method according to any one of the preceding claims, characterised in that the grey water is automatically aerated.

15. A method according to any one of the preceding claims, characterised in that 5 the settled dirt particles accumulate in the funnel-shaped depression (21) of the first storage tank (20).

16. A method according to any one of the preceding claims, characterised in that the sludge and dirt accumulated in the funnel-shaped depression (21) of the 10 first storage tank (20) is removed by suction to the overflow by means of a syphon (28).

17. A method according to any one of the preceding claims, characterised in that the minimal water level in the first storage tank (20) does not fall below the 15 separating wall (23) between the first (24) and the second (25) chambers.

18. A method according to any one of the preceding claims, characterised in that contaminants with a density that is less than that of the grey water remain in the trickle filter and are completely decomposed. 20

19. A method according to any one of the preceding claims, characterised in that contaminants with a density that is less than that of the grey water reach the second chamber (25) of the first storage tank (20). 25

20. An apparatus (10) to reuse grey water with at least two storage tanks (20; 40) for grey water, each of which has a sludge outlet provided in the bottom region, characterised in that the first storage tank (20) has a bioreactor (24) and that the second storage tank (20) has a syphon (44) that upon reaching a specified water level in the second storage tank (40) returns a portion of the 30 water from the second storage tank (40) to the first storage tank (20).

21. An apparatus according to claim 20, characterised in that the first storage tank (20) is divided into two, while the first chamber has a bioreactor (24) and the second chamber an inclined clarifier (26). 20

22. An apparatus according to claim 20 or 21, characterised in that the bioreactor (24) is a trickle filter.

23. An apparatus according to any one of claims 20 to 22, characterised in that a 5 perforated sheet metal is disposed above the bioreactor (24) or trickle filter to distribute the water.

24. An apparatus according to any one of claims 20 to 23, characterised in that the bioreactor (24) is an embankment of growth bodies. 10

25. An apparatus according to any one of claims 20 to 24, characterised in that at least one storage tank (20; 40) has a syphon (28; 44) to remove the sludge.

26. An apparatus according to any one of claims 20 to 25, characterised in that 15 between the first (20) and the second storage tank (40) a disinfecting device (42), in particular a UV lamp, is provided.

27. An apparatus according to any one of claims 20 to 26, characterised in that the second storage tank (40) is provided above the first storage tank (20). 20

28. An apparatus according to any one of claims 20 to 22, characterised in that the first (24) and the second chamber of the first storage tank (20) are separated by a separating wall, while there is a hydraulic connection between the two chambers in the lower region of the first storage tank (20). 25