Cleaning and infiltration system

Description

[0001] The invention relates to a purification and infiltration system for rainwater according to the preamble of claim 1, comprising a storage / infiltration stage and a stage upstream of the storage / infiltration stage, wherein the storage / infiltration stage is designed to receive the rainwater for intermediate storage and to release it for infiltration and the stage upstream of the storage / infiltration stage is coupled to the storage / infiltration stage in such a way that an outflow of the rainwater from the stage upstream of the storage / infiltration stage into the storage / infiltration stage is only possible when the stage upstream of the storage / infiltration stage is flooded.

[0002] For the temporary storage and infiltration of fluids, especially rainwater, infiltration trenches are often used. These contain distribution pipes and are filled with either gravel or infiltration devices (hollow bodies). Modern storage / infiltration systems often contain modular hollow bodies that together form the static retention of the container and, depending on the application, are encased in an open-pore membrane, such as a nonwoven fabric (infiltration system) or foil (storage system).

[0003] Such storage / infiltration systems are sensitive to contamination from solid deposits as well as the ingress of oil or other light liquids. The infiltration systems are equipped with a casing made of water-permeable material through which the temporarily stored rainwater can seep into the ground at a defined rate and speed. If, for example, a rainfall event introduces a corresponding amount of contaminants into the system, solids settle as sediment. As a result, the water-permeable casing will clog to such an extent that water drainage is no longer possible or can only occur to a limited extent.

[0004] To prevent such clogging, a treatment stage is often installed upstream of the storage / infiltration system. This stage cleans the rainwater of foreign matter and / or foreign substances before it is fed into the storage / infiltration system. The inflow from the treatment stage to the storage / infiltration system is usually via a hydrostatic gradient. Consequently, the rainwater can only flow from the treatment stage to the storage / infiltration stage when the treatment stage is flooded.

[0005] However, this design means that a residual amount of precipitation remains in the treatment stage after the rainfall event has ended. Without subsequent precipitation, the remaining precipitation cannot overcome the hydrostatic gradient and thus cannot drain into the storage / infiltration stage. However, residual precipitation that remains in the treatment stage and cannot drain away can lead to undesirable anaerobic organic digestion processes and re-dissolution of substances, as well as to inhibited biological degradation of the contaminants by microorganisms. Furthermore, this volume of water blocks a potential retention volume.

[0006] The state-of-the-art treatment and infiltration systems do not yet allow for the prevention of fouling processes in the treatment system caused by rainwater remaining in the treatment system or for the release of the storage space.

[0007] KR 101 288 606 B1 describes an infiltration basin designed to reduce point-source contaminants in runoff water by installing a filter tank, a pretreatment basin, and a collection well. This infiltration basin comprises a pretreatment tank, a collection well, a filter tank, and filter nets. The pretreatment tank has an upper wall and a lower wall. An inlet pipe and a base with through holes are connected to the upper wall. The lower wall consists of a water outlet opening and an overflow section. The collecting basin consists of the base with the through holes, the water overflow hole, and the overflow section. The collecting basin consists of the lower wall, which is connected to the upper wall by a drain pipe. The filter tank is installed between the pretreatment tank and the collecting basin. The filter tank consists of the base with the through holes.

[0008] Furthermore, KR 100 966 038 B1 discloses a rainwater infiltration system comprising a precipitation stage, a filtration stage, and a storage stage. The filtration stage comprises a filtration tank and a phosphorus removal layer. Several holes for filtering rainwater are formed in the bottom of the filtration tank. The phosphorus removal layer is formed inside the filtration tank. The phosphorus removal layer is formed by inserting filter materials.

[0009] Finally, KR 101 222 885 B1 discloses a rainwater collection system comprising a body, a filter layer, a rainwater outlet, and a device for removing rainwater. The housing includes a rainwater inlet, a rainwater outlet, a sand trap, a tank for separating suspended solids, and a filter tank. The filter layer includes two sponge filters and an activated carbon filter. The initial rainwater drainage opening is formed on the bottom surface of the sandbox and includes an opening and closing plate, a float, and a post. The opening and closing plate covers the inlet of the first rainwater drainage opening. The post opens the opening and closing plate through the weight of the float and allows the opening and closing plate to close the initial rainwater drainage opening when the float floats on the water.

[0010] Based on this, the object of the invention is to provide such a cleaning and infiltration system in which the aforementioned problems are reduced or avoided.

[0011] This problem is solved by the subject matter of patent claim 1. Preferred developments can be found in the subclaims.

[0012] According to the invention, the drainage element is designed and arranged in such a way that rainwater can still flow out of the stage upstream of the storage / infiltration stage even when the stage is no longer flooded to such an extent that the rainwater flows into the storage / infiltration stage. Thus, a reduction in the rainwater level or complete drying out is possible even if the storage / infiltration stage is arranged higher, for example, to discharge rainwater into a sewer. In principle, the drainage element should at least enable a reduction in the rainwater level in the stage upstream of the storage / infiltration stage.

[0013] A key aspect of the invention is that during normal operation of the treatment and infiltration systems, i.e., when the treatment stage is flooded, the majority of the rainwater seeps into the ground via the storage / infiltration stage, while at the same time only a smaller portion seeps through the drainage element as a leak. According to the invention, the majority of the rainwater that seeps into the ground via the storage / infiltration stage when the treatment stage is flooded is at least 95%, particularly preferably 99%, and most preferably 99.9%.

[0014] According to a preferred development of the invention, the drainage element is designed and arranged in such a way that it enables the stage upstream of the storage / infiltration stage to dry out. Due to the drainage element, in this design the rainwater can drain away almost completely and the stage upstream of the storage / infiltration stage can thus dry out. If in this case we are talking about the stage upstream of the storage / infiltration stage drying out, this means that this stage is not permanently filled with rainwater, but the rainwater can be discharged essentially completely via the drainage element into the soil surrounding the storage / infiltration system or drainage element or into a canal or receiving water when the flooding of this stage is no longer sufficient to allow outflow into the storage / infiltration stage.When it is stated that the stage upstream of the storage / infiltration stage can "essentially" dry out, this is intended to express that, for various reasons, a small amount of precipitation water can naturally always remain behind, e.g., due to roughness or the ingress of obstructions into the stage. However, the amount of precipitation water remaining is so small that the desired effects of drying out, described below, are not impaired.

[0015] When the stage upstream of the storage / infiltration stage, which may be designed as a purification stage, dries out, aerobic conditions are created in this stage, meaning oxygen is supplied to the contaminants that are retained by the purification stage during the cleaning process. The aerobic conditions improve the biological degradation and conversion of the contaminants in the purification stage. The drying out of the purification stage is particularly advantageous for the biological degradation of light liquids such as oils, fats, and all other hydrophobic organic materials. While these float on top of the fluid and are thus difficult for the microorganisms responsible for degradation to reach, the hydrophobic materials form a film over the retained solids during dries out.This increases the contact area between the microorganisms responsible for degradation and the light liquids, which promotes degradation.

[0016] Furthermore, the drying process ensures that the cavities of the treatment stage are "dried out," preventing damage to the inner walls. This allows separated sediments and light liquids, in particular, to be further stabilized and decomposed aerobically or removed. The cleaning effect is designed to be maintained regardless of the fluid level, even when the treatment stage is drying out.

[0017] According to a preferred development of the invention, the storage / infiltration stage and the drainage element are designed to release the rainwater for infiltration into the soil surrounding the storage / infiltration system or drainage element, into a sewer network, or into a receiving watercourse. The release of the rainwater to the soil occurs, for example, via a fluid-permeable material through which the temporarily stored rainwater can seep into the soil at a defined volume and speed. The fluid-permeable material can be a fleece or a fluid-permeable, open-pore membrane. Furthermore, the release of the rainwater to the environment can additionally or alternatively occur via boreholes in the outer walls of the containers of the storage / infiltration stage and / or the drainage element.The diameter of the boreholes determines the defined amount and speed at which the rainwater can be released into the ground. The drainage element can be configured to drain into the ground via micro-infiltration or into the sewer or receiving waters via micro-throttles.

[0018] In principle, it is possible for the stage upstream of the storage / infiltration stage to perform a variety of functions. However, according to a preferred embodiment of the invention, it is provided that the stage upstream of the storage / infiltration stage is a purification stage, or that the stage upstream of the storage / infiltration stage is a treatment stage, which in turn is preceded by a purification stage. Accordingly, the rainwater is either first fed to a purification stage before flowing into the storage / infiltration stage, or it is fed to a purification stage, from where it is fed to a treatment stage before flowing into the storage / infiltration stage. Depending on requirements, the treatment stage can therefore be inserted between the purification and the storage / infiltration stage.

[0019] If the stage upstream of the storage / infiltration stage is a purification stage, the purification stage cleans the rainwater of impurities before it is absorbed by the storage / infiltration stage. This protects the storage / infiltration system from clogging and ensures its long-term performance.

[0020] An additional possible treatment stage treats the rainwater after the purification process in the treatment stage before it flows into the storage / infiltration stage. Technical filters can be used to treat the rainwater. Examples include X-filters with sand, gravel, and / or activated carbon, precoat filters, candle filters, room filters, stratified bed filters, simple mechanical filters such as screens, membranes, and sieves, and / or magnetic filters.

[0021] According to a preferred embodiment of the invention, the purification stage has an inlet through which the rainwater can be fed to the purification stage, wherein the inlet has a hydrostatic gradient. Consequently, it is possible to feed the rainwater to the purification stage via the inlet without the application of force, for example, without the application of force by pumps.

[0022] The inlet can, for example, comprise a canal, an inlet shaft, or a sewer system. The storage / infiltration system can be connected to the sewer network of a municipality or catchment area.

[0023] A significantly preferred development of the invention is that the rainwater can be fed to the storage / infiltration stage via an inlet, wherein the inlet is positioned such that the rainwater can only reach the inlet at a predetermined fill level in the stage upstream of the storage / infiltration stage. This ensures that the stage upstream of the storage / infiltration stage also has a storage function. The stage upstream of the storage / infiltration stage must "fill up," i.e., be flooded, until the rainwater can reach the inlet to the storage / infiltration stage.

[0024] A preferred development of the invention is that the purification stage and / or the treatment stage are designed to receive the rainwater for temporary storage. Because the inlet to the purification stage and / or treatment stage, as well as the inlet to the storage / infiltration stage, have a hydrostatic gradient, the individual stages must be flooded so that the rainwater can flow into the next stage. Consequently, the purification stage and / or treatment stage can also be used for temporary storage of the rainwater.

[0025] According to a preferred embodiment of the invention, the drainage element is positioned such that the inlet to the drainage element has a hydrostatic gradient. This ensures that the rainwater can be fed to the drainage element without the application of force, for example, by pumping.

[0026] In principle, the drainage element can be designed to be water-permeable in many ways. However, according to a preferred embodiment, the drainage element has holes and / or is coated with a water-permeable textile. A geotextile, for example, can serve as the water-permeable textile. The geotextile can be made either of natural fibers, such as reed, jute, and / or coconut, or of synthetic fibers, such as polypropylene, polyamide, polyester, and / or polyethylene. The diameter of the holes in the housing of the drainage element determines the speed at which the rainwater can seep into the ground.

[0027] In a preferred embodiment of the invention, the drainage element is connected to the stage upstream of the storage / infiltration stage either directly or via a pipeline leading away from the storage / infiltration stage. The drainage element can be flexibly positioned during installation of the treatment and infiltration system, allowing for targeted adaptation to local conditions.

[0028] According to a preferred embodiment of the invention, the drainage element is controllable in such a way that its dry-fall function can be switched on or off or regulated. This is made possible by the drainage element being controllable, preferably mechanically or electromechanically. The inflow to the drainage element can be regulated by closing and opening, for example, a flap.

[0029] As already mentioned, the purification stage serves to purify the rainwater. According to a preferred embodiment of the invention, the purification stage is designed to remove solids, light liquids, and / or dissolved substances from the rainwater.

[0030] Road traffic, in particular, is responsible for a large proportion of the contaminants contained in rainwater, with its inputs, for example, from tire or brake system wear and light fluids such as mineral oil hydrocarbons (MOHCs) and polycyclic aromatic hydrocarbons (PAHs). In addition, a wide variety of substances from industry and agriculture enter the storage / infiltration system along with the rainwater. The treatment stage is designed to remove these contaminants from the rainwater. The contaminants are removed before the rainwater is absorbed by the storage / infiltration stage or an intermediate stage.

[0031] To remove contaminants from rainwater, the treatment stage preferably comprises several sections, each with a maintenance option. Due to the fact that the contaminants are a mix of different types of contamination, the treatment stage comprises several sections that, in combination, clean the rainwater of these contaminants. The sections can be tailored to the expected contaminants in terms of their cleaning performance and cleaning principle. This allows for different physical and chemical-physical mechanisms of action to be deployed.

[0032] The treatment and infiltration system has several differently positioned maintenance openings, ensuring access to each stage for maintenance of the entire stage or individual sections. Maintenance of a stage can also be performed via the inlet or inlet of the stage.

[0033] According to a preferred development of the invention, the cleaning stage comprises a sedimentation section, a sorption section and / or a membrane filter section.

[0034] The sedimentation section is designed to retain sedimentable solids. These solids settle as sediment on the bottom of the section. The maintenance option allows the sediment to be vacuumed or removed during maintenance, for example.

[0035] The sorption section is designed to retain light liquids as well as finely particulate solids and dissolved substances. Furthermore, the sorption section serves to separate the sedimentation section from the membrane filter section, preventing coarser or smaller amounts of foreign matter from reaching the membrane filter section. In principle, the sorption section can comprise a filter layer, for example, a sorption substrate for removing heavy metals. However, the sorption section is preferably constructed in multiple layers to meet different requirements. For this purpose, the sorption section is constructed in multiple layers, consisting of different filter layers. The sorption section comprises, for example, a layer of coalescence fabric, a layer of sorption fabric, and an ion exchange surface.In particular, it is intended that the sorption section can be inspected and / or replaced using the maintenance option. Alternatively, a sorption section can also be integrated into the sedimentation section. For example, an oil separator can be integrated into the sedimentation section. In the downstream sorption section, further separation of light liquids can then take place using coalescence fabric, for example. Alternatively, the sorption section can also be arranged downstream of the storage / infiltration stage. This should then enable, for example, further biological treatment of the rainwater using biofiltration.

[0036] The membrane filter section is designed to remove further foreign matter using a membrane. The membrane should be designed to effectively remove foreign matter from the rainwater that cannot be removed by settling and / or filtration, particularly foreign matter in the size range smaller than 0.63 µm. Therefore, the membrane pores must be designed to separate foreign matter in the size range smaller than 0.63 µm. However, the separated foreign matter must not lead to blockage, i.e., excessive hydraulic influence on the membrane. Cleaning, preferably by rinsing, must also be possible.

[0037] To ensure that no foreign substances already present in the treatment stage are released, particularly when filling the treatment stage, and thus introduced into the storage / infiltration stage, the treatment stage is designed in such a way that the foreign substances are retained by the treatment stage. In particular, this means a sustained retention of the foreign substances. The treatment stage is therefore designed in such a way that a renewed fluid introduction does not lead to remobilization of the previously sedimented solids or renewed release of the adsorbed substances. Remobilization is also prevented during drying out in order to prevent further transport of the foreign substances. The sorption section upstream of the membrane filter section preferably ensures that foreign substances from the sedimentation area do not enter the membrane filter section during the drying out process.

[0038] In this context, a preferred development of the invention provides for flow-reducing structures to be provided in the inlet and / or in the treatment stage. The inlet and / or the treatment stage are therefore equipped with mechanical or structural elements that reduce the flow of the rainwater. This ensures that the flow is low enough so that foreign matter in the treatment stage, in particular solids that have already settled, does not remobilize. The flow-reducing structures influence, for example, the inflow geometry of the treatment stage, resulting in a defined inflow without turbulence. The flow-reducing structures can be, for example, flow separators, baffles, submersible walls, or sludge walls. These installations serve to hydraulically and qualitatively optimize the inlet and / or the treatment stage.Furthermore, obstacles in the inlet and / or treatment stage may be present that slow the flow of the rainwater. These could be grooves, elevations, depressions, or similar roughness.

[0039] The invention is explained in more detail below using a preferred embodiment with reference to the drawings.

[0040] The drawings show Fig. 1 schematically shows a cleaning and infiltration system according to a preferred embodiment of the invention, Fig. 2a schematically shows a cleaning and infiltration system according to a further preferred embodiment of the invention, Fig. 2b schematically shows a cleaning and infiltration system similar to Fig. 2a with an additional drainage element into the surrounding soil, Fig. 2c schematically a cleaning and infiltration system similar to Fig. 2a with a drainage element between successive stages, Fig. 3a schematically a cleaning and infiltration system similar to Fig. 1 with overflowing treatment stage and Fig. 3b schematically a cleaning and infiltration system similar to Fig. 1 when the cleaning stage is not overloaded.

[0041] In built-up areas, such as roads or parking lots, storage / infiltration systems are usually installed underground. Fig. 1 shows a schematic diagram of a treatment and infiltration system 1 installed under a road 7. Fig. 1 , as well as the Fig. 2a , 2b and 2c , only show the structure of the respective treatment and infiltration system 1 without rainwater.

[0042] Stage 22, which precedes the storage / infiltration stage 2, is in Fig. 1 a purification stage 3. The rainwater can be fed to purification stage 3 via an inlet 9a. The inlet 9a has a hydrostatic gradient so that the rainwater can be fed to purification stage 3 without the application of force. Purification stage 3 has maintenance openings 14 that enable above-ground maintenance work on the underground purification and infiltration system 1.

[0043] If the level of the rainwater rises, for example during a persistent rainfall event, the treatment stage 3 becomes flooded, allowing the rainwater to be fed to the storage / infiltration stage 2 via an inlet 4. Because the treatment stage 3 must be flooded so that the rainwater can flow into the storage / infiltration stage 2, the treatment stage 3 serves as an intermediate storage facility for the rainwater. In the storage / infiltration stage, the rainwater treated in the treatment stage 3 is not only stored but also seeps into the soil surrounding the treatment and infiltration system. The drainage element 5 enables the treatment stage to dry out when the rainfall event subsides.It also features a hydrostatic gradient so that the remaining rainwater that could not be fed into the storage / infiltration system via the inlet can be fed to the drainage element 5 without the application of force. The remaining rainwater can seep into the soil 6 via the drainage element 5, allowing the treatment stage 3 to dry out.

[0044] As already mentioned, the stage 22 preceding the storage / infiltration stage 2 can also be a treatment stage 8, which is preceded by a purification stage 3. This structure is shown in Fig. 2 shown schematically. The cleaning stage 3 and the treatment stage 8 are connected to each other via an inlet 9b. This inlet 9b also has a hydrostatic gradient so that both the cleaning stage 3 and the treatment stage 8 serve as intermediate storage for the rainwater. Both the cleaning stage 3 and the treatment stage 8 each have a maintenance opening 14 for maintenance work. In this embodiment, the drain element 5 is connected to the treatment stage 8 via a leading pipe 15 and an inlet 9c to the drain element 5. The rainwater can be fed to the storage / infiltration stage 2 via an inlet 4. In the storage / infiltration system, the rainwater seeps into the soil 6.

[0045] Fig. 2b shows a similar structure as Fig. 2a , whereby the treatment stage 3 is provided with its own drainage element 5', which not only allows the rainwater from the treatment stage 3 to drain via the inlet 9b into the treatment stage 8, but - of course to a much lesser extent - also allows it to drain into the surrounding soil, so that the treatment stage can dry out. Alternatively, Fig. 2c a structure in which, instead of such an outlet 5' into the ground, an outlet 5" is provided, which creates an additional connection between the cleaning stage 3 and the treatment stage 8. In this way, the cleaning stage 3 can also dry out, since the rainwater from the cleaning stage 3 can now still flow into the treatment stage 8 via this outlet 5" if the water level in the cleaning stage is not sufficiently high.

[0046] The decisive factor for the functioning of the treatment and infiltration system 1 with drainage element 5 is the respective fill level or level of the rainwater 13. Fig. 3a shows schematically a cleaning and infiltration system 1 similar to Fig. 1 with overflow cleaning level 3, while Fig. 3b a cleaning and infiltration system 1 similar to Fig. 1 schematically shows cleaning stage 3 when not blocked.

[0047] As from Fig. 3a As can be seen, the rainwater 13 is fed to the treatment stage 3 via an inlet 9a. The rainwater usually contains foreign substances 12 in the form of solids, light liquids and dissolved substances. These foreign substances 12 represent pollution that must be removed in the treatment stage. To clean the rainwater 13, the treatment stage is divided into a sedimentation section 16, a sorption section 17 and a membrane filter section 18. The sorption section 17 comprises coalescence fabric 19, sorption fabric 20 and ion exchange surfaces 21. The membrane filter section 18 comprises membrane filters (not shown). When the treatment stage 3 is flooded, the cleaned rainwater 13 can be fed to the storage / infiltration stage 2 via an inlet 4.The container of storage / infiltration stage 2 is covered with a water-permeable textile 11 so that the rainwater 13 can seep through the water-permeable textile 11 into the soil 6. As shown in . Fig. 3a As can be seen, at the same time a small proportion of the rainwater 13 seeps through the drainage element 5. The drainage element 5 has holes 10 through which the rainwater 13 can be released into the soil 6. The diameter of the holes 10 defines the speed at which the rainwater 13 can be released into the soil 6. Since the diameter is selected to be relatively small, the proportion of the rainwater 13 that is released into the soil 6 through this leakage is relatively small compared to the proportion that is released to the soil 6 via the storage / infiltration stage 2.

[0048] If no more rainwater 13 is fed into the treatment stage 3 via the inlet 9a, the level of rainwater 13 in the treatment stage drops so that it is no longer flooded. This condition is in Fig. 3b shown. The remaining rainwater 13 can no longer be discharged into the soil via the storage / infiltration stage. To still allow the treatment stage 3 to dry out, the drainage element is coupled to the treatment stage 3 via an inlet 9c. The drainage element 5 has bores 10 through which the rainwater 13 can be discharged into the soil 6. The remaining rainwater 13 therefore does not seep into the soil 6 via the storage / infiltration stage 2, but rather via the drainage element 5. The treatment stage 3 can therefore dry out almost completely. List of reference symbols

[0049] 1 Cleaning and infiltration system 2 Storage / infiltration stage 3 Cleaning stage 4 Drain 5 Drain element 6 Soil 7 Road 8 Treatment stage 9 Inlet 9a Inlet to cleaning stage 9b Inlet to treatment stage 9c Inlet to drain element 10 Bores 11 Water-permeable textile 12 Foreign matter, solids, light liquids, dissolved substances 13 Rainwater 14 Maintenance opening 15 Discharge pipe 16 Sedimentation section 17 Sorption section 18 Membrane filter section 19 Coalescence fabric 20 Sorption fabric 21 Ion exchange surface 22 Stage upstream of the storage / infiltration stage

Claims

1. A purifying and infiltration system (1) for rainwater (13), comprising a storage / infiltration stage (2) and a stage (22) upstream of the storage / infiltration stage (2), wherein the storage / infiltration stage (2) is designed to receive within itself the rainwater (13) for temporary storage and to dispense it for infiltration, the stage (22) arranged upstream of the storage / infiltration stage (2) is coupled to the storage / infiltration stage (2) in such a way that an outflow of the rainwater (13) from the stage arranged upstream of the storage / infiltration stage (2) into the storage / infiltration stage (2) is possible only when the stage (22) arranged upstream of the storage / infiltration stage (2) is backed up, the stage (22) arranged upstream of the storage / infiltration stage (2) is a purifying stage (3) or the stage (22) arranged upstream of the storage / infiltration stage (2) is a treatment stage (8) which is arranged downstream of a purifying stage (3), and the stage (22) arranged upstream of the storage / infiltration stage (2) has a drain element (5), which then also still allows an at least partial draining of rainwater (13) present in the stage (22) arranged upstream of the storage / infiltration stage (2) when the rainwater (13) no longer flows out from the stage (22) arranged upstream of the storage / infiltration stage (2) into the storage / infiltration stage (2), characterised in that the drain element (5) is embodied in such a way that, when the stage (22) arranged upstream of the storage / infiltration stage (2) is overflowing, a main component of the rainwater (13) of at least 95% can infiltrate via the storage / infiltration stage (2), whereas at the same time a smaller part can infiltrate as leakage through the drain element (5).

2. The purifying and infiltration system (1) according to claim 1, characterised in that the drain element (5) allows the stage (22) arranged upstream of the storage / infiltration stage (2) to run dry.

3. The purifying and infiltration system (1) according to claim 1, characterised in that the storage / infiltration stage (2) and the drain element (5) in the installed state are configured to dispense the rainwater (13) for infiltration in an earth region surrounding (6) the storage / infiltration stage (2) or the drain element (5) into a sewer network or into a runoff capability.

4. The purifying and infiltration system (1) according to any one of claims 1 to 3, characterised in that the purifying stage (3) has an inflow (9a), via which the rainwater (13) can be fed to the purifying stage (3), wherein the inflow (9a) has a hydrostatic gradient.

5. The purifying and infiltration system (1) according to any one of claims 1 to 4, characterised in that the purifying stage (3) and / or the treatment stage (8) are designed to receive within themselves the rainwater (13) for temporary storage.

6. The purifying and infiltration system (1) according to any one of claims 1 to 5, characterised in that the purifying stage (3) is designed to purify the rainwater (13) of solids, light liquids and / or dissolved substances (12).

7. The purifying and infiltration system (1) according to any one of claims 1 to 6, characterised in that the purifying stage (3) comprises a sedimentation portion (16), a sorption portion (17) and / or a membrane filter portion (18).

8. The purifying and infiltration system (1) according to any one of the preceding claims, characterised in that the rainwater (13) can be fed via an inflow (4) of the storage / infiltration stage (2), wherein the inflow (4) is positioned in such a way that the rainwater (13) can reach the inflow (4) merely at a predetermined fill level of the stage (22) arranged upstream of the storage / infiltration stage (2).

9. The purifying and infiltration system (1) according to any one of the preceding claims, characterised in that the drain element (5) is positioned in such a way that an inflow (9c) to the drain element (5) has a hydrostatic gradient.

10. The purifying and infiltration system (1) according to any one of the preceding claims, characterised in that the drain element (5) has bores (10) and / or is sheathed with a water-permeable textile.

11. The purifying and infiltration system (1) according to any one of the preceding claims, characterised in that the drain element (5) is connected to the stage (22) arranged upstream of the storage / infiltration stage (2) directly or via a pipeline (15) conducting away from the stage (22) arranged upstream of the storage / infiltration stage (2).

12. The purifying and infiltration system (1) according to any one of the preceding claims, characterised in that the drain element (5) can be controlled in such a way that its drain function can be switched on or off or can be regulated.