Buried small sewage treatment plant with additional water tank

Description

[0001] The invention relates to a small wastewater treatment plant comprising a first container with a feed for wastewater, in which preliminary clarification takes place as a result of solid particles settling to the bottom of the first container, and a second container which is connected to the first container via an overflow, through which pre-clarified water can be fed to the second container for further clarification.

[0002] A small-scale wastewater treatment plant is used to purify wastewater, primarily for single-family and multi-family homes, especially for residential units with five to twenty occupants. Typically, a small-scale wastewater treatment plant is used in small settlements, restaurants, or mountain huts when connecting to a large municipal wastewater treatment plant is not feasible for technical, regulatory, or financial reasons. Wastewater treatment is carried out using two treatment tanks. The first tank performs the initial treatment, and the pre-treated water is then fed into the second tank, where it undergoes further purification through a filter device, usually a biological filter. The treated wastewater is then discharged from the second tank via a lower outlet, for example, into the surrounding soil.During operation, the first tank is always filled to overflowing with wastewater, while the second tank does not collect any wastewater and is therefore largely empty. Such a small-scale wastewater treatment plant is usually installed underground in the garden. During heavy rain or in areas with high groundwater levels, a considerable buoyancy force acts on the empty second tank, especially when surrounded by liquid. This buoyancy force can reach 30,000 N (equivalent to a weight of 3 tons) for a tank with a volume of 3 m³, and significant precautions must be taken to counteract this buoyancy, for example, by anchoring the tank in the ground or using a concrete slab.

[0003] EP 3 636 405 A1 describes a small wastewater treatment plant comprising three rotationally molded tanks. All three tanks are used for the treatment of wastewater. The wastewater enters the first tank at the top via an inlet, and the treated wastewater exits the small wastewater treatment plant at the third tank via an outlet at the top.

[0004] US 2016 / 376177 A1 describes a wastewater tank for underground use. In this tank, a plastic container is connected to a concrete container that at least partially surrounds the plastic container, thereby reducing hydrostatic buoyancy. During the manufacture of the concrete container (but not during operation of the wastewater tank), the plastic container can be filled with ballast, such as water, sand, and / or stones.

[0005] JP 2015 148434 A describes an underground water system, for example for a residential building, with a buried water tank. The bottom of the water tank is in contact with the ground and it is filled with rainwater. The water can be used for heating and cooling the residential building. Problems arising in connection with a small wastewater treatment plant are not addressed in this document.

[0006] US 3,933,641 A describes a small wastewater treatment plant with three rigidly connected tanks. Pre-filtration takes place in the first tank, and further filtration with various filters occurs in the second tank. A third tank, located below the second tank, serves as a collection tank for the filtered wastewater, which, mixed with water from another tank, is sprayed onto the ground surface. At least the second and third tanks are arranged vertically, one above the other. During operation, the second tank has a low fill level with wastewater. The third tank is filled with filtered wastewater from the second tank.

[0007] The object of the invention is to provide a small wastewater treatment plant whose range of application and economic use are improved.

[0008] This problem is solved for a small wastewater treatment plant with the features of claim 1. Advantageous further developments are specified in the dependent claims.

[0009] According to the invention, in addition to the first tank for primary clarification and the second tank for further filtration of the wastewater, at least one third tank is arranged to which rainwater can be fed. This third tank collects rainwater and can be removed via a discharge opening. The at least three tanks are arranged horizontally side by side and rigidly connected to one another. When the unit comprising the three tanks is installed underground and surrounded by groundwater or rainwater, the rainwater-filled third tank reduces the hydrostatic buoyancy of the entire unit. This reduces the risk of the entire small wastewater treatment plant, made primarily of lightweight plastic, floating to the surface, thereby saving costs and improving the overall efficiency of the system.For example, the effort required for an anchoring device to prevent floating due to high hydrostatic buoyancy forces can be reduced, thus mitigating the dangerous situation.

[0010] At the installation site of a small wastewater treatment plant, a reservoir for service water for commercial, agricultural, or domestic irrigation applications is often also required. Frequently, a rainwater harvesting system is provided on the property for this purpose. In the invention, the third reservoir serves as the collection reservoir, complementing the small wastewater treatment plant with the necessary first and second reservoirs. Integrating the third reservoir for rainwater reduces the overall amount of excavated soil, the material required for backfilling the reservoirs with gravel and sand, and, depending on the soil conditions, also the effort required to construct a concrete base for the reservoirs. In this way, the range of applications for the small wastewater treatment plant with integrated rainwater reservoir is further improved, as is its cost-effectiveness.

[0011] The third water container can typically be connected to a rainwater collection system for filling. When needed, water for irrigation is drawn from this third container via a water extraction device, preferably using a pump.

[0012] According to a preferred embodiment of the invention, the small wastewater treatment plant is characterized in that the at least three tanks and their rigid connection to one another are prefabricated in the factory. This allows for cost-effective industrial prefabrication and reduces the assembly effort at the installation site R21007E. Costs can also be saved in logistics because, instead of several tanks, only one tank system needs to be purchased, transported, and stored.

[0013] The at least three containers for the small wastewater treatment plant are made of plastic material and are suitable for use in the ground.

[0014] Exemplary embodiments of the invention are explained below with reference to the figures. These show: Fig. 1 shows a small wastewater treatment plant with an integrated rainwater tank, and Fig. 2 shows different arrangements of the tanks on a base area.

[0015] In Fig.1 Figure 8 shows a small wastewater treatment plant 8 according to the invention. A first tank 9 serves for the preliminary treatment of wastewater, which is fed in towards P1 via an inlet 12. In this first tank 9, the wastewater undergoes preliminary treatment due to the settling of solids to the bottom. The wastewater flows according to arrows P2, P3, and P4 to a pre-filter 15. The pre-treated wastewater flows via an overflow at the level of the wastewater surface 16 in the direction of arrow P5 to a distribution device 17 in a second tank 10. There, the pre-treated wastewater is distributed onto a filter device designed as a biofilter 20 and flows downwards in the direction of arrows P6, exiting the second tank 10 as treated wastewater via at least one wastewater outlet 21. The two tanks 9 and 10 are connected by a single, continuous flow system.10 have container openings on their upper sides that can be closed with lids, namely a container opening 13, a container opening 14 for the pre-filter 15, a container opening 18 for the biofilter 20 and a control opening 19 for checking the contents of the second container 10.

[0016] A third container 11 serves to hold process water, which is typically supplied from a rainwater harvesting system via a rainwater inlet 26 along arrow P7 through a closable container opening 24. The supplied water is directed towards arrow P9 via a bend 27 to calm the water flow. The water level is indicated by reference numeral 23. A siphon 29 with a drain 30 defines the maximum fill level. The water is discharged according to arrow P10. Water can be drawn via a floating water intake 28 in the direction of arrow P8 using a pump (not shown) and supplied for further use. The interior of the third container 22 can be inspected via a closable inspection opening 25.

[0017] The three containers 9, 10, 11 are arranged side by side on a horizontal base G and rigidly connected to one another. Each container 9, 10, 11 is welded to its adjacent container along their facing sides or bolted together using fasteners such as eyelets or adapters. Each container is made of thermoplastic material, preferably polyethylene, polypropylene, or glass fiber reinforced plastic. The rigid connection between the containers is preferably achieved by plastic welding. Each container has a volume of 2.5 m³ to 5 m³. The bottoms of each container 9, 10, 11 rest on the horizontal base G. The three containers 9, 10, 11 are located below ground level.The filled third container 11, in conjunction with the first container 9, compensates for a hydrostatic buoyancy force that acts particularly on the largely empty container 10 when surrounded by water, e.g., groundwater. The three containers 9, 10, 11 and their rigid connection to each other are prefabricated as a single unit in a factory and transported to the site in this state.

[0018] Fig.2 Figure 1 shows a schematic top view of two different arrangements of the three containers 9, 10, 11. In the upper view, the containers 9, 10, 11 are arranged in a row along an axis A and welded together at their sides by welds 32. In the lower view, the three containers 9, 10, 11 are arranged side by side, offset from one another.

[0019] Numerous variations of the small wastewater treatment plant are possible. The plant can be supplemented with an additional water tank. Tanks 9, 10, and 11 can have different volumes. The small wastewater treatment plant with an additional rainwater tank is preferably installed below ground level. Reference symbol list

[0020] 8 Small wastewater treatment plant 9 First tank for primary treatment 10 Second tank for further treatment 11 Third tank for water 12 Wastewater inlet 13 Tank opening 14 Tank opening pre-filter 15 Pre-filter 16 Wastewater surface 17 Distribution device 18 Tank opening filter 19 Filter inspection opening 20 Biofilter 21 Wastewater outlet 23 Rainwater surface 24 Tank opening 25 Rainwater outlet inspection opening 26 Rainwater inlet 27 Calmed rainwater inlet 28 Floating rainwater intake 29 Rainwater outlet siphon 30 Water outlet 32 ​​Weld A axis G Base area P1 to P10 Directional arrows

Claims

1. Small wastewater-treatment plant (8) with an integrated rainwater-collection tank, comprising a first tank (9), which is composed of plastic and has a feeding means for wastewater and in which pre-treatment is carried out as a result of solid parts sinking to the bottom of the first tank (9), a second tank (10), which is composed of plastic and is connected to the first tank (9) via an overflow via which pre-treated wastewater is able to be fed to the second tank (10), wherein, during operation, the first tank (9) is in a state filled to the overflow with wastewater, a filter device (20) in the second tank (10), to which the pre-treated wastewater is fed from above for further filtering, and at least one drain (21) below the filter device (20), via which the filtered wastewater is able to be discharged from the second tank (10) and out of the small wastewater-treatment plant (8) as purified wastewater, and, during operation, the second tank (10) is largely empty, wherein there is arranged at least one third tank (11), serving for receiving rainwater and composed of plastic, to which rainwater is able to be fed via a rainwater inlet (27), said rainwater being collected in the third tank (11) and able to be removed via a removal opening, wherein the at least three tanks (9, 10, 11) are arranged next to one other horizontally and are connected to one another rigidly, and wherein, in the case of the small wastewater-treatment plant being used underground, the third tank (11) filled with rainwater, together with the first tank (9) filled with wastewater, compensates for a hydrostatic buoyancy force.

2. Small wastewater-treatment plant according to Claim 1, characterized in that the second tank (10) is arranged between the first tank (9) and the third tank (11).

3. Small wastewater-treatment plant according to Claim 1 or 2, characterized in that the three tanks (9, 10, 11) are welded to one another or are connected to one another by means of connecting elements.

4. Small wastewater-treatment plant according to one of the preceding claims, characterized in that each tank (9, 10, 11) is of cuboidal form, and in that in each case two tanks (9, 10; 10, 11) are welded or screwed to one another at their sides, preferably of the same size, that face one another.

5. Small wastewater-treatment plant according to one of the preceding claims, characterized in that the three tanks (9, 10, 11) are arranged along an axis, and in that the respective bottoms of the at least three tanks (9, 10, 11) lie in a plane.

6. Small wastewater-treatment plant according to one of the preceding claims, characterized in that each tank (9, 10, 11) has at its top side at least one access opening which is able to be closed off by a cover.

7. Small wastewater-treatment plant according to one of the preceding claims, characterized in that each tank consists of thermoplastic material, preferably of polyethylene or of polypropylene or of glass-fibre-reinforced plastic.

8. Small wastewater-treatment plant according to one of the preceding claims, characterized in that each tank has a volume of 2.5 m3 to 5 m3.

9. Small wastewater-treatment plant according to one of the preceding claims, characterized in that the third tank (11) contains a removal device by way of which water is able to be removed from the third tank (11).

10. Small wastewater-treatment plant according to one of the preceding claims, characterized in that the at least three tanks (9, 10, 11) and their rigid connections to one other are prefabricated at the factory.