FILTER SYSTEM FOR TREATING CONTAMINATED LIQUIDS

Abstract

The invention relates to a filter system for treating contaminated liquids, having a filter container (11) that is equipped with a filter bed (12) comprising filter granulate as the filter material, a retaining element (13) being provided for the filter material via the filter bed. In order to allow the retaining element (13) to be lightly cleaned after backwashing and prevent filter material from being lost during the backwash, the retaining element (13) has a substantially vertically arranged filter screen (14) which is arranged at least partly outside of the filter container (11) and encloses a cavity, and liquid can flow outwards from the inside during the backwash. The cavity is open at the bottom such that retained filter material falls back into the filter bed (12). Because the flow within the filter bed (14) is oriented downwards, at least one turbine blade (18) can be provided, and a channel (16) can provided from the filter container (11) to the head space (17) of the filter screen (14). Preferably, a dissolver disc or a stirring mechanism (15) is provided in order to improve the flow formation. Alternatively, instead of a turbine blade, a funnel (15′) can be arranged on the lower end of the filter bed (14).

Claims

1. A filter installation for treating contaminated water, the installation comprising: a container; a filter bed in the container and formed of filter granules as filter material; a filter-material trap for the filter material above the filter bed and formed of a substantially vertically extending filter mesh that is at least partially outside the container, that forms a separation chamber, and that can be flowed through from inside to outside during backwashing, the separation chamber being downwardly open such that retained filter material falls back into the filter bed.

2. The filter system according to claim 1, further comprising: a cleaning system for the filter mesh.

3. The filter system according to claim 2, further comprising: a passage extending from the container to an upper end of the separation chamber of the filter mesh, and at least one turbine blade provided on a shaft that can be rotated inside the filter mesh by a drive.

4. The filter system according to claim 3, in that further comprising: a dissolver disk or an agitator at an end of the shaft.

5. The filter installation according to claim 1, further comprising: a funnel that extends downward from a lower end of the separation chamber, and a passage extending from the container extending to an upper end of the separation chamber of the filter mesh, a cross-section of the passage being greater than a cross-section of an outlet end of the funnel.

6. The filter system according to claim 2, wherein the cleaning system comprises at least one scraper is provided that can be moved along an inner surface of the filter mesh by a drive.

7. The filter system according to claim 2, wherein the cleaning system comprises at least one high pressure nozzle for directing a high-pressure fluid jet against an inner surface of the filter mesh.

8. A filter system comprising: a container having a lower outlet; a filter bed in the container above the outlet; an inlet port for introducing a liquid to be filtered into the container above the filter bed; a concentric inner and outer tube extending upward from the container and forming an annular passage opening downward into the container and upward at an upper end of the outer tube; a tubular filter mesh of mesh size adapted to trap particles forming the filter bed and concentrically inside the inner tube; and a backwash-liquid output port open through the outer tube toward the mesh such that backwash liquid passing through the mesh is stripped of particles of the filter bed by the mesh and pass downward in the mesh and back into the filter bed.

9. The filter system according to claim 8, further comprising: a downwardly tapering funnel on a lower end of the inner tube.

10. The filter system according to claim 8, wherein the inner and outer tubes form a compartment surrounding the mesh, into which the backwash-liquid outlet port opens, and that is upwardly and downwardly closed.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The present invention will be described in more detail with reference to the accompanying drawings.

[0017] FIG. 1 shows a cross section through a first embodiment of a filter system according to the invention; and

[0018] FIG. 2 shows the filter-material trap thereof on an enlarged scale;

[0019] FIG. 3 shows a second embodiment of a filter system according to the invention; and

[0020] FIG. 4 shows the filter-material trap thereof on an enlarged scale.

SYSTEM FOR CARRYING OUT THE INVENTION

[0021] The filter system according to FIGS. 1 and 2 has a container 11 in which a filter bed 12 on a nozzle floor 12a is provided. A disperser 21 above the filter bed 12 and that receives the liquid to be filtered from an inlet port 22 and distributes it over the filter bed 12. The liquid flows through the filter bed 12 and the nozzle floor 12a to an outlet port 24 at the lowest point of the container 11.

[0022] For backflushing the filter, a backflushing inlet port 23 is provided through which a backflushing gas can be introduced, and the backflushing gas or liquid exits via the outlet port 24. Normally, the filter bed 12 is first loosened by gas, after which liquid is introduced, optionally together with the backflushing gas, into the filter bed.

[0023] In conventional filter systems, the backwash liquid is mostly outputted via the inlet port 22, but this has the disadvantage that filter material is entrained, in particular with a high throughput of backwashing liquid that is desired in order to efficiently clean the filter bed 12.

[0024] In order to eliminate this disadvantage, according to the invention a filter-material trap 13 is provided. This filter-material trap 13 is located in the uppermost region of the container 11, partially inside and partially outside the container 11. It consists essentially of a cylindrically tubular filter mesh 14. This filter mesh 14 is located in a tube 28, so that an annular chamber is formed between the tube 28 and the filter mesh 14. This annular chamber is closed at the top and bottom and is connected to a backwash-fluid outlet port 25.

[0025] The tube 28 is surrounded by an outer tube 29 tightly connected to a collar 30 of the container 11. There is thus a further annular space between the pipe 28 and the outer pipe 29 or the collar 30 that forms a passage 16 for supplying the backflushing liquid into the upper space 17 of the filter-material trap 13. The upper space 17 connects the passage 16 to the interior of the filter mesh 14, but the annular chamber between the tube 28 and the filter mesh 14 is, however, separate.

[0026] The filter-material trap functions as follows:

[0027] During backwashing, water is pumped from below via the outlet port 24 into the container 11 and flows through the filter bed 12, thereby detaching contaminants (solids, oil, etc.) and carries them upward.

[0028] The process becomes more efficient at a higher backflushing rate (m.sup.3/m.sup.2.Math.h), but in conventional filters this entails the risk of a filter-material discharge.

[0029] In order to avoid this risk, in the filter system according to the invention, the backwash water is conducted into the passage 16 and from there via the upper space 17 down into the interior of the tubular filter mesh 14.

[0030] Inside the filter mesh 14 there is a shaft 27 with turbine blades 18 that are rotatable by a drive 26. During back-flushing, the drive 26 is switched on and the turbine blades 18 generate a desired flow and scrape the inner surface of the filter mesh 14. This results in a main flow indicated by arrows 31 during the backflushing process, so that flow is produced in the interior of the filter mesh 14 whose vertical component is directed downward. The backwash water then flows through the filter mesh 14 whose mesh size is selected as a function of the particle size of the filter medium, from inside to outside and finally reaches the backwash liquid outlet port 25, where the backwash water is discharged with the contaminants. Since the vertical component of the flow in the interior of the filter mesh augmented by the vertically extending turbine blades 18 is downward, entrained filter granules are flushed to a considerable extent already during the back-flushing toward the filter bed 12 and do not reach the filter mesh 14 at all. The desired flow inside the filter mesh 14 and thus also in the container 11 can be influenced by a dissolver disk or an agitator 15 at the end of the shaft 27. The position of the dissolver disk or agitator 15 can be defined according to the filter medium.

[0031] The filter system according to FIGS. 3 and 4 differs from the filter system just described in that the filter mesh 14 has a funnel 15′ at the bottom and that no turbine blades are provided for generating a forced flow. The inclination of the wall of the funnel 15′ is so steep that filter material cannot remain thereon. In this embodiment, although in some cases the backwash water also flows through the opening of the funnel 15′ into the interior of the filter mesh 14, this proportion can be kept low if the cross-section of the passage 16 is considerably larger than the cross section of the opening of the funnel 15′. Thus, in this case too, a main flow 31 is formed whose vertical component is at least largely directed downward, so that even in this case the filter granulates carried along are flushed to a considerable extent already during the back-flushing toward the filter bed 12 and do not reach the filter mesh 14 at all.

[0032] Nevertheless, the filter mesh 14 tends to clog. For this reason, a shaft 27 driven by a drive 26, in particular by an electric motor, is provided inside the filter mesh 14, which shaft 27 has radially projecting arms 27a each carrying a respective scraper 18′ that slides along the inner surface of the filter mesh 14. During back-flushing or only afterward, the drive 26 is switched on, and the scrapers 18′ clean the filter mesh 14.

[0033] The filter mesh 14 can also be cleaned hydraulically, in particular with a water jet.

[0034] The retained filter material falls back into the container 11 at the latest after backwashing via the funnel 15′ at the lower end of the filter mesh 14.