FI58442B - SAETT OCH ANORDNING FOER FILTRERING AV VAETSKA - Google Patents

Description

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Patent ·] · National Board of Registration (44) NihttvSktlpeKK. J. KuulLullutau pym.-

Patent · och registerstyrelsan 'Anaökan utltgd och utt.skrlfcan publfcmd 31.10.80 (32) (33) (31) Requested atuotkaut — Bagtrd prlorltat 25.08.73

England-England (GB) * + 0368/73 Proven-Styrkt (71) Simon-Hartley Limited, Etruria Works, Stoke-on-Trent, Staffordshire,

England-England (GB) (72) Eric Paul Austin, Sandbach, Cheshire, John Trevor Allanson, Stoke-on-Trent, Staffordshire, England-England (GB) (7 * +) Oy Jalo Ant-Wuorinen Ah (5I +) Method and the present invention relates to the filtration of liquids and in particular, but not exclusively, to the removal of suspended solids from sewage in tertiary treatment steps.

The most common method of filtering a liquid to remove suspended contaminants involves causing the liquid to flow through a horizontal layer containing a fine filter media, such as sand. This method has the great disadvantage that the filtration process often has to be interrupted and the filter medium washed upstream.

For example, British Patent 1,327,058 discloses a method in which the filtration of a liquid is proposed to be effected by flowing it horizontally through a layer forming a vertical sand column which continuously moves downwards, whereby sand is removed from the bottom of the bed, washed and recycled back to the top. We have found that filtration according to this method is not particularly satisfactory because the filter media layer can become clogged very quickly. Attempts to move the sand column faster to compensate for this cause problems in that the filter layer ceases to be well packaged and thus no longer filters efficiently.

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The method presented in Finnish patent application 2385/71 uses a free inclined filter medium surface, which, however, is not long enough for the material to be filtered to be divided into different layers according to its size, and even if this happens, the mixing arms constantly mix the layer distribution. In the device according to this publication, the flow of the liquid to be cleaned takes place countercurrently to the movement of the bed.

It is an object of the present invention to provide a new filtration method and apparatus for carrying it out, which at least to some extent avoids the above-mentioned disadvantages.

The present invention therefore relates primarily to a method of filtering a liquid, comprising forming a layer of fines in a substantially vertical wall container having particles of different sizes, continuously removing said material from the bottom of the layer, e.g., for washing, and passing fines above the layer, and the method is known that the fines are introduced into the container through an opening therein bounded by the edge of the flow plate, the fines flowing past that edge forming a freely extensible top surface extending downwards from that edge so that the ingredients, when poured downwards along the surface, are distributed in size and form a top layer , which is predominantly large in the ingredient, on the inner layer, which is predominantly small in the ingredient, and that the liquid to be filtered is led into the tank from said opening through a separate opening so that it flows downwards through the bed, whereby the liquid enters the bed through the substantially extending upper surface and first flows through the outermost sublayer.

The invention also relates to a filtration device comprising a layer of fines of different sizes in a container with substantially vertical walls, means for continuously removing fines from the bottom of the layer and means for guiding a replacement fines above the layer, characterized by a flow plate a conductive orifice from which a replacement fines are introduced into the bed, the fines flowing through the orifice solely by gravity and passing the edge to form a free-flowing upper surface of the layer , so that the upper surface, which consists mainly of larger particles, where the larger particles accumulate in the lower part of the casting surface, substantially covers the smaller particles. and an opening separate from said orifice through which the liquid to be filtered is directed to flow downwards through the bed, whereby the incoming liquid flow meets the free-flowing surface of the whole bed evenly distributed and first flows through this outermost sublayer.

The invention will be explained in more detail below with reference to the accompanying drawing, in which two embodiments of a filtration device according to the invention are shown by way of example only. In it, Fig. 1 shows a vertical cross-section of a first embodiment of a device according to the invention with a filter vessel having a rectangular horizontal cross-section, and Fig. 2 a partially cut-away perspective view of a parasitic embodiment of the device in which the filter vessel has a circular horizontal cross-section.

It can be seen from Figure 1 that this embodiment of the device according to the invention comprises a substantially vertical filter vessel, indicated in its entirety by reference numeral 10. The vessel 10 has a substantially rectangular horizontal cross section which decreases at the lower end 11 in connection with the tube 12 described below.

The inclined spacer 13 extends in the container 10 between its opposite walls and is thus arranged so that its lower edge 14 is spaced from the side wall 15 of the container 10. Its upper edge 10 is correspondingly spaced from the opposite wall 17 of the container 10, but joins a vertical plate 18 directed 4 58442 from there upwards to the top of the vessel 10. Above the baffle 13 there is a sand cleaning chamber 19 in the space 20 at the upper end of the vessel 10. The lower part of the chamber 19 is bounded by plates 21 and 22 extending from opposite edges of the chamber outlet 23 to the side wall 15 of the vessel 10 respectively.

The vessel 10 has a layer 24 of finely divided filter medium, which in this example is sand, which is fed to the vessel 10 through a chamber 15. The sand fed to the vessel 10 enters the storage 25 collected above the baffle 13 and sand flows from the lower end of the storage 25 past the lower edge 14 of the baffle 13, giving the layer 24 a free sloping top surface 26. The sand flows downwards along the sloping surface 26, sorting the sand particles by size. Smaller particles tend to stay at the top of the sloping surface while larger particles roll down the surface. The sand particles entering the vessel 10 near the side wall 15 tend to drain vertically downwards without separation.

In use, the liquid to be filtered is fed through a supply pipe 27 to the vessel 10 as the liquid flows over the overflow plate 28 and below the spacer plate 13 so that it penetrates the layer 24 through its free inclined surface 26. The liquid becomes filtered as it passes through the layer 24, after which it drains through the filtrate outlet in the wall 15 of the screen 10 provided with the screen 29 and is discharged through the pipe 30.

During filtration, sand is continuously removed from the lower end of the layer 24 to the pipe 12 and lifted to the top of the layer 24 via the pipe 31, using the flap principle, whereby air is supplied to the pipe 12 for this purpose via a supply line 32. Thus, the layer 24 is caused to move downward continuously, relatively slowly. The pipes 31 open into the chamber 19. Some of the water supplied to the device via the supply pipe 27 is led from the water side of the spacer through the pipe 33 to the space above the sand storage 25 and the spacer 13, below the outlet 23 of the chamber 19 for washing water. This washing water can be controlled by means of a valve 34 and it is clear that the washing water flows upwards through the chamber 19 and washes the sand fed through the pipe 31 of the chamber 19.

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The wash water containing the impurities washed out of the sand flows from the chamber 19 to the space 20, from where it flows out through the outlet pipe 35.

Due to the sorting effect described above, the sand particles of layer 24 become separated so that the coarser particles are on the water inlet side, the finer particles on this side, while particles of all sizes are on the water inlet side. The approximate boundaries of these zones are shown in the drawing by dotted lines. As a result of this separation, the water to be filtered flows first mainly between the coarse particles, then between the finer particles and finally between the mixed particles, the latter remaining relatively clean as they move downwards through the vessel 10. As a result, the filtration process is very efficient and the layer 24 does not quickly clog, preventing the liquid from flowing freely into the screen 29.

If desired, a second septum 36 may be used to provide a second free sloping surface 37 for directing a layer of substantially coarse particles downward over the filtrate outlet screen 29.

Reference is now made to Figure 2, in which the device shown is substantially similar to the device of Figure 1 and in which the corresponding parts are denoted by the same reference numerals. In this embodiment, the filter layer 24 has a substantially circular horizontal cross-section and has a free inclined surface 26 in the center which is substantially in the shape of an upwardly opening cone. The liquid to be filtered thus flows outwards through the layer 24 from its central part and is collected along the circumference of the filter nozzle 10. The spacer 13 used in the embodiment described above has been replaced by a downwardly opening conical jacket 38, whereby the liquid to be filtered is fed into the jacket 38 through a pipe 39.

The sand of layer 24 is recycled by removing it from the bottom of layer 24 through a plurality of angled tubes 12 and 31 each opening into the sand washing chamber 19, whereby the wash water flowing over the threshold 40 enters a space 20 which is circular and flows out through an outlet tube 35.

If, in one of the embodiments, the filter layer 24 becomes too contaminated for any reason, it is of course possible to countercurrently wash it by supplying water to the lower part of the layer 24 or via pipes 30.

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It is clear that the invention is not limited only to the examples given above, but that many modifications which are obvious to a person skilled in the art and which fall within the scope of the following claims are possible.

Instead of continuously removing the substance from the bottom of the bed, the substance can be removed periodically. Correspondingly, the liquid to be filtered can be fed intermittently.

The removed material does not need to be washed and recycled if a new replacement is added to the layer.

It is obvious that when using a circular vessel, the liquid to be filtered can flow towards the middle part of the vessel, whereby the filter layer has an upwardly directed conical upper surface.

It is clear that the device shown works successfully for certain types of filterable liquids, although a filter material consisting of suitable particles of the same size is used, but it is of course more advantageous to use a filter material which is distributed according to size as described above.

When designed, the filter media can be washed with a portion of the liquid to be filtered after it has drained through the filter bed.

Claims (6)

A method for filtering liquid, wherein a bed of grainy material comprising particles of varying size is provided in a container with substantially vertical walls, said material being continuously removed from the bottom of the bed and grainy replacement material being fed to the top of the bed, characterized in that the grainy material is supplied through an opening bounded by an edge of a screen plate in the container, the grainy material flowing past said edge forming a free inclined upper surface extending downwardly from said edge, so that the particles move downwardly along the surface. is distributed by size and forms an outer layer of predominantly larger particles over an inner layer of predominantly smaller particles, and that the liquid for filtration is supplied to the container through a passage separate from said inlet for flow downstream through the bed, the liquid entering the bed. essentially only through the inclined upper surface and first it flows through γ dry the particle layer. A liquid filtration apparatus according to claim 1, comprising a bed of grainy material containing particles of varying sizes in a container with substantially vertical walls, means for continuously removing grainy material from the bottom of the bed and means for supplying replacement material to the top surface.