GB2170420A - Filtration apparatus - Google Patents

Abstract

Water is fed to a filter chamber 1 enclosing filter elements 7 from an overhead supply tank 3, and filtered water flows to outlet 38 through storage chamber 2 above the filter chamber. As elements 7 clog, the level in siphon 5, connected to chamber 1 on the upstream side, rises until it overflows the siphon at 5c, causing a valve in vessel 6 downstream of the siphon to open. Thereupon the contents of chamber 2 are backflushed through elements 7 and over siphon 5 to outlet 25. When chamber 2 is empty, line 8 breaks the siphon action, and the valve is automatically closed to start a new filtering cycle. <IMAGE>

Description

SPECIFICATION Filtration apparatus The present invention relates to filtration apparatus which operates to counter-wash or back-wash the filtering material.

The invention relates to filtration apparatus having a facility to counter was the filtering materials and more specifically is related to filtration apparatus with a facility to counter wash the filtering materials which is capable of such counter-wash operation automatically without necessity of unloading them from the filter tank when the filtering materials in the filter tank exhibit a choked or blocked state necessary to wash ("counter-wash" meaning to wash by passing cleaning water in a direction contrary to the original direction of water flow during the normal filtering).

According to the present invention there is provided filtration apparatus comprises a filter vessel having unfiltered water supply means leading into said filter vessel and filter means therein which communicate on the normally downstream side thereof with a clean water or filtered water vessel located above said filter vessel and having water outlet-means in an upper region, siphon means connected to be in communication with said filter vessel and having its upper portion higher than the level of water in the filtered water vessel sufficient with respect to the supply which is regulated to enable the filter means in the filter vessel to be counter washed or back-washed by water from the filtered water vessel upon operation of said siphon means, automatic opening and closing means for the water passage in the downstream side of the siphon means which operates to open said passage when the siphon means is filled and to close said passage when the level of water in the filter vessel or filtered water vessel drops to a predetermined level as a result of the siphon action.

The porous filter materials used in the filtration apparatus may be porous ceramics, styrol resin, natural or synthetic fibre, metallic mesh, sintered metal etc., these filter materials are regulated in the extent of 1 -100 u porosity, and are generally used for their high stability. Porous filter materials such as these are necessary to change new ones or wash them to reuse when the suspension substance (abridge it as s.s.below) in the original water fall their filtering ability by choking sticked to the filtering materials.Although there are former filter devices unnecessary to unload the filtering materials from the filter tank and yet can counter wash them, but a flaw of the former filter devices is not only the whole filter device's structure is too complicated, but also needs some clean water other than the original water, because they are necessary to set up a flow route of clean water to counter wash the filtering materials other then the flow route of original water.

In addition, because the known filtration apparatus generally used forced pressure filtering methods for passing the filtering materials by pressurising and supplying original water to the filter tank, the suspension solids (s.s.) in the original water stick firmly to the filter materials, so it was not only necessary to supply clean water at more than equal high pressure to counter-wash the said filter materials but it was also difficult to achieve a sufficient removal effect. Furthermore, in order to automatically start the cleaning of filter materials, it was necessary to detect any change of original water pressure caused by the choking or clogging of filter materials in every detail and the automatic control therefore has caused trouble also.

This invention provides filtration apparatus with a facility to counter-wash the filter materials which can avoid or minimize previous disadvantages.

The invention will be described further, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a schematic vertical sectional view of filtration apparatus forming a first embodiment of the invention and having a plurality of filter members; Figure 2 is a schematic vertical sectional view of filtration apparatus forming a second embodiment of the invention which is a simplified modification of the apparatus of Figure 1 in that there is provided only a single filter member; Figure 3 is an enlarged fragmentary sectional detail of the filter tank of the apparatus of Figure 1; Figure 4 is an enlarged fragmentary sectional detail of part of Figure 3 showing the arrangement of filter members in more detail; and Figure 5 is an enlarged fragmentary sectional detail of automatic opening and closing means contained in the embodiments of Figures 1 and 2.

In the drawings Figure 1 illustrates filtration apparatus having a plurality of filter members and Figure 2 illustrates filtration apparatus having a single filter member. In the drawings, the same reference numerals are applied to the same or similar components or similarly functioning components since the basic structure and function is common. In the drawings there is illustrated a filter tank 1, a clean water tank 2 connected above the filter tank 1, an original supply water tank 3 located higher than the clean water tank 2.

A flow speed-reduction tank 4 is provided in communication with tanks 1 and 3. A contrary or inverted U-tube 5 for siphoning water from the lower end of rising tube portion 5a is connected to original water supply portion 1a of filter tank 1. An automatic opening and closing means 6 is provided connected to the lower end of the descending tube portion 5b of the said U-tube 5. One or more filtering members are provided in filter tank 1 in the form of vertically disposed tube members 7 of filtering material (each referred to herein as a filter tube). The web portion or upper portion 5c of the inverted tube 5 is located at a higher level than the upper end of the clean water tank 2.The interior of upper portion of upper portion 5c and interior of the base portion of the clean water tank 2 are interconnected by connecting pipe 8.

As shown in Figures 3 and 4 each said filter tube 7 is nipped and held by an upper end cover plate 10a and a lower end cover plate 10b in a concentri cally fixed arrangement and separated by a regular circular spacing from an inner apertured of porous tube 9. Each apertured tube 9 with plurality of apertures at its walls opens at one end into the clean water tank 2 with its upward end portion penetrating partition wall 11 between the filter tank 1 and clean water tank 2 and with its lower end portion being closed by cap 12. An outer tube 13 with continuous side walls is secured outwardly of and concentrically spaced from each filter tube 7 and being spaced by regular circular annular space 14.

The upper end of each outer tube 13 is secured above the end of tube 7 to cover plate 10a, and the lower end of each tube 13 is open. In the single filter tube embodiment of Figure 2 the surrounding wall of filter tank 1 also serves with equivalent function as the outer tube 13 of Figures 1, 3 and 4.

The automatic opening and closing means 6 as shown in detail in Figure 5 includes a main opening and closing valve 15 in the upper section, a sub-opening and valve 16 in the lower section, and a water tank 18 with built-in or interior float 17.

The main opening and closing valve 15 is provided with a conical valve seat 19, and comprises valve box or housing 20 with its upper end connected to descending tube portion 5b of the inverted U-tube 5 and a conical displaceable valve body 22 movable-up and down inside valve housing 20. Valve body 22 is provided with a through passage or passages 21 of up and down direction. At the side of the conic valve seat 19 against which valve body 22 abuts there are one or more valve passages 23 closed by said movable valve body 22 when located thereagainst in its lower limit position. A water discharge tank or chamber 24 with said upper and lower two valves 15 and 16 located therein is provided with water discharge pipe 25 and in communication with said valve passage 23.

The sub valve 16 has a needle-valve body 27 displaceable in valve passage 26 to open and close such and being disposed concentrically within movable valve body 22 at the bottom of valve housing 20 by up and down movement. An upper axle section 27a of needle valve body 27 extends above the top of movable valve body 22 and is movable up and down relative thereto and may also thrust upwards the movable valve body 22 by upward movement. The downstream or under space 28 of the valve 26 which is opened and closed by valve body 27 not only is series connected or communicates with the water discharge chamber 24 via connecting hole 29 but also is series connected or communicates with the water tank 18 via connecting hole 30.The float 17 inside the water tank 18 is able by upward movement to thrust up the needle valve body 27 of the opening and closing sub-valve 16 by action of its upwardly projecting extension or axle section 17a. A small calibered siphon tube 31 is provided for uncorking or releasing the water inside the water tank 18. A connecting tube 32 communicates the inside of water tank 18 with the interior of the upper portion of the upper portion 5c of U-tube 5.

An explanation of the use, function and operation of the apparatus will now follow. River water, polluted or contaminated industrial water, general waste fluid etc., water with reduced suspension substance (referred to as s.s.) or water treated in advance (all referred to herein as original or unfiltered water) is supplied via supply pipe 33 to the head tank 3 and is treated in the apparatus. Unfiltered water overflows via water supply tube 34 from original water tank 3 and also flows through water pipe 35 and through reduction tank 4 so as to provide a regular water level or head of water.

Its flow speed is reduced here and flows via water pipe 36 and flow regulation valve 37 and through openings la in the bottom of filter tank 1 into the original water supply section 1a and into the filter tank 1.

Clean water after being filtered in the filter tube(s) 7 inside filter tank 1 flows into filtered or clean-water tank 2, and once clean water tank 2 is filled to the regular level L1, the filtered water overflows via the water pipe 38 at the upper end of the clean water tank to be subsequently utilized as feed water. An air uncork vent tube 39 is provied at the top of clean water tank 2. A part of original water supplied to the original water supply section la of the filter tank 1 flows in the rising tube, section 5a of the inverted U-tube 5 and rises naturally by the pressure of water. The flow regulation valve 37 inside the water pipe 36 is regulated and adjusted to maintain the water discharged from water outlet 38 at a prescribed volume of water.In this case, a difference of the volume of water between the original water level L2 in the rising tube section 5a of the U-tube 5 and the clean water level L1 becomes the first filtering water head H1.

In the filtering operation as the volume of suspended substance (s.s.) refiltered material is deposited on filter tube 7 increases, the resistance to current flow through the filter tube 7 increases and the flow of water being filtered decreases. On the other hand, because the pressure of the original water is constant, the original water level in the rising tube section 5a rises and finally a part of original water flows through the upper U-turn portion 5c of the U-tube 5 and into the descending tube portion 5b leading to opening and closing means 6.

As indicated in Figure 5, the displaceable valve body 22 and the needle valve body 27 of the opening and closing sub-valve 16 are located in the position of descended limit and the valve passage 23, 26 which are opened and closed by these valve bodies 22, 27 and since such valves are closed, the original water is retained inside the descending tube portion Sb. Air inside the U tube 5 is expelled through connecting tube 32, water tank 18, connecting holes 30, 29, water discharge chamber 24 and the water discharge pipe 25.

The gradual rising level of original water flowing into the descending tube portion 5b finally reaches the level L3 thus filling the whole inverted U tube 5 including the upper bend or end portion 5c and as a result, the original water flows into the water tank 18 from the upper portion of the inside of the portion 5c of tube 5 via connecting tube 32. As a result of the original water flowing in tank 18 the float 17 rises and its upper end projecting portion 17a causes the needle valve body 27 of sub-valve 16 and opens the valve passage 26. As a result of the valve body 27 causing the displaceable valve body 22 of the main valve 15 continuously, the valve passage 23 is opened.Original water inside the descending tube portion 5b is consequently discharged rapidly fromo the water discharge chamber 25 through valve housing 20 via valve passage 23 and through water discharge chamber 24 and as a result, a siphon action is commenced so that the original water is discharged continuously.High head water suction effect created by the siphonic action acts upon the clean water inside the clean water tank 2 through the supply por tion-1a and the filter tank 1 such that the water drainage volume per hour unit created by the siphon is sufficiently greater than the water supply volume per hour unit supplied through water supply tube 36, with the result that the clean water inside clean water tank 2 can be drawn continuously from the water discharge tube through the filter tank 1 and the inverted U-shaped tube 5 together with original water supplied by water supply tube 36. This action thus provides high water head counter-wash or back-wash water through the filter tube(s) 7.

Consequently, the difference of water level between original water level L3 reached at upper end of the inverted U tube 5 and clean water level L1 in the clean water tank 2, is the initial counter-wash water head H2 acting against the filter tube(s) and starts the above mentioned counter-washing operation.The suspended solids which accumulate on the outer surface of the filter tube(s) are backwashed by pressure equivalent to the low to high water level head, in other words equivalent to filtering commencement water head H1 to the counter-washing commencement water head H2 which becomes a high water head counter-wash water so the filter tube(s) can be cleaned out by the clean water inside the clean water tank 2 which is flowing in a contrary to normal direction, from the inside to the outside of the filter tube(s) 7 inside the filter tank 1.

Once the clean water level in the clean water tank 2 reaches to the lower limit level L4 which is equivalent to the opening or entry level of the connecting tube 8, air then flows, via tube 8, to the upper portion 5c of the U tube 5 so the siphon operation stops and consequently, original water supplied by the supply tube 36 then flows in the filter tank again and begins the normal filtering operation. At the same time, original water in the rising tube portion 5a of the tube 5 flows back to the level L2 equivalent to the filtering commencement water head H1.

During the counter washing operation of the filter tube or tubes 7 based on the above mentioned siphon action, water inside the water tank 18 by means of automatic opening and closing means 6 is discharged gradually via the siphon tube 31, although because much more water than discharged via tube 31 flows into the water tank 18 continuously from the connecting tube 32 and through valve passage 26 of the opening and closing sub valve 16 and the water discharge tank, the float 17 is maintained in its floating or upper raised portion until a change in level occurs.Consequently, when the counter-wash operation is finished, water inside the tube portion 5b completely flows out through the valve passage 23 of the main opening and closing valve 15 and the valve passage 26 of the opening and closing sub valve 16, and the water inside the water tank 18 is then discharged by the siphon tube 31. The float 17 thus then descends the following therewith, the needle valve body 27 and the displaceable valve body 22 which descend to the lower limit position under the action of gravity and the valve passages 23, 26 are each closed. Thus, the disposition and setting for the next counter-wash operation is re-established.

The filtration apparatus with a capability to counter-wash the filtering members of this invention operated and utilized as mentioned above and its special features and modifications are described as follows. In filtering apparatus which is constructed to effect the passage of clean water through a filter tank containing porous filtering members via clean water tank built on the above mentioned filter tank, one end of an inverted U-siphon tube of which upper, cross-connecting portion is higher than the level (L1 in the embodiment) of clean water in the mentioned clean water tank is connected to a supply section of original water of the filter tank.An automatic opening and closing means is connected to the other end of the inverted U-tube 5 and is capable of providing an open route when the siphon tube 5 is in a full water condition whilst capable of providing a closed passage when the clean water level of the above mentioned water tank becomes lower than a fixed water level (L4 in the embodiment) and the siphonic action is stopped.

In the filtering apparatus of the invention, only by regulating the supply volume of the original water and the supply pressure against the filter tank creating the original water level in the rising tube portion of the inverted U tube at the time of commencement of the filtering operation may the filtering operation be started and performed to the extent of a pressure difference matched to the low water head (H1) equivalent to the difference of water level (L2-L1) between the original water level and the clean water level, till a pressure difference matched to the medium water head (H2) equivalent to the difference of the water level (L3-L1) between the original water level inside the inverted U tube and the clean water level when it has reached the upper end of the said inverted U tube, and start the siphon operation automatically as soon as the pressure difference matched to said medium water head breaks out by the choking of the filtering materials, and force the clean water in the clean water tank to counter flow by the pressure difference in a counter direction matched to the high water head, to counter- wash the filtering member or members in the filter tank. Furthermore, once the regular volume of clean water counter has flowed and the counter-washing oper ation finished, it is the apparatus automatically restored to its original filtering operation status.

Therefore, because it is not necessary to provide a separate flow route of cleaning water for counter washing the filtering member or members other than the flow route of the original water as with the former equipment, not only may the structure of the whole present filter apparatus be very simple, but it is also not necessary to prepare cleaning water other than the original water. In addition, as mentioned above, because the passing pressure difference of the original water against the filtering member or members is controlled to be very low and even though only the clean water inside the clean water tank above the filter tank counterflows, suspended solids in the original water stick lightly at the surface of the filtering materials and, a sufficient cleaning efficiency is also achieved.

Furthermore, because the commencement of the counter-washing operation and the resumption of the filtering operation occur automatically, it is not necessary to detect the delicate change of the original water pressure accompanying the filtering member(s) or materials becoming choked, and only a control of the change of the original water inside the inverted U tube or of clean water inside the clean water tank and opening or closing of the automatic opening and closing means is required so the control system is very simple and a highly automatic control operation is achieved.

It is not intended that the automatic opening and closing means used in the present invention still be limited to the automatic opening and closing means 6 shown in the embodiments. For instance, a magnetic opening and closing valve etc., or any other suitable opening and closing means can be utilized.

Also, it is not intended the structure inside the filtering tank of the invention be limited to the structure utilizing a filter tube as shown in the drawings, but in the case where it comprises a filter tank as shown in the drawings a filter tube may be fixed vertically and the original water forced to pass the said filter tube while it flows upward from below in the filter tank.If the current of the original water in the filter tank at the time of filtering operation becomes a so-called "short circuit current" or a "channelling current", then the original water does not flow evenly to the surfaces of the wholly efficient filtering materials of the filter tubes, the breaking depth of s.s. against the filtering materials at the portion (the portion where a current speed of the original water is faster and shifts gradually by the choking of the filtering materials) where the flow of the original water is much inside surface of the filtering materials of the filter tube increases, in general, compared with the case the original water flows evenly in the surface of the filter tube, the adherence of s.s. against the filtering materials increases.This situation results in a bad influence in the counter-washing operation of the filtering materials wherein the clean water is caused to counter-flow by the siphonic action. Furthermore, at the time of the counter-washing operation, because the cleaning water (clean water in the clean water tank) may become a short circuit current or a channelling current, it only counter-washes the surface of the filtering materials at the portion where the cleaning water passes, the current resistance decreases particularly by the particle cleaning and the cleaning water increasinlgy only flows to that portion so it is impossible to clean the surface of the wholly efficient filtering materials evenly.

In consideration of the above said respects, regulation was made as shown in Figure 1 and Figure 2 to prevent the current of original water becoming a short circuit current or a channelling current by arranging the location of the entrance of original water against the filter tank 1, the fixed filter tank 7 vertically and the location of the entrance of original water against the filter tube 7. Furthermore, it was arranged as shown in Figure 4 the original water or the clean water at the time of counterwashing flow in the surface of the wholly efficient filtering materials at all the filter tube 7 evenly by fixing an outer tube 13 which had a water leading operation against every filter tube 7.

Figure 3 illustrates a combined filter lens 1 including an experimental arrangement where two filter tubes 7 at locations A and B does not have fixed outer tubes 13 and where the other filter tubes 7 have fixed outer tubes 13 surrounding filters 7 fixed at the locations C - E. In the subaction of the surrounding of the filters 7, secured outer tubes 13 cause a slow current of repose state of the current indicated xxx in the surroundings of the outer tubes 13 only as shown in Figure 4, and in the original water current space 14 between filter 7 and outer tube 13 there is caused a current of original water with the expected current speed closing the full length and full surrounding as the arrows show.In comparison, it has been found that, since in the surrounding of filter tube 7 at locations A and B without outer tube 13, a slow current or repose status of the current indicated xxx is created in the portion connected to the surrounding wall of the filter tank and causes a slow current indicated xxx and the channelling current indicated an oblique arrow between the filter tube 7, so the original water can not be flowed evenly in the whole surface of its efficient filtering materials in the filter tube 7 where the outer tube 13 located in the position A and B is not fixed.

As mentioned above, the original water can be made to flow evenly over the surface of the wholly efficient filtering materials of all the filter tubes 7 by fixing an outer tube 13 around each filter tube 7, and the filtering efficiency is thus raised and facilitates the possibility of cleaning of suspended solids adhering against the filtering materials by counter-washing. Thus the filter material surface can be washed clean in the counter-washing operation, so the anticipated counter-washing efficiency can be expected.

Claims (20)

1. Filtration apparatus comprises a filter vessel having unfiltered water supply means leading into said filter vessel and filter means therein which communicate on the normally downstream side thereof with a clean water or filtered water vessel located above said filter vessel and having water outlet means in an upper region, siphon means connected to be in communication with said filter vessel and having its upper portion higher than the level of water in the filtered water vessel sufficient with respect to the supply which is regulated to enable the filter means in the filter vessel to be counter-washed or back-washed by water from the filtered water vessel upon operation of said siphon means, automatic opening and closing means for the water passage in the downstream side of the siphon means which operates to open said passage when the siphon means is filled and to close said passage when the level of water in the filter vessel or filtered water vessel drops to a predetermined level as a result of the siphon action.

2. Filtration apparatus as claimed in Claim 1, in which the unfiltered water supply means is such as to enable a constant head or pressure of water to be provided which is above that of the upper end of the siphon means or sufficient to fill such.

3. Filtration apparatus as claimed in Claim 1 or 2, in which a water flow speed reduction tank is provided adjacent to the inlet of said filter vessel.

4. Filtration apparatus as claimed in any of Claims 1 to 3, in which a flow regulation valve is provided adjacent the inlet of the filter vessel to enable the supply flow to be regulated with respect to the suction capacity of the siphon means to enable the desired back-washing operation to be effected.

5. Filtration apparatus as claimed in any of Claims 1 to 4, in which one or more tubular filtering members is or are provided as said filter means and are closed at their upstream end and communicate at their downstream end with said filtered water vessel.

6. Filtration apparatus as claimed in Claim 5 in which each filter tube has an outer tube surrounding such and extending along the length thereof and being open at the downstream end to allow flow of unfiltered water therealong.

7. Filtration apparatus as claimed in Claim 5 or 6, in which each tube has a porous or apertured inner tube running along the length thereof and leading at its downstream end through wall means into said upper filtered water vessel.

8. Filtration apparatus as claimed in Claim 5 in which a single filter tube is provided and the walls of the filter vessel extend closely therearound to influence the flow of unfiltered water thereat.

9. Apparatus as claimed in any of Claims 1 to 8, wherein venting means are provided in an upper region of said filtered water vessel.

10. Filtration apparatus as claimed in any of Claims 1 to 9, in which said siphon means is an inverted generally U-shaped siphon tube with its upper end being located above the normal level of water in the filtered water tank.

11. Filtration apparatus as claimed in any of Claims 1 to 10, in which a duct communicates between a lower desired water level in the filtered water level in the filtered water vessel and the upper end of the siphon means to break said siphon action when said lower level is reached during back washing.

12. Filtration apparatus as claimed in any of Claims 1 to 11 in which a connecting duct or tube is provided between the upper end of said siphon means and said automatic opening and closing means and communicates water thereto when said siphon means is filled to such operating level and actuates said automatic opening and closing means so as to open said passage to permit the siphon action to take place.

13. Filtration apparatus as claimed in any of Claims 1 to 12, in which said automatic opening and closing means comprises valve means operable to open and close the outlet passage of the siphon means and actuator means for said valve means wherein said actuator means operates in response to said siphon means being operatively filled with water to open said valve means and passage to permit flow of water through the siphon means, and operates in response to said siphon means being other than operatively filled with water to close said valve means and passage.

14. Filtration apparatus as claimed in Claim 13, wherin said actuator means is buoyant means or a float which has means for engaging said valve means.

15. Filtration apparatus as claimed in Claim 14, in which said float is located in a chamber adjacent said valve means and said chamber has a water inlet duct communicating with the upper end of the siphon means so as to receive water therefrom when filled whereupon said float is raised by water in said chamber and actuates said valve means to open the outlet passage of the siphon means.

16. Filtration apparatus as claimed in Claim 15, in which said valve means is located abvoe said float and comprises a valve housing or seat with an inlet passage from the siphon means and outlet passages to discharge and to the float chamber, a displaceable valve body which in the lowermost position closes the outlet passages to discharge but provides a through passage to the float chamber via one of said outlet passages in which one part of a displaceable needle valve is located and operable by projection of said float, another part of said needle valve being displaceably mounted in said valve body.

17. Filtration apparatus as claimed in Claim 16, in which ducts communicate said outlet passages to discharge with said float chamber.

18. Filtration apparatus as claimed in Claims 1 to 17, in which. said float chamber is provided with siphon means of restricted flow which operates to drain said float chamber after said siphon action has been broken to thereby return said automatic opening and closing means to the closed condition.

19. Filtration apparatus constructed and arranged to operate substantially as herein described with reference to and as illustrated in the accompanying drawing.

20. In filtration apparatus including a facility to counter-wash the filter materials and wherein clean water passes through a filter tank containing porous filter materials into a clean water tank located on said filter tank, the improvement of there being connected one end of an inverted U-tube for siphonic action and of which upper U-bend portion is higher than normal level of clean water in said clean water tank, to a supply section of original water for the filter tank, and there being connected to the other end of this siphon tube an automatic opening and closing means capable of changing an opening passage when the siphon tube is in a full water state and on the contrary, capable of changing a closing route when the clean water level of said water tank becomes lower than a fixed water level.