GB2461119A - Water filter - Google Patents

Abstract

A water filter consisting of a sealed cylindrical vessel 1 which in use has one or more water inlets 2 at the top and at least one outlet at the bottom 15 and between the inlet and outlet are one or more layers of filter media 16 - 19, characterised by at least one inlet being adapted to discharge water into the vessel so that in use the flow of water into the vessel causes water within the vessel to rotate about the vertical axis of the vessel. Preferably water within the vessel is caused to rotate by means of a distribution head 7 having an upper and lower circular flat plain separated by a vertical side wall in which are located holes 9 through which water entering the vessel can pass. Preferably an arrangement of pipes and valves allows backwashing of the water filter.

Description

A HIGH EFFICIENCY MEDIA FILTER

The present invention relates to an improved water filter which introduces a new and improved method of feeding the water into a filter vessel so as to improve the efficiency of the filtration system by removing the inefficiencies which can occur due to the flow arrangements in existing filter systems.

Water or media filters as they are sometimes known, are used in many different areas but the more common are drinking and bottled water filtration, industrial process water filtration, sea, river, canal or loch water filtration, swimming pool filtration, contaminant removal for environmental uses and cooling tower, chiller or air conditioning applications.

The typical construction of a media base water filter is a sealed cylindrical vessel with a water inlet at the top and an outlet at the bottom. Contained within the vessel are various layers of filter media starting with a very fine layer at the top and finishing with a coarse layer at the bottom. At the top of the vessel above the medial layers, is a receiving area known as the upper plenum into which the inlet pipe feeds and at the bottom separated from the coarse media by a plate through which water can pass is a water collection area known as the lower plenum to which the outlet pipe is attached. Various piping arrangements are possible for reversing the water flow, a process known as backwashing which is done to clean the filter. For reverse flow, usually there would be a takeoff pipe at the top and a feed pipe at the bottom connected either independently or to one of the existing pipes via appropriate valves.

Traditional self cleaning media fitters can remove solids down to 20 micron, at this level efficiencies are as high as 80% removal but can be as low as 30%.

Media filters; which employ sand and other minerals as the filter material; are also used but on filtration of less than 10 micron the sand soon blinds and bacteria colonise the sand and start to grow which process soon blocks the filter bed. Because of this media based filtration generally only offers reliable filtration down to the 20 micron level.

Theoretically 10 micron filtration is possible but this can only be sustained if the feed water contains only a low level of contamination thus reducing the amount of work the filter has to perform. The design of these filters relies on a steady flux rate. The flux rate is the rate of unit flow per hour, per unit area of the filter usually expressed as m3/hr/m2 of filter. Traditionally for fine filtration to 10 micron the flux rate is reduced to flows typically 10-15 m3/hr/m2.

The problem is that by using even finer media to give high quality water the flow rate or flux rate as it is often known, needs to be slow. The traditional media is either sand or garnet or a mix. The finer the media, the finer the filtration, but also there will be a higher pressure drop and a lower flux rate. Biological contamination in this type of filter can cause rapid pressure build up which is the trigger for the system to automatically stop and backwash out the contamination.

Backwashing is brought about by shutting off valves in the supply inlet or inlets and the outlet to the filter and opening valves in the backwash pipes which effectively reverses the flow of water through the filter thus driving out the contamination through a separate backwash outlet at the top or what is normally input side of the filter system.

The water borne contamination can and often does contain biological elements which combine within the bed and start to proliferate, this is helped by the near ideal conditions within the filter environment which are normally required for such proliferation. The colonies of bacteria then create high pressure areas within the top bed surface, thereby diverting the water to less high density areas of the filter bed. The result of this is to create high velocity areas, which in turn causes channelling, sometimes known as rat holing, and the result is filter media bypass and a loss of filtration efficiency.

When the filter is backwashed the higher density bacterial colonies are heavier than normal contamination and are therefore less likely to be removed under the backwashing process, they therefore remain within the bed to act as seed for the next batch of dirty water. This results in ever shortening periods between backwash times using more and more backwash water which is run out to waste treatment. Filtration efficiency is typically less than 80% at 10-20 micron.

It is the object of the present invention to overcome the difficulties in existing filter design by introducing an additional process water inlet known as a vortix bed stabiliser to achieve a high efficiency filter leading to filter efficiencies typically at 1.0 micron greater then 86% In this specification a secondary water inlet pipe connects to a secondary discharge head which secondary head is known, in this specification, by the term "vortix bed stabiliser" and it is located within the upper plenum chamber.

According to the invention there is provided a water filter consisting of a sealed cylindrical vessel with a main water inlet at the top and an outlet at the bottom.

Contained within the vessel are various layers of filter media starting with a very fine layer at the top and finishing with a coarse layer at the bottom. At the top of the vessel above the media layers, is a receiving area known as the upper plenum into which the inlet pipe feeds and at the bottom separated from the coarse media by a plate through which water can pass is a water collection area known as the lower plenum to which the outlet pipe for filtered water is attached. The said water filter is characterised by the provision of an additional secondary water inlet pipe connected to and taking it's feed from the main water inlet pipe. The said secondary water inlet pipe connects to a secondary discharge head known as the "vortix bed stabiliser" and it is located within the upper plenum chamber.

According to a second feature of the invention there is provided a water filter in accordance with the first feature where the vortex bed stabiliser incorporates one or more discharge hotes through which water passes on its way to the fitter media According to a third feature of the invention there is provided a water filter in accordance with the second feature where the vortex bed stabiliser incorporates one or more discharge holes through which water passes on its way to the filter media, which holes are positioned preferably, but not exclusively tangentially, so as to assist a rotational flow in the upper plenum chamber.

According to a fourth feature of the invention there is provided a water filter in accordance with the first feature where the vortex bed stabiliser is circular consisting of, in use, an upper circular flat plain to which an inlet pipe is attached and a lower circular flat plain which plains are separated by a vertical side wall in which one or more holes, which are positioned preferably but not exclusively tangentially, are provided through which inlet water can pass into the filter.

According to a fifth feature of the invention there is provided a water filter in accordance with any previous feature where the said vortex bed stabiliser is fed by a supply pipe which is connected to the main water inlet pipe According to a sixth feature of the invention there is provided a water filter in accordance with any previous feature where the said vortex bed stabiliser is fed by a supply pipe which is connected to the main water inlet pipe and incorporates a flow adjustment valve.

The invention will now be described by way of example with reference to the drawings in which: -Figure 1 Is a cross section of the water filter showing all of the working parts including the media filters.

Figure 2 Is a more detailed drawing of the water inlet arrangements showing the main and secondary water inlet pipes and the secondary feed pipe connected to the vortix bed stabiliser.

Figure 3 Is a closer illustration of the discharge holes in the vortix bed stab iliser.

Referring now to figure 1, the filter vessel 1, is fed at the top by the main inlet pipe 2, through inlet valve 3. the inlet flow is divided and part of the flow goes into secondary inlet pipe 4, it passes through the flow adjustment valve 6, and travels on to the distribution head 7 known as the vortix bed stabiliser. In this mode the valve 10, in pipe 11 is closed. The main water volume is presented to the vessel in a tangential manner via pipe entry 2, this main flow creates the vortex within the top of the plenum chamber.

In other filters of this type the inlet 8, from the main inlet pipe 2, is in the side of the vessel or central to the vessel and therefore the water flow would tend to be circular as can be seen by referring to figure 2. However the flow in these arrangements tends to thin down the level of the filter media on the periphery of the vessel and carry it to the centre of the vessel where it builds up so that the level of the top of the filter media is a slope downwards from the centre or one side of the vessel. The effect of this is to reduce the efficiency of the filter media by allowing breakthrough of water to the support media, as this presents itself as the area of least resistance.

To overcome this difficulty in the present invention the vortex bed stabiliser 7, also inputs water through holes 9. These holes are arranged so that a circular motion is imparted to the water flow.

Referring to figure 2 the secondary water flow can be seen. The flow is along pipe 4 through valve 6, and on to the vortix bed stabiliser 7 where it exits into the upper plenum chamber via discharge holes 9. It can be seen the angle of the discharge holes 9 is arranged to facilitate a circular motion in the water flow.

The flow arrangements so far described have the effect of stabilising the media by dispersing the conical build up created by the inlet vortex in the top filter and thereby eliminating the possibility of water by pass within the bed seen in other filters of this type. The flow arrangement described also ensures that biological colonisation cannot occur. The continual motion of the filter media eliminates the possibility of biological fouling.

Flow through the filter system itself follows conventional practise in that water passes through different layers of media shown as 16, 17, 18, 19, in figure 1.

These layers are gradually coarser until layer 19 which is the coarsest of all.

The water then passes through nozzles 20 into a lower plenum chamber 21 and finally leaves the filter through valve 14 into pipe 15. During normal flow, valve 12, the backwash inlet valve, would be closed.

The backwashing operation would reverse the flow by closing valve 14 and opening valve 12 at the bottom of the filter and closing valves 3 which in turn stops the flow to valve 6 and opening valve 10 at the top of the filter. The flow would then be from pipe 13 to pipe 11, upwards through the filter. The backwash water is of such a flow that the bed is fluidised which in turn releases all of the contamination contained within the filter bed and within the top plenum chamber, this is ejected via pipe 11, to waste, the backwashing process lasts 5- 6 minutes which is far less then conventional filters due to the volume of contamination held away from the bed by the action of the vortex and associated stabiliser.

It will be appreciated that the water inlet system so described can take many forms and that the present invention is intended to be limited only by the scope of the claims and includes any secondary discharge system which is added to supplement the flow of water into the upper plenum chamber of the filter.

The term vortix bed stabiliser therefore in this specification is intended to be a functional description and to include any secondary water inlet in addition to the main water inlet which by directing a secondary water inlet flow is intended to assist in stabilising the movement of the filter media comprising the top media bed and is not intended to be limited to the positions shown in the drawings or to the shape and configuration of the vortix bed stabiliser 7, show in the drawings, in fact in some circumstances one or more simple nozzles or simply the end of a pipe positioned to cause a secondary flow will suffice.

Claims (7)

1. CLAIMS1. A water filter consisting of a sealed cylindrical vessel which in use has one or more water inlets at the top and at least one outlet at the bottom and between the said inlets and outlet are one or more layers of filter media characterised by at least one of the said inlets being adapted to discharge water into the vessel so that in use the flow of water into the vessel causes water within the vessel to rotate about the vertical axis of the said vessel.
2. 2. A water filter according to claim I consisting of a sealed cylindrical vessel which in use has a main water inlet at the top and one or more outlets at the bottom and between the said inlet and outlet are one or more layers of filter media the said vessel also having at least one additional inlet which is adapted so that in use the said additional inlet discharges water into the vessel so as to cause water within the vessel to rotate about the vertical axis of the said vessel.
3. 3. A water filter according to claim 1 or 2 in which the said additional inlet is connected to the main water inlet either inside or outside the vessel.
4. 4. A water filter according to any previous claim in which one or more of the said inlets has means for causing water within the vessel to rotate about the vertical axis of the said vessel.
5. 5. A water filter according to any previous claim in which the said means for causing water within the vessel to rotate about the vertical axis of the said vessel consists in use of an upper circular flat plain to which the inlet pipe is attached and a lower circular flat plain which plains are separated by a vertical side wall in which are located holes through which the water entering the vessel can pass into the vessel.
6. 6. A water filter according to claim 5 where the said holes are positioned tangentially so as to provide a discharge of water which causes the water within the vessel to rotate about the vertical axis of the vessel.
7. 7. A water filter according to any previous claim in which any of the inlet or outlet pipes may contain a flow adjustment valve.