WO2004064978A1

WO2004064978A1 - A filter system

Info

Publication number: WO2004064978A1
Application number: PCT/AU2004/000061
Authority: WO
Inventors: Sarah Elizabeth Chenery Lobban; Mark Richard Lobban
Original assignee: Sarah Elizabeth Chenery Lobban; Mark Richard Lobban
Priority date: 2003-01-21
Filing date: 2004-01-21
Publication date: 2004-08-05
Also published as: AU2003900226A0

Abstract

A filter arrangement (41) for liquids containing solids such as olive waste, the filter has a tapered cylindrical filter membrane (55), a rotatable a helical brush arrangement (51) on an axle (48) inside the membrane, an inlet means (45) to supply liquid to be filtered into an inlet end of the cylindrical filter membrane and exit means (46) to extract sludge from the other exit end of the filter membrane. The taper can be in the range of 0 to 10 degrees. Bristles of the brush are just spaced away from the filter membrane. Pressure may be used within the filter membrane and vacuum outside to assist with filtration. Sludge extraction may be continuous or intermittent.

Description

A FILTER SYSTEM

FIELD OF INVENTION

This invention relates to a device, which is used to extract oils, solids, suspended solids and organic matter from liquids such as wastewater.

BACKGROUND OF THE INVENTION

The invention will be particularly discussed in relation to its application to the treatment of wastewater produced when fruits, foods and beverages are processed but it is not restricted to this application.

During the processing of many foods including fruit and also in the case of processing olives for the extraction of olive oil a liquid waste product is produced containing organic matter including oils, suspended solids and other raw materials and is commonly referred to as wastewater or effluent.

For many fruit, food and beverage processing companies disposal of the wastewater produced is a problem. Currently most of this wastewater is discharged into waterways, sewage, soakage on land, into the storm water system or the environment in general. This is detrimental to the environment as oil, for instance, covers the surface of waterways blocking off the essential properties these environments need to survive. The variable sometimes high level of organic loads in the wastewater can overload the biological capacity of the waterways or soils ecosystem by demanding excess oxygen (biochemical oxygen demand). Turbid discoloured water blocks out light preventing photosynthesis by aquatic fauna and sediments can smother the surface blocking out the natural resource requirements of living biological ecosystems. There have been many proposals to deal with wastewater liquid and solids resulting from fruit, food and beverage production, but these have all required space, high maintenance and/or a large initial capital outlay.

One of these systems, for instance, requires a septic tank system in which heat and accelerant chemicals are added to break down the wastewater and produce compostable matter and methane gases. This system requires a minimum tank capacity of two hundred cubic metres for a standard 2 tonne processing system, mechanical aeration and chemical additives. This limits the capacity and usefulness of the system.

It is also desirable to have a system by which the oils in wastewater, particularly olive oil wastewater, can be recovered.

These problems are overcome by the present invention, which requires no additional chemicals and requires very little space. This invention provides a system by which oils, solids, suspended solids, organic matter and water can be separated from the wastewater.

A further problem which may be addressed by this invention is the shortage of potable water and the necessity of reuse of waste waters. Waters such as sewage and septic tank effluent may be processed by micro-filtration, ultra-filtration and /or reverse osmosis to provide water for reuse.

BRIEF DESCRIPTION OF THE INVENTION

In one form the invention is said to reside in a filter arrangement for liquids containing solids, the filter arrangement including a substantially cylindrical filter membrane having a longitudinal axis, a brush arrangement within the cylindrical filter membrane, the brush arrangement being adapted to be rotated on an axis co- axial with a longitudinal axis of the cylindrical filter membrane, inlet means to supply liquid to be filtered into an inlet of the cylindrical filter membrane and exit means to extract sludge from an exit of the filter membrane and a filtrate exit.

In one embodiment the longitudinal axis of the cylindrical filter membrane may be horizontal and in an alternative embodiment the longitudinal axis of the cylindrical filter membrane may be vertical.

The cylindrical filter membrane may be parallel sided or may be tapered or frusto- conical and have a taper in the range of 0 to 10 degrees.

In one arrangement the filter membrane may be used so that the smaller diameter of the cylindrical filter membrane is at the inlet of the filter arrangement and the larger diameter is at the exit and the brush arrangement is correspondingly tapered or alternatively the filter membrane is used so that the smaller diameter of the cylindrical filter membrane is at the exit of the filter arrangement and the larger diameter is at the inlet and the helical brush arrangement is correspondingly tapered.

The filter membrane may have aperture sizes in the filter membrane ranging from about 5,000 microns to about 0.001 microns. The filter membrane may be constructed from perforated metal or alternatively may be constructed from a group selected from a semi-permeable membrane, a synthetic semi-permeable membrane or a ceramic.

There can be further included a housing around the filter arrangement. The housing can include a liquid inlet connected to the inlet means, a sludge outlet connected to the exit means and a filtrate exit pipe connected to the filtrate exit.

There can be further included a vacuum system to apply a vacuum to the filtrate exit. There can also be a pressure system to apply pressure to the wastewater at the filtrate inlet.

The sludge outlet can include a valve to restrict the outflow of sludge. The valve to restrict the outflow of sludge may include means to intermittently operate the valve. Such intermittent operation may be at regular intervals such as each minute or two minutes or may be activated when load on the motor reaches a certain level indicating a build up of sludge.

Vacuum can be applied to the sludge outlet to remove the sludge either continuously or periodically. The vacuum applied may be up to -lOOpsi.

In one embodiment the brush arrangement may be mounted on an axle within and co-axial with the longitudinal axis of the cylindrical filter membrane and there can be a drive arrangement such as a direct drive motor or using an indirect pulley or gear system to rotate the brush arrangement.

Preferably the brush arrangement includes a helical brush flight. The helical brush flight comprises a helical brush with bristles of the brush extending so that they are spaced from the cylindrical filter membrane by a distance of from just touching to a 50 mm spacing. Preferably the spacing is from 0.2 m to 10 mm.

In one embodiment the brush arrangement comprises short bristles mounted onto an auger on the axle. In an alternative the brush arrangement comprises longer bristles mounted directly onto a carrier on the axle. The brush arrangement may comprise bristles made from a material selected from the group comprising metal fibres, natural fibres, nylon fibres, polypropylene fibres or a composite of metal and polypropylene fibres. The brush arrangement may have bristles which vary in stiffness and size along the length of the brush arrangement. The helical flight can have a helical pitch of between 0.5:1 to 2:1 being the ratio of diameter of the brush to pitch length. The brush arrangement may be rotated in the cylindrical filter membrane such that the helical flights of the brush cause sludge to be moved to the exit with the brush fibres allowing water to flow between the bristles.

There can be further included an auger on the axle and associated with the inlet means to carry liquids to be processed into the filter arrangement and an auger on the axle and associated with the exit means to assist with removal of sludge from the exit means.

The brush arrangement can be rotated at speeds of from 60 rpm to 5,000 rpm.

The filter arrangement according to the present invention can further include a filter membrane washing arrangement. The filter membrane washing arrangement can be adapted to supply either cold or hot water to clean the filter membrane and the water is supplied in the inlet means or be adapted to supply either cold or hot water to clean the filter membrane and the water is supplied as a spray onto the outside of the screen.

In an alternative form the invention resides in a multi stage filter arrangement including a plurality of filter arrangements for filtering liquids containing solids as discussed above wherein the filter arrangements are arranged in series.

The multi stage filter arrangement may include gravity feed between the stages or there may be a pump to pump feed and to provide pressurisation between the stages.

There can also be means to apply a vacuum to the filtrate side of each stage.

The multi stage filter arrangement can include a settling tank after the final stage.

Such a multi stage filter arrangement can have three stages, a first stage having a filter membrane with a filter aperture size range of from 3000 microns to 1000 microns, a second stage having a filter membrane with a filter aperture size range of from 1000 microns down to 200 microns and third stage having a filter membrane with a filter aperture size range of from 200 microns to 35 microns.

In an alternative form the invention resides in a multi stage filter arrangement including a plurality of filter arrangements for filtering liquids containing solids as discussed above wherein the filter arrangements are arranged in parallel.

It has surprisingly been found that the bristles of the brush help to de-emulsify the olive oil for instance in a plant used for processing of olive oil factory wastewater. The olive oil is carried out in the sludge and can be recovered by centrifuging or other methods. The mechanism of de-emulsifying is not clearly understood but it is believed to relate to the action of the tips of the fibres on the emulsified oil but the applicant is not bound to this explanation. The removal of olive oil from the wastewater has considerable advantage in reducing the BOD of the filtrate so that it can be disposed by conventional means such as discharge into waterways, as sewage, soakage on land, or into the environment in general.

In an alternative embodiment, the cylindrical filter membrane may have variable aperture size extending from larger apertures at the inlet end of the cylindrical filter membrane to smaller apertures at the exit end of the cylindrical filter membrane.

Liquid may be supplied to the inlet means at substantially atmospheric pressure or at a pressure suitable for the filtering process.

A settling tank can act as secondary treatment equipment. Other existing tertiary wastewater treatment technologies can be used for downstream refinement and polishing. The sludge from the or each exit means may be passed to a settling tank or to further processing to extract oil or other products.

In a preferred embodiment the apparatus according to the present invention may be used for the reprocessing of waste-waters such as sewage and septic tank effluent as well as industrial wastes. In such a situation the filter membrane may be formed from a very fine pored film or material such as a synthetic polymer membrane. There may be pressure applied to the liquid within the filter membrane and a vacuum applied to the outside of the membrane to assist with extraction of liquid such as water through the membrane. The use of the brush on the inside of the membrane will help to keep the membrane clean and where the brush is a helical brush it will tend to push sludge towards the sludge outlet. As in earlier embodiments the brush bristles preferably do not touch the filter membrane so that wear on the membrane does not occur and there is not excess load on the motor. The brush bristles can, however, set up turbulence which will assist with keeping the filter membrane clear of deposited solids.

The sludge at the sludge outlet could be removed at intervals by briefly opening of a solenoid valve in the sludge outlet. At the same time the application of pressure and vacuum, inside and outside the membrane respectively, may be stopped to prevent excess pressure being applied to the outlet. Vacuum assistance for the removal of the sludge may also be used.

There may be several stages in such a process with a first stage being a micro- filtration stage with pore sizes down to 0.1 μm. A next stage could be an ultra- filtration stage with pore sizes down to 0.01 μm. A next stage could be a nano- filtration stage with pore sizes down to 0.001 μm. A final stage could be in effect a reverse osmosis stage with pore sizes down to 0.0001 μm. In a further form the invention is said to reside in a method of filtering waste water including the steps of supplying waste water to a filter system as described above, continuously cleaning the filter membrane using the brush arrangement and withdrawing filtrate from the filtrated exit.

The equipment may be constructed from materials suitable for the type of product being processed. For instance, if the materials being processed are food grade products then food grade materials should be used. Materials can include plastics, glass or other fibre reinforced plastics and metals such as stainless steel. Stainless steel may be grade 304 or grade 316 stainless steel. Grade 304 may be used where less corrosion resistance is needed. Grade 316 may be used where corrosion and a stronger material is needed. In unusual environments fibreglass or ceramic glaze may be used to line the internal surface of the housings.

BRIEF DESCRIPTION OF THE DRAWINGS

This then generally describes the invention but to assist with understanding, reference will now be made to the accompanying drawings which show preferred embodiments of the invention.

In the drawings.

Figure 1 shows one example of the wastewater treatment arrangement by which both water and solids can be removed from wastewater according to this invention; Figure 2 shows an embodiment of a wastewater treatment apparatus according to the invention;

Figure 3 shows a filter housing of the embodiment shown in Figure 2;

Figure 4 shows a filter membrane of the embodiment shown in Figure 2;

Figure 5 shows a typical helical brush arrangement of the embodiment shown in Figure 2; Figure 6 shows an alternative embodiment of a filter system according to the invention;

Figure 7A and 7B show a transverse and longitudinal cross section of helical brush arrangement of one embodiment of the invention; and Figure 8A and 8B show a transverse and longitudinal cross section of helical brush arrangement of an alternative embodiment of the invention.

DESCRIPTION OF PREFERRED EMBODIMENTS

Referring to Figure 1 it can be seen that in general the wastewater treatment arrangement according to this embodiment for removal of oil, water and solids from a wastewater comprises of a series of stainless steel housing cylinders, with cylindrical membrane screens inside each of the housing cylinders. Inside each of the screens is a helical brush attached to a shaft which rotates on the horizontal axis. A cone shaped cyclone separator and a sinuous flow and overflow flow tank come after the separator cylinders.

In olive oil processing, wastewater flows from a centrifugal separator 1, which works to separate oil from solids and water by rotating the mix in a steel drum at high speeds.

The wastewater from the centrifugal separator is pumped via pump 2 from the separator through a pipe 3 and through into the first housing cylinder 4.

Inside housing cylinder 4 is a cylindrical membrane screen 5 with a shaft 6 through the centre. The membrane screen 5 comprises a perforated stainless steel cylinder. A helical brush 7 with relatively coarse bristles is mounted onto a carrier which is welded to the shaft 6. Waste water is fed into the interior of the membrane screen 5. The rotating helical brush 7 thickens the oils and solids while pushing the solids through and out the exit pipe 8 and the screened filtrate passes through the membrane screen. Membrane screen 5 is enclosed by a housing cylinder 4, which collects the screened filtrate and channels it down pipe 9 and into the next cylinder 10 of a multistage filtration process.

A pump 31 is provided between the first stage and the second stage to pressurise the feed to the second stage.

In the next stage the filtered wastewater enters a mesh membrane screen 11 from pipe 9. The second rotating helical brush 12 has bristles which are softer but a thicker ply than the first helical brush 7. The rotating helical brush 12 thickens the oils and solids while pushing the solids through and out the exit pipe 13 and the screened filtrate passes through the membrane screen 11. The membrane screen 11 is enclosed by a housing cylinder 10, which collects the screened filtrate and channels it down pipe 14 and into cylinder 15, the next stage in the multistage filtration process.

In the third stage the filtered wastewater enters an even finer mesh membrane screen 16 from pipe 14. The second rotating helical brush 17 has bristles which are still softer but of a similar ply to the second helical brush 12. The rotating helical brush 12 thickens the oils and solids while pushing the solids through and out the exit pipe 18 and the screened filtrate passes through the membrane screen 16. The membrane screen 16 is enclosed by a housing cylinder 15, which collects the fine-screened filtrate and channels it down pipe 19 and into a cyclone separator 20.

Filtration in the third stage is assisted by application of a vacuum by vacuum system 32 to the annular space between the membrane screen 16 and housing cylinder 15.

Pipe 19 connects to a cone shaped cyclone separator 20 that extracts emulsified fine particulate solids through pipe 21. Water from pipe 21 may discharge into any appropriate further treatment, effluent disposal or re-use system. The remainder of the oil and wastewater is channelled into the sinuous flow and overflow tanks 22. The tank has six chambers 23, 24, 25, 26, 27 and 28. Chamber 23 allows for the skimming off of any remaining solids into a holding tank 29 via pipe 31 and pipe 32 extending from chamber 27 catches the majority of the remaining oil and solids and also skims them off in to a holding tank 29 to be recycled through the separator and at regular intervals the separated olive oil may be collected.

Chamber 24 encourages settling by allowing the water to gently overflow into chambers 25, 26 and 27. Any remaining oil is again skimmed of by the naturally occurring overflow mechanism in the last chamber 28. Chamber 28 pipes the treated water out through pipe 30. Pipe 30 can lead into any appropriate further treatment, effluent disposal or re-use system.

Figures 2 to 5 show more detail of a further embodiment of a filter system for wastewater.

Figure 2 shows an assembly of a two-stage filter system. Figure 3 shows the casing for each stage, Figure 4 shows the filter membrane and Figure 5 shows the helical brush.

Looking generally at Figure 2 it will be seen that the two stage filter system is mounted on a frame 40 and includes a first stage generally shown as 41 and a second stage generally shown as 42. Each stage 41 and 42 is essentially the same except the size of the apertures in the filter membrane as will be discussed below.

The stage 41 has a housing 44 mounted to the frame 40. The housing 44 has a wastewater inlet 45, a sludge outlet 46 and a filtrate outlet 47. A shaft 48 passes through the centre of the housing and is rotated by a motor 49 and gearbox 50. A bearing 72 on one end of the shaft 48 supports the axle in an aperture 74 in the housing 44 and at the other end the shaft is supported in the filter membrane 55 as discussed below. On the shaft 48 is mounted a helical brush assembly 51 and at the inlet end there is a feed auger 39 also mounted onto the shaft 48. There is also provided an outlet auger 38 also mounted onto the shaft 48 to assist with transporting the sludge from the end of the brush to the outlet 46.

As can be particularly seen in Figure 4 the spiral brush 51 is formed with a metal base or carrier 52 into which is received bristles 70 with the metal base 52 being helically wound around and affixed to the shaft 48. It will be noted that in this embodiment the outer periphery of the brush 51 is slightly tapered along the length of the brush so that typically it has a greater diameter at the outlet end 53 than the inlet end 54.

Mounted into the housing 44 and surrounding the brush 51 is a cylindrical and tapering filter membrane 55 which is shown in detail in Figure 5. The filter membrane at the inlet end 56 has a ring seal 57 which fits into the housing 44 at 58. The outlet end of the screen 59 has a seal ring 60 which fits into the housing 44 at 61 and also a bearing member 62 which supports the end 76 of the shaft 48. The clearance of the brush from the screen when it is mounted into the screen is preferably in the range of 0.2 mm up to 50 mm.

A water spray system 63 is provided in the housing 44 to spray wash water onto the screen 55 when required. Preferably the wash water is hot water.

Wastewater is provided to the inlet 45 and the auger 52 moves the wastewater and organic material into the filter where the bristles of the brush 51 cause the organic matter to be moved towards the outlet end 46 and the water through the mesh of the screen 55.

The mesh screen may have an aperture diameter of 1 to 3 mm in the first stage. Filtrate from the first stage is passed through outlet 47 into the second stage 42 which is essentially similar to the first stage except that the mesh size of the screen is smaller and the bristles of the brush in the second stage are somewhat softer and less rigid. The mesh screen in the second stage 42 may have an aperture diameter of from 1 mm down to 35 microns.

Filtrate from the second stage 42 passes out through outlet 65 and sludge passes out through outlet 66.

In each of the sludge outlets 46 and 66 there is provided a valve arrangement 67. The valve arrangement 67 is normally closed and can be periodically activated to open it to allow removal of sludge. Activation of the valve 67 can be done at regular intervals such as once per minute for one or two seconds or may be activated when load on the motor driving the rotating brush increases to a selected value indicating build up of sludge in the exit.

The sludge from the outlet 46 and outlet 66 can be treated with a centrifuge to remove olive oil before being sent to composting and the filtrate from the outlet 65 can be sent to further processing as discussed earlier or to waste. Alternatively the sludge from the outlet 46 and outlet 66 can be treated in settling tanks to allow the de-emulsified oil to separate from the solids.

Further processing can include the sinuous flow and overflow tanks of the type discussed in relation to Figure 1.

An alternative embodiment of filter system according to the invention is shown in Figure 6.

In this embodiment the filter system is substantially vertical with the longitudinal axis of the filter membrane and helical brush being vertical. In this embodiment the filter system 80 has a housing 82 with a cap 83 which can be screwed onto the housing. A suitable seal arrangement such as an O-ring is provided between the housing 82 and cap 83. In the cap 83 there is an inlet 85 and an outlet 87 for the filter arrangement. The cap also includes an upper bearing 89 for a brush shaft 91. A lower bearing 93 is provided for the lower end of the brush shaft 91 and the lower bearing is mounted in the lower end 85 of the housing 82. A sludge outlet 95 is provided at the lower end 85 of the housing 82.

A cylindrical and tapered filter membrane 97 is provided within the housing 82 and its longitudinal axis is concentric with the axle 91. The filter membrane has at its lower end a ring seal 99 which fits into the lower end of the housing 85 at 101 and at the upper end of the cylindrical filter membrane 97, a ring seal 103 fits into a housing 105 which is received in the cap 83. The inlet 85 enters the inside of the filter membrane 97 and the outflow 87 takes liquid from this annular space between the outside of the filter membrane 97 and the main housing 82. On the axle 91 and within the filter membrane 97 is mounted a helical brush arrangement 109. At the lower end of the helical brush, the brush is replaced with a solid auger 111. In use, the brush is rotated by drive pulley 113 on shaft 91 (from a motor, not shown) so that the helical flights drive sludge down towards the sludge outlet 95 and the solid auger portion 111 assists with compacting the sludge. When sufficient sludge has been compacted an extra load is provided onto the auger, a sensor associated with the motor can activate a valve to open the exit and allow the sludge to be discarded. Alternatively, the valve can be operated at regular intervals such as every minute or two minutes during use to open the valve and release the built up sludge.

Figure 7A and 7B show longitudinal and transverse cross-sectional views of one embodiment of a helical brush flight. On the axle 120 a brush carrier 122 is welded by means of welds 124 and a number of brush bristles 126 are crimped into the carrier. In practice the brush is crimped into the carrier in a straight line and then the carrier 122 with the bristles mounted into it is wound around the axle 120. In the embodiment shown in Figures 8A and 8B, the axle 120 has an auger portion 130 wound in a spiral manner onto it and welded by means of welds 132 to the axle 120. On the upper end of the auger portion 130 is a bristle carrier 134 and crimped into the bristle carrier 134 are short bristles 136.

As discussed earlier it is preferred that the bristles of the helical brush arrangement of the various embodiments do not touch the filter membrane in use but are spaced from it by from 0.2 to 50 millimetres so that extra load is not placed on the motor.

Throughout this specification various indications have been given as to the scope of the invention but the invention is not limited to any one of these but may reside in two or more of these combined together. The examples are given for illustration only and not for limitation.

Claims

THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS:

1. A filter arrangement for liquids containing solids, the filter arrangement including a substantially cylindrical filter membrane having a longitudinal axis, a brush arrangement within the cylindrical filter membrane, the brush arrangement being adapted to be rotated on an axis co-axial with a longitudinal axis of the cylindrical filter membrane, inlet means to supply liquid to be filtered into an inlet of the cylindrical filter membrane and exit means to extract sludge from an exit of the filter membrane and a filtrate exit.

2. A filter arrangement as in Claim 1 wherein the longitudinal axis of the cylindrical filter membrane is substantially horizontal.

2. A filter arrangement as in Claim 1 wherein the longitudinal axis of the cylindrical filter membrane is substantially vertical.

3. A filter arrangement as in Claim 1 wherein the cylindrical filter membrane is tapered or frusto-conical and has a taper in the range of 0 to 10 degrees.

4. A filter arrangement as in Claim 3 wherein the filter membrane is used so that the smaller diameter of the cylindrical filter membrane is at the inlet of the filter arrangement and the larger diameter is at the exit and the brush arrangement is correspondingly tapered.

5. A filter arrangement as in Claim 3 wherein the filter membrane is used so that the smaller diameter of the cylindrical filter membrane is at the exit of the filter arrangement and the larger diameter is at the inlet and the helical brush arrangement is correspondingly tapered.

6. A filter arrangement as in Claim 1 wherein the filter membrane has aperture sizes in the filter membrane ranging from about 5,000 microns to about 0.001 microns.

7. A filter arrangement as in Claim 1 wherein filter membrane is constructed from perforated metal.

8. A filter arrangement as in Claim 1 wherein filter membrane is constructed from a group selected from a semi-permeable membrane, a synthetic semi- permeable membrane or a ceramic.

9. A filter arrangement as in Claim 1 further including a housing around the filter arrangement.

10. A filter arrangement as in claim 9 further including a vacuum system to apply a vacuum to the filtrate exit.

11. A filter arrangement as in Claim 9 wherein the housing includes a liquid inlet connected to the inlet means, a sludge outlet connected to the exit means and a filtrate exit pipe connected to the filtrate exit.

12. A filter arrangement as in Claim 11 wherein the sludge outlet includes a valve to restrict the outflow of sludge.

13. A filter arrangement as in Claim 11 wherein the valve to restrict the outflow of sludge includes means to intermittently operate the valve.

14. A filter arrangement as in Claim 1 wherein the brush arrangement is mounted on an axle within and co-axial with the longitudinal axis of the cylindrical filter membrane.

15. A filter arrangement as in Claim 1 including a drive arrangement to rotate the brush arrangement.

16. A filter arrangement as in Claim 1 wherein the brush arrangement includes a helical brush flight.

17. A filter arrangement as in Claim 16 wherein the helical brush flight comprises a helical brush with bristles of the brush extending so that they are spaced from the cylindrical filter membrane by a distance of from 0.2 to 50 mm.

18. A filter arrangement as in Claim 14 wherein the brush arrangement comprises short bristles mounted onto an auger on the axle.

19. A filter arrangement as in Claim 14 wherein the brush arrangement comprises bristles mounted directly onto a carrier on the axle.

20. A filter arrangement as in Claim 1 wherein the brush arrangement comprises bristles made from a material selected from the group comprising metal fibres, natural fibres, nylon fibres, polypropylene fibres or a composite of metal and polypropylene fibres.

21. A filter arrangement as in Claim 1 wherein the brush arrangement has bristles which vary in stiffness and size along the length of the brush arrangement.

22. A filter arrangement as in Claim 16 wherein the helical flight has a helical pitch of between 0.5:1 to 2:1 being the ratio of diameter of the brush to pitch length.

23. A filter arrangement as in Claim 16 wherein the brush arrangement is rotated in the cylindrical filter membrane such that the helical flights of the brush cause sludge to be moved to the exit with the brush fibres allowing water to flow between the bristles.

24. A filter arrangement as in Claim 14 further including an auger on the axle and associated with the inlet means to carry liquids to be processed into the filter arrangement.

25. A filter arrangement as in Claim 10 further including an auger on the axle and associated with the exit means to assist with removal of sludge from the exit means.

26. A filter arrangement as in Claim 1 wherein the brush arrangement is rotated at speeds of from 60 rpm to 5,000 rpm.

27. A filter arrangement as in Claim 1 further including a filter membrane washing arrangement.

28. A filter arrangement as in Claim 27 wherein the screen washing arrangement is adapted to supply either cold or hot water to clean the filter membrane and the water is supplied in the inlet means.

29. A filter arrangement as in Claim 27 wherein the screen washing arrangement is adapted to supply either cold or hot water to clean the filter membrane and the water is supplied as a spray onto the outside of the screen.

30. A multi stage filter arrangement including a plurality of filter arrangements for filtering liquids containing solids as defined in Claim 1 wherein the filter arrangements are arranged in series.

31. A multi stage filter arrangement as defined in Claim 30 including gravity feed between the stages.

32. A multi stage filter arrangement as defined in Claim 30 including a pump to pump feed and to provide pressurisation between the stages.

33. A multi stage filter arrangement as defined in Claim 30 including a settling tank after the final stage.

34. A multi stage filter arrangement as defined in Claim 30 having three stages, a first stage having a filter membrane with a filter aperture size range of from 3000 microns to 1000 microns, a second stage having a filter membrane with a filter aperture size range of from 1000 microns down to 200 microns and third stage having a filter membrane with a filter aperture size range of from 200 microns to 35 microns.

35. A multi stage filter arrangement including a plurality of filter arrangements for filtering liquids containing solids as defined in Claim 1 wherein the filter arrangements are arranged in parallel.

36. A method of filtering waste water including the steps of supplying waste water to a filter system as in Claim 1, continuously cleaning the filter membrane using the brush arrangement and withdrawing filtrate from the filtrated exit.

37. A method as in Claim 36 further including providing pressure assistance to the filtering process.

38. A method as in Claim 36 further including providing vacuum assistance to the filtering process.

39. A method as in Claim 36 further including intermittent removal of sludge through the exit means.