WO2001008805A1

WO2001008805A1 - Fibres/solids separating system

Info

Publication number: WO2001008805A1
Application number: PCT/AU2000/000900
Authority: WO
Inventors: Paul Woodley
Original assignee: Teagan Pty. Ltd.
Priority date: 1999-07-30
Filing date: 2000-07-28
Publication date: 2001-02-08
Also published as: MY130666A; TW527220B; AUPQ193499A0

Abstract

A method and apparatus for clarifying wastewater containing solid and/or fibrous materials is described in which the incoming wastewater stream containing the solid or fibrous materials is aerated. The aerated incoming stream is conveyed to and through a separation vessel (6) having a baffle arrangement (12) where it is evenly distributed by the baffle arrangement (12) to allow the wastewater stream to be de-aerated. As the incoming wastewater stream de-aerates by passage through the baffle arrangement (12) the contamination of solids and fibre material is floated to the surface of the wastewater by the rising air or gas bubbles floating to the top of the separation vessel (6). In one embodiment the baffle arrangement (12) includes three substantially circular baffle plates (16, 18) and (20) arranged in partially overlying spaced apart relationship to define a tortuous flow path through which the aerated wastewater flows to assist in facilitating release of the gas or air from the wastewater to float the solid/fibrous materials to the top of the treatment vessel (6) where it is removed as a sludge or foam. The flowpath is such that two different zones are formed, one being a quiescent zone of substantially clarified wastewater and the other being a turbid zone containing fibre/solids material where no eddy currents or similar are produced to mix the two zones at their interface. In one example the sludge/foam or similar is further treated in a hydro-cyclone defoamer (60) or similar vessel.

Description

FIBRES/SOLIDS SEPARATING SYSTEM

The present invention relates generally to separation apparatus and methods of using such apparatus, particularly apparatus for separating solid material or fibrous material from liquids. More particularly, the present invention relates to an apparatus and method for separating fibres and solids from aqueous solutions or the like, as one step in an overall wastewater treatment system from a variety of sources. Even more particularly, the present invention relates to an improved separation tank having a baffle arrangement and to a method of using the tank to clarify the wastewater admitted to the tank. The present invention finds particular application in an installation and method for clarifying effluent or wastewater from the food industries, such as for example in the manufacture of fruit juice and other beverages, in which the separation tank is part of the installation for removing solid and fibrous material from the effluent or wastewaters .

Although the present invention will be described with particular reference to one form of the apparatus and to a method of using that form of the apparatus for separating fibres and solids from a product stream in the food and beverage industries, it is to be noted that the scope of the present invention is not limited to the described embodiment, but rather the scope of the present invention is more extensive so as to include other arrangements of the apparatus, including other arrangements of the baffle arrangement located in the tank and of the tank for removing fibres and solids, and the use of these arrangements in applications other than that specifically described to treat a wide variety of substances including product streams, wastewater streams, effluent streams and the like.

Regulations concerning the disposal of wastewater from manufacturing processes are becoming increasingly more stringent. Discharge of effluent from industrial processes, particularly processes that involve the manufacture of food products and beverages, containing contamination in the form of solids, fibres and the like, is becoming increasingly more regulated so that direct disposal to the conventional drainage system i-s no longer tolerated without some attempt to clean the wastewater prior to discharge to reduce the amount of contaminants or pollutants being discharged with the wastewater. Therefore, there is an increasing need to reduce the levels of contaminants or pollutants in wastewater prior to the wastewater being discharged to the normal drainage system.

One example of the food and drink industry to which the present invention relates is the manufacture of fruit juices or drinks, such as for example orange juice, orange drink or the like. Other fruits that are made into juices or drinks to which the present invention is applicable include lemon, lime, pineapple, grapefruit and the like. Using oranges as an example, during the conversion of oranges to orange juice/drink, one step in the process results in fibrous material and/or solid particles being separated from the juice component. The solid/fibrous material forms one component of the product stream being formed. However, with tightening legislation, lesser amounts of solids/fibrous material can be discharged or are desired in the final drink product. Thus, there is a need for an apparatus and method which can be used to remove greater amounts of solids/fibres from liquid streams, including wastewater streams prior to their discharge, particularly discharge to the normal drainage or outlet, and from product streams to produce a more clarified product such as a fruit juice, a fruit drink substantially free of solids and/or fibres.

The present invention seeks to provide a method and apparatus which results in increased separation of solid material and/or fibrous material from liquid streams originating from manufacturing processes, particularly in the food and beverage industries, such as for example, the manufacture of orange juice/drink, which will reduce the amount of solid/fibrous contaminants or pollutants to a level which is acceptable for discharge to the normal drainage system, or waste outlet or to have a more clarified product and thus satisfy the increasingly more stringent regulations concerning the disposal of effluents or wastewater and consumer demands .

According to one aspect of the present invention there is provided a separation vessel for clarifying wastewater containing solid and/or fibrous materials including an inlet for introducing aerated or gasified wastewater into the vessel, a baffle arrangement located in close proximity to the inlet so that wastewater introduced through the inlet flows through the baffle arrangement in such a manner as to release the entrained air or gas from the wastewater, a first outlet for discharging clarified water substantially free of solid and/or fibrous material, and a second outlet for discharging the solid and/or fibrous material separated from the wastewater in the separation vessel, wherein the baffle arrangement includes a plurality of individual baffle members located in at least partially overlying spaced apart relationship, for defining a flowpath for the incoming aerated wastewater to flow through and around the baffle arrangement such that the flowpath is substantially tortuous and/or prevents the formation of eddy currents within the vessel, thereby contributing to entrapment of the solid/fibrous material within the air or gas bubbles to at least assist in facilitating separation of the solid/fibrous material from the wastewater.

According to another aspect of the present invention there is provided a method of separating substantially solid/fibrous material from wastewater in a separation vessel, including the steps of introducing through an inlet an aerated or gasified wastewater containing the solid/fibrous material as one component to the separation vessel, allowing the wastewater to flow through a baffle arrangement including a number of individual baffle members arranged in at least partially overlying spaced apart relationship defining a substantially tortuous or convoluted flowpath for assisting in releasing the air or gas bubbles from the wastewater to thereby assist in separating the fibres/solid from the wastewater, discharging clarified water from a first outlet, allowing the air or gas entrained in the wastewater to rise to the surface of the separation vessel thereby conveying the solid/fibrous material, and discharging from a second outlet the solid/fibrous material from the separation vessel, thereby separating the solid/fibrous material from the wastewater with the aid of the release of the gas or air from the watewater.

Typically, the baffle members are baffle plates. More typically, the baffle plates are substantially circular, preferably circular. However, they may be of any suitable shape, size or configuration to satisfy the requirements of separating the actual fibres/solids being processed. More typically, the baffle plates are vertically spaced apart from each other defining a substantially vertical gap therebetween. Even more typically, the gap forms part of the flow path for releasing the air or gas bubbles from solution in the wastewater. Even more typically some of the baffle plates are substantially horizontally spaced apart from each other as well as being vertically separated from each other. It is to be noted that any suitable gas or combinations of gases can be used in the present invention to aerate or gasify the watewater. Suitable gases include air, oxygen, nitrogen, carbon dioxide, the inert gases or the like. Further, it is to be noted that the term aerated is not restricted to the use of air only, but is a general term to include any gas or combination of gases, including oxygen and air.

Further it is to be noted that the present invention finds particular application in clarifying a product stream, such as a fruit juice or fruit drink stream, by removing fibres/solids from the product stream to produce a clarified final product substantially free of fibres/solids.

The present invention will now be described by way of example with reference to the accompanying drawings, in which:

Figure 1 is a schematic view of an installation containing as one component a fibre/solid separation tank in accordance with the present invention;

Figure 2 is a schematic vertical cross-section view of one form of the fibre/solid separation tank of the present invention; - Figure 3 is a schematic top plan view of the embodiment of Figure 2;

Figure 4 is a more detailed view of the baffle arrangement of the present invention in the form of diffusion/distribution plates located towards the base of the fibre/solid separation tank of figure 2; and

Figure 5 is a schematic vertical cross-section of one form of a de-foamer used to separate solid/fibres material from foam which finds application in the vessel of the present invention. One form of an installation incorporating the separation tank of the present invention will now be described. In the form of the installation illustrated in the drawings and generally denoted by reference numeral 2, there is an aerated wastewater conduit 4 for supplying a mixture containing wastewater and other contaminants or pollutants such as fibres and/or solids, typically from an orange juice/drink manufacturing plant, to a separation tank 6. The cylindrical separation tank 6 is provided having an inverted conical base 8 and a conical top cover 10. The conical base 8 of separation tank 6 is provided with an outlet 13 for discharging clean water substantially free of solid/fibrous material from tank 6 after having been treated. The inlet conduit 4 is connected to base 8 and is in fluid communication with an internal supply conduit 11 which extends from the supply conduit 4 to a baffle arrangement in the form of a diffuser/distributor generally denoted as 12.

The purpose of the diffuser/distributor 12 is to evenly distribute incoming aerated wastewater over a defined area of the tank corresponding to the size of the perimeter of the baffle arrangement and to define a tortuous or convoluted flow pathway for the aerated wastewater to travel through to allow any entrained gas or air to be released from the aerated or gasified wastewater.

With particular reference to Figure 4, one form of the diffuser/distributor 12 will now be described. However, it is to be noted that the distributor 12 may take any suitable form. The arrangement illustrated in Figure 4 comprises an inverted conical manifold 14 having an apex directed to the lower end of tank 6 and which is connected to one end of internal supply conduit 11 for admitting the aerated wastewater mixture to the manifold. A series of spaced apart baffles or plates are located in a prearranged pattern over the surface of the conical manifold and extend beyond the perimeter of manifold 14. In one embodiment, there are three individual circular plates 16, 18, 20 which form the baffle arrangement. In this arrangement two plates 16, 18 are located in side by side, horizontally spaced apart relationship at about the same level to each other, located closer to the manifold and vertically spaced apart from the rim of the manifold at about the same distance by a pair of posts 22 attached to the rim of the conical manifold. Thus, the two plates 16, 18 form a pair of adjacent baffles at the same height. A pair of similar posts 24 provided at or towards the edge of the circular plates 16, 18 for mounting a centrally located circular plate 20 above the other two lower circular plates 16, 18, so that an arrangement of three partially overlapping, spaced apart circular plates is formed as shown in Figure 4. It is to be noted that plates 16, 18 and 20 can take any suitable size or shape. The aerated mixture being admitted to the conical manifold 14 is caused to flow around the three circular plates 16, 18, 20 so as to spread out over the area of the manifold and is caused to flow in the spaces between the manifold 14.and the three circular staggered plates 16, 18 and 20 and between the plates to form a tortuous or convoluted pathway, so that the aerated mixture is distributed over a pre-determined area of the manifold. By flowing through and around the baffle arrangement as described the entrained gas or air is released from the wastewater and is free to rise to the upper surface of the tank taking fibre and solids particles with the gas or air as it rises in the form of bubbles . Turning now to the top of separation tank 6, a solids/fibre removing assembly 26 is located at or towards the top of the tank for removing solid and fibre material which has been separated in the tank by entrainment within air or gas bubbles rising to the surface in tank 6 to form a sludge, foam or similar at the top of the level of liquid in the tank. The removal subassembly 26 includes a sludge/fibre overflow weir in the form of a tapered trough 30 having a mouth 32 in the form of a slot, as shown more particularly in Figure 3. A otorised scraper assembly is installed at the top of the separation tank for rotation internally within the tank so as to push the sludge/fibre material accumulating at the top of the tank into the open mouth 32 of the tapered trough 30 for discharge from the tank. The scraper assembly includes a motor 34 and a paddle 36 which slowly rotates on the surface of the sludge in the separation tank to push the sludge towards trough 30.

The scraper assembly can be mounted so as to be rotatable in a clockwise and/or anticlockwise direction for moving the sludge/fibre that accumulates at the top of the liquid in the tank. The base of tapered trough 30 is provided with an outlet connected to a discharge conduit 38 which passes through the side wall of tank 6 and extends to a suitable collection vessel. One form of this collection vessel is a de-foamer, the details of which will be described later in this specification. A level control arrangement is provided so as to control the level of liquid in the separation -tank in order to assist operation of the solid/fibre removing assembly by maintaining a constant level within tank 6. The level control arrangement includes an auxiliary tank in the form of a balance tank 40 located to one side of separation tank 6. One end of a discharge conduit 42 is connected to outlet 13 of tank 6 whereas the other end of discharge conduit 42 is connected to an inlet of the balance tank 40. Tank 40 is provided with an outlet and outlet conduit 46 to ensure that the clarified liquid phase is fresh liquid, and that due to the continual flow of clarified liquid from separation tank 6 through the balance tank 40 to the outlet conduit 46, there is no possibility of stagnant liquid being trapped in the balance tank. A vent pipe 48 provides fluid communication between the respective upper ends of separation tank 6 and balance tank 40. Tank 40 is provided with a sensor to detect the level of clarified water in tank 40 so as to maintain a corresponding level of liquid in separation tank 6 in order that the sludge foam collecting at the top surface of the liquid in tank 6 can be removed through the overflow weir and trough 30.

In operation of the installation of the present invention, an aerated mixture of waste including solids and/or fibres is produced as the waste stream of a manufacturing plant, typically making orange juice/drink, and this aerated mixture is fed via supply conduit 4 and internal conduit 11 into conical manifold 14 where it is discharged into tank 6. The flow path of the incoming wastewater stream is around the edges of plates 16, 18, 20 in order to be diffused and distributed within the separation tank. The incoming aerated wastewater mixture or stream may be formed in a variety of apparatus or by a variety of methods . One way of forming this aerated mixture is using an induced cyclonic separator, such as for example as described in international patent application no. PCT/AU98/00691. Alternatively, any other suitable type of aerator may be used to aerate a waste mixture from a food or beverage manufacturing plant or similar.

It is to be noted that as the size and spatial arrangement of the plates 16, 18, 20 forming the distribution means are adjustable both in size and in shape, this arrangement can be adjusted to vary the flow rate of the incoming aerated mixture being treated, so as to create low or high velocities or low or high back pressures in separation tank 6 between manifold 14 and the overflow weir located at or towards the top of tank 6. The introduction of incoming aerated waste feed is adjusted so that two zones are formed at or towards the base of the separation tank having interface 28. One of the zones, designated zone A and identified as such in Figure 1, which is located below interface 28, is a zone of a clear liquid substantially free of contaminants or pollutants, such as the particulate material or fibrous material contained in the incoming aerated waste feed, whereas the other zone, located above interface 28, which is designated zone B and identified as such in Figure 1, is a zone of contaminated liquid containing the particulate or fibrous material as well as the rising air or gas bubbles in which the solids/fibres become entrained or entrapped. It is to be noted that zone B extends from interface 28 to the top level of the separation tank 6 at the level of mouth 32. The small air droplets previously formed when aerating the waste feed prior to being introduced into tank 6 allow particulate matter or fibrous material to be trapped within the air bubbles, so that as the air bubbles float towards the top surface of contaminated zone B the solid or fibrous particles are correspondingly floated to the top of tank 6 thus separating these materials from the wastewater. It is to be noted that in operation of the present invention the distributor 12 evenly distributes the incoming wastewater so that liquid/air and solid/fibre components are evenly distributed over the area of the tank or over a predetermined area of the tank only. Further, it is to be noted that the selection of the size, shape and arrangement of the plates forming the baffle arrangement 12 is selected so that the clean zone A and the turbid zone B, respectively, are formed within the separation tank 6 by preventing the formation of eddy currents that allow turbid material, from zone B to enter and/or re-enter the clear zone A, thereby preventing mixing of the materials in these two zones and maintaining interface 28 separating both zone A and zone B.

The accumulation of the solid or fibrous material within the air bubbles forms a sludge or similar foam or the like at the top surface of the liquid in the separation tank. Motorised scraper 34 is operated to turn paddle 36 so as to push the sludge material consisting of the accumulated solid and fibrous material entrapped with the air and air into the open mouth 32 of the trough 30, whereupon the sludge travels downwardly through the tapered trough 30 and is discharged from the separation tank through the discharge conduit 38. This sludge can be further treated, as will be described in more detail below, or can be de-foamed or allowed to settle for ultimate disposal in an appropriate manner according to requirements .

Whilst the small air bubbles are floating the contamination caused by the solids and fibrous materials to the top of the separation tank, clear zone A is forming at the bottom of the tank in the volume near to conical base 8. The clear liquid in zone A is discharged through outlet conduit 13 and fed via conduit 42 to balance tank 40. As balance tank 40 is in fluid communication with separation tank 6, the level of clear liquid in balance tank 40 is the same as the level of sludge and contaminated liquid in the separation tank. Sensor 50 which detects the level of - Il ¬

liquid in tank 40 is operated to maintain a constant level in separation tank 6 as the level in the separation tank is the same as the level in the balance tank. If the level in the balance tank rises above the position of the sensor, valve 52 is operated to discharge clear liquid from the balance tank via discharge conduit 46, whereas, if no liquid is detected by the sensor in the auxiliary tank, the discharge valve 52 is closed thereby allowing more clear liquid to flow from tank 6 to accumulate in the balance tank until the sensor detects the correct level and shuts valve 52. By sensor 50 continually monitoring the level in balance tank 40, the level in the separation tank 6 is maintained constant at or about the level of the open mouth of the overflow weir, thereby allowing continual removal of sludge from tank 6 to maintain separation of the solids/fibres from the wastewater.

By using the apparatus and method of the present invention, it is possible to clarify wastewater containing solids or fibrous contaminants into a first fraction which is a clarified or clear liquid suitable for discharge to the normal drainage system of the factory, and a second fraction consisting mainly of a foam or sludge of solid or fibrous materials which is able to undergo further treatment. This further treatment includes a de-foaming or de-aerating or de-gassing system which is primarily designed to collapse the foam or sludge formed in the separation tank to allow economical and efficient disposal of the solid and fibrous material. This system will now be described in more detail. With particular reference to Figure 5, the foam or sludge comprising solid and/or fibrous material suspended in a liquid or gas is treated in a de-foamer or de-foaming hydrocyclone generally denoted as 60. A vacuum pump 62 is located in discharge conduit 38 from separation tank 6 to draw foam from the tank into the de-foaming hydrocyclone 60. Foam which contains liquid, solid and gaseous material is pumped into inlet chamber 64 of the de- foamer 60 through conduit 66 and inlet 68 so that it becomes pressurised in chamber 64. The de-foamer 60 is provided with an inlet head or inlet body 70 having tangentially oriented inlet ports 72 and axial outlet ports 74 so that the foam material is admitted tangentially to the central axis of the de-foamer and discharged co-axially with the longitudinal axis of the de-foamer 60 as shown by arrows C in Figure 5. A suitable inlet body or head is described in Australian patent no. 695500. As the material exiting from inlet body 70 is discharged in a cyclonic pattern, solid material entrained in the foam is thrown by centrifugal force to the outer surface of the conical or tapered sides 76 of the body of the de-foamer 60 as shown by arrow D in Figure 5, whilst the air, gas or liquid forms into a central swirling core aligned along the central axis of the body of the de-foamer as shown by arrows E of Figure 5. The solid material which is rotating at high velocity travels along the inside of wall 76 of the de-foamer where it accumulates at the bottom of the de-foamer body to fall through central chute 78 for subsequent discharge through discharge valve 80. Simultaneously with the solid or fibrous material collecting at the bottom of the de-foamer body, air or gas or liquid rotating in the core is forced out to atmosphere through vent pipe 82 which is located along the central axis of the upper part of the hydrocyclone de-foamer 60. It is to be noted that pressure in the chamber of the de-foamer can be varied as required by adjusting controls, such as outlet valves 84 and 86 for controlling discharge of sludge or air, respectively, so that there is ready separation of solid and fibrous materials from the gaseous or air component of the foam being introduced into the hydrocyclone body. Thus, the solid and/or fibrous material is separated from the foam and can be collected as solids for appropriate discharge. Advantages of the apparatus and method of the present invention include:

Ready separation of solid particles and fibrous material from liquid, allowing discharge of a wastewater stream from a manufacturing plant to be discharged directly through the normal drainage system of the factory or manufacturing plant . A de-foamer is provided in which a hydrocyclone arrangement is used to separate solid and fibrous materials from gaseous material, allowing for more economical and efficient disposal of the waste and fibrous material as solid material. The described arrangement has been advanced by explanation and many modifications may be made without departing from the spirit and scope of the invention which includes every novel feature and novel combination of features herein disclosed. Those skilled in the art will appreciate that the invention described herein is susceptible to variations and modifications other than those specifically described. It is understood that the invention includes all such variations and modifications which fall within the spirit and scope.

Claims

1. A separation vessel for clarifying a liquid stream containing solid and/or fibrous materials including an inlet for introducing aerated or gasified liquid stream into the vessel, characterised in that the veasel is provided with a baffle arrangement located in close proximity to the location of the inlet so that the liquid stream introduced through the inlet flows through the baffle arrangement in such a manner as to release entrained air or gas from the liquid stream, a first outlet for discharging clarified water substantially free of solid and/or fibrous material, and the second outlet for discharging the solid and/or fibrous material separated from the liquid stream in the separation vessel, wherein the baffle arrangement includes a plurality of individual baffle members located in at least partially overlying spaced apart relationship for defining a flow path for the incoming aerated liquid stream to flow through and around the baffle arrangement such that the flow path is substantially tortuous and/or prevents the formation of eddy currents or similar within the vessel, thereby contributing to entrapment or the like of the solid/fibrous materials within the air or gas bubbles to at least assist in facilitating separation of the solid/fibrous material from the liquid stream.

2. A method of separating substantially solid/fibrous materials from a liquid stream in a separation vessel, including the steps of introducing through an inlet an aerated or gasified liquid stream containing the solid/fibrous material as one component to the separation vessel, characterised in that the method further includes allowing the liquid stream to flow through a baffle arrangement including a number of individual baffle members arranged in at least partially overlying spaced apart relationship defining a substantially tortuous or convoluted flow path for assisting in releasing entrained air or gas from the liquid stream to thereby assist in separating the fibres/solid from the liquid stream, discharging clarified liquid from a first outlet, allowing the air or gas entrained in the liquid stream to rise to the surface of the separation vessel thereby conveying the solid/fibrous material to a second outlet, and discharging from the second outlet the solid/fibrous material thereby separating the solid/fibrous material from the liquid stream with the aid of the release of the gas or air from the liquid stream during passage through the baffle arrangement .

3. A method or apparatus according to any preceding claim characterised in that the baffle member is a baffle plate.

4. A method or apparatus according to any preceding claim characterised in that there is one, two, three, four or more individual baffle plates arranged with respect to each other to form the baffle arrangement .

5. A method or apparatus according to any preceding claim in which the baffle plates are substantially circular, preferably circular.

6. An apparatus or method according to any preceding claim characterised in that the baffle plates are vertically spaced apart from each other defining a substantially vertical gap there between as part of the flow path for the incoming liquid stream.

7. An apparatus or method according to any preceding claim characterised in that the entrained air or gas is released from the liquid stream as a result of passage of the liquid stream through the baffle arrangement.

8. A method or apparatus according to any preceding claim characterised in that the baffle plates are substantially horizontally spaced apart from each other as well as being vertically spaced apart from each other to define the flow path.

9. A method or apparatus according to any preceding claim characterised in that the gas or air entrained in the aerated or gasified liquid stream is in the form of bubbles or similar.

10. A method or apparatus according to any preceding claim characterised in that there are three baffle plates arranged in spaced apart relationship to each other.

11. A method or apparatus according to any preceding claim characterised in that two of the baffle plates are located in spaced apart side by side relationship at about the same level and a third baffle plate is located vertically above the two lower baffle plates so as to partially overlie both of the two lower baffle plates.

12. A method or apparatus according to any preceding claim characterised in that the baffle arrangement further includes an inverted conical base or manifold.

13. A method or apparatus according to any preceding claim in which the two lower baffle plates are located relatively closer to the inverted conical base or manifold.

14. A method or apparatus according to any preceding claim characterised in that the baffle plates are supported and or separated from each other by substantially vertically extending posts located between the baffle plates .

15. A method or apparatus according to any preceding claim in which the tortuous or convoluted flow path is around and through the individual baffle plates.

16. A method or apparatus according to any preceding claim in which the incoming liquid stream to be treated is distributed over a predetermined area of the baffle arrangement by passage through the baffle arrangement.

17. A method or apparatus according to any preceding claim characterised in that the gas or air of the aerated liquid stream is released by the liquid stream flowing through and around the baffle plates.

18. A method or apparatus according to any preceding claim characterised in that the fibre and/or solids material is floated to the surface of the vessel by the gas or air rising through the vessel.

19. A method or apparatus according to any preceding claim in which the vessel is a separation tank.

20. A method or apparatus according to any preceding claim characterised in that the solid/fibre material is collected at the surface of the separation tank in the form of a sludge, foam or similar.

21. A method or apparatus according to any preceding claim characterised in that the tank is provided with a removal sub-assembly for removing the sludge, foam or similar from the top of the separation tank, said removal sub-assembly including a motorised scraper for scraping the sludge, foam or similar over an overflow weir.

22. A method or apparatus according to any preceding claim characterised in that the scraper assembly can be mounted so as to be rotatable in a clockwise direction or an anti-clockwise direction or both for moving the sludge containing the solids and fibres to a discharge outlet.

23. A method or apparatus according to any preceding claim characterised in that the separation tank is provided with a level control arrangement so as to maintain the level of the wastewater in the separation tank between an upper and a lower limit.

2 . A method or apparatus according to any preceding claim characterised in that the level control arrangement includes an auxiliary tank in the form of a balance tank located to one side of the separation tank.

25. A method or apparatus according to any preceding claim characterised in that the separation tank is in fluid communication with the balance tank so that control of the level in the balance tank effects control of the level in the separation tank to a corresponding level.

26. A method or apparatus according to any preceding claim characterised in that the baffle arrangement is adjustable so as to vary the flow rate of the incoming aerated liquid stream or mixture to adjust the amount of separation of the solids/fibres from the liquid stream.

27. A method or apparatus according to any preceding claim characterised in that there are two discrete zones within the separation tank, the first zone located at or towards the base of the separation tank being a quiescent zone containing substantially clarified liquid and the second zone being a substantially turbid zone containing solids/fibrous material.

28. A method or apparatus according to any preceding claim characterised in that an interface exists between the lower clarified zone and the upper turbid zone.

29. A method or apparatus according to any preceding claim characterised in that the gas/air bubbles rising in the separation tank float through the turbid zone.

30. A method or apparatus according to any preceding claim characterised in that there is substantially no mixing between the clarified zone and the turbid zone.

31. A method or apparatus according to any preceding claim characterised in that there is a further treatment assembly connected to the discharge outlet of the separation tank.

32. A method or apparatus according to any preceding claim characterised in that the further treatment sub- assembly includes a defoaming vessel, such as a de-foaming hydrocyclone or similar.

33. A method or apparatus according to any preceding claim characterised in that the defoamer or defoaming vessel is provided with an inlet member for converting substantially tangentially oriented incoming sludge material into a substantially axially directed outlet stream for separation in the vessel.

34. A method or apparatus according to any preceding claim characterised in that the defoamer is a hydro-cyclone or similar apparatus.

35. A method or apparatus according to any preceding claim characterised in that the solid or fibrous material of the sludge or foam is separated from the air, gas or liquid of the foam in the hydro-cyclone defoamer.

36. A method or apparatus according to any preceding claim characterised in that the liquid stream is the product stream from a fruit juice or fruit drink or beverage manufacturing plant and the solids/fibres are removed from this product stream to form the fruit juice or drink.

37. A method or apparatus for clarifying, a liquid stream containing solid and/or fibrous materials substantially as hereinbefore described with reference to the accompanying drawings .