AU777426B2

AU777426B2 - Treatment of contaminated liquids

Info

Publication number: AU777426B2
Application number: AU50525/00A
Authority: AU
Inventors: Alban Timmons
Original assignee: QED Occtech Ltd
Current assignee: QED Occtech Ltd
Priority date: 1999-08-06
Filing date: 2000-08-04
Publication date: 2004-10-14
Anticipated expiration: 2020-08-04
Also published as: AU5052500A

Description

AUSTRALIA

PATENTS ACT 1990 COMPLETE SPECIFICATION FOR A STANDARD PATENT (Original) APPLICATION NO:

LODGED:

COMPLETE SPECIFICATION LODGED:

ACCEPTED:

PUBLISHED:

RELATED ART: QED 4 :W- NAME OF APPLICANT: ACTUAL INVENTOR(S): ADDRESS FOR SERVICE: INVENTION TITLE: LORD COMPANY Patent Trade Mark Attorneys 4 Douro Place West Perth, Western Australia, 6005

AUSTRALIA.

"TREATMENT OF CONTAMINATED

LIQUIDS"

DETAILS OF ASSOCIATED PROVISIONAL APPLICATION

NO'S:

Australian Provisional Patent Number PQ2054 filed on August 6, 1999 The following Statement is a full description of this invention including the best method of performing it known to me/us: 2

TITLE

"TREATMENT OF CONTAMINATED

LIQUIDS"

The present invention relates to treatment of contaminated liquids particularly, but not exclusively, treatment of industrial, agricultural and domestic effluent.

Vessels for separating contaminants from liquids are well known in the art and are generally in the form of a cylindrical tank, with a conical bottom where the apex of the conical bottom is lower than the outer side thereof.

Inlets maybe positioned so as to produce a circular flow to the liquid in the vessel and i: outlets may be positioned at the bottom, top and sides of the vessel to enable the drawing off of various fractions of the separated liquid stream, depending on its S relative specific gravity.

For the purposes of this specification, a vessel or vessels of aforementioned type will S 15 be hereinafter referred to as a "treatment vessel" or "treatment vessels" The inlet of a treatment vessel is typically situated at the outer edge of the treatment vessel, and is typically arranged in such a manner so as to introduce liquid for treatment tangentially and thereby create laminar, circular flow within the treatment :"vessel. As the liquid nears the centre of the treatment vessel, the speed decreases and the direction of the flow is changed to a vertical up and down flow towards the top and bottom outlets.

It is preferred that no circular flow takes place at the centre part of the treatment vessel so as to allow the contaminants to separate.

Separation takes place within the treatment vessel as the speed of flow slows toward the centre of the treatment vessel. Thus, while contaminants are suspended at the rate of flow at the outer part of the treatment vessel, these will be released as the speed of flow decreases toward the centre of the treatment vessel and will separate into their fractions depending on their specific gravity.

Separation can be aided by the prior addition of a variety of chemical substances.

The methods for introducing contaminated liquids tangentially into a treatment vessel so as to produce circular flows and the methods for operating such treatment vessels are well known.

It is often the practice to use more than one treatment vessel within a single separator system where more than one operation is required within the separator system. Thus, one treatment vessel may be used for removing those contaminants where the specific 10 gravity of the contaminants is lighter than the carrying liquid, and another treatment vessel may be used for removing those contaminants where the specific gravity of the contaminants is heavier than the carrying liquid, and another treatment vessel may be used to concentrate the contaminants removed.

A problem with existing treatment vessels and in separator systems is that the heaviest contaminants are directed downward toward the apex of the conical bottom of the treatment vessel and can build up a plug which does not flow out of the treatment vessel as desired.

*The present invention seeks to mitigate such plugging of treatment vessels by the separation of heavy contaminants therein and to increase the efficiency of operation of same beyond that of prior art treatment vessels and clarifiers.

In accordance with a first aspect of the present invention, there is provided a method for mitigating plugging of a bottom outlet of a treatment vessel used in a treatment system for separating heavy contaminants from a base liquid, the method comprising reintroducing clarified liquid obtained from a treatment vessel within the separator system in a manner so as to produce a downward circular flow to scour out a conical portion of the treatment vessel adjacent the bottom outlet and assist in removing heavy contaminants accumulating at the bottom outlet.

In accordance with a second aspect of the present invention, there is provided a treatment system for separating heavy contaminants from a base liquid treated therein, the system comprising; a plurality of treatment vessels each including a conical portion at a lower end thereof; at least one clarified liquid source derived from one or more of the treatment vessels.

10 a clarified liquid inlet disposed at a side of the or each treatment vessel to re-introduce the clarified liquid into the treatment vessel from one of the clarified liquid sources at, or proximate to, the conical portion thereof; wherein, in use, the clarified liquid is reintroduced in a manner so as to cause a downward circular flow to scour out the conical portion and assist in removing the heavy contaminants that accumulate at a bottom outlet of the treatment vessel.

In accordance with a third aspect of the present invention, there is provided a treatment vessel for separating heavy contaminants from a base liquid treated therein, the treatment vessel comprising; a cylindrical portion having a central axis and a top; a conical portion adjacent a lower end of the cylindrical portion, the conical portion having a bottom outlet arranged to discharge heavy contaminants from the treatment vessel; a clarified liquid source derived from the treatment vessel or another treatment vessel in a treatment system; and at least one clarified liquid inlet disposed at a side of the treatment vessel to reintroduce clarified liquid into the treatment vessel from the clarified liquid source at, or proximate to, the conical portion thereof; wherein, in use, the clarified liquid is reintroduced in a manner so as to cause a downward circular flow to scour out the conical portion and assist in removing heavy contaminants that accumulate adjacent the bottom outlet of the treatment vessel.

A further problem with existing separator vessels is that the change of flow characteristic from a circular, laminar flow to a vertical flow is not always controlled as may be desired.

10 The present invention seeks to improve flow patterns within separator vessels so as to increase the efficiency of the separation within the vessel beyond that of prior art separator vessels and clarifiers.

In accordance with a fourth aspect of the present invention, there is provided a treatment vessel for separating heavy contaminants from a base liquid treated therein, the treatment vessel including; a cylindrical portion; a conical portion disposed at the bottom of the cylindrical portion, the conical portion .having an apex at a lowermost point; at least one inlet being disposed at a side of the cylindrical portion to introduce liquid into the treatment vessel in a manner so as to produce a circular flow therein; two or more outlets, at least one disposed at the apex and at least one disposed at a top of the treatment vessel; and flow modifying means centrally disposed within the treatment vessel and extending substantially along the entire axial extent of the cylindrical portion, wherein the flow 6 modifying means allow for circular flow of liquid within the treatment vessel proximate to outer sides thereof while providing for the flow of liquid at the centre of the treatment vessel to be modified to travel in the axial directions.

Preferably, said flow modifying means comprises an axial vane having a radial extent substantially less than the diameter of said cylindrical portion. By virtue of the physical presence of the vane along the central longitudinal axis of the cylindrical portion, continued circular, laminar flow of the liquid is impeded by the vane proximate to the centre of the vessel and is encouraged to travel axially, either upwardly or downwardly depending upon the relative specific gravity of the liquid, 10 whilst liquid flow proximate to the side of the vessel is left relatively unhindered.

Preferably, the radial extent of the vane increases progressively toward the diameter "of the vessel, from an axial position intermediate the top and the conical portion of the *vessel, towards the top of the vessel. In this manner circular, laminar flow of the liquid is impeded by the vane proximate to the top of the vessel, promoting only axial travel thereof as it progresses towards the other outlet at the top of the vessel.

'Preferably, the radial extent of the vane increases progressively towards the diameter of the vessel from an axial position intermediate the top and the conical portion of the vessel, towards the conical portion of the vessel. In this manner circular, laminar flow of the liquid is impeded by the vane proximate to the conical portion of the vessel, promoting only axial travel thereof as it progresses towards the outlet at the apex of the conical portion of the vessel.

Preferably, the flow modifying means comprises a plurality of axial vanes intersecting each other coaxially with the central axis of the vessel.

The present invention will now be described, by way of example, with reference to the accompanying drawings, in which:- Figure 1 is a cross sectional side elevation of the vessel in accordance with the first and second aspects; Figure 2 is a plan view of Figure 1; Figure 3 is a cross sectional side elevation of the vessel in accordance with the third embodiment; Figure 4 is a plan view of Figure 3; Figure 5a is a side elevation showing another form of vane for use in the vessel; 10 Figure 5b is a similar view to Figure 5a but showing a further alternative form of o• vane; Figure 6a is a schematic plan view showing another embodiment of the vessel using a different vane configuration than the first embodiment; and Figure 6b is a similar view to Figure 6a but showing a further embodiment having another further vane configuration.

The first and second aspects of the present invention are directed towards a separator system using one or more treatment vessels 11 as shown in Figures 1 and 2. The treatment vessel 11 comprises a right circular cylindrical portion 13 having a conical portion 15 at a lower end thereof and a top 17. The height of the cylindrical portion 13 is preferably no more than one and a half times the diameter of the cylindrical portion 13.

The conical portion 15 has an apex 15a lower than the side 15b thereof The top 17 is open and has an annular gutter 19 disposed around an upper edge 13b of the 8 cylindrical portion 13, the latter defining an intermediate lip between the annular gutter 19 and the top of the cylindrical portion 13.

Inlets 21 for the vessel, defined by a pair of conduits 21a and 21b, are tangentially disposed at the side of the cylindrical portion 13 to introduce contaminated base liquid into the vessel tangentially so as to produce a circular flow of liquid within the treatment vessel 11. The conduits 21a and 21b are spaced apart from each other vertically, with the conduit 21a disposed approximately midway along the length of the cylindrical portion 13 of the treatment vessel 11, and the conduit 21b disposed proximate to midway between the conduit 21 a and the top of the conical portion 15 of 10 the treatment vessel 11. Furtherstill, the openings of the conduits 21a and 21b are .::angularly spaced apart around the circumference of the cylindrical portion 13 by approximately 90' as shown in Figure 2 of the drawings.

A plurality of different sets of outlets are provided for the treatment vessel 11.

Bottom outlets 23 are disposed at the apex 15a and are defined by a pair of conduits 23a and 23b for discharging liquid through the apex 15a from the treatment vessel 11.

An upper outlet 25 (or set of outlets not shown) is provided proximate to the top 17 of the treatment vessel 11 and is defined by a conduit connected to a bottom of the annular gutter 19 in order to discharge liquid therefrom.

A further set of outlets 27 are disposed about of the cylindrical portion 13 intermediate the top 17 and bottom of the cylindrical portion 13. These outlets in the present embodiment are defined by four conduits 27a, 27b, 27c and 27d which are axially spaced apart along the treatment vessel 11 to discharge different fractions of the liquid from within the treatment vessel 11, depending upon the relative specific gravity thereof, as will be described in more detail later.

Flow modifying means comprising a pair of centrally disposed vanes 29, are provided adjacent the top of the cylindrical portion 13. In the present embodiment, two vanes 29a and 29b are disposed in an orthogonally intersecting relationship. The radial extent of the vanes 29 increases progressively towards the circumference of the cylindrical portion 13 as shown in Figure 1, as the vane 29 extends axially towards the top 17 of the treatment vessel 11.

In Figures 1 and 2 there are shown clarified liquid inlets 31 comprising a pair of conduits 31 a and 3 lb disposed at the side of the treatment vessel 11 proximate to the conical portion 15 in a tangential manner so as to reintroduce the clarified liquid into 10 the treatment vessel 11 tangentially in this region. These conduits 31a and 31b are connected to a clarified liquid source being a branch from one or more of the outlet conduits 27a, 27b, 27c or 27d of the treatment vessel 11 or another treatment vessel 11 provided in the separator system.

As can be seen in Figure 1, conduit 3 la is connected to the side wall of the cylindrical portion 13 proximate to the top of the conical portion 15; and the conduit 31b is connected to the side 15b of the conical portion 15 at a position intermediate the top of the conical portion 15 and the apex 15a. Furthermore, both conduits 31a and 31b are oriented slightly lower at ends adjacent the treatment vessel 11 so that clarified liquid introduced into the treatment vessel 11 therethrough is directed with a downward directional component towards the apex 15a of the conical portion S15 in a manner to be described in more detail later.

The separator system of Figures 1 and 2 comprises one or more treatment vessels 11, as described above. Accordingly, the conduits 31a and 31b are connected either to the clarified liquid outlets 27a, 27b, 27c and 27d of the same treatment vessel 11, or one or more of the clarified liquid outlets 27a, 27b 27c and 27d from a treatment vessel 11 disposed subsequently in the series of treatment vessels 11 constituting the separator system, or both.

Now describing the manner of operation of the separator system, contaminated base liquid is supplied to a treatment vessel via the inlets 21.

In the case of a single treatment vessel separator system, the inlets 21 are connected to some contaminated base liquid source and the outlets 27 provide different fractions of the clarified decontaminated base liquid.

In the case of the separator system comprising a plurality of treatment vessels 11, the 10 treatment vessels 11 are connected in series so that the inlets 21 of all subsequent treatment vessels 11 are connected to one or more of the outlets 27 of a preceding S treatment vessel 11 or in the case of a preceding treatment vessel dedicated to treating a low volume of light contaminants, to the upper outlet 25 and/or in the case of a preceding vessel dedicated to treating a low volume of heavy contaminants, to the bottom outlet 23b additionally or alternatively to the outlets 27. Thus, the outlets 27 ."of all preceding treatment vessels 11 in the series are connected to the inlets 21 of a subsequent treatment vessel 11, additionally and/or alternatively to the outlets 25 and 23b, depending upon whether the treatment vessel 11 is dedicated to handling low volumes of light or heavy contaminants, respectively.

The tangential positioning of the inlets 21 is provided to introduce base liquid containing heavy and light contaminants into the treatment vessel 11 in a tangential manner so as to produce a circular flow therein. Frictional forces between the circulating flows and the internal surfaces of the treatment vessel 11 produce laminar flows within the circulating liquid which facilitate the displacement of the heavy and 11 light contaminants, under gravity, through the liquid. Heavy contaminants, having a relative specific gravity greater than that of the residual decontaminated base liquid, travel down towards the apex 15a of the conical portion 15; whilst light contaminants, having a specific gravity greater than the contaminated base liquid, travel upward towards the top 17 of the treatment vessel 11.

The vanes 29 assist in impeding the circular flows proximate to the central longitudinal axis adjacent the top of the cylindrical portion 13 and in directing the flow upwardly in the axial direction.

This separation of heavy and light contaminants allows relatively clarified, 1o decontaminated base liquid to remain midway between the top and bottom of the cylindrical portion 13, allowing this to be drawn off and discharged via the outlets 27.

As described, the outlets 27 are spaced apart axially of each other to enable different fractions of clarified decontaminated base liquid to be drawn off from the treatment vessel 11.

Importantly, the clarified liquid inlets 31 reintroduce clarified liquid to the treatment vessel 11 in a tangential manner, so as to circulate the liquid containing heavy contaminants proximate to the conical portion 15 of the treatment vessel 11 in a downward direction which causes a downward circular flow of liquid to scour out the conical portion 15 and assist in removing the heavy contaminants accumulating at the bottom outlet 23 of the treatment vessel 11. In this way, plugging of the apex 15a and hence the bottom outlets 23 is avoided by fluidising the heaviest contaminants continuously, enabling them to flow through one or other of the outlets 23a or 23b, which ever is connected into the system.

12 In alternative embodiments, one or the other of the conduits 31 a or 31 b is provided to achieve the scouring effect, dependent upon the propensity of the particular treatment vessel 11 to plugging.

In further embodiments still, the provision of the flow modifying means may be altered to include different sized and configured pairs of vanes 29, or be eliminated entirely.

The treatment vessel in the first and second aspects of the present invention differs from prior art separator and clarifier vessels in that the design allows for the reintroduction of clarified liquid into the vessel to scour out heavy contaminants 10 which have congregated at the conical bottom of the vessel.

The fourth aspect of the present invention is directed towards a treatment vessel 11 comprising a right circular cylindrical portion 13, a conical portion 15 and a top 17.

The treatment vessel 11 shown in Figures 3 and 4 is similar to the vessel 11 shown in Figures 1 and 2 and like reference numerals denote like parts.

Flow modifying means comprising a pair of centrally disposed vanes 29, are provided to extend axially along substantially the entire extent of the cylindrical portion 13 of the treatment vessel 11. In the present embodiment, two vanes 29a and 29b are disposed in an orthogonally intersecting relationship as shown in Figures 1 and 2. The vanes 29a and 29b extend the full height of the cylindrical portion 13 from the top 17 of the treatment vessel 11 to the top of the conical portion The vanes 29 are particularly shaped so as to have a radial extent substantially less than the diameter of the cylindrical portion 13 from a position spaced from the top 17 of the vessel to a position spaced above the top of the conical portion Furthermore, the radial extent of the vanes 29 increases progressively towards the 13 circumference of the cylindrical portion 13 as shown in Figure 1, as the vane 29 extends axially towards the top 17 of the treatment vessel 11; and in addition as also shown in Figure 1, as the vane 29 extends axially towards the conical portion 15 of the treatment vessel 11.

As shown in the drawings, this increase of radial extent approaches the full diameter of the treatment vessel 11 proximate to the top 17 of the cylindrical portion 13 and proximate to the bottom of the cylindrical portion 13. Moreover, the vanes 29 are fixedly mounted to the inner wall of the cylindrical 13 portion at the outer radial ends of the fUlly extended radially portions thereof for fixedly disposing the flow S 10 modifying means within the treatment vessel 11.

Now describing the manner of operation of the treatment vessel 11, the tangential positioning of the inlets 21 is provided to introduce base liquid containing heavy and light contaminants into the treatment vessel 11 in a tangential manner so as to produce a circular flow therein. As the radial extent of the vanes 29 is significantly less than the diameter of the treatment vessel 11 at the axial position of the inlets 21, the circular flow of liquid can travel relatively unhindered, whereby the frictional forces between the circulating flows and the internal surfaces of the treatment vessel 11 produce laminar flows within the circulating liquid which facilitate the displacement of heavy and light contaminants, under gravity, through the liquid. Heavy contaminants, having a relative specific gravity greater than that of the residual decontaminated base liquid travel axially down towards the apex 15a of the conical portion 15; whilst light contaminants, having a specific gravity greater than the contaminated base liquid, travel axially upwardly towards the top 17 of the treatment vessel 11.

14 As the change in direction of the liquid from a circular flow, proximate to the outer sides of the cylindrical portion 13, to an axial, vertical direction is not always controlled as may be desired, the vanes 29 assist in impeding the circular flows proximate to the centre axis of the cylindrical portion 13 and in directing the flow upwardly or downwardly in the axial direction. This axial direction of flow is increased the closer the liquid travels towards the opposing ends of the cylindrical portion 13, improving the discharge of light contaminants from the top 17 and heavy contaminants through the conical portion 15, whilst promoting the circular and laminar flow of the liquid on its entry into the treatment vessel 11.

S o 10 This separation of heavy and light contaminants allows relatively decontaminated base liquid to remain midway between the top 17 and bottom of the cylindrical portion 13, allowing this to be drawn off and discharged via the outlets 27.

As described, the outlets 27 are spaced apart axially of each other to enable different fractions of decontaminated base liquid to be drawn off from the vessel.

As shown in Figures 5a and 5b, in other embodiments of the treatment vessel 11, the flow modifying means can comprise differently shaped axial vanes. In the case of Figure 5a, an axial vane 31 is provided which has an increased radial extent approaching the diameter of the cylindrical portion 13 of the treatment vessel 11 towards the top axial end thereof only, and not the bottom. In Figure 5b, the outer radial extent of the vane 33 is curved from the intermediate axial portion of the vane towards the opposing ends thereof with increasing axial extent, as opposed to the sharp linear progression as illustrated in the vanes 29 described in the first embodiment.

In other embodiments, the number of axial vanes disposed within the treatment vessel 11 can be increased. As shown in Figure 6a, there are three equi-angularly disposed vanes 35 and in Figure 6b there are four equi-angularly disposed vanes 37. The greater the number of vanes, the greater the degree of axial control of the liquid flow.

The treatment vessel 11 in the fourth aspect of the present invention differs from known prior art separator and clarifier vessels in that the design allows the flow within the vessel to be controlled and modified for the full length of the cylindrical portion 13 of the treatment vessel 11.

It should be appreciated that the scope of the present invention is not limited to the o 10 particular embodiments herein described and that minor modifications or changes to the vessel design and vane configuration are envisaged to fall within the scope of the present invention and do not depart from the spirit of the same.

Claims

1. A treatment vessel for separating heavy contaminants from a base liquid treated therein, the treatment vessel comprising; a cylindrical portion having a central axis and a top; a conical portion adjacent a lower end of the cylindrical portion, the conical portion having a bottom outlet arranged to discharge heavy contaminants from the treatment vessel; a clarified liquid source derived from the treatment vessel or another treatment vessel in a treatment system; and at least one clarified liquid inlet disposed at a side of the treatment vessel to reintroduce clarified liquid into the treatment vessel from the clarified liquid source 15 at, or proximate to, the conical portion thereof; wherein, in use, the clarified liquid is reintroduced in a manner so as to cause a tangential flow having a downward directional component disposed towards an apex of the conical portion so as to scour out the conical portion and assist in removing heavy contaminants that accumulate adjacent the bottom outlet of the treatment 20 vessel. .0.0 0 .0 0 0

2. A treatment vessel in accordance with Claim 1, wherein the or each clarified ee liquid inlet comprises a conduit in fluid communication with the treatment vessel and oriented tangentially with respect to the treatment vessel at or proximate to the conical portion.

3. A treatment vessel in accordance with Claim 2, wherein the or each conduit has an inner first end located within the treatment vessel and an outer second end 17 remote from the treatment vessel, the first end being positioned lower than the second end.

4. A treatment system in accordance with Claim 2 or 3, wherein a first clarified liquid inlet conduit is provided for admission of the clarified liquid at a side of the conical portion and a second clarified liquid inlet conduit is provided for admission of the clarified liquid at a lower end of the cylindrical portion of the treatment vessel, adjacent the conical portion.

A treatment vessel according to any one of Claims 1 to 4, wherein at least one contaminated liquid inlet is disposed at a side of the cylindrical portion to introduce liquid into the treatment vessel in such a manner as to produce a circular flow in the cylindrical portion, and at least one clarified liquid outlet disposed in a wall of the cylindrical portion.

6. A treatment vessel according to Claim 5, wherein a flow modifying means is centrally disposed within the treatment vessel and extends substantially along the entire axial central axis of the cylindrical portion, the flow modifying means allowing for circular flow of liquid within the treatment vessel proximate to outer sides thereof while providing for the flow of liquid at the centre of the treatment vessel to be modified to travel in an axial direction.

7. A treatment vessel in accordance with Claim 6, wherein the flow modifying 20 means comprises at least one axial vane positioned adjacent the central axis of the .cylindrical portion, the or each vane having a radial extent substantially less than that of the cylindrical portion along a portion of the length of the vane such that circular flow of the liquid is impeded by the vane adjacent the central axis and circular liquid flow adjacent the outer sides of the vessel is relatively unhindered.

8. A treatment vessel in accordance with Claim 7, wherein the radial extent of the or each vane is greater along a portion of the vane adjacent the top of the cylindrical portion thus impeding circular flow of the liquid adjacent the top of the cylindrical portion.

9. A treatment vessel in accordance with Claim 8, wherein the radial extent of the portion of the vane adjacent the top of the cylindrical portion increases progressively as the vane extends toward the top of the cylindrical portion.

A treatment vessel in accordance with either Claim 8 or 9, wherein the portion of the vane adjacent the top of the vessel extends substantially across the cylindrical portion.

11. A treatment vessel in accordance with Claim 7, wherein the radial extent of the or each vane is greater along a portion of the vane adjacent the conical portion of the treatment vessel.

12. A treatment vessel in accordance with Claim 11, wherein the radial extent of ie• the portion of the vane adjacent the conical portion increases progressively as the vane extends toward the conical portion.

13. A treatment vessel in accordance with either claim 11 or 12, wherein the portion of the vane adjacent the conical portion extends substantially across the cylindrical portion.

14. A treatment vessel in accordance with any one of claims 7 to 13, wherein a plurality of vanes are provided, the vanes intersecting along the central axis and being equi-angularly spaced about the central axis.

A treatment vessel in accordance with any one of Claims 5 to 14, wherein the or each contaminated liquid inlet comprises at least one conduit in fluid communication with the cylindrical portion of the treatment vessel, the or each conduit being oriented tangentially in relation to the cylindrical portion of the treatment vessel.

16. A treatment vessel in accordance with Claim 15, wherein two contaminated liquid conduits are provided, the two contaminated liquid conduits being spaced angularly about 900 apart with reference to the cylindrical portion.

17. A treatment vessel in accordance with any one of the preceding claims wherein an annular gutter is provided circumferentially around the top of the cylindrical portion. l0

18. A treatment vessel in accordance with Claim 17, wherein a conduit is provided in fluid communication with the annular gutter, for discharge of liquid flowing from the top of the cylindrical portion into the annular gutter.

19. A treatment vessel in accordance with any one of the preceding claims, wherein the cylindrical portion of the treatment vessel is provided with a plurality of outlets to allow for discharge of clarified liquid from the treatment vessel.

20. A treatment vessel in accordance with Claim 18, wherein the outlets are vertically spaced apart along the cylindrical portion so that the liquid discharged from each outlet has a different specific gravity.

21. A treatment vessel in accordance with either Claim 19 or 20, wherein the 20 outlets are spaced apart radially around the cylindrical portion of the treatment vessel.

22. A treatment system for separating heavy contaminants from a base liquid treated therein, the system comprising: a plurality of treatment vessels each including a conical portion at a lower end thereof; at least one clarified liquid source derived from one or more of the treatment vessels. a clarified liquid inlet disposed at a side of the or each treatment vessel to re- introduce the clarified liquid into the treatment vessel from one of the clarified liquid sources at, or proximate to, the conical portion thereof; wherein, in use, the clarified liquid is reintroduced in a manner so as to cause a tangential flow having a downward directional component disposed towards an apex of the conical portion to scour out the conical portion and assist in removing the heavy contaminants that accumulate at a bottom outlet of the treatment vessel.

23. A treatment system in accordance with Claim 22, wherein the plurality of treatment vessels are arranged in series and the clarified liquid introduced into each treatment vessel is derived from the same treatment vessel or a subsequent treatment vessel in the treatment system.

A treatment vessel substantially as hereinbefore described with reference to the accompanying drawings.

25. A treatment system substantially as hereinbefore described with reference to the accompanying drawings. g DATED THIS 24TH DAY OF AUGUST 2004 QED Occtech Limited By its Patent Attorneys LORD AND COMPANY PERTH, WESTERN AUSTRALIA