RAG RELIEF FOR OVERFLOW SCREEN

Abstract

The present invention relates to a venturi device for a combined sewage overflow system, the venturi device comprising: a body defining a fluid passageway therethrough, the body having a first end portion defining a fluid inlet; a second end portion opposing the first end portion, the second end portion defining a fluid outlet and an opposing venturi inlet in fluid communication with the fluid outlet: and a mid-portion located between the first and second end portions; and a venturi pipe located between the first fluid outlet and the venturi inlet and in fluid communication with both, wherein the venturi pipe is narrower in cross section than the venturi inlet, and wherein the fluid inlet comprises an intake funnel that decreases in width in a direction towards the fluid passageway. The present invention further provides a CSO system including such a venturi device.

Claims

1. A venturi device for a combined sewage overflow system, the venturi device comprising: a body defining a fluid passageway therethrough, the body having a first end portion defining a fluid inlet; a second end portion opposing the first end portion, the second end portion defining a fluid outlet and an opposing venturi inlet in fluid communication with the fluid outlet: and a mid-portion located between the first and second end portions; and a venturi pipe located between the fluid outlet and the venturi inlet and in fluid communication with both, wherein the venturi pipe is narrower in cross section than the venturi inlet, and wherein the fluid inlet comprises an intake funnel that decreases in width in a direction towards the fluid passageway.

2. A venturi device as claimed in claim 1, wherein the intake funnel is a concentric reducer.

3. A venturi device as claimed in claim 1, wherein the intake funnel is an eccentric reducer.

4. A venturi device as claimed in claim 1, wherein the fluid outlet comprises an outlet funnel that increases in width in a direction away from the fluid passageway.

5. A venturi device as claimed in claim 4, wherein the outlet funnel is a concentric reducer.

6. A venturi device as claimed in claim 4, wherein the outlet funnel is an eccentric reducer.

7. A venturi device as claimed in claim 1, wherein the intake funnel is quadrilateral in cross-section.

8. A venturi device as claimed in claim 1, wherein the venturi pipe is configured to mix fluid air from the venturi inlet with fluid from the fluid inlet.

9. A combined sewage overflow system comprising: (i) a CSO having a body comprising a first chamber; an escape chamber arranged adjacent the first chamber and separated from the first chamber by a perforated screen, wherein the first chamber and the escape chamber are in fluid communication with one another; a second chamber arranged adjacent the first chamber and in fluid communication with the first chamber, wherein the body defines an effluent inlet for effluent ingress into the first chamber; and wherein the body defines an effluent outlet for effluent egress from the second chamber; and (ii) a venturi device as claimed in claim 1 located within the body of the CSO, wherein the fluid inlet is arranged within the first chamber and adjacent the perforated screen to receive fluid from the first chamber, and the venturi inlet is arranged to receive fluid from the first chamber distal to the perforated screen.

10. A system as claimed in claim 9, wherein the fluid outlet of the venturi device is arranged within the second chamber.

11. A system as claimed in claim 9, wherein the body further defines an escape outlet in the escape chamber thereby defining a fluid passageway between the escape chamber and the exterior of the CSO body.

12. A system as claimed in claim 9, wherein the body further comprises an effluent channel providing a fluid passage between the effluent inlet and the effluent outlet, the fluid channel being arranged along a portion of a base of the tank and extending through the first chamber and the second chamber.

13. A system as claimed in claim 9, wherein the body further comprises a weir partition arranged between the effluent channel and the escape chamber, wherein the weir partition extends from the base of the body to above the level of the perforated screen.

14. A system as claimed in claim 13, wherein the second chamber is defined by a portion of the body and at least a portion of the weir partition.

15. A system as claimed in claim 13, wherein the escape chamber is defined by a portion of the body, at least a portion of the weir partition and at least a portion of the perforated screen.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0042] An embodiment of the invention will now be described, by way of example only, and with reference to the accompanying drawings, in which:

[0043] FIG. 1 is a perspective view of a first embodiment of a venturi device in accordance with a first aspect of the present invention;

[0044] FIG. 2 is a side view of the venturi device of FIG. 1;

[0045] FIG. 3 is a front view of the venturi device of FIG. 1; and

[0046] FIG. 4 is a plan view of the venturi device of FIG. 1.

[0047] FIG. 5 is a perspective view of a first embodiment of a combined sewage overflow (CSO) system in accordance with a second aspect of the present invention with the venturi device omitted;

[0048] FIG. 6 is a view from above of the CSO system of FIG. 5;

[0049] FIG. 7 is a cross-sectional view through B-B in FIG. 6;

[0050] FIG. 8 is a cross sectional view through A-A in FIG. 6;

[0051] FIG. 9 is a cut-away perspective view of the CSO system of FIG. omitting the escape chamber;

[0052] FIG. 10 is a cut-away perspective view of the CSO system of FIG. 5 including the escape chamber;

[0053] FIG. 11 is a perspective view of the CSO system of FIG. 5 with the venturi device included:

[0054] FIG. 12 is a cross-sectional view of the embodiment of FIG. 11;

[0055] FIG. 13 is a view from the front of the embodiment of FIG. 11;

[0056] FIG. 14 is a view from above of the embodiment of FIG. 11;

[0057] FIG. 15 is a cut-away perspective view of the embodiment of FIG. 11;

[0058] FIG. 16 is a view from above of the embodiment of FIG. 11;

[0059] FIG. 17 is a cross-sectional view through C-C in FIG. 16;

[0060] FIG. 18 is a cross-sectional view through D-D in FIG. 16;

[0061] FIG. 19 is a perspective view of a first embodiment of a venturi device in accordance with a second aspect of the present invention;

[0062] FIG. 20 is a side view of the venturi device of FIG. 19;

[0063] FIG. 21A is a front view of the venturi device of FIG. 19, and

[0064] FIG. 21B is a rear view of the venturi device of FIG. 19.

DETAILED DESCRIPTION OF THE INVENTION

[0065] The same figure references are used throughout the figures to indicate the same features.

[0066] FIGS. 1 to 4 show various views of a first embodiment of a venturi device in accordance with a first aspect of the present invention. FIGS. 5 to 10 show various views of a typical CSO forming part of an embodiment of a CSO system in accordance with a second aspect of the present invention. FIGS. 11 to 18 show various views of the venturi device of FIGS. 1 to 4 located within the CSO of FIGS. 5 to 10 to form an embodiment of a CSO system in accordance with a second aspect of the present invention. FIGS. 19 to 21B show a second embodiment of a venturi device in accordance with a second aspect of the present invention.

[0067] Venturi device 10 comprises a body 12 defining a fluid passageway therethrough. Body 12 has a first end portion 14 defining a fluid inlet 16, and a second end portion 18 opposing the first end portion 14, the second end portion 18 defining a fluid outlet 20. Body 12 further defines a venturi inlet 22 opposing the fluid outlet 20 and in fluid communication with fluid outlet 20. Fluid outlet 20 has an increased circumferential diameter when compared with that of the venturi pipe 26.

[0068] Venturi device 10 further comprises a mid-portion 24 located between the first and second end portions 14, 18.

[0069] A venturi pipe 26 is located between the fluid outlet 20 and the venturi inlet 22 and is in fluid communication with both fluid outlet 20 and venturi inlet 22. Venturi pipe 26 has a reduced circumferential diameter when compared with that of venturi inlet 22.

[0070] Fluid inlet 16 comprises an intake funnel that decreases in circumferential diameter in a direction towards mid-portion 24. The intake funnel in the illustrated embodiment is quadrilateral in cross-section. However, it is to be appreciated that any other suitable cross-sectional shape may be used, such as but not limited to, circular, oval, pentagonal or the like.

[0071] In use, fluid receive through venturi inlet 22 is mixed with fluid from fluid inlet 22 in venturi pipe 26.

[0072] CSO 50 comprises a body 52 having first chamber 54 and an escape chamber 56 located adjacent first chamber 54 and separated from first chamber 54 by a screen 58. As screen 58 is provided with perforations, first chamber 54 and escape chamber 56 are in fluid communication with one another.

[0073] A second chamber 60 is located adjacent first chamber 54 and is in fluid communication with first chamber 54 via effluent channel 62. Effluent channel 62 extends from effluent inlet 64 located in body 52 through first chamber 54 into second chamber 60 towards effluent outlet 66. Effluent enters the CSO body 52 via effluent inlet 64 in first chamber 54 and exits the CSO body 52 via effluent outlet 66 in second chamber 60 and enters a pipeline (not shown) to a sewage treatment facility.

[0074] Venturi device 10 is located within the CSO body 52 such that the fluid inlet 16 receives effluent from first chamber 54, venturi inlet 16 is located adjacent the effluent channel in first chamber 54 and receives fluid from effluent inlet 64. The fluid received through venturi inlet 16 may comprise air, effluent or a mixture of the two depending on the level of effluent in CSO 50.

[0075] Fluid outlet 20 is arranged within second chamber 16 distal to effluent inlet 64 and receives fluid from venturi inlet 16 via venturi pipe 26. Fluid outlet 20 then delivers fluid into effluent channel 62 where it flows to effluent outlet 66 and exits the CSO body and flows onwards for sewage treatment.

[0076] CSO body 52 further defines an escape outlet 68 located in escape chamber 56 through which fluid received in escape outlet 68 can exit the CSO body and be released into the environment e.g. watercourse or the like.

[0077] CSO body 52 further comprises a weir partition 70 located between effluent channel 62 and escape chamber 56. Weir partition 70 extends from the base of CSO body 52 to above the level of perforated screen 58.

[0078] Perforated screen 58 is a fixed perforated plate fabricated from stainless-steel screen. However, it is to be appreciated that any other suitable material known to the skilled person and suitable for purpose may be used as an alternative. Screen 58 is provided with circular perforations of 6 mm in diameter. However, it is to be appreciated that the perforations could be any other suitable shape, including square and of alternative dimension provided that the dimensions are suitable to prevent sewage solids and rag from passing through the screen and into escape chamber 56.

[0079] In a flooding event, effluent flow rate through effluent channel 62 will increase and, until the flooding dissipates, the sewage level in first chamber 54 will continue to rise. The speed at which the effluent level rises is dependent upon the level of flooding and the increase in effluent entering the sewerage system. When a certain flow limit is exceeded, the effluent level within first chamber 54 will rise to the level of the perforated screen 18 and be forced to pass through it. The screened effluent will then flow into escape chamber 56 and be released from the CSO 50 via escape outlet 66 and into the environment via an output pipe (not shown) which leads to the watercourse. Sewage solids and rag are retained in first chamber 54 by screen 58. When the flood conditions abate and the effluent levels fall in the first and second chambers, the hitherto trapped rag (other than that embedded in the screen) will pass forward through effluent outlet 66 and onward to the Treatment Works.

[0080] Fluid inlet 16 of venturi device 10 is located near to and just below the level of perforated screen 58 in first chamber 54. In use, venturi device 10 acts to continually draw down a flow from near to the perforated screen 58 through fluid inlet 16 in first chamber 54 during a flood event. This draw down of flow is induced by the action of the venturi pipe 26 located in the fluid passageway in venturi device body 12. The fluid flow into the venturi pipe 26 is forced by pressure from the wider venturi inlet 18 via first tapered portion (converging section) 17 into the narrower venturi pipe 26, which increases the velocity of the fluid flow and reduces the pressure within venturi pipe 26. Fluid flow from fluid inlet 16 is then drawn down through the fluid passageway in venturi device body 12 to the venturi pipe 26 by means of the reduced pressure within venturi pipe 26, where it combines with the fluid flow in venturi pipe 26 and out via second tapered portion 19 (diverging section) towards the fluid outlet 20. On exiting through fluid outlet 20 in second chamber 60, effluent flow passes into effluent channel 62 and flows towards effluent outlet 66, where it exits the CSO body and flows onwards for sewage treatment.

[0081] Rather than sewage solids and rag being retained at the screen 58 as would be the normal situation with conventional CSO screens, the draw down flow under pressure serves to dislodge some or all of the sewage solids and rag and draw them back down into the fluid flow, thereby reducing the percentage of rag in the mixture and thus assisting in keeping the screen clear from potential blockages due to lodged debris.

[0082] Thus, the action in venturi pipe 26 coupled with the draw down induced fluid flow from fluid inlet 16 serves to feed the sewage waste, including dislodged sewage solids and rag from screen 58 through the venturi device body 12 and towards fluid outlet 20 in second chamber 60.

[0083] It is to be noted and appreciated that the venturi device 10 of the CSO system of the present invention operates to keep the screen 58 clear of sewage solids and rag without the need for any external power source or mechanical assistance and operates by exploiting the hydraulics of a venturi.

[0084] Therefore, the present invention is continually reducing the solids content accumulating in the first chamber 54. Further, there is reduced burden on the perforated screen 58 as the screen remains unblocked, improving screen performance and promoting it to operate more efficiently during flood events. There is reduced maintenance requirement as cleaning will not be required on the frequent basis currently required by conventional CSO systems. Finally, there is a reduced requirement for an increased screen area to compensate for gradual screen blockage, thereby reducing the material and manufacturing costs and potentially the size of the CSO device itself.

[0085] In the first embodiment of a venturi device described in FIGS. 1 to 4, tapered sections 17 and 19 are concentric reducers i.e. the cone-shape reduces or enlarges equally about a centre line.

[0086] In the second embodiment of a venturi device described in FIGS. 19 to 21B, the tapering sections 17 and 19 are eccentric reducers i.e. the taper is only on the one side of respective converging and diverging sections. The advantage of using such a design is that it encourages any bottom hanging silt to flow unrestricted through the venturi device and onward to the treatment works, thereby avoiding the potential for build up of silt along the entrance to the venturi and the consequential loss of performance that can be experienced when this occurs.

[0087] Although aspects of the invention have been described with reference to the embodiment shown in the accompanying drawings, it is to be understood that the invention is not limited to the precise embodiment shown and that various changes and modifications may be effected without further inventive skill and effort. For example, rather than being released to the environment, non-solid effluent from escape chamber 56 may be fed into large holding tanks for future treatment or release post-flood event. Although the embodiment shown includes only one venturi device 10, more than one venturi device 10 may be included in a single CSO system in accordance with a second aspect of the present invention.