AU2006202600A1 - A device for separating pollutants entrained in a liquid - Google Patents

Description

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AUSTRALIA

PATENTS ACT 1990 COMPLETE SPECIFICATION FOR A STANDARD PATENT

ORIGINAL

INO

INO

CIA

Name of Applicant: Actual Inventor: Beresford Concrete Products Pty Ltd Raymond Linden Temple Address of Service is: SHELSTON IP Margaret Street SYDNEY NSW 2000 CCN: 3710000352 Attorney Code: SW Telephone No: Facsimile No.

(02) 9777 1111 (02) 9241 4666 Invention Title: A Device for Separating Pollutants Entrained in a Liquid Details of Associated Provisional Application No. 2005903314 dated 23 June 2005 The following statement is a full description of this invention, including the best method of performing it known to us:- FIELD OF THE INVENTION The present invention relates to a device for separating pollutants entrained in a liquid and in particular to a device for separating gross pollution or silt entrained in a liquid.

The invention has been developed primarily for use as a gross pollutant trap and as a silt arrestor for treating water in a drainage system and will be described hereinafter with reference to this application. However, it will be appreciated that the invention is not limited to this particular field of use.

BACKGROUND OF THE INVENTION Any discussion of the prior art throughout the specification should in no way be considered as an admission that such prior art is widely known or forms part of common general knowledge in the field.

Increased focus on the conservation and management of water resources has lead to the implementation of water quality treatment and flood management structures in urban drainage systems to control pollutants such as sediment and manage stormwater flows. The aesthetic quality and hydraulic efficiency of water is reduced as litter, debris and sediment accumulate in the water system. Streams and rivers become degraded as chemical and biological pollutants are washed into the water system. In addition, the erosive potential of stormwater flows has increased because the urbanisation of water catchments has increased runoff volume and flow peaks. Stormwater and quality treatment measures now focus on reducing water flow, encouraging infiltration where possible and removing chemical and biological pollutants.

Gross pollutant traps (GPTs) are used to intercept litter, vegetation, debris and coarse sediments. These structures usually include a trash rack to collect litter and debris, and a settling area where sedimentation can occur.

Sedimentation is an effective pollutant removal mechanism, since heavy minerals and nutrients often geochemically adsorb to clay particles and metal salts, such as iron ion and manganese oxyhydroxides. Many pollutants also adhere to fine sediment.

A separator has been proposed for separating silt and other objects from water having a separator body through which the water, having debris entrained therein, flows through an inlet to an outlet, and a port for diverting flow from the outlet during moderate flows whereby the debris entrained in the water is removed. A floor of the separator body is raised to form a hump adjacent to or in which the port is located to divert the flow of liquid.

A filter assembly has been proposed for installation in a chamber including a flow guide extendable across the chamber providing a path between the chamber inlet and a chamber outlet. A diversion means associated with the flow guide is adapted to divert water from the flow guide and a returning inlet is associated with the flow guide and adapted to return treated water to the flow guide or to allow treated water to pass through to the chamber outlet wherein the return outlet is located downstream of the diversion means. The flow guide transversely extends across the chamber to divert some of the inlet flow into the chamber through the diversion means, whilst allowing the rest of the flow to pass through to the chamber outlet. A short conical pipe downwardly extends from the flow guide to allow treated water from the chamber to flow to the return outlet.

Both the separator and the filter assembly described above disclose complex arrangements for diverting the flow of water into a chamber for treatment, the water being allowed to collect in and fill the chamber to permit sedimentation of gross pollutants.

OBJECT OF THE INVENTION It is an object of the present invention to overcome or ameliorate at least one of the disadvantages of the prior art, or to provide a useful alternative.

It is an object of the invention in its preferred form to provide a device for separating gross pollutants and silt entrained in water with improved efficiency that is simple in structure and reduces the speed of water flows in the system.

SUMMARY OF THE INVENTION The present invention provides a device for separating pollutants entrained in a liquid, said device including: a tank with an inlet for the ingress of said liquid, a settling chamber, and an outlet for the egress of said liquid; a conduit in fluid communication with said chamber and said tank outlet, and a baffle adjacent to said inlet for diverting said liquid passing from said inlet into said chamber, such that a circumferential flow of said liquid is formed in said chamber to promote separation of said pollutants from said liquid, and said liquid flows from said chamber into said conduit for discharge from said tank through said outlet.

Preferably, the baffle is shaped to induce the circumferential flow in the chamber. The baffle is preferably an arcuate plate. The baffle plate may have a concave, parabolic or part-parabolic profile.

Preferably, the circumferential flow circulates around a central axis of the chamber. It is preferred that the settling chamber is substantially cylindrical.

Preferably, the conduit is in fluid communication with the tank inlet.

Preferably, the baffle diverts the flow of the liquid so that it flows downwardly into the settling chamber.

The baffle preferably cooperates with the conduit to divert the liquid into the settling chamber. Preferably, the baffle is located at least partially in the conduit.

The baffle is preferably located on the invert of the conduit to divert the flow of liquid. The conduit may include a cut-out section in a sidewall for receiving the baffle. Preferably, the cut-out section is larger in size than the baffle.

Preferably, the baffle includes a secondary baffle member. The secondary baffle member is preferably substantially orthogonal to the baffle. The secondary baffle member preferably forms a substantially planar surface lying in a substantially horizontal plane of the tank.

The baffle preferably forms a weir to restrict the flow of liquid into the conduit. Preferably, the baffle has a height lower than the height of the sidewalls of conduit. Preferably, the weir permits an overflow of the liquid to bypass the settling chamber and enter the conduit, where the flow of liquid is excessive.

Preferably, the conduit includes a first conduit portion in fluid communication with the settling chamber and a second conduit portion in fluid communication with the tank outlet. It is preferred that the first conduit portion extends into the settling chamber from the second conduit portion.

Preferably, the second conduit portion is substantially orthogonal to the first conduit portion. The first conduit portion preferably lies in a substantially vertical plane and the second conduit portion lies in a substantially horizontal plane relative to the tank.

It is preferred the first conduit portion is substantially parallel to the longitudinal axis of the tank. Preferably, the first conduit portion is coaxial with the longitudinal axis. Preferably, the first conduit portion is a cylindrical pipe. The first conduit portion preferably includes a screen to filter gross pollutants.

Preferably, the second conduit portion includes an aperture to fluidly connect the first and second conduit portions. The second conduit portion is preferably rectilinear in cross-section. The second conduit portion may be semicircular in cross section.

Preferably, the device is a gross pollutant trap, a silt arrestor, or a combination of both devices.

The liquid is preferably water or stormwater.

-6- BRIEF DESCRIPTION OF THE DRAWINGS A preferred embodiment of the invention will now be described by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a perspective view of a device according to the invention; Figures 2 to 5 are perspective views showing the device of Figure 1 in use; Figure 6 is an exploded side elevation view of another embodiment of the invention; Figure 7 is a plan view of the device taken on line 7-7 of Figure 6; Figure 8 is a part plan view of the baffle and conduit of the device of Figure 6; Figure 9 is a side elevation view of the baffle and conduit of Figure 6; and Figure 10 is an exploded side elevation view of further embodiment of the invention.

PREFERRED EMBODIMENTS OF THE INVENTION Referring to the drawings, the device for separating pollutants entrained in water has a tank 1 with an inlet 3 for the ingress of water, a cylindrical settling chamber 5 and an outlet 7 for the egress of water from the tank 1. A conduit 9 extends substantially across the tank 1 and is in fluid communication with the settling chamber 5 and the tank outlet 7. A baffle plate 11 is provided adjacent the inlet 3 for diverting water passing from the inlet 3 into the settling chamber 5 such that a circumferential flow 12 of the water is formed in the settling chamber 5. This promotes separation of pollutants from the water and the water flows into the conduit 9 for discharge from the tank 1 through the outlet 7.

As best seen in Figure 1, the baffle plate 11 is arcuately shaped and is located on the floor or invert 13 of the conduit 9 to divert the flow of water passing through the inlet 3 towards the settling chamber 5. A portion of one of the sidewalls 15 and 17 of the conduit 9 has been removed to accommodate the baffle plate 11 on the conduit invert 13.

The radius of curvature of the baffle plate 11 influences the degree by which s the flow of water is diverted. The height of the baffle plate 11 is less than the height of the sidewalls 15 and 17 of the conduit 9. This allows the baffle plate 11 to act as a weir restricting the flow of water into the conduit 9. When there is an excessive flow of water, the excess water can flow over the weir 11 into the conduit 9 and bypass the settling chamber 5. This permits the device to manage stormwater flows in turbulent weather conditions. As the baffle plate 11 sits on the invert 13, the conduit 9 cooperates with the baffle plate 11 to divert the flow of water downwardly towards the settling chamber 5 and facilitates the formation of the circumferential flow 12 in the settling chamber The conduit 9 includes a rigid cylindrical pipe 19 extending substantially vertically downward into the settling chamber 5 and a channel 21 which extends across the tank 1 in a substantially horizontal plane. The pipe 19 forms an inlet 23 for the conduit 9 and is connected to an aperture 25 formed in the invert 13 of the channel 21. Treated water flows from the settling chamber 5 into the conduit pipe 19 and then flows up into the channel 21 through the aperture 25. Water then flows through an outlet 27 of the channel 21 and is discharged from the tank outlet 7. The baffle plate 11 forms an end wall of the channel 21 to inhibit the backflow of treated water towards the tank inlet 3.

Referring to Figures 2 to 5, in use the device is installed at a suitable location between two pipes 29 and 31 in a drainage system. Water entrained with pollutants flows from the pipe 29 through the inlet 3 of the tank 1. The water is diverted by the baffle plate 11 and the conduit invert 13 towards and into the settling chamber 5, as best seen in Figures 2 and 3. The momentum of the diverted flow carries the water around the walls of the settling chamber 5, resulting in a circumferential flow 12 within the chamber 5. The circumferential flow 12 circulates around a central axis 32 of the settling chamber 5. As water continues to -8be diverted by the baffle plate 11, it gradually fills the settling chamber 5, as best shown in Figure 4. The circumferential flow 12 of the water promotes separation of pollutants entrained in the water such as sediment and silt. The sediment settles towards the bottom 33 of the settling chamber 5. Since most of the circumferential flow 12 is concentrated towards the sidewalls of the chamber and the water surface, the sediment is less likely to be disturbed by the circumferential flow 12 at the bottom 33. Other less dense pollutants such as leaves, plastic bottles and other floatable litter tend to congregate at the water surface around the pipe 19. As the settling chamber 5 gradually fills, the less dense pollutants rise with the water surface but do not enter the conduit 9 due to the height of the sidewalls 15 and 17 of the channel 21. The circumferential flow 12 also inhibits the floatable debris from congregating near the baffle plate 11. The treated water, with significantly reduced amounts of pollutants and sediment, then flows up through the cylindrical pipe 19 into the channel 21 for discharge from the tank outlet 7.

As best seen in Figure 5, where the flow of water is excessive, the excess water 34 is permitted to flow over the baffle plate 11 directly into the channel 21 and bypass the settling chamber 5 for discharge through the tank outlet 7. The baffle plate 11 in effect acts as a weir restricting the flow of water through the inlet 3 into the channel 21 of the conduit 9 except in overflow conditions. The device is thus able to manage excessive flows of stormwater which may occur in heavy storms or turbulent weather.

The device of Figure 1 is designed to operate as an oil and silt arrestor, which requires a significantly large settling tank to promote sedimentation.

Referring to Figures 6 to 9, another embodiment of the device is specially designed as a gross pollutant trap (GPT). Corresponding features of the GPT have been given the same reference numerals as the device in Figure 1.

The main differences between the GPT and the device of Figure 1 are in the design of the baffle plate 35, conduit 37 and the overall size of the settling chamber 39. In the GPT, the baffle plate 37 has a curvature that is substantially partparabolic, as best seen in Figures 7 and 8.

The cylindrical pipe 41 of the conduit 37 includes an imperforate portion 43 and a screen 45, as best seen in Figure 6. The screen 45 inhibits the passage of gross pollutants greater than the screen mesh size into the conduit 37. This inhibits the contamination of treated water passing through the conduit 37 and discharging from the tank outlet.

The conduit 37 has a sidewall 49 adjacent the tank inlet 3 provided with a cut-out section 51 that is larger than the baffle plate 35, leaving a gap 53, as best shown in Figure 9. The cut-out section 51 permits the insertion and fitting of the baffle plate 35 in the channel 47. In addition, the cut-out section 51 facilitates the movement of large floatable debris such as large plastic bottles from the inlet 3 into the settling chamber 39. This ensures that floatable debris does not block or clog the flow of water from the inlet 3 to the settling chamber 39. In contrast, the arrestor of Figure 1 has a portion of the sidewall 15 removed to avoid clogging or blocking of the water flow.

The GPT of Figures 6 to 9 operates in a similar manner as the device of Figure 1 described above. However, in the GPT the screen 45 filters out gross pollutants and inhibits the pollutants becoming entrained in the treated water flowing into the pipe 41 and the conduit 37.

A further embodiment in the form of a combined GPT and silt arrestor is illustrated in Figure 10, where corresponding features have been given the same reference numerals. As this embodiment combines the features of both a GPT and an arrestor, the settling chamber 55 is substantially larger than the chamber of the GPT of Figures 6 to 9 to promote sedimentation. In addition, the conduit 57 has a smaller width in comparison to the GPT of Figure 6, with the pipe 59 having a screen 61 of greater length. The combined GPT arrestor operates in a substantially similar manner as the GPT of Figures 6 to 9, but with the sedimentation promoting characteristics of the arrestor of Figure 1.

In the GPT and the combined GPT/arrestor embodiments of Figures 6 to a pair of risers 63 and 65 are provided to prevent debris falling into the GPT and the combined GPT/arrestor. A removable cover 67 is also provided to permit access to the GPT and arrestor for inspection and/or service.

The risers 63 and 65 permit adjustment of the depth of the GPT and the combined GPT/arrestor to take into account variations between the level of the cover 67 and the pipes 29 and 31 of the stormwater drainage system. The depth of the device is determined by the invert levels of the pipes of the stormwater drainage system and the cover 67 being at or above ground level. Consequently, the risers 63 and 65 are used as spacers to vary the depth of the device between the cover 67 and the tank inlet 3 and outlet 7, whose respective invert levels correspond to the invert levels of the pipes 29 and 31. Additional risers can be provided to further increase the depth of the device.

The device can be easily and conveniently maintained and serviced by removing the cover 67 to access the tank 1. Any light litter or pollutants such as leaves, plastic and floatable debris can be removed from the water surface by using a scoop. Sediment at the bottom of the settling chamber is removed using a suction hose.

A prototype silt arrestor and a prototype GPT were made in accordance with Figure 1 and Figures 6 to 9. It was discovered that both the GPT and the silt arrestor resulted in improved maximum head loss coefficients indicating that the invention in its preferred forms reduces the speed of water that flows in the system.

The measured head loss coeffecient of the GPT reached a maximum for flow rates between 200 and 300 L/s and upstream pipe velocities between 0.8 and 1 m/s. The maximum head loss coefficient of the silt arrestor was improved for a flow rate of 46.1 L/s.

Both the GPT and arrestor were tested for sediment removal rates using coarse sediments of between 2 to 5 mm in diameter and fine sediments of between 0.075 mm to 0.38 mm in diameter. The prototype GPT had a 100% retention rate for flow rates of up to 256 L/s. Increasing the flow rate up to the settling chamber capacity of 448 L/s reduced the retention rate to 89%. Fine sediment retention rates for the GPT varied from 94% for low flow rates of 32 L/s to 33% at the chamber -11capacity of 448 L/s. The measured fine sediment retention rate for the silt arrestor was 88% at a flow rate of 46.1 L/s.

It will be appreciated that the embodiments of the invention provide a simple, convenient and efficient means for removing pollutants from water flows in pipe networks or stormwater channels in urban drainage systems.

The invention can be constructed from any suitable material providing sufficient structural integrity, although concrete is preferred. Other suitable materials include steel, stainless steel, fibreglass, fibre reinforced concrete, plastic and stone. Embodiments of the invention are preferably constructed with brick, blocks or suitable masonry. Other embodiments of the invention replace the invert of the conduit with a secondary baffle member located substantially orthogonal to the baffle plate to facilitate the diversion of the flow of water.

It will be recognised that the height of the baffle plate and the radius of curvature and the height of the baffle plate can be varied according to operational requirements. In particular, the height of the baffle plate can be varied from the height of the inlet pipe obvert or soffit to a height above the inlet pipe soffit.

Similarly, the size of the settling chamber can be varied depending on the capacity required.

Although the invention has been described with reference to specific examples, it will be appreciated by those skilled in the art that the invention may be embodied in many other forms.

Claims (25)

1. 2. The device of claim 1, wherein the baffle is shaped to induce the circumferential flow in the chamber.
2. 3. The device of claim 2, wherein the baffle is an arcuate plate.
3. 4. The device of claim 3, wherein the baffle plate has a concave, parabolic or part-parabolic profile. The device of any one of the preceding claims, wherein the circumferential flow circulates around a central axis of the chamber.
4. 6. The device of any one of the preceding claims, wherein the settling chamber is substantially cylindrical.
5. 7. The device of any one of the preceding claims, wherein the conduit is in fluid communication with the tank inlet.
6. 8. The device of any one of the preceding claims, wherein the baffle diverts the flow of the liquid so that it flows downwardly into the settling chamber. -13-
7. 9. The device of any one of the preceding claims, wherein the baffle cooperates with the conduit to divert the liquid into the settling chamber. The device of any one of the preceding claims, wherein the baffle is located at least partially in the conduit. s 11. The device of claim 10, wherein the baffle is located on the invert of the conduit to divert the flow of liquid.
8. 12. The device of claim 10 or claim 11, wherein the conduit includes a cut-out section in a sidewall for receiving the baffle.
9. 13. The device of claim 12, wherein the cut-out section is larger in size than the baffle.
10. 14. The device of any one of the preceding claims, wherein the baffle includes a secondary baffle member. The device of claim 14, wherein the secondary baffle member is substantially orthogonal to the baffle.
11. 16. The device of claim 15, wherein the secondary baffle member forms a substantially planar surface lying in a substantially horizontal plane of the tank.
12. 17. The device of any one of the preceding claims, wherein the baffle forms a weir to restrict the flow of liquid into the conduit.
13. 18. The device of claim 17, wherein the baffle has a height lower than the height of the sidewalls of conduit.
14. 19. The device of claim 17 or claim 18, wherein the weir permits an overflow of the liquid to bypass the settling chamber and enter the conduit. -14- The device of any one of the preceding claims, wherein the conduit includes a first conduit portion in fluid communication with the settling chamber and a second conduit portion in fluid communication with the tank outlet.
15. 21. The device of in claim 20, wherein the first conduit portion extends into the settling chamber from the second conduit portion.
16. 22. The device of claim 20 or claim 21, wherein the second conduit portion is substantially orthogonal to the first conduit portion.
17. 23. The device of claim 22, wherein the first conduit portion lies in a substantially vertical plane and the second conduit portion lies in a substantially horizontal plane relative to the tank.
18. 24. The device of any one of claims 20 to 23, wherein the first conduit portion is substantially parallel to the longitudinal axis of the tank. The device of claim 24, wherein the first conduit portion is coaxial with the longitudinal axis.
19. 26. The device of any one of claims 20 to 25, wherein the first conduit portion is a cylindrical pipe.
20. 27. The device of any one of claims 20 to 26, wherein the first conduit portion includes a screen to filter gross pollutants.
21. 28. The device of any one of claims 20 to 27, wherein the second conduit portion includes an aperture to fluidly connect the first and second conduit portions.
22. 29. The device of any one of claims 20 to 28, wherein the second conduit portion is rectilinear in cross-section. The device of any one of claims 20 to 28, wherein the second conduit portion is semi-circular in cross section.
23. 31. The device of any one of the preceding claims, wherein the device is a gross pollutant trap, a silt arrestor, or a combination of both devices.
24. 32. The device of any one of the preceding claims, wherein the liquid is water or stormwater.
25. 33. A device for separating pollutant entrained in a liquid, substantially as herein described with reference to any one of the embodiments of the invention illustrated in the accompanying drawings and/or examples. DATED thisl9th Day of June 2006 Shelston IP Attorneys for: BERESFORD CONCRETE PRODUCTS PTY LTD