AU2004100884B4

AU2004100884B4 - A pollutant trap

Info

Publication number: AU2004100884B4
Application number: AU2004100884A
Authority: AU
Inventors: Geoffrey Colin Dixon; Daniel Brian Penny
Original assignee: FOX ENVIRONMENTAL SYSTEMS Pty
Current assignee: FOX ENVIRONMENTAL SYSTEMS Pty Ltd
Priority date: 2002-11-20
Filing date: 2004-10-18
Publication date: 2005-03-24
Anticipated expiration: 2011-11-20
Also published as: AU2004100884A4

Description

AUSTRALIA

Patents Act 1990 COMPLETE SPECIFICATION INNOVATION PATENT Applicant: FOX ENVIRONMENTAL SYSTEMS PTY LTD Invention Title: A POLLUTANT TRAP The following statement is a full description of this invention, including the best method of performing it known to me/us: 2 S A POLLUTANT TRAP c o FIELD OF THE INVENTION o The present invention relates to pollutant traps 00 5 for retaining pollutants from polluted run-off.

.BACKGROUND TO THE INVENTION 00 When rain falls on concreted or paved surfaces or 00 the like, it will flow across these surfaces to enter stormwater pipes as run-off. In doing so, the rainwater orun-off can become polluted with litter, debris, dirt and o oils. As these pollutants are harmful to the environment, it is desirable that at least some of them be removed from the rainwater run-off before it eventually flows through the stormwater pipes and into natural waterways and/or the ocean.

One solution has been to direct all run-off into a large "end of line" pollutant interceptor unit. These units need to be of a size large enough to handle the full volume of rain falling onto the surface. These units are expensive (due to their size), difficult to handle and install and take up a large amount of space, which may be a problem in some locations such as in Inner City car parks. Furthermore, the unit requires periodic clean outs and generates large volumes of polluted water that needs to be transported to disposal sites.

An alternative solution proposed has been to provide a number of smaller containers on-site which contain a baffle wall and a filter basket and have an outlet connected to the stormwater pipes. These smaller containers act to trap the pollutants on-site by the weir action of the baffle wall and the filtering out of large debris in the filter basket, whilst allowing cleaned runoff to pass through to the stormwater pipes. However, when the rainfall and hence the run-off exceeds the maximum flow through the container, the container floods, causing trapped pollutants in the container to re-enter \\brsl0\home $\SherylM\Keep\Spci\?P54499.cc 1]C/10/04 3 o the run-off, thus enabling polluted run-off to enter the C stormwater pipes.

O SUMMARY OF THE INVENTION 00 5 According to an aspect of the present invention there is provided a pollutant trap for capturing and retaining pollutants from polluted run-off comprising: 00 a chamber having an open top and an exit 00 aperture, the run-off entering the chamber, in use, through the open top and exiting through the exit aperture; o a filter in the open top which limits the flow of run-off into the chamber; a baffle inside the chamber between the open top and exit aperture of the chamber for creating a weir; and a by-pass, for directing run-off flowing to the filter in excess of a maximum flow rating of the filter through the filter without significantly affecting the liquid level in the chamber.

Preferably, the bypass provides a conduit through the filter for excess run-off from above the base of the filter.

Preferably, the baffle is curved in profile.

However, any conduit or plate, capable of creating a weir in the chamber, could be used as the baffle.

Preferably, the by-pass provides a conduit for the excess run-off through the filter and the baffle.

Preferably, the bypass provides a conduit for the excess run-off into the chamber.

Preferably, the bypass provides a conduit for the excess run-off into the chamber proximate the exit aperture.

Alternatively, the bypass may provide a conduit for the excess run-off past the entire chamber.

Preferably, the pollutant trap, in use, further comprises an air gap between the base of the filter and the maximum liquid level of the chamber.

\\bri sO1 \home$ \SherI\Keep\Speci\ P54499 doc 18/10/04 4 S Preferably, the maximum liquid level is maintained below the base of the filter at all run-off o flowrates. Thus, there is always an air gap.

0 Preferably, the maximum liquid level in the 00 5 chamber is maintained below the base of the filter by a maximum flow rating of the exit aperture being at least equal to or greater than the sum of the maximum flow 00 00 rating of the filter and a maximum flow rating of the 0 bypass.

2 10 Preferably, the pollutant trap further comprises oa grate to protect the pollutant trap from damage from 0 heavy objects passing over the pollutant trap. More ci preferably, the grate protects the filter from damage.

Preferably, the grate is positioned above the filter.

Preferably, the grate is lockable.

Preferably, the grate is lockable by a spring loaded slide bolt.

Preferably, the grate is manufactured of a durable metal such as galvanised steel.

Preferably, the pollutant trap, in use, is installed so that the grate is flush with or slightly below the ground.

Preferably, the filter is in the form of a filter basket.

Preferably, the filter has a plurality of apertures. The size, number and arrangement of the plurality of apertures controls the flow of run-off through the filter.

Preferably, the maximum flow ratings of the filter and bypass are based on the "Average Recurrence Interval" which is the average, or expected, value of the periods between exceedances of a given rainfall intensity.

Preferably, the filter removes from the run-off litter, debris and any other solids too large to pass through the filter.

Preferably, the baffle directs run-off flowing '\brOrl l\hCme$\SherylM\Keep\Speci\P54499-dcc 1i/10/04 o into the chamber towards the bottom of the chamber.

C( Preferably, in use, silt settles at the bottom of o the chamber.

O Preferably, in use, free floating hydrocarbons 00 0 5 float at the top of the liquid in the chamber.

Preferably, the maximum flow rating of the filter is low enough to avoid significant disturbance of the 00 00settled silt and floating hydrocarbons.

o Preferably, the exit aperture is connected to a stormwater pipe. The stormwater pipe may form part of a oliquid drainage system.

o Preferably, the exit aperture is connected to the stormwater pipe by an exit pipe.

Preferably, the bypass comprises a tubular socket and an elbow tube.

Preferably, the elbow tube connects to the tubular socket.

Preferably, the tubular socket extends upwardly from the base of the filter.

Preferably, the tubular socket is fixed to the base of the filter.

Preferably, the tubular socket has apertures at either end to enable excess run-off to enter the bypass to bypass the filter.

Preferably, the elbow tube is open at both ends.

Preferably, the elbow tube comprises a vertical portion and a horizontal portion.

Preferably, the horizontal portion of the elbow tube is connected to the baffle. The horizontal portion of the elbow tube may be integrally formed with the baffle.

Preferably, the horizontal portion of the elbow tube provides an opening through the baffle for directing the excess run-off through the baffle.

Preferably, the vertical portion is adapted to connect to the tubular socket through the base of the filter.

\\hrisol\hom.e$\SherylM\Keep\Spec\P54499.doc I610//4 -6- 0 Preferably, the vertical portion has a friction CA fit inside the tubular socket.

o Preferably, the end of the vertical portion O inside the tubular socket abuts an internal lip in the 00 5 tubular socket.

Preferably, the pollutant trap retains at least of the hydrocarbons from the in-flowing run-off when 00 00it is equal to or below the maximum flow rating of the filter.

Preferably, the pollutant trap retains at least o99% of particles greater than 0.3mm in size from the ino flowing run-off when it is equal to or below the maximum flow rating of the filter.

BRIEF DESCRIPTION OF THE DRAWINGS Preferred embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a schematic side view of a pollutant trap according to the present invention arranged for use; Figure 2 is a top view of the pollutant trap of Figure 1; Figure 3 is a front view of the pollutant trap of Figure 1; Figure 4 is a further side view of the pollutant trap of Figure 1; Figure 5 is a cut-away top view of the pollutant trap of Figure 1; Figure 6 is an exploded side view of components of a by-pass in the pollutant trap of Figure 1; Figure 7 is a further top view of the pollutant trap of Figure 1; and Figure 8 is a top view of an alternative pollutant trap to that of Figure i.

DETAILED DESCRIPTION OF THE DRAWINGS Referring firstly to Figures 1 to 3, a pollutant \\brisOl\home$\SherylA\Keep\Speci\P54499.doc 1/1/0104 7 o trap 10 for retaining pollutants from polluted run-off C( according to a preferred embodiment of the present o invention comprises a chamber 11, a filter basket 12 in an O open top 13 of the chamber 11 through which run-off enters 00 5 the chamber 11 and an exit aperture 14 through which runoff exits the chamber 11. The pollutant trap 10 also comprises a bypass for directing run-off flowing to the 00 filter basket 12 in excess of a maximum flow rating of the 00 ofilter basket 12 through the filter basket 12, without significantly affecting the liquid level in the chamber 011.

o The bypass 16 provides a conduit for excess runoff from above the base of the filter basket 12 to a location inside or outside of the chamber 11. For ease of instalment of the pollutant trap 10, it is preferred that the bypass 16 provides a conduit for the excess run-off to a location inside the chamber 11 so that there is only one exit (the exit aperture 14) from the chamber 11 to be connected to a stormwater pipe 22.

The pollutant trap 10 also comprises a baffle wall 15 inside the chamber 11 between the open top 13 and exit aperture 14 of the chamber 11 for creating a weir.

The bypass 16 provides a conduit for the excess run-off through the filter basket 12 and the baffle wall A heavy duty service grate 17 protects the pollutant trap 10, in particular the filter basket 12, from heavy objects such as people or cars passing over the pollutant trap 10. The grate 17 is manufactured of a durable metal such as galvanised steel and is positioned above the filter basket 12. The grate 17 may be lockable by a spring loaded slide bolt (not shown). In use, the grate 17 is installed so that the grate 17 is flush with or slightly below the ground In use, the exit aperture 14 of the chamber 11 is connected by an exit pipe 21 to the stormwater pipe 22.

The stormwater pipe 22 may be part of any liquid drainage system which directs run-off exiting the chamber 11 \\bris1 \home$\Shery1M\Keep\Speci\ 54499 doe i&/0/04 8 o through the exit aperture 14 to either further treatment C or discharge in natural waterways and/or the ocean.

o The filter basket 12 limits the flow of run-off 0 into the chamber to its maximum flow rating by the size, 00 5 number and arrangement of apertures in the filter basket 12. If the flow of run-off into the filter basket 12 is equal to or less than the maximum flow rating of the 00 filter basket 12 then normal operation of the pollutant 00 otrap 10 occurs.

2 -10 During normal operation of the pollutant trap run-off flows along the ground 20, into and out of the o chamber 11 along a normal flow path 30 as shown in Figure i. Flowing along the normal path 30, the run-off passes through the service grate 17 and the filter basket 12. In addition to limiting the run-off flowrate into the chamber 11, the filter basket 12 removes from the run-off litter, debris and any other solids too large to pass through the filter basket 12. Having entered the chamber 11 through the filter basket 12, the run-off is directed down towards the bottom of the chamber 11 by the baffle wall 15 before flowing under the wall 15 to reach the exit aperture 14.

Thus the baffle wall 15 creates a weir action in the chamber 11, allowing silt 33 to settle out at the bottom of the chamber 11 and free floating hydrocarbons to rise up into and be retained in an "oil trap" layer 34 on top of the liquid in the chamber 11 on the entry side of the baffle wall Referring in particular to Figure 5 the crosssectional area of the weir 25 (the outlet side of the baffle wall 15) is greater than the cross-sectional area of the exit aperture 14 so that the vertical transference rate of aqueous liquids through the chamber 11 is such that it does not cause significant disturbance of the settled silt 33.

Furthermore, in order to create sufficient weir action in the chamber 11, the exit aperture 14 needs to be located as far away as possible from the floor of the \\brisl\home?\Shery.M\Keep\Speci\54499.doc 1/10/04 9o chamber 11. However, it must also be noted that this height is limited by the need for the exit pipe 21 o connected to the exit aperture to have sufficient concrete 0 protection from people, vehicles, etc, passing over the 00 pollutant trap The baffle wall 15 (as shown in Figure 5) is curved, preferably with a curvature equivalent to the 00 Ti rae nee 00 opposing wall of the chamber 11. This creates an even 0 1 "pull" across the floor of the chamber 11 and under the baffle wall 15. However, any shaped wall or conduit may be oused for the baffle wall 15 so long as it creates a weir oin the chamber 11.

When the flow of run-off into the filter basket 12 exceeds the maximum flow rating of the filter basket 12, the filter basket 12 fills with water until the water level in the basket is such that run-off enters the bypass 16 and flows along the excess flow path 35 as shown in Figure 1. The bypass 16 enables the excess run-off to bypass the filter basket 12 and the baffle wall 15 and enter the chamber 11 proximate to the exit aperture 14 of the chamber 11. By virtue of the sizing of the exit aperture 14 and hence the flow therethrough, the excess run-off rapidly exits the chamber 11 after flowing through the bypass 16. The maximum flow rating of the exit aperture 14 is at least equal to or greater than the sum of the maximum flow rating of the filter basket 12 and the maximum flow rating of the bypass 16. Thus, the excess flow bypassing the filter basket 12 does not substantially affect the maximum liquid level inside the main chamber 11, hence the air gap 32 is always maintained inside the chamber 11 and the liquid level in the chamber 11 never reaches the base of the filter basket 12 (and the chamber 11 does not flood). In fact, the liquid level in the chamber 11 may drop slightly as run-off begins to flow through the bypass 16. This is because the run-off flow tends towards the path of least resistance. Thus as the flow through the bypass 16 increases, the flow through the \\bri 0l\hame$\SherytM\Keep\Speci\P544 9 9 .doc 18/10/04 10 -0I o filter basket 12 may decrease slightly. Furthermore, the litter and debris captured by the filter basket 12 does o not escape because of the downward pressure generated by o the run-off flowing through the filter basket 12. Thus, 0C 0 5 the pollutant trap 10 of the present invention avoids the problems in the prior art associated with flooding of the chamber 11.

00 Referring in particular to Figure 6, the bypass 00 o16 comprises a tubular socket 40 and an elbow tube 41.

The tubular socket 40 extends upwardly from the base of othe filter basket 12 and is fixed thereto. The socket ohas apertures at either end to enable excess run-off to enter the bypass 16 to bypass the filter basket 12. The elbow tube 41 is open at both ends and comprises a vertical portion 42 and a horizontal portion 43. The horizontal portion 43 is connected to the baffle wall and provides an opening therethrough for directing the excess run-off past the baffle wall 15 to enter the chamber 11 proximate to the exit aperture 14. The horizontal portion 43 (and hence the elbow tube 41) may be integrally formed, for example of roto-moulded plastic.

The vertical portion 42 is adapted to connect to the tubular socket 40 through the base of the filter basket 12. In use, the vertical portion 42 of the elbow tube 41 has a friction fit inside the tubular socket 40, with the end of the vertical portion 42 abutting an internal lip 44 in the tubular socket Assembly of the pollutant trap 10, thus usually involves pushing the tubular socket 40 (and hence the filter basket 12) over the vertical portion 42 of the elbow tube 41 until the vertical portion 42 abuts the internal lip 44.

Referring now to Figures 7 and 8, Figure 7 illustrates how a single exit pipe 21 directs run-off from inside the chamber 11, including the excess run-off which has flown through the bypass 16, into a stormwater pipe 22. Figure 8, shows an alternative arrangement, in which \\brisl\hme$\SherylM\Keep\Speci\P54499.doc 18/10/04 11 o a similar pollutant trap 110 has an exit pipe 121 C1 directing flow from the container 111 into the stormwater o pipe 122 and a separate bypass exit pipe 50 which directs excess run-off through the bypass 16 directly into the 5 stormwater pipe 122. Thus, in the pollutant trap 110 of Figure 8, the excess run-off bypasses the chamber 111 completely.

00 During operation of the pollutant trap 10, under 00 Seither normal or excess flow conditions, the pollutant 10 trap 10 retains at least 95% of the hydrocarbons and at o least 99% of particles greater than 0.3mm in size from the o inflowing run-off when it is less than the maximum flow rating of the filter basket 12. Over time, the volume of retained pollutants builds up inside the chamber 11 and thus regular servicing of the pollutant trap 10 according to a preferred embodiment of the present invention is required to remove the retained pollutants. The retained pollutants can then be transported elsewhere for appropriate treatment and/or disposal.

The maximum flow ratings of the filter basket 12 and the bypass 16 are based on the "Average Recurrence Interval" which is the average, or expected, value of the periods between exceedances of a given rainfall intensity. In a preferred embodiment of the present invention, rainfall intensity having an ARI of three months is used to calculate the maximum flow rating of the filter basket 12. Although, other ARI's may be used, the ARI of three months represents a rainfall intensity in which the majority of pollutants are usually washed from a surface.

The maximum flow rating of the bypass 16 is calculated (based on the Australian Standard AS3500) from the rainfall intensity having an ARI of either 10 or years.

Having designed the pollutant trap 10 to have a maximum flow rating for the bypass 16 and the filter basket 12, it is possible to use the same pollutant trap \\brisol\home$\SherylM\KeepNSpeci\P54495.doc L8/120/04 12 o 10 (ie. has the same design parameters) in different (N locations where the "first flush" and/or the ARI is odifferent by using different numbers of the pollutant 0 traps 10 to service a surface having polluted run-off.

00 00 5 The number of pollutant traps 10 required for a surface can be calculated according to the following equations: 00 A Q(t) 00 Ax Q' o (Fw(r max) F(himsx max)) where; n number of pollutant traps A area of surface Q(t) rainfall intensity for an ARI of t t specified time interval for ARI calculation (typically 10 or 20 years) F(filter max), F(bypass max) maximum flowrates (ie. maximum flow ratings) of the filter and bypass respectively and; A x Q(t) F (jliirmax) where Q(t) rainfall intensity for an ARI of T (typically 3 months) T specified time interval for ARI calculation (typically 3 months) The number of pollutant traps 10 actually required is the greater number of traps 10 calculated from these equations.

The components of the pollutant trap 10 may be manufactured of polyethylene but are understood not to be limited to this material.

In the claims which follow and in the preceding description of the invention, except where the context requires otherwise due to express language or necessary implication, the word "comprise" or variations such as \\brisOl\home$\SherylM\Keep\Spci\PS4499.doc 18/10/04 13 o "comprises" or "comprising" is used in an inclusive sense, C1 ie. to specify the presence of the stated features but not o to preclude the presence or addition of further features O in various embodiments of the invention.

00 00 00 0 0 0 0

(N

\\brisl\home$\SherylM\Keep\Speci\P54499 .doc 18/10/04

Claims

2. A pollutant trap as claimed in claim 1, in use, further comprising an air gap between the base of the filter and the maximum liquid level of the chamber.
3. A pollutant trap as claimed in either claim 1 or 2, wherein the maximum liquid level in the chamber is maintained below the base of the filter by a maximum flow rating of the exit aperture being at least equal to or greater than the sum of the maximum flow rating of the filter and a maximum flow rating of the bypass.
4. A pollutant trap as claimed in any of the preceding claims wherein the bypass comprises a tubular socket and an elbow tube. A pollutant trap for treating polluted run- off substantially as hereinbefore described with reference to the accompanying drawings. Dated this 19 t day of October 2004 FOX ENVIRONMENTAL SYSTEMS PTY LTD By its Patent Attorneys GRIFFITH HACK \\brls'fl\,Otime$\SherylM\Keep\Speci\P54499.doc 1S/10/04