AU2003100955A4

AU2003100955A4 - High flow rate surface in gross pollutant collection trap

Info

Publication number: AU2003100955A4
Application number: AU2003100955A
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: 2003-11-20
Publication date: 2004-02-26
Anticipated expiration: 2011-11-20

Description

AUSTRALIA

Patents act 1990 COMPLETE

SPECIFICATION

INNOVATION

PATENT

HIGH FLOW RATE 'SURFACE

IN'

GROSS POLLUTANT COLLECTION

TRAP

The following statement is a full description of this invention, including the best method of performing it known to me: This invention facilitates the removal of pollutants from stormwater run-off and ensures that the captured pollutants cannot reinfiltrate the outflow during rainfall intensities that cause flow to the unit to exceed the design flow rates of the unit. This is achieved by the unique design of the trash/silt collection basket and the location and dimensions of the by-pass path.

Page 1 FOX HIGH FLOW RATE 'SURFACE IN' GROSS POLLUTANT COLLECTION

TRAP

Background Traditionally, stormwater has flowed into gutter gully pits and then into the waterways via overland channels or stormwater piping. As environmental awareness evolved, the need to treat the stormwater run off was recognised. This has been achieved with varying degrees of success by the use of equipment that either removes the floating debris by straining or settling. Some attempts have been made to remove hydrocarbons by the utilising of absorption materials or weirs. The equipment used in this application has taken the generic name of a 'Gross Pollutant Collection Trap'.

Fox Environmental Systems Pty Ltd found that they were able to adapt components used in their other systems to fulfil this application. These units were referred to as Fox Model BGPCT units. The unit is installed in paved areas where the risks of pollutants are high but the volumes expected are low to moderate. Typical applications are car parking areas and industrial units where there is a need to prevent things like silt and trash as well as motor vehicle oil leaks from entering the stormwater collection system.

It was found rainfall of a high intensity was capable of presenting run-off to the BGPCT that was greater than the unit could handle which could have the effect of reinfiltrating captured pollutants back into the stormwater network. The Fox High Flow Rate 'Surface In' Gross Pollutant Collection Trap eliminates this risk.

Description of the Invention The Fox High Flow Rate 'Surface In' Gross Pollutant Collection Trap, (hereafter referred to as the BGPCT with Flow By) is specifically designed to simplify the removal of floating debris, silts, solids and minor amounts of hydrocarbons from stormwater runoff generated by rainfall of a design Average Rainfall Intensity (ARI) whilst making provision to handle flows generated by unusual storm intensities.

The BGPCT with Flow By can be installed singularly or in multiple numbers, sufficient to cater for the runoff generated by the area to be protected, with the grated inlet at ground level and the area graded to introduce runoff into the unit over the grate. A trash/silt basket into which is fitted a By-pass tube removes floating debris and silt. This basket will be designed to limit the flow rate of stormwater through the unit. When the rain intensity increases to a rate above design flow limits the excess flow is caused to By-pass the main chamber and discharge beyond the unit. This bypass enables the flow velocity through the main chamber to be maintained at the design rate and therefore retaining trapped silts and solids and hydrocarbons.

Page 2 How it works.

Figure 1 shows the alternate flow paths through the unit.

Under 'treatable' storm intensities (design ARI), runoff will travel over the ground surface and carry with it any silts or gross pollutants such as cans, packets or other solids as well as any minor hydrocarbon spills. Larger items are prevented from entering the unit by the grate and trash basket. The volume of runoff which enters the chamber is controlled by the size and number of holes and their location in the trash/silt basket.

Within the chamber separation of silt, hydrocarbons and clean water occurs. The clean water will leave the chamber under the weir wall and continue into the stormwater system.

When rainfall of an intensity greater the design ARI is encountered, the flow rate of the trash basket is exceeded and the water level will rise in the basket until 'flow by' occurs. By directing flow to the exit pipe via the flow-by route the water velocity within the basket and the main chamber is maintained at the design rate and no reinfiltration of retained pollutants can occur.

Detailed description with reference to the drawing.

Reference to the attached drawings will show the main components of the unit.

Figure 2 is a Plan of the unit, Figures 3 4 are Elevations showing the main parts.

A Main Chamber of suitable material and size will contain a Trash/silt Basket (2) and Service Grate Configured within the chamber will be a Wall or Baffle which will provide a weir by isolating the inlet path from the Outlet pipe A Bypass Tube will enable a route for runoff from the inflow point for volumes exceeding the design rate of the unit. The Figure 5 details the most common arrangement however, alternative arrangements including that shown in Figures 6 will also be utilised.

The unit is preferably manufactured from polyethylene however other materials could also be used. The specific dimensions of the unit are not limited.

Claims

1. A chamber of suitable size and shape has an open top into which is fitted a trash/silt basket that is protected by a service grate.

2. The basket referred to in claim 1 has a specific combination of size, number and location of outlet holes that provide a design flow-rate and promote the retention of quantities of pollutants, there is also a high flow by-pass tube fitted in the base of the basket.

3. The chamber referred to in claim 1 has an outlet pipe installed in the side having a specific location and size relative to the treatable flow rate of the unit and is fitted with an internal wall that will isolate the outlet pipe from the open top.

4. The combination of the basket design as referred to in claim 2 and the size and location of the outlet pipe referred to in claim 3 ensures that an air gap is always maintained between the surface of retained liquid in the chamber main body and the trash/silt basket. The high flow by-pass tube referred to in claim 2 will by-pass the main liquid body and direct run-off that exceeds the design flow-rate, to a location that does not have any effect on the retained pollutants within the unit.