AU769866B2 - Gross pollutant trap - Google Patents

Description

P/00/011 Regulation 3.2

AUSTRALIA

Patents Act 1990 COMPLETE SPECIFICATION FOR A STANDARD PATENT

ORIGINAL

C

Actual Inventor: HARLEY COOKE Address for Service: A.P.T. Patent and Trade Mark Attorneys GPO Box 772, Adelaide, SA 5001 Invention Title: GROSS POLLUTANT TRAP Details of Associated Provisional Application No: PP7953 dated 24th December 1998 The following statement is a full description of this invention, including the best method of performing it known to us:- 22/09/2003 15:34 +61-8-82723255 APT PAGE 24/38 2 This invention relates to a gross pollutant trap. In a preferred form the gross pollutant trap is manufactured substantially of concrete and delivered pre-cast to an installation site.

BACKGROUND OF THE INVENTION Recently there has been considerable concern regarding rubbish within stormwater drain systems which includes natural as well as man made watercourses. Rubbish, including plastic bottles, paper, leaves, twigs, boxes and much more, often finds its way into watercourses and is carried downstream by water flowing within the drain system. This rubbish, depending upon flow, can become strewn along a watercourse making the watercourse look unsightly. It can also cause environmental damage.

In response to this local authorities are now installing various filters and traps to catch rubbish and allow for its disposal. These installations are typically manufactured in-situ and generally have an inlet and an outlet. The outlet allows water to flow out of the installation into the watercourse and often stones are placed beneath the outlet to reduce erosion.

These solutions have a number of problems and whilst just two principle problems Swill be discussed there are others. Other problems will be apparent from the following discussion.

Firstly, the requirement that the installation be built in-situ means that the construction process takes time and this is of course within a watercourse. Any stormwater flowing during the construction process cart considerably hinder the construction process and may lead to additional problems such as erosion.

Secondly, the outlets of such installations often become blocked leading to overflow of stormwater in an uncontrolled manner. This is exacerbated by a climate where there are relatively long periods of dry weather as occurs in much of Australia. For example, over the summer months in southern Australia, rubbish accumulates widely over the drainage area and this rubbish does not necessarily o o include only man made items. Of major concern is organic matter such as leaves which of course are not generally picked up since they are part of the natural x environment. This rubbish is spread over the drainage area it is therefore, not readily collectable. Even should the traps and filters be cleared of rubbish prior to COMS ID No: SMBI-00425546 Received by IP Australia: Time 16:21 Date 2003-09-22 22/09/2003 15:34 +61-8-82723255 APT PAGE 25/38 3 rain, when rain occurs there is often considerable run-off which collects and carries the dispersed rubbish into the stornwater drain system and very quickly the traps and filters become blocked and the installations overflow leading to erosion. At the time of the rainfall it is impractical to clear all blocked installations and so resulting erosion must be accepted as damage to be borne and repaired.

OBJECT OF THE INVENTION It is an object of this invention to provide a gross pollutant trap to obviate or minimise at least one of the aforementioned problems, or at least provide the public with a useful choice.

SUMMARY OF THE INVENTION The invention may be said to reside, not necessarily in the broadest or only form, in a gross pollution trap including: a chamber; an inlet to the chamber for inflow of fluid; a general outlet to the chamber for outflow of fluid when fluid within the chamber exceeds a first level a bottom of said chamber set below the first level to retain nonfloating debris; an overflow outlet to the chamber for outflow of fluid when fluid within the chamber exceeds a second level higher than the first level a direction of .20 outflow from the overflow outlet being transverse to the direction of overflow; a walled erosion resistant spillway having an exit, the spillway extending from an outer surface of the chamber beneath the general and the overflow outlets and being for receiving all fluid outflow from the general. and the overflow outlets and conducting fluid to the exit; and the chamber being adapted that in use fluid flow from the inlet undergoes backwash to reduce the flow velocity of the fluid prior to flowing out from the overflow outlet and thereby debris tends to remain within the chamber.

9 9 "The debris may include flotsam of many forms including that which is naturally 30 buoyant and that which will sink in still or near still fluid. Silt, sand and other COMS ID No: SMBI-00425546 Received by IP Australia: Time 16:21 Date 2003-09-22 22/09/2083 15:34 +61-8-02723255 APT PAGE 26/38 4 similar matter tends to be carried by flowing fluids but once the flow has reduced sufficiently will tend to settle to the bottom.

In one form the overflow outlet is upstream from the portion of the cbamber causing the backwash and the location of the overflow outlet is so that during high fluid flow when the fluid level exceeds the second level debris tends to collect upstream and proximal the portion of the chamber causing the backwash and the overflow outlet is further upstream where the debris tends not to collect yet the flow velocity is reduced thereby allowing fluid outflow of the overflow outlet in a controlled fashion. Having the overflow outlet upstream of the area where debris tends to collect yet where the fluid velocity is reduced permits the outflow to be less forceful and generally carrying less debris. Obviously, should the gross pollution trap become totally clogged with debris then some will be card'ed with the outflow but this is regarded as an unusual condition due to abnormal events or lack of maintenance of the gross pollution trap. It will be appreciated that a skilled address will from the teachings herein and non-inventive experimentation be able to determine a location of the overflow outlet to suit a design of a chamber if different from the following embodiment.

It will be appreciated that whilst the invention is directed mainly to application within stormwater drain systems the invention could be used in other applications suffering from similar problems such as formaing part of waste treatment for industrial establishments. Accordingly, the fluid will Often be stormwater but is not limited to water. Without intending to limit the scope of the invention for :explanative purposes the fluid will be taken as being water and the application of the invention will be to a gross pollutant trap within a stormwater drain system.

The walled spillway alows, any overflow to be controlled rather than uncontrolled.

Further, any overflow is directed by the spillway to an exit from which it travels into a watercourse. In keeping with current practice, the watercourse may be suitably prepared for water flow from the gross pollutant trap by the location of stones. In this way erosion may be controlled and damage may be averted.

During storm events water flowing into a gross pollutant trap will normally be S...directed to the general outlet at considerable flow velocity. Where the general outlet becomes blocked, whether Muly or only in part, or where the in flow exceeds the capacity of the genera] outlet then water banks up within the chamber about the S S*6general outlet forming a backwash off the wall of the general outlet back towards COMS ID No: SMBI-00425546 Received by IP Australia: Time 16:21 Date 2003-09-22 22/09/2003 15:34 +61-8-82723255 APT PAGE 27/38 the inlet. This backwash may significantly slow the water flow causing relatively slow surface water movement and accumulation of debris about the general outlet.

Placement of the overflow outlet where the flow velocity is somewhat reduiced and debris is less concentrated allows water to flow out of the overflow outlet in a controlled fashion. It will be appreciated that water flow within the chamber is very dependant upon the in flow conditions and as such "slow" water mnovement and similar terms and phrases are relative to the flow condition.

In one form, the fluid flow path between the inlet and the general outlet goes through first filter means whereas the flow path between the inlet and the overflow outlet does not go through the first filter means. Under normal conditions it may be desirable to filter the fluid and the filter means may comprise a mesh screen placed before the general outlet. Such filter means may filter considerable rubbish.

However during storm events this first filter means may become clogged but because the overflow outlet is not within the flow path though the first filter means the overflow outlet is not as readily blocked. There are known gross pollutant traps where filter blockage leads to uncontrolled overflow of water and hence erosion.

In another form the inlet and the general outlet are within opposite sides of the chamber, and the overflow outlet is in a side of the chamber not opposite the inlet.

This configuration is one way to conveniently create the backwash and the relatively slow water flow about the overflow outlet.

According to one form there is provided second filter means within the flow path *~*between the inlet and thbe general outlet and said second filter is upstream of the first filter means. The second filter means may be coarser in filtration than the first filter means and may be intended Co filter larger debris. Alternatively the second filter may not fully cover the flow path either in a horizontal or a vertical dimension or both thereby in high flow events a flow path is generally maintained irrespective of the blockage state of' the second filter. Further where the second filter is coarser then the chances of significant blockage is less likely compared with a finer gauge filter- *30 In one form, the fluid outflow capacity of the overflow outle t is gr-eater than the fluid outflow capacity of the general outlet. Preferably the overflow outlet has a a. capacity exceeding the likely needs of the gross pollutant trap and may far exceed :the capacity of the inlet. In another form the overflow outlet is rectilinear in shape and a major axis is substantially horizontal when the trap is in place. The large COMS ID No: SMBI-00425546 Received by IP Australia: Time 16:21 Date 2003-09-22 22/09/2003 15:34 +61-8-82723255 APT PAGE 28/38 6 horizontal capacity of the overflow outlet can allow the water to overflow in a relatively slow manner and so limit the momentum of the outflowing water.

The chamber may be substantially box like, the inlet and the general outlet are in opposite sides of the chamber, and there are two overflow outlets in opposite sides extending between the sides including the inlet and general outlet.

In another form the chamber is divided into two parts by a weir, and one part being proximal to the inlet housing a removable basket for collection of debris and filtering of the fluid and to be removed from the trap for emptying. Further, there may be weep holes through the weir proximal a bottom side of the chamber. Also the second filter means may comprises a rack hinged to allow the rack to rotate upwardly to direct filtered matter to fall into the basket.

It may be preferred that the gross pollutant trap include at least one lid to the chamber within which is an inspection hatch. Typically the lid may be of considerable size and is therefore so difficult to manipulate by a single person. The inspection hatch allows a person to check the trap which may be later emptied by a suitably equipped group of workmen.

In one form the gross pollutant trap constructed of concrete and may be pre-cast and deliverable to a site of installation in a cast condition. By pre-casting the trap installation may be considerably quicker and so conducted within less time and less risk of a storm event occurring within the time of construction.

.BRIEF DESCRIPTION OF THE DRAWINGS To assist in the understanding of the invention a preferred embodiment will now be described with reference to the accompanying drawings: Figure 1 is a sketch of a front perspective view of a gross pollutant trap; Figure 2 is a sketch of an underside perspective view of the'gross pollutant trap; Figure 3 is a sketch of a front view of the gross pollutant trap; Figure 4 is a sketch of a rear view of the gross pollutant trap; Figure 5 is a sketch of a top plan view of the gross pollutant trap; COMS ID No: SMBI-00425546 Received by IP Australia: Time 16:21 Date 2003-09-22 22/89/2003 15:34 +61-8-82723255 APT PAGE 29/38 7 Figure 6 is a sketch of a side view of the gross pollutant Imap; Figure 7 is a sketch of a bottom plan view of the gross pollutant trap; and, Figure 8 is a sketch of a cross sectional view of the gros s pollutant trap S along AA' of Figure It will be appreciated that Eigures 1 to 7 inclusive show the gross pollutant trap without internal fittings and lids. Throughout the figures the same reference numeral will be used to refer to the same feature in all views.

The preferred embodiment is a pre-cast concrete gross pollutant trap that is deliverable to a site of installation in a cast condition. The overall size of the crap is about 4.5 in long by 3 mn wide by 2 m high with concrete wall thickness of about 150 Min.

The trap is substantially box like and includes a chamber divided into two parts, a trap chamber and a silt chamber by a weir with weep holes through the weir proximal a bottom side of the chamber. A walled spillway extends from an outer surface of the chamber. There is provided an inlet directing fluid inflow into the chamber, a general outlet (11) and two overflow outlet (12 and 13). The outlets permit outflow of the fluid being stormwater from the chamber once the fluid within the chamber has exceeded respectively a first and a second level as can be seen when considering -figures 3, 4 and 8. The general outlet permits outflow of water under ordinary conditions whilst the overflow outlets, .:2'permnit outflow under extraordinary conditions such as the general outlet being blocked or abnormal flow conditions as may occur when there is a storm. The fluid outflow capacity of the overflow outlets is greater than the fluid outflow capacity of the general outlet by a considerable factor in this embodiment and the overflow outlet is substantially -rectilinear in shape with a major axis substantially horizontal.

r. ~:This allows substantial flow out through a wide aperture and so not enhance a concentrated flow. The inlet and the general outlet are in opposite sides of the chamber, and there are two overflow outlets in opposite sides extending between the sides including the inlet and general outlet.

The chamber is adapted so that the flow from the inlet undergoes backwash by :hitting side (15) to reduce the velocity of the fluid prior to flowing out from the overflow outlet. The reduction in water surface velocity tends to collect any debris COMS ID No: SMBI-00425546 Received by IP Australia: Time 16:21 Date 2003-09-22 22/09/2003 15:34 22/9/603 1534 +1-8-82723255' APT PG 03 PAGE 30/38 8 near side (15) and so the debris tends to remain Wkithint the chamber. Under very high flow conditions and where the trap is very ful with debris then some debris will flow out through the overflow outlets hut ordinarily the slowing of the water flow tends to reduce debris out flow. All outflow fromn the chamber whether through the general outlet or the overflow outlets falls upon the erosion resistant spillway and is conducted by the walls (16 and 17) to the exit (28).

Within the fluid flow path between the inlet and the general outlet there are first filter means (18) which consists of a mesh screen. The first filter means may be made of wire mesh having holes of approximately 12 mmn x 12 mm and wire diameter of approximately 2.5 mnm and set back from wall (15) by approximately 500 num. The first filter means is removably located within the silt chamber between brackets proj ecting from the ver tical sides of the gross polluti trap (not shown). By removing the first filter means it may be cleaned. The flow path between the inlet and the overflow outlet does not go through the first filter means.

Within the chamber in the part proximal to the inlet housing is a removable basket (19) approximately 1400 x 1400 x1000 nun for collection of debris and filtering of the fluid and to be removed from the trap for emptying. The basket sits within the trap chamber so thar floating debris and rubbish wilt tend to flow into or over the basket- There is also provided second filter means (20) within the flow path between the inlet and the general outlet and said second filter is upstream of the first. filter means. The second filter means comprises a mesh rack hinged to allow the rack to *..*rotate upwardly to direct filteredl matter to fall into the. basket and this is shown by the dashed and solid line drawing of the same in figure 8. The second filter means is coarser than the first filter means and again made of wire mesh with a pipe frame and if desired supporting cross members. The wire may be approximately 4 mm, diameter with 50 nurn x 50 mam holes. To aid collection the basket has chain (21) bywhich it can be lifted. The chain is hooked onto hook (22) suspended below! beam (23) when not in use and so is relatively easily grasped for lifting purposes.

The trap has two lids (24 and 25) to the chamber. Within each is an inspection hatch (26 and 27). The large lids are of considerable size and weight and so not readily manipulated by a single person. The inspection hatches are by comparison readily manipulated by a single person, though may incorporate a lock to prevent COMS 1D No: SMBI-0042 5546 Received by IP Australia: Time 16:21 Date 2003-09-22 22/09/2003 15:34 22/9/0031534 +61-8-82723255 APT PG 13 PAGE 31/38 9 unauthorised access, and allow a person to determine the extent of fill within the trap. This would be a routine operation.

The general outlet (11) is circular with a diameter of about 450 mm but other dimensions may be used as desired. The bottom edge of the general outlet is approximately level wit the effective height of the weir or a little lower. It will be appreciated in Figure 8 that whilst the weir is slightly lower than the bottom of the general outlet frame of the second filter means, being approximately 50 nun outside diameter pipe, brings the effective height of the weir uip to that of the bottom edge of the general outlet.

The overflow outlets are 900 mm long by 200 nun though these dimensions may be altered whilst keeping within the principles disclosed herein. The bottom edge of each overflow outlet is approximately 250 mm above the bottom edge of the general outlet and again if desired this could be altered.

During low flow conditions then by having the bottom edge of the general outlet level with or lower than the effective height of the weir water flows into the trap chamber and through the weep holes into the silt chamber and thence 10 the general outlet. In this way gross debris tends, to remain in the trap chamber with smaller debris such as silt and partly decomposed organic matter such as leaves possibly finding its way into the silt chamber. Plastic bottles, cans and other rubbish may initially be floating debris but after a period of time within water tend to sink to the bottom. Due to the relative effective height of the weir with respect to the bottom edge of the general outlet this sunk rubbish tends to remain within the basket.

During periods of high flow, water carrying some debris may flow over the weir into the silt chamber. The second filter means filters the larger debris and the first filter means the smaller debris which often consists of leaves, twigs, paper and other organic matter. When low flow conditions return some of the material caught by the second filter means falls into the trap chamber and may then become contained -within the basket.

The decomposable smaller debris caugbt by the first filter means will lend over time to sink to the bottom of the silt chamber and decompose.. This and any silt which may have settled or been carried into the silt chamber from the trap chamber through the weep holes may be routinely removed. A pump may be wmed to empty the silt chamber and thereby substantially the trap chamber of water, silt and COMS ID No: SM8I-0042554 6 Received by IP Australia: Time 16:21 Date 2003-09-22 22/09/2003 15:34 +61-8-82723255 APT PAGE 32/38 sediment. After emptying the silt chamber the basket may be emptied and then the remaining water, silt and sediment within the trap chamber may be pumped out.

This water, silt and sediment may then be disposed in a suitable manner such as by taking the water, sediment and silt to a land fill site.

The walls of the spill way, having a thickness of 150 mm, are spaced from the sides of the gross pollutant trap to form the spillway between the sides of the gross pollution trap and the walls. The spillway is approximately 300 mm wide at one end distal the exit and this may be wider towards the exit. The wall may be 500 mm or more high. This permits the spillway to be relatively large compared to the overflow outlets and the general outlet so allowing a slowing of out flowing water, particularly that emerging from the overflow outlets. Also the high walls tend to contain water flowing out of the overflow outlets and so direct the water to the exit.

The trap chamber (3)has a sloped in flow spillway (29) of approximately 700 mm length onto which in flowing water falls. The inlet is 450 mm in diameter but this may be changed to suit stormwater piping feeding water to the gross pollution trap.

Water flowing into the larger volume of the gross pollution trap slows the water flow to a certain extent. By having the water fall onto the in flow spillway water over the basket is relatively non turbulent. Accordingly, sediment and debris will tend not to be stirred up as water flows in during normal conditions and so flowing out water will tend to be cleaner than if the sediment and debris was stirred up.

During construction a suitable hole is dug and the pre-cast trap is delivered to the site and installed into the hole. The hole is suitably backfilled. The outflow is backfilled with erosion resistant material as is known to the art. As all outflow, including overflow is via the exit of the spillway the water is directed to the erosion resistant material and so the risk of damage is reduced.

Periodically the trap would be inspected and as required rack rotated to allow held rubbish to fall into the basket. The basket would be emptied using the chain and suitable equipment as required.

During a normal operation debris carried by stormwater is filtered by the basket, 30 rack and screen with the filtered water flowing out the general outlet. When a stormwater event occurs the water level rises within the trap and a backwash is created by the front wall (15) within which the general outlet lies. The water flows out of not only the general outlet but also the overflow outlets. The velocity of the COMS ID No: SMBI-00425546 Received by IP Australia: Time 16:21 Date 2003-09-22 22/89/2003 15:34 +61-8-82723255 APT PAGE 33/38 11 water is somewhat slowed and debris will tends to some extent to collect about the front wall. The water outflow is all directed by the spillway to the spillway exit and thus along the stormwater drain. Should the trap become clogged by debris then the general outlet will clog first and the water level will rise within the trap until overflow occurs through the overflow outlets.

It will be appreciated that this disclosure is not intended to limit the invention to preferred embodiment or details thereof. A person skilled in the art would readily be able to conceive other embodiments of the invention and as such these other embodiments would all fall within the spirit of the invention disclosed herein.

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@000 COMS ID No: SMBI-00425546 Received by IP Australia: Time 16:21 Date 2003-09-22

Claims (13)

1. A gross pollution trap including: a chamber; an inlet to the chamber for inflow of fluid; a general outlet to the chamber for outflow of fluid when fluid within the chamber exceeds a first level a bottom of said chamber set below the first level to retain nonfloating debris; an overflow outlet to the chamber for outflow of fluid when fluid within the chamber exceeds a second level higher than the first level a direction of outflow from the overflow outlet being transverse to the direction of overflow; a walled erosion resistant spillway having an exit, the spillway. extending from an outer surface of the chamber beneath the general and tbe overflow outlets and being for receiving all fluid outflow from the general and the overflow outlets and conducting fluid to the exit; and the chamber being adapted that in use fluid flow torn the inlet undergoes backwash to reduce the flow velocity of the fluid prior to flowing out from the 0****overflow outlet and thereby debris tends to remain within the chamber. A gross pollution trap as in claim 1 including a spillway wail spaced apart *20 from the overflow outlet and extend upwardly to act as a barrier to ove-rshoot of outflow from the overflow outlet.

3. A gross pollution trap as in claim 1. wherein the overflow outlet is ups .tream from the portion of the chamber adapted to cause the backwash and the location of the overflow outlet is adapted so that during high fluid flow when the fluid level 25 exceeds the second level debris tends to collect upstream and proximal the portion of the chamber causing the backwash and the overflow outlet is further upstream where the debris tends not to collect yet the flow velocity is reduced thereby allowing fluid outflow of the overflow outlet in a controlled fashion. C.4. A gross pollution trap as in either claim I or claim 3 wherein the fluid flow :30 path between the inlet and the general outlet goes through first filter means whereas COMS 1D No: SMBI-00425546 Received by IP Australia: Time 16:21 Date 2003-09-22 22/09/2003 15:34 22/9/6631534 +61-8-82723255 APT PG 53 PAGE 35/38 13 the flow path between the inlet and the overflow outlet does not go through the first filter means. A gross pollution trap as in any one of the preceding claims wherein the first filter means comprises a mesh screen placed before the general outlet.

6. A gross pollution trap as in claim 5 wherein the first filter means is removable from the gross pollution trap.

7. A gross pollution trap as in any one of the preceding claims wherein the inlet and the general cutlet are within opposite sides of the chamber, andi the overflow outlet is in a side of the chamber not opposite the inlet.

8. A gross pollution trap as in claim 7 including a further overflow outlet in a wall opposite the other said overflow outlet.

9. A gross pollution trap as in any one of the claims 1 6 wherein the chamber is substantially box like, the inlet and the general outlet are in opposite sides of the chamber, and there are two overflow ou tlets in opposite sides eatendi rig between the sides including the inlet and general outlet. A gross pollution trap as in claim 9 wherein there are weep holes through the weir proximal a bottomn side of the chamber. 444,44It1 A gross pollution trap as in claim 10 wherein the chamber is divided into two parts by a weir, and one part being proximal to the* inlet housing a removable 20 basket for collection of debris and filtering of the fluid and to be removed from the trap for emptying.

12. A gross pollution trap as in any one of claims 9, 10 and 11 wherein, when in use, the height of the weir is equal to or greater than the height of the bottomn edge of the general outlet.

13. A gross pollution trap as in any one of the preceding claims including second filter means within the flow path between the inlet and the general outlet and said second filter is upstream of the first filter means. 0 14. A gross pollution trap as in claim 13 wherein the second filter meWans is 44** coarser in filtration than the first filter means. COMS ID No: SMBI-00425546 Received by IP Australia: Time 16:21 Date 2003-09-22 22/09/2003 15: 34 22/9/0831534+61-8-82723255 APT PG 63 PAGE 36/38 14 A gross pollution trap as in either claim 13 or 14 wherein the second filter does not fully cover the flow path between inlet and general outlet either in a horizontal or a vertical dimension or both thereby in h igh flow events a flow path is generally maintained irrespective of the blockage state of the second filter.

16. A gross pollution trap as in claim 13, 14 or 15 including a basket adapted to collect debris and rubbish and wherein the second filter means includes a rack hinged to allow the rack to rotate upwardly to direct filtered matter to fall into the basket.

17- A gross pollution trap as in any one of the preceding claims wherein the fluid outflow capacity of the overflow outlet or outlets is greater than the fluid outflow capacity of the general outlet.

18. A gross pollution trap as in any one of the preceding claims wherein the overflow outlet or outlets has a fluid conducting capacity exceeding the capacity of the inlet.

19. A gross pollution trap as in any one of the preceding claims wherein the over flow outlet is rectilinear in shape and is adapted that a major axis is substantially horizontal when the trap is in use. A gross pollution trap as in any one of the preceding claims wherein the gross pollutant trap includes at least one lid to the chamber within which is an inspection hatch. *21. A gross pollution trap as in any one of the preceding claims constructed of concrete and supplied to an installation site in pre-cast form.

22. A gross pollution trap as in any one of the preceding claims including a sloped inlet spillway beneath the inlet adapted so that fluid inflow falls onto the inlet spillway. *23. A gross pollution trap substantially as disclosed herein with reference to the 0600 accompanying drawings. Dated this 22nd day of September 2003 A. P. T. Patent aind Trade Mark Attorneys COMS ID No: SMBI-00425546 Received by IP Australia: Time 16:21 Date 2003-09-22