AU2007202042B2 - A filter assembly for collecting floatable litter - Google Patents

Description

1 A FILTER ASSEMBLY FOR COLLECTING FLOATABLE LITTER FIELD OF INVENTION The present invention relates to a filter assembly for the collection of floatable 5 litter carried along stormwater drains. The present invention has particular but not exclusive application for the collection of floatable litter at an end of line discharge outlet. PRIOR ART 10 Gross litter such as plastic products, bottles and containers; paper and paper products; and vegetative debris are washed down roadways and gutters through stormwater drains and usually discharged into local waterways. This type of litter pollutes the waterways environment and can cause blockage or damming of the waterways. Where the waterways are stagnant for relatively long periods of time or 15 rely on tidal movement to flush the litter from the waterways, the accumulated litter begins to rot. This is of particular importance in man-made canal estates which have a limited flow of water through the canal, In these canals rotting litter accumulates creating an unsightly and smelly environment for the residents bordering the canal. Some Councils have addressed the problem by employing workers to pick up 20 the litter after it has entered the waterways. This is a relatively labour intensive and costly solution with too few workers employed to collect large amounts of dispersed litter. Another approach used by a Council is to position a net bag over the discharge outlet to collect litter as it is discharged. When the bag is full, it is released from the discharge outlet and floats from an anchored position until Council workers 26 empty the contents from the bag and reposition the emptied bag over the discharge outlet. However, litter escapes from the discharge outlet into the waterways while there is no bag around the discharge outlet. Furthermore the bag containing the floating litter is unsightly and the litter rots until the Council workers remove it. 30 OBJECT OF THE INVENTION It is an object of the present invention to provide an alternative device for collecting floatable litter from a stormwater drain, 2 STATEMENT OF THE INVENTION In one aspect the invention is a filter assembly for collecting floatable litter in a channel member including an upstream screen that extends across the channel member and positioned 5 to direct flow, and a downstream screen that extends across the channel member and arranged to receive the directed flow and collect floatable debris, A filter assembly for collecting floatable litter in a stormwater channel member with two side walls including 10 an upstream screen that extends across the channel member to form a gap between the upstream screen and one of said side walls, said upstream screen is positioned to direct flow, and a downstream mesh screen that extends across the channel member and overlaps the gap, said downstream screen is positioned relative to the upstream is screen to receive the flow and floatable debris directed from the upstream screen and passing through the gap. Both screens preferably extend from a channel member sidewall. Preferably both screens extend from the same sidewall. Both screens preferably extend only partly across the channel member. 20 The downstream screen preferably extends across the channel member to a greater extent than the upstream screen. The downstream screen or both screens are preferably mesh screens to allow water but not floatable debris to pass through the screens. The mesh screens may have apertures between 3mm and 50mm. The preferable mesh aperture is 25mm. 25 The downstream screen is preferably substantially at right angles to the direction of the water flow. However the downstream screen may be curved or u shaped. The downstream screen preferably includes a mesh flange that extends substantially upstream. The downstream screen with the flange preferably forms an 30 L-shape. The downstream screen preferably has a mesh top wall to prevent debris from floating over the screen during large flows. In one preferred form the downstream screen is an L-shaped screen that extends from a channel member sidewall across the channel member floor to 2o% overlap the stormwater pipe outlet. The flange preferably extends upstream to a position that substantially corresponds to the position of the free end of the upstream screen thereby forming a gate between the free end of the upstream screen and the flange. 5 The upstream screen is preferably disposed at an angle. The upstream screen is preferably disposed at an angle inclined upstream and towards the stormwater pipe. The position of the upstream screen is maintained preferably by 3 one or more suitable bracing members. In an alternative form the upstream screen may be a triangular shaped screen. The upstream and downstream screens may form an integral basket. The integral basket may be removable for cleaning purposes. The removable integral 5 basket preferably has locating means for positioning the basket within the channel member. The locating means may be in the form of complementary ridges and recesses. The removable integral basket may also have lifting points for lifting the basket out of the channel. Alternatively the screens may be fixed in position and collected floatable 10 debris is removed from the installed filter assembly. The screens maybe retro-fitted into preexisting channels and stormwater drains. in a further aspect the invention is a filter assembly for collecting floatable litter including 15 a channel member having a base wall, an end wall with an aperture for the positioning of a pipe, opposing sidewalls and a removable top wall; an upstream screen that extends across the channel base wall and positioned to direct flow, and a downstream screen that extends across the channel base wall and 20 arranged to receive the directed flow and collect floatable debris. The variations of the screens are described above. The channel member preferably has an end wall in which a stormwater pipe is fitted for introducing stormwater into the filter assembly. The opposing end is open to allow water to pass out of the filter assembly. The opposing sidewalls preferably 25 diverge as they extend towards the open end of the channel member thereby increasing the volume that the flow may occupy. Increasing the volume reduces the energy in the flow and thus the water is discharged with relatively less force . The screens are preferably arranged in the channel member so that there is a gap formed between the top of the downstream screen and the removable top wall. 30 The gap allows water to flow over the downstream screen during large flows. The removable top wall preferably includes a grate which provides a discharge outlet for water accumulated in the channel member during very large flows.

4 With new sites, the filter assembly may be prefabricated and assembled off site and subsequently installed as a drain discharge outlet. In another aspect the invention is a filter assembly for collecting floatable litter from a stormwater drain including a plurality of filter screens locatable in a channel 5 member wherein each screen extends partly across the channel member and is substantially at right angles to the direction of the water flow, said screens are arranged so that adjacent screens are offset relative to each other and have overlapping portions. The phrase, "adjacent screens are offset relative to each other' means that 10 adjacent screens are nonaligned or staggered. The screens filter stormwater passing there through and include a mesh portion and a frame. The mesh portion has an aperture that may vary between 3mm and 50mm. Preferably the mesh aperture of the screen is 25mm. Preferably the screens are arranged so that adjacent screens extend from 15 alternate opposing sidewalls of the channel member. Alternatively one or more screens may be spaced from both sidewalls of the channel member. With relatively larger flows there may be three or more screens located within the filter assembly. With relatively smaller flows the filter assembly includes two screens. 20 The screens preferably extend from the channel member floor to the top of the channel member walls. The mesh portion may extend to the channel member floor. Alternatively there may be a space between the screen and the floor to allow sediment and other nonfloatable particulate debris to move past the screen. Preferably the space 25 between the screen and the channel member floor is 50mm or less. The screens may also have handles that project above the channel member walls. Where the screen extends from the sidewall of the channel member, there is a gate formed between the free end of the screen and the adjacent channel member 30 wall. The gate allows stormwater from an overflow or screen blockage to pass around the screen unhindered. The width of the gate may vary depending on the diameter of the inlet pipe. Preferably the gate width is the same as the inlet pipe diameter. In one embodiment 5 a filter assembly with a 300mm diameter inlet pipe has a gate width of 300mm. The width of the gate may range between 150mm and 1500mm. Where the screens extend from the sidewalls, the largest gate width is preferably the width of half the distance between the opposing channel member sidewalls. In this case the 5 overlapping portion is the midway point. The screens may be any suitable shape but preferably they are curved, U shaped or straight. The screens may also have an end flange to assist in collecting litter or directing the flow to a downstream screen, In one embodiment each screen is L shaped with a flange extending upstream from the free end of the screen and 10 substantially at right angles with the direction of flow. In another embodiment each screen except the last downstream screen is T shaped with a flange extending substantially perpendicular to the screen having an upstream portion to assist in collecting litter and a downstream portion to direct the flow towards the next screen. The filter assembly preferably has a top wall. The top wall has slots through 15 which the screens may be lifted to allow the litter to be removed for purposes of cleaning the filter assembly. Alternatively the top wall has access ports which allows top entry removal of the litter from the filter assembly. The filter assembly may be retrofitted to existing channel members. The filter assembly may alternatively be a prefabricated unit able to be 20 installed on-site. The prefabricated filter assembly includes a reinforced concrete channel member, an end wall attachable to the channel member and a stormwater pipe, a top wall having access ports or slots and a plurality of filter screens locatable in the channel member. The filter assembly may be formed as a one-piece unit or assembled on-site. 25 The arrangement of the filter screens is preferably as described above. The channel member Is preferably a U-shaped box section. The channel member may have parallel sides. Alternatively the channel member is wedge shaped with the end wall attachable at the narrow end. The end wall has an aperture which serves as an inlet and into which a 30 stormwater pipe is fitted. The end wall is preferably formed with the channel member as a single unit. Different sized channel member units may be formed where longer channel members have end walls with comparatively wider apertures. In a preferred form 6 there are at least three different size units with the length of the channel member and the positioning of the screens corresponds with the width of the aperture diameter in the end wall. Alternatively the end wall may be bolted to the end of the channel member prior to installing the fitter assembly. An end wall having an aperture that is 5 slightly larger than the on site stormwater pipe may be selected and bolted to the end of the channel member. A suitable top wall as described above may be attached before or after the filter assembly is attached to the stormwater pipe. The prefabricated filter assembly may form a culvert. 10 The prefabricated filter assembly may be installed in any suitable location providing there is access for periodical removal of the collected litter. The prefabricated filter assembly may be installed near an end of line stormwater drain before the flow is discharged into the waterways. The prefabricated filter assembly may be installed in tidal affected areas. In these areas the tide may push the litter off 15 the screens and upstream of the screens. When the tide recedes the litter is recollected by the screens and prevented from entering the waterways. BRIEF DESCRIPTION OF THE DRAWINGS In order that the present invention be more readily understood and put into 20 practical effect, reference will now be made to the accompanying drawings wherein: Figure ' is a diagrammatic view of the first preferred embodiment of the filter assembly; Figure 2 is a further diagrammatic view of the first preferred embodiment shown in Figure 1; 25 Figure 3 is a sectional plan view of the first preferred embodiment shown in Figure 1; Figure 4 and 5 are diagrammatic perspective views of the installed filter assembly shown in Figure 1; Figure 6 and 7 are diagrammativ Yiew of cleaning the filter aosembly ahown 30 in Figure 4; Figure 8 is a diagrammatic view of a prefabricated filter assembly of a second preferred embodiment; Figure 9 is a plan view of the top wall of the second preferred embodiment; 7 Figure 10 is a plan view of a third preferred embodiment; Figure 11 is a diagrammatic view of the third preferred embodiment; Figure 12 is a plan view of the top wall of the third preferred embodiment; and Figure 13 is a plan view of an alternate top wall for the third preferred 5 embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT FIRST PREFERRED EMBODIMENT With reference to Figures 1 to 3 there is shown a first preferred embodiment 10 of a filter assembly 10 for collecting floatable litter. The filter assembly 10 includes a substantially U-shaped channel section 11, an open ended mesh basket 12, and a removable lid 13. The channel section 11 has two opposed converging side walls 15, an end wall 16 positioned at the narrow end of the section 11 and a base wall 17. The end 15 wall 16 has an aperture 18 into which a storm water pipe 19 can be mounted. The aperture 18 has a diameter that is slightly larger than the diameter of the storm water pipe 19. The base wall 17 has externally projecting anti-erosion footings 20 to maintain the installed position of the filter assembly 10. The base wall 17 of the channel section 11 has two spaced apart internal recesses 21 for locating the open 20 ended basket 12. The recesses 21 are substantially V-shaped and assist in maintaining the position of the basket 12 during large flows. With particular reference to figure 2, the open ended basket 12 has two mesh sidewalls 25, 26, a mesh end wall 27 and a mesh floor 28. The open ended basket 12 has a mesh top wall 29 that extends across a portion of the top between the 25 sidewalls 25, 26 and adjacent the mesh end wall 27. The mesh walls 25, 26, 27, 28 and 29 have a 25 mm aperture size. The relative length of the top wall 29 may vary depending on the particular requirements of the filter assembly 10. The top wall 29 serves to retain the collected debris especially during large flows. The basket 12 also has a first or upstream mesh screen 30 extending from 30 the sidewall 26 and inclined upstream away from mesh end wall 27, The upstream screen 30 serves to direct flow and floatable debris into the basket 12. The end wall 27 and sidewall 25 serve as the second or downstream screen to collect floatable debris.

8 The floor 28 has two V-shaped ridges 31 complementary to and for locating within recesses 21. The upper portion of the frame 33 of the filter assembly has 4 fastening points in the form of a loop member 34 at each corner of the frame 33. The loop members 34 serve as lifting sites for lifting the basket 12 from the channel 5 section 11 for cleaning purposes. The basket 12 can be positioned in the channel section 11 so that the floor 28 lies on the channel base wall 17 and the sidewall 26 abuts the corresponding channel sidewall 15. When the basket 12 is located within the channel section 11, the position of the basket 12 allows the removable lid 13 to be fastened to the channel section 11 without the loop members 34 interfering with 10 the positioning of the lid 13. Consequently there is a gap between the upper portion of the frame 33 and the removable lid 13 which allows water to overflow the basket 12 when there is a large flow. With particular reference to figure 1, there is an alternative embodiment of the basket 12. Basket 12a is substantially L-shaped with an end wall 27a, side wall 25a 15 and top wall 29a. Basket 12a is fixed in position in the channel 11. Screen 30a is fixed to the channel sidewall 15 and serves as a baffle to direct the flow and floatable debris into the basket 12a. Basket 12a is manually cleaned out or a suction hose is placed into the basket 12a and floatable debris is sucked out. Basket 12a is not removed. 20 The removable lid 13 is fastenable to the top surface of channel sidewalls 15 by threaded bolts or key locks .40. The removable lid 13 also has a centrally located removable grate 41 which allows excess water from large flows to escape rather than be dammed within the channel section 11 and storm water pipe 19. The channel section 11, end wall 16 and removable lid 13 are constructed of 25 precast reinforced concrete whereas the basket 12 is made of stainless steel, The basket 12 can alternatively be made of galvanized steel or plastic. The assembled prefabricated filter assembly 10 forms a modular unit that can be installed on site. With reference to Figures 3, 4 and 5, the filter assembly 10 is installed as a storm water drain discharge outlet 43 discharging water into the waterways 44, 30 Storm water flowing along gutters 45 and through storm water pipes 19 is filtered for floatable debris before the water is discharged into the waterways 44. Water passes from the storm water pipe 19 and into the basket 12. The position of the basket 12 relative to the storm water pipe outlet 46 enables substantially all the water flow to 9 enter into the basket 12. Floatable debris carried with the storm water also enters the basket 12 and accumulates in the basket 12 unable to pass through the mesh end wall 27. The first or upstream screen 30 redirects water flow and flood water debris into the basket 12. Water in the basket 12 can be discharged through the 5 apertures in the mesh end wall 27 and sidewall 25. The discharged water then flows into the waterways 44. When there are larger flows accumulated water may overflow the basket 12 through the gap between the upper portion of the frame 33 and the removable lid 13. When there are very large flows, the accumulated water may escape through the grate 41. The basket 12 is located and retained within the 10 channel section 11 by the positioning of the V-shaped ridges 31 in the recesses 21 so that during large flows the basket 12 is not dislodged from its position. To clean the basket 12, the lid 13 is removed and basket 12 is holstered by its loop members 34 by crane 50 and tilted so that the floatable debris falls out through the open end of the basket 12 into a truck tray 51 for disposal. Figures 6 and 7 show 15 how the collected floatable debris is removed from the basket 12. SECOND PREFERRED EMBODIMENT With reference to Figure 8 and 9 there is shown a second preferred embodiment of a prefabricated filter assembly 110 for collecting floatable litter and 20 including a U-shaped channel section 111, end wall 112, first T-shaped screen 113, second L-shaped screen 114 and a top wall 115. The U-shaped channel section 111, end wall 112 and top wall 115 are constructed of precast reinforced concrete whereas the screens 113, 114 are made of stainless steel. The screens can alternatively be made of galvanized steel or 25 plastic. The prefabricated filter assembly 110 when assembled forms a modular unit that can be installed on site. The U-shaped channel section 111 has sidewalls 117, 118 that are substantially perpendicular with respect to the floor 119. The sidewalls 117, 118 are not parallel and the U shaped channel section forms a wedge shape with the end 30 wall 112 mounted suitably by bolting onto the narrow end of the channel section 111. The end wall 112 has an aperture 116 into which a stornwater pipe end (not shown) is fitted, The diameter of the aperture 116 is slightly larger than the diameter of the stormwater pipe to allow fitting and sealing of the stormwater pipe. End walls with 10 different sized apertures may be mounted to the U-shaped channel section. The choice of end wall will depend on the diameter of the stormwater pipe at the installation site. The open end 120 of the channel section 111 may include anchor points to which a boat may be tied or there may be a suitable landing extending from 5 the end 120. Screen 113 abuts sidewall 118 and extends partly across between the walls 117, 118. Screen 113 is T-shaped with leg portion 121 at substantially right angles to the direction of flow and an arm portion 122 substantially in line with the direction of flow. The arm portion 122 has an upstream portion 123 and a downstream portion 10 124. Screen 114 abuts wall 117 and extends partly towards wall 118. The screen 114 is L-shaped with a leg portion 125 at substantially right angles to the direction of flow and an upstream portion 126 extending upstream and substantially In line with the direction of flow. 15 The upstream portions 124, 126 serve to collect floatable litter washed downstream in the stormwater pipes. The downstream portion 124 serves to direct flow to the screen 114. Screens 113 and 114 have overlapping portions. The screens 113, 114 extend from the floor to the top of the sidewalls 117, 20 118. In an alternative embodiment the screens may be spaced from the floor to allow sediment and other particulate debris to pass. Each of screens 113, 114 have a 76mm handle (not shown) protruding from the top of the screen. The handles allow workers to lift the screens 113, 114 while the filter assembly 10 is being cleaned. 25 The screens 113, 114 have a mesh with a 25mm aperture. The width of both gates 127, 128 between the screen 113 and the wall 117 and between the screen 114 and the wall 118 respectively are approximately 300mm each. These widths are the same as the diameter of the stormwater pipe. The top wall 115 has slots 130, 131 through which the handles of screens 30 113, 114 respectively project. When the filter assembly 110 is cleaned, the screens 113, 114 are lifted through the slots 130, 131 respectively allowing the litter to be easily removed.

11 Stormwater enters channel section 111 through the stormwater pipe and flows to the screen 113. Litter is collected by screen 113 and the water and smaller sized debris pass through the mesh of screen 113. Some of the stormwater flow will pass through gate 127 and be directed to screen 114 by downstream portion 124. 5 Stormwater flow will also be directed through gate 127 when litter blocks the passage of water through screen 113. Screen 114 filters litter that has bypassed or overflowed from screen 113. Stormwater subsequently passes through the mesh of screen 114 or through gate 128 and is discharged to the waterway. Workers clean the filter assembly 110 by lifting screens 113, 114 through slots 10 130, 131 making the collected litter easily accessible for removal from the open end 120 of the filter assembly 110. Where the filter assembly 110 is installed adjacent a waterway, workers may approach the filter assembly from the waterway using a boat and tying up to a suitable anchor point. The workers may then alight from the boat, lift screens 113, 114 and rake out the collected litter. 15 THIRD PREFERRED EMBODIMENT With reference to Figures 10 to 13 there is shown a third embodiment of the fliter assembly 150. The filter assembly 150 has a U-shaped channel section 151. The U-shaped channel section 151 has non-parallel sidewalls 152, 153 and floor 20 154. The U-shaped channel section 151 is formed into a wedge with an end wall 155 bolted onto the narrow end of the U-shaped channel section 161. The end wall 155 has an aperture 156 into which fits a stormwater pipe. The filter assembly 150 includes L-shaped screens 157, 158 that extend from walls 152, 153 respectively. The screens 157, 158 have overlapping portions. The open end of the channel 25 section 151 discharges the stormwater. The filter assembly 151 has a top wall 160 which has slots 161, 162 through which screens 157, 158 can be lifted. Screens 157, 158 preferably have retractable handles to enable them to be easily lifted from the floor 154. Where there is only waterway access to the filter assembly 150, the ability to lift the screens 157, 158 provides a method of easily cleaning the filter 30 assembly 150. An alternate top wall 170 is shown in Figure 13 which has access ports 171, 172 to allow workers access to the litter collected by screens 157, 158 respectively.

12 The access ports 171, 172 provide top entry removal of collected litter. In this case a deducting truck can be used to clean the filter assembly 160. ADVANTAGES 5 An advantage of the filter assembly is that it is relatively cheap to manufacture and easy to install as a prefabricated unit or as a basket or screens in existing discharge outlets. Another advantage is that the collected litter is retained within the filter assembly and is not unsightly. A further advantage is that it satisfies current Work 10 Place and Safety requirements because the basket containing the collected litter is mechanically lifted and emptied rather than manually emptied. A further advantage of the filter assembly is that it dissipates flow energy thereby limiting the amount of erosion caused by the discharging flow from the filter assembly. 15 VARIATIONS It will of course be realised that while the foregoing has been given by way of illustrative example of this invention, all such and other modifications and variations thereto as would be apparent to persons skilled in the art are deemed to fall within 20 the broad scope and ambit of this invention as is herein set forth. Throughout the description and claims this specification the word "comprise" and variations of that word such as "comprises" and "comprising", are not intended to exclude other additives, components, integers or steps.

Claims (13)

1. A filter assembly for collecting floatable litter in a stormwater channel member with two side walls including s an upstream screen that extends across the channel member to form a gap between the upstream screen and one of said side walls, said upstream screen is positioned to direct flow, and a downstream mesh screen that extends across the channel member and overlaps the gap, said downstream screen is positioned relative to the 10 upstream screen to receive the flow and floatable debris directed from the upstream screen and passing through the gap. 2 A filter assembly as claimed in claim 1 wherein both screens are mesh screens. 15

3. A filter assembly as claimed in claim 1 and 2 wherein both screens extend from the same channel member side wall and the downstream screen extends across the channel member to a greater extend to the upstream screen. 20 4. A filter assembly as claimed in any one or the preceding claims wherein the downstream screen is a mesh screen substantially at right angles to the direction of the water flow.

5. A filter assembly as claimed in any one of the preceding claims wherein the 25 downstream screen is substantially L-shaped with an arm portion extending upstream and the upstream screen is inclined towards the storm water pipe so that a gap is formed between the free end of the upstream screen and the arm portion. 30 6. A filter assembly as claimed in any one of the preceding claims wherein the screens form an integral removable basket.

7. A filter assembly as claimed in claim 1 including 13ca a channel member having a base wall, an end wall with an aperture for the positioning of a pipe, opposing sidewalls and a removable top wall; 14 an upstream screen that extends across the channel base wall and positioned to direct flow, and a downstream screen that extends across the channel base wall and arranged to receive the directed flow and collect floatable debris. 5 B. A filter assembly as claimed in claim 7 wherein the downstream screen is a mesh screen.

9. A filter assembly as claimed in claim 8 wherein both screens are mesh 10 screens.

10. A filter assembly as claimed in any one of claims 7, 8 or 9 wherein both screens extend from the same channel member side wall and the downstream screen extends across the channel member to a greater extend 15 than the upstream screen, both of said screens or only the downstream screen has a mesh wall.

11. A filter assembly as claimed in any one of claims 7 to 10 wherein the downstream screen is substantially L-shaped with an arm portion extending 20 upstream and the upstream screen is inclined towards the storm water pipe so that a gap is formed between the free end of the upstream screen and the arm portion.

12. A filter assembly as claimed in any one of claims 7 to 11 wherein the screens 25 form an integral removable basket,

13. A filter assembly as claimed in any one of claims 7 to 12 wherein opposing chamber member side walls diverge as they extend towards the open end of the chamber member. 30

14. A filter assembly as claimed in any one of claims 7 to 13 wherein there is a gap formed between the top of the downstream screen and the removable top wall for allowing excess water to flow over the downstream screen, 15

15. A filter assembly as claimed in any one of claims 7 to 14 wherein the removable top wall has a grate for discharging water during large flows.

16. A filter assembly as claimed in any one of claims 7 to 15 wherein the 6 downstream screen has a mesh top wall for preventing escape of floatable debris.

17. A filter assembly as substantially described herein with reference to and as illustrated by the accompanying drawings. 10