WO1999054564A1

WO1999054564A1 - Rapid storm water filtration

Info

Publication number: WO1999054564A1
Application number: PCT/AU1999/000295
Authority: WO
Inventors: Scott Wade Roy
Original assignee: Ecosol Pty. Ltd.
Priority date: 1998-04-20
Filing date: 1999-04-20
Publication date: 1999-10-28

Abstract

This invention relates to a gross pollution filter apparatus for use in a water drainage system and in particular to a filter for capturing gross pollution along or at a termination point of a storm water drainage system which has an inlet and an outlet lower than the inlet which coincide with the level of the flow grade of an existing pipe. The filter apparatus is arranged to direct incoming water and gross pollution into a holding chamber which is located below the level of the inlet and an outlet from the holding chamber is located between the level of the inlet and outlet and covered by a filter mesh so that water can flow out the holding chamber outlet through the filter mesh and towards the outlet of the filter apparatus and in doing so creating a water barrier between the inlet and the outlet which encourages the incoming water and gross pollution to flow into the holding chamber but when the holding chamber is full the water barrier ceases and the water and gross pollution flow via a by-pass channel(s) to the outlet.

Description

"RAPID STORM WATER FILTRATION"

This invention relates to a gross pollution filter apparatus for use in a water drainage system and in particular to a filter for capturing gross pollution along or at a termination point of a storm water drainage system.

BACKGROUND

Water quality degradation is a problem of growing proportions. One measure of water quality is the amount of gross pollution that is carried from our roads and streets into our storm water system and eventually into the reservoirs that we rely on for potable water. Our rivers, lakes, dams and ultimately the ocean are becoming the repository for gross pollution which readily enters the catchment system and lowers the quality of these very important water sources.

Gross pollution comprises 90% organic matter like branches, twigs, leaves, and soil, the remainder being non-organic matter like plastic containers, bags, wrappers; paper; cans; and cigarette butts.

In one example of a storm water drainage system, storm water and gross pollution collected from road surfaces and household roofs ends up in the underground storm water drainage system. Ground level storm water entry points along the road surfaces called gully traps, allow a variety of various sizes of gross pollution into the storm water drainage system. Typical drainage systems comprise underground pipes and sometimes exposed water conduits, which are used to carry storm water to holding reservoirs, rivers and ocean outflows. Gross pollution is likely to accumulate in large quantities at the outflows of drainage systems and concern about the environmental impact of high concentrations of this gross pollution is justified.

Filtering of storm water using current techniques is a costly and time consuming undertaking and it is not unusual for water authorities to prefer to address the problem by cleaning up the very visible consequences of gross pollution which emits from the drainage system rather than actually reducing the contamination of the storm water system at its source or along the path to the point of outflow. Sometimes gross pollution or filtering is undertaken at intermediate points along the drainage system but the typical approach is to install end of line grates which tend to quickly foul up and require constant maintenance and it is well known that grates do not capture oil and oil like contaminates.

Similar considerations also apply to the treatment of polluted industrial water.

Some of the less than desirable features of prior and current storm water and gross pollution filters include:

• use of metal elements which require anti-rusting treatment or the alternative use of expensive stainless steel elements

• moving parts which require maintenance and periodic replacement, which are liable to jam, corrode and require frequent cleaning to maintain their efficiency

• use of large areas adjacent the existing drainage system for providing settling reservoirs which are sometimes many times wider than the drains and conduits with which they are associated

• high hydraulic head loss between the inlet and outlet resulting in low filter efficiency at low and high flow rates and great disruption to the drainage layout providing unwanted restrictions and prohibitions to the retro-fitting of such filters to existing drainage systems • small time intervals between pollution collection are required when many small gross pollution filters are incorporated into the drainage system, in addition to which the existing shapes of gross pollutant collection containers are often difficult to access, empty and clean

• in-line grate type filters for different types of pollutants require relatively large areas compared with the areas already occupied by the storm water drains so that they can handle the some time large volumes of water and gross pollutants. Large grates often require the manufacture of unique elements at greater cost than desirable

• different efficiency at different flow rates, and often the poorest efficiency occurs at both low and high flow rates which are more common than intermediate flow rate conditions

• blockages caused particularly by sediment build up at the inlet and outlet of the filter apparatus create unwanted head loss

• the accumulation of certain types of pollutants can be a health hazard

• cause unnecessary use of overflow routes which by-pass the filter apparatus

• prior arrangements also include apertured and solid weirs which induce a back pressure along the incoming storm water pipe during and certainly after the filter arrangement becomes inefficient and unable to adequately filter the flow of incoming storm water carrying gross pollutants.

These and other problems are reduced or eliminated by the invention disclosed herein.

BRIEF DESCRIPTION OF THE INVENTION

In its broadest form a gross pollution filter apparatus for use in water drainage systems carrying water and gross pollution comprising an inlet, an outlet lower than said inlet, a water filter means in fluid communications with said inlet and having a holding chamber located below the level of said inlet for retaining a portion of the gross pollution and having a water filter means outlet covered by a filter element for passing water and restraining the passage through the filter element of gross pollution, said water filter means outlet being located between the level of said inlet and said outlet arranged so that filtered water flowing out the water filter means outlet creates a water barrier to the flow of water and gross pollution between said inlet and said outlet.

In a further aspect of the invention the water barrier subsides when the flow of water through the filter means decreases such that water and gross pollution passes more easily from the inlet to the outlet via one or more by-pass channels than from the inlet into the water filter means.

In a further aspect of a gross pollution filter wherein the filter apparatus is located in the existing line and flow grade of a pipe system such that the inlet and outlet lie along the existing flow grade.

In a yet further aspect of a gross pollution filter apparatus one or more of the filter elements are removable for replacement, cleaning or access to the holding chamber.

In an aspect of a gross pollution filter apparatus there is a siphon providing water communications between said holding chamber and the exterior of said apparatus for siphoning water from said holding chamber.

In a further aspect of the invention a gross pollution filter apparatus has a removable cover, so as to allow when removed, access to the water filter means and said holding chamber for cleaning and maintenance. Embodiments of the invention will now be described in some further detail with reference to and as illustrated in the accompanying figures. These embodiments are illustrative and not meant to be restrictive of the scope of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 depicts a side view of an embodiment of an in-line filter apparatus of the invention in place along a drainage system pipe;

Fig. 2 depicts a top perspective view of the filter apparatus of Fig. 1;

Fig. 3 depicts a perspective end view of a partial breakaway of the filter apparatus of Fig. 1;

Fig. 4 depicts a longitudinal section view of the filter apparatus of Fig. 1.; and

Fig. 5 depicts an external perspective view of the filter apparatus of Fig. 1.

DETAILED DESCRIPTION OF AN EMBODIMENT OF THE INVENTION

The gross pollution filter apparatus 10 of this embodiment is located along a storm water pipework 12 and is arranged to interpose a filter assembly 20 in the flow 16 of storm water flowing along the pipework which may be entrained with gross pollutants to trap and retain the gross pollutants in the chamber 21 and allow water to flow between its inlet 14 and outlet 22.

Like numerals are used to identify like elements in the embodiment of the invention depicted in Figs. 1-5.

The filter apparatus will continue to intercept gross pollutants until it becomes totally blocked at which time it is arranged to allow the flow of water and its entrained gross pollutants between its inlet 14 and outlet 22. The inlet 14 of the filter apparatus accommodates a storm water pipe 12 from which water and gross pollutants 16 flow into the filter apparatus and over an inlet area 18 which has a slight slope toward a water filter assembly 20 having an inlet 19. The slope of the inlet area is the same as the existing slope of the storm water pipe and the same as the paths 24 and 26 (Fig. 2) to the outlet 22 taken by water and gross pollutants when the filter apparatus is in a by-pass condition caused when the filter assembly 20 becomes blocked.

Incoming water and gross pollutants are arranged to initially follow a straight path over the inlet area 18 and into a inlet 19 of the embodiment of a filter assembly 20 depicted in Figs. 1-5. The upper entrance region of the filter assembly 20 is formed by upright walls 7 and 9 which rise above the level of the inlet area and are capped by horizontal wall 11 which lies coincident with the plane of the top of the filter assembly 20. The walls extend over a relatively small portion of a chamber 21 all of which is located below the level of the inlet. A solid end wall 28 forms a barrier to the exit of filtered water from the filter assembly 20 forcing the water to exit via the filter element 36 which is located above the level of the existing slope of the storm water pipe.

Incoming water and gross pollutants 16 are shown as flow path 27 in Fig. 1 entering the water filter assembly 20. The water filter assembly 20 is located so as to receive the direct flow of water and gross pollutants from the storm water pipework and in this embodiment the chamber 21 and the filter element 36 are elongate.

The elongate chamber 21 is preferably formed by a pair of longitudinal substantially vertical walls 23 and 25 (Fig. 2) which may be extended upwards to form a structure above the level of the pipe 12. The elongate chamber 21 also comprises a front lateral substantially vertical wall 32 as well as a rear lateral substantially vertical wall 34 and all of the walls are constructed preferably of water impervious material such as concrete. 7

The chamber 21 is the volume within which the gross pollutants collect and from which they can be emptied on a regular or as needs basis. The size of the chamber volume will thus impact on how often it needs to be emptied so as to maintain preferable gross pollution capture characteristics.

The water filter 20 depicted in Figures 1 to 5 is merely a preferable shape and is sized to accommodate a predetermined amount of trapped gross pollutants. The exact quantity deemed sufficient to be stored in the chamber may depend on the desired frequency for emptying the filter as well as the amount of gross pollutants which are likely to be entrained in the storm water carried by a particular storm water pipe system flowing into the gross pollution filter apparatus 10.

The shape of the filter assembly is only preferably elongate and rectangular since such a shape conveniently fits along a portion of the path of existing storm water pipes. However, it would be possible to use other shapes such as for example cylindrical or square. Furthermore, it would also be possible to offset any of these shapes from the existing line of the storm water pipe.

The water filter element 36 preferably a mesh positioned so as to extend above and along the level of the bottom of the existing storm water pipe. The filter element is preferably trapezoidal in shape and sits over the chamber 21 but its shape could also be other shapes for example, semi-circular or rectangular. The height of the filter element is chosen to be a proportion of the height of the storm water pipe since the height of the designed flow capacity of the storm water pipe should preferably be accounted for, since that will be the likely maximum height to which water and gross pollutants will be carried in worst case flow conditions. The material most suitable for the filter element is stainless steel mesh or alternatively may be galvanised mesh having aperture sizes suitable for restricting the passage of a predetermined size of gross pollutant. The filter element is preferably arranged to 8

have movable (not shown) access panels so as to provide access for cleaning and any maintenance required.

The water filter arrangement 20 becomes a repository for retained gross pollution and should be a depth suitable for being emptied with the available means to clean gross pollutants from that depth. For example, vacuum equipment will have an optimum depth at which it will work. Having determined the required volume of the filter arrangement the depth of the chamber, the height of the water filter element and the protective cover assembly configuration the optimum depth can be calculated. The maximum volume of collected gross pollutants will be determined by the volume of the chamber 21 and filter element 36 as well as by the desired flow capacity of the apertures of the filter elements which need to allow the various flow levels to be impeded to the least degree. Small apertures in the filter elements will require longer or greater areas of filter element to ensure adequate flow of filtered water even though some proportion of the apertures will be blocked by gross pollution.

The shape of the overall filter arrangement of this embodiment is rectangular, however, it could be tapered in width from the filter assembly inlet to the rear wall. Alternatively the water filter arrangement and in particular the holding chamber could be cylindrical or it could comprise a number of cells one adjacent the other. It could also be in line of the incoming storm water pipe and the outlet of the filter arrangement could be off-line of the incoming storm water pipe but connected via another pipe to the existing line.

It has been found that the majority of the entrained gross pollution collects in the holding chamber near and below the water filter inlet. Floating or buoyant gross pollution will eventually become rotted or water logged and sink to the bottom of the holding chamber along its length. The filter apparatus of this embodiment will not filter oil and other lighter than water fluids to any significant degree. Filtered water passes from the holding chamber through the filter element 36 and onto the adjacent channels 24 and 26 (Fig. 2) and thence to the filter apparatus outlet 22.

The channels 24 and 26 are of sufficient volume to accommodate the maximum incoming flow rate and in a preferred embodiment are each half the inner diameter of the incoming storm water pipe and have a height at least that again so that when the water filter assembly is blocked the maximum anticipated flow volume of the storm water pipe can be accommodated with minimal head loss and flow rate restriction through the by-pass channels 24 and 26.

Outflow from the filter assembly 20 into the by-pass channels 24 and 26 is depicted by flow arrows 46 and 48 which are merely pictorial representations of the flow path of filtered water once the chamber 21 fills with water and which then exits the filter assembly through the water filter element 36 to eventually flow through outlet 22.

The water filter assembly outlet is thus located all along the length of the lower level of the filter element 36 (on both sides in this embodiment) which lies between the inlet 14 and the outlet 22 of the filter apparatus 10, the outlet 22 being lower than both the water filter outlet and the inlet 14.

As is more clearly depicted in Fig. 2, the filtered water exiting the water filter outlet takes a number of paths to the filter assembly outlet 22. The paths 46 and 48 being the most direct. The inlet and outlet flow also encourages a circular flow path 56 in the vicinity of the inlet area 18, as is pictorially depicted in Fig. 2. This water flow pattern creates a barrier of filtered water to the flow of unfiltered water from the storm water pipe 12 flowing into the by-pass paths 24 and 26 of the filter apparatus 10. 10

Furthermore, the walls and the boundary walls 60, 62, 64 and 66 also preferably contribute to the formation of a circular flow pattern in the filtered water exiting the water filter outlet. Walls 64 and 66 are preferably set at 45° to the storm water pipe 16 as this seems to minimise a potentially low flow area of water movement within the filter apparatus 10 adjacent the storm water inlet 14. Furthermore, the pressure of the flow of storm water 16 entering the filter apparatus 10 via the inlet 14 acts beyond the end of the inlet area encouraging the flow path 56 and consequently the flows 46 and 48 to flow towards the outlet 22. While the circular flow path 56 exists the majority of gross pollutants entrained in the incoming flow are directed into the water filter assembly 20 and once the filter arrangement becomes full of gross pollutants the circular flow path 56 ceases and water and gross pollution flows directly between the inlet and the outlet.

It is preferable for the flow capacity of the filter apparatus outlet 22 to be equal to or greater than the maximum flow capacity of the inlet 12 and a smooth transition of the filtered water can preferably be assisted by providing a tapered pre-outlet region (not shown) filtered water flowing from the channels 24 and 26 into the outlet 22.

Fig. 2 more clearly depicts preferable flow paths and also clearly shows the dual purpose of water barrier flow 56.

The created water barrier flow 56 intercepts and directs the majority of initial and continuing flow 16 of incoming water and gross pollution into the filter means 20 through its inlet 19. Water barrier flow 56 also prevents filtered water which exits from the water filter outlet mixing immediately with incoming water and pollutants. It is preferable for the width of the channel between the end of the inlet 19 and the nearest wall 64 combined with the height of the channel between the inlet 14 and the channel 24 to be equal to or greater than the maximum flow volume of the inlet 14 so 11

that in a full by-pass condition the fact that the filter means is full, the filter apparatus does not create an impassable blockage in the storm water system.

Fig. 2 also depicts the original storm water pipeline 12-12 as being merely interposed by the filter assembly 10 without requiring realignment of the original pipeline path either in direction or grade. This allows for retro-fitting of a filter arrangement of the invention into an existing pipe system. However, filter arrangements may be fully or partially offset from the original pipeline path.

Flow within the filter means can be vigorous and turbulent during high flow rates and most all of the gross pollution will be entrained within the filter means 20. However, smaller particles, suspended particles and of course dissolved pollutants move through the filter element 36 depicted in Fig. 2. The flow paths associated with filter element 36 are shown as arrows 46 and 48 into channels 24 and 26 respectively which eventually flow to the outlet 22.

Channels 24 and 26 are the water communication paths of the filter assembly adjacent the water filter element 36 and lead towards the filter outlet 22.

As described previously the width of each of the two by-pass channels in combination with their heights are preferably capable of each sustaining at least half the flow volume equal to the maximum flow volume entering the input 14 so as to ensure that by-pass water and gross pollution has niinimum resistance to flow towards the filter outlet 22 and thus minimises the head loss effect of having a filter apparatus in the drainage system.

A siphon tube 68 (Fig. 3) is an optional element of the filter arrangement of the invention. Siphoning is sometimes required to remove still water from the filter means which could otherwise become a breeding area for mosquitos and other 12

insects, as well as an unwanted repository of decaying matter which could become a health hazard.

In high flow rate circumstances the majority of incoming water and pollutants are restrained and retained by the filter means 20 and filtered water exits the filter assembly outlet leaving the filter apparatus through its outlet 22. The water barrier created during this high flow circumstance assists in keeping the incoming water with its entrained gross pollution separate from the outgoing filtered water.

However, it has been found that in low flow rate situations the water barrier is equally effective.

The hydraulic head loss of the filter arrangement in both high and low flow rates conditions is very similar, caused in the most part by the small head loss created by the additional turbulence created in actually filtering the storm water.

The most benefit of the filter arrangement of the invention occurs when the filter means becomes clogged with gross pollutants. As the resistance of water flowing through the filter member becomes greater its consequence is to reduce the effectiveness of the water barrier and thus make it easier for incoming water and pollutants to flow directly to the outlet from the inlet, and as discussed previously, when water and gross pollution take the by-pass path there is little or no head loss during this filter by-pass operation.

This characteristic is in stark contrast to other filter arrangements for example weirs, which when they become blocked require the incoming water to overflow the blocked weir causing maximum head loss during the overflow condition and which also encourages gross pollution to back up into the source storm water system. This high head loss situation then remains until the weir is cleared of gross pollution. 13

Clearly, the filter arrangement of the invention avoids this and ensures that during by-pass conditions the flow properties of the storm water system are not degraded in any substantial way.

The embodiment of the filter arrangement of the invention disclosed in this specification is also arranged to minimise areas of dead water, but other variations of the embodiment may also exist to achieve the aims of the invention while also being able to nτinimise dead water regions.

In this embodiment of the filter arrangement there is a distributed filter assembly outlet located so as to create a water barrier but one or more filter assembly outlets could be arranged to maximise the amount and location of filtered water to create the water barrier described.

The materials used to construct the embodiment of the filter apparatus and arrangement of this invention are primarily concrete and perforated stainless steel sheeting. However, different applications such as in chemical factories may require use of lighter materials such as plastics and aluminium or those types of material which may have special characteristics for use with certain chemicals.

Perforated stainless steel sheets are the preferred filter element material since they may be easily cut to size and are readily replaceable. Furthermore, a variety of standard perforated stainless steel sheets having not only a variety of sizes but a variety of aperture sizes are readily available thus making the choice of aperture size a matter of what minimum size of pollutants is to be filtered, while ensuring that the total aperture volume provided in all of the sheets is great enough to accommodate the anticipated flow rates of the pipe work along or at the end of which the filter apparatus is installed. 14

It is preferable that there be a smooth transition between the storm water pipe 12 into the filter apparatus 10 at its inlet 14 and also at the outlet 22. Likewise it is preferable for there to be a smooth transition from the filter means outlet to the path/s 24 and 26 which lie between the inlet 14 and the outlet 22 of the filter apparatus.

It is also preferable for all of the upper external surface of the filter apparatus to be capped with one or more removable covers. This provides for safety and allows for access to the filter assembly for cleaning and maintenance.

It will be noted that the overflow condition provides a flow path which is self cleaning and is the same grade as the existing storm water pipe work, therefore ensuring no build-up at either the entrance or the exit of the filter apparatus of gross pollutants and a maintenance of hydraulic flow characteristics of the existing water pipe system.

It will be appreciated by those skilled in the art, that the invention is not restricted in its use to the particular application described, nor is it restricted to the feature of the preferred embodiment described herein. It will be appreciated that various modifications can be made without departing from the principles of the invention, therefore, the invention should be understood to include all such modifications within its scope.

Claims

15THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS:

1. A gross pollution filter apparatus for use in water drainage systems carrying water and gross pollution comprising: an inlet, an outlet lower than said inlet, a water filter means in fluid communications with said inlet and having a holding chamber located below the level of said inlet for retaining a portion of the gross pollution and having a water filter means outlet covered by a filter element for passing water and restraining the passage through the filter element of gross pollution, said water filter means outlet being located between the level of said inlet and said outlet arranged so that filtered water flowing out the water filter means outlet creates a water barrier to the flow of water and gross pollution between said inlet and said outlet.

2. A gross pollution filter apparatus according to claim 1 wherein said water barrier subsides when the flow of water through said filter means decreases such that water and gross pollution passes more easily from said inlet to said outlet via one or more by-pass channels than from said inlet into said water filter means.

3. A gross pollution filter apparatus according to claim 1 wherein said filter apparatus is located in the existing line and flow grade of a pipe system such that said inlet and said outlet lie along said existing flow grade.

4. A gross pollution filter apparatus according to claim 1 wherein said filter element comprises one or more removable filter elements which are removable for replacement, cleaning or access to said holding chamber.

5. A gross pollution filter apparatus according to claim 1 further comprising a siphon providing water communications between said holding chamber and the 16

exterior of said gross pollution filter apparatus for siphoning water from said holding chamber.

6. A gross pollution filter apparatus according to claim 1 wherein said gross pollution filter apparatus has a removable cover, so as to allow when removed, access to said water filter means and said holding chamber for cleaning and maintenance.

7. A gross pollution filter apparatus according to claim 1 wherein said one or more by-pass channels together have a maximum flow volume of at least the maximum flow volume of said inlet.

8. A gross pollution filter apparatus according to claim 1 wherein said filter element comprises a grill or mesh.

9. A gross pollution filter apparatus according to claim 8 wherein said filter element is of stainless steel.

10. A gross pollution filter apparatus according to claim 1 wherein said filter element is located above said water filter means outlet and begins at the same level and at the same position as said water filter outlet.

11. A gross pollution filter apparatus according to claim 10 wherein said filter element has a semi-circular cross-sectional shape spaning said holding chamber.

12. A gross pollution filter apparatus according to claim 1 wherein said holding chamber is elongate and constructed of water impervious material.

13. A gross pollution filter apparatus according to claim 1 wherein said flow paths are adapted so as to minimise dead flow areas.