AU724337B2 - A filter assembly - Google Patents

Description

1 "A FILTER ASSEMBLY" This invention relates to a filter assembly.

This invention has particular application to filter assemblies for stormwater drains and the like for filtering runoff water prior to discharge. However this invention is not limited to such application and may be used as an inline process filter which is particularly suitable for variable rate liquid flows. However for illustrative purposes only, the present invention will be described hereinafter in relation to its use with stormwater drains.

Stormwater drains typically discharge directly into streams and the like and carry large amounts of debris and other contaminating matter into the streams. In recent years there has been a growing awareness of the need to minimise pollution resulting from stormwater runoff.

One of the difficulties associated with the outlet from .stormwater drains is that the contaminants can range from :i relatively large lightweight objects such as aluminium drink cans and plastic bags as well as liquid contaminants such as 20 oils and greases improperly discharged into the stormwater drains. In addition stormwater drains gather poisons and other chemicals which have been applied to lawns and plants as well as to buildings and machinery and particles from industrial processes.

S 25 Another difficulty associated with stormwater runoff is that the runoff may range from a trickle to a raging torrent and any apparatus placed in line in the stormwater drain must be capable of handling the full range of flows if it is to be effective. Some local authorities have made attempts to filter stormwater runoff by placing a mesh fence across streams downstream of a stormwater discharge. These are suitable for catching relatively large articles only and require frequent clearing. In addition such filters represent a hazard in small creeks and the like as during periods of flooding they snare persons who may be unaware of their presence.

This invention aims to alleviate at least one of the above disadvantages and to provide apparatus for and a methods of filtering variable rate liquid flows.

With the foregoing in view, this invention in one aspect resides broadly in a filter assembly including:a housing; a plurality of filtering elements in the housing; inlet means to the housing from which liquid may pass to the filtering elements; 20 outlet means from the housing through which filtered liquid may be discharge from the housing, and the filtering elements being arranged to filter different liquid flows through the inlet means.

The different flow paths from the inlet preferably S 25 result from different inlet flow characteristics which may be velocity, volume or viscosity dependent characteristics for 3 example. Alternatively, the filter assembly may include active control means which are actuated to direct incoming fluid along different flow paths.

The active control means may be externally controlled by electronic control means, for example, or the active control means may be moved by control devices from an inactive position to an active blanking position for blanking lower velocity flows from certain parts of the filter assembly when the inlet flow velocity, volume or level reaches a predetermined amount. Suitably such control devices, which utilise the flow for actuating the flow control means are biased to an inactive position to which they return when the flow volume, velocity or level reduces.

The filter assembly may be flow volume dependent and may include S separate flow passages through which different flow volumes will preferentially *i a pass. The'flow passages may be separated vertically or longitudinally such that all low flow volumes will pass through the lowest orfirst flow passage while the maximum volume flow will pass through an elevated flow passage or a flow passage downstream from the low flow passage.

In a preferred embodiment the filter assembly includes a housing having opposed side wall portions; an inlet to the housing in one of said opposed sidewall portions; a first outlet in the other of said side wall portions; oo:o 20 a primary filter extending between the underside portions of the inlet and the first outlet; a filter chamber in said housing below said primary filter wherein said primary filter filters water entering the filter chamber and passes full water flows to the first outlet.

4 In a preferred form of the invention the inlet means is an inlet aperture formed opposite a main outlet aperture from the housing and at a position elevated above the main outlet aperture such that high velocity/volume liquid flow to the inlet means has a flow trajectory across the housing towards e a *a o the main outlet for direct discharge of a substantial portion of the incoming liquid through the outlet aperture, whereas a low velocity/volume liquid flow to the inlet will pass through a respective one or ones of the filter elements adapted to filter such flows.

In one embodiment, the flow may range from a trickle through the inlet means, wherein the flow passes through a primary filter, a secondary filter and a tertiary filter prior to being discharged from the housing through a plurality of outlet apertures constituting the outlet means, whereas a medium flow will pass only from the inlet means along a different path through the primary and secondary filters, whereas full flow through the inlet will pass substantially unimpeded through the filter assembly.

In a preferred embodiment of the invention the primary filter is a relatively coarse filter which extends between the underside portions of the inlet and outlet such that water flowing therebetween but not passing directly through *the outlet aperture can pass through the primary filter for discharge or for passage to the secondary filter. Suitably the primary filter is a bar type filter with closely spaced bars extending between the opposed walls of the housing •beneath the apertures therein forming the inlet and main outlet apertures.

Part of the primary filter may be shielded to prevent passage of liquid therethrough. The shielded portion may be adjacent the inlet to prevent trickle flow falling directly from the inlet into the housing beneath the primary filter or the shielded portion may be adjacent the main outlet aperture to deflect high velocity flow through the main outlet. In a preferred form the main outlet aperture is larger than the inlet aperture.

Suitably the primary filter is a bar type filter which provides substantially unimpeded progress of contaminants such as soft drink cans or the like across the housing to the outlet while permitting smaller sized contaminants to pass between the bars to the secondary filter. The secondary filter may also include a bar type filter for separating relatively large solids from the liquid and there may be provided a secondary outlet aperture through which those solids may be discharged from the housing. The secondary S" filter may also include an active or fine filter adapted for filtering further contaminants which may be included in liquid which passes through the bar type filter element of the secondary filter.

The tertiary filter is suitably disposed directly Sbeneath the inlet and may entrap silt and the like which may act as a filter for further liquid trickling through the Sfilter assembly. Suitably the outlet from the tertiary filter is fed to the secondary filter for discharge through 25 the secondary outlet aperture.

In a further aspect this invention resides in a method 6 of filtering variable rate liquid flows including:providing a catchment having a common liquid flow inlet and flow dependent paths therethrough, and arranging respective filter means in the catchment to intercept flows passing along selected ones of the flow dependent paths. Preferably the catchment means is a filter assembly as herein defined.

A method of filtering liquid flows including providing a filter assembly as claimed in any one of the preceding claims to receive flows through a common inlet; separating different flows depending on their flow characteristics; :.:,*filtering different flows; and discharging liquid from the outlets.

In order that this invention may be more readily understood and put into se: practical effect, reference will now be made to the accompanying drawings which S 15 illustrate a typical embodiment of the invention and wherein:- Fig.1 is a top perspective view of the filter assembly; F 2ie S" Fig. 2 is a side cross-sectional view of the filter assembly of Fig. 1; i'°o.o Fig. 3 is a transverse cross-sectional view of the filter assembly of Fig. 1; S• Fig. 4 is a perspective view of the lid for the filter assembly of Fig.1 and Fig. 5 collectively illustrates the primary, secondary and tertiary filters; Figs. 6 and 7 illustrate alternate discharge collectors for the filter assembly of Fig. 1.

The filter assembly 10 illustrated in Fig. 1 includes a concrete housing 11 which expands downstream from an inlet wall 12 to the outlet wall 13. The i 7 housing may be in the order of 2.4 metres long, 1.8 metres wide and between 1.2 and 1.5 metres deep. The inlet wall is provided with a circular inlet aperture 14 in the order of 450mm diameter whereas the outlet aperture is larger and is in the order of 600mm wide by 500mm deep. A primary filter 16 extends between the walls 12 and 13 beneath the inlet and outlet apertures and is formed as a bar type filter with bars extending longitudinally as illustrated with relatively wide spacings therebetween, in the order of 25mm. Rubbish such as drink containers will be supported by the primary filter and pass therealong through to the main outlet aperture 15 through which they will be discharged either by gravitational flow along 10 the inclined primary filter or with water flow during a rainy period. The end portion o-_ of the primary filter adjacent the main outlet aperture 15 is closed to provide a deflector 18 for deflecting water flows impinging thereon through the main outlet aperture A curved ridged portion 20 extends along the base 21 of the housing 15 directly beneath the primary filter 16. The filter assembly may include a secondary Coc.

filter in the form of a relatively fine wedgewire filter of the type used in the manufacture of bore screens and the like. This filter extends the full length of the housing such that water passing through the primary filter will then pass through the secondary filter onto the bridge portion where it will be separated by the curved ridge and directed to a respective one of the opposite sides of the housing.

Any solid matter too large to pass through the secondary filter will pass along that filter to the elongate outlets which extend across the end wall beneath the main outlet. Suitably the wedge wires are aligned parallel to the bars of the D primary filter to facilitate passage of solid material thereacross to the outlets.

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8 Further active filters which are preferably in the form of removable mat type filters 26 are supported on the outer base wall portions 25 of the housing extending along either side of the ridge portion 20 and through which the liquid can flow for final discharge through the side outlets 27. The removable filter mats may be aerated nylon or similar filter material which is removable and washable. The filter may also include an active ingredient for filtering chemicals such a activated carbon. The secondary and primary filters may be associated with shielding means which shields them from any flow which is sufficient to dislodge the filtered waste therefrom to the outlet. The shielding means may be provided with active externally controlled operating means or may be moved a non-shielding position to an shielding when an inlet flow characteristic reaches a predetermined level.

A tertiary filter 30 is located in the base of the housing directly beneath the inlet 14. The tertiary filter includes a front dividing wall 31 which is also formed of a wedgewire material with an spacing between wires of up to 1 mm. The tertiary 15 filter receives any trickle flow passing go* ooo9 o**o a 4 through the inlet 14. Such flow often contains large amounts of silt and other solids material which will be retained behind the filter wall 31. The silt retained therein will itself act as a filter for incoming flows through the inlet 14.

The main outlet aperture 15 discharges through a flexible shield filter 35 which may be in the form of hanging chains which is adapted to impede the progress of solid materials passing through the outlet 15 such that they are caused to fall downwardly into the rubbish collector which may be in the form of an open wire bin 38 as illustrated in Fig. 6 or in the form of an open tray 39 as illustrated in Fig. 7 which has a side wall 40 formed as a ramp along which bobcat or the like vehicle may be driven to clear out the .9 99 S 15 rubbish collected in the collector 39. The open wire bin may be provided with lifting hooks or the like to enable it to be emptied into the back of a truck or discharge at an appropriate location as desired.

9 In use, trickle flows through the inlet 14 will pass to the tertiary filter 30 whereby silt and the like material will be retained. The liquid will pass through the wedgewire wall 31 to the filter mats 26 for further filtering before .9 discharge through the outlets 27. If the flow through the inlet is somewhat greater, the water will bypass the tertiary filter 30 and will pass through the primary filter direct to the secondary filter for treatment as described above.

For full flow conditions, such as during a storm flow or the like, the water flow through the inlet will be at such a velocity that it will carry substantially fully across the primary filter to the main outlet aperture 15 or to the deflector 18 for deflection through the main outlet aperture 15 whereby it will bypass the filters and be discharged directly through the outlet The flexible shield filter 35 will act to deflect some of the large solid rubbish into the rubbish collector although in such conditions much of the rubbish will be discharged directly without impedance of the flow. This will facilitate prevention of a back pressure buildup in the stormwater drains which may result in local flooding at the *inlets to the stormwater drains if the stormwater can not by drained away quickly.

S• 15 It will of course be realised that the above has been given only by way of illustrative example of the invention and that all such modifications and variations thereto as would be apparent to persons skilled in the art are deemed to fall within the broad scope and ambit of the invention as is 20 defined in the appended claims.

Claims (16)

1. A filter assembly including: a housing having opposed side wall portions; an inlet to the housing in one of said opposed sidewall portions; a first outlet in the other of said side wall portions; a primary filter extending between the underside portions of the inlet and first outlet; a filter chamber in said housing below said primary filter wherein said primary filter filters water entering the filter chamber and passes full water flows to the first outlet. a 0

2. A filter assembly as claimed in claim 1, wherein the primary filter prevents •V passage of relatively large solid debris into the filter chamber.

3. A filter assembly as claimed in claims 1 or 2, wherein the inlet has an inlet aperture formed opposite a first outlet aperture and at a position elevated above the Sfirst outlet aperture. q

4. A filter assembly as claimed in claim 3, wherein the primary filter is a relatively coarse filter.

A filter assembly as claimed in any one of claims 2 to 4, wherein the primary filter is a bar type filter with closely spaced bars extending between the opposed walls of the housing and having shielding means thereon to deflect high velocity flow through the outlet.

6. A filter assembly as claimed in any one of claims 3 or 4, wherein the first outlet aperture is larger than the inlet aperture. c- c.!k 12

7. A filter assembly as claimed in any one of the preceding claims, wherein there is a secondary filter located below the primary filter.

8. A filter assembly as claimed in any one of the preceding claims, wherein a tertiary filter is located at the base of the housing and includes a front dividing wall.

9. A filter assembly as claimed in claim 8 wherein the front dividing wall extends between opposing side walls.

A filter assembly as claimed in any one of the preceding claims wherein there are removable mat type filters locatable on a housing base wall.

11. A filter assembly as claimed in claim 10 wherein the mat type filters include an active ingredient for filtering chemicals such as activated carbon.

12. A filter assembly as claimed in any one of the preceding claims wherein the first outlet has a flexible shield filter that impedes the progress of solid materials passing through the first outlet to direct them downwardly into a rubbish collector.

13. A filter assembly as claimed in claim 12 wherein the flexible shield filter is in the form of hanging chains.

14.A filter assembly substantially as hereinbefore described with reference to the accompanying drawings.

A method of filtering liquid flows including providing a filter assembly as claimed in any one of the preceding claims to receive flows through a common inlet; separating different flows depending on their flow characteristics; filtering different flows; and Sdischarging liquid from the outlets. 13

16. A method of filtering liquid flows as substantially described herein with reference to the accompanying drawings. DATED THIS SEVENTEENTH DAY OF JULY 2000 C-M CONCRETE PRODUCTS PTY LTD *a* S** a a f* a f a o *a a f ft **tf *ft PIZZEYS PATENT AND TRADE MARK ATTORNEYS