AU704217B3

AU704217B3 - A filter assembly

Info

Publication number: AU704217B3
Application number: AU78950/98A
Authority: AU
Inventors: Eric S. Ball
Original assignee: Orenco Systems Inc
Current assignee: Orenco Systems Inc
Priority date: 1994-12-09
Filing date: 1998-08-10
Publication date: 1999-04-15
Anticipated expiration: 2001-11-20
Also published as: AU7895098A

Description

P:\OPER\RSHW366696.PE'I 5/8/98 A FILTER

ASSEMBLY

This invention relates to a filter assembly for filtering solids from the effluent of a wastewater collection container.

1 0 Sewage wastewater having a concentration of waste solids is typically collected in a wastewater container such as a septic tank. In the wastewater Scollection container the solids distribute into an upper 1. horizontal scum layer and a lower horizontal sludge layer with a relatively clear horizontal liquid layer therebetween. Liquid from the relatively clear horizontal layer is intermittently discharged from the container as effluent, while ideally, all the solids remain in the 20 collection container to be decomposed by the action of 20 anaerobic bacteria. However, some solids are nevertheless discharged from a conventionally operated wastewater container because, as the decomposition of solids proceeds, gas is produced. Bubbles of product gas attach to some solids, which causes those solids to migrate from 25 the sludge layer to the scum layer; the gas-lifted solids return to the sludge layer when the attached gas bubbles are released. These migrating solids may become entrained in the effluent discharged from the container, consequently degrading the quality of the effluent, and increasing the extent, and thus the expense, to which the effluent requires secondary treatment.

Various filtering devices have been associated with the wastewater container outlet in an attempt to prevent the discharge of solids with the liquid effluent.

For example, a cylindrical mesh screen may surround a gravity flow outlet, a siphon intake or the intake of a discharge pump. Cylindrical mesh screens are shown, for

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P:\OPER\RS\W3666.96.pr 5/8/98 -2example, in Graves US Patent No. 5,207,896, Grimshaw US Patent No. 3,662,890 and Ball US Patent No. 4,439,323. However, such a screen tends to become clogged with adhering solids which may even cause the screen to collapse. The clogged or collapsed screen must then be removed from the container and cleaned or replaced. As shown in Zabel US Patent No. 4,710,295, it is also known to cause the effluent to flow through the open bottom of a filtering device containing in its walls horizontally oriented elongate slots out through which the effluent flows to a gravity eooo 10 flow outlet of the wastewater collection container. However, such slots are still subject to clogging and they also permit horizontally oriented solids to enter the effluent flow.

Thus, a need exists for a more effective method of 15 filtering solids from the effluent from a wastewater collection 9* *container while overcoming the problems of the prior art *.systems.

According to the present invention, there is provided a 20 filter assembly for use in the treatment of waste water, said filter assembly being adapted in use to be positioned within a housing within a waste water collection chamber for containing waste water having a concentration of waste solids distributed into a lower horizontal sludge layer and an upper horizontal scum layer with a horizontal layer of liquid therebetween with said housing being so arranged that liquid is permitted to flow from said horizontal layer into said housing, said filter assembly comprising a filter having a filter surface area wherein in use the filter is immersed in the waste water whereby liquid flowing from said horizontal layer into said housing can P:\OPR\RSH\43666-96.PET 23/2/99 -3thereafter flow from one side of said filter to an opposite side thereof through said filter surface area and thereafter to flow through a liquid effluent outlet, and a generally horizontal plate arranged to fit closely within the housing, said filter surface area comprising multiple filter enclosures carried by the plate, said filter enclosures being arranged to receive a flow of liquid in parallel through said enclosures with the liquid flow in each of the enclosures being separate from that in each other enclosure.

°000 O0 An embodiment of the invention will now be described, by *000 way of example only, with reference to Figures 5 and 6 of the accompanying drawings, the other figures of the drawings and corresponding description being included to facilitate a better understanding of the preferred embodiment.

FIG. 1 is a partially sectional side view of a portion of a wastewater collection container; FIG. 2 is a sectional view taken along line 2-2 of FIG. i, S0 shown at an enlarged scale; FIG. 3 is a partially sectional side view of an alternative form of wastewater collection chamber; FIG. 4 is a sectional view taken along line 4-4 of FIG. 3, shown at an enlarged scale; 5 is a partially sectional side view of a wastewater collection chamber having a filter assembly in accordance with a preferred embodiment of the invention; FIG. 6 is an enlarged partially sectional view of the gravity flow outlet and tubular filtering surface shown in FIG.

P:\OPER\RSH\43666-96.ET 5/8/98 -4- Referring now to FIG. 1, an open-topped cylindrical housing 12 is immersed in a wastewater collection container such as a septic tank receiving, typically from a residence, raw sewage wastewater having a significant concentration of waste solids. In the container the solids distribute into a lower horizontal sludge layer 14 and an upper horizontal scum layer 16 with a horizontal layer 18 of liquid therebetween. Access to the housing 12 is through a riser 20 and cover 22. The housing 12 may rest on the bottom 24 of the collection container 10 as shown, *.00 or alternatively it may include an annular collar (not shown), which rests on the top 26 of the container, for suspending the housing in the container.

The housing 12 is essentially impervious to the 15 passage of liquid to its interior except through an encircling series of apertures 30 in the vertical wall of the housing. The open top or the housing 12 is located well above the maximum liquid level 28 in the container so no liquid will spill over the top. The location of 20 the apertures 30 in the housing 12 corresponds with a liquid level that is about 70% of a predetermined minimum liquid level 32 in the container 10. The maximum 28 and minimum 32 liquid levels are maintained by a float assembly 34 and pump 36 which cooperate to discharge effluent incrementally in the manner described in U.S.

Patent No. 4,439,323, which is incorporated by reference herein. The float assembly 34 includes an on/off float 38, whose setting determines a maximum liquid level 28 and the minimum liquid level 32 in the container 10 under normal operating conditions, a high level alarm float and a redundant off and low level alarm float 42. Thus, the apertures 30 are located in the top of the lower twothirds of the relatively clear liquid layer 18, and will remain in the clear liquid layer as the scum layer and sludge layer gradually grow toward each other over time.

The apertures 30 may vary in size, and in a preferred embodiment the apertures are circular, having a 1-3/8 inch diameter.

Multiple mesh screen tubular filter enclosures 44 are located within the housing 12 and provide a filtering surface area through which liquid entering the housing through the apertures 30 must flow before exiting the container 10 as effluent. The number and size of the tubular filter enclosures, which may be made of a polypropylene mesh screen preferably having a mesh opening about 1/8 inch square, provide a filtering surface area greater than the interior surface area of the housing 12.

In the exemplary embodiment shown in FIGS. 1 and 2, each "filter enclosure 44 has an open top end 46 surrounded by 15 a top plate 48 (FIG. 2) and an open bottom end 50 sur- .rounded by a bottom plate 52. The plates may be made of polymer such as polypropylene. The top plate 48 defines the bottom of a chamber 54 containing the float assembly **34 and the bottom plate 52 defines a chamber 56 located 20 in the bottom of the housing 12. A vertical cylindrical casing 58 defines a chamber 60 which communicates with the bottom chamber 56 and contains the effluent pump 36.

Liquid enters the housing 12 through the apertures 30 and flows in parallel into the respective 25 tubular filter enclosures through their surrounding mesh .eo..i screens. Filtered liquid enters the chambers 54 and 56 through the open ends 46, 50 of the filter enclosures 44.

When the liquid level in the housing 12 reaches the predetermined maximum level 28 the float 38 activates the pump 36 and filtered liquid effluent is pumped from'the chamber 60 and through a liquid effluent outlet conduit 62. Thus, in operation, solids are excluded from the effluent, first by the apertures 30 in the vertical wall of the housing 12 and then by the filtering surfaces of the tubular filter enclosures 44. The large surface area provided by the multiple tubular filter enclosures 44 efficiently excludes from the effluent any solids which P:\OPER\RSH\43666-96.PET 5/8/98 -6may enter the housing 12. Such solids will fall to the surface of the bottom plate 52 for degradation by anaerobic bacteria.

As shown in FIG. 3, a filtering surface area is provided so that liquid flows in parallel out of the respective tubular filter enclosures through their surrounding mesh screens. As previously described, the housing 12, which is immersed in the wastewater in the container 10, contains the float assembly 34 in the chamber 54 and the pump 36 in the chamber 60. Multiple tubular filter enclosures 44, similar to the tubular filter enclosures previously described, are surrounded by the housing 12. Each filter enclosure 44 has an open top end 46 surrounded by the top plate 48, and a closed bottom end 50 sealed by a bottom plate 64 in which it is embedded (FIG. The bottom plate 64 defines the chamber 56 located in the bottom of the housing 12 and includes openings 66 located between the closed bottom ends 50 of the filter enclosures 44. The apertures 30 in S. 20 the vertical wall of the housing 12 are generally located with respect to the relatively clear horizontal layer as described previously, but are above the top plate 48 to provide fluid communication between the clear liquid layer 18 and the open tops 46 of the tubular filter enclosures 44. Liquid enters the housing 12 from the clear liquid layer 18 through the apertures 30 and flows in parallel through the open tops 46 of the multiple tubular filter enclosures 44 and then through their surrounding mesh screens. The filtered liquid enters the chamber 56 through the openings 66 in the bottom plate 64, and flows into the chamber 60. When the liquid level in the housing 12 reaches the predetermined maximum level 28, the pump 36 is activated to discharge filtered liquid effluent from the container. Solids are excluded from the liquid effluent by the apertures 30 and the mesh filtering surfaces.

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P:\OPR\RSH\43666-96.PET 5/8/98 -7- Filtered effluent can be discharged from a wastewater collection container through the intake of a pump such as 36 or any other incremental effluent discharge apparatus such as a siphon, or in various other ways.

FIGS. 5 and 6 illustrate a filter assembly in accordance with a preferred embodiment of the present invention for filtering the effluent discharged from a wastewater collection container 70 having a grayity flow effluent outlet 72 accessible through a riser 74 and a cover 76. A vertical portion of the outlet 72 is a housing 78 defining an encircling series of apertures similar in location, in relation to the relatively clear horizontal layer of liquid, and size to the apertures previously described. Multiple tubular filter enclosures 15 82 provide a filtering surface area in the housing 78.

Each filter enclosure 82 includes a mesh screen similar to those described previously, with a closed bottom end 84 enclosed by and sealed in a bottom plate 86 and an "open top end 88 surrounded by a top plate 90. The top plate 90 defines the bottom of a chamber 92 in fluid communication with a horizontal outlet conduit 94. A connecting member 96 connects the top plate 90 to a cap 98 which fits snugly in a top portion 100 of the outlet 72. A handle 102, attached to the cap 98, is accessible through the riser 74, and an extension (not shown) is attachable to the handle 102 to extend the handle into the riser if desired. Each plate 86, 90 has a diameter only slightly smaller than the inside diameter of the housing 78 so that when the plates are inserted into the housing, liquid generally enters the housing only through -7athe apertures 80. As shown, the liquid flows into the tubular filter enclosures 82 through their surrounding mesh screens, although it will be understood that the housing and the filtering surfaces could be constructed similar to the apparatus shown in FIG. 3 so that the liquid would flow out of the filter enclosures through the mesh screens.

*C a P:\OPER\RSH43666-96.089. 30/3/98 -8- In operation, liquid flows from the relatively clear horizontal layer 18 through the apertures 80 in the housing 78 and thereafter in parallel through the multiple tubular filter enclosures 82 to the chamber 92. Filtered effluent flows through the chamber 92 to the liquid effluent outlet conduit 94.

Any solids entering the housing 78 are excluded from the effluent by the filtering surfaces and fall to the bottom plate 86 for digestion by anaerobic bacteria. The filtering surfaces are readily removec from the housing 78 for inspection or cleaning by removing the cover 76 from the riser 74, grasping the handle 102 and lifting the filter assembly from the container In the embodiment described the multiple filtering 5 enclosures are particularly resistant to clogging and thus to collapse, and require cleaning only as often as the container requires pumping to remove the accumulated sludge.

The terms and expressions which have been employed in the S 20 foregoing specification are used therein as terms of description and not of limitation, and there is no intention, in the use of such terms and expressions, of excluding equivalents of the features shown and described or portions thereof, it being S recognised that the scope of the invention is defined and limited only by the claims which follow.

Throughout this specification and claims which follow, unless the context requires otherwise, the word "comprise", and variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated integer or group of integers or steps but not the exclusion of any other integer or group of integers.

P:\OPERRSH\43666-96PET 23J2/99 -9- THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS:i. A filter assembly for use in the treatment of waste water, said filter assembly being adapted in use to be positioned within a housing within a waste water collection chamber for containing waste water having a concentration of waste solids distributed into a lower horizontal sludge layer and an upper horizontal scum layer with a horizontal layer of liquid therebetween with said housing being so arranged that liquid is permitted to flow from said horizontal layer into said housing, said filter assembly comprising a filter having a filter surface area wherein in use the filter is immersed in the waste water whereby liquid flowing from said horizontal layer into said housing can thereafter flow from one side of said filter to an opposite side thereof through said filter surface area and 0 thereafter to flow through a liquid effluent outlet, and a generally horizontal plate arranged to fit closely within the housing, said filter surface area comprising multiple filter enclosures and carried by the plate, said filter enclosures S being arranged to receive a flow of liquid in parallel through 0* said enclosures with the liquid flow in each of the enclosures being separate from that in each other enclosure.

e* 00 2. A filter assembly according to claim 1 in combination with a said housing into which the filter assembly is fitted in use, 00 00 wherein the totality of the filter surface area of the 0: enclosures is greater than the totality of the interior surface area of the housing.

3. A filter assembly according to claim 1 or claim 2, comprising a handle assembly attached to the plate and extending above the plate for manipulating the filter assembly.

DATED this 23rd day of February, 1999.

ORENCO SYSTEMS, INC.

By its Patent Attorneys: DAVIES COLLISON CAVE

Claims

9.° permitted to flow from said horizontal layer into said housing, said filter assembly comprising a filter having a filter [.surface area wherein in use the filter is immersed in the waste water whereby liquid flowing from said horizontal layer into 999 said housing can thereafter flow from one side of said filter to an opposite side thereof through said filter surface area and thereafter to flow through a liquid effluent outlet, and a generally horizontal plate arranged to fit closely within the housing, said filter surface area comprising multiple filter enclosures beneath the plate and carried by the plate, said filter enclosures being arranged to receive a flow of liquid in parallel through said enclosures with the liquid flow in each of the enclosures being separate from that in each other enclosure.