WO2007100539A2

WO2007100539A2 - Traveling bridge filter system

Info

Publication number: WO2007100539A2
Application number: PCT/US2007/004320
Authority: WO
Inventors: Donald D. Ricketts
Original assignee: Wasterwater Technology, Inc.
Priority date: 2006-02-22
Filing date: 2007-02-21
Publication date: 2007-09-07
Also published as: WO2007100539A3

Abstract

A filtering device includes, in a tank, one or more filters acted on by a traveling bridge. The filters includes multiple filter panels, arranged in series or in parallel. The bridge, as it moves down an axis of the tank, carries a backwash system to clean the filters.

Description

TRAVELING BRIDGE FILTER SYSTEM CROSS-REFERENCE TO RELATED APPLICATIONS

[001] This application claims priority from U.S. Provisional Patent Application No. 60/775,329, filed February 22, 2006.

Background of the Invention

1. Field of the Invention

[002] The present invention involves new filter systems for the types of filters known as traveling bridge filters. The invention may be implemented in new filter systems or used as a retrofit modification of existing filter systems.

2. Description of the Related Art

[003] The traveling bridge filter is a type of rapid gravity filter originally developed in the 1940's. Thousands have been installed worldwide and many are still in operation 20, 30 and even 40 years later.

[004] In summary, a traveling bridge filter system includes a tank having a particulate filter media or bed at the bottom of the tank which operates by straining out solids on the surface of the media. The solid coating that forms thereon limits the penetration of solids into the media and allows control of filtrate quality. As this coating gets thick, more of finer suspended solids are removed and headloss increases.

[005] A backwash cycle of predetermined interval and duration is conducted with utilization of a traveling bridge which traveling bridge, located on rails or tracks above the tanks, straddles and transverses the tank from end to end, supporting apparatus for backwashing the filter media.

[006] One of the drawbacks of the original traveling bridge filters is the requirement to drain the tank to replace/repair the filter media. Another drawback was that breakthrough/failure in the filter media caused the entire filter capacity of the tank to be lost until repairs were completed.

[007] Recently, a modification of the traveling bridge filter system has been proposed in which a pile cloth has been proposed as a filter media in place of the original particulate (or "sand") filter media. In the proposed modification, the pile filter cloth is formed as a cross-sectional diamond shape mounted in a plurality of rows extending from one end of the tank to another. While the pile cloth is more efficient than the sand filter as a filtering media, the modification requires the suction heads, also formed in the cross-sectional shape of a diamond, in order to compliment the diamond shape of the filter media, to traverse the pile cloth to backwash ali four sides of the diamond shaped filter. However, like the original traveling bridge filter system, a break or failure in the diamond shaped media requires immediate shutdown of the entire tank with subsequent draining of the tank to repair/replace the damaged section of media. Therefore, like its predecessor, the proposed modification still does not avoid the drawbacks of prolonged down time when only a portion of the filter media fails. Moreover, the complicated geometry of the diamond- shaped media and its related backwash system greatly complicates the filtration system, its operation and maintenance.

SUMMARY OF THE INVENTION

[008] The proposed modification of the original traveling bridge system does not overcome the disadvantages of the original traveling bridge system which are completely avoided by use of the invention in both newly constructed and retrofit traveling bridge systems.

[009] The invention provides a modular series of improved filter media comprising simple planar shape, which can be readily backwashed with a filter head comprising a planar shape. In the most preferred embodiments of the invention these modular filter components can be arranged either end to end or side by side to form a portion, or all, of the filter media in a new or retrofitted tank. Because of their increased filtering capacity, the modular filters do not require the same area as did the previously existing sand filter media, and therefore existing tanks can be expanded to higher capacities, or alternatively, can be maintained at designed capacity without utilizing the entire tank floor area.

[010] Even in newly designed construction, the tank may initially be sized to accommodate more than the number of modular units installed, with additional capacity being provided by installation of additional modular filter units as demand increases.

[011] The invention resides in the novel modular unit, its filtering media, and their arrangement in a traveling bridge system, the use of planar vertically arranged backwash heads on a traveling bridge, and the method of use of the foregoing as well as methods of retrofitting traveling bridge filter tanks.

[012] The invention will be further appreciated by reference to the appended drawings and the description of the preferred embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

[013] FIG. 1 is an schematic plan view of a typical traveling bridge filtering system according to the present invention having a pair of modular, removable filter panels arranged side by side in a tank;

[014] FIG. 2 is a front view of the tank along line A-A of FIG. 1

[015] FIG. 3 is an elevation view of the system of FIG. 1 taken along line B-B;

[016] FiG. 4 is a section view of the system of FIG. 1 taken along side C-C;

[017] FIG. 5 is a section view of the system of FIG. 1 taken along line D-D;

[018] FIG. 6 is a schematic plan view of a second embodiment of the invention when the modular filter panels are not only arranged side by side, but also end to end;

[019] FIG. 7 is a section taken along A-A of FIG. 6;

[020] FIG. 8 is an elevation view of FIG. 6 taken along side B-B thereof;

[021] FIG. 9 is a view taken along side C-C of FIG. 6;

[022] FIG. 10 is a section view taken along line D-D of FIG. 6;

[023] FlG. 11 is a schematic plan view of a third embodiment of the invention showing an even greater capacity of a traveling bridge filter system than that shown in FIGS. 1 and 6; [024] FIG. 12 is a section view taken along line A-A of FIG. 11 ;

[025] FIGS. 13A-13D are schematic views of the back, face section and side views respectively of a backwash head suitable for use in the invention; and

[026] FIGS. 14A-14D are schematic representations of the filtering and backwashing cycles of the invention.

[027] Throughout the following description, the same numerals are used in various figures to denote the same, or like, elements. However, it is to be understood that the use of such numerals is to exemplify the invention and it is not required that the same size, capacity, shape, arrangement or structure is to be referred from the use of the same numerals in the different figures of this specification.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[028] Although the invention can be utilized with but a single filter unit in a traveling bridge filter, the preferred embodiments have multiple filter units arranged in a single tank. Therefore, in one of the preferred embodiments, FIG. 1 schematically illustrates the invention in one of the simplest embodiments.

[029] It is to be understood that in retrofitting existing tanks, the original sand filter and its backwash head are most preferably removed to permit installation of the system of the invention.

[030] Traveling bridge 14 is propelled by traveling bridge drive motor and gear 15 over tank 2 which contains wastewater. A pair of filter panel disconnect couplings 3, 3 connects a pair of modular removable filter panels 4, 4, arranged in side-by-side, upstanding orientation, within the wastewater in tank 2. Influent pipe 1 introduces sufficient wastewater into tank 2 to at least partially, typically completely, submerge removable filter panels 4,4. A suitable float switch 18 controls the height of wastewater in tank 2. Traveling bridge 14 supports a manifold system 8 connected to backwash head assemblies 8a, 8b (FIG. 2) for backwashing the filter media of removable filter panels 4. Most preferably, the filter media comprises pile threads secured to a backing as described in U.S. Patent 6,103,132. Although described as being upstanding, the orientation of the filter panels 4 need not be perfectly vertical. Thus, the term upstanding (with respect to the orientation of the filter panels 4) is intended to include any angle between 45° and 135 or 65° and 115° with respect to the horizontal. Preferably the filter panels 4 are positioned at an angle between 75° and 105° and most preferably between 85° and 95° with respect to the horizontal. The upstanding panels 4 may also be vertical.

[031] In its most preferred embodiment, such a pile thread fabric is supported on a mesh backing arranged on a supporting frame such that two pile thread fabric backed filters are arranged with their large planar surfaces parallel such that the pile threads face the wastewater and the space between the parallel filters receives the filtrate. By suitably choosing the components of the pile thread filters, solids of 10 microns or less, e.g., smaller than 5 microns, can be removed from the wastewater. Such filtering efficiency can remove pathogenic microorganisms (e.g., protozoans, bacteria and viruses that are less than about 5 microns in size). Examples of some microorganisms which can be removed include Cryptosporidium, giardia lamblia, and entamoeba histolytica.

[032] Limit switches 19, 19 are provided to limit the travel of traveling bridge 14 and its supported manifold and backwash head assembly over tank 2. A high pressure backwash pump 11 acts as a source of high pressure backwash fluid 12 to backwash/treat the filter media. Clean water discharge pipe 6, as well as overflow water discharge pipe 7, are provided as well. A pump 10 is utilized to remove reject wastewater discharged through conduit 13 during the vacuuming through conduit 13a during the backwash cycle. Pump 10 may be a centrifugal or positive displacement pump, although centrifugal pumps are preferred. Suitable pumps are available under the name "Johnson 3000" or "Gorman Rupp 12B20" although equivalent pumps may be substituted. As shown in FIG. 2, a control panel 20 can be installed to control the various functions of the traveling bridge filter. A clean out pipe 17 may also be provided as shown in FIGS. 2-3, although the system can be set to run automatically upon, e.g., expiration of time or a sensed condition of the outlet flow or of one or more of the filter media.

[033] As shown in FIG. 4, each of removable filter panels 4 can be provided with handles 4a, 4a to facilitate removal of the panels by lifting out of tank 2 for replacement. However, since each of the removal panels throughout this description is modular, it can act independently of the other modular panels. Thus, the removal of one or more panels does not interrupt the function of the filtering of the remaining filter panels. Typically, the panels 4 can each interact with a separate outlet port 4b (not shown), and removal of a particular panel 4 automatically or manually closes the respective outlet port 4B.

[034] FIG. 4 better illustrates the track component 15b upon which wheels 15a of traveling bridge 15 traverse tank 2. As traveling bridge 15 moves above tank 2, its supported backwash apparatus moves first in the direction of arrow A and then in the direction of arrow B, carrying with it the suction head assemblies including supply line 8h and vacuum riser pipe 8c, although any repeating or non-repeating movement can be utilized. The shape of the tank can be any shape, but in order to increase efficiency of the apparatus of the invention, the tank 2 is preferably rectangular in shape, more preferably the tank 2 is longer than it is wide, for example, 200' long by 20' wide.

[035] The vacuum/backwash head 8b (FIG. 5), shown in greater detail in FIGS. 14A - 14D, not only backwashes filter media 3 (FIGS. 14A, 14B) in which solids collected on pile thread of the media 3 are released by the suction applied into vacuum conduits 8c, but one or a series of high pressure nozzles 8f can apply a source of high pressure fluid against the pile threads of media 3 (FIGS. 14C, 14D) to assist in removal of the solids, or treatment of the filter cloth. Simultaneously or sequentially, a treating solution such as a mildewcide, bacteriocide or other treating spray can be forced through nozzle 8f to treat filter media 3. The treating solution may be in a container and drained from the container either periodically or when necessary, e.g., in response to a sensed condition. It is important to note that the backwash cycle can be commenced in a timed manner or in response to conditions within the tank or effluent, e.g., wastewater level too high or filtered effluent quality out of specification. In the backwashing cycle, it is not necessary that the extended faces 8b of backwash head 8 contact the filter media 3 although such is not precluded by the present invention.

[036] In other embodiments of the invention as shown, for example in FIGS. 6 -10 and 11-12, the number of modular filter panels may be increased from that shown in the embodiment of FIGS. 1-5 and arranged both end-to-end as well as side-by-side. However, the general operation by these higher capacity systems will not be changed in a general manner from that previously disclosed. It will be readily understood that the number of modular filter panels can be duplicated without limit except for the size of the tank. In retrofit applications, due to the higher filtering efficiency of the pile thread media 3, the placement of removal filter panels 4 in the existing tank will not decrease the capacity of the originally designed tank. However, in new installations not only may multiple removable filter panels 4 be provided in any number and configurations, but multiple tanks, each with their own set of removal filter panels 4 can be integrated into a system servicing filtering needs from a small numbers of residences or businesses, through subdivisions, towns, cities and counties without departing from the spirit and scope of the invention.

[037] Although each filter 50 can include a single filter panel 4 (Fig. 1 ), each filter 50 may be formed from multiple filter panels 4, arranged typically in series or parallel (Fig. 6). The multiple filter panels 4 are arranged such that removal of one or more of the modular panels 4 permits the remainder of the panels 4 in the filter 50 to function without the need to drain the tank 2 or interrupt the filtering process.

[038] As the modular filter panels of the invention comprise large opposed planar surfaces, the backwash head need only be a linear head designed to move from end-to-end of the tank. Complicated geometric designs of the filter and backwash head are avoided making the backwash cycle a simple and straightforward traverse of the head over the filter cloth. The modular nature of the filter panels permits removal of one (or more) panels from the tank by simple lifting of the panels from the tank without draining the tank or impairing the filtering by the remaining modular units. Even if a filter is ruptured during use, that panel may be shut down without impairing the filtrate quality generated by the remaining panels.

[039] It will be understood by those skilled in the art that the forgoing examples were made by way of illustration only and not by way of limitation and that various modifications may be made without departing from the scope and teachings of the invention.

Claims

I/We claim:

1. An apparatus for filtering liquid comprising: a tank, the tank having a chamber defined by walls and a bottom; at least one filter comprising at least one upstanding planar filter panel, the filter in fluid communication with a discharge pipe; at least one backwash system, the backwash system comprising a backwash head mounted to a bridge, each of the at least one backwash systems associated with a filter; wherein the bridge is moveably connected to the walls and comprises a traveling element for moving the bridge along the walls and the backwash head through the tank.

2. The apparatus of claim 1, wherein the wall comprises a track and the traveling element comprises wheels, such that the traveling element rolls along the track.

3. The apparatus of claim 1 , wherein the at least one filter comprises at least two filter panels.

4. The apparatus of claim 3, wherein each of the plurality of filter panels comprises a discharge pipe.

5. The apparatus of claim 3, wherein each of the plurality of filter panels comprises a planar filter medium.

6. The apparatus of claim 5, wherein the plurality of filter panels are arranged in series.

7. The apparatus of claim 1 , comprising a plurality of filters arranged in parallel.

8. The apparatus of claim 1, wherein the modular filter panel comprises at least one handle for lifting the filter panel out of the tank.

9. The apparatus of claim 8, further comprising tracks positioned as to direct the filter panel during lifting out of the tank.

10. The apparatus of claim 1, wherein the filter panel comprises a filter medium comprising pile threads secured to a backing.

11. The apparatus of claim 1 wherein the backwash system comprises a vacuum backwash source.

12. The apparatus of claim 1 , wherein the filter is oriented vertical with respect to the bottom of the tank.

13. A method of cleaning a filtering apparatus comprising filters in a tank, the filters each comprising at least one upstanding filter panel, each of the filters associated with a backwash system, the backwash systems mechanically connected to a traveling bridge, the method comprising: moving the bridge along an axis of a tank, ; cleaning a first segment of the filters in proximity to the associated backwash system by directing a backwash flow through the backwash systems; and advancing the bridge along the tank, such that the backwash systems are in proximity to a second segment of the filters.

14. The method of cleaning of claim 13, further comprising repeating the cleaning step, during the advancing step.

15. The method of claim 13, further comprising permitting the cleaning step after a sensed condition, the sensed condition indicating the need for the cleaning step.

16. The method of claim 13, further comprising removing at least one filter panel without interrupting the advancing and cleaning steps.

17. A method of constructing an apparatus for filtering liquid comprising: providing a tank having walls; placing at least one filter in the tank, the at least one filter comprising at least one upstanding planar filter panel; and moveably positioning a backwash system on the tank, the backwash system comprising one backwash head associated with each of the at least one filter.

18. The method of claim 17, wherein the positioning step comprises locating the backwash system on a bridge, wherein the bridge is in or on tracks on the walls of the tank.

19. The method of claim 17, further comprising removing a particulate filter from the tank prior to the placing step.

20. The method of claim 17, further comprising removing an existing backwash system prior to the positioning step.

21. A method of repairing the apparatus of claim 1 , comprising removing a filter panel from the tank, without interrupting operation of the apparatus.