CA2262626C - Apparatus for distributing gas and liquid during concurrent gas/liquid backwash in flat bottom flumes - Google Patents
Apparatus for distributing gas and liquid during concurrent gas/liquid backwash in flat bottom flumes Download PDFInfo
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- CA2262626C CA2262626C CA002262626A CA2262626A CA2262626C CA 2262626 C CA2262626 C CA 2262626C CA 002262626 A CA002262626 A CA 002262626A CA 2262626 A CA2262626 A CA 2262626A CA 2262626 C CA2262626 C CA 2262626C
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- Prior art keywords
- flume
- liquid
- gas
- filter tank
- backwash
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D24/00—Filters comprising loose filtering material, i.e. filtering material without any binder between the individual particles or fibres thereof
- B01D24/02—Filters comprising loose filtering material, i.e. filtering material without any binder between the individual particles or fibres thereof with the filter bed stationary during the filtration
- B01D24/20—Filters comprising loose filtering material, i.e. filtering material without any binder between the individual particles or fibres thereof with the filter bed stationary during the filtration the filtering material being provided in an open container
- B01D24/24—Downward filtration, the container having distribution or collection headers or pervious conduits
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D24/00—Filters comprising loose filtering material, i.e. filtering material without any binder between the individual particles or fibres thereof
- B01D24/46—Regenerating the filtering material in the filter
- B01D24/4631—Counter-current flushing, e.g. by air
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- Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Devices And Processes Conducted In The Presence Of Fluids And Solid Particles (AREA)
- Feeding, Discharge, Calcimining, Fusing, And Gas-Generation Devices (AREA)
Abstract
A concurrent backwash distribution apparatus for a filter (11) having a filter tank (13) and a plurality of underdrain laterals (24) includes a baffle (10) positioned in a common main conduit (12) to define a secondary flume (14) between the baffle (10) and the underdrain laterals (24). The secondary flume (14) is in fluid communication with common main conduit (12) and the underdrain laterals (24). The baffle (10) has at least one flume liquid metering orifice (16) located adjacent a bottom of the baffle (10) so that it is below a gas liquid interface (23) in the secondary flume (14) during concurrent gas/liquid backwash operations. A flow distribution plate (18) is positioned between the secondary flume (14) and the underdrain laterals (24), the flow distribution plate (18) having at least one liquid metering orifice (22) and at least one gas metering orifice (20). The baffle (10) may be an upstanding partition (26) or an L-shaped partition (30). The baffle (10) creates adequate room for low velocity flow of backwash liquid in flat bottom flumes, while at the same time providing clearance for flow of backwash gas.
Description
2 PCT/US97/13512 APPARATUS FOR DISTRIBUTING GAS AND
LIQUID DURING CONCURRENT GAS/LIQUID
BACKWASH IN FLAT BOTTOM FLUMES
BACKGROUND OF THE INVENTION
1. Field of the Invention This invention relates to apparatus for distributing gas and liquid simultaneously from a common main conduit to filter underdrain laterals for backwash of filter media and, more particularly, to distribution of gas and liquid from a common main conduit that is roughly at the same elevation as the underdrain laterals.
2. Description of the Prior Art In a typical gravity filter for filtering water and wastewater, filter underdrain laterals are laid on the 25 filter floor one next to the other in parallel rows to define gas and liquid flow conduits below a bed of filtering media. The conduits make possible the collection of filtered liquid during filtration and the distribution of gas and liquid for backwash. A common main conduit (known as a "flume") is located immediately next to a filter tank to collect the filtered liquid from the underdrain laterals during filtration and to distribute gas or liquid to the underdrain laterals during gas (typically air) or liquid (typically water) backwash. The common main conduit also distributes gas and liquid simultaneously to each of the underdrain laterals during concurrent gas and liquid backwash. In some installations, the common main conduit has its floor located on the same elevation as the filter floor (see Fig. 1). Consulting engineers and contractors prefer this arrangement, known as a "flat bottom flume", because it is easier and cheaper to install.
The interface of gas and liquid in the underdrain laterals during concurrent gas and liquid backwash is only a few inches above the filter floor. The interface of gas and liquid in the common main conduit at this time would be even lower than that inside the laterals due to friction IPEAIUS '~ ~ FEg 1998 loss through the wall sleeves. The wall sleeves connect the common main conduit to the underdrain laterals. There is, therefore, practically no room in flat bottom flumes for flow and distribution of liquid to the underdrain laterals during concurrent gas and liquid backwash.
In order to provide uniform distribution of liquid to the underdrain laterals, the flow velocity of liquid inside the common main conduit should be limited to 2 feet per second or lower. Generally, the smaller the cross-sectional area for the flow path of liquid, the greater the velocity. Since the floor of the conduit is on the same elevation as the filter floor in flat bottom flumes, the only way to provide greater cross-sectional area for the flow of liquid to keep velocity at less than 2 feet per second is to raise the interface of gas and liquid from the floor by reducing gas pressure during concurrent gas and liquid backwash. However, as shown in Fig. 5, passage for the gas to the underdrain laterals will then be blocked by the liquid and there will not be any gas flow to the underdrain laterals.
The alternatives are to provide room below the interface of gas and liquid inside the common main conduit by lowering the floor elevation for liquid flow and distribution (see Fig. 2), or providing separate means for the flow and distribution of gas and liquid (see Figs. 3 and 4).
In the case of Fig. 2, extra excavation, form work and concrete structural work are required. This is very expensive for both retrofit jobs and new construction.
In addition, baffles or individual wall sleeves with elbows are required to direct liquid flow to laterals. In the case of Figs. 3 and 4, a stainless steel gas header with branches and tubes to each individual underdrain lateral is very expensive to fabricate and install. The individual gas tubes from the gas header to each underdrain lateral, pDJ!ENDED SHEET
_PCT/US97/13512 tPEAIUS 2'~ FEB 1998 shown in Fig. 4, may cause cross connection problems between unfiltered and filtered water since the individual tubing must go through the filter media bed.
It is therefore an object of this invention to create room inside the common main conduit by raising the interface of gas and liquid during concurrent gas and liquid backwash, while at the same time providing clear passages inside the common main conduit for gas f low to the underdrain laterals.
SUMMARY OF THE INVENTION
,:~ Accordingly, there is provided a concurrent backwash distribution apparatus for a filter having a filter tank, with a plurality of underdrain laterals positioned in the filter tank and a filter media bed positioned above the underdrain laterals. A common main conduit is positioned adjacent the filter tank and in fluid communication with the underdrain laterals. The floor of the filter tank may have the same elevation as a floor of the common main conduit.
The concurrent backwash distribution apparatus may comprise a baffle positioned in the main conduit so that it defines a secondary f lume between the baf f le and '"~ the underdrain laterals. The secondary flume is in fluid communication with the common main conduit and the underdrain laterals. The baffle has at least one flume liquid metering orifice located in the baffle and positioned below a gas/liquid interface in the secondary flume during a concurrent gas/liquid backwash operation in the filter.
A fluid distribution plate may be positioned between the secondary flume and the underdrain laterals, the fluid distribution plate having at least one lateral liquid metering orifice and at least one gas metering orifice. The lateral liquid metering orifice may be
LIQUID DURING CONCURRENT GAS/LIQUID
BACKWASH IN FLAT BOTTOM FLUMES
BACKGROUND OF THE INVENTION
1. Field of the Invention This invention relates to apparatus for distributing gas and liquid simultaneously from a common main conduit to filter underdrain laterals for backwash of filter media and, more particularly, to distribution of gas and liquid from a common main conduit that is roughly at the same elevation as the underdrain laterals.
2. Description of the Prior Art In a typical gravity filter for filtering water and wastewater, filter underdrain laterals are laid on the 25 filter floor one next to the other in parallel rows to define gas and liquid flow conduits below a bed of filtering media. The conduits make possible the collection of filtered liquid during filtration and the distribution of gas and liquid for backwash. A common main conduit (known as a "flume") is located immediately next to a filter tank to collect the filtered liquid from the underdrain laterals during filtration and to distribute gas or liquid to the underdrain laterals during gas (typically air) or liquid (typically water) backwash. The common main conduit also distributes gas and liquid simultaneously to each of the underdrain laterals during concurrent gas and liquid backwash. In some installations, the common main conduit has its floor located on the same elevation as the filter floor (see Fig. 1). Consulting engineers and contractors prefer this arrangement, known as a "flat bottom flume", because it is easier and cheaper to install.
The interface of gas and liquid in the underdrain laterals during concurrent gas and liquid backwash is only a few inches above the filter floor. The interface of gas and liquid in the common main conduit at this time would be even lower than that inside the laterals due to friction IPEAIUS '~ ~ FEg 1998 loss through the wall sleeves. The wall sleeves connect the common main conduit to the underdrain laterals. There is, therefore, practically no room in flat bottom flumes for flow and distribution of liquid to the underdrain laterals during concurrent gas and liquid backwash.
In order to provide uniform distribution of liquid to the underdrain laterals, the flow velocity of liquid inside the common main conduit should be limited to 2 feet per second or lower. Generally, the smaller the cross-sectional area for the flow path of liquid, the greater the velocity. Since the floor of the conduit is on the same elevation as the filter floor in flat bottom flumes, the only way to provide greater cross-sectional area for the flow of liquid to keep velocity at less than 2 feet per second is to raise the interface of gas and liquid from the floor by reducing gas pressure during concurrent gas and liquid backwash. However, as shown in Fig. 5, passage for the gas to the underdrain laterals will then be blocked by the liquid and there will not be any gas flow to the underdrain laterals.
The alternatives are to provide room below the interface of gas and liquid inside the common main conduit by lowering the floor elevation for liquid flow and distribution (see Fig. 2), or providing separate means for the flow and distribution of gas and liquid (see Figs. 3 and 4).
In the case of Fig. 2, extra excavation, form work and concrete structural work are required. This is very expensive for both retrofit jobs and new construction.
In addition, baffles or individual wall sleeves with elbows are required to direct liquid flow to laterals. In the case of Figs. 3 and 4, a stainless steel gas header with branches and tubes to each individual underdrain lateral is very expensive to fabricate and install. The individual gas tubes from the gas header to each underdrain lateral, pDJ!ENDED SHEET
_PCT/US97/13512 tPEAIUS 2'~ FEB 1998 shown in Fig. 4, may cause cross connection problems between unfiltered and filtered water since the individual tubing must go through the filter media bed.
It is therefore an object of this invention to create room inside the common main conduit by raising the interface of gas and liquid during concurrent gas and liquid backwash, while at the same time providing clear passages inside the common main conduit for gas f low to the underdrain laterals.
SUMMARY OF THE INVENTION
,:~ Accordingly, there is provided a concurrent backwash distribution apparatus for a filter having a filter tank, with a plurality of underdrain laterals positioned in the filter tank and a filter media bed positioned above the underdrain laterals. A common main conduit is positioned adjacent the filter tank and in fluid communication with the underdrain laterals. The floor of the filter tank may have the same elevation as a floor of the common main conduit.
The concurrent backwash distribution apparatus may comprise a baffle positioned in the main conduit so that it defines a secondary f lume between the baf f le and '"~ the underdrain laterals. The secondary flume is in fluid communication with the common main conduit and the underdrain laterals. The baffle has at least one flume liquid metering orifice located in the baffle and positioned below a gas/liquid interface in the secondary flume during a concurrent gas/liquid backwash operation in the filter.
A fluid distribution plate may be positioned between the secondary flume and the underdrain laterals, the fluid distribution plate having at least one lateral liquid metering orifice and at least one gas metering orifice. The lateral liquid metering orifice may be
3 AMEyDED SHEET
contiguous with its corresponding gas metering orifice, and together they may form an inverted T-shape.
The baffle preferably extends to a height which is less than a height of the common main conduit to define a clearance above the baffle. The flume liquid metering orifice is preferably positioned adjacent a bottom of the baffle.
The apparatus may include a filter tank wall separating the secondary flume and the laterals, the filter l0 tank wall having at least one opening therein for fluidly connecting the secondary flume with the laterals. The f low distribution plate may be positioned between the filter tank wall and the laterals. The opening in the filter tank wall is preferably sufficiently large to provide passage of both gas and liquid therethrough during concurrent gas/liquid backwash operations.
The baffle may be an upstanding partition positioned in the main conduit and spaced from a sidewall thereof. Alternatively, the baffle may be an inverted L-shaped partition, having a vertical portion and an upper horizontal portion. The upper horizontal portion has a plurality of openings therein. The invention also includes a method of introducing backwash gas and a backwash liquid to a filter having a filter tank.
Further details and advantages of the invention will become apparent upon reading the following detailed description, in conjunction with the accompanying drawings, in which like reference numerals represent like parts.
In one embodiment the concurrent backwash distribution apparatus for a filter having a filter tank, a flume positioned adjacent said filter tank and in fluid communication with said filter tank, comprises: a separator device positioned in said flume so as to define a secondary flume between said separator device and said filter tank, said secondary flume in fluid communication with said flume and said filter tank, said separator
contiguous with its corresponding gas metering orifice, and together they may form an inverted T-shape.
The baffle preferably extends to a height which is less than a height of the common main conduit to define a clearance above the baffle. The flume liquid metering orifice is preferably positioned adjacent a bottom of the baffle.
The apparatus may include a filter tank wall separating the secondary flume and the laterals, the filter l0 tank wall having at least one opening therein for fluidly connecting the secondary flume with the laterals. The f low distribution plate may be positioned between the filter tank wall and the laterals. The opening in the filter tank wall is preferably sufficiently large to provide passage of both gas and liquid therethrough during concurrent gas/liquid backwash operations.
The baffle may be an upstanding partition positioned in the main conduit and spaced from a sidewall thereof. Alternatively, the baffle may be an inverted L-shaped partition, having a vertical portion and an upper horizontal portion. The upper horizontal portion has a plurality of openings therein. The invention also includes a method of introducing backwash gas and a backwash liquid to a filter having a filter tank.
Further details and advantages of the invention will become apparent upon reading the following detailed description, in conjunction with the accompanying drawings, in which like reference numerals represent like parts.
In one embodiment the concurrent backwash distribution apparatus for a filter having a filter tank, a flume positioned adjacent said filter tank and in fluid communication with said filter tank, comprises: a separator device positioned in said flume so as to define a secondary flume between said separator device and said filter tank, said secondary flume in fluid communication with said flume and said filter tank, said separator
4 device having at least one flume liquid metering orifice located in said separator device, said flume liquid metering orifice positioned so as to convey liquid from said flume to said secondary flume during a concurrent gas and liquid backwash of the filter and so as to be below a gas/liquid interface in said secondary flume during said concurrent gas/liquid backwash operation in said filter.
The separator device may comprise a baffle which extends to a height which is less than a height of said flume to define a clearance above said baffle. The apparatus may include a plurality of flume liquid metering orifices in said separator device, each flume liquid metering orifice positioned adjacent a bottom of said separator device. The apparatus may include a filter tank wall separating said secondary flume and said filter tank, said filter tank wall having at least one opening therein for fluidly connecting said secondary flume with said filter tank. The apparatus may include a flow distribution plate positioned between said filter tank wall and laterals, said flow distribution plate having at least one lateral liquid metering orifice and at least one gas metering orifice, both of which are in fluid communication with said opening in said filter tank wall.
The separator device may comprise an upstanding partition positioned in said flume and spaced from a sidewall thereof. The separator device may comprise an inverted L-shaped partition having a vertical portion and an upper horizontal portion, said upper horizontal portion having a plurality of openings therein.
A flow distribution plate may be positioned between said filter tank wall and said laterals, at least one liquid metering orifice and at least one gas metering orifice in said plate being in fluid communication with said opening in said filter tank wall.
In a further embodiment the concurrent backwash distribution apparatus for a filter having a filter tank, 4a with a plurality of underdrain laterals in said filter tank and a filter media bed positioned above said underdrain laterals, a flume positioned adjacent said filter tank and in fluid communication with said underdrain laterals, a floor of said filter tank having substantially the same elevation as a floor of said flume, comprises: a separator device positioned in said flume so as to define an auxiliary flume between said separator device and said underdrain laterals, said secondary flume in fluid communication with said flume and said underdrain laterals, said separator device having at least one flume liquid metering orifice located in said separator device in a lower part thereof, said flume liquid metering orifice positioned so as to convey liquid from said flume to said secondary flume during a concurrent gas and liquid backwash of the filter and so as to be below a gas/liquid interface in said secondary flume during the concurrent gas/liquid backwash operation in said filter; said separator device extending to a height which is less than a height of said flume to define a clearance above said separator device; and a filter tank wall separating said auxiliary flume and said laterals, said filter tank wall having at least one opening to provide fluid communication between said laterals and said auxiliary flume.
The apparatus may include a flow distribution plate positioned between said filter tank wall and said laterals, said flow distribution plate having at least one lateral liquid metering orifice and at least one gas metering orifice, both of which are in fluid communication with said opening in said filter tank wall.
The separator device may be an upstanding partition positioned in said flume and spaced from a sidewall thereof .
A method of introducing a backwash gas and a backwash liquid to a filter having a filter tank, comprises the steps of: a) concurrently introducing said 4b backwash gas and said backwash liquid into an enclosed flume positioned adjacent said filter tank; b) establishing a first gas/liquid interface in said enclosed flume; c) passing said backwash liquid through at least one flume liquid metering orifice which is in fluid communication with said enclosed flume, said flume liquid metering orifice positioned below said first gas/liquid interface; d) establishing a second gas/liquid interface in said enclosed flume, said second gas/liquid interface positioned below said first gas/liquid interface; e) passing said backwash liquid into said filter tank through an opening in a filter tank wall separating said enclosed flume and said filter tank; and f ) passing said backwash gas through an opening which is above the second gas/liquid interface and below the first gas/liquid interface from said enclosed flume into said filter tank simultaneously with said backwash liquid.
The method may include the step of passing said backwash gas and said backwash liquid through a flow distribution plate positioned between said enclosed flume and said filter tank. The method may include the step of passing at least one of said backwash gas and said backwash liquid through a separator device positioned in said enclosed flume to define said second gas/liquid interface. The method may include the step of passing said backwash liquid and backwash gas into a plurality of underdrain laterals in said filter tank. In the method said separator device may be a baffle, said flume liquid metering orifice located in said baffle.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a schematic view of a filter having a flat bottom flume according to the prior art;
Fig. 2 is a schematic view of a filter having an excavated flume according to the prior art;
Fig. 3 is a schematic view of a filter having a flat bottom flume and a gas header inside the flume according to the prior art;
~c f _PCTlUS97~ 13 51~
lFcA/US ~'~ r~~ 1998 Fig. 4 is a schematic view of a filter having a gas header with drop tubes through the media bed according to the prior art;
Fig. 5 is a schematic view of a filter wherein gas pressure in the flume has been reduced to allow the liquid surface to rise according to the prior art;
Fig. 6 is a schematic view of a filter having a flat bottom flume with a baffle installed in the flume according to the present invention;
Fig. 7 is an elevational view of a flow distribution plate according to the invention;
Fig. 8 is a schematic view of a filter having a center flat bottom flume with two upstanding concrete partitions in the flume according to a second embodiment of the invention; and Fig. 9 is a schematic view of a filter having a center flat bottom flume with two stainless steel inverted L-shaped partitions in the flume according to a third embodiment of the invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
As shown in Fig. 6, the invention includes a baffle 10 positioned inside a common main conduit or flume '~
12 to create a small secondary flume 14 within the main conduit. Main conduit 12 is formed in a filter 11 and positioned next to a filter tank 13. Main conduit 12 and filter tank 13 share a common filter floor 15 so that the floors of main conduit 12 and filter tank 13 are at the same elevation. Flume liquid metering orifices 16 are located adjacent the bottom of the baffle 10 for the flow of liquid from the main conduit 12 to the secondary flume 14 during concurrent gas and liquid backwash. The liquid metering orifices 16 are sized such that the differential pressure across the orifices raises the interface of gas and liquid in the main conduit 12 to a level which provides sufficient area to reduce the flow velocity of liquid to 2
The separator device may comprise a baffle which extends to a height which is less than a height of said flume to define a clearance above said baffle. The apparatus may include a plurality of flume liquid metering orifices in said separator device, each flume liquid metering orifice positioned adjacent a bottom of said separator device. The apparatus may include a filter tank wall separating said secondary flume and said filter tank, said filter tank wall having at least one opening therein for fluidly connecting said secondary flume with said filter tank. The apparatus may include a flow distribution plate positioned between said filter tank wall and laterals, said flow distribution plate having at least one lateral liquid metering orifice and at least one gas metering orifice, both of which are in fluid communication with said opening in said filter tank wall.
The separator device may comprise an upstanding partition positioned in said flume and spaced from a sidewall thereof. The separator device may comprise an inverted L-shaped partition having a vertical portion and an upper horizontal portion, said upper horizontal portion having a plurality of openings therein.
A flow distribution plate may be positioned between said filter tank wall and said laterals, at least one liquid metering orifice and at least one gas metering orifice in said plate being in fluid communication with said opening in said filter tank wall.
In a further embodiment the concurrent backwash distribution apparatus for a filter having a filter tank, 4a with a plurality of underdrain laterals in said filter tank and a filter media bed positioned above said underdrain laterals, a flume positioned adjacent said filter tank and in fluid communication with said underdrain laterals, a floor of said filter tank having substantially the same elevation as a floor of said flume, comprises: a separator device positioned in said flume so as to define an auxiliary flume between said separator device and said underdrain laterals, said secondary flume in fluid communication with said flume and said underdrain laterals, said separator device having at least one flume liquid metering orifice located in said separator device in a lower part thereof, said flume liquid metering orifice positioned so as to convey liquid from said flume to said secondary flume during a concurrent gas and liquid backwash of the filter and so as to be below a gas/liquid interface in said secondary flume during the concurrent gas/liquid backwash operation in said filter; said separator device extending to a height which is less than a height of said flume to define a clearance above said separator device; and a filter tank wall separating said auxiliary flume and said laterals, said filter tank wall having at least one opening to provide fluid communication between said laterals and said auxiliary flume.
The apparatus may include a flow distribution plate positioned between said filter tank wall and said laterals, said flow distribution plate having at least one lateral liquid metering orifice and at least one gas metering orifice, both of which are in fluid communication with said opening in said filter tank wall.
The separator device may be an upstanding partition positioned in said flume and spaced from a sidewall thereof .
A method of introducing a backwash gas and a backwash liquid to a filter having a filter tank, comprises the steps of: a) concurrently introducing said 4b backwash gas and said backwash liquid into an enclosed flume positioned adjacent said filter tank; b) establishing a first gas/liquid interface in said enclosed flume; c) passing said backwash liquid through at least one flume liquid metering orifice which is in fluid communication with said enclosed flume, said flume liquid metering orifice positioned below said first gas/liquid interface; d) establishing a second gas/liquid interface in said enclosed flume, said second gas/liquid interface positioned below said first gas/liquid interface; e) passing said backwash liquid into said filter tank through an opening in a filter tank wall separating said enclosed flume and said filter tank; and f ) passing said backwash gas through an opening which is above the second gas/liquid interface and below the first gas/liquid interface from said enclosed flume into said filter tank simultaneously with said backwash liquid.
The method may include the step of passing said backwash gas and said backwash liquid through a flow distribution plate positioned between said enclosed flume and said filter tank. The method may include the step of passing at least one of said backwash gas and said backwash liquid through a separator device positioned in said enclosed flume to define said second gas/liquid interface. The method may include the step of passing said backwash liquid and backwash gas into a plurality of underdrain laterals in said filter tank. In the method said separator device may be a baffle, said flume liquid metering orifice located in said baffle.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a schematic view of a filter having a flat bottom flume according to the prior art;
Fig. 2 is a schematic view of a filter having an excavated flume according to the prior art;
Fig. 3 is a schematic view of a filter having a flat bottom flume and a gas header inside the flume according to the prior art;
~c f _PCTlUS97~ 13 51~
lFcA/US ~'~ r~~ 1998 Fig. 4 is a schematic view of a filter having a gas header with drop tubes through the media bed according to the prior art;
Fig. 5 is a schematic view of a filter wherein gas pressure in the flume has been reduced to allow the liquid surface to rise according to the prior art;
Fig. 6 is a schematic view of a filter having a flat bottom flume with a baffle installed in the flume according to the present invention;
Fig. 7 is an elevational view of a flow distribution plate according to the invention;
Fig. 8 is a schematic view of a filter having a center flat bottom flume with two upstanding concrete partitions in the flume according to a second embodiment of the invention; and Fig. 9 is a schematic view of a filter having a center flat bottom flume with two stainless steel inverted L-shaped partitions in the flume according to a third embodiment of the invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
As shown in Fig. 6, the invention includes a baffle 10 positioned inside a common main conduit or flume '~
12 to create a small secondary flume 14 within the main conduit. Main conduit 12 is formed in a filter 11 and positioned next to a filter tank 13. Main conduit 12 and filter tank 13 share a common filter floor 15 so that the floors of main conduit 12 and filter tank 13 are at the same elevation. Flume liquid metering orifices 16 are located adjacent the bottom of the baffle 10 for the flow of liquid from the main conduit 12 to the secondary flume 14 during concurrent gas and liquid backwash. The liquid metering orifices 16 are sized such that the differential pressure across the orifices raises the interface of gas and liquid in the main conduit 12 to a level which provides sufficient area to reduce the flow velocity of liquid to 2
5 AMENDED SHEET
_PCTlUS97/13512 IPEAIUS 2'~ FEB 1998 feet per second or lower during concurrent gas and liquid backwash.
The secondary flume 14 serves as a passage for the gas and liquid during concurrent gas and liquid backwash. A flow distribution plate 18 (Fig. 7) with gas metering slots 20 and lateral liquid metering orifices 22 of rectangular shape are also provided. Although shown schematically at an equal level in Fig. 6, the interface of gas and liquid in the secondary flume 14 may be lower than that in underdrain lateral 24 due to headloss through , the gas metering slot 20 in the flow distribution plate 18.
'_ Liquid will flow to the underdrain laterals 24 through the liquid metering orifices 16 and 22 while gas will flow through the secondary flume 14 and the gas metering slots 20 and then to the underdrain laterals 24. Where convenient, one extended flow distribution plate 18 having a plurality of liquid and gas metering orifices, one each corresponding to a lateral, may be provided.
For gas only backwash, gas will flow through the secondary flume 14 to the underdrain laterals 24, although the interface of gas and liquid in the main conduit 12 would drop to the same level as the interface 23 of gas and liquid in the secondary flume 14 because there will be no liquid flow at this time. For backwash with liquid only, liquid will flow through the secondary flume 14 as well as the liquid metering orifices 16 and 22 to the underdrain laterals 24 since there would not be any gas inside the main conduit 12 or the underdrain laterals 24.
Referring to Fig. 8, a first alternative arrangement for the apparatus according to the present invention is shown. Two upstanding concrete partitions 26 are positioned in main conduit 12, each partition spaced from a sidewall 28 of main conduit 12 to form secondary flumes 14. As with baffle 10, the partitions 26 do not extend the full height of main conduit 12 so as to define
_PCTlUS97/13512 IPEAIUS 2'~ FEB 1998 feet per second or lower during concurrent gas and liquid backwash.
The secondary flume 14 serves as a passage for the gas and liquid during concurrent gas and liquid backwash. A flow distribution plate 18 (Fig. 7) with gas metering slots 20 and lateral liquid metering orifices 22 of rectangular shape are also provided. Although shown schematically at an equal level in Fig. 6, the interface of gas and liquid in the secondary flume 14 may be lower than that in underdrain lateral 24 due to headloss through , the gas metering slot 20 in the flow distribution plate 18.
'_ Liquid will flow to the underdrain laterals 24 through the liquid metering orifices 16 and 22 while gas will flow through the secondary flume 14 and the gas metering slots 20 and then to the underdrain laterals 24. Where convenient, one extended flow distribution plate 18 having a plurality of liquid and gas metering orifices, one each corresponding to a lateral, may be provided.
For gas only backwash, gas will flow through the secondary flume 14 to the underdrain laterals 24, although the interface of gas and liquid in the main conduit 12 would drop to the same level as the interface 23 of gas and liquid in the secondary flume 14 because there will be no liquid flow at this time. For backwash with liquid only, liquid will flow through the secondary flume 14 as well as the liquid metering orifices 16 and 22 to the underdrain laterals 24 since there would not be any gas inside the main conduit 12 or the underdrain laterals 24.
Referring to Fig. 8, a first alternative arrangement for the apparatus according to the present invention is shown. Two upstanding concrete partitions 26 are positioned in main conduit 12, each partition spaced from a sidewall 28 of main conduit 12 to form secondary flumes 14. As with baffle 10, the partitions 26 do not extend the full height of main conduit 12 so as to define
6 AMENDED SHEET
~~T/~~ 9 7 / 13 512 IPEAIUS 2'~ FEB 1998 a clearance 27 for flow of gas and liquid over the tops of the partitions into secondary flumes 14. Flume liquid metering orifices 16 are positioned at the bottoms of partitions 26 and have a predetermined diameter and spacing. This arrangement is appropriate for filters having center flumes, with a filter tank 13 and underdrain laterals 24 positioned on either side of the main conduit 12. It is contemplated this arrangement could be used in new construction. A distribution plate 18 is present, as '''~ 10 discussed above.
Referring to Fig. 9, a second alternative arrangement for the invention is shown. Stainless steel partitions 30 have an inverted L-shape and are positioned in main conduit 12, which forms part of a center flume, as discussed above. Secondary flumes 14 are formed between sidewalls 28 and stainless steel partitions 30. Holes 32 in an upper horizontal portion 34 of stainless steel partitions 30 provide fluid communication between secondary flumes 14 and main conduit 12 for gas flow during gas only and gas/liquid concurrent backwash and also for liquid f low ~'', during "liquid only" backwash. Flume liquid metering orifices 16 are positioned near the bottom of a vertical portion of each partition 30. The remainder of the arrangement is as discussed above. The second alternative arrangement shown in Fig. 9 is exemplary of an application of the invention to existing facilities.
Holes 32 may, for example, be four inches in diameter and located along horizontal portion 34 at a spacing of six inches. Generally, the sizes and spacing for orifices 16, 20, 22 and 32 of the present invention must be calculated and designed according to the specific features of the installation with which the invention is to be used. The details for this engineering will be apparent to those skilled in the art upon reading the instant
~~T/~~ 9 7 / 13 512 IPEAIUS 2'~ FEB 1998 a clearance 27 for flow of gas and liquid over the tops of the partitions into secondary flumes 14. Flume liquid metering orifices 16 are positioned at the bottoms of partitions 26 and have a predetermined diameter and spacing. This arrangement is appropriate for filters having center flumes, with a filter tank 13 and underdrain laterals 24 positioned on either side of the main conduit 12. It is contemplated this arrangement could be used in new construction. A distribution plate 18 is present, as '''~ 10 discussed above.
Referring to Fig. 9, a second alternative arrangement for the invention is shown. Stainless steel partitions 30 have an inverted L-shape and are positioned in main conduit 12, which forms part of a center flume, as discussed above. Secondary flumes 14 are formed between sidewalls 28 and stainless steel partitions 30. Holes 32 in an upper horizontal portion 34 of stainless steel partitions 30 provide fluid communication between secondary flumes 14 and main conduit 12 for gas flow during gas only and gas/liquid concurrent backwash and also for liquid f low ~'', during "liquid only" backwash. Flume liquid metering orifices 16 are positioned near the bottom of a vertical portion of each partition 30. The remainder of the arrangement is as discussed above. The second alternative arrangement shown in Fig. 9 is exemplary of an application of the invention to existing facilities.
Holes 32 may, for example, be four inches in diameter and located along horizontal portion 34 at a spacing of six inches. Generally, the sizes and spacing for orifices 16, 20, 22 and 32 of the present invention must be calculated and designed according to the specific features of the installation with which the invention is to be used. The details for this engineering will be apparent to those skilled in the art upon reading the instant
7 AMENDED SHEET
specification. The following example is instructive in this regard.
EXAMPLE
I. Design Data Filter: Two (2) bays with H-flume.
Each bay 14'-0" x 38'-0", 532 sf.
Flume: To feed both bays.
6'-0" wide x 4'-0" high.
Bottom of flume and bottom of filter are on the same elevation.
Laterals: Length, 14'-0".
Number of laterals, 38 per bay.
Backwash: Air only, 3 scfm/sf.
Air/water concurrent, 3 scfm/sf air and
specification. The following example is instructive in this regard.
EXAMPLE
I. Design Data Filter: Two (2) bays with H-flume.
Each bay 14'-0" x 38'-0", 532 sf.
Flume: To feed both bays.
6'-0" wide x 4'-0" high.
Bottom of flume and bottom of filter are on the same elevation.
Laterals: Length, 14'-0".
Number of laterals, 38 per bay.
Backwash: Air only, 3 scfm/sf.
Air/water concurrent, 3 scfm/sf air and
8 gpm/sf water.
Water only, 20 gpm/sf.
Underdrain: Universal° Type S with IMS~ Caps.
Media: 72" above IMS~ Caps.
General Operation:
Referring to the embodiment shown in Fig. 8, a secondary flume is provided inside the main flume to allow for the passage of air to the underdrain laterals for air/water concurrent backwash. The water orifices at the bottom of the flume partition are designed to maintain a certain water depth in the main flume for uniform distribution of backwash water to the underdrain laterals during concurrent backwash.
For air scour with air anly, the air/water interface in the main flume will drop to the same elevation as in the secondary flume. Air will flow above the partitions to the secondary flume and then through the flow distribution plate to the underdrain laterals.
For air/water concurrent backwash, water will be admitted to the main flume and will flow to the secondary flume through the water orifices in the partitions. Both air and water are measured through the orifices in the flow distribution plate to the underdrain laterals.
For water only backwash, water will flow to the secondary flume from the clearance 27 as well as through the water orifices in the partitions to the secondary flume, and then through the flow distribution plate to the laterals.
II. Air/Water Interface in Laterals Test data with 6" and 24" of water above the Universai~ Type S Blocks with IMS° Caps for concurrent backwash with 3 scfm/sf air and 8 gpm/sf water has indicated that the interface of air and water in the primary chamber of the lateral was 5.3" below the top of the block or 6.7" above the filter floor.
During air/water concurrent backwash, the water level in the filter is usually 6" above the media, or 78"
above the IMS° Caps in this case.
For 78" of water, the air/water interface in the primary chamber of the lateral for the same air and water flow rates is estimated to be 6.9" above the filter floor.
During "air only" backwash, the air/water interface will be slightly lower than that above.
III. Air Pressure in Laterals Air pressure in the primary chamber of the lateral is equal to the sum of the pressure drop through the orifices in the lateral, the pressure drop through the IMS° Caps, and the water height above the IMS° Caps.
Water only, 20 gpm/sf.
Underdrain: Universal° Type S with IMS~ Caps.
Media: 72" above IMS~ Caps.
General Operation:
Referring to the embodiment shown in Fig. 8, a secondary flume is provided inside the main flume to allow for the passage of air to the underdrain laterals for air/water concurrent backwash. The water orifices at the bottom of the flume partition are designed to maintain a certain water depth in the main flume for uniform distribution of backwash water to the underdrain laterals during concurrent backwash.
For air scour with air anly, the air/water interface in the main flume will drop to the same elevation as in the secondary flume. Air will flow above the partitions to the secondary flume and then through the flow distribution plate to the underdrain laterals.
For air/water concurrent backwash, water will be admitted to the main flume and will flow to the secondary flume through the water orifices in the partitions. Both air and water are measured through the orifices in the flow distribution plate to the underdrain laterals.
For water only backwash, water will flow to the secondary flume from the clearance 27 as well as through the water orifices in the partitions to the secondary flume, and then through the flow distribution plate to the laterals.
II. Air/Water Interface in Laterals Test data with 6" and 24" of water above the Universai~ Type S Blocks with IMS° Caps for concurrent backwash with 3 scfm/sf air and 8 gpm/sf water has indicated that the interface of air and water in the primary chamber of the lateral was 5.3" below the top of the block or 6.7" above the filter floor.
During air/water concurrent backwash, the water level in the filter is usually 6" above the media, or 78"
above the IMS° Caps in this case.
For 78" of water, the air/water interface in the primary chamber of the lateral for the same air and water flow rates is estimated to be 6.9" above the filter floor.
During "air only" backwash, the air/water interface will be slightly lower than that above.
III. Air Pressure in Laterals Air pressure in the primary chamber of the lateral is equal to the sum of the pressure drop through the orifices in the lateral, the pressure drop through the IMS° Caps, and the water height above the IMS° Caps.
9 CA 02262626 1999-O1-29 __..
PCT/US 9 7 ~ 13 512 ~PE~S ~ ~ F~8 1998 h = 0.0463 * (Q/CA)2 * P2/T
Where h = Loss of head through orifices in lateral and Cap, inches of water.
Q = Air flow rate in primary chamber, cfm.
C = Orifice coefficient.
A - Orifice area in primary and secondary chambers, and also in Cap, in2.
PZ = Pressure in primary chamber, psia.
~_ .::;a T = Absolute temperature of air in lateral.
From test results with 3 scfm/sf air and 8 gpm/sf water, (CA)2 was found to be 0.000998 per foot of lateral.
Let p - Air pressure in primary chamber, in inches of water.
Then, for 1'-0" of lateral:
h = p - 78 Q = 3 scfm * 14.7/(14.7 + p/27.7) - 1221.6/(p +
407.2) P2 = p/27.7 + 14.7 Assume air temperature in lateral is 68° F, then T = 460 + 68 = 528 p - 78 = 0.0463 * [(1221.6)/(p + 407.2)]2 (p/27.7 + 14.7)/(0.000998 * 528) Solve for p = 87.6" of water.
This is the air pressure in the primary chamber with 78" of water above the IMS° Caps and when 3 scfm/sf air and 8 gpm/sf water are used for concurrent backwash.
AMENDED SHEET
IV. Air/Water Interface in Secondary Flume Air and water will enter the lateral from the secondary flume through a distribution orifice plate as shown in Fig. 7. The air/water interface in the secondary flume should be maintained at the same level as in the lateral so as to avoid splashing in the lateral.
Assume air pressure in the secondary flume - p inches of water.
For water, Q = CAS/ ( 2 gh ) Where Q = 8 * 14 = 112 gpm = 0.2496 cfs C = 0.62 A = Area of water distribution orifice in flow distribution plates 18 15.175 in2 = 0.1054 ft2 h = (p - 87.6)/12 ft.
Therefore, 0.2496 = 0.62 * 0.1054~r [2 * 32.2 * (p - 87.6)/12]
Solve for p = 90.32" of water.
For air, h = 0.0463 * (Q/CA)2 * PZ/T (see III above).
Where h = 90.32 - 87.6 = 2.72"
Air flow = 3 * 14 = 42 scfm Q = 42 * 14.7/(14.7 + 90.32/27.7) - 34.37 cfm C = 0.65 A = Orifice area, in2 P2 = 14.7 + 90.32/27.7 = 17.96 psia T = 528°
Therefore, 2.72 = 0.0463 * (34.37/0.65A)2 17.96/528 Solve for A = 1.27 in2 Extend the orifice (top of the slot) to 8.75"
from the floor.
The revised air pressure is 90.3" of water and the air/water interface is 7" from the floor.
V. Air/Water Interface in Flume In order to maintain a reasonably good distribution of water to the laterals during concurrent backwash, the flow velocity of water in the flume should be maintained at not higher than 2 fps.
Filter area = 532 sf/bay = 1,064 sf/filter Concurrent water flow = 8 * 1,064 = 8,512 gpm =
18.97 cfs Width of primary flume between baffles 26 = 4.33 ft.
Therefore, the required water depth = 18.97/(2 4.33) - 2.189' or 26.27"
VI. Concurrent Backwash Water Orifice Since the bottom of the flume is on the same elevation as the filter floor, the water surface in the flume will have to be maintained at 26.27" - 7" or 19.27"
above the water surface in the secondary flume. A small orifice through the 4" concrete partition with headloss of 19.27" is therefore required to measure the water f low from the flume to the secondary flume for concurrent backwash.
Q = CA~J ( 2 gh ) Where Q = 112 gpm or 0.2496 cfs C = 0.62 h = 19.27" = 1.6' 0.2496 = 0.62 * A * ~ (2 * 32.2 * 1.6) A = 0.0396 ft2 = 5.7 in2 Use 2-11/16" diameter holes near bottom of partitions (flume liquid metering orifice 16) VII. Alternate Make partition with stainless steel plate instead of concrete as shown in Fig. 9. Width of primary flume between the partitions 30 is 4.97 ft.
Air/Water Interface In Flume Required water depth = 18.97/(2 * 4.97) - 1.91' - 23"
Water Orifices Near Bottoms Of Partitions h = 23 - 7 = 16" - 1.333' 0.2496 = 0.62 * A * 'J (2 * 32.2 * 1.333) A = 0.0434 ft2 = 6.25 in2 Use 2'/e" diameter holes 16 @ 12" c/c.
The baffle 10 inside the common main conduit 12 can be made of concrete, stainless steel or any other suitable material. The addition of baffle 10 to common main conduit 12 is the most cost-effective means for the distribution of gas and liquid simultaneously to filter underdrain laterals 24 for concurrent gas and liquid backwash of filter media.
Having described the presently preferred embodiments and best mode of the invention, certain variations and modifications may be made without departing from the spirit and scope of the invention. It is not intended to limit the invention except as set forth in the following claims.
PCT/US 9 7 ~ 13 512 ~PE~S ~ ~ F~8 1998 h = 0.0463 * (Q/CA)2 * P2/T
Where h = Loss of head through orifices in lateral and Cap, inches of water.
Q = Air flow rate in primary chamber, cfm.
C = Orifice coefficient.
A - Orifice area in primary and secondary chambers, and also in Cap, in2.
PZ = Pressure in primary chamber, psia.
~_ .::;a T = Absolute temperature of air in lateral.
From test results with 3 scfm/sf air and 8 gpm/sf water, (CA)2 was found to be 0.000998 per foot of lateral.
Let p - Air pressure in primary chamber, in inches of water.
Then, for 1'-0" of lateral:
h = p - 78 Q = 3 scfm * 14.7/(14.7 + p/27.7) - 1221.6/(p +
407.2) P2 = p/27.7 + 14.7 Assume air temperature in lateral is 68° F, then T = 460 + 68 = 528 p - 78 = 0.0463 * [(1221.6)/(p + 407.2)]2 (p/27.7 + 14.7)/(0.000998 * 528) Solve for p = 87.6" of water.
This is the air pressure in the primary chamber with 78" of water above the IMS° Caps and when 3 scfm/sf air and 8 gpm/sf water are used for concurrent backwash.
AMENDED SHEET
IV. Air/Water Interface in Secondary Flume Air and water will enter the lateral from the secondary flume through a distribution orifice plate as shown in Fig. 7. The air/water interface in the secondary flume should be maintained at the same level as in the lateral so as to avoid splashing in the lateral.
Assume air pressure in the secondary flume - p inches of water.
For water, Q = CAS/ ( 2 gh ) Where Q = 8 * 14 = 112 gpm = 0.2496 cfs C = 0.62 A = Area of water distribution orifice in flow distribution plates 18 15.175 in2 = 0.1054 ft2 h = (p - 87.6)/12 ft.
Therefore, 0.2496 = 0.62 * 0.1054~r [2 * 32.2 * (p - 87.6)/12]
Solve for p = 90.32" of water.
For air, h = 0.0463 * (Q/CA)2 * PZ/T (see III above).
Where h = 90.32 - 87.6 = 2.72"
Air flow = 3 * 14 = 42 scfm Q = 42 * 14.7/(14.7 + 90.32/27.7) - 34.37 cfm C = 0.65 A = Orifice area, in2 P2 = 14.7 + 90.32/27.7 = 17.96 psia T = 528°
Therefore, 2.72 = 0.0463 * (34.37/0.65A)2 17.96/528 Solve for A = 1.27 in2 Extend the orifice (top of the slot) to 8.75"
from the floor.
The revised air pressure is 90.3" of water and the air/water interface is 7" from the floor.
V. Air/Water Interface in Flume In order to maintain a reasonably good distribution of water to the laterals during concurrent backwash, the flow velocity of water in the flume should be maintained at not higher than 2 fps.
Filter area = 532 sf/bay = 1,064 sf/filter Concurrent water flow = 8 * 1,064 = 8,512 gpm =
18.97 cfs Width of primary flume between baffles 26 = 4.33 ft.
Therefore, the required water depth = 18.97/(2 4.33) - 2.189' or 26.27"
VI. Concurrent Backwash Water Orifice Since the bottom of the flume is on the same elevation as the filter floor, the water surface in the flume will have to be maintained at 26.27" - 7" or 19.27"
above the water surface in the secondary flume. A small orifice through the 4" concrete partition with headloss of 19.27" is therefore required to measure the water f low from the flume to the secondary flume for concurrent backwash.
Q = CA~J ( 2 gh ) Where Q = 112 gpm or 0.2496 cfs C = 0.62 h = 19.27" = 1.6' 0.2496 = 0.62 * A * ~ (2 * 32.2 * 1.6) A = 0.0396 ft2 = 5.7 in2 Use 2-11/16" diameter holes near bottom of partitions (flume liquid metering orifice 16) VII. Alternate Make partition with stainless steel plate instead of concrete as shown in Fig. 9. Width of primary flume between the partitions 30 is 4.97 ft.
Air/Water Interface In Flume Required water depth = 18.97/(2 * 4.97) - 1.91' - 23"
Water Orifices Near Bottoms Of Partitions h = 23 - 7 = 16" - 1.333' 0.2496 = 0.62 * A * 'J (2 * 32.2 * 1.333) A = 0.0434 ft2 = 6.25 in2 Use 2'/e" diameter holes 16 @ 12" c/c.
The baffle 10 inside the common main conduit 12 can be made of concrete, stainless steel or any other suitable material. The addition of baffle 10 to common main conduit 12 is the most cost-effective means for the distribution of gas and liquid simultaneously to filter underdrain laterals 24 for concurrent gas and liquid backwash of filter media.
Having described the presently preferred embodiments and best mode of the invention, certain variations and modifications may be made without departing from the spirit and scope of the invention. It is not intended to limit the invention except as set forth in the following claims.
Claims (29)
1. A concurrent backwash distribution apparatus for a filter having a filter tank, a flume positioned adjacent said filter tank and in fluid communication with said filter tank, said concurrent backwash distribution apparatus comprising:
a separator device positioned in said flume so as to define a secondary flume between said separator device and said filter tank, said secondary flume in fluid communication with said flume and said filter tank, said separator device having at least one flume liquid metering orifice located in said separator device, said flume liquid metering orifice positioned so as to convey liquid from said flume to said secondary flume during a concurrent gas and liquid backwash of the filter and so as to be below a gas/liquid interface in said secondary flume during said concurrent gas/liquid backwash operation in said filter.
a separator device positioned in said flume so as to define a secondary flume between said separator device and said filter tank, said secondary flume in fluid communication with said flume and said filter tank, said separator device having at least one flume liquid metering orifice located in said separator device, said flume liquid metering orifice positioned so as to convey liquid from said flume to said secondary flume during a concurrent gas and liquid backwash of the filter and so as to be below a gas/liquid interface in said secondary flume during said concurrent gas/liquid backwash operation in said filter.
2. The apparatus of claim 1 including a plurality of underdrain laterals positioned in said filter tank and a filter media bed positioned above said underdrain laterals with a flow distribution plate positioned between said secondary flume and said underdrain laterals, said flow distribution plate having at least one lateral liquid metering orifice and at least one gas metering orifice.
3. The apparatus of claim 2 wherein each lateral liquid metering orifice is contiguous with a corresponding gas metering orifice.
4. The apparatus of claim 1 wherein said separator device comprises a baffle which extends to a height which is less than a height of said flume to define a clearance above said baffle.
5. The apparatus of claim 1 including a plurality of flume liquid metering orifices in said separator device, each flume liquid metering orifice positioned adjacent a bottom of said separator device.
6. The apparatus of claim 1 including a filter tank wall separating said secondary flume and said filter tank, said filter tank wall having at least one opening therein for fluidly connecting said secondary flume with said filter tank.
7. The apparatus of claim 6 including a flow distribution plate positioned between said filter tank wall and laterals, said flow distribution plate having at least one lateral liquid metering orifice and at least one gas metering orifice, both of which are in fluid communication with said opening in said filter tank wall.
8. The apparatus of claim 6 wherein said opening in said filter tank wall is sufficiently large to provide passage of both gas and liquid therethrough during said concurrent gas/liquid backwash operation.
9. The apparatus of claim 1 wherein said separator device comprises an upstanding partition positioned in said flume and spaced from a sidewall thereof.
10. The apparatus of claim 1 wherein said separator device comprises an inverted L-shaped partition having a vertical portion and an upper horizontal portion, said upper horizontal portion having a plurality of openings therein.
11. A concurrent backwash distribution apparatus for a filter having a filter tank, with a plurality of underdrain laterals positioned in said filter tank and a filter media bed positioned above said underdrain laterals, a common main conduit positioned adjacent said filter tank and in fluid communication with said underdrain laterals, said concurrent backwash distribution apparatus comprising:
a baffle positioned in said common main conduit so as to define a secondary flume between said baffle and said underdrain laterals, said secondary flume in fluid communication with said common main conduit and said underdrain laterals, said baffle having at least one flume liquid metering orifice located in said baffle, said flume liquid metering orifice positioned so as to convey liquid from said flume to said secondary flume during a concurrent gas and liquid backwash of the filter and so as to be below a gas/liquid interface in said secondary flume during said concurrent gas/liquid backwash operation in said filter;
said baffle extending to a height which is less than a height of said common main conduit to define a clearance above said baffle.
a baffle positioned in said common main conduit so as to define a secondary flume between said baffle and said underdrain laterals, said secondary flume in fluid communication with said common main conduit and said underdrain laterals, said baffle having at least one flume liquid metering orifice located in said baffle, said flume liquid metering orifice positioned so as to convey liquid from said flume to said secondary flume during a concurrent gas and liquid backwash of the filter and so as to be below a gas/liquid interface in said secondary flume during said concurrent gas/liquid backwash operation in said filter;
said baffle extending to a height which is less than a height of said common main conduit to define a clearance above said baffle.
12. The apparatus of claim 11 including a flow distribution plate positioned between said secondary flume and said underdrain laterals, said flow distribution plate having at least one liquid metering orifice and at least one gas metering orifice, each liquid metering orifice being contiguous with a corresponding gas metering orifice.
13. The apparatus of claim 11 including a plurality of flume liquid metering orifices in said baffle, each flume liquid metering orifice positioned adjacent a bottom of said baffle.
14. The apparatus of claim 11 including a filter tank wall separating said secondary flume and said laterals, said filter tank wall having at least one opening therein for fluidly connecting said secondary flume with said laterals.
15. The apparatus of claim 14 wherein a flow distribution plate is positioned between said filter tank wall and said laterals, at least one liquid metering orifice and at least one gas metering orifice in said plate being in fluid communication with said opening in said filter tank wall.
16. The apparatus of claim 14 wherein said opening in said filter tank wall is sufficiently large to provide passage of both gas and liquid therethrough during said concurrent gas/liquid backwash operation.
17. The apparatus of claim 11 wherein said baffle is an upstanding partition positioned in said main conduit and spaced from a sidewall thereof.
18. The apparatus of claim 11 wherein said baffle is an inverted L-shaped partition having a vertical portion and an upper horizontal portion, said upper horizontal portion having a plurality of openings therein.
19. A concurrent backwash distribution apparatus for a filter having a filter tank, with a plurality of underdrain laterals in said filter tank and a filter media bed positioned above said underdrain laterals, a flume positioned adjacent said filter tank and in fluid communication with said underdrain laterals, a floor of said filter tank having substantially the same elevation as a floor of said flume, said concurrent backwash distribution apparatus comprising:
a separator device positioned in said flume so as to define an secondary flume between said separator device and said underdrain laterals, said secondary flume in fluid communication with said flume and said underdrain laterals, said separator device having at least one flume liquid metering orifice located in said separator device in a lower part thereof, said flume liquid metering orifice positioned so as to convey liquid from said flume to said secondary flume during a concurrent gas and liquid backwash of the filter and so as to be below a gas/liquid interface in said secondary flume during the concurrent gas/liquid backwash operation in said filter;
said separator device extending to a height which is less than a height of said flume to define a clearance above said separator device; and a filter tank wall separating said secondary flume and said laterals, said filter tank wall having at least one opening to provide fluid communication between said laterals and said secondary flume.
a separator device positioned in said flume so as to define an secondary flume between said separator device and said underdrain laterals, said secondary flume in fluid communication with said flume and said underdrain laterals, said separator device having at least one flume liquid metering orifice located in said separator device in a lower part thereof, said flume liquid metering orifice positioned so as to convey liquid from said flume to said secondary flume during a concurrent gas and liquid backwash of the filter and so as to be below a gas/liquid interface in said secondary flume during the concurrent gas/liquid backwash operation in said filter;
said separator device extending to a height which is less than a height of said flume to define a clearance above said separator device; and a filter tank wall separating said secondary flume and said laterals, said filter tank wall having at least one opening to provide fluid communication between said laterals and said secondary flume.
20. The apparatus of claim 19 including a flow distribution plate positioned between said filter tank wall and said laterals, said flow distribution plate having at least one lateral liquid metering orifice and at least one gas metering orifice, both of which are in fluid communication with said opening in said filter tank wall.
21. The apparatus of claim 19 wherein said separator device is an upstanding partition positioned in said flume and spaced from a sidewall thereof.
22. The apparatus of claim 1 wherein said flume has a floor which is at substantially the same elevation as a floor of said filter tank.
23. The apparatus of claim 11 wherein said common main conduit has a floor which is at substantially the same elevation as a floor of said filter tank.
24. The apparatus of claim 11 wherein said baffle positioned within said common main conduit has a lower part attached to said common main conduit, said baffle having a vertical portion spaced from a sidewall of said common main conduit.
25. A method of introducing a backwash gas and a backwash liquid to a filter having a filter tank, said method comprising the steps of:
a) concurrently introducing said backwash gas and said backwash liquid into an enclosed flume positioned adjacent said filter tank;
b) establishing a first gas/liquid interface in said enclosed flume;
c) passing said backwash liquid through at least one flume liquid metering orifice which is in fluid communication with said enclosed flume, said flume liquid metering orifice positioned below said first gas/liquid interface;
d) establishing a second gas/liquid interface in said enclosed flume, said second gas/liquid interface positioned below said first gas/liquid interface;
e) passing said backwash liquid into said filter tank through an opening in a filter tank wall separating said enclosed flume and said filter tank; and f) passing said backwash gas through an opening which is above the second gas/liquid interface and below the first gas/liquid interface from said enclosed flume into said filter tank simultaneously with said backwash liquid.
a) concurrently introducing said backwash gas and said backwash liquid into an enclosed flume positioned adjacent said filter tank;
b) establishing a first gas/liquid interface in said enclosed flume;
c) passing said backwash liquid through at least one flume liquid metering orifice which is in fluid communication with said enclosed flume, said flume liquid metering orifice positioned below said first gas/liquid interface;
d) establishing a second gas/liquid interface in said enclosed flume, said second gas/liquid interface positioned below said first gas/liquid interface;
e) passing said backwash liquid into said filter tank through an opening in a filter tank wall separating said enclosed flume and said filter tank; and f) passing said backwash gas through an opening which is above the second gas/liquid interface and below the first gas/liquid interface from said enclosed flume into said filter tank simultaneously with said backwash liquid.
26. The method of claim 25 including the step of passing said backwash gas and said backwash liquid through a flow distribution plate positioned between said enclosed flume and said filter tank.
27. The method of claim 25 including the step of passing at least one of said backwash gas and said backwash liquid through a separator device positioned in said enclosed flume to define said second gas/liquid interface.
28. The method of claim 25 including the step of passing said backwash liquid and backwash gas into a plurality of underdrain laterals in said filter tank.
29. The method of claim 27 wherein said separator device is a baffle, said flume liquid metering orifice located in said baffle.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US2311696P | 1996-07-31 | 1996-07-31 | |
| US60/023,116 | 1996-07-31 | ||
| PCT/US1997/013512 WO1998004332A1 (en) | 1996-07-31 | 1997-07-31 | Apparatus for distributing gas and liquid during concurrent gas/liquid backwash in flat bottom flumes |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2262626A1 CA2262626A1 (en) | 1998-02-05 |
| CA2262626C true CA2262626C (en) | 2005-07-26 |
Family
ID=21813223
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002262626A Expired - Lifetime CA2262626C (en) | 1996-07-31 | 1997-07-31 | Apparatus for distributing gas and liquid during concurrent gas/liquid backwash in flat bottom flumes |
Country Status (3)
| Country | Link |
|---|---|
| AU (1) | AU3743697A (en) |
| CA (1) | CA2262626C (en) |
| WO (1) | WO1998004332A1 (en) |
Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CA2389155A1 (en) | 2001-06-06 | 2002-12-06 | United States Filter Corporation | Filter media retaining cap and hold down grid |
| US6991726B2 (en) | 2002-07-01 | 2006-01-31 | Usfilter Corporation | Filter having a media retaining plate |
| US6830684B2 (en) | 2002-07-10 | 2004-12-14 | U.S. Filter Corporation | Integrated liquid and gas distribution device for underdrain block laterals |
| US8226834B2 (en) | 2005-05-17 | 2012-07-24 | Xylem Water Solutions Zelienople, Llc | Apparatus and method for distributing gas and liquid during backwash in filter underdrain flumes using dual separation |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5068034A (en) * | 1990-05-03 | 1991-11-26 | Unilift Corporation | Purification underdrain with means to compensate for flow and pressure differences between laterals |
| US5328608A (en) * | 1992-05-27 | 1994-07-12 | The F.B. Leopold Co., Inc. | Mutli-lateral filter underdrain block |
-
1997
- 1997-07-31 CA CA002262626A patent/CA2262626C/en not_active Expired - Lifetime
- 1997-07-31 WO PCT/US1997/013512 patent/WO1998004332A1/en active Application Filing
- 1997-07-31 AU AU37436/97A patent/AU3743697A/en not_active Abandoned
Also Published As
| Publication number | Publication date |
|---|---|
| CA2262626A1 (en) | 1998-02-05 |
| WO1998004332A1 (en) | 1998-02-05 |
| AU3743697A (en) | 1998-02-20 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| EEER | Examination request | ||
| MKEX | Expiry |
Effective date: 20170731 |