Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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METHOD AND APPARATUS
FOR FILTERING A LIQUID
BACKGROUND OF THE INVENTION
l.Field of the Invention
The present invention relates to the
treatment of liquids and, more particularly, pertains
to a method and apparatus for filtering liquids.
2. Description of the Prior Art
It is well known to filtrate a liquid by
supplying the same to a bed of particulate filter
media contained in a tank having a truncated conical
bottom end portion configured to prevent the
farmation of stagnant or aead zones within the bed of
particulate filter media. For instance, United States
Patent No. 4, 126, 546 issued on November 21, 1978 to
Hjelmner et al. discloses a sand filter comprising a
main tank having a funnel-like shape bottom portion.
The geometry of the main tank results in the filter
being relatively tall wr-Eich presents a number of
disadvantages. The liquid to be filtered is delivered
along a vertical direction into the sand and passed
gradually upwardly theret:hrough to form a pool of
filtrated liquid above tht~ top surface of the bed of
sand. Deflectors must be provided to prevent
particles of sand to come in direct contact with the
outlet end of each delivery pipe used to supply the
liquid to be treated. R single central transport
device is provided to continuously convey dirty
particles of sand from t~~e bottom of the tank to a
washing device immersed in the pool of filtrated
liquid. The dirty particles flows downwardly through
a single annular wash path defined in the washing
device in counter-current with a wash liquid before
being recycle onto the top of the filter bed. A
deflector is provided underneath the washing device
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to distribute the cleaned particles of sand on the
top surface of the filter bed.
Although the sand filter described in the
above mentioned patent ~s effective, it has been
found that there is a nE~ed for a more compact and
lightweight filter which is adapted to provide an
improved distribution of a particulate filter media.
SUMMARY OF THE INVENTION
It is therefore an aim of the present
invention to provide ,=~ relatively compact and
lightweight filter for filtering a liquid by causing
it to flow through particulate filter media.
It is also an aim of the present invention
to provide a filter which allows continuous washing
of the particulate fiater media and effective
distribution thereof.
It is a further aim of the present
invention to provide an improved washing device for
continuously washing dirty particles of filter media.
Therefore, in accordance with the present
invention, there is provided a filter for filtering a
liquid by causing the same to flow upwardly through a
particulate filter media, comprising a main tank, at
least two upstanding sub-i-ecipients integrated within
the main tank for conta;.ning a particulate filter
media adapted to fi:Lter a liquid seeping
therethrough, inlet me;~ns for delivering and
distributing the liquid ~.:~ be treated into the sub-
recipients, and outlet means disposed above a top
surface of the sub-recipients for discharging the
liquid as a filtrated liduid. The provision of the
sub-recipients allows to reduce the height of the
filter.
In accordance with a further general aspect
of the present inventi~7n there is provided an
apparatus for filtering a liquid comprising a main
tank, at least two laterally separate beds of
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particulate filter media contained in respective sub-
recipients integrated within the main tank, inlet
means for delivering a liquid to be treated into both
sub-recipients, and outlet:: means for discharging the
liquid which has seeped through the beds of filter
media.
In accordance with a further general aspect
of the present invention, there is provided a device
for washing particulate filter media contaminated
during filtration of a ~~iquid, comprising a hollow
body defining a wash patr~, filter media inlet means
for directing a flow of dirty filter media in a
downward direction along the wash path, washing fluid
inlet means for receivinc a flow of wash liquid in
counter-current to the filter media along the wash
path, and a plurality of axially spaced-apart arrays
of agglomeration breaking members distributed along
at least a portion of t.:he wash path, each array
including a number of side-by-side agglomeration
breaking members extending across the wash path.
BRIEF DESCRIPTION OF THE Dr~AWINGS
Having thus generally described the nature
of the invention, referen.~e will now be made to the
accompanying drawings, shc;wing by way of illustration
a preferred embodiment thereof, and in which:
Fig. 1 is a schematic, simplified
elevational view of an apparatus for filtering a
liquid in accordance wi~:h a first embodiment of
present invention;
Fig. 2 is a scruematic top plan view of a
liquid delivery pipe network of the apparatus of
Fig. l;
Fig. 3 is a schematic perspective view of a
washing device forming pant of the apparatus of Fig.
l;
Fig. 4 is a schematic perspective view of
the internal structure of the separator of Fig. 3;
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Fig. 5 is a schematic top plan view of the
washing device shown in relation with the upper
section of the apparatus of Fig. 1;
Fig. 6 is a schematic perspective view of a
filtered liquid outlet ~tnd a waste liquid outlet
provided at an upper end of the apparatus of Fig. 1;
Fig. 7 is a scl-:ematic perspective view of
the waste liquid outlet;
Fig. 8 is a sc~~ematic perspective view of
an end portion of a filter media return pipe of the
washing device of Fig. 3;
Fig. 9 is a top plan view of a backwash
system of the apparatus of Fig. 1;
Fig. 10 is a schematic, simplified
elevational view of an apparatus for filtering a
liquid in accordance with a second embodiment of the
present invention;
Fig. 11 is a schematic top plan view of the
apparatus of Fig. 10, illustrating the disposition of
a washing device forming p:~rt of the apparatus;
Fig. 12 is a schematic perspective view of
the internal structure c:f a part of the washing
device;
Fig. 13 is an enlarged elevational view of
a return pipe of the apparatus of Fig. 10;
Fig. 14 is a r~ransversal cross-sectional
view taken along line 14-14 in Fig. 13; and
Fig. 15 is a l..~ngitudinal cross-sectional
view taken along line 15-1~i in Fig. 14.
DESCRIPTION OF THE PREFERR:~~D EMBODIMENTS
Now referring .o the drawings, and in
particular to Fig. 1, an apparatus 10 for filtering a
liquid, such as water, will be described. The
apparatus 10 of the instant invention is particularly
suitable for filtering water before being directed to
an aqueduct. However, other applications are
contemplated as well.
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The apparatus 10 comprises a main tank 12
having a cylindrical side wall 14, a flat bottom wall
16 and a top wall 18. A secondary tank 20 having a
cylindrical side wall 22 and an open bottom end 24 is
mounted on the top wall 18 of the main tank 12. As
seen in Fig. 6, the main tank 12 and the secondary
tank 20 communicate together via a circular opening
26 defined in the top wall 18 of the main tank 12.
The main tank 12 and the wecondary tank 20 are formed
of a thermoplastic material, such as polyethylene.
According to a preferred embodiment of the present
invention, the secondary tank 20 is welded to the
main tank 12. AlternativF.~ly, the secondary tank 20
and the main tank 12 could be integrally molded. A
lid (not shown) may be disposed on the top open end
of the secondary tank 20 to prevent external agents
from altering the filtered liquid contained in the
secondary tank 20.
As seen in Fig. 2, a liquid delivery pipe
network 28 is provided for discharging the liquid to
be processed into the main tank 12. The liquid
delivery pipe network 28 basically includes a
manifold 30 having one inlet 32 and four outlets 34,
each of which is connected to a valve 36 which in
turn is connected to a delivery line 38. The inlet 32
of the manifold 30 is adapted to be connected to a
source (not shown) of liquid to be processed. Each
delivery line 38 is compo~>ed of a linear plastic pipe
40 connected to a curv:~d plastic pipe 42 having
consecutive perpendicular portions 44 and 46. As seen
in Fig. 1, the distal or bottom end of portion 46 of
each curved pipe 42 is welded to the bottom wall 16
of the main tank 12. Each portion 46 is provided with
a pair of lateral opposed outlets 48 through which
the liquid to be treated is discharged in a
horizontal direction. Such a multiple delivery piping
system provides improved distribution of the liquid
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to be filtered, thereby contributing to enhance the
overall efficiency of the filtration process.
As seen in Fig. 2, each vertical pipe
portion 46 is received ~n a frusto-conical plastic
recipient 50 having its smaller diameter end welded
to the bottom wall 16 of the main tank 12. The
frusto-conical recipients 50 extend upwardly from the
bottom wall 16 above the lateral opposed outlets 48
up to approximately a thin-d of the height of the main
tank 12. The inner spice of the frusto-conical
recipients 50 around the pipe portions 46 is filled
with a granular filter n;edia (not shown), such as
sand. Accordingly, the lateral opposed outlets 48
through which the liquid to be processed is
discharged are buried in the filter media. The
provision of such fru~to-conical recipients 50
advantageously allows to reduce the overall height of
the apparatus 10 by reducing the distance between the
bottom of the tank 12 and the top surface of the bed
of filter media for a given top surface of filter
media. It is understood that the number of frusto-
conical recipients varies with the size of the main
reservoir 12.
According to a preferred embodiment of the
instant invention, concrete is poured within the main
tank 12 around the frusto-conical recipients 50 after
the apparatus 10 has been shipped and installed at
the appropriate location so as to prevent potential
entrapment of stagnant wager within the main tank 12,
which could result in un,:3esirable bacterial growth.
According to another embodiment of the present
invention, the frusto-conical recipients 50 are
integrally molded with th~~ main tank 12 so as to form
the bottom wall 16 thereC.~f, thereby eliminating the
need of pouring concrete within the main tank 12 in
order to fill the space between the frusto-conical
recipients 50.
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In operation, the liquid to be treated is
continuously supply into the filter media through the
liquid delivery pipe netw<~rk 28, thereby forcing the
liquid to rise in the filter media through seepage.
Eventually, the supplied liquid seeps up out of the
granular filter media to form a pool of filtered
liquid above the frusto-conical recipients 50 and the
concrete. The level of filtered liquid is raised
until it reaches the uppe~° end of the secondary tank
20 where the overflow of filtered liquid is collected
via a filtered liquid outlet 52.
As seen in Fig. 6, the filtered liquid
outlet 52 is essentially composed of a plastic box 54
welded to the outer surface of the cylindrical side
wall 22 of the secondary tank 20 for receiving the
overflow of filtered lquid passing through an
opening 56 defined at the upper end of the
cylindrical side wall 22 of the secondary tank 20.
The filtered liquid collected by the plastic box 54
is directed to a desired location via an outlet line
58 extending from an undersurface of the box 54.
As seen in Fig 1, the apparatus 10 further
includes a filter media cleaning or washing system 60
adapted to be continuous-~y operated to prevent the
filter media from being negatively altered by the
liquid to be filtered. In other words, the filter
media cleaning system 60 allows the filter media to
substantially preserve its original condition,
thereby ensuring the overall quality of the filtering
process. The filter media cleaning system 60
essentially includes a source (not shown) of
pressurized gas, such as sir, which is operational to
force some liquid and fi:i.ter media to be displaced
upwardly from the frusto-conical recipients 50 to a
washing device 62 via four conduits 64 extending from
the washing device 62 into respective ones of the
frusto-conical recipients 50.
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More specifically, each conduit 64 includes
a first plastic pipe 67 and a second plastic pipe 66.
The plastic pipe 67 of each conduit 64 is connected
at an upper end thereof to the source of pressurized
gas to convey the gas into the filter media. The
pipe 66 of each conduit 6~ defines a passage through
which may flow the liquid and filter media. As seen
in Fig. 1, the lower enc:~ portions of the pipes 66
extend into the pipes 46 of the unfiltered liquid
delivery lines 38. It is noted that the liquid
delivery lines 38 are configured to prevent the
liquid to be treated to flaw past the outlets 48.
As seen in Figl. 1, 3 and 4, the washing
device 62 is disposed oi.tside of the main tank 12
within the secondary tank 20 and includes a container
68 into which the conduits 64 extend for discharging
filter media to be washed. A number of vertically
spaced-apart arrays of transversally extending
elongated members 70 are disposed below the fluid and
filter media delivery end of the conduits 64 within
the container 68 in order to break up aggregates of
filter particles and to create a turbulence in the
flow of filter media flowing therethrough by gravity
to effect effective separation of the aggregated
particles. As seen in Fig. 4, each array of elongated
members includes a number of laterally spaced-apart
elongated members 70 which are in offset relationship
with the elongated mem~~ers 70 of the adjacent
vertically spaced-apart axray. According to the first
illustrated embodiment c:f the present invention,
successive arrays alternately include four and five
elongated members 70. Thke elongated members 70 are
mounted at opposed ends thereof to a pair of support
plates 72 which are in turn mounted to the inner
surface of the container 68.
Four filter media return pipes 74 extend
from the container 68, below the vertically spaced-
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apart arrays of transversally extending elongated
members 70, through the tap wall 18 of the main tank
12 for returning the granular or particulate filter
media into respective frmsto-conical recipients 50.
Throughout their passage through the washing device
62, the filter particles encounter clean filtered
liquid flowing upwardly ti~rough the returns pipes 74
from the immersed bottom ends thereof.
As seen in Figs. 1, 5 and 7, a waste liquid
outlet 76 is connected to the washing device 62 via a
pipe 78 for discharging the liquid which has been
directed into the washing device 62.
More specifically, the waste liquid outlet
76 includes a plastic box 80 which is welded to the
outer surface of the secondary tank 20 for receiving
the waste liquid from the pipe 78, which extends
through the cylindrical side wall 22 of the secondary
tank 20. The waste or dirty liquid is evacuated from
the box 80 through an cuatlet line 82 formed of a
number of end-to-end plastic pipes extending
downwardly from the bottrm wall 84 of the box 80. A
weir 86 extends upwardly from the bottom wall 84 of
the box 80 upstream of the pipe 82 at an elevation
which is at least equal tc: the pipe 78 to ensure that
the waste fluid will pass from the washing device 62
to the waste liquid outlet 76 at an appropriate flow
rate such as to allow the:: particles of filter media
to sink in the washing device 62. Accordingly, the
level of liquid within tY:e container 68 and the box
80 will be substantially equal.
In operation, pz~essurized gas is discharged
through the lower end of the pipes 67 of the
conduits 64 into the fi~.ter media and the liquid
contained in the frusto-conical recipients 50,
thereby giving rise to t~ze formation of bubbles. As
the pressure within the passage deffined by the outer
pipe 66 of each conduit 6~ is less than the pressure
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within the main tank 12, the bubbles escape through
the passage of each conduit 64 bringing with them
some filter media particles. Therefore, it can be
said that the bubbles ha~.re a lifting effect on the
particles of filter media.
At their exit t'rom the discharged end of
the passages of the conduits 64, the bubbles come in
contact with the liquid contained in the washing
device 62. This results in the bursting of the
bubbles, thereby allowing the filter media particles
to flow down by gravity. ,~~ substantial portion of the
liquid lift with the particles of filter media will
be discharged through the waste liquid outlet 76 with
little portion thereof flowing back into the main
container 12 via the return pipes 74. The vertically
spaced-apart arrays of transversally extending
members 70 will promote turbulence, thereby causing
the separation of the filter media particles. Indeed,
as the filter particles are heavier they will sink,
while the liquid will ter;d to remain trapped within
the container 68 with the overflow being discharge
through the waste liquid outlet 76. Accordingly, the
particles of filter medi:~ will flow back into the
frusto-conical recipients 50 via the return pipes 74.
The filtered liquid which flows upwardly through the
return pipes 74 and iz2to the container 68 is
discharged from the wash.~g device 62 via the waste
liquid outlet 76. It is understood that the height of
weir 86 can be varied t_:.~ control the quantity of
liquid withdrawn from tree pool of filtered liquid
contained in the main tank 12.
From the above, it can be appreciated that
the filter media cleanzng system 60 allows to
continuously clean the porous filter media even
during the filtration of a supplied liquid.
As seen in Figs. 1 and 8, the lower end
portion of each return pipe 74 defines a hole for
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receiving therethrough one of the conduits 64,
thereby reducing the number of holes to be defined in
the top wall 18 of the main tank 12.
Fig. 9 illust?rates a drain system 88
disposed on the bottom wall 16 of the main tank 12.
The drain system 88 includes a plurality of
perforated drain pipes 90 which extend below the
frusto-conical recipients 50 for collecting the
liquid and particles to be drained. The drain pipes
90 are connected to a valve 92 for selectively
allowing or blocking flaw through the perforated
drain pipes 90.
One advantage of the present invention is that the
apparatus 10 does not have to be pre-assembled before
being shipped. The apparatus 10 may be readily
assembled on site. Moreover, as almost all the
principal components of ttve apparatus 10 are made of
thermoplastic, the total weight thereof is
considerably inferior to the weight of conventional
steel filtering apparatus. The fact that the
apparatus 10 is essentially made of thermoplastic,
also prevents the same from being subject to
corrosion.
Figs. 10 to 15 illustrate a second filter
110 similar to the first filter 10 but having an
alternate washing device .60 mounted outwardly above
a main tank 112 of the filter 110. The washing device
160 comprises a distribution box 194 including a
cylindrical container 196 connected in flow
communication with a zone of filtrated liquid in the
main tank 112 via an upstanding pipe 198. The
overflow of filtrated liquid is discharged from the
main tank 112 via the upstanding pipe 198 as it flows
over a weir 200 (see Fi<~,. 12) extending between a
pair of parallel partiti~:an walls 202 extending in
sealing engagement with an inner surface of the
cylindrical container 19E~ to form with two other
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partition walls 204 and 206 a separate and isolated
sub-compartment within the cylindrical container 196.
The filtrated liquid flowing over the weir 200 is
conveyed to a desired lccation via an outlet line
158.
According to tree illustrated embodiment,
the dirty filter media is delivered into the bottom
portion of the cylindrical container 196 via four
transport pipes 164 having respective upper ends
spaced downwardly from th~> weir 200. As seen in Fig.
12, two pairs of diametrically opposed weirs 208
extends from the bottom wall 210 of the cylindrical
tank 196 about an upper portion of the upstanding
pipe 198 to divide th<~ bottom portion of the
cylindrical container 19:; into four equal filter
media receiving compartments 212. The dirty filter
media is delivered int-:o the filter receiving
compartments 212 by the transport pipes and flows
downwardly back into the main tank 112 via four
return pipes 174 extending downwardly from the bottom
wall 210 of the cylindrical container 196. The bottom
open end of each return pipe 174 is immersed in the
filtrated liquid contained in the main tank 112 and
is in vertical alignment with a corresponding conical
recipient (not shown) int~~rated in the bottom of the
main tank 112 to conta.n the particulate filter
media, as explained with respect to the first
embodiment of the present invention. Throughout their
passage through the return pipes 174, the particles
of filter media encounters a counter-current flow of
filtrated liquid supplied to the washing device 160
through the immersed bott«m open ends of the return
pipes 174. The filtrated liquid flowing upwardly into
the washing device 160 is discharged through an
outlet line 182 extending from the cylindrical
container 196 at a location spaced downwardly from
the weir 200. A pair of parallel weirs 214 extending
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from a bottom wall 216 between the partition wall 204
and the inner surface of the cylindrical container
196 regulates the flow of filtrated liquid withdrawn
from the main tank 112.
As seen in Figs. 13 to 15, axially spaced
apart arrays of agglomeration breaking members 170
are integrated in each of the return pipes 174. Each
array includes a number of laterally spaced-apart
agglomeration breaking members 170 extending across
the fluid passage defined by the associated return
pipe 174. The agglomeration breaking members 170 of
adjacent arrays extend at right angles to each
others. It has been fc~.znd that this arrangement
provides improved separation of the agglomerated
particles of filter media. The agglomeration breaking
members 170 are provided in the form of elongated
cylinders and are supported at opposed ends thereof
in radial bores defined through the associated return
pipes 174. A sleeve 218 is mounted on each return
pipe 174 to prevent removal of the agglomeration
breaking members 170.
As seen in Fig. 13, each set of arrays of
agglomerating breaking members 170 is provided in a
pipe segment 220 which fc:~rms an acute angle with a
vertical axis. According to a preferred embodiment of
the present invention this angle is about 35 degrees.
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