Note: Descriptions are shown in the official language in which they were submitted.
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~ . ~RAVELING R~T~ FILT~R WIT~ SURF~ OE WAS~
This invention relates generally to liquid
~ filtration ~ystems and, more ~specifically, to
traveling bridge-type cle~ sr device~ for
~equentially cle~ni n~ a plura].ity o~ downward flow,
su~y~ e~l ~olid~ f~lter units located within a
relatively large filtration tank.
It i~ ~ell known in the art ~o utilize
filtration tank3 divided into a plurality of filter
cell~, one adjacent the other, and all contai~ing a
multi-layer arrangement o~ granular ~ilter media
~uçh a~ sand, gravel and the like. In downward flow
filtration ~y~tem~ o~ ~hi8 type, w24ter or o~her
liguid con~a{ning ~ p~n~e~ solid partic}e3 ~ 8
i~,L,G~c~ into the ~iltration tanX from above and
clarified water i8 drawn off from a ch.-~er beneath
the filter c~ . During downward flow through the
individual c~118, parti~ulat~ ~atter ~,en~L-A~d
within tha layer~ of g~n~ r ~iltar media.
~ ually, th~ partic~lat~ matter clog~ thQ filter
media, thereby re~lc~ n~ ~ha filtering capability o~
tho ~y~tem. Thu~, thera i8 a need ~or periodic
cl~n~q of thu filgsr cellq. It i3 al80 known to
maintaln s~h units in co~t~ n-~o~ operation duri~g
cl~n~n~ by tho u~ o~ trav~ling bridge devic~s
which move from one filter cell to the next, to
backwash individual cells while permitting the
filtration process to continue in the remaining
cells.
Example~ of traveling bridge apparatu~ of thi8
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~ . type may be seen in U.S. Patent Nos. 4,540,487;
4,486,307; 4,133,766; 3,984,3~6; 2,235,227, and
649,409. Typically, traveling bridge system~
include an overhead carxiage, movable along tracks,
guideways or the like, which carries, e.g., a
backwash hood succe~sively ~nga~eable with th~ upper
end of each ~ilter cell. For a downflow t~pe
filter, water or other treatment liguid is generally
introduced into the cell from below, in a
counterflow arrany~ t to the normal filtering
direction. The backwash hood typically includes a
suction head for drawing out fluid and debri~ forced
to the surface of ~he filter cell a~ a result of the
backwa~h. As the backwash of an individual cell is
completed, the traveli~g bridge will index the
backwa~h hood to the next ad~acent cell. See, for
example, U.S. Patent ~o. 4,308,141, in which a
modular filter 8y3tem i~ dlscloRed, and wherein a
traveling bridge type backwa~h system is indexed to
successive filter unlt~.
Thare are al~o known in the prior art devices
for bre~k~ng up a mat or lay~r of material which :
forms on th~ s~r~ace o~ a filter ~ed. For example,
in U.S. Patent No. 2,33~,749, a pair of surface
rakin~ --h~n~ ~m are utilized on either 3ide of a
backwa~h eai~son. In U.S. Patent No. 2,194,071, a
ov~rhead s~rfac~ wa~h ~ystem is di~closed wherein a
spray head having fixed ~t~ i8 sus~~nded from a
carriage, enabling wa~h liquid to be d~rected
do~.~wdrdly onto the upper surface o~ the filter bed
~ a~ the carriage move~ along the length of the ~ank.
A conv~ntional, 3tationary backwa~h 3ystem is
utilized to wash the loosened material upwardly into
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one or more stationary discharge troughs.
U.S. P~ent Nos. 4,152,265 and 4,454,034
disclose traveling bridge filtration systems which
combine backwash operations with the u~ ation of
mechanical scarifying blades which are said to break
up and loosen the mat on the surface of the bed.
In the present invention, a unique combination
of filter cell cleaning devices is provided in a
traveling bridge configuration. In one exemplary
embodiment, an elongated, rectangular filtration
tank is divided into a plurality of individual cells
by a plurality of laterally spaced, substantially
parallel partitions ext~n~i ng across the width of
the tank. The tank i8 further provided with tracks
or guideways supporting a traveling bridge for
~v~ -nt along the top of the tank, in a direction
transverse to the orientation of the upright
partition~. In an exemplary embodiment of the
invention, the traveling bridge compri~es a carriage
from which i8 ~uspended surface wash means as well
as backwa~h means, located wi~hin a ~ingle hood
assembly, a~a..g~d ~or ~equential ~ealing engagement
with each filt2r cell.
The single surface wash/backwash hood assembly
of thi~ exemplary emko~ t of the invention
e~tends acro~s substantially the full width of the
tank, l.e., along substantial}y the entire length of
~he indi~idual filter cells. The hood per se
includes a pair o~ lower side wall portions which
are spaced apart a distance corresponding to the
distance between the individual cell partitions, as
well as upper side wall portions which are inclined
toward each other and which intersect at a hood
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apex.
Located within the hood, and extending
substantially parallel to, and midway between, the
lateral lower side wall portions o~ the hood, is a
surface wash manifold, extending substantially
acro~s the width of the tank, and provided at spaced
positions along it~ leng~h with a plurality of
discharge nozzles from which liquid is dispen~ed
under pres~ure onto the upper surface of the filter
bed. The surface wash manifold is connected to a
substantially vertically oriented s~rface wash
conduit which extends upwardly through the hood to
fir~t fluid surface wash pump mounted on the
traveling bridge carriage.
In the exemplary embodiment, water i5 supplied
to the pump from a clean water trough ad~acent the
tank, although it will be appreciated that water may
also be supplied from any fresh or clean water
source.
A horizontal backwash manifold i~ al80 located
within the hood, above the ~ur~ace wa~h manifold,
and generally coextensive therewith. The bacXwa~h
mani~old ~8 preferably located in the area of the
lnclined upper wall portions of the hood. The
backwash manifold is connected substantially m~dway
along its lens~h to a ~ertical suction conduit ~hlch
also extends upwardly, through the hood, to a second
fluid bacXwa~h pump mounted on the travellinq bridge
carriage. This second pump is a suction pump, ~he
inle~ side of which is connected to the vertical
suction conduit.
The horizontal backwash manifold is provided
with a plurality of uniformly arranged aperture3
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~ extending along its length and about its periphexy
to uniformly draw liguid and accompanying debris
upwardly out of ~ filter cell in a dire~tion
opposite the normal filter flow direction to
thoroughly backwash the ~ilter media.
In order to index the hood assembly to
successive cells along the length of the filtration
tanX, the hood assembly 1~ rec:iprocable vertic~lly a
distance sufficient to enable the hood as~embly to
disengage from the cell partitions or wall~, and to
clear the adjacent cell partitions during lateral
mo~ nt to the ne~t cell. To this end, portions of
the vertical surface wash conduit and vertical
backwa~h conduit, respectively, may be provided with
fle~ible, e.g., bellows-type, connectors whlch
permit a relatively small degree of vertical
mov~ nt of the hood structure vis-a-vis the
vertically fixed carriage.
Accordingly, in it3 broadest aspect, the
! pre~ent invention relates to a traveling bridge
filtar cle~n~ng sy~tem including a liguid filtration
tank divlded into a plurality o~ ad~acent ~ilter
cells, each of ~he cells cont~ nl ng filter medla; R
traveli~g bridge carriage located above the tank and
movable along the tank, the carriage mounting
sur~ace wash means and backwa~h means within a
single hood a-~embly adapted to ~ealingly enga~e
successive ones of the filter cells.
For eac~ individual cell, the carriage mounted
first and second pumps may b~ ~imultaneously
activated 30 that the mat or crust of material
present on ~he upper surface of the filter bed is
broken up by the surface wash, while at the same
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~ . time, the backwash expand~i and cleans the filter
media from below, drawing dirt and debris as well as
the broken surface ~ru~t or mat mat~rlal upwardly
into the suction conduit locatad in the hood
assembly. In this way, tha filter media i~
effectively cleaned, the formation of mudballs i~
preventsd, and the ~ull filtration capability of ~he
cell is re~tored.
It will therefore be appreciated that the
present invention provide~ a unique combination of
surface wash and backwash means in a single hood
assembly within a traveling bridge filter cleaning
system, which effectively cleans successive cells of
a multi-cell tank without disturbing the filtering
proces~ in the ~ -1 n~ ~g cell~.
Additional object~ and advantages of the
subject invention will become apparent from the
detailed descriptlon which follows.
Embodiments of the invention will ~e described
with reference to the accompanying drawings, in which:
FIGUR~ 1 is a schematic ~ide view of a
traveling bridge type flltration ystem ln
accordance with the invention;
FIGURE 2 i3 a 3ch~ ~tic plan view of the
- filtration tank shown in FIGUR~ 1 with the traveling
bridge components L~ ed ~or clarity; and
FIGURE 3 is a schematic end view of a traveling
bridge filtration system shown in FIGUR~ 1.
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Referring now to FIGURES 1-3, a su~pended
solids filtration apparatus in acc~rdance with this
invention includes a substantially rectangular tank
10 comprising side wall~ 12, e!nd walls 14 and a
bottom wall 16. The tank is dlivided into a
plurality of filter cells 18 by generally upright,
spaced partition~ 20 which extend from one side of
the tanX to ~he other, in a substantially parallel
arrangement, and substantially transversely of the
direction of elongation of the tank. It will be
appreciated, however, that the shape of the tank and
the orientation of the filter cell partition~ may be
varied in accordance wi~h de~ign requirements, etc.
The tank include~ an underdrain or subfloor 22
resting on the partitions 20, and which supports a
multi-layer filter media bed compri~ing, preferably,
layers of gravel 24, sand 26 and anthracite 28 (or
other suitable filter media). The ~pace between
bottom wall 16 and ~ubfloor 22 compri~eq a chamber
30 which for~s a claarwell. The filtered water
flows past a weir area 32 including a vertical
baffle 33 and out o~ the tank via an outlet 34.
Under normal CiL~l ~ances, the water or other flu~d
to be treated ~8 ~upplied to the tank at a level
above the filter media by any quitable m~ans (not
shown) and ~h~ tank i8 filled to a level 36.
In accordanc~ with one exemplary embodiment of
this invention, sur~ace wash and backwash means are
movably supported on a carriage 38 provided with a
plurality of wheels 40 which are guided along tracX~
or guideways 42 on an upper extension 44 of the
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~ . tank. It will be appreciated that the tracks or
guideways may also be part of an overhead framewor~
or the liXe, ~eparate from thoa tanX design.
Further, in thi~ regard, it i3 to be noted that the
carriage and controls for tndl~i ng the carriage are
not part of thi~ invention, alld may be of any
conYentional constructlon.
The carr~age 38 support~ a oombined sur~ace
wa~h and backwash device 46 in s~t~pende~
relationship vis-a-vi~ the carriage.
The cr 'ined surface wash/ba~kwash devic.e 46 of
this inv~ntion includes a single hood ~tructure 48
which extends acro3~ the tank, along ~ub~tantially
the entire length of ~he filter cells 18. The hood
48 include~ a pair of lower side wall portion3 50
which are ~p~eA apart a di~tance corre~pon~ng
substantially to the distance between the ~ilter
cell partitions 20. Tapered wall portion~ 52 extend
inwardly and upwardly from the parallel side wall
portion to an apex 54, although it will be
- under~tood that other hood configurations may bs
u~ilized.
Located withln th~ hood 48, and e~t~n~ng
substantially parallel to the ~id~ wall portions 50
i~ a surface wa~h manifold 56 provided with a
plurality of nozzles 58 ext~n~ ng from ei~her side :
o~ tha manifold, and ln- 8p~e~ relation~hip along
the length thcreof. A surface wa~h fluid ~upply
conduit 60 extend~ substantially vertically upwardly
from the mani old and out of the hood 48 to a pump
62 mounted on the carriage 38. It will be
under~tood that conduit 60 i3 connected to the
outlet ~ide of th~ pump, while a cond~it 64 i~
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~ . connected to the inlet ~ide of the pump. Conduit 64
3Upplies li~uid to the pwmp and, in one exemplary
Pmbodiment, the supplied liqui~d originates in a
trough 66 mounted to one ~ide of the filtration
tank. The trough 66 receiYe3 filtered water from
the weir area 32, and to thi~ ~end, a pipe 68 extend~
between the trough and the wei:r area thereby
providin~ a ready ~upply of liquid for the surfacQ
wash pump.
Alternatively, fre~h clean water from any
suitable source may be ~upplied to the surface wash
device.
The laterally spaced, substantially parallel
~ide wall~ ~0 are provided along their lowermo~t
surface~ with se~lin~ means ~uch as rubber gasket~
68 which ara secured ~her~to by any ~uitable mean~,
enabllng air and water ~ight ~eal~ to be establlshed
between the hood 48 and individual filter cell~ 18.
The backwash device include3 a backwash ~uction
conduit 72 which exte~d~ do~ ardly from a suction
pump 74 mounted on the carriage 38. The ~uction
conduit 72 ~tend~ through the hood 48,
appro~imat~ly midway along th~ length of the hood,
and i8 cvn~ ed to a horizontal backwa~h ma~i~old
76 which ~tends generally parallel to the cell
partition~ 20 and 8ubstantially acros~ the antire
width of th~ tank, wi~hin an upper portion o~ the
hood, ~etween th~ incli~ed portions 52 of the hood
sidewalls. The manifold 76 ~s also provided with a
plurality of parforation~ (not ~hown) which provida
for substantially uniform ~uction within the hood 48
across the respective cell 18.
It will he appreciated that in a cell cleaning
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~ operation, carriage 38 will successively index the
surface wash and backwash means within the hood 48
to the individual filter cells~ 18, in the direction
of the arrow 7B in EIGURE 1. At the same time, it
will be appreciated that means mu~t be provided to
move the bood 48 vertically toward the cells 18.
The -v~ -~t is required to enable sealing
engagament between the hoo~ 48 and an individual
cell 18. After cleaning, tha surface wa~h/backwa~h
hood i~ retracted vertically upwardly away from the
cells a relatively small distance, e.g., on the
order of two ;n~hes~ to provide clearance which
permit~ horizontal in~; ng of the hood assembly to
the next cell. The vertical reciprocatory v~- -nt
may be effected by any conventional mean~ (not
shown), such as hydraulic cylinders, ~acks, etc.,
along with conventional control~.
In order to permit relative movement between
the hood 48 and carriage 38, flexible couplings 78,
80 are interpo~ed in conduits 72, 60, respectively.
The couplings may be in the nature of a bellow~ or
any other ~uit~ble flexing mean~.
It is . fur~her ~eature of the invent~on that
the tank includ~, a~ one end thereof, horizontal and
vertical wall portion 82, 84 to create an e~tended
tank portion which accc odate~ the traveling brldge
carriage when not in use, enabling unre~tricted
acce~ fro~ above to all of the filter cells.
In operation, after the carriage has been moved
to one end of the tank, i.e., to the far right in
FIGURE 1, t~e surf~ce wa~h/backwash hood i~ lowered
into position, beneath water level 36, such that the
seals or gasXats 68 engage the upper end~ of the
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partitions 20 of the fir~t filter cell 18. After
surface wash and backwash are completed as to the
first cell, the hood assembly is retracted upwardly
and moved laterally Yia carriage 38 to the next
filter cell 18 and thereafter lowered into position
so that the hood 48 engages the second filter cell,
et~. This procedure may be repeated until the last
cell i~ reached at the far le~t ~ide of the tank
(FIGURE 1).
It will be appreciated that as the hood
assembly is lowered into po~ition over a subjacent
filter cell, qasXets 68 on the hood wall~ establish
a hydraulic seal which isolates the filter cell 18
from the re ~; ni n~ cells in the tanX, and wh~ch
prevents debris in the one cell from moving into one
or bo~h ad;acent cells.
During surface wash, pump 62 supplie3 water
under pres ure to the horizontal surface wash
manifold 56 via conduit 60. The water is di~charged
through the plurality of nozzle~ 58 and brea~s up
any crust or mat-like material Which has formed on
the surfac~ o~ th~ fllter bed. Suitable ~crePnln~
material may be used if des~red to cover the
perforations in the manifold 56 to prevent clogg~ng
of the p~rforation~ with dislodg~d debris, filter
media, etc.
BacXwa~h i~ carrl~d ou~ simultaneou~ly with the
abov2 d~scribed surface wash. During backwash,
-Ruct1on i8 created in the hori~ontal ~uctio~
manifold 76 via pump 74, drawing water upwardly,
countercurrent to the normal flow, through the
underdrain or sub floor 22, filter media layers 24,
26, 28, hood 48, manifold 76 and backwa~h suction
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conduit 7~, all thç while cleansing the filter media
and removing particulate matter, including that
dislodged in the ~urface wash operation. From pump
74, the backwa~h liquid is discharged through a ho~e
to a trouqh or drain (not shown) in a conventional
~nn~r .
While the invention has been described in
connection with what i~ pre~ently considered to be
the most practical and preferred embodiment, it i8
to be understood that the invention i~ not to be
limited to the disclo~ed embo~ -nt, but on the
contrary, i8 intended to cover various modifications
and eguivalent arr~n~ -nts included within the
spirit and ~cope of the appended claims.
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