Apparatus for granular media filter

Apparatus for backwashing the filter media of a liquid filtering machine while at the same time enabling the machine to filter liquid. The machine is of the type having a tank and a continuous bed of granular filter media in the tank through which liquid having suspended solids therein for removing the solids. The apparatus comprises a partitioning chamber and a carriage for selectively supporting and conveying the chamber above the media bed, with the chamber being insertable into the bed to isolate a portion thereof from the remainder of the bed. The apparatus further comprises a mechanism to selectively allow insertion of the chamber into the bed and to remove it, and a pump to draw liquid through the isolated portion of the bed to backwash it, while filtration may proceed in the remainder of the bed. Apparatus for removing the media from the chamber and replacing it with new, cleaned or regenerated media is also disclosed.

BACKGROUND OF THE INVENTION 
The present invention relates to the separation of solids from liquids by 
filtration through granular media and, more particularly, to an 
improvement in apparatus for granular media filters of the type having a 
tank and a bed of granular filter media in the tank through which liquids 
having suspended or dissolved solids therein flow for removing the solids 
to clean the liquid. 
Granular media filters are known for removing solids from liquids. Such 
filters have long been utilized for potable water treatment but have only 
recently been introduced to wastewater treatment plants, where the solids 
may comprise microbial flocs, coagulant residues, and a variety of other 
relatively unpredictable substances. Such filters normally include a tank 
for receiving flowing liquid containing suspended solids, a bed of 
granular media supported within the tank, means for removing liquid which 
has passed through the media (filtrate), and means for periodically 
washing the granular media to remove particulates collected therein during 
filtration. Because the washing step is usually accomplished by passing 
liquid through the bed in a direction opposite to the flow direction for 
filtration, the washing step is usually referred to as backwashing. 
In one well-known granular media filter construction, filtration is 
accomplished in the downward direction so that filtrate is removed from 
beneath the media. Such "downflow" filters may be capable of either 
semi-continuous or continuous operation. In this latter operation, 
partitioning walls are fixedly mounted to form a plurality of individual 
cells within the granular media bed so that backwashing can be 
accomplished in one of the cells while filtration proceeds in the other 
cells. Such filtering machines are shown in U.S. Pat. Nos. 3,239,061 and 
4,151,265. 
In "semi-continuous" granular media filters, the entire granular bed is 
used simultaneously for filtration until the bed collects solids to the 
extent that its resistance to flow adversely affects the rate of operation 
of the machine, or the effectiveness of removing solids. Then the machine 
is removed from filtration service and the entire bed is cleaned as a 
unit. 
Granular media filters may also be of the type used to remove dissolved 
solids from liquid. Such filters typically use filter media of activated 
carbon, which physically adsorbs dissolved solids from the liquid. Over 
time, the activated carbon may adsorb so much dissolved solids material as 
to become saturated or spent. In this event, the spent filter media must 
be removed from the filter, and new or regenerated media delivered to the 
filter. Similiarly, in granular media filters of the above-described type 
used to remove suspended solids, the media may after long usage be 
rendered unsuitable for further filtering, even if backwashed. This media 
must then be removed, and new media or media cleaned by methods other than 
backwashing must be delivered to the filter. With either type of filter, 
the filtration operation of the filter must be terminated while the filter 
media is being replaced. 
SUMMARY OF THE INVENTION 
A primary object of the present invention is to provide an improved 
granular media filter wherein a particular volume or section of the 
filtration bed can be isolated for backwashing or for removal of the 
filter media while allowing filtration to proceed in the remainder of the 
bed. More particularly, an object of the present invention is to provide 
novel and economical ways and means to isolate selected portions from the 
remainder of the granular bed, without providing fixed partitioning walls, 
so as to enable backwashing or removal of the isolated sector while 
filtration proceeds in the remainder of the bed. 
To the above-stated ends, the present invention provides apparatus for a 
granular media filter wherein the granular bed in continuous--which is to 
say, is not sectionalized by fixed partition members--and which includes a 
selectively-positionable partitioning mechanism for insertion into the bed 
to isolate a selected section from the remainder of the bed so that 
backwashing or removal of the filter media can be accomplished in the 
isolated section while filtration proceeds in the remainder of the bed. 
Further objects and advantages of the present invention can be readily 
ascertained from the following description and appended drawings, which 
are offered by way of example and not in limitation of the present 
invention, the scope of which is defined by the appended claims and 
equivalents.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The filtering machine of FIG. 1 includes an open rectangular basin or tank 
11 having upstanding sidewalls 13a and 13b, a bottom wall 15 and endwalls 
(not shown). A generally horizontal member 19, herein referred to as an 
underdrain support means, is mounted within the tank 11 adjacent the 
bottom wall 15. The purpose of the underdrain support means 19 is 
three-fold. First, as its name implies, it supports an overlying 
filtration bed 23 composed of granular media. Second, the illustrated 
underdrain support means includes conventional underdrain nozzles 20 which 
cooperatively assist in backwashing the bed to remove collected 
particulates. Third, the underdrain support means includes drainage ports, 
herein nozzles 20, through which filtrate passes after having percolated 
through the granular bed. The filtrate receiving chamber 21 below the 
underdrain support means is basically an open cavity extending beneath the 
entire extent of the bed. That is, the filter receiving chamber need not 
contain any complex system of pipes or headers to accommodate backwashing. 
Ultimately, filtrate is collected in clearwells, not shown, located at an 
end of the filtrate receiving chamber 21, or, alternatively, along a side 
of the chamber 21. 
The granular media which comprises the filtration bed 23 can be composed of 
various materials. For example, the granular media can be gravel, sand, 
anthracite, activated carbon, or various resins of pre-selected grain 
size. It can be composed either of a single material or of two or more 
different materials laid in strata. Also, intermixed granular medias are 
known. In any such embodiment, the bed 23 is continuous and fills a 
substantial portion of the tank 11 above the support means 19 and has a 
generally horizontal upper surface. The purpose of the bed is to remove 
solids from influent liquid which percolates through the bed; to this end, 
the bed performs the functions of straining, intercepting, retaining 
and/or adsorbing solids. 
The machine of FIG. 1 further includes means for distributing influent 
liquid containing solids across the surface of the granular bed. The 
illustrated influent distribution means includes an open trough or flume 
27 supported along sidewall 13b of the tank 11, and ports 29 formed 
through the side wall of the flume at spaced-apart intervals. The ports 29 
are in liquid-flow communication with the flume 27 so that influent liquid 
passes from the flume through the ports 29 to distribution across the 
surface of the filtration bed 23 in a uniform, relatively non-turbulent 
flow pattern. These same fucntions can be achieved by other influent 
distribution means such as, for example, a system of manifolds and pipes. 
Referring still to FIG. 1, there is shown apparatus of this invention which 
includes a selectively-movable carriage mechanism which supports and 
conveys a partitioning chamber means 33 across the upper surface of the 
bed 23 along the length of the tank 11. The illustrated carriage mechanism 
comprises a bridge 31 which traverses the tank 11 and is supported and 
guided on the sidewalls 13a and 13b by parallel rail members 39a and 39b 
which extend lengthwise of the respective sidewalls. An indexing means 
moves the bridge 31 to selected spaced-apart locations along the rails. 
Preferably the indexing means comprises an electric gearmotor operatively 
coupled to drive wheels (not shown) mounted to the bridge, and limit 
switches to disengage power to the drive wheels when the bridge 31 reaches 
the preselected location on the rails. It should be understood, however, 
that the above-described bridge 31 and indexing means are only examples of 
various means which can be utilized to convey the partitioning means 33 to 
predetermined locations above the surface of the filtration bed 23. For 
example, the partitioning means 33 can be supported directly from the 
rails. 
Alternately, the partitioning chamber means may be supported by means other 
than by the walls of the tank 11, such as would be the case for a truck 
mounted portable backwashing system in which a boom from the truck may 
serve as the carriage mechanism. 
The partitioning chamber means 33 shown in FIGS. 1 and 2 includes an 
elongated box-like chamber 41 having vertically extending sidewalls 42a 
and 42b, endwalls 43a and 43b, a topwall 44, and an open bottom. The 
partitioning chamber 41 spans the width of the filter bed. The width of 
chamber 41 defines the width of the section of the filtration bed which is 
to be isolated for backwashing and, accordingly, is matter of design 
choice. Normally, the isolated section would be between about 1.3 to about 
2.6 feet in width. For reasons which will become obvious hereinafter, the 
vertical extent of the sidewalls and endwalls should slightly exceed the 
depth of the bed 23, say by about eight to twelve inches in order to, 
inter alia, accommodiate expansion of the granular bed. 
As best shown in FIG. 2, the partitioning chamber 41 is suspended from the 
bridge 31 or other suitable carriage mechanism by a pair of reciprocatable 
mechanisms, generally indicated by numeral 47, for selective up-and-down 
movement. (In the following, only one of the reciprocatable mechanisms 47 
will be described in detail; the other mechanism of the pair is 
functionally identical.) In its uppermost position, the reciprocatable 
mechanisms 47 raises the chamber 41 sufficiently that the lower edges of 
the sidewalls and endwalls are spaced above the surface of the bed 23. In 
the lowermost position, the sidewalls and endwalls extend into the bed so 
that their edges rest against the underdrain support 19. In essence then, 
the partitioning chamber is dimensioned so that, in its downward-most 
position, it is submerged below the surface of the freeboard liquid and 
encloses or isolates a portion of the granular bed while leaving the 
afore-mentioned clearance between the surface of the bed and the top of 
the chamber. 
The normal liquid level within the tank 11 during filtration is usually 
about 26 to about 42 inches above the underdrain support means 19. For the 
illustrated embodiment of the partitioning chamber 41, the liquid depth 
extends above the topwall 44, when the chamber is fully inserted into the 
granular bed. 
As shown both in FIGS. 1 and 2, a backwash withdrawal means is mounted in 
communication with the interior of the partitioning chamber 41. The 
illustrated backwash withdrawal means comprises a conduit 49 connected at 
its one end in liquid-flow communication with the interior of the 
partitioning chamber and at its other end with a pump 51 mounted to travel 
with the bridge 31. A manifold, not shown, can be mounted in communication 
with the conduit 49 internal of the chamber 41 to uniformly draw backwash 
liquid across the horizontal extent of the chamber. In the illustrated 
embodiment, the pump 51 discharges spent backwash liquid into an open 
trough 53 mounted within or next to the influent launder 27 and extending 
the length thereof. 
At this juncture, it should be appreciated that the partitioning chamber 
means 41 can have various functionallyequivalent, structural embodiments. 
For example, the endwalls 43a and 43b of the chamber can be eliminated if 
the ends of the chamber (which would then be open) are in a generally 
sealing relationship with the interior sidewalls 13a and 13b of the tank 
11. As another example, the top wall of the chamber 41 can be eliminated 
and the sidewalls extended upward to prevent freeboard liquid from flowing 
downward into the chamber when the same is fully inserted into the bed 23. 
Moreover, the chamber may be of any sectional shape, such as square, 
rectangular circular, or wedge shaped. In the lexicon of the present 
invention, these various embodiments are all to be understood to be 
encompassed by the term "partitioning chamber means." 
Further, it should be understood that auxiliary backwash withdrawal means 
can be employed. Thus, in addition to the above-described withdrawal 
means, a pump means can be connected to force air or liquid into the 
partitioning chamber during or prior to backwashing to assist in the 
backwash. That is, the air or liquid conveyed by the auxiliary pump would 
assist in dislodging and discharging particulates from the granular bed 
during or prior to backwashing. One such auxiliary backwash apparatus 80 
is shown in FIG. 4 to comprise a series of probes or lances 81 carried on 
a movable manifold 83 in communication with a source of pressurized air or 
liquid (not shown) via tubing 85 and means, such as cylinder 87, for 
selectively raising the probes above the bed and lowering the probes into 
the bed 23. 
Also mounted in communication with the interior of the illustrated 
partitioning chamber 41 are selectively operable release-valve means, 
illustrated in FIGS. 1 and 2 as valves 57. Each of the illustrated valves 
includes an annular seat 59 which is mounted to the top wall 44 of the 
partitioning chamber in registry with an aperture formed through the 
topwall, and a circular valve plate 61 mounted for selective closure 
against the seat. In the illustrated embodiment, the closure plates 61 are 
connected to the reciprocatable mechanisms 47a and 47b which, in turn, 
provide selective opening and closing of the respective valves. 
As shown in FIGS. 2 and 3, each one of the pair of reciprocatable 
mechanisms includes a crank mechanism 65 mounted to the bridge 31 and an 
elongated linkage member 63 which is pivotably connected to its lower end 
to the topwall 44 of the partitioning chamber and at its upper end to the 
crank mechanism 65. In the illustrated embodiment, each linkage member 63 
has a vertically-elongated slot 67 formed near its lower end; horizontal 
pin members 69 (herein referred to as lift pins) are freely received in 
slots 67 with the other end of the pins being fixed to vertically-disposed 
guide shafts 71. Each guide shaft is rigidly fixed at its lower end to the 
partitioning chamber 41, thereby establishing pivotal connections between 
the linkage member and the partitioning chamber. At its upper end, the 
guide shafts 71 are slidably received in a registered pair of guiding 
means 73, one pair being on each side of the bridge 31. Thus, the guide 
shafts 71 and guiding means 73 function to restrain the partitioning 
chamber from movement in other than the vertical direction. At the lower 
end of the linkage members 63, second pin member 77 is rigidly affixed to 
the linkage member to enable opening and closing of the circular valve 
plates 61. 
In operation, the reciprocatable mechanisms 47a and 47b jointly serve to 
raise and lower the partitioning chamber 41 and to selectively open the 
valves 57. The operation of the reciprocatable mechanism can be best 
understood with reference to FIG. 3, where it can be seen that the 
vertical position of valve closure plate is controlled by the linkage 
member in the sense that, when the reciprocatable mechanism 47a begins its 
upward travel, the valve closure plate 61 begins to lift from its seat 59, 
except for any slack introduced by attachment between the pin 77 and the 
closure plate 61. Initiation of upward travel of the partitioning chamber 
41 is controlled by the dimension of the slot 67 in the linkage arm 63; as 
a result, the partitioning chamber will not begin to be lifted until the 
pin member 69 reaches the bottom of the slot 67. Thus, FIG. 3(a) shows the 
linkage member in its fully raised position, at which time the valves 57 
are open; FIG. 3(b) shows the linkage member just after it has begun 
downward travel--the partitioning chamber and linkage falling freely as 
indicated by the lift pin 69 being located about midway within the slot 
67; FIG. 3(c) shows the half-lowered position, at which time the valves 57 
are completely closed; FIG. 3(d) shows the fully lowered position, when 
the partitioning chamber 41 is resting on the support means 19; and FIG. 
3(e) shows the partly-raised position with the pin member 77 raising the 
circular valve plate 61 to open the valves 57. 
Usage and operation of the afore-described filtering machine can be readily 
understood by first considering the condition where the reciprocatable 
mechanism has raised the partitioning chamber 41 fully from the granular 
bed. At that time, the total extent of the granular bed is utilized for 
filtration; which is to say, influent liquid containing suspended solids 
is distributed from the flume 27 across the entire surface of the granular 
bed and the liquid percolates downward so that suspended solids are caught 
in the interstices in the bed. This filtration operation will continue for 
a preselected period of time or until some controlling event occurs, such 
as the measured hydraulic head loss across the filter reaching a 
predetermined value due to flow resistance arising from captured solids 
lodged in the interstices of the bed 23, whereupon the bridge 31 will 
automatically advance to travel on the rails 39a and 39b. (As the bridge 
travels, the partitioning chamber 41, depending upon the vertical position 
selected, can be made to skim floating debris on the liquid surface or to 
level the surface of the granular bed.) Once a preselected position has 
been reached above the bed, the reciprocatable mechanisms 47a and 47b will 
be actuated to cause the partitioning chamber 41 to travel downward until 
it rests against the underdrain support member 19. In the preferred 
embodiment, the weight of the partitioning chamber 41 is sufficient to 
enable it to sink into the bed when the reciprocatable mechanisms are 
actuated. Downward travel of the partition chamber is faciliated by 
initiating operation of the backwash pump 51 as the partitioning chamber 
enters into the filter media bed so as to destabilize media below the 
partitioning chamber, thereby easing penetration of the sidewalls and 
endwalls 42a and 42b and 43b into the bed. Alternatively, means may be 
provided to positively force downward motion of the partitioning chamber 
into the bed. 
Once the partitioning chamber 41 has come to rest against the underdrain 
support 19, the backwash pump 51 continues to draw liquid into the 
backwash discharge conduit 49. This pumping action causes filtrate to flow 
from the filtrate-receiving chamber 21 upwardly through the nozzles 20 
into the isolated sector of the granular bed. The pumping action is 
sufficiently vigorous to expand, or fluidize, the granular bed so that 
collected particulates and other solids are sheared from the granules and 
entrained in the flow of backwashing liquid and, therewith, carried to 
discharge into the trough 53. It should be emphasized that while the 
selected sector of the bed is being backwashed, filtration is taking place 
in the remainder of the bed. After a preselected period of time, the 
backwash pump 51 is shut off and the partitioning chamber is raised. The 
release valves 57 will open just prior to the partitioning chamber 41 
begins to rise, thereby allowing liquid to flow into the upper region of 
the partitioning chamber, starting normal filtration and thereby 
preventing granular bed material from being drawn upward with the 
retracting partitioning chamber. Upward travel of the partitioning chamber 
continues until its sidewalls are above the bed surface, at which time 
filtration proceeds normally in the previously isolated sector of the bed. 
The afore-described cycle then resumes, with the bridge progressively 
traveling across the surface of the filter bed 23 until all sections of 
the bed are sequentially backwashed. 
Referring to FIG. 4, there is shown a second embodiment of the apparatus of 
this invention, which is adapted to remove filter media, which is no 
longer suitable for further filtering, from the media bed and replace it 
with suitable (e.g., new, cleaned or regenerated) media. The apparatus 
comprises a partitioning chamber 41a and means, such as eductor 91 shown 
in FIG. 4 or a pump (not shown), for removing the filter media in the 
partitioning chamber. The eductor comprises a first or inlet tube 93 
having a bottom opening adapted to be positioned adjacent the bottom of 
the bed 23, an annular housing 97 in communication with a source of fluid 
under pressure and a second or outlet tube 99 on the housing. In the 
operation of the eductor, fluid under pressure is delivered to the housing 
97 and flows out the outlet tube 99 creating a pressure drop for drawing 
filter media up the inlet tube 93 
The filter media withdrawn from the chamber via eductor 91 is then either 
disposed of or processed in a cleaning or regenerating operation. In this 
latter regard, filter media of the type such as sand used to entrap and 
retain suspended solids in a liquid may be conveyed to suitable cleaning 
apparatus (not shown) located on the carriage, at the tank 11 or at some 
distance therefrom. Filter media of the type which not only entraps and 
retains suspended solids but also adsorbs or chemically reacts with 
suspended or dissolved solids in a liquid, may be removed for transport to 
suitable regeneration apparatus, in which the media is heated to evaporate 
and burn off the solids in the filter media. 
New filter media, cleaned filter media or regenerated filter media, as the 
case may be, is delivered to the chamber 41a to replace the withdrawn 
media via the tubes 101. If the filter media is to be cleaned by apparatus 
at the tank 11, the tubes 101 are in communication with the cleaning 
apparatus and the same media withdrawn from the chamber is returned to the 
chamber. If the filter media withdrawn from the chamber is to be disposed 
of or is to be cleaned or regenerated at a location apart from the tank, 
the tubes 101 are in communication with a source of supply of the new, 
cleaned or regenerated media, and the media withdrawn from the chamber is 
replaced with different media. Rakes or other suitable apparatus (not 
shown) may be provided in the chamber 41a for distributing the media 
delivered via tubes 101 throughout the chamber to a uniform height. 
Various alternative structural arrangements can be provided within the 
scope of the above-described invention. For example, the filter tank can 
be circular and the partitioning chamber mechanism can be mounted to pivot 
about the center of the tank; in this embodiment, the partitioning 
mechanism would, preferably have a wedge-like shape and would be supported 
at the tank periphery by a circular rail. In this embodiment, the carriage 
mechanism is indexed circumferentially across the surface of the bed in 
the circular tank, cleaning successive sectors. Moreover, as previously 
indicated, the partitioning chamber means may be mounted on a truck or 
other movable support external to the tank 11 to enable the apparatus of 
this invention to service numerous tanks. Lastly, while the reciprocatable 
mechanisms have been shown and described as comprising a series of cranks 
and linkages, it is contemplated that they may also comprise chain and 
sprocket arrangements or cable and pulley arrangements.