Note: Descriptions are shown in the official language in which they were submitted.
BACKGROUND OF T~IE INVENTIO_
The use of biolo~ical filters or habitats in the treat-
ment of liquid wastes, such as sewage and industrial wastes, has
become quite common and widespread. There are several different
types of apparatus for the distribution of the li~uid wastes over
the biological habitat or filter media. Similarly, there are -
several different types of filter media and numerous methods of
treatment and auxiliary apparatus used in connection with the
biological filter.
Two of the most common approaches for the distribution
of liquid wastes over a biological filter are through the use of
fixed nozzles or stand pipes and the use of a movable (prefer-
ably rotary) arm or arms which periodically advance over the
entire filter media. These types of distribution systems have
various relative advantages and disaclvantages, and both are in
wid2spread use presently. In recent years, high-rate and low-
rate trickling filters have been vast:ly improved by reason of
the advent of new forms of filter meclia. Earl~ biological habi-
tats ~imply employed rock as the filter media over which the
liquid wastes were distributed and on which the biological slimes
grew. The new forms of filter media can be broadly classified -
into t~o groups, namely, vertical media and horizontal media. In
the vertical media, virtually all of the surfaces providing the
area over which the liquid wastes flow and on which the biological
slimes ~row are vertically extending. In the horizontal media,
the primary growing surfaces are upwardly and/or downwardly fac-
ing horizontal surfaces. Additionally, the vertical media has
most usually been formed of plastic material. An example of a
typical vertical filter media construction is shown in U. S.
Patent No. 3,347,381. An example of a typical horizontal filter
media is shown in U. S. Patent No. 3,496,101. Whether these new
~l~4~31
1 orms of filter media are used as a replacement for rock in an
existing biological filter system or are employed in specially
designed and newly constructed filters, several problems have
been encountered which reduce the effectiveness of these media
as employed as a habitat in biological filters. The problems
have been heightened substantially when vertical media is em-
ployed, but exist to some extent in connection with horizontal
media and certain distribution systems.
In a fixed nozzle liquid wastes distribution system,
achievement of a uniform distribution of the li~uid wastes over
the top of the filter media is quite difficult. This problem
of an uneven distribution is caused, in large part, by the fact
that the rate at which sewage is discharged over t~e filter may
vary substantially from day-to-day and within the day, causing
large changes in the flow rate out the fixed stand pipes or
nozzles and changes in the area over which the nozzles disperse
the liquid wastes. The problem wit~l fixed stand pipes is fur-
ther heightened when vertical media is used in that the vertical
channels tend to maintain the flow of liquid wastes in the pre-
determined vertical channels into which the wastes entered atthe top of the filter. Thus, although the vertical media is
usually staggered, the lateral distribution or dispersion of
the liquid wastes is relatively minimal as it travels in verti-
cal channels from the top of the filter to the bottom.
When a rotary arm distribution system is used, the
- li~uid wastes are more evenly distributad over the top of the
filter by reason of the constant motion of the rotary arm over
all portions of the filter. The changes in flow rate or load-
ing of the filter tend to affect all portions of the filter in
the same way and do not create dry spots and attendant failure
in the growth of biological slimes. Accordingly, rotary arm
:1~41~3~
1 distribution means are preferred when vertical channel plastic
filter media i5 employed. The rotary arm apparatus, however,
creates a different but related problem. As the rotary arm
passes over a portion of the filter, there is a tremendous surge
or pulse in the flow rate of liquid wastes over that portion of
the filter onto which the wastes have been discharged by means
of the rotary arm. Again, the vertical media is particularly
adversely affected by the surge encountered when rotary arm
distribution means are employed. The high flow rate combines
with the vertical channel to build up a substantial velocity
of liquid sewage in the vertical channels of the media, with
the result that biological slimes do not grow effectively and
are eroded from the upper surfaces of the filter media. One so-
lution to this problem has been to construct the media to a very
substantial height, for example, as high as 21 feet or more. In
such a construction, a portion of the upper filter area, when a
rotary arm distribution means is employed, may not contain any
substantial quantity of biological slimes, since the flow rate
of liquid sewage surging from the rotary arm at the upper eleva-
tions in the filter media is too high to allow biological growth.Similarly, although to a lesser extent, horizontal media may have
its upper surfaces eroded and washed free of biological slimes
as a result of the surge from the rotary arm distribution appa-
ratus. Typical rotary arm distribution means are shown in U. S.
Patent Nos. 2,168,208 and 2,355,640, while typical fixed-nozzle
liquid wastès treatment apparatus may be seen in U. S. Patent
Nos. 3,112,261 and 3,496,101.
Accordingly, it is an object of the present invention
to provide a liquid wastes redistribution apparatus and method
; 30 which will effect an even distribution of liquid wastes over
the top of a biological habitat for a wide range of filtex load
. "
~4l~3l
1 rates and tend to reduce the surges in flow rate onto the habitat.
It is another object of the present invention to pro- ^
vide a liquid wastes redistribution apparatus and method which
may be readily employed with a variety of distribution means and
filter media constructions at either existing or new installa-
tions.
Another object of the present invention is to provide
a liquid wastes redistribution apparatus and method which is
easy to construct, install, operate and maintain.
Still another object of the present invention is to
~;~ provide a liquid wastes treatment apparatus and method which in-
creases the durability of the combined filter and redistribution
system, affords cost savings in the construction of the filter
media and operation of the filter, and improves the overall fil-
ter strength.
Other objects and advantages of the liquid wastes re-
distribution apparatus and method c~f the present invention will
become apparent and are set out in more detail in connection with
; the description of the preferred embodiments.
: `; 20 SUMMARY OF THE INVENTION
The apparatus and method of the present invention is ,
comprised, briefly, of a liquid wastes distribution media posi-
tioned between the top of biological filter media and distribu-
`~ tion discharge outlets. The redistribution media is formed wlth
a plurality of vertically spaced and superimposed layers of up-
wardly facing substantially horizontal surfaces with openings
therethrough for downward flow of the liquid wastes to the fil-
ter media. The horizontal surfaces are formed and arranged to
interrupt, retard and redistribute the liquid wastes and may in-
clude, as one aspect of the invention, a maze~like flow channel
to reduce surges in filter loading. Lath-like horizontally
,
1 oriented, relatively spaced, side-by-side members preferably
provide th~ redistribution media, and the layers of members may
be relatively staggered and/or oriented in an intersecting man-
ner to eliminate vertical channels.
DESCRIPTION OF THE DRAWINGS
FIGURE 1 is a si~e elevational view of a schematic
representation of a biological filter having a redistribution
apparatus constructed in accordance with the present invention
installed thereon.
FIGURE 2 is an enlarged, fragmentary, cross-sectional
j view of that area of the apparatus of FIGURE 1 encircled by
line 2-2.
FIGURE 3 is a side elevational view of the redistribu-
tion apparatus of the present invention installed on horizontal
; media and used with a rotary arm distribution means.
FIGURE 4 iS an enlar~ed, t:op plan view of liquid wastes
redistribution apparatus constructecl in accordance with the pres-
ent invention.
FIGURE 5 is a side elevational view of the redistribu-
tion apparatus shown in FIGURE 4.
FIGURE 6 is an enlarged, side elevational view, in cross-
se¢tion, of the alternative embodiment o~ the redistribution ap-
paratus of the pre~ent invention shown in FIGURE 3 and constructed
to control surgin~.
DESCRIPTION OF THE PREFERRED El~BODIMENT
The liquid wastes redistribution apparatus and method
of the present invention may be conveniently used with conven-
tional biological filter apparatus, as shown in FIGURE 1. The
liquid wastes treatment apparatus shown in FIGURE 1 includes a
filter media, generally designated 21, having a plurality of sur-
~aces, shown in FIGURE 2 as being vertically extending surfaces 22,
31
1 which provide a biological habitat over which liquid wastes flow
and on which biological slimes grow. Additionally, distribution
means, generally designated 23, is provided with distribution
outlets 24, positioned over the top of media 21 for discharge of
liquid wastes 26 on the top of the media and gravitation of the
liquid wastes down through the media.
Additionally, the biological filter will normally con-
tain a collecting basin or under-drain 27 on which media 21 is
supported by a plurality of foundation runners 28, which allow
flow of liquid wastes on the sloping under-drain 27 to collection
basin 29 for gravitational or pumped flow (schematically repre-
sented by arrow 31) to other treatment apparatus, such as clari-
fiers and the like. Sewage distribution means 23 includes verti-
cal stand pipes 32 on which distribution outlets or nozzles 24
are mounted and which stand pipes are supplied by supply pipe 33.
The liquid wastes are preferably pumped rom a tank or basin 34,
which may be a primary clarifier, or a mixing basin. Pump 36
withdraws the liquid sewage from basin 34 and conduit 37 supplies
the basin either from a clarifier or after screenin~.
The liquid wastes treatment apparatus thus far described
is in widespread use, and there are numerous variations commonly
employed in connection with such apparatus, including changes in
piping configurations, pumping or gravitational flow, and collec-
tion basin geometries. Additionally, other forms of fixed nozzle
~ distribution means have been employed, such as systems in which the
; stand pipes 32 in the filter media are eliminated and an overhead
supply system employed. Additionally, the use of movable or ro-
tary arm distribution systems will be described in more detail
in connection with the apparatus of FIGURE 3.
In order to insure an even distribution of liquid wastes
over the top of filter media 21, the apparatus of the present in-
41;~;31
1 vention includes a liquid wastes redistribution media, generally
designated 41, positioned between the top 42 of filter media 21
and beneath discharge outlets 24 of distribution means 23. As
best may be seen in FIGURE 2, filter media 41 is formed with a
plurality of vertically spaced and superimposed layers 46-50 of
upwardly facing substantially horizontally extending surfaces 52
formed to define openings 53 therethrough for the downward flow
of liquid wastes from outlets 24 through the redistribution media
to filter media 21. Thus, as the liquid wastes 26 hit layer 50
of the redistribution media, horizonta~ surfaces 52 cause the
downward flow of the liquid waste to be interrupted and retarded
with a redistribution in a lateral direction of a portion of the
wastes. As the wastes progress downwardly under the action of
gravity, each successive layer tends to further disperse or
laterally redistribute the liquid wastes and to slow down their
; downward flow so that by the time the wastes have reached
media 21, their downward flow is greatly reduced and more evenly
distributed over the plan area of top 42 of the media. When
evenly distributed over the vertical media, the undesirable ef-
fect of channeling the liquid wastes in individual vertical
channels, as defined by surfaces 22 in the filter media, it is
not as significant since the flow in each channel is now more
nearly equal. Additionally, and very importantly, the retarding
effect of the horizontal surfaces in the redistribution media
will cause the liquid sewage to have a much lower downward
velocity. This in turn results in vertically extending sur-
faces 22 in the ilter media adjacent top 42 being able to sup-
port and retain biological slimes and act as an effective bio-
logical habitat. Thus, the redistribution media tends to elimi-
nate erosion off the upper surfaces of the vertical channels in
filter media 21. ~ccordingly, a foot or even less of redistri-
:1~4~;~31
1 bution layers can be used with vertical plastic media in a fil-
ter which lower in height without decreasing substantially the
filter performance. The importance of such a reduction in the
plastic filter media hei~ht is twofold. First, the reduction
in filter hei~ht will have an attendant savings in costs of
;~ media. Additionally, increased filter height normally requires
increased pumping cost in order to pump the liquid wastes to a
height where they may be distributed over the filter media.
Accordingly, a savings in filter media height results in an
attendant savings in pumping cost.
While the redistribution media of the present inven-
tion may be most advantageously employed as positioned over the
top of the filter media, it may also be positioned within the
filter media. As above noted, the vertical channels in plastic
media confine the liquid sewage to a single downwardly extending
path. The effect is to maintain a relatively high velocity in
the downward ~low o~ the liquid wast;es and to elim.~nate lateral
movement of the wastes within the filter media. Accordingly,
several layers of redistribution media may be positioned at
various levels throughout the vertical height of filter media 21
in order to slow the downward velocity of the liquld wastes and
to ~urther redistribute and even out the flow in each vertical
channel of the plastic media. Since plastic vertical media is
typically manufactured in cube-like units which are self-support-
ing and stacked on one another, it is a simple matter to inter-
sperse the filter media with layers of redistribution media.
In FIGURE 1 such an intermediate zone of layers of redistribu-
tion media within filter media 21 is shown at zone 54.
Redistribution media 41 may be constructed of a number
of different materials and arrays of horizontally extending sur-
faces. It has been found to be preferable and advantageous,
231
1 however, to employ a media, which has been found to be effec-
tive as a horizontal filter media, as the redistribution media.
Such a media is set forth and described in detail in U. S.
Patent No. 3,496,101. Briefly, this redistribution media is
provided by lath-like members 56 which provide upwardly facing
surfaces 52 and downwardly facing surfaces 57. The members 56
are positioned in the layers of the redistribution media in
side-by-side and generally parallel and spaced apart relation
to define openlngs 53 therebetween. Members 56 are supported
on cross members or supporting members 58, usually by the use
of fasteners or adhesives. The redistribution media may be
formed of wood, such as redwood or pressure treated fir, and
additionally may be formed of plastic material. Since the pri-
mary purpose of the redistribution media is not to afford a bio-
logical habitat, but rather to redistribute and retard the down-
ward flow of the liquid wastes, the redistribution media need
not be constructed or positioned in a manner desi~ned to opti-
mize its e~fectiveness as a biological habitat.
In order to minimize the number of layers which may
be required in the redistribution media in order to effect even-
in~ out and retardation of flow of the liquid wastes, it is a
further feature of the present invention that the layers of re-
distribution media may be relatively horizontally displaced in
relation to the next vertically adjacent layer to superimpose
horizontal surfaces over openings in the adjacent layers. This
may best be seen by reference to FIGURE 4 wherein lath-like mem-
bers 61 form the top layer in the redistribution media and lath-
like members 62 form the third layer in the media. As will be
seen, laths 62 are in superimposed relation to the openings 63
between laths 61. Thus, by horizontally displacing layer three
relative to layer one, in the media of FIGURE 4, the laths in
Z31
1 the third layer are aligned with the openings in the first
layer of the media. In FIGURE 2 laths 56 are all superimposed
over each other, as are openings 53, creating the possibility
that liquid wastes may fall down openings 53 without impacting
any of the laths. In FIGURES ~ and 5 the second and fourth
layers of laths have been perpendicularly oriented to the first
and third layers such that the longitudinal axes of laths 66
in the second layex of FIGURES 4 and 5 are perpendicular to
the longitudinal axes of laths 61 and 62. Similarly, the lon-
gitudinal axes of laths 67 are perpendicular to the axes of 61and 62. Additionally, the layers including laths 66 and 67 are
also relatively horizontally displaced so that the laths are
superimposed with the openings. Thus, the orientation of the
layers and their relative positioning in FIGURES 4 and 5 result
in there being no uninterrupted vertical channel down which
liquid waste may travel before impac:ting the filter media.
While it has been found that this staggering and criss- -
crossing of layers of media is undesirable if the entire filter
is to be constructed of horizontal media, the stag~ering and
crisscrossing of media is highly desirable when the media is
used as a redistribution media, since its primary function is
not as a biological habitat. It should also be noted that the
alignment of laths as shown in FIGURE 2 may require a few more
layers in order to insure an evening of the downward flow over
a given horizontal area, this alignment works in a satisfactory
fashion in most instances and is a substantial improvement over
discharge of the liquid wastes directly on the top of the ver-
tical filter media. This is particularly true since there is
considerable splashing off of the horizontal surfaces. Thus,
a relatively small depth of redistribution media composed with
the depth of filter media virtually eliminates the opportunity
^-10--
1231
1 for liquid wastes to pass down the channels defined by open-
ings 53. A further height reduction in the redistribution media
can be accomplished, however, by staggering and crisscrossing
the layers.
The use of a redistribution media as above described
has several additional advantages attendant thereto. First,
a common problem encountered with plastic media, whether verti-
cal or horizontal, is that it checks and breaks down under ultra-
violet li~ht on ~he top surfaces which are exposed to the sun-
light. Use of a redistribution media, particularly if it is awood media, will eliminate the exposure to sunlight and this
breakdown of the plastic filter media. Additionally, and very
important, biological filters must often be walked upon by in-
stallation and maintenance personnel. Thus, the filter media
is subject to localized loading which is much greater than would
be experienced in merely supporting the weight of the media
above it. Thus, plastic media has not infrequently been crushed
by personnel installing the same or at a later date working
upon the media. One approach to avoid the problem has been the
use of portable walkways, such as ~oards and the like which are
removed after installation and/or maintenance. Another approach
has been to cover the entire top 42 of media 21 with a single
perforated sheet having enough strength to transfer localized
loads over a greater surface area. The redistribution media
of the present invention can be formed of a relatively heavy
gauge material which can be readily walked upon and will trans-
fer localized loads over a substantial surface area. Thus, the
need for a self-supporting plastic media which further is formed ;
to support local~zed loads can be eliminated, and the plastic
media can be manufactured out of a thinner gauge material. Thus,
the use of redistribution media of the present invention can
1~4~
; 1 result in a substantial cost savings in the ability to reduce
the gauge of the material in the filter media. It might be
noted further that since the redistribution media is preferably
of a relatively heavy gauge, it may be constructed of plastic
material which the ultraviolet light from the sun will check
and cause to break down, but which can be sufficiently strong
so that the loss in mechanical strength from the sunlight is
not significant. The redistribution media of the present in-
vention, therefore, has the effect of reducing the cost of the
filter media and increasing the overall strength and durability
of the biological filter.
Referring now to FIGURE~ 3 and 6, an alternative em-
bodiment of the redistribution media of the present invention
may be described. In FIGURE 3 a schematic representation of
the biological filter system is illustrated in which incoming
liquid wastes enter tank 71 through conduit 72 and are pumped
by pump 73 through conduit 7~ to a rotary arm-type of distribu-
tion means 76. The rotary arm distribution means is fairly ef-
fective in evenly distributing the liquid wastes over the top
surface of the filter media, but as above described, the primary
defect of such distribution apparatus is that they cause surges
or impulses in the flow rate over the filter media. In a manner
similar to that previously described in connection with FIGURE 1,
the biological filter is provided with an under-drain 77 includ-
- ing a collecting basin 78 from which filter under-drain flow may
be pumped for further treatment. Mounted on under-drain 77 are
runners 79 and a filter media, generally designated 81. Super-
imposed over filter media 81 is a redistribution media, generally
designated 82
In order to act as a surge control apparatus, the re-
distribution media of the present invention may be formed with
~6~41'~:3i
1 the horizontally upwardly facing surfaces oriented and con-
structed in a manner resulting in a substantial delay and slow-
ing of the downward progress of the liquid wastes through the
redistribution media. Thus, as best may be seen in FIGURE 6,
redistribution media 82 includes upwardly facing surfaces 83-
86, with surface 83 defining an inlet opening 88 and the remain-
ing surfaces defining a maze-like flow channel 89 formed to im-
part a horizontal component to the direction of flow of the
liquid wastes deposited over the redistribution media. The re-
distribution maæe is formed with a discharge opening, or in thiscase openings 91, for flow of the liquid wastes onto the top sur-
face of filter media 81. The redistribution media of FIGURES 3
and 6 can be formed of lath-like members, for example by posi-
tioning members 56 in FIGURE 2 in abutting relation, but is pref-
erably formed as shown in FIGURE 6.
The filter media illustrated in FIGURE 6 is illustrated
as horizontal media of the type disc;Losed in U. S. Patent No.
3,~96,101 and of the type that may be employed as a redistribu-
tion media, as illustrated in FIGURE 2. Since horizontally ex-
tending filter media tends to redistribute the liquid wastes as
;~ they travel down throu~h the filter, location of the discharge
; openings 91 in the redistribution media over only a portion of
the top surface of the filter media is not too critical.
When a rotary arm distribution means is employed, the
surge as the arm passes over a unit of redistribution media is
quite substantial. This is particularly true at the outer ends
of the rotary arm, where the volume and velocity of liquid wastes
must be greater in light of increased speed at which the arm
passes over an area. Accordingly, in order to slow the surge
and even out the flow~ the partitions 84 and 85 in media 82
cause the direction of flow of the liquid wastes to be reversed
~13~
`:
~4:~31
1 several times and the flow rate correspondingly reduced over thepeak rate at which flow was discharged from the distribution means
76 onto the upper surface 83 of the redistribution media. It is
preferable in order to reduce the downward flow rate and spread
the tirne over which the liquid wastes are discharged on the filter
media to construct the redistribution media with a flow channel 89
which has a greater horizontal than vertical length. Thus, the
flow channel as illustrated in FIGURE 6 is substantially longer in
the horizontal direction than the height of the redistribution media.
In order to both control surging and obtain an even dis-
tribution, it is possible to combine the redistribution media con-
struction shown in FIGURE 2 with the redistribution media construc-
tion shown in FIGURh` 6. There~ore, if what has heretofore been
described as filter media 81 in FIGURE 6 was merely layers of re-
distribution media which in turn were superimposed over a vertical
filter media such as media 21, as shown in FIGURE 2, both surge
control and even distribution can be achieved. This approach is
particularly ad~antageous when vertical filter media is employed
since discharge openings 91 will tend to cause preferential ~low of
2~ the liquid ~astes from the surge controlling flow channel 89. It
should be noted that the inlet opening 88 and the flow channel
throughout its length, as well as discharge openings 91, must be of
s~bstantial dimension in order to avoid plugging by solids carried
in the liquid wastes. Accordingly, the first discharge opening 91
; must be of substantial dimension and will, for that reason, be the
~; opening from which most of the li~uid wastes are discharged from
the redistribution means. This phenomenon is precisely the problem
which has~been encountered in connection with prior redistribution
systems which have been employed. If a single perforated sheet is
attempted to be used to evenly disperse liquid wastes over a given
area of filter, the holes must be relatively small in order to
-14-
~r~ 3~
1 insure an even distribution. When the holes are small, however,
they plug, and when the holes are large enough to avoid plugging,
they result in preferential discharge onto the filter media and
uneven distribution.
In the redistribution media and method of the present
invention, the horizontal orientation of surfaces to cause an im-
pacting or impinging of the liquid wastes thereon for retardation
of the downward flow of such wastes is of substantial importance.
Ob~iously, some skewing or tilting from a perfectly horizontal
position can be tolerat~d with the redistribution media being
effective both in retarding and in redistributing the liquid
wastes. If, by contrast, vertical media of the type of media 21
in FIGURE 2 is attempted to be employed, however, neither re-
tardation nor horizontal dispersement of the liquid wastes is ac-
complished.
As will be obvious, several forms of maze-like channels
can be employed to spread the time of discharga over the filter
media out over that which is the resuLt of the rotary arm. Addi-
tionally, the length of the maze-like flow channel can be increased
i~ accordance with the desired delay and normal operating condi-
tions of the biological filter. In connection with a maze-like
channel, the surfaces need not be so nearly horizontal if the ef-
fect is to delay and even out the flow over the media with respect
to time.
