SCHALLER, Elaine (32 Bermuda Lake Drive, Palm Beach Gardens, FL, 33418, US)
SCHALLER, Elaine (32 Bermuda Lake Drive, Palm Beach Gardens, FL, 33418, US)
What is claimed is:
l.A density current baffle for use in a clarifier tank, said density baffle
comprising :
a first baffle portion having a lower end, an upper end and an
intermediate central portion, said lower end of said baffle portion being
coupled to a side wall of said clarifier tank, said upper end of said
baffle portion being disposed, at a predefined angle, away from said
side wall of said clarifier tank such that said first baffle portion slopes
upwardly and away from said side wall.
2.The density current baffle as claimed in claim 1, wherein said upper
end is provided with an end flange for receiving a mounting bracket,
said mounting bracket having a first end coupled to said end flange
and a second end coupled to said side wall of said tank wall.
3.The density current baffle as claimed in claim 1, wherein said angle
of attachment of said first baffle portion to said tank wall is
substantially in the range of 35° to 60°.
4. The density current baffle as claimed in claim 1, wherein said angle
of attachment of said first baffle portion to said tank wall is about 45
degrees.
5.The density current baffle as claimed in claim 2, wherein said
attachment bracket is a downwardly sloping panel member which
together with said density current baffle form a substantially closed
baffle, so that solid materials may be prevented from building up
behind said upwardly sloping central baffle portion.
β.The density current baffle as claimed in claim 1, wherein the clarifier
tank has a water level, said baffle being located below the water level
of the clarifier tank.
7.The density current baffle as claimed in claim 1, wherein the baffle
further comprises an end attachment bracket intregally formed with
the baffle as a one piece member.
8. The density current baffle as claimed in claim I 1 wherein said baffle
further comprises a rigidizing flange depending upward from said
upper edge of baffle for providing enhanced rigidity to the baffle.
9. The density current baffle as claimed in claim 7, wherein the end
attachment bracket further comprises a mounting flange securable to
the tank wall and a mounting surface for receiving the first lateral side
of the baffle of a next adjacent density current baffle.
10. The density current baffle as claimed in claim 1, wherein the
peripheral wall of the clarifier tank has a radius of curvature, and
wherein the lower end of the baffle has a radius of curvature which
corresponds to the radius of curvature of the clarifier tank.
11. A density current baffle for use in a clarifier tank, said density
baffle comprising:
a first baffle portion having a lower end, an upper end and an
intermediate central portion; and
an angled attachment bracket coupled to said first baffle portion
for securing the baffle to the clarifier tank wall so that said upper end
of said baffle portion is disposed, at a predefined angle, away from
said side wall of said clarifier tank such that said intermediate central
portion of said first baffle portion slopes upwardly and away from said
side wall.
12. The density current baffle as claimed in claim 11, wherein said
attachment bracket is coupled to said baffle at a first end of said
baffle.
13. The density current baffle as claimed in claim 11, wherein said
attachment bracket is intregally molded with said baffle from a
reinforced fiberglass composite.
14. A density current baffle for use in a clarifier tank, said density
baffle comprising:
a first baffle portion having a lower end, an upper end and an
intermediate central portion, said lower end of said baffle portion being
coupled to a side wall of said clarifier tank, said upper end of said
baffle portion being disposed, at a predefined angle, away from said
side wall of said clarifier tank such that said first baffle portion slopes
upwardly and away from said side wall; and
an upper plate having a lower edge connection for coupling said
upper plate to said upper end of said baffle portion and an upper wall
flange for attachment of the upper plate to the side wall of said
clarifier tank, said upper plate being disposed, at a predetermined
angle, away from said side wall of said clarifier tank such that said upper plate slopes downwardly and away from said side wall.
15. The density current baffle as claimed in claim 14, further
comprising a relief vent mounted within said upper plate.
16. The density current baffle as claimed in claim 14, further
comprising mounting legs for securing the lower end of said first baffle
portion to said side wall so that said lower end of said first baffle
portion is spaced apart from said tank wall so as to allow water to flow
behind said baffle.
17. The density current baffle as claimed in claim 16, further
comprising a plurality of relief vents mounted with said upper wall
flange so as to allow water to flow behind said spaced apart first baffle
portion and out of said plurality of relief vents in said upper plate.
18. The density current baffle as claimed in claim 14, wherein said
upper end is provided with an end flange for receiving a mounting
bracket, said mounting bracket having a first end coupled to said end
flange and a second end coupled to said side wall of said tank wall.
19. The density current baffle as claimed in claim 14, wherein said
angle of attachment of said first baffle portion to said tank wall is
substantially in the range of 35° to 60°. |
IMPROVED DENSITY CURRENT BAFFLE FOR A CLARIFIER TANK
Related Application:
This application claims the benefit of priority from U.S.
Provisional Patent Application No. 60/899,327 filed on February 2,
2007, the entirety of which is incorporated herein by reference.
Field of the Invention:
The present invention is in the field of wastewater treatment
clarifier tanks. More particularly, the present invention is in the field of
density current baffles used in clarifier tanks.
Background:
In the field of waste water treatment, clarifier tanks are used to
separate waste solids from the water as one of the last stages of
treatment. The clarifier tanks typically consist of a circular or
rectangularly-configured tank in which a centrally mounted, radially-
extending arm is slowly moved or rotated about the tank at or
proximate the surface of the carrier liquid.
Waste water enters the tank either through the bottom of the
tank or through some other entry port. Thereafter, the aim is to have
the solid waste, or sludge, settle to the bottom of the tank with the
cleaner water escaping over a weir into an effluent or launder channel
before final processing and release to the environment.
A major deterrent to effective solids removal is the presence of
sludge density currents that form within the tank. These currents
create hydraulic short circuits that bypass the tanks' main clarification
volume and allow solids to enter the effluent. The effectiveness of
clarifier tanks is measured in the amount of total suspended solids
(TSS) that leave the clarifier tank through the effluent channel.
In order to reduce the TSS output into the effluent channel, a
number of modifications have been made to these tanks, one of which
is commonly referred to as a density current baffle. These baffles,
situated along the outer wall of the tank, facing inward and downward,
are designed to redirect these currents back towards the center of the
tank and thus away from the effluent channel.
In the past several attempts have been made to design effective
bafflers for such clarifier tanks.
For example, U.S. Pat. No. 4,780,206 to Beard et al. relates to a
turbulence control system for an intra-channel clarifier which reduces
turbulence within and allows the removal of sludge from the clarifier.
U.S. Pat. No. 4,816,157 to Jennelle is directed to an apparatus and method for clarifying solids from a solids-containing liquid having
a multilayer baffle system and integral solids removal sump. The
multilayer baffle system includes a first set of baffles placed above the
main liquid flow path for minimizing horizontal flow and creating local
turbulence so as to promote settling and assure that no solids settle on
the baffles.
U.S. Pat. No. 5,049,278 to Galper relates to a modular plate
settler for use in a liquid clarifier system having one or more inlet
ports for receiving an influent flow of liquid. The modular plate settler
comprises a parallelogram-shaped enclosure provided with a full
bottom opening for receiving the influent flow of liquid from the
settling tank.
U.S. Patent No. 5,252,205 to Schaller is directed to an improved
baffle system which is constructed as a modular unit and that consists
of a plurality of inter-engaged individual baffles, each formed as a
unitarily-integrated element incorporating both the panel member and
an integral end bracket for suspended securement of the baffle to the
peripheral wall of the clarifier tank.
Finally, U.S. Patent No. 5,597,483 to Schaller is directed to a
vented baffle system where one or more of the baffles are provided
with a relief valve means for venting the pressure in a space formed
between the junction of the lower side of the panel member and the
peripheral tank wall. The resulting system provides a vented baffle
system in which pressure exerted by the build up of gases in the space
may be alleviated. Both U.S. Patent No. 5,252,205 and 5,597,483 are
incorporated by reference.
Each of these existing baffle designs, while effective at reducing
the TSS % exiting through the effluent channel, still exhibit a number
of drawbacks. For example, the existing baffle designs do not perform
well when the flow through the clarifier tank is low. Furthermore, the
performance of these baffles depends upon their location relative to
the sludge blanket, but the sludge blanket height is often unknown or
changes. Yet another drawback is that the performance of existing
baffle designs become unstable when the flow changes suddenly, such
as after a rain storm, resulting in an increase in solids entering into the
effluent channel.
Objects and Summary:
The present invention looks to overcome the drawbacks
associated with the prior art and to provide an improved baffle design
for clarifier tanks that is more effective in redirecting the flow of the
density currents and the solids back toward the center of the tank,
resulting in an improvement (reduction) in TSS over existing baffle designs.
To this end, the present invention is directed to a density current
baffle for use in a clarifier tank. The baffle includes a first baffle
portion having a lower end, an upper end and an intermediate central
portion. The lower end of the baffle portion is coupled to a side wall of
the clarifier tank. The upper end of the baffle portion is disposed, at a
predefined angle, away from the side wall of the clarifier tank such
that the first baffle portion slopes upwardly and away from the side
wall.
Brief Description of the drawings:
The present invention can be best understood through the
following description and accompanying drawings, wherein:
Figure 1 illustrates an exemplary baffle in a clarifier tank,
according to one embodiment;
Figure 2 illustrates a central baffle portion of the
exemplary baffle from Figure 1, according to one embodiment;
Figure 3 illustrates an upper panel of the exemplary baffle
from Figure 1, according to one embodiment;
Figure 4 illustrates an exemplary baffle from Figure 1,
according to one embodiment;
Figure 5 illustrates an alternative baffle, according to
another embodiment;
Figure 6 illustrates an alternative baffle, according to
another embodiment;
Figure 7 illustrates an alternative consecutive baffle
arrangement, according to another embodiment;
Figure 8A is a close up of an upper panel of the exemplary
baffle from Figure 3, according to one embodiment;
Figure 8B is a close up of adjoining upper panels from
Figures 3 and 7, according to one embodiment;
Figure 9A is a prior art illustration of solid waste flows in a
clarifier tank having a baffle;
Figure 9B is an illustration of the solid waste flows in a
clarifier tank having a baffle of the present invention; and
Figures 10A-10D are a comparison of relative TSS
reduction in the effluent channels in a clarifier tank having a
baffle of the present invention against prior art baffles and tanks
with no baffles.
Detailed Description:
In one embodiment, as illustrated in Figure 1, an upward sloping
density current baffle 10 is shown within a clarifier tank 12. As shown,
clarifier tank 12 is a typical clarifier tank having a central tank portion
T, and outer tank wall 14 and an effluent channel E. Density baffle 10
is typically located along outer wall 14 several feet (eg. 3 ft.) below
the water level which is usually substantially aligned with the level of
the spillway into the effluent channel.
It is understood that baffle 10 may be employed in other shaped
tanks 12, (non-circular, square, rectangular, oval etc.) and may be
employed at various heights along tank walls. However, for the
purposes of illustration, the salient features of inverted density current
baffle 10 are described below in conjunction with a typical round
clarifier tank having a radius of substantially 100 ft, with a height of
tank wall 14 ft.
In a first exemplary arrangement as shown in Figure 2, density
current baffle 10 maintains a central baffle portion 20 that is
configured to be attached, at a lower end, to side wall 14. A series of
mounting legs 50 may be periodically disposed along the bottom edge
of central baffle portion 20 so a to allow connection to tank wall 14. The upper portion of central baffle portion 20 extends outwardly, away
from side wall 14 towards the center of tank 12. A stiffening flange 51
is disposed along the side edges of portion 20 configured to provide
added stability to baffle 10 under current conditions and also to
provide connection and abutment surface for contacting adjacent
central baffle portions 20 as discussed in more detail below.
Preferably, central baffle portion 20 further maintains an upper
connection flange 52 that is also configured to provide stability to
baffle 10 under current conditions as well as to provide a connection
means for attaching to an upper plate 28 of baffle 10.
In one embodiment of the present invention, as shown in Figure
3, an upper plate 28 is a panel configured to adjoin against connection
flange 52 of central baffle portion 20, thereby forming a closed baffle
10 against tank wall 14 as shown in Figure 1. Such an arrangement
assists in preventing sludge and other solid materials from building up
behind the upward sloping central baffle portion 20, reducing the need
for periodic cleaning.
As shown in Figure 3, upper plate 28 maintains an integral side
bracket 60 with wall attachment flange 61 configure to allow for
attachment of upper plate 28 to tank wall 14. A lower edge connection
flange 62 is provided for coupling to upper connection flange 52 of
central baffle portion 20.
An upper wall flange 63 is also provided for attachment to tank
wall 14. Along upper wall flange 63, a series of vents 65 may be
employed to allow for flow of water and suspended solids behind upper
plate 28 and connected central baffle portion 20 so that the solids do
not get trapped behind baffle 10.
Vents 65 act as a relief conduit 24 which vents the pressure
exerted by the buildup of gas which may accumulates in the space
formed between upper panel 28, central baffle portion 20 and tank
wall 14. Optionally, vents 65 may be provided with a venting flap 66.
This venting flap 66 is positionable in a first open position when the
pressure exerted by the buildup of gas reaches a predetermined level
and positionable in a second closed position when the pressure exerted
by the buildup of gas reaches a second predetermined level. Although
upper panel 28 is shown with vents 65, it is understood that upper
panesl 28, constructed with multiple vents, a single vent or no vents
depending on installation and construction requirements, are also
within the contemplation of the present invention.
Figure 4 illustrates a side view of central baffle portion 20 and
upper plate 28 coupled into baffle 10 and attached to side wall 14.
Baffle 10 is formed when lower edge connection flange 62 of upper
panel 28 is coupled to upper connection flange 52 of central baffle portion 20.
In the present arrangement as shown in Figure 4, mounting legs
50, which are periodically disposed along the bottom edge of central
baffle portion 20, are configured to support central baffle portion 20
away from tank wall 14. Thus, the bottom edge of central baffle
portion 20 is not directly connected to tank wall 14 in a continuous
manner but rather is coupled but held apart from tank wall 14 in a
manner than allows solids and water to flow behind baffle 10. Thus,
as shown in Figure 4, the combination of mounting legs 50 of central
baffle portions 20 and vents 65 of upper panels 28 result in baffle 10
allowing water and solids to freely flow through and behind baffle 10,
preventing their capture behind baffle 10 which could result in
unwanted trapping of gasses and solids.
In another arrangement of the present invention as shown in
Figure 4, the angle 21 at which central baffle portion 20 is disposed
away from tank wall 14 is substantially 45°. However, the invention is
not limited in this respect. Any angle of attachment to side wall 14
may be used that is sufficient to provide an improved flow of solid
waste towards the center of tank 12 as discussed in more detail below.
In another exemplary arrangement, the angle 23 at which upper
plate 28 is attached to side wall 14 is substantially 60°. However, the
invention is not limited in this respect. Any angle of attachment to
side wall 14 may be used that is sufficient to provide stable support
and protection for baffle portion 20 as well as supporting the improved
flow of solid waste towards the center of tank 12 is within the
contemplation of the present invention.
It is noted that angles 21 and 23 may be modified for each
installation based on various environmental conditions, including but
not limited to physical tank dimensions, expected TSS content of
water, expected sludge blanket thickness and height etc...
It is understood that central baffle portion 20, upper plate 28
and the accompanying components may be all integrally formed or
may be fashioned as separate elements and put together during
installation.
In a currently preferred implementation, the individual baffle 10
components are fabricated from a molded reinforced fiberglass
composite as one-piece, unitarily-integrated units. Most preferably,
the thickness of the fiberglass panels is in the range of from about
3/16th to l/4th of an inch, a range that provides substantial structural
strength and rigidity while remaining sufficiently lightweight for
unusual ease of installation.
In another embodiment of the present invention, as illustrated in Figure 5,the upward sloping central baffle portion 20 is configured
attached to side wall 14 using a modified upper mounting bracket 29 instead of a full upper panel 28. This upper mounting bracket 29,
unlike full upper panel 28, is not a full plate, but is instead some form
of one or more frame brackets, thus leaving the upper side of baffle 10
open leaving only lower central baffle.
In another arrangement of the present invention, Figure 6 shows
upward sloping central baffle portion 20 that is retro-fitted under a
standard baffle of the prior art, as typically shown in either U.S. Patent
No. : 5,252,205 or 5,597,483 to Schaller, both of which are
incorporated herein by reference. In this configuration, central baffle
portion 20 of the present invention is mounted or fixed against the
underside of an existing flat baffle.
In another arrangement of the present invention, regardless of
the details of construction set forth above, a series of central baffle
portions 20 and upper plates 28 forming baffle 10 are configured to be
supplied around the entire or substantial portion of the circumference
of clarifier tank 12. For example, as shown in Figure 7, upper plates
28 and central baffle portions 20 may be arranged in a consecutive
manner with adjoining edges. Adjoining edges of baffles 10 may be
bolted together and may optionally have overlapping/recessed edge
notches for stability.
In addition to central baffle portions 20 and upper plates 28,
such a consecutively mounted baffle 10 may further employ a common
mounting brackets, whereby integral side bracket 60 of upper plate 28
of a first upper panel 28 and central baffle portion 20 may be
employed to support the free end of an adjacent upper panel 28 and
central baffle portion 20
In the arrangement shown in Figure 7, central baffle portions 20
are interconnected and attached in an end-to-end arrangement so that
each central baffle portion 20, when combined, form a smoothly
continuous, upwardly and inwardly (i.e. toward the center or central
portion of the clarifying tank T) sloping surface. The upper plates 28
are also similarly arranged.
Interconnection and securement of immediately-adjacent central
baffle portions 20 and upper plates 28, during installation of the
inventive baffle system 10 is effected in one embodiment by attaching
a second lateral end of a first central baffle portion 20/upper plate 28
to an adjacent central baffle portion 20/upper plate 28, at the point of
support from bracket 60.
In one arrangement as shown in close up Figure 8A, an edge of
upper plate 28 may be recessed (70) by an amount substantially
corresponding to the thickness of a neighboring upper plate 28 so that
when the first end of an adjacent upper plate 28 is abutted against the
first central baffle portion, the two adjacently-abutting upper plates 28
form a smoothly-continuous surface by virtue of the shiplap-type joint through which they are interconnected as illustrated in Figure 8B. This
joint is formed above bracket 60 such that the same bracket 60
supports the adjoining edges of both upper panels 28. A securing bolt
may be used to fasten adjacent upper plates 28 at these connection
points. Similar uniform connections may be applied to adjacent
central baffle portions 20.
Furthermore, brackets 60, optionally unitarily formed with upper panels 28 and the overlap connection joints advantageously permit
appropriate adjustment, during installation of the inventive baffle
system 10, of the relative positions of adjacently-disposed baffle
members (20 and 28) to compensate for unanticipated irregularities in
the curvature or contour of the clarifier tank wall 14.
As should be further apparent, the individual baffle members 20
and 28 are additionally secured to the clarifier tank wall via flange 63
(for upper panel 28) or fastening members 50 (for central baffle
portions 20), by rivets or screws or other fasteners or the like.
Securement of the individual baffle members to the tank wall 14 may
be effected as each baffle element is attached to the next-adjacent
baffle element in baffle system 10, or after a plurality of baffle
members have been connected one-to-another, or in a combination or
mixture of such steps as a general matter of design choice.
Using the design for baffle 10, as illustrated in the above Figure
4 as an exemplary model, Figures 9A (Prior Art) and 9B shows a side
by side comparison of the flow of solids from the bottom of the tank
upwards towards the effluent channel of clarifier tank 12 of the
present invention as compared to the Prior Art (Fig 9A). As noted in
the background, the main purpose of clarifier density baffles is to
direct the current of solids back towards the center of tank 12 in order
to reduce the flow of solid waste exiting into the effluent channel. As
seen in Fig. 9B in the highlighted area "H" in the flow diagram,
inverted density current baffle 10 of the present invention provides an
improved solid flow back towards the center of the tank in comparison
to the prior art (Fig. 9B) downward facing flat baffles which, while
providing some center-ward direction of solids, allows a significant
portion to curl back towards the effluent channel after flowing over the
tip of the baffle.
Figures 1OA - 1OD are charts, based on computer modeled flow
results, showing the relative reduction in the concentration of
suspended solids in the effluent channel. The first line on each of the
charts, labeled NB, shows the test results for a clarifier tank having no
density baffle. The second lines, labeled NEFCO DCB, shows the
effluent TSS reduction using a standard downward slopping density baffle such as those described in the prior art.
Figure 1OA specifically relates to a test using standard peak
loading (waste water entering bottom of tank) having a low sludge
blanket. Figure 1OB shows the results for the test using the same
standard loading but having a high sludge blanket. Figure 1OC shows
the results for the test using a high loading (peak loading +20%) with
a low sludge blanket. Figure 1OD shows the results for the test using
the same high loading but having a high sludge blanket.
According to the model results, the prior art baffle reduces total
suspended solids in manner consistent with actual test results from
prior installations and assists in confirming that the test parameters
were properly established.
According to one embodiment of the present invention, the
lowest line in the chart on Figures 10A-10D, labeled IOOA - IOOD
respectively, represent the model test results for a baffle design 10
according to the present arrangement of density current baffle 10
having an upward sloping baffle portion 20, such as that shown in
Figure 4.
The following table 1 summarizes the results as compared to the
prior art (DCB) arrangement
Table 1 : Percent Reduced Solids compared to Baseline
Peak Hourly plus 20%, High Blanket | 61% | 90%
Average 35% 80%
These results demonstrate two significant advantages in the
performance of density current baffle 10 over the prior art baffle(s) as
follows.
First, the upward slopped density current baffle 10 reduced
solids by and average of 80% over the case with no baffle, and 69%
over the case of prior art straight baffle(s) tested in the same
environment, both of which represent very significant improvements in
clarifier performance.
Secondly, the wide variations in effluent solids on the "NB" (no
baffle) and "NEFCO DCB" (prior art) graph lines early in the time
sequence are caused by random transients that are induced by the
model. In contrast, the upward sloping straight baffle, such as density
current baffle 10, provides a damping action that limits the impact of
these transients on effluent solids. This is particularly important in
reducing solids overflow after events which disturb the normal flow rates such as heavy rain storms.
This improvement is further highlighted by the test results which
show even larger percentage improvements in the high volume (peak +20%) instances in Figures 1OC and 1OD with 90% and 95%
improvements over no-baffle designs and 92% and 74% over prior art
baffle designs.
While only certain features of the invention have been illustrated
and described herein, many modifications, substitutions, changes or
equivalents will now occur to those skilled in the art. It is therefore, to
be understood that this application is intended to cover all such
modifications and changes that fall within the true spirit of the
invention.
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