Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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APPARATUS FOR SEPARATING PARTICULATES FROM A FLUID STREAM
BACKGROUND OF THE INVENTION
1. Field of the Invention
[001] The present invention relates to systems for separating particulates
from fluids
such as drain water and stormwater. Such particulates include particulates
that float under
most fluid movement conditions, particulates that do not float under most
fluid movement
conditions, and particulates that may be caught up in the fluid stream when
the fluid is
flowing, but that may otherwise float or be suspended within the fluid when
the fluid is
substantially stagnant. More particularly, the present invention relates to a
separation system
that may be independent, or form part, of a larger fluid transfer system.
2. Description of the Prior Art
[002] Fluid transfer systeins have been and will remain an important aspect of
municipal services and commercial facilities management. The protection of
ground water
and natural bodies of water requires systems for diverting and/or treating
water that contacts
roadways, parking lots, and other man made structures. If such diversion or
treatment
systems are not provided, particulates and contaminants located on or forming
part of such
structures may be carried by drain water or stormwater to the natural water
bodies and
contaminate them. Local, state and federal laws and rules require
municipalities, businesses
and, in some instances, private entities, to establish means to reduce
particulate and
contaminant levels permissibly transferred to natural bodies of water from
property under
their control. Particular requirements may vary from jurisdiction to
jurisdiction, but all are
likely to become more, rather than less, stringent.
[003] Previously, municipal water transfer and treatment facilities provided
the only
mechanism for diverting contaminated water away from natural bodies of water,
either for
holding or treatment for subsequent transfer to natural settings. In general,
that process
involved, and continues to involve, the establishment of a system of drains,
such as in a
parking lot or at a street curb, by which water enters a system of pipe
conduits. Eventually,
the water received from the drains reaches either a final outlet destination
or is directed to a
treatment system for contaminant removal. For purposes of the description of
the present
invention, "contaminated water" is to be understood to mean any water
including floating
particulates, such as StyrofoamTM containers and oil, for example; non-
floating particulates,
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such as sand and silt, for example; and entrained contaminants, such as
dissolved nutrients or
metals, for example.
[004] Land development produces increased levels of drain water and stormwater
runoff, resulting in increased strain on existing water transfer and treatment
infrastructure and
an increased likelihood of natural water contamination. In an effort to reduce
the impact of
development on natural resources and municipal services, initial upstream
fluid treatment has
becoine a requirement in many land development, restoration and repair
projects. That is,
requirements in various forins have been established to ensure that before
contaminated water
enters the municipal water transfer and/or treatment system, it must be
treated in a manner
that reduces the level of contaminants entering the municipal system.
Therefore, most new
land development plans and upgrades to existing paved surfaces involve the
insertion of a
preliminary separation system, generally for connection to the municipal water-
handling
infrastructure.
[005] Any preliminary separation system must be designed with the capability
to
receive fluid flowing in at a wide range of rates. For example, a mild
rainfall resulting in rain
accumulation of less than 0.25 inches over a span of 24 hours produces a
relatively low flow
rate through the system. On the other hand, for example, a torrential rainfall
resulting in rain
accumulation of more than two inches over a span of three hours produces
relatively high
flow rates through the system. It is desirable, then, to have a separation
system capable of
handling variable fluid flow rates with reduced likelihood of backup and
flooding of the
surface above. It is also desirable to control the flow through the system
such that trapped
particulates are not scoured or washed out of the device and re-entrained
during high flows
for passage downstream.
[006] In addition to having a reasonable fluid flow throughput capacity, the
separation systein inust be capable of performing the separation function for
which it is
intended. Specifically, it may be required to remove from the fluid flow path
a certain
number, type, or size of particulates. For example, some California
municipalities require the
removal of any particulates with dimensions greater than five millimeters. It
would be
preferable to have such a separation system that can rernove from the fluid
flow path the
particulates for which it is designed at the widest range of flow rates but
without causing
baclcup or scouring/washout. For that reason, soine such systems are designed
with a bypass
mechanism to permit direct flow through of fluid without preliminary treatment
when
relatively high flow rates are reached. Unfortunately, ineffectively designed
separation
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systems fail to provide the best particulate removal and further fail to do so
under flow rates
that may not be particularly high.
[007] There is an increasing need and requirement for separation systems
associated
with drain water and stormwater introduction to municipal water handling
systems.
However, it is important that they not be prohibitively expensive in order to
ensure that
meeting those needs and requirements is feasible. It is also of importance
that such
separation systems are relatively easy to access for inaintenance. It is also
preferable that
separation systems provide a reasonable arrangement for storing accumulated
particulates to
minimize the possibility of clogged inlets and outlets and to extend the
required maintenance
cycle. Inline treatment systems of relatively modest size are particularly
desirable for
incorporating into existing fluid transfer systems, however, they may be prone
to shorter
maintenance cycles as a result of competing goals of reduced size, exit
blockage
minimization, and flow through capacity requirements.
[008] Therefore, what is needed is a separation system that may or may not be
part
of a larger fluid handling system that is effective in accommodating varied
fluid flow rates.
What is also needed is such a separation system that conforms or substantially
conforins with
established particulate removal requireinents. Further, what is needed is such
a separation
system that is configured to minimize clogging possibilities and to inaxiinize
particulate
removal capability in a cost effective arrangement. Yet further, what is
needed is such a
separation system that includes means to minimize exit blockage under
anticipated fluid flow
conditions without compromising separation capability.
SUMMARY OF THE INVENTION
[009] It is an object of the present invention to remove particulates
including, but not
limited to, trash, oil, dirt, and grease from fluid systems. It is also an
object of the present
invention to provide a separation system that is effective in accommodating
varied fluid flow
rates. It is another object of the present invention to provide such a
separation system that
conforms or substantially conforins with established particulate removal
requirements.
Further, it is an object of the invention to provide such a separation system
that is configured
to miniinize clogging possibilities and to maximize particulate reinoval
capability in a cost
effective arrangement. Yet further, it is an object of the present invention
to provide such a
separation system that includes means to minimize exit blockage under
anticipated fluid flow
conditions without compromising separation capability.
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[010] These and other objectives are achieved with the present invention. The
invention is a fluid separation system including an apparatus for screening
particulates from
the fluid stream in a manner that reduces flow blockage without compromising
fluid flow
through capacity. For the purpose of the description of the present invention,
the types of
particulates principally to be separated from the fluid stream passing through
the fluid
separation system are those particulates that may be caught up in the fluid
stream when the
fluid is flowing, but that may otherwise float, sink, or be suspended within
the fluid when the
fluid is substantially stagnant. Such particulates will be referred to herein
as neutrally-
buoyant particulates. Examples of such particulates include, but are not
limited to,
newspapers, plastic and paper bags, envelopes, leaves, branches, and anything
else that may
not otherwise always float or always sink under all fluid movement conditions.
[011] The screening apparatus is preferably combined with a diverter element
of a
separation system, such as a baffle, wherein the diverter is arranged to shape
fluid flow
patterns and to prevent floating particulates from exiting the separation
system. More
particularly, the screening apparatus aids the diverter by capturing any
entrained or neutrally-
buoyant floatables from circumventing the diverter without substantially
reducing fluid flow
rate past the diverter. The screening apparatus is substantially porous and
may extend from
and beyond the diverter. The objects of the present invention may be further
advanced by the
addition of a secondary screening apparatus of the present invention. The
secondary
screening apparatus is designed to capture floating particulates, particularly
when the fluid
surface elevation in the separation system is relatively high. As the fluid
surface elevation is
lowered under reduced fluid flow conditions, the secondary screening apparatus
retains a
portion of the floating particulates above the fluid surface elevation for
subsequent removal.
The secondary screening apparatus thereby reduces the amount of floating
particulates in the
separation system that may block the system exit. Further, the secondary
screening apparatus
may allow any particulates residing thereon to dry out when the fluid surface
elevation drops.
That drying slows particulate decomposition and may make particulate removal
easier.
Moreover, the retention of the particulates out of the fluid on the secondary
screening
apparatus prevents the leaching out of any contaminants retained on those
particulates into
the fluid.
[012] In one aspect of the invention, an apparatus is provided for separating
particulates, including floating, non-floating, and neutrally-buoyant
particulates, from a fluid.
The apparatus includes a tank having a bottom and interior sidewalls to define
a storage
chamber, an inlet at a first location on the interior sidewalls for receiving
the fluid, and an
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outlet at a second location on the interior sidewalls for transferring the
fluid out of the tank, a
baffle positioned in the tank and having a lower portion including a bottom
spaced above the
bottom of the tank, and a screen positioned in the tank, wherein the screen
extends from the
bottom of the baffle into the lower portion of the storage chamber. The screen
inay be
fabricated of a porous material such as perforated metal, for example, but is
not limited
thereto. One portion of the screen may be porous while another portion is non-
porous. The
leading edge of the screen, defined as that portion of the screen first
contacted by the fluid
stream within the storage chamber prior to exiting the storage chamber, may be
non-porous.
The apparatus may also include a second screen spaced above the substantially
vertically
oriented screen, wherein the second screen is substantially horizontally
oriented and
positioned above the expected resting fluid surface in the tank. In an
alternative embodiment,
the second screen may be of conical shape. The apparatus inay also include a
collection weir,
wherein the second screen may be separate from, or removably affixed to, the
collection weir.
The combination of the collection weir and the second screen including a port
through which
fluid from the storage chamber passes before passing onto the second screen.
The bottom
surface of the second screen is preferably disposed above a crown of the tank
inlet.
[013] In another aspect of the invention, an apparatus to improve the
separation of
particulates, including neutrally-buoyant particulates, from a fluid passing
into a separation
tank including an inlet, an outlet, and an arrangement for diverting at least
a portion of the
fluid from the inlet into the tank prior to the fluid exiting via the outlet
is provided. The
apparatus is a screen positionable within the tank and configured to filter
out relatively large
particulates from the diverted fluid prior to the fluid exiting the tank via
the outlet, the screen
is further configured to minimize the inhibition of fluid flow from the tank
to the outlet. The
screen is fabricated of a porous material such as perforated metal, and one
portion may be
porous while another is non-porous, the non-porous portion preferably being
the leading edge
of the screen. The apparatus may include a second screen spaced above the
substantially
vertically oriented screen, wherein the second screen is substantially
horizontally oriented
and positioned above the expected resting fluid surface in the tank. Further,
the second
screen inay form part of a collection weir system, the combination of the
collection weir and
the second screen including a port through which fluid from the tank passes
before passing
onto the second screen. A system including just the second screen
alternatively provides
means for retaining floating particulates out of the tank when the fluid level
within the tank
recedes.
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[014] In an alternative embodiment of the invention, a separation system for
separating floating and non-floating particulates from a fluid includes a tank
having a bottom
and interior sidewalls to define a storage chamber, an inlet at a first
location on the interior
sidewalls for receiving the fluid, and an outlet at a second location on the
interior sidewalls
for transferring the fluid out of the tank, an upper baffle spaced from the
interior sidewalls of
the tank and having an upper baffle bottom and an upper baffle port to allow
fluid entering
the tank to pass from behind the upper baffle into the storage chainber, a
bypass including an
inlet flow control means for controlling fluid flow from the inlet through the
upper baffle
port, the bypass spaced between the upper baffle and the tank interior
sidewalls, a lower
baffle having a lower baffle bottom spaced above the bottom of the tank,
wherein the lower
baffle is positioned within the tank below the level of the upper baffle, and
a weir positioned
between the inlet flow control means and the outlet, the weir configured to
divert fluid from
the inlet to the upper baffle port under relatively low fluid flows and to
divert one portion of
the fluid from the inlet to the upper baffle port and to allow the remaining
portion of the fluid
to flow from the inlet to the outlet under relatively high fluid flows.
[015] In another alternative embodiment of the present invention, a separation
system for separating floating and non-floating particulates from a fluid
includes a tank
having a bottom and interior sidewalls to define a storage chainber, an inlet
at a first location
on the interior sidewalls for receiving the fluid, and an outlet at a second
location on the
interior sidewalls for transferring the fluid out of the tank, a baffle having
a bottom, a first
side baffle wall, a second side baffle wall and a port, wherein the baffle is
positioned within
the tank, the bottom of the baffle spaced above the bottom of the tank, a
bypass including an
inlet flow control means on the second side baffle wall between the inlet and
the port of the
baffle, a screen extending from the bypass into the storage chamber, and a
weir positioned to
divert fluid from the inlet to the baffle port under relatively low fluid
flows and, under
relatively high fluid flows, to divert one portion of the fluid from the inlet
to the baffle port
while allowing the remaining portion of the fluid to flow from the inlet to
the outlet without
entering the storage chamber through the baffle port.
[0161 The details of one or more examples related to the invention are set
forth in
the accompanying drawings and the description below. Other features, objects,
and
advantages of the invention will be apparent from the description and
drawings, and from the
appended claims.
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BRIEF DESCRIPTION OF THE DRAWINGS
[017] FIG. 1 A is a perspective view of a particulate separation tank
including the
screen apparatus of the present invention. FIG. I B is a cross-sectional
elevation view of the
tank at Section A-A of FIG. l A, showing the inlet, the outlet and the
associated pipe sockets.
[018] FIG. 2 is a partial cutaway perspective view of the particulate
separation tank
including the screen apparatus of the present invention from behind the baffle
and the screen.
[019] FIG. 3 is a cross-sectional perspective view of a particulate separation
tank
showing the retention section or storage chamber, the tank inlet pipe socket,
the baffle, and
the screen of the present invention.
[020] FIG. 4 is a cross-sectional elevation view of a section of a particulate
separation tank, showing a first embodiment of the screen, baffle, baffle port
and pipe
sockets.
[021] FIG. 5 is a cross-sectional elevation view of a section of a
particulates
separation tank, showing a second embodiment of the screen, baffle, baffle
port and pipe
sockets.
[022] FIG. 6 is a cutaway perspective view froin a first angle of an optional
second
screen apparatus of the present invention.
[023] FIG. 7 is a cutaway perspective view from a second angle of the optional
second screen apparatus of the present invention.
[024] FIG. 8A is a cutaway perspective view of an alternative embodiment of
the
second screen apparatus. FIG. 8B is a cross-sectional elevation view of the
embodiment of
8A.
[025] FIG. 9 is a plan view of an alternative embodiment of the separation
system of
the present invention, showing the upper baffle and the lower baffle in an
arrangement to
enable high fluid flow bypass.
[026] FIG. 10 is a perspective view of the alternative combination of the
upper
baffle and lower baffle, showing the bypass portion of the separation system.
[027] FIG. 11 is a perspective view of an alternative embodiment of the
separation
system of the present invention, showing a baffle and screen combination in an
arrangement
to enable high fluid flow bypass.
[028] FIG. 12A is a cross-sectional elevation view of an embodiment of the
interior
walls of the tank having helical-shaped corrugations for fluid shaping in the
storage chamber.
FIG. 12B is a partial cut-away perspective view of the helical-shaped
corrugations of the
interior walls of the storage chamber.
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DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[029] A separation system 10 including a screen apparatus of the present
invention is
illustrated in the accompanying drawings. As illustrated in FIGS. 1 A and 1 B,
the system 10
includes a tank 11 having an inlet pipe socket 50 and an outlet pipe socket
60. The tank 11 is
preferably made of concrete but may alternatively be fabricated in whole or in
parts of metal,
plastic, such as fiberglass, or other suitable materials. It may be fabricated
of an existing
manhole or manhole design and modified in the manner to be described herein.
The inlet
pipe socket 50 shown in FIG. lA is used to connect the tank 11 to an upstream
fluid source or
transfer system, such as through an upstream conduit (not shown). Similarly,
the outlet pipe
socket 60 shown in FIG. 1 A is used to connect the tank to a downstream fluid
transfer
system, such as through a downstream conduit (not shown). For example, the
upstream fluid
transfer system may include a drainage system from a roadway or a parking lot
and the
downstream fluid transfer system may include a municipal water treatment plant
or natural or
artificial surface waters. It is to be understood that the tank 11 may not be
specifically
connected to an upstream conduit transfer arrangement, nor to a downstream
conduit transfer
arrangement. Instead, fluid may enter the tank l 1 through some form of inlet,
and may exit
the tank 11 through some form of outlet, including spilling directly out of
the tank onto or
into an unspecified container, body of fluid, or any sort of receptacle.
[030] The tank 1 l includes an inlet 12 associated with the inlet pipe socket
50, an
outlet 13 associated with the outlet pipe socket 60, a diverter for directing
fluid flow and/or
for trapping particulates, such as baffle 14, and a screen 100, as shown in
FIG. 2. The tank
1 l establishes a storage chamber 16 defined by a tank bottom 17, sidewalls 18
in a cylindrical
forin that may alternatively be in a polygonal form, and a lid 19. The lid 19
shown in FIGS.
1 A and I B substantially completely covers the tank 1 l and may include an
access port with
access port cover 72 for accessing the interior of the storage chamber 16 for
maintenance
purposes without removing the entire lid 19. Alternatively, the height of the
sidewalls 18 and
the baffle 14 may be set to ensure that they are above the highest possible
fluid surface
elevation, thereby eliminating the need for a lid while allowing the interior
of the tank 1 l to
be open for inspection.
[031] The baffle 14 is located within the tank l 1 as a sectional wall
removably
attachable to an interior side 20 of the sidewalls 18. The baffle 14 may
optionally be
positioned within the tank 1 l by means other than attachment to the interior
side 20 of the
tank 11. For example, it may be slottingly fitted into the tank 11, attached
to the bottom 17 of
the tank 11, or suspended within the tank 11. The baffle 14 extends downward
from a top
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area 21 of the tank l 1 to a point above the tank bottoin 17 and effectively
divides the tank 11
into a bypass region behind the baffle 14 and a treatment region that is the
storage chamber
16 in front of and below the baffle 14. An inner sidewall 22 of the baffle 14
is configured to
prevent floating particulates from exiting the storage chamber 16 of the tank
11. As
illustrated in FIG. 2, an outer sidewall 30 of the baffle 14 and the screen
100 are spaced from
the interior side 20 of the tank 11. The tank 11 may include a flow control
system 40
designed to aid in the shaping of fluid flowing into the storage chamber 16
and an outlet tube
50 that reduces the likelihood of any floating material, such as oil, exiting
the outlet 13
through the screen 100. The outlet tube 50 preferably extends below the
expected fluid
surface elevation such that any floatables passing through the screen 100
would be trapped
under the flow control system 40. A tube arrangement of the type shown in FIG.
2 may not
be desired or required for a separation system having a solid structure, such
as a baffle,
extending below flow control system 40. Instead, an outlet port may be used,
as any floating
particulates would be trapped by the solid structure. As shown in FIGS. 2 and
3, the baffle
14 includes a baffle port 27 spaced from the tank inlet 12. The baffle port 27
is preferably
configured to direct flow entering the tank I 1 at the tank inlet 12 in a
manner that generates a
fluid flow tangential to the inner sidewall 22 of the baffle and the interior
side 20 of the
sidewalls 18 of the tank 11. The baffle 14 may terminate at or below the level
of the flow
control system 40.
[0321 The shape and dimensions of the baffle port 27 may be varied or selected
as a
function of the particular flow conditions to be expected. However, as shown
in FIG. 4, one
embodiment of the baffle port 27 is shaped to have a smaller opening nearer
the inlet 12 and
increase in size and extending downwardly toward the tank bottom 17 moving
away from the
inlet 12. As a result, under low fluid flow conditions, the fluid is
restricted from immediately
entering the storage chamber 16 through the baffle port 27 as it passes
between the outer
sidewall of the baffle 14 and weir 24 until reaching the inner sidewall 22 of
the baffle 14.
That shaping of the baffle port 27 enables the fluid to enter the storage
chamber 16
tangentially. The noted shape of the baffle port 27 also allows relatively
high fluid flows to
enter the storage chamber 16 without unnecessary restriction. A baffle port 27
of constant
dimensions would be less effective in regulating fluid flow under all flow
conditions. Under
relatively low flow conditions, the weir 24 diverts all fluid into the storage
chamber 16.
Under relatively high flow conditions, the baffle port 27 becomes submerged
and floating
particulates within the storage chamber 16 are retained therein by the inner
sidewall 22 of the
baffle 14 and that portion of the interior side 20 of the tank not behind the
baffle 14.
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Eventually, the flow rate is such that the fluid surface elevation exceeds the
height of the weir
24 and bypass occurs.
[0331 In operation, the tank 11 enables the separation of particulates from a
fluid.
The fluid enters the tank 11 via the tank inlet 12 and initially passes behind
the baffle 14.
The fluid then passes through the baffle port 27 to the interior sidewall 22
of the baffle where
a swirling motion is established along the inner sidewall 22 of the baffle 14
and interior side
20 of the tank 11. The swirling motion of the fluid directs floating
particulates to the center
of the storage chamber 16 at or near the surface water elevation, dependent
upon fluid flow
rate, as indicated above. Non-floating particulates are directed downwardly to
the tank
bottom 17 and swept to the center of the tank 11. The treated fluid then
passes through the
screen 100, and out of the tank 11 via the outlet 13, either directly or
through outlet tube 50.
The screen 100 aids in supplemental filtering of neutrally-buoyant
particulates from the fluid
prior to the fluid exiting. That is, the screen 100 is preferably positioned
within the tank 11
between where floating particulates are expected to accumulate above and non-
floating
particulates are expected to accumulate below. The weir 24 diverts fluid
through the baffle
port 27 and forms part of a bypass arrangement wherein relatively high fluid
flows result in a
portion of the fluid passing from the inlet 12 to the outlet 13 without being
treated in the
storage chamber 16.
[0341 As shown in FIGS. 2-4, the screen 100 includes an upper screen portion
101
removably attachable to the interior side 20 of the tank 11. When the tank 11
is deployed for
use in treating fluid, the baffle 14 and the screen 100 are preferably
oriented substantially
vertically. The screen 100 further includes a first or leading edge side
screen flange 102 at
screen leading edge 104, and a second or trailing edge side screen flange 103
at screen
trailing edge 105, for removable attachment of the screen 100 to the interior
side 20 of the
tank 11. The screen 100 preferably extends downwardly from the baffle 14 into
the lower
portion of the storage chamber 16, extending closer to the tank bottom 17 than
does the baffle
14. As shown in FIG. 2, a bottom portion of the screen 100 includes screen
extension 106
extending from the screen 100 to the interior side 20 of the tank 11 in the
region of the tank
l 1 behind the screen 100. The screen extension 106 prevents particulates such
as neutrally-
buoyant particulates from passing up behind the screen 100 to the tank outlet
13. The screen
extension 106 may be made of the same material as is the main body of the
screen 100. The
screen extension 106 is preferably configured to allow any relatively small
particulates that
may be located behind the baffle 14 to pass therethrough and fall to the tank
bottom 17 of the
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storage chamber 16. The screen 100 is preferably configured and arranged to
aid in the
separation of neutrally buoyant particulates frotn the fluid in the storage
chamber 16.
[035] The baffle 14 shown in FIGS. 2-4 is formed with a single curvature
aspect to
direct the fluid flow within the tank 11, and an angled weir 24 to direct the
fluid flow through
the baffle port 27. The screen 100 is preferably similarly curved to minimize
fluid flow
pattern disruption. Alternatively, the baffle 14 may be formed of a complex
curvature, and
the weir 24 may also be curved. If the baffle 14 is shaped with such complex
curvature, the
screen 100 may also be similarly curved, although that is not specifically
required, as the
fluid flow pattern is likely already established by the time the screen
leading edge 104 is
reached and the likelihood of producing turbulence with a screen curvature
different from the
baffle curvature at the screen trailing edge 105 is minimized; however, a
screen 100 of
different curvature would likely complicate the manufacturing of the present
invention.
[036] The screen 100 shown in FIGS. 2-4 includes a plurality of openings that
make
it substantially completely porous. The flanges 102 and 103 may be solid or
porous,
dependent upon the method for affixing the screen 100 to the interior side 20
of the tank 11.
The screen 100 may be fabricated of a metallic material, such as a perforated
metal, or a non-
metallic material such as a plastic screen. In an alternative embodiment of
the screen 100
shown in FIG. 5, the screen leading edge 104 of the screen 100 is nonporous.
That is, the
material selected to fabricate the screen 100 may be made with a porous
section and a non-
porous section. Alternatively, the screen 100 may be fabricated of two pieces
joined
together, one solid and the otlier porous. The solid leading edge 104 of the
screen 100 of
FIG. 5 is designed to improve fluid velocity distribution at the tank-to-
screen ititerface. The
improved fluid velocity distribution reduces particulate accumulation on the
screen 100 at
that interface. Particulates accumulating at the leading edge 104 ]-nay cause
a build up that
would prevent follow-on particulates from reaching the screen 100 downstream,
thereby
accelerating the need for screen maintenance. The extent to which the leading
edge 104
retnains nonporous should be determined by the expected flow conditions,
maintenatlce
scheduling, and the operational environment.
[037] As illustrated in FIGS. 6 and 7, a supplemental second screen 200 may be
deployed in the tank 11 as a means to filter floating particulates. When the
tank 11 is
deployed for use in fluid filtering, the second screen 200 is preferably
oriented substantially
horizontally with respect to the centerline of the tank 11. However, it is to
be understood that
the second screen 200 may be oriented at an angle that aligns it other than
horizontally with
respect to the centerline of the tank 11. The second screen 200 includes a
plurality of
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openings that make it substantially porous. A collection weir system 201
includes a screen
port 202 forined as part of an arcuate frame 203 that is removably attachable
to the interior
side 20 of the tank 1 1 at frame flange 204. The second screen 200 is
preferably retained in
place by the frame 203 at a position above the crown elevation of inlet 12
such that the baffle
port of the baffle 14 will become fully submerged when the fluid surface
elevation reaches
the second screen 200. The frame 203 may be positioned above the second screen
200 as an
frame upper section 205. Alternatively, the frame 203 may be a split frame
having a frame
upper section 205 above the position of the second screen 200, and a frame
lower section 206
below the screen 200. For either version, the frame upper section 205 further
includes a weir
plate 207. The height of the weir plate 207 in combination with the frame
upper section 205
in combination define the fluid surface level at which fluid in the screen
port 202, and any
floating particulates contained therein, spills out above the upper portion of
the second screen
200. The second screen 200 may also be used without the collection weir system
201 and
without the screen 100. In that embodiment, the second screen 200 includes the
screen port
202 and is positioned above the resting fluid surface to retain thereon
floating particulates
entering through the screen port 202.
[038] With continuing reference to FIGS. 6 and 7, in operation, the second
screen
200 in combination with the arcuate frame 203 provide a means for keeping
floating
particulates in the center of the tank 11, particularly at relatively low
fluid flow rates, and in
capturing floating particulates when the fluid surface elevation in the tank
is very high.
Specifically, storage chamber fluid, represented by arrow 210, swirling in the
storage
chamber 16 has a fluid surface elevation that rises with fluid entry into the
tank 11. Between
storm events, the standing elevation of the fluid is at the bottom level of
the outlet 13. Under
relatively low flow conditions, that level is substantially maintained, and
the frame lower
section 206 acts to capture floating particulates as a baffle, but does so in
a manner that keeps
the floating particulates away from baffle 14 and screen 100. That function by
the frame
lower portion 206 improves the fluid flow either through the screen 100, or
directly under the
baffle 14, by reducing floating particulate blockage.
[039] As the fluid flow rate increases into the tank 11, the fluid elevation
surface
rises. The frame lower portion 206 continues to center any floating
particulates in the tank
11. Further, the underside of second screen 200 blocks floating particulates
from entering the
upper region of the storage chamber 16 as the fluid elevation continues to
rise. When the
fluid elevation exceeds the screen 200, submerging the baffle port, the fluid
and any floating
particulates not otherwise trapped on the underside of the screen 200 enter
the screen port
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202, represented by arrow 211. When the fluid surface elevation exceeds the
height of the
frame upper portion 205 and weir plate 207, the fluid containing floating
particulates,
represented by arrows 212, spills over into an area above the second screen
200. As the
incoming fluid flow rate subsides and the fluid surface elevation drops,
floating particulates
in the fluid 212 are captured on the upper surface of the second screen 200.
These floating
particulates are thereby prevented from re-entering the lower part of the
storage chamber 16
where the outlet is located and cannot block the fluid from exiting the tank
11. Those
floating particulates not captured by second screen 200 recede back into port
202 and are
prevented from re-entering the storage chamber 16 by frame lower portion 206.
[040] The screen 100 of the present invention improves the separation of
entrained
floating or neutrally-buoyant particulates from a treated fluid by trapping
them prior to
exiting the tank 11. The second screen 200 and the collection weir system 201
provide
supplemental means for capturing floating particulates and/or isolating
floating particulates
from the area of the storage chamber 16 where the treated fluid passes to the
tank outlet 13.
The screen apparatus and the suppleinental screen apparatus improve
particulate removal for
a system for separation floating and non-floating particulates from a fluid
stream. Either or
botli devices may also extend maintenance periods by reducing blockage
situations.
[041] In an alternative embodiment of the second screen 200' shown in FIGS. 8A
and 8B, the second screen 200' is configured to direct floating particulates
toward a second
screen port 202', effectively replacing the diverting function of the
collection weir system
201. Specifically, the second screen 200' is conical in shape, and preferably
a truncated cone
shape. The second screen 200' includes a second screen port 202' that is shown
substantially
centered in the space between the interior side 20 of the tank 1 l and the
interior sidewall of
the baffle 14, but may alternatively be positioned off center. A screen apex
220 of the second
screen 200' is preferably positioned farthest above the resting fluid surface.
The preferred
conical shape of the second screen 200' directs floating particulates toward
the second screen
port 202' as the fluid elevation rises. When the fluid surface exceeds the top
of the second
screen port 202', any floating particulates therein spill over above the
second screen 200' and
remain thereon as the fluid recedes.
[042] A first alternative embodiment of the fluid diversion and bypass portion
comprising the baffle arrangement and the bypass of the separation system 10
is shown in
FIGS. 9 and 10. This first alternative embodiment includes an upper baffle 300
and a lower
baffle 310 positionable within the tank l 1 shown in the other figures. The
tank 1 l remains
configured to separate particulates from a fluid entering the storage chamber
16 in the manner
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WO 2006/065964 PCT/US2005/045368
previously described. A tank including the alternative arrangement of FIGS. 9
and 10
continues to function as a means to separate particulates from a fluid
entering the tank,
however, the alternative arrangement enables a greater volume of fluid to
bypass the tank
storage chamber, such as storage chamber 16, under relatively high flow
conditions. The
upper baffle 300 is preferably spaced further from the tank interior side, but
at smaller radius
of curvature than the baffle 14 of FIG. 2, for example. The radius of
curvature is preferably
maintained to be greater than or equal to approximately half the radius of
curvature of the
tank. This arrangement allows a greater volume of fluid to bypass the tank
storage chamber
while simultaneously maintaining the development of separation-enhancing
swirling patterns
in the storage chamber. That is, the combination of the upper baffle 300 and
the lower baffle
310 baffle continues to isolate the storage chamber from the bypass in the
inanner previously
described. Systems incorporating an upper baffle with a radius of curvature
smaller that one
half the radius of curvature of the tank, for exa-nple, can have little or no
developinent of
swirling flow in the storage chamber resulting in poor separation performance.
The upper
baffle 300 is spaced from the interior side by bypass flow control system 40'.
The upper
baffle 300 includes a bottom 301 that is approximately at the level of the
botto-n of the
bypass flow control system 40'. The lower baffle 310 is spaced more closely to
the tank
interior side than the upper baffle, but below the bypass flow control system
40' and at a
radius of curvature more closely matching the interior dimensions of the tank
within which
the baffle and bypass are positioned. The lower baffle 310 includes a bottom
311 arranged to
be spaced above the bottom of the tank.
[043] The bypass flow control system 40' includes a bypass plate 41', an inlet
flow
control zone 42', an outlet flow control zone 43', a weir 44', a head
equalization baffle 45',
and an outlet port 50'. The dimensions of the bypass plate 41' define the
displacement of the
upper baffle 300 from the interior side of the tank. The upper baffle 300
includes an upper
baffle port 302 through which fluid entering the tank passes from the inlet
flow control zone
42' into the tank storage chamber. The weir 44' diverts fluid through the
baffle port 302 into
the tank storage chamber. Treated fluid within the storage chamber passes
behind the lower
baffle 310 and into the outlet flow control zone 43' through the outlet port
50'. As the fluid
entering the tank 1 l reaclies a relatively high flow rate, the baffle port
302 becomes fully
submerged, with a portion of the fluid diverted through the baffle port 302
while the balance
spills over the weir 44', bypassing the treatment provided by the storage
chamber.
Particulates in the fluid entering the storage chainber through the baffle
port 302 continue to
be treated as before, with floating particulates retained in the upper portion
of the storage
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chamber by the upper baffle 300 and, to an extent, the lower baffle 310, and
nonfloating
particulates retained in the bottom of the tank. The head equalization baffle
45' moderates
the flow rate through the storage chamber when flow over weir 44' occurs. Low
flows
passing only through the baffle port 302 are allowed to freely discharge
through outlet port
50' and underneath the head equalization baffle 45'. However, as flow crests
the weir 44'
and enters the area above outlet port 50', the additional flow is restricted
by the head
equalization baffle 45' and begins to rapidly submerge the outlet port 50'.
This pooling of
fluid creates an additional resistance to flow through the outlet port 50'.
This arrangement
results in a relatively consistent flow rate through the storage chamber even
as flow through
the entire system increases. When the fluid level in the outlet flow control
zone 43' rises
above the level of the head equalization baffle 45', it spills over and exits
the tank. The top
of the head equalization baffle 45' is preferably at a level equal to or
higher than the top of
the weir 44'.
[044] The portion of the separation system shown in FIGS. 9 and 10 inay
further
include a wedge 315 positioned between the weir 44' and the back side of the
baffle 300 at
about the crown of the baffle port 302 at the weir 44' to baffle 300
interface. The wedge 315
is configured and arranged to prevent particulates froin becoming wedged into
the space
occupied by the wedge 315. When the wedge 315 is not placed in what is
effectively a dead
space, particulates, and floating particulates specifically transported by
relatively high fluid
flows to and over the weir 44', become entrapped in that space and disrupt
fluid flow. The
wedge 315 is preferably shaped to conform to the dimensions of the space
between the baffle
300 and the weir 44'. The use of the wedge 315 is not limited to deployment in
a separation
systein for relatively high fluid bypass such as the systein represented in
FIGS. 9 and 10. It
may also be used in any separation system in which a baffle with port and
fluid bypass
behind the baffle are used.
[045] A second alternative embodiment of the fluid diversion and bypass
portion of
the system of the present invention is shown in FIG. 11. The second
alternative embodiment
is similar to the first alternative embodiment shown in FIGS. 9 and 10 as it
is intended to
provide for high fluid volume bypass when needed and as compared to the
arrangement of
the separation system 10 shown in FIG. 2. It is also similar to the first
embodiment of FIGS.
9 and 10 in that baffle 300 remains in use; however, the lower baffle 310 is
replaced by
screen 320. The screen 320 is positioned below bypass plate 41' and is
attachable to the
interior side of the tank and or the underside of the bypass plate 41'. The
screen 320 extends
downwardly into the lower portion of the tank storage chamber from the bypass
plate 41',
CA 02588600 2007-05-24
WO 2006/065964 PCT/US2005/045368
whereas the bottom of the upper baffle 300 substantially terminates at the
bypass plate 41'.
The radius of curvature of the screen 320 is greater than the radius of
curvature of the baffle
300 in this alternative embodiment of the fluid diversion and bypass portion
of the separation
system.
[046] As earlier noted, when a screen forms part of the separation system, and
that
screen is positioned within the tank at or below the level of the bypass flow
control system
40' (or 40 for the first embodiment of the separation system 10), the outlet
tube 50 is
preferred over the outlet port 50' as the storage chamber outlet so that any
floating
particulates that pass through the screen 320 (or screen 100) remain trapped
under the bypass
plate 41' (or bypass plate 41). Wlien a solid structure such as the lower
baffle 310 of FIGS. 9
and 10 is used instead of the screen 100 or screen 320, such floating
particulates are blocked
by that structure and the outlet tube 50 is not required, and the outlet port
50' may be used
instead.
[047] A bottom portion of the screen 320 includes screen extension 321
extending
from the screen 320 back to the interior side of the tank behind the screen
320, substantially
as shown in FIG. 2 regarding screen 100 and screen extension 106. The screen
extension 321
prevents particulates such as neutrally-buoyant particulates from passing up
behind the screen
320 to the tank outlet via outlet tube 50. The screen extension 321 may be
made of the same
material as is the main body of the screen 320. The screen extension 321 is
preferably
configured to allow any relatively small particulates that may be located
behind the baffle
300 to pass therethrough and fall to the bottom of the tank storage chamber.
The screen 320
and the screen extension 321 are preferably configured and arranged to aid in
the separation
of neutrally buoyant particulates from the fluid in the storage chamber. The
second
alternative embodiment of the portion of the separation system as shown in
FIG. 11 may
further include the wedge 315 described above.
[048] As illustrated in FIGS. 12A and 12B, the interior side 20 of the
sidewalls 18 of
the tank 11 inay optionally be corrugated. The corrugations 90 are in a
helical orientation
with the helix spiraling downwardly from the tank inlet 12 to the tank bottom
17. The
specific angle of the corrugations 90 may be selected as a function of the
desired fluid flow
rate down into the storage chamber 16; however, that angle should match the
downward flow
trend of the fluid under average flow conditions. The corrugations 90 are
designed to aid in
the sinoothing of the fluid flow within the tank 11. In the alternative, the
corrugations 90
may be oriented with the helix angle opposing the fluid flow pattern (that is,
spiraling
downwardly froin the tank outlet 13 instead) to produce more turbulence of the
flow pattern
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WO 2006/065964 PCT/US2005/045368
along the interior side 20 of the sidewalls 18 if that is determined to be of
interest. The weir
24 may also or alternatively be configured to aid in fluid smoothing prior to
entry into the
storage chamber 16, such as by forming corrugations on the side thereof closer
to the baffle
port 27, the corrugations of the type shown in FIGS. 12A and 12B. Further, the
inner
sidewall 22 of the baffle 14 may additionally or alternatively be so
configured. It is also to be
noted that additional or alternative flow-disrupting projections, such as
ribs, may form part of
the interior of the tank 11.
[049] While the present invention has been described with particular reference
to
certain embodiments of the screening systems, it is to be understood that it
includes all
reasonable equivalents thereof as defined by the following appended claims.
17
