Title: Water pollution trap with clay collector
Abstract: A chamber having an inlet for receiving polluted storm-water runoff and an outlet for the storm water to flow out. Within the chamber is a pivotal filter that catches clay during typical storm flows and pivots out of the way during higher flows. In alternative embodiments, there are included a screen, one or more baffles, and/or a collection reservoir for further dispersing, detaining, and/or filtering the storm water.
Patent Number: 6,936,163 Issued on 08/30/2005 to Use, et al.
| Inventors:
|
Use; Clark Joseph (2208 Liberty La., Conyers, GA 30094);
Moll; John Sebastian (1495 Chalet Cir., Lawrenceville, GA 30043)
|
| Appl. No.:
|
310244 |
| Filed:
|
December 5, 2002 |
| Current U.S. Class: |
210/131; 210/155; 210/156; 210/254; 210/305; 210/496; 210/521; 210/532.1; 210/540 |
| Intern'l Class: |
B01D 036/04 |
| Field of Search: |
210/131,155,156,162,163,170,299,300,254,305,307,521,532.1,540,496,446,459
|
References Cited [Referenced By]
U.S. Patent Documents
| 231544 | Aug., 1880 | Darst.
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| 1397471 | Nov., 1921 | Walker.
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| 1666756 | Apr., 1928 | Sass.
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| 1758743 | May., 1930 | Harman.
| |
| 1999637 | Apr., 1935 | Pettepher.
| |
| 2782929 | Feb., 1957 | Colket.
| |
| 4268396 | May., 1981 | Lowe.
| |
| 4980070 | Dec., 1990 | Lieberman.
| |
| 5286383 | Feb., 1994 | Verret et al.
| |
| 5505860 | Apr., 1996 | Sager.
| |
| 5543064 | Aug., 1996 | Batten.
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| 5632888 | May., 1997 | Chinn et al.
| |
| 6079571 | Jun., 2000 | Stowell.
| |
| 6190545 | Feb., 2001 | Williamson.
| |
| 6428692 | Aug., 2002 | Happel.
| |
| 6478954 | Nov., 2002 | Turner et al.
| |
| 2002/0057944 | May., 2002 | Adams.
| |
| 2003/0121848 | Jul., 2003 | Use et al.
| |
| 2003/0121849 | Jul., 2003 | Use et al.
| |
| 2003/0121850 | Jul., 2003 | Use et al.
| |
| 2003/0164341 | Sep., 2003 | Use et al.
| |
Other References
Pandit, Ashok, PH.D., P.E. & Gopatakrishnan, Ganesh; "Physical Modeling of a
Stormwater Sediment Removal Box"; Jun. 1996; 19 pgs; Civil Engineering Program,
Florida Institute of Technology; Melbourne.
Pitt, Robert, Robertson, Brian, Barron, Patricia, Ayyoubi, Ali, Clark, Shirley;
"Stormwater Treatment at Critical Areas the Multi-Chambered Treatment Train (MCTT)";
Mar. 1999; 14 pgs; Deparment of Civil and Environmental Engineering, The University
of Alabama at Birmingham; Birmingham.
"Storm Water Technology Fact Sheet Water Quality Inlets"; Berg, 1991; 6 pgs;
EPA 832-F-99-029; United States Environmental Protection Agency Office of Water,
Washington, D.C.
|
Primary Examiner: Upton; Christopher
Attorney, Agent or Firm: Gardner Groff, P.C.
Parent Case Text
CROSS-REFERENCE TO RELATED APPLICATIONS
This application claims the priority benefit of U.S. Provisional Patent Application
Ser. No. 60/345,128, filed Dec. 31, 2001, and a continuation in part of U.S. Non-Provisional
Patent Application Ser. No. 10/217,186, filed Aug. 12, 2002 now U.S. Pat. No. 6,797,161
, which are hereby incorporated herein by reference in its entirety.
Claims
1. A trap for separating pollutants from a liquid, comprising:
a chamber having an inlet and an outlet; and
a pivotal fibrous filter disposed in the chamber between the inlet and the outlet,
wherein the pivotal fibrous filter is configured to separate some of the pollutants
from the liquid and pivots from a filtering position when a typical flow of the
liquid is flowing through it toward a bypass position in response to a larger-than-typical
flow of the liquid engaging it, wherein in the bypass position the pivotal fibrous
filter permits the liquid to flow out of the chamber outlet without passing through
the filter.
2. The pollution trap of claim 1, wherein the pivotal filter comprises a fibrous
filtration member made of coconut fiber.
3. The pollution trap of claim 2, wherein the pivotal filter further comprises
a frame removably holding the fibrous filtration member.
4. The pollution trap of claim 1, wherein the pivotal filter leans against an
end wall of the chamber at a location above the chamber outlet when in the filtering
position, and moves to a larger angle from horizontal in the bypass position than
in the filtering position.
5. The pollution trap of claim 1, further comprising a collection reservoir disposed
in the chamber between the inlet and the pivotal filter, wherein the collection
reservoir has a front wall with a skimming edge for skimming floating portions
of the pollutants into the collection reservoir, a rear wall, and a bottom wall
extending between therebetween and disposed above the chamber floor to permit the
liquid to flow under the collection reservoir in a longer flow route.
6. The pollution trap of claim 5, wherein the pivotal filter is pivotally coupled
to the collection reservoir.
7. The pollution trap of claim 1, wherein the chamber has an at-rest liquid level
when none of the liquid is flowing into the chamber, and further comprising a screen
disposed in the chamber between the inlet and the pivotal filter, wherein the screen
is disposed at or above the at-rest liquid level so that the screen retains some
of the pollutants, allows the liquid to pass therethrough, and suspends the retained
pollutants above the at-rest liquid level.
8. The pollution trap of claim 1, further comprising one or more baffles disposed
in the chamber between the inlet and the pivotal filter, wherein each of the baffles
comprises a panel with apertures defined therein that permit some of the liquid
and pollutants to pass therethrough, and wherein the baffles are configured and
positioned in the chamber forming at least one gap through which the liquid may
flow around the baffles to increase liquid residence time in the chamber to encourage
settling of some of the pollutants.
9. The pollution trap of claim 1, wherein the pollutants comprise clay and the
pivotal filter is adapted to filter out at least some of the clay.
10. A trap for separating pollutants from a liquid, comprising:
a chamber having an inlet and an outlet; and
a pivotal fibrous filter disposed in the chamber between the inlet and the outlet,
wherein the pivotal fibrous filter is configured to separate some of the pollutants
from the liquid.
11. The pollution trap of claim 10, wherein the pivotal filter pivots from a
filtering position when a typical flow of the liquid is flowing through it toward
a bypass position in response to a larger-than-typical flow of the liquid engaging it.
12. The pollution trap of claim 11, wherein the pivotal filter comprises a frame
supporting a fibrous filtration member.
13. The pollution trap of claim 12, wherein the fibrous filtration member is
removably held in the frame.
14. The pollution trap of claim 12, wherein the fibrous filtration member is
made of coconut fiber.
15. The pollution trap of claim 11, wherein the pivotal filter leans against
an end wall of the chamber at a location above the chamber outlet when in the filtering position.
16. The pollution trap of claim 15, wherein the pivotal filter is at a smaller
angle from horizontal in the filtering position than in the bypass position.
17. The pollution trap of claim 11, wherein the chamber has an at-rest liquid
level when none of the liquid is flowing into the chamber, and wherein the pivotal
filter is disposed at or below the at-rest liquid level when in the filtering position.
18. The pollution trap of claim 11, further comprising a collection reservoir
disposed in the chamber between the inlet and the pivotal filter, wherein the collection
reservoir has a front wall with a skimming edge for skimming floating portions
of the pollutants into the collection reservoir, a rear wall, and a bottom wall
extending between therebetween and disposed above the chamber floor to permit the
liquid to flow under the collection reservoir in a longer flow route.
19. The pollution trap of claim 18, wherein the pivotal filter is pivotally coupled
to the collection reservoir.
20. The pollution trap of claim 18, wherein the pivotal filter is disposed under
the reservoir.
Description
TECHNICAL FIELD
The present invention relates generally to water pollution traps and, more particularly,
to oil/grit separators for separating and collecting various pollutants from storm-water runoff.
BACKGROUND OF THE INVENTION
During rainstorms, water that is not absorbed into the ground runs off into
storm sewer systems for delivery into freshwater systems such as streams, rivers,
lakes, and wetlands. While flowing across parking lots, landscaped areas, and other
surfaces, the storm-water runoff picks up debris and pollutants and carries them
into the storm sewer systems. Particularly large amounts of pollutants are picked
up at shopping centers with large parking lots, oil-change and auto-repair shops,
gas stations, and so forth. These pollutants include motor oil and other hydrocarbons,
particulate matter such as sand and grit, and miscellaneous debris such as vegetative
matter, paper, plastic, and foam cups. For example, about 200 pounds of miscellaneous
debris and 500 pounds of sand and grit is commonly carried off by storm-water runoff
from some one-acre parking lots in 90 days.
To maintain freshwater systems, most cities and counties have regulations requiring
that some of the pollutants be removed from the storm-water runoff before entering
their storm sewer systems. In order to meet these regulations, facilities typically
install on-site pollution traps to filter the storm-water runoff. These pollution
traps are sometimes referred to as "oil/grit separators."
Most conventional pollution traps provide only "first flush" filtration during
the typical local storm event, but permit bypassing the filtration stage for larger
storms. In fact, many jurisdictions require bypassing, some even at typical storm
water flows. Bypassing filtration is a problem because most pollutants are more
easily picked up and transported by storm water during higher flow periods. Unfortunately,
just when the traps are needed most, a lot of pollutants bypass them and are delivered
into the storm sewer systems. And most pollution traps that do not provide for
bypassing accommodate the larger flows because they are oversized, which adds significantly
to the cost to build, install, and maintain them.
Another problem with many pollution traps is they simply filter the storm
water at the natural flow rate of the storm water passing through it. The faster
the storm water flows through the trap, the less particulate matter pollutants
can settle in the trap. Some other traps detain the storm water for a brief time
to allow some of the particulate matter to settle. But these traps only detain
the water for a few minutes at most, and even a small water flow will cause the
particles to be re-suspended in the water. Therefore, these pollution traps allow
a lot of particulate matter pollutants to pass though them, even before bypass occurs.
In addition, the filtering systems of some pollution traps include screens for
capturing miscellaneous debris. These screens are typically partially submerged
in the water in the middle of the trap so that the debris is always floating in
the water. Because the debris is always floating, it does not block the screen.
The problem with this configuration is that vegetation, paper, and other absorbent
miscellaneous debris tends to become waterlogged, rot, and deteriorate into smaller
parts. These small parts then pass through the screen, are re-suspended in the
water, and are carried out of the trap. Moreover, vegetative matter contains nitrogen
and phosphorus and carries other pollutants such as fertilizer, pesticides, and
oils. And paper products carry inks and other surface adherents. So now these additional
pollutants also pass through the screen with the deteriorated debris and out of
the trap.
In general, typical known pollution traps are designed for a typical water flow.
Often the pollution traps are ill-suited to operating effectively over a widely
differing range of water flows. Indeed, sometimes greater than typical storms can
overwhelm known pollution traps.
Accordingly, it can be seen that a need remains for a pollution trap
that stays on-line and filters all the storm-water runoff from a parcel of land,
without bypassing filtration or overflowing during larger-than-typical storms.
In addition, there is needed a pollution trap that is effective for removing particulate
matter from the storm water and is still somewhat effective even when the flow
is well above that of a typical storm. Furthermore, a need exists for such a pollution
trap that is cost-efficient to build, install, and maintain. It is to the provision
of a pollution trap meeting these and other needs that the present invention is
primarily directed.
SUMMARY OF THE INVENTION
The present invention provides an innovative trap for separating pollutants from
storm water runoff. The trap separates pollutants such as miscellaneous debris
including vegetative matter, plastic, and paper, particulate matter including sand,
grit, and clay, and/or floating matter including motor oil, other hydrocarbons,
and detergents. In addition, the trap can be used to separate other pollutants
from other liquids, as may be desired in a particular application.
Generally described, the water pollution trap includes a chamber and a
pivotal filter positioned between an inlet and an outlet of the chamber. The chamber
has a floor, a worst storm water level when the water is flowing through the chamber
at a maximum water flow rate, and an at-rest water level when none of the water
is flowing into the chamber. The pivotal filter is configured to filter out at
least some of the clay or other pollutants.
In an exemplary embodiment of the present invention, the pivotal filter is constructed
of a rigid frame holding a removable fibrous filtration member. The fibrous filtration
member may be made of, for example, coconut fiber or another material for filtering
clay or other particulate matter.
The pivotal filter pivots from a filtering position when a typical flow of the
water is flowing through it toward a bypass position in response to a larger-than-typical
flow of the water pushing against it. In this way, the pivotal filter stays in
the filtering position during typical storms or between storms. But during larger-than-typical
storms, the upward force of the water against the pivotal filter pushes it out
of the way so that it does not impede the flow of the water out of the chamber.
In addition, the pivotal filter can be used in combination with other filtration
stages positioned in the chamber, including a screen, one or more baffles, and/or
a collection reservoir with a skimming edge. The screen is configured to suspend
at least some of the miscellaneous debris or other pollutants above the at-rest
liquid level. The baffles are configured to increase water residence time in the
chamber to encourage settling of the particulate matter or other pollutants. And
the collection reservoir is configured to skim at least some of the floating matter
or other pollutants into it.
The screen is positioned at or above the at-rest water level so that the screen
retains some of the pollutants, allows the water to pass through it, and suspends
the retained pollutants above the at-rest water level. In this way, the suspended
retained pollutants are kept dry when there is no storm so that they do not waterlog,
deteriorate, and pass through the screen. The screen can be, for example, basket-shaped
but with an open side adjacent the inlet.
The baffles are each configured and positioned in the chamber to form at least
one gap through which the water may flow around the baffle. In this way, the water
flows around the baffles in a longer flow route through the chamber, without flowing
any faster. Preferably, the collective flow area through the baffles is significantly
greater than the flow area of the inlet to cause the linear speed of the flow to
slow substantially while maintaining the volume of the flow constant. This increases
the residence time of the water in the chamber, which encourages settling of some
of the pollutants.
In addition, the baffles may have apertures in them that permit at least some
of the liquid to pass through them. In this way, the apertured baffles disperse
the water, which further encourages settling of some of the pollutants.
The collection reservoir has a skimming edge that is positioned at or adjacent
the worst storm water level to skim floating pollutant matter into the collection
reservoir. As the water flow through the chamber increases during larger-than-typical
storms, the floating pollutants rise with the water level until they are skimmed
off the surface of the water and into the reservoir, instead of bypassing the trap.
In order to provide for adjusting the skimming edge for the maximum water flow
at a particular installation, the skimming edge may be provided on a weir member
that is vertically adjustable and mounted to a front wall of the collection reservoir.
In addition, the bottom of the collection reservoir may be positioned above the
chamber floor to permit the water to flow under the collection reservoir. In this
way, the water flow route through the chamber is increased to further encourage
settling of some of the pollutants.
In this exemplary combination embodiment, the screen, baffle, reservoir, and
pivotal
filter filtration stages cooperate to provide a significant increase in performance
over conventional pollution traps. In particular, the screen suspends at least
some of the miscellaneous debris above the at-rest water level, the baffles increase
water residence time in the chamber to encourage settling of the particulate matter,
the collection reservoir skims at least some of the floating matter into it but
allows the water to flow under it, and the pivotal filter filters out at least
some of the suspended clay. It will be understood by those skilled in the art that
these filtration stages can be used in this or other configurations for separating
other pollutants from other liquids.
Accordingly, the pollution trap stays on-line and routes all the storm-water
runoff through it, instead of bypassing or overflowing during larger-than-typical
storms. In particular, the pollution trap pivotal filter catches clay during typical
storm flows and pivots out of the way without causing the trap to overflow during
higher flows. Additionally, when the pivotal filter is used in combination with
the screen, baffles, and collection reservoir, the pollution trap induces settling
of particulate matter, reduces waterlogging of absorbent miscellaneous debris,
and collects floating hydrocarbons during larger-than-typical storms when more
of these pollutants are carried by the storm water, thereby providing improved
filtration of pollutants from the storm water. Furthermore, the pollution trap
is cost-efficient to build, install, and maintain.
These and other features and advantages of the present invention will become
more apparent upon reading the following description in conjunction with the accompanying
drawing figures.
BRIEF DESCRIPTION OF THE DRAWING FIGURES
FIG. 1 is a side view of a pollution trap according to a first exemplary embodiment
of the present invention, showing a chamber housing a screen, two baffles, a collection
reservoir, and a pivotal filter.
FIG. 2 is a cross-sectional view of the pollution trap of FIG. 1 taken at line 2-2.
FIG. 3 is an exploded perspective view of the screen of the pollution trap of
FIG. 1, showing the major components of the screen.
FIG. 4 is a side view of the screen of FIG. 3.
FIG. 5A is a side view of a first alternative embodiment of the screen of the
present invention, showing a screen that has a top.
FIG. 5B is a side view of a second alternative embodiment of the screen, showing
a screen with a bottom that is angled.
FIG. 5C is a side view of a second alternative embodiment of the screen, showing
a screen with a bottom that is curved.
FIG. 6 is a cross-sectional view of the second baffle of the pollution trap
of FIG. 1 taken at line 6-6, showing the major components of the
second baffle.
FIG. 7A is a side view of a first alternative embodiment of the baffles of the
present invention, showing a first baffle mounted to the screen and having a bottom
gap, and a second baffle having a top gap.
FIG. 7B is a side view of a second alternative embodiment of the baffles, showing
a first baffle having both top and bottom gaps and a second baffle having an intermediate gap.
FIG. 7C is a plan view of a third alternative embodiment of the baffle, showing
a single baffle having side gaps.
FIG. 7D is a plan view of a fourth alternative embodiment of the baffles, showing
a first baffle having side gaps, a second baffle having an intermediate gap, and
a third baffle having side gaps.
FIG. 7E is a plan view of a fifth alternative embodiment of the baffles, showing
two L-shaped and opposing baffles.
FIG. 7F is a perspective view of a sixth alternative embodiment of the baffles,
showing a first baffle having top corner gaps and a second baffle having a bottom
intermediate gap.
FIG. 8 is a cross-sectional view of the collection reservoir of the pollution
trap of FIG. 1 taken at line 8-8, showing the major components of
the collection reservoir.
FIG. 9 is a detail view of a portion of the collection reservoir of FIG. 8,
showing a weir adjustably mounted to a front wall of the reservoir.
FIG. 10A is a plan view of a first alternative embodiment of the collection
reservoir of the present invention, showing a collection reservoir with a curved
front wall.
FIG. 10B is a side view of a second alternative embodiment of the collection
reservoir, showing a collection reservoir forming a tapered gap.
FIG. 10C is a side view of a third alternative embodiment of the collection
reservoir, showing a float for automatically adjusting the weir.
FIG. 10D is a side view of a fourth alternative embodiment of the collection
reservoir, showing a collection reservoir that extends to the chamber floor.
FIG. 10E is a plan view of a fifth alternative embodiment of the collection
reservoir, showing a collection reservoir with the outlet positioned under it.
FIG. 11 is an exploded perspective view of the pivotal filter of the pollution
trap of FIG. 1, showing a frame holding a fibrous filtration member.
FIG. 12 is an exploded perspective view of a first alternative embodiment of
the pivotal filter of the present invention, showing the frame provided by a channel
that holds the fibrous filtration member.
FIG. 13 is a schematic diagram of the pollution trap of FIG. 1, showing the
pollution trap at-rest when no water is flowing into the chamber.
FIG. 14 is a schematic diagram of the pollution trap of FIG. 1, showing the
operation of the pollution trap during a typical storm event with a typical water
flow rate into the chamber.
FIG. 15 is a schematic diagram of the pollution trap of FIG. 1, showing the
operation of the pollution trap during a worst storm event when a predetermined
maximum water flow is flowing into the chamber.
FIG. 16 is a flow diagram showing a maintenance process for cleaning the pollution
trap of FIG. 1.
FIG. 17 is a side view of a portable spill clean-up apparatus according to a
second exemplary embodiment of the present invention, showing a vehicle, a portable
pollution trap similar to the one of FIG. 1, and a pollution trap operating system.
FIG. 18 is a schematic view of the pollution trap operating system of FIG. 17.
FIG. 19 is a side view of an alternative embodiment of the portable pollution
trap of the present invention, showing the pollution trap having a chamber housing
a collection reservoir.
FIG. 20 is a flow diagram showing a process for using the portable spill clean-up
apparatus of FIG. 17 to clean up a spill of a floatable pollutant.
DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS
Referring now to the drawing figures, wherein like reference numerals represent
like parts throughout the several views, the pollution trap of the present invention
provides for separating pollutants from storm-water runoff and retaining the pollutants
in the trap or a nearby storage container. The pollution trap is well suited for
filtering pollutants including floatable matter such as motor oil, other hydrocarbons,
and detergents, particulate matter such as sand, dirt, and grit, and miscellaneous
debris such as vegetative matter from trees, shrubberies, etc., paper and plastic
trash, aluminum foil wrappers, foam cups, and so forth. In addition, a person of
ordinary skill in the art could adapt the pollution trap described herein in order
to separate other types of pollution or other types of matter from liquids other
than storm water, if so desired.
The pollution trap of the present invention includes a pivotal filter for separating
clay and other pollutants from the storm-water runoff. The pollution trap may additionally
include a screen, baffles, and/or a collection reservoir. For illustration purposes,
the trap will be described herein including the pivotal filter and these other
filtration stages. It will be understood, however, that the trap can be provided
with only the pivotal filter or with the pivotal filter in combination with these
and/or other filtration stages selected to provide the pollutant separation desired
in a particular application.
FIGS. 1-2 show a first exemplary embodiment of the present invention, referred
to generally as the pollution trap
10. The pollution trap
10 includes
a chamber
12 that houses the screen
100, the baffles
200,
the collection reservoir
300, and the pivotal filter
400. In a typical
commercial embodiment, the screen
100 is positioned adjacent an inlet to
the chamber
12, the baffles
200 are positioned between the screen
and an outlet to the chamber, the collection reservoir
300 is positioned
between the baffles and the outlet, and the pivotal filter
400 is positioned
between the collection reservoir and the outlet. It will be understood that, while
in the exemplary embodiment the pollution trap
10 includes all four of these
filtration stages
100-
400, in alternative embodiments such as those
described below the present invention can be provided with only one of these stages
or with various configurations and combinations of them in various other positions.
In the first exemplary embodiment, the chamber
12 is rectangular and is
formed by end walls
14 and
16, sidewalls
18 and
20,
a floor
22, and a lid
24. The chamber end walls
14 and
16,
side walls
18 and
20, and floor
22 are made of reinforced
concrete, and may be sealed with a coating such as a bituminous material for making
the chamber watertight. The concrete chamber
12 is pre-cast and hauled to
the installation location, though it could be cast on-site if so desired.
For convenience in constructing, hauling, and installing the chamber
12,
it can be formed into two or more sections. For example, a base section
13
can be made with a standard size, and one or more riser sections
15 can
be made in a variety of heights or custom-made per job. In this way, the height
of the riser section
15 is selected so that the lid
24 will be at
about ground level given the depth at which the base section
13 will be
installed. In installations where the top of the base section
13 is at grade,
no riser section
15 would be used. Alternatively, the chamber
12
can be integrally made as a single piece.
The lid
24 covers the open top of the chamber
12, and can be at
least partially removable in order to provide ready access to the inside of the
chamber for maintenance of the trap
10. For example, the lid
24 can
be made of three steel panels, with a fixed middle panel and two end panels pivotally
coupled to the middle one. Alternatively, the lid
24 can be made of concrete
and include a steel manhole ring and cover. In addition, when the lid
24
and the chamber walls
14,
16,
18, and
20 are installed
in areas where they are driven over, they can be sized and/or reinforced to withstand
the traffic loadings they are subjected to.
Of course, the lid
24 and the chamber walls
14,
16,
18,
and
20 can be made in other regular or irregular shapes and configurations,
and can be made of other strong and durable materials, as may be desirable in a
given application. For example, the chamber walls
14,
16,
18,
and
20 could be made of fiberglass, hard plastic, or a composite, and/or
the chamber
12 could be generally L-shaped or triangular with two inlets
and one outlet.
Additionally, the chamber
12 has an inlet opening
26
in one of the end walls
14 through which the water flows into the chamber
and an outlet opening
28 in the other end wall
16 through which the
water flows out. The inlet
26 and the outlet
28 are sized and shaped
to receive or otherwise connect to the pipes
27 of conventional storm sewer
systems. If desired, the inlet
26 and the outlet
28 can include stub-outs
for connecting to the conventional storm sewer pipes
27. The stub-outs can
be provided by, for example, sections of metal or PVC pipe.
The inlet
26 and the outlet
28 are sized to handle a predetermined
maximum flow rate based on the tributary area to be drained and the worst storm
event the trap is intended to handle. For example, the maximum flow rate can be
based on the 25-year storm (the worst storm over a 25-year period for the geographic
location, on average), or for an otherwise-defined catastrophic or larger-than-normal
storm. Of course, during most storms, the inlet
26 and the outlet
28
do not see anywhere close to the water flow intensity of the 25-year storm.
Furthermore, a worst storm (maximum) water level
30 is defined
in the chamber
12 when the water is flowing through the chamber at the maximum
water flow rate, and an at-rest water level
32 when no water is flowing
into it. More particularly, the at-rest water level
32 at its highest is
at the bottom of the outlet
28, because the water cannot flow out of the
chamber
12 when it is at this level. And, of course, the worst storm water
level
30 is higher than the at-rest water level
32. Moreover, because
the worst storm water level
30 is defined by the water level during the
worst storm event, it is determined at least in part by the size of the inlet
26,
the outlet
28, and the chamber
12.
In a typical commercial embodiment, the chamber is 11 feet high (6 foot base
plus
5 foot riser), 5 feet wide, and 10 feet long, with 6 inch thick walls. And the
inlet and the outlet are 15 inch openings positioned about 4 feet above the chamber
floor, with the bottom of the outlet positioned about 0.1 foot lower than the bottom
of the inlet. With these dimensions, the trap can successfully handle (without
overflowing or bypassing) about 9.2 cubic feet per second (cfs), which is greater
than the volume flow rate for the 25-year storm for a typical installation with
a 1 acre tributary area. At this flow rate, the vertical exit velocity is about
one foot per second, which is slow enough to retain particles larger than 20 microns
in the pollution trap. For comparison, many conventional traps bypass at only 1
to 2 cfs, which often occurs during a typical "first flush" storm event.
It will be understood that many variations of these dimensions may be used, depending
on the size, grade, ground covering, and use of the tributary area to be drained,
the typical and maximum rainfall during the design worst storm event, the local
restrictions on flow rates, any physical space limitations for the pollution trap,
and so forth. For example, in some other embodiments, the inlet and the outlet
are provided by 18 or 24 inch openings for handling greater maximum flow rates,
and the chamber riser section is only 2 or 3 feet high where the base section is
installed closer to grade.
To put it more succinctly, the inlet
26 and the outlet
28 are designed
to handle the predetermined maximum flow rate of storm water for a maximum design
storm event, for example, the 25-year storm. This typically means matching the
inlet
26 and the outlet
28 to the size of the storm sewer pipe, whether
preexisting or new. If the storm sewer pipe is under pressure, then the inlet
26
may be sized larger to slow down the water flow as it enters the chamber
12.
And the outlet
28 may be the same size as the inlet
26 or larger.
In any event, the chamber
12 is designed so that all of the water that can
be delivered into it from the inlet
26 can pass through it and out of the
outlet
28. Finally, the filter stages
100,
200,
300,
and
400 are configured so that they permit passing through the chamber
12
of the maximum water flow during the maximum design storm event, so the reservoir
300 does not overflow and the trap
10 does not need to be bypassed.
Referring now to FIGS. 1-4, the screen
100 catches most to all of
the floating miscellaneous debris such as vegetative matter, plastic, and paper
that might otherwise collect in the chamber
12 and/or be washed over into
the reservoir
300. To filter the storm-water as it enters the chamber
12,
the screen
100 is positioned adjacent the inlet
26 and flush against
the end wall
14. Also, the screen
100 is vertically positioned at
or just above the at-rest water level
32, and thus at or just below the
bottom of the inlet
26.
In this position, during a storm the screen
100 collects and retains the
debris as it enters the chamber
12, allows the water to pass through it,
and suspends the retained debris above the at-rest water level
32. After
the storm, the water level drops down to the at-rest water level
32, so
the debris is suspended in the air and can now dry out. In this way, the suspended
debris does not become waterlogged, break down into smaller pieces, and wash through
the screen
100. And the nitrogen, phosphorus, fertilizer, pesticides, oils,
inks, surface adherents, and other pollutants contained in or carried by vegetative
matter and paper also remain trapped by the screen
100. The result is a
significant increase in the amount of debris and other pollutants retained over
time by the screen
100 relative to conventional traps.
In addition, as the debris builds up on the screen
100 over time, it tends
to mat together, particularly the leaves and other vegetative matter. This matted
debris then creates a natural filter on the screen
100 that provides additional
levels of filtration. The way it works is the matted debris begins to stop larger
gravel and sand particles. These particles fill the spaces in the matted debris
and, in a "beaver dam" effect, cause smaller particles to be trapped. The result
is that very fine particles, pollen, mud, sand, etc., are collected in the built-up
layers of the matted debris on the screen
100. And these particles are often
retained there because the water flow through the trap
10 is normally not
very great. That is, typical storms often produce a water flow only few inches
deep through the inlet
26, very often amounting to barely a trickle. So
the particles trapped by the matted debris are often retained there and not washed
away through the screen
100.
Furthermore, the screen
100 preferably extends all the way across
the chamber
12. That is, the ends of the screen are adjacent the sidewalls
18 and
20 of the chamber. With the screen
100 being long relative
to the diameter of the inlet
26, as the storm-water enters the chamber
12
it is free to disperse laterally. The dispersing and screening of the water by
the screen
100 tends to break up any organized eddies and vortices. This
encourages settling of the particulate matter pollution within the chamber
12.
Turning now to the construction of the screen
100, in a typical commercial
embodiment it is basket-shaped but with an open side
101 that is adjacent
the inlet
26 for allowing the debris into the chamber
12. The generally
basket-shaped screen
100 is provided by a rigid frame
102 that holds
a liner
104. The frame
102 is made of aluminum grating and has a
bottom
106, a side
108, and ends
110. The liner
104
is made of aluminum ¼ inch mesh and has a bottom
112, a side
114,
and ends
116. Accordingly, the frame bottom
106 and the liner bottom
112 are positioned at or above the at-rest water level
32.
For ease of removing the trapped debris and particles from the screen
100,
it is provided with handles
118 and removably mounted in the chamber
12.
For example, the screen
100 can be supported on mounting structures
120
such as mounting brackets, pins, bolts, or other mounting structures. The mounting
structures
120 support the screen
100 and restrain it from lateral
or downward movement, but permit removal of the screen by lifting it from the brackets.
Thus, the screen
100 does not have to be decoupled from the mounting structures
120 for its removal from the chamber
12.
Alternatively, the screen
100 can be made in other shapes,
sizes, and materials, and be positioned elsewhere in the chamber
12. For
example, the liner can be made of 1/16 or ⅛ inch mesh, perforated panels,
lattice structures, or other structures with filtering spaces, made of stainless
steel, plastic, a composite, or another material, and constructed without ends
and/or extending only part of the way across the chamber. Or the liner can be eliminated
and the screen provided with the smallest desired filtering spaces in the frame
instead of in the liner. And the frame can be provided a structure other than grating
but still having openings in it, made of stainless steel or another suitable material,
and constructed without the ends and/or extending only part of the way across the chamber.
FIGS. 5A-5C depict several alternative embodiments of the screen. In a first
alternative embodiment shown in FIG. 5A, the screen
100a has a bottom
106a and a side
108a, and additionally includes a top
122a. In a second alternative embodiment shown in FIG. 5B, the screen
100b has a bottom
106b that is angled. And in a third
alternative embodiment shown in FIG. 5C, the screen
100c has a bottom
106c that is curved. These embodiments can be provided with or without
ends, which are not shown in the respective drawings. It will be understood that
the screen can be provided in alternatively-configured embodiments not described
herein but that provide the same above-described advantages.
Referring now to FIGS. 1,
2 and
6, each one of the baffles
200 is configured and positioned in the chamber
12 to form at least
one gap
202 through which the water can flow to get around the baffle. So
instead of the water naturally flowing straight through the chamber
12,
it is diverted around the baffles
200 through the gaps
202. The diverted
flow of the water around the baffles
200 results in a longer flow route
through the chamber
12. Also, the water flows past the baffles
200
no faster than when it entered the chamber
12, as described in detail below.
Because the water travels the longer route around the baffles
202 but is
not throttled, the water resides in the chamber
12 for a longer time. This
increased water residence time encourages the particulate matter carried by the
water to settle to the floor
22 of the chamber
12.
The position, configuration, and number of the baffles
200 and the gaps
202 formed by them are selected depending on the water residence time desired
for a particular installation. For example, in the presently described embodiment,
two baffles
200′ and
200" are provided. The first baffle
200′
has a bottom
204′ positioned at the chamber floor
22 and a
top
206′ positioned below the worst storm water level
30.
In this position, a top gap
202′ is formed between the baffle top
204′ and the worst storm water level
30 to encourage the water
to flow over the baffle
200′. The baffle top
204′ may
be positioned at the at-rest water level
32 so that the water begins flowing
over it at the outset of storm water flowing into the chamber
12. Or the
baffle top
204′ may be positioned higher, closer to the worst storm
water level
30, so that the water only begins flowing over it sometime after
the storm has begun or only during larger storms.
The second baffle
200", which is shown in FIG. 6, has a bottom
204"
that is positioned above the chamber floor
22 and a top
206" that
is positioned at or above the worst storm water level
30. In this position,
a bottom gap
202" is formed between the baffle bottom
204" and the
chamber floor
22 to encourage the water to flow under the baffle
200".
But the water cannot flow over the baffle top
206", at least not during
typical storms or larger-than-typical storms up to the worst storm event.
In addition, the first baffle
200′ has sides
208′
and the second baffle
200" has sides
208", with the sides
208′
and
208" preferably extending substantially all the way across the chamber
12. That is, the baffle sides
208′ and
208" are positioned
at the sidewalls
18 and
20 of the chamber
12. In this position,
the water can not flow around the baffle sides
208′ and
208",
but instead is forced to flow up over the first baffle top
206′ through
the gap
202′ and then down under the second baffle bottom
204"
through the gap
202". Thus up-and-down water flow produces the longer flow
route and increased residence time of the water in the chamber
12.
As used herein, the second baffle top being positioned "at" the worst storm water
level is intended to include being positioned adjacent to but just below the worst
storm water level. And the first baffle bottom being positioned "at" the chamber
floor is intended to include being positioned adjacent to but just above or recessed
down into the chamber floor. Also, the sides of the baffles being positioned "at"
the chamber sidewalls is intended to include being positioned adjacent to but spaced
slightly from or recessed into the chamber sidewalls.
Furthermore, one or both of the baffles
200 may be provided with
apertures
210 in them. The apertures
210 permit some of the water
and the pollutants carried by it to pass through the baffles
200. When some
of the water flows through the apertures
210 while the rest of the water
is impeded by the baffles
200, the water flow tends to disperse and break
up any organized eddies and vortices. As with the screen
100, this encourages
settling of the particulate matter in the chamber
12.
Also, some of the oil and/or other floating matter may be forced below the
water surface upon entering the chamber
12, and the water flow dispersal
provides some time for it to rise back to the water surface. In addition, the apertures
210 permit the floating matter to pass through them. Accordingly, the first
baffle
200′ has the apertures
210 along all or much of its
height, with lower apertures for permitting the temporarily submerged floating
matter through and upper apertures for permitting the remaining floating matter
through. Similarly, the second baffle
200" has apertures
210 in its
upper portion
212 for permitting the floating matter through. But to encourage
the water to flow down through the lower gap
202", and because by now most
to all of the floating matter has returned to the water surface, the lower portion
212 of the second baffle
200" need not have any apertures
210.
As mentioned above, the water flows past the baffles
200 no faster than
when it entered the chamber
12. This is because for each of the baffles
200′ and
200", the combined cross-sectional area of the gap
around it and the apertures in it is larger than or equal to the cross-sectional
area of the inlet
26. For example, in a typical commercial embodiment, the
cumulative area of the baffle gap and apertures is three to five times greater
than the inlet area. In this way, the water flows freely into the chamber
12
at the inlet
26 and is not throttled as it passes around the baffles
200.
Instead, the water slows down in the chamber
12, or at least is allowed
to continue no faster than its inlet flow rate, to encourage the particulate matter
to settle.
Turning now to the construction of the baffles
200, in a typical commercial
embodiment they are provided by panels that are generally flat and made of aluminum,
stainless steel or another metal. The width of each of the gaps in the panels is
at least about 3 inches. The diameter of the apertures is 1 inch, arranged in an
array on 1¼ centers. The lower portion of the panel with no apertures is about
15" high. The panels are mounted in the chamber by conventional mounting structures
such as mounting brackets, pins, bolts, or other mounting structures. In this configuration,
the water flow rate through the trap is kept under about 1.0 feet per second even
during the maximum storm event, which is slow enough to enable the trap to collection
about 2 inches of particulate matter in typical installations.
Alternatively, the baffles may be provided by panels that are curved,
zigzagged, corrugated, L-shaped, have a combination of these profiles or shapes,
or are otherwise configured. Also, the baffles may be made of fiberglass, plastic,
a composite, or another material. The size, number, and position of the gaps and
the apertures may vary and be selected to provide the water flow dispersion, route,
and rate desired for a particular installation. Accordingly, sometimes only one
baffle is provided, and other times more than two are used. In some installations,
each or particular ones of the baffles have gaps formed at both the top and the
bottom, at one or both sides, all the way around them, and/or at intervals in a
serrated or scalloped configuration, or otherwise. In addition, the apertures may
be arranged in an array with a regular pattern or an irregular arrangement. And
some of the apertures may be larger than other ones. Furthermore, the baffles may
be configured and positioned primarily for dispersing the water, primarily for
lengthening the flow route through the chamber, or both.
FIGS. 7A-7F depict several alternative embodiments of the baffles. FIGS. 7A
and 7B are elevation views showing alternative top and/or bottom baffle gap configurations,
while FIGS. 7C-7D are plan views showing side gap configurations.
In a first alternative embodiment of the baffles shown in FIG. 7A, the first
baffle
200a′ is coupled to the screen
100 so that it does
not need to be mounted to the chamber
12. Also, the first baffle
200a′
has bottom gap
202a′ so that the water flows under it, and
the second baffle
200a" has top gap
202a" so that the
water then flows back up over it.
In a second alternative embodiment shown in FIG. 7B, the first baffle
200b′
has both bottom and top gaps
202b′ so that the water flows
both under and over it. And the second baffle
202b" has an intermediate
gap
202b" between its top and bottom, for example, along its horizontal
centerline, through which the water flows. In this configuration, the gap
202b"
may be provided by a slot in the second baffle or two separate panels may be provided
to form the second baffle.
In a third alternative embodiment shown in FIG. 7C, only one baffle
200c
is provided, and it has side gaps
202c formed vertically at its
sides
208c. In this configuration, the water is diverted around the
sides
208c of the baffle
200c.
In a fourth alternative embodiment shown in FIG. 7D, the first baffle
200d′
and a third baffle
200d′" have side gaps
202d′
and
202d′", and the second baffle
202d" has
an intermediate gap
202d". In this configuration, the water flows
around the sides of the first baffle
200d′ through the first
gaps
202d′, inward toward the center of the chamber
12,
through the intermediate gap
202d" between the sides of the second
baffle
200d", back outward toward the sides of the chamber
12,
and around the sides of the third baffle
200d′" through the
third gap
202d′".
In a fifth alternative embodiment shown in FIG. 7E, the first baffle
200e′
and the second baffle
202e" are generally L-shaped and opposing each
other to form side gaps
202e′ and
202e" and
an intermediate channel
216e. In this configuration, the water flows
around one side of the first baffle
200e′ through the first
gap
202e′, reverses direction and flows back toward the first
baffle through the intermediate channel
216e, then reverses direction
again and flows through the second gap
202e".
In a sixth alternative embodiment shown in FIG. 7F, the first baffle
200f′
has top corner gaps
202f′ and the second baffle
202f"
has a bottom intermediate gap
202f". In this configuration, the water
flows upward and laterally to the sides of the chamber
12, over the first
baffle
200f′ through the top corner gaps
202f′,
back downward and toward the center of the chamber
12, and under the second
baffle
200f" through the bottom intermediate gap
202f".
It will be understood by those skilled in the art that other configurations, positions,
numbers, and sizes of the baffles can be provided to accomplish the above-stated
functions of dispersing the water flow and increasing the water residence time.
Referring now to FIGS. 1,
2,
8, and
9, the collection
reservoir
300 has a front wall
302 and a skimming edge
304
positioned at the worst storm water level
30, or at a selected storm water
level for a lesser storm event to allow oil collection at that selected level.
The skimming edge
304 skims into the reservoir
300 at least some
of the oil and/or other pollution floating on the surface of the water. And at
least the portion of the front wall
302 below the at-rest water level
32
extends all the way across the chamber
12, so the water cannot flow around
the sides of the reservoir
300. So instead of the floating matter flowing
through and out of the chamber
12 on the water surface, it is skimmed into
the reservoir
300 and thereby segregated from the water.
In addition, the collection reservoir
300 divides the chamber
12
into a front sub-chamber
46 and a rear sub-chamber
48. The sub-chambers
46 and
48 provide pools with sufficient depths to encourage settling
of the particulate matter, and are in fluid communication through a gap
47.
The rear sub-chamber
48 has a cross-sectional area larger than that of the
inlet so that the water flows slower through it. In this way, the particulate matter
flows under the collection reservoir
300 through the reservoir gap
47,
then back up through the rear sub-chamber
48 and out of the chamber
12
through the outlet
28. Because of this longer flow route, because the water
is flowing slower, and because of the gravitational forces on the particulate matter
as the water decelerates up through the rear sub-chamber
48 to get out of
the chamber
12, more of the particulate matter settles to the chamber floor
22 instead of flowing out of the trap
10.
The reservoir gap
47 is defined by a bottom wall
306 of the collection
reservoir
300, the floor
22 of the chamber
12, and the chamber
sidewalls
18 and
20, to allow the water to flow under the reservoir.
In order to keep the water from flowing any faster than when it entered the chamber
12, the cross-sectional area of the reservoir gap
47 is the same
as or larger than the cross-sectional area of the inlet
26. Preferably,
the water is slowed by sizing the reservoir gap
47 larger than the area
of the inlet
26, for example, by a factor of about three to five. By keeping
the flow rate relatively slow, more of the particulate matter will settle in the
chamber
12.
In the first exemplary embodiment, the collection reservoir
300 is formed
by the front wall
302, a rear wall
308, sidewalls
310, and
the bottom wall
306 extending between them. For standardized traps, the
skimming edge
304 can be defined on the front wall
302 or another
component of the reservoir
300. To provide for adjustability for site-specific
conditions, however, the skimming edge
304 can be defined by the top of
a weir member
312 that is adjustably mounted to the front wall
302
or another part of the reservoir
300.
The weir
312 is preferably adjustably mounted to the front wall
302
by bolt-and-slot assemblies
314. Alternatively, another suitable mounting
may be used instead. For example, the front wall and the weir may be provided with
a series of holes that can be selectively aligned for receiving a bolt (with unused
holes plugged), or the weir can slide on a trac
