STORMWATER FILTRATION TANK

RESERVOIR DE FILTRATION D'EAUX DE RUISSELLEMENT

English Abstract

A single tank for primary or inline treatment of stormwater runoff. The tank
consists of multiple concentric or eccentric compartments that are cylindrical
or
rectangular in shape. The inner compartment receives the untreated water
through a perforated catch-basin cover or an inline inlet pipe. The partially
treated water from this compartment, and any other compartment thereafter,
overflows into a receiving compartment that completely surrounds the source
compartment. The combination of gravity, density gradients, pipe siphon
arrangement and laminar flow conditions created by the shape of each of the
treatment compartment forces maximum separation of oils and sediments
without the need for moving parts or chemicals. A mixture of non-compacted,
oleophilic and oleophopic media is installed in one or some of the final
compartment to coalesce residual free and partially emulsified oil droplets
and
separate them from water. The media will also help knock out residual
suspended solids. Other types of media like Mica, sand, activated carbon or
bacterial growth enhancing media can be used in conjunction of or instead of
the
oil-removal media to remove other pollutants.

Claims

Claims
1. A multi-compartment stormwater filtration tank consisting of concentric or
eccentric compartments so that inner compartment is surrounding by the
next outer compartment.
2. A multi-compartment stormwater filtration tank as claimed in claim 1 in
which the water enters the most inner compartment through a catch-basin
cover or through an inlet pipe. The water then has to flow through a funnel
that is fitted near the top of this compartment. The funnel traps oils and
other floating matter below the funnel's surface. It also reduces
turbulence, which enhances sedimentation of solids in this compartment.
3. A multi-compartment stormwater filtration tank as claimed in claim 2 that
is
fitted with a bypass pipe outlet located above the funnel in the first and
most inner compartment. During high flow conditions the space between
the funnel and the bypass outlet fills up with water until water starts to
flow
through the bypass to the tank's outlet, without disturbing the oils or
sediments that were trapped below the funnel.
4. A multi-compartment stormwater filtration tank as claimed in claim 3 in
which water is siphoned from inside one compartment then discharged
near the bottom of the next surrounding compartment. This allows only the
least contaminated water from one compartment to enter the next
compartment and provides enough time for settleable solids to settle to
the bottom and free oils to float to the top of the receiving compartment.

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5. A multi-compartment stormwater filtration tank as claimed in claim 4 in
which the siphon point for the outlet of any compartment is located at an
elevation above the siphon point of the outlet of the previous
compartment. During flow conditions, free oil will float and get trapped
above the siphon point of each compartment. Under no flow conditions,
water inside the last compartment will drain out until the water level
reaches the siphon point for the outlet of this compartment. This will also
be the water level inside all other compartments. Since the siphon points
inside these compartments are all below the siphon point for the last
compartment, any oil trapped in these compartments above their siphon
points will not be able to escape to the next compartment.
6. A multi-compartment stormwater filtration tank as claimed in claim 5 in
which the one-compartment-inside-the-other configuration promotes
increased separation of pollutants. Water leaving one compartment has to
travel to near the bottom of the next surrounding compartment then travel
upward and around the circumference of the receiving compartment to the
compartment's outlet, which is located at 180 degrees from the
compartment's inlet. This arrangement creates laminar flow patterns,
prevents channeling and maximizes the retention time of each droplet of
water, droplet of oil and particle of sediment. Therefore, increasing the
amount of sediments that drops to the bottom or oils that float to the top of
each compartment.
7. A multi-compartment stormwater filtration tank as claimed in claim 6 that
incorporates the use of a mixture of oleophilic and oleophobic media to
coalesce residual oil and separate it from water just before said water is
discharged out of the treatment unit. The oleophilic media attracts residual
colloidal and partially emulsified oil droplets, while the oleophobic medial
repels these droplets towards the oleophilic media. Oil droplets that collect
on the surface of the oleophilic media will then coalesce and gain enough
buoyancy to float to the surface.
8. A multi-compartment stormwater filtration tank as claimed in claim 7 in
which water entering a media-filled compartment is directed into an open
space below a none-compacted body of media, then flows upward through
the body of media. This arrangement helps knock out any remaining
residual solids back to the bottom of the compartment, without clogging up
the media.
9. A multi-compartment stormwater filtration tank as claimed in claim 8 in
which additional compartments can be added to treat higher stormwater
runoff flow rates or higher loads of pollutants.

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10.A multi-compartment stormwater filtration tank as claimed in claim 9 in
which additional media can be added to treat different types of pollutants.
11.A multi-compartment stormwater filtration tank as claimed in claim 10
which incorporates an overflow pipe arrangement that directs the overflow
from the inlet compartment directly to the unit's outlet without allowing the
overflow water to enter the other compartments. This pipe arrangement
reduces the chances of contaminating final compartments with untreated
water from previous compartments.
12.A multi-compartment stormwater filtration tank as claimed in claim 11
which is manufactured in whole or in part from suitable concrete, metal or
plastic material or a mixture of suitable materials.
13. A multi-compartment stormwater filtration tank as claimed in claim 12 that
has one or more catch-basin access covers. When the tank is used as an
inline filtration tank, then all covers shall be solid. When the tank is used
a
primary filtration tank, then only the cover covering the most inner
compartment shall be perforated or slotted to allow surface water to enter
the tank into the most inner compartment.
14.A multi-compartment stormwater filtration tank as claimed in claim 13 in
which the entire pipe assembly can be cleaned from ground level by
pressurizing water from a clean water source or by vacuuming water
through the pipe assembly through pipe cleaning ports that are located
just below the catch-basin covers.
15. A multi-compartment stormwater filtration tank as claimed in claim 14 in
which the entire pipe assemblies are supported on removable plates that
are inserted inside slotted guides in the sides of the compartment walls.
The entire plate and pipe assembly can be removed so that the pipe
assembly can be inspected, cleaned, repaired or upgraded. The plate can
then be inserted back through the slotted guides.
16. A multi-compartment stormwater filtration tank as claimed in claim 15 in
which the middle compartment is fitted with a riser pipe for vacuuming oil
trapped at the surface of each compartment during scheduled tank clean
up.

Description

CA 02510998 2005-07-11
Description
A single tank that is designed for the removal of floatable, colloidal and
partially
emulsified oil as well as other floatable and perceptible material from
rainwater
(stormwater) runoff. The tank consists of multiple concentric or eccentric
compartments that are cylindrical or rectangular in shape. In a typical
arrangement, stormwater runoff is received in the most inner compartment,
through a slotted catch-basin cover or through an inlet pipe. The water then
has
to flow to the bottom of the compartment through a funnel located above the
compartment's center. Heavy sediment and trash will fall to the bottom while
lighter-than-water objects and most of the free oils will float to the surface
and get
trapped below the funnel. An overflow bypass pipe is located above the funnel
and is directly connected to the unit's outlet. During high flow conditions,
the
water level above the funnel will rise until the water starts to flow through
the
bypass line. This arrangement keeps the oils trapped below the funnel and
prevents the water from scouring the sediments at the bottom of this
compartment. A pipe arrangement siphons partially treated water from this
compartment into the bottom of the next surrounding outer compartment. In this
compartment, water as well as any pollutants are forced to travel up and
around
the compartment's circumference to its outlet which is located at 180 degrees
from the inlet. This forces the water into a laminar flow pattern thus
providing the
conditions for most of the fine sediment to settle at the bottom and most of
the
remaining free oil to float to the top. Water from this compartment is then
directed
the same way into subsequent similar surrounding compartments. The number of
these compartments depends on the flow and/or the load of the pollutants to be
treated. One or more of these compartments can contain a mixture of oieophiiic
and oleophobic media. In a media-filled compartment, the water enters the

CA 02510998 2005-07-11
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compartment through an open space below the media. The water fills up this
space all around the compartment's circumference, then flows upward making
direct contact with the media. The oleophilic media attracts remaining
colloidal
and partially emulsified droplets of oil to its surface while the oleophobic
media
repels other oil droplets towards the oleophilic media. The oil droplets
coalesce
on the surfaces of the oleophilic media then gain enough buoyancy to float to
the
surface. The presence of the media and the upward flow pattern also forces
residual fine sediments to stay at the bottom of this compartment. If the
removal
of other pollutants such as dissolved hydrocarbons or phosphates is desired
then
other types of media such as Mica, sand, activated carbon or bacterial growth
enhancing media can be used. The outlet of a pipe siphon arrangement from one
compartment is always higher than the outlet of the pipe siphon arrangement of
the previous compartment. Therefore, when water flow into and out of the tank
stops, the water level will remain at the level of the tank's final outlet.
This will
prevent the oils trapped above the outlets of all previous siphon arrangement
from being drained out of these compartments and eventually out of the unit.
Treated water from the last outer compartment can be directed to a stormwater
pond, on-site stormwater detention or infiltration arrangements, further on-
site
treatment steps or for direct discharge into a natural water way.

CA 02510998 2005-07-11
LEGEND
1- Inlet pipe (Optional)
2- Inlet funnel
3- Overflow bypass pipe
4- First and most inner compartment
5- Pipe siphon arrangements
6- Second compartment
7- Media-filled compartment
8- Media- as described in text
9- Last and most outer compartment
10- Outlet Pipe
11- Riser to remove oil during cleanup
12- Catch-basin Covers
13- Side view of removable pipe assembly

Representative Drawing