CA2510998A1

CA2510998A1 - Stormwater filtration tank

Info

Publication number: CA2510998A1
Application number: CA002510998A
Authority: CA
Inventors: Hisham Younis
Original assignee: Individual
Current assignee: Individual
Priority date: 2005-07-11
Filing date: 2005-07-11
Publication date: 2007-01-11

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.

Description

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 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.

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

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.

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.

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.