Liquid purification or separation – Flow – fluid pressure or material level – responsive – Fluid pressure responsive by-pass
Reexamination Certificate
2002-08-12
2004-09-28
Upton, Christopher (Department: 1724)
Liquid purification or separation
Flow, fluid pressure or material level, responsive
Fluid pressure responsive by-pass
C210S156000, C210S300000, C210S305000, C210S521000, C210S532100, C210S540000
Reexamination Certificate
active
06797161
ABSTRACT:
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.
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 better induces settling of particulate matter and reduces waterlogging of absorbent miscellaneous debris, to provide improved filtration of pollutants from the storm water. 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 pollution trap includes a chamber, a screen, one or more baffles, a collection reservoir with a skimming edge, and a pivotal filter. The chamber has an inlet, an outlet, 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 screen, the baffles, the collection reservoir, and the pivotal filter are each positioned in the chamber between the inlet and the outlet.
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. The collection reservoir is configured to skim at least some of the floating matter or other pollutants into it. And 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 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.
For example, two baffles can be provided with the first baffle having a bottom gap to encourage the water to flow over it and the second baffle having a top gap to encourage the water to flow under it. In this configuration, the water flows under the first baffle through the bottom gap and then back up and over the second baffle through the top gap. Of course, the baffles can be provided in other configurations such as with side gaps, intermediate gaps, corner gaps, or a combination of these.
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 ski
Moll John Sebastian
Use Clark Joseph
Gardner & Groff, P.C.
Upton Christopher
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