U.S. Pat. Nos. 5,746,911 and 6,264,835, both titled “Apparatus for separating a heavy fluid from a light fluid” teach physical separators that accomplish a great deal and are an important factor in environmental protection. However, they do not remove dissolved contaminants: nor do they remove sediment particles in the fine silt and clay size range.
Filtration is a proven method of removing dissolved and very fine impurities from a fluid. The most commonly used filter in the stormwater industry is a depth filter. A depth filter uses a media (sand, for example) that the fluid must pass through. The removal is achieved by a combination of two mechanisms: transport and attachment. In a sand filter, the individual grains obstruct the flow of the water, forcing the fluid to take a more tortuous path through the filter. When this happens, the fluid comes into contact with far more of the media than it would if it were to flow straight through the filter. The fluid, along with the impurities to be removed, is in contact with the individual grains of sand or other filter media. Bringing the contaminants into contact with the filter media is the first stage—the contaminants are transported into contact with the filter media.
In order to remove the pollutants from the fluid, the media must have some way of capturing and retaining the contaminant. This can be accomplished in a number of ways, first chemical bonding on reactive media to simple sedimentation in the interstices between the media components. When designed carefully, media filtration is capable of removing large pollutant loads from influent fluid streams.
The selection of filter media can depend on many factors, including the type of contaminants targeted for removal, the desired flow rates through the filter, the cost and weight of the media, etc. While filtration is a proven technology in fields like wastewater and drinking water treatment and industrial processes, it is relatively new in the field of stormwater treatment.
One of the challenges of stormwater management is dealing with the highly variable runoff flow rates that result from storms. In stormwater applications, treatment devices are subjected to widely varying flow rates, from very slow trickles to the runoff resulting from torrential downpours. To accommodate these variations, many stormwater treatment devices are designed with an internal by-pass. The internal by-pass allows flows in excess of the intended treatment capacity to pass through the unit untreated, while continuing to treat flows within the intended range. This is a viable technology because of the “first flush” effect in stormwater runoff. During the beginning of a storm event, a “flush” of contaminants is carried off of a site with the first bit of runoff. This flush includes the pollutants that have collected on that site since the last storm, and comprises the majority of the pollution load from each storm event. If the first flush is treated adequately, a majority of the potential contaminants will be removed during that treatment, and the subsequent by-pass flows during extreme storms will not contain the same heavy pollutant loads.
Filters that clean fluids, namely gasses and liquids are well known.
Filters for cleaning runoff water are well known but are not only expensive to manufacture but require expensive maintenance.
Filters made by rolling a strip of fabric into a spiral coil having several laps are well known, see U.S. Pat. No. 5,160,039 to Colburn and U.S. Pat. No. 4,861,465 to Augustyniak.
U.S. Pat. No. 6,099,729 to Cella teaches a filter having a hollow cylinder with a single lap of a pleated filtering element passing around the cylinder. The pleated element has several layers of flexible material.
One object of the invention is to provide a filter that will clean both liquids and gasses.
Another object of the invention is to reduce the cost of the filter and its maintenance.
Still another object of the invention is to provide a simple, yet very effective, filter for runoff water that has a low initial cost as well as low maintenance costs.
The invention not only provides a new filter but also a new method of making the filter.
Basically, the invention comprises providing two or more strips of flexible material (including a filtering media), stacking the strips and wrapping the contiguous strips around a center line to provide a filtering element wherein at least part of the wrapped strips overlaps the first lap. In its broadest form the amount of overlap may be small, for example 10°, however two laps (720°), three laps (1080°), or preferably about ten to fifteen laps may be employed.
The fluid (liquid and/or gasses) to be filtered is preferably fed to the filter in a direction parallel to said center line although it is within the scope of the broader aspects of the invention to pass the fluid through the roll in any suitable way and/or direction.
In the preferred form of the invention there are three strips which are stacked and wrapped into a roll. When the strips have been wrapped and the fluid is fed to them it enters the first of the three strips. The second of the three strips is a filtering media and the third strip is a drain for discharging the fluid from the filter. The first strip not only receives the incoming fluid but redirects the fluid to pass the fluid through said filtering media to said drain.
To achieve the aforesaid redirecting function the first strip is open to receive fluid at its input end but closed to such flow at its other end. As a result, the water is redirected from a vertical incoming flow to a flow that has a horizontal component.
The drain is closed to the fluid at the input side of the filter but open at the output side of the filter.
The foregoing wrapped filter may be fed by a reservoir the bottom of which is the input side of the filter. The reservoir may have a by-pass outlet to discharge the water when the incoming water has a very large rate of flow.
While, the invention is shown in the context of a filter for runoff water, the broader aspects of the invention teach how to make and use the filter in any context in which filters may be used.
The complete invention comprises a filter cartridge that is placed in a housing. Contaminated fluid enters the housing and pools on the top of the filter cartridge. The fluid may be contaminated with solid particles, undesirable gases, dissolved chemicals, or other pollutants. From the top of the filter cartridge, the contaminated fluid enters the cartridge by flowing downward, flows horizontally through the filter media, and then flows downward out of the cartridge itself. The filter housing contains the inlet and outlet means that convey the contaminated fluid to and the treated fluid away from the invention.
The method of constructing the invention is also a part of this application. The filter cartridge is constructed by rolling a layered filter around a center line.
The completed filter cartridge is housed in another structure, as shown in
In a typical filter for filtering runoff water: (a) the strips 7 and 9 are made of polypropylene cloth have a thickness of 0.3 inches and a width of 30 inches; and (b) the filter strip 8 is made of high grade geotextile fabric, has a thickness of 0.3 inches and a width of 30 inches.
Each input cloth 9 has one side edge that will be at the bottom end of the filter of
For some applications the filter media 8 may preferably be sand or some other layer of small particles, in which case permeable layers 11 may be used. The permeable layers 11 are optional and are preferably used when it is necessary to do so in order to hold the filter media in place. They may be made of porous cloth.
Contaminated fluid enters the filter through inlet means 13. (
If the flow into the invention through inlet means 13 exceeds the flow capacity of the filter media, the fluid is backed up in contaminated fluid storage chamber 5. When the head in this chamber rises, whether that rise is due to rising fluid surface elevation or rising pressure, the fluid within the filter cartridge 16 is driven through the filter media more quickly. The increased flow rate serves to relieve the rising head upstream from the invention.
The modified form of the invention comprises an alternate layering of the rolled filter. The filter cartridge is again constructed by rolling a layered filter around a center line.
In the modified form of the invention, the completed filter unit is placed in the invention housing in the same manner as it is in the preferred form.
The operation of the first modified form of the invention is very similar to that of the preferred form.
The contaminated fluid flows from the contaminated fluid storage chamber 205 into cartridge inlet layer 107 through openings 110. In the cartridge inlet layer 107, the fluid makes a 90 degree turn in either direction and flows through permeable barrier 111 (when present) and into the filter media 108. The fluid flows through the filter media 108, where the contaminants are removed by the media, passes through permeable barrier 111 when present, and into one of two of the fluid outlet drains 109. In the fluid outlet drain 109, the fluid once again makes a 90 degree turn and flows downward, out of the filter cartridge through openings 112.
The treated fluid flow from the filter cartridge 216 into the outlet chamber 218 of the main structure 215. The treated fluid then flows to the outlet means 217 and exits the invention through said outlet means.
I hereby claim the benefit of my prior copending Provisional Application Ser. No. 60/543,942, filed Feb. 12, 2004.
Number | Date | Country | |
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60543942 | Feb 2004 | US |