The concepts disclosed herein relate generally to the field of filtration of storm water run-off as captured, controlled, and transported by storm water drainage systems. More particularly, these concepts relate to methods and apparatus to filter storm water or surface water run-off to remove hydrocarbons, organic liquids, and particulate matter, as well to eradicate bacteria in the storm water run-off.
As a result of society's high level of use of products containing hydrocarbons or organic liquids, it is not uncommon for such components to be flushed in significant amounts into storm water drainage systems. It is therefore necessary to provide apparatus and methods to remove such contaminants from the storm water prior to discharge of the storm water from the storm water system. In a common conventional approach, a filtration structure capable of capturing the hydrocarbons and organic liquids is disposed at the ingress points of the storm water system, i.e., filter units are positioned in the storm drains such that the contaminants are immediately captured, and storm water passing into the storm water drainage system downstream of the filter units is relatively contaminant-free. In another method, filtration units are positioned at the points of exit of the storm water system, such that contaminants are removed from the storm water prior to its discharge into the environment. For example, an excellent filtration material for this purpose is sold under the trademark X-TEX®, the composition of which is disclosed in commonly assigned U.S. Pat. No. 6,632,501, the drawings and disclosure of which are hereby specifically incorporated herein by reference.
Another problem inherent in storm water discharge is microbial contamination. Bacteria in relatively high concentration may in some circumstances be flushed into the storm water system, but significant microbial contamination of discharge water results from the fact that storm water systems comprise vast networks of storm drains, conduits, collectors and the like, which provide reservoirs of stagnant water that is a breeding ground for microbes.
It should be recognized that all storm water run-off entering a storm water system does not pass fully through the system. As noted above, there are often a large number of areas in a storm drain system where the storm water remains resident in the system for extended periods of time, stagnating. For example, an outlet pipe at the base of a storm drain is typically connected to a catch basin several inches above the bottom of the basin. This configuration results in several inches of water remaining trapped in the bottom or sump of each catch basin after a storm.
Likewise, long runs of connected drainpipes often do not have a continuous down-slope, and consequently, storm water can be trapped in pockets of the conduit system. This trapped water is a prime breeding ground for bacteria, to the point that the bacterial concentration discharging from the storm system after large rains may exceed recognized safe limits.
Providing anti-microbial agents in combination with filtration media at the ingress or discharge points of the storm system does not satisfactorily address this problem, because the time that the bacteria is in contact with the anti-microbial agents positioned at such ingress or discharge points is extremely short, and thus, the effectiveness of the anti-microbial action at such points is very limited, especially for anti-microbial agents disposed at the discharge points of the storm water system, since the discharge water may have extremely high concentrations of bacteria due to the bacterial growth occurring in the sump areas of the storm water system.
It would thus be desirable to provide a method and apparatus for effectively reducing the bacterial concentration in storm water discharge, as well as filtering other contaminants from the water before discharging the water.
Bacterial discharge from a storm water system is eliminated or substantially reduced in concentration by providing a combination filtration and anti-microbial apparatus that is disposed in sump areas of the storm water system such that, in addition to removing hydrocarbon and liquid organic contaminants, the concentration of bacteria in storm water that remains resident in the sump areas after a storm event is eradicated or greatly reduced. The combination filtration and anti-microbial medium is disposed in the resident (i.e., retained) water within the system rather than being positioned merely as a pass-through, thereby increasing the contact time between the anti-microbial agents and the bacteria such that large amounts of bacteria are eradicated and explosive bacterial growth within the sump areas is precluded prior to such bacteria being flushed from the system during the next storm event. In various exemplary embodiments, the anti-microbial agent is adhered to, combined with, impregnated in, or otherwise joined to the filtration media, or to some other portion of the apparatus (such as a porous cover encapsulating a bulk filter media). One exemplary type of filtration media comprises a mass of delustered hydrophobic and lipophilic fibers.
Various different exemplary aspects of the concepts disclosed herein are directed to anti-microbial storm water filters, anti-microbial sump filters, methods for reducing microbial contamination of storm water systems, and methods for fabricating anti-microbial filters that are useful in such applications.
Where the anti-microbial agent is associated with the filtration media, it should be recognized that the effective life of the filtration media may be increased by reducing the growth of bacteria, mold, algae, and the like on the filtration media itself.
This Summary has been provided to introduce a few concepts in a simplified form that are further described in detail below in the Description. However, this Summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter.
Various aspects and attendant advantages of one or more exemplary embodiments and modifications thereto will become more readily appreciated as the same becomes better understood by reference to the following detailed description, when taken in conjunction with the accompanying drawings, wherein:
Exemplary embodiments are illustrated in referenced Figures of the drawings. It is intended that the embodiments and Figures disclosed herein are to be considered illustrative rather than restrictive. No limitation on the scope of the technology and of the claims that follow is to be imputed to the examples shown in the drawings and discussed herein.
The concepts disclosed herein encompass a method and apparatus for substantially reducing or eliminating hydrocarbon, liquid organic, and bacterial contamination of storm water discharging from a storm water system into the environment. Such method and apparatus can be implemented in any water system that holds or retains water, so that the retained water can become stagnant and act as a breeding ground for undesirable microbes.
Storm water systems are well known and extremely common, typically including large numbers of storm drains and catch basins located in roadway curbs, within large paved areas such as parking lots, in drainage ditches, and the like. The storm drains allow the storm water to flow into catch basins, sumps, or other temporary storage volumes. Conduits are connected to such volumes and transport the storm water to discharge points where the storm water is returned to the environment. A storm water system is often a vast network, and there are numerous components or areas that act as sumps, either intentionally or unintentionally, where storm water is retained and remains resident within the system for extended periods of time, or at least until a subsequent storm event occurs. Such storage volumes/sumps are generally present in the bottom of each catch basin, beneath the storm drains, since the drainpipes are often connected several inches or more above the bottom of the catch basins. In addition, storage volumes/sumps are also often present where long stretches of pipe are not properly installed to achieve the continuous downward slope required to direct storm water in a desired direction, or where shifting of the pipes over time results in a degradation of the slope, creating unintended low spots that do not drain completely.
Because storm water may remain in such storage volumes/sumps for extended periods of time, and because the storage volumes/sumps will not necessarily be completely flushed upon subsequent storm events, the water retained in the storage volumes/sumps is a prime habitat for bacterial growth. As a result, extremely high bacterial concentrations can be evident in the discharge water when flushing of the storm system occurs, for example, during and immediately after a storm event.
The concepts disclosed herein can solve this problem by providing a combination filtration and anti-microbial structure that can be introduced into the storage volumes/sumps of the storm water system (regardless of whether such storage volumes/sumps are intentional or unintentional). The combination filtration and anti-microbial structure thus serves as a resident filter and treatment apparatus. While it is contemplated that the combined filtration and anti-microbial structure can also be employed in a pass-though filter and treatment apparatus, by being positioned, for example, at an outflow pipe, the time during which the bacterial contamination in the water is exposed to the anti-microbial structure will be much less, and the anti-microbial agent may be less effective. Accordingly, somewhat more effective anti-microbial action can be achieved if such a structure is deployed in locations where stagnant water can accumulate even during non-storm conditions, as opposed to locations that are intermittently exposed to water during storm events. Yet, it is not intended that the present concept and approach be in anyway limited only for use in locations where stagnant water accumulates.
It should be recognized that many different types of filter material can be beneficially employed to implement sorbent material 52. A very useful filtration media will adsorb hydrocarbon and liquid organic contaminants, since the presence of these components in storm discharge water is undesirable. Particularly effective filter media include: sorbents based on an amorphous mixture including a majority of synthetic fibers and a minority of natural fibers; sorbents based on amorphous delustered synthetic fibers; sorbents based on non-woven textiles including a majority of synthetic fibers and a minority of natural fibers; and sorbents based on non-woven textiles, including delustered synthetic fibers. Examples of such sorbents are disclosed in commonly assigned U.S. Pat. No. 6,632,501, the disclosure and drawings of which have been specifically incorporated herein by reference. Sorbents of this type are currently marketed under the trademark X-TEX®.
Furthermore, it should also be recognized that many different materials can be used to implement anti-microbial agent 54. The term “anti-microbial” as used herein is intended to include any compound, product, composition, article, etc., that reduces the growth and proliferation of microbial organisms, including but not limited to bacteria, protozoa, molds, fungi, and the like. Such an agent can be suitably bonded, adhered, grafted, impregnated or otherwise joined to a portion of the storm water filter. In some embodiments, particularly where the sorbent is implemented as a non-woven textile, the anti-microbial agent is suitably bonded, adhered, grafted, impregnated or otherwise joined to the sorbent. In other embodiments, particularly where the sorbent is implemented as an amorphous bulk material, for example, encapsulated in a porous cover, the anti-microbial agent is suitably bonded, adhered, grafted, impregnated or otherwise joined to a component of the storm water filter other than the amorphous bulk material (such as the porous cover), so that removal or replacement of the amorphous bulk sorbent material will not affect the anti-microbial properties of the storm water filter. Thus, it should also be recognized that the anti-microbial agent can be incorporated into some other portion of the storm water filter (i.e., some portion other than the sorbent material or a porous cover encapsulating an amorphous bulk sorbent material).
In general, there are two types of anti-microbial technology. A first technology is based on adding a leachable anti-microbial agent to a physical structure (where the leachable anti-microbial agent acts as a poison), while the second technology is based on permanently binding an anti-microbial agent to a physical structure. A possible undesirable characteristic associated with the leachable anti-microbial technology is that at some point, all of the active anti-microbial agent will have migrated away from the physical structure, leaving the physical structure within no anti-microbial properties. In contrast, when the anti-microbial agent is permanently bound to a physical structure, the physical structure continues to exhibit anti-microbial properties until the anti-microbial coating is physically removed. Some types of permanently bound anti-microbial coatings generally include a silane component that acts as the glue to permanently bind to the anti-microbial coating to a surface, and a chemical or other type of agent that kills microorganisms by physical interaction (such as piercing cellular membranes or by applying a lethal electrical potential). With respect to the concepts disclosed herein, the permanently bound anti-microbial coatings can have an advantage over the leachable anti-microbial agents. Many anti-microbial agents that include a silane binding component and a chemical agent are known and are commercially available, and can be beneficially employed to achieve a storm water filter as disclosed herein. An example of one such organosilane anti-microbial agent is described in U.S. Pat. No. 5,954,869. The permanently bound anti-microbial coatings can be readily applied to a surface by spraying the surface with the combination of the silane and the chemical agent, or by dipping a physical object, such as a component of the filter, into a solution comprising the silane and the chemical agent.
During use, the storm water filter is left in a storage volume/sump of the storm water system until its effectiveness becomes diminished, at which time it is replaced. In this manner, storm water within the sump areas is constantly treated such that the concentration of microbes is severely diminished or reduced to zero, prior to the water in the sumps being flushed from the system by the next storm event. In addition, the filter media removes (by adsorption) hydrocarbon and organic liquid contaminants in the sump water. The presence of the anti-microbial agent also prolongs the effective life of the filter media itself, since growth of bacteria, mold or other microbial species on the filter media that may interfere with the effectiveness for filtering other contaminants from the storm water is generally precluded. As noted above, the anti-microbial agent can be permanently bound to a portion of the storm water filter. It is expected that permanently binding the anti-microbial agent to the storm water filter will result in a relatively long service life. However, the anti-microbial surface coating can be physically removed (i.e., by abrasion), and over time, the anti-microbial properties of the storm water filter will likely diminish. Furthermore, where the anti-microbial coating is applied to the sorbent material, saturation of the sorbent material with hydrocarbons may interfere with the anti-microbial coating, requiring cleaning or replacement of the sorbent material. Particularly where the filter is implemented as a fabric (either a woven fabric, a needle punched fabric, or a non-woven fabric), such a filter will also beneficially remove sediments. In general, the use of non-woven fabrics or needle punched fabrics is more cost-effective, as such fabrics are generally less expensive to manufacture.
The incubation containers were filled with 40 liters (10.6 Gals) of the synthetic contaminated storm water and allowed to equilibrate for 30 minutes. Initial samples were taken in sterile bacteria sample bottles. The anti-microbial flotation apparatus and the control flotation apparatus were positioned in each of the containers, and the timed sampling sequence was begun. Water samples were taken using a 20 ml sterile glass tube. Four samples were taken from each corner of the container and two from the center; these samples were combined into sterile bacteria bottles for each timed sample event submitted for testing. The timed sequence of sampling progressed from minutes to hours. The samples were maintained at 4° C., and submitted for analysis within 24 hours of sampling. The samples were analyzed by Method SM9222D for Fecal Coliform MF; the results are summarized in
To verify that the covalently bonded anti-microbial treatment (i.e., the permanently bound anti-microbial coating) will retain its efficacy and not leach off the filtration fabric after repeated washing and drying cycles, the following test was performed. The non-woven textile treated with the silanequat anti-microbial coating was washed 10 times with warm water and rung dry between washings. The treated non-woven fabric was allowed to hang dry overnight. This washing cycle was done to ensure that any silanequat not covalently bonded to the fabric's fiber would be washed off along with any other component within the fabric that could be chemically detrimental to the fecal coliform. The washed fabric was attached to the flotation apparatus and placed within the incubation container. The conditions of the first procedure described above were duplicated, and the results are summarized in
The test filter with the anti-microbial coating, as compared to the control filter without the anti-microbial coating, removed 95 percent of the population of fecal coliforms in the first 30 minutes of contact, and 100 percent within a three hour period in the control study. The efficacy of the washed fabric removed over 76 percent of the fecal coliforms within the first 30 minutes of contact, and 96.6 percent within three hours. Both stagnant water tests using the treated fabric and the washed fabric maintained 100 percent removal after 24 hours. It should be noted that this study was only monitoring the efficacy for fecal coliform bacteria. Other gram (+) and gram (−) bacteria, mycelial fungi, yeasts, and algae were also being killed in the simulated storm water. Both the anti-microbial treated test filter and the untreated test filter (i.e., the control) experienced a severe drop from the initial bacteria levels. This initial drop may be due to bacterial uptake into the fiber matrix, shock to the bacteria being transferred into a new environment, or some component leaching off the unwashed fabric that was detrimental to the bacteria. The fecal coliform population stabilized to 800-1000 cfu/100 ml in the untreated control, but dropped to non-detectable levels with the treated fabric. The washed fabric illustrated similar efficiency; however the initial fecal coliform count was 900 at the start of the test. This may be due to the longer stabilization time allowed before taking the initial sample.
Unlike a chemical pollutant, bacterial contamination is dynamic and grows exponentially from one bacterium into billions within 24 hours under optimal conditions. Bacteria will also adapt and mutate to develop resistant strains when water-soluble antimicrobial agents or disinfectants are used. This mutation occurs because the water-soluble anti-microbial agents become diluted out to sub-lethal levels, allowing adapting resistant forms to persist and endangering storm water from becoming infected with resistant bacterial populations. The test filter with the permanent anti-microbial coating tested in the study discussed above was designed to overcome these problems by using an immobilized surface-bonded silanequat that kills bacteria by molecular penetration and electrical action. Since the anti-microbial is covalently bonded to the non-woven fabric, it will not dilute to sub-lethal levels and the physical kill mechanism will not be consumed by repeated contact with bacteria. The non-woven textile comprising a majority of the delustered synthetic fibers and a minority of natural fibers represents a particularly effective material, which exhibits excellent oil absorption properties and vast interstitial spaces. The fabric's open design allows the free flow of water in every direction and has great wicking ability. When coupled with a surface immobilized anti-microbial agent, the resulting fabric becomes a powerful delivery system for bacterial removal in storm water systems. The fabric can be cut, formed or molded for use in any new or existing Best Management Practice (BMP) storm water system or design. Beneficial areas of applications would include cisterns, pipes, drain basins, culverts, cooling towers and any other stagnant water areas contaminated with bacteria or oil. Note that binding the anti-microbial to the filter media increases the effective life of the filtration media by reducing the growth of bacteria, mold, algae and the like on the filtration media itself.
Tendrils 82 can be fabricated from the non-woven textile fabric employed in test filter 60 (i.e., a non-woven textile comprising a majority of delustered synthetic fibers and a minority of natural fibers that exhibits oil absorbent properties, vast interstitial spaces, and allows free flow of water through the fabric), which has been coated with an anti-microbial agent permanently bonded to the fabric. It should be recognized that the fabric can be treated with the anti-microbial agent after the fabric has been manufactured (such that the anti-microbial agent is bonded to the surface of the fabric), or alternatively, the fibers can be treated with the anti-microbial agent before the fibers are formed into the fabric, such that the anti-microbial agent is bonded to the fibers, and therefore distributed throughout the vast interstitial spaces defined by the fibers. In at least one embodiment, however, one (or more, or all) of the tendrils are configured as a porous cover 81 (see
It has been determined that delustering enhances the sorbency of synthetic fibers, which inherently have a sheen due to their smooth outer surface. The delustering effect has been empirically determined, and it is believed that at least two mechanisms are responsible for the increase in the sorbency of delustered fibers. First, delustering significantly roughens the surface of individual fibers, substantially increasing the surface area of each fiber, and thus enabling a greater amount of adsorption per fiber. Second, it should be noted that rough surfaces of the individual fibers, in combination with the mix of short and long fiber lengths, enable a surprisingly cohesive wad of fiber sorbent to be achieved. The rough surfaces provide fiber-to-fiber traction, enabling adjacent fibers to better adhere to one another. The mix of a minor portion of relatively long fibers to a majority of relatively short fibers ensures that sufficient relatively long fibers are present to help bind the wadded mass together without the need for binding agents normally employed to bind amorphous masses of fiber together. This wadded mass configuration ensures that a significant amount of interstitial volume is available for absorption of contaminants. Thus, delustering is believed to enhance sorption by providing more sites for both adsorption and absorption to occur. Although the wadded mass of fibers, with its majority of relatively short fibers providing significant surface area, begins to sorb hydrocarbon products immediately upon contact, it may be desirable to leave the wadded mass in contact with the hydrocarbon product to be sorbed for at least sufficient time (for example, 10 minutes or more) to enable most of the contaminants to be absorbed. While the process of adsorbing hydrocarbon products onto surfaces of the relatively short fibers, and the surfaces of relatively long fibers occurs rapidly, the process of absorption is expected to require more time to reduce contaminant concentration in the water being filtered, to acceptable levels. Absorption will occur in interstitial regions within the wadded mass. Delustering using titanium dioxide is one effective technique, since it adds a significant amount of surface area to each individual fiber surface, as well as helping the fibers maintain a wadded mass configuration in which a plurality of interstitial volumes are available for absorption. Accordingly, it is believed that leaving the sorbent wadded mass of the present invention in contact with hydrocarbon products to be sorbed for additional time will enable hydrocarbon products to be more fully absorbed into these interstitial volumes within the wadded mass of delustered fibers.
If virgin synthetic fibers are to be used to produce a sorbent for use in an anti-microbial filter in accord with the concepts disclosed herein, such virgin synthetic fibers can be delustered to enhance their oil absorbency properties. If recycled synthetic textile products are shredded to generate a fiber sorbent, further delustering is not likely to be required, because the majority of synthetic fibers used in the textile industry are delustered to enhance their value in textiles. It should be noted that while a mixture of a majority of delustered synthetic fibers and a minority of natural fibers provides better absorbency, a particularly useful filter media can also be produced using only synthetic fibers. A filter media comprising only (or a majority of) natural fibers is less desirable, because such natural fibers do not have the affinity for oil and other hydrocarbons that synthetic fibers exhibit.
A wadded mass/non-woven textile 30 comprising a majority of delustered synthetic fibers and a minority of natural fibers is schematically illustrated in
While the concepts disclosed above have been described as a combination of the filter media and anti-microbial media, it is also possible to accomplish the anti-microbial treatment of sump areas utilizing a fabric or other matrix to carry the anti-microbial agent, where the matrix does not exhibit filtration properties. Thus, an additional aspect of the concepts disclosed herein encompasses an anti-microbial sump insert comprising a support structure/matrix and an anti-microbial coating. For example, the oil absorbent fabric tendrils of
Mid-filter 102 is optional (i.e., it is not required to obtain the benefits of enhancing the service life of the anti-microbial filter), but may be included to provide additional benefits. For example, mid-filter 102 can include activated carbon to remove hydrocarbons or other contaminants that are not removed by the pre-filter. It is likely that the service life of mid-filter 102 will also be enhanced by the pre-filter, such that mid-filter 102 may not need to be replaced as often as the pre-filter. This enables mid-filter 102 to include relatively more expensive filtration media configured to address specific filtration needs. For example, mid-filter 102 can also incorporate zeolites, a class of filter media that can be used to selectively remove contaminants such as heavy metals. It should be recognized that activated carbon and zeolites can be used individually or in combination in mid-filter 102. Furthermore, it should be recognized that other filtration media can be beneficially incorporated into one or more mid filters 102 to address specific filtration needs (thus it should be recognized that the filter train may include more than the three specific filters shown in
It should be recognized that the discussion above employs both the terms absorb (and absorbent) and adsorb (and adsorbent). In general, the term adsorb is associated with a physical process whereby a fluid (generally a liquid) is attracted to the physical surface of a material. Similarly, the term absorb is generally associated with a physical process whereby a fluid (generally a liquid) is trapped in a volume defined in a material (like the pores in a sponge). Particularly with respect to the exemplary delustered synthetic fiber based sorbent material described in detail above, both the terms adsorb and absorb apply to the exemplary material. In amorphous bulk form and in fabric form, the exemplary delustered synthetic fiber based material exhibits a large volume of interstitial spaces into which a liquid can be absorbed. Furthermore, the delustered synthetic fibers themselves have a very large surface area onto which a liquid can be adsorbed. Thus, a delustered synthetic fiber based filter material is both an adsorbent and an absorbent.
Although the concepts disclosed herein have been described in connection with the preferred form of practicing them and modifications thereto, those of ordinary skill in the art will understand that many other modifications can be made thereto within the scope of the claims that follow. Accordingly, it is not intended that the scope of these concepts in any way be limited by the above description, but instead be determined entirely by reference to the claims that follow.
This application is based on a prior copending provisional application Ser. No. 60/700,074, filed on Jul. 18, 2005, the benefit of the filing date of which is hereby claimed under 35 U.S.C. § 119(e). This application is further a continuation-in-part of a copending patent application Ser. No. 10/646,944, filed on Aug. 21, 2003, which itself is a divisional application of co-pending patent application Ser. No. 09/875,591, filed on Jun. 6, 2001, issued as U.S. Pat. No. 6,632,501 on Oct. 14, 2003, the benefit of the filing dates of which is hereby claimed under 35 U.S.C. § 120.
Number | Date | Country | |
---|---|---|---|
60700074 | Jul 2005 | US |
Number | Date | Country | |
---|---|---|---|
Parent | 09875591 | Jun 2001 | US |
Child | 10646944 | Aug 2003 | US |
Number | Date | Country | |
---|---|---|---|
Parent | 10646944 | Aug 2003 | US |
Child | 11457665 | Jul 2006 | US |