WO2000071229A1

WO2000071229A1 - Filtration process and filter

Info

Publication number: WO2000071229A1
Application number: PCT/US2000/014744
Authority: WO
Inventors: Joseph G. Adiletta
Original assignee: Pall Corporation
Priority date: 1999-05-26
Filing date: 2000-05-26
Publication date: 2000-11-30
Also published as: AU5301200A

Abstract

A filter and method for treating fluids (e.g., wastewater) are disclosed. The inventive filter comprises a filter element comprising a fibrous web comprising aromatic polyamide fibers, particularly poly-meta-phenylene isophthalamide fibers and/or fibers of an aromatic copolyamide, singly or in various blends. In some embodiments, a binder compatible with the fibers is also included in the filter element. Advantageously, the element is heat and chemically resistant and has an extended use-life even upon exposure to wastewater and other fluids that are typically subjected to elevated temperatures and often include harsh chemicals. In some embodiments of the invention, potential pathogens, e.g., Cryptosporidium parvum, can be removed from the fluid being treated, for example, municipal water supplies.

Description

FILTRATION PROCESS AND FILTER

CROSS-REFERENCE TO RELATED PATENT APPLICATIONS This patent application claims the benefit of U.S. provisional application no.

60/135,968, filed May 26, 1999, which is incorporated by reference.

TECHNICAL FIELD OF THE INVENTION The present invention pertains generally to a fluid treatment process and a fibrous web for use in the process. In particular, the present invention relates to treating high- temperature fluids and/ or fluids that contain harsh chemicals, and is particularly useful for filtering wastewater to recover purified water and to reduce effluents.

BACKGROUND OF THE INVENTION

Many types of fluids contain various harsh chemicals and/or are subjected to very high temperatures. For example, wastewater is generated in chemical-heat environments such as in nuclear power water filtering, as well as in a number of other environments, such as municipal water treatments, food processing plants, laundries, textile plants, pharmaceutical plants, and the like. Treating (e.g. , filtering) such wastewater to reduce effluents and recycle useable water is important in the overall effort to reduce pollution and conserve water. However, existing approaches for treating waste water have been unsatisfactory .

A significant problem compromising the efficiency and quality of wastewater treatments is the lack of a suitable filter element that can withstand the high temperatures and exposure to harsh chemicals (such as acidic or alkaline substances) that are associated with wastewater treatments, while also having the necessary mechanical strength for accommodating such rugged applications. Conventional filter elements have not been able to withstand the elevated temperatures typically encountered in wastewater applications, which typically exceed about 100 °C (about 212 °F) and often reach approximately 200 °C (about 400 °F) or higher. These filter elements have also been unable to withstand chemical attack by cleaning agents, sterilizing agents, and/or other chemicals used or provided in wastewater treatment processes. For example, harsh chemicals found in wastewater often include one or more of the following chemicals: citric acid, caustic soda, sodium hypochlorite, ozone, hydrogen peroxide, lauryl sulfate, ethylenediaminetetraacetic acid (EDTA), hot water, and peracetic acid.

Because of the inadequate heat and chemical resistance, the pore structure (e.g. , the pore size) of media utilized in conventional wastewater filter elements could not be retained. In some instances, harsh chemicals commonly found in wastewater cause the fibers in fibrous filtration media to swell such that the pore size of the media undesirably decreases. In other instances, the fibers degrade such that the pores undesirably enlarge. Moreover, even water can be destructive, and therefore considered to be a "harsh" chemical, inasmuch as conventional filter elements have been susceptible to fiber hydrolysis.

Filter elements utilized in conventional approaches for treating wastewater have also been ill-suited for accommodating "backwashing" (i.e., fluid flow reversal) without experiencing a loss in integrity. In this regard, irrespective of the normal flow of fluid through the filter, it is not unusual to have the fluid flow reversed, either accidentally (e.g., due to a surge in fluid pressure downstream from the filter) or intentionally (e.g. , to flush an accumulated cake of paniculate matter from the surface of the filter). Conventional wastewater treatment filter elements readily come apart or become damaged during backwashing.

From the foregoing, it will be appreciated that there exists a need in the art for a filter and method for treating fluids (e.g., wastewater) utilizing a filter element that demonstrates sufficient chemical resistance, heat resistance, and mechanical strength in order to be long-lasting. It will also be appreciated that there exists a need for a high- temperature fluid (e.g. , wastewater) treatment process and filter that is able to withstand backwashing. The present invention provides such a process and filter. These and other advantages of the present invention, as well as additional inventive features, will be apparent from the description of the invention provided herein.

BRIEF SUMMARY OF THE INVENTION The present invention provides a filter and a process for treating fluids (e.g. , wastewater) which employs at least one filter element comprising a fibrous web comprising aromatic poly amide fibers, wherein the filter element can withstand exposure to high- temperature fluids, particularly high-temperature liquids and/or gases (e.g., having temperatures in excess of about 100 °C (about 212 °F)), and/or fluids that contain harsh chemicals.

Advantageously, the filter element according to embodiments of the invention is heat and chemically resistant and, therefore, is compatible with fluids having high temperatures and/or one or more harsh chemicals. Strictly by way of example, the filter element according to the invention is resistant to various harsh (in the context of the present invention) chemicals, such as, for example, hydrocarbons, acids, bases, alcohols, glycols, ozone, hydrogen peroxide, boron, lithium (and salts thereof), hydrazine, chlorine dioxide, hypochlorite, water, deionized water, lauryl sulfate, ethylenediaminetetraacetic acid (EDTA), gasoline, caustic soda, ammonia, or any combination thereof. The inventive filter element is even resistant to very alkaline fluids (e.g., fluids having a pH of about 10.5 to about 12 or more) and acidic fluids (e.g., fluids having a pH of about 5 to about 3 or less). With respect to water, the filter element of the present invention is resistant to fiber hydrolysis. Furthermore, the inventive filter element is resistant to fluids at high- temperatures (e.g. , water), such as those fluids having a temperature of about 135 °C

(about 275 °F) or higher, and the filter element according to embodiments of the invention is even resistant to temperatures of about 177 °C (about 350 °F) or higher.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention provides a filter and method for treating fluids utilizing a filter element that is heat and/or chemically resistant. Accordingly, the filter element according to embodiments of the invention has a longer use-life than filter elements used in conventional fluid (e.g., wastewater) treatment processes. Particularly, the filter of the present invention comprises at least one porous filter element comprising a fibrous web comprising (a) fibers of an aromatic copolyamide, (b) aromatic polyamide fibers having repeating units characterized by the following formula:

(Formula I), or (c) a combination (including blends) thereof. In some embodiments, the web includes at least one binder compatible with the fibers, while in other embodiments, the presence of the binder is not necessary.

In some embodiments, the fibrous web includes fibers of any suitable aromatic copolyamide. By way of example, the structure of the aromatic copolyamide can include an aromatic diacid, at least one diary 1 diamine, and at least one aryl diamine. Any suitable diary 1 diamine can be selected, such as, for example, a 3,4'-diaryldiamine. Optionally, the diaryl diamine can include a spacer between the two aryl groups thereof. In this respect, any suitable spacer can be included. By way of example, and not by way of limitation, the spacer can be selected from an oxygen, an alkyl (e.g. , a C,-C₆ alkyl), an amine, or the like. In preferred embodiments, the spacer is an oxygen. With respect to the aryl diamine component, any suitable aryl diamine can be used according to the invention, such as, for example, a phenylene diamine. In some embodiments, the aryl diamine is a p-phenylene diamine. In addition, any suitable aromatic diacid can be selected. In this respect, suitable aromatic diacids can include, for example, a phthalic acid. For example, the aromatic diacid component preferably can be terephthalic acid. In a preferred embodiment, the aromatic copolyamide is co-poly-(paraphenylene/3,4'-oxydiphenylene terephthalamide), e.g., TECHNORA^®, which is commercially available from Teijin.

In an embodiment, the filter element utilized in a fluid treatment process comprises a fibrous web comprising fibers including a polymer having monomeric recurring units characterized by formula II below:

(Formula II).

It is believed that Formula II corresponds to monomers found in fibers commercially available under the name CONEX^® (brand name of Teijin) (poly-m-phenylene isophthalamide). See, for example, U.S. Patents 5,705,446 and 5,327,714. In any event, fibers commercially available under the names CONEX^® and TECHNORA^® are particularly desirable in accordance with the present invention. It is to be noted that the desired fibers can be used individually or in combination (e.g., in a blend), for example, to tailor the physical and chemical properties of the filter element to suit a particular application. By way of example, the web can comprise a blend of poly-meta-phenylene isophthalamide fibers (e.g., CONEX^®) and aromatic copolyamide fibers (e.g., TECHNORA^®). In embodiments including at least one binder, any suitable binder or combination of binders compatible with the selected fibers can be utilized. If included, the binder is provided to enhance the strength and life of the filter element. The binder should also be compatible with the fluid being treated and the treatment conditions. By way of example, in some embodiments, suitable binders that can be included in the inventive filter element include, but are not limited to, phenolic resin, epoxy resin, acrylic resin, ethylene vinyl acetate, ethylene vinyl chloride, polytetrafluoroethylene, fluoroethylene, polypropylene (at lower temperatures, e.g., 100 °C), polyamide (e.g., KYMENE^®, such as grade 4308 thereof, commercially available from Hercules) and any combination thereof.

If included, the amount of binder included in the filter element can vary depending upon the application. Typically, the amount of binder is at least about 1 % by weight of the filter element, preferably by weight of the fibrous web, more preferably in a range of from about 3% by weight to about 30% by weight of the fibrous web. Although binders can be provided in amounts less than about 8% by weight (such as, for example, from about 3% by weight to about 5 % by weight) of the fibrous web to give some wet strength, in more rugged applications, such as most wastewater treatments (especially where backwashing occurs), the amount of binder is desirably about 9% by weight to about 18% by weight or more of the fibrous web, and most preferably, the binder is present in an amount of about 12% by weight of the fibrous web.

In addition, the filter media of the present invention preferably are substantially free of (i.e., containing less than 2% by weight of) glass fibers. In this respect, the preferred embodiments of filter elements of the present invention are resistant to high temperatures and harsh chemicals without requiring glass fibers to reinforce the mechanical strength of the element. However, if desired, in some embodiments, glass fibers (e.g. , up to about 35% by weight glass fibers) can be included as part of the element, the web, or part of the filter. Likewise, the preferred embodiments of the filter elements of the present invention do not require the presence of a support or substrate. However, if desired, the filter element can be provided as a laminate, e.g., with a substrate or support. For example, the substrate or support can be of any suitable material, depending upon the application, and, in some embodiments, can be of a material that exhibits resistance to harsh chemicals and/or high temperatures, e.g., glass fibers, or exhibits less resistance to harsh chemicals and/or high temperatures, such as, for example, polyester, KEVLAR^®, poly ether sulfone, or the like. One of ordinary skill in the art will be knowledgeable concerning various techniques for incorporating the substrate and/or glass fibers in accordance with the invention.

Notably, media according to some embodiments of the invention desirably are lacking, or substantially lacking (i.e., less than about 2% by weight of the web, for example, less than about 1 % by weight of the web), an inorganic oxide coating or other surface coating.

The filter element in the context of the present invention comprises a fibrous web comprising a fibrous mass of fibers, preferably non- woven fibers, which can be formed, e.g., as a filtration sheet, in accordance with any suitable procedure. Fiber forming procedures are well known and readily appreciated by those of ordinary skill in the art. The fibers can be of any suitable diameter and density, depending upon the desired filtration characteristics of the filter element, as is also well known in the art. In this respect, finer fibers (e.g., a diameter of about 4 μm or less) are more preferable than fibers that are more coarse. As such, TECHNORA^® fibers generally are preferred over CONEX^® fibers inasmuch as TECHNORA^® fibers are finer than CONEX^® fibers. In addition, TECHNORA^® fibers generally exhibit more chemical resistance than CONEX^® fibers in many embodiments of the present invention. The filter element may be prepared with relatively uniform fibers throughout the web so as to have a relatively uniform pore structure, or the filter element can be comprised of discrete layers or a continuous series of fibers of varying diameter which are layered to form a filter element of a graded pore structure, preferably such that the pores of the filter element are smaller in the direction of normal fluid flow (rather than in the direction of fluid flow during backwashing). See, for example, U.S. Patents 4,594,202 and 4,726,901.

The filter element can have any suitable void volume. The preparation of non- woven fibrous filter elements with particular structures (e.g. , pore ratings) and void volumes is within the ordinary skill in the art. It will be appreciated that, as void volume increases, however, the filter element may become less rigid and more susceptible to damage during use in some applications, particularly, involving backwashing, in the absence of suitable support materials. The void volume of the fibrous web is preferably 7 less than about 80% , more preferably less than about 78%, and most preferably about 60% to about 75% .

The filter element can have any suitable pore structure, e.g., a pore size, or a pore rating, such as an average pore rating ranging from submicron (e.g., 0.01 μm) to about 100 μm or larger. In some embodiments, the pore rating preferably is less than about 40 μm (e.g., 0.1 μm- 40 μm), more preferably, less than about 35 μm, even more preferably, a pore rating of less than about 30 μm. In some embodiments according to the invention, such as, for example, in the removal of potential pathogens (e.g., viruses and/or microorganisms such as protozoa or bacteria), the filter element has a relatively small pore rating of about 2.0 μm or less (e.g., from about 0.4 μm to about 1 μm, such as about 0.45 μm), and might correspond to a first bubble point of, for example, about 381-406 cm water column (about 150-160 inch water column). Strictly by way of example, filter elements having such relatively small pore ratings are useful in removing (from the fluid being treated, for example, municipal water supplies) protozoa of the genus Cryptosporidium (e.g., Cryptosporidium parvum, which is a species thereof that parasitizes humans), which can cause health problems if ingested. In addition, embodiments of the filter element of the invention also can be used to remove radiation particles (e.g., from nuclear wastewater). Depending upon the application, the fibers (e.g., in the form of pulp) can be, for example, refined, or size-modified, e.g. , to reduce the average pore rating in the resulting element. In this regard, the filter element can be used in different configurations. For example, one or more elements can be used to provide a series of pre-filters having progressively decreasing pore ratings. Such applications may require filter elements having pore ratings of about 40-100 μm or perhaps even larger. Regardless of the pore rating, the filter element of the preferred embodiment of the present invention is chemically and heat resistant such that the average pore rating is substantially retained (e.g. , varies by less than about 12%) despite exposure to elevated temperatures and harsh chemicals.

Methods for refining the fibers in order to reduce the diameter, and preferably the length, of the fibers to generate a smaller pore structure in the resulting filter element will be apparent to one of ordinary skill in the art. For example, the fibers can be dispersed in a fluid, with the dispersion then subjected to fibrillation, particularly mechanical fibrillation, under conditions sufficient to reduce the average diameter, and preferably length, of the fibers. See, for example, U.S. Patents 5,709,798 and 5,529,844. 8

The most preferred filter element is prepared from such processed fibers (as refined, if applicable) by fibrous sheet-forming techniques which are well-known in the art, such as conventionally modified Fourdrinier paper making processes. High-energy beaters, such as Cowles® and Kady Mill® beaters, are utilized to prepare a dispersion of the fibers (as refined, if applicable) in a fluid such as water with appropriate surfactants and dispersants, as will be apparent to one of ordinary skill in the art.

If included, the binder can be incorporated into the web in any suitable manner. In addition, if desired, other additives or reinforcing components, such as glass fibers, can be included as well. Having made the dispersion, with appropriate binder resin treatment (and possibly other components), the dispersion is typically pumped onto the Fourdrinier machine (or other suitable paper forming machine) to form a wet laid random fibrous web which can be used as a filter element in accordance with the present invention.

The web is then allowed to dry by any suitable means, after which it is allowed to stand for a sufficient length of time to develop its full strength as a filter element, e.g., for about 3-12 hours or more depending on the binder characteristics. In a preferred embodiment, the filter element according to the invention is surprisingly more rigid, and less susceptible to deformation or degradation, than conventional wastewater treatment filter elements. The filter element of the inventive process and filter is compatible with all types of fluids, including liquids and/or gases. The filter element can be included in a filter device. Typical filter devices comprise a housing including at least one inlet and at least one outlet defining a fluid flow path between the inlet and the outlet, and a filter comprising a filter element of the present invention disposed across the fluid flow path or tangentially to the fluid flow path. In this respect, the filter devices can be constructed to operate in crossflow or tangential flow mode as well as dead-end mode. Accordingly, the fluid to be treated can be passed, for example, tangentially to the filter element surface, or passed perpendicular to the filter element surface. Methods for treating fluids in accordance with embodiments of the invention include, for example, passing the fluid through the filter element (e.g. , passing the fluid from the first, or upstream, side of the element to the second, or downstream, side) or passing the fluid tangentially to the first surface of the element (e.g., allowing a portion of the fluid to pass from the first surface to the second surface to a first outlet, and allowing another portion to pass across the first surface to a second outlet). If desired, the treated fluids (e.g., now having reduced effluents and/or a reduced level of potential pathogens), can be recycled.

Illustratively, the device can include a filter element in a substantially planar or pleated form. In an embodiment, the element can have a hollow generally cylindrical form. If desired, the device can include a filter comprising the filter element in combination with upstream and/or downstream support or drainage layers. The device can include a plurality of filter elements and/or fibrous webs, e.g., to provide a multilayered filter element.

The inventive filter element can be used to treat a variety of fluids comprising a variety of chemicals and/or under high-temperature conditions. For example, the filter element according to the present invention can be used to treat fluids comprising one or more harsh chemicals. By way of example, in some embodiments, the inventive filter element can be used to treat fluids comprising chemicals such as, for example, hydrocarbons (e.g., toluene, ethylene dichloride, and the like), acids (e.g., citric acid, boric acid, humic acid, sulfuric acid, peracetic acid, and the like), bases (e.g., sodium hydroxide, ammonium hydroxide, lithium hydroxide, and the like), alcohols (e.g., isopropyl alcohol, ethanol, and the like), glycols (e.g. , ethylene glycol, propylene glycol, and the like), as well as other exemplary chemicals, such as, but not limited to, ozone, hydrogen peroxide, boron, lithium (and salts thereof), hydrazine, chlorine dioxide, hypochlorite, water, deionized water, lauryl sulfate, ethylenediaminetetraacetic acid (EDTA), gasoline, caustic soda, ammonia, and any combination thereof. Furthermore, the inventive filter element is resistant to fluids (e.g., water) at temperamres of at least about 100 °C (about 212 °F), such as those fluids having a temperature of about 135 °C (about 275 °F) or higher, and the filter element according to embodiments of the invention is even resistant to temperatures of about 177 °C (about 350 °F) or higher.

The present invention is illustrated by the following representative Examples. It will be understood that these Examples are illustrative and not limiting in nature.

EXAMPLE 1 This Example illustrates the tensile strength of an embodiment of the present invention as compared with the tensile strength of conventional filtration sheets. In particular, this Example compares filtration sheets containing TECHNORA^® (co-poly- (paraphenylene/3,4'-oxydiphenylene terephthalamide) fibers, with filtration sheets containing glass fibers, and filtration sheets containing KEVLAR^® fibers. Using conventional techniques, series of filtration sheets were prepared using commercially available TECHNORA^® fibers, KEVLAR® fibers, or glass fibers wherein each sheet included a binder. All of the filtration sheets in each of these series included the same amount of the same binder (i.e., 10 wt. % of a phenolic-epoxy resin, particularly, phenolic BKS 2600 from Georgia Pacific and epoxy EPON 826 from Shell).

Each of these sheets was cut into 1 inch (2.54 cm) by 3 inch (7.62 cm) samples and tested for tensile strength determinations under various conditions (described below). For purposes of this Example, one set contained one sample of each sheet containing TECHNORA®, KEVLAR®, or glass fibers. The tensile strength was measured on a Thwing- Albert Instrument Co. electronic machine where one end of the sample was clamped and the other end stretched under the following parameters: 3.81 cm/min (1.5 in/min) crosshead speed and 3.81 cm (1.5 inch) grip distance. At the point that the samples ruptured, the tensile strength was recorded as the tensile load/width at the maximum load (lbs/inch). Once particular samples were tested to determine their respective tensile strengths, the samples were essentially destroyed (ruptured) and, therefore, could not be re-tested under different conditions. For this reason, the samples were cut from the same sheets so as to simulate testing the same sheets under different conditions.

First, the tensile strength of a set of unchallenged sheets (i.e. , not subjected to harsh chemicals) was tested in order to establish control sample data. The unchallenged test results are identified in the following Table as "dry" samples. The remaining samples were exposed to various chemicals and/or high temperatures by immersing the samples in a beaker (with test liquid) supplied with a magnetic stirrer.

A second set of samples was tested for tensile strength after soaking these samples in deionized (DI) water at a temperature of 200 °F (93 °C) for 150 hours. A third set of samples was tested after soaking for 150 hours in deionized water at an ambient temperature. Such a test was conducted to determine whether the samples were subject to fiber hydrolysis. A fourth set of samples was tested after soaking for 150 hours in an acidic (2% citric acid) solution. A fifth set of samples was tested after soaking the samples for 150 hours in an alkaline solution (sodium hydroxide) having a pH of 12. A sixth set of samples was tested after soaking the samples for 150 hours in isopropyl alcohol at an ambient temperature. Lastly, a seventh set of samples was tested after soaking the samples for 150 hours with unleaded gasoline. 11

After the samples were tested under the different conditions, the results were recorded and then compared with the control data. In this regard, the percentage of tensile strength retention was denoted, which correlates the tensile strength of the samples that were soaked under various conditions as compared to the tensile strength of the control (i.e., dry) samples. The results are provided in the Table. In the Table, "TS" refers to tensile strength in lbs/inch and " % TS" refers to the percentage of tensile strength retained as compared with the control samples.

As seen in the Table, the filtration sheets according to an embodiment of the invention, i.e. , including TECHNORA^® (co-poly-(paraphenylene/3,4'-oxydiphenylene terephthalamide)) and a binder, retained significantly more tensile strength after being subjected to the challenges as compared with filtration sheets containing KEVLAR^® or glass fibers. EXAMPLE 2 This Example illustrates the tensile strength retention of embodiments of the present invention after being subjected to a chlorination soak for an extended period of time. In particular, this Example relates to filtration sheets containing TECHNORA® (co-poly- (paraphenylene/3,4'-oxydiphenylene terephthalamide)) fibers and either (a) a phenolic- epoxy binder (i.e., phenolic BKS 2600 commercially available from Georgia Pacific and epoxy EPON 826 commercially available from Shell), or (b) an acrylic binder (i.e., grades 596 or 604 commercially available from BF Goodrich).

Two series of filtration sheets are prepared as described in Example 1. Each filtration sheet includes TECHNORA® fibers and one of the two binders. In the latter respect, one series of filtration sheets includes 12 wt. % of the phenolic-epoxy binder while the other series of filtration sheets includes 12 wt. % of the acrylic binder. The tensile strength of the filtration sheets is tested as described in Example 1. In particular, one set of samples from each series (i.e., control samples) is tested without being subjected to any challenges in order to establish the tensile strength of the dry samples. In addition, the tensile strength is tested for eight other sets of samples from each series after the samples are subjected to soaking for various periods of time (i.e., 25 hours, 50 hours, 150 hours, 300 hours, 600 hours, 1,200 hours, and 1,800 hours, respectively) in a solution including 3 ppm hypochlorite. The samples including TECHNORA® fibers and 12 wt. % of the phenolic binder retain over about 70% tensile strength as compared with the tensile strength of the dry (control) samples. Meanwhile, the samples including TECHNORA® fibers and 12 wt. % of acrylic binder retain over 42 % tensile strength (at each of the aforementioned time intervals) as compared with the tensile strength of the dry (control) samples.

All of the references and patents cited herein are hereby incorporated in their entireties by reference.

While this invention has been described with emphasis upon preferred embodiments, it will be obvious to those of ordinary skill in the art that variations of the preferred products and methods may be used and that it is intended that the invention may be practiced otherwise than is specifically described herein. Accordingly, this invention includes all modifications encompassed within the spirit and scope of the invention as defined by the subjoined claims.

Claims

WHAT IS CLAIMED IS:

1. A filter comprising a filter element including a fibrous web comprising fibers of an aromatic copolyamide.

2. The filter of claim 1, wherein the aromatic copolyamide comprises an aromatic diacid, at least one diaryl diamine, and at least one aryl diamine.

3. The filter of claim 1, wherein said diaryl diamine is a 3,4'-diaryldiamine.

4. The filter of claim 2, wherein the diaryl diamine comprises a spacer between the two aryl groups thereof.

5. The filter of claim 4, wherein the spacer is selected from the group consisting of an oxygen, an alkyl, and an amine.

6. The filter of claim 4, wherein the spacer is an oxygen.

7. The filter of claim 2, wherein said aryl diamine is a phenylene diamine.

8. The filter of claim 2, wherein said aryl diamine is a p-phenylene diamine.

9. The filter of claim 2, wherein said aromatic diacid is a phthalic acid.

10. The filter of claim 2, wherein said aromatic diacid is terephthalic acid.

11. The filter of any of claims 1-10, wherein the aromatic copolyamide is co- poly-(parapheny lene/3 ,4 ' -oxydiphenylene terephthalamide) .

12. The filter of any of claims 1-11, wherein the filter element has an average pore rating of less than about 40 μm.

13. The filter of any of claims 1-12, further comprising a binder compatible with the fibers.

14. The filter of claim 13, wherein the binder is selected from the group consisting of phenolic resin, epoxy resin, acrylic resin, polytetrafluoroethylene, fluoroethylene, polypropylene, ethylene vinyl acetate, polyamide, ethylene vinyl chloride, and any combination thereof.

15. The filter of any of claims 13-14, wherein the binder is present in an amount of at least about 1 % by weight of the web.

16. The filter of any of claims 13-14, wherein the binder is present in an amount ranging from about 9% to about 18% by weight of the web.

17. A filter comprising a filter element including a fibrous web comprising fibers of co-poly-(paraphenylene/3,4'-oxydiphenylene terephthalamide).

18. The filter of claim 17, wherein the filter element has an average pore rating of less than about 40 μm.

19. The filter of claims 17 or 18, wherein the filter element further comprises a binder compatible with the fibers.

20. The filter of claim 19, wherein the binder is selected from the group consisting of phenolic resin, epoxy resin, acrylic resin, polytetrafluoroethylene, fluoroethylene, polypropylene, ethylene vinyl acetate, polyamide, ethylene vinyl chloride, and any combination thereof.

21. A filter comprising: a filter element including a fibrous web comprising fibers of at least one aromatic polyamide comprising repeating units of the formula:

wherein the filter element has an average pore rating of less than about 40 μm.

22. A filter comprising: a filter element including a fibrous web comprising fibers of at least one aromatic polyamide comprising repeating units of the formula:

and at least one binder compatible with the fibers.

23. The filter of claim 22, wherein the filter element has an average pore rating of less than about 40 μm.

24. The filter of any of claims 22 or 23, wherein the binder is selected from the group consisting of phenolic resin, epoxy resin, acrylic resin, polytetrafluoroethylene, fluoroethylene, polypropylene, polyamide, ethylene vinyl acetate, ethylene vinyl chloride, and any combination thereof.

25. The filter of any of claims 22-24, wherein the binder is present in an amount of at least about 1 % by weight of the web.

26. The filter of any of claims 22-25, wherein the binder is present in an amount ranging from about 9% to about 18% by weight of the web.

27. The filter of any of claims 21-26, wherein said aromatic polyamide is poly- meta-phenylene isophthalamide. 16

28. The filter of any of claims 1-27, wherein the web comprises a combination of poly-meta-phenylene isophthalamide fibers and aromatic copolyamide fibers.

29. The filter of any of claims 1-28, wherein the filter element is substantially free of an inorganic oxide coating.

30. The filter of any of claims 1-29, further comprising a support, a substrate, and/or glass fibers.

31. A method for treating a fluid comprising: providing a fibrous web comprising fibers of an aromatic copolyamide; and contacting said fibrous web with said fluid.

32. A method for treating a fluid comprising: providing a fibrous web comprising fibers of at least one aromatic polyamide comprising repeating units characterized by the formula:

wherein said fibrous web has a pore rating of less than about 40 μm; and contacting said fibrous web with said fluid.

33. A method for treating a fluid comprising: providing a fibrous web comprising fibers of at least one aromatic polyamide comprising repeating units characterized by the formula:

and at least one binder compatible with the fibers; and contacting said fibrous web with said fluid.

34. The method of any of claims 31-33, wherein the fluid has a temperature of at least about 100 °C.

35. The method of any of claims 31-34, wherein the fluid comprises at least one harsh chemical.

36. The method of claim 35, wherein the harsh chemical is selected from the group consisting of hydrocarbons, acids, bases, alcohols, glycols, ozone, hydrogen peroxide, boron, lithium, lithium salts, hydrazine, deionized water, chlorine dioxide, hypochlorite, water, lauryl sulfate, ethylenediaminetetraacetic acid (EDTA), gasoline, caustic soda, ammonia, chlorine dioxide, and any combination thereof.

37. The method of any of claims 31, 32, or 34-36, wherein said fibrous web further comprises at least one binder compatible with the fibers.

38. The method of claims 33 or 37, wherein the binder is selected from the group consisting of phenolic resin, epoxy resin, acrylic resin, polytetrafluoroethylene, fluoroethylene, polypropylene, polyamide, ethylene vinyl acetate, ethylene vinyl chloride, and any combination thereof.

39. The method of claims 33, 37, or 38, wherein the binder is present in an amount of at least about 1 % by weight of the web.

40. The method of any of claims 33 or 37-39 wherein the binder is present in an amount ranging from about 9% to about 18% by weight of the web.

41. The method of any of claims 31 or 33-40, wherein said fibrous web has an average pore rating of less than about 40 μm.

42. The method of any of claims 31 or 34-41, wherein the aromatic copolyamide comprises an aromatic diacid, at least one diaryl diamine, and at least one aryl diamine.

43. The method of claim 42, wherein said diaryl diamine is a 3,4'-diaryldiamine.

44. The method of claim 42, wherein the diaryl diamine comprises a spacer between the two aryl groups thereof.

45. The method of claim 44, wherein the spacer is selected from the group consisting of an oxygen, an alkyl, and an amine.

46. The method of claim 44, wherein the spacer is an oxygen.

47. The method of claim 42, wherein said aryl diamine is a phenylene diamine.

48. The method of claim 42, wherein said aryl diamine is a p-phenylene diamine.

49. The method of claim 42, wherein said aromatic diacid is a phthalic acid.

50. The method of claim 42, wherein said aromatic diacid is terephthalic acid.

51. The method of any of claims 31 or 34-50, wherein the aromatic copolyamide is co-poly-(paraphenylene/3,4'-oxydiphenylene terephthalamide).

52. The method of any of claims 32-41 , wherein said aromatic polyamide is poly-meta-phenylene isophthalamide.

53. The method of any of claims 31-52, wherein the web comprises a combination of poly-meta-phenylene isophthalamide fibers and aromatic copolyamide fibers.

54. The method of any of claims 31-53, wherein said fluid is a liquid.

55. The method of any of claims 31-53, wherein said fluid is a gas.

56. The method of any of claims 31-53, wherein said fluid comprises a liquid.

57. The method of any of claims 31-56, wherein said fluid has a pH of about 5 or less.

58. The method of any of claims 31-56, wherein said fluid has a pH of at least about 10.5.

59. The method of any of claims 31-58, wherein the web is substantially free of glass fibers.

60. The method of any of claims 31-59, wherein the web is substantially lacking an inorganic oxide coating.

61. The method of any of claims 31-60, wherein the fluid includes at least one pathogen.

62. The method of any of claims 31-60, wherein the method includes depleting the level of microorganisms in the fluid.