WO2011017702A1

WO2011017702A1 - Enhanced n-halamine based water treatment method and device

Info

Publication number: WO2011017702A1
Application number: PCT/US2010/044893
Authority: WO
Inventors: Jennifer Keene; Nevada Ruehlen; Steven Carver
Original assignee: Halosource, Inc.
Priority date: 2009-08-07
Filing date: 2010-08-09
Publication date: 2011-02-10
Also published as: BR112012002697A2

Abstract

A gravity-fed water treatment system is described that purifies water by inactivating bacteria, protozoa, and viruses. In this system, water is first filtered to remove bacteria and protozoa. This can be accomplished by multiple means, such as ceramic filters containing activated carbon. The filtered water then flows into a purification cartridge housing a purification media, such as the compounds or polymers containing N-halamine described by Worley et al. and Bridges et al. This same purification cartridge also houses an adsorptive media that reduces any residual halogen concentrations in the treated water. The contact quality in the purification media chamber is such that the viral particles are saturated with halogens, becoming irreversibly inactivated.

Description

ENHANCED N-HALAMINE BASED WATER TREATMENT METHOD AND

DEVICE

CROSS-REFERENCE TO RELATED APPLICATION This application claims the benefit of U.S. Provisional Application

No. 61/232329, filed August 7, 2009, which is fully incorporated herein expressly by reference.

BACKGROUND

Compounds containing N-halamines are described by Worley et al. in U.S. Patent Nos. 5,490,983; 5,670,646; 5,889,130; 6,020,491 ; 6,294,185; and 6,548,054; and by

Bridges et al. U.S. Patent No. 7,441,665; and U.S. Patent Application Publication

No. 2008/0202992. These compounds may be used in the treatment of water and generally result in the presence of residual halogen in the treated water. In certain applications, it is desirable to remove some or all of the residual bromine or chlorine from the treated water. The device and method described here were designed for that purpose.

SUMMARY

This summary is provided to introduce a selection of concepts in a simplified form that are explained in greater detail in the Detailed Description. This summary is not intended to identify key features or to be used as an aid in determining the scope of the claimed subject matter.

A gravity-fed water treatment system is described that purifies water by inactivating bacteria, protozoa, and viruses. In this system, water is first filtered to remove bacteria and protozoa. This can be accomplished by multiple means, such as ceramic filters containing activated carbon. The filtered water then flows into a purification cartridge housing a purification media, such as the compounds or polymers containing an N-halamine described by Worley et al. and Bridges et al. This same purification cartridge also houses an adsorptive media that reduces any residual halogen concentrations in the treated water. The contact quality in the purification media chamber is such that the viral particles are saturated with halogens, becoming irreversibly inactivated.

The adsorptive media contained in the purification cartridge directly below the N-halamine media can be any adsorptive media capable of reducing halogen levels in water, such as activated carbon granules, an activated carbon block, or equivalents. It is sized to reduce the residual halogen level to less than 1 ppm and will maintain this performance for approximately 1,000 to 3,000 N-halamine bed volumes. As the halogen residual imparted by the N-halamine media stabilizes to levels below taste and odor thresholds, the adsorptive media concurrently becomes exhausted and will no longer remove residual halogen from the treated water.

In one embodiment, a cartridge is disclosed. The cartridge includes: a first chamber having first and second openings on opposite ends and containing a N-halamine compound within; a second chamber having third and fourth openings on opposite ends and containing adsorptive media within, wherein the second chamber is juxtaposed next to and can be concentrically aligned with the first chamber; a first porous barrier separating the first chamber from the second chamber; and a second porous barrier at one opening of the second chamber that is not next to the first chamber.

The cartridge of the first embodiment may further include a third chamber having fifth and sixth openings on opposite ends and is empty of water treatment chemicals, wherein the third chamber is juxtaposed next to and is concentrically aligned with the first chamber, and a third porous barrier separating the third chamber from the first chamber.

The cartridge of the first embodiment may further include a mounting cap attached to the cartridge, a watertight seal between the mounting cap and the third chamber, and an opening in the mounting cap that opens into the third chamber.

The cartridge of the first embodiment may further include carbon in the second chamber.

The cartridge υf the first embodiment may further include a brominated N-halamine compound in the first chamber.

The cartridge of the first embodiment may further include an empty bed volume is at least 0.9 minutes in the first chamber .

The cartridge of the first embodiment may include an N-halamine compound that is a polymer having the formula:

wherein Rj and R2 are independently selected from C_j-C₄ alkyl, phenyl, and aryl, and X is chlorine or bromine. In one embodiment, X is bromine. In another embodiment, the polymer is a crosslinked polymer.

The cartridge of the first embodiment may further include an N-halamine compound that is a polymer having the formula:

wherein X and X' are independently chlorine, bromine, or hydrogen, provided that at least one of X or X' is chlorine or bromine; and R₃ is hydrogen or methyl. In one embodiment, the polymer is a crosslinked polymer. In another embodiment at least one of X or X' is bromine.

While the cartridge of the first embodiment may have three chambers concentrically aligned, meaning the centers of each chamber are aligned on a single axis, in other embodiments the cartridge may have chambers that are not in alignment. For example, one embodiment of the cartridge has the chambers placed one on top of the other to create a vertical configuration. It is also possible to place the chambers in a row or horizontally disposed next to each other.

In a second embodiment, a water purification system is disclosed. The system may include,

(i) an upper container;

(ii) a lower container;

(iii) a base separating the upper container from the lower container;

(iv) a filter in the upper container;

(v) a cartridge in the lower container, the cartridge comprising:

(a) a first chamber having first and second openings on opposite ends and containing a N-halamine compound within;

(b) a second chamber having third and fourth openings on opposite ends and containing adsorptive media within;

(c) a first porous barrier separating the first chamber from the second chamber;

(d) a second porous barrier at one opening of the second chamber, wherein the second chamber is juxtaposed next to and is concentrically aligned with the first chamber, wherein the second porous barrier leads to the lower container;

(e) a third chamber having fifth and sixth openings on opposite ends and is empty of water treatment chemicals, wherein the third chamber is juxtaposed next to and is concentrically aligned with the first chamber;

(f) a third porous barrier separating the third chamber from the first chamber; and

(g) a mounting cap attached to the cartridge;

(h) a watertight seal between the mounting cap and the third chamber; and

(j) an opening in the mounting cap that opens into the third chamber;

(vi) the filter having an outlet that leads to the opening in the mounting cap of the cartridge.

The second embodiment may further include carbon in the second chamber.

The second embodiment may further include a brominated N-halamine compound in the first chamber.

The second embodiment may further include an empty bed volume of at least 0.9 minutes in the first chamber. The second embodiment may further include an N-halamine compound that is a polymer having the formula:

wherein Rj and R2 are independently selected from C1-C4 alkyl, phenyl, and aryl, and X is chlorine or bromine. In one embodiment, X is bromine. In another embodiment, the polymer is a crosslinked polymer.

The second embodiment may further include an N-halamine compound that is a polymer having the formula:

wherein X and X' are independently chlorine, bromine, or hydrogen, provided that at least one of X or X' is chlorine or bromine; and R₃ is hydrogen or methyl. In one embodiment, the polymer is a crosslinked polymer. In another embodiment, at least one of X or X' is bromine. In a third embodiment, a method for producing potable water from a gravity fed system, wherein the system includes an upper container, a lower container and, a base separating the upper container from the lower container. The method includes filtering water from the first container and delivering the filtered water to a cartridge in the second container; treating the filtered water with a N-halamine containing compound in a first chamber of the cartridge to produce purified water; removing residual halogen from the purified water with an adsorptive media in a second chamber of the cartridge to produce potable water; and delivering the potable water from the second chamber to the lower container.

The third embodiment may further include carbon as the adsorptive media in the second chamber.

The third embodiment may further include an N-halamine containing compound in the first chamber that is brominated.

The third embodiment may further include an empty bed volume in the first chamber of at least 0.9 minute.

The third embodiment may further include an N-halamine containing compound that is a polymer having the formula:

wherein X and X' are independently chlorine, bromine, or hydrogen, provided that at least one of X or X' is chlorine or bromine; and R₃ is hydrogen or methyl. In one embodiment, the polymer is a crosslinked polymer. In another embodiment, at least one of X or X' is bromine.

DESCRIPTION OF THE DRAWINGS

The foregoing aspects and many of the attendant advantages of this invention will become more readily appreciated as the same become better understood by reference to the following detailed description, when taken in conjunction with the accompanying drawings, wherein:

FIGURE 1 shows an illustration showing one embodiment of the water purification cartridge and system described in this invention;

FIGURE 2 shows a cross-sectional illustration of the purification cartridge from

FIGURE l ;

FIGURE 3A shows a perspective view of a purification cartridge in accordance with one embodiment of the invention;

FIGURE 3 B shows an exploded view of a purification cartridge in accordance with one embodiment of the invention;

FIGURE 4 shows a cross-sectional view of a purification cartridge in accordance with one embodiment of the invention;

FIGURE 5 shows a cross-sectional view of a purification cartridge in accordance with one embodiment of the invention; FIGURE 6 shows a cross-sectional view of an enlarged portion of the purification cartridge of FIGURE 5;

FIGURE 7 shows a illustration of a chamber cap in accordance with one embodiment of the invention;

FIGURE 8 shows a cross-sectional view of a portion of the chamber cap of

FIGURE 7.

DETAILED DESCRIPTION

Though certain device embodiments will be illustrated and described, it should be appreciated that various changes can be made without departing from the spirit and scope of the invention.

FIGURE 1 shows one embodiment of the water purification system (1) described here. It includes an upper container (2), a lower container (3), and a base (30) separating the two. The lower container (3) may include a spigot (6) for dispensing purified water.

The upper container (2) may have an open top, allowing untreated water to be poured into the device, or the top may be covered.

The water purification system (1) includes a filter (4) in the upper container (2). This filter (4) is connected to the base (30) that separates the upper container (2) from the lower container (3), preventing untreated water from entering the lower container (3) without first passing through the filter (4). The base (30) may be integral to the upper container (2), or the lower container (3), or it may be a separate component joining the two containers.

The filter (4) can be a ceramic gravity-fed filter that is commercially available. These ceramic filters (4) are capable of removing bacteria such as Klebsiella terrigena and E. coli, as well as protozoa such as Cryptosporidium oocysts. The filter (4) may also contain activated carbon to reduce organic species found in untreated drinking water sources. The activated carbon is not required, but may be added for enhancing the taste and odor of the treated water.

The outlet of the ceramic filter (4) passes through the base (30) and leads to the inlet of the purification cartridge (5), as illustrated in FIGURE 2. A threaded nipple (31) at the bottom of the ceramic filter (4) provides an outlet for water that has flowed through the ceramic filter (4). This nipple (31) is passed through an aperture (8) in the center of the detachable mounting cap (24) of the purification cartridge (5). The mounting cap (24) and aperture (8) are illustrated in FIGURE 3A. Water exiting the nipple flows into an upper chamber (19) of the purification cartridge (5), as illustrated in FIGURE 2. The nipple (31) may project more than halfway down into this upper chamber (19).

Since the mounting cap (24) is detachable from the main body (10) of the purification cartridge (5), it is initially placed over the nipple (31) without the main body (10) of the purification cartridge (5) attached. This allows a nut (not shown) to be threaded onto the nipple (31), holding the mounting cap (24) firmly against a sealing washer (32). This creates a watertight seal between the ceramic filter (4) and the mounting cap (24).

The main body (10) of the purification cartridge (5) forms a watertight seal with the mounting cap (24) by incorporating an O-ring (1 1), as illustrated in FIGURE 4. This O-ring (1 1) seats in a groove between a pair of rings (13) around the upper end of the main body (10). The adjoining portion of the mounting cap (24) consists of an annular ring (16) projecting downward. The inner diameter of the annular ring (16) is slightly larger than the outer diameter of the rings (13) on the main body (10), permitting the rings (13) to fit inside the annular ring (16). When the main body (10) is inserted into the mounting cap (24), the O-ring creates a watertight seal preventing water from bypassing the purification cartridge (5).

A flange (12) welded, molded or otherwise attached to the main body (10), projects outward as a flat surface below the rings (13). This flange (12) includes keyhole slots (7) spaced equidistant from one another. A keyhole slot may have a wider opening followed by a narrower opening to allow a device to lock into place. Mating to the keyhole slots (7) in the flange (12) of the main body (10) are tabs (14) positioned around the outer diameter of the mounting cap (24). The tabs (14) project downward and include flared ends (15) that can pass through the wider opening of the keyhole slots (7), but not the narrower opening. By inserting the flared ends (15) through the wider opening of the keyhole slots (7) and applying a twisting motion, the tabs (14) slide into the narrower opening and the two pieces are locked together, with the O-ring creating a watertight seal. The ability to disconnect the main body (10) from the mounting cap (24) allows for replacing the purification media (17), the adsorptive media (18), or the entire main body (10) may be exchanged for a new unit.

In one possible configuration illustrated in FIGURE 2, the main body (10) of the purification cartridge (5) is divided into three chambers: the upper chamber (19), middle chamber (33), and lower chamber (34). Water is allowed to pass by gravity from chamber to chamber before exiting the purification cartridge (5) and accumulating in the lower container (3) of the system.

As illustrated in FIGURE 5, the upper chamber (19) remains empty, while the middle chamber (33) contains purification media (17) and the lower chamber (34) houses the adsorptive media (18). The three chambers are in concentric alignment, sharing the same center axis. This permits the main body (10) to be built from a single molded plastic piece, such as a cylindrical shape with an open top and bottom. The three chambers can share the same cylindrical outer wall of a single diameter, or, alternatively, any chamber can be made a different diameter to accommodate a different volume. In other embodiments, the main body can be formed from other shapes and alignments.

Referring to the cross-sectional view of the purification cartridge (5) in FIGURE 4, it is illustrated that the upper chamber (19) is separated from the middle chamber (33) of the main body (10) by a porous barrier (22). This porous barrier (22) may include a porous mesh (35) co-molded with a plastic support frame and serves to contain the purification media (17) within the middle chamber (33). The support frame may be formed integral with the main body or may be a separate component. The mesh may be integral to the frame or may be a separate component. Other configurations of a porous barrier are also envisioned as part of this disclosure.

The middle chamber (33) is separated from the lower chamber (34) by the intermediate porous barrier (23). This intermediate porous barrier (23) can be a rigid mesh, semi-rigid porous material, a plastic screen, or other similar embodiments. It may be attached to a seat or ring inside the main body (10). The porous barrier (23) prevents the purification media (17) in the middle chamber (33) from mixing with the adsorptive media (18) in the lower chamber (34).

There is also a porous barrier (9) at the bottom of the lower chamber (34). This porous barrier (9) may be a porous mesh material co-molded with a plastic frame, similar to the porous barrier (22) separating the upper chamber ( 19) from the middle chamber (33). It may be removable from the purification cartridge (5), as shown in FIGURE 6, where the porous barrier (9) attaches by a snap fit to the lower end of the main body (10). The snap fit is achieved by a grooved ring (21) projecting upward from a horizontal frame piece on the porous barrier (9), which mates to a circumferential bump (20) formed around the inside of the bottom end of the main body (10). The porous barrier (9) is attached to the main body (10) by pressing the two parts together until the bump snaps into the groove.

The purification media (17) in the middle chamber (33) is an N-halamine compound that acts as a contact biocide to inactivate viruses such as poliomyelitis, rotavirus, and MS2. The middle chamber (33) empty bed contact time, defined as V/Q, should be at least 0.9 minutes. Water leaving the middle chamber (33) after contact with the purification media (17) may contain residual levels of halogen, which are reduced when the water then flows through the adsorptive media (18) in the lower chamber (34).

The purification media (17) referred to here can include any of the compounds known as N-halamines disclosed in any of U.S. Patent Nos. 5,490,983; 5,670,646;

5,889,130; 6,020,491 ; 6,294,185; 6,548,054; 7,441,665; and U.S. Patent Application

Publication No. 2008/0202992. All patents and applications are expressly incorporated by reference. These N-halamines are cyclic groups comprised of 4- to 7-membered rings.

At least three members of the ring are carbon, up to two of which may form a carbonyl group. One to three members of the ring are nitrogen heteroatom, and the ring may also contain one oxygen heteroatom. Representative N-halamine groups include, but are not limited to halogenated hydantoins, oxazolidinones, and imidazolidinones.

N-halamine and precursor groups can be incorporated into polymers by functionalizing the group with a polymerizable moiety such as a vinyl group. (A precursor refers to the amine group without halogen.) Alternatively, a polymer, such as polystyrene, can be modified to introduce the N-halamine or precursor groups on the polymer. N-halamines provide purification when microorganisms become inactivated after coming into contact with halogen atoms bound to the nitrogen atoms of the cyclic amines. The halogen can include chlorine, bromine, or both. The purification media (17) may be a loose powder, as described in U.S. Patent No. 5,490,983, but preferably it is in the form of larger particles, such as the beads described in U.S. Patent Nos. 6,548,054 and 7,687,072.

Representative purifying media (17) includes, but is not limited to, compounds selected from a heterocyclic N-halo amine, an N-halo hydantoin, a polystyrene having pendent N-halo hydantoin groups, or a crosslinked polystyrene having pendent N-halo hydantoin groups. Representative chemical formulae of the purifying media (17) include, but are not limited to, the following structures: Structure I:

Rj and R-2 are independently selected from Cj-C4 alkyl, phenyl, and aryl, and X must be chlorine or bromine for the polymer to be biocidal.

Structure II:

X and X' are independently chlorine, bromine, or hydrogen. At least one of X or X' must be chlorine or bromine for the polymer to be biocidal. R₃ is hydrogen or methyl.

The polystyrene polymer of either Structure I or Structure II may be crosslinked using an agent, such as divinylbenzene, to form a particle size range large enough to allow for retention on a porous barrier material. The crosslinking agent can be present in an approximate amount from 3% to 10% by weight of the total weight of the chosen polymer (Structure I or Structure II). One form of the purifying media (17) is a 3% to 10% crosslinked Structure I or II, where X is bromine in Structure I, or either one or both of X and X' is bromine in Structure II.

As the halogen, X of Structure I and X and/or X' of Structure II, is consumed during water treatment, it may be replenished by the addition of small doses of halogen to the untreated water. Halogen from the water is transferred to the precursor N-halamines to any one or both positions X and X'. By continuously or intermittently introducing halogen in contact with the purification media (17), N-halamines can be recharged with halogens to regain biocidal efficacy once depleted, or to maintain biocidal efficacy indefinitely.

After passing through this purification media (17), the treated water may contain halogen, such as chlorine or bromine, that can be removed by the adsorptive media (18) housed in the lower chamber (34) of the purification cartridge (5). Adsorptive media (18) can include, but is not limited to, carbon granules, activated carbon, and other similar materials. The amount of adsorptive media (18) contained in the lower chamber (34) is adequate to reduce the residual halogen released from the purification media (17) to less than 1 ppm and will maintain this performance for approximately 1,000 to 3,000 N-halamine bed volumes. N-halamine purification media (17) is believed to work by contact, and is not designed to release halogen for purification. Therefore, the adsorptive media (18) is optional for applications in which it is desirable to reduce the amount of halogen present in the treated water that has been released from the purification media (17).

After contact with the adsorptive media (18), treated water flows through the porous barrier (9) located at the outlet of the purification cartridge (5) and collects as purified water in the lower container (3).

EXAMPLES

A purification cartridge as disclosed above was tested for efficacy. A gravity feed system as described in FIGURE 1 was assembled using a commercially available diatomaceous ceramic filter (Doulton Sterasyl) attached to the N-halamine device as described in FIGURES 1-8. The appropriate amount of brominated N-halamine disinfecting media (30 cc of HaloPure BR, HaloSource Inc.) was filled in the appropriate cavity (FIGURE 4, #33) followed by filling the downstream chamber (FIGURE 4, #34) with commercially available 12x40 coconut-based activated carbon granules (3 grams of Calgon Carbon Corp.). Dechlorinated city tap water containing 10⁶ cfu/ml of E. coli (ATCC# 1 1229) and 10⁴ pfu/ml of MS2 bacteriophage ((#15597-B1) was used throughout the experiment. On a daily basis the upper reservoir was filled with the challenge water and water allowed to percolate through the ceramic body and N-halamine device. Periodically, samples were taken to measure the bacterial and viral efficacy as well as measure the residual bromine in the treated water using a HACH Spectrophometer 2800.

Table 1

Table 1 shows residual halogen and microbial efficacy data from an enhanced

N-halamine based water treatment device. Water samples were taken directly from the outlet of the device. Volume is measured in liters (L), halogen is measured in parts per million (ppm), microbial counts are measured in colony forming or plaque forming units per milliliter (cfu/mL, pfu/mL) and microbial efficacy is measured in log reduction value (LRV). Bacterial efficacy was calculated using pour plate dilutions onto Endo agar followed by incubation for 24 hours at 37°C. Colonies were hand counted to quantify cfu/ml of challenge and treated water. The log reduction reported in the log-base 10 difference between the challenge and the treated water. Viral efficacy was calculated using E. coli (ATCC #15597) as the infected strain as MS2 cannot be directly counted. Efficacy was calculated using pour plate dilutions onto agar followed by incubation for 24 hours at 37°C; after which the number of plaques was counted. The log reduction reported in the log-base 10 difference between the challenge and the treated water.

While illustrative embodiments have been illustrated and described, it will be appreciated that various changes can be made therein without departing from the spirit and scope of the invention.

Claims

CLAIMS The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A cartridge, comprising:

a first chamber having first and second openings on opposite ends and containing a N-halamine compound within;

a second chamber having third and fourth openings on opposite ends and containing adsorptive media within;

a first porous barrier separating the first chamber from the second chamber; and a second porous barrier at one opening of the second chamber, wherein the second chamber is juxtaposed next to the first chamber.

2. The cartridge of Claim 1, wherein the second chamber is concentrically aligned with the first chamber.

3. The cartridge of Claim 2, further comprising a third chamber having fifth and sixth openings on opposite ends and is empty of water treatment chemicals, wherein the third chamber is juxtaposed next to and is concentrically aligned with the first chamber, and a third porous barrier separating the third chamber from the first chamber.

4. The cartridge of Claim 3, further comprising a mounting cap attached to the cartridge, a watertight seal between the mounting cap and the third chamber, and an opening in the mounting cap that exits into the third chamber.

5. The cartridge of Claim 4, wherein the mounting cap is detachable from the cartridge.

6. The cartridge of any one of Claims 1 to 5, comprising carbon in the second chamber.

7. The cartridge of any one of Claims 1 to 5, comprising a brominated N-halamine compound in the first chamber.

8. The cartridge of any one of Claims 1 to 5, wherein the first chamber empty bed volume is at least 0.9 minutes.

9. The cartridge of any one of Claims 1 to 5, wherein the N-halamine compound is a polymer having the formula:

wherein R₁ and R.2 are independently selected from C1-C4 alkyl, phenyl, and aryl, and X is chlorine or bromine.

10. The cartridge of Claim 9, wherein X is bromine.

1 1. The cartridge of Claim 9, wherein the polymer is a crosslinked polymer.

12. The cartridge of any one of Claims 1 to 5, wherein the N-halamine compound is a polymer having the formula:

wherein X and X' are independently chlorine, bromine, or hydrogen, provided that at least one of X or X' is chlorine or bromine; and R₃ is hydrogen or methyl.

13. The cartridge of Claim 12, wherein the polymer is a crosslinked polymer.

14. The cartridge of Claim 12, wherein at least one of X or X' is bromine.

15. A water purification system, comprising:

(i) an upper container;

(ii) a lower container;

(iii) a base separating the upper container from the lower container;

(iv) a filter in the upper container;

(v) a cartridge in the lower container, the cartridge comprising:

(d) a second porous barrier at one opening of the second chamber, wherein the second chamber is juxtaposed next to and is concentrically aligned with the first chamber, wherein the second porous barrier exits to the lower container;

(f) a third porous barrier separating the third chamber from the first chamber;

(g) a mounting cap attached to the cartridge;

(h) a watertight seal between the mounting cap and the third chamber; and (j) an opening in the mounting cap that opens into the third chamber;

16. The water purification system of Claim 15, wherein the mounting cap is detachable from the cartridge.

17. The water purification system of Claim 15 or 16, comprising carbon in the second chamber.

18. The water purification system of Claim 15 or 16, comprising a brominated N-halamine compound in the first chamber.

19. The water purification system of Claim 15 or 16, comprising a first chamber empty bed volume of at least 0.9 minutes.

20. The water purification system of Claim 15 or 16, wherein the N-halamine compound is a polymer having the formula:

wherein Rj and R/j are independently selected from C1-C4 alkyl, phenyl, and aryl, and X is chlorine or bromine.

21. The water purification system of Claim 20, wherein X is bromine.

22. The water purification system of Claim 20, wherein the polymer is a crosslinked polymer.

23. The water purification system of Claim 15 or 16, wherein the N-halamine compound is a polymer having the formula:

24. The water purification system of Claim 23, wherein the polymer is a crosslinked polymer.

25. The water purification system of Claim 23, wherein at least one of X or X' is bromine.

26. A method for producing potable water from a gravity fed system, the system including an upper container separated from a lower container, the method comprising:

filtering water from the first container and delivering the filtered water to a cartridge in the second container;

treating the filtered water with a N-halamine containing compound in a first chamber of the cartridge to produce purified water;

removing residual halogen from the purified water with an adsorptive media in a second chamber of the cartridge to produce potable water; and

delivering the potable water from the second chamber to the lower container.

27. The method of Claim 26, wherein the adsorptive media in the second chamber is carbon.

28. The method of Claim 26, wherein the N-halamine containing compound in the first chamber is brominated.

29. The method of Claim 26, wherein the first chamber empty bed volume is at least 0.9 minutes.

30. The method of Claim 26, wherein the N-halamine containing compound is a polymer having the formula:

wherein Rj and R2 are independently selected from CJ-C4 alkyl, phenyl, and aryl, and X is chlorine or bromine.

31. The method of Claim 30, wherein X is bromine.

32. The method of Claim 30, wherein the polymer is a crosslinked polymer.

33. The method of Claim 26, wherein the N-halamine containing compound is a polymer having the formula:

34. The method of Claim 33, wherein the polymer is a crosslinked polymer.

35. The method of Claim 33, wherein at least one of X or X' is bromine.