FRANDSEN, Mikkel, Vestergaard (Rue de Mercerie 14, Lausanne, CH-1003, CH)
CLAIMS
1. A water purification unit having a number of compartments for water flow success- sively through these compartments, the unit comprising - a compartment with an iodine releasing resin for killing microbes in water,
- a downstream compartment with an iodine scavenger, the iodine scavenger being configured for releasing chlorine during iodine scavenging, the amount of released chlorine being configured for oxidation of trivalent arsenide to pentavalent arsenide,
- a further downstream compartment with a arsenide removal resin configured for re- moval of arsenide from the water.
2. A water purification unit according to any preceding claim, wherein the iodine scavenger resin is a strong ion exchange resin.
3. A water purification unit according to claim 2, wherein the iodine scavenger resin is a strong base anion exchange resin.
4. A water purification unit according to claim 3, wherein the strong base anion exchange resin comprises activated alumina.
5. A water purification unit according to claim 4, wherein the activated alumina is provided in the commercial resin AAFS50.
6. A water purification unit according to any one of the claims 3-5, wherein the strong base anion exchange resin comprises ferric oxide.
7. A water purification unit according to claim 6, wherein the strong base anion exchange resin comprises the commercial resin AD33R or AD33L.
8. A water purification unit according to any preceding claim, wherein a void space is provided between the compartment with the iodine releasing resin and compartment with the iodine scavenging resin, the void space having a volume configured for substantial extension of the reaction time between the iodine and water contaminants.
9. A water purification unit according to claim 8, wherein the void space has a volume comparable to the volume of the compartment with the iodine releasing resin.
10. A water purification unit according to any preceding claim, wherein a compartment is provided with activated carbon for iodine removal.
11. A water purification unit according to claim 10, wherein the activated carbon is silver loaded.
12. A water purification unit according to claim 10 or 11, wherein the compartment with activated carbon is downstream of the iodine scavenging resin.
13. A water purification unit according to claim 10 and 11, wherein the activated carbon is mixed with the iodine scavenger resin.
14. A water purification unit according to any one of the claims 10-13, wherein the activated carbon is located upstream of arsenic removing compartment.
15. A water purification unit according to any preceding claim, wherein the unit comprises a compartment containing Dowex™ Marathon™ A.
16. A water purification unit according to any preceding claim, wherein the unit is portable unit.
17. A water purification unit according to claim 16, wherein the unit is tubular.
18. A water purification unit according to claim 17, wherein the unit has length of less than 40 cm.
19. A water purification unit according to claim 18, wherein the unit has length ofless than 35 cm.
20. A water purification unit according to one of the preceding claims 16-19, wherein the unit has diameter of less than 50 mm.
21. A water purification unit according to claim 20, wherein the unit has diameter of less than 40 mm.
22. A water purification unit according to any one of the preceding claims 16-20, wherein the unit has a mouth peace for sucking of water through the unit
23. A water purification unit according any preceding claim, wherein the amount and efficiency of the iodine releasing resin is configured to release a certain amount of iodine in the water, the amount and efficiency of the iodine scavenger resin is configured in dependence of the certain amount of iodine to release a certain amount of chlorine in the water, the certain amount of chlorine is configured for oxidation of a sub- stantial amount of arsenide at an arsenide content in the water of the order of up to 2000 parts per billion
24. A water purification unit according to claim 23, wherein the substantial amount of arsenide is more than 50 %.
25. A water purification unit according to claim 24, wherein the substantial amount is higher than 99%
26. A water purification unit according to claim 25, wherein the substantial amount is higher than 99.9%.
27. A water purification unit according to claim 23, wherein the substantial amount is all arsenic in excess of at most 10 parts per billion.
28. A water purification unit according to any preceding claim, wherein the amount of iodine releasing resin is between 5 and 30 % of the inner volume of the unit.
29. A water purification unit according to any preceding claim, wherein the amount of iodine releasing resin is between 15 and 25 % of the inner volume of the unit.
30. A water purification unit according to any preceding claim, wherein the amount of iodine scavenger resin is between 5 and 40 % of the inner volume of the unit.
31. A water purification unit according to any preceding claim, wherein the amount of iodine releasing resin is between 20 and 30 % of the inner volume of the unit.
32. A water purification unit according to any preceding claim, wherein the amount of arsenic removing resin is between 5 and 50 % of the inner volume of the unit.
33. A water purification unit according to any preceding claim, wherein a compartment is provided with activated carbon for iodine removal and the amount of activated carbon is between 5 and 50 % of the inner volume of the unit.
34. A water purification unit according to claim 33, wherein the amount of activated carbon is between 20 and 40 % of the inner volume of the unit.
35. A water purification unit according to any preceding claim, wherein the unit is a portable unit with a mouthpiece for sucking water through the unit, the length of the unit is less than 40 cm, the diameter is less than 50 mm, the amount of iodine releasing resin is between 5 and 50 % of the inner volume of the unit, the amount of iodine scavenger resin is between 5 and 50 % of the inner volume of the unit, the amount of arsenic removing resin is between 5 and 50 % of the inner volume of the unit.
36. A water purification unit according to claim 35, wherein the length of the unit is around 25 cm, the diameter is around 30 mm, the amount of iodine releasing resin is between 10 and 30 % of the inner volume of the unit, the iodine scavenger resin is a strong base anion exchange resin with a volume between 10 and 30 % of the inner volume of the unit, the arsenic removing resin is AD33 or AAFS50 or a mixture of AD33 or AAFS50 with a volume of between 5 and 50 % of the inner volume of the unit.
37. A water purification unit according to claim 36 or 37, wherein a compartment is provided with activated carbon for iodine removal and the amount of activated carbon is between 5 and 50 % of the inner volume of the unit.
38. A water purification unit according to claim 38, wherein the amount of activated carbon is between 20 and 40 % of the inner volume of the unit.
39. A water purification unit according to claim 38 or 39, wherein the activated carbon is silver loaded.
40. A method for purification of water, the method comprising establishing a flow of water through a number of successive compartments,
- providing a compartment with an iodine releasing resin and killing microbes in water with the released iodine, - providing a downstream compartment with an iodine scavenging resin, the iodine scavenging resin releasing chlorine during iodine scavenging,
- oxidizing trivalent arsenide to pentavalent arsenide with the chlorine released from the resin
- providing a further downstream compartment with an arsenide removal resin and removing arsenide from the water by the arsenide removal resin. |
Water purification including arsenic removal
FIELD OF THE INVENTION
The present invention relates to portable systems and methods for removing arsenide from ground water
BACKGROUND OF THE INVENTION
Arsenic is a naturally occurring contaminant found in a large number of ground wa- ters, for example in Bangladesh and a number of states in the US. Being without odour and taste, no warnings are typically recognised during consumption of arsenic containing water. Especially in Bangladesh, many people are suffering from chronic poisoning appearing with painful, disturbed skin pigmentation and calluses on the palms and the hands. For example, according to information on the Internet site http://www.sos- arsenic.net, in India, 48.7% water smaples had arsenic concentration above 10 ppb and 23.8% above 50 ppb. In Bangladesh these values were 43.0% and 31.0% respectively. Almost 9 million people in India was drinking water with more than 10 ppb arsenic and 7 million people with more than 50 ppb arsenic. These facts have resultet in an increased focus on low cost but efficient means for arsenic removal from ground wa- ter.
Typical removal of arsenic from water implies ferric and aluminium oxides. Companies as Alcan® and Adedge® have developed systems with resins containing such oxides for arsenic removal.
Normally, arsenic occurs in water in trivalent form and in pentavalent form, where the trivalent Arsenite As +3 form is regarded as more toxic, whereas the pentavalent Arsenate form As +5 is easier to remove. Therefore, As +3 is oxidised to As +5 in conventional processes in order to remove the entire As content to below certain levels, typically to less than 10 micrograms per litre corresponding to 10 ppb (parts per billion).
A system for As removal from ground water is disclosed in US patent No. 6,461,535 by de Esparza. In this case, a clay, a coagulant, such as ferric chloride and aluminium sulphate, and an oxidizer, such as calcium hypochlorite, are used for adsorbing the arsenic onto the coagulated colloidal mixture. In order for the clay to settle from the water before use of the water, a waiting time of 15-20 minutes are necessary.
A different system is disclosed in European patent application EP 1 568 660 for removing As with a strong base anion exchange resin comprising at least one metal ion or metal-containing ion whose arsenate salt has a K 31 , no greater than 10 "5 .
In rural areas, where clean drinking water is scarce, a commercially available water purification suction unit has achieved increases popularity. The unit is marketed under the name LifeStraw® by the Vestergaard Frandsen Group. The unit is used for water filtration by sucking water from the water source directly through the unit and into the mouth. The suction unit is compact and has a mouth piece, measures only 25 cm in length and 29 mm in width, and acts instantaneous in order for the water sucked through the unit to be safe for human consumption. The unit contains a specially developed halogen-based resin that is extraordinarily effective to kill bacteria, for example bacteria, such as Shigella, Salmonella, Enterrococus, Staphylococcus Aureus and E .CoIi, on contact, a textile pre-filters to remove particles larger than to 6 microns, and activated carbon to withhold excessive iodine and bad smell & taste. This unit removes efficiently disease causing micro organisms which spread diarrhoea, dysentery, typhoid, and cholera. Though having a number of advantages, namely the ability of almost instantaneous cleaning of the water, the light weight, portable construction, the low cost of the device making it suitable for distribution in poor regions, it is not useful for removing arsenide from water.
DESCRIPTION / SUMMARY OF THE INVENTION
It is therefore the object of the invention to provide a compact water cleaning device, preferably in the format of LifeStraw®, which is also suitable for removal of arsenide.
This purpose is achieved by a water purification unit having a number of compartments for water flow successively through these compartments, the unit comprising
- a compartment with an iodine releasing resin for killing microbes in water,
- a downstream compartment with an iodine scavenger, the iodine scavenger being configured for releasing chlorine during iodine scavenging, the amount of released chlorine being configured for oxidation of trivalent arsenide to pentavalent arsenide, - a further downstream compartment with a arsenide removal resin configured for removal of arsenide from the water.
With a purification unit according to the invention, a compact device is provided, for not only cleaning water on a general basis but also for removing arsenic. The compact property is achieved by using the chlorine — which in LifeStraw® is a waste product — for successful oxidation of arsenic in order to facilitate removal of arsenic. Thus, no additional substances are required for oxidising arsenic, which is in contrast to prior art techniques, where a variety of substances is added for the oxidation of arsenide. Thus, the invention utilises a combination of knowledge from entirely different fields, namely the know-how of cleaning water in primarily poor tropical countries with compact, portable units like LifeStraw® and the know-how of arsenic removal in modern household apparatuses or larger facilities.
It should be acknowledged that the invention by rather low cost makes it possible for economically poor regions not only to get access to biologically cleaned water but also access to arsenic free water at the same time. The LifeStraw® product is already experiencing increased popularity in remote regions with difficult access to clean water, and an extended LifeStraw® product with arsenic removal capabilities would not imply much higher costs for the end user. The fact of providing in remote regions such a compact, low cost product with high quality decontamination properties including removal of arsenic, is in sharp contrast to the statement in US patent No. 6,461,535 col. 1 line 49 to 57 "The removal of chemical elements such as arsenic from water, however, requires resort to more sophisticated processes. In developed countries, reverse osmosis, ion exchange, and activated carbon are conventional techniques used in purifying water in large agglomerations. However, the above conventional techniques for removing impurities, such as arsenic from ground water, are generally prohibitive or unavailable to small populations living in remote dwellings."
By the invention, both ion exchange and activated carbon can be used, as it will becomes apparent in the following, at costs and with a compactness that does not prevent access to clean water in remote dwellings and in even very poor regions. Thereby, spreading of diseases following bad drinking water can be drastically reduced, espe- cially, if governments and non-governmental organisations support the distribution of such compact devices among people in poor regions.
However, it should be noted that application of the invention is not limited to poor and remote regions but may be used in a variety of other applications. For example, due to its compactness, it is suited for general outdoor activities as well. Especially, in US mountainous regions, where water appears clean at first sight and suitable for drinking, but contains the odourless, tasteless and dangerous arsenic, the user may be sure that the light weight, portable unit, such as an extended, arsenic removing LifeStraw®, prevents later suffering from arsenic induced illness due to the double function of the invention, where biological and chemical cleaning is performed at the same time at a degree which makes direct drinking through a unit according to the invention possible.
In a preferred embodiment, the iodine scavenger resin is a strong ion exchange resin, for example a strong base anion exchange resin. Choosing such a resin promotes the compactness of the unit. It is well known to use activated carbon for iodine removal. However, this substance is not as efficient as strong ion exchange resins and rather large quantities are required. In order to achieve a compact unit, especially in the case of the LifeStraw® product, a strong base anion exchange resin has been investigated instead. The use of this resin, as described above, opens the possibility for arsenic oxidation without loosing compactness.
One possibility is an arsenic removing resin that comprises activated alumina, for example as known from the commercially available Alcan® resin named AAFS50. Alternatively, the arsenic removing resin comprises ferric oxide, for example as known from the commercial Adedge® resins named AD33R or AD33L. These commercially available resins contain substances for arsenic oxidation themselves. Thus, in case that the invention is used together with these commercial resins, the chlorine oxidation of As(III) to As(V) may be used to reduce the amount of these commercial resins, such that primarily the As(V) removal property is utilised. A reduction of the amount of such commercial resins is of high interest due to the substantial costs of these resins.
For this reason also, a thin layer of ferric oxide, possibly enriched with or substituted by aluminium oxide, is considered as a useful solution.
The iodine needs to be active for a certain time in order to achieve a good result with respect to biological cleaning. The active time depends on the flow from the iodine releasing resin to the iodine scavenger. In the case of LifeStraw®, where water is sucked directly through the compact unit by the mouth for drinking from a contaminated water source, the activation time may be necessary to be extended, which can be achieved by including a void space between the iodine releasing resin and the iodine scavenger resin. The volume of the void space should in this case be chosen to provide a substantial extension of the reaction time between the iodine and water contaminants during the water flow through the volume typical for the device when sucked by a mouth. The term "substantial extension" covers an extension of the flow time which, typically, is in the order of the flow time through the iodine releasing resin compart- ment. Thus, the void space may have a volume comparable to the volume of the compartment with the iodine releasing resin. For the LifeStraw product, the flow time is 100-150 ml/minute, which is also feasible for the invention in the case of a comparable design.
In addition to remove excess chlorine and other taste or odour properties of the cleaned water, a compartment may, optionally, be provided with activated carbon for iodine removal, for example in the form of granular activated carbon (GAC). Optionally, the GAC may be silver loaded.
The activated carbon may be used downstream of the iodine scavenging resin. This configuration has the advantage that the scavenging resin primarily takes up the iodine and releases correspondingly chlorine for the arsenic oxidation, for example in the form of hypochlorite with a large amount of active chlorine. Alternatively, the activated carbon is mixed with the iodine scavenger resin. In this case, the activated car- bon takes up part of the iodine without release of chlorine. Thus, by mixing activated carbon, which is able to take up iodine without release of chlorine, and the iodine scavenger resin that is able to release chlorine as a result of the uptake of iodine, a desired ratio between the uptake of iodine and the release of chlorine may be achieved in accordance with predetermined amounts necessary for a proper arsenic oxidation on
the one hand and a long term, low cost functioning of the device on the other hand, securing sufficient iodine release and removal.
As activated carbon also takes up chlorine, it has to be ensured that the chlorine is in the water for a time sufficiently long enough to assure a proper conversion of As(III) to As(V). Therefore, it is preferred to provide the activated carbon upstream of the arsenic removing compartment.
The invention can be employed in a number of physical embodiments. However, the preferred solution utilising the potential for high compactness, is a portable water purification unit, for example tubular as the LifeStraw® product. In order to be carried around, the unit is advantageously shorter than 40 cm, or even shorter than 35 cm. For example, LifeStraw® has a length of 25 cm, a width of 29 mm, and a dry weight of 95 grams. Accordingly, the unit in the portable embodiment is preferred to have a diame- ter of less than 50 mm, rather less than 40 mm. Such a tube may be provided with a mouth peace for sucking of water through the unit, just like LifeStraw®.
The amount and efficiency of the iodine releasing resin should be adjusted to achieve a certain arsenic removal, for example down to a level of less than 10 ppb. The amount of resin necessary to achieve this is dependent on the arsenic content in the water, and the final arsenic level to be achieved. Thus, the unit according to the invention may be configured to release a certain amount of iodine in the water; the amount and efficiency of the iodine scavenger resin may then be configured - in dependence of the certain amount of iodine - to release a certain amount of active chlorine in the wa- ter; this certain amount of active chlorine is configured for oxidation of a substantial amount of arsenide. For safety reasons, despite a possibly low amount of arsenic, the resin may be configured for secure working also at high contents of arsenic, for example of the order of up to 1000 or 2000 parts per billion. In comparison, it may be mentioned that the level of arsenic in many water sources in Bangladesh is 1200 ppb ex- ceeding by far the admissible limit of 50 ppb for the Bangladesh drinking water.
The unit according to the invention may use the aforementioned removal of arsenic as a pre-stage for a second removal stage. For example, the iodine scavenger may release sufficient chlorine to remove more than 50% of the arsenic, for example 99% or even
99.9% of it. Whereas in a second stage, for example, comprising the aforementioned AD33 from Adedge® or AFSS50 from Alcan®, the remaining arsenic content may be removed to a very low degree.
A multiple stage arrangement may be useful in the case, where a first product is used for removing the first part of arsenic, for example 95%, and the second stage is used to reduce the content to a very low degree. The reason for using two stage removal could be that the first product is by far cheaper than the second product. Thus, a low cost first stage may be used for removing the first coarse arsenic content, whereas the sec- ond, more expensive stage may be used to remove the last part of the arsenic below a predetermined level, such as 10 ppb.
For example, it has been disclosed in Shaban W. Al Rmalli et al. "A biomaterial based approach for arsenic removal from water" published in J. Environ. Monit. , 2005, 7, 279-282 that biological material can be used for arsenic removal. Biological material such as dried roots of the water hyacinth plant (Eichhornia crassipes) can remove arsenic from water. In the article, examples are given for 96% arsenic removal. Though the removal speed was rather slow, namely 30 minutes for 80% removal and 60 minutes for 96% removal of arsenic, the results are promising and have a potential for improvement of the arsenic removal properties. Such low cost, biological material may be considered as a candidate for a first stage for arsenic removal as discussed above.
Further interesting material for arsenic removal is available from the US company VeeTech, P. C. under the commercial names G2 and HIX. These products may be candidates for a single step arsenic removal or in a two stage arsenic removal system according to the invention.
Whether only one stage is used or whether two or more stages for arsenic removal are used, the aim is to reduce the arsenic to below a very low level, for example the Internationally recognised lower level of 10 parts per billion.
In order to leave an impression of the relative amounts of resins in the unit according to the invention, the following typical numbers are helpful. Thus, the amount of iodine
releasing resin is, typically, between 5 and 30 %, preferably between 15 and 25 %, of the inner volume of the unit. The amount of iodine scavenger resin is, typically, between 5 and 40 %, preferably, between 20 and 30 % of the inner volume of the unit. The amount of arsenic removing resin is, typically, between 5 and 50 % of the inner volume of the unit. If present, the amount of activated carbon is, typically, between 20 and 40 % of the inner volume of the unit.
In comparison with the LifeStraw® product, a preferred water purification unit according to the invention is a portable unit with a mouthpiece for sucking water through the unit, the length of the unit is less than 40 cm, the diameter is less than 50 mm. The amount of iodine releasing resin is between 5 and 50 % of the inner volume of the unit, the amount of iodine scavenger resin is between 5 and 50 % of the inner volume of the unit, and the amount of arsenic removing resin is between 5 and 50 % of the inner volume of the unit.
In a further preferred solution, the water purification unit has a length of around 25 cm and a diameter of around 30 mm. The amount of iodine releasing resin is between 10 and 30 % of the inner volume of the unit, the iodine scavenger resin is a strong base anion exchange resin with a volume between 10 and 30 % of the inner volume of the unit, and the arsenic removing resin is AD33 or AAFS50 or a mixture of AD33 or AAFS50 with a volume of between 5 and 50 % of the inner volume of the unit. In addition, the purification unit may comprise a compartment with activated carbon for iodine removal. The amount of activated carbon is between 5 and 50 %, or rather between 20 and 40% of the inner volume of the unit. The carbon may be silver loaded.
As iodine releasing resin, a number of products are on the market as well as for the iodine scavenger. Promising results have been achieved by using Dowex™ Marathon TM A produced by Dow Chemical.
All the above mentioned different embodiments may be included in a method for purification of water, the method comprising establishing a flow of water through a number of successive compartments,
- providing a compartment with an iodine releasing resin and killing microbes in water with the released iodine,
- providing a downstream compartment with an iodine scavenging resin, the iodine scavenging resin releasing chlorine during iodine scavenging,
- oxidizing trivalent arsenide to pentavalent arsenide with the chlorine released from the resin - providing another compartment with an arsenide removal resin; thus removing arsenide from the water by the arsenide removal resin.
A unit according to the invention is preferably dimensioned so as to be a portable filter unit, especially with a mouthpiece and dimensions as the LifeStraw® product. How- ever, other dimensioning is possible. Also, instead of a mouthpiece the unit may be provided with tubing for a controlled water flow and proper connection, such as in a household filter unit.
The unit according to the invention may be used as part in a water bag, where extrac- tion of the water from the water bag is through a unit according to the invention. The extraction may occur by actively sucking water out of the bag, by exerting pressure on the bag, or the extraction may occur by gravity, a principle known from the products Katadyn Camp® and the Katadyn Siphon® made by the Swiss company Katadyn Pro- dukte AG.
An additional cleaning means that may be incorporated in the unit according to the invention is an ultra violet (UV) lamp, for example as it is disclosed US patent application No. 2005/258108. Such a lamp may be used in addition to the above means for cleaning the water. For example, the UV LED (Light Emitting Diode) lamp may be used for disinfection under those circumstances, where the chemistry in the unit is not sufficient. Thus, with relatively little chemistry inside the unit, the unit may still be able to perform satisfactory, even when the contamination suddenly overshoots expectations for contamination levels.
An on-off procedure of an UV LED requires some means for measuring the actual contamination level or means for registering the lack of total removal of contaminants. The latter may be performed with an electronic circuit, the conduction through which is governed by the contamination. In this case, there has to be taken into regard the amount of ions present in the water due to released cleaning agents. However, after a
GAC section, the water is believed to should have been cleaned and a high conduction in the water would indicate an unsatisfactory cleaning.
An electronic circuit in the unit, for example at the exit side, may as well be used for indicating, whether the cleaning process is satisfactory within predetermined levels on a general basis. For example, a small electronic circuit and a battery or solar cell may be used to illuminate a lamp or to change colour of an indicator in order to show missing function, for example when the chemical products are exhausted.
SHORT DESCRIPTION OF THE DRAWINGS
The invention will be explained in more detail with reference to the drawing, where FIG. 1 illustrates a first embodiment according to the invention, FIG. 2 illustrates a second embodiment according to the invention.
DETAILED DESCRIPTION / PREFERRED EMBODIMENT
FIG. 1 illustrates a first embodiment of a unit according to the invention. The unit 1 has a water inlet 2 for inlet of a contaminated water flow 3 containing As and a water outlet 4 for 5 outflow of cleaned, arsenic-free water. The unit 1 comprises a first compartment 6 with an iodine releasing resin for release of iodine, which is illustrated by arrow 11. The iodine is primarily used for killing microbes. Water with iodine flows into a downstream compartment 7 with an iodine removing resin, where iodine is removed as illustrated by the stopping of arrow 11 and chlorine released, which is illus- trated by arrow 12. The chlorine from compartment 7 oxidizes As(III) to As(V), such that the amount of As(III) is gradually reduced, which is illustrated by the arrow 9.As(V) is removed by the arsenic removal resin in compartment 8, which is illustrated by the arrow 10.
The unit in FIG. 1 may be used for water cleaning and arsenic removal, although FIG. 1 illustrates only the basic principles and may be supplemented with other means to optimize the functioning.
An improved system is illustrated in FIG. 2. For example, the unit 1 may in addition have a chlorine removing compartment 13. The resin in this compartment 13 may be activated carbon in the granular form (GAC), optionally silver loaded. In order for the iodine to work long enough on the microbes to achieve a proper effect, there may be provided a void space 14 between the iodine resin 6 and the iodine scavenger 7, the size of the void space 14 adjusted relatively to the water flow and the predetermined necessary reaction time.
In addition, the water inlet 2 may be followed by a mechanical filter 15 in order to filter away larger particles or microbes. For example, the mechanical filter may be textile filter for removing particles or microbes with a size larger than 6 micrometer, as it is used in the LifeStraw® product. Further illustrated in FIG. 2 is a mouth piece 16 as a water outlet.
The built up of the LifeStraw® product is illustrated in FIG. 3, because the invention may be used in third design, optionally with small amendments, such as an increased length due to the added arsenic removal function. LifeStraw®, as illustrated in FIG. 1, comprises a mouthpiece 22 with a removable end cap 21 and another end cap 33 covering an inlet clip 3 in the opposite end of the tubular body 26. A thin polypropylene filter 15 covers an polyethylene bag as the water entrance with a thick polypropylene filter 28 just before a compartment filled with iodine releasing resin 29. Another filter arrangement 28, 24 with a strainer 27 is found after the iodine compartment. Separated by a void space 20, is a GAC containing compartment 25.