Figure 5 In the wilderness water purification should be carried

WILDERNESS WATER DISINFECTION

O bjectives:

Describe how to disinfect water in wilderness situations or in developing countries.

REMOVING PARTICULATE MATERIAL

River water—essentially all glacial streams—often contains a large amount of suspended particulate material that gives the water a terra cotta color. (Glacial streams are milky, gray, or grayish tan.) In the Grand Canyon and the upstream tributaries of the Colorado River the condition of the water depends on whether thunderstorms have recently occurred upstream. The water is often clear. At other times, the Colorado is described as “liquid mud,” and the silt can be removed from equipment only by vigorous scrubbing. It frequently cannot be completely removed from clothing. Following a storm, side streams are as muddy as the river.

If such water is placed in a container and allowed to stand, much of the suspended material settles, although the water may retain some color. Hours may be required. Filling the buckets in the evening allows the water to be filtered the next morning.

However, allowing the water to stand may not be necessary. River water that appears quite muddy can contain surprisingly little suspended material when viewed in small quantities such as a water bottle or bucket.

The water can be completely cleared by filtration. Filters used for disinfecting water perform this function well, but do become obstructed. A filter that can be manually cleaned is essential. For large groups a large volume filter such as the Katadyn Explorer (4 l/min) serves quite well. The filter can be removed in seconds and scrubbing it for about twenty or thirty seconds with a brush or scrubber gets rid of the obstruction. Usually two to three liters can be filtered before cleaning is necessary. The smaller MSR filter also can be easily cleaned, but can filter only about one liter between cleanings.

Other filtering devices, including cloth and coffee filters, also help remove sediment. Flocculation can be used to clear murky water, but is rarely necessary. The alum needed for flocculation may not be readily available.

DESIRABLE CHARACTERISTICS OF WATER DISINFECTION SYSTEMS

A water disinfections sys­tem for wilderness use must be:

•  Sim­ple and con­venient;

•  Rela­tive fast;

•  Small and light­weight

•  Dependable.

Wilderness adventurers do not use systems that are not simple, conve­nient, and fast. Hikers and backpackers do not carry systems that are not small and light­weight. If a sys­tem is not reli­able, it should not be used at all.

GOALS OF WATER DISINFECTION

The obvious goal of water disinfections is preventing harmful or dis­com­forting infections by water borne microor­ganisms. Interestingly, disinfection techniques for small quanti­ties of water usually kill all organ­isms that are present, unlike munici­pal water sys­tems that typical­ly moni­tor water quality by deter­mining the number of coliform or­gan­isms present.

The most common water-borne parasites that produce diarrheal diseases, are amoebae ( Entamoeba histolytica ,) giardia ( Giardia lamblia ,) and cryptosporidia ( Cryptospo-ridium parvum ). When they are elimi­nated from the body, all of these organisms form cysts that are much more resis­tant to chemical agents or heat than the unpro­tected organisms.

Amoebiasis tends to come on slowly and produce only mild diarrhea at first, even though later effects from Amoebae can be disastrous. Many individuals harboring these organisms may be unaware that they have an infestation.

Although giardiasis has been blamed for a variety of awful diarrheal disorders, over half of the individuals exposed to the organism do not develop infestations. Of those who are infested, only about one-fourth develop symptoms. Typical symptoms appear about a week after infestation and consist of three or four soft stools daily. Feelings of bloating, increased flatulence, and foul-smelling eructations (“rotten egg burps”) are common, but for most individuals the condition is more of a nuisance than it is incapacitating. Accounts of copious, disabling diarrhea are common, but in most instances laboratory studies to rule out a coinfection have not been performed.

Cryptosporidia has been known to infect animals since 1907, but the first human infection was recognized in 1976. Although originally thought to infect only immunocompromised individuals, since 1986 cryptosporidia has been recognized as a worldwide parasite that affects individuals of all ages. Organisms are probably present in all major streams and lakes in the United States.

Numerous therapeutic agents have been tried for this organism; none have had any significant benefit. The parasite is only eliminated when the host develops immunity. As a result, infestations are far worse in immunocompromised persons. Cryptosporidiosis is a common first indication of the existence of HIV infection, and a number of immunocompromised individuals die as the result of their infestation. It is feared in the AIDS community.

A number of bacteria cause diarrheal disease. Probably the most common is E. coli, which produce endotoxins that are the most frequent cause for "traveller's diarrhea." Staphylocci produce toxins that cause gastrointestinal disease, and salmonella, shigella, yersinia, and campylobacter colonize the intestinal tract and produce diarrheal disease.

Much "traveller's" diarrheal disease is the result of viral infection, particular­ly by Norwalk-like agents (noroviruses) and rota­viruses. These organisms can produce dehydrating diarrhea, although the infections rarely last more than two or three days. Other water borne virus­es cause much more signifi­cant infec­tions. Hepatitis A has long been known to result from fecal con­tamina­tion of water. Hepatitis E, which produces epidemics that are associated with a 10 to 20 percent mortality during pregnancy, is predom­inantly transmitted by contaminated water. Transfusion and intravenous drug abuse typically transmit hepatitis C, but a significant number of individuals with that infection have no history of such incidents. Contaminated water has been proposed as a source.

Other organisms such as coxsackie, polio, and echoviruses enter the body through the gastrointestinal tract, although their principle manifestations are in other organs.

TECHNIQUES FOR WATER DISINFECTION

The currently available and reasonably convenient methods for field water disinfection are heat, the combination of microfiltration and chemical treatment, and ultraviolet light.

HEAT

Boiling water is safe and reliable. The Centers for Disease Control (CDC) and the Environmental Protection Agency (EPA), which is responsible for water disinfection programs in the US, recommend that water be brought to a rolling boil for one minute to insure parasites are killed. Since water boils at a lower temperature at higher altitudes, these agencies recommend boiling water for three minutes at altitudes above 2,000 meters (6,500 feet).

ALTITUDE BOILING TEMP

Sea Level     100ºC

10,000 ft     90ºC

14,000 ft     86ºC

19,000 ft     82ºC

Boiling is a time proven technique for water disinfection that is simple and reliable, but boiling is inconvenient and time consuming, particularly for quantities of water larger than one or two liters. An open fire leaves an unsightly residue without heavy, bulky fire pans.

MICROFILTRATION

Concern about cryptosporidia, which unlike other parasites are resistant to halide disinfectants, has made microfiltration an essential element of water disinfection. The Centers for Disease Control and Prevention (CDC) states that backpacking filters used to remove these parasites should have absolute (not nominal) pore size of one micron or smaller

The following do not “promise the filter removes cryptosporidium:”

•  Effective against giardia or against parasites

•  Carbon filter

•  Water purifier

•  EPA approved

•  Activated carbon

•  Removes chlorine

•  Ultraviolet light

•  Pentiodide resins

The generally available filters have smaller pore sizes, usually about 0.3 to 0.4 microns. Some of the most widely used filter and their websites are:

General Ecology (First Need ® ) http://www.general-ecology.com/

Katadyn Products http://www.katadyn.ch/site/ch_en/home/?L=en

Northern Mountain Supply (SweetWater) http://www.northernmountain.com/dept/HC

Mountain Safety Research (MSR) http://www.msrcorp.com/

PUR/Exstream Products http://www.purwaterfilter.com/expor.html

Sawyer Products http://www.sawyerproducts.com/

These filter pores are much too large to re­move virus­es. In fact, as the pores enlarge with use, they probably allow passage of small bacteria, such as the vibrios that cause cholera. After filtration the water must be chemi­cally treated to destroy those organisms.

Many filter incorporate an ­iodine containing resin to destroy viruses (optional for some filters). Such products are effective but have the significant disadvan­tage of lacking any indication that the iodine has been exhausted.

SIZE COMPARISON

(MICROMETERS)

Katadyn ® Filter Pore   0.2 m m

Giardia Cysts     6.0 m m

Cryptosporida Cysts   4.0 m m

Bacteria (Diam)   1.5 to 3.0 m m

Viruses   0.004 to 0.06 m m

Filters are relatively bulky (for backpacking) and expen­sive, and can be rapid­ly obstruct­ed by sediment in the water. The ob­struction can be prevented with prefil­ters, but can be relieved in some systems only by replacing the filter, which costs almost as much as the entire system. For some filters obstructing sedi­ment can be removed by scrub­bing.

CHEMICAL DISINFECTION SYSTEMS

Chemical disinfection systems provide the desired features of simplicity, speed, small size, and lightweight, and are reliable for all organisms except cryptosporidia (and perhaps cyclospora.) Although many chemicals are effec­tive, only preparations that contain iodine or chlorine (halide) systems are readily availa­ble and have been proven by ex­ten­sive use. Silver com­pounds are used in other coun­tries but have not been ap­proved by the FDA for the United States.

IODINE AS A WATER DISINFECTANT

During World War II, a search for a simple, reliable water disinfec­tant was initiated because chlorine based sys­tems were too undependable. The in­ves­tigat­ing team found that diato­mic iodine (I 2 ) and the various ions resul­ting from the reaction of molecular iodine with water consis­tently and reliably disinfects water con­taining as many as ten million bacte­ria per millili­ter, a con­centra­tion approxi­mately ten times greater than grossly polluted water. (The effec­tive­ness of iodine was dem­on­strat­ed on raw sewage from the Cambridge, MA, sewage system.) Un­like chlo­rine, iodine is fast, resists inacti­vation by organic com­pounds, is active over a wide pH range, and is available in sta­ble prep­ara­tions.

At 23ºC (73ºF), even in moder­ate­ly tur­bid water with moder­ate amounts of organic color, an iodine con­centra­tion of 8 mg/l (8 parts per million) eradi­cates bac­te­ria, viruses, parasites, and para­sitic cysts other than cryptosporidia. A con­tact time of only ten mi­nutes already includes a con­sider­able margin of safe­ty. (About ninety seconds is adequate for eliminating nonparasitic organisms.)

However, an io­dine concentration of 8 mg/l (8 parts per million) is only needed to destroy parasitic cysts. A con­centra­tion of 0.5 to 1.0 mg/l eliminates other microor­ga­nisms. If filters are used to eliminate cryptosporidia and other parasites, such small concentrations could be used, but no preparations that supply such a limited quantity of iodine are currently available. They can only be prepared by diluting or using smaller quantities of existing preparations.

IODINE DISIN­FECTION PRECAUTIONS

In cold water (0º to 5ºC or 32º to 41ºF) the chemical activity of iodine is slower, just as all chemical reactions are slower at lower tempera­tures. Contact time should be increased to twenty min­utes to insure complete disinfection. Cloudy, heavi­ly contami­nated water requires more iodine to compensate for binding of the disinfec­tant by organic com­pounds; however, doubling the iodine concen­tration to 16 mg/l or doubling the contact time is sufficient. If the water has been filtered, such precautions are probably unnecessary, but no studies have been performed.

Masking Iodine's Taste

If water has been filtered and then disinfected with 0.5 to 1.0 mg/l of iodine, such a small concentration cannot be tasted. If larger quantities are used and individuals find the iodine taste objec­tion­able, several methods for mas­king its taste are avail­able. Because such proce­dures inactivate the iodine, they must not be used before enough time has elapsed for the micro­orga­nisms to be de­stroyed.

Artificial flavorings added to hide the taste usually contain ascorbic acid, which reacts with iodine and impairs its anti­mi­crobial activity. Potable Aqua ® is now supplied with ascorbic acid tablets—to be added after disinfection is complete—to eliminate the iodine taste. The iodine can be converted to tasteless sodium iodide with an equal weight of sodium thiosulfate. The water can be filtered through acti­vated charcoal, which, by adsorption, physi­cal­ly re­moves the iodine (and some odors, inorganic materials, and microorganisms, but not enough to make the water suitable for con­sumption.)

.)

Persons with known thyroid dys­function should determine how they react to water disinfected with iodine at home before relying on iodine water disinfection in the wilderness or while travelling. The uncom­mon indi­viduals who are allergic to iodine, in­cluding iodine-contain­ing com­pounds in radiographic contrast media, and those with thyroid dysfunction who react adversely must not use iodine for water disin­fection. For such individuals a filtration system to physical­ly remove bacteria, parasites, and para­sitic cysts followed by chlorine to kill viruses of­fers a reliable alternative.

ACUTE IODINE TOXICITY

Some years ago several publications claimed the iodine used for water disin­fec­tion could be dangerous­ly toxic. The skull and crossed bones on tincture of iodine is famil­iar. How­ever, iodine is only weakly poi­son­ous. The third edition of Goodman and Gilman`s Text­book of Pharma­cology states,

" that iodine is highly toxic ... is a popu­lar falla­cy." The lethal dose is 2 to 3 g, but survival after inges­tion of 10 g has been re­ported. Iodine in such large quan­tities is a strong gastroin­tes­tinal irritant and causes imme­diate vomit­ing, which elimi­nates most of the iodine. That remaining in the gastro­in­tes­tinal tract is largely neutral­ized by the intes­tinal contents. (The im­mediate treat­ment for iodine poison­ing is adminis­tra­tion of star­chy food.)

Accidental iodine poisoning is rare; almost all fatali­ties are suici­dal, but suc­ces­sful suicide is uncom­mon if the victim receives medi­cal care. Between 1915 and 1936 no deaths oc­curred among 327 pa­tients who arrived alive at Boston City Hospital ­follow­ing at­tempted suicide with iodine.

CHRONIC IODINE TOXICITY

Ingested iodine is absorbed as iodide, and an average adult requires 150 to 200 m g a day. Daily consump­tion of one to two liters of water disin­fec­ted with 8 mg/l of iodine would provide thirty to eighty times that amount, but individuals with normal thyroid function would not be affected by such quantities. (Even less effect would be produced by 0.5 to 1.0 mg/day.) The rec­ommended daily dose of expectorant potas­sium iodide for asth­matics ranges from 1.2 to 8.0 g (0.9 to 6.0 g of iodine.)

Iodine can cause fetal goiters that produce re­spiratory ob­struction at birth, but the moth­ers of infants with iodide goiters are almost all asthma­tics who have con­sumed a gram or more of iodine daily for many months or years.

Inmates of three Florida prisons drank water disin­fected with 0.5 to 1.0 mg/l of iodine for fifteen years. No detri­mental effects on the gen­eral condition or thy­roid function of previously healthy per­sons were detec­ted with care­ful med­ical and biochemi­cal moni­toring. Of 101 infants born to in­mates who had been in prison for 122 to 270 days, none had detectable thyroid en­largement. Howev­er, all four individu­als with hyper­thyroid­ism became more symp­tomatic while con­sum­ing iodina­ted water.

These studies indicate that indi­viduals with normal thyroid func­tion, including pregnant women, can con­sume water disin­fected with 8 mg/l of iodine for at least several months with no ill effects. A system that incorpo­rates a filter and adds only 0.5 to 1.0 mg/l of iodine would elimi­nate the risk of iodide goiter.

IODINE PREPARATIONS

Tri- to Pentaiodide Resins

Many portable water filters include secondary filters composed of iodine containing resins. Water passing through the secondary filters is exposed to the iodine, which has been clearly demonstrated to kill bacteria and viruses. Since such devices should remove all microorganisms some manufacturers have called them water “purifiers”.

However, these iodide resins are associated with several problems. The water is exposed to the resin for such a short time that some manufacturers have recommended that cold water be filtered twice.

A small amount of iodine is released into the water as it passes through the filter, but the quantity is usually quite small—too little to taste and possibly too little to continue effectively disinfecting the water. However, with continued use, the iodine in the filter is totally removed. None of the filters currently available offer any means for determining when such exhaustion has occurred. Repeatedly replacing the filters after every 100 liters or water that are disinfected is somewhat expensive, and keeping the records needed to determine that a filter has been used for that quantity of water is tedious.

Tetraglycine Hydroperiodide

Tablets containing tetragl­ycine hydroperiodide are widely sold under trade names such as Globaline â and Potable-Aqua â . One fresh tablet dissolved in a liter of water provides an iodine concentration of 8 mg/l. A major advantage of tetra­glycine hydro­periodide tablets is their con­venience. A small bottle of fifty tablets can be carried easily. Sealed bottles can be stored for months with little loss of iodine. The manufacturer of Potable-Aqua â claims four years.

The principal disadvantage of tetraglycine hydroperiodide is its ten­den­cy to dissociate after exposure to air. In stu­dies to document their stabili­ty, te­traglycine hydroperiodide tablets placed in a single layer in an open dish at 60ºC (140ºF) lost 40 percent of their iodine in seven days. At room tempera­ture and 100 percent humidity, the tablets lost 33 percent of their iodine in four days. Studies to deter­mine the rate of dissocia­tion of tablets in a small bottle opened several times a day for one or two week­ends a month, the pattern of weekend out­doorsmen, have not been re­ported.

Tetraglycine hy­droperiodide tab­lets (and other iodine prepara­tions) add a definite brown color to the water if 8mg/l is present. Tightly capping and re­frig­era­ting bottles of the tablets may help retard iodine loss, but they probably should be discar­ded a few months after open­ing. The manufacturer of Potable-Aqua â recommends a year.

Saturated Aqueous Iodine Solution

In 1975 Kahn and Visscher described a procedure for disinfecting water with a saturated aqueous solution of iodine. Iodine crystals (2 to 8 g, USP grade, resublimed) are placed in a 30 cc (1 oz) clear glass bottle with a paper lined Bakelite cap. (The details are important.) The bottle is filled with water, shaken vigorously, and allowed to stand for one hour to produce a saturated solution. One half of this saturated solu­tion (15 cc) is poured into one liter of water to be disin­fected. If the temperature of the water in the 30 cc bottle is 20ºC (68ºF) or higher, which can be achieved easily by carrying the bottle in a shirt pock­et, the iodine concentration in the disinfected water would be about 9 mg/l.

Saturated aqueous iodine solutions have two distinct advantages:

The bottle contains enough iodine to disinfect up to 8,000 liters of water, depending on how it is used.

If crystals can be seen in the bottom, enough iodine for disinfection is known to be present, so the system is totally reliable.

This technique for water disinfection has been denounced, even in terms such as "it can kill you," because in decanting the supernatant, iodine crystals could be poured into the water to be consumed. This hazard appears insignificant. Iodine is so weakly toxic that three or four crys­tals would not be expected to produce any symptoms. Individuals who have used this technique extensively have found that small flakes of iodine are com­mon­ly caught by surface tension in the small bottle, poured into the large bottle, and ingested without producing any detectable ill effects. A jar with a sleeve in its neck to prevent decanting the iodine crystals, "Polar Pure," is commercially available. On its surface this jar also has a temperature indicator and data for calculating the volume of satura­ted iodine solu­tion that would contain 8 mg of io­dine. However, this jar is too large to fit into a shirt pocket.

A saturated aqueous solution of iodine has been singled out as being uniquely ineffective at low temperatures for eradicating giardia cysts. However, all of the disinfectants tested in that study produce their antimicrobial effects by releasing diatomic iodine. A difference in effectiveness when all act through the same mechanism is puzzling, and extensive use of this system has not been associated with infestations. If microfiltration is used to remove cryptosporidia, this question is moot.

One real problem with saturated iodine solutions is the tendency for the water to freeze and break the bottle. (Such a small amount of iodine is dissolved in the water the freezing temperature is not significantly lowered.) Leaving an air space in the bottle by not refilling it after its last use in the evening would allow the water to expand as it freezes and prevent breaking the bottle. Alternatively, the bottle must be kept warm—inside a sleeping bag. (Glass is the only satisfactory container for aqueous iodine solutions.)

Saturated iodine solutions are widely used for water disinfection because they are convenient and reliable. For informed adults, extensive experience indicates the method is safe, although chil­dren must not be entrus­ted with a poten­tially lethal quantity of iodine.

CONCENTRATED ALCOHOLIC IODINE SOLUTIONS

A concentrated solu­tion of iodine in 95 percent ethanol could provide a compact source of iodine for disinfect­ing large quantities of water. A solution of 8 g of iodine in 100 cc of ethanol (a fully satu­rated solution would con­tain over 20 g of io­dine) would con­tain enough iodine to disin­fect 1,000 liters or 250 gallons of unfiltered water or 2,000 or more gallons of filtered water. The 8 mg of iodine needed to disinfect one liter of water would be present in only 0.1 cc of the solution; enough iodine for five gal­lons (twenty liters) would be con­tained in 2 cc. Tu­berculin or insulin syringes could be used to ac­curately meter such small quantities. This prepa­ration would be reliable be­cause the concentra­tion of iodine could only increase if the al­cohol evapo­rated.

Tincture of Iodine

Tincture of iodine is useful for water disinfec­tion be­cause it is so readily available, particu­larly in developing coun­tries, or in the US after a major disaster such as an earthquake when gas mains are broken and electrical lines are down. (Te­tra­glycine hydroper­iodide is almost equally avail­able from outdoor equip­ment retail­ers). The major disad­vantag­es of io­dine tincture are its taste and its iodide com­ponent. Many have found the iodine taste im­parted by the tinc­ture to be much stronger than that of other preparations contain­ing similar quanti­ties of iodine. The U.S. Phar­maco­poeia (USP) standard solution is two per­cent iodine and 2.4 percent sodi­um io­dide in fifty percent ethanol. (Dif­ferent concen­tra­tions are also sold as "tinc­ture.") The iodide has no dis­infec­tant activity and increas­es total iodine in­take.

Tincture of iodine resists free­zing. Also, it can be used to disin­fect skin, but aque­ous solutions are just as effec­tive for that purpose and do not sting. Addition of 0.4 cc of a two percent solution to a liter of water pro­vides an io­dine con­centration of 8 mg/l. A dropper that dispenses a pre­cise vol­ume should be used. The tincture must be stored in glass bottles.

CHLORINE DISINFECTION

The effectiveness of chlo­rine for water disinfection is well docu­mented. However, the disinfec­tant action of chlo­rine is pH sensi­tive, and if organic resi­dues are present, chlorine combines with am­monia ions and ami­no acids to form chloramines, which release chlo­rine slowly and incon­sis­tently.

Although most municipal water sys­tems in North America use chlorine as a disin­fectant, free chlorine levels in the water must be constantly moni­tored to ensure they are ade­quate for disinfec­tion. Monitoring is not practical in the wilderness or in de­ve­loping countries. Further­more, chlo­rine com­pounds that have been advo­cated for wilderness water disin­fec­tion, such as Halazone (which has not been manufactured for fifteen years) or chlorine bleaches, are unsta­ble and of question­able reliabili­ty.

Most bleaches for home laundry use are five percent sodi­um hypo­chlo­rite solu­tions, which could disinfect water effec­tive­ly. How­ever, the solu­tions are very unsta­ble, which ren­ders them un­suitable for wilder­ness water disinfec­tion be­cause much of the chlorine is lost as the solu­tion slosh­es around while being trans­ported. Solid or pow­der beach prepara­tions are not avail­able in a form that allows an ap­propriate quantity for wa­ter disinfec­tion to be easily deter­mined.

If liquid bleach is used for water disinfection, the standard procedure is to add two drops to a liter of water with a temperature above 60º F or 16º C and allow it to stand for thirty minutes. If the water is colder, it should be allowed to stand for forty-five minutes. (For iodine the comparable times are ten and twenty minutes, and cold water is 40º F or 5ºC.) If a slight odor of chlorine is not present at that time more should be added.

Preparations such as SafeAqua.com use a chlorine-based system that employs a diffe­rent approach. Ini­tially far more chlo­rine is added to the water than is needed for disinfec­tion (superchlorina­tion). In the presence of excessive chlo­rine pH inacti­va­tion or binding by organic material are not signif­i­cant. After the water has been disinfect­ed, the chlo­rine is driven off.

(The first such preparation was the Sierra Water Purifier. The writer was able to find references to a change in name to “Sanitizer” but could not find the product in any supplier's website.)

These systems are much more suita­ble for disinfecting rela­tively large quan­tities of water — five to ten gallons or twenty to forty liters — than the one or two liters that would be carried in a backpack. The thirty percent hy­dro­gen peroxide used to drive off the chlorine by Sierra Water Purifier is caustic. (It is used in cosmetic dentist­ry to bleach teeth! Ninety-nine percent H 2 O 2 is used for fuel for the thruster rockets that control the positioning of spacecraft. ) Some in­dividuals have found they get the solution on their fingers every time they use it, and that it produces a burning sen­sa­tion that lasts thirty to sixty minutes. The skin may be blanched, although no permanent injury is produced.

This procedure should be reli­able; the presence of a "strong smell of chlo­rine" should be unmistakable. Additionally, the system is small, light weight, and relatively simple, although two com­pounds must be added to the water instead of one. It is more expen­sive than the iodine based systems, but still is relatively cheap. Hydrogen peroxide, if used to drive off the chlorine, im­parts a delightful "sparkle."

A zinc brush can be used to remove the chlorine instead of hydrogen peroxide or other agents. Since zinc catalyses the remove of chlorine instead of reacting with the halide, it is not used up and can last indefinitely.

MSR MIOX PURIFIER

In the fall of 2003 MIOX Corporation (www.MIOX.com), in association with Mountain Safety Research (MSR), released a new chlorine-based water disinfection system for individuals. Various much larger units that employ the same electrolysis procedure have been in operation since MIOX was formed in 1994. The U.S. Forest Service uses these devices in several parks, and they have proven quite valuable in developing countries. (MIOX was one of nine companies to receive the presidential “E” award for excellence in exporting in 2002.)

U.S. military forces in Afghanistan are testing the individual units, and the government had agreed to purchase 8,000 by the end of 2003. The Purifier was the Grand Award winner in the General Innovation category for Popular Science's “Best of What's New” Issue.

The system operates by sending an electrical current through a saline solution (brine), which produces a mixture of oxidants, most importantly hypochlorous acid, the most effective chlorine-based disinfectant compound. In appropriate concentrations the solution from the small, individual unit effectively eliminates bacteria and viruses from water in thirty minutes. Parasites take longer. Cryptosporidia—against which hypochlorous acid is eventually effective, unlike chlorine or iodine—require four hours.

The device contains a small chamber on top into which a salt pellet—or rock salt or common table salt—is placed. About a quarter teaspoon of water is placed in a second chamber underneath the first, and the unit is shaken to mix the salt and water and produce a saline solution. A button is pushed to send an electric current—produced by two three-volt lithium camera batteries—through the solution. Pressing the button once provides enough oxidants to disinfect one-half liter of water. Pressing it twice yields enough for a liter, pressing three times provides enough for two liters, and pressing four times yields enough for four liters. One salt pellet lasts for approximately fifty liters of water, and one set of batteries can disinfect about 200 liters.

A green light indicates when the oxidant mixture has been generated, which takes five seconds to two minutes. Combinations of red and green constant and blinking lights indicate whether the solution is too strong, too weak, too salty, or the batteries are running low. A chart aids in interpreting the signals. After the solution has been stirred into the water to be disinfected, test strips are provided to determine whether the water has been adequately treated.

The solution is reported to add no taste or odor to the water. A number of on-line publications proclaim that it eliminates pumping water through a filter to remove cryptosporidia, but four hours is a long time to wait for disinfection to take place. Water disinfection systems must be fast or they will not be used.

The unit is approximately the size of a Maglight and weighs 3.5 ounces, although the entire kit, which includes test strips, and instruction booklet, a reference card, and a carrying sack weighs 8 ounces. It is available on-line from a number of companies for $129.50. Replacement batteries cost $6.80. Additional test strips and salt tablets cost $17.95.

(For comparison, Polar Pure Iodine Crystal Kits cost $10.50 and will treat up to 2,000 liters of water; Potable Aqua Iodine Tablets cost $4.95 for fifty tablets, and taste neutralizer adds an additional $2.00. Filters, which often would be needed along with the MIOX Purifer, range in cost from about $50 to about $150, although most are less than $100.)

This system appears to be most valuable for individuals who are allergic to iodine or who are hyperthyroid and must use some disinfectant other than iodine. Usually water will need to be filtered—four hours is a long wait. A bottle of tetraglycine hydroperiodide tablets or saturated aqueous iodine is much smaller than this device and far cheaper.

STERI-PEN ULTRAVIOLET WATER DISINFECTION

A new product recently released by Hydro-Photon, Inc., called Steri-Pen, disinfects water with ultraviolet light. Time (magazine) thought enough of this device to list it among their “Inventions of the Year” for 2001.

The manufacturer states that in studies carried out at the University of Maine, University of Arizona, University of North Carolina, and Oregon Health Sciences University, this product was demonstrated to eliminate viruses, bacteria, and protozoa well enough to meet the EPA Guide Standard and Protocol for Testing Microbiological Water Purifiers. (It destroyed in excess of 99.9999% of bacteria, 99.99% of viruses, and 99.9% of protozoa.)

The reports on the tests at these four institutions can be downloaded from Hydro-Photon's website (www.hydrophoton.com). They sound convincing. Among the organisms against which this device was effective were cryptosporidia and giardia.

The device is seven inches long and about one-and-a-half inches on each side. It weighs six to eight ounces with batteries, depending on the battery type. It is smaller and lighter than currently available filters. It operates on four AA batteries and is capable of disinfecting 16 ounces of water in about sixty seconds. A liter of water takes eighty seconds. (The ultraviolet light source on the instrument's tip is inserted into the water and stirred.) Alkaline batteries provide twenty to forty water treatments; rechargeable batteries provide sixty to seventy treatments; lithium batteries provide 130 to 140 treatments.

The device costs $199, so it is not cheap. Four lithium batteries would cost $11.90. The Steri-Pen could be a moderately expensive replacement for filtration and chemical disinfection, particularly for individuals who can not use iodine. How well it would stand up to being crammed into a backpack and other rigors of outdoor use is not stated. The device appears to be particularly useful for travelers because a glass of water could be very easily disinfected in a hotel room in only sixty seconds.