Bacterial Removal by Inexpensive Portable Water Treatment Systems for Travelers

0. Schlosser, C. Robert, C. Bourderioux, M. Rey, and M.R. de Roubin

Background: There are many personal, portable water treatment systems for travelers on the market, including chemical agents, iodine resin purifiers and filters.  However, information on the real efficacy of these systems in the field is often lacking. We have therefore estimated the capabilities of several inexpensive personal portable water treatment systems for travelers to remove bacteria in various situations of water quality, using stressed indigenous strains of bacteria.

Methods: Four chemical agents (Drinkwell chlorine, Hydroclonazone, Aquatabs, 2% iodine in ethanol), two iodine resin purifiers (the straw PentaPure Outdoor Ml-E, the PentaPure Traveler purifying and filtration system) and four filters (the flexible bottle Pres2Pure, the hand-pump filters Mini Ceramic, First Need Deluxe, and WalkAbout) were evaluated in triplicate using both turbid and clear water at 25°C.  Bacteria were counted by conventional culturing techniques, colori­metric and fluorescent assays of coliforms and Escherichia coli enzyme activities (Colilert/Quantitray method), and viable but not culturable bacteria were assessed quantitatively by 5-cyano-2,3-dilotyl-tetrazolium staining.

Results:  The best systems were the three hand-pump filters, Mini Ceramic, First Need Deluxe and WalkAbout. All had a submicron filtration element that completely removed 3 log (99.9%) or more of viable bacteria, and no coliforms or E. coli were detected in the effluent. The PentaPure Traveler removed more than 99.3% of the viable bacteria. The only chem­ical agents that gave a bacterial inactivation of over 2 log in clear water were the Drinkwell chlorine, the Aquatabs and the 2% iodine in ethanol.  The three other devices, Hydroclonazone, Outdoor Ml-E and Pres2Pure performed poorly, as coliforms and E. coli were detected in the treated water by the Colilert method. The chemical agents and the iodine resin straw performed poorly on raw river water; coliforms and E. coli were detected in the treated water.

Conclusion: These data demonstrate the differences between the systems tested. The effectiveness of other devices on the market should also be tested, so as to help travelers and hikers select the most appropriate portable water treatment system.

            In most industrialized countries, waterborne diseases are at a relatively low level, even if outbreaks still occur as reported by national surveillance systems that exist in the USA, in the United Kingdom or in Finland. The pathogens that have been targeted as being the most important in the West are the human enteric viruses and the protozoans Giardia lamblia and Cryptosporidium parvum, because they are resistant to the disinfection with chlo­rine.  Bacterial pathogens are sensitive to disinfection, and cholera and typhoid fever are good examples of water-borne diseases controlled in industrialized countries by sanitation and water treatment during the 20th century.

       In many parts of the world, the water is not safe to drink.  Poorer areas lack sewage collection and water treatment facilities, the maintenance of the systems is bad, and unprotected water sources are heavily polluted.  Waterborne bacterial disease outbreaks involved pathogens such as Vibrio cholerae, Shigella, Salmonella typhi, Campy­lobacter jejuni, Escherichia coli (enterotoxigenic E. coli, E. coli  0157:H7), or Yersinia, and the impact of water sup­ply and water quality on health have been investigated in numerous studies in the developing world. Travelers from industrialized countries are not immune to many infectious fecal organisms, so they are at risk from water­borne infection when they go to developing countries.

            Hikers and campers in wilderness areas are also exposed to waterborne disease if they drink raw water from rivers and lakes. Giardiasis accounts for most cases of diarrhea in backpackers, but Campylobacter enteritis infection has also been reported among hikers who drank untreated surface water, and among campers who drank untreated water from wells.

       Therefore, safe water is a priority for travelers. They are usually advised to drink bottled water, especially car­bonated water. Boiled water (a rolling boil) is proba­bly the safest. This concern about waterborne disease has led to the development of portable water treatment systems for travelers. They may be chemical agents, iodine resin purifiers, or filters. Sport and mountain goods stores, pharmacies and commercial web sites sell devices at various prices and of differing quality.  Information about the real efficacy of these systems in the field is often lacking.  We have, therefore, estimated the capabilities of several inexpensive portable, personal water treatment systems for travelers to remove indigenous bacteria from water of varying quality.  We have tested only the removal of bacteria, without regard to viruses or parasites.

Methods

Systems

       Four chemical agents, two iodine resin purifiers, and four filters were evaluated. These devices were selected from the products available on the French market on the basis of their low purchase price, under US $140.  Each device tested was new. The four chemical agents were three chlorine compounds (Drinkwell chlorine, Aquatabs, and Hydroclonazone), and 2% iodine in ethanol.

Table 1  Characteristics of Chemical Agents

                                                                                                                                                                                                           Contact

Name                            Manufacturer                                  Active Chemical                                      Dose                  Time

Drinkwell chlorine       MS Water GmbH Elsa,                         25 mg/ml Sodium hypochlorite            3 d/L*              60 min*

                                           Switzerland

Aquatabs                      Medentech Ltd., Wexford, Ireland   3.5 mg Sodium dichloroisocyanurate     1 tab/L*          30 min*

Hydroclonazone          Promedica La Chaussée                12.2 mg Tosylchloramide (chloramine)    1 tab/L*                   60 min*

                                                Saint-Victor, France                  

2% Iodine in ethanol    Local pharmacy                              2% Iodine in ethanol                                         5 d/L**            30 min****

                                                                                                                                                                             10 d/L***        30 rnin****

*As recommended by manufacturer  **clear water  ***in turbid water  ****As recommended by the CDC   tab=tablet; d=drops.

       The dose and the contact time of the chlorine com­pounds were those in the manufacturers' instructions.  The 2% iodine in ethanol doses and contact times were those recommended by the CDC.

       Two iodine resin purifiers were tested.  One was the PentaPure straw Outdoor Ml-E (WTC/Penta­Pure Inc., West St. Paul, USA), which has a prefilter, an iodine resin element, and an activated charcoal bed.  The capacity is 475 liters or 9 months of use whichever comes first.  The other was the PentaPure Traveler puri­fication and filtration system, which is fastened to the faucet.  This system has a prefilter, an iodine resin, an acti­vated charcoal bed, and a 1 mm filter.  The maximum flow rate is 1 L/min and the capacity is 1000 liters or 12 months of use, whichever comes first.

       The four portable water filters were a flexible bottle (Pres2Pure), and three hand-pump filters (Mini Ceramic First Need Deluxe and WalkAbout). Each system was operated according to the manu­facturer's instructions.

Table 2 Characteristics of Filters (Manufacturer's Data)

Name                                   Manufacturer                   Operating Mode           Pumping rate  Capacity (L)

Pres2Pure                            CrystalPure                    USA Flexible bottle                  NA          750

      Mini Ceramic                      Katadyn Produkt AG         Hand pump                               0.5           7000

                                                      Walliseflen, Switzerland      

      First Need   Deluxe            General Ecology, Inc.        Hand pump and                          1.7           400

                                                      Exton, USA                           gravity

      WalkAbout                        SweetWater hand pump                                                       0.7             380

                                                     Longmont, USA

Results

     No Enterococci were detected in any treated water sample. The best results were obtained with the Mini Ceramic filter, with a 3.25 log (99.94%) removal of viable bacteria in each experi­ment.  The First Need Deluxe removed more than 2.5 log (99.7%) from each clear water sample.  The WalkAbout gave a 3 log removal in the first test, but the device released viable bacteria after this first test, due to system contamination.  It was therefore cleaned, disinfected with bleach and thoroughly rinsed before the next test.  The first two tests with the Outdoor Ml-E indicated a removal of less than 0.5 log, with considerable inter­fering bacteria in the effluent that prevented coliform counting.  The system was disinfected with bleach, and the third test gave a removal of 1.32 log, which is the only value recorded.

Tests on Turbid Water

The hand pump filters decreased the turbidity of raw river water greatly (> 95%), down to 0.15-0.30 NTU with the Mini Ceramic, and the WalkAbout and a little less with the First Need Deluxe which gave 0.90-2.15 NTU from 42.70 NTU for raw water samples.  The Outdoor Ml –E iodine purifier straw only decreased tur­bidity by 38.4%, and the turbidity of the effluent from 52.30 NTU raw water was still 38.60 NTU

Conventional culturing techniques showed total coliforms and thermotolerant coli forms when turbid water samples were treated with chemicals, with the straw Outdoor Ml-E and, one time, with the WalkAbout filter (2 total coliforms/100 mL in the effluent from a sample containing 57,000 total col­iforms/100 mL).  The effluent after treatment with Aquatabs= 2% iodine-ethanol and the straw Outdoor Ml-E still contained Enterococci.  The charcoal agents and the Outdoor Ml-E straw did not inactivate the coliforms and E. coli in turbid water, as detected by the ColilertÒ/QuantitrayÒ method (E. coli up to 12.4/100 mL in the effluent from the Outdoor Ml -E' straw).  But nei­ther coliforms nor E. coli were detected in the effluents from the three hand pump filters (see Table 4).  This per­formance was confirmed by the removal of more than 3 log (99.9%) of viable bacteria using the CTC-staining method.

There was a clear relationship between the turbid­ity of the untreated water and the performance of the chemical agents and the straw Outdoor Ml-E: the more turbid the water, the fewer bacteria were inacti­vated.

Discussion

Chemical agents, iodine resin purifiers and filters were tested with clear and turbid water, to determine their performance with different qualities of water that might be encountered when staying in hotels or trekking in wilderness areas.  River water was used because it con­tains indigenous strains of bacteria rather than strains from laboratory collections.  Many of the bacteria in aquatic systems can enter a starvation state when stressed by nutritional deficiency or other environmental factors (pH, temperature, oxidants, etc.). These stressed bacte­ria may be biologically active (viable) but will not be detected on growth medium.  They are viable but not culturable, but retain their ability to infect humans, ani­mals, or plants.  Stressed bacteria are smaller than normal (usually forming small spheres) and resistant to a wide range of antibacterial substances, including disinfecting agents.  Thus, stressed indigenous bacteria may be 10 to 100 times more resistant than bacteria from laboratory collections.

The indigenous viable bacteria may be counted by direct epifluorescent microscopy after stain­ing them with CTC fluorochrome. In addition to counting culturable bacteria by con­ventional techniques (which may lead to overestimation of the efficacy of the systems, particularly chemical agents), we therefore used CTC staining to count viable bacteria, and so obtain a better assessment of the efficacy of the systems.  Because we enumerated viable indigenous bacteria without the culture step, the results of this study appear to indicate a lower performance of the treat­ment systems than most published data based on con­ventional culture techniques to enumerate laboratory grown bacteria or indigenous bacteria.

It is not possible to examine water for the presence of all possible pathogens.  The use of indicator organisms is universally accepted for assessing the hygienic quality of water and the efficacy of disinfection.  Thermotoler­ant coliforms are commonly used indicators of fecal pollution for routine purposes.  Among this group, E. coli is regarded as the indicator of choice for assessing fecal contamination. Total coliforms are indicators of the treatment efficacy and allow detection of regrowth phe­nomena in the distribution network.

The European Community regulation (98/83/EU directive) states that safe drinking water must not con­tain any E. coli or Enterococcus in 100 mL, and the WHO guidelines for drinking water quality recommend no E. coli and no thermotolerant coliforms in 100 mL of drink­ing water samples. Because enteric viruses, protozoan cysts and helminthes eggs are known to be more resistant to disin­fection than E. coli and Enterococcus, the absence of the latter organisms will not necessarily indicate freedom from the former.  Similarly, because viruses are much smaller than bacterial indicators, the absence of the latter in effluent from subnmicron filtration devices will not nec­essarily indicate the absence of viruses.  Further research is needed to assess the removal of viruses and parasites with the tested treatment systems.

This study demonstrates the differences in efficacy of the systems. The best systems were the three hand-pump filters, Mini Ceramic First Need Deluxe and WalkAbout, which removed 3 log (99.9%) or more bacteria, with no colifoms or E. coli detected in the effluent.  The efficacy of a filtration device depends on the porosity of the car­tridge and on the quality of the overall device, particu­larly the internal seal.

As expected, the chemical agents performed very poorly with raw river water because the active agent was consumed by the organic and inorganic matter and by the suspended particles.  It should be possible to increase the efficacy of the chemical agents by using a larger dose and/or a longer contact time, because the efficacy of the chemical agents depends on the product Con­centration x Time.  In practice, the concentration is limited by the toxicity and the bad taste of the chemi­cal and its by-products, and the contact time is limited by the impatience of the traveler.  The ability of chem­icals to inactivate bacteria varies inversely as the water turbidity.  The best solution in this case is to remove particles and organic matter by filtration (e.g., coffee fil­ters) before disinfection.

       Drinkwell chlorine Aquatabs and 2% iodine in ethanol performed the same as the PentaPure Traveler with clear water samples, but these chemical agents all required a certain contact time.  Hydroclonazone did not inactivate coliforms and E. coli in clear water with a contact time of 60 min. The manufacturer's recom­mended contact time is 1-2 hours. We did not test Hydroclonazone with a 2 hour contact time, for the rea­son given above.

       The bactericidal activity of chemical agents, espe­cially chlorine compounds, varies greatly with the pH, organic content, and temperature of the water to be treated.  The pH, total organic carbon, and turbidity of the water sam­ples were determined and experiments were performed at 25°C.  Chemicals would have inactivated fewer bac­teria in cold water samples.  Hence, contact times should be increased with cold water.

       Iodine resin purifiers and filters should be effective for the designed operational life of the equipment.  The devices we tested were new and experiments were only performed at 0% of their lifetime.  The good results with the three hand-pump filters should therefore be confirmed after varying intervals. In other respects, devices with a cleanable filter element can be contaminated while clean­ing, and an internal seal can be damaged when remov­ing and replacing the filter cartridge.  Great care must be taken when following the manufacturer's instructions.

References

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2.       PHLS Communicable Disease Surveillance Center.  Surveil­lance of waterborne disease and water quality.  Commun Dis Rep 1999; 9:305-308.

3 .      Lahti K, Hiisvirta L. Causes of waterborne outbreaks in com­munity water systems in Finland: 1980-1992.  War Sci Tech 1995: 31:33-36.

4.       Hunter PR.  Waterborne diseases: Epidemiology and ecol­ogy- Chichester:John Wiley and Sons, 1997.

5.       Barbour AG, Nichols CR, Fukushinia T. An outbreak of gia­rdiasis in a group of campers.  Am J Trop Med Hyg 1976: 25:384-389.

6.         Wright RA, Spencer HC, Brodsky R-E, Vernon TM.  Giar­diasis in Colorado: an epidemiologic study.  Am J Epidemiol 1977: 105:330-336.

This article was extracted from a report to: J Travel Med 2001: 8:12-18.