Bacterial removal from inexpensive portable water treatment systems for travelers

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 M1-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 degrees 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 M1-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. CONCLUSIONS: 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.