Evaluation of a microbiological water purifier for inactivation of viruses, bacteria and Giardia cysts

Development of the need for personal water treatment devices has evolved from consumer interest in improving and ensuring the quality of drinking water. The need also extends to the quality of untreated or partially treated waters such as that used by hikers, campers, recreational home and boat owners, and families or communities having individual home and small water sources. It is essential that such devices be capable of removing all types of pathogenic microorganisms likely to be found in contaminated water. For this reason the U.S. Environmental Protection Agency has suggested such units be capable of removing Klebsiella terrigena, Giardia cysts and enteric viruses. Three identical water purifiers were evaluated for the inactivation of rotavirus SA-11, hepatitis A virus, poliovirus type 1, the bacterial virus MS-2, Klebsiella terrigena and Giardia muris cysts. The units depend upon a thermal cycler combined with activated carbon for removal of the test organisms. The units were challenged with the organisms suspended in tapwater after 4, 76 and 240 cycles of operation. The units were also tested with a 'worst case' water quality of 1500 mg/l dissolved solids, 10 mg/l organic matter and with a water turbidity of 30 NTU. In all cases, complete inactivation of the viruses, bacteria and cysts occurred after operation of the 35-minute cycle. This resulted in a greater than 3-log (99.9%) inactivation of cysts, a greater than 6 log (99.9999%) inactivation of K. terrigena and 4-log (99.99%) inactivation of viruses. In conclusion, these units would comply with criteria guidelines suggested by the U.S. Environmental Protection Agency for the operation of microbial water purifiers.