THE DISINFECTION EFFICACY OF A POINT-OF-USE WATER-TREATMENT SYSTEM AGAINST BACTERIAL, VIRAL AND PROTOZOAN WATERBORNE PATHOGENS

A point-of-use (POU) water treatment system (WTS), comprised of a pres sed activated carbon block filter followed by an ultraviolet (UV) ligh t reactor, was evaluated for microbial disinfection efficacy following the general guidelines of the United States Environmental Protection Agency Guide Standard and Protocol for Testing Microbiological Water P urifiers. The POU WTS was challenged against bacterial, viral and prot ozoan waterborne pathogens including Vibrio cholerae, Shigella dysente riae serotype 2, Escherichia coil 0157:117, Salmonella typhi, hepatiti s A virus strain HM 175, poliovirus type 1 strain Lsc2ab, simian rotav irus SA11, Cryptosporidium parvum oocysts, Giardia lamblin cysts and c oliphage MS2. The POU WTS was tested for the removal/inactivation of e ach challenge organism in separate 16-to 20-day test periods under var ious conditions of water quality, at the system's maximum recommended flow rate and at 70% of the lamps normal UV intensity. For each organi sm tested, microbial challenges were conducted over the course of the test period at 0, 50, 100 and 150% of the system manufacturer's rated water treatment capacity. Each microbial challenge consisted of 30 L o f influent water containing approximately 10(5) bacterial cfu/mL, 10(4 ) viral pfu/mL or 10(3) protozoan cysts/mL. Influent and effluent wate r samples were taken during the challenges and assayed for the particu lar pathogen and the percent reduction calculated. Effluent water samp les were also taken and assayed for the possible presence of the patho gens following two 60-h stagnation periods. The POU WTS was found to e ffectively remove and/or inactivate greater than 99.9999% of the bacte rial pathogens, greater than 99.99% of the viruses and greater than 99 .9% of the protozoan cysts and oocysts tested to 150% of the water tre atment capacity of the POU WTS. These findings suggest that a properly designed and operated POU WTS may be a practical approach to removing microbiological waterborne pathogens From drinking water. (C) 1997 El sevier Science Ltd.