The disinfection efficacy of a point-of-use water treatment system against bacterial, viral and protozoan waterborne pathogens

Abstract

A point-of-use (POU) water treatment system (WTS), comprised of a presed activated carbon block filter followed by an ultraviolet (UV) light 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 Purifiers. The POU WTS was challenged against bacterial, viral and protozoan waterborne pathogens including Vibrio cholerae, Shigella dysenteriae serotype 2, Escherichia coli 0157:H7, Salmonella typhi, hepatitis A virus strain HM 175, poliovirus type 1 strain Lsc2ab, simian rotavirus SA11, Cryptosporidium parvum oocysts, Giardia lamblia cysts and coliphage MS2. The POU WTS was tested for the removal/inactivation of each challenge organism in separate 16- to 20-day test periods under various conditions of water quality, at the system's maximum recommended flow rate and at 70% of the lamps normal UV intensity. For each organism 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 of influent water containing approximately 10 5 bacterial cfu/mL, 10 4 viral pfu/mL or 10 3 protozoan cysts/mL. Influent and effluent water samples were taken during the challenges and assayed for the particular pathogen and the percent reduction calculated. Effluent water samples were also taken and assayed for the possible presence of the pathogens following two 60-h stagnation periods. The POU WTS was found to effectively remove and/or inactivate greater than 99.9999% of the bacterial 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 treatment 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.