AWWA WQTC55203

This research was initiated to determine the sensitivity of Aeromonas spp. to ultraviolet (UV) disinfection. Aeromonas hydrophila is a contaminant listed on the US Environmental Protection Agency's 1998 Contaminant Candidate List (CCL). Three different Aeromonas spp. (A. hydrophila, A. sobria and A. caviae) were tested using membrane filtration (MF). For comparison purposes, one strain of the water quality indicator organism Escherichia coli was also investigated. A low-pressure UV source was used in all experiments in conjunction with a collimated beam apparatus. Organisms were grown on both selective and non-selective media after UV exposure. Aeromonas spp. were found to be sensitive to UV irradiation, with fluences of less than 7 mJ/cm 2 giving between 5-7 log10 reductions. However, some Aeromonas spp. counts from non-selective media were significantly higher than those obtained with selective agar. E. coli also showed differences between the selective and non-selective media. These findings suggest that selective agars may underestimate the number of viable organisms found after exposure to UV irradiation. Includes 21 references, tables, figures.