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Abstract

Johnson, C.H., S.L. Hayes, S. Sabaratnam, E.W. Rice, L.A. Boczek, and D.J. Reasoner. 2002. Monitoring for Aeromonas spp. after treatment with common drinking water disinfectants. JEMREST 1:52-63

DOI: 10.4029/2002jemrest1no14

The sensitivity of Aeromonas spp. to free chlorine, chloramine and ultraviolet (UV) disinfection was determined. Selective and non-selective monitoring media were evaluated to assess recovery of chlorine or UV-stressed organisms. Aeromonas hydrophila is a contaminant listed on the USEPA's 1998 Contaminant Candidate List (CCL). Experiments using free chlorine indicated that the Aeromonas spp. were readily inactivated under all conditions studied. The organisms were inactivated by more than five orders of magnitude within a one minute exposure to free chlorine at two temperatures. Reductions of the organisms with 2.0 mg/L of monochloramine reached approximately 2 orders of magnitude following 4 minutes, with greater than five orders of magnitude inactivation after 8 minutes of exposure. Aeromonas spp. were found to be sensitive to UV irradiation, with fluences of less that 7 mj/cm2 giving between 5-7 log10 reductions. For free chlorine there was no observable difference in recovery of chlorine-stressed organisms between selective and non-selective media. However, with UV disinfection, some Aeromonas spp. counts on non-selective media were significantly higher than those obtained on selective agar. These findings suggest that selective agars may underestimate the number of viable Aeromonas recovered after exposure to UV irradiation.

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