AWWA WQTC58793

AWWA WQTC58793 A Comparison of the Response of Pathogenic and Non-Pathogenic E. coli Following UV Irradiation
Conference Proceeding by American Water Works Association, 11/02/2003

Zimmer-Thomas, J.L.; Slawson, R.M.; Huck, P.M.

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A strain of pathogenic E. coli O157:H7 and non-pathogenic E. coli were exposed to ultraviolet (UV)radiation from both low- and medium-pressure lamps using a bench-scale collimated beam apparatus.E. coli O157:H7 was more sensitive to low doses of UV showing higher levels of inactivation.Following irradiation, samples were exposed to light and dark conditions to investigate photo anddark repair potential, respectively. Following low doses (5 and 8 mJ/cmsup2/sup) of low-pressure UVexposure, E. coli O157:H7 was observed to reach maximum levels of photo repair more rapidlycompared to a strain of non-pathogenic E. coli. Low levels of dark repair were also observed in E.coli O157:H7 following low-pressure UV exposure at these doses. Following higher low-pressureUV doses of 20 and 40 mJ/cmsup2/sup low levels of photo repair of E. coli O157:H7 were evident; however,no dark repair was detected at these higher doses. Following medium-pressure UV exposure at lowdoses (5 and 8 mJ/cmsup2/sup), limited photo repair was observed in both strains when exposed to lightconditions. No dark repair was evident following medium-pressure UV exposure at these low doses. Includes 20 references, figures.