AWWA WQTC50355

Enumeration of Aeromonas hydrophila was performed using Ampicillin-Dextrin Agar. Biochemical characterization of environmental isolates included the use of API and biolog detection methods, whereas blood agar hemolysis was used to test for virulence. Enumeration was conducted in source water, in various sites within a water treatment plant, and in the distribution systems. The presence of A. hydrophila was studied in both bulk water and biofilm within full scale and simulated (annular reactors) drinking water distribution systems. The study was conducted over a one-year period. Presumptive aeromonas sp. counts on source waters approached 10 3 CFU/mL during summer months and filtered water counts ranged from <1 to 168 CFU/100mL. Also, 4.3% of the plant effluent samples (after disinfection), 11.7% of the distribution bulk water samples and 21.0% of the biofilm samples provided presumptive Aeromonas sp results. Furthermore, A. hydrophila was definitely identified in 10.5% of the biofilm samples, but never in the treatment plant effluent or distributed bulk water, showing disinfectant efficiency on suspended bacteria. On the other hand, the presence of A. hydrophila in biofilms within the distribution system and positive isolates from simulated systems indicate potential for regrowth and contamination in drinking water distribution systems. Includes 6 references, table, figures.