AWWA JAW59120

In recent years, a variety of viral, bacterial, and protozoan agents have been implicated as waterborne agents that pose a risk to human health. Although Cryptosporidium and Giardia have been the focus of concern (and most regulatory action), emerging waterborne pathogens include Escherichia coliO157:H7 and Aeromonas hydrophila. This research was undertaken to determine whether these and other pathogens are effectively removed by current surface water treatment technology. Cryptosporidium parvumoocysts, Encephalitozoon intestinalis spores, enteropathogenic E. coliO157:H7, A. hydrophila,and bacteriophage MS2 were subjected to pilot-scale conventional treatment with alum coagulation, flocculation, sedimentation, and filtration. The study tested the effects of filter run time, alternative loading rates, alternative filter media, and pH on pathogen removal. Results indicated that turbidity breakthrough at the end of a filter run was accompanied by the breakthrough of all pathogens tested, with a more rapid breakthrough of A. hydrophilaand E. coliO157:H7. Filtration rate and alternative filter media configurations had no apparent effect on pathogen removal. A pretreatment and filtration pH of 5.7 achieved better pathogen removal for C. parvumoocysts through sand filtration and for E. coliO157:H7 and bacteriophage MS2 through dualmedia and trimedia filtration. Although conventional treatment offers an effective barrier against some microbial threats, it is a poor defense against others. Compared with Cryptosporidium, certain pathogens reach filter breakthrough faster and are more poorly removed by conventional means. A multiple-treatment barrier approach may provide surface water suppliers with a better safeguard against emerging waterborne pathogens. Includes 21 references, table, figures.