Free Available Chlorine Disinfection Criteria for Fixed Army Installation Primary Drinking Water
Technical rept. 1974-1978
ARMY MEDICAL BIOENGINEERING RESEARCH AND DEVELOPMENT LAB FORT DETRICK MD
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This report is a comparative evaluation of the kinetic inactivation by Free Available Chlorine FAC of the following disaggregated microorganisms, prepared to be free of extraneous chlorine demand. Bacteria tested were Escherichia coli ATTCs 11229 and 23985 Salmonella typhimurim, Shigella boydii, and Vibrio cholerae. Viruses included f2 coliphage, polioviruses I LSc and Brunhilde, coxsackie B3, and echovirus 7. A chlorine-resistant yeast, Rhodotorula rubra, was also included for testing. Baseline studies were performed in chlorine demand-free water buffered to pH 5,7, and 9 temperatures were 6 degC and 22 degC. Data revealed that disinfection efficiency was reduced during low temperature and high pH test conditions. All the enteroviruses exhibited anomalous 2-stage disinfection kinetics at pH 5, making disinfection of these viruses as fast or faster at pH 7 than at pH 5. Further studies were done using synthetic interference water, designed to individually assess the effects of natural water constituents including color organic acids, hardness cations, and turbidity inorganic on FAC disinfection kinetics. The levels of constituents used did not exceed those specified by various regulatory agencies for primary drinking water. A final testing medium was composed of all the individual constituents run at 6 deg C and pH 9. Results indicated that 5 C.U. fulvic acid and 5 N.T.U. bentonite turbidity produced negligible effects on FAC disenfection at pH 5, 7, and 9. However, the presence of divalent cation Mg or Ca enhanced disinfection of enteroviruses and f2 coliphage at pH 9 by 20 to 90 percent.
- Water Pollution and Control