To better understand the mode of action of monochloramine, its effect on the structural and physiological integrity of Escherichia coli B was studied. The disinfectant did not severely damage the cell envelope of the bacterium or affect nucleic acid function. Inhibition of typical protein‐associated biological activities, e.g., bacterial transport, respiration, and substrate dehydrogenation, were observed at concentrations normally used for disinfection. Differences in rates of kill and inhibition of various biological activities suggest that the shoulder formation on inactivation curves was due to reactions at many sensitive sites in the bacterium, the extent of which determined whether the organism remained recoverable.

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Ammonia has been shown to be virucidal in sludge and NH4Cl solutions, although the rates at which viruses are inactivated have not been thoroughly studied. In the present studies, the kinetics of the poliovirus type 1 (strain CHAT) and bacteriophage f2 inactivation were examined in such a way that the effects of OHand NH4' could be separated from those of NH3. Purified virus stocks were placed into solutions of NH4Cl and control solutions containing an equivalent concentration of NaCl and incubated at 20°C. The percentage of virus surviving was calculated, and the kinetics were evaluated by constructing semilogarithmic plots of data. At all pH values and NH3 concentrations studied, the kinetics of the inactivation of both viruses were pseudo-first order. OHhad no measurable effect on the viruses, whereas the effects of NH4' and Na+ were similar. A doseresponse relationship between NH3 and the viruses was also found. Bacteriophage f2 was approximately 4.5 times more resistant to the effects of NH3 than was poliovirus.

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