Chlorination of pure bacterial cultures in aqueous solution

The fate and distribution of chlorine in aqueous solutions containing four pure bacterial cultures was studied. Solutions were subjected to chlorination at different initial free chlorine concentrations. Resulting concentrations of residual chlorine were determined by both DPD/FAS titration and membrane introduction mass spectrometry (MIMS). In all cases, false-positive breakpoint chlorination curves, probably attributable to the formation of chloroorganic-N compounds, were observed by DPD/FAS titration, while little or no inorganic residual chloramine was found by MIMS. Free chlorine was observed in similar quantities by both methods after chlorine demand by bacterial cellular materials in solution was satisfied. These results indicated the residual chloramines existed in the form of organic chloramines; these compounds are generally recognized as being poor antimicrobial agents. Further investigation confirmed that the bacterial cells were the source of organic-N compounds. The kinetics of chlorination of pure bacterial suspensions was also studied. The pattern of residual chlorine decay following chlorination of the bacterial suspensions indicated rapid initial free chlorine consumption, followed by slow free chlorine consumption, with trace quantities of inorganic chloramine being formed.