Effects of initial microbial density on disinfection efficiency and explanatory mechanisms

Kaymak, Baris

doi:10.17918/etd-195

Cited by 4 publications

(2 citation statements)

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“…When n was set at 1.2, R 2 values for each condition individually varied between 0.89 and 0.97. Values for n vary widely in the literature, but other researchers have found similar n values when testing E. coli inactivation with monochloramine at pH 8, including n ) 1.19 (30) and 1.23 (31). Variation in n values has been reported for monochloramine inactivation of different organisms and at different pH values (31,32).…”

Section: Selection Of Bacterial Strain and Design Of Culture Mediummentioning

confidence: 88%

“…Values for n vary widely in the literature, but other researchers have found similar n values when testing E. coli inactivation with monochloramine at pH 8, including n ) 1.19 (30) and 1.23 (31). Variation in n values has been reported for monochloramine inactivation of different organisms and at different pH values (31,32). A rigorous validation of the applicability of a single n value to model bacterial inactivation with monochloramine would require testing of a wide range of disinfectant concentrations and exposure times, which was not undertaken because the goal of this study was not to validate a single n value, but to compare inactivation kinetics across growth states.…”

Section: Selection Of Bacterial Strain and Design Of Culture Mediummentioning

confidence: 89%

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Effect of Growth Conditions on Inactivation of Escherichia coli with Monochloramine

Berry

Raskin

2008

Environ. Sci. Technol.

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Reduced susceptibility of bacteria to disinfection is a serious concern in drinking water distribution systems (DWDS), yet the mechanisms and conditions governing reduced susceptibility are not well characterized. The effects of growth temperature, growth rate, and growth mode (suspended growth versus growth in biofilms) on inactivation kinetics of Escherichia coli exposed to monochloramine were studied in order to understand growth conditions that may reduce susceptibility of bacteria to disinfectants in DWDS. Cells grown at a suboptimal temperature (20 degrees C) were significantly less sensitive to monochloramine inactivation (using 0.5 and 5.0 mg/L monochloramine (as Cl2)) than cells grown at an optimal temperature (37 degrees C). Cells grown in biofilms were also significantly less sensitive than cells grown in suspension. No difference in inactivation kinetics was observed for cells grown in monolayer versus multilayer biofilms and between cells grown at different growth rates in chemostat bioreactors. Biofilm cells were estimated to grow at specific growth rates (mu) averaging between mu = 0.08 and 0.13 h(-1), which were approximately within the range of tested suspended growth conditions (mu = 0.04-0.10 h(-1)) using fluorescence in situ hybridizations targeting 16S rRNA. This result indicates that the reduced susceptibility of biofilm cells to monochloramine inactivation is not related to their specific growth rate within the range tested in this study. This work suggests that growth at suboptimal temperatures and growth in biofilms are important factors contributing to reduced susceptibility of bacteria to inactivation with monochloramine.

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