Collections > Master's Papers > Gillings School of Public Health > Efficacy of Sodium Hypochlorite for Disinfecting Raoultella terrigena Cells in Varying Preparation Conditions, and in Multiple Test Water Matrices Under Point-of-Use Conditions

Variability and lack of specificity in conditions for laboratory performance evaluations for point-of-use drinking water technologies creates situations where different and inconsistent results are produced from systems that bear no resemblance to water conditions or settings where a point-of-use device is implemented in the field. To evaluate various test conditions, experiments were conducted with sodium hypochlorite under model point-of-use conditions to: (i) determine the impact on disinfection efficacy of varying free chlorine concentrations; (ii) characterize disinfection performance in chemically defined and natural test water matrices; and (iii) determine the influence of cell preparation and handling on bacterial reductions. Free chlorine doses from 0.5 to 5.0 mg/L produced consistent disinfection results with log10 reductions at one minute ranging from 4.8 to 6.5 log10, respectively. Washing of cells had substantial impact on free chlorine log10 reductions while storage over 14 days had little impact. Test water matrices with high organic load significantly influenced chlorine residual and reduced microbial reductions. Therefore, preparation and testing conditions need to be specified in detail to achieve consistent microbial reduction performance.