Inactivation of particle-associated Escherichia coli with chlorine dioxide

In this paper, the inactivation of both free Escherichia coli (FE) and particle-associated E. coli (PAE) with chlorine dioxide (ClO₂) were investigated using granular activated carbon effluent water samples. The inactivation rate of FE was higher than that of PAE and the reactivation ratio of PAE was higher than that of FE, indicating the threat of particle-associated bacteria. Response surface methodology (RSM) was applied to determine the factors influencing the disinfection efficiency of ClO₂ in inactivating PAE. The experimental results indicated that particle concentration was a principal factor influencing the PAE inactivation efficiency, presenting a negative correlation, while exposure time and ClO₂ dosage revealed a positive correlation. The inactivation kinetics of PAE using ClO₂ was also investigated and the results demonstrated that PAE inactivation with ClO₂ fitted the Chick–Watson kinetic model. The inactivation rate constants of PAE were found to follow the Arrhenius expression with an activation energy of 107.5 kJ/mol, indicating a relatively strong temperature dependence. However, there are minor effects of pH and initial ClO₂ dosage on PAE inactivation rate constant.