Bacterial inactivation kinetics, regrowth and synergistic competition in a photocatalytic disinfection system using anatase titanate nanofiber catalyst

This work studied the inactivation kinetics, bacterial regrowth and synergistic competition in the photocatalytic disinfection of a sewage isolated Escherichia coli (ATCC 11775) in an annular slurry photoreactor (ASP) system using anatase titanate nanofibers catalyst (TNC). The inactivation performance and disinfection kinetics of the TNC–ASP system were investigated with respect to operation conditions: TNC loading, pH, aeration rate and inoculums size. At the optimum conditions, a 99.999% inactivation of 7 × 106 CFU mL−1 E. coli was achieved in 60 min. The modified Hom model was used to perfectly-fit the sigmoid-shaped disinfection kinetic profile. The residual disinfecting effect was evaluated by post-irradiation Fenton reaction. It was found that the 1.0 mg L−1 Fe2+ in conjunction with low chemical oxygen demand (COD) was able to initiate the post-photocatalytic Fenton reaction, where substantial bacterial regrowth was suppressed after 24 h treatment. Studies on the synergistic effect of COD concentration on the inactivation and the bacterial regrowth potential revealed that the E. coli could regrowth at a COD concentration over 16 mg L−1. Thus, significant removal of COD has to be ensured in a photocatalytic disinfection process to successfully maintain the biostability of the treated water.