Effect of solar simulated N-doped TiO2photocatalysis on theinactivation and antibiotic resistance of an E. coli strain in biologicallytreated urban wastewater

The effect of N-doped TiO2(NDT) photocatalysis on the inactivation of an antibiotic resistantEscherichia coli strain selected from a biologically treated urban wastewater effluent was investigated.NDT was prepared by sol–gel method and characterized by thermogravimetric analysis, X-ray diffrac-tion, FTIR and Laser Raman spectra and UV–visible reflectance spectra. XRD analysis revealed that anataseis the only crystalline phase in NDT photocatalyst and UV–visible reflectance spectra showed that theabsorption onset shifted toward visible region (about 500 nm). The NDT photocatalyst was comparedwith commercially available TiO2powders (namely Millennium PC50 and PC100), under solar simulatedradiation (250 W lamp) and different photocatalysts loadings (0.025–0.5 g L−1). The higher inactiva-tion rate (8.5 × 105CFU 100 mL−1min−1, after 10 min of irradiation) of antibiotic resistant E. coli strainwas observed for NDT photocatalyst at 0.2 g L−1dose. Kinetic test at the optimum photocatalyst load

The effect of N-doped TiO2(NDT) photocatalysis on the inactivation of an antibiotic resistantEscherichia coli strain selected from a biologically treated urban wastewater effluent was investigated.NDT was prepared by sol–gel method and characterized by thermogravimetric analysis, X-ray diffrac-tion, FTIR and Laser Raman spectra and UV–visible reflectance spectra. XRD analysis revealed that anataseis the only crystalline phase in NDT photocatalyst and UV–visible reflectance spectra showed that theabsorption onset shifted toward visible region (about 500 nm). The NDT photocatalyst was comparedwith commercially available TiO2powders (namely Millennium PC50 and PC100), under solar simulatedradiation (250 W lamp) and different photocatalysts loadings (0.025–0.5 g L−1). The higher inactiva-tion rate (8.5 × 105CFU 100 mL−1min−1, after 10 min of irradiation) of antibiotic resistant E. coli strainwas observed for NDT photocatalyst at 0.2 g L−1dose. Kinetic test at the optimum photocatalyst load-ing showed that total inactivation can be achieved after 60 min of irradiation. Antibiotic resistant test(Kirby–Bauer) on survived colonies showed that solar photocatalytic process with NDT did not signifi-cantly affect resistance of E. coli strain to tetracycline and vancomycin as irradiation time increased, buta decreasing trend (p < alpha= 0.05) in resistance to ciprofloxacin (p = 0.0311) and sensitivity to cefuroxime(p = 0.0018) was observed.