Wastewater disinfection by solar heterogeneous photocatalysis: effect on tetracycline resistant/sensitive Enterococcus strains

Solar simulated heterogeneous photocatalysis (SSHP) with suspended TiO₂ was investigated in the inactivation of tetracycline resistant/sensitive Enterococcus (TRE/TSE) strains in the effluent of an urban wastewater treatment plant (UWTP). The effect of solar simulated disinfection (SSD) on the inactivation of the same Enterococcus strains was investigated as control. SSHP process (0.05 g l^-1 of TiO₂) was found to be effective in the inactivation of both Enterococcus strains with total inactivation (~7 log unit) observed after 60 min of irradiation. On the contrary, SSD process did not show any significant inactivation after 90 min of irradiation. The effect of both processes on the antibiotic resistance phenotypes of the surviving enterococci was also evaluated. TRE cells surviving the SSHP treatment showed that disinfection process did not affect the antibiotic resistance pattern after 45 min irradiation. The same was observed for the TSE strain. Accordingly, antibiotic resistance can spread into the receiving water body when antibiotic resistant strains survive to disinfection process.