Assessment of thin-film photocatalysis inactivation of different bacterial indicators and effect on their antibiotic resistance profile

Abstract

The presence of bacterial pathogens in water bodies, alongside their growing antibiotic resistance, endanger access to freshwater sources and necessitate their successful inactivation with a proper disinfection technology. In the present study, a parallel plate reactor (PPL) with immobilized photocatalyst was used as a disinfection system for the inactivation of two bacterial indicators (Escherichia coli and Enterococcus faecalis) in aqueous samples. Experiments were carried out at parallel plate reactor configuration (PPL) operated in recycling batch mode. Titanium Tetraisopropoxide (TTIP) based thin-film coated photocatalyst surfaces were used and assessed operations parameters were; pH, initial bacteria concentration, source and type of bacteria. The effect of the photocatalytic process on antibiotic resistance profile of target bacteria was also investigated as it may serve as a pioneering step in the field of well-established and modern disinfection method development, without causing proliferation of antibiotic resistance. The observed courses of bacterial inactivation and the final disinfection rates point out diversity in the level of interaction between different type/source of bacteria and photocatalyst of concern. According to the results, a stationary phase of bacteria inactivation proceeded with a rapid and efficient one for the case of E. faecalis (99% removal after 180 min and 99.9% removal after 240 min), while the trend for E. coli is more likely to be described as extended along the process time. Among the tested antibiotics, E. coli Minimum inhibition concentration (MIC) values for beta-lactam, macrolide and aminoglycoside groups were considerably altered (namely Ampicillin, Cefaclor, Clarithromycin - Erythromycin and Amikacin, respectively). PC oxidation was approved to be efficient on bacterial inactivation and trigger alterations on resistance behaviour of E.coli and Enterococcus sp. strains.