Switzerland decided in 2014 to upgrade major wastewater treatment plants with an additional purification stage to reduce the discharge of micropollutants into the environment. To reach this goal, Technologies based on oxidation (ozonation) and/or adsorption (activated carbon or sand filter) are available. However, data about the release of antibiotic resistance after the advanced treatments is still lacking. Therefore, we need to investigate the distribution of antibiotic resistance in different advanced treatments to know whether they would be effective to eliminate or reduce antibiotic resistant bacteria and associated resistance genes.
This project is focused on the fate of antibiotic resistance in advanced treatment, with a focus on the effects of the biological post-ozonation treatment. We will take samples from at least 5 installations that represent different situations regarding the type of filter material (sandfilter and granulated active carbon) and the age/history of filter material. Metagenomics and Q-PCR will be used to research the shift of bacterial populations and antibiotic resistance genes. Flow cytometry and bacterial cultivation will be used to enumerate microbial cell numbers, and the prevalence of cultivable antibiotic resistant bacteria. Our data will assess the removal of antibiotic resistance by advanced treatment the potential for regrowth in biological post-treatment and will provide proper recommendations for maximizing a positive effect of the new purification levels on the release of resistant bacteria.