Potential of constructed wetland for the removal of antibiotics and antibiotic resistant bacteria from livestock wastewater

This study aimed to evaluate the potential of CWs to remove bacteria, including antibiotic resistant bacteria, and antibiotics from livestock (swine production) wastewater. Microcosms were assembled with Phragmites australis (Cav.) Trin. ex Steud and feed with wastewater spiked or not with 100 µg/L of enrofloxacin or of ceftiofur, alone or as a mixture. Wastewater (spiked or not) was treated during twenty one-week cycles. Treated wastewater was collected at weeks 1, 2, 4, 8, 14, 18 and 20 to evaluate the removal of pollutants, including nutrients, organic matter, metals and added antibiotics, and total cultivable and antibiotic resistant bacteria (enterobacteria and enterococci), which were enumerated in plate culture media. After treatment, a significant reduction in pollutants load (up to 99% depending on the parameter) was observed regardless of the presence of the veterinary antibiotics. Antibiotics were also significantly removed (removal > 90%). High removal rates were achieved for enterobacteria and enterococci bacteria during the experimental period, in the presence or absence of antibiotics (mean removals between 86 and 100%). For antibiotic resistant bacteria initially present in the influent wastewater mean removals > 90% were obtained, and no significant effect of time or of antibiotic presence was observed. This study is, to our knowledge, the first to focus on the removal of enrofloxacin and ceftiofur resistance in faecal bioindicators in CWs fed with livestock wastewater. Results confirm CWs as a green alternative to reduce the risks associated with the release of livestock effluents into the environment.