Antibiotic resistance and microbial indicator removals in a constructed wetland treating wastewater for agricultural reuse

Objective of the study was the assessment of hygienization efficiency of a horizontal sub-surface flow constructed wetland (CW), followed by UV disinfection, for treating and reusing wastewater in agriculture. Treatments efficiencies were evaluated in terms of removal of microbial indicators, antibiotic resistance genes (ARGs) and antibiotic resistant enterococci. Good hygienization efficiencies were obtained by the studied wastewater treatment solution: CW achieved average removal of microbial indicators ranging from 2.10 ± 0.94 log CFU/100 ml for E. coli to 1.62 ± 0.59 for enterococci; UV disinfection reduced both E. coli and enterococci to undetectable level. Different effects of the applied treatments were observed on the monitored antibiotic resistance determinants. CW reduced only ARGs (average removals of 0.87 - 1.71 log unit gene copies/ml) although with variable performance during time. UV treatment showed any significant effect on the ARGs concentrations.