Enhancing pharmaceutical removal in a full-scale constructed wetland with effluent recirculation

Emerging organic micropollutants pose a threat to aquatic environments even at trace levels. Among the many different groups of emerging pollutants, pharmaceutical residues are of special concern because of their toxicity and long-term effects on biota. Natural wastewater treatment systems are effective at eliminating pharmaceuticals, but removals are usually incomplete. In this regard, effluent recirculation can help to improve the removal of pharmaceuticals in natural wastewater treatment systems with the goal of producing a better-quality effluent for reuse. This is particularly interesting for water-scarce regions such as semi-arid islands of this study. The obtained results provide evidence that effluent recirculation can significantly improve the removal of pharma-ceuticals in natural wastewater treatment systems. Of the 11 compounds studied, the highest concentrations and detection frequencies (in decreasing order) were those of caffeine, paraxanthine, nicotine, ibuprofen, naproxen and atenolol. The average removals increased from 87.5% (no recirculation) to 97% (100% recirculation ratio), and these results are associated with an improved ammonium and total N removal with 100% recirculation. To the knowledge of the authors, this is the first study showing the positive effect of effluent recirculation on the removal of pharmaceuticals in a full-scale natural wastewater treatment system.