Removal of pharmaceuticals by a pilot aerated sub-surface flow constructed wetland treating municipal and hospital wastewater

- Elevated concentrations of pharmaceutical residues in surface waters are observed due to discharge of wastewater effluent.
- The impact of aeration on the performance of a pilot constructed wetland was studied.
- Continuous aeration facilitated efficient removal of organic matter and ammonium at high organic loading.
- The removal of pharmaceuticals metformin and valsartan was significantly improved during aeration.

Constructed wetlands are often used as decentralized wastewater treatment and as treatment systems for small communities. The effluent is usually discharged in small water courses in which the aquatic ecosystem can be put at risk by pharmaceutical residues present in the effluent. This study describes the performance of a pilot-scale aerated subsurface-flow constructed wetland treating municipal and hospital wastewater. Especially the effect of active aeration on the removal of selected pharmaceuticals is assessed. The removal of metformin and valsartan is significantly increased when continuous aeration is applied (99 ± 1% vs. 68 ± 32% for metformin and 99 ± 1% vs. 17 ± 19% for valsartan), although the micro-organisms can adapt to degrading metformin also in anoxic conditions. At the hospital site high concentrations of pharmaceuticals are measured in the influent. Atenolol and bisoprolol are efficiently removed (>75% and >50%, respectively), although the effluent concentrations of these compounds remain high (up to 0.5 μg/L). Only limited removal of carbamazepine, diclofenac, gabapentin and sulfamethoxazole is achieved. Intermittent aeration (50%) provides equally efficient removal of the selected pharmaceuticals as continuous aeration.