Removal efficiency of pharmaceuticals in constructed wetlands in Sweden

The release of pharmaceutical residues to the environment is a growing problem of global concern. Many studies have reported the negative effects of pharmaceutical residues on fish and other aquatic organisms. This master thesis has assessed five constructed wetlands (CWs) on their removal efficiency of active pharmaceutical substances. Influent and effluent wastewaters were analyzed for 24 common pharmaceutical substances in constructed wetlands in Eskilstuna, Hässleholm, Nynäshamn, Trosa and Oxelösund. The pharmaceuticals found in highest concentration in the influent were some common anti-inflammatory substances: naproxen, ibuprofen and diclofenac; a few antihypertensive substances: atenolol, hydrochlorothiazide, furosemide and metoprolol and the sedative substance, oxazepam. The concentrations varied between 0.7 μg/l and 10 μg/l. The removal efficiency was determined for 19 of the 24 substances. For 47% of the substances there was an observed removal efficiency of greater than 80% and for 47% of the substances a removal efficiency of 20–80% was observed. Diclofenac, furosemide, hydrochlorothiazide and naproxen showed the greatest removal efficiencies, 74–100%. In general, all five constructed wetlands showed high removal efficiencies for most pharmaceutical compounds, with greater removal efficiencies observed in Oxelösund, Nynäshamn and Trosa. The higher removal efficiency in these wetlands is believed to be due to their characteristic hydraulics, where wastewater basins are filled and emptied, whereas the basins in Eskilstuna and Hässleholm have continuous flow of wastewater. A comparison of removal efficiencies was also assessed for summer and winter conditions in Eskilstuna, Nynäshamn, Trosa and Oxelösund wetlands. The observed removal efficiencies were significantly greater during summer conditions.