Assessment of the contribution of various constructed wetland components for the removal of pharmaceutically active compounds

Constructed wetland (CW) is being used to attenuate pharmaceutically active compounds (PhACs) from wastewater. In this study, the fate of three PhACs - atenolol (ATL), carbamazepine (CBZ), and diclofenac (DCF) was investigated in each component of the CW. The acclimatized microbes showed effective degradation of PhACs at initial concentrations of 100 mu g/L under different redox conditions, with degradation rates in the order of ATL > CBZ > DCF. The hydroponics study with Canna indica removed 19.3-31.2 % without substrate materials (initial PhACs:100 mu g/L each). The breakthrough and sorption capacity of unplanted CW followed the order: natural zeolite (1.6-2.15 mu g/g) < Light-weight expanded clay aggregate (LECA) (5.37-8.27 mu g/g) < waste autoclaved aerated concrete (AAC) block (9.27-10.79 mu g/g) < wood charcoal (24.1-26.4 mu g/g), according to their surface and textural properties. Eventually, four laboratory-scale CW units with enriched microbes, C. indica, and different supporting materials were monitored for the removal of organics, nutrients, and PhACs. A significant variation (p < 0.05) in the pollutant's removal was observed with the four supporting materials. The synergistic interaction among AAC blocks, macrophytes, and microbial population in the system exhibited higher removal of COD, TN, TP, and PhACs as 88.6%, 81.6%, 77.6%, and 95.3%, respectively. In addition, the estimated PhACs mass balance corroborated that biodegradation (80.57-93%) dominated over sorption and phytodegradation in the CWs. The abundance of Proteobacteria, Bacteroidetes, Actinobacteria, and Planctomycetes in enriched consortia contributed to the degradation of PhACs. Owing to the highly porous nature of waste AAC blocks, a relatively higher microbial activity was observed in the CW unit with AAC as substrate material.

Automated summary

Constructed wetland (CW) is an effective method for attenuating pharmaceutically active compounds (PhACs) from wastewater. The degradation of PhACs in CW is influenced by redox conditions and different components of the system. Plants and substrate materials play important roles in the removal of organics, nutrients, and PhACs from wastewater in CW.