Carbamazepine removal in three pilot-scale hybrid wetlands planted with ornamental species

- CBZ removal was increased by using two-stage hybrid constructed wetlands.
- The better configurations included HSSF-CWs as a first stage.
- In the HSSF-CWs prevailed a reductive environment and anoxic conditions.
- Two ornamental species (I. sibirica and Z. aethiopica) were able to take up CBZ.
- I. sibirica exhibited the highest capacity for CBZ uptake, mainly in the roots.

The aims of this one-year study, were to evaluate the removal of carbamazepine (CBZ) in three pilot-scale two-stage hybrid constructed wetlands as well as to evaluate the performance of three emergent species (Thypha latifolia, Iris sibirica and Zantedeschia aethiopica) planted as a polyculture. The systems included horizontal subsurface flow wetlands (HSSF-CW), vertical subsurface flow wetlands (VSSF-CW) and stabilization ponds (SP). The three different configurations were: HSSF-CWs followed by SPs, HSSF-CWs followed by VSSF-CWs and VSSF-CWs followed by HSSF-CWs, which were identified as system I (SI), system II (SII) and system III (SIII) respectively. In addition, measurements of DO, Eh and pH, were taken in situ in order to know the internal system conditions. Out of the three hybrid systems, two were equally effective (SI and SII) and superior to SIII (p > 0.05). In these two systems (HSSF-CWs- SPs and HSSF-CWs-VSSF-CWs) the average mass removals were 62.5 ± 4.5% and 59.0 ± 4.5%, respectively. CBZ removal was more effective under reductive environment (∼−60 to +50 mV) and near-anoxic conditions (<1.5 mg/L of DO). In addition, the two ornamental plants exhibited a better capacity to tolerate and take up CBZ in comparison to T. latifolia. These results demonstrate that it is possible to obtain higher CBZ removal efficiencies in CWs than those reported so far, under subtropical climate by using hybrid systems planted with a polyculture that include ornamental species and using a ground local filter material.