Removal of decabromodiphenyl ether (BDE-209) using a combined system involving TiO₂ photocatalysis and wetland plants

There is a rising concern about the capability of sewage treatment works in treating emerging chemicals, such as polybrominated diphenyl ethers (PBDEs). A combined photocatalysis (TiO₂ and visible light) and constructed wetland system (planted with Oryza sativa (rice cultivar: Hefengzhan) and Phragmites australis (common reed)) was designed to study PBDEs removal efficiencies. After the pre-treatment in TiO₂ suspension, the artificially BDE-209 spiked sewage (78.2 and 782 nmol/L) was discharged into the sub-surface flow constructed wetland tanks planted with rice and common reed, respectively. The treated sewage, soil, plant roots, shoots, rice grains and hulls were collected and analyzed for PBDEs by GC–MS. The removals of BDE-209 in the combined systems (93.6 ± 2.19% (78.2 nmol/L) and 92.1 ± 1.11% (782 nmol/L)) were significantly higher than those in the photocatalytic systems (56.3 ± 5.78% (78.2 nmol/L) and 54.7 ± 9.47% (782 nmol/L)), which could be explained by the enhanced biodegradability of PBDEs in photocatalysis, led to its better dissipation by rice plants. Therefore, this combined system might help to degrade BDE-209 in the wastewater effluent, reducing its potential entry into aquatic food chains.