Enhanced nutrient removal and mechanisms study in benthic fauna added surface-flow constructed wetlands: The role of Tubifex tubifex.

This study designed a combined benthic fauna-T. orientalis-substrate-microbes surface-flow constructed wetlands (SFCWs) through the addition of T. tubifex. Results showed that, the removal efficiencies of nitrogen and phosphorus in the tested SFCWs achieved 81.14±4.16% and 70.49±7.60%, which were 22.27% and 27.35% higher than that without T. tubifex. Lower nitrate (2.11±0.79mg/L) and ammonium (0.75±0.64mg/L) were also observed in the tested SFCWs, which were 3.46mg/L and 0.52mg/L lower than that without T. tubifex. Microbial study confirmed the increased denitrifiers with T. tubifex. The lower nitrogen in effluent was also attributed to higher contents of nitrogen storage in sediment and T. orientalis due to the bioturbation of T. tubifex. Furthermore, with T. tubifex, higher proportions of particulate (22.66±3.96%) and colloidal phosphorus (20.57±3.39%) observed promoted phosphorus settlement and further absorption by T. orientalis. The outcomes of this study provides an ecological and economical strategy for improving the performance of SFCWs.