Nitrogen and phosphorus removal comparison between periphyton on artificial substrates and plant-periphyton complex in floating treatment wetlands

Artificial substrates (ASs) and floating treatment wetlands (FTWs) have been widely used in the treatment of polluted surface water. In fact, periphyton on ASs functions in nutrient removal, while the plant-periphyton complex functions in FTWs. However, the nutrient removal performance of the periphyton on ASs and the plant-periphyton complex in FTWs has not been systematically compared. Thus, ASs and FTWs were established in a mesocosm experiment to compare nitrogen and phosphorus removal between the two ecological treatment techniques. The results showed that the total nitrogen removal efficiency was 60.4% in the AS treatments and 65.3% in the FTWs, while the total phosphorus removal efficiency was 83.7% in the AS treatments and 39.45% in the FTWs. Periphyton on the ASs absorbed 2.5 g N m−2 and 0.85 g P m−2, accounting for 20.8% of the N removal and 18.7% of the P removal. Sedimentation contributed to 71.3% of the N removal and 56.1% of the P removal in the AS treatments. For the plant-periphyton complex in the FTWs, 25.1% of the N and 53.0% of the P accumulated in plant tissue. Most of the reduced N (47.1%) was removed by other pathways, which was likely the effect of periphyton attached on plant roots and floating rafts. The nutrient removal efficiencies and pathways of AS and FTW treatments showed different characteristics, providing a reference for the selection of treatment measures for polluted surface water remediation.