Assessment of plants radial oxygen loss for nutrients and organic matter removal in full-scale constructed wetlands treating municipal effluents

Bidirectional cross flow wetlands with different plant species were set to investigate seasonal variation in radial oxygen loss (ROL) and its effects on COD and NH4+-N removal. Findings demonstrated a strong seasonal effect on the rate of ROL, with Arundo donax var.versicolor showing the highest ROL of 2.99 μmol·h-1·g-1. Additionally, ROL showed strong positive correlations with plant total biomass (P < 0.01), aboveground biomass (P < 0.01), height, maximum root length (P < 0.01), root porosity (P < 0.01), and removal efficiency of COD and NH4+-N (P < 0.01). Furthermore, high-throughput sequencing analysis of substrate samples from three wetland units planted with Thalia dealbata, Canna indica and Arundo donax var. versicolor revealedProteobacteria as the predominant rhizospheric phylum. Relative abundance of Alpha- and Gamma-Proteobacteria were higher in the Arundo donax var.versicolor samples due to its higher oxygen transport capacity. These results demonstrate that root properties are important determinants for selecting appropriate plants for constructed wetland.