Mechanistic study on the role of design and management factors in regulating phosphorus treatment performance in constructed wetlands

Surface flow constructed wetlands (SFCWs) have been recommended for treating phosphorus in agricultural drainage, with their performance correlated to design and management. However, the mechanisms by which these factors regulate phosphorus removal remain unclear. Understanding these mechanisms is crucial to promoting and applying SFCWs. In this study, field pilot-scale SFCWs were subjected to orthogonal tests to investigate the effect of aspect ratios (2:1, 4:1, 8:1), plant species ( Typha latifolia , Juncus effusus , Vallisneria natans ), and hydraulic loading rates (HLR) (0.23, 0.45, 0.68 m d ‐1 ) on phosphorus removal. The results showed that sediment storage was the primary pathway for total phosphorus (TP) removal, followed by plant uptake and periphyton assimilation. No significant differences in phosphorus treatment performance were observed across different levels of aspect ratio, plant species, and HLR. However, careful selection of these factors remained crucial for the sustainability of SFCWs. Plant species influenced plant uptake by affecting the biomass of both designed plants and weeds, while aspect ratio and HLR impacted it by impacting weed biomass. Sediment storage was influenced by plant species through their regulation of flow dispersion and designed plant biomass. The impact of HLR on sediment storage was mediated by its effect on flow dispersion and dissolved inorganic phosphorus concentration. Additionally, aspect ratio influenced sediment storage through its effect on flow dispersion. Overall, an aspect ratio of 8:1, Typha as the plant species, and an HLR of 0.45 m d ‐1 promote rapid plant establishment, extend sediment lifespan, enhance plant uptake and sediment storage capacity, and simplify management. • Sediment storage dominated TP removal in SFCWs, followed by plant uptake. • Aspect ratio, plant species, and HLR influenced the sustainability of TP removal. • Plant uptake was related to plant biomass and P fractions in the sediment. • Sediment storage was related to water conditions and plant biomass.