Development of reactive fillers in constructed wetland and its performance of nitrogen and phosphorus removal

Abstract:

[Objective] Constructed wetland fillers as denitrification electron donors can remove nitrogen and phosphorus efficiently and stably, but the selection method and mechanism of filler are still unclear. [Methods] In this study, pyrrhotite, siderite and agricultural waste (sawdust, etc.) were used as fillers in constructed wetlands, and their effects on denitrification, nitrogen and phosphorus removal in constructed wetlands were studied. [Results] The results show that the ore combination with a mass ratio of 1:1 and wood chips are used as a mixed filler with a mass ratio of 3:1, the removal rates of NO₃^--N and PO₄^3--P reached 88.6% and 88.9% after eight cycles of domestication. The results of scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and community analysis showed that the microorganisms could effectively use the ore and its secondary products and sawdust for efficient and lasting nitrogen and phosphorus removal, and the functional bacteria Thiobacillus, Romboutsia and Lysobacter were enriched. [Conclusion] This study provides theoretical basis and guiding significance for the selection of new fillers in the practical application of constructed wetlands.