Author(s): Junheng Pan; Baoshan Shi; Xiangju Cheng; Dantong Zhu
Linked Author(s): Xiangju Cheng, Dantong Zhu
Keywords: Nitrogen removal driving force functional genes microbial co-occurrence network structural equation modeling nitrogen removal performance
Abstract: The performance optimization of horizontal subsurface flow constructed wetlands (HSSF CWs), regarded as efficient constructed wetlands (CWs) for nitrogen removal, has emerged as a significant topic in the field of water treatment. In this study, we conducted an investigation and comparison of three CWs through mechanistic tests: the unplanted group (CW_0), the Cyperus involucratus Rottboll planted group (CW_CR), and the Thalia dealbata Fraser planted group (CW_TF). We integrated the Phylogenetic Investigation of Communities by Reconstruction of Unobserved States 2 (PICRUSt2) function predictions, microbial co-occurrence networks, and structural equation modeling (SEM) to systematically investigate the effects of C/N ratio, plant factors, key functional genes, and microbial community structure on nitrogen removal performance as well as their interactions. The results indicated that an increase in the C/N ratio (from 3 to 8) significantly enhanced nitrogen removal performance, with the CW_CR at a C/N ratio of 8 demonstrating the highest nitrogen removal performance. Furthermore, the impact of plant species on nitrogen removal performance demonstrated significant variation across different C/N ratios. The community characteristics and co-occurrence network analysis of microorganisms further revealed that the presence of plants not only enriched microbial diversity within the CWs but also promoted synergistic cooperation among microorganisms, thereby forming a more complex and tightly interconnected microbial network that influenced the response of the CWs to carbon sources. Moreover, distinct plant species induced variations in the key phyla of the microbial network. The structural equation modeling analysis indicated that during the increase in the C/N ratio, the alterations in carbon sources and microbial community structure affected total nitrogen (TN) removal efficiencies by regulating the abundance of functional genes. The primary mechanism involved promoting denitrification while inhibiting nitrification to enhance nitrogen removal performance. Notably, the increase in nirS gene abundance contributed most significantly to TN removal efficiencies. The findings of this study not only demonstrated the potential for effectively regulating the abundance of functional genes to significantly enhance nitrogen removal performance through adjustments to the C/N ratio or optimization of microbial community structure, thereby significantly enhancing nitrogen removal performance, but also provided a scientific basis and identified new research directions for the performance optimization of CWs.
Year: 2025