Can saturation levels’ optimization abate the pressure of C/N ratio variation and low temperature on vertical flow constructed wetland for nitrogen removal?

作者：Shangwu Zuo, Yueyuan Wang, Jiawei Xie, Juan Wu, Fei Zhong, Yebin Lu, Yang Yang, Shuiping Cheng · 发表于：Journal of environmental chemical engineering · 年份：2025 · DOI：10.1016/j.jece.2025.116789 · 被引用次数：8 · 研究领域：Constructed Wetlands for Wastewater Treatment

Currently, it remains unclear whether optimizing saturation levels can mitigate the adverse effects of carbon-to-nitrogen (C/N) ratio fluctuations and low temperatures on nitrogen removal in vertical flow constructed wetlands (VFCWs). To answer this, eight VFCWs with different saturation levels were operated under different influent C/N ratios in different seasons. The impacts of saturation levels on water purification performance and its underlying mechanisms were then investigated. The results showed that optimizing saturation levels significantly enhanced nitrogen removal efficiency ( P < 0.05). At low (C/N = 3.3) and middle (C/N = 6.3) ratios, a 77.7 % saturation level achieved optimal TN removal efficiencies of 53.0 % and 81.5 %, respectively. However, at high C/N ratios (10.9), saturation levels ≤ 55.5 % proved more effective, exhibiting TN removal rates ≥ 79.2 %. When subjected to low temperatures (< 15 °C), the 77.7 % saturation level maintained the highest TN removal efficiency (40.0 %). Notably, TN removal efficiency showed significant quadratic relationships with saturation levels at low and middle C/N ratios ( P < 0.05), while showing significant negative linear correlations at high C/N ratio ( P < 0.05). Partial saturation operation created optimal redox conditions for functional microbial communities in VFCWs. Specifically, ammonium-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB) were enriched in the unsaturated zone, while denitrifying bacteria th...