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Mesocosm-Scale Constructed Wetland Design for Wastewater Treatment
Published on: May 2, 2025
Biochar enhances nitrogen removal and mitigates N2O emissions under salinity stress: Mechanism exploration and
Shuyuan Zhao1, Yang Luo2, Fucheng Guo3
1College of Environment and Ecology, Key Laboratory of the Three Gorges Reservoir Region's Eco-Environment, Ministry of Education, Chongqing University, Chongqing 400044, China.
Abstract:
Advanced treatment of high-salinity nitrogenous wastewater is a critical global environmental challenge. Salinity stress severely suppresses biological nitrogen removal, leading to excessive nitrogen release into aquatic environments and exacerbating eutrophication. This study systematically investigated different salinity stresses on denitrification and its mitigation by Typha latifolia biochar (TLBC, pyrolyzed at 300 °C). Increasing salinity (5/15/25 g/L NaCl) induced significant accumulation of NO3--N, NO2--N, and TN, with N2O emissions 1.4-2.5 folds higher than the non-saline control. In contrast, TLBC addition improved nitrogen removal (TN = 0 mg/L) and reduced N2O emissions to 13.1%-14.3% of those in salinity-stressed groups. TLBC promoted denitrification by stimulating extracellular polymeric substances secretion to protect cell membrane integrity, enhancing carbon source utilization efficiency, boosting energy metabolism and denitrifying enzyme activities, and enriching salt-tolerant microorganisms (e.g., Klebsiella, Castellaniella). Furthermore, a 120-day operation of TLBC-enhanced constructed wetlands (CWs) under high-salinity stress (25 g/L NaCl) confirmed NO3--N and TN removal efficiencies were 1.2-1.4 and 1.2-1.5 folds higher, respectively, with N2O emissions reduced to 29.7% of those in CWs without TLBC. These findings confirm that TLBC effectively mitigates salinity stress on denitrification, supporting it as a sustainable amendment for the advanced treatment of high-salinity nitrogenous wastewater.
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