首页|Enhancing nitrogen removal in constructed wetlands:The role of influent substrate concentrations in integrated vertical-flow systems
Enhancing nitrogen removal in constructed wetlands:The role of influent substrate concentrations in integrated vertical-flow systems
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Recent advancements in constructed wetlands(CWs)have highlighted the imperative of enhancing nitrogen(N)removal efficiency.However,the variability in influent substrate concentrations presents a challenge in optimizing N removal strategies due to its impact on removal efficiency and mechanisms.Here we show the interplay between influent substrate concentration and N removal processes within integrated vertical-flow constructed wetlands(IVFCWs),using wastewaters enriched with NO3--N and NH4+-N at varying carbon to nitrogen(C/N)ratios(1,3,and 6).In the NO3--N enriched systems,a positive correlation was observed between the C/N ratio and total nitrogen(TN)removal efficiency,which markedly increased from 13.46±2.23％to 87.00±2.37％as the C/N ratio escalated from 1 to 6.Conversely,in NH4+-N enriched systems,TN removal efficiencies in the A-6 setup(33.69±4.83％)were marginally 1.25 to 1.29 times higher than those in A-3 and A-1 systems,attributed to constraints in dissolved oxygen(DO)levels and alkalinity.Microbial community analysis and metabolic pathway assessment revealed that anaerobic denitrification,microbial N assimilation,and dissimilatory nitrate reduction to ammonium(DNRA)predominated in NO3--N systems with higher C/N ratios(C/N ≥ 3).In contrast,aerobic denitrification and microbial N assimilation were the primary pathways in NH4+-N systems and low C/N NO3--N systems.A mass balance approach indicated denitrification and microbial N assimilation contributed 4.12-47.12％and 8.51-38.96％in NO3--N systems,respectively,and 0.55-17.35％and 7.83-33.55％in NH4+-N systems to TN removal.To enhance N removal,strategies for NO3--N domi-nated systems should address carbon source limitations and electron competition between denitrifica-tion and DNRA processes,while NH4+-N dominated systems require optimization of carbon utilization pathways,and ensuring adequate DO and alkalinity supply.
State Key Laboratory of Urban Water Resource and Environment,School of Environment,Harbin Institute of Technology,No.73 Huanghe Road,Nangang District,Harbin 150090,China
Institute of Chemical Engineering in Heilongjiang Province,3# Nanhu load.High Tech R & D Zone of Harbin City.Harbin 150028,China
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