首页|Hematite-facilitated microbial ammoxidation for enhanced nitrogen removal in constructed wetlands
Hematite-facilitated microbial ammoxidation for enhanced nitrogen removal in constructed wetlands
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Constructed wetlands(CWs)are widely applied for decentralized wastewater treatment.However,achieving efficient removal of ammonia(NH4+-N)has proven challenging due to insufficient oxygen.In this study,natural hematite(Fe2O3)was employed as a CW substrate(H-CWs)for the first time to drive anaerobic ammonia oxidation coupled with iron(Ⅲ)reduction(Feammox).Compared to gravel constructed wetlands(G-CWs),ammonia removal was enhanced by 38.14％to 54.03％and nitrous oxide(N2O)emissions were reduced by 34.60％in H-CWs.The synergistic removal of ammonia and nitrate by H-CWs also resulted in the absence of ammoxidation by-products.Inhibitor and 15N isotope tracer incubations showed that Feammox accounting for approximately 40％of all ammonia removal in the H-CWs.The enrichment of iron phosphate(Fe3Fe4(PO4)6)promoted the accumulation of the Feammox intermediate compound FeOOH.Microbial nanowires were observed on the surface of H-CW substrates as well,suggesting that the observed biological ammoxidation was most likely related to extracellular electron transfer(EET).Microbial and metagenomics analysis revealed that H-CWs elevated the integrity and enhanced the abundance of functional microorganisms and genes associated with nitrogen metabolism.Overall,the efficient ammonia removal in the absence of O2 together with a reduction in N2O emissions as described in this study may provide useful guidance for hematite-mediated anaerobic ammonia removal in CWs.
Key Laboratory of the Three Gorges Reservoir Region's Eco-Environment(Ministry of Education),Chongqing University,Chongqing 400045,China
College of Environment and Ecology,Chongqing University,Chongqing 400045,China
Faculty of Geosciences and Environmental Engineering,Southwest Jiaotong University,Chengdu 610031,China
National Natural Science Foundation of ChinaChongqing Science Fund for Distinguished Young Scholars(China)Fundamental Research Funds for the Central Universities(China)
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