title: Assessing nitrogen transformation processes in a trickling filter under hydraulic loading rate constraints using nitrogen functional gene abundances.
abstract: A study was conducted of treatment performance and nitrogen transformation processes in a trickling filter (TF) used to treat micro-polluted source water under variable hydraulic loading rates (HLRs), ranging from 1.0 to 3.0 m(3)/m(2) d. The TF achieved high and stable COD (97.7-99.3%) and NH4(+)-N (67.3-92.7%) removal efficiencies. Nitrification and anaerobic ammonium oxidation were the dominant nitrogen removal processes in the TF. Path analysis indicated that amoA/anammox and amoA/(narG+napA) were the two key functional gene groups driving the major processes for NH4(+)-N and NO2(-)-N, respectively. The analysis also revealed that anammox/amoA and nxrA/(nirK+nirS) were the two key functional gene groups affecting processes associated with the NO3(-)-N transformation rate. The direct and indirect effect of functional gene groups further confirmed that nitrogen transformation processes are coupled at the molecular level, resulting in a mutual contribution to nitrogen removal in the TF.
authors.affiliation: Key Laboratory of Water and Sediment Sciences, Ministry of Education, Department of Environmental Engineering, Peking University, Beijing 100871, China.
authors.forename: Honglei
authors.initials: H
authors.lastname: Wang
authors.affiliation: Key Laboratory of Water and Sediment Sciences, Ministry of Education, Department of Environmental Engineering, Peking University, Beijing 100871, China. Electronic address: jiguodong@pku.edu.cn.
authors.forename: Guodong
authors.initials: G
authors.lastname: Ji
authors.affiliation: State Environmental Protection Key Laboratory of Wetland Ecology and Vegetation Restoration, School of Environment, Northeast Normal University, Changchun 130117, China.
authors.forename: Xueyuan
authors.initials: X
authors.lastname: Bai
authors.affiliation: State Environmental Protection Key Laboratory of Wetland Ecology and Vegetation Restoration, School of Environment, Northeast Normal University, Changchun 130117, China. Electronic address: he-cg@nenu.edu.cn.
authors.forename: Chunguang
authors.initials: C
authors.lastname: He
mesh_terms: D064751:Ammonium Compounds / Q000302:isolation & purification; D001419:Bacteria / Q000235:genetics* / Q000254:growth & development; D001673:Biodegradation, Environmental; D057919:Biological Oxygen Demand Analysis; D005374:Filtration / Q000295:instrumentation*; D005798:Genes, Bacterial; D058465:Nitrification; D009584:Nitrogen / Q000302:isolation & purification / Q000378:metabolism*; D012044:Regression Analysis; D014865:Waste Disposal, Fluid; D014867:Water / Q000737:chemistry*
chemical_list: D064751:Ammonium Compounds; D014867:Water; D009584:Nitrogen
keywords: Functional gene group; Hydraulic loading rate; Nitrogen transformation process; Path analysis; Trickling filter