title: Effects of HRT and water temperature on nitrogen removal in autotrophic gravel filter.
abstract: Organic Carbon added to low ratio of carbon to nitrogen (C/N ratio) wastewater to enhance heterotrophic denitrification performance might lead to higher operating costs and secondary pollution. In this study, sodium thiosulfate (Na2S2O3) was applied as an electron donor for a gravel filter (one kind of constructed wetland) to investigate effects of hydraulic retention time (HRT) and water temperature on the nitrate removal efficiency. The results show that with an HRT of 12 h, the average total nitrogen (TN) removal efficiencies were 91% at 15-20 °C and 18% at 3-6 °C, respectively. When HRT increased to 24 h, the average TN removal increased accordingly to 41% at 3-6 °C, suggesting denitrification performance was improved by extended HRT at low water temperatures. Due to denitrification, 96% of added nitrate nitrogen (NO3(-)-N) was converted to nitrogen gas, with a mean flux of nitrous oxide (N2O) was 0.0268-0.1500 ug m(-2) h(-1), while 98.86% of thiosulfate was gradually converted to sulfate throughout the system. Thus, our results show that the sulfur driven autotrophic denitrification constructed wetland demonstrated an excellent removal efficiency of nitrate for wastewater treatment. The HRT and water temperature proved to be two influencing factors in this constructed wetland treatment system.
authors.affiliation: School of Environmental Science and Engineering, Shanghai Jiaotong University, Shanghai 200240, PR China.
authors.forename: Jing-hang
authors.initials: JH
authors.lastname: Xu
authors.affiliation: School of Environmental Science and Engineering, Shanghai Jiaotong University, Shanghai 200240, PR China. Electronic address: heshengbing@sjtu.edu.cn.
authors.forename: Sheng-bing
authors.initials: SB
authors.lastname: He
authors.affiliation: School of Environmental Science and Engineering, Shanghai Jiaotong University, Shanghai 200240, PR China.
authors.forename: Su-qing
authors.initials: SQ
authors.lastname: Wu
authors.affiliation: School of Environmental Science and Engineering, Shanghai Jiaotong University, Shanghai 200240, PR China.
authors.forename: Jung-Chen
authors.initials: JC
authors.lastname: Huang
authors.affiliation: School of Environmental Science and Engineering, Shanghai Jiaotong University, Shanghai 200240, PR China.
authors.forename: Wei-li
authors.initials: WL
authors.lastname: Zhou
authors.affiliation: School of Environmental Science and Engineering, Shanghai Jiaotong University, Shanghai 200240, PR China.
authors.forename: Xue-chu
authors.initials: XC
authors.lastname: Chen
mesh_terms: D052818:Autotrophic Processes; D005374:Filtration; D009584:Nitrogen / Q000737:chemistry*; D013696:Temperature; D013885:Thiosulfates / Q000737:chemistry; D014865:Waste Disposal, Fluid / Q000379:methods*; D014872:Water Movements; D014874:Water Pollutants, Chemical / Q000737:chemistry*
chemical_list: D013885:Thiosulfates; D014874:Water Pollutants, Chemical; C017717:sodium thiosulfate; D009584:Nitrogen
keywords: Constructed wetland; HRT; Nitrogen removal; Sulfur autotrophic de-nitrification