亚铁对水平潜流人工湿地污染物去除能力的分层效应影响
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摘要
通过模拟试验,考察并探讨不同浓度亚铁添加对水平潜流人工湿地中氮和COD去除能力的影响以及作用机理。结果表明:添加亚铁有利于水平潜流人工湿地各层中总氮、硝态氮和铵态氮的去除效果,而且添加亚铁浓度为50mg/L的人工湿地系统优于其他各处理组,但是过高的亚铁添加又限制了氮的去除效果,尤其是对下层铵态氮的去除能力有抑制作用,但是均高于对照组,而且亚铁添加影响了湿地系统这3种无机形态的氮分层效应。亚铁的添加促进试验初期人工湿地对COD的去除能力,在一定程度上影响了各层COD的去除效果。亚铁离子进入人工湿地后,系统中各层铁元素浓度迅速下降,但是由于铁元素的变价结构及其易水解特性,使得各处理系统出水pH先增加后趋于平稳,且下层pH低于上层和中层,同时也使得系统各层氧化还原电位(ORP)发生变化。亚铁添加促进了湿地系统中ORP的分层,却减缓了ORP的下降。
For understanding the effect of ferrous iron addition on contaminant removal in different layers of horizontal subsurface flow constructed wetlands,the nitrogen and COD removal and their mechanisms were investigated in this study.The results showed that addition of ferrous iron was beneficial to the removal of total nitrogen,nitrate nitrogen and ammonium nitrogen,and the removal of nitrogen was optimized at the ferrous iron concentration of 50mg/L.However,the excessive ferrous iron addition inhibited nitrogen removal,especially for the removal of ammonium nitrogen in the lower layers,while the nitrogen removal with ferrous iron addition was greater than that without ferrousiron.As well,ferrous iron addition altered the layering effect of the three inorganic forms of nitrogen.At the beginning of the experiment,ferrous iron addition improved the COD removal,affecting the COD removal in the different layers.Iron concentrations in the different layers dropped rapidly after the input of ferrous iron,while pH values in the effluent increased first and then kept in a stable trend due to the valence structure and hydrolytic characteristics of iron.The pH value in the lower layer was lower than those in the upper and middle layers.Iron properties also caused the changes of oxidation reduction potential(ORP)in different layers.Addition of ferrous iron promoted the layering effect of ORP,but slowed down the decrease of ORP.
For understanding the effect of ferrous iron addition on contaminant removal in different layers of horizontal subsurface flow constructed wetlands,the nitrogen and COD removal and their mechanisms were investigated in this study.The results showed that addition of ferrous iron was beneficial to the removal of total nitrogen,nitrate nitrogen and ammonium nitrogen,and the removal of nitrogen was optimized at the ferrous iron concentration of 50mg/L.However,the excessive ferrous iron addition inhibited nitrogen removal,especially for the removal of ammonium nitrogen in the lower layers,while the nitrogen removal with ferrous iron addition was greater than that without ferrousiron.As well,ferrous iron addition altered the layering effect of the three inorganic forms of nitrogen.At the beginning of the experiment,ferrous iron addition improved the COD removal,affecting the COD removal in the different layers.Iron concentrations in the different layers dropped rapidly after the input of ferrous iron,while pH values in the effluent increased first and then kept in a stable trend due to the valence structure and hydrolytic characteristics of iron.The pH value in the lower layer was lower than those in the upper and middle layers.Iron properties also caused the changes of oxidation reduction potential(ORP)in different layers.Addition of ferrous iron promoted the layering effect of ORP,but slowed down the decrease of ORP.
引文
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[2]平安,种云霄,余光伟,等.使用含铁基质的水平潜流人工湿地间隙水亚铁离子及理化环境的动态变化[J].环境科学学报,2014,34(12):3043-3049.
[3] Saeed T,Sun G.A review on nitrogen and organics removal mechanisms in subsurface flow constructed wetlands:Dependency on environmental parameters,operating conditions and supporting media[J].Journal of Environmental Management,2012,112:429-448.
[4]潘晓峰,祝惠,阎百兴,等.外源铁补给对潜流人工湿地脱氮效率影响的模拟研究[J].湿地科学,2015,13(3):350-355.
[5]侯庆杰.XP1菌株的脱氮特性及其强化人工湿地脱氮[D].济南:山东大学,2011.
[6]王苏艳,宋新山,赵志淼,等.亚铁对水平潜流人工湿地反硝化作用的影响[J].环境科学学报,2016,36(2):557-563.
[7]程龙,李怀,阎百兴,等.无植物水平折流式潜流人工湿地对氮和磷的净化效果[J].湿地科学,2016,14(2):219-225.
[8]刘树元,阎百兴,王莉霞.潜流人工湿地中氮磷污染物净化的分层效应研究[J].环境科学,2011,32(3):723-728.
[9] Liu S Y,Yan B X,Wang L X.The layer effect in nutrient removal by two indigenous plant species in horizontal flow constructed wetlands[J].Ecological Engineering,2011,37:2101-2104.
[10]国家环境保护总局.水和废水监测分析方法[M].4版.北京:中国环境科学出版社,2002.
[11] Coby A J,Picardal F,Shelobolina E,et al.Repeated anaerobic microbial redox cycling of iron[J].Applied and Environmental Microbiology,2011,77(17):6036-6042.
[12] Song X S,Wang S Y,Wang Y H,et al.Addition of Fe2+increase nitrate removal in vertical subsurface flowconstructed wetlands[J].Ecological Engineering,2016,91:487-494.
[13] Huang B,Chi G Y,Chen Y,et al.Removal of highly elevated nitrate from drinking water by pH-heterogenized heterotrophic denitrification facilitated with ferrous sulfidebased autotrophic denitrification[J].Bioresource Technology,2011,102(21):10154-10157.
[14] Khan N,Seshadri B,Bolan N,et al.Chapter one-root iron plaque on wetland plants as a dynamic pool of nutrients and contaminants[J].Advances in Agronomy,2016,138:1-96.
[15] Wu J,Zhang J,Jia W L,et al.Impact of COD/N ratio on nitrous oxide emission from microcosm wetlands and their performance in removing nitrogen from wastewater[J].Bioresource Technology,2009,100(12):2910-2917.
[16] Liu H,Chen Z,Guan Y,et al.Role and application of iron in water treatment for nitrogen removal:A review[J].Chemosphere,2018,204:51-62.
[17] Oopkaup K,Truu M,N7lvak H,et al.Dynamics of bacterial community abundance and structure in horizontal subsurface flow wetland mesocosms treating municipal wastewater[J].Water,2016,8:457.
[18] Muehe E M,Gerhardt S,Schink B,et al.Ecophysiology and the energetic benefit of mixotrophic Fe(Ⅱ)oxidation by various strains of nitrate-reducing bacteria[J].FEMS Microbiology Ecology,2009,70(3):335-343.
[19]刘树元,阎百兴,王莉霞.人工湿地中氨氮反应与pH变化关系的研究[J].水土保持学报,2010,24(3):243-246.