生物炭对潜流人工湿地污染物去除及N_2O排放影响
|
摘要
生物炭作为一种生物质废弃物的热解产物,逐渐被应用于受污染水体治理.生物炭具有提高孔隙、吸附氮磷、控制温室气体排放等作用.通过在温室内构建生物炭投加比为40%、30%、20%、10%和0%的微型潜流湿地系统(分别命名为BW-40、BW-30、BW-20、BW-10和CW-K),探究生物炭投加对湿地污染物去除及N_2O排放的影响.结果表明,投加生物炭可以提高出水氧化还原电位(oxidation-reduction potential,ORP),降低电导率(conductivity,Cond),但影响均不显著(P> 0. 05).5组湿地系统中化学需氧量(COD)去除率均达到90%,但随着生物炭投加比的增加,氨氮(NH_4~+-N)和总氮(TN)的去除效果显著提高(P <0. 05).湿地NH_4~+-N平均去除率为(34. 76±14. 16)%～(57. 96±10. 63)%,TN平均去除率为(70. 92±5. 68)%～(80. 21±10. 63)%.各湿地系统N_2O的平均释放通量在13. 53～45. 30 mg·(m~2·d)~(-1)之间,生物炭投加可以通过减少亚硝态氮(NO_2~--N)累积浓度和积累时间,实现N_2O减排,并显著减少湿地中N_2O排放占TN去除的百分比(P <0. 05). 40%的生物炭投加比可以实现70. 13%的N_2O减排效果.
Biochar,pyrolyzed from agricultural biomass wastes,has been widely used as an improver in wastewater treatment to regulate the oxygen distributions and microbial communities because of its extended surface area and porous structure. In addition,biochar has been shown to play a role in enhancing the porosity,adsorbing ammonium(NH_4~+ -N),and reducing nitrous oxide(N_2O)emissions. In this paper,five groups of constructed microcosm wetlands(CW) were built in a greenhouse with different biochar doses of 40%,30%,20%,10%,and 0%(named as BW-40,BW-30,BW-20,BW-10,and CW-K,respectively) to investigate the influences of biochar on pollutant removal efficiencies and N_2O emissions. The results showed that the concentration of effluent dissolved oxygen(DO) was less than 0. 5 mg·L~(-1),and the p H was stable at around 7. 2 in every CW. Additionally,the effluent oxidation-reduction potential(ORP) was found to have moderately increased with the increases in the quantity of biochar,and the conductivity(Cond) test results showed the opposite trend. However,the effects of biochar on DO,p H,ORP,and Cond were not significant(P > 0. 05). The chemical oxygen demand(COD) removal rates were up to 90% in all CWs. On the other hand,significantly higher removal efficiencies for NH_4~+ -N and total nitrogen(TN) were found in CWs filled with biochar(P < 0. 05). The average NH_4~+ -N removal rates were(57. 96 ± 10. 63) %,(51. 12 ± 11. 74) %,(48. 55 ± 8. 75) %,(43. 95 ± 9. 74) %,and(34. 76± 14. 16) % in BW-40,BW-30,BW-20,BW-10,and CW-K,respectively,while the total nitrogen(TN) average removal rates were(80. 21 ± 10. 63) %,(78. 48 ± 5. 73) %,(76. 80 ± 4. 20) %,(75. 88 ± 5. 85) %,and(70. 92 ± 5. 68) %,respectively.Nitrate(NO_3~--N) was not detected in the CWs for there were sufficient carbon sources and suitable denitrification environments.Moreover,the average fluxes of N_2O ranged from 13. 53 mg·(m~2·d)~(-1) to 45. 30 mg·(m~2·d)~(-1) in the experimental systems.Compared with the control,the reduction rates of N_2O in the BW-40,BW30,BW20,and BW10 were 70. 13%,68. 26%,50. 83%,and 37. 90%,respectively,and the ratios of N_2O emissions to the removed nitrogen in CWs with biochar were significantly lower than those in the CW without biochar. Positive correlations were observed between the N_2O fluxes and nitrite(NO_2~--N) concentrations,and the lower N_2O emissions could be attributed to the higher oxygen transfer and lower NO_2~--N accumulation rates in response to the biochar addition. These results demonstrate that biochar could be used as an amendment to strengthen the nitrogen removal and reduce the N_2O emissions in CWs.
Biochar,pyrolyzed from agricultural biomass wastes,has been widely used as an improver in wastewater treatment to regulate the oxygen distributions and microbial communities because of its extended surface area and porous structure. In addition,biochar has been shown to play a role in enhancing the porosity,adsorbing ammonium(NH_4~+ -N),and reducing nitrous oxide(N_2O)emissions. In this paper,five groups of constructed microcosm wetlands(CW) were built in a greenhouse with different biochar doses of 40%,30%,20%,10%,and 0%(named as BW-40,BW-30,BW-20,BW-10,and CW-K,respectively) to investigate the influences of biochar on pollutant removal efficiencies and N_2O emissions. The results showed that the concentration of effluent dissolved oxygen(DO) was less than 0. 5 mg·L~(-1),and the p H was stable at around 7. 2 in every CW. Additionally,the effluent oxidation-reduction potential(ORP) was found to have moderately increased with the increases in the quantity of biochar,and the conductivity(Cond) test results showed the opposite trend. However,the effects of biochar on DO,p H,ORP,and Cond were not significant(P > 0. 05). The chemical oxygen demand(COD) removal rates were up to 90% in all CWs. On the other hand,significantly higher removal efficiencies for NH_4~+ -N and total nitrogen(TN) were found in CWs filled with biochar(P < 0. 05). The average NH_4~+ -N removal rates were(57. 96 ± 10. 63) %,(51. 12 ± 11. 74) %,(48. 55 ± 8. 75) %,(43. 95 ± 9. 74) %,and(34. 76± 14. 16) % in BW-40,BW-30,BW-20,BW-10,and CW-K,respectively,while the total nitrogen(TN) average removal rates were(80. 21 ± 10. 63) %,(78. 48 ± 5. 73) %,(76. 80 ± 4. 20) %,(75. 88 ± 5. 85) %,and(70. 92 ± 5. 68) %,respectively.Nitrate(NO_3~--N) was not detected in the CWs for there were sufficient carbon sources and suitable denitrification environments.Moreover,the average fluxes of N_2O ranged from 13. 53 mg·(m~2·d)~(-1) to 45. 30 mg·(m~2·d)~(-1) in the experimental systems.Compared with the control,the reduction rates of N_2O in the BW-40,BW30,BW20,and BW10 were 70. 13%,68. 26%,50. 83%,and 37. 90%,respectively,and the ratios of N_2O emissions to the removed nitrogen in CWs with biochar were significantly lower than those in the CW without biochar. Positive correlations were observed between the N_2O fluxes and nitrite(NO_2~--N) concentrations,and the lower N_2O emissions could be attributed to the higher oxygen transfer and lower NO_2~--N accumulation rates in response to the biochar addition. These results demonstrate that biochar could be used as an amendment to strengthen the nitrogen removal and reduce the N_2O emissions in CWs.
引文
[1] Zhang X W,Hu Z,Ngo H H,et al. Simultaneous improvement of waste gas purification and nitrogen removal using a novel aerated vertical flow constructed wetland[J]. Water Research,2018,130:79-87.
[2] Fu G P,Huangshen L K,Guo Z P,et al. Effect of plant-based carbon sources on denitrifying microorganisms in a vertical flow constructed wetland[J]. Bioresource Technology,2017,224:214-221.
[3] Liu F F, Fan J L, Du J H, et al. Intensified nitrogen transformation in intermittently aerated constructed wetlands:removal pathways and microbial response mechanism[J].Science of the Total Environment,2019,650:2880-2887.
[4] Maucieri C,Barbera A C,Vymazal J,et al. A review on the main affecting factors of greenhouse gases emission in constructed wetlands[J]. Agricultural and Forest Meteorology,2017,236:175-193.
[5] Paranychianakis N V,Tsiknia M,Kalogerakis N. Pathways regulating the removal of nitrogen in planted and unplanted subsurface flow constructed wetlands[J]. Water Research,2016,102:321-329.
[6] Kizito S,Lv T,Wu S B,et al. Treatment of anaerobic digested effluent in biochar-packed vertical flow constructed wetland columns:role of media and tidal operation[J]. Science of the Total Environment,2017,592:197-205.
[7] Fan J L,Liang S,Zhang B,et al. Enhanced organics and nitrogen removal in batch-operated vertical flow constructed wetlands by combination of intermittent aeration and step feeding strategy[J]. Environmental Science and Pollution Research,2013,20(4):2448-2455.
[8] Wu H M,Zhang J,Ngo H H,et al. Evaluating the sustainability of free water surface flow constructed wetlands:methane and nitrous oxide emissions[J]. Journal of Cleaner Production,2017,147:152-156.
[9] Huang L,Chen Y C,Liu G,et al. Non-isothermal pyrolysis characteristics of giant reed(Arundo donax L.)using thermogravimetric analysis[J]. Energy,2015,87:31-40.
[10]王宁,黄磊,罗星,等.生物炭添加对曝气人工湿地脱氮及氧化亚氮释放的影响[J].环境科学,2018,39(10):4505-4511.Wang N,Huang L,Luo X,et al. Impact of biochar on nitrogen removal and nitrous oxide emission in aerated vertical flow constructed wetland[J]. Environmental Science, 2018, 39(10):4505-4511.
[11] Cayuela M L,Sánchez-Monedero M A,Roig A,et al. Biochar and denitrification in soils:when, how much and why does biochar reduce N2O emissions?[J]. Scientific Reports,2013,3:1732.
[12] He S,Ding L L,Wang X,et al. Biochar carrier application for nitrogen removal of domestic WWTPs in winter:challenges and opportunities[J]. Applied Microbiology and Biotechnology,2018,102(22):9411-9418.
[13] Zhou X,Jia L X,Liang C L,et al. Simultaneous enhancement of nitrogen removal and nitrous oxide reduction by a saturated biochar-based intermittent aeration vertical flow constructed wetland:effects of influent strength[J]. Chemical Engineering Journal,2018,334:1842-1850.
[14]黄磊,陈玉成,赵亚琦,等.生物炭添加对湿地植物生长及氧化应激响应的影响[J].环境科学,2018,39(6):2904-2910.Huang L,Chen Y C,Zhao Y Q,et al. Influence of biochar application on growth and antioxidative responses of macrophytes in subsurface flow constructed wetlands[J]. Environmental Science,2018,39(6):2904-2910.
[15]国家环境保护总局.水和废水监测分析方法[M].(第四版).北京:中国环境科学出版社,2002.
[16] 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.
[17] Lyu W L,Huang L,Xiao G Q,et al. Effects of carbon sources and COD/N ratio on N2O emissions in subsurface flow constructed wetlands[J]. Bioresource Technology,2017,245:171-181.
[18] Saeed T,Sun G Z. A comparative study on the removal of nutrients and organic matter in wetland reactors employing organic media[J]. Chemical Engineering Journal,2011,171(2):439-447.
[19] Sun Y F,Qi S Y,Zheng F P,et al. Organics removal,nitrogen removal and N2O emission in subsurface wastewater infiltration systems amended with/without biochar and sludge[J].Bioresource Technology,2018,249:57-61.
[20] Vymazal J,Kr?pfelováL. Removal of organics in constructed wetlands with horizontal sub-surface flow:a review of the field experience[J]. Science of the Total Environment,2009,407(13):3911-3922.
[21] Zhou X,Liang C L,Jia L X,et al. An innovative biocharamended substrate vertical flow constructed wetland for low C/N wastewater treatment:impact of influent strengths[J].Bioresource Technology,2018,247:844-850.
[22] De Rozari P,Greenway M,El Hanandeh A. Nitrogen removal from sewage and septage in constructed wetland mesocosms using sand media amended with biochar[J]. Ecological Engineering,2018,111:1-10.
[23] Li J,Fan J L,Zhang J,et al. Preparation and evaluation of wetland plant-based biochar for nitrogen removal enhancement in surface flow constructed wetlands[J]. Environmental Science and Pollution Research,2018,25(14):13929-13937.
[24] Maltais-Landry G,Maranger R,Brisson J. Effect of artificial aeration and macrophyte species on nitrogen cycling and gas flux in constructed wetlands[J]. Ecological Engineering,2009,35(2):221-229.
[25] Li M,Wu H M,Zhang J,et al. Nitrogen removal and nitrous oxide emission in surface flow constructed wetlands for treating sewage treatment plant effluent:effect of C/N ratios[J].Bioresource Technology,2017,240:157-164.
[26] Sanchez-Monedero M A,Cayuela M L,Roig A,et al. Role of biochar as an additive in organic waste composting[J].Bioresource Technology,2018,247:1155-1164.
[27]刘秀红,杨庆,吴昌永,等.不同污水生物脱氮工艺中N2O释放量及影响因素[J].环境科学学报,2006,26(12):1940-1947.Liu X H,Yang Q,Wu C Y,et al. N2O emissions from different biological nitrogen removal processes and factors affecting N2O production[J]. Acta Scientiae Circumstantiae,2006,26(12):1940-1947.
[28] Zhang S N,Liu F,Xiao R L,et al. Emissions of NO and N2O in wetland microcosms for swine wastewater treatment[J].Environmental Science and Pollution Research,2015,22(24):19933-19939.
[29] Feng Z J,Zhu L Z. Impact of biochar on soil N2O emissions under different biochar-carbon/fertilizer-nitrogen ratios at a constant moisture condition on a silt loam soil[J]. Science of the Total Environment,2017,584-585:776-782.
[30] Zhu X,Burger M,Doane T A,et al. Ammonia oxidation pathways and nitrifier denitrification are significant sources of N2O and NO under low oxygen availability[J]. Proceedings of the National Academy of Sciences of the United States of America,2013,110(16):6328-6333.
[2] Fu G P,Huangshen L K,Guo Z P,et al. Effect of plant-based carbon sources on denitrifying microorganisms in a vertical flow constructed wetland[J]. Bioresource Technology,2017,224:214-221.
[3] Liu F F, Fan J L, Du J H, et al. Intensified nitrogen transformation in intermittently aerated constructed wetlands:removal pathways and microbial response mechanism[J].Science of the Total Environment,2019,650:2880-2887.
[4] Maucieri C,Barbera A C,Vymazal J,et al. A review on the main affecting factors of greenhouse gases emission in constructed wetlands[J]. Agricultural and Forest Meteorology,2017,236:175-193.
[5] Paranychianakis N V,Tsiknia M,Kalogerakis N. Pathways regulating the removal of nitrogen in planted and unplanted subsurface flow constructed wetlands[J]. Water Research,2016,102:321-329.
[6] Kizito S,Lv T,Wu S B,et al. Treatment of anaerobic digested effluent in biochar-packed vertical flow constructed wetland columns:role of media and tidal operation[J]. Science of the Total Environment,2017,592:197-205.
[7] Fan J L,Liang S,Zhang B,et al. Enhanced organics and nitrogen removal in batch-operated vertical flow constructed wetlands by combination of intermittent aeration and step feeding strategy[J]. Environmental Science and Pollution Research,2013,20(4):2448-2455.
[8] Wu H M,Zhang J,Ngo H H,et al. Evaluating the sustainability of free water surface flow constructed wetlands:methane and nitrous oxide emissions[J]. Journal of Cleaner Production,2017,147:152-156.
[9] Huang L,Chen Y C,Liu G,et al. Non-isothermal pyrolysis characteristics of giant reed(Arundo donax L.)using thermogravimetric analysis[J]. Energy,2015,87:31-40.
[10]王宁,黄磊,罗星,等.生物炭添加对曝气人工湿地脱氮及氧化亚氮释放的影响[J].环境科学,2018,39(10):4505-4511.Wang N,Huang L,Luo X,et al. Impact of biochar on nitrogen removal and nitrous oxide emission in aerated vertical flow constructed wetland[J]. Environmental Science, 2018, 39(10):4505-4511.
[11] Cayuela M L,Sánchez-Monedero M A,Roig A,et al. Biochar and denitrification in soils:when, how much and why does biochar reduce N2O emissions?[J]. Scientific Reports,2013,3:1732.
[12] He S,Ding L L,Wang X,et al. Biochar carrier application for nitrogen removal of domestic WWTPs in winter:challenges and opportunities[J]. Applied Microbiology and Biotechnology,2018,102(22):9411-9418.
[13] Zhou X,Jia L X,Liang C L,et al. Simultaneous enhancement of nitrogen removal and nitrous oxide reduction by a saturated biochar-based intermittent aeration vertical flow constructed wetland:effects of influent strength[J]. Chemical Engineering Journal,2018,334:1842-1850.
[14]黄磊,陈玉成,赵亚琦,等.生物炭添加对湿地植物生长及氧化应激响应的影响[J].环境科学,2018,39(6):2904-2910.Huang L,Chen Y C,Zhao Y Q,et al. Influence of biochar application on growth and antioxidative responses of macrophytes in subsurface flow constructed wetlands[J]. Environmental Science,2018,39(6):2904-2910.
[15]国家环境保护总局.水和废水监测分析方法[M].(第四版).北京:中国环境科学出版社,2002.
[16] 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.
[17] Lyu W L,Huang L,Xiao G Q,et al. Effects of carbon sources and COD/N ratio on N2O emissions in subsurface flow constructed wetlands[J]. Bioresource Technology,2017,245:171-181.
[18] Saeed T,Sun G Z. A comparative study on the removal of nutrients and organic matter in wetland reactors employing organic media[J]. Chemical Engineering Journal,2011,171(2):439-447.
[19] Sun Y F,Qi S Y,Zheng F P,et al. Organics removal,nitrogen removal and N2O emission in subsurface wastewater infiltration systems amended with/without biochar and sludge[J].Bioresource Technology,2018,249:57-61.
[20] Vymazal J,Kr?pfelováL. Removal of organics in constructed wetlands with horizontal sub-surface flow:a review of the field experience[J]. Science of the Total Environment,2009,407(13):3911-3922.
[21] Zhou X,Liang C L,Jia L X,et al. An innovative biocharamended substrate vertical flow constructed wetland for low C/N wastewater treatment:impact of influent strengths[J].Bioresource Technology,2018,247:844-850.
[22] De Rozari P,Greenway M,El Hanandeh A. Nitrogen removal from sewage and septage in constructed wetland mesocosms using sand media amended with biochar[J]. Ecological Engineering,2018,111:1-10.
[23] Li J,Fan J L,Zhang J,et al. Preparation and evaluation of wetland plant-based biochar for nitrogen removal enhancement in surface flow constructed wetlands[J]. Environmental Science and Pollution Research,2018,25(14):13929-13937.
[24] Maltais-Landry G,Maranger R,Brisson J. Effect of artificial aeration and macrophyte species on nitrogen cycling and gas flux in constructed wetlands[J]. Ecological Engineering,2009,35(2):221-229.
[25] Li M,Wu H M,Zhang J,et al. Nitrogen removal and nitrous oxide emission in surface flow constructed wetlands for treating sewage treatment plant effluent:effect of C/N ratios[J].Bioresource Technology,2017,240:157-164.
[26] Sanchez-Monedero M A,Cayuela M L,Roig A,et al. Role of biochar as an additive in organic waste composting[J].Bioresource Technology,2018,247:1155-1164.
[27]刘秀红,杨庆,吴昌永,等.不同污水生物脱氮工艺中N2O释放量及影响因素[J].环境科学学报,2006,26(12):1940-1947.Liu X H,Yang Q,Wu C Y,et al. N2O emissions from different biological nitrogen removal processes and factors affecting N2O production[J]. Acta Scientiae Circumstantiae,2006,26(12):1940-1947.
[28] Zhang S N,Liu F,Xiao R L,et al. Emissions of NO and N2O in wetland microcosms for swine wastewater treatment[J].Environmental Science and Pollution Research,2015,22(24):19933-19939.
[29] Feng Z J,Zhu L Z. Impact of biochar on soil N2O emissions under different biochar-carbon/fertilizer-nitrogen ratios at a constant moisture condition on a silt loam soil[J]. Science of the Total Environment,2017,584-585:776-782.
[30] Zhu X,Burger M,Doane T A,et al. Ammonia oxidation pathways and nitrifier denitrification are significant sources of N2O and NO under low oxygen availability[J]. Proceedings of the National Academy of Sciences of the United States of America,2013,110(16):6328-6333.