碱预处理对固体碳源生物可利用性及其强化生物脱氮效能的影响
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摘要
土著微生物的反硝化作用对阻控硝酸盐向地下水淋失具有重要意义,但碳源不足是关键限制因素。本研究利用Ca(OH)2对玉米芯和麦秸固体碳源进行预处理以提高其生物可利用性,并优选出外加碳源在室内模拟构建不同材料配比的强化脱氮层,对出水pH、硝态氮、亚硝态氮含量等进行监测,考察不同脱氮层的脱氮效能。结果表明,玉米芯的最佳碱处理条件为0.1g Ca(OH)2/g干物质、处理温度70℃、处理时间6h,而麦秸为0.1g Ca(OH)2/g干物质、95℃和24h,处理后其酶解还原产糖量分别提高了2.4和3.3倍。未处理玉米芯构建的脱氮层只能去除60%～67%的硝态氮,而以小粒径(24～50目)碱预处理玉米芯为碳源的脱氮层启动速度快,且亚硝酸盐积累少,对硝态氮的去除率可稳定在90%以上。
The indigenous denitrifier is important to prevent nitrate leaching to ground water.The insufficient carbon sourceis the key limiting factor of in-situ denitrification.In this study,corncob and wheat straw were pretreated by Ca(OH)2 to improve their bio-availability.The optimal carbon source was utilized as filling material in bench-scale laboratory model denitrification layers.The pH,nitrate,nitrite etc.in effluent were monitored to compare nitrogen removal performance of different denitrification layers filled with different substrates.The result shows that the optimum alkali treatment condition of corncob was 0.1 g Ca(OH)2 g-1 dry biomass,70℃and 6 hpretreatment time and that of wheat straw was 0.1 g Ca(OH)2 g-1 dry biomass,95℃and 24 h.The reducing sugar yields of corncob and wheat straw increased by 2.4 and 3.3 times after treatment respectively.The corncob had higher bioavailability than wheat straw whether they were pretreated with alkali or not.Therefore,the corncob materials were selected as additional carbon sources to strengthen the efficiency of the denitrification layer.The denitrification layer with untreated corncob removed 60%～67% nitrate,while the alkali-pretreated corncob(24～50 mesh)as carbon source exhibited a shorter startup time,a lower nitrite accumulation and a higher nitrate removal rate(>90%).The results provide an insight into the application of alkali-treated agricultural residues as denitrification carbon sources to alleviate nitrate transport to groundwater.
The indigenous denitrifier is important to prevent nitrate leaching to ground water.The insufficient carbon sourceis the key limiting factor of in-situ denitrification.In this study,corncob and wheat straw were pretreated by Ca(OH)2 to improve their bio-availability.The optimal carbon source was utilized as filling material in bench-scale laboratory model denitrification layers.The pH,nitrate,nitrite etc.in effluent were monitored to compare nitrogen removal performance of different denitrification layers filled with different substrates.The result shows that the optimum alkali treatment condition of corncob was 0.1 g Ca(OH)2 g-1 dry biomass,70℃and 6 hpretreatment time and that of wheat straw was 0.1 g Ca(OH)2 g-1 dry biomass,95℃and 24 h.The reducing sugar yields of corncob and wheat straw increased by 2.4 and 3.3 times after treatment respectively.The corncob had higher bioavailability than wheat straw whether they were pretreated with alkali or not.Therefore,the corncob materials were selected as additional carbon sources to strengthen the efficiency of the denitrification layer.The denitrification layer with untreated corncob removed 60%～67% nitrate,while the alkali-pretreated corncob(24～50 mesh)as carbon source exhibited a shorter startup time,a lower nitrite accumulation and a higher nitrate removal rate(>90%).The results provide an insight into the application of alkali-treated agricultural residues as denitrification carbon sources to alleviate nitrate transport to groundwater.
引文
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[19]姜应和,李超.树皮填料补充碳源人工湿地脱氮初步试验研究[J].环境科学,2011,32(1):158-164.JIANG Ying-he,LI Chao.Preliminary study on denitrification capacity of constructed wetlands filled by bark[J].Environmental Science,2011,32(1):158-164.
[20]Shen Z,Zhou Y,Liu J,et al.Enhanced removal of nitrate using starch/PCL blends as solid carbon source in a constructed wetland[J].Bioresource Technology,2015,175:239-244.
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[22]Oh J,Silverstein J.Acetate limitation and nitrite accumulation during denitrification[J].Journal of Environmental Engineering,1999,125(3):234-242.
[2]刘贯群,周书玉,黄修东,等.多种方法识别青岛大沽河平原区地下水硝酸盐污染来源[J].环境科学学报,2017,37(1):347-356.LIU Guan-qun,ZHOU Shu-yu,HUANG Xiu-dong,et al.Multiple methods to recognize sources of underground water nitrate contamination in plain area of Dagu River,Qingdao,China[J].Acta Scientiae Circumstantiae,2017,37(1):347-356.
[3]Pu J,Feng C,Liu Y,et al.Pyrite-based autotrophic denitrification for remediation of nitrate contaminated groundwater[J].Bioresource Technology,2014,173:117-123.
[4]邵留,徐祖信,金伟,等.以稻草为碳源和生物膜载体去除水中的硝酸盐[J].环境科学,2009,30(5):1414-1419.SHAO Liu,XU Zu-xin,JIN Wei,et al.Nitrate removal from wastewater using rice straw as carbon source and biofilm carrier[J].Environmental Science,2009,30(5):1414-1419.
[5]马玉霞,谭蕾蕾,沈志强,等.Ca(OH)2预处理的秸秆作为固体碳源的反硝化性能[J].环境工程技术学报,2017,7(2):168-174.MA Yu-xia,TAN Lei-lei,SHEN Zhi-qiang,et al.Study on denitrification performance using calcium hydroxide pretreated straw as solid carbon source[J].Journal of Environmental Engineering Technology,2017,7(2):168-174.
[6]崔美,黄仁亮,苏荣欣,等.木质纤维素新型预处理与顽抗特性[J].化工学报,2012,63(3):677-687.CUI Mei,HUANG Ren-liang,SU Rong-xin,et al.An overview on lignocellulose pretreatment and recalcitrant characteristics[J].CIESC Journal,2012,63(3):677-687.
[7]Schipper L A,Mcgill A.Nitrogen transformation in a denitrification layer irrigated with dairy factory effluent[J].Water Research,2008,42:2457-2464.
[8]胡秋龙,熊兴耀,谭琳,等.木质纤维素生物质预处理技术的研究进展[J].中国农学通报,2011,27(10):1-7.HU Qiu-long,XIONG Xing-yao,TAN Lin,et al.Advances in pretreatment technologies of lignocellulosic biomass[J].Chinese Agricultural Science Bulletin,2011,27(10):1-7.
[9]Vincent S.Chang M N,Chul-Ho Kim A M T H.Oxidative lime pretreatment of high-lignin biomass[J].Applied Biochemistry and Biotechnology,2001,94(1):1-28.
[10]Lin L,Yan R,Liu Y,et al.In-depth investigation of enzymatic hydrolysis of biomass wastes based on three major components:Cellulose,hemicellulose and lignin[J].Bioresource Technology,2010,101:8217-8223.
[11]Ayeni A O,Hymore F K,Mudliar S N,et al.Hydrogen peroxide and lime based oxidative pretreatment of wood waste to enhance enzymatic hydrolysis for a biorefinery:Process parameters optimization using response surface methodology[J].Fuel,2013,106:187-194.
[12]Hu R,Zheng X,Xin J,et al.Selective enhancement and verification of woody biomass digestibility as a denitrification carbon source[J].Bioresource Technology,2017,244:313-319.
[13]Alvira P,Tomás-PejóE,Ballesteros M,et al.Pretreatment technologies for an efficient bioethanol production process based on enzymatic hydrolysis:A review[J].Bioresource Technology,2010,101:4851-4861.
[14]Jeoh T,Ishizawa C I,Davis M F,et al.Cellulase digestibility of pretreated biomass is limited by cellulose accessibility[J].Biotechnology and Bioengineering,2007,98(1):112-122.
[15]Zhong X,Wu Y,Xu Z.Bioclogging in porous media under discontinuous flow condition[J].Water Air Soil Pollut,2013,224:1543.
[16]朱洁,陈洪斌.人工湿地堵塞问题的探讨[J].中国给水排水,2009,25(6):24-28,33.ZHU Jie,CHEN Hong-bin.Discussion on constructed wetlands clogging[J].China Water&Wastewater,2009,25(6):24-28,33.
[17]Calderer M,MartíV,De P J,et al.Effects of enhanced denitrification on hydrodynamics and microbial community structure in a soil column system[J].Chemosphere,2014,111:112-119.
[18]Rust C M,Aelion C M,Flora J R V.Control of pH during denitrification in subsurface sediment microcosms using encapsulated phosphate buffer[J].Water Research,2000,34(5):1447-1454.
[19]姜应和,李超.树皮填料补充碳源人工湿地脱氮初步试验研究[J].环境科学,2011,32(1):158-164.JIANG Ying-he,LI Chao.Preliminary study on denitrification capacity of constructed wetlands filled by bark[J].Environmental Science,2011,32(1):158-164.
[20]Shen Z,Zhou Y,Liu J,et al.Enhanced removal of nitrate using starch/PCL blends as solid carbon source in a constructed wetland[J].Bioresource Technology,2015,175:239-244.
[21]付昆明,曹相生,孟雪征,等.污水反硝化过程中亚硝酸盐的积累规律[J].环境科学,2011,32(6):1660-1664.FU Kun-ming,CAO Xiang-sheng,MENG Xue-zheng,et al.Characteristics of nitrite accumulation during wastewater denitrification[J].Environmental Science,2011,32(6):1660-1664.
[22]Oh J,Silverstein J.Acetate limitation and nitrite accumulation during denitrification[J].Journal of Environmental Engineering,1999,125(3):234-242.