基于CFD模拟技术的开孔氧化沟特性分析
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摘要
针对传统氧化沟工艺溶解氧调控困难、曝气区高流速造成能量浪费等问题,通过在氧化沟缺氧区廊道弯道处开设孔洞、设置挡水墙与导流板等措施,提出了一种新型开孔变速氧化沟流态调节理论与技术方案。首先通过计算流体力学模拟开孔氧化沟方案的流态调节效果,模拟结果表明,开孔廊道平均流速为0.20~0.26 m/s,明显高于其他廊道,表明开孔方案可以显著提高缺氧区廊道流速,实现氧化沟变速流态调节效果。其次,建立开孔氧化沟中试系统,通过对比等速氧化沟与开孔氧化沟工艺对有机物的去除效果和微生物群落分布验证开孔方案的可实施性。结果表明,两种工艺对有机物的去除率基本相当,其中COD、SS、TP和NH_4~+-N的去除率在95%以上,而开孔氧化沟工艺对TN的去除率略高于等速氧化沟。两组氧化沟系统中反硝化细菌种类一致,相对丰度分别为1.51%和1.49%,表明氧化沟开孔流态调节方案不会影响系统的运行效果和微生物种类,只是改变了开孔廊道的流态分布。同时采用现场流态测定方法对氧化沟流态和沉泥情况进行了分析,结果表明,开孔方案能够提高氧化沟缺氧区廊道流速,减缓低流速区沉泥现象。因此,在不影响运行效果的基础上,开孔方案减小了氧化沟系统缺氧区廊道推进器功率8.4 k W,达到节能21.2%的目的。
The present paper is to report a new variable-velocity oxidation ditch developed by trepanning in the anoxic zone and installing a retaining-leading wall to cope up with the difficulty in the dissolved oxygen control and energy waste in the high velocity aeration zone due to the traditional oxidation ditch process. To deal with the problem,we have managed to create a novel variable-velocity oxidation ditch process by trepanning on the anoxic zone and installing the retaining and guide walls. And,in turn,we have simulated the flow velocity of the trepanning project via the computational fluid dynamics( CFD). Thus,the results of our simulation indicate that the average flowing rate tends to be0. 20-0. 26 m/s on the variable-velocity gallery,while that of other galleries tends only to be merely 0. 14-0. 18 m/s. The above said results demonstrate that there lies some possibility to improve the corridor flow rate in the anoxic zone and gain variable speed flow control effect of the aforementioned scheme remarkably. Besides,we have also offered a pilot-scale oxidation ditch in this paper. Therefore,comparing the organic removal efficiency and the microbial community structure of the constant-velocity to that of the variable-velocity oxidation ditch process,it can be found that the 2 processes turn to be almost identical on the removal behavior of COD,SS,TP,and NH+4-N,which can all reach over 95%.However,the removal efficiency of TN processed by the variablevelocity oxidation ditch has been found slightly higher than that of the constant-velocity one. But,in contrast,the species of the denitrifying bacteria mainly based on the 3 types of bacteria,including Thauera,Zoogloea,and Hyphomicrobium in the two groups,prove to be consistent,with their relative abundance turning to be1. 51% and 1. 49%,correspondingly. Moreover,the results reveal that the oxidation ditch on the orifice flow state regulation can only change the flow pattern of the open corridor instead of influencing the running effect and microorganism species of the system. At the same time,it is possible to analyze the oxidation ditch flow and the sludge conditions of the variable-velocity oxidation ditch with the velocity measuring method. This may imply that the trepanning scheme can not only improve the corridor flowing rate in the said zone,but can also decelerate the sedimentation of the sludge in a low flow rate zone. Yet,no sludge stratification trace has been found in the aerobic zone under the microporous aeration. Neither can the variable-velocity oxidation ditch be found to reduce the propelling energy by 21. 2% without influencing the operation effect.
The present paper is to report a new variable-velocity oxidation ditch developed by trepanning in the anoxic zone and installing a retaining-leading wall to cope up with the difficulty in the dissolved oxygen control and energy waste in the high velocity aeration zone due to the traditional oxidation ditch process. To deal with the problem,we have managed to create a novel variable-velocity oxidation ditch process by trepanning on the anoxic zone and installing the retaining and guide walls. And,in turn,we have simulated the flow velocity of the trepanning project via the computational fluid dynamics( CFD). Thus,the results of our simulation indicate that the average flowing rate tends to be0. 20-0. 26 m/s on the variable-velocity gallery,while that of other galleries tends only to be merely 0. 14-0. 18 m/s. The above said results demonstrate that there lies some possibility to improve the corridor flow rate in the anoxic zone and gain variable speed flow control effect of the aforementioned scheme remarkably. Besides,we have also offered a pilot-scale oxidation ditch in this paper. Therefore,comparing the organic removal efficiency and the microbial community structure of the constant-velocity to that of the variable-velocity oxidation ditch process,it can be found that the 2 processes turn to be almost identical on the removal behavior of COD,SS,TP,and NH+4-N,which can all reach over 95%.However,the removal efficiency of TN processed by the variablevelocity oxidation ditch has been found slightly higher than that of the constant-velocity one. But,in contrast,the species of the denitrifying bacteria mainly based on the 3 types of bacteria,including Thauera,Zoogloea,and Hyphomicrobium in the two groups,prove to be consistent,with their relative abundance turning to be1. 51% and 1. 49%,correspondingly. Moreover,the results reveal that the oxidation ditch on the orifice flow state regulation can only change the flow pattern of the open corridor instead of influencing the running effect and microorganism species of the system. At the same time,it is possible to analyze the oxidation ditch flow and the sludge conditions of the variable-velocity oxidation ditch with the velocity measuring method. This may imply that the trepanning scheme can not only improve the corridor flowing rate in the said zone,but can also decelerate the sedimentation of the sludge in a low flow rate zone. Yet,no sludge stratification trace has been found in the aerobic zone under the microporous aeration. Neither can the variable-velocity oxidation ditch be found to reduce the propelling energy by 21. 2% without influencing the operation effect.
引文
[1]INSEL G,SOZEN S,GORGUN E,et al.Evaluation of nitrogen removal efficiencies for predenitrification and alternating system[J].Fresenius Environmental Bulletin,2001,10(3):257-261.
[2]MANTZIARAS I D,KATSIRI A.Reaction rate constants and mean population percentage for nitrifiers in an alternating oxidation ditch system[J].Bioprocess&Biosystems Engineering,2011,34(1):57-65.
[3]LI Zhiping(李志平),GUO Yumei(郭玉梅),XING Meirong(邢美容),et al.The analysis of nitrification of upgrading on a carrousel oxidation ditch in Kunming[J].Technology of Water Treatment(水处理技术),2014,40(10):123-127.
[4]YANG Huimin(杨慧敏),ZHANG Kui(张奎),LI Jianzheng(李建政).New approach to treating urban wastewater by means of a hybrid oxidation ditch process[J].Journal of Safety and Environment(安全与环境学报),2006,6(4):23-26.
[5]ZHANG Hua(张华),ZHANG Xuehong(张学洪),GUO Zhoufang(郭周芳),et al.Study on influencing factors of biological nutrient removal in microporous aeration oxidation ditch[J].Technology of Water Treatment(水处理技术),2014,40(4):103-106.
[6]FU Dexun(傅德薰).Numerical simulation of fluid mechanics(流体力学数值模拟)[M].Beijing:National Defence Industry Press,1993:3-6.
[7]LARSEN R D,MADYCH W R,CRAWFORD E F.Piecewise constant and piecewise linear expansions[J].Computers&Chemistry,1977,1(4):267-271.
[8]LITTLETON H X,DAIGGER G T,STROM P F.Application of computational fluid dynamic to closed-loop bioreactors:I.Characterization and simulation of fluid-flow pattern and oxygen transfer[J].Water Environment Research,2007,79(6):600-612.
[9]LEI L,NI J R.Three-dimensional three-phase model for simulation of hydrodynamics,oxygen mass transfer,carbon oxidation,nitrification and denitrification in an oxidation ditch[J].Water Research,2014,53(8):200-214.
[10]LIU Y C,SHI H C,XIA L,et al.Study of operational conditions of simultaneous nitrification and denitrification in a Carrousel oxidation ditch for domestic wastewater treatment[J].Bioresource Technology,2010,101(3):901-906.
[11]ZHANG Qirong(张杞蓉),PU Xiaojing(普晓晶).Analysis of hydrodynamics and simulation on flow field of oxidation ditch[J].Shanxi Architecture(山西建筑),2014,40(36):177-178.
[12]SHI Xiaochun(师晓春).Operation effect of improved oxidation ditch[J].Technology of Water Treatment(水处理技术),2016,10(42):114-116.
[13]GUO X S,ZHOU X,CHEN Q W,et al.Flow field and dissolved oxygen distributions in the outer channel of the Orbal oxidation ditch by monitor and CFD simulation[J].Journal of Environmental Science,2013,25(4):645-651.
[14]PENG Dangcong(彭党聪),HAN Yun(韩芸),WANG Xiaochang(王晓昌),et al.Design optimization of zoning oxygen supply in biological denitrification oxidation ditch based on reaction kinetics[J].China Water and Wastewater(中国给水排水),2011,8(8):44-46.
[15]TANG Xiuhuan(唐秀欢),YANG Ning(杨宁),BAO Lihong(包利红),et al.CFD simulation of the radioactive gas dispersion in Xi'an pulsed reactor site environment[J].Journal of Safety and Environment(安全与环境学报),2014,14(5):133-140.
[16]TAO Wenquan(陶文铨).Numerical heat transfer(数值热传学)[M].Xi'an:Xi'an Jiaotong University Press,2001:25-28.
[17]DENG Haifa(邓海发),CHEN Guoming(陈国明).CFD-based quantitative hazard assessment of oil spills in deep water drilling[J].Journal of Safety and Environment(安全与环境学报),2012,12(2):233-236.
[18]State Environmental Protection Administration of China(国家环境保护总局).Water and wastewater monitoring methods(水和废水监测分析方法)[M].Beijing:China Environmental Science Press,2002:211-213.
[19]HE L,JI F Y,ZHOU W W,et al.Deposition pattern,effect on nitrogen removal and component analysis of deposited sludge in a carrousel oxidation ditch[J].Desalination&Water Treatment,2014,52(31):6079-6087.
[20]ZHAO Xingming(赵星明),WANG Xuan(王萱),HUANG Tinglin(黄廷林).Study on simulation of reducing settling sludge in curved conduit of oxidation ditch[J].Environmental Engineering(环境工程),2007,25(6):37-39.
[21]YANG Yahong(杨亚红).Study of variable-velocity oxidation ditch with fine-bubble aeration in WWTP(微孔曝气变速氧化沟处理城市污水技术研究)[D].Xi'an:Xi'an University of Architecture and Technology,2014.
[22]ZHAO Xingming(赵星明),XU Zhiwei(徐志伟).Calculation of head loss and function of divers in oxidation ditch[J].China Water and Wastewater(中国给水排水),2000,16(7):35-37.
[23]LIU Guangli(刘广立),ZHONG Yunxiao(种云霄),FAN Qingjuan(樊青娟),et al.Hydrodynamic effects of the oxidation ditch on removal efficiency and energy consumption[J].Environmental Science(环境科学),2006,27(11):2323-2326.
[24]ZHOU Xin(周鑫),GUO Xuesong(郭雪松),LIU Junxin(刘俊新),et al.Study on energy consumption characteristics of urban sewage treatment by oxidation ditch process[J].Water&Wastewater Engineering(给水排水),2011,37(8):31-34.
[25]LI Jin(李晋),YANG Chunfeng(杨春风),XIAO Benyi(肖本益),et al.Operation station of strengthening removal of nitrogen and energy saving in asconoid type oxidation ditch[J].Technology of Water Treatment(水处理技术),2014,40(5):117-120.
[2]MANTZIARAS I D,KATSIRI A.Reaction rate constants and mean population percentage for nitrifiers in an alternating oxidation ditch system[J].Bioprocess&Biosystems Engineering,2011,34(1):57-65.
[3]LI Zhiping(李志平),GUO Yumei(郭玉梅),XING Meirong(邢美容),et al.The analysis of nitrification of upgrading on a carrousel oxidation ditch in Kunming[J].Technology of Water Treatment(水处理技术),2014,40(10):123-127.
[4]YANG Huimin(杨慧敏),ZHANG Kui(张奎),LI Jianzheng(李建政).New approach to treating urban wastewater by means of a hybrid oxidation ditch process[J].Journal of Safety and Environment(安全与环境学报),2006,6(4):23-26.
[5]ZHANG Hua(张华),ZHANG Xuehong(张学洪),GUO Zhoufang(郭周芳),et al.Study on influencing factors of biological nutrient removal in microporous aeration oxidation ditch[J].Technology of Water Treatment(水处理技术),2014,40(4):103-106.
[6]FU Dexun(傅德薰).Numerical simulation of fluid mechanics(流体力学数值模拟)[M].Beijing:National Defence Industry Press,1993:3-6.
[7]LARSEN R D,MADYCH W R,CRAWFORD E F.Piecewise constant and piecewise linear expansions[J].Computers&Chemistry,1977,1(4):267-271.
[8]LITTLETON H X,DAIGGER G T,STROM P F.Application of computational fluid dynamic to closed-loop bioreactors:I.Characterization and simulation of fluid-flow pattern and oxygen transfer[J].Water Environment Research,2007,79(6):600-612.
[9]LEI L,NI J R.Three-dimensional three-phase model for simulation of hydrodynamics,oxygen mass transfer,carbon oxidation,nitrification and denitrification in an oxidation ditch[J].Water Research,2014,53(8):200-214.
[10]LIU Y C,SHI H C,XIA L,et al.Study of operational conditions of simultaneous nitrification and denitrification in a Carrousel oxidation ditch for domestic wastewater treatment[J].Bioresource Technology,2010,101(3):901-906.
[11]ZHANG Qirong(张杞蓉),PU Xiaojing(普晓晶).Analysis of hydrodynamics and simulation on flow field of oxidation ditch[J].Shanxi Architecture(山西建筑),2014,40(36):177-178.
[12]SHI Xiaochun(师晓春).Operation effect of improved oxidation ditch[J].Technology of Water Treatment(水处理技术),2016,10(42):114-116.
[13]GUO X S,ZHOU X,CHEN Q W,et al.Flow field and dissolved oxygen distributions in the outer channel of the Orbal oxidation ditch by monitor and CFD simulation[J].Journal of Environmental Science,2013,25(4):645-651.
[14]PENG Dangcong(彭党聪),HAN Yun(韩芸),WANG Xiaochang(王晓昌),et al.Design optimization of zoning oxygen supply in biological denitrification oxidation ditch based on reaction kinetics[J].China Water and Wastewater(中国给水排水),2011,8(8):44-46.
[15]TANG Xiuhuan(唐秀欢),YANG Ning(杨宁),BAO Lihong(包利红),et al.CFD simulation of the radioactive gas dispersion in Xi'an pulsed reactor site environment[J].Journal of Safety and Environment(安全与环境学报),2014,14(5):133-140.
[16]TAO Wenquan(陶文铨).Numerical heat transfer(数值热传学)[M].Xi'an:Xi'an Jiaotong University Press,2001:25-28.
[17]DENG Haifa(邓海发),CHEN Guoming(陈国明).CFD-based quantitative hazard assessment of oil spills in deep water drilling[J].Journal of Safety and Environment(安全与环境学报),2012,12(2):233-236.
[18]State Environmental Protection Administration of China(国家环境保护总局).Water and wastewater monitoring methods(水和废水监测分析方法)[M].Beijing:China Environmental Science Press,2002:211-213.
[19]HE L,JI F Y,ZHOU W W,et al.Deposition pattern,effect on nitrogen removal and component analysis of deposited sludge in a carrousel oxidation ditch[J].Desalination&Water Treatment,2014,52(31):6079-6087.
[20]ZHAO Xingming(赵星明),WANG Xuan(王萱),HUANG Tinglin(黄廷林).Study on simulation of reducing settling sludge in curved conduit of oxidation ditch[J].Environmental Engineering(环境工程),2007,25(6):37-39.
[21]YANG Yahong(杨亚红).Study of variable-velocity oxidation ditch with fine-bubble aeration in WWTP(微孔曝气变速氧化沟处理城市污水技术研究)[D].Xi'an:Xi'an University of Architecture and Technology,2014.
[22]ZHAO Xingming(赵星明),XU Zhiwei(徐志伟).Calculation of head loss and function of divers in oxidation ditch[J].China Water and Wastewater(中国给水排水),2000,16(7):35-37.
[23]LIU Guangli(刘广立),ZHONG Yunxiao(种云霄),FAN Qingjuan(樊青娟),et al.Hydrodynamic effects of the oxidation ditch on removal efficiency and energy consumption[J].Environmental Science(环境科学),2006,27(11):2323-2326.
[24]ZHOU Xin(周鑫),GUO Xuesong(郭雪松),LIU Junxin(刘俊新),et al.Study on energy consumption characteristics of urban sewage treatment by oxidation ditch process[J].Water&Wastewater Engineering(给水排水),2011,37(8):31-34.
[25]LI Jin(李晋),YANG Chunfeng(杨春风),XIAO Benyi(肖本益),et al.Operation station of strengthening removal of nitrogen and energy saving in asconoid type oxidation ditch[J].Technology of Water Treatment(水处理技术),2014,40(5):117-120.