摘要
紫外消毒技术由于其高效性,广谱性,安全性等特点,在水处理消毒领域应用越来越广泛,相应对紫外消毒设备的研究也越来越多。目前,国外已利用计算流体力学(CFD),采用数值模拟进行紫外设备开发优化;国内生产商主要是模仿国外厂家进行生产,缺乏核心技术,紫外消毒效果无法得到保证。本课题利用CFD数值模拟技术,从光强分布,流态分布以及剂量拟合三个方面建立紫外消毒模型,并采用生物方法对模型进行验证;利用CFD模型对腔体式紫外消毒反应器、明渠式紫外消毒系统进行结构优化及消毒效率预测评估;最后对紫外剂量同步技术进行了初步探究。
紫外消毒CFD模型的建立及验证,结果表明:紫外消毒反应器内光强分布不均匀,进出口处光强较弱,随着与灯管距离的增大而降低;反应器内前段,反应器内壁处光强小而流速大,是影响消毒效率的原因;有效剂量随处理流量的增加而降低,呈乘幂关系;有效剂量随透光率的降低而降低,在高流量下受透光率影响不大。模拟结果与实验结果趋势相符,柱源模型误差范围为2.9%~12.0%,线源模型误差范围为5.5~21.4%,柱源模型更精确,可以较准确的计算紫外反应器消毒效率。
腔体式紫外反应器的数值模拟,结果表明:基本模型的消毒灭活率1.73个log,t10/HRT为21.0%;挡板的添加有利于流体内部交换,使不同粒子接受的剂量趋于均匀,提高了整体的消毒效率,优化后模型的t10/HRT为59.6%,灭活率为2.02个log。
明渠式紫外消毒系统的数值模拟,结果表明:渠道内灯管呈矩阵对称分布,光强在近灯管处最大,近壁面处较小;明渠前段及内壁处光强小而流速大,降低了消毒效率;通过对明渠进行结构的改进,系统内最低光强由由1.3mw/cm2增加至7.2mw/cm2,低剂量(小于20mJ/cm2)的区域消除,高剂量范围内分布更均匀,有利于系统消毒效率的提高。
剂量同步主要通过操作参数优化实现:对于结构已定的小型单灯管腔体式紫外消毒反应器,可优化的操作参数主要是停留时间(流量控制);对于复杂的多灯管紫外消毒系统,主要控制参数为灯管有效输出,灯管排布以及流量控制。
CFD数值模拟可以精确模拟紫外消毒过程,为紫外消毒设备的设计运行,强化反应器的处理效果提供有利的支持,为系统优化设计和剂量同步提供依据。
UV disinfection is used widely in the field of water disinfection because of its high efficiency, broad spectrum and safety features. Accordingly, the people are concerning of UV disinfection equipment much more than before. At present, the domestic producers imitate foreign manufacturers, the main production is lack of core technologies and the disinfection efficiency can not be guaranteed. Computational fluid dynamics (CFD) was used in this research. Based on intensity field, flow field and equivalent reduction dose, established numerical simulation model of UV disinfection. Using bioassay verified the CFD model on the condition of the UVT (80%~95%) and the flow rate (240~600L/h). In addition, optimized the structure of existing UV disinfection reactor and forecasted the disinfection efficiency of channel-type UV system. At last, UV dose of synchronization technology was inquiried preliminarily.
The numerical simulation and bioassay showed that: light intensity was uneven in the UV reactor, light intensity was wake at the entrance and decreased with the distance increased from the lamp; the UV intensity was weak while the velocity was large adjacent to the wall near the inlet of the reactor, which affected disinfection efficiency adversely; RED increased with the increase of flow rate and decrease of the transmittance; transmittance had merely a slight impact on RED of high flow; the results showed that the model predicted the disinfection efficiency with good accuracy, RED of simulation and experimental under different conditions had a difference of 2.9~12.0%with cyclinder model while 5.5~21.4% with line model; the cyclinder model could accurately calculate the efficiency of UV disinfection reactor.
Optimized the tube UV reactor's structure, the results showed that: the basic model of disinfection inactivation rate was 1.73log while t10/HRT was 21.0%; baffle added was conducive to the internal fluid exchange, so that the different doses of particles received more uniform and improved the overall disinfection efficiency; the optimized model t10/HRT was 59.6% while inactivation rate was 2.02log.
Open channel UV disinfection system’s numerical simulation results showed that: UV lights within the channel was symmetrical, the UV intensity near the lamp was the maximum, near wall was small; the UV intensity was small while velocity was large in front of the channel and the channel wall that reduced the disinfection efficiency; through the open channel structural improvements, the minimum UV intensity increased from 1.3mw/cm2 to 7.2mw/cm2 and low dose (less than 20mJ/cm2) region eliminated while high dose range was more evenly that improved the whole system efficiency.
Dose synchronization achieved primarily through the optimization of operation parameters: for the small single lamp chamber reactor, disinfection efficiency depends mainly on water quality and residence time, operating parameters can be optimized primarily was residence time (flow control); For complex multi-lamp UV disinfection system, the main control parameters were effective output of the lamp, the lamp arrangement and flow.
CFD numerical simulation can accurately simulate the UV disinfection process, provide support for UV disinfection equipment design and operation, strengthen the treatment effect of UV reactor , provide the basis for system optimization and dose synchronization.
引文
1.陈健,王长生.紫外线消毒技术在给排水中的应用.中国给排水. 2002,18(7): 29~31
2. GB18918-2002,城镇污水处理厂污染物排放标准
3.孙文俊,刘文君,胡田甜,等.紫外线消毒系统中强度分布的理论计算与生物验证对比.环境科学学报. 2008,28(3): 563~567
4. B. A. Wols, L. Shao, Uijttewaal, et al. Evaluation of Experimental Techniques to Validate Numerical Computations of the Hydraulics inside a UV Bench-Scale Reactor. Chemical Engineering Science. 2010,65(15): 4491~4502
5. I. S. Hornsey, Snowball. Purification of Water Supplies Using Ultraviolet Light. Elsevier Applied Science. 1988,10(2):171~191
6. K. Craig , C. Traversay, B. Bowen, et al. Hydraulic Study and Optimisation of Water Treatment Processes Using Numerical Simulation. Drinking Water Treatment. 2002,2(5-6):135~142
7. G. P. Feifer. Formation and Processing of UV Photoproducts: Effects of DNA Equence and Chromatinenvironment. Photochemistry and Photobiology 1997,65(9):270~283
8. C. C. E. Meulemans. The Basic Principles of UV Disinfection of Water. Ozone Science Engineering. 1987,12(9):299~314
9. G. B. Knudson. Photoreactivation of UV Irradiated Legionella Pneumoplila and Other Legionella Species. Applied and Environmental Microbiology. 1985,6(49):975~980
10. K. Oguma, H. Katayama, H. Mitani, S. Morita. Determinationof Pyrimidine Dimers in Escherichia Coli and Cryptosporidium Parvum During UV Light Inactivation, Photoreactivation and Dark Repair. Applied and Environmental Microbiology. 2001,67(10):4630~4637
11. O. Hoyer. Testing Performance and Monitoring of UV Systems for Drinking Water Disinfection. Water Supply. 1998,16(1-2):424~429
12. J. A. Parker, J. L. Darby. Particle-Associated Coliform in Secondary Effluents: Shielding from Ultraviolet Light Disinfection. Water Environment Research.1995,67(7):1065~1075
13. B. G. Oliver, E. G. Cosgrove. The Disinfection of Sewage Treatment Plant Effluents Using Ultraviolet Light. Canadian Journal of Chemical Engineering. 1975,53(9):170~174
14. J. K. Rice, M. Ewell. Examination of Peak Power Dependence in the UV Inactivation of Bacterial Spore’S. Applied and Environmental Microbiology. 2001,67(12):5830~5832
15. J. D. Malley. Quantum Conditional Probability and Hidden-Variables Models. Physical Reviewa. 1998,58(2):812~820
16. M. T. Severin, R. S. Suldan. Effects of Temperature on Ultraviolet Light Disinfection. Water Science and Technology. 1983,17(2):717~721
17. E. Whitby. The Effect of UV Transmission, Suspended Solids and Photoreactivation on Microorganisms in Wastewater Treated with UV Light. Water Science and Technology. 1993,27(3-4):379~386
18.吕东明, Wayne Lem,李新,等.紫外消毒设备设计的几点重要考虑因素.水工业市场. 2009,11(10):19~20
19. USEPA. Design Manual for Municipal Wastewater Disinfection. 1986, EPA,625/1-86/021:157~247
20. B. A. Younis, T. H. Yang. Computational Modeling of Ultraviolet Disinfection. Water Science and Technology. 2010,62(8):1872~1878
21. GAGW. UV Systems for Disinfection in Drinking Water Supplies-Requirements and Testing, 2001. DVGW-W294
22. NWRI&AWWARF. Ultraviolet Disinfection Guidelines for Drinking Water and Water Reuse (1nd). 2000.12
23. NWRI&AWWARF. Ultraviolet Disinfection Guidelines for Drinking Water and Water Reuse (2nd). 2003.5
24. USEPA. Ultraviolet Disinfection Guidance Manual (Draft). EPA 815–D–03-007.2003
25. GB/T 19837-2005,城市给排水紫外线消毒设备
26. GB50014-2006,室外排水设计规范
27. Fluent Inc. Fluent 6.2 User’S Guide. USA, 2005
28. S. S. Jin, K. G. Linden, J. Ducoste, et al. Impact of Lamp Shadowing and Reflection on the Fluence Rate Distribution in a Multiple Low-Pressure UVLamp Array. Water Research. 2005,39(12): 2711~2721
29. Z. Nunovic, K. G. Pennell. Development and Performance of a Fluence Rate Distribution Model for a Cylindrical Excimer Lamp. Environmental Science and Technology. 2008,42(5): 1605~1614
30. S. K. Unluturk, H. Arastoopour, T. Koutchma. Modeling of UV Dose Distribution in a Thin-Film UV Reactor for Processing of Apple Cider. Journal of Food Engineering. 2004,65(1): 125~136
31. D. A. Lyn, E. R. Blatchley. Numerical Computational Fluid Dynamics Based Models of Ultraviolet Disinfection Channels. Journal of Enviromental Engineering. 2005,131(6): 831~849
32. A. Munoz, S. Craik, S. Kresta. Computational Fluid Dynamics for Predicting Performance of Ultraviolet Disinfection Sensitivity to Particle Tracking Inputs. Journal of Environmental Engineering and Science. 2007,6(3): 285~301
33. D. Liu, J. J. Ducoste, S.S. Jin, K. Linden. Evaluation of Alternative Fluence Rate Distribution Models. Journal of Water Supply: Research and Technology Aqua. 2004.53(6): 391~408
34. X. Zhao, S. M. Alpert, J. J. Ducoste. Assessing the Impact of Upstream Hydraulics on the Dose Distribution of Ultraviolet Reactors Using Fluorescence Microspheres and Computational Fluid Dynamics. Environmental Enginneer Science. 2009,26(5): 947~959
35. D. A. Sozzi, F. Taghipour. Computational and Experimental Study of Annular Photo-reactor Hydrodynamics. International Journal of Heat and Fluid Flow. 2006,27(6): 1043~1053
36. K. P. Chiu, Savoye, D. A. Lyn. Effect of UV System Modifications on Disinfection Performance. Journal of Enviromental Engineering. 1999,125(5): 459~469
37. S. J. Lim, Y. J. Lee. Enhancement of UV Disinfection Efficiency by Arraying Inclined Lamps. Korean Journal of Chemical Engineering. 2006,23(4): 595~600
38.莫君毅,张树阁,章迪康.紫外线消毒器辐射剂量的CFD模拟.农机化研究. 2007,2(2): 191~206
39.唐玲.基于CFD的紫外消毒模型的开发.哈尔滨工业大学硕士论文. 2008,67
40. J. R. Bolton. Calculation of Ultraviolet Fluence Rate Distributions in an Annular Reactor: Significance of Refraction and Reflection Water Research.2000, 34(13): 3315~3324
41. E. R. Blatchley. Numerical Modeling of UV Intensity: Application to Collimated Beam Reactors and Continuous-Flow Systems. Water Reserch. 1997,32 (7): 2205~2218
42. M. L. Janex, A. Nace. UV Fluence Rate Evaluation in a UV System: Simulating the Impact of Operating and Design Parameters. Inter Water and Irrigation. 2003,23(2): 17~20
43. S. Elyasi, F. Taghipour. Simulation of UV Photoreactor for Water Disinfection in Eulerian Framework. Chemical Engineering Science. 2006,61(14): 4741~4749
44. Romero, Alfano, Marchetti, Cassano. Modeling and Parametric Sensitivity of an Annular Photoreactor with Complex Kinetics. Chemistey Engineering Science. 1983,38: 1593~1605
45. A. E. Cassano, C. A. Martin, R. J. Brandi, et al. Photoreactor Analysis and Design: Fundamentals and Applications. Industrial and Engineering Chemistry Research. 1995,34(7): 2155~2201
46. M. Bass. Latest Advances in UV Disinfection Hydrodynamic Simulation and Relation to Practical Experiences. Proceeding Aquatech Amsterdam. 1996,46(4): 581~590
47. Z. Do-Quang, R. Djebbar, E. R. Blatchley, J. M. Lain. Computational Fluid Dynamics Modeling of Ultraviolet Disinfection Reactor Performance: Optimization of Flow in Vertical Lamp Open Channel. Environmental Engineering Conference Edmonton ASCE-CSCE. 1997,38(6): 71~78
48. F. Taghipour, A. Sozzi. Modeling and Design of Ultraviolet Reactors for Disinfection By-Product Precursor Removal. Desalination. 2005,176(1–3): 71~80
49.张光辉,顾平,于丹丹.紫外线消毒器水力特性的研究.水处理技术. 2008,34(2): 16~20
50. A. Cabaj, R. Sommer, D. Schoenen. Biodosimetry: Model Calculations for UV Water Disinfection Devices with Regard to Dose Distributions. Water Research. 1996, 30(4): 1003~1009
51. Z. Bohrerova, H. Mamane, J. J. Ducoste, et al. Comparative Inactivation of Bacillus Subtilis Spores and MS-2 Coliphage in a UV Reactor: Implications forValidation. Journal of Environmental Engineering-Asce.2006,132(12): 1554~1561
52. K. Chiu, D. A. Lyn, P. Savoye, et al. Integrated UV Disinfection Model Based on Particle Tracking. Journal of Environmental Engineering-ASCE. 1999, 125(1): 7~16
53. http://www.wendang365.cn/view/7712,饮用水和回用水的紫外消毒指导方针
54.张永吉,刘文君.浊度对灭活大肠杆菌和MS-2噬菌体的影响.中国给水排水. 2006, 22(1):27~31