Breakthrough tests on preferential flow in municipal solid waste
-
摘要: 城市生活垃圾具有大孔隙特性,优先流是垃圾中水分运动的重要形式,目前垃圾中优先流基本规律尚不明确,优先流数值分析时相关参数的选取尚缺乏依据。通过垃圾柱穿透试验研究城市生活垃圾中的优先流,以Cl-为示踪剂,进行了不同埋深和龄期试样、不同高度试样和不同入渗强度的穿透试验,得到溶质穿透曲线,运用对数正态分布模型和双峰概率密度模型拟合试验结果,定量分析了垃圾中优先流规律。结果表明,通过大孔隙运移的溶液占比在55%~70%之间,垃圾中优先流现象明显。随着垃圾的埋深和龄期增加,参与溶质运移的孔隙比例增加,但通过大孔隙运移的比例减少,优先流程度降低;试样高度增加,参与溶质运移的孔隙比例增加,但其内部大孔隙贯通性变差,通过大孔隙运移占比减小,优先流程度降低;入渗强度增大,参与溶质运移的大孔隙占比增加,优先流程度增大。双峰概率密度模型比对数正态分布模型能更好地描述垃圾中溶质运移的优先流规律,同时为使用两域模型进行垃圾水分运移分析时的参数取值提供了依据。Abstract: The municipal solid waste (MSW) is characterized by large pores, so the water flow in MSW often takes the form of preferential flow. The fundamental rules of the preferential flow in MSW has not been revealed thoroughly at present, and parameters in numerical analysis still need to be studied further. The solute breakthrough tests are carried out by using Cl- as a tracer to investigate the preferential flow in MSW. The influences of depth and age, sample heights and infiltration rates on the preferential flow are considered. The regression analysis is performed using the log-normal probability distribution model and bimodal probability density model. The results show that 55% to 70% of the total solute is transported through large pores, indicating that the preferential flow is obvious in MSW. The proportion of pores that participates in solute movement increases as the depth and ages increase, but the proportion of solute movement through large pores decreases, such that the degree of preferential flow decreases. As heights of the MSW sample increase, the connectivity of large pores in MSW decreases and the proportion of solute movement through large pores decreases, so the degree of preferential flow decreases. As the infiltration rate increases, the proportion of solute movement through large pores increases and the degree of preferential flow increases. The bimodal probability density model is more suitable than the log-normal probability distribution model to characterize the preferential flow in MSW. The analysis helps to determine the parameters in two-domain model in analysis of water movement in MSW.
-
Keywords:
- municipal solid waste /
- preferential flow /
- breakthrough test /
- regression analysis
-
[1] ZEISS C, UGUCCIONI M.Mechanisms and patterns of leachate flow in municipal solid waste landfills[J]. Journal of Environmental Systems, 1994, 23(3): 247-270. [2] HENDRICKX J M H, FLURY M. Uniform and preferential flow mechanisms in the vadose zone. Conceptual models of flow and transport in the fractured vadose zone[M]. Washington D C: National Academy Press, 2001: 149-187. [3] WEILER M, NAEF F.An experimental tracer study of the role of macropores in infiltration in grassland soils[J]. Hydrological Processes, 2003, 17(2): 477-493. [4] KULLI B, GYSI M, FLÜHLER H. Visualizing soil compaction based on flow pattern analysis[J]. Soil & Tillage Research, 2003, 70(1): 29-40. [5] 牛健植, 余新晓, 邵文伟, 等. 森林生态系统优先流研究[M]. 北京: 科学出版社, 2013: 81-87.
(NIU Jian-zhi, YU Xin-xiao, SHAO Wen-wei, et al.Study of soil preferential flow in the ecological system of forest[M]. Beijing: Science Press, 2013: 81-87. (in Chinese))[6] 张文杰. 城市生活垃圾填埋场中水分运移规律研究[D]. 杭州: 浙江大学, 2007.
(ZHANG Wen-jie.Experimental and numerical study on water/leachate transport in landfill of municipal solid waste[D]. Hangzhou: Zhejiang University, 2007. (in Chinese))[7] WATSON G, WOODMAN N.Laboratory scale delineation of ‘preferential flow’ in landfill[C]// 2nd Workshop on Geophysical Measurements at Landfills. Malmö, 2012. [8] ROSQVIST N H, DOLLAR L H, FOURIE A B.Preferential flow in municipal solid waste and implications for long-term leachate quality: valuation of laboratory-scale experiments[J]. Waste Management Research, 2005, 23(4): 285-295. [9] ÖMAN C, ROSQVIST H.Transport fate of organic compounds with water through landfills[J]. Water Research, 1999, 33(10): 2247-2254. [10] FELLNER J, BRUNNER P H.Modeling of leachate generation from MSW landfills by a 2-dimensional 2-domain approach[J]. Waste Management, 2010, 30(11): 2084-2095. [11] WHITE R E, DYSON J S, HAIGH R A, et al.A transfer function model of solute transport through soil 2: illustrative applications[J]. Water Resources Research, 1986, 22(2): 248-254. [12] JURY W A.Simulation of solute transport using a transfer function model[J]. Water Resources Research, 1982, 18(2): 363-368. [13] GUPTA A, DESTOUNI G, JENSENB M B.Modelling tritium and phosphorus transport by preferential flow in structured soil[J]. Journal of Contaminant Hydrology, 1999, 35(4): 389-407.
计量
- 文章访问数:
- HTML全文浏览量: 0
- PDF下载量:
下载:
