Similar articles

Abstract: cover systems are used to prevent water infiltration into a waste body. They also play an important role in controlling landfill gas transport from the waste body to the atmosphere. It is important to assess the flux of landfill gas at the surface of a cover system by considering the coupled effects of rainwater infiltration and gas transport in the cover soils. We have developed a 1D mathematical model for coupled transient gas and water transport in unsaturated cover soils. The coupled model was solved by the finite element method. Results obtained by the proposed model agreed well with experimental data. Based on the proposed solution, the influences of gas pressure, gas permeability, and the thickness of the cover soils on soil gas concentration profiles were investigated. The difference in soil gas concentration reached up to 31% as the thickness of cover increased from 1 to 2 m. Gas concentration at a depth of 0.2 m decreased by 6% as the amplitude of atmospheric gas pressure fluctuation increased from 20 to 100 Pa. The gas concentration increased by only 3% when gas permeability increased by a factor of 2 for a relatively long period of gas migration (e.g., 60 h) under the given conditions. Results suggest that both diffusion and advection should be considered when estimating gas transport in unsaturated cover soils. The numerical model can be used in the design of cover systems in relation to gas breakthrough time, breakthrough concentration, and flux.

The authors attemped to develop an one-dimensional coupled model for gas and moisture transport in layered soil cover systems at landfills. The model was solved by using the commercial software (COMSOL). Parametric study was carried out to investigate the influences from atmospheric gas pressure, gas permeability and thickness of soil cover on the distribution of gas concentration. The study is of interest to the researchers in the area of geoenvironmental engineering. Overall, the technical approach is solid, and results and conclusions appear to be reasonable.

填埋场非饱和成层覆盖层一维气水耦合运移模型

[1]Amini, H.R., Reinhart, D.R., Niskanen, A., 2013. Comparison of first-order-decay modeled and actual field measured municipal solid waste landfill methane data. Waste Management, 33(12):2720-2728.

[2]Bartelt-Hunt, S.L., Smith, J.A., 2002. Measurement of effective air diffusion coefficients for trichloroethene in undisturbed soil cores. Journal of Contaminant Hydrology, 56(3-4):193-208.

[3]Binning, P.J., Postma, D., Russell, T.F., et al., 2007. Advective and diffusive contributions to reactive gas transport during pyrite oxidation in the unsaturated zone. Water Resources Research, 43(2):W02414.

[4]Bustos, C.I., Toledo, P.G., 2003. Contact angle hysteresis effects on the relative permeability of gas and condensate in three-dimensional pore networks. Latin American Applied Research, 33(1):45-50.

[5]Chen, Y.C., Wu, C.H., Hu, H.Y., 2000. Numerical simulation of gas emission in a sanitary landfill equipped with a passive venting system. Journal of Environmental Science and Health Part A-Toxic/Hazardous Substances & Environmental Engineering, 35(9):1735-1747.

[6]Chen, Y.C., Chen, K.S., Wu, C.H., 2003. Numerical simulation of gas flow around a passive vent in a sanitary landfill. Journal of Hazardous Materials, 100(1-3):39-52.

[7]Choi, J.W., Tillman, F.D., Smith, J.A., 2002. Relative importance of gas-phase diffusive and advective trichloroethene (TCE) fluxes in the unsaturated zone under natural conditions. Environmental Science & Technology, 36(14):3157-3164.

[8]COMSOL, 2013. COMSOL Multiphysics, 3rd Edition. Available from http://www.comsol.com/products/3.5/ [Accessed on Mar. 3, 2013].

[9]Feng, S.J., Jiang, W.K., Li, X.L., 2013. Estimation of maximum saturated depth in two-layered drainage blankets over the barrier in landfill cover system. Environmental Earth Sciences, 70(6):2907-2917.

[10]Feng, S.J., Zheng, Q.T., Xie, H.J., 2015. A model for gas pressure in layered landfills with horizontal gas collection systems. Computers and Geotechnics, 68:117-127.

[11]Fityus, S.G., Smith, D.W., Booker, J.R., 1999. Contaminant transport through an unsaturated soil liner beneath a landfill. Canadian Geotechnical Journal, 36(2):330-354.

[12]Jung, Y., Imhoff, P.T., Augenstein, D.C., et al., 2009. Influence of high-permeability layers for enhancing gas capture and reducing fugitive methane emissions from landfills. Journal of Environmental Engineering-ASCE, 135(3):138-146.

[13]Kim, H., 2000. Oxygen Transport through Multi-layer Caps over Mine Waste. PhD Thesis, University of Wisconsin-Madison, USA.

[14]Kim, H., Benson, C.H., 2004. Contributions of advective and diffusive oxygen transport through multilayer composite caps over mine waste. Journal of Contaminant Hydrology, 71(1-4):193-218.

[15]Kim, J., Kim, J., Jung, H., et al., 2013. Experiment on gas entry pressure and gas permeability of concrete silo for a low- and intermediate-level waste disposal facility in Korea. Nuclear Engineering and Design, 265:841-845.

[16]Kwon, O., Cho, W., 2011. Field applicability of self-recovering sustainable liner as landfill final cover. Environmental Earth Sciences, 62(8):1567-1576.

[17]Li, Y.C., Cleall, P.J., Ma, X.F., et al., 2012. Gas pressure model for layered municipal solid waste landfills. Journal of Environmental Engineering, 138(7):752-760.

[18]Li, Y.C., Zheng, J., Chen, Y.M., et al., 2013. One-dimensional transient analytical solution for gas pressure in municipal solid waste landfills. Journal of Environmental Engineering, 139(12):1441-1445.

[19]Mbonimpa, M., Aubertin, M., Aachib, M., et al., 2003. Diffusion and consumption of oxygen in unsaturated cover materials. Canadian Geotechnical Journal, 40(5):916-932.

[20]Menard, C., Ramirez, A.A., Nikiema, J., et al., 2012. Biofiltration of methane and trace gases from landfills: a review. Environmental Reviews, 20(1):40-53.

[21]Moon, S., Nam, K., Kim, J.Y., et al., 2008. Effectiveness of compacted soil liner as a gas barrier layer in the landfill final cover system. Waste Management, 28(10):1909-1914.

[22]Nastev, M., Therrien, R., Lefebvre, R., et al., 2001. Gas production and migration in landfills and geological materials. Journal of Contaminant Hydrology, 52(1-4):187-211.

[23]Poulsen, T.G., Christophersen, M., Moldrup, P., et al., 2001. Modeling lateral gas transport in soil adjacent to old landfill. Journal of Environmental Engineering-ASCE, 127(2):145-153.

[24]Reichenauer, T.C., Watzinger, A., Riesing, J., et al., 2011. Impact of different plants on the gas profile of a landfill cover. Waste Management, 31(5):843-853.

[25]Rowe, R.K., Quigley, R.M., Brachman, R.W.I., et al., 2004. Barrier Systems for Waste Disposal Facilities. Taylor & Francis, London.

[26]Scheutz, C., Kjeldsen, P., Bogner, J.E., et al., 2009. Microbial methane oxidation processes and technologies for mitigation of landfill gas emissions. Waste Management & Research, 27(5):409-455.

[27]Townsend, T.G., Wise, W.R., Jain, P., 2005. One-dimensional gas flow model for horizontal gas collection systems at municipal solid waste landfills. Journal of Environmental Engineering, 131(12):1716-1723.

[28]Wickramarachchi, P., Kawamoto, K., Hamamoto, S., et al., 2011. Effects of dry bulk density and particle size fraction on gas transport parameters in variably saturated landfill cover soil. Waste Management, 31(12):2464-2472.

[29]Woodman, N.D., Siddiqui, A.A., Powire, W., et al., 2013. Quantifying the effect of settlement and gas on solute flow and transport through treated municipal solid waste. Journal of Contaminant Hydrology, 153:106-121.

[30]Yanful, E.K., 1993. Oxygen diffusion through soil covers on sulphidic mine tailings. Journal of Geotechnical Engineering-ASCE, 119(8):1207-1228.

[31]You, K.H., Zhan, H.B., 2012. Can atmospheric pressure and water table fluctuations be neglected in soil vapor extraction Advances in Water Resources, 35:41-54.