Modelling Groundwater Flow and Contaminant Migration in Heterogeneous Fractured Media at a Municipal Solid Waste Landfill in Nanjing Lishui, China

Abstract

The migration of groundwater flow and contaminants in fractured medium is complicated owing to the strong heterogeneity and anisotropy of fractured rock mass. Taking the environmental restoration and groundwater protection of the Lishui domestic waste landfill in Nanjing as the background, the groundwater environmental impact assessment and prediction are conducted for the groundwater environmental pollution that may be caused by the leakage of the landfill leachate after the closure of the domestic waste landfill. The strata of the landfill site are clay-cobble gravel, strongly and moderately weathered breccia, with obvious anisotropy and significant differences in rock mass permeability. A 3D numerical model of groundwater flow and contaminant migration in the landfill area is established by integrating the hydrogeological field tests and a conceptual model in the study area. Based on the parametric inversion method, the heterogeneous anisotropic permeability coefficient of the fractured medium is calibrated, and the temporal and spatial migration characteristics of contaminants such as ammonia nitrogen and mercury are predicted using the corrected model under the normal and failure conditions of the antiseepage curtain. The calculated results show that when the antiseepage fails, the maximum migration distances of contaminants in the horizontal direction after 100 days in the old and new landfills are 7.66 m and 15.64 m, respectively, and the maximum migration distances after 20 years are 192.5 m and 113.89 m, respectively. The migration direction and distances of contaminants are consistent with the hydrogeological conditions of the study area. The model calculation results provide a corresponding basis for the antiseepage control of contaminants.

Experimental and numerical simulation of solute transport in non-penetrating fractured clay

“…Non-penetrating fractured groundwater flow is the transient groundwater flow in a heterogeneous anisotropic medium, which can be calculated and simulated using the Boussinesq Eq. ( 1 ) 55 : where Ω is domain of fractured media; x , y and z are the space coordinates; K x , K y , K z are the hydraulic conductivities along coordinate three axes; K n is the hydraulic conductivity in normal direction of boundary surface; t is time; n is the normal direction of boundary surface; and is domain of the first and second type boundary, respectively; h 0 is the initial groundwater table; h f is the hydraulic head in the fractured system; h 1 is the known groundwater table in the first type boundary; μ is the specific yield for unconfined aquifer and specific storage for confined aquifer; q is the unit area flux of the second type boundary, its value is positive for groundwater inflow and negative for outflow; W is the sinks and sources, such as the evaporation, precipitation and pumping rate. Model of solute transport The solute transport process is the result of a combination of factors.…”

Critical Study Quality Management for the Anti-Seepage System in Macau’s Landfill Area

“…The project's scale is determined by the amount of waste generated and landfill requirements in the Macau region. The primary objectives of the project include [10] (Figure 5):…”