Monitoring Leachate Migration in Compacted Soil Using Digital Image Technique

As leachate has been a source of groundwater contamination worldwide, this paper examines the phenomenon of leachate migration on different gradations of compacted laterite soil used as sanitary landfill liners. Three different soil gradations (30%, 40% and 50% with respect to fines content) used in this study were compacted in circular acrylic columns to provide a clear visualization of leachate migration into the soils. Digital image technique was used in capturing photos at successive time intervals to monitor the leachate migration. The captured digital images were fed into Matlab and converted into hue-saturation-intensity (HSI) format. Surfer software then read the HSI and generated 2D contour plots. The results of the experiments showed that the leachate moves downward faster in the soil gradation with the least fines content. Hydraulic conductivity values decrease with increase in time duration and equally with increase in fines content. The hydraulic conductivities of the leachate for 30%, 40% and 50% fines were 3.64×10-9m/s, 2.40×10-9m/s, and 1.24×10-9m/s respectively. This reveals that for tropical laterite soils, gradation containing 50% fines content provides better hydraulic conductivity. The use of noninvasive digital image technique can enable designers/engineers to monitor and visualize the leachate migration in compacted soils in waste containment application systems

Monitoring Leachate Migration in Compacted Soil Using Digital Image Technique

As leachate has been a source of groundwater contamination worldwide, this paper examines the phenomenon of leachate migration on different gradations of compacted laterite soil used as sanitary landfill liners. Three different soil gradations (30%, 40% and 50% with respect to fines content) used in this study were compacted in circular acrylic columns to provide a clear visualization of leachate migration into the soils. Digital image technique was used in capturing photos at successive time intervals to monitor the leachate migration. The captured digital images were fed into Matlab and converted into hue-saturation-intensity (HSI) format. Surfer software then read the HSI and generated 2D contour plots. The results of the experiments showed that the leachate moves downward faster in the soil gradation with the least fines content. Hydraulic conductivity values decrease with increase in time duration and equally with increase in fines content. The hydraulic conductivities of the leachate for 30%, 40% and 50% fines were 3.64×10-9m/s, 2.40×10-9m/s, and 1.24×10-9m/s respectively. This reveals that for tropical laterite soils, gradation containing 50% fines content provides better hydraulic conductivity. The use of noninvasive digital image technique can enable designers/engineers to monitor and visualize the leachate migration in compacted soils in waste containment application systems

Geospatial Multi Criteria Selection of Best Sanitary Landfill Site and their Geotechnical and Digital Image Analysis.

Contaminations caused by municipal waste affect not only the soil but also water and air. In many parts of the world, there are many uncontrolled landfills that often lack the necessary anti-fouling barrier systems which causes leachate to permeate the underlying groundwater making it toxic for consumption. This research presents a sustainable method in which sanitary landfills can be sited using geospatial multi criteria method and the subsequent application of geotechnical and digital image analysis. Due to the large volume of spatial data, thus, Geographic Information System was used to handle, evaluate, and process these data. Meanwhile, Analytical Hierarchy Process was applied to solve decision making problems where multiple alternatives and competing objectives are involved. The results revealed three most suitable sites for sustainable sanitary landfilling in the research area. These most suitable sites were further examined using geotechnical criteria in laboratory to obtain the best site. Engineering property relating to permeability was investigated. The results show that only one amongst the three sites achieved maximum regulatory range of permeability value of 10-9 m/s. Additionally, computer modeling through digital image technique was used to visualize the leachate flow and validate the laboratory experimentation. The leachate migrated through the soil covering a depth of 2.51 mm in one month, having a velocity of 10-9 m/s which is within the recommended permeability value. Therefore, this model could be used as a guide for sustainable sanitary landfilling in developed and developing countries

Numerical modelling of leachate migration in compacted tropical laterite soil

To protect groundwater from leachate contamination in sanitary landfill involve the use of hydraulic barriers i.e. liners and covers. Nonetheless, can these barriers continue to impede the migration of leachate over a long period? A full-scale experiment would be prohibitively costly and time consuming. The only feasible recourse therefore is to construct a model, which reasonably portray the behaviour of the full-scale system and simulate the relevant physical parameters and describes the overall significant characteristics of the transport phenomena. This research investigates the long-term performance of compacted tropical laterite soil liners at various gradations against leachate migration in sanitary landfills using numerical modeling. Series of laboratory experimentation were carried out using three different laterite soil gradations (30%, 40% and 50% with respect to fines content) compacted at optimum moisture content using British Standard light energy. Leachate was poured on the compacted soil in an acrylic column and its migration was monitored using Digital Image Technique (DIT). Subsequently, PetraSim computer software a graphical interface used to solve problems related to contaminant transport was applied to predict the velocity of leachate migration. The predicted velocity values for 30%, 40% and 50% fines are 4.5 x 10-7 m/s, 7 x 10-9 m/s, and 8 x 10-10 m/s, respectively. This shows that the laterite soil with 50% fines content is more compatible with the leachate and can be used as soil liner. The outcome of this research would enable designers to use non-destructive method to monitor and predict leachate migration in compacted soil liners to simulate leachate migration in waste containment applications

Sanitary landfill siting using GIS and AHP: A case study in Johor Bahru, Malaysia

One of the major problems affecting municipalities is solid waste management. There is a difficulty in selecting suitable sites for waste disposal as it involves different factors to be considered before site selection. Currently, waste generation in Johor Bahru has steadily increased over the last few years and the only existing sanitary landfill is reaching its capacity limits, which means that a new sanitary landfill site needs to be constructed. In this study, geographic information system (GIS) and analytical hierarchy process (AHP) methods were utilized with the integration of dynamic data such as future population and projection of waste production in order to provide suitable sites for the construction of a sanitary landfill in the study area. Thirteen criteria were considered for this study, namely water bodies, soil, geology, slope, elevation, residential areas, archeological sites, airports, population, road, railway, infrastructure, and land use. AHP was used to determine the weights for each criterion from the pairwise comparison matrix. Consistency index and consistency ratio were checked and confirmed to be suitable. The results obtained from AHP were assigned to each criterion in GIS environment using weighted overlay analysis tool. The final potential site map was produced, and the three most suitable potential landfill sites were identified

Engineering characteristics of compacted laterite soil as hydraulic barrier in waste containment application

The primary objective of hydraulic barriers in containment facilities is to prevent migration of leachate directly into the underlying subsurface during both the active disposal period and the post-closure period. Liner system is, therefore, one of the most important elements of a modern sanitary landfill. In order to achieve an effective soil lining system, a minimum criterion of 30% fines content is required to fulfil the hydraulic conductivity requirement of ≤ 1 × 10-9 m/s as specified by most regulatory agencies and researchers. Studies reveal that at this percentage, laterite soils are vulnerable to leachate permeation, which will contaminate the groundwater. Therefore, this research aims to determine the effects of gradation on engineering properties of laterite soil with respect to hydraulic conductivity, volumetric shrinkage strain, and unconfined compressive strength. In order to satisfy the regulatory requirements of soil liner, tests were carried out on natural soil (30% fines) and two reconstituted soil samples (40% fines and 50% fines). The effects of fines content that is required to provide the recommended criteria of ≤ 1 × 10-9 m/s hydraulic conductivity, ≤ 4% volumetric shrinkage and ≥ 200 kN/m2 unconfined compressive strength at their permissible limits were plotted. The overall acceptable zone was obtained at moulding water contents ranged between 24-28% for 50% fines content. Based on the laboratory experimental results, a minimum fines content of 50% must be achieved to fulfil the engineering characteristics requirements to prevent groundwater contamination in tropical laterite soil

Soil water characteristic curves for laterite soil at different water contents and methods as lining system

Preventing groundwater contamination from the most common method of solid waste disposal technique i.e. landfilling is by proving hydraulic barriers. Accordingly, water movement in unsaturated soil is important in the analysis of leachate migration in soil material used as hydraulic barrier in waste containment systems. A full-scale experiment would be prohibitively costly and time consuming. The only feasible recourse therefore is to construct a model, which reasonably portray the behaviour of the full-scale system and simulate the relevant physical parameters and describes the overall significant characteristics of the transport phenomena. This paper presents the trends and patterns of soil water characteristic curves (SWCC) in terms of volumetric water content versus soil suction developed for compacted laterite soil specimens using data from pressure plate tests. Specimens were prepared at three different water contents corresponding to dry of optimum, optimum, and wet of optimum conditions. Models suggested by Brooks and Corey (BC), van Genuchten (VG), and Fredlund and Xing (FX) were used to obtain curve fitting parameters using the program "SWRC Fit" which performed nonlinear fitting of soil water retention curves. The SWRC Fit can simultaneously calculate the fitting parameters of these models with Root Mean Square Error values and draw the fitting curves. By comparing the results of the models using SWRC Fit, the model that best fits the laterite soil investigated will be chosen to be used for further analysis. The results show that the BC model represents the soil water retention curves better than the VG and FX models when the soil has distinct air entry suction. On the other hand, the VG and FX models can fit most soil water retention curves very well when discussion on the pore-size distribution is desired