- Copyright ©2011. The American Association of Petroleum Geologists/Division of Environmental Geosciences. All rights reserved.
Engineered landfill liner systems are expensive to install and represent a challenge to several developing countries. Alternatively, native soils, preferentially clays, can be used as cost-effective bottom liners. The purpose of this work is to justify the reliance on the ability of the clays at the Kharga-Dakhla land stretch, Western Desert, Egypt, to act as a containment and barrier for pollutants that might be generated in a landfill leachate. This is particularly valid in hyperarid regions where many environmental requirements for landfill liner design are relaxed, as precipitation is rare and percolation to buried wastes is practically absent. The availability of native clays and clay-bearing sediments in the study area, both on surface and subsurface, makes it a potential landfill site. Collaborating techniques have been used to determine the mineralogical, geochemical, and geotechnical characteristics of the sediments constituting the Quseir Formation (Upper Cretaceous). These techniques include x-ray diffraction analysis, differential thermal analysis, cation exchange capacity (CEC), swelling properties, Atterberg limits, porosity, and hydraulic conductivity. The obtained results indicate that the investigated clayey sediments are dense and compact. They have low hydraulic conductivity that ranges from 1 × 10 −10 to 4.96 × 10 −11 cm/s, with moisture content that does not exceed 7%. The swelling values of samples containing smectite range between 250 and 500%. The plasticity limit of the red clay (floor of the Dakhla Oasis) ranges between 11 and 18%, which indicates its suitability as a landfill lining material. Values for CEC are generally high and increase with increasing smectite content. It reaches as much as 69 meq/100-g sample, indicating enhanced ability for natural attenuation and can act within the containment system for metal pollutants. The obtained mineralogical, geochemical, and geotechnical data suggest that the studied clays can be used, effectively, as a viable alternative liner system for solid waste and/or secured landfills, replacing the costly state of the art liner systems. Satisfying siting criteria, the availability of the clays, and the easy way and their low cost of extraction provide a cost-effective solution to the problem of landfill lining in developing countries.
Ashraf M. El Maghraby is an assistant professor at Cairo University; now, he is temporarily engaging the deanship of scientific research at King Abdulaziz University, Jeddah, Saudi Arabia, as a consultant. El Maghraby received his Ph.D. in geology during a cooperation program between Cairo University and the University of Nebraska at Lincoln. El Maghraby has more than 25 yr of experience as an environmental geologist; he has published scientific research in geology, environmental geology, hazardous waste landfills, used oils, mining impacts, medical geology, environmental impact assessment, and other areas of research.
Ahmed M. El Kammar is a professor emeritus of geochemistry and mineralogy at the Department of Geology, Faculty of Science, Cairo University, Giza, Egypt. He received scholarships for geochemical research from the Geotechnical Institute, Arsenal, Obj. 214, Vienna, Austria, and from the Geological Institute, University of Bergen, Norway. He also received a Fulbright fellowship for advanced research in environmental geochemistry, University of Virginia, and a fellowship from the International Atomic Energy Agency (IAEA) for training on groundwater hydrology in the IAEA isotope hydrology section of the IAEA in Vienna, Austria. El Kammar has published many articles on geochemistry and environmental geochemistry, including river sediments, heavy metals, clay minerals, phosphate ores, and others.
Mohamed S. Mabrouk is a graduate student from the Geology Department of Cairo University. He is now doing his Ph.D. in geochemistry of the Nile River sediments. Mabrouk received his M.Sc. degree on environmental application of clays, particularly as landfill liner. Mabrouk is now a teaching assistant at the Geology Department of Cairo University for the laboratory work of minerals and rocks.