the alumina sheet of the montmorillonite minerals, with magnesium or iron ...... agent), di-alkyl sulfosuccinate (wetting agent) and lignosulfonates (dispersants).
PART I Introduction 1. General Environmental engineering investigates hazardous waste contaminants, their pathways, transport, fates and disposition. It also explores ways of protecting groundwater, thereby protecting humans and the environment from hazardous wastes. Petroleum products, for instance, account for sixty-nine percent of soil contamination in Quebec (Environment Quebec, 1994).
Landfills are currently one of the most effective ways to dispose of wastes. Underground storage tanks (UGST) are also used to store hydrocarbon fluids that include different types of fuels. The bottom part of the landfills and UGST is critical. This liner material and its composition prevent heavy metals and leachate from seeping through to the groundwater. Failure of this layer presumably causes most landfill failures.
2. Statement of the problem Many liners are made watertight with clayey materials, such as sand-bentonite mixtures, that retain liquid and solid toxic wastes. Although, many cases were reported for high leakage of bentonite liners (Chapuis, 2002), they remain in use. In Quebec, for example, 450 projects built since 1980 involved more than 1000 liners. Overtime, the principal 1
function of liners is reduced and contaminants leak through them. As these toxic contaminants infiltrate the subsoil and the groundwater, they have serious ramifications on the stability of constructions and the safety of humans and animals.
Failure of landfill liners is a problematic issue for engineers and a costly one for governments, societies and the environment. To protect groundwater, the structure of a natural landfill liner needs to preserve its properties in harsh conditions for a sustained time span. In addition, the type of disposed materials in landfills and storage tanks is changing and it is starting to include alternative fuels such as biofuel or ethanol fuel.
Hence, this research focuses on the changes within the sand/bentonite liner structure due to the percolation of biofuel and ethanol fuel. There is also a need for an in-depth study of how interaction with these fuels might cause failure in the sand-bentonite liners.
In the other hand, landfill liners or clay barriers should be repaired once they are fractured. A destroyed liner is often repaired by removing all or part of it, and replacing it with a new liner. Applying in situ treatment for the liner requires a new technology. This is a big challenge since no in situ technology is available for such remediation yet.
Stabilization in high depths, known as grouting, cannot be applied for fine materials like clay bentonite, one of the main components of natural liners. Indeed, the injection of 2
grout requires high hydraulic pressure that can be destructive to the formulation of liner; therefore, other methods of grouting are required. Thesis suggests the use of grouting by means of electrokinetics phenomena. However, standard electrokinetics grouting cannot be used because the liner contains hydrocarbon residuals that are not soluble in water. Thus, a new approach is necessary; electrokinetics washing is required before electrokinetics grouting.
Furthermore, it is necessary to design a multifunctional electrodes system. The electrodes can work at first as a system providing washing conditioning liquid. Then, the same system can provide an adequate grout to the pretreated (washed) liner. Hence, there is a need to look for an adequate washing liquid for liner pretreatment.
Usually, applying a surfactant removes hydrocarbons. However, hydrocarbons are hardly removed by electrokinetics washing with water. Thus, applying a surfactant that is transported by an electrokinetics system seems an adequate approach for liner pretreatment. For the system to work, though, a suitable type of electrical field surfactant should be selected.
3. Objectives Containment barriers commonly use clays for their low permeability as liners in landfills 3
and settling ponds. The properties of the fluid passing through liner material affect the liner’s structure. Thus, in the presence of alternative fuels, the dispersed orientation of clay particles alters the clay’s permeability. The percolation of fluids might result in changes in the microstructure of clay fabrics.
Leaking fluids destroy clay barriers, even though the liners are designed to prevent these percolations. In practice, when subjected to organic liquids, the clay liner leaks and destroys the clay microstructure, thereby increasing the permeability of the liner.
This research aims to study qualitatively and quantitatively the sand-bentonite characteristics and the effect of the following elements on the liner’s hydraulic conductivity before and after the liquid infiltration: Pressure Type of permeate Erodibility of fine particles in the liner mixture Free swelling index Shrinkage limit Percentage of fines particles (the content of bentonite clay)
Furthermore, this study evaluates the impact of alternative fuels (biofuel and ethanol fuel) on the permeability of sand-bentonite liners. It establishes an empirical model to predict 4
the hydraulic conductivity of liners under the influence of these liquids for different parameters. Then, using of hydraulic conductivity as an indicator of liner behavioiur (performance, failure), it can provide guidelines for formulation, maintenance and rehabilitation of liners. Since a new technology for liner rehabilitation is needed, the thesis develops a technique, which involves the remediation of liners, including stabilizers and in situ high depths remediation.
4. Thesis structure This thesis consists of four parts as follows: Part I includes an introduction: statement of the problem and objectives of this research, and a literature review (chapter 1).
Part II comprises research methodology and experimental work (chapter 2), tests results and analysis (chapter 3), and the empirical modelling of an indicator of liners performance (chapter 4).
Part III focuses on the rehabilitation of liner using two-step electro-silicatization technology (chapter 5).
Part IV includes conclusions, contributions, recommendations and future work (chapter 6). 5
Chapter 1 Literature Review 1.1 Introduction This chapter outlines research related to landfill liners, including composition, types, characteristics, experimental tests, and failures.
1.2 Natural liners Kayabali (1997) investigated features of novel materials for an impervious liner in sanitary landfills. Natural zeolites and commercial powdered bentonite were used for different experiments such as compaction, hydraulic conductivity and strength. A bentonite/zeolite ratio of 0.05-0.10 was found ideal as landfill liner material for its low hydraulic conductivity, high cation exchange capacity (CEC), and ability to reduce the thickness of base liners for sanitary landfills.
Sheu et al. (1998) investigated the physical and hydraulic conductivity behaviours of a mudstone material from southwestern Taiwan. Their study examined readily available mudstone to replace the synthetic flexible membrane liner widely used in sanitary landfills in Taiwan due to the scarcity of clay materials. They concluded that the mudstone — with a liquid limit of 34.1%, a plasticity index (PI) of 15.2%, a percentage of fines (
