No description available.

No description available.

No description available.

No description available.

The quantity of waste generated in Libya, as in other developing countries, has been increasing dramatically for many years due to a rapid urban expansion associated with high population growth. Until now, this waste has been dumped into very large open tip sites located close to urban areas. These sites lack any form of engineered control system to prevent groundwater contamination and environmental degradation from the air and ground pollution. A high risk of groundwater contamination occurs in many water wells around the dumping sites. There is an urgent need to fmd an affordable and feasible long-term solution to protect groundwater supplies and the surrounding environment. However, the construction of engineered landfills usually requires the installation of a lining system. To be efficient, the lining system material should have a low hydraulic conductivity that should not increase under the action of leachates. This research provides a comprehensive physical and chemical laboratory investigation of an arid Libyan soil to assess its suitability in a landfill lining system. The clay mineralogy tested using XRD showed that compositions of all soil types tested are similar and are predominately illite and kaolinite. Batch equilibrinm testes were used to characterise the soil adsorption properties. The results of this assessment indicate that Libyan clays is not wholly satisfactory according to the criteria and guidelines available for landfill mineral liners. However, a bentonite was used to improve Libyan soils' performance as landfill liner. The results showed that bentonite improved the engineering characteristics of the Libyan soils tested, and proved to be a better additive as it lowered the hydraulic conductivity, and increased the adsorption capacity of the soils. Bentonite thus showed that it has the potential of being used as an additive to Libyan soils to improve its containment qualities.

Advanced oxidation processes, namely photo-Fenton, Fenton-like, Fenton and UV/H202 and plasma have been investigated for the removal of organic matters from landfill leachate. Fenton's oxidation was the most effective and the most effective ratio 1/10 (Fe2+/H202) COD removal reached 50-80% and the biodegradability increased by 40 to 60 %. The oxidation batch treatment was performed on different synthetic leachate concentration and two types of doses:(single and triple Fenton's reagents. The first single Fenton's reagent removal efficiency of COD was less than those of a triple Fenton's reagents for all tested leachates under similar operating conditions. The COD removal of domestic landfill leachate and a glucose based-synthetic one as a function of the operating variables (H202, Fe2+, Ti02 , UVand Plasma) led to results that ranged between 30% and 90% while the removal efficiencies decreased in the order: photo-Fenton > Fenton-like > Fenton > UVIH202, > UV. Fenton process however generated an important quantity of iron sludge which will require further disposal. The advanced plasma process which relies on cold liquid plasma as source of light for radical productions was used as a new technique to treat landfill leachate solutions. The efficiency of single plasma process and its combination with conventional Fenton catalytic process as an integrated process on COD removal were investigated. The experimental procedure was carried out in a bench-scale continuous stirred tank catalytic reactor where the plasma unit probe was immersed in the liquid phase generating periodic pulses for various periods of time. The process involved the use of both Fe2+ catalyst and hydrogen peroxide while the plasma process required an additional NaCl diluted solution to promote the electrolysis by increasing the conductivity of the operating solutions.

No description available.

There are a large number of unlined and historical landfill sites across Britain, contaminating groundwater and soil resources as well as posing a threat to human health and local communities. There is an essential requirement for robust methodology when carrying out risk-based site investigations prior to risk assessment and remediation of landfill sites. This research has focused upon the methods used during site investigations for two reasons. Firstly, the site investigation is often conducted using field instruments and methods that do not account for the heterogeneous conditions found at landfill sites. Interpreting geophysical conditions between sampled points is a common practise. Given the complex and heterogeneous conditions at landfill sites, such methodology introduces uncertainty into data sets. Secondly, risk estimation models that simulate groundwater flow and contaminant transport require extensive field information. The data used during model construction will significantly impact contaminant transport simulations. Modelling guidelines also need further development, ensuring that sound modelling practises are adhered to during model construction. To address these concerns, four research objectives were identified: (1) Two new multi-spatial field assessment methods (remote sensing and ground penetrating radar), previously applied in other fields of science, were tested on landfill sites; (2) Kriging was used as a tool to improve landfill-sampling strategies; (3 & 4) Groundwater flow and contaminant transport models were used to evaluate whether different scales of field data and modelling practises influenced modelling assumptions and simulation. The utility of novel field- and airborne-based remote sensing methodologies in identifying the location and intensity of vegetation stress caused by leachate migration and inferring pathways of near surface contamination using patterns of vegetation stress was proven. The results from the kriging investigations demonstrated that additional insight into field conditions could be resolved to identify locations of additional sampling points, and provide information about variability in hydrological data sets. The Ground Penetrating Radar investigations provided three types of valuable near-surface information that could assist in determining landfill risks: buried landfill features, leachate plume locations and local hydrogeological conditions. These combined methods provided detailed synoptic geophysical and contaminant information that would otherwise be difficult to determine. Their application and acceptance as site assessment methods (used under certain landfill conditions) could increase the accuracy of assessing risks posed by landfill leachate. These applications also demonstrated that the most effective site assessments are achieved when integrated with other field data such as soil, vegetation, and groundwater quantity measurements, contaminant concentrations and aerial photographs, providing comprehensive information needed for risk estimation modelling. The modelling analyses found that close attention must be paid to site-specific and model-specific characteristics, as well as modelling practises. These factors influenced model results. By using additional data to infer model parameters, it was evident that the amount of data available will influence the way in which risk will be perceived. The more data that was available during model construction, the higher the risk prediction. This was the case for some seventy- percent of the models. By improving the accuracy of site investigation methodology, and by adhering to robust assessment and modelling practices, a higher level of quality assurance can be achieved in the risk assessment and remediation of contaminating landfill sites. If the improvements and recommendations presented in this research are considered, uncertainties inherent in the site investigation could be reduced, therefore enhancing the accuracy of landfill risk assessment and remedial decisions.

Hydraulic conductivity is a measurement of the ease of movement of a fluid through a medium and is therefore a key parameter in the design of landfill leachate management systems. Hydraulic conductivity of landfilled wastes may be affected by several factors such as overburden stress from the weight of overlying waste, water content, the type, age and pre-processing of the waste, and the presence of landfill gas. A further factor that may affect leachate movement through wastes is the predominantly horizontal orientated structure of compacted wastes. This anisotropic structure may result in hydraulic conductivity in the horizontal direction being greater than that in the vertical direction. However existing research has been effectively limited to evaluating hydraulic conductivity in a single plane and so the presence of anisotropic flow in waste remains unproven. Consequently, modelling of leachate and contaminant movement in landfills may be compromised by the use of isotropic, or assumed anisotropic, hydraulic conductivity values. The object of this research has been to assess for the first time the inherent anisotropy of two different waste samples by measuring and comparing the vertical and horizontal hydraulic conductivities over a range of stresses typical of landfill conditions. In this thesis, factors affecting the measurement of hydraulic conductivity of wastes are discussed, and details of the samples tested and test methodology are given. The results of the tests are shown and alternative test methods are discussed. The effects of gas accumulation and pore water pressure on waste hydraulic conductivity encountered during testing are also reported as further research has developed from this important finding.

The use of geosynthetics in landfill construction introduces potential planes of weakness. As a result, there is a requirement to assess the stability along the soil/geosynthetic and geosynthetic/geosynthetic interfaces. Stability is governed by the shear strength along the weakest interface in the system. Repeatability interface shear strength testing of a geomembrane/geotextile interface at low normal stresses suitable for capping systems showed considerable variability of measured geosynthetic interface shear strengths, suggesting that minor factors can have a significant influence on the measured shear strength. This study demonstrates that more than one test per normal stress is necessary if a more accurate and reliable interface shear strength value is to be obtained. Carefully controlled inter-laboratory geosynthetic interface shear strength comparison tests undertaken on large direct shear devices that differ in the kinematic degrees of freedom of the top box, showed the fixed top box design to consistently over estimate the available interface shear strength compared to the vertically movable top box design. Results obtained from measurement of the normal stress on the interface during shear with use of load cells in the lower box of the fixed top box design, raise key questions on the accuracy, reliability and proper interpretation of the interface shear strength data used in landfill design calculations. Tests on the geocomposite/sand interface have shown the interface friction angle to vary with the orientation of the geocomposite's main core, in relation to the direction of shearing. Close attention needs to be paid to the onsite geocomposite placement in confined spaces and capping slope corners, as grid orientation on the slope becomes particularly important when sliding is initiated. Attempts to measure the pore water pressure during staged consolidation and shear along a clay/geomembrane interface in the large direct shear device suggest that this interface is a partial drainage path.