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This thesis examines the problems of change in the technology of waste management in a rural area of Cameroon during the period 1960-1979. Chapter One sets the scene for the analysis. A brief account of the important features of the whole United Republic of Cameroon is followed by a precise description of the study area. This highlights the wider implications for waste management to be discussed in the rest of the thesis. The second chapter develops an analytical model from social theory which is used in the rest of the thesis to explain how change in the technology of waste management takes place in the rural areas. The model is eclectic. In it society is regarded as a collection of individual actors who have individual objectives. In order to achieve their objectives actors require resources. The nature of the resources which actors possess is largely conditioned by the pattern of interdependencies. All social actors are creative in their behaviour but their creativity may be limited by circumstances. Thus the process of interaction among actors is subject to various constraints. Focussing attention upon such conceptions of human behaviour provides a fruitful approach to an analysis of power relations among actors. Of particular importance in this thesis is the distribution of power in society. The power which actors have results in some forms of action being possible for some actors but impossible for others. This model is used to generate hypothesis which relate to waste management. Chapter Three discusses the design aid methods of collecting the empirical evidence to test the hypotheses illuminated by the theoretical model. Both conventional and some non-conventional methods are used. On the bases of their varied levels of perception and degrees of power, five groups of actors were identified in these rural areas: the rural economic elite, the rural literate, the traditional authorities, the traditional healers and the illiterate peasants. For the purpose of a more careful detail and closer examination these actors were disaggregated and each examined separately in chapters four to eight. The rural economic elite are examined to show how their resources are deployed to bring about sanitation changes as well as the implications for the waste/disease relationship. The analysis of the rural literate is concerned with the key question of whether change in the technology of waste management is associated with the actor's formal education. In other words does actors' formal education change their perception? Does changed perceptions change actions, habits and customs? Does the formal educational system itself promote good hygiene by both precept and example? Traditional authorities are analysed in chapter six to find out their impact on village communal sanitation changes. Chapter seven examines the role of traditional healers on waste management and other community sanitation behaviour. It investigates in what sense the healers have power in the community, how far the use of that power is conducive to good sanitation and why healers are resistant to change. The eighth chapter examines the pattern and level of change in waste management among illiterate peasants. It provides explanations for this pattern of change and the implications for the health of the people. The conclusion draws out the essence from the empirical evidence analysed in chapters four to eight and relates these to the theoretical model. It indicates and establishes the goodness of fit between the evidence and the model as well as the comprehensiveness of the nature of the explanationa offered by the model. It highlights both the strengths and weaknesses of that model. It indicates some wider implications of the findings with brief recommendations for the policy maker. Finally it suggests areas that are in urgent need of further research.

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The potential to recycle greater volumes of water may provide a financial incentive for the removal of metal ions from waste water. Selective recovery of metals, in a cost effective manner has the potential to improve the economics of the operation, by providing a commodity rather than waste requiring ever more expensive disposal. Six technologies were investigated, via reference to the available literature, and a process combining chelation of metal ions by a water-soluble polymer with ultrafiltration (polymer enhanced ultrafiltration) was selected for further investigation. The overall aim of this investigation was to assess the feasibility of applying polymer enhanced ultrafiltration for preferential concentration of metals from wastewater. Wastewaters investigated were effluent from steelmaking operations, and landfill leachate. Three “key factors” were considered critical to the viability of the process: 1. Polymer reuse, and safety; 2. Application to real systems; 3. Membrane selection. The research reported here investigated the first two key factors and the applicability of mathematical models reported in the literature. Experimental work showed that correct preparation of the polymer would likely reduce leakage to acceptable levels. Selective recovery of metals from wastewater was shown to be feasible, although retention of metals was apparently due to several mechanisms. Indeed in some instances selective concentration of metals was achieved without the addition of a polymer. In several instances other waste treatment techniques would be required to provide an effluent suitable for disposal. In addition there was considerable potential for pre-treatment of wastewater to improve the economics of the process.

The environmental impact of different methods for dealing with municipal solid waste is examined in the light of public opinion, and the future of landfilling is discussed. Measures adopted by some Member States of the European Union in order to tackle their waste packaging and in order to renovate their waste management are presented. The effect of the German Packaging Ordinance on the recovery industry in Europe is analysed together with the changes brought about in the waste collection industry by the application of the polluter-pays-principle. The evolution of EU environmental policy since the adoption of the Treaty of Rome is described and relevant Directives and Court cases are referred to in order to illustrate EU waste policy. The conflicting attitudes of the public, governments and waste and packaging industries are underlined and the problem of waste definition is also raised. Finally, a numerical model is presented which uses FORTRAN as a programming language. The model is designed to compare the profitability of different collection and sorting methods and to find the optimal way of achieving a particular recycling target. The optimisation technique of simulated annealing is applied to the problem. The model is implemented for a typical medium sized town in the UK and the results obtained are presented.

Chapter one introduces the historical background, development and need for monitoring techniques utilising absorbent tube sampling methods and highlights the rapid increase in environmental awareness that has occurred as technology has advanced. A short summary covering the sources of volatile organic compounds (VOCs) is included. Chapter two presents a synopsis of the experimental methods and theory associated with adsorbent tube sampling and analysis. The application of both passive and active sampling techniques has been discussed with the emphasis on maintaining sampling and analytical integrity. Chapter three covers the key sources of error in both sampling and analysis and defines statistical terms that are used in analytical science. The measurement and calculation of tube dimensions, diffusion coefficients, mass uptake rates, limit of detection and quantification are presented. Chapter four outlines the findings from an inter-laboratory calibration exercise to investigate external calibration methods at low nanogram levels. The use of certified reference materials and preparation of standards is discussed. Chapters five and six assess the likely errors to be encountered when using passive sampling techniques for long term environmental monitoring, and cover aspects of sampling accuracy, bias and precision. Particular attention is devoted to assessing changes in the mass uptake rate and back diffusion during passive sampling. Chapters seven to ten detail research related to the application of adsorbent tube trapping for the sampling and analysis of VOCs in soil gases. Work has focused on enhancing both the qualitative and quantitative information that can be obtained from soil gas surveys by the use of heated sampling techniques to increase the recovery of less volatile compounds. The feasibility of an indoor test facility to simulate soil and soil gas contamination is also discussed.

This thesis presents a general framework for the finite element simulation of powder forming processes. As the compaction process involves a very large reduction in volume, the behaviour of the powders is assumed to be that of a rate-independent elasto-plastic material. The process is therefore described by a large displacement finite element formulation for the spatial discretization. A generalized Newmark scheme is used for the time domain discretization and then the final nonlinear equations are solved by a Newton-Raphson procedure. A combination of a Mohr-Coulomb and elliptical cap model is utilised as a constitutive model to describe the nonlinear behaviour of powder materials in the concept of the generalized plasticity formulation for the description of cyclic loading. The finite element approach adopted is characterized by the use of 'interface' elements in which a plasticity theory of friction is incorporated to simulate sliding resistance at the powder-tool interface. The constitutive relations for friction are derived from a Coulomb friction law. Efforts have been made to develop an automatic and generally applicable adaptive procedure in the analysis of powder forming processes. A-posteriori Zienkiewicz-Zhu estimator using <I>L<SUB>2</SUB></I> norm of strain by a recovery procedure is proposed. The simulation of the deformation is shown as well as the distribution of stress and relative density. The results clearly indicate that the algorithm makes it possible to simulate the powder forming problems efficiently and automatically. It has been shown that the proposed adaptive finite element approach is capable of simulating metal powder compaction processes in an efficient and accurate manner. A method is presented for applying the mixed formulation to study the prediction of localization phenomena in a dynamic plasticity problems. This has focused on the performance of mixed u<SUP>- π</SUP> triangular and quadrilateral elements to study their efficiency in indicating localization for various mesh refinements. It has also been shown that if a correct approximation is used then both the uniform and non-uniform mesh refinements will converge to the correct answer and clearly indicate the localization phenomenon.

The approach to addressing many environmental problems requires a strong foundation in chemical science and engineering. A prime example is the developing subject of environmental engineering, where a multidisciplinary field is led by chemists and chemical engineers. This thesis presents a collection of research publications, which are of both an applied and multidisciplinary nature, primarily directed towards developing technology for energy and environmental sustainability. This has included the development of sensors for in-situ environmental monitoring and the application of nanocrystalline semiconductor photocatalysts for treatment of air, waste and potable waters. The development of laser processing methods for catalyst production and modification and the design and assessment of advanced photocatalytic reactors is also presented. Research on the reduction of carbon dioxide to fuel products is also considered. Real time in-situ sensors for environmental monitoring are an area that has seen a significant growth over the past twenty years. In this thesis, I detail my research into optical and electrochemical sensors for detection of organic chemicals and heavy metals in both the marine environment and in contaminated land. The other key research theme is the topic of water remediation using semiconductor photocatalysis. This has included treatment of industrial effluent, drinking water and water used in aquaculture. In particular, I have led research on the photocatalytic removal of cyanotoxins in water, a technique pioneered at RGU. These highly toxic chemical metabolites of cyanobacteria have been responsible for the deaths of animals and humans through ingestion of contaminated water.

Close Circuit Television (CCTV) surveys of sewers are widely used in the UK to assess the structural integrity of sewer pipes. The video images are examined visually, and classified into five grades according to the degree of damage that can be observed. For severely damaged pipes, this technique is adequate, but there is considerable doubt in classifying pipes with very slight damage. In addition, the archiving of very many video tapes is expensive, and repeated access to video images of particular sections of pipe is difficult and time consuming. Therefore, an automatic sewer-pipe inspection system is required, based on the CCTV survey, which can extract and assess the structural condition of sewer pipes to ensure accuracy, efficiency and economy of sewer pipe examination. To this end, the objective of the thesis is to investigate the practical use of computer vision for automatic pipe-joint assessments, and the main effort is concentrated on software development. Initial damage in sewer pipes is associated with changes in shape of the pipe profile, with the undamaged profile being circular. Preliminary work was conducted to investigate the use of the pipe joint as a measure of the pipe shape. Automated pipe-joint shape assessments were investigated using existing software, but this could not handle images from video tapes. However, a manual technique proved that pipe joints could be used to assess pipe shape change. The main achievement of this work is the investigation of image processing algorithms, and associated software development, for pipe-joint boundary extraction which work with relatively poor contrast and noisy background as well as boundary shape recognition and analyses which deal with incomplete boundary outlines. Also a reference circle for the undamaged profile was estimated for use in pipe-joint shape discrimination. For most video pictures, reasonable results would be obtained with these algorithms. Two algorithms have been investigated for crack detection, one based on boundary curvature analysis, the other on a new boundary segment analysis technique. Also a neural network was introduced into pipe-joint shape discrimination. A Sewer Image Processing System (SIPS) has been established, using Microsoft Windows application software, which is based on the image processing techniques developed in this work.

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