1. This thesis addresses the major problem of providing 'safe' drinking water to small rural and urban populations, which are dependent upon polluted surface water sources. The problem is addressed in the context of the Andean highlands of Colombia and based on gravity flow systems, but the solutions proposed may be applicable in other parts of the world. 2. The central hypothesis of the thesis is that the appropriate combinations of different type of filtration stages provide a uniform quality of water of low risk to consumers. Where institutional and community development make chemical disinfection constantly reliable, the addition of low dose terminal disinfection should be enough to ensure that the drinking supply is safe. 3. The hypothesis was initially tested in the Cauca River valley at pilot scale. A range of designs of upflow, downflow and horizontal flow coarse gravel filters followed by slow sand filtration were compared in an intensive evaluation for their ability to remove key water quality parameters. A novel dynamic fine gravel filter was developed by the author and introduced in advance of the coarse gravel filters to cope with peaks of suspended solids. 4. Highly improved filtrates were achieved during the pilot scale trials and detailed comparative analyses demonstrated the strengths and weaknesses of all component stages. Bacteriological and turbidity removals were particularly impressive compared with earlier studies in Peru and elsewhere. The most efficient combinations of filtration stages consistently achieved five-log faecal coliform removal and this contributed to the full-scale application of the technology within the region. 5. Full scale systems in a range of locations in the Cauca Valley, and elsewhere in Colombia, have demonstrated convincingly that the combination of dynamic gravel filtration, single or multistage coarse gravel filtration and slow sand filtration provide a robust, reliable and efficient technology. It can be successfully operated and maintained at community level, and even without terminal disinfection, multistage filtration provides a consistently low risk drinking water. The inclusion of terminal disinfection provides a fail-safe barrier against occasional high peaks of pollution. 6. The work carried out during the course of this thesis has established multistage gravel filtration as an essential technology when dealing with polluted waters of highly variable quality, and more appropriate and economical than so-called 'conventional' water treatment for small to medium size rural and urban communities. 7. The research has introduced and established dynamic fine gravel filters as a vital and economical component in multistage filtration, which is capable of dealing with occasional high peaks of pollution within established routines of maintenance. 8. The studies on full-scale systems over the past 5 to 10 years have demonstrated that the technology is sustainable in the hands of local operators as a result of a participatory and joint- learning project approaches. 9. The limits of the technology with respect to extremes of raw water quality have been defined. A selection procedure to identify and combine filtration stages in a treatment plant is proposed. It is based on a set of treatment objectives, contamination levels in raw water sources, and removal efficiencies expected at each treatment stage.

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Accidental and deliberate discharges from maritime transportation activities have been widely perceived as major sources of pollution. Preventive and control management strategies have therefore been progressively introduced internationally to reduce and eliminate these inputs to the marine environment. The long-term effectiveness of these measures, applied to vessels operating in the waters around the British Isles, is the research question that has been under investigation by the author since 1971. Following analyses of stakeholders' interests and concerns, and associated information requirements, the aims and objectives of a phased work programme were identified. These focused primarily upon three vessel-source marine pollutants; oil or oily mixtures, packaged dangerous or harmful goods and garbage. After a review of the literature, assessment strategies, designs, methodologies and analytical techniques were devised and applied over varying spatial and temporal scales. A data acquisition and management system, utilising questionnaire returns from 13 reporting organisations, was employed to support an annual survey on marine oil pollution. A similar approach, combined with published information, facilitated a characterisation of packaged chemical incidents around the coastline and changes over time. To determine different sources and other attributes of marine litter, an ocean-focused beach survey design was devised and applied on the shores of the English Channel, Irish Sea, North-East Atlantic Ocean and North Sea. A series of surface drift experiments and an open-water sighting survey provided further information on movements and densities of marine litter in the open sea. Research outputs, including the publications submitted, have been reviewed and identified as authoritative sources of information by the competent authorities and other interested parties. These include the Department of the Environment, Transport and the Regions, European Commission, International Maritime Organisation, Royal Commission on Environmental Pollution, Smithsonian Institution for Short-Lived Phenomena and the United States National Oceanic and Atmospheric Administration.

Mercury is one of the most toxic heavy metals, and many serious incidents have resulted from mercury poisoning. The methylation of mercury and its amplification by marine life have aggravated this pollution problem. Studies over the last three decades have shown that the toxicity of mercury is related to chemical form. A basic aim of the research has been to devise new methodology for the measurement and speciation of mercury. Key points of the investigation reported were the literature review of methodologies and techniques for mercury speciation and the development of a novel manifold which incorporates microcolumns of sulphydryl cotton which have a relatively high affinity and selectivity for inorganic and / or organomercury, and to utilise a continuous flow procedure for mercury speciation based on flow injection-atomic fluorescence spectrometry. This new and novel system has been used for the determination and speciation of mercury in a variety of water samples. The other column packing materials, eg. xanthate cotton, activated alumina and 8-hydroxy-quiniline were also investigated. A further aspect of element speciation concerns the development of a field sampling technique using sulphydryl cotton columns. Sample collection and preconcentration using microcolumns at the site of sampling was successfully performed. Preliminary experiments indicated that the field sampling technique in combination with FIA-AFS was a robust and potentially useful speciation tool. Field surveys on mercury distribution and speciation in the Manchester Ship Canal and the River Rother have been intensively carried out in collaboration with the National Rivers Authority (North West Region). The analytical data on different mercury species in waters of the Manchester Ship Canal are reported for the first time. A high correlation between organomercury and organolead in the Manchester Ship Canal is found and the related data have been assessed in order to clarify the possible origins for organomercury. Related work concerning participation in interlaboratory studies is reported in the Appendices.

Linear alkylbenzene sulphonates (LAS) and alkylphenol polyethoxylates (APEO), the surfactants most used in this country, are complex mixtures of oligomers and homologues. Due to their excellent surface active properties they are widely used as ingredients in many detergent formulations both in the home and more importantly in industry. For several years research has been carried out in order to understand the environmental impact of these widely used groups of compounds. However, some of the analytical techniques developed are not able to give reliable information concerning individual oligomer / homologue levels. As the toxicological profile of these compounds is dependent on the individual levels present this data is of great importance. Surfactants are most often introduced into the environment through wastewaters. In order to try and actively contribute to this area, laboratory investigations were undertaken to develop chromatographic techniques which would be able to determine individual oligomer / homologue levels in environmental surface water samples. Even if extensive sample clean up is used these samples are by nature, very 'complex'. Mass spectrometry lends itself to the analysis of environmental samples as it is able to give detailed structural data which aids in eliminating signal contributions from interfering compounds. To this end, work was carried out in order to develop liquid chromatography methods which are compatible with conventional mass spectrometers and could be used for the determination of the environmental levels of both LAS and APEO.

Dans ce travail, nous avons résolu deux problèmes pratiques en agriculture en les modélisant en des problèmes de contrôle optimal. Un accent est mis sur les problèmes de contrôle optimal non linéaires, puisque les entrées résultantes de la modélisation sont non linéaires. On a fourni un moyen de choisir des valeurs adaptées pour le poids entre minimiser la pollution engendrée par un ajout abusif d’engrais et d’insecticides et maximiser le rendement des céréales. Le premier problème consiste à maximiser une production céréalière en tenant compte des effets néfastes de la pollution dégagée par un ajout abusif des engrais. Par la suite, dans le second problème, on a raffiné le premier problème en introduisant la contrainte de la présence des criquets. Pour les applications numériques, on a utilisé des données réelles du ministère de l’agriculture Algérien et des données de l’Institut National de la Protection des Végétaux (INPV). / In this work, we have solved two practices problems in agriculture by modeling in problems of optimal control. An emphasis is placed on nonlinear control optimal problems, since the output of the resulting models are nonlinear. It provided a way to choose defaults for the weight between minimizing pollution caused by an improper addition of fertilizers and insecticides and maximize cereal production. The first problem is to maximize cereal production taking into account the detrimental effects of pollution generated by adding abusive fertilizers. Subsequently, the second problem, we refined the first problem by introducing the constraint of the presence of locusts. For digital applications, were used actual data from the Algerian Ministry of Agriculture and Data from the National Institute of Plant Protection (INPV).

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Samples collected from Kuwait were screened for microorganisms capable of oil degradation. A wide range of bacteria and fungi were able to degrade oil. The bacterial and fungal isolates differed in their ability to degrade crude oil. Rhodococcus isolates were more active than fungi in n-alkane biodegradation. Fungi also utilised one or more of the aromatic hydrocarbons studied while bacteria failed to do so.