Description: Das Projekt "Optimization of coprecipitation processes in apatite-based filter materials for the removal of fluoride from drinking water" wird vom Umweltbundesamt gefördert und von Eawag - Das Wasserforschungsinstitut des ETH-Bereichs durchgeführt. The aim of the research project is to optimize the function of a calcium phosphate filter material for implementation in developing countries. It is estimated that more than 200 million people worldwide rely on drinking water with fluoride concentrations exceeding the WHO guideline of 1.5 mg/L. Excess fluoride intake causes different types of fluorosis, primarily dental and skeletal fluorosis, depending on the level and period of exposure. Fluoride is the 13th most abundant element in the earth crust and often has a natural rock-derived origin in groundwater. Fluoride levels appear to be controlled by the precipitation of a calcium fluoride mineral (fluorite). Groundwaters with low dissolved calcium contents appear to have higher fluoride concentrations. For similar reasons alkaline sodic groundwaters in which calcium is not soluble, mainly found in arid climates appear to have elevated fluoride contents. While industrialized countries commonly use activated alumina to remove fluoride from drinking water, fluoride removal is yet uncommon in low and middle-income countries. Insufficient removal efficiency, complicated maintenance and/or unaffordable costs particularly for rural population are the main reasons why implementation in developing countries is still rare. Bone char as a filter media is available and has been implemented on a local scale in different countries such as Kenya, Tanzania, and Thailand. Bone char contains hydroxyapatite, a Ca phosphate mineral. Fluoride is primarily removed by the exchange of the hydroxide ion for fluoride. Filter life can be prolonged by a factor of ten with the addition of dissolved calcium and phosphate ions that precipitate on available hydroxyapatite surfaces. It is desirable to develop apatite-based filter materials that do not depend on bone char, which is difficult to produce and may not be accepted because of ethical reasons in some countries. Preliminary experiments have demonstrated the feasibility of using hydroxyapatite granules instead of bone char. It is proposed to examine the processes that control surface precipitation on hydroxyapatite. In model systems, the surface precipitation rate of fluor/hydroxyapatite with addition of dissolved calcium and phosphate will be examined under neutral to slightly alkaline pH conditions. The influence of silicate, sulphate and carbonate, which are known to be incorporated in apatite minerals, will be studied. The structure of bone char and hydroxyapatite granules will be examined using spectroscopic, microscopic and wet-chemical techniques and the results will be used to interpret column experiments. This work is part of cooperative project with a Kenyan non-governmental organization that is currently the main producer of bone char-based filtration systems in the Rift Valley. . The ultimate aim is to develop a Rift-Valley network of organizations that can produce and maintain fluoride removal filter units.
Types:
SupportProgram
Origin: /Bund/UBA/UFORDAT
Tags: Aluminiumoxid ? Calciumfluorid ? Calciumphosphat ? Fluorose ? Fluorgehalt ? Fluorid ? Hydroxid ? Phosphat ? Silikat ? Carbonat ? Calcium ? Entfluoridierung ? Granulat ? Primärbatterie ? Kenia ? Main ? Thailand ? Tansania ? Leitfaden ? Knochen ? Regenwasser ? Filter ? Verfahrensoptimierung ? Genossenschaft ? Forschungsprojekt ? Technik ? Trinkwasser ? Wirkungsgrad ? Sediment ? Filtration ? Chemikalien ? Entwicklungsland ? Grundwasser ? Nichtstaatliche Organisation ? Flussspat ? Landbevölkerung ? Erdkruste ? Exposition ? Instandhaltung ? Ionen ? Arides Klima ? Kosteneffizienz ? Mineral ? Tal ? Industrieland ? Richtlinie ? Kosten ? Niederschlag ? Konzentrat ? Filtermaterial ? Korn ?
License: cc-by-nc-nd/4.0
Language: Deutsch
Time ranges: 2008-01-01 - 2011-12-31
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