Conditions for biological precipitation of iron by Gallionella ferruginea in a slightly polluted ground water |
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| Institution: | 1. Department of Chemistry and Applied Engineering Science, University of Aalborg, Denmark;2. Institute for Storage Ring Facilities, University of Aarhus, Denmark;3. Department of Chemistry, Royal Veterinary and Agricultural University, Copenhagen, Denmark;1. Graduate School of Agriculture, Kyoto University, Kitashirakawa-oiwake-cho, Sakyo-ku, Kyoto, Kyoto 606-8502, Japan;2. Faculty of Life and Environmental Science, Shimane University, Nishikawatsu-cho 1060, Matsue, Shimane 690-8504, Japan;3. Research Fellow of Japan Society for the Promotion of Science, Japan;1. Universidade Estadual Paulista “Júlio de Mesquita Filho” – UNESP, Programa de Pós-Graduação em Ciência e Tecnologia de Materiais, POSMAT, Bauru, SP, Brazil;2. Universidade Federal do Ceará – UFC, Departamento de Física, Fortaleza, CE, Brazil;3. Universidade Estadual Paulista “Júlio de Mesquita Filho” – UNESP, Departamento de Física, Bauru, SP, Brazil;1. Institute of Applied Mathematics, Academy of Mathematics and Systems Sciences, Academia Sinica, PR China;2. Institute of Mathematics, Jagiellonian University, ?ojasiewicza 6, 30-348 Kraków, Poland;3. Department of Mathematics, Faculty of Science and Technology, University of Macau, Av. Padre Tomás Pereira, Taipa Macau, China |
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| Abstract: | A sand filter has been built as a pilot plant with the purpose of biological precipitation of Fe from ground water polluted with mainly chlorinated aliphatics. The ground water is pumped directly from a well in a polluted ground water aquifer in Esbjerg, Denmark. The pollution includes trichlorethylene and tetrachlorethylene together with smaller amounts of pesticides. Furthermore the best conditions for Fe precipitating bacteria were not expected to be present because of a relatively high O2 content, up to 6.7 mg/l, a low Fe content, 0.2 mg/l and a pH of ～5 in the ground water. Added FeSO4 increased the Fe content of the ground water to about 4 mg/l. These rather extreme conditions for precipitating Fe were observed over a period of 3 months. The goal of the research was to observe the mechanism of Fe precipitation in a sand filter in the above-mentioned conditions comparative to normal conditions for biotic as well as abiotic Fe mineralization in sand filters of fresh water treatment plants. The Fe precipitating bacterium Gallionella ferrugenia was found to dominate the biotic Fe oxidation/precipitation process despite the extreme conditions. A huge amount of exopolymer from Gallionella was present. The precipitated Fe oxide was determined to be ferrihydrate. The rate of the Fe oxidation/precipitation was found to be about 1000 times faster than formerly found for abiotic physico-chemical oxidation/precipitation processes. The hydrophobic pesticides and some of their degradation products were not adsorbed in the filter. An added hydrophilic pesticide was adsorbed up to 40%. Trichlorethylene was not adsorbed in the filter. The reason for the poor adsorption of the hydrophobic compounds and trichlorethylene is due to the pronounced hydrophilic property of the exopolymers of Gallionella and the precipitated ferrihydrite. |
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