Homogeneous, heterogeneous and biological oxidation of iron(II) in rapid sand filtration
| Autor: | T. Hiemstra, B. Hofs, G.K. Reijnen, J.A.M. van Paassen, M.M. Nederlof, C. G. E. M. van Beek |
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| Rok vydání: | 2012 |
| Předmět: |
Bodemscheikunde en Chemische Bodemkwaliteit
Inorganic chemistry Iron oxide engineering.material ferrous iron law.invention atom exchange Hydrous ferric oxides chemistry.chemical_compound Iron bacteria Extracellular polymeric substance Adsorption law fe(ii) oxidation gallionella-ferruginea organic-matter Filtration Water Science and Technology Civil and Structural Engineering WIMEK aqueous systems ground-water chemistry kinetics metal (hydr)oxides engineering Hydroxide Water treatment isotope fractionation Soil Chemistry and Chemical Soil Quality |
| Zdroj: | Journal of Water Services Research and Technology-Aqua, 61(1), 1-13 Journal of Water Services Research and Technology-Aqua 61 (2012) 1 |
| ISSN: | 1605-3974 0003-7214 |
| Popis: | Homogeneous, heterogeneous and biological oxidation may precipitate iron(II) as iron(III) hydroxides. In this paper we evaluate the conditions under which each of these processes is dominant in rapid sand filtration (RSF). It is demonstrated that in the presence of iron(III) hydroxide precipitates homogeneous oxidation is negligible compared with heterogeneous oxidation. As soon as iron oxidizing bacteria (IOB) are present, biological oxidation may contribute substantially, in particular under conditions of slight acidity and low oxygen concentration. As the oxidation step is preceded by an adsorption/uptake step, the competition between heterogeneous and biological oxidation is not determined by the oxidation rate, but by the adsorption or uptake rate. Extracellular polymeric substance (EPS), excreted by all kinds of bacteria, may serve as an initial adsorbent for dissolved iron(II) and iron(III) hydroxides. Because adsorption and oxidation of iron (II) either on biofilms (or EPS) or on mineral surfaces, are chemical processes, 'EPS iron oxidation' is not considered as a biological process. The so-called 'biological iron oxidation' actually refers to a treatment method characterized by high filtration rates and limited oxygen supply, where iron(II) is removed mainly by heterogeneous oxidation. The contribution of oxidation of iron(II) by IOB in this method is variable and may even be absent. |
| Databáze: | OpenAIRE |
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