Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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Record number 490559
Title Homogeneous, heterogeneous and biological oxidation of iron(II) in rapid sand filtration
Author(s) Beek, C.G.E.M. van; Hiemstra, T.; Hofs, B.; Nederlof, M.M.; Paassen, J.A.M. van; Reijnen, G.K.
Source Journal of Water Services Research and Technology-Aqua 61 (2012)1. - ISSN 0003-7214 - p. 1 - 13.
Department(s) Soil Chemistry and Chemical Soil Quality
Publication type Refereed Article in a scientific journal
Publication year 2012
Keyword(s) ferrous iron - fe(ii) oxidation - gallionella-ferruginea - isotope fractionation - metal (hydr)oxides - aqueous systems - organic-matter - atom exchange - ground-water - kinetics
Abstract 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.
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