Removing iron under anoxic conditions : removing iron by operating rapid sand filters in intermittent regeneration mode
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F. Schoonenberg Kegel
|Auteur(s)||Schoonenberg Kegel, F.|
|Delft : TU Delft|
|Toelichting (Engels)||Aeration and rapid sand filtration are common practice for the treatment of iron, manganese and ammonium containing ground water for more than a century. Nevertheless, this process has not become obsolete. On the contrary, this thesis assumes that enhanced rapid sand filters remain standard treatment technology in the 21st-century. Iron can be removed by homogeneous, heterogeneous and biological oxidation. The potential advantages of heterogeneous iron oxidation over homogeneous iron removal are high filtration rates, excellent iron removal and reduced losses of backwash water as demonstrated by the excellent performance of the pre-filters of water treatment plant Grobbendonk. Heterogeneous iron oxidation dominates at Grobbendonk because the supernatant is slightly anoxic and the pH is low. Thus adsorption and oxidation occur simultaneously. The target feed water in this thesis is deep anoxic ground water, characterized by high iron and methane concentrations. The typical high methane values demand intensive aeration to prevent excessive formation of mucus or slime by methanotrophic bacteria. This research focuses therefore on heterogeneous iron oxidation that can be applied by running an adsorptive filter under anoxic conditions and regenerate it intermittently under oxic conditions. In other words, adsorption and oxidation are separated in time. This work consists of three main parts: characterization of filter medium, batch experiments and pilot plant experiments.|
Technische Universiteit Delft