Pilot-scale vanadium adsorption onto in-situ biogenic amorphous ferric hydroxide

Abstract

In order to reach 4 μg l−1 vanadium in drinking water adsorption onto in-situ biogenic amorphous ferric hydroxide (AFH) is identified as robust new treatment. The evaluation of its technical feasibility and robustness was the aim of this study. As approach at pilot-scale, Fe(II) and oxygen was dosed before pilot waterworks and Fe(II) subsequently biotically oxidized and precipitated in a filter bed. The so in-situ generated biogenic AFH served as adsorbent for vanadium removal. Results show that an initial vanadium concentration of 30 μg l−1 was removed to below 4 μg l−1, if at least 3 mg l−1 Fe(II) were dosed, resulting in a loading of 8.7 mg V per g AFH. A vanadium concentration of 60 μg l−1 with a dosage of 3 mg l−1 Fe(II) was the upper limit for sufficient removal. Vanadium removal increased with increasing pH in the technical setup, due to faster oxidation of Fe(II) in the supernatant, even though adsorption capacity of AFH decreases with increasing pH. A filtration velocity of 20 m h −1 represented the highest velocity to undercut 4 μg l−1 vanadium in the effluent. By mixing Fe(II) containing groundwater with oxygen and vanadium containing water prior to an adsorption filter with AFH sufficient removal was reached, however dependent on the resulting Fe(II) concentration.