Person: Zerelli, Sami Sofiene
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Sami Sofiene
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Veröffentlichung Pilot-scale vanadium adsorption onto in-situ biogenic amorphous ferric hydroxide(2023) Mahringer, Daniel; Ruhl, Aki Sebastian; Zerelli, Sami SofieneIn order to reach 4 (micro)g 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 (micro)g l-1 was removed to below 4 (micro)g 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 (micro)g 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 (micro)g 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. © 2023 by the authorsVeröffentlichung Redox Behavior of Chromium in the Reduction, Coagulation, and Biotic Filtration (RCbF) Drinking Water Treatment(2023) Mahringer, Daniel; Ruhl, Aki Sebastian; Zerelli, Sami SofieneThe chromium (Cr) limit values are currently tightened to 25 (micro)g L-1 (EU), 5 (micro)g L-1 (Germany), and possibly 10 (micro)g L-1 Cr(VI) (California). The combined process of chemical reduction, coagulation, and biotic filtration (RCbF) efficiently removes Cr(VI) in drinking water. In this study, redox-active substances (O2, NO3-, Fe2+, MnO2) were investigated concerning their effect on the RCbF process. The experiments were performed at two-stage pilot waterworks for biological iron and manganese removal. O2 or NO3- as oxidants affected the RCbF process, neither by consumption of the reductant Fe(II) nor by re-oxidation of already formed Cr(III) in the supernatant of the filter bed. However, the oxidation of Cr(III) by O2 to Cr(VI) with MnO2 as a mediator was identified as potential risk for Cr breakthrough. Up to one third of the initial Cr(III) concentration was oxidized to Cr(VI) in the second filter bed within a contact time of only 5 min. The kinetically relevant mechanism seemed to be the formation of Cr(III)Fe(III)-hydroxides and not the reduction of Cr(VI) by Fe(II). Further, the mixing of Cr(VI) containing raw water with Fe(II) containing groundwater was determined as a chemical-free alternative for the RCbF process, depending on the resulting Fe(II) concentration after mixing. © 2023 by the authorsVeröffentlichung Pilot scale hexavalent chromium removal with reduction, coagulation, filtration and biological iron oxidation(2020) Dippon-Deissler, Urs; Mahringer, Daniel; Ruhl, Aki Sebastian; Zerelli, Sami SofieneCr(VI) is identified as highly toxic, therefore a far-reaching limitation of total chromium or Cr(VI) in drinking water was proposed by the Germany Environment Agency. There is a lack in efficient treatment processes to reach Cr(VI) concentrations below 1 (my)g L-1. In this study, the combination of chemical reduction, coagulation and filtration (RCF) was further developed by adding biological iron removal as filtration step (RCbF). The aim of this enhancement was to reach lower effluent concentrations and a higher robustness regarding process parameters. The effectiveness of Cr(VI) removal was investigated using two-stage pilot-scale waterworks. RCbF reaches Cr(VI) effluent concentrations below 0.5 (my)g L-1 despite variations of pH, filtration velocity, or Cr(VI) influent concentrations. Fe(II) dosage and hence molar excess of Fe(II) over Cr(VI) was identified as the key parameter for Cr(VI) removal. Low oxygen dosage for biological iron removal improved the efficiency of RCbF compared to RCF. The co-precipitation of Cr(III) and Fe(III) as solid solution in the supernatant of the filter bed was promoted by low oxygen concentrations making Cr(VI) the preferred oxidant. RCbF was shown to be a suitable treatment process for reaching a low limit value for total chromium or Cr(VI) concerning technical feasibility. © 2020 The Authors.