Delft University of Technology, Faculty of Civil Engineering and Geosciences, Department of Water Management, Stevinweg 1, 2628 CN Delft, the Netherlands.
Delft University of Technology, Faculty of Civil Engineering and Geosciences, Department of Water Management, Stevinweg 1, 2628 CN Delft, the Netherlands.
Water Res. 2024 Sep 15;262:122128. doi: 10.1016/j.watres.2024.122128. Epub 2024 Jul 22.
Iron-based adsorbents are commonly used to remove arsenic (As) from water for drinking water purposes. Here, we study the role of biological As(III) oxidation on iron-based adsorbents in filters and its effect on overall As uptake. A lab-scale filter with iron oxide coated sand (IOCS), a commonly used adsorbent, was operated with water containing As(III) and As(V), while water samples were taken periodically over its height. As(III) oxidation initiated after approximately 10 days and increased to a first order rate constant of 0.09 s after 57 days resulting in full oxidation of As(III) in <50 s. Consequently, the filter shifted from an As(III) to an As(V) adsorbing filter. Oxidation was not observed after inhibiting the microbial activity using sodium azide confirming its biogenic nature. This implies that As(III) oxidizing biomass can grow on iron-based adsorbents in water filters without requiring inoculation. As the experimental conditions were similar to full-scale As treatment plants, we believe that biological As(III) oxidation is widely overlooked in these systems. Occurrence of biological oxidation is, however, beneficial for removal, as at pH <8 the adsorption capacity for As(V) can be up to 10-fold higher than for As(III). With these new insights, arsenic treatment using iron-based adsorbents can be further optimized. We suggest a more robust new design with a biological active As(III) oxidizing top layer and an As(V) adsorbing bottom layer.
铁基吸附剂常用于饮用水中去除砷 (As)。在这里，我们研究了生物 As(III) 氧化在过滤器中对铁基吸附剂的作用及其对总砷吸收的影响。使用涂覆有氧化铁的砂 (IOCS) 的实验室规模过滤器来操作含有 As(III) 和 As(V) 的水，同时定期从其高度采集水样。As(III) 氧化在大约 10 天后开始，并在 57 天后增加到 0.09 s 的一级速率常数，导致在 <50 s 内完全氧化 As(III)。因此，过滤器从 As(III)吸附过滤器转变为 As(V)吸附过滤器。使用叠氮化钠抑制微生物活性后未观察到氧化，证实其具有生物成因。这意味着在水过滤器中的铁基吸附剂上，无需接种，As(III) 氧化生物量就可以生长。由于实验条件与全规模砷处理厂相似，我们认为在这些系统中广泛忽视了生物 As(III) 氧化。然而，生物氧化的发生有利于去除，因为在 pH<8 时，As(V)的吸附容量比 As(III)高 10 倍。有了这些新的见解，可以进一步优化使用铁基吸附剂处理砷。我们建议采用更稳健的新设计，具有生物活性的 As(III) 氧化顶层和 As(V) 吸附底层。
