Faculty of Civil Engineering and Geosciences, Delft University of Technology, The Netherlands.
Water Sci Technol. 2010;62(11):2702-9. doi: 10.2166/wst.2010.463.
The principle of subsurface or in situ iron and arsenic removal is that aerated water is periodically injected into an anoxic aquifer through a tube well, displacing groundwater containing Fe(II). An oxidation zone is created around the tube well where Fe(II) is oxidised. The freshly formed iron hydroxide surfaces provide new sorption sites for soluble Fe(II) and arsenic. The system's efficiency is determined based on the ratio between abstracted volume with reduced iron/arsenic concentrations (V) and the injected volume (V(i)). In the field study presented in this paper, the small-scale application of this technology was investigated in rural Bangladesh. It was found that at small injection volumes (<1 m³) iron removal was successful and became more effective with every successive cycle. For arsenic, however, the system did not prove to be very effective yet. Arsenic retardation was only limited and breakthrough of 10 µg/L (WHO guideline) was observed before V/V(i)=1, which corresponds to arrival of groundwater at the well. Possible explanations for insufficient arsenic adsorption are the short contact times within the oxidation zone, and the presence of competing anions, like phosphate.
地下或原位铁和砷去除的原理是，通过管井将充氧水周期性地注入缺氧含水层，从而置换含 Fe(II)的地下水。在管井周围形成一个氧化带，在此处 Fe(II)被氧化。新形成的氢氧化铁表面为可溶性 Fe(II)和砷提供了新的吸附位点。该系统的效率取决于提取的还原铁/砷浓度（V）与注入量（V(i)）之间的比值。在本文介绍的实地研究中，该技术的小规模应用在孟加拉国农村进行了研究。结果发现，在小注入量（<1 立方米）时，铁的去除是成功的，并且每个后续周期的效果都更好。然而，对于砷来说，该系统的效果并不明显。砷的阻滞作用非常有限，在 V/V(i)=1 时就出现了 10 µg/L（世界卫生组织指南）的突破，这相当于地下水到达井中。砷吸附不足的可能原因是氧化带内的接触时间短，以及存在竞争阴离子，如磷酸盐。
