Removal of arsenic by <i>Acidothiobacillus ferrooxidans</i> bacteria in bench scale fixed-bed bioreactor system

In the present study arsenic contaminated simulated water and groundwater was treated by the combination of biological oxidation of tri-valent arsenite [As (III)] to penta-valent arsenate [As (V)] in presence of <i>Acidothiobacillus ferrooxidans bacteria</i> and its removal by adsorptive filtration in a bioreactor system. This method includes the immobilisation of <i>A.ferrooxidans</i> on Granulated Activated Carbon (GAC) capable of oxidising ferrous [Fe (II)] to ferric [Fe (III)]. The Fe (III) significantly converts the As (III) to As (V) and ultimately removed greater than 95% by the bed of GAC, limestone, and sand. The significant influence of Fe (II) concentration (0.1–1.5 gL⁻¹), flowrate (0.06–0.18 Lh⁻¹), and initial As (III) concentration (100–1000 µgL⁻¹) on the arsenic removal efficiency was investigated. The simulated water sample containing the different concentration of As (III) and other ions was used in the study. The removal of other co-existing ions present in contaminated water was also investigated in column study. The concentration of arsenic was found to be &lt;10 µgL⁻¹ which is below Maximum Contaminant Level (MCL) as per WHO in treated water. The results confirmed that the present system including adsorptive-filtration was successfully used for the treatment of contaminated water containing As (III) ions.本研究采用嗜酸氧化亚铁硫杆菌（Acidothiobacillus ferrooxidans）介导的生物氧化工艺，将三价亚砷酸盐[As(III)]氧化为五价砷酸盐[As(V)]，并结合生物反应器系统内的吸附过滤工艺，处理含砷污染模拟水与地下水。该工艺将嗜酸氧化亚铁硫杆菌（A.ferrooxidans）固定于颗粒活性炭（Granulated Activated Carbon, GAC）表面，该载体可将亚铁[Fe(II)]氧化为三价铁[Fe(III)]。三价铁可高效将As(III)转化为As(V)，最终通过GAC、石灰石与砂组成的滤床去除超过95%的砷。本研究考察了亚铁浓度（0.1~1.5 g·L⁻¹）、进水流量（0.06~0.18 L·h⁻¹）以及初始As(III)浓度（100~1000 μg·L⁻¹）对除砷效率的显著影响。试验采用含不同浓度As(III)与其他共存离子的模拟水样开展研究，同时通过柱试验考察了污染水中其他共存离子的去除效果。结果显示，处理后水中砷浓度低于10 μg·L⁻¹，符合世界卫生组织（WHO）规定的最大污染物限值（Maximum Contaminant Level, MCL）要求。研究结果证实，本研究所采用的吸附-过滤耦合系统可成功处理含As(III)的污染水体。