Iron and manganese removal from groundwater using limestone filter with iron-oxidized bacteria

Laboratory-scale experiments were carried out to investigate the removal efficiency of iron and manganese from groundwater using limestone filter assisted with iron-oxidized bacteria. Column studies were conducted using limestone with a particle size between 0.6 and 2.36 mm and run at different operation times with a flow rate of 4 L/h and retention time of 2.94 min. Iron-oxidized bacteria were extracted from groundwater samples and cultured in an agar plate with nutrient agar solution for the bacteria duplication. Iron-oxidized bacteria resulted in a change in limestone composition as shown in X-ray diffraction and scanning electron microscope results due to the destruction of limestone particles for easier adsorption. Results show that the limestone filter assisted with IOB has better performance than the filter of limestone alone, in removing Fe and Mn. The maximum removal efficiency of Fe and Mn was 81.72% and 83.63%, respectively, at an operation time of 2 h. Iron-oxidized bacteria catalyze the oxidation of adsorption process as well as the soluble Fe(II) and Mn(II) to insoluble Fe(III) and Mn(IV). In addition, the results revealed that the increase in operation time resulted in increasing the rate of Fe and Mn oxidation. Operation time was found to be an influential factor on the removal process where the optimum values of pH and turbidity were achieved at 1.5 h of operation time. Furthermore, Fe concentration was decreased with the increase in operation time, while Mn concentration was increased with the increase in operation time. Overall, this study demonstrates that the limestone filter assisted with iron-oxidized bacteria is an effective filtration process for Fe and Mn removal in groundwater.