Fabrication, characterization and performance analysis of a two-step arsenic bio-filter column using Delftia spp. BAs29 and fired red mud pellets.

Arsenic (As) is considered to be a grave inorganic pollutant, contaminating major aquifers worldwide. In this study, a two-step approach has been designed to combat this toxic metalloid by combining a highly efficient As (III) oxidizing bacteria; Delftia sp. BAs29 and fired red mud pellets to remove the total As from groundwater including both As (III) and As (V) ions. The maximum capacity of As (III) oxidation by Delftia sp. BAs29 was seen to be 95.65% for 500 ml of As contaminated groundwater using an optimized As (III) concentration of 300 ppb and 6.5 g of bacterial cell mass for 7 days. The second step indicated the maximum As (V) adsorption capacity by the stacked red mud pellets to be 97.91% for 500 ml of As contaminated groundwater using the optimized pore size of 106-125 μm for 7 days. The efficiency of As removal increased to 98.76% at a flow rate of 50 ml/h on combining of both the steps. In addition, the morphological properties, chemical composition, and the crystal structure of the As (V) adsorbed red mud pellets were characterized. The techno-economic feasibility of this entire unit was studied using SuperPro 10 software to estimate its optimal demand and potential. Hence, it is believed that scaling up of this two-step bio-filter column can serve as a potent filtration unit to eliminate As, both at the household and industrial level in the near future.