Arsenic Detoxification Using Arsenic‐Resistant Bacteria <i>Bacillus cereus</i> SP21 and <i>Bacillus toyonensis</i> SP23: A Laboratory‐Scale Study

Groundwater is the most important source for drinking, cooking and other household purposes. Agriculture is also largely dependent on groundwater. In this study, arsenic was detoxified by microbial oxidation using arsenic-resistant bacteria (ARB) in synthetic water. Two bacterial strains of Bacillus cereus (SP21) and Bacillus toyonensis (SP23), which are resistant to arsenic (As³⁺), were tested well up to 100 ppm. Optimization of arsenic for oxidation using different carbon sources (glucose, cellulose and starch), of which 1.5% cellulose was the best concentration, considering different temperatures and pH values. Oxidation of arsenite (As³⁺ to As⁵⁺) through a lab-scale column filled with immobilized bacterial cells and a synthetic medium through a lab-scale bioreactor. Samples were taken at regular intervals and processed for the oxidation of arsenite to arsenate (846 nm). The reduction of arsenate to arsenite (869 nm) was determined according to the corresponding protocol using the molybdenum blue method with a UV spectrophotometer. The selected arsenic-tolerant bacterial strains Bacillus cereus SP21 and Bacillus toyonensis SP23 achieved maximum removal of arsenic by the immobilized bacterial cell inclusion method.