Comparative Analysis and Risk Assessment of Heavy Metal Detoxification by Using Bacterial Strains

Abstract

This study evaluated the detoxification efficiency of Pseudomonas aeruginosa, Bacillus cereus, and Escherichia coli for the bioremediation of six heavy metals: arsenic (As), nickel (Ni), chromium (Cr), copper (Cu), lead (Pb), and mercury (Hg). Detoxification performance was evaluated through Bacterial Detoxification Efficiency (BDE), Risk Assessment Index (RAI), and Toxicity Removal Index (TRI). P. aeruginosa indicated the highest performance, achieving up to 80% metal removal and reducing chromium and mercury concentrations to 3.2 ± 0.2 mg/L and 2.5 ± 0.1 mg/L, respectively. B. cereus demonstrated moderate detoxification efficiency (60–75%), while E. coli showed the lowest efficacy, with final chromium and mercury levels of 10 ± 0.4 mg/L and 9.5 ± 0.4 mg/L. Additionally, P. aeruginosa effectively reduced nickel and copper to 4.0 ± 0.2 mg/L and 4.5 ± 0.2 mg/L, respectively, while B. cereus achieved reductions to 6.5 ± 0.3 mg/L (Ni) and 5.5 ± 0.3 mg/L (Cu). The highest BDE values were recorded for chromium (0.7075) and mercury (0.7125) by P. aeruginosa, and for cadmium (0.5375) by B. cereus. RAI analysis revealed that chromium, arsenic, and cadmium posed the most significant health risks, with values ranging from 16 to 50, 22.5 to 40, and 17.5 to 47.5, respectively.