Preliminary Evaluation of Nonsterile Petroleum Oil–Contaminated Wastewater Bioremediation Using Immobilized <scp><i>Bacillus licheniformis</i></scp> on Bentonite Mineral

This study explores the preliminary application of Bacillus licheniformis immobilized on bentonite for the bioremediation of nonsterile petroleum oil-contaminated wastewater (POCW), simulating real environmental conditions. The effectiveness of the treatment was evaluated based on the reduction of key pollutants, including chemical oxygen demand (COD), biological oxygen demand (BOD), total dissolved solids (TDS), total suspended solids (TSS), oil and grease (OG), phenol, potentially toxic elements (iron, lead, nickel, and total chromium), color, and turbidity with reference to the Indonesian National Environmental Quality Standards for industrial effluents (NEQS No. 5/2014). The immobilized bacteria demonstrated high removal efficiencies for OG (up to 98%), turbidity (70%-91%), lead (90%-92%), iron (79%-84%), and COD (79%-87%). Moderate reductions were observed for BOD (38%-79%), phenol (20%-79%), TSS (79%-91%), color (37%-47%), and chromium (52%-90%), while nickel (13%-28%) and TDS (11%-15%) showed relatively lower removal efficiencies. These findings highlight the potential of Bacillus licheniformis, supported by the adsorptive capacity of bentonite, to substantially reduce multiple pollutants in POCW, although further optimization is recommended to enhance the removal of certain contaminants to meet stringent environmental thresholds.