APPLICATION OF RESPONSE SURFACE METHODOLOGY FOR OPTIMIZATION THE BIODEGRADATION PROCESS OF PETROLEUM-CONTAMINATED BEACH SAND USING BIO-OIL SPILL DISPERSANT (OSD) AND Bacillus subtilis CYA27

Abstract

Oil pollution in coastal ecosystems from recurrent oil spills poses a critical environmental challenge, particularly in regions such as the Malacca Strait and the northern coast of West Java. Crude oil is rich in persistent organic pollutants (POPs) that are resistant to natural degradation, leading to long-term ecological risks and threats to coastal communities. Urgent and effective remediation strategies are therefore essential to mitigate these impacts. Bioremediation, which harnesses microbial activity to degrade hydrocarbons, offers a promising, environmentally friendly alternative to conventional clean-up methods. This study investigates the bio-degradation efficiency of crude oil-contaminated sand using a combination of Bio-OSD dispersant and Bacillus subtilis CYA27 under controlled laboratory conditions. Response Surface Methodology (RSM) via Design Expert software (DX13) was employed to optimize key variables, including the dispersant-to-oil ratio (DOR) and bacterial dosage. Experimental trials evaluated response parameters such as Total Petroleum Hydrocarbon (TPH) degradation, Chemical Oxygen Demand (COD), Total Dissolved Solids (TDS) reduction, pH, and bacterial population. The optimized conditions recommended by the RSM model were a DOR of 0.77:1 and a 5% bacterial dosage. These parameters achieved 50.25% TPH degradation, COD reduction to 895.41 mg/L, pH adjustment to 8.21, and a bacterial population of 6.39 Log CFU/mL. The model achieved a desirability score of 0.64, indicating satisfactory optimization though further refinement could enhance efficiency. The findings demonstrate the potential of integrating dispersants with microbial agents as a viable approach for bioremediation of oil-polluted coastal environments, contributing valuable insights for sustainable pollution management.