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 areas caused by oil spills is a critical environmental issue that requires proactive measures. Repeated oil spills have occurred worldwide, including in the Malacca Strait and the northern coast of West Java. Crude oil contains persistent organic pollutants (POPs) that are difficult to degrade. This study evaluates the biodegradation efficiency of crude oil-contaminated sand using Bio-OSD and Bacillus subtilis CYA27 under controlled laboratory conditions. Bioremediation was optimized using Design Expert software (DX13) to determine the ideal dispersant-to-oil ratio (DOR) and B. Subtilis CYA27 dosage. Based on the sand washing process results, the center point (0) for the addition of OSD was determined with a DOR of 1.25:1, the upper limit was 1.75:1, the lower limit was 0.75:1, and the alpha (+) and alpha (-) values were 1.95:1 and 0.54:1, respectively. Independent variables included OSD concentration (DOR) and bacterial dosage, with response parameters such as Total Petroleum Hydrocarbon (TPH) degradation, Chemical Oxygen Demand (COD), Total Dissolved Solids (TDS) reduction, pH, and bacterial population. Optimal condition that recommended by RSM Model at a DOR of 0.77:1 and a 5% bacterial dosage, achieving 50.25% TPH degradation, COD of  895.41 mg/L, TDS reduction, pH 8.21, and a bacterial population of 6.39 Log CFU/mL. The model’s desirability score was 0.64, A good optimum point has a high desirability score, preferably close to 1.