ارزیابی تجربی تجزیه زیستی گازوییل

Produced water, which is commonly generated during oil and gas extraction processes, is considered one of the most significant and environmentally challenging byproducts in the petroleum industry. This wastewater typically contains a complex mixture of organic and inorganic pollutants, including high concentrations of dissolved salts, heavy metals, and various hydrocarbons. Due to its large volume, persistent contaminants, and potential environmental risks, effective and sustainable treatment of produced water has become a serious concern for both industry and environmental regulatory agencies. High salinity and the presence of recalcitrant compounds such as diesel fuel further complicate conventional treatment processes and reduce the efficiency of physical or chemical methods. One important feature of this bacterial strain is that at moderate to high salinity levels, it adapts to hypersaline environments by producing proline instead of glutamate and glutamine. Proline, known as a compatible solute, has stronger osmotic properties than glutamate and helps maintain intracellular water balance without damaging proteins or cellular structures, thereby supporting cell survival in high-salinity conditions. In this study, a biological method was experimentally evaluated for the treatment of synthetic produced water contaminated with diesel. The bacterial strain used, Halobacillus halophilus, is a halophilic microorganism known for its high tolerance to elevated salt concentrations, making it a suitable candidate for treating hypersaline wastewater. Biodegradation of diesel is particularly challenging due to its hydrophobic nature and complex hydrocarbon structure, which makes it poorly soluble in water and resistant to microbial attack. To overcome these challenges, modifications were applied to the experimental design. To improve microbial growth and enhance metabolic activity, nutrient supplementation with nitrogen (N) and phosphorus (P) was performed. Additionally, emulsifying agents, including Tween 80 and Span 60, were added to increase the bioavailability of diesel by dispersing it into fine droplets in the aqueous phase. A synthetic wastewater containing diesel was prepared based on a carbon/nitrogen/phosphorus (C: N: P) ratio of 110:5:2, which is reported in the literature as optimal for bacterial growth and hydrocarbon biodegradation. The effects of varying diesel concentrations (50 and 100 mg/L) and salinity levels (6, 13, and 35 g/L NaCl) on biodegradation efficiency were investigated under constant temperature and pH conditions. Since high salinity interferes with Chemical Oxygen Demand (COD) testing, Biological Oxygen Demand (BOD) was used as a more accurate indicator for assessing organic pollutant degradation. The BOD values for 50 mg/L diesel at salinities of 6, 13, and 35 g/L were measured as 1500, 1700, and 1800 mg/L, respectively. For 100 mg/L diesel, these values were 2000, 2100, and 1600 mg/L, respectively. These results indicate that the biodegradation efficiency of H. halophilus depends on salinity, with optimal performance observed at moderate salinity levels. Interestingly, at 50 mg/L diesel, the reaction rate constant increased with salinity, while at 100 mg/L, biodegradation efficiency decreased at the highest salinity level (35 g/L). These findings suggest that lower salinity (6 g/L) reduces microbial metabolic activity compared to higher levels (13 and 35 g/L), likely due to the halophilic nature of the bacterial strain. This study highlights the critical role of optimizing environmental conditions to ensure effective bioremediation of saline hydrocarbon-contaminated wastewater by Halobacillus halophilus.