Effect of surfactants on heterotrophic activity in a petroleum contaminated soil under aerobic conditions

With the ongoing advancements in industrialization, the importance of petroleum resources has become increasingly evident. However, these developments have also resulted in significant environmental pollution due to petroleum hydrocarbons (PHCs). In this study, the microbial communities in both contaminated and uncontaminated soils were initially analyzed to identify key taxonomic families involved in degrading PHCs. Thereafter, impact of surfactants on PHCs solubility and bioavailability to microorganisms were investigated in the petroleum-contaminated soil. This study evaluated the dissolution efficiency of seven surfactants, including cationic, anionic, and nonionic types at various critical micelle concentrations (CMCs). Native PHC-degrading microorganisms were selectively enriched under aerobic conditions using the most efficacious surfactants identified. Microbial community analyses revealed that the taxonomic families Sphingomonadaceae, Nocardioidaceae, and Moraxellaceae played a major role in PHC degradation. The results showed that surfactants significantly enhance the bioavailability of PHCs to microorganisms, improving solubility and speeding up biodegradation. Among the surfactants tested, CTAB at three different CMC levels showed the highest soluble COD consumption under aerobic conditions, achieving up to 90% removal efficiency. TRIX, on the other hand, offered a good balance between COD removal efficiency and environmental safety, demonstrating significant effectiveness in aerobic conditions. Additionally, TRIX at 1 CMC in aerobic enrichment was effective in removing TPH, achieving nearly 2000 mg/kg removal from the originally contaminated soil. These findings suggest that surfactants can encourage the growth of strong, surfactant-resistant hydrocarbon-degrading microbial communities, making them promising options for the bioremediation of petroleum-contaminated soils.