Bioremediation of Crude-Oil Polluted Soil Using Sawdust, Poultry Droppings, and Grass Trimmings through Optimization of Biostimulant Levels Using Box-Behnken Statistical Design

The escalating issue of crude oil pollution necessitates innovative and sustainable remediation strategies. This study investigated the efficacy of sawdust, poultry droppings, and grass trimmings, both individually and in combination, as biostimulants for bioremediation of crude oil-contaminated soil. Employing the Box-Behnken statistical design, we optimized interactions between these organic amendments to enhance Total Petroleum Hydrocarbon (TPH) removal, identifying optimal levels and synergistic effects. The bacteria identified in the crude oil-contaminated soil included Bacillus, Micrococcus, Pseudomonas, Staphylococcus, and Enterococcus. The results revealed significant interactions between the biostimulants, with sawdust exhibiting highly significant interactions (p < 0.001) and poultry droppings showing significant interactions (p < 0.005). The effects of sawdust, grass trimmings, and poultry droppings on TPH removal followed a linear path, underscoring their consistent and predictable impact on the bioremediation process. The model's high coefficient of determination (R^² = 0.9776) confirmed its robustness. Furthermore, the bioremediation process yielded substantial reductions in ecotoxicity levels, corroborating the efficacy of these organic amendments for cost-effective and sustainable remediation of oil-contaminated sites. This study provides a promising framework for future bioremediation strategies, leveraging locally sourced and eco-friendly materials.