Optimized Production of Bioremediation Agent for Application in the Eco-Recovery of Oil Spill Site

Abstract

Abstract This study investigates the application of an optimization process in the formulation of a bioremediation agent modelled to mimics bioaugmentation and biostimulation and that offers a short half-life high degradation efficiency less intrusive and benign to petroleum spill-threatened biodiversity. Several optimized methods and processes were followed to harness the plethora of rhizobacterial isolates from aged oil contaminates sites, screening, and selection of isolates with potential for hydrocarbon degradation based on their specific enzymes activity and catabolic gene assay. One Variable At a Time (OVAT) is applied to screen and select the best agrowaste materials with limiting organic nutrients to support high throughput rhizobacterial isolates cultivation and for which the isolates showed a high substrate utilization affinity. The Monod model was used to establish the optimum organic nutrient capacity as estimated from their agrowaste materials proximate assay. These led to the selection of four rhizobacterial isolates and three agrowaste materials that constitutes the independent factors in the enhancement of petroleum hydrocarbon removal from contaminated soil. To further optimize this process, a multivariate statistical technique of the Box-Behnken method of 15 runs design having the independent variables of bacterial consortia (Pseudomonas fluorescens, Achromobacter agilis, Bacillus thuringiensis, and Staphylococcus lentus) of 5 to 7% inocula size, nitrogen nutrient (corn steep liquor) of 0.331 to 0.662 mgkg-1 and phosphorus nutrient (poultry droppings) 39.4 to 197.4 mgkg-1 was adopted and the model resulted in the randomization of nutrients and consortia in ratios designed to formulate a bioremediation agent. To this composition, a rich potassium source (plantain peels char) of 22.0 mgkg-1 was added. A bioremediation application study was set-up to follow the Box-Behnken modelled results and was monitored for 56d with initial Total Petroleum Hydrocarbon (TPH) content of 9744 mgkg-1 and Total Hydrocarbon Content (THC) of 964 mgkg-1. The model response from the treated sample shows a half-life of 6d, with degradation efficiency of 89.6% and 88.7% for TPH and THC removal after 21d of the study. This study established the feasibility of the application of an optimization model in the development of an efficient bioremediation agent suitable for the eco-recovery of oil spill sites.