Synergistic adsorption and biodegradation of heavy crude oil by a novel hybrid matrix containing immobilized Bacillus licheniformis: Aqueous phase and soil bioremediation

Recently, slurry phase bioremediation as a simple and economical method is shown to be a successful technique for remediation of clayey soils. Besides, the use of microbial cell immobilization as a promising technique has drawn the attention of some researchers. The primary objective of this survey is to examine the synergistic adsorption and biodegradation performance of heavy crude oil by an isolated Bacillus licheniformis immobilized in a novel hybrid matrix (PUF/alginate/microbial cell) in aqueous phase. Isotherm studies and adsorption kinetics of crude oil on PUF matrix were carried out and their results revealed a good correlation between experimental data and Langmuir's isotherm and maximum monolayer coverage was found out to be 1.25 g/g PUF. The other objective of this research is examination of hybrid matrix in slurry phase bioremediation of heavy crude oil polluted clayey soil as a reluctant model soil. In order to model, optimize, and investigate the factors affecting the total organic carbon (TOC) reduction, response surface methodology (RSM) was applied. For this purpose, the effect of three variables including crude oil concentration (5000-25,000 mg/kg dry soil), soil salinity (0-10%), and water to soil ratio (WSR: 2-10) have been studied. In this study, TOC reduction was achieved in ranging from 39% to 80% in crude oil polluted soil after 21 days. Additionally, experiments by polyurethane foam (PUF)-immobilized cell, alginate-immobilized cell, and freely cell suspended systems were conducted to compare the performance of hybrid-immobilized cell with other systems. Our results showed the superiority of immobilized cells in hybrid matrix of PUF/alginate compared to other immobilized cell (IC) and free cell (FC) systems. Overall, the results indicated that the hybrid matrix with simultaneous adsorptionbiodegradation capacity is potentially suitable for further development for oil spill treatment and it can be used as an efficient cleaning method in TOC removal from actual polluted soils.

Automated summary

The study demonstrated the successful application of slurry phase bioremediation and microbial cell immobilization in the remediation of heavy crude oil pollution, showing the advantages of hybrid matrix in TOC reduction and adsorption-biodegradation capacity through experimental results.