Buried and surface oil degradation – Evaluating bioremediation to increase PAHs removal through linear mathematical models

A bioremediation approach with tide simulation for buried and surface oil degradation was tested for removal of two, three and four rings polycyclic aromatic hydrocarbons (PAHs). Linear models depicted degradation constants of individual PAH as simple additive function of their initial concentrations (C0) in contaminated sand, hydrophobicity, sampling layer and treatment conditions. For all PAHs and treatment conditions, the degradation of oil in buried layers was faster than at the surface. Naturally-occurring microorganisms proved to be efficient for bioremediation of PAHs and were stimulated by fertilizer addition (biostimulation, BS). Bioaugmentation (BA) by addition of a slurry of a native oil-degraders pre-stimulated consortium did not show faster PAH degradation than BS. Degradation was more rapid for PAH present at low C0 and with intermediate hydrophobicity. Bioremediation of beach sand either with surface or buried crude oil is a cost-effective strategy to clean-up different hydrocarbon families, including persistent ones, such as PAHs. •Bioremediation to remove PAHs from buried and surface oil evaluated through mathematical models.•PAH physic-chemical properties, initial amount and oil contaminated layer depth influence biodegradation.•Degradation was more rapid for PAHs with low concentration and with intermediate hydrophobicity.•Biostimulation and bioaugmentation using autochthonous microorganisms increased removal.•Linear models are suitable tools to assess additive factors/variables influencing bioremediation.