Abstract
Oil pollution has been a worldwide concern especially in environments where treatment is quite difficult to apply. Marine polluted sediments, in particular, constitute one of the most recalcitrant environments for bioremediation and are often the final repository of petroleum contaminants, as a result of runoff and deposition. Aerobic hydrocarbon degraders present in the sediments are tackling the pollution under oxygen-limited or oxygen-depleted conditions. Research has focused on new ways to enhance bioremediation under anoxic conditions, however aerobic bioremediation is faster, and hence more effort should be made to sustain oxygen concentration levels. In this review, the different bioremediation techniques used for the decontamination of marine sediments are briefly discussed, and focus is primarily given to the different oxygenation methods used for enhancing aerobic bioremediation and the aeration methods that are suitable for in situ application, as well as state of the art technologies that make in situ aeration an appealing approach. Based on the technologies analyzed, suggestions are made for sediment bioremediation techniques in different marine environments.
Highlights
To achieve high dissolved oxygen concentrations, oxygen is sparged at a low flow rate to optimize the contact time between oxygen and the contaminated zone which could be further increased by oxygen entrapment in the sediments
Ex situ techniques that involve the dredging of contaminated sediments often come at higher costs, attributed to excavation and transport and present high probability of contaminant spreading during the removal
In situ techniques tend to be less invasive to the environment and cost-effective; their application must be in accordance with a number of factors
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Engineered bioremediation modifies the environmental conditions (physical, chemical, biochemical, or microbiological) to enhance the degradation capacity of the native microorganisms [8]. It is an ecofriendly approach for restoring contaminated ecosystems without causing additional damage. Field research after the Deepwater Horizon accident showed that indigenous microbial communities play a pivotal role in oil spill remediation [11] Exploiting these hydrocarbon-degrading microbes for bioremediation purposes is of great importance. Intrinsic bioremediation relies solely on the microorganisms to return the environment to its original state prior to contamination, while engineered bioremediation is either based on stimulating the autochthonous microorganisms for faster biodegradation of the pollutants, or on the addition of allochthonous microorganisms targeted to degrade petroleum hydrocarbons with ease [13]. In situ aerobic bioremediation techniques may have additional advantages here as they require limited space, cause minimum disturbance, and can lead to faster removal of recalcitrant compounds
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