Abstract
Acute and chronic pollution of environments with crude oil does not bode well for biota living within the vicinity of polluted environments. This is due to environmental and public health concerns on the negative impact of crude oil pollution on living organisms. Enhancing microbial activities by adding nutrients and other amendments had proved effective in pollutant removal during bioremediation. This study was carried out to determine how microbial group respond during remediation by enhanced natural attenuation (RENA) during a field-scale bioremediation. Crude oil-polluted soil samples were collected (before, during, and after remediation) from a site undergoing remediation by enhanced natural attenuation (RENA) at Ikarama Community, Bayelsa State, Nigeria, and were analyzed for total petroleum hydrocarbon (TPH), polyaromatic hydrocarbon (PAH), and a shift in microbial community. The gas chromatography-flame ionization detector (GC-FID) results showed that the pollutant concentrations (TPH and PAH) reduced by 98 and 85%, respectively, after the remediation. Culturable hydrocarbon utilizing bacteria (CHUB) was highest (8.3 × 104 cfu/g) for sample collected during the remediation studies, whilst sample collected after remediation had low CHUB (6.1 × 104 cfu/g) compared to that collected before remediation (7.7 × 104 cfu/g). Analysis of 16S rRNA of the isolated CHUB showed they belonged to eight bacterial genera namely: Achromobacter, Alcaligenes, Azospirillus, Bacillus, Lysinibacillus, Ochrobactrum, Proteus, and Pusillimonas, with Alcaligenes as the dominant genus. In this study, it was observed that the bacterial community shifted from mixed group (Gram-positive and -negative) before and during the remediation, to only the latter group after the remediation studies. The betaproteobacteria groups were the dominant isolated bacterial phylotype. This study showed that RENA is an effective method of reducing pollutant concentration in crude oil-polluted sites, and could be applied to other polluted sites in the Niger Delta region of Nigeria to mitigate the devastating effects of crude oil pollution.
Highlights
Pollution of environments has been of concern to the society, especially in developing countries witnessing tremendous and rapid industrialization
This study showed that remediation by enhanced natural attenuation (RENA) is an effective method of reducing pollutant concentration in crude oil-polluted sites, and could be applied to other polluted sites in the Niger Delta region of Nigeria to mitigate the devastating effects of crude oil pollution
Crude oil-polluted soil samples were collected from Ikarama, a site undergoing remediation by enhanced natural attenuation (RENA) and were analyzed for reduction in pollutant concentration, and corresponding shift in microbial population pre, during, and post remediation
Summary
Pollution of environments (air, land and water) has been of concern to the society, especially in developing countries witnessing tremendous and rapid industrialization. One of the classes of pollutants that posses an imminent danger is hydrocarbons. In this class of pollutant, the polyaromatics are more environmental and public health concerns due to their carcinogenic, mutagenic, recalcitrant, and other detrimental effects on living organisms (Erdogmus et al 2015). Accidental discharge and spillage during crude oil exploration are the major cause of the former, whilst the causes of the latter are vast ranging from emission from exhausts, indiscriminate discharge of used crude product(s) emanating from automobile repair and construction sites into surrounding water bodies and land.
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