Assessing the Potential of Mechanical Aeration Combined with Bioremediation Process in Soils and Coastal Sediments Impacted by Heavy Metals

Microorganisms make use of heavy metals through enzymatic, non-enzymatic processes or bioaccumulation in bacterial cells in insoluble or particulate forms and by-products. Increasing effectiveness of bioremediation is still being explored and other stimulation techniques cited by various authors used mostly EDTA, nitrogen fertiliser and other amendments. The use of mechanical aeration combined with bioremediation using Bacillus subtilis, Bacillus cereus, Pseudomonas aeruginosa and Pseudomonas fluoresecens offer a greener approach with more efficient remediation capabilities. Zinc exceeded the permissible limit recommended by FAO/WHO by more than two folds while other metals were close to the threshold limit posing a dangerous threat to human health. Implementation of the current package treatment showed statistically significant decreases in heavy metal concentrations in both soils and coastal sediments in a 90 days experiment under atmospheric conditions. For sediments, 21.4% to 100% bioremediation was achieved under mechanical aeration conditions representing an increase of up to 60% efficiency compared to non-aeration while for soil highest efficacy achieved was 63.1%. However, the mechanisms and pathways of bioremediation were noticed to depend according to biotic and abiotic factors. This article provides an insight on the comparison between proposed stimulation technique and other methods reported.