Document Type : Article
Authors
1
Civil and Environmental Engineering Faculty, Tarbiat Modares University
2
Civil and Environmental Engineering Faculty; Tarbiat Modares University
3
Environment and Sustainable Development Research Institute, Iran Environmental Protection Organization
10.24200/j30.2024.64744.3340
Abstract
Petroleum-based products are the primary energy source for industry and daily life. However, leakage and spillage frequently occur during the exploration, production, refining, transportation, and storage of these compounds. Soil contamination caused by crude oil is a significant concern with worldwide impacts on ecosystems and human health. Various biological and non-biological methods have been developed to remove oil pollutants in situ or ex-situ. Meanwhile, bioremediation, in which microorganisms break down organic pollutants, is one of the most efficient techniques for cleaning soils contaminated with chemical compounds. Bioremediation is an emerging sustainable and economical technology to maximize the metabolism of organic pollutants, especially petroleum compounds, and minimize the ecological effects caused by their spills. The objective of this study, which was conducted on a laboratory scale, was to investigate the impact of different factors such as soil humidity, nutrient ratio, and inoculum of microorganisms, on the biological treatment of sandy soil contaminated with 4000 mg of diesel per kilogram of soil. The performance of the process was evaluated in terms of total petroleum hydrocarbons (TPH) removal efficiency, soil microbial respiration, and soil microbial population. Three doses of Pseudomonas Putida were added to the soil as a pre-adapted pure bacterial strain. The soil was also stimulated with three levels of ammonium nitrate and potassium dihydrogen phosphate as nutrients. The obtained results indicate that the increase in nutrients available to the bacterial species improves the growth rate of the soil microbial population and subsequently increases the oil pollutant removal efficiency. Due to the high TPH removal efficiency, the appropriate rate of microbial respiration, and sufficient final microbial population, 8% by weight humidity, the nutrient ratio of 100:10:1, and 5% by volume bacterial inoculation was determined as the optimal value for the biological cleaning of diesel-contaminated soil by Bioaugmentation and Biostimulation process. Under the given conditions, after seventy days of the cleaning operation, the TPH removal efficiency reached 86%.
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