Optimizing the Use of Biological Washing in Rehabilitating the Contaminated Soil of South Tehran Oil Refinery

Bioleaching is a non-invasive, relatively affordable and environmentally friendly method through which toxic compounds are decomposed with the help of microorganisms and with the help of enzymatic reactions. This study was conducted in order to use biological leaching to rehabilitate contaminated soil and resistant to biological decomposition by heavy metal lead and phenanthrene around the south Tehran oil refinery. The design of the experiment was done with the response surface method. In the bioleaching method, the purified strain (Pseudomonas aeruginosa) was isolated from the soil of the refinery. Environmental pH (3, 5, 7, 9, 11), pollutant to biomass ratio (7.50, 15, 22.50, 30, 37.5 mg/g) and retention time (1, 2, 3, 4, 5 hours) were considered as main variables. pH was the most important parameter influencing the removal of lead and phenanthrene from soil. The highest percentage of lead removal with 96.79% pH is equal to 8, pollutant ratio to Live current is equal to 30 W/W and time of  2 hours was obtained. In the case of phenanthrene, the highest percentage of phenanthrene removal (97.4%) in pH was equal to 7, the pollutant to living organism ratio was equal to 22.5 W/W and the time was measured for 1 hour. The results of this study showed that the use of bacteria increased the efficiency of the removal process compared to the cleaning process without bacteria (42% for phenanthrene and 67% for lead).