1Department of Environmental Science, Islamic Azad University, Ardabil Branch, Ardabil, Iran
2Department of Soil Science and Engineering, University of Mohaghegh Ardabili, Ardabil, Iran
3Department of Soil Science and Engineering, University of Tehran, Karaj, Iran
Iran an oil-rich country and encounters oil pollution of soil and water. Bioremediation of these pollutants is an appropriate solution compared to the physical and chemical remediation methods. Therefore, the aim of this study was to determine the rate of gasoil bioremediation by two indigenous bacterial isolates (from oil contaminated soils in south of Tehran oil refinery) in two different media including soil and soil-sawdust mixture. The isolation of two superior indigenous bacteria was conducted thorough three steps: i) Isolation and purification of indigenous oil degrading bacteria in a soil extract agar as a selective media, ii) The study of efficiency of the isolates in a liquid mineral based media with 7% (V/V) of gas oil. iii) The comparison of the respiration rates of the isolates in a media containing 3% (W/W) gas oil. The results indicated that in optimal environmental conditions (temperature, 27±2 °C, humidity 60% Water Holding Capacity and daily manual aeration), bacterial isolates were able to degrade, about 78.87% and 93.53% of gasoil during the period of 45 days in soil and soil-sawdust mixture media, respectively. These results imply the role of sawdust in improving of aeration, water holding capacity and consequently, increasing bioavailability of gasoil to bacteria.