Recent Proportionate Treatment Methods for Crude Oil Contamination Evaluation of the Tehran Refinery Site Soil

Objectives: The aim of this study was to find the optimal biological methods to remove crude oil contaminants, especially polycyclic aromatic hydrocarbons (PAHs), from the soil of the lands around the Tehran Refinery site. Materials and Methods: In this study, soil sampling was conducted from five points of the west side of the refinery area through a zigzag sampling method. The soil characteristics were identified in the soil laboratory where PAH contamination was also examined. Advantages and disadvantages of biological, physical, and thermochemical methods of soil treatment were retrieved from the literature. The biological methods were confirmed as the optimum treatment methods which had been more extensively evaluated according to the soil texture, remediated compounds, cost, and timing. Results: The soil was largely composed of silt and clay (silt:41 - 42%, clay: 40 - 43%, sand: 15 - 18%). The average moisture content of the saturated soil was 12.96%,; average electricity conductivity was 18.64 DSm-1; average pH of the paste was 8.36; and average percentage of organic carbon was 0.19%. Result of the laboratory analysis reported the average content of total nitrogen as 0.026%, phosphorus as 14.3 mg/kg-1 and potassium content as 3.4 mg/kg-1. Content of the crude oil derivatives was less than 0.5 %. Conclusions: An efficient method for treating the current low level soil contamination around the Tehran Refinery site is phytoremediation, a cost effective method that helps to create beautiful landscapes around the refinery site. Soil vapor extraction (SVE) should be used in large PAH levels (higher than the current rate). Soil washing is the most time-effective method, which is suitable for cases of emergency soil contamination with petroleum.