Use of natural absorber to reduce petroleum carbohydrate from oil industries wastewater (Case Study: Tehran oil refinery)

Petroleum hydrocarbons are considered as the most major aquatic and terrestrial ecosystem pollutants in the world. The US Environmental Protection Agency (EPA) has announced that it is harmful to the environment. It is toxic and cause cancer, too. Polycyclic aromatic hydrocarbons enter the soil and the groundwater through oil tanks leak, so cause environmental pollution. Polycyclic aromatic hydrocarbons (PAHs) are organic compounds that are mostly colorless, white, or pale yellow solids. They are a ubiquitous group of several hundred chemically related compounds, environmentally persistent with various structures and varied toxicity. They have toxic effects on organisms through various actions. Generally, PAHs enter the environment through various routes and are usually found as a mixture containing two or more of these compounds, e.g. soot. Some PAHs are manufactured in the industry. The mechanism of toxicity is considered to be interference with the function of cellular membranes, as well as enzyme systems which are associated with the membrane. It has been proved that PAHs can cause carcinogenic and mutagenic effects and they are also potent immune-suppressants. Effects have been documented on immune system development, humoral immunity and host resistance. PAHs can be formed both during biological processes and as products of incomplete combustion from either natural combustion sources (forest and brush fires) or by man-made combustion sources. Thus, PAHs are commonly detected in air, soil, and water. Therefore, PAHs are considered ubiquitous in the environment. The ubiquitous nature of PAHs in the environment has been well recognized in researches. The term “PAH” refers to compounds consisting of only carbon and hydrogen atoms. Chemically the PAHs are comprised of two or more benzene rings which are bonded in linear, cluster, or angular arrangements. Such molecular arrangements are considered toxic. Although there are many types of PAHs, most regulations, analyses, and data reporting focus on only a limited number of PAHs, typically between 14 and 20 individual PAH compounds. Petroleum contaminated is currently treated using three processes: physical, chemical, and biological. A range of cleaning techniques have been successfully developed to limit the environmental impacts caused by oil pollution, but timely and effective remediation is necessary to mitigate the detrimental effect of petroleum hydrocarbons on the environment. The present study aims to evaluate the efficiency of PAHs adsorption prediction of the groundwater contamination. Adsorption of these pollutants using the various natural adsorbents is among the crucial objectives of this study, as well. This investigation has been done in these steps: at first, the ecological characteristics of Tehran Oil Refinery have been identified and the water quality of its wastewater treatment plant was evaluated, briefly. In the second step, to estimate PAHs adsorption in soil and optimize the adsorption process using activated carbon, bentonite, talk powder, rice bran, and saw dust, we prepared a rectangular pilot plant with an interlaced plate as drainage at the end of it, and after packing it with each of the adsorbents in specific weight and height, oily wastewater containing (PAHs) influence on it. The column pressure head and its conditions have been stable during experiments. The adsorption of PAHs on these adsorbents was estimated by measuring the concentration of PAHs in effluents of the drainage, every 30 minute intervals up to 4 hour, and the bed of adsorbents at the end of experiments.
Since water has seriously been polluted by PAHs nowadays, PAHs adsorption by the Bentonite, Talcum powder and Clay is considered in this research. Then, PAHs distribution coefficient and the maximum adsorption have been determined according to the results, by Freundlich adsorption isotherms, and Langmuir isotherm. This study also compares the suitability of two predictive models, Freundlich isotherm and Langmuir isotherm, in analyzing the adsorption of PAHs on soil and the five types of adsorbents which were mentioned above. The results indicated, the adsorption data were well fitted by the Freundlich model. Also, Results show that the Bentonite has a high potential for PAHs adsorption. Distribution coefficient (kd) and the maximum adsorption are 0.008 lit/g and 0.101 mg/g. Since distribution coefficient for the absorbents including clay and Talk powder 0.0028 lit/g and 0.0023 lit/g, respectively. Furthermore, the maximum adsorption coefficient for the absorbents including clay and Talk powder is 0.042 mg/g and 0.003 mg/g in this research.