Petroleum hydrocarbons are one of the most common groups of organic pollutants in the environment. Bioremediation of soils contaminated with petroleum compounds is an effective process for cleaning petroleum pollutants in the environment. In the present research, to reduce  light naphtha (1%) pollutant in in a sandy loam soil, different bioremediation methods including biostimulation, bioaugmentation, and integrated treatment (including both bioaugmentation and biostimulation) were used. This experiment was done as a split-plot design with three factors (pollution, bioremediation, and time) with 3 repetitions in 3 kg pots. After running the experiment at time intervals of 0, 5, 10, 15, 20, 30, 45, 60, 90 and 120 days, samples were taken from the test pots and parameters including basal respiration (BR) and substrarte-induced respiration (SIR) were measured. The results showed that application of bioremediation treatments had reduced light naphta pollution. Also, petroleum pollution had affected the activity of soil microorganisms, such that the maximum amount of BR and SIR was obtained in the early days; but with the passing of time, BR had a sharper drop compared to SIR. Seemingly, the microbial community responded to added glucose as a simple and available carbon source, and SIR was less reduced, but, probably, basal respiration encountered lack of carbon sources and decreased more. The results showed that, among the bioremediation treatments, integrated treatment had a greater effect on the reduction of petroleum hydrocarbons than other bioremediation treatments at the probability level of (P<0.01). The use of integrated treatment, in addition to increasing the active microbial population involved in the decomposition of petroleum compounds and providing optimal conditions for their activity, stimulates the indigenous soil microbial population and is a suitable method for removing petroleum compounds.

Water pollution by petroleum compounds is one of the most environmental challenges in oil-rich countries as it can have unsuitable effects on human health and the environment. Application of an efficient method for treating wastewaters containing oil materials is of great importance. Thus, this study investigated the using of the electrocoagulation for treating oil effluents for the first time.
First, the effluent of the oil catchment of Kharg was sampled over 30 days. Then, the concentrations of total petroleum of hydrocarbons (TPHs) were compared before and after the treatment by the electrocoagulation method. Also, the optimum values of influencing parameters including solution pH, current density, contact and aeration time, electrode type, hydraulic detention time and distance of electrodes were reported.
The highest removal of TPHs (94%) was attained at the following conditions: Fe-Fe electrodes, contact time of 30 min in the presence of aeration, 1.5 Cm of electrode distance and current density of 20 mA Cm-2.
It was found that the electrocoagulation method can be applied as a suitable way for treating effluents containing petroleum compounds.

Among the various adsorbents used, sawdust appears to be the most attractive material in terms of cost, versatility and abundance. In the present research, synthetic contaminated water with gasoline was used. Adsorption of petroleum compounds on four types of sawdust (Walnut, Poplar, Beech and Pine) was studied by using batch adsorption techniques. It was found that walnut sawdust has higher adsorption capacity than other types of sawdust. It was also observed that equilibrium adsorption capacity was a function of pH, temperature, and H 2O2 concentration in solution. Maximum adsorption of petroleum compounds was obtained at pH 8. The adsorption of petroleum compounds was increased by decreasing the temperature and H 2O2 concentration in the solution. The maximum equilibrium capacity of walnut sawdust was 84.03 sawdust gr COD mg nd 606.37 sawdust gr TPH mg obtained at pH 8 and+ a temperature of 10˚C. The experimental adsorption data were fitted to a Freundlich and Langmuier adsorption model. Calculated correlation coefficients indicated that the Freundlich model was best suited, indicating that the nature of walnut sawdust is heterogeneous. In this study, to illustrate the relation between q e, C e, pH and temperature, regression analysis was taken into consideration. The obtained model (with R 2 =0.985) improved the correlation coefficient at least 1.13% compared to the Freundlich model. The maximum and minimum error of the predicted values of q e to the experimental data was obtained as 14.29% and 0.034% for regression model, while these errors for the Freundlich model were 52.15% and 1.63%.

Soil contamination with petroleum compounds since the petroleum exploration in the last century in Iran، and accumulation of these compounds in the environment threaten the health of soil and water resources of the country. The current research was conducted with the purpose of reaching to an efficient approach for the remediation of soils polluted with petroleum compounds. In this research the effect of five experimental treatments including various species of Bacillus and Pseudomonas bacteria with and without barely (Karron cv.) planting on the bio-degradation of those compounds in an artificially polluted loam soil was investigated. Analysis of the data indicated that the maximum purification belonged to the Bacillus 2 treatment. With barely planting this bacteria reduced soil total petroleum hydrocarbons up to %72. 5 during 105 days. Without barely the reduction became %59. 8 at the same period. The rate of bio-degradation was also highest at the same treatment، meaning that during a 20-day the reduction of catumination became %40. Degredation rate considerably increased with the presence of bacteria in the soil comparing to the barely planting alone. Inoculating of contaminated soil with bacteria without the need for particular nursery seems to be enough to control effectively the soil pollution. Among the several examined bacteria، Bacillus 2 turned to be the most suitable one for removing the petroleum- loased contamination.

Water resources are affected by different pollutants because of population growth، increasing water demand، and development of industries. A group of these pollutants are petroleum compounds which contain hazardous compounds such as BTEX. These compounds may cause undesirable health effects. In this study، activated carbon along with ozonation process was used for petroleum hydrocarbon removal from water samples. Samples were taken from groundwater resources located around Tehran Petroleum Refinery Plant. Activated carbon dosages were equal to 0. 5، 3، and 5. 5 g/l، and ozone flow was 2. 5 l/min. Response surface methodology based on Box-Behnken was used to assess the effect of independent variables on the response function and prediction of the best response value. Analysis of variance (ANOVA) was applied for statistical analysis of the responses. High value for R2 (0. 98) shows that removal of COD can be described by this model. Although the value of R2 adjusted (0. 96) was less than R2، however، it can be concluded that the model has fit the experimental data favorably. Use of an oxidant together with activated carbon can increases removal efficiency for organic compounds. In this study it was observed that efficiency of petroleum compounds'' removal was greatly increased by addition of activated carbon as a catalyst with ozonation process.

Vetiver plant is from Poaceae family with high resistance, environmental compatibility and high ability for pollutants absorption, so can be used in environmental pollutions removal processes. Among petroleum compounds, polycyclic aromatic hydrocarbons are known as primary pollutants due to their stability in the environment. Phenanthrene usually has the highest concentration and most polluting among the petroleum aromatic compounds. In this study, vetiver was planted in pot with phenanthrene concentrations of zero (negative control), zero with acetone (positive control), 250, 500, 1000, 2000 and 4000 mg/kg soil dry weight and its physiological effects were investigated. At the highest concentration of phenanthrene the amount of chlorophyll and carotenoids decreased 20% and 21%, respectively, but phenolic compounds, proline and antioxidant activity were increased. Root and shoot weight at a concentration of 250 mg phenanthrene was significantly reduced compared to the control, but at subsequent concentrations, its decreasing slope was reduced. Root length and root volume also decreased. As phenanthrene is accumulated in root, so shows more decreases compare to shoot. Maximum accumulation of phenanthrene in vetiver root was 519 ppm in 4000 mg/kg soil dry weight phenanthrene concentration. Due to the resistance of vetiver to high concentrations of phenanthrene and its accumulation in roots, this plant can be used as a very suitable plant for the phytoremediation process of petroleum compounds.

Leakage of petroleum compounds from Tehran Oil Refinery (TOR) has caused soil contaminations in this area. These compounds can enter the groundwater and cause direct or indirect hazardous effects.This research is focused on Poly Aromatic Hydrocarbons (PAHs), the main group of petroleum compounds. Gas Chromatography (GC) analysis are made on 19 samples collected in grid sampling from sides and center of the stream adjacent to the TOR. Also according to the geotechnical properties of the area and considering the physical and hazardous quality of the contaminants, clean up levels are assessed for the groundwater preservation. Among 16 poly aromatic priority pollutants, four compounds which have the highest concentrations in the area and also have carcinogenic effects are evaluated. These compounds are benzo[a]pyren (BaP), benzo[k]fluoranthene (BaK), benzo[a]anthracene (BaC), and chrysene (Chr). This study showed that the concentration of BaP, BkF, and BaA were higher than the allowable concentrations. Also in case of BaP, maximum evaluated concentration (638 ppm) was 50 times higher than the allowable concentration (13.2 ppm). Different dispersing mechanisms are also evaluated and applicable methods are discussed in order to control the contaminants. In addition, based on geotechnical properties of the soil and considering physical specifications of the contaminants, biologic methods and phyto-remediation via phyto-transformation and rhizosphere-bioremediation are recommended to clean up the site.

Petroleum pollution is the most important soil pollution. Bioremediation is an effective and usable technology for remediation of polluted soils. Some microorganisms have bioremediation potency for petroleum compounds. In this research Tabriz city was selected as a cold area of Iran for studying of native bacteria with biodegradation potency of crude oil. Soil samples were collected from polluted soils of Tabriz refinery and their bacteria were accommodated to crude oil. The bacterial strains exited in the samples were isolated، grouped and determined. The growth ability and petroleum removal efficiency were evaluated for the each bacterium at the different crude oil concentrations during a month. In this research، seven bacterial species were found that are well accommodated to crude oil. The highest petroleum removal efficiency (98%) was determined for Pseudomonas aerogenesis at concentration of 0. 5%. Biological removing of crude oil with high efficiency is possible by soil bacterial flora، as an environmental friendly method، even for soil cleaning of the industrial areas in cold temperature regions.

Aromatic hydrocarbons are an important group of environmental pollutants which are produced from different sources such as refineries and petrochemical, pharmaceutical, paint, and plastics industries. These environmental pollutants can be removed by different methods such as evaporation, chemical degradation, biological degradation, and adsorption. Biological methods are preferred selective methods because of simplicity, utilization of environmental-friendly microorganisms, and production of safe materials such as water and carbon dioxide (Singh et al. 2007). Bioremediation is a process for the conversion of toxic materials into non-toxic and safe ones based on metabolic activity of microorganisms capable of using organic and petroleum pollutants as carbon and energy sources. It is a useful technology with no environmental disruption (Sungpetch, 1998). Streptomyces species, which belong to the category of Actinomycetes, are gram-positive and non-moving strains. Most of them produce spores and produce most of clinically useful antibiotics of natural origin. These species have different genus and some of them can degrade aromatic compounds such as benzene, toluene, and even complex petroleum compounds (Claessen et al. 2006).

The most important problem of oil industries and refineries is the leakage and spraying of oil compounds and products through transportation systems on agricultural soils. Penetration of petroleum compounds in the soil causes the fertility of the agricultural soil to decrease drastically. The seeds of agricultural and garden plants either do not grow at all or do not grow optimally in soils contaminated with petroleum compounds. Seed coating is one of the ways to enhance the plants’ seed germination in contaminated soils with diesel. The use of natural materials is preferable to chemicals to prevent the aggravation of environmental pollutants. The main aim of this study was to evaluate the effect of calcium alginate as a coating layer on maize seed for germination in contaminated soil with diesel. This experiment was organized in a two-way ANOVA (4 × 4) in which factor A consisted of four levels of diesel-contaminated soil (0, 2, 4, 6%), and factor B consisted of calcium alginate concentrations (0, 1, 2, 3%). Experimental treatments' effects were studied in a completely randomized design with four replications. Experimental variables included some components of vegetative growth, hormones, and enzymes. The most important results showed that seeds coated with calcium alginate concentrations (1, 2, 3%) under diesel-contaminated soils increased germination percentage, shoot and root lengths, and shoot fresh weight while decreasing the activity of antioxidant enzymes including catalase, superoxide dismutase, as well as malondialdehyde production. Also, the results showed that 2 and 3% of calcium alginate concentrations produced the highest amount of Gibberellin A3 hormone, while these concentrations produced the lowest amount of abscisic acid hormone in the coated seeds under diesel-contaminated soils