Iranian Journal of

Background and Objectives: The use of surfactants enhance the bioavailability of nonbiodegradable contaminants such as PAHs. Biosurfactants are more environmental friendly. In this study the ability of removing phenenthrene from soil by biosurfactant was assessed and compared with that of chemical surfactant. Materials and Methods: A soil sample free of any organic or microbial contamination was artificially spiked with phenanthrene at two concentrations. Then, mineral salt medium at constant concentration of chemical surfactant TritonX-100 and rhamnolipid MR01biosurfactant was added to it in order to have the proportion of 10% w:v (soil:water). A microbial consortium with a potential of phenanthrene biodegradation was inoculated to the soil slurry in two densities (OD=1 and 2) and then it was aerated on a shaker. After eight weeks, the residual concentration of phenanthrene in the soil was extracted by ultrasonic and was analyzed using HPLC. MPN test was used for measuring microbial population. This study was conducted based on the two level full factorial design of experiment. Results: It was found that chemical surfactant exhibited higher PHE removal efficiency than the biosurfactant. Using 120 mg/L of TritonX-100 and rhamnolipid, the PHE removal for the soil contaminated with 50 mg PHE/kg dry soil was 98.5 and 88.7% respectively, while the removal efficieny was decreased to 87 and 76% respectively for the soil contaminated with 300 mg PHE/kg. In the absence of surfactant, the removal efficiency at concentrations of 50 and 300 mg PHE/kg dry soil was achieved 60.76 and 51% respectively. The phenanthrene removal efficiency in OD=2 was more higher than OD=1. In the presence of rhamnolipid, the maximum microbial populations was observed in the second week, while it decreased in the presence of TritonX-100. Conclusion: Use of biosurfactants can be considered as a suitable option in low level pollutant sites. Chemical surfactants as ex-situ has achieved more satisfactory results in high level contaminant sites.

Background & Objectives: Polycyclic aromatic hydrocarbons (PAHs) are considered as important organic contaminants due to their high toxicity and carcinogenic properties. Among PAHs, phenanthrene is found in most contaminated sites. Sorption and desorption of phenanthrene in soil affect the fate of the contaminant in soil-water system. Presence of organic matter (OM) in the soil matrix can also affect sorption and desorption of phenantherene. In this research, effect of soil organic matter on sorption of phenanthrene in kaolin soil was studied. Materials & Methods: The sorption of sorption of phenanthrene in kaolin clay was assessed in the presence and absence of organic matter. These two soil types were used in batch sorption experiments of Phenanthrene to determine the sorption properties. Results: It was found that organic matter increases the cation exchange capacity, water content, and pH of the soil. Sorption of phenantherene in both kaolin and OM-added kaolin was better fitted with Freundlich linear model. Moreover. soil organic matter increased phenanthrene sorption in soil. Conclusion: It was observed that with 41.04% increase in OM, distribution coefficient of phenanthrene sorption in soil increased by 36.69%.