Iranian Journal of Chemical Engineering (IJChE)

Abstract Polycyclic aromatic hydrocarbons (PAH) are toxic, mutagenic, and carcinogenic compounds. Removal of these compounds has a great importance for environment. Removal of PAHs from soil is difficult as these chemicals are persistent in the soil. In this research, bioremediation of soil contaminated by (PAH) using Bacillus subtilis DSMZ 3256 (B.subtilis) strains was studied. The effect of electrokinetic on biodegradation of PAH was investigated. Fluorene and phenanthrene were selected as PAH and were mixed with soil. The bioremediation experiment was initially performed at 30oC and different humidities. The results represented 12.2 and 11.9% removal of fluorene and phenanthrene at 40% relative humidity after 7 days, respectively. The effects of electrokinetic on this process were studied at different current densities. It was found that the electrokinetic can reduce the biodesulfurization time. According to the results, the removal percents of fluorene and phenanthrene after 4 days under current density 1.82 mA/cm2 were 39.4 and 37.2, respectively.

Abstract orption ofcontaminants in soil and sequestration in soil particles is a process, the mechanisms of which are not well understood as yet. The aim of this study was to investigate sequestration and bioavailability of crude oil as a contaminant in three different soils. For this purpose, three different soil samples with different textures (loamy sand, loam, and clay loam) but with the same organic carbon were collected. After sterilization, the soils were spiked with crude oil. Each soil sample was contaminated as aged and fresh, and inoculated with a consortium ofthree bacterial isolates. Respiration was analyzed on days 0, 30, 60, and 90 after inoculation. Bacterial population was also assessed at the beginning and at the end ofthe bioremediation and residual contaminant at the end ofthe bioremediation process. The results showed that in soils with the same organic carbon, texture is an important parameter in aging and sequestration of the contaminant. In addition, it was observed that the best degradation was accomplished in the loam soil, due to more bioavailability as compared to the clay loam soil and less inhibitory effect of the contaminant on microbial growth, resulting from lower bioavailability, as compared to the loamy sand soil.

Abstract Soil contamination with TNT is a serious environmental hazard due to the toxic and mutagenic effects of TNT. Bioremediation is an environmentally safe method in the treatment of explosive-contaminated sites. In the present research, after selection of superior bacteria in the aqueous phase, bioremediation of TNT contaminated clay soil
at 1000mg/kg was performed in slurry phase, which resulted in a maximum TNT removal of 89% after 15 days. Afterwards, the effects of operational and environmental factors were examined via the two-level fractional factorial design method ( 7 3 IV2 − ) for seven factors, i.e., glucose (2, 8g/l), yeast extract (0, 0.2g/l), (NH 4)2SO 4 (0.1, 0.5g/l),
Tween80 (1, 5g/l) and slurry concentrations (20, 40%w/v) as well as inoculum size (5, 10%v/v) and temperature (20, 35˚C). Among these factors, significant factors were found to be slurry, surfactant and glucose concentrations as well as inoculum size. In addition, considerable interactions were observed between glucose and the other significant factors.

Abstract Contamination of soils with nitroaromatic hydrocarbons, due to their toxic effects, is one of the environmental issues. Therefore, the purpose of this study is to examine para-nitrophenol (PNP) biodegradation in a microcosm consisting of kaolan clayey soil by A. faecalis, the superior bacterium among the four examined bacterial species. Preliminary experiments were performed in slurry phase to investigate biodegradation of PNP by A. faecalis in shaking flasks at initial concentrations of 25 and 50mgkg-1  which resulted in 72 and 57% PNP removals after 20 days, respectively. To identify the effective factors on PNP biodegradation, experiments were carried out in shake flasks at various levels of eight factors, i.e. PNP, glucose and yeast concentrations, temperature, soil-water ratio, initial pH, inoculum size as well as PNP concentration in pre-exposure based on Plackett-Burman design method. Results showed 20.9 up to 75.5% PNP removal in soil slurry after 12 days within the design space. Analysis of variance revealed that temperature, inoculum size, yeast extract concentration, pH and soil-water ratio are the most effective factors on PNP biodegradation, respectively.