This research work demonstrates the feasibility of accelerating bioremediation of a clay soil by supplementing with (NH4)2SO4, KH2PO4, sucrose (as an inducer for growth) and tween 80. The soil contained 7% residual gasoil. The bioremediation was stimulated by moisture adjustment to 10%, and inoculating with hydrocarbon degrading microorganisms. (NH4)2SO4 and KH2PO4 were added to the soil to obtain soil samples with C: N: P ratios of 100: 1. 4: 1. 4, 100: 6. 4: 1. 9, 100: 11. 4: 2. 4, and 100: 21. 4: 3. 4. The C: N: P of 100: 11. 4: 2. 4 resulted in more than 78% gasoil removal for duration of two months. Tween 80, in the range of 0-20mL/ (kg soil), was added to the soil samples with C: N: P ratio of 100: 1. 4: 1. 4. More than 84% removal was achieved when 10 mL/kg tween 80 was added to the soil. Sucrose, in the range of 0-20 g/(kg soil), was added to the soil samples with the C: N: P ratio of 100: 1. 4: 1. 4. For the sucrose level of 20 g/(kg soil), 79% removal was obtained in two months. Additional experiment was also conducted at two porosity levels of 54% and 22%. The removal percentage in the soil with high porosity was almost twice as compared to soil with low porosity.

A mathematical model has been developed and simulated to describe contaminated soil bioremediation. The model equations consist of a system of three nonlinear partial differential equations. Dimensional analysis of the model equations has been performed, and solution of these equations has been conducted by an implicit finite difference method. A computer program is runed for solving the model equations and by using this program, the influence of the principal parameters (porosity, soil aggregate radius, and partition coefficient of the substrate) on the fate of chemicals has been studied. The rates of substrate, oxygen diffusion and biodegradation rate have been found to be the controlling mechanisms for remediation in the aggregates.

The amount of petroleum hydrocarbon and heavy metals in sediment of Persian Gulf’s shore at 8 selected stations were determined and showed the maximum of 143.6 and 58.6 mg/kg sediment, respectively. The above maximum amounts were related to Emam Hassan zone which is located at 50 kilometers to west Boushehr port. bioremediation of contaminated sediment were studied in slurry and solid state fermentation. 8 bacteria types were isolated. Four species Em2, SH, GN1 and GN3 presented maximum PAH (Poly Aromatic Hydrocarbons) removal efficiency. Biodegradation efficiency under slurry conditions was observed after about 45 days which during this period, naphthalene and phenanthrene showed 73 and 66% removal efficiency, respectively. Under solid-state conditions, microbial activity of mixed and pure culture was studied. The results presented that the mixed culture due to strength and tolerance of different strains for growth, showed higher degradability compared to pure strains, but due to insufficient mixing under solid state conditions, mass transfer rate of nutrient reduced which caused to reduce cell activity, therefore removal efficiency under slurry conditions was higher.