Laboratory-scale bioremediation experiments on diesel and Polycyclic aromatic hydrocarbons contaminated soils
Laboratory investigations were performed to estimate the potential of bioslurry for bioremediation of PAHs and TPH-contaminated soil of Azimabad region in the south of Tehran refinery plant. The soil slurry-Sequencing Batch Reactor (SS-SBR) consisted of covered 8L Plexiglas vessel with a working volume of 6L. The reactor was equipped with a 400 rpm speed mixer. Oxygen was supplied through a fine-bubble diffuser at the bottom. A granular activated carbon trap as used to collect volatile organics in effluent air, fill period was relatively instantaneous, and Draw period lasted approximately 1 minute so the recent period comprised essentially the entire cycle time. In draw period a fraction of slurry (10%) was removed from period a fraction of slurry (10%) was removed from the SS-SBR weekly and it replaced with untreated slurry. This volumetric replacement volume of slurry (the recycle fraction) remained in the reactor to provide acclimated microorganism for the next batch of untreated slurry. The soil used in slurry studies was poorly graded sand with clay (SP-SC) which contaminated with approximately 67500 mg/kg TPH and 500mg/kg PAHS and passed through a sieve with an opening diameter of 0.5mm tap water was added to produce solids concentration of 10% (0.1kg dry soil/l slurry). Ammonias nitrate and phosphate were added to provide a C: N: P ratio of approximately 60:2:1 process performance .The TPH concentrations were determined by Gas chromatography with Flame Ionization Detector (GC-FID) after ultrasonic extraction the PAHS concentrations were determined with both of High performance liquid chromatography (HPLC) an GC-FID after silica-gel clean up. The results have shown high overall removal efficiency for TPH close to 96%. whereas PAHs were not detected at the end of each cycles.
