Biological Treatment Of Petroleum Contaminated Soils By Soil Slurry-sequencing Batch Reactors (SS-SBRs)

Abstract

The soil slurry-sequencing bath reactor (SS-SBR) was studied to treat poorly graded sand with clay (SP-SC) contaminated by aged petroleum hydrocarbons and polycyclic aromatic hydrocarbons (PAHs) with concentrations of 23000 mg/kg and 750 mg/kg respectively. An 8 L bioreactor was operated with a 10% solid concentration (0.1 kg dry soil/L slurry). The fill period was relatively instantaneous, and the draw period lasted approximately 1 minute so the react period comprised essentially the entire cycle time. In the draw period a fraction of slurry (10%) was removed from the SS-SBR weekly and it was replaced with untreated slurry. This volumetric replacement strategy provided 70 days hydraulic retention time (HRT). The process performance was assessed by monitoring total petroleum hydrocarbons (TPH) and PAH concentrations, pH, dissolved oxygen (DO), oxygen uptake rate (OUR) and colony forming units (CFU). Due to a high concentration of TPH, silica gel clean up was performed to specify PAH degradation. The results have shown high overall removal efficiency for TPH close to 97% whereas biodegradation of PAHs has been performed with a removal efficiency of 90%.