Experimental analysis and modeling aspects of the removal of polycyclic aromatic hydrocarbons in soil slurry bioreactors
Polycyclic Aromatic Hydrocarbon (PAH)-contaminated soils are a great environmental and public health concern nowadays. Aerobic soil-slurry bioreactor technology has emerged as an effective and feasible technique with a high remediation potential, especially for the fine soil fractions, which often contain the highest pollution levels and are hard to treat with conventional approaches. However, the mechanisms involved in the PAH removal in the bioreactor are still not completely understood. In addition to the biological processes, important mass transfer mechanisms need to be considered (gas-liquid oxygen mass transfer, sorption-desorption, volatilization, etc.) . For this study, a mechanistic approach was developed, in which the bioslurry process was deconstructed using a model system. Each part was isolated and analyzed individually. Then, the global process was studied and the results of the analysis of the individual parts were used to understand the global bioremediation treatment. Among the results obtained, it was demonstrated that clay presence in soils can strongly affect oxygen transfer in slurry systems , the pollutant bioavailability was limited by the desorption process, particularly when organic matter was present in the soil and volatilization can be the major removal process during the lag phase period in biodegradation. The results of this research work can be extrapolated to the study of real contaminated soil remediation. The mechanistic approach can be used as a generic method to investigate the slurry bioreactor treatment for any type of soil, different pollutants and microbial communities, and other operating conditions.