Simulating A Bioventing Reactor With A Fluid Dynamics Model Using A Universal Biodegradation Rate Coefficient (UBRC)

摘要

Bioventing is a simple but effective method to remediate gasoline-contaminated soil. However, predicting the effectiveness of bioventing requires first order degradation rates. Normally, these rates are determined in small-scale laboratory tests. The challenge is applying these small-scale results to field scenarios. To assist with the scale-up of the results to the field, medium scale bioreactor tests were completed to see if small-scale results are still valid. Included with the medium scale experiments was the development of a three dimensional numerical model using computational fluid dynamics to simulate the airflow needed for optimum bioventing. The modelling system consists of a cylindrical reactor, with a well located in the center of equally distributed contaminated soil, to which a small vacuum is applied. The model simulates the effective profiles of the air velocity and pressure gradients. The simulation showed that various aspects of bioventing systems including well screen depth, airflow rate and water content impact volatilization and ultimately the degradation behaviour. The biggest impact was from pore-gas velocities, showing the importance of appropriate values to maintain optimum degradation conditions when determining the biodegradation rate coefficient.