Bioremediation Modeling of an Aquifer Contaminated by Benzene Using the Slow-Release Oxygen Source Technique

Groundwater contamination caused by petroleum products has become a common problem. These hazardous chemicals themselves soak down into groundwater through the soil or rock and cause significant health risk. Benzene, one species of chemicals, gives rise to specific concerns due to its relatively high water solubility and toxicity. For the removal of benzene in aquifer, natural biodegradation has indicated its limited ability because of the lack of dissolved oxygen (DO) in groundwater. A new method, namely the slow-release oxygen source (SOS) technique, could increase concentration of dissolved oxygen in groundwater and accelerate biodegradation processes. Therefore, the paper first built a transport model including benzene, DO and microbial species. Relevant program codes were developed on the basis of MODFLOW/MT3DMS. Then, a two-dimensional synthetic aquifer with a point source of benzene was simulated by the modified model to analyze the treatment efficiency of SOS. There were seven schemes designed by using different locations of well and oxygen release rates. Their treatment efficiencies were analyzed. The results showed that the modified model can be used to simulate benzene transport under SOS technique where Monod kinetic reactions occur. It was more efficient when placing release oxygen well was close to contamination sources of groundwater. For the same location of well, higher release rate of oxygen would enhance the effect of bioremediation. Enough dissolved oxygen maybe accelerates the growth of microbial species, and more benzene could be consumed by increasing microbial mass.