Simulation of effects of ethanol on benzene plume length using RT3D with a general substrate interaction module
Gomez, Diego E.
Alvarez, Pedro J.
Master of Science
A mathematical module was developed to evaluate the effect of the common fuel additive, ethanol, on benzene fate and transport in groundwater, and to discern the most influential benzene plume-elongating mechanisms. The module, developed for the RT3D (Reactive Transport in 3-Dimensions) model, includes previously evaluated fate and transport processes (advection, dispersion, adsorption, biodegradation and depletion of molecular oxygen during ethanol degradation) and substrate interactions (dilution of benzene metabolic flux, catabolite repression and microbial populations shifts) previously not considered. Benzene plume elongation predictions, based on literature model parameters, were on the order of 22%-40% for a constant source of E10 gasoline (10% v/v ethanol), which compares favorably to field observations (56%, Ruiz-Aguilar et al., 2003). Oxygen depletion during ethanol degradation was the principal mechanism hindering benzene natural attenuation, followed by metabolic flux dilution. When oxygen is not limiting, model simulations showed that microbial growth on ethanol could offset negative substrate interactions and enhance benzene degradation, resulting in shorter plumes.
Environmental science; Environmental engineering