Biodegradation modelling of a dissolved gasoline plume applying independent laboratory and field parameters

Biodegradation of organic contaminants in groundwater is a microscale proce ss which is often observed on scales of 100s of metres or larger. Unfortuna tely, there are no known equivalent parameters for characterizing the biode gradation process at the macroscale as there are, for example, in the case of hydrodynamic dispersion. Zero- and first-order degradation rates estimat ed at the laboratory scale by model fitting generally overpredict the rate of biodegradation when applied to the field scale because limited electron acceptor availability and microbial growth are not considered. On the other hand, Field-estimated zero- and first-order rates are often not suitable f or predicting plume development because they may oversimplify or neglect se veral key field scale processes. phenomena and characteristics. This study uses the numerical model BIO3D to link the laboratory and field scales by a pplying laboratory-derived Monod kinetic degradation parameters to simulate a dissolved gasoline field experiment at the Canadian Forces Base (CFB) Bo rden. All input parameters were derived from independent laboratory and fie ld measurements or taken from the literature a priori to the simulations. T he simulated results match the experimental results reasonably well without model calibration. A sensitivity analysis on the most uncertain input para meters showed only a minor influence on the simulation results. Furthermore , it is shown that the flow field, the amount of electron acceptor (oxygen) available, and the Monod kinetic parameters have a significant influence o n the simulated results, it is concluded that laboratory-derived Monod kine tic parameters can adequately describe field scale degradation, provided al l controlling factors are incorporated in the field scale model. These fact ors include advective-dispersive transport of multiple contaminants and ele ctron accepters and large-scale spatial heterogeneities. (C) 2000 Elsevier Science B.V. All rights reserved.