Schirmer, Mario

2000, Schirmer, Mario, Molson, John W, Frind, Emil O, Barker, James F

Biodegradation of organic contaminants in groundwater is a microscale process which is often observed on scales of 100s of metres or larger. Unfortunately, there are no known equivalent parameters for characterizing the biodegradation process at the macroscale as there are, for example, in the case of hydrodynamic dispersion. Zero- and first-order degradation rates estimated 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 for predicting plume development because they may oversimplify or neglect several key field scale processes. phenomena and characteristics. This study uses the numerical model BIO3D to link the laboratory and field scales by applying laboratory-derived Monod kinetic degradation parameters to simulate a dissolved gasoline field experiment at the Canadian Forces Base (CFB) Borden. All input parameters were derived from independent laboratory and field measurements or taken from the literature a priori to the simulations. The simulated results match the experimental results reasonably well without model calibration. A sensitivity analysis on the most uncertain input parameters 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 on the simulated results, it is concluded that laboratory-derived Monod kinetic parameters can adequately describe field scale degradation, provided all controlling factors are incorporated in the field scale model. These factors include advective-dispersive transport of multiple contaminants and electron accepters and large-scale spatial heterogeneities. (C) 2000 Elsevier Science B.V. All rights reserved.

1999, Schirmer, Mario, Butler, Barbara J, Roy, James W, Frind, Emil O, Barker, James F

An analysis of aerobic m-xylene biodegradation kinetics was performed on the results of laboratory batch microcosms. A modified version of the computer model BIO3D was used to determine the Monod kinetic parameters, k(max) (maximum utilization rate) and K-S (half-utilization constant), as well as the Haldane inhibition concentration, K-I, for pristine Borden aquifer material, The proposed method allows for substrate degradation under microbial growth conditions. The problem of non-uniqueness of the calculated parameters was overcome by using several different initial substrate concentrations. With a relative-least-squares technique, unique kinetic degradation parameters were obtained. Calculation of the microbial yield, Y, based on microbial counts from the beginning and the end of the experiments was crucial for reducing the number of unknowns in the system and therefore for the accurate determination of the kinetic degradation parameters, The kinetic parameters obtained in the present study were found to agree well with values reported in the literature. (C) 1999 Elsevier Science B.V. All rights reserved.