| Bioremediation has become an important remediation technology during the past few years. However, limited understanding of processes, data limitations and parameter uncertainty, and computationally intensive numerical solutions have reduced the interest to perform detailed field-scale modeling, especially with nonlinear Monod expressions. In most modeling efforts, the emphasis has been on aerobic biodegradation and use of simple reaction kinetics such as zero- or first-order and instantaneous reaction kinetics. Recently, denitrification has also been included in a number of modeling efforts. Use of nitrate is important both in natural attenuation and in enhanced biodegradation modeling because of its high background concentration in natural subsurface, high energy potential, and high solubility. While use of simple reaction kinetics such as zero- or first-order and instantaneous reaction kinetics may be justified for oxygen due to its high energy potential and fast degradation rate, more complex reaction kinetics such as Monod-kinetics are required to accurately model the anaerobic biodegradation processes such as denitrification, Mn(IV)-reduction, Fe(III)-reduction, sulfate-reduction, and methanogenesis. The understanding of the anaerobic biodegradation processes has improved greatly over the recent years. But due primarily to the computational burden and lack of field biokentic data, modeling efforts with anaerobic biodegradation processes are scarce. This research, first, investigated the current status of biodegradation modeling with anaerobic electron acceptors; second, addressed crucial aspects and concerns relating to anaerobic biodegradation; third, developed a theoretical framework and a conceptual model to include all the electron acceptors—aerobic and anaerobic; and fourth, developed a robust, accurate and efficient numerical scheme to solve the complex biodegradation equations.; The tasks conducted in this research will significantly contribute to the following: (1) Better understanding of the biodegradation theory and concepts as well as knowledge gaps and limitations in field application of biodegradation technology. (2) Conceptualization and theoretical development of a field-scale biodegradation model with alternate electron acceptors. (3) Use of more realistic Monod kinetics in biodegradation modeling. (4) Development of an efficient numerical algorithm capable of routinely solving fieldscale biodegradation analysis using limited computational resources with reasonable accuracy. |
