Transport of dissolved hydrocarbons influenced by oxygen‐limited biodegradation: 1. Theoretical development

Abstract

Many hydrocarbons and related organic contaminants are rapidly degradable in the presence of oxygen. Unfortunately, exchange of oxygen with subsurface contaminant plumes is often slow. In this paper, equations are developed for simulating the simultaneous growth, decay, and transport of microorganisms, as well as the transport and removal of hydrocarbon and oxygen. These equations are solved by conventional numerical techniques to study the impact of microbial kinetics, horizontal mixing, adsorption, and vertical exchange with the unsaturated zone on biodegradation. In the region near the hydrocarbon source, any available oxygen will be rapidly consumed. In the body of the hydrocarbon plume, oxygen transport will be rate limiting and the consumption of oxygen and hydrocarbon can be approximated as an instantaneous reaction. The major sources of oxygen to the plume appear to be transverse mixing, advective fluxes when adsorption is significant and vertical exchange with the unsturated zone. In a companion paper (R. C. Borden et al., this issue), hydrocarbon transport is simulated at a hazardous waste site where oxygen‐limited biodegradation is known to occur.