Framework for a Mixed-Culture Biofilm Model to Describe Oxidized Nitrogen, Sulfur, and Selenium Removal in a Biofilm Reactor

摘要

Biofilm reactors are an emerging environmental biotechnology used for the removal of seleniumrnfrom industrial wastewater. Bioreactor models for selenium removal that are based on thernmechanistic description of biofilms are few in number, but a dynamic model that is based onrnmechanistic principles (chemical and biochemical) and is capable of describing seleniumrnremoval is needed for efficient and more rigorous process design and optimization. This paperrnsummarizes variables, processes, and rate expressions for both chemical and biochemicalrnconversions inside a mixed-culture biofilm containing facultative heterotrophs, sulfate reducingrnbacteria, and autotrophic denitrifiers. Chemical and biochemical processes in the biofilm modelrnare based on theoretical considerations. Chemical processes include acid-base equilibriarnreactions primarily to describe substrate. The proposed mathematical description of ourrnmultispecies selenium removal biofilm is based on the general one-dimensional model ofrnWanner and Gujer (1985) and Wanner and Reichert (1995). It is assumed that ions do notrnundergo chemical or biological transformation, but the ions do not maintain a constantrnconcentration profile across the one-dimensional biofilm. State variables, processes, and kineticrnexpressions in the biofilm model are structured using (Peterson) matrix notation. The frameworkrnfor a mechanistic mathematical model describing a dynamic one-dimensional biofilm has beenrndeveloped and presented.