The Interaction Between Adsorption And Microbial Growth In Biological Activated Carbon (Bac) Processes

Date of Award


Degree Type


Degree Name

Doctor of Philosophy (PhD)


Biomedical and Chemical Engineering


Chi Tien


Chemical engineering

Subject Categories

Biochemical and Biomolecular Engineering


The use of granular activated carbon is considered to be the most practical method for the removal of biologically persistent materials from water and wastewater. Although the nature and function of activated carbon are commonly conceived to be those of adsorbents, abundant evidence suggests that microbial activity greatly enhances the apparent adsorption capacity of granular activated carbon when carbon is used for the treatment of water and liquid waste.

In the analytical part of this work, a bi-layer microbial film model is formulated to describe the interaction of faculative denitrifier and activated carbon in carbon columns operated in expanded-bed mode. The model assumes that the microbial activity is confined mainly within the biofilm and the rate of biodegradation is first order and dissolved organic substrate limiting. Oxygen and/or nitrate are the electron acceptors for the energy yielding metabolism. Since oxygen is the preferential electron acceptor, it is depleted in the outer region of the biofilm. Nitrate diffuses through the outer aerobic region and becomes the electron acceptor in the inner anoxic region. Dissolved organic substrate is removed through its oxidation throughout the biofilm as well as adsorption onto activated carbon. For the adsorption process, linear adsorption isotherm and Glueckauf's linear driving force approximation are used. Bioregeneration is included in the model and is affected by the desorption of dissolved organic carbon.

Numerical algorithms for the solution of the bi-layer model are developed based on the method of characteristics commonly used for the solution of fixed-bed processes. Procedures which can be used for the determination of the model parameters are proposed.

In order to validate the bi-layer model, experiments on the removal of valeric acid (as the organic substrate), and sodium nitrate from aqueous solutions were conducted in expanded beds of activated carbon with and without the presence of oxygen. . . . (Author's abstract exceeds stipulated maximum length. Discontinued here with permission of school.) UMI


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