W11 PM Advances in Biorestoration Strategies for Contaminated Sediments
Wednesday, 16 November 2005: 1:50 PM - 5:30 PM in 343-344

(HAW-1122-310045) Biogeochemical Considerations for Model Predictions of Solute Biodegradation in Sorbent-Water Systems.

Haws, N¹, Bouwer, E¹, Ball, W¹, ¹ Johns Hopkins University

ABSTRACT- The bioavailability of a contaminant for microbial uptake (and thus the effectiveness of the bioremediation strategy) is dependent on how contaminants are sequestered by sediment particles and interact with co-existing solutes. It is therefore important to consider the biogeochemical conditions for which the contaminant(s) exist in order to understand how sensitive modeling predictions of bioremediation efficacy are to the assumptions inherent in the model formulation. In this study, a suite of numerical simulations of hypothetical batch system are conducted to investigate the sensitivity of different modeling approaches in simulating the bio-attenuation of co-existing solutes (TCE and toluene) in sorbent - water systems. The results are insensitive to the type of sorption model in systems with low sorption strength and slow biodegradation rates, and insensitive to the biodegradation rate model if mass transfer controlled. Also, differences among model results are generally greater when evaluated in terms of total mass removal rather than aqueous phase concentration reduction. In general, the fate of the cometabolite is more sensitive to the proper consideration of co-solute effects than is the fate of the primary substrate. A preliminary guide for assess such sensitivities for a given system is a graphical comparison of a characteristic mass transfer rate coefficient (mt) versus a characteristic biodegradation rate coefficient (bio). By indicating relative sensitivities to the different processes and how these sensitivities may be expected to change with time, this graphical approach can guide the selection of an appropriate level of model complexity needed to suitably predict bioremediation.

Key words: Sediments