A Systematic Approach to Uncovering ...

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XVI International Conference on Computational Methods in Water Resources (CMWR-XVI) Ingeniørhuset

A Systematic Approach to Uncovering Scale-independent Rate Formulations for Bioreduction of Hematite in Sediments at a Field Site
Author:Chun-Wen Chen <ch674162@pegasus.cc.ucf.edu)> (University of Central Florida)
Gour-Tsyh (George) Yeh <gyeh@mail.ucf.edu> (University of Central Florida)
William D. Burgos <wdb3@email.psu.edu> (The Pennsylvania State University)
Morgan L. Minyard <mlm503@psu.edu> (The Pennsylvania State University)
Presenter:Chun-Wen Chen <ch674162@pegasus.cc.ucf.edu)> (University of Central Florida)
Date: 2006-06-18     Track: Special Sessions     Session: Multi-Disciplinary Approaches To Reactive Transport Simulation In Aquifer Systems

This presentation focuses on a systematic modeling approach in search of scale- independent rate formulations for biological reduction of hematite. Biological and chemical processes controlling Fe(III) reduction are very complex including direct bioreduction of ferric irons, microbial growth, secondary reactions of biogenic ferrous iron adsorptions, iron complexation, precipitation of ferrous minerals, and re-oxidation. A reaction network of five reactions was proposed to describe these processes under laboratory-controlled batch and column experiments which were conducted using sediments taken from a field site. The key reaction in the experiments is the direct bioreduction of hematite. Four possible rate formulations were proposed to describe this key reaction. Two kinds of simulations were conducted to verify the rate formulations and reaction parameters: the first one is batch modeling and the second one is column modeling. Simulation results indicated that while all rate formulations can adequately model batch experiments, only the formulation based on dual Monod kinetics with inhibition of ferrous iron and the effect of DMRB is “universal.” Furthermore, only this rate formulation can be upscaled to column experiments. Iterative modeling between batch and column experiments revealed that the equilibrium assumptions for surface hydration of hematite and adsorption of biogenic ferrous irons onto hematite may have to be revoked and substituted with kinetic rate formulations.