Assessing chromate reduction by dissimilatory iron reducing bacteria using mathematical modeling.

Area of Science:

• Environmental microbiology
• Biogeochemistry
• Chemical engineering

Background:

• Chromate (Cr (VI)) is a widespread environmental contaminant in soil and groundwater.
• Reduction to trivalent chromium (Cr (III)) mitigates its toxicity.
• Dissimilatory iron-reducing bacteria (IRB) offer a promising approach for Cr (VI) remediation.

Purpose of the Study:

• To develop and compare mathematical models for Cr (VI) reduction pathways.
• To investigate the performance of an IRB-based reactor for Cr (VI) treatment.
• To elucidate the interplay between microbial and chemical reduction mechanisms.

Main Methods:

• Development of three mathematical models: chemical reduction, microbial reduction, and combined biotic-abiotic reduction.
• Simulation of an IRB-based stirred-flow reactor treating Cr (VI) contaminated medium.
• Model validation using experimental data under varying conditions.

Main Results:

• The model incorporating both chemical and microbial Cr (VI) reduction pathways accurately predicted experimental data.
• Single-pathway models failed to capture the system's performance.
• The two-pathway model's validity was confirmed by independent experimental results.
• Organic carbon availability and Cr (VI) loading rates influenced the relative contribution of each pathway.

Conclusions:

• Both microbial and chemical pathways are crucial for Cr (VI) reduction mediated by IRB.
• A combined biotic-abiotic reduction model is essential for accurate system prediction.
• Reactor performance is sensitive to operational parameters like carbon source and Cr (VI) concentration.