Modeling chromium(VI) reduction by Escherichia coli 33456 using ceramic pearl as a supporting medium

A mathematical model was developed to describe the reduction of Cr(VI) by Escherichia coli (E. coli) 33456 in a fixed biofilm reactor. A laboratory-scale column reactor was conducted to verify the model system. The batch kinetic tests were independently conducted to determine the biokinetic parameters used in the model simulation. With the assumed values of initial biofilm thickness (L _f0), the mathematical model simulated well the experimental results for Cr(VI) effluent concentration, effluent concentration of suspended E. coli cells, and Cr(III) production. The concentration of suspended E. coli cells reached up to 1.2 mg cell/L while the thickness of attached E. coli cells was estimated to be 32.6 μm at a steady-state condition. At the steady state, the removal efficiency of Cr(VI) was about 92 % and the effluent concentration of Cr(III) was approximately 1.6 mg/L. The approaches presented in this study can be employed for the design of a pilot-scale or full-scale fixed biofilm reactor to treat Cr(VI)-containing wastewater.