A mathematical Model for Cadmium Removal using A sulfate Reducing Bacterium: Desulfovibrio alaskensis 6SR

In this work, an unstructured-type mathematical model was developed to simulate cadmium (Cd2+) removal by Desulfovibrio alaskensis 6SR, which is a recently described sulfate reducing bacterium, whose capacity for removing heavy metals are being studied. Three processes are considered in the model: 1) the sulfate reduction process, 2) the consumption of lactate as carbon source, and 3) the metal removal. The model was tested with different initial Cd2+ concentrations (50, 100, 170, and 190 mg/L), and it accurately predicted the behavior of experimental data with satisfactory correlation coefficients (R2 > 0.97). In addition, the model showed that the H2S production rate and initial concentration of Cd2+ are key operating variables in a bioreactor. Desulfovibrio alaskensis 6SR was able to remove more than 99.9% of cadmium in a batch process, where the initial concentration was 170 mg/L. The model, applied to a continuous process, predicted a maximum Cd2+ removal of 99.1% with the same initial concentration. Also, the model predicted the inhibitory effect of initial Cd2+ concentrations above 190 mg/L. The mathematical model developed can be used for optimization and control purposes.