Selenium Reduction by Batch Cultures of Escherichia coli Strain EWB32213

Batch studies on selenium reduction were conducted to assess the reduction rate of Se(VI) as well as Se(IV) using Escherichia coli Strain EWB32213 isolated in the laboratory. The rate of Se(VI) reduction to Se(IV) in the first stage was faster than that of Se(IV) reduction to Se(0) in the second stage. The Se(VI) reduction was complete within 1.5 days, with the Se(VI) concentration ranging from 10 to 400 mg/L, while a Se(IV) concentration higher than 100 mg/L was only partially reduced to Se(0) after 10 days. The batch culture was capable of reducing Se(VI) and Se(IV) upon Se(VI) and Se(IV) respikes, albeit at decreasing rates. The data were successfully analyzed with a two-stage kinetic model using both the Simplex and Universal Global algorithms embedded in a computer program package. Eight biokinetic parameters of μ1 of 1.9875 mgVSS/mgSe(VI)-d-1, μ2 of 0.1206 mgVSS/mg Se(IV)-d-1, K1 of 206.8446 mg/L, K2 of 50.0748 mg/L, KI of 792.0883 mg/L, b of 0.3824 d-1, Y1 of 0.6299 mgVSS/mg Se(VI), and Y2 of 0.7004 mgVSS/mg Se(IV) were obtained. The good fit of the data to the model simulation indicated the robustness and rigorousness of the model.