Arsenite Oxidation by Alcaligenes Faecalis Strain O1201 in a Continuous-Flow Bioreactor

$\mathrm{As}\left(\mathrm{III}\right)$ oxidation by a pure bacterial culture, Alcaligenes faecalis strain O1201, was evaluated using a continuous stirred tank reactor. The bioreactor system was operated for 204 days under a wide range of influent $\mathrm{As}\left(\mathrm{III}\right)$ concentrations $(500–\mathrm{8,000}\mathrm{mg}∕\mathrm{L})$ and hydraulic retention times $(25.6–90.7\mathrm{h})$ with citrate as the sole carbon and energy source at pH 7 and 30°C. Nine steady-state conditions were obtained with $\mathrm{As}\left(\mathrm{III}\right)$ oxidation efficiency exceeding 95%. The system quickly recovered from an $\mathrm{As}\left(\mathrm{III}\right)$ overloading at $\mathrm{15,000}\mathrm{mg}∕\mathrm{day}∕\mathrm{L}$ while it operated at a HRT of $12.8\mathrm{h}$ . A material balance analysis revealed that nearly all the $\mathrm{As}\left(\mathrm{III}\right)$ removed in the continuous stirred tank reactor (CSTR) was oxidized to $\mathrm{As}\left(\mathrm{V}\right)$ and only 3.2% of the $\mathrm{As}\left(\mathrm{III}\right)$ fed to the CSTR was unaccounted for. Biokinetic parameters, $k_{\mathrm{mc}}=0.86\mathrm{mg}∕\mathrm{mg}$ cell dry weight/h and $K_c=70\mathrm{mg}∕\mathrm{L}$ , for $\mathrm{As}\left(\mathrm{III}\right)$ oxidation were obtained using the Monod expression and data obtained at steady-state conditions.