Iron oxidation in a ceramic membrane bioreactor using acidophilic bacteria isolated from an acid mine drainage

Abstract

This study aims at investigating the iron oxidation and filtration performances of a ceramic membrane bioreactor (CMBR) inoculated with a mixed culture of iron-oxidizing acidophilic bacteria isolated from a real acid mine drainage (AMD). The CMBR was fed with a synthetic solution containing 1400 mg/L Fe2+ at pH 1.5-2.5. High iron oxidation performances (around 97%) at HRT range of 48-12 h were observed. Further decreasing HRT to 6 h led to significant decrease in the Fe2+ oxidation performances. CMBR was operated at varying fluxes. Significant fouling was not observed provided that flux was 5 LMH or lower. The mixed culture was composed of Acidiphilium cryptum and Alicyclobacillus cycloheptanicus. In addition to continuous flow experiments in CMBR, Fe2+ oxidation experiments were conducted under batch conditions. Oxidation kinetics well fitted Monod equation with a specific maximum iron oxidation rate and half-saturation constant of around 3.35 mg-Fe2+/(gVSS.min) and 549 mg/L, respectively.