Antimony Removal in a Lab-scale Anaerobic Upflow Fluidized Bed Reactor Packed with PVA Gel-beads Inoculated with a Desulfovibrio sp. Strain

Abstract

 A lab-scale anaerobic upflow fluidized bed reactor (FBR) was developed to treat synthetic wastewater containing antimony (Sb) and sulfate. The FBR was filled with polyvinyl alcohol (PVA) gel beads and inoculated with a Desulfovibrio sp. strain as a sulfate-reducing bacterium. Desulfovibrio sp. can dissimilatory reduce sulfate to sulfides. Sb(V) is then reduced to Sb(III) by the sulfide formed, which precipitates antimony trisulfide (Sb₂S₃). Wastewater contained 22.8 mg/L Sb, 98.6 mg/L sulfate, and 360 mg C/L lactate. The FBR was operated with hydraulic retention time (HRT) of 24 to 1 h at 28 ℃. The removal of sulfate and Sb decreased from 96.8% to 89.4% and from 93.7% to 49.0%, respectively, when the HRT was reduced from 24 h to 3 h. The maximum removal rate for sulfate and Sb was 68.6 mg/L/h at HRT of 1 h and 3.76 mg/L/h at HRT of 3 h, respectively. These results indicate that the rate-limiting step for Sb removal in the FBR is the chemical reduction of Sb(V) by sulfide rather than enzymatic sulfate reduction. The PVA gel beads and sludge accumulated in the FBR consisted mainly of Sb and sulfur, presumably Sb₂S₃. The Sb content in the PVA－gel beads and sludge increased up to 15.7 mg/g－dry and 109 mg/g－dry, respectively.