Characterization of a Moderately Halotolerant Antimony-Removing Desulfovibrio sp. Strain Isolated from Landfill Leachate

Abstract

Antimony (Sb) is a harmful contaminant posing a risk to the environment and human health. Antimony-containing industrial wastewater often contains sulfate; therefore, it is suitable to apply sulfate-reducing bacteria (SRB) to remove Sb from such water. SRB anaerobically reduce sulfate to sulfide. Sb(V) is then reduced to Sb(III) by sulfide to produce an antimony trisulfide (Sb2S3) precipitate. This wastewater often exhibits a high salinity, which inhibits biological reactions. This study aimed to isolate and characterize a halotolerant bacterium capable of removing Sb from wastewater. A Desulfovibrio sp. strain was isolated from a mixed bacterial culture derived from a leachate sample from the Nam Son landfill in Vietnam. The isolated strain, NSLLH1b, removed 86% of the 50 mg/L of Sb(V) in 3 days at 180 mg/L of sulfate and 360 mg-C/L of lactate, at a pH of 7.0 and at 28 °C. It anaerobically removed >80% of the Sb(V) at 12.5–100 mg/L in 14 days at initial concentrations of >100 mg/L of sulfate, >250 mg-CL of lactate, and 0.2–15 g/L of NaCl, and a pH of 5–8, resulting in orange precipitation. An analysis using scanning electron microscopy–energy-dispersive X-ray spectroscopy confirmed that the precipitation consisted mainly of Sb and sulfur, supposedly as Sb2S3. This moderately halotolerant bacterium can be used for simultaneously removing Sb and sulfate from wastewater.