Biogenic Hydrogen Sulfide Production Using Elemental Sulfur and Low-Cost Organic Substrates to Remove Metal Ions from Mining Effluents

Abstract

One of the best technologies available for metal removal from mining effluents is the precipitation of metals as sulfides. However, the high cost and difficulty in managing reagents limit its widespread application. Recent literature suggests the use of sulfur-reducing bacteria (S°RB) as a safe and effective alternative to producing H2S. Nevertheless, direct substrates for S°RB are high-cost low molecular compounds. This research aimed to evaluate the ability to produce sulfides by sulfur-reducing consortia in fixed-bed bioreactors using complex organic substrates. Consortia enriched using cellulose or Spirulina as electron donors were phylogenetically characterized by fluorescent in situ hybridization. Microorganisms belonging to Bacteria and Archaea were involved, being the most representative of the δ-Proteobacterias. The results obtained in test tube culture indicated that these consortia could use cellulose and Spirulina in alkaline conditions, resulting in high sulfide production. Upflowed fixed-bed bioreactors were implemented to establish optimal parameters., resulting in H2S volumetric productivities ranging from 1.94 to 2.94 mol/m3∙day. In conclusion, an active biomass with significant sulfidogenic activity can be generated in bioreactors under an upflowed regime using cellulose or Spirulina.

Keywords

• sulfur reducing bacteria
• elemental sulfur
• hydrogen sulfide
• metal removal
• bioreactors
• bioprocess