Complete removal of arsenic and zinc from a heavily contaminated acid mine drainage via an indigenous SRB consortium

Abstract

Acid mine drainages (AMD) are major sources of pollution to the environment. Passive bio-remediation technologies involving sulfate-reducing bacteria (SRB) are promising for treating arsenic contaminated waters. However, mechanisms of biogenic As-sulfide formation need to be better understood to decontaminate AMDs in acidic conditions. Here, we show that a high-As AMD effluent can be decontaminated by an indigenous SRB consortium. AMD water from the Carnoulès mine (Gard, France) was incubated with the consortium under anoxic conditions and As, Zn and Fe concentrations, pH and microbial activity were monitored during 94days. Precipitated solids were analyzed using electron microscopy (SEM/TEM-EDXS), and Extended X-Ray Absorption Fine Structure (EXAFS) spectroscopy at the As K-edge. Total removal of arsenic and zinc from solution (1.06 and 0.23mmol/L, respectively) was observed in two of the triplicates. While Zn precipitated as ZnS nanoparticles, As precipitated as amorphous orpiment (am-AsS) (33-73%), and realgar (AsS) (0-34%), the latter phase exhibiting a particular nanowire morphology. A minor fraction of As is also found as thiol-bound As (14-23%). We propose that the formation of the AsS nanowires results from AsS reduction by biogenic HS, enhancing the efficiency of As removal. The present description of As immobilization may help to set the basis for bioremediation strategies using SRB.

A Review of Acid Mine Drainage in a Water-Scarce Country: Case of South Africa

“…This is one of the processes that occur in compost bioreactors. Sulphate reducing bacteria (SRB) are used in these reactors which are very sensitive to acidity (even to moderate acidity) (Le Pape et al, 2017). For the process to run optimally, additional alkali may be required a part from the one produced by the SRB.…”

“…The process uses microbiological population and processes for conversion of sulphates to sulphides by SRB. Also, the precipitation of metal sulphides and conversion of any excess H 2 S produced to elemental sulphur using sulphide-oxidizing bacteria is part of the process (Le Pape et al, 2017). The general key features of the biological sulphate removal process include the pre-treatment to remove metals by precipitation as sulphides, hydroxides, or carbonates, the dosing of an electron donor and carbon source such as alcohol, sugar, H 2 gas, and even complex substrates such as sewage sludge, the addition of nutrients, including sources of nitrogen, phosphate, potassium, and trace minerals and sulphate reduction in an anaerobic reactor which converts sulphates to sulphides.…”

“…The general key features of the biological sulphate removal process include the pre-treatment to remove metals by precipitation as sulphides, hydroxides, or carbonates, the dosing of an electron donor and carbon source such as alcohol, sugar, H 2 gas, and even complex substrates such as sewage sludge, the addition of nutrients, including sources of nitrogen, phosphate, potassium, and trace minerals and sulphate reduction in an anaerobic reactor which converts sulphates to sulphides. The advantages of this technology are high removal of heavy metals, stable and small sludge production, very high water recovery ( about 98%) and low operation costs (for anaerobic process only) ( Le Pape et al, 2017) The weaknesses of the technology are sensitivity to environmental conditions such as temperature, acidity and pH , dependency on carbon dosing source, not able to adapt to fluctuating feed water quality, also the capital ( for both anaerobic and aerobic systems) and operational costs (aerobic systems) of these systems are significant ( Le Pape et al, 2017).…”

“…(Nordstrom et al, 2017;Perez et al, 2016;Simate, 2017). Some of the advantages of sulphides treatment include effective metal removals for most metals, low retention time requirement, and reduced sludge volumes (Nordstrom et al, 2017;Perez et a., 2016;Le Pape et al, 2017;Simate , 2017 ) The weaknesses of sulphides treatment are significant and include potential for toxic hydrogen sulphide gas emissions and residual sulphides in treatment of effluents. Also, the soluble sulphides process may result in smell problems and the complexities of the systems frequently result in higher capital and operating costs than lime treatment.…”

Removal of Arsenic Using Acid/Metal-Tolerant Sulfate Reducing Bacteria: A New Approach for Bioremediation of High-Arsenic Acid Mine Waters

“…Particularly, the growth of SRB can decline significantly under high As concentrations, due to its toxicity. Even so, several studies have shown that bacteria can tolerate low pH and can be an alternative for the treatment of acid mine waters [19][20][21][22]. Thus, bioremediation systems that are based on acid/metal-tolerant SRB could be used for the treatment of acidic metallic waters, but it is still necessary to study its feasibility of operation under specific conditions.…”