Applications of sulfate reducing prokaryotes

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The use of SRB for treatment of acidic metal and sulfate containing process- and wastewaters in mining and metallurgical industries has become a topic of scientific and commercial interest in the last 15 years. SRB are used to improve water quality by removing metals and raising pH in liquids and effluents. A side effect may be that metal is also recovered.

Process liquid & effluent factorsSulfate reducing prokaryotesEngineered environments for sulfate reducing prokaryotesH2S and alkalinityBiological production of immobilization chemicalsSulfidesPhysicochemical factorsMass-transferTemperaturePHRedox potentialO2CO2NutrientsFe2+Fe3+InhibitorsHeavy metalsStrainMicrobial diversityPopulation densityActivitySpatial distributionMetal toleranceAdaptation abilityMicrobial factorsMetal Bearing SolutionsMetal Bearing SolutionsMetal Bearing SolutionsMetal Bearing Solutions
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Biological treatment of waste- and process water from the mining and metallurgical industries offers an interesting alternative to conventional technologies. Biological treatment essentially consists of biological reduction of sulfur oxyanions to sulfide followed by chemical precipitation of metal sulfides. In this way dissolved metals and sulphate are concentrated into a solid. Compared to conventional chemical treatment with lime and hydroxide, the biological treatment can achieve much lower effluent sulphate (< 250 mg/l vs. ~1500 mg/l) and metal (ppb- vs. ppm-level) concentrations. This high rate technology has a constant and predictable effluent quality; this in contrast to for example constructed wetlands where the removal of metals can range between 0 and 99%[1]

The first full-scale applications for groundwater treatment with SRB was realised in 1992 by PAQUES BV at the site of Nyrstar Budel B.V. The installation in the picture uses an organic energy source (electron donor).

First full-scale biological sulfate reduction installation.
First full-scale biological sulfate reduction installation.

For a more concentrated sulfate solution and high load applications, a system with hydrogen gas is preferred.

Full scale biological sulfate reduction installation with hydrogen gas as electron donor.
Full scale biological sulfate reduction installation with hydrogen gas as electron donor.

In environments where groundwater has been contaminated by waste water and acid mine drainage, microbial sulfate reduction can be exploited in subsurface permeable reactive barriers. A permeable reactive barrier is a passive, in-situ technique: groundwater treatment proceeds within the aquifer and long-term maintenance of the installation is unnecessary. This method consists of installing an appropriate reactive material into the aquifer, so that contaminated water flows through the material (see figure below). The reactive material induces chemical reactions that remove the contaminants from the water or otherwise cause a change that decreases the toxicity of the contaminated water. For the treatment of water contaminated with acid mine drainage, a number of studies have shown the effectiveness of this method.

Image:Mimi_barrier.png

References

  1. Aisling D. O’Sullivan, Declan A. Murray, Marinus L. Otte, Mine Wat. Env., 23(2) (2004), 58-65.

See also

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