Sulfate-Reducing Bacteria (SRB)

Definition - What does Sulfate-Reducing Bacteria (SRB) mean?

Sulfate-reducing bacteria (SRB) are bacteria that can obtain energy by oxidizing organic compounds or molecular hydrogen while reducing sulfate to hydrogen sulfide. Most sulfate-reducing bacteria can also reduce other oxidized inorganic sulfur compounds, such as sulfite, thiosulfate/elemental sulfur.

Sulfate-reducing bacteria is the most important microbe for anaerobic corrosion of buried pipelines in soils. SRB can remove molecular hydrogen from the cathode, leading to cathodic depolarization of the metal surface. Iron sulfide or scale by SRB is accumulated on surfaces of metals, which accelerates the dissolution of the iron.

Corrosionpedia explains Sulfate-Reducing Bacteria (SRB)

SRB comprise several groups of bacteria that reduce sulphate to sulphide and produce carbonate which increase the pH. Sulfate-reducing bacteria can create problems when metal structures are exposed to sulfate-containing water by:

  • Interacting water and metal creating a layer of molecular hydrogen on the metal surface
  • Oxidizing the hydrogen while creating hydrogen sulfide or scale

Sulphate-rich wastewaters are generated by many industrial processes and cause an unbalance in the natural sulfur cycle. Sulfate-reducing bacteria are considered as a possible way to deal with acid mine waters that are produced by other bacteria.

SRB are capable of causing severe corrosion of iron material in a water system because they produce enzymes which have the power to accelerate the reduction of sulphate compounds to the corrosive hydrogen sulphide, thus SRB act as a catalyst in the reduction reaction.

SRB occur naturally in surface waters, including seawater. Bacteria accumulation can lead to pitting of steel, and the buildup of H2S increases the corrosiveness of the water, thus increasing the possibility of hydrogen blistering or sulfide stress cracking.

Some sulfate-reducing bacteria can reduce hydrocarbons such as benzene, toluene, ethylbenzene, and xylene, and have been used to clean up contaminated soils. Their use has also been proposed for other kinds of contaminations.

Since it also occurs in sour crude oil, it is the major microbial-induced corrosion causative bacteria in pipeline systems of oil & gas industries. Hydrogen sulfide from sulfate-reducing bacteria also plays a role in the biogenic sulfide corrosion of concrete. SRB can be used to biologically treat sulphate-rich wastewater.

Sulfate-reducing bacteria can cause the external or internal corrosion of water or wastewater pipelines and pipelines for petroleum and natural gas. The formation of galvanic cells by massive growth of sulfate-reducing bacteria under suitable conditions makes the corrosion much worse than just the effect of the hydrogen sulfide on the metal or concrete.

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