Biogenic sulfide corrosion

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Biogenic sulfide corrosion is a bacterially mediated process of forming hydrogen sulfide gas and the subsequent conversion to sulfuric acid that attacks concrete and steel within wastewater environments. The hydrogen sulfide gas is biochemically oxidized in the presence of moisture to form sulfuric acid. The effect of sulfuric acid on concrete and steel surfaces exposed to severe wastewater environments can be devastating. [1] In the USA alone, corrosion causes sewer asset losses estimated at $14 billion per year. [2] This cost is expected to increase as the aging infrastructure continues to fail. [3]

Contents

Environment

Corrosion may occur where stale sewage generates hydrogen sulfide gas into an atmosphere containing oxygen gas and high relative humidity. There must be an underlying anaerobic aquatic habitat containing sulfates and an overlying aerobic aquatic habitat separated by a gas phase containing both oxygen and hydrogen sulfide at concentrations in excess of 2 ppm. [4]

Conversion of sulfate to hydrogen sulfide

Fresh domestic sewage entering a wastewater collection system contains proteins including organic sulfur compounds oxidizable to sulfates (SO2−4) and may contain inorganic sulfates. [5] Dissolved oxygen is depleted as bacteria begin to catabolize organic material in sewage. In the absence of dissolved oxygen and nitrates, sulfates are reduced to hydrogen sulfide (H2S) as an alternative source of oxygen for catabolizing organic waste by sulfate-reducing bacteria (SRB), identified primarily from the obligate anaerobic species Desulfovibrio . [4]

Hydrogen sulfide production depends on various physicochemical, topographic, and hydraulic parameters [6] such as:

Conversion of hydrogen sulfide to sulfuric acid

Some hydrogen sulfide gas diffuses into the headspace environment above the wastewater. Moisture evaporated from warm sewage may condense on unsubmerged walls of sewers, and is likely to hang in partially formed droplets from the horizontal crown of the sewer. As a portion of the hydrogen sulfide gas and oxygen gas from the air above the sewage dissolves into these stationary droplets, they become a habitat for sulfur oxidizing bacteria (SOB), of the genus Acidithiobacillus . Colonies of these aerobic bacteria metabolize the hydrogen sulfide gas to sulfuric acid (H2SO4). [4]

Corrosion

Sulfuric acid produced by microorganisms will interact with the surface of the structure material. For ordinary Portland cement, it reacts with the calcium hydroxide in concrete to form calcium sulfate. This change simultaneously destroys the polymeric nature of calcium hydroxide and substitutes a larger molecule into the matrix causing pressure and spalling of the adjacent concrete and aggregate particles. [7] The weakened crown may then collapse under heavy overburden loads. [8] Even within a well-designed sewer network, a rule of thumb in the industry suggests that 5% of the total length may/will suffer from biogenic corrosion. In these specific areas, biogenic sulfide corrosion can deteriorate metal or several millimeters per year of concrete (see Table).

SourceThickness loss

(in mm/year)

Material type
US EPA, 1991 [9] 2.5 – 10Concrete
Morton et al., 1991 [10] 2.7Concrete
Mori et al., 1992 [11] 4.3 – 4.7Concrete
Ismail et al., 1993 [12] 2 – 4Mortar
Davis, 1998 [13] 3.1Concrete
Monteny et al., 2001 [14] 1.0 – 1.3Mortar
Vincke et al., 2002 [15] 1.1 – 1.8Concrete

For calcium aluminate cements, processes are completely different because they are based on another chemical composition. At least three different mechanisms contribute to the better resistance to biogenic corrosion: [16]

A mortar made of calcium aluminate cement combined with calcium aluminate aggregates, i.e. a 100% calcium aluminate material, will last much longer, as aggregates can also limit microorganisms' growth and inhibit the acid generation at the source itself.

Prevention

There are several options to address biogenic sulfide corrosion problems: impairing H2S formation, venting out the H2S, or using materials resistant to biogenic corrosion. For example, sewage flows more rapidly through steeper gradient sewers reducing time available for hydrogen sulfide generation. Likewise, removing sludge and sediments from the bottom of the pipes reduces the amount of anoxic areas responsible for sulfate-reducing bacteria growth. Providing good ventilation of sewers can reduce atmospheric concentrations of hydrogen sulfide gas and may dry exposed sewer crowns, but this may create odor issues with neighbors around the venting shafts. Three other efficient methods can be used involving continuous operation of mechanical equipment: chemical reactant like calcium nitrate can be continuously added in the sewerage water to impair the H2S formation, an active ventilation through odor treatment units to remove H2S, or an injection of compressed air in pressurized mains to avoid the anaerobic condition to develop. In sewerage areas where biogenic sulfide corrosion is expected, acid-resistant materials like calcium aluminate cements, PVC or vitrified clay pipe may be substituted to ordinary concrete or steel sewers.

Existing structures that have extensive exposure to biogenic corrosion such as sewer manholes and pump station wet wells can be rehabilitated. Rehabilitation can be done with materials such as a structural epoxy coating, this epoxy is designed to be both acid-resistant and strengthen the compromised concrete structure.

See also

Related Research Articles

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Hydrogen sulfide is a chemical compound with the formula H2S. It is a colorless chalcogen-hydride gas, and is poisonous, corrosive, and flammable, with trace amounts in ambient atmosphere having a characteristic foul odor of rotten eggs. Swedish chemist Carl Wilhelm Scheele is credited with having discovered the chemical composition of purified hydrogen sulfide in 1777.

<span class="mw-page-title-main">Sewerage</span> Infrastructure that conveys sewage or surface runoff using sewers

Sewerage is the infrastructure that conveys sewage or surface runoff using sewers. It encompasses components such as receiving drains, manholes, pumping stations, storm overflows, and screening chambers of the combined sewer or sanitary sewer. Sewerage ends at the entry to a sewage treatment plant or at the point of discharge into the environment. It is the system of pipes, chambers, manholes or inspection chamber, etc. that conveys the sewage or storm water.

Sulfide (also sulphide in British English ) is an inorganic anion of sulfur with the chemical formula S2− or a compound containing one or more S2− ions. Solutions of sulfide salts are corrosive. Sulfide also refers to large families of inorganic and organic compounds, e.g. lead sulfide and dimethyl sulfide. Hydrogen sulfide (H2S) and bisulfide (SH−) are the conjugate acids of sulfide.

Anaerobic respiration is respiration using electron acceptors other than molecular oxygen (O2). Although oxygen is not the final electron acceptor, the process still uses a respiratory electron transport chain.

The purple sulfur bacteria (PSB) are part of a group of Pseudomonadota capable of photosynthesis, collectively referred to as purple bacteria. They are anaerobic or microaerophilic, and are often found in stratified water environments including hot springs, stagnant water bodies, as well as microbial mats in intertidal zones. Unlike plants, algae, and cyanobacteria, purple sulfur bacteria do not use water as their reducing agent, and therefore do not produce oxygen. Instead, they can use sulfur in the form of sulfide, or thiosulfate (as well, some species can use H2, Fe2+, or NO2−) as the electron donor in their photosynthetic pathways. The sulfur is oxidized to produce granules of elemental sulfur. This, in turn, may be oxidized to form sulfuric acid.

<i>Acidithiobacillus</i> Genus of bacteria

Acidithiobacillus is a genus of the Acidithiobacillia in the phylum "Pseudomonadota". This genus includes ten species of acidophilic microorganisms capable of sulfur and/or iron oxidation: Acidithiobacillus albertensis, Acidithiobacillus caldus, Acidithiobacillus cuprithermicus, Acidithiobacillus ferrianus, Acidithiobacillus ferridurans, Acidithiobacillus ferriphilus, Acidithiobacillus ferrivorans, Acidithiobacillus ferrooxidans, Acidithiobacillus sulfuriphilus, and Acidithiobacillus thiooxidans.A. ferooxidans is the most widely studied of the genus, but A. caldus and A. thiooxidans are also significant in research. Like all "Pseudomonadota", Acidithiobacillus spp. are Gram-negative and non-spore forming. They also play a significant role in the generation of acid mine drainage; a major global environmental challenge within the mining industry. Some species of Acidithiobacillus are utilized in bioleaching and biomining. A portion of the genes that support the survival of these bacteria in acidic environments are presumed to have been obtained by horizontal gene transfer.

<span class="mw-page-title-main">Sulfate-reducing microorganism</span> Microorganisms that "breathe" sulfates

Sulfate-reducing microorganisms (SRM) or sulfate-reducing prokaryotes (SRP) are a group composed of sulfate-reducing bacteria (SRB) and sulfate-reducing archaea (SRA), both of which can perform anaerobic respiration utilizing sulfate (SO2−
4) as terminal electron acceptor, reducing it to hydrogen sulfide (H2S). Therefore, these sulfidogenic microorganisms "breathe" sulfate rather than molecular oxygen (O2), which is the terminal electron acceptor reduced to water (H2O) in aerobic respiration.

<span class="mw-page-title-main">Sewer gas</span> Gases produced and collected in sewer systems

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The important sulfur cycle is a biogeochemical cycle in which the sulfur moves between rocks, waterways and living systems. It is important in geology as it affects many minerals and in life because sulfur is an essential element (CHNOPS), being a constituent of many proteins and cofactors, and sulfur compounds can be used as oxidants or reductants in microbial respiration. The global sulfur cycle involves the transformations of sulfur species through different oxidation states, which play an important role in both geological and biological processes. Steps of the sulfur cycle are:

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Sulfur-reducing bacteria are microorganisms able to reduce elemental sulfur (S0) to hydrogen sulfide (H2S). These microbes use inorganic sulfur compounds as electron acceptors to sustain several activities such as respiration, conserving energy and growth, in absence of oxygen. The final product of these processes, sulfide, has a considerable influence on the chemistry of the environment and, in addition, is used as electron donor for a large variety of microbial metabolisms. Several types of bacteria and many non-methanogenic archaea can reduce sulfur. Microbial sulfur reduction was already shown in early studies, which highlighted the first proof of S0 reduction in a vibrioid bacterium from mud, with sulfur as electron acceptor and H
2 as electron donor. The first pure cultured species of sulfur-reducing bacteria, Desulfuromonas acetoxidans, was discovered in 1976 and described by Pfennig Norbert and Biebel Hanno as an anaerobic sulfur-reducing and acetate-oxidizing bacterium, not able to reduce sulfate. Only few taxa are true sulfur-reducing bacteria, using sulfur reduction as the only or main catabolic reaction. Normally, they couple this reaction with the oxidation of acetate, succinate or other organic compounds. In general, sulfate-reducing bacteria are able to use both sulfate and elemental sulfur as electron acceptors. Thanks to its abundancy and thermodynamic stability, sulfate is the most studied electron acceptor for anaerobic respiration that involves sulfur compounds. Elemental sulfur, however, is very abundant and important, especially in deep-sea hydrothermal vents, hot springs and other extreme environments, making its isolation more difficult. Some bacteria – such as Proteus, Campylobacter, Pseudomonas and Salmonella – have the ability to reduce sulfur, but can also use oxygen and other terminal electron acceptors.

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<span class="mw-page-title-main">Calcium aluminate cements</span> Rapidly setting hydraulic cements

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References

Notes

  1. ↑ O'Dea, Vaughn, "Understanding Biogenic Sulfide Corrosion", MP (November 2007), pp. 36-39.
  2. ↑ Brongers et al., 2002
  3. ↑ Sydney et al., 1996; US EPA, 1991
  4. 1 2 3 Sawyer&McCarty p.461&462
  5. ↑ Metcalf & Eddy p.259
  6. ↑ US EPA, 1985
  7. ↑ USDI pp.9&10
  8. ↑ Hammer p.58
  9. ↑ United States Environmental Protection Agency, 1991. Hydrogen Sulphide Corrosion in Wastewater Collection and Treatment Systems (Technical Report)
  10. ↑ Morton R.L., Yanko W.A., Grahom D.W., Arnold R.G. (1991) Relationship between metal concentrations and crown corrosion in Los Angeles County sewers. Research Journal of Water Pollution Control Federation, 63, 789–798.
  11. ↑ Mori T., Nonaka T., Tazaki K., Koga M., Hikosaka Y., Noda S. (1992) Interactions of nutrients, moisture, and pH on microbial corrosion of concrete sewer pipes. Water Research, 26, 29–37.
  12. ↑ Ismail N., Nonaka T., Noda S., Mori T. (1993) Effect of carbonation on microbial corrosion of concrete. Journal of Construction Management and Engineering, 20, 133-138.
  13. ↑ Davis J.L. (1998) Characterization and modeling of microbially induced corrosion of concrete sewer pipes. Ph.D. Dissertation, University of Houston, Houston, TX.
  14. ↑ Monteny J., De Belie N., Vincke E., Verstraete W., Taerwe L. (2001) Chemical and microbiological tests to simulate sulfuric acid corrosion of polymer-modified concrete. Cement and Concrete Research, 31, 1359-1365.
  15. ↑ Vincke E., Van Wanseele E., Monteny J., Beeldens A., De Belie N., Taerwe L., Van Gemert D., Verstraete W. (2002) Influence of polymer addition on biogenic sulfuric acid attack. International Biodeterioration and Biodegradation, 49, 283-292.
  16. ↑ Herisson J., Van Hullebusch E., Gueguen Minerbe M., Chaussadent T. (2014) Biogenic corrosion mechanism: study of parameters explaining calcium aluminate cement durability. CAC 2014 – International Conference on Calcium Aluminates, May 2014, France. 12 p.
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