Substrate Availability, pH, and Temperature Influence Methanogenesis and Mild Steel Corrosion

ABSTRACT

Solid deposits of corroded pipelines in the Niger Delta were analyzed both chemically and microbiologically. The addition of substrate, especially acetate, significantly stimulated the methane production ranging from 0.85 to 1.60 mmole compared with 0.65 mmole of the control. Acetotrophic and hydrogenotrophic methanogens had their optimal methane production and corrosion rate at pH 5.5. All three types of methanogens produced the most methane at 37°C. Methane production by methanogens correlated strongly with corrosion rate. Pyrosequencing surveys show dominance of acetotrophic, hydrogenotrophic, and methylotrophic methanogens in the samples with no significant presence of sulfate-reducing bacteria (SRB), most likely due to the presence of the biocide, tetrakis-hydroxymethyl phosphonium sulfate. Our study shows that methanogens were one possible cause of pipeline failures in samples from the Niger Delta without the syntrophic association with SRB.

KEYWORDS:

• Methanogenesis
• microbiologically influenced corrosion
• pH
• substrate
• sulfate-reducing bacteria
• temperature

Acknowledgments

The authors thank an anonymous reviewer for suggesting that their results resemble those of Rotaru et al., showing that Methanosaeta could directly use electrons as well as acetate.

Funding

This work was supported through grants from Petroleum Technology Development Fund (PTDF), Nigeria. The authors acknowledged the grants from Gerrit Voordouw that funded the molecular aspect of the research work.