ABSTRACT
Microbiologically influenced corrosion (MIC) is an umbrella term for a range of mechanisms in which bacteria, such as sulfate-reducing bacteria (SRB), use elemental metals as part of their primary or secondary metabolism, producing H2S and degrading the structural integrity of the metal over time. Estimates vary, but the consensus is that over 40% of corrosion-related maintenance costs in the oil and gas industry are caused by MIC and reservoir souring.
Halophytes are plant species that grow irrigated by seawater. These plants are of interest because they can be grown in salt-affected soils where other crops cannot. Halophytes have been shown to produce a wide variety of very active phytochemicals, including potent antimicrobials as a coping strategy to the hostile environment that high salinity poses.
Extracts from these plants have proved to be inhibiting drug-resistant bacteria like E. coli and K. pneumoniae, and fungi like A. niger, and have been used in efficient contamination control in anaerobic fermentation (ethanol fermentation with yeast).
In our ongoing studies with industrial water systems, we have found that adding these extracts to flasks with a growing mixed microbial anaerobe culture resulted in a >99.5% decrease in SRB activity (measured by H2S concentration) and a >90% reduction in general microbial activity (measured by ATP activity). Visual inspection of stainless-steel coupons in the flasks showed visible corrosion products in untreated samples compared to samples with added halophyte extracts. Genetic sequencing of the bacterial cultures showed a significant reduction in the relative abundance of SRB species in cultures where extracts were added.
This study will highlight the importance of using alternatives to existing biocide regimes and discuss how this can be implemented for more sustainable mitigation of MIC in industrial water systems.
