Effect of the THPS biocide on the structure and diversity of populations in a microbiologically induced corrosion process.

L. DOMINICCI; DEL PANNO M.T.; VIERA M.

Manchester

Simposio; IBBS 17 - The 17th International Biodeterioration & Biodegradation Symposium; 2017

In different stages of oil productionand processing, oil is storage in tanks, where sedimentation of water and sludge occurs with the consequent microbialcontamination provoking sludge accumulation, pipe and tank corrosion,emulsification and degradation of the product. The study of microbialcommunities present in those systems is of particular interest, especially the sulphatereducing microorganisms (SRM) (bacteria and arqueas), which are the main responsibleof the microbiologically influenced corrosion (MIC). Usually, the development of those microorganisms is controlled by theaddition of substances with bactericidal and/or bacteriostatic properties. Theobjective of the present work was to evaluate the effect of a biocide (bis(tetrakis hydroxymethyl) phosphonium sulfate; THPS) on MIC in a batchfractionated assay. Fifty flasks containing sterilized tank water wereinoculated with a bacterial suspension obtained by enrichment from a storage tankwater sample. A set of 25 flask was treated with THPS (250 ppm) leaving therest as control. Finally, a volume of oil and two carbon steel coupons were addedto all flasks and incubated under anoxic conditions. The population dynamicswere analysed by counting of heterotrophic bacteria and SRB for 60 days,observing the reduction of the planktonic SRB and the absence of the sessile SRBafter 30 days with THPS. However, a low density of SRB was newly detected formingbiofilm after 60 days. PCR-DGGE, with primers directed to the 16SrDNA ofBacteria and Arqueas, and the gene apsof SRB were used. From the analysis of the gel, differences in the communitydeveloped in the presence of THPS were observed. Sequencing analysis of 16SrDNAbefore and after the test allowed the identification of the predominant generaof the resilient populations. The electrochemical tests together with themorphological analysis performed by SEM of the exposed coupons showed aninhibitory effect of the biofilms.