The microbiological composition of the biofilm, formed on the surface of sewage treatment constructions grids, and the seasonal variation in the number of its main components were examined. The strain Ch.5 was isolated and identified from the enrichment culture of sulfate-reducing bacteria. It was classified as belonging to Desulfomicrobium genus according to its physiological and biochemical characteristics.

Abstract.1 A number of new quaternary pyridinium salts with amide fragment and aryl substituents have been obtained, demonstrating the inhibition efficiency of 50.0-97.2 % under the biocorrosion of mild steel, induced with sulfate-reducing bacteria of Desulfovibrio and Desulfomicrobium genera. It has been established that inhibition efficiency of the studied quaternary salts is caused by their effect on microbiological factor.

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Triazoloazepinium bromides act as biocides against sulfate-reducing bacteria and can produce an effect on mild steel microbial corrosion. It has been established that under the competing adsorption, the compounds with the properties of corrosion inhibitors can form a film, which protects the steel surface, before it is settled by corrosively active microorganisms.The protective film ensures the inhibition efficiency of up to 98.7%. With triazoloazepinium bromides of the 2nd group, corrosively active microorganisms colonize the steel surface before the inhibitor creates the protective layer. In this case, the biocorrosion accelerates by up to 6.25 times. Different effect of triazoloazepinium bromides on steel biocorrosion rate is explained by the molecular structure.

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