Assessment of bacterial pollution of closed water supply systems of galvanized productions

This work is devoted to assessment of the bacterial contamination of drainage systems in a galvanic production. In the course of the study, two strains of microorganisms which cause microbial contamination and lead to a decrease in the efficiency of the process equipment were isolated from water and wash sediment samples taken in the industrial water supply system of the enterprise and identified. Our study of the morphological and cultural properties of the isolated strains of bacteria has allowed them to be attributed to the genus Bacillus. As a result of a metagenomic analysis of the composition of microbial communities for the 16S rRNA gene (16S rDNA variable regions) according to the GenBank database on an ABI Prism 3730 automatic sequencer, the homology of the first strain with typical strains of the subgroup B. velezensis and B. amyloliquefaciens was established within 99.4–99.9%. When identifying the second isolated strain, the homology with B. altitudinis was 99.7%. Our study of the properties of the isolated strains has shown that they are neither pathogenic nor toxigenic. To reduce the microbial load in the technical water supply system, a series of experiments was carried out to select a biocide. Several variants of disinfectants of various groups were tested, namely: oxidizing ones (chloramine (a chlorine derivative of ammonia), hydrogen peroxide) and non-oxidizing ones (polymeric derivatives of polyhexamethylene guanidine (PHMG) produced by JSC NPK Mediana-filter and polyazolidine ammonium ionohydrate (PAG-M) produced by LLC “Constanta”). The polymeric compounds were found to be more effective than the chlorine-based disinfectants. An aqueous solution of polyhexamethylene guanidine had the best bactericidal effect on the microorganisms, therefore it was recommended to combat the existing bacterial contamination.