EFFECT OF IONS OF TRANSITIONAL d-METALS ON THE DYNAMICS OF MICROORGANISM SURVIVAL IN THE PRESENCE OF PHOSPHONIC ACIDS

Abstract

Metal corrosion is a complex process that can be substantially modified by the influence of various factors, including the presence of microorganisms in water-circulation systems. Proceeding from the above, in this work the effect of ions of transitional d-metals on the dynamics of microorganism survival was studied in the presence of well-known antisludge agents - oxyethylenediophosphonic acid (OEDFA) and nitrilotrimethylphosphonic acid (NTMFA). Microorganisms of the various systematic groups belonging also to the different physiological groups and having opposite types of life strategies have been selected for our researching: Bacillius sp. and Pseudomonas sp. They differ significantly in terms of survival opportunities under the influence of factors that can exist in closed water consumption systems (sudden temperature changes, oxygen starvation, the presence of toxic substances added to water for its conditioning). The influence of microorganisms on corrosion processes was studied in the stationary bioreactors in a volume of 125 ml. A solution of 0.1% NaCl was used as a model environment, to which corrosion inhibitors - d-metals (Zn2+ and Cr3+) and phosphonic acids (OEDFA and NTMFA) in concentration of 5 mg/dm3 had been adding.The results of our research have shown the possibility of transition metal ions act as regulators and modifiers of growth processes of microorganisms that are under conditions of osmotic stress and fasting. Representatives of the studied groups of the microorganisms demonstrated a different level of resistance to the presence of phosphonic acids and Zn2+ and Cr3+ ions at a concentration of 5 mg/dm3 in the model solution.So, in case of cultivating microbial cells in an osmotically unfavorable environment for them (0.1% NaCl solution without the addition of organic substances), almost linear dynamics of the dying out of bacterial cells of both species was observed without manifestations of significant difference. A similar effect may be due to the absence of nutrient elements in the model solution or the lack of osmotic-active components. Adding to the cultivation medium of phosphonic acids at a concentration of 5 mg/dm3 did not lead to statistically significant changes in the obtained dependencies. The greatest changes in the dynamics of microbial cell survival were observed when chromium ions were added to the cultivation medium, which was expressed as a decrease in the percentage of viable cells of Bacillus sp. (up to 24%) and a significant increase in survival among Pseudomonas sp. (up to 78%) compared to the survival without the addition of metal ions. The obtained results indicate the expediency of taking into account the possibility of the existence of microbiological contamination in reversible water supply systems in view of the influence of microbial cells on the processes of corrosion that occur there.Key words: ions of transient d-metals, phosphonic acids, microorganisms, survival dynamics, closed water supply systems