Hidden Threat in Drinking Water: Viable but Non-Culturable Microorganisms

Abstract

The monograph considers new methods of purification of drinking water from microorganisms that are in a viable but non-culturable state, and technologies for their neutralization and deep extraction using new approaches to assessment and monitoring of drinking water quality The first part of the monograph characterizes the viable but non-culturable state of microorganisms, which occurs under the influence of natural and anthropogenic stressors. However, the existing classical microbiological methods of analysis do not allow to detect them in water, because these microorganisms are not cultivated on classical differential diagnostic agar media. As a result, there is a danger of underestimating the number of viable pathogenic microorganisms and obtaining false negative results when analyzing drinking water at water treatment plants, which in turn can lead to a threat to the health of the consumer of such water. The second part presents the results of studies of the conditions of transition of microorganisms into a viable but non-culturable state when using sodium hypochlorite in different concentrations to disinfect water from the sanitary-indicative microorganism Escherichia coli and the yeast-like fungus Candida albicans. Based on experimental data, a method for detecting microorganisms that are in a viable but non-culturable state in drinking water has been developed. The method is based on the reclamation of cells that are in a viable but non-culturable state in liquid nutrient salt medium M-9, followed by their cultivation on agar differential diagnostic nutrient medium. The third part presents the results of research of drinking water of the city of Kyiv on the total number of microorganisms detected by classical microbiological methods of analysis and the proposed method of detection of microorganisms that are in a viable but non-culturable state. The fourth part of the monograph proposes an effective method of purification of drinking water from microorganisms that are in a viable but non-culturable state by contact flocculation, using as a flocculant cationic flocculant polydiallyldimethylammonium chloride (DB-45), which has antimicrobial properties. It is revealed that the application of the proposed technological method provides effective removal and inactivation of these microorganisms in drinking water. The monograph is intended for microbiologists, biotechnologists, doctors, veterinarians, employees of drinking water treatment plants, as well as students, graduate students and teachers of higher educational institutions of biological, medical and agricultural profile.