Variability of bacterial biofilms under environmental stress conditions in water supply networks – a review

Abstract

This paper presents a literature review in the aspect of the phenomenon of occurrence of bacterial biofilm on internal surfaces of pipelines. The aim of the paper was to highlight the risks for water consumers resulting from the presence of biofilm in tap water pipelines, as well as the difficulties in water quality maintenance for the production plants. The paper addresses the many aspects of the presence of biofilm structures in water supply networks, as responses of biofilm to stress, highly specific environmental conditions in pipelines or potential strategies of biofilm removal. Stress conditions occurring in water supply networks as a result of water disinfection at water production plants and constant presence of a disinfectant in pipelines affect the development, variability, and biodiversity of biological films. The presence of biofilm resistant to the applied disinfectants in the water distribution network can threaten the health of water consumers, particularly when the biological membrane is inhabited by pathogenic forms. Various molecular mechanisms characteristic of biofilms permit the survival of microorganisms in water supply networks. They include among others phenomena of horizontal gene transfer or efflux pumps. The flexibility of bacterial genomes makes it difficult to eliminate microbiological films, rendering the applied disinfectants ineffective. Moreover, the removal of biofilm is much more difficult than the removal of planktonic cells. This paper also includes an insight into bacterial biodiversity in tap water systems reported in last years worldwide. As it is necessary to continuously search for new strategies of elimination of biological film present on the inner surface of pipelines in water supply networks, some new strategies proposed in the literature were also pointed out.