Biofouling occurs without exception in all water systems, with undesirable effects such as biocorrosion and deterioration of water quality. Drinking water associated biofilms represent a potential risk to human health by harbouring pathogenic or toxin-releasing microorganisms. This is the first study investigating the attached microbiota, with potential threat to human health, in a public water system in Romania. The presence and the seasonal variation of viable faecal indicators and opportunistic pathogens were investigated within naturally developed biofilms in a drinking water treatment plant. Bacterial frequencies were correlated with microbial loads in biofilms as well as with physical and chemical characteristics of biofilms and raw water. The biofilms assessed in the current study proved to be extremely active microbial consortia. High bacterial numbers were recovered by cultivation, including Pseudomonas aeruginosa, Escherichia coli, Aeromonas hydrophila, intestinal enterococci and Clostridium perfringens. There were no Legionella spp. detected in any biofilm sample. Emergence of opportunistic pathogens in biofilms was not significantly affected by the surface material, but by the treatment process. Implementation of a water safety plan encompassing measures to prevent microbial contamination and to control biofouling would be appropriate.
Microbial activity in drinking water-associated biofilmsAbbreviations DWTP -drinking water treatment plant; SRB -sulphate reducing bacteria; MPN -most probable number; TOC -total organic carbon. IntroductionDrinking water quality is dependent on the specific composition and activity of microbial populations present during water treatment, storage and distribution [1]. As in most aquatic environments, biofilms are the predominant mode of microbial growth in drinking water networks [2].Flemming et al. [3] estimated that approximately 95% of bacterial cells are attached to pipe walls, as biofilm communities, while less than 5% are found in the water phase. Bacterial adhesion and biofilm formation at the inner surfaces of water systems, from source abstraction to the consumers tap, represent a complex challenge to water professionals. Biofilms may play a beneficial role in drinking water treatment, as biological filters [4][5][6]. On the other hand, detrimental effects known as biofouling may occur, including microbially induced corrosion, disinfectant depletion, aesthetic problems i.e. colour, odour and taste degradation and microbiological deterioration of drinking water [7]. The complex structure of biofilms associated with drinking water processing and distribution is generally However, detrimental effects such as biofouling (i.e., biocorrosion and water quality deterioration) may also occur. In this study microbiological processes and factors influencing the activity of bacteria in biofilms were investigated by conventional cultivation methods. The presence of bacteria belonging to different ecophysiological groups was assessed during drinking water treatment, in biofilms developed on concrete, steel and sand surfaces. Influences of the treatment process, type of immersed material and physico-chemical characteristics of raw/bulk water and biofilms upon the dynamics of bacterial communities were evaluated. Results revealed intense microbial activity in biofilms occurring in the drinking water treatment plant of Cluj. Ammonification, iron reduction and manganese oxidation were found to be the predominant processes. Multiple significant correlations were established between the evolution of biofilm bacteria and the physico-chemical parameters of raw/ bulk water. The type of immersed material proved to have no significant influence upon the evolution of microbial communities, butthetreatmentstage,suggestingthattheprocessesappliedrestrictmicrobialgrowthnotonlyinbulkfluidbutinbiofilms,too.©VersitaSp.zo.o.Brought to you by | MIT Libraries Authenticated Download Date | 5/11/18 1:28 PM
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