Fungi in water samples of a full-scale water work

This study aimed to assess the efficacy of the treatments used to eliminate fungal propagules in water plants and to investigate the biodiversity of fungal taxa in treated and drinking water. We investigated water from nine sites in two water plants and from one fountain. Up to 25 samples from each site were analysed. Identification of fungi was carried out mainly by matrix-assisted laser desorption ionisation–time of flight (MALDI-TOF) mass spectrometry (MS) or, if no MALDI-TOF MS reference spectra were available, by internal transcribed spacer (ITS), partial transcription elongation factor 1 (tef1) or partial beta-tubulin sequencing. A total of 92 taxa could be identified by either MALDI-TOF MS or sequencing. The taxonomic spectrum is in agreement with that reported in publications on fungal communities of drinking water. The treatment steps used reduced significantly fungal colonisation of the water: even if the final products (drinking water) from both plants differ statistically in their fungal colony-forming units (CFUs) content, the difference is not biologically meaningful. A multivariate analysis showed a separation of the sampling sites of the two plants, reflecting the different origin of the raw water and the different water treatment processes. Reduction of fungal CFU and number of taxa by the treatment steps was similar in the two plants and not influenced by the treatment methods. In both plants, the first step was responsible for at least 90% reduction of CFU. Low CFU levels were maintained over the whole process chain and the water transport to the drinking water fountain did not significantly modify the CFU number.