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We examined the variations of bacterial populations in treated drinking water prior to and after the final chlorine disinfection step at two different surface water treatment plants. For this purpose, the bacterial communities present in treated water were sampled after granular activated carbon (GAC) filtration and chlorine disinfection from two drinking water treatment plants supplying the city of Paris (France). Samples were analyzed after genomic DNA extraction, polymerase chain reaction (PCR) amplification, cloning, and sequencing of a number of 16S ribosomal RNA (rRNA) genes. The 16S rDNA sequences were clustered into operational taxonomic units (OTUs) and the OTU abundance patterns were obtained for each sample. The observed differences suggest that the chlorine disinfection step markedly affects the bacterial community structure and composition present in GAC water. Members of the Alphaproteobacteria and Betaproteobacteria were found to be predominant in the GAC water samples after phylogenetic analyses of the OTUs. Following the chlorine disinfection step, numerous changes were observed, including decreased representation of Proteobacteria phylotypes. Our results indicate that the use of molecular methods to investigate changes in the abundance of certain bacterial groups following chlorine-based disinfection will aid in further understanding the bacterial ecology of drinking water treatment plants (DWTPs), particularly the disinfection step, as it constitutes the final barrier before drinking water distribution to the consumer's tap.

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Aims:  We performed a preliminary assessment of the eukaryotic 18S rDNA diversity present in finished drinking water samples from three different surface water treatment plants supplying water to the city of Paris (France). Methods and Results:  A molecular analysis was performed on a sample from each site based on sequencing of PCR amplified and cloned 18S ribosomal RNA genes. Overall, the 18S rDNA sequences combined from all samples could be affiliated to the Amoebozoa (20·8% of the phylotypes), Ciliophora (25%), Metazoa (33·3%), Fungi (8·3%), Cercozoa (4·2%) and unclassified eukaryotes (8·3%) groups. Conclusions:  The 18S rDNA sequences affiliated to the Amoebozoa, Ciliophora and Metazoa lineages were found to be the most abundant phylotypes observed in the drinking water samples. Phylotypes found to be present in two, or all three, samples (41·7% of the total) may represent groups with members adapted to drinking water treatment plant (DWTP) ecosystem conditions. Significance and Impact of the Study:  This study shows that finished drinking water can contain 18S rDNA sequences representing a variety of eukaryotic taxa. Further research is needed to better characterize the eukaryotic biodiversity of DWTPs and the effects of the finished drinking water diversity on the downstream water distribution network.

e Nonpigmented and late-pigmenting rapidly growing mycobacteria (RGM) have been reported to commonly colonize water production and distribution systems. However, there is little information about the nature and distribution of RGM species within the different parts of such complex networks or about their clustering into specific RGM species communities. We conducted a large-scale survey between 2007 and 2009 in the Parisian urban tap water production and distribution system. We analyzed 1,418 water samples from 36 sites, covering all production units, water storage tanks, and distribution units; RGM isolates were identified by using rpoB gene sequencing. We detected 18 RGM species and putative new species, with most isolates being Mycobacterium chelonae and Mycobacterium llatzerense. Using hierarchical clustering and principal-component analysis, we found that RGM were organized into various communities correlating with water origin (groundwater or surface water) and location within the distribution network. Water treatment plants were more specifically associated with species of the Mycobacterium septicum group. On average, M. chelonae dominated network sites fed by surface water, and M. llatzerense dominated those fed by groundwater. Overall, the M. chelonae prevalence index increased along the distribution network and was associated with a correlative decrease in the prevalence index of M. llatzerense, suggesting competitive or niche exclusion between these two dominant species. Our data describe the great diversity and complexity of RGM species living in the interconnected environments that constitute the water production and distribution system of a large city and highlight the prevalence index of the potentially pathogenic species M. chelonae in the distribution network. N onpigmented and late-pigmenting rapidly growing mycobacteria (RGM) are ubiquitous in soil and water environments (1-6). Most are harmless saprophytes, but some, such as Mycobacterium chelonae and Mycobacterium abscessus, are opportunistic pathogens that are causing increasing concern (7-9). Potentially pathogenic RGM are associated with a wide spectrum of diseases in humans, including pulmonary tract, skin, soft tissue, and disseminated infections (10-14), mostly in patients with predisposing conditions (e.g., lung diseases, chronic obstructive pulmonary disease, cystic fibrosis, genetic predisposition, or immunosuppressive therapy). Contamination and hypersensitive reactions are often due to environmental exposure (associated with, for example, hot tubs, metalworking fluids, or contaminated dust) (15-19), and many outbreaks following invasive medical procedures have been reported over the last decade (20-25). Tap water may be an important source of contamination in urban environments (13,18,(26)(27)(28)(29)(30).RGM are commonly recovered from water treatment and distribution systems (31-38), probably because they can form biofilms (2, 39-41) and resist chlorination and oligotrophic conditions (42,43). Mycobacterium chelonae and Mycobact...

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During Autumn 1982, many consumers complained in Paris about a musty taste. Complaints were located only in a quarter of Paris which was supplied by a surface water treatment plant. The experiments and tests have shown that this taste appeared only in the network. Musty taste was detected neither on the river nor at the outlet of the plant. Some hypotheses have been made and experiments have been conducted later because this episode of complaints stopped suddenly. It appeared that some chlorophenols were produced in the plant. These compounds were biomethylated further by fungi in the network leading to chloroanisole which give a musty taste detectable a very low concentration.