Variations of bacterial 16S rDNA phylotypes prior to and after chlorination for drinking water production from two surface water treatment plants

Abstract

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.

Bacterial community change through drinking water treatment processes

“…Using culture-dependent technique, Norton and LeChevallier (2000) found that Pseudomonas (affiliated with Gammaproteobacteria) and Sphingomonas (affiliated with Alphaproteobacteria) were the predominant isolates in the BAC filter effluent. A recent study using clone library analysis indicated that Alphaproteobacteria and Betaproteobacteria were predominant in the BAC filter effluent (Poitelon et al 2010). In this study, Alphaproteobacteria, Betaproteobacteria, and Actinobacteria were found to be major bacterial groups in the BAC filter effluent.…”

“…The bar represents 1 % sequence divergence DWDs (Lu et al 2013). Moreover, the composition of the bacterial community in chlorinated (or chloraminated) water might be much different from that in non-chlorinated (or non-chloraminated) water (Norton and LeChevallier 2000;Berry et al 2006;Eichler et al 2006;Kormas et al 2010;Poitelon et al 2010). Unfortunately, very few research works have provided the phylogenetic description of bacterial community in the sand filter effluent and the BAC filter effluent.…”

“…However, biomass developed in biofilters might be a source of bacterial contamination in DWDS (Niemi et al 2009;Liao et al 2012). Therefore, concerns regarding the microorganisms in the effluents of filters have been raised (Norton and LeChevallier 2000;Poitelon et al 2010). Pathogenic or opportunistic microorganisms from may enter DWDS as a result of improper management (Villarreal et al 2010).…”

“…Since the presence of certain bacteria may lead to water quality problems in the downstream DWDS, knowledge of the bacterial ecology in the effluents of drinking water treatment units will be of practical importance. Unfortunately, only very few works have investigated the microbial communities in the effluents of drinking water treatment units (Eichler et al 2006;Poitelon et al 2010). Therefore, the bacterial community in the effluents of drinking water filters remains poorly understood.…”

“…It is generally accepted that chlorination can result in a dramatic shift in the composition of the bacterial community (Norton and LeChevallier 2000;Eichler et al 2006;Kormas et al 2010;Poitelon et al 2010), yet little information is available on the bacterial community change through other drinking water treatment units. Pinto et al (2012) found that filtration by dual media rapid sand filters in a drinking water plant played a primary role in shaping the bacterial community in DWDS.…”