Microbial communities associated with the problem of bacterial regrowth in chloraminated drinking
water distribution systems (DS) have two main components: the autotrophic nitrifiers growing on
ammonia released from chloramine decay; and, the heterotrophs relying on biodegradable organic
material. While nitrifying populations have been extensively studied, microbial ecological
knowledge on heterotrophic populations is limited even though some studies have indicated that
heterotrophs may be the dominant component, or could even initiate regrowth in DS. The types of
heterotrophic organisms inhabiting chloraminated DS can potentially influence disinfection strategies.
The objectives of this study were to: identify heterotrophic bacteria in pilot- and full-scale DS using
culture-independent methods; and, comparatively evaluate heterotrophic communities to
understand if pilot-scale adequately represents the real scale. Monthly samples were obtained from
two parallel pilot-scale DS with high and low chloramine dose, and three full-scale systems at a
geographically different location, which included finished water and two separate tanks in
downstream DS. Two additional pilot systems were run for a shorter period and sampled for the
observation of early community development. Organisms in DS samples were identified based on
their 16S rRNA sequences and community fingerprints were generated using automated ribosomal
intergenic spacer analysis (ARISA). Most of the retrieved 16S rRNA sequences (>95%) were related
to heterotrophic bacteria. Both phylogenetic analyses and community fingerprints showed that the
heterotrophic communities in pilot- and full-scale were significantly different. However, a significant
number of sequences common to all systems excluding finished water indicated organisms that are
well-adapted to chloraminated environments. These included bacteria from the Sphingomonadales
order, Mycobacterium and Curvibacter genera, and an uncultured lineage of Rhizobiales. In addition,
there were full-scale distribution system sequences, previously not reported in other environments
related to drinking water. In conclusion, pilot-scale DS are useful for investigating certain
subpopulations of microbiota in chloraminated distribution systems, but are not perfect models that
can simulate the overall microbial dynamics in the full-scale. Culture-based methods are needed to
determine the potential environmental roles of the chloraminated distribution system organisms
discovered in this work using molecular techniques. Includes 32 references, tables, figures.
| Edition : | Vol. - No. |
| File Size : | 1
file
, 1.3 MB |
| Note : | This product is unavailable in Ukraine, Russia, Belarus |
| Number of Pages : | 20 |
| Published : | 11/01/2008 |
