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#Ed rust, belleville,il free
The goals of our work were to use pilot-scale conventional and biological treatment to study (i) microbial population changes throughout the distribution system, including biofilm samples and water column samples (ii) the impact of postdisinfection with free chlorine on microbial populations and (iii) the impact of corrosion control and pipe materials on microbial populations. While the numbers of organisms in conventionally and biologically treated systems may not differ significantly, the population composition may reveal the largest impact of biologically activated filtration. Although concerns regarding the higher levels of heterotrophic plate count (HPC) bacteria in the effluents of biological filters have been raised, the changes in the composition of distribution system microbial populations resulting from a shift in the nutrient levels following biological treatment may have a much more dramatic impact on water quality. One of the primary reasons that utilities implement biological treatment is to reduce nutrient levels in the treated water, which in turn can limit the potential for bacterial regrowth in the distribution system. The study showed that the iron pipe surface dramatically influenced the composition, activity, and disinfection resistance of biofilm bacteria.īiological treatment provides numerous benefits for drinking water utilities, including removal of micropollutants, improved treatment processes (i.e., coagulation, color removal, and oxidation of iron and manganese), taste and odor control, and reduced chlorine demand of treated water ( 16, 32). Iron pipes stimulated the rate of biofilm development, and bacterial levels on disinfected iron pipes exceeded those for chlorinated polyvinyl chloride pipes. Removal of assimilable organic carbon by the biologically active filters slowed the rate of biofilm accumulation, but biofilm levels were similar to those found in conventionally treated water within several weeks. Chlorination of biologically treated water produced the same shifts toward gram-positive bacteria. Prechlorination with free chlorine resulted not only in reduced plate count values but also in a dramatic shift in the composition of the bacterial population to predominately gram-positive bacteria.
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Data generated during this study indicated that suspended bacteria have little impact on biofilms, and despite treatment (conventional or biological), suspended microbial populations were similar following disinfection. The Microbial Identification System for fatty acid analysis was utilized in this study to identify a large number of organisms (>1,400) to determine population changes in both conventionally and biologically treated water and biofilms. This pilot study compares the compositions of bacterial biofilms in pipe networks supplied with water containing either high levels of biodegradable organic matter (BOM) or low levels of BOM (conventionally or biologically treated, respectively).