A Pilot Study of Bacteriological Population Changes through Potable Water Treatment and Distribution

Abstract

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). 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. 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. 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. Chlorination of biologically treated water produced the same shifts toward gram-positive bacteria. 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. Iron pipes stimulated the rate of biofilm development, and bacterial levels on disinfected iron pipes exceeded those for chlorinated polyvinyl chloride pipes. The study showed that the iron pipe surface dramatically influenced the composition, activity, and disinfection resistance of biofilm bacteria.Biological 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). 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. 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. 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.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. Identification and characterization of these populations were made possible through the use of f...

Bacterial community change through drinking water treatment processes

“…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.…”

“…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.…”

“…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).…”

Detection of potentially novel bacterial components of the human skin microbiota using culture-independent molecular profiling

“…and Acidovorax spp. are frequently detected in water-distribution systems in developed countries (Norton & LeChevallier, 2000;Williams et al, 2004), and Acinetobacter spp., Dietzia maris and Bacillus spp. are commonly found in soil and in lakes.…”

Zoonotic aspects of Mycobacterium bovis and Mycobacterium avium-intracellulare complex (MAC)

“…Mycobacteria of MAC have the capacity to survive and multiply under a wide range [128] and low oxygen level [16]. Thus, their ability to utilise many substances as nutrients enables them to grow successfully in many biotopes.…”