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Activated sludge
Published in Nick F. Gray, Water Science and Technology: An Introduction, 2017
While microbial analyses, especially of filamentous microorganisms causing bulking and foaming, are routinely done using simple staining techniques using light and phase microscopies, there is now the possibility to identify a wider range of bacteria in wastewater systems using DNA analysis (Prasse et al., 2015). Although routinely done at the research level, especially to study diversity and phylogeny of bacterial groups, it is increasingly common to look at assemblages of bacteria that carry out specific tasks or that may affect performance, a process known as community fingerprinting. Specific bacterial groups of interest to operators are such anaerobes that produce volatile acids required in P-removal, high P accumulators, nitrifiers, denitrifying bacteria and those bacteria that may be indicative of low nitrogen (i.e. nitrogen-fixing bacteria) such as Azonexus sp. and Azohydromonas sp. Problematic bacteria associated with excessive filament development resulting in bulking or foaming, as well as iron- and sulphur-reducing bacteria can also be evaluated. While lists of specific genera or species of bacteria can be identified, it is more common to express them in terms of percentages of the total bacterial population.
The application of molecular tools to study the drinking water microbiome – Current understanding and future needs
Published in Critical Reviews in Environmental Science and Technology, 2019
Characterizing microbial populations is an important first step to elucidate the complexity of microbial ecology in drinking water systems. Two major types of PCR amplification methods can be carried out. The first type of PCR-based methods is generally termed ‘community fingerprint’. It analyzes the amplified 16S rRNA genes and generates a pattern-based profile of community structure, most commonly represented by a banding pattern of nucleic acid fragments resolved by gel electrophoresis. In general, these community fingerprinting methods allow one to rapidly examine the microbial diversity within a microbial ecosystem, or compare the differences and similarities on the microbial community structure among different ecosystems (Liu & Stahl, 2007). Many microbial fingerprinting methods were developed in 1990s, including DGGE (denaturing gradient gel electrophoresis), T-RFLP (terminal restriction fragment length polymorphism), PCR-ALH (amplicon length heterogeneity), and SSCP (single-strand-conformation polymorphism) (Liu & Stahl, 2007).