Microbial Communities in Danish Wastewater Treatment Plants with Nutrient Removal

Artur Tomasz Mielczarek

Research output: PhD thesis

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Abstract

Activated sludge treatment plants are the most used wastewater treatment systems worldwide for biological nutrient removal from wastewater. Nevertheless, the treatment systems have been for many years operated as so called “black-box”, where specific process parameters were adjusted without the deep understanding of their influence on the key microbes. In order to ensure optimal operation, process optimization and trouble-shooting, it is crucial to understand the structure and function of the microbial communities and the factors controlling their composition and activity.
This study was devoted into detailed analysis of almost fifty full-scale treatment plants (Microbial Database over Danish Wastewater Treatment Plants.) in order to learn more about the activated sludge communities and the rules that govern their presence and growth. This is one of the first such comprehensive long-term investigations of the microbial community in full-scale wastewater treatment plants, where conventional identification, molecular identification by quantitative Fluorescent In Situ Hybridization and extensive process information related to treatment plant design and process performance have been compiled.
The microbial populations in Danish full-scale activated sludge wastewater treatment plants with nutrient removal have been screened and it was possible to present so called “Danish standard activated sludge” for this type of plants. The key functional groups have been identified and they constituted up to 80% of total biomass. It was possible to identify a group of core microorganisms that is common for all investigated Danish plants. Their population variations were analysed over the years and it was demonstrated that they were relatively stable during the time of investigation and similar between the plants. In spite of the population’s similarity, it has been proven by statistical measures that the presence of two functional groups, namely Polyphosphate Accumulating Organisms/Glycogen Accumulating Organisms (PAO/GAO) and filamentous bacteria, in each treatment plant had its own unique microbial fingerprint.
Additionally, only few correlations between bacterial presence and different process parameters or treatment design have been revealed. It was not possible to relate presence of any applied treatment system and abundance of any bacteria group, but one. For plants carrying out biological P-removal, it was shown that plants with return sludge Side-Stream Hydrolysis (SSH) instead of the normal anaerobic process tank tended to have significantly fewer unwanted GAOs in contrast to many plants with traditional mainstream anaerobic tank and thus it was proposed that this system might be an effective strategy of control and prevention of unwanted GAO.
Original languageEnglish
Place of PublicationAalborg
Publisher
Print ISBNs978-87-90033-87-3
Publication statusPublished - 2 May 2012

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