Abstract
BackgroundThe activated sludge process is one of the most widely used methods for treatment of wastewater and the microbial community composition in the sludge is important for the process operation. While the bacterial communities have been characterized in various activated sludge systems little is known about archaeal communities in activated sludge. The diversity and dynamics of the Archaea community in a full-scale activated sludge wastewater treatment plant were investigated by fluorescence in situ hybridization, terminal restriction fragment length polymorphism analysis and cloning and sequencing of 16S rRNA genes.ResultsThe Archaea community was dominated by Methanosaeta-like species. During a 15 month period major changes in the community composition were only observed twice despite seasonal variations in environmental and operating conditions. Water temperature appeared to be the process parameter that affected the community composition the most. Several terminal restriction fragments also showed strong correlations with sludge properties and effluent water properties. The Archaea were estimated to make up 1.6% of total cell numbers in the activated sludge and were present both as single cells and colonies of varying sizes.ConclusionsThe results presented here show that Archaea can constitute a constant and integral part of the activated sludge and that it can therefore be useful to include Archaea in future studies of microbial communities in activated sludge.
Highlights
The activated sludge process is one of the most widely used methods for treatment of wastewater and the microbial community composition in the sludge is important for the process operation
The F/M-ratio was higher at the time of the clone library sample collection (May 2007) compared with the times when samples were collected for fluorescence in situ hybridization (FISH) (December 2007) and terminal restriction fragment length polymorphism (T-RFLP) analyses (May 2003 - August 2004) (Table 1)
Based on DNA similarity the sequences were assigned to operational taxonomic units (OTUs)
Summary
The activated sludge process is one of the most widely used methods for treatment of wastewater and the microbial community composition in the sludge is important for the process operation. The diversity and dynamics of the Archaea community in a full-scale activated sludge wastewater treatment plant were investigated by fluorescence in situ hybridization, terminal restriction fragment length polymorphism analysis and cloning and sequencing of 16S rRNA genes. An important factor for the operation of activated sludge wastewater treatment plants (WWTPs) is the solid-liquid separation in which flocculation and settling are important processes [1]. The bacterial community has been characterized in a number of activated sludge systems [8,9] but very little is known about archaeal communities in sludge. The composition of the methanogenic community in anaerobic sludge has been shown to be crucial for the structure and integrity of granules [18,19,20] and if methanogens are present in activated sludge they may contribute to the floc structure
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