The Microbial Database for Danish wastewater treatment plants with nutrient removal (MiDas-DK) – a tool for understanding activated sludge population dynamics and community stability

Abstract

Since 2006 more than 50 Danish full-scale wastewater treatment plants with nutrient removal have been investigated in a project called 'The Microbial Database for Danish Activated Sludge Wastewater Treatment Plants with Nutrient Removal (MiDas-DK)'. Comprehensive sets of samples have been collected, analyzed and associated with extensive operational data from the plants. The community composition was analyzed by quantitative fluorescence in situ hybridization (FISH) supported by 16S rRNA amplicon sequencing and deep metagenomics. MiDas-DK has been a powerful tool to study the complex activated sludge ecosystems, and, besides many scientific articles on fundamental issues on mixed communities encompassing nitrifiers, denitrifiers, bacteria involved in P-removal, hydrolysis, fermentation, and foaming, the project has provided results that can be used to optimize the operation of full-scale plants and carry out trouble-shooting. A core microbial community has been defined comprising the majority of microorganisms present in the plants. Time series have been established, providing an overview of temporal variations in the different plants. Interestingly, although most microorganisms were present in all plants, there seemed to be plant-specific factors that controlled the population composition thereby keeping it unique in each plant over time. Statistical analyses of FISH and operational data revealed some correlations, but less than expected. MiDas-DK (www.midasdk.dk) will continue over the next years and we hope the approach can inspire others to make similar projects in other parts of the world to get a more comprehensive understanding of microbial communities in wastewater engineering.

Sludge bulking impact on relevant bacterial populations in a full-scale municipal wastewater treatment plant

“…Significant decrease of the abundances of the main relevant bacteria including Nitrosomonas, Candidatus Accumulibacter phosphatis and Thauera belonging to the class Betaproteobacteria was observed when serious sludge bulking occurred. In a previous study investigating over 50 Danish WWTPs with nutrient removal, the abundances of these were quite stable in different seasons [26]. Therefore sludge bulking should be the main reason for the significant changes of bacterial communities in the present study.…”

Candidatus Accumulibacter phosphatis clades enriched under cyclic anaerobic and microaerobic conditions simultaneously use different electron acceptors

“…Chimeric sequences were removed using UCHIME (Edgar et al 2011). The most representative sequences from each OTU were taxonomically classified using the MIDas-DK database (Mielczarek et al 2013).…”

“…Results correspond to the taxonomic distribution of 45 samples from the lab-scale SBR, 23 samples from the pilot-scale SBR and 38 samples from the full-scale WWTP Nine Springs. The name of each genus-level taxon in this figure correspond to the one proposed in the MIDAS database(Mielczarek et al 2013).…”

Prokaryote species richness is positively correlated with eukaryote abundance in wastewater treatment biofilms

“…For the functional assignment we first linked the OTUs to potential using the MiDas database (Mielczarek et al . ). We first matched our OTUs to the 146 bacteria identified in the MiDas database at the family level.…”