The structure of microbial communities of activated sludge of large-scale wastewater treatment plants in the city of Moscow

Abstract

Microbial communities in wastewater treatment plants (WWTPs) play a key role in water purification. Microbial communities of activated sludge (AS) vary extensively based on plant operating technology, influent characteristics and WWTP capacity. In this study we performed 16S rRNA gene profiling of AS at nine large-scale WWTPs responsible for the treatment of municipal sewage from the city of Moscow, Russia. Two plants employed conventional aerobic process, one plant-nitrification/denitrification technology, and six plants were operated with the University of Cape Town (UCT) anaerobic/anoxic/oxic process. Microbial communities were impacted by the technology and dominated by the Proteobacteria, Bacteroidota and Actinobacteriota. WWTPs employing the UCT process enabled efficient removal of not only organic matter, but also nitrogen and phosphorus, consistently with the high content of ammonia-oxidizing Nitrosomonas sp. and phosphate-accumulating bacteria. The latter group was represented by Candidatus Accumulibacter, Tetrasphaera sp. and denitrifiers. Co-occurrence network analysis provided information on key hub microorganisms in AS, which may be targeted for manipulating the AS stability and performance. Comparison of AS communities from WWTPs in Moscow and worldwide revealed that Moscow samples clustered together indicating that influent characteristics, related to social, cultural and environmental factors, could be more important than a plant operating technology.

Figure 1

Schemes of three types of bioreactors showing the different compartments and flow directions. Anaerobic, anoxic and oxic zones are colored in green, violet and blue, respectively.

Figure 2

Neighbor joining tree illustrating weighted UniFrac distances between microbial communities of AS samples from 9 WWTPs (three replications). Sample IDs are shown in brackets after the WWTP number.

Figure 3

Bacterial and archaeal community composition in AS samples according to the results of 16S rRNA gene sequencing. The composition is displayed at the phylum level. Average values for three replicas are shown for each WWTP.

Figure 4

Network of co-occurring abundant microbial OTUs of AS based on correlation analysis. A connection stands for a strong (Spearman’s rho > 0.6) and significant (adjusted p value < 0.001) correlation. OTUs are colored according to phylum. Co-presence and mutual exclusion of OTUs are shown in white and red lines, respectively.

Figure 5

Neighbor joining tree illustrating clustering based on the Bray–Curtis dissimilarity between microbial communities of AS samples from 9 WWTPs obtained in this study and ones reported by a Global Water Microbiome Consortium (http://gwmc.ou.edu/). Samples are colored according to geographic location.