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.
Highlights
The removal of numerous pollutants produced by agriculture, industry, and households is important for the protection of natural ecosystems and human health
This study showed that the type of treatment process exerted significant effects on microbial community structures, it was overwhelmed by geographical separation, and the compositions of activated sludge (AS) microbial communities were significantly different between any two continents[10]
This study provides the data on the composition of microbial communities of AS from large-scale WWTPs of the Moscow city and the evidences of the impact of purification technology
Summary
The removal of numerous pollutants produced by agriculture, industry, and households is important for the protection of natural ecosystems and human health. The first stage includes physical methods of water purification, the second stage—chemical and/or biological treatment in bioreactors with suspended or attached activated sludge (AS). At the same time a high diversity and differences of microbial communities of AS were noted, which was associated with climatic factors and the specificity of certain treatment plants: the share of the industrial component in the total influent, the temperature regime, the peculiarity of the used technologies and the exploitation of plants[9]. It has been shown that there is a relationship between the diversity and composition of the microbial community and the performance of treatment facilities[2], the authors noted that the real effect is not the performance itself, but the variation of indicators such as chemical oxygen demand, the retention time of suspended matter etc. The GWMC study included WWTPs from 23 countries on 6 continents, the distribution of samples was geographically biased and covered mostly North America, Western and Central Europe, Eastern Asia (mostly China), Australasia, and several cities in South America and South Africa[10]
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