Abstract
Wastewater treatment is crucial to environmental hygiene in urban environments. However, wastewater treatment plants (WWTPs) collect chemicals, organic matter, and microorganisms including pathogens and multi-resistant bacteria from various sources which may be potentially released into the environment via WWTP effluent. To better understand microbial dynamics in WWTPs, we characterized and compared the bacterial community of the inflow and effluent of a WWTP in Berlin, Germany using full-length 16S rRNA gene sequences, which allowed for species level determination in many cases and generally resolved bacterial taxa. Significantly distinct bacterial communities were identified in the wastewater inflow and effluent samples. Dominant operational taxonomic units (OTUs) varied both temporally and spatially. Disease associated bacterial groups were efficiently reduced in their relative abundance from the effluent by the WWTP treatment process, except for Legionella and Leptospira species which demonstrated an increase in relative proportion from inflow to effluent. This indicates that WWTPs, while effective against enteric bacteria, may enrich and release other potentially pathogenic bacteria into the environment. The taxonomic resolution of full-length 16S rRNA genes allows for improved characterization of potential pathogenic taxa and other harmful bacteria which is required to reliably assess health risk.
Highlights
Drinking water is a critical resource for which it is challenging to maintain hygiene in urban areas under persistent anthropogenic influence[1,2,3,4]
These studies have provided relatively little taxonomic resolution since molecular identification has been limited to short hypervariable regions of the 16S rRNA gene due to amplicon size constraints in sequencing on the Illumina or Roche 454 platforms[5,12,13,35,36]
Sequence similarity, we were able to identify a total of 7,068 operational taxonomic units (OTUs) of which 3,860 were left after rarefaction
Summary
Drinking water is a critical resource for which it is challenging to maintain hygiene in urban areas under persistent anthropogenic influence[1,2,3,4]. Bacterial communities of wastewater include members of different taxonomic, biochemical (e.g. N2-fixation, nitrification, denitrification, sulphur oxidation) and physiological (e.g. anaerobic, aerobic, phototrophic, heterotrophic) groups, of which many provide functional advantages for water cleaning, such as nutrient removal. There are few studies comparing WWTP bacterial communities in inflow and effluent with the few undertaken restricted to a few countries, i.e. the USA, Hong Kong (China), and Spain[5,12,13,35,36] These studies have provided relatively little taxonomic resolution since molecular identification has been limited to short hypervariable regions of the 16S rRNA gene due to amplicon size constraints in sequencing on the Illumina or Roche 454 platforms[5,12,13,35,36]. Inflow and effluent samples from a WWTP in Berlin (Germany) were collected every three months for one year to characterize in detail and compare the bacterial communities including potentially pathogenic bacteria
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