Microbial community structure and dynamics in wastewater treatment over a year

Abstract

Wastewater treatment plants are necessary for the release of effluent into the natural environment. The wastewater treatment plant functions as a bioreactor cultivating a diverse microbial community for the removal of nutrients such as carbon, nitrogen, and phosphorous from the effluent. The Tahuna treatment plant was the focus of this study because there was simultaneous removal of nitrogen and phosphorous, although the treatment plant was not designed for both these processes. Biochemical parameters were taken, specifically; dissolved oxygen, pH, oxidation-reduction potential, total suspended solids, total phosphorous, dissolved reactive phosphorous, nitrogen levels, and temperature. Through the use of Ion Torrent sequencing of the 16S rRNA gene, and analysis of sequences using the RDP and MIDAS databases, this study was able to elucidate the diversity of microbes within the Tahuna wastewater treatment plant. The analysis of the biochemical parameters and sequencing results revealed the presence and activity of functional groups of organisms important in wastewater. These organisms were involved in ammonium oxidation, nitrite oxidation, denitrification and phosphorous removal. Ammonium was metabolised by the ammonium oxidising bacteria Nitrosomonas producing nitrite. The nitrite was subsequently converted to nitrate by the nitrite oxidising bacteria Nitrospira. Finally, Dechloromonas functioned as a denitrifying phosphorous accumulating organism in the treatment plant. As a denitrifying phosphorous accumulating organism, Dechloromonas was able to metabolise nitrate into dinitrogen gas as well as accumulate phosphorous for removal. The community remained relatively stable over the course of the study, with CAP and CAA plots as well as ANCOM analysis revealing that the greatest driver of the microbial community was temporal change.