Factors that drive bacterial community composition in activated sludge

FEDERICO IBARBALZ; EVA L. M. FIGUEROLA; LEONARDO ERIJMAN

Mar del Plata

Congreso; Congreso Argentino de Microbiología General; 2012

Sociedad Argentina de Microbiología General

The process of activated sludge (AS) is the most widely used method for treatment of wastewater worldwide. It relies on the aerobic degradation of organic matter by a highly dynamic mixture of microorganisms, which are subsequently separated by gravity settling owing to their ability to aggregate into flocs. The aim of the work was to investigate the factors that drive the bacterial community composition in AS. Based on previous surveys of bacterial communities in AS and on the concept of ecological coherence of high taxonomic ranks (meaning that the members of a taxon share functional traits that distinguish them from members of other taxa), we hypothesized that there would be a consistent set of bacterial taxa common to AS plants, regardless the origin of the wastewater and the plant configuration. We applied 454 pyrosequencing of 16S rRNA genes to evaluate bacterial communities in several full-scale biological wastewater treatment plants (WWTP) sampled at different times, including systems treating wastewater from different industries and domestic wastewater and labscale reactors fed with synthetic sewage. Cluster analysis at the 5% level revealed a clear separation by WWTP, indicating the existence of distinctive core communities associated to each treatment plant. The influence of environmental and process parameters on the bacterial community structure was evaluated using canonical correspondence analysis (CCA). The first ordination axis correlated with pH. The second canonical axis correlated to the BOD to COD ratio (a proxy of the biodegradability of the wastewater) and Dissolved Oxygen (DO). Firmicutes and Lentisphaeras were associated to high pH, Acidobacteria and Chlorobi to high DO. As regards with sites, separation of the ‘textile’ WWTP was strongly influenced by pH, while the ‘whey’ WWTP showed to be influenced by the BOD to COD ratio. In conclusion, the bacterial community structure of AS plants is unique to each system. The taxa distribution is driven primarily by the wastewater composition, pH and DO.