From macro to lab-scale: Changes in bacterial community led to deterioration of EBPR in lab reactor

Abstract

A laboratory scale sequencing batch reactor (SBR), fed with synthetic wastewater containing a mixture of organic compounds, was operated for nearly six months. Despite maintaining the same operational conditions, a deterioration of enhanced biological phosphorus removal (EBPR) occurred after 40 days of SBR operation. The P rel /C upt ratio decreased from 0. 28 to 0. 06 P-mol C-mol -1 , and C requirements increased from 11 to 32 mg C h -1 g -1 of mixed liquor suspended solids. A FISH analysis showed that the percentage of Accumulibacter in an overall community of polyphosphate accumulating organisms (PAOs) and glycogen accumulating organisms (GAOs) dropped from 93% to 13%. An increase in abundance of Gammaproteobacteria (from 2. 6% to 22%) and Alphaproteobacteria (from 1. 8% to 10%) was observed. The number of Competibacter increased from 0. 5% to nearly 9%. Clusters 1 and 2 of Defluviicoccus-related GAOs, not detected before deterioration, constituted 35% and 27% of Alphaproteobacteria, respectively. We concluded that lab-scale experiments should not be extended implicitly to full-scale EBPR systems because some bacterial groups are detected mainlyin lab-scale reactors. Well-defined, lab-scale operational conditions reduce the number of ecological niches available to bacteria. © 2013 Versita Warsaw and Springer-Verlag Wien.