Characterizing and contrasting the microbial ecology of laboratory and full-scale EBPR systems cultured on synthetic and real wastewaters

The anthropogenic discharge of phosphorus (P) into surface waters can induce the proliferation of cyanobacteria and algae, which can negatively impact water quality. Enhanced biological P removal (EBPR) is an engineered process that can be employed to efficiently remove significant quantities of P from wastewater. Within this engineered system, the mixed microbial consortium (MMC) becomes enriched with polyphosphate accumulating organisms (PAOs). To date much knowledge has been developed on PAOs, and the EBPR process is generally well understood; nonetheless, the engineered process remains underutilized. In this study, investigations were conducted using qPCR and Illumina MiSeq to assess the impacts of wastewater (synthetic vs. real) on EBPR microbial ecology. While a strong relationship was demonstrated between EBPR metrics (P:C; influent VFA:P) and excellent P removal across diverse EBPR systems and MMCs, no such correlations existed with the specific MMCs. Moreover, MMCs exhibited distinct clusters based on substrate, and qPCR results based on the putative PAO Accumulibacter did not correlate with BLASTN eubacterial results for either Accumulibacter or Rhodocyclaceae. More critically, PAO-based sequences aligned poorly with Accumulibacter for both eubacterial and PAO primer sets, which strongly suggests that the conventional PAO primers applied in FISH and qPCR analysis do not sufficiently target the putative PAO Accumulibacter. In particular, negligible alignment was observed for PAO amplicons obtained from a MMC performing excellent EBPR on crude glycerol (an atypical substrate). A synthetic wastewater-based MMC exhibited the best observed BLASTN match of the PAO amplicons, raising concerns about the potential relevance in using synthetic substrates in the study of EBPR.