Does reactor staging influence microbial structure and functions in biofilm systems? The case of pre-denitrifying MBBRs

Fabio Polesel, Elena Torresi, Marlene Mark Jensen, Jane Fowler, Monica Escola Casas, Barth F. Smets, Magnus Christensson, Kai Bester, Benedek G. Plósz

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Abstract

To date, a number of treatment technologies and configurations have been tested to improve the elimination of conventional and trace (e.g., pharmaceutical residues) pollutants via biological wastewater treatment. Bioreactor staging and the moving bed biofilm reactor (MBBR) technology have emerged as promising bioengineered solutions (Plósz et al., 2010) for this purpose. In this study, we combined the two solutions and investigated microbial functions (heterotrophic denitrification, pharmaceutical removal) and structure of the microbial community in staged MBBRs for pre-denitrification. A three-stage MBBR system (S1+S2+S3), fed with pre-clarified wastewater, was operated at laboratory-scale with (i) controlled biomass exposure to organic substrate (COD); and (ii) enhanced the physical retention of biomass, thus inducing adaptation to different substrate exposure conditions. During long-term operation (~500 days) of the three-stage MBBR under continuous-flow conditions, biofilm samples were collected to assess the temporal evolution of the microbial structure in terms of functional gene abundance and biodiversity. A set of batch experiments (day 471) was performed to assess denitrification and pharmaceutical removal in each MBBR, following prolonged biofilm exposure to specific COD availability.
Results from batch experiments showed declining denitrification potential and pharmaceutical biotransformation rate constants (kbio, L gTSS-1 d-1) from MBBR S1 (exposed to highest COD availability) to S3 (exposed to lowest availability). These findings indicate that the exposure to tiered substrate availability influenced the capacity of utilizing a different range of carbon sources in each MBBR, thus impacting denitrification and pharmaceutical biotransformation. Preliminary analysis on the microbial community based on qPCR (quantitative polymerase chain reaction) showed differences in the abundance of genes (nirS, nirK, nosZ) encoding for denitrifying enzymes in the three staged MBBRs. Further microbial characterization through 16sRNA sequencing (Illumina) is currently under investigation to determine whether differences in microbial functions should be associated to differences in the microbial diversity in the three MBBRs.
Original languageEnglish
Publication date2016
Number of pages1
Publication statusPublished - 2016
EventInternational Conference on Emerging Contaminants (EmCon2016) and Micropollutants (WiOW2016) in the Environment - Sydney, Australia
Duration: 20 Sep 201623 Sep 2016

Conference

ConferenceInternational Conference on Emerging Contaminants (EmCon2016) and Micropollutants (WiOW2016) in the Environment
Country/TerritoryAustralia
CitySydney
Period20/09/201623/09/2016

Keywords

  • Moving bed biofilm reactors
  • Reactor staging
  • Pharmaceuticals
  • Denitrification
  • qPCR
  • DNA sequencing

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