Shaping biofilm microbiomes by changing GAC location during wastewater anaerobic digestion

Najiaowa Yu, Bing Guo, Yang Liu

Department of Civil and Environmental Engineering, University of Alberta, Edmonton, Alberta T6G 1H9, Canada.

Abstract

The addition of granular activated carbon (GAC) to up-flow anaerobic sludge blanket (UASB) reactors treating synthetic wastewater enhanced methane production by stimulating direct interspecies electron transfer (DIET). A modified UASB reactor with GAC packed in plastic carriers that allowed the GAC to float in the upper reactor zone achieved enhanced performance compared to a UASB reactor with GAC settled at the bottom of the reactor. Microbial communities in the biofilms developed on settled or floated GAC were compared. Methanosarcina (56.3–73.3%) dominated the floated-GAC biofilm whereas Methanobacterium (84.9–85.1%) was greatly enriched in the settled-GAC biofilm. Methanospirillum and Methanocorpusculum were enriched in the floated-GAC biofilm (8.8–19.8% and 5.1–9.5%, respectively), but only existed in low abundances in the settled-GAC biofilm (3.4–3.6% and 0–0.4%, respectively). The floated GAC developed bacterial communities with higher diversity and more syntrophic bacteria enrichments on its surface, including Geobacter, Smithella, and Syntrophomonas, than the settled-GAC biofilm. Common hydrogen-donating syntrophs and hydrogenotrophic archaea, Methanospirillum and Methanoregula, were identified as potential electro-active microorganisms related to DIET.

Key words: Microbial community, Direct interspecies electron transfer (DIET), Granular activated carbon, Anaerobic digestion.