Abstract
Upflow anaerobic sludge blanket (UASB) reactor has served as an effective process to treat industrial wastewater such as purified terephthalic acid (PTA) wastewater. For optimal UASB performance, balanced ecological interactions between syntrophs, methanogens, and fermenters are critical. However, much of the interactions remain unclear because UASB have been studied at a “macro”-level perspective of the reactor ecosystem. In reality, such reactors are composed of a suite of granules, each forming individual micro-ecosystems treating wastewater. Thus, typical approaches may be oversimplifying the complexity of the microbial ecology and granular development. To identify critical microbial interactions at both macro- and micro- level ecosystem ecology, we perform community and network analyses on 300 PTA–degrading granules from a lab-scale UASB reactor and two full-scale reactors. Based on MiSeq-based 16S rRNA gene sequencing of individual granules, different granule-types co-exist in both full-scale reactors regardless of granule size and reactor sampling depth, suggesting that distinct microbial interactions occur in different granules throughout the reactor. In addition, we identify novel networks of syntrophic metabolic interactions in different granules, perhaps caused by distinct thermodynamic conditions. Moreover, unseen methanogenic relationships (e.g. “Candidatus Aminicenantes” and Methanosaeta) are observed in UASB reactors. In total, we discover unexpected microbial interactions in granular micro-ecosystems supporting UASB ecology and treatment through a unique single-granule level approach.
Highlights
Upflow anaerobic sludge blanket (UASB) reactors are widely implemented as an effective biotechnology for treating various wastewaters types
The wastewater contains 2,752 mgTOCÁL−1 composed of TA, 4.5 mM; BZ, 6.0 mM; isophthalic acid (IA), 2.1 mM; orthophthalic acid (OA), 1.0 mM; PT, 0.6 mM; trimellitic acid (TMA), 1.0 mM; methanol (MT), 24.3 mM; acetate (AC), 35.7 mM; and methyl acetate (MA), 1.2 mM
To examine the heterogeneity of microbial community structure within individual granules, 300 individual granules with diameters greater than 1mm were collected individually from one lab-scale (U1) and two identical full-scale (E and F) UASB reactors and categorized into groups defined via granule size (GSA: 1-2mm, GSB: 2-3mm, and GSC: 3-4mm)
Summary
Upflow anaerobic sludge blanket (UASB) reactors are widely implemented as an effective biotechnology for treating various wastewaters types In addition to reactor operation [2, 3], balance between three primary niches (syntrophs, methanogens, and fermenters) is known to be necessary for mineralization of organic pollutants to CH4 and CO2 [2, 4, 5] based on previous studies implementing 16S rRNA-based tools (e.g., high-throughput DNA sequencing) [6,7,8,9] While such studies provide a “macro”-level view of the reactor ecosystem, fluorescence in situ hybridization (FISH) on individual granules has shown intricate microbial composition and spatial distribution in each granule [5, 10]. We discover unexpected diversity among granules and novel microbial networks in full-scale reactors and provide valuable insight into resolving the biological complexity of full-scale reactors, a major hurdle in improving wastewater treatment
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