BioProject

Rapid granular sludge development was observed, in a laboratory-scale (LS) integrated fixed-film - sequencing batch reactor (IF - SBR), when an anoxic phase was introduced during the react phase. More...

Rapid granular sludge development was observed, in a laboratory-scale (LS) integrated fixed-film - sequencing batch reactor (IF - SBR), when an anoxic phase was introduced during the react phase. Four IF - SBRs (R 1–4) were seeded with activated sludge from a municipal wastewater treatment plant (Cataraqui Bay wastewater treatment plant, Kingston, Ontario, Canada). The IF – SBRs were fed anoxically with glucose and sodium acetate based synthetic wastewater. Granular sludge developed rapidly within ten days of the start-up in IF - SBR 1 (R 1) operated with relatively short oxic (2 hour) and long anoxic periods (3.25 hours), in six hours SBR cycle. Whereas, filamentous growth was observed in IF - SBR 2 (R 2) and IF - SBR 3 (R 3) operated with relatively longer oxic (3 and 4 hours respectively) and shorter anoxic periods compared to R 1. During granule formation in R 1, extracted extracellular polymeric substances (EPS) increased from 99 ± 2 mg/g mixed liquor suspended solids (MLSS) (in seed biomass) to 272 ± 2 mg/g MLSS (in granular sludge). Confocal laser scanning microscopy (CLSM) revealed that β-polysaccharide (βPS) and amyloid adhesins were predominant in the periphery and core of the granules, respectively. 16S rRNA gene sequencing (using Illumina MiSeq) revealed rapid selection and relative abundance of bacterial genera including: Flavobacterium (related to family Flavobacteriaceae), Sediminibacterium (Chitinophagaceae), Gemmatimonas (Gemmatimonadaceae), Rhodobacter (Rhodobacteraceae), Caulobacter (Caulobacteraceae), Dechloromonas and Zoogloea (Rhodocyclaceae) and bacterial genera related to family Comamonadaceae, in R 1 granules and biofilms (compared to R 2-4 flocs and biofilms). The functional activity of bacteria that were selected and predominant in R1 (compared to R 2-4) include: quorum sensing (QS), EPS production, EPS hydrolysis, denitrifying bacteria (DNB) and denitrifying phosphorous accumulating bacteria (DNPAO) for structural and functional stability of the granular sludge. The rapid selection of these of bacteria in granular sludge with introduction of anoxic conditions are advantageous because it would require less aeration energy for biological nutrient removal (BNR) in same vessel. Combination of granular sludge and IFAS system has a potential to further improve efficiency of BNR. Less...