Presentation Information
[P03-397]Structural responses of the sludge flocs and microbial communities to solid–liquid separation deterioration of microaerobic activated sludge process for ammonium retention
○Tomohiro Inaba1, Tomoyuki Hori1, Tomo Aoyagi1, Hidenobu Aizawa1, Hiroshi Habe1 (1. National Institute of Advanced Industrial Science and Technology (AIST) (Japan))
Keywords:
Microaerobic activated sludge (MAS),Ammonium retention and recovery,Solid–liquid separation deterioration,Sludge floc structure,Microbial community dynamics
Reactive nitrogen in industrial wastewater, particularly ammonium, is attracting attention as the potential energy carrier and feedstock. Microaerobic activated sludge (MAS) process has been proposed to retain and recover ammonium in the wastewater. MAS promotes organic carbon oxidation, while suppressing nitrification. During the operation, solid–liquid separation can be unstable in response to fluctuations of the organic loading and dissolved oxygen (DO), leading to the effluent quality deterioration. The microbiological mechanisms of this process instability remain poorly understood. Thus, this study aims to investigate structural changes in the sludge flocs and microbial communities associated with the solid–liquid separation deterioration during the MAS operation.
A 10-L single-tank laboratory-scale MAS reactor was operated to treat a synthetic industrial wastewater under microaerobic conditions, for which DO was maintained at approximately 0.5 mg/L by adjusting aeration rate. The microbial communities were assessed by 16S rRNA gene amplicon sequencing, while the sludge floc structures were non-destructively visualized by confocal reflection microscopy. Due to the treatment, 60–70% of the total nitrogen in the influent was retained as NH4+-N. A transient deterioration of the effluent quality, e.g., increases in the turbidity (~58.1 NTU) and suspended solids (SS: ~136.0 mg/L), was observed. The sequencing indicated that the phyla Flavobacteriia and Alphaproteobacteria were enriched in the effluent SS during the operation with high turbidities. Their relative abundances in the SS were 15.7- and 21.8-fold higher, respectively, than those in the bulk sludge. These bacterial groups enriched specifically in the effluent SS were associated with the turbidity increases and further the floc structure destabilization. The microscopy showed that the mean volumetric fractions of microbial cells within the sludge flocs were 1.6–1.8-fold higher during the operation with high turbidities than with low turbidities. The higher volumetric fractions were indicative of the lower relative abundances of the non-cellular matrix components, possibly weakening the sludge floc integrities. Consequently, the results provided insights into the formation and maintenance of the sludge microbial communities and floc structures, contributing to the long-term stable operation of the MAS process.
This presentation is partially based on results obtained from projects JPNP14004 and 18016 commissioned by the New Energy and Industrial Technology Development Organization (NEDO).
A 10-L single-tank laboratory-scale MAS reactor was operated to treat a synthetic industrial wastewater under microaerobic conditions, for which DO was maintained at approximately 0.5 mg/L by adjusting aeration rate. The microbial communities were assessed by 16S rRNA gene amplicon sequencing, while the sludge floc structures were non-destructively visualized by confocal reflection microscopy. Due to the treatment, 60–70% of the total nitrogen in the influent was retained as NH4+-N. A transient deterioration of the effluent quality, e.g., increases in the turbidity (~58.1 NTU) and suspended solids (SS: ~136.0 mg/L), was observed. The sequencing indicated that the phyla Flavobacteriia and Alphaproteobacteria were enriched in the effluent SS during the operation with high turbidities. Their relative abundances in the SS were 15.7- and 21.8-fold higher, respectively, than those in the bulk sludge. These bacterial groups enriched specifically in the effluent SS were associated with the turbidity increases and further the floc structure destabilization. The microscopy showed that the mean volumetric fractions of microbial cells within the sludge flocs were 1.6–1.8-fold higher during the operation with high turbidities than with low turbidities. The higher volumetric fractions were indicative of the lower relative abundances of the non-cellular matrix components, possibly weakening the sludge floc integrities. Consequently, the results provided insights into the formation and maintenance of the sludge microbial communities and floc structures, contributing to the long-term stable operation of the MAS process.
This presentation is partially based on results obtained from projects JPNP14004 and 18016 commissioned by the New Energy and Industrial Technology Development Organization (NEDO).
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