Oxygen transfer and uptake, nutrient removal, and energy footprint of parallel full-scale IFAS and activated sludge processes

ABSTRACT The size of bacterial aggregates can determine both nutrient removal and sludge/water separation in activated sludge processes. In this study, the bacterial community structures and network associations of different sized aggregates obtained from a full-scale membrane bioreactor plant over a one-year period were investigated. Our results showed that biodiversity of larger sized aggregates was significantly higher than that of smaller ones and that the bacterial compositions of different sized aggregates differed significantly from each other. Bacteria related to nutrient removal (e.g. denitrification, hydrolysis and fermentation) were found to be significantly more abundant in larger aggregates than smaller ones. Network analysis revealed significant difference in species–species interactions, topological roles of individual OTU and keystone populations among different sized aggregates. Moreover, the occurrence of keystone OTUs affiliated with denitrifiers (Thermomonas) in networks of large and medium aggregates may suggest that denitrification influences bacterial interactions in large and medium aggregates. Overall, our results indicate the aggregates size-dependence of bacterial community separation in activated sludge. The current findings not only can provide guidance for process design and operation optimization, but also highlight the necessity for paying more attentions to the aggregate-based community, metabolic function and gene expression of activated sludge in future studies.

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Comparative Analysis of Parallel IFAS and ASP Reactors: Oxygen Transfer and Uptake, Nutrient Removal, Carbon and Energy Footprint

Proceedings of the Water Environment Federation ◽

10.2175/193864711802867243 ◽

2011 ◽

Vol 2011 (1) ◽

pp. 485-502 ◽

Cited By ~ 1

Author(s):

Diego Rosso ◽

Sarah E. Lothman ◽

Alan L. Stone ◽

Don Howard ◽

W. James Gellner ◽

...

Keyword(s):

Comparative Analysis ◽

Nutrient Removal ◽

Oxygen Transfer ◽

Energy Footprint

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Fine Bubble Aeration Using a High Density Diffuser System

Water Science & Technology ◽

10.2166/wst.1992.0756 ◽

1992 ◽

Vol 26 (9-11) ◽

pp. 2437-2440 ◽

Cited By ~ 1

Author(s):

K. Thatcher

Keyword(s):

Activated Sludge ◽

Oxygen Transfer ◽

Oxygen Demand ◽

High Density ◽

Plant Performance ◽

Energy Usage ◽

High Quality ◽

Transfer Rates ◽

Fine Bubble ◽

Activated Sludge Processes

Current developments with the activated sludge processes with highly concentrated effluents highlight the requirement to (a) reduce energy usage (b) promote the production of high quality effluent. Having observed the efforts being made to improve plant performance we became aware that current methods had to be improved. It was also noted that a period of stagnation had occurred in the development of effective aeration systems. Improved aeration methods are needed which would allow for oxygen transfer efficiencies to be greater than 2kg/kWh. Such oxygen transfer rates should be continually variable in line with the oxygen demand prevailing at any given time. In our study of activated sludge plants we found that operational and electrical/mechanical maintenance was proving to be time consuming and very costly. With these problems in mind we have designed and developed the Fine Bubble High Density Diffuser System.

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The Microbial Database for Danish wastewater treatment plants with nutrient removal (MiDas-DK) – a tool for understanding activated sludge population dynamics and community stability

Water Science & Technology ◽

10.2166/wst.2013.151 ◽

2013 ◽

Vol 67 (11) ◽

pp. 2519-2526 ◽

Cited By ~ 18

Author(s):

A. T. Mielczarek ◽

A. M. Saunders ◽

P. Larsen ◽

M. Albertsen ◽

M. Stevenson ◽

...

Keyword(s):

Wastewater Treatment ◽

Activated Sludge ◽

Nutrient Removal ◽

Wastewater Treatment Plants ◽

Amplicon Sequencing ◽

Temporal Variations ◽

Full Scale ◽

16S Rrna Amplicon Sequencing ◽

Specific Factors ◽

Operational Data

Since 2006 more than 50 Danish full-scale wastewater treatment plants with nutrient removal have been investigated in a project called ‘The Microbial Database for Danish Activated Sludge Wastewater Treatment Plants with Nutrient Removal (MiDas-DK)’. Comprehensive sets of samples have been collected, analyzed and associated with extensive operational data from the plants. The community composition was analyzed by quantitative fluorescence in situ hybridization (FISH) supported by 16S rRNA amplicon sequencing and deep metagenomics. MiDas-DK has been a powerful tool to study the complex activated sludge ecosystems, and, besides many scientific articles on fundamental issues on mixed communities encompassing nitrifiers, denitrifiers, bacteria involved in P-removal, hydrolysis, fermentation, and foaming, the project has provided results that can be used to optimize the operation of full-scale plants and carry out trouble-shooting. A core microbial community has been defined comprising the majority of microorganisms present in the plants. Time series have been established, providing an overview of temporal variations in the different plants. Interestingly, although most microorganisms were present in all plants, there seemed to be plant-specific factors that controlled the population composition thereby keeping it unique in each plant over time. Statistical analyses of FISH and operational data revealed some correlations, but less than expected. MiDas-DK (www.midasdk.dk) will continue over the next years and we hope the approach can inspire others to make similar projects in other parts of the world to get a more comprehensive understanding of microbial communities in wastewater engineering.

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Oxygen transfer in activated sludge – new insights and potentials for cost saving

Water Science & Technology ◽

10.2166/wst.2011.607 ◽

2011 ◽

Vol 63 (12) ◽

pp. 3034-3038 ◽

Cited By ~ 16

Author(s):

J. Henkel ◽

P. Cornel ◽

M. Wagner

Keyword(s):

Activated Sludge ◽

Nutrient Removal ◽

Oxygen Transfer ◽

Transfer Rate ◽

Oxygen Transfer Rate ◽

Organic Load ◽

Current Opinion ◽

Conventional Activated Sludge ◽

Current State ◽

Activated Sludge Systems

The α-factor has the greatest impact on the calculation of the required standard oxygen transfer rate (SOTR) in activated sludge systems equipped with submerged aeration systems. Knowing the dependencies of the α-factor leads to a better design of the aeration devices and, consequently, to a more efficient use of aeration energy. Applying the current state of knowledge about oxygen transfer leads to the conclusion that, in contrast to current opinion, simultaneous aerobic stabilization requires the same SOTR as conventional activated sludge systems with advanced nutrient removal, even though a higher organic load is degraded.

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