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Applied and Environmental Microbiology, April 2004, p. 2420-2428, Vol. 70, No. 4
0099-2240/04/$08.00+0     DOI: 10.1128/AEM.70.4.2420-2428.2004
Copyright © 2004, American Society for Microbiology. All Rights Reserved.

Relationship of Species-Specific Filament Levels to Filamentous Bulking in Activated Sludge

Jiangying Liao, Inchio Lou, and Francis L. de los Reyes III*

Department of Civil, Construction and Environmental Engineering, North Carolina State University, Raleigh, North Carolina

Received 14 August 2003/ Accepted 19 December 2003

To examine the relationship between activated-sludge bulking and levels of specific filamentous bacteria, we developed a statistics-based quantification method for estimating the biomass levels of specific filaments using 16S rRNA-targeted fluorescent in situ hybridization (FISH) probes. The results of quantitative FISH for the filament Sphaerotilus natans were similar to the results of quantitative membrane hybridization in a sample from a full-scale wastewater treatment plant. Laboratory-scale reactors were operated under different flow conditions to develop bulking and nonbulking sludge and were bioaugmented with S. natans cells to stimulate bulking. Instead of S. natans, the filament Eikelboom type 1851 became dominant in the reactors. Levels of type 1851 filaments extending out of the flocs correlated strongly with the sludge volume index, and extended filament lengths of approximately 6 x 108 µm ml–1 resulted in bulking in laboratory-scale and full-scale activated-sludge samples. Quantitative FISH showed that high levels of filaments occurred inside the flocs in nonbulking sludge, supporting the "substrate diffusion limitation" hypothesis for bulking. The approach will allow the monitoring of incremental improvements in bulking control methods and the delineation of the operational conditions that lead to bulking due to specific filaments.

* Corresponding author. Mailing address: Department of Civil, Construction and Environmental Engineering, North Carolina State University, Campus Box 7908, Raleigh, NC 27695-7908. Phone: (919) 515-7416. Fax: (919) 515-7908. E-mail: fldelosr{at}eos.ncsu.edu.

Applied and Environmental Microbiology, April 2004, p. 2420-2428, Vol. 70, No. 4
0099-2240/04/$08.00+0     DOI: 10.1128/AEM.70.4.2420-2428.2004
Copyright © 2004, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

  • Mota, C., Head, M. A., Ridenoure, J. A., Cheng, J. J., de los Reyes, F. L. III (2005). Effects of Aeration Cycles on Nitrifying Bacterial Populations and Nitrogen Removal in Intermittently Aerated Reactors. Appl. Environ. Microbiol. 71: 8565-8572 [Abstract] [Full Text]  


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