Nocardia foaming control in activated sludge process treating domestic wastewater


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In this study, filamentous bacteria (Nocardia amarae) were identified as the major causal microorganism in foaming sludge. The results of growth kinetics study indicated that N. amarae had a relatively strong affinity for non-readily biodegradable fatty acids. N. amarae was able to consume various fatty acids at a constant growth yield from 0.413 to 0.487 g/gCOD. Under common F/M ratio (less than 0.5 gBOD/gMLSS/d) used in activated sludge processes, specific growth rate of N. amarae was found to be more significant than that of non-filamentous bacteria. Based on this feature, a novel technique feast–fast operation (FFO) was developed for the foaming control. The sludge volume index (SVI) rapidly decreased from 300 to 80 mL/g and further stabilized at about 70 mL/g and the system was free from stable foam, while the BOD removal efficiency was maintained above 95%. This control technology effectively suppressed the overgrowth of filaments and improved the settleability of activated sludge without adverse effects on the treatment performance and the process stability. Copyright © 2007 Elsevier Ltd. All rights reserved.
Original languageEnglish
Pages (from-to)3381-3388
JournalBioresource Technology
Issue number9
Publication statusPublished - Jun 2008


Tsang, Y. F., Sin, S. N., & Chua, H. (2008). Nocardia foaming control in activated sludge process treating domestic wastewater. Bioresource Technology, 99(9), 3381-3388. doi: 10.1016/j.biortech.2007.08.012


  • Foaming control
  • Wastewater treatment
  • Filamentous bacteria
  • Long-chain fatty acids

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