Linking biofilm growth to fouling and aeration performance of fine-pore diffuser in activated sludge

Manel Garrido-Baserba, Pitiporn Asvapathanagul, Graham W. McCarthy, Thomas E. Gocke, Betty H. Olson, Hee Deung Park, Ahmed Al-Omari, Sudhir Murthy, Charles B. Bott, Bernhard Wett, Joshua D. Smeraldi, Andrew R. Shaw, Diego Rosso

Research output: Contribution to journalArticlepeer-review

38 Citations (Scopus)


Aeration is commonly identified as the largest contributor to process energy needs in the treatment of wastewater and therefore garners significant focus in reducing energy use. Fine-pore diffusers are the most common aeration system in municipal wastewater treatment. These diffusers are subject to fouling and scaling, resulting in loss in transfer efficiency as biofilms form and change material properties producing larger bubbles, hindering mass transfer and contributing to increased plant energy costs. This research establishes a direct correlation and apparent mechanistic link between biofilm DNA concentration and reduced aeration efficiency caused by biofilm fouling. Although the connection between biofilm growth and fouling has been implicit in discussions of diffuser fouling for many years, this research provides measured quantitative connection between the extent of biofouling and reduced diffuser efficiency. This was clearly established by studying systematically the deterioration of aeration diffusers efficiency during a 1.5 year period, concurrently with the microbiological study of the biofilm fouling in order to understand the major factors contributing to diffuser fouling. The six different diffuser technologies analyzed in this paper included four different materials which were ethylene-propylene-diene monomer (EPDM), polyurethane, silicone and ceramic. While all diffusers foul eventually, some novel materials exhibited fouling resistance. The material type played a major role in determining the biofilm characteristics (i.e., growth rate, composition, and microbial density) which directly affected the rate and intensity at what the diffusers were fouled, whereas diffuser geometry exerted little influence. Overall, a high correlation between the increase in biofilm DNA and the decrease in αF was evident (CV < 14.0 ± 2.0%). By linking bacterial growth with aeration efficiency, the research was able to show quantitatively the causal connection between bacterial fouling and energy wastage during aeration.

Original languageEnglish
Pages (from-to)317-328
Number of pages12
JournalWater Research
Publication statusPublished - 2016 Mar 1

Bibliographical note

Funding Information:
This research was funded by the Water Environment Research Foundation (contract number INFR2R12 ) and the United States Environmental Protection Agency , with the support of the Irvine Ranch Water District, Hampton Roads Sanitation District, DC Water, and Southern California Edison. The authors thank David M. Hayden of the Irvine Ranch Michelson Water Reclamation Plant for the invaluable help and Alice K. Robinson of BKT for the help during field work. We thank Taek-Seung Kim for the EDX analyses.

Publisher Copyright:
© 2015 Elsevier Ltd.


  • Activated sludge
  • Aeration
  • Biofilm
  • Efficiency
  • Fine-pore diffuser
  • Fouling

ASJC Scopus subject areas

  • Ecological Modelling
  • Water Science and Technology
  • Waste Management and Disposal
  • Pollution


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