From Guoqiang Liu et al. Formation of filamentous microorganisms impedes oxygen transfer and decreases aeration efficiency for wastewater treatment
This topic was brought to my attention last week when a facility that I am working with noticed that Thiothrix filaments appeared to be reducing oxygen transfer efficiency in the aeration basin. While low D.O. promoting filamentous growth is well known, I was not familiar with how much filamentous bulking can reduce OTE.
Oxygen Transfer Efficiency (OTE) refers to how effectively oxygen is delivered and dissolved in water under specific conditions. Systems are designed based on predicted OTE as conditions vary in working wastewater treatment systems.
When you compare floc forming sludge (FFS) versus filamentous bulking sludge (FBS), OTE decreases by up to 50%. Filament length also impacts the results with longer filaments, such as Thiothrix, having more impact on OTE than short filament that do not extend from the floc. The studies proposed that the loss in transfer efficiency related to:
Good reference articles on the topic:
Ken Campbell et al. Filamentous organisms degrade oxygen transfer efficiency by increasing mixed liquor apparent viscosity: Mechanistic understanding and experimental verification
https://www.sciencedirect.com/science/article/abs/pii/S0043135420301068
Guoqiang Liu et al. Formation of filamentous microorganisms impedes oxygen transfer and decreases aeration efficiency for wastewater treatment
https://www.sciencedirect.com/science/article/abs/pii/S0959652618311521
Xianwei Wu et al. Thiothrix eikelboomii interferes oxygen transfer in activated sludge
https://www.sciencedirect.com/science/article/abs/pii/S0043135418310364
Oxygen Transfer Efficiency (OTE) refers to how effectively oxygen is delivered and dissolved in water under specific conditions. Systems are designed based on predicted OTE as conditions vary in working wastewater treatment systems.
When you compare floc forming sludge (FFS) versus filamentous bulking sludge (FBS), OTE decreases by up to 50%. Filament length also impacts the results with longer filaments, such as Thiothrix, having more impact on OTE than short filament that do not extend from the floc. The studies proposed that the loss in transfer efficiency related to:
- Viscosity – filamentous typically being more viscous.
- Filaments attaching to bubble surface reducing air/water interface.
- EPS on filaments acting in a manner similar to surfactants which reduce air/water interface.
Good reference articles on the topic:
Ken Campbell et al. Filamentous organisms degrade oxygen transfer efficiency by increasing mixed liquor apparent viscosity: Mechanistic understanding and experimental verification
https://www.sciencedirect.com/science/article/abs/pii/S0043135420301068
Guoqiang Liu et al. Formation of filamentous microorganisms impedes oxygen transfer and decreases aeration efficiency for wastewater treatment
https://www.sciencedirect.com/science/article/abs/pii/S0959652618311521
Xianwei Wu et al. Thiothrix eikelboomii interferes oxygen transfer in activated sludge
https://www.sciencedirect.com/science/article/abs/pii/S0043135418310364
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