Nocardia Gram Stain from http://web.deu.edu.tr/atiksu/ana52/nocardia1.jpg
Usually present in low concentrations, Nocardia sp. of microbes can cause foaming problems when conditions promote a bloom and associated hydrophobic biological polymers. Nocardia foam is dark brown, stable, and viscous. Under the microscope, the foam contains substantial amounts of biomass in the matrix. Easily identifed by branching and gram positive stain, Nocardia organisms and foam are readily identifed by on-site operators.
Nocardia over-growth is encouraged by the following:
Nocardia over-growth is encouraged by the following:
- Long sludge age (MCRT) or low F/M
- High O&G or long chain fatty acids in the influent
- Usually seen at higher temperatures
- Aeration basins with subsurface weirs trap the Nocardia organisms in the foam inside the aeration basin
- Reduce F/M or MCRT
- Mechanically skim foam - which is wasting the concentrated Nocarida biomass
- Use water spray to "knockdown" the foam - some facilities have added chlorine to water spray to directly disrupt the nocardia organisms
- Prevent O&G from entering the aeration basin
- In the long run - selectors (anaerobic zones before aeration basin) can provide some control
- To some extent, bioaugmentation can keep the Nocardia population from blooming, but it is most effective when used before the bloom occurs. Make sure to use bioaugmentation products that can degrade long chain fatty acids and grease that is used by the slower growing Nocardia sp.
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