Example 1 - Zoogleal (Non-filamentous) bulking
In typical activated sludge and decline phase growth systems, often Zooglea type organisms are the most common genera found when looking at DNA. In addition to degrading many organic components of BOD5, these organisms are also great for denitrification and making EPS needed for floc/biofilm formation. Problems come when high Zooglea (or Thauera) populations meet conditions that cause excess EPS production. Example triggers include:
- high soluble BOD5 (they store soluble BOD as EPS)
- Low N or P which slows cell metabolism - resulting in organics being stored in EPS
Example 2 - Sphaerotilus natans
A common sheathed filament, S. natans can often be seen in filamentous bulking sludges. Under normal conditions with sufficient D.O., S. natans grows as a typical floc forming organisms. In response to stress of low D.O., we see the formation of the sheath and filamentous growth.