Floc, often referred to as "bugs" is composed of:
- Living and dead bacteria
- Extracellular biopolymers (EPS) functioning as glue creating a biofilm that serves to trap stored insoluble organics being acted on by extracellular enzymes and protecting cells from surrounding environment.
- Inorganics - EPS also contains grit and other inorganics trapped in the matrix
Both protozoa and metazoan prey on either free bacteria or graze on the floc. This grazing and filter feeding helps improve wastewater operation.
- Filter feeders remove free bacteria cells from solution and encourage floc formation by consuming cells not in the biofilm (floc). You can watch stalk ciliates actively filtering free floating cells while attached to floc. In the case of "young sludge" - high F/M - you will see flagellates and amoeba moving along consuming free cells.
- Grazing feeders move along developing floc and consume outer layers of the biofilm. Grazing feeders include free crawling ciliates, rotifers, water bears, and other metazoan. By grazing on the outer layers, these organisms reduce excess EPS and help keep the biomass active and aerobic. All are good for improving floc density and settling.
While it is possible, a healthy ecosystem contains both primary producers and predators. This relationship between predator and prey ensures no overgrowth of any single organism and a more diverse biomass. So, just note the indicator organisms present and relate activity to where the system is on the growth curve. Don't worry about protozoa or metazoan eating all the biomass.
Poster with indicator organisms and how they relate to the growth curve is available for download here
https://asterbio.com/bug-poster/