The masses of bacteria held together by slime and fungal filaments to form mesh-like structures are called as
primary sludge
Flocs
activated sludge
anaerobic sludge
As we have learnt,
Secondary treatment or Biological treatment -
Flocs
- wherein
The first step allows vigorous growth of useful aerobic microbes into flocs (masses of bacteria associated with fungal filaments to form mesh like structures).