Question

The masses of bacteria held together by slime and fungal filaments to form mesh-like structures are called as:
A. primary sludge
B. flocs
C. activated sludge
D. anaerobic sludge

Answer 1

Hint: In the sewage treatment, the microbes are used for the reduction of organic water. The combination of bacterial and fungal filaments form a mesh like network which helps in reducing the biological oxygen demand of the polluted water.

Complete Answer:
- The combination of bacterial and fungal filament help in the aerobic decomposition and the filament help in trapping the particles in the sewage tank during the secondary treatment of sledge. This combination is known as flocs.
- Floc is a special type of bio aggregate or biofilm. It appears as a suspension of cells floating in water. The bacterial slime and the fungal filament is held together by a matrix which consists of polysaccharides, proteins and other biopolymers called as EPS or extracellular polymeric substances.
- Primary sludge is the precipitated solids which are obtained after the primary treatment of sewage.
- Activated sludge is sewage process treatment in which biological floc is developed which reduces the organic content of the sewage. In this process oxygen or air is passed through the sewage.
- Anaerobic sludge is the sludge which is treated anaerobically in the absence of air.

The correct answer is (B). The masses of bacteria held together by slime and fungal filaments to form mesh-like structures are called flocs.

Note: The activated sludge is treated with oxygen which allows the organic matter to be decomposed by the bacteria. This allows the bacteria to obtain its nutrition from the waste and also convert ammonia to nitrate.