During secondary treatment of sewage, the masses of bacteria held together by fungal hyphae to form mesh like structures called __________.

During the secondary treatment of sewage, the primary effluent is passed into large aeration tanks where it is constantly agitated mechanically and air is pumped into it.

This allows vigorous growth of useful aerobic microbes into flocs.

Flocs are masses of bacteria associated with fungal filaments (hyphae) to form mesh-like structures.

Answer: flocs