Large quant

(a) The primary effluent is passed into large aeration tanks to facilitate the growth of essential aerobic microbes which gets associated with the fungal filaments to form flocs. This takes place due to the constant agitation and the pumping of air which takes place in the aeration tank.

(b) The scientific term used for sediment is Activated Sludge. It acts as an inoculum and some of it is pumped back into the aeration tank.

(c) In the final step, the anaerobic bacteria digest the aerobic bacteria and the fungi (flocs) present in the sludge. During digestion, the bacteria produce a mixture of gases like methane, hydrogen sulphide and carbon dioxide which constitutes the biogas.