question_answer 18)

  Methanogenic bacteria are not found in (a) rumen of cattle                                                          (b) gobar gas plant (c) bottom of water-logged paddy fields                               (d) activated sludge

Answer:

                  (d)Methanogenic bacteria (that produce methane) are not found in activated sludge. The microbes present in the activated sludge are aerobic bacteria that grow rapidly and form floes. During secondary treatment of wastewater it is in the digesters where other kinds of bacteria which grow anaerobically, digest the bacteria and the fungi in the bacteria and fungi in the sludge producing mixture of gases such as methane, hydrogen sulphide and CO2which form the biogas.