Methanogenic bacteria are not found in

1. rumen of cattle

2. gobar gas plant

3. bottom of water-logged paddy fields

4. activated sludge

(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 flocs.

During secondary treatment of wastewater itis in the digestors where other kinds of bacteria

which grow anaerobically, digest the bacteria and the fungi in the sludge producing mixture of

gases such as methane, hydrogen sulphide and CO2 which form the biogas.

Page 184, XII NCERT