How can sewage be used to generate biogas ? Explain.
Sewage basically consists of human excreta. It may contain many microbes that may also be pathogenic. Gas made from the anaerobic digestion of agricultural and animal waste is called biogas. Treatment of sewage includes the following two stages:
- Primary treatment: Involves physical removal of particles by filtration and sedimentation
- Secondary treatment: Involves digestion of organic matter by bacteria
In anaerobic sludge digesters, anaerobic bacteria act on the activated sludge to produce biogas (CH4, CO2 and H2S). The effluent from secondary treatment plant is released into water bodies. Microbial technology for sewage treatment is very effective; no technology has been able to beat it till date. The anaerobic bacteria such as Methanobacterium produce methane along with CO2 and H2 during the secondary treatment.