microbes play a dual role when used for sewage treatment as they not only help to retrieve usable water but also generate fuel . explain??
Microbes are employed in the secondary stage of sewage treatment. After the primary treatment ie sewage is mixed with air and aerobic bacteria grow into it. It produces floc which settles in the settling tank in the next stage and forms activated sludge. This activated sludge is then put for anaerobic digestion where microbes act on it anaerobically. During this process gases like methane, hydrogen sulphide, carbon dioxide are produced which act as fuels.