Question : Microbes play a dual role when used for sewagetreatment as they not onlyhelp to retrieve usablewater butalsogenerate fuel. Writehow this happens?

Question : Microbes play a dual role when used for sewagetreatment as

1.	Question : Microbes play a dual role when used for sewagetreatment as they not onlyhelp to retrieve usablewater butalsogenerate fuel. Writehow this happens?
Answer» Solution :Sewage is TREATED in sewagetreatment plants to makeit less polluting . Thistreament is carried outin two STAGE . (i)Primary treatment : Primary treatmentis a physical process of REMOVAL of small and large particles through filtration and SEDIMENTATION. ii. Secondary treatment : It is a BIOLOGICAL process, thatemploys the heterotrophic bacteria naturally present in the sewage . Thebacterial flows are allowed to sediment, that is calledactivatedsludge . The remainingmajorpart of the sludgein pumpen intolarge tanks called anaerobicsludge digesters. Duringthis digestion, bacteria produce a mixtureof gases. Herethese gases form biogas and can beused as source of energy as inflammable.