The document discusses sewage treatment using microbes. It explains that sewage contains large amounts of organic matter and microbes, some pathogenic. Before disposal in water bodies, sewage undergoes treatment to reduce pollution. Treatment involves aerobic and anaerobic microbes that reduce biochemical oxygen demand and digest sludge, producing biogas. Treatment has two stages - primary filtration and sedimentation remove solids, while secondary aeration and settling uses microbes to consume organic matter and reduce demand.