The document summarizes water purification methods used in Kanpur, India. It discusses purification on a large, medium, and small scale. Purification on a large scale involves coagulation, sedimentation, filtration, and disinfection of water sources like rivers and lakes. Medium scale purification adds bleaching powder or chlorinated lime to wells and springs. Small scale involves boiling or adding chemicals like bleaching powder. The municipal water supply covers 80% of Kanpur using treatments like pre-chlorination, coagulation, sedimentation, filtration, and chlorination. Reverse osmosis removes more impurities but also minerals and recovers only 5-15% of water.