Water is vital for life. Earth is the only place in the universe where life exists and the main reason for this is the presence of water on the earth. Earth is called the “water planet” because 80% of its surface is covered with water or ice. 22 March has been declared as “World Water Day”. The General Assembly of the United Nations proclaimed the period 2005–2015 as the International Decade for action on “Water for life”.Wastewater is the water that has been adversely affected in quality by the waste materials. Waste materials are released from industries, households and agriculture. Sewage is wastewater having dissolved and suspended impurities released from homes, industries, hospitals, offices and other users. Impurities present in water are known as contaminants. Sewage is a complex mixture containing suspended solids, organic and inorganic impurities, nutrients, saprotrophic and disease causing bacteria and other microbes. Sewers are the big and small pipes carrying sewage. Sewerage system is a transport system that carries sewage from the point of being produced to the point of disposal that is the water treatment plant. Wastewater treatment is the process of removing contaminants from wastewater. In Wastewater Treatment Plant, water is treated in four steps namely separation of large objects, passing of water through grit and sand removal tank, settlement of water in a large tank and pumping of air into clarified water. Solid wastes that settle at the bottom of the settling tank called sludge. The sludge is then transferred to a separate tank where it is decomposed by anaerobic bacteria. Poor sanitation causes pollution which leads to several water borne diseases. Sanitation and hygiene consciousness can play a vital role in eliminating these diseases. Biogas is a mixture of methane and carbon dioxide produced by the bacterial decomposition of organic waste. We all should realise our responsibility in maintaining the water sources in a healthy state.