Wastewater The water which gets contaminated after various works; like washing, bathing, mopping, etc. is called wastewater. World Water Day: 22nd March International Decade for Action on Water for Life (2005 – 2015): It was declared by the General Assembly of the United Nations. Its main goal was to reduce the number of people who do not have access to safe drinking water; by half. Sewage Treatment: The process of removing impurities from waste water before it can be reused or sent to the water bodies is called sewage treatment or cleaning of water. Sewage: The liquid waste which has water as its largest component; along with various types of impurities; is called sewage. Composition of Sewage Type of impurities Examples Organic impurities Human faeces, animal waste, oil, urea (urine), pesticides, herbicides, fruits and vegetables Inorganic impurities Nitrates, phosphates, metals Nutrients Phosphorus, ni