Cities in India are dreaming of becoming New York and London but we seldom worry about as basic an issue as sewage and its disposal in our country. The Centre for Science and Environment (CSE) has brought out a two-volume book titled Excreta Matters: Report on the State of India’s Environment to highlight how only 20 per cent of sewage is being treated in the country. Sunita Narain, director general, CSE, talks about the murky issue plaguing the water sources in this interview to Rashme Sehgal.