Joseph Bazalgette
Victorian London became one of the few large cities in the world to be free of epidemics carried by the water supply. The British later built the water and sewage systems in many other countries, especially those in, or connected with, the British Empire (Cairo, Khartoum, New Delhi and so on). The growth in population has made the water unsafe again in many places, but round about 1900 a clean water supply was available in many parts of the world. All this was a consequence of Snow's work, and Bazalgette's engineering.