"When the plumbers and sanitary engineers had done their work... diseases began to vanish."
Lewis Thomas, medical researcher and essayist
It was probably more the need to get rid of foul smells than an understanding of the health hazards of human waste that led to the first proper sewage systems. While most early settlements grew up next to natural waterways—-into which waste from latrines was readily channeled—the emergence of major cities exposed the inadequacy of this approach.
Early civilizations, like that of the Babylonians, dug cesspits below floor level in their houses and created crude drainage systems for removing storm water. But it was not until around 2500 B.C.E. in the Indus Valley that networks of precisely made brick-lined sewage drains were constructed along the streets to convey waste from homes. Toilets in homes on the street side
were connected directly to these street sewers and were flushed manually with clean water.
Centuries, later, major cities such as Rome and Constantinople built increasingly complex networked sewer systems, some of which are still in use. These days the waste is transported to industrial sewage works rather than to the sea or rivers.
After its installation, the early sewage technology of many cities in Western Europe remained in place without improvement. As recently as the late nineteenth century it was often so inadequate that fatal contagious diseases caused by foul water, such as cholera and typhoid, were still common.
