Changes

The history of sanitation parallels the history of cities and urban life. Places of high density population only grew to new levels when developments in sanitation were possible. The first innovations in prehistory and early historical periods led to developments in late antiquity, such as that seen in Rome, the Near East, Central Asia, and East Asia. However, after this period, relatively modest development occurred. This resulted in urban populations rarely surpassing one million prior to 1800. It was only with the development of modern sewage systems, pumps, chemical treatments, modern toilets, filtration, and filtration activated sludge that sanitation greatly improvedand now allows our modern cities to be possible. This has now led us to the point where modern cities can grow to far greater sizes, reaching levels never seen in size and human historypopulation has subsequently greatly expanded.