Changes

With the beginning of settled life, a new problem arose as people began to live in one place throughout the year. That problem was public sanitation. With increased population, the need to adequately remove human waste and maintain relatively clean water supplies became an increasing challenge. By prehistory, this challenge was addressed in societies, with increasing sophistication as cities grew and became more complex.

In the Near East and Central Asia, qanat systems, or underground water channels, brought safe drinking water to urban places as well as bringing water to fields. Cities also utilized natural small streams and created artificial channels to wash out waste water away from them. The Qin and Han dynasties utilized plumping systems within their cities that developed sewer systems that were already around by the Bronze Age in China <ref>For more on water and sanitation systems in late antiquity, see: Liebeschuetz, J. H. W. G. (2015). East and West in late antiquity: invasion, settlement, ethnogenesis and conflicts of religion. Leiden: Brill.</ref>.

==Later Periods==

In the Medieval Period, cities began to utilize small open canals along streets to move waste water out of cities. Sometimes natural stream were utilized to move waste away from a city, although this had the detrimental result of polluting water downstream. By the late Medieval period, however, cities were developing more sanitary policies and becoming administered by central municipalities that managed issues of waste water and the provision of drinking water. public latrines were constructed, although by the 16th centuries flush toilets were also utilized at least by the royalty <ref>For more on Medieval sanitation, see: Gies, F., & Gies, J. (1999). Daily life in medieval times: a vivid, detailed account of birth, marriage, and death; food, clothing, and housing; love and labor, in the Middle Ages. New York: Black Dog & Leventhal Publishers, pg. 138.</ref>.

In the 20th century, sewage treatment plants began to be established with the innovation of using activated sludge or natural bacteria and protozoa as part of the waste water treatment process. In this case, tanks or pools of waste water would be treated with bacteria to help breakdown waste. Chemical treatment was also utilized <ref>For more on modern sanitation systems, see: Jenkins, D., Wanner, J., IWA Conference Activated Sludge - 100 Years and Counting, & International Water Association (Eds.). (2014). Activated sludge - 100 years and counting: [papers delivered at the Conference “Activated Sludge ... 100 Years and Counting!” held in Essen, Germany, June 12th to 14th, 2014]. London: IWA Publ.</ref>.

==Conclusion==

==References==