presented ground-breaking ideas and descriptions of hydrological and hydrogeological perceptions such as components of the hydrological cycle, groundwater quality, and driving factors of groundwater flow. he also gave an early description of a water filtration process. sub-saharan africa in post-classical kilwa plumbing was prevalent in the stone homes of the natives. the husani kubwa palace as well as other buildings for the ruling elite and wealthy included the luxury of indoor plumbing. in the ashanti empire, toilets were housed in two story buildings that were flushed with gallons of boiling water. medieval europe agkistro byzantine bath. a 1939 conceptual illustration showing various ways that typhoid bacteria can contaminate a water well (center) waterworks (wasserkunst) and fountain from 1602 in wismar, germany christianity places an emphasis on hygiene. despite the denunciation of the mixed bathing style of roman pools by early christian clergy, as well as the pagan custom of women naked bathing in front of men, this did not stop the church from urging its followers to go to public baths for bathing, which contributed to hygiene and good health according to the church fathers, clement of alexandria and tertullian. the church built public bathing facilities that were separate for both sexes near monasteries and pilgrimage sites; also, the popes situated baths within church basilicas and monasteries since the early middle ages. pope gregory the great urged his followers on value of bathing as a bodily need. contrary to popular belief bathing and sanitation were not lost in europe with the collapse of the roman empire. public bathhouses were common in medieval christendom larger towns and cities such as constantinople, paris, regensburg, rome and naples. and great bathhouses were built in byzantine centers such as constantinople and antioch. there is little record of other sanitation systems (apart of sanitation in ancient rome) in most of europe until the high middle ages. unsanitary conditions and overcrowding were widespread throughout europe and asia during the middle ages. this resulted in pandemics such as the plague of justinian (541–542) and the black death (1347–1351), which killed tens of millions of people. very high infant and child mortality prevailed in europe throughout medieval times, due partly to deficiencies in sanitation. in medieval european cities, small natural waterways used for carrying off wastewater were eventually covered over and functioned as sewers. london's river fleet is such a system. open drains, or gutters, for waste water run-off ran along the center of some streets. these were known as "kennels" (i.e., canals, channels), and in paris were sometimes known as “split streets,” as the waste water running along the middle physically split the streets into two halves. the first closed sewer constructed in paris was designed by hugues aubird in 1370 on rue montmartre (montmartre street), and was 300 meters long. the original purpose of designing and constructing a closed sewer in paris was less-so for waste management as much as it was to hold back the stench coming from the odorous waste water. in dubrovnik, then known as ragusa (latin name), the statute of 1272 set out the parameters for the construction of septic tanks and channels for the removal of dirty water. throughout the 14th and 15th century the sewage system was built, and it is still operational today, with minor changes and repairs done in recent centuries. pail closets, outhouses, and cesspits were used to collect human waste. the use of human waste as fertilizer was especially important in china and japan, where cattle manure was less available. however, most cities did not have a functioning sewer system before the industrial era , relying instead on nearby rivers or occasional rain showers to wash away the sewage from the streets . in some places, waste water simply ran down the streets, which had stepping stones to keep pedestrians out of the muck, and eventually drained as runoff into the local watershed. john harington's toilet in the 16th century, sir john harington invented a flush toilet as a device for queen elizabeth i (his godmother) that released wastes into cesspools. after the adoption of gunpowder, municipal outhouses became an important source of raw material for the making of saltpeter in european countries. in london, the contents of the city's outhouses were collected every night by commissioned wagons and delivered to the nitrite beds where it was laid into specially designed soil beds to produce earth rich in mineral nitrates. the nitrate rich-earth would be then further processed to produce saltpeter, or potassium nitrate, an important ingredient in black powder that played a part in the making of gunpowder. classic and early modern mesoamerica the classic maya at palenque had underground aqueducts and flush toilets; the classic maya even used household water filters using locally abundant limestone carved into a porous cylinder, made so as to work in a manner strikingly similar to modern ceramic water filters. in spain and spanish america, a community operated watercourse known as an acequia, combined with a simple sand filtration system, provided potable water. sewage farms for disposal and irrigation “sewage farms” (i.e. wastewater application to the land for disposal and agricultural use) were operated in bunzlau (silesia) in 1531, in edinburgh (scotland) in 1650, in paris (france) in 1868, in berlin (germany) in 1876 and in different parts of the usa since 1871, where wastewater was used for beneficial crop production. in the following centuries (16th and 18th centuries) in many rapidly growing countries/cities of europe (e.g. germany, france) and the united states, “sewage farms” were increasingly seen as a solution for the disposal of large volumes of the wastewater, some of which are still in operation today. irrigation with sewage and other wastewater effluents has a long history also in china and india; while also a large “sewage farm” was established in melbourne, australia, in 1897. modern age water supply until the enlightenment era, little progress was made in water supply and sanitation and the engineering skills of the romans were largely neglected throughout europe. it was in the 18th century that a rapidly growing population fueled a boom in the establishment of private water supply networks in london. london water supply infrastructure developed over many centuries from early mediaeval conduits, through major 19th-century treatment works built in response to cholera threats, to modern, large-scale reservoirs. the first screw-down water tap was patented in 1845 by guest and chrimes, a brass foundry in rotherham. the first documented use of sand filters to purify the water supply dates to 1804, when the owner of a bleachery in paisley, scotland, john gibb, installed an experimental filter, selling his unwanted surplus to the public. the first treated public water supply in the world was installed by engineer james simpson for the chelsea waterworks company in london in 1829. the practice of water treatment soon became mainstream, and the virtues of the system were made starkly apparent after the investigations of the physician john snow during the 1854 broad street cholera outbreak demonstrated the role of the water supply in spreading the cholera epidemic. sewer systems many industrialized cities had incomplete public sanitation well into the 20th century. outhouses in brisbane, australia, around 1950.a significant development was the construction of a network of sewers to collect wastewater. in some cities, including rome, istanbul (constantinople) and fustat, networked ancient sewer systems continue to function today as collection systems for those cities' modernized sewer systems. instead of flowing to a river or the sea, the pipes have been re-routed to modern sewer treatment facilities. basic sewer systems were used for waste removal in ancient mesopotamia, where vertical shafts carried the waste away into cesspools. similar systems existed in the indus valley civilization in modern-day pakistan and in ancient crete and greece. in the middle ages the sewer systems built by the romans fell into disuse and waste was collected into cesspools that were periodically emptied by workers known as 'rakers' who would often sell it as fertilizer to farmers outside the city. archaeological discoveries have shown that some of the earliest sewer systems were developed in the third millennium bce in the ancient cities of harappa and mohenjo-daro in present-day pakistan. the primitive sewers were carved in the ground alongside buildings. this discovery reveals the conceptual understanding of waste disposal by early civilizations. however, until the enlightenment era, little progress was made in water supply and sanitation and the engineering skills of the romans were largely neglected throughout europe. this began to change in the 17th and 18th centuries with a rapid expansion in waterworks and pumping systems. the tremendous growth of cities in europe and north america during the industrial revolution quickly led to crowding, which acted as a constant source for the outbreak of disease.: 4–8 as cities grew in the 19th century concerns were raised about public health.: 33–62 as part of a trend of municipal sanitation programs in the late 19th and 20th centuries, many cities constructed extensive gravity sewer systems to help control outbreaks of disease such as typhoid and cholera.: 29–34 storm and sanitary sewers were necessarily developed along with the growth of cities. by the 1840s the luxury of indoor plumbing, which mixes human waste with water and flushes it away, eliminated the need for cesspools. modern sewerage systems were first built in the mid-nineteenth century as a reaction to the exacerbation of sanitary conditions brought on by heavy industrialization and urbanization. baldwin latham, a british civil engineer contributed to the rationalization of sewerage and house drainage systems and was a pioneer in sanitary engineering. he developed the concept of oval sewage pipe to facilitate sewer drainage and to prevent sludge deposition and flooding. due to the contaminated water supply, cholera outbreaks occurred in 1832, 1849 and 1855 in london, killing tens of thousands of people. this, combined with the great stink of 1858, when the smell of untreated human waste in the river thames became overpowering, and the report into sanitation reform of the royal commissioner edwin chadwick, led to the metropolitan commission of sewers appointing joseph bazalgette to construct a vast underground sewage system for the safe removal of waste. contrary to chadwick's recommendations, bazalgette's system, and others later built in continental europe, did not pump the sewage onto farm land for use as fertilizer; it was simply piped to a natural waterway away from population centres, and pumped back into the environment. liverpool, london and other cities in the uk the great stink of 1858 stimulated the construction of a sewer system for london. in this caricature in the times, michael faraday reports to father thames on the state of the river. as recently as the late 19th-century sewerage systems in some parts of the rapidly industrializing united kingdom were so inadequate that water-borne diseases such as cholera and typhoid remained a risk. from as early as 1535 there were efforts to stop polluting the river thames in london. beginning with an act passed that year that was to prohibit the dumping of excrement into the river. leading up to the industrial revolution the river thames was identified as being thick and black due to sewage, and it was even said that the river “smells like death.” as britain was the first country to industrialize, it was also the first to experience the disastrous consequences of major urbanization and was the first to construct a modern sewerage system to mitigate the resultant unsanitary conditions. during the early 19th century, the river thames was effectively an open sewer, leading to frequent outbreaks of cholera epidemics. proposals to modernize the sewerage system had been made during 1856 but were neglected due to lack of funds. however, after the great stink of 1858, parliament realized the urgency of the problem and resolved to create a modern sewerage system.: 9 liverpool however, ten years earlier and 200 miles to the north, james newlands, a scottish engineer, was one of a celebrated trio of pioneering officers appointed under a private act, the liverpool sanitory act by the borough of liverpool health of towns committee. the other officers appointed under the act were william henry duncan, medical officer for health, and thomas fresh, inspector of nuisances (an early antecedent of the environmental health officer). one of five applicants for the post, newlands was appointed borough engineer of liverpool