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Friday, October 28, 2016

The Brief History of Sewers

     Imagine walking through the streets of any European city during the 1500s. Your nostrils would be assaulted by many smells coming from open-air markets as well as the stench coming from nearby open cesspools. As one got further away from the markets, one would find shallow roadside trenches filled with human excreta flowing to the cesspools near the market. People just threw a mixture of human waste and water out of their houses.  Nowadays about the only noticeable sign of a sewer are the manhole covers 
     At first in Europe people did their business on the ground near dwellings. As the population grew this became a problem and the community pit came into existence. This evolved into the privy or "outhouse" which was nothing more than a structure atop a hole in the ground. Today it's recognized that outhouses were not environmentally sound because they deprive the soil of the nutrients and by concentrating wastes it promotes pollution of groundwater. 

     Before the advent of piped water in the late 1700s European cities stored excreta in cesspools (they allow some drainage of liquids) or in vault privies (no drainage). The "night soil" as it was called was removed by "scavengers" and either taken to farms or dumped into pits in the ground or into rivers. 
     In ancient Rome, the wealthy elite had indoor toilets and running water to remove excrement via sewers. Later, European cities developed crude sewer systems, usually open gutters but sometimes covered trenches, though they had no running water. Obviously the lack of running water resulted in putrefying matter stagnating until it rained. These were actually storm sewers and many cities made it illegal to dump human wastes into them. The advent of piped water changed all that. 

     In the United States the first waterworks was installed in Philadelphia in 1802 and by 1860 136 cities had piped water systems. By 1880, the number was up to 598. Piped water also resulted in per-capita usage increasing from from 3-5 gallons per person per day to 30-50 gallons per person per day. 
     Obviously, if water gets piped in, it has to get piped out and most homes used cesspools. But cesspools often overflowed resulting odors and of water-borne diseases. To solve these problems, cesspools were connected to the city's crude sewer systems which ran along the streets. The result was epidemics of cholera. In Paris in 1832, 20,000 people died of cholera.
Modern public urinals
     Engineers eventually designed closed sewer systems which used water to carry away excrement. But, the question remained...where should it be carried to? Carry it out to farmland as fertilizer? Some claimed that water purifies itself so just pipe it straight into lakes, rivers, and oceans. By 1910, the debate was over and sewage was being dumped into whatever body of water was convenient. That was a bad idea because cities drawing their drinking water downstream from sewage discharges began having outbreaks of typhoid.
     Thus was born another debate: whether to treat sewage before dumping it into water bodies used for drinking or treat the drinking water. Public health officials said treat it before dumping and sanitary engineers said treat the water before drinking. The engineers won and as cities began to filter and disinfect their drinking water, typhoid became less of a problem. 
     Throughout the 1900s century industrialization produced a lot of waste and sewers were the cheapest place to dump. The result was vast sums of money were allocated to construct sewer systems to serve both homes and industry. The problem was excrement mixed with industrial wastes were usually toxic. The result was by the 1950s just about every body of water that this waste was piped into was polluted. This resulted in a change. 
     Waste was treated before it got dumped. First is the primary treatment where stuff that floats is screened out. The secondary treatment speeds up biological decomposition by forcing oxygen into them. It's both energy-intensive and expensive and still leaves many nutrients and toxic chemicals in the water. The stuff that results from these two processes is called sludge...de-watered, sticky black "cake" which consists of everything that can go down the drains in homes and industries. 
     Sludge can contain pathogens, micro-pollutants, heavy metals and other hazardous material. Sewage plants must then treat the sludge. Following treatment sludge is either dumped in a landfill incinerated, sold or used as fertilizer. 
     In the United States, according to USDA standards, organic foods are those that are produced in such a way that they protect natural resources and use only approved substances and sewage sludge is one of the prohibited substances. 
     Jon Schladweiler, the Historian of the Arizona Water Association, has researched and collected materials related to the history of sewage conveyance systems. The site, The History of Sanitary Sewers, is jam-packed with sewer fact: time lines, articles, exhibits, links and more.

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