 |
Click here for other language: |
|
| Sewerage Facts >
Sewage |
| |
| The Evolution Of Sewage Treatment |
|
As societies moved from nomadic
cultures to building more permanent sites, the concern over
waste (solid and wastewater) disposal became an important
concern. As we will see it has been an issue that has been
dealt with many different ways and knowledge has been lost
and regained. When groups were living as hunters and gathers,
the natural decomposition dealt with refuse and human wastes
naturally. As cities developed other mechanisms were necessary
to address waste issues. What we must understand "until recently,
wastewater sanitation focused on minimizing health risks,
primarily infections diseases. More recently, the scope of
wastewater management issues has broadened to include chronic
health risks and environmental concerns" (Burks & Minnis,
1994:1). |
| |
| Domestic Wastewater
Treatment In The Ancient World |
| >
3500 Before Common Era (BCE) To 500 Common Era (CE) |
|
During the Neolithic period (10,000 BCE) movement by nomadic
tribes addressed the waste created by human activities. This
nomadic movement allowed the earth or the soils treat the
waste. In the ancient world cultures or societies developed
waste treatment technologies. These varied by the skills the
various cultures developed. The City of Ur, by 3500 BCE, had
an average population of 65,000 people per square mile (a
high population density which produced considerable waste).
The populace of the city dealt with their waste problem by
simply sweeping their wastes into the streets. This caused
the street levels to rise and would require, every so often
the raising of house doors. These "[practices that were satisfactory
in semi-permanent small villages were not necessarily suitable
in an urban environment" (Savas, 1977:11). Nor are these practices
acceptable today. We can compare this to cities of the Indus
Valley (present day Pakistan) from about 2500 to 1500 BCE
Some houses had bathrooms with water flushing toilets. They
had well-designed drainage systems. Houses had rubbish chutes,
and there were rubbish bins placed around the city for refuse
disposal. This was a great leap in waste treatment. (Kahn,
2000:119; Savas, 1977:11).
Moving back to the Mediterranean cultures, we see developments
in waste treatment technologies. In the Egyptian city of Herakopolis
(BCE 2100), the average person treated their wastes much like
those in Ur, they threw the wastes into the streets. However,
"in the elite and religious quarters, there was a deliberate
effort made to remove all wastes, organic and inorganic to
locations outside the living and/or communal areas, which
usually meant the rivers." There is also religious teachings
that dealt with waste. Mosaic law (BCE 1300) tells "to remove
his own refuse and bury it in the earth." Nehemiah tells of
rebuilding Jerusalem where there was a refuse gate where the
city wastes were to be dumped. And the Talmud called for the
streets of Jerusalem to be washed daily (Savas, 1977:12).
The Minoan Culture on the Island of Crete between 1500-1700
BCE had a highly developed waste management system. They had
very advanced plumbing and designed places to dispose of organic
wastes. Knossos, the capital city, had a central courtyard
with baths that were filled and emptied using terra-cotta
pipes. This piping system is similar to techniques used today.
They had flushing toilets, with wooden seats and an overhead
reservoir. "Excavations reveal four large separate drainage
systems that emptied into large sewers built of stone." The
Minoan royals were the last group to use flushing toilets
until the re-development of that technology in 1596 (Kahn,
2000: 119-120).
The first 'dumps' was developed by the
Greeks (Athens) circa 500 BCE In the development of waste
management, Athens, in
320 BCE, passed the first known edict banning the disposal
of refuse in the streets. In the continued development of
waste management, by 300 BCE, one of the responsibilities
of the Greek city-state was the removal of waste. "The expenses
[for waste removal were] covered by levees on landowners.
This system was sufficiently viable to last for eight hundred
years, until the general breakdown of civic order"(Savas,
1977:13). In the use of water the early Greeks understood
the relationship between water quality and general public
health. This concern was passed onto the Romans.
The Romans' waste treatment management practices were the
most developed of any civilization prior to the nineteenth
century. In fact, the Romans' waste management systems were
better than those in the middle age. The Romans were very
advanced technologically. We see the evidence of this in their
buildings, roads, and aqueducts that are still standing and
in some cases still in use. The Romans' concern for water
is best illustrated in their aqueducts. They developed them
to provide water to their cities. The water was used for baths,
fountains, public conveniences, and for flushing sewers. The
Romans were concerned with locating good water supplies, and
they were concerned with obtaining pure water, as stressed
by ancient physicians and engineers (History of Technology
Vol. II., 1956: 660-674).
The early Roman Republic was concerned
with the extension of the city's water supply, as well as
the construction of
aqueducts. In fact by 125 BCE, the city's water supply had
been doubled to meet the rapid expansion (History of Technology
Vol. II., 1956:670). The development of these aqueducts required
engineering skills. What we must understand, is the aqueduct
systems developed by the Romans were vast. In every part
of their Empire they built aqueducts, and the majority of
the
systems were underground. What we see today is just the tip
of the iceberg. As we have seen the Romans put the water
to
many uses. Particularly in Rome, they used the water to flush
their sewers. "The Romans employed water-carrying devices
to send most of their wastes to nearby the River Tiber
via
open sewers as early as the 6th century B.C.[E.]. By the
3rd Century, the sewers in Rome were vaulted underground
networks
called the Cloaca Mixima" (Burks & Minnis, 1994:1). These
building projects continued and "by the 4th Century [C.E.],
Rome had 11 public baths over 1300 public fountains, and
856
private baths. Not only were there private water-flushed
toilets, there were public ones. In [C.E.], 315 Rome had
144 [public
water-flushed toilets]" (Kahn, 2000:121).
Even with all these advances and waste management, Rome was
still an unhealthy city. Disposal of the sewage to the Tiber
River and dumping wastes outside the city still caused health
concerns (Savas, 1977:14). The fall of Rome, in the fifth
century C.E., brought an end to plumbing development (Burks
& Minnis, 1994:2). In fact "with the fall of the [Roman] Empire
the lack of central authority and consequently of adequate
public funds led to the decline of all public services. Their
organization was left to private citizens or to municipal
authorities. Only in certain large urban centers did even
remnants of Roman systems survive" (History of Technology,
Vol. II, 1956:689).
|
| |
| Domestic Wastewater Treatment
In The Middle Ages |
| > 500
Common Era (CE) To 1500 Common Era (CE) |
|
The fall of the Roman Empire in the west
turned an urban society into a rural one. "By 500 [C.E.],
'the taps were being turned off all over Europe; they would
not be turned on again
for nearly a thousand years: Sanitation technology entered
its dark ages'" (Kahn, 2000:121). There was massive depopulation
of Rome and most of the western Empire. The deurbanization
of the west changed waste treatment. "The reduced population
density, therefore, rendered traditional methods of waste
disposal (tossing it out of the house) more viable" (Savas,
1974:14). Also, without monitoring the sewers and streets,
hygienic conditions fell below the Imperial Roman Standards
(History of Technology, Vol. II., 1956:689-690). This demise
in sanitation brought back "the outhouse, open trenches,
and the chamber pot ... at all levels of society" (Kahn,
2000:122).
This loss of knowledge and hygienic practice brought many
problems. During the middle ages, "the ages-old practice of
separating drinking water and human wastes was largely abandoned,
and human wastes could easily migrate from waste pits into
wells. Epidemics raged in the cities, but the relationship
between excrement and disease was not recognized" (Burks &
Minnis, 1994:2). In the middle ages people simply threw their
waste into the streets. "Open gutters in the middle of the
streets carried refuse, while rain-water pouring from the
roofs was not properly drained. The streets, seldom paved,
were often mud-pools from which the excreta of pigs and other
animals leaked into wells and private plots" (History of Technology
Vol. II, 1956:690). The habits of rural life, which might
be harmless on the farm, could and did prove to be fatal in
the growing towns of Medieval Europe. Over time in the Medieval
era, cities began to grow. The size of the city was determined
by the walls; this increased the population density, and with
people still practicing their rural habits, the potential
for disease developed. In this period the rivers of the two
major European cities, London and Paris, were open sewers
(Savas, 1974:14 and Kahn, 2000:122-124).
The sanitary conditions in medieval cities lead to rampant
disease and death during the middle ages. The waste and excrement
provided food for the rats, thus bringing disease-carrying
ticks and fleas into human contact. "[D]iseases directly related
to human wastes wiped out many hundreds of thousands of people
in the Middle Ages. This included dysentery, typhus (which
comes from bad sanitation and is highly contagious), and typhoid
fever (from human feces and urine)" (Kahn, 2000:124). The
conditions in medieval towns and cities as urbanization developed
were very poor. The Greek and Roman concern with safe water
was lost in this period. The technology to secure safe water
was also lost.
As the middle ages went on, changes did occur. Most of the
water changes in water issues were speared-head by religious
orders. "Near Milan, the Cistercians introduced the use of
city refuse and sewer water as fertilizers on their land about
1150 C.E. (History of Technology Vol. II, 1956:681-690). Even
during the unwashed period, "many abbeys in Britain had piped
water before 1200 [C.E.]. The Christchurch Monastery at Canterbury,
for example, had running water, purifying tanks, and wastewater
drainage from toilets, and the monastery was spared from the
Black Plague in 1349" (Kahn, 2000:122).
By the end of the 12th and the beginning of the 13th centuries,
changes began to take place. Following the major plagues of
the 12th century, waste management became a priority. In 1372
Edward the Third of England proclaimed that "throwing rushes,
dung, refuse and other filth and harmful things into the [Thames]
shall no longer be allowed" (Savas, 1974:15). Following this
line, in 1388 an act of Parliament "forbade the throwing of
filth and garbage into ditches, rivers, and water" And by
the late 14th century London had an organized scavenger system
(people would go around and pick up dead animals); yet "[u]ltimately
, legislation and scavenging tended to be relatively ineffective.
This was not, however, because of ignorance but rather because
offenders and offended alike were unable to devise adequate
alternatives to the available methods of collection and disposal.
Moreover, except for those in heavily polluted areas, popular
opinion was very much against such measures" (Savas, 1974:15-16,
History of Technology Vol. II, 1956:691).
During the Renaissance more concern was given to health and
water issues. The cesspool was one of the technical developments
of the Renaissance. It is a simple pit, which allowed solids
to settle and the liquid to seep into the ground. Periodically,
the cesspools would have to be cleaned out (Burks & Minnis,
1994:3). As the 15th century came to a close, there were other
management changes that impacted sanitation. Henry the VI
(England) established a Commission of Sewers, which "provided
for severe penalties for the pollution of streams and made
special provisions for the disposal of tanner and brewers
wastes." Henry the VII outlawed slaughterhouses in cities
or towns, because of the danger of disease for the people
(Savas, 1974:16). There was a new awareness of the role that
human and animal wastes played on human health by the end
of the 15th century.
|
| |
| Domestic Wastewater Treatment
In The Modern World: 500 CE To 1900 CE |
|
In the early modern period there was still little change
in the understanding and disposal of human wastes. Wastes
were still disposed of in rivers, and water sources were being
contaminated. These practices were brought to the New World.
As developments grew to cities, the Colonies had to address
waste issues. In 1644 eighteen years after taking control
of Manhattan Island, "residents were directed to take all
wastes out of the fort," and in 1648 a law was passed prohibiting
hogs and goats from running in the streets (Savas, 1974:17-19).
The major changes in waste treatment came in the 19th century.
In 1860 Louis Moureas invented the "septic tank"; however,
it would not be given this name until 1895. Septic tanks at
this stage were large and were used to treat sewage from communities.
"The main purpose of these tanks was to remove gross solids
before discharge into the nearest stream or river." Here we
see an understanding of removing the solids, a potential problem
for public health. Nevertheless, a problem remained: "effluent
was largely untreated and caused pollution of streams and
rivers" (Kahn, 2000:135-136). The pollution of water was not
solved by a septic tank. Even with pre-treatment, the need
for disposal technology was becoming evident.
Edward Frankland, in 1868, developed trickling sand filter
technology. He devised a system consisting of six-foot high,
ten-inch wide cylinders, filling each with different medias
like sand and soil. He then ran sewage at different doses
through the different tanks. He calculated the capabilities
of the different media in purifying the wastewater. Unfortunately,
little data is available to report on at this time. The Experimental
Station at Lawrence, Massachusetts, created in 1887, by the
Massachusetts State Board of Health worked on disposal issues.
"At the station in 1893, a sand bed was first used to filter
the effluent from a septic tank, reducing the land areas needed
for sewage disposal. The land acceptance rates were established
to maintain an efficiently-working sand-filter" (Burks & Minnis,
1994:3-5).
What was driving these changes? Disease -- it pushed plumbing
and disposal development. The scourge of the 19th century
was cholera. The urbanization of cities and the industrial
revolution also increasing city populations lead to increased
human waste. In the mid-19th century a world-wide epidemic
of cholera occurred. Cholera was worse in the poor areas,
but even the wealthy were not immune (Kahn, 2000:123-125).
The English physician John Snow discovered the relationship
of cholera to water. He traced this disease from its origins
in India and the path it took to Europe. Snow traced the contamination
to public wells, which were being contaminated by privy vaults
in the epidemic of 1854 in London (Kahn, 2000:125, Burks &
Minnis, 1994:2-4). Thus, the sewer was developed. "The British
engineers led the way in sewer construction and separation
of wastes from drinking water" (Kahn, 2000:125). But this
only took the issue of sanitation to the river. The pollution
of the rivers, especially the Thames in London, began the
call for sewage treatment. The need to solve this health care
concern in large cities marked the 19th century as the beginning
of municipal socialism (Savas, 1974:19-20). The classic example
of this effort is New York City.
|
| |
| A Case Study - The Development
Of Wastewater Treatment In New York City |
|
New York City provides an excellent case
study in the development of wastewater management. In the
19th century New York City
was a developing urban center, which lacked the infrastructure
to deal with its wastewater. In the city in the early part
of the century, "people obtained their own water from wells
and cisterns and were responsible for discarding their wastes"
(Goldman, 1997:11). Both water supply and waste disposal
were private matters in the city. The city's efforts to manage
waste were particularly ineffective. Each house was responsible
for its waste disposal, which meant they built privies. "Regulations
mandated that privies be constructed of stone, mortar, and
brick and be dug at least five feet deep." The completed
privies were also to be inspected. Even with what appeared
to be a
rigorous code, petitions for wood privies were regularly
approved. The city would only get involved if privies overtly
were a
threat to public health. The other concern was privy vaults
were meant to function as temporary storage for wastes,
they
were not for permanent disposal (Goldman, 1997:19-21).
The understanding of treatment of waste was very limited
at this time. "The belief that running water purified effluents
was widely held during the first half of the nineteenth century,
so the potential for water pollution did not raise the concern
that the 'nuisances' on land had" (Goldman, 1997:22). We see
that, from time to time, the treatment was to dispose of particular
obnoxious effluent from privies directly to the river. The
treatment of on-site waste was, in a sense, vault and haul.
Yet, the city did have a sewer system. The system that did
exist in the early nineteenth century was developed to handle
storm water. There was limited access to these sewer systems
because of the limited access to water, which was needed to
flush waste through the sewers. Before 1840 there were limited
sewer developments; with the exception of a few wealthy neighborhoods,
most of the city was left to wallow in dampness. The flood
water carried street debris and animal wastes through the
streets. "The earliest sewers were merely open trenches placed
together in the center on the sides of a street." This was
a health problem, because the sun would heat the standing
water and quicken decomposition, producing an unhealthy brew
(Goldman, 1997:40-45). In the early part of the nineteenth
century, the treatment of waste in New York City was little
different from the late middle age.
During this period sewers were done on a street-by-street
basis. This could even be blocked if a people on the street
were opposed to sewering. At this time those opposed to sewers
"feared that sewers were unhealthy and generated offensive
smells." This system precluded any possibility of an organized
and integrated system. There was no overall design for the
city to dispose of storm water, much less wastewater (Goldman,
1997:44-46). The limited water supply made a water-based waste
disposal system unacceptable. However, with the arrival of
the Croton aqueduct, water overwhelmed the existing sewer
systems. This required a change in thinking regarding a water-based
disposal system.
By the end of the 1860's physicians and
engineers were part of the city management on full-time,
year-round basis (Goldman,
1997:146). This change greatly impacted the development of
public health issues and the development of sewering the
city.
The Croton Aqueduct Department laid 39,000 linear feet of
sewers in 1865. By the end of the decade the department had
laid an additional 271,000 linear feet. They were draining
the city. "Each district was approached as an entity and
treated in its entirety. A system of intercepting sewers
was planned
that took into consideration street grade and anticipated
sewage volume. The goal was to ensure the smooth and continuous
flow of sewage from small pipes into larger ones and finally
to a limited and specified number of sites for disposal
into
the rivers" (Goldman, 1997:158).
The city put the economic resource to
build sewers in the engineers' hands. And they built a comprehensive
wastewater
disposal system. Yet, even into the 1880's their project
was still not complete. In some affluent neighborhoods problems
still existed. "Property owners had built house drains but
never connected them to sewers, so that the sewage discharged
into the loose rock filling the streets. At other times,
house drains emptied their contents into underground watercourses.
All too often, property owners sought economy at the expense
of efficiency and effectiveness" (Goldman, 1997:162). The
task of sewering New York was a long and arduous task.
The
goal to sewer the city was achieved by public funding pushed
by public health concerns.
The problems of wastewater treatment and reuse will always
be a part of society's concern. The development of large or
municipal treatment plants, which was considered the solution
in mid-19th century, is no longer considered the answer. The
cost of constructing these plants is too high, and most local
municipalities cannot afford to build them, and the national
government is not looking to help fund new plants. This is
evident in the 1997 Environmental Protection Agency's Response
to Congress On Use of Decentralized Wastewater Treatment Systems
(EPA 832-R-97-001b).
|
| |
|
|