Measures of Central Tendency: Mean, Median and Mode
Water Pollution
1. Water Pollution
Submitted To:-
Miss Nusrat
Submitted By:-
Muhammad Sajjad (907)
BS (hons) 6th Semester (2009-13)
Department of Geography,
Govt. College University
Faisalabad
Ph# +923346544625
Govt. College
University Faisalabad
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2. Contents
Water Pollution......................................................................................................................... 1
Govt. College University Faisalabad.......................................................................................... 1
Contents................................................................................................................................... 2
1.What is Pollution ................................................................................................................... 4
2.Water Pollution...................................................................................................................... 4
3.Introduction to H2O............................................................................................................... 8
4.Basic Types of Water Pollution.............................................................................................. 9
a)Surface Water Pollution..................................................................................................... 9
b)Groundwater Pollution.................................................................................................... 10
c)Microbiological Pollution................................................................................................. 10
d)Oxygen Depletion Pollution............................................................................................. 10
e)Nutrient Pollution............................................................................................................ 10
f)Suspended Matter Pollution............................................................................................. 11
g)Chemical Pollution........................................................................................................... 11
5.Major Types of Pollutants.................................................................................................... 11
a)Petroleum Products......................................................................................................... 11
b)Pesticides and Herbicides ............................................................................................... 11
c)Heavy Metals................................................................................................................... 12
d)Hazardous Wastes .......................................................................................................... 12
e)Excess Organic Matter .................................................................................................... 13
f)Sediment ......................................................................................................................... 13
g)Infectious Organisms ...................................................................................................... 13
h)Thermal Pollution ........................................................................................................... 14
6.Sources of Water Pollutants................................................................................................ 14
a)Point Source..................................................................................................................... 14
b)Non Point Source............................................................................................................. 14
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3. 7.Solutions to Water Pollution................................................................................................ 17
7.1.What kind of daily footprints do you leave? Are they large and deep or small and light?
......................................................................................................................................................... 17
7.2.Solutions to Water Pollution #1 Enforce Existing Laws................................................. 18
7.3.Solutions to Water Pollution #2 – Stop Nutrient and Pesticide Pollution .....................18
7.4.Solutions to Water Pollution #3 – Drive Less................................................................ 18
7.5.Solutions to Water Pollution #4 – Use Green Household and Personal Care Products . 19
7.6.Solutions to Water Pollution #5 – Use Less Plastic and Don’t Litter ..............................19
8.Case Study (Toxic Mud Spill Latest Insult to Polluted Danube River) ................................... 19
9.Laws for Water pollution..................................................................................................... 20
10.Water Treatment .............................................................................................................. 22
a)Industrial water treatment.............................................................................................. 22
b)Denitrification.................................................................................................................. 22
c)Septic tanks and sewage treatment................................................................................. 23
d)Ozone wastewater treatment.......................................................................................... 23
11.National Drinking Water Standards................................................................................... 25
12.Federal water Legislation................................................................................................... 28
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5. Agency (EPA) reports that about 37 percent of the country’s lakes and estuaries, and
36 percent of its rivers, are too polluted for basic uses such as fishing or swimming
during all or part of the year. In developing nations, more than 95 percent of urban
sewage is discharged untreated into rivers and bays, creating a major human health
hazard.
Most types of water pollution only affect the immediate area but sometimes the
pollution can travel hundreds or thousands of miles and then it is called transboundary
pollution.
Canada flushes some 200 billion liters of raw sewage directly into natural
waterways every year, from the St. Lawrence River to the Strait of Juan de Fuca and
the Pacific Ocean. That’s only a fraction of the three trillion liters of sewage
Canadians produce annually—about 6 percent, in fact—but it’s still enough to fill
more than 40,000 Olympic-sized swimming pools ( Larry West 2010).
Water pollution refers to the degradation of water quality. Water Pollution occurs
when the water becomes overloaded with too much of one thing and the aquatic
organisms cannot keep up with their cleaning responsibilities. Some organisms may
die and others may grow too fast. Water pollutant include heavy metals, sediments,
certain radioactive Isotopes, heat, fecal coliform bacteria, Phosphorus, Nitrogen,
Sodium, and other useful elements as well as certain photogenic bacteria and viruses.
What is a pollutant?
“A pollutant is any biological, physical or chemical substance that in an identifiable
excess in known to be harmful to other desirable living organisms”
Today the primary water pollution problem in the world is the lack of clean,
disease free drinking water. In the past, epidemics of waterborne disease such as
cholera have been responsible for the deaths of people in the United States.
It is the fundamental principle that the quality of water determines its potential
uses. The major uses of water today are agriculture, industrial processes, and domestic
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6. supply. Water for domestic supply must be free of pollutants like insecticides,
pesticides, pathogens, and heavy metals. It should taste good, should be odorless, and
should not be harmful to plumbing and household appliances. The quality of water for
industrial use varies widely depending on the process involved, some process may
involved distilled water, other need water that is not highly corrosive or that is free of
particles that could clog or otherwise damage the equipment.
The pollution of rivers and streams with chemical contaminants has become one
of the most critical environmental problems of the century. The marine fisheries
supported by ocean ecosystems are an essential source of protein, particularly for
people in developing countries.
Water pollution is a major global problem which requires ongoing evaluation and
revision of water resource policy at all levels (international down to individual
aquifers and wells). It has been suggested that it is the leading worldwide cause of
deaths and diseases, and that it accounts for the deaths of more than 14,000 people
daily. An estimated 700 million Indians have no access to a proper toilet, and 1,000
Indian children die of diarrheal sickness every day. Some 90% of China's cities suffer
from some degree of water pollution, and nearly 500 million people lack access to
safe drinking water. In addition to the acute problems of water pollution in developing
countries, developed countries continue to struggle with pollution problems as well.
In the most recent national report on water quality in the United States, 45 percent of
assessed stream miles, 47 percent of assessed lake acres, and 32 percent of
assessed bays and estuarine square miles were classified as polluted. Water is
typically referred to as polluted when it is impaired by anthropogenic contaminants
and either does not support a human use, such as drinking water, and/or undergoes a
marked shift in its ability to support its constituent biotic communities, such as fish.
Natural phenomena such as volcanoes, algae blooms, storms, and earthquakes also
cause major changes in water quality and the ecological status of water.
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10. Trash from human consumption, such as water bottles, plastics and other waste
products, is most often evident on water surfaces. This type of pollution also comes
from oil spills and gasoline waste, which float on the surface and affect the water and
its inhabitants.
b) Groundwater Pollution
This type of pollution is becoming more and more relevant because it affects our
drinking water and the aquifers below the soil. Groundwater pollution is usually
caused by highly toxic chemicals and pesticides from farming that leak through the
ground to contaminate the wells and aquifers below the surface.
c) Microbiological Pollution
Microbiological pollution is the natural form of water pollution that is caused by
microorganisms in uncured water. Most of these organisms are harmless but some
bacteria, viruses, and protozoa can cause serious diseases such as cholera and typhoid.
This is a significant problem for people in third world countries who have no clean
drinking water and/or facilities to cure the water.
d) Oxygen Depletion Pollution
Microorganisms that thrive in water feed on biodegradable substances. When
there is an influx of biodegradable material from such things as waste or erosion from
farming, the numbers of these microorganisms increase and utilize the obtainable
oxygen. When these oxygen levels are depleted, harmless aerobic microorganisms die
and anaerobic microorganisms thrive. Some of these organisms produce damaging
toxins like sulfide and ammonia.
e) Nutrient Pollution
Nutrients are usually found in wastewater and fertilizers. These can cause excess
vegetation in the water such as algae and weeds, using up the oxygen in the water and
hurting the surrounding marine life and other organisms in the water.
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11. f) Suspended Matter Pollution
This type of pollution occurs when pollutants enter the water and do not mix in
with the water molecules. These suspended particles form fine silt on the waterbed,
harming the marine life by taking away the nutrients and disturbing their habitat.
g) Chemical Pollution
Due to the nature of industry these days and the mass production in industrial
plants and farms, we have a lot of chemical run-off that flows into the nearby rivers
and water sources. Metals and solvents flow out of factories and into the water,
polluting the water and harming the wildlife. Pesticides from farms are like poison to
the wildlife in the water and kill and endanger the aquatic life. If birds or humans eat
these infected fish the toxins are transferred to us and we swallow these dangerous
pesticides and toxins, affecting our health. Petroleum is a different type of chemical
pollutant that dramatically affects the aquatic life. This oil kills the fish and marine
life and sticks to the feathers of birds, causing them to lose their ability to fly.
5. Major Types of Pollutants
a) Petroleum Products
Oil and chemicals derived from oil are used for fuel, lubrication, plastics
manufacturing, and many other purposes. These petroleum products get into water
mainly by means of accidental spills from ships, tanker trucks, pipelines, and leaky
underground storage tanks. Many petroleum products are poisonous if ingested by
animals, and spilled oil damages the feathers of birds or the fur of animals, often
causing death. In addition, spilled oil may be contaminated with other harmful
substances, such as polychlorinated biphenyls (PCBs).
b) Pesticides and Herbicides
Chemicals used to kill unwanted animals and plants, for instance on farms or in
suburban yards, may be collected by rainwater runoff and carried into streams,
especially if these substances are applied too lavishly. Some of these chemicals are
biodegradable and quickly decay into harmless or less harmful forms, while others are
non biodegradable and remain dangerous for a long time.
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12. When animals consume plants that have been treated with certain non
biodegradable chemicals, such as chlordane and dichlorodiphenyltrichloroethane
(DDT), these chemicals are absorbed into the tissues or organs of the animals. When
other animals feed on these contaminated animals, the chemicals are passed up the
food chain. With each step up the food chain, the concentration of the pollutant
increases. In one study, DDT levels in ospreys (a family of fish-eating birds) were
found to be 10 to 50 times higher than in the fish that they ate, 600 times the level in
the plankton that the fish ate, and 10 million times higher than in the water. Animals
at the top of food chains may, as a result of these chemical concentrations, suffer
cancers, reproductive problems, and death.
Many drinking water supplies are contaminated with pesticides from widespread
agricultural use. More than 14 million Americans drink water contaminated with
pesticides, and the Environmental Protection Agency (EPA) estimates that 10 percent
of wells contain pesticides. Nitrates, a pollutant often derived from fertilizer runoff,
can cause methemoglobinemia in infants, a potentially lethal form of anemia that is
also called blue baby syndrome.
c) Heavy Metals
Heavy metals such as copper, lead, mercury, and selenium, get into water from
many sources, including industries, automobile exhaust, mines, and even natural soil.
Like pesticides, heavy metals become more concentrated as animals feed on plants
and are consumed in turn by other animals. When they reach high levels in the body,
heavy metals can be immediately poisonous, or can result in long-term health
problems similar to those caused by pesticides and herbicides. For example, cadmium
in fertilizer derived from sewage sludge can be absorbed by crops. If these crops are
eaten by humans in sufficient amounts, the metal can cause diarrhea and, over time,
liver and kidney damage. Lead can get into water from lead pipes and solder in older
water systems; children exposed to lead in water can suffer mental retardation.
d) Hazardous Wastes
Hazardous wastes are chemical wastes that are either toxic (poisonous), reactive
(capable of producing explosive or toxic gases), corrosive (capable of corroding
steel), or ignitable (flammable). If improperly treated or stored, hazardous wastes can
pollute water supplies. In 1969 the Cuyahoga River in Cleveland, Ohio, was so
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13. polluted with hazardous wastes that it caught fire and burned. PCBs, a class of
chemicals once widely used in electrical equipment such as transformers, can get into
the environment through oil spills and can reach toxic levels as organisms eat one
another.
e) Excess Organic Matter
Fertilizers and other nutrients used to promote plant growth on farms and in
gardens may find their way into water. At first, these nutrients encourage the growth
of plants and algae in water. However, when the plant matter and algae die and settle
underwater, microorganisms decompose them. In the process of decomposition, these
microorganisms consume oxygen that is dissolved in the water. Oxygen levels in the
water may drop to such dangerously low levels that oxygen-dependent animals in the
water, such as fish, die. This process of depleting oxygen to deadly levels is called
Eutrophication.
f) Sediment
Sediment, soil particles carried to a streambed, lake, or ocean, can also be a
pollutant if it is present in large enough amounts. Soil erosion produced by the
removal of soil-trapping trees near waterways, or carried by rainwater and floodwater
from croplands, strip mines, and roads, can damage a stream or lake by introducing
too much nutrient matter. This leads to eutrophication. Sedimentation can also cover
streambed gravel in which many fish, such as salmon and trout, lay their eggs.
g) Infectious Organisms
A 1994 study by the Centers for Disease Control and Prevention (CDC) estimated
that about 900,000 people get sick annually in the United States because of organisms
in their drinking water, and around 900 people die. Many disease-causing organisms
that are present in small numbers in most natural waters are considered pollutants
when found in drinking water. Such parasites as Giardia lamblia and Cryptosporidium
parvum occasionally turn up in urban water supplies. These parasites can cause
illness, especially in people who are very old or very young, and in people who are
already suffering from other diseases. In 1993 an outbreak of Cryptosporidium in the
water supply of Milwaukee, Wisconsin, sickened more than 400,000 people and killed
more than 100.
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14. h) Thermal Pollution
Water is often drawn from rivers, lakes, or the ocean for use as a coolant in
factories and power plants. The water is usually returned to the source warmer than
when it was taken. Even small temperature changes in a body of water can drive away
the fish and other species that were originally present, and attract other species in
place of them. Thermal pollution can accelerate biological processes in plants and
animals or deplete oxygen levels in water. The result may be fish and other wildlife
deaths near the discharge source. Thermal pollution can also be caused by the removal
of trees and vegetation that shade and cool streams.
6. Sources of Water Pollutants
Pollution entering rivers and streams can be classified according to the nature of
its sources. It could be
a) Point Source
Point source pollution (PS) comes directly from a known source like an industrial or
sewage outfall pipe. Point sources are typically associated with manufacturing processes.
However, point sources also include discharges from water treatment plants and large
animal feeding operations.
b) Non Point Source
Nonpoint source pollution (NPS) can be defined as pollution that comes from many
miscellaneous or diffuse sources rather than from an identifiable, specific point. Nonpoint
source pollution can originate from urban environments such as yards in neighborhoods
or from agricultural production areas such as crop fields. Chemicals, waste products and
soil that are carried by rain into streams or rivers become a part of NPS. Common
examples are fertilizers, herbicides, pesticides, spilled motor oil and wastes from pets,
wildlife and livestock. Other significant sources of NPS include
• Litter
• Disposal of wastes in catch basins
• Hazardous waste improperly stored or discarded
• Improperly operating septic systems
• Erosion from construction sites, farms or home sites
• Acid deposition including acid rain and fog
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15. • Pollution from roadways and road salting activities
• Leaking sewer lines
• Discharge of sewage and garbage from ships and boats
• Improper use of fertilizers and pesticides
• Cleansers and other compounds used on ships in the urban or agriculture environment
and boats to prevent barnacles and algae from accumulating
• Animal feeding operations
Water pollutants result from many human activities. Pollutants from industrial
sources may pour out from the outfall pipes of factories or may leak from pipelines
and underground storage tanks. Polluted water may flow from mines where the water
has leached through mineral-rich rocks or has been contaminated by the chemicals
used in processing the ores. Cities and other residential communities contribute
mostly sewage, with traces of household chemicals mixed in. Sometimes industries
discharge pollutants into city sewers, increasing the variety of pollutants in municipal
areas. Pollutants from such agricultural sources as farms, pastures, feedlots, and
ranches contribute animal wastes, agricultural chemicals, and sediment from erosion.
The oceans, vast as they are, are not invulnerable to pollution. Pollutants reach
the sea from adjacent shorelines, from ships, and from offshore oil platforms. Sewage
and food waste discarded from ships on the open sea do little harm, but plastics
thrown overboard can kill birds or marine animals by entangling them, choking them,
or blocking their digestive tracts if swallowed.
Water pollution can also be caused by other types of pollution. For example,
sulfur dioxide from a power plant’s chimney begins as air pollution. The polluted air
mixes with atmospheric moisture to produce airborne sulfuric acid, which falls to the
earth as acid rain. In turn, the acid rain can be carried into a stream or lake, becoming
a form of water pollution that can harm or even eliminate wildlife. Similarly, the
garbage in a landfill can create water pollution if rainwater percolating through the
garbage absorbs toxins before it sinks into the soil and contaminates the underlying
groundwater (water that is naturally stored underground in beds of gravel and sand,
called aquifers).
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17. Nutrients Phosphorus and nitrogen from agriculture and urban land use
Agriculture, urban, and industrial use of mercury, lead,
Heavy metals
selenium, cadmium and so on
Sulfuric acid from coal and some metal mines: industrial
Acids
processes that dispose of acids improperly
Runoff from construction sites, agriculture runoff, and natural
Sediment
erosion
Warm to hot water from power plants and other industrial
Heat
facilities
Contamination by nuclear power industry, military and natural
Radio activity
sources
Source:
7. Solutions to Water Pollution
The key solutions to water pollution come down to individual responsibility
because we all have a direct impact on the environment. From the toilet we flush to
the garbage we throw away, we stamp our footprints into our environment on a daily
basis.
7.1. What kind of daily footprints do you leave? Are they large and deep or
small and light?
While millions of people take advantage of common conveniences such as buying
plastics or driving cars, our environment is slowly being degraded. For example, the
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18. Environmental Protection Agency (EPA) has designated 40 percent of our rivers and
lakes as unsafe for swimming and fishing.
7.2. Solutions to Water Pollution #1 Enforce Existing Laws
Our first solution to water pollution, therefore, is pretty simple – tell your
politicians to enforce existing laws. When a politician touts his new anti-pollution bill
that he claims will clean up the environment, it means little if they continue to allow
existing laws to go unenforced. Tell your politicians what you think. Encourage them
to enforce existing laws such as the Clean Water Act. Beyond enforcing laws, there
are some practical steps that we can take as individuals to limit the pollution in our
neighborhoods and cities.
7.3. Solutions to Water Pollution #2 – Stop Nutrient and Pesticide Pollution
If you are putting “normal” fertilizer, pesticides, and other chemicals on your lawn
or in your gardens, you are contributing to the pollution problem. While you may find
these products helpful, much of their volume is being washed off your lawn and into
the nearest waterway. They also tend to degrade the quality of your soil, causing more
and more reliance on the chemicals over time.
7.4. Solutions to Water Pollution #3 – Drive Less
Nitrogen deposition from air pollution is a big part of the nutrient pollution
problem. How much we drive, how large a vehicle we have, and many other factors
contribute to how much pollution we are putting out individually. Be conscious of the
emissions that your car spews out and keep your car well maintained. Think about
leaning towards a hybrid or electric car if you drive a lot of miles every day. Use
public transportation more often. Our government pays a lot of money to put these
public systems in place. Driving less is something we can all do better at, and all of
the relatively small differences each person makes will add up when summed across
millions of drivers.
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19. 7.5. Solutions to Water Pollution #4 – Use Green Household and Personal Care
Products
As consumers and citizens we have an obligation to know what effect our
consumer by-products are having on the planet. Many of the chemicals found in our
food, household cleaners, personal care products, and medications are all being
dumped back into the waterways. These chemicals are NOT adequately filtered
through municipal water treatment facilities. Thus, if we are not drinking filtered
water, we are consuming many of these chemicals (as well as other dangerous
contaminants) on a daily basis.
7.6. Solutions to Water Pollution #5 – Use Less Plastic and Don’t Litter
At the rate we’re going, the growing impact of plastic pollution on our oceans will
be one of the big disaster stories of this century. Try to figure out ways you can use
less plastic, especially plastic storage bags. This type of plastic is easy for wildlife to
swallow and eventually causes death. Plastic factories also deliver much of the
pollution that is not bio-degradable. Simply say no to bottled water! I know it is
convenient to drink bottled water, but the environmental impact of bottled water
plastic is huge!
Over 1.5 billion tons of plastic water bottles end up in U.S. landfills
each year. It takes over 300 years for plastic to degrade.
8. Case Study (Toxic Mud Spill Latest Insult to Polluted Danube River)
The recent reservoir failure that flooded several towns in Hungary with toxic red
mud is the latest environmental insult to Europe's Danube River. But it is not the first,
nor the worst, disaster of its kind, experts say. And unless steps are taken to safeguard
similar industrial plants and mining facilities around the world, these kinds of
accidents will continue to happen, they warn. On October 4, a so-called tailing dam
that held waste products, including arsenic and mercury, from the Ajkai Timfoldgyar
aluminum-processing plant in the town of Ajka, Hungary, collapsed. This released an
estimated 184 million gallons (697 million liters) of highly alkaline red mud into the
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20. Marcal River and nearby towns, killing at least eight people. The toxic flood reached
the Danube River—Europe’s second-largest river—last Thursday, sparking fears of
downstream contamination.
Hungary Prime Minister Viktor Orban called the spill the country's biggest
ecological disaster. One of the biggest threats facing the Danube today is human
alterations to the river made for navigation purposes, according to a 2004 European
Commission report. Projects to deepen, dam, or straighten the river and remove
"bottlenecks" to vessel passage are changing the river's traditional floodplain
landscape and water flow into deltas, as well as destroying wetlands and other
protected habitats, according to the environmental nonprofit WWF. There are
currently projects underway to restore the Danube's floodplains, and a recent plan by
the International Commission for the Protection of the Danube River (ICPDR) aims to
halt the illegal dumping of hazardous materials into the river.
9. Laws for Water pollution
There are many laws that protect the world’s oceans, rivers and lakes
from unnecessary water pollution. Each continent and country may differ in which laws
they enforce but they aim to have the same overall positive influence.
In Europe, there have been a number laws enforced to protect the surrounding
ocean from marine dumping.
• In 1989, the dumping of industrial waste was terminated in all countries in North-
Western Europe, apart from the UK. Dumping was terminated in the UK in 1993.
• In 1990, the dumping of sewage sludge was terminated in all countries in North-
Western Europe, apart from the UK. Dumping was terminated in the UK in 1998.
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21. • Guidelines have been developed and are currently being reviewed regarding the
dumping of polluted materials.
• Dumping of nuclear waste in European waters has been terminated since 1986.
There are a number of directives given in the European Union
Environmental Legislation:
• The proposed water framework directive aims to achieve a number of objectives
regarding health and environmental issues:
o Enforce sufficient drinking water provisions.
o Enforce sufficient provisions if water for other economic requirements.
o Protection of the environment from water pollution.
o Provide alleviation of the adverse impacts of floods and droughts.
o The directive aims to achieve a good status for ground waters and surface
waters in Europe by the year 2010.
• The urban waste water directive aims to protect surface inland waters and coastal
waters from pollution by regulating the collection and treatment of urban waste water.
• The nitrate from agricultural sources directive aims to protect waters against pollution
caused by nitrates, especially nitrates from agricultural sources such as fertilisers.
This will enable marine and freshwaters to be protected from eutrophication.
• The drinking water directive aims to establish strict standards regarding the quality of
drinking water. The directive provides parameters and analysis methods, these
standards must be met to ensure safe drinking water.
• The surface water for drinking water abstraction directive and measurement and
sampling of surface waters directive and information exchange decision are integrated
to form a framework that deals with water protection of all waters, not just those used
by humans.
• The fish water directive and shell water directive aims to protect waters from
pollution that are primarily used for fishing.
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22. • The groundwater directive aims to protect groundwater from dangerous pollutants by
controlling the direct and indirect discharges of certain substances into the
groundwater.
• The bathing water directive aims to keep good standards in the quality of bathing
water in freshwater and coastal water areas.
10.Water Treatment
Water treatment could be
a) Industrial water treatment
Before raw sewage can be safely released back into the environment, it needs
to be treated correctly in a water treatment plant. In a water treatment plant,
sewage goes through a number of chambers and chemical processes to reduce the
amount and toxicity of the waste.
The sewage first goes through a primary phase. This is where some of the
suspended, solid particles and inorganic material is removed by the use of filters.
The secondary phase of the treatment involves the reduction of organic, this is
done with the use of biological filters and processes that naturally degrade the
organic waste material.
The final stage of treatment is the tertiary phase; this stage must be done
before the water can be reused. Almost all solid particles are removed from the
water and chemical additives are supplied to get rid of any left-over impurities.
b) Denitrification
Denitrification is an ecological approach that can be used to prevent the
leaching of nitrates in soil; this in turn stops any ground water from being
contaminated with nutrients.
Fertilizers contain nitrogen, and are often applied to crops by farmers to help
plant growth and increase the yield.
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23. Bacteria in the soil convert the nitrogen in the fertilizer to nitrates, making it
easier for the plants to absorb.
Immobilization is a process where the nitrates become part of the soil organic
matter.
When oxygen levels are low, another form of bacteria then turns the nitrates
into gases such as nitrogen, nitrous oxide and nitrogen dioxide.
The conversion of these nitrates into gas is called denitrification. This prevents
nitrates from leaching into the soil and contaminating groundwater.
c) Septic tanks and sewage treatment
Septic tanks treat sewage at the place where it is located, rather than
transporting the waste through a treatment plant or sewage system. Septic tanks
are usually used to treat sewage from an individual building.
• Untreated sewage from a property flows into the septic tank and the
solids are separated from the liquid.
• Solid material is separated depending on their density. Heavier
particles settle at the bottom of the tank whereas lighter particles, such
as soap scum, will form a layer at the top of the tank.
• Biological processes are used to help degrade the solid materials.
• The liquid then flows out of the tank into a land drainage system and
the remaining solids are filtered out.
d) Ozone wastewater treatment
Ozone wastewater treatment is a method that is increasing in popularity. An
ozone generator is used to break down pollutants in the water source. The
generators convert oxygen into ozone by using ultraviolet radiation or by an
electric discharge field.
Ozone is a very reactive gas that can oxidize bacteria, moulds, organic
material and other pollutants found in water.
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24. Using ozone to treat wastewater has many benefits:
• Kills bacteria effectively.
• Oxidizes substances such as iron and sulphur so that they can be filtered
out of the solution.
• There are no nasty odours or residues produced from the treatment.
• Ozone converts back into oxygen quickly, and leaves no trace once it has
been used.
The disadvantages of using ozone as a treatment for wastewater are:
• The treatment requires energy in the form of electricity; this can cost
money and cannot work when the power is lost.
• The treatment cannot remove dissolved minerals and salts.
• Ozone treatment can sometimes produce by-products such as bromate that
can harm human health if they are not controlled.
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30. Voulgaropoulos, A., K. Fytianos, et al. (1987). "Correlation of some organic pollution
factors in water systems in Northern Greece." Water Research 21(3): 253-256.
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