water pollution sources

8/7/2019 water pollution sources

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Water Pollution

Degradation of water quality

Water is considered polluted when it is rendered unsuitable for a specific purpose

Access to safe drinking water is the world¶s major water pollution issue

The quality of water desired depends on its potential use

The EPA has set limits for concentrations of certain pollutantsin water



Water Quality - Classification of

Water Pollutants

Signs of water pollution?

± Bad tasting drinking water

± Masses of aquatic weeds

± Disgusting odors

± Decreasing fish populations

± Floating oil and raw sewage




Water Pollutants Classification of water pollutants

± Oxygen-demanding wastes (ODW)

± Pathogenic organisms ± Plant nutrients

± Synthetic organic compounds (SOCs)

± Oil

± Sediments

± Heat




Water Pollutants

Oxygen-Demanding Wastes (ODW)

± Dissolved Oxygen

Aquatic organisms require oxygen for cellular

respiration

Dissolved oxygen (DO) is often a limiting factor for

survival of aquatic organisms




Water Pollutants

ODW

± Dissolved Oxygen

Factors that control DO levels:

± Water temperature

± Elevation above sea level

± Degree of turbulence

± Stream channel geometry ± Density of aquatic plants




Water Pollutants ODW

± Dissolved Oxygen

Water Temperature ± DO decreases with increasing water temperature

Elevation Above Sea Level

± DO decreases with increasing elevation




Water Pollutants

ODW

± Dissolved Oxygen

Turbulence

± DO increases with increasing turbulence caused by

waterfalls, rapids, etc

Stream Channel Geometry ± Wide, shallow channel has greater DO than narrow, deep

channel




Water Pollutants

ODW

± Organic substances that cause depletion or

removal of DO

± Food source for aquatic bacteria

± DO is removed as bacteria feed on ODW




Water Pollutants

ODW

± Sources of ODW

Sewage

Paper mills

Food processing

Slaughterhouses




Water Pollutants

ODW

± Biochemical Oxygen Demand - the amount of

dissolved oxygen that bacteria require to

decompose ODW in a given volume of water




Water Pollutants

ODW

± Biochemical Oxygen Demand (BOD)

Measurement

± 5-day test

± Incubation at 20 degrees C

± BOD = DO (day 0) - DO (day 5)




Water Pollutants

ODW

± Biochemical Oxygen Demand (BOD)

Characteristic BOD Levels

± Untreated Sewage 100-400 mg/L

± Feedlots 100-10,000 mg/L

± Pure Water 1 mg/L




Water Pollutants

ODW

± Environmental Impacts of low DO

Disappearance of plant and animal life

Shift from aerobic to anaerobic conditions

³Oxygen Sag´




Water Pollutants

Pathogenic Organisms

± Types of pathogens:

Viruses

Bacteria

Protozoa (unicellular)

Parasitic worms




Water Pollutants

Pathogenic Organisms

± Diseases caused by water-borne pathogens:

Amoebic Dysentery

Bacterial Dysentery

Typhoid fever

Cholera

Hepatitis

Schistosomiasis




Water Pollutants Plant Nutrients

± Plants require 15-20 nutrients for growth:

Carbon Nitrogen

Phosphorus

Potassium

Sulfur





± Nitrogen and phosphorus are limiting nutrients for

plant growth

± E utrophication - the natural enrichment of water

with plant nutrients





± E utrophic E cosystem - ecosystems that are relatively

high in fertility and biological productivity

± Oligotrophic E cosystem - ecosystems that are

relatively low in fertility and biological productivity





± C ultural E utrophication - accelerated

eutrophication caused by human activities





± Signs and effects of cultural eutrophication:

Dense growth of rooted plants Increased growth of blue-green algae

Increased populations of trash fish

Foamy layers on surface of water





± Sources of nutrients responsible for cultural

eutrophication: Domestic Sewage

Urban Runoff

Industrial Sources

Agricultural Sources





± Management practices to minimize cultural

eutrophication: Two types of water pollution sources in a watershed:

± P oint Source

± Non- P oint Source P ollution





± Management practices to minimize cultural

eutrophication: Nutrient management

± Determine point and nonpoint sources of nutrients and the size of

each source

± On-site treatment of nutrients

± Rate and timing of nutrient application




Water Pollutants Synthetic Organic Compounds (SOCs)

± Examples:

Fuels Plastics

Pesticides

Fertilizers

Food additives Pharmaceuticals





± Pesticides

Environmental Impacts ± Bioaccumulation

± Interference with reproduction

± Birth Defects

± Reduced biodiversity and productivity

± Tumors and convulsions





± Oil (Hydrocarbons)

Sources ± Impervious surfaces

± Oil leaks

± Auto emissions

± Improper disposal of waste oil





± Oil (Hydrocarbons)

Environmental Impacts ± Degrade appearance of water surfaces

± Limit air exchange between atmosphere and water

± Lowered DO levels

± Increased BOD

± Impair habitat

± Reduced biodiversity

± Death




Water Pollutants Sediment

± Factors controlling sediment loss:

Chemical and physical characteristics of the soil Slope steepness

Type and density of vegetation cover

Rainfall




Water Pollutants Sediment

± Environmental Impacts

Filling of channels and harbors with sediment Decreased biodiversity of aquatic animals

Increased turbidity




Water Pollutants Heat (Thermal Pollution)

± Sources

Cooling water in industrial processes Natural heating by sunlight


Decreased DO

Increased rates of chemical reactions

False temperature cues to aquatic life

Death to aquatic organisms






Decreased DO ± ³Thermal Blanket´

» Warm water is less dense than cold water

» Warm layer forms ³blanket´ over cooler, more dense water

» Warm water cannot dissolve as much atmospheric oxygen as cooler

water » Rate of exchange of oxygen between warm water and cooler water

is very slow

» Cooler water is ³atmospherically unreplenished´

» Death to aquatic organisms






Increased rates of chemical reactions ± The rate of any chemical reactions approximately doubles with

every 10C increase in temperature

± In thermally polluted waters, fish require more DO because of

increased respiration rates

± Increased respiration occurs in response to higher water temperature






False temperature cues given to aquatic life ± Fish spawn and migrate in response to temperature cues

± Optimum temperature range for fish species



Disease-Causing Agents

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BIOCHEMICAL OXYGEN

DEMAND (BOD)

The biochemical oxygen demand (BOD) is the amount of oxygen requiredfor the bacterial decomposition of organic matter in water.

Natural sources, agricultural runoff , and human sewage contribute tothe BOD of bodies of water.

An excessive BOD causes water¶s dissolved oxygen content to fall belowthe level needed to support the entire biological community.

A sudden discharge of organic matter , such as raw sewage, into awaterway produces three zones: a pollution zone, an activedecomposition zone, and a recovery zone.

Streams are naturally able to degrade organic waste; however, when thiscapacity is exceeded, the stream¶s recovery may be delayed and manyorganisms destroyed.



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Fig 21.3 Relationship between dissolved

oxygen and biochemical oxygen demand

(BOD) f or a stream f ollowing the input of

sewage.



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W

ATERBORNE DISEASE The global availability of clean drinking water is the

primary water pollution problem today

Many serious human diseases and epidemics arecaused by waterborne pathogens.

A. OUTBREAK IN MILWAUKEE, WISCONSIN ± As the C ryptosporidium epidemic illustrates, modern water

treatment facilities cannot guarantee pathogen-free water supplies.



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WATERBORNE DISEASE

B. FECAL COLIFORM BACTERIA

A fecal coliform bacteria count is the standard measure of microbial pollution and disease potential in a source of

drinking water.

Though not themselves pathogenic, the presence of fecalcoliform bacteria indicates that water is contaminated withhuman and/or animal waste that may carry pathogens.

C. OUTBREAK IN WALKERTON, ONTARIO

This episode reminds us that vigilant testing of water suppliesis necessary to protect public health.



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NUTRIENTS

Excessive levels of nutrients, particularlynitrogen and phosphorus, can lead to seriouswater pollution problems such aseutrophication.

A. MEDICAL LAKE: AN EXAMPLE

While not directly harmf ul to aquatic life,excess nutrients can severely disrupt anddamage an aquatic ecosystem



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NUTRIENTS

B. EUTROPHICATION

E utrophication is the process by which excess

nutrients stimulate the growth of aquatic plants, which then decompose; this bacterialdecomposition raises the BOD and may lead toa die-off of many aquatic species.

Eutrophication may be a natural process or cultural in origin.



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Oil

Oil enters the ocean from tanker and offshore

drilling accidents, normal shipping activities, and

land runoff .

A. EXXON VAL D EZ : PRINCE WILLIAM

SOUND, ALASKA

Most of the components of crude oil arebiodegradable, so although the acute effects of spills

can be disastrous, it is not certain what long-term

threats to ecosystems they may pose.



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ACID MINE DRAINAGE

Acid mine drainage is water, high in sulfuricacid, draining from coal and metal mines intowaterways.

Acid drainage runoff can pollute both surfaceand underground water systems.

In some areas of the U.S., acid mine drainageis the most serious water pollution problem..



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SUR FACE-WATER

POLLUTION

S urface waters become polluted when their capacityto dilute, remove, or convert a harmful substance totolerable levels is exceeded.

Point sources of water pollutants are distinct, discreteoutlets such as pipes or wells.

Nonpoint sources of pollution are diffuse andintermittent and may be influenced by a variety of natural and human land-use factors; these sourcesinclude ur ban runoff , agriculture, mining , and forestry.



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SUR FACE-WATER

POLLUTION

Because of their diffuse nature, nonpoint sources aregenerally more difficult to monitor and control thanare point sources.

Water pollution can be addressed by sourcereduction or treating polluted water to remove or convert pollutants.

Running water such as in rivers and streamsgenerally responds more quickly and completely tocleanup efforts than does still water such as in lakesand ponds.



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GROUNDWATER POLLUTION

G roundwater , a vital source of drinking water in the

U.S., can be contaminated by any number of toxins as

a result of land-use and waste disposal practices.

Bacterial breakdown of pollutants does not generally

occur in the anaerobic environment of groundwater.

Because groundwater (versus surface water) moves

slowly, pollutants that reach it may remain

concentrated for long periods.



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GROUNDWATER POLLUTION

A. PRINCIPLES OF GROUNDWATER

POLLUTION: AN EXAMPLE

The cleanup of groundwater contaminated by leaking

underground storage tanks illustrates the complexity

of remediation efforts.

B. LONG ISLAND, NEW YORK S altwater intrusion and aquifer pollution from urban

runoff and landfill leachate threaten the water

supplies of many urban and coastal areas.



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WASTEWATER TREATMENT

By law, wastewater must be treated to meet federalstandards before discharge into waterways.

A SEPTIC-TANK DISPOSAL SYSTEMS

In many rural areas, individual residences dischargesewage directly to in-ground septic systems, where

microbial digestion of solid and liquid nutrients occurs;treated wastewater is then fed into a drain field whichslowly releases the water to the soil.

water pollution sources

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