CHAPTER 2-Water Pollution

8/11/2019 CHAPTER 2-Water Pollution

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CHAPTER 2- WATER POLLUTION

CLASSIFICATION OF POLLUTION SOURCES

Point sources pollution

Point source pollution is contamination that enters the environment through any

discernible, confined, and discrete conveyance, such as a smokestack, pipe, ditch,

tunnel, or conduit.

Point source pollution remains a major cause of pollution to both air and water.

Point sources are differentiated from non-point sources, which are those that spread

out over a large area and have no specific outlet or discharge point.

Example point source of water pollution: municipal sewage treatment plant

discharges, industrial plant discharges.

Example point source of air pollution : power plants, smelters, industrial and

commercial boilers, wood and pulp processors


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Dispersed pollution

Dispersed sources are broad, unconfined areas from which pollutants enter a body of

water.

The characterization of a source as either a point or a distributed source can depend

on how one choose to aggregate the individual emissions that compose the source

and on the spatial scales of the interest.

Example of water pollution : Surface runoff from farms

Example of air pollution : all cars in a city for evaluation of city air quality

Thermal Pollution

harmful increase in water temperature in streams, rivers, lakes, or occasionally,

coastal ocean waters

Cause :

i. dumping hot water from factories and power plants

ii. removing trees and vegetation that shade streams, permitting sunlight to

raise the temperature of these waters

Major sources:

i. electric power plants and industrial factories


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In most electric power plants, heat is produced when coal, oil, or

natural gas is burned or nuclear fuels undergo fission to release huge

amounts of energy.

This heat turns water to steam, which in turn spins turbines to

produce electricity.

After doing its work, the spent steam must be cooled and condensed

back into water.

To condense the steam, cool water is brought into the plant and

circulated next to the hot steam.

In this process, the water used for cooling warms 5 to 10 Celsius

degrees (9 to 18 Fahrenheit degrees), after which it may be dumped

back into the lake, river, or ocean from which it came.

Similarly, factories contribute to thermal pollution when they dump

water used to cool their machinery

ii. removing vegetation

Streams and small lakes are naturally kept cool by trees and other tall

plants that block sunlight

People often remove this shading vegetation in order to harvest the

wood in the trees

Left unshaded, the water warms by as much as 10 Celsius degrees (18

Fahrenheit degrees)

Even the removal of vegetation far away from a stream or lake can

contribute to thermal pollution by speeding up the erosion of soil into

the water, making it muddy.

Muddy water absorbs more energy from the sun than clear water does,

resulting in further heating

Impact to aquatic life :

can kill native fish, shellfish, and plants. When water in an area warms

more than they can tolerate, species that cannot move, such as rootedplants and shellfish, will die

Algae and other plants grow more rapidly in warm water than in cold

the bacteria that decompose their dead tissue use up oxygen, further

reducing the amount available for animals


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Soil erosion and its impact

Soil erosion is a gradual process that occurs when the impact of water or wind

detaches and removes soil particles, causing the soil to deteriorate.

Soil erosion by water, and the impact of sediment-attached nutrients (i.e.,

phosphorus) on lakes and streams, creates problems for both agricultural land and

water quality.

Soil erosion may be a slow process that continues relatively unnoticed, or it may

occur at an alarming rate causing serious loss of topsoil. The loss of soil from

farmland may be reflected in reduced crop production potential, lower surface water

quality and damaged drainage networks.

Sediment deposition in a waterway makes the water more turbid and does not allow

as much light to penetrate the water. This causes problems for aquatic plants that

need sunlight in order to perform photosynthesis

Furthermore, suspended sediments in the water have the potential of clogging the

gills of aquatic organisms and covering the stream bottom

Also, with an increased amount of particles in the water, dissolved oxygen levels are

reduced because of higher water temperatures.

Controlling erosion

Controlling soil erosion will:

sustain or improve crop yields

reduce drainage costs

retain nutrients and chemicals where applied

reduce hazards when working on eroding soil, and

help improve water quality.

Management of soil for water and wind erosion control is based on sensible soil

conservation practices. The majority of these practices are recognized components of

good soil, crop, and water management. For effective erosion control:

a. Maintain good soil structure

I. Maintaining good soil structure on your property is a great soil erosion

control method.


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II. It is also a great management plan to keep your property soil erosion

free.

III. Improving soil structure frequently is one step to maintaining it.

IV. Relying organic matter and manure are 2 simple ways to controlling soil

erosion and maintaining soil structure.

V. Watering and residues are also 2 methods which help control erosion.

VI. Tillage practices which avoid unnecessary breakdown of soil structure

are another way to control soil erosion.

b. Protect the soil surface by adequate crop and residue cover

I. Residue and crop covers are 2 ideally ways for soil erosion control.

II. The benefits of proper crops on all types of soils is vitally important as

they act as shields to the soil and the intercept the force of water and rain

delicately and therefore the soil will be protected against soil erosion from

these natural forces.

III. Root systems of the crop covers will help stabilize the underlying soil

which will control the soils erosion.

c. Use special structural erosion control practices where necessary.

Matting is a great soil erosion control product. There are various types of matting

which are all made from different components and suit different types of soils. Some

of the commonly known forms of matting used for soil erosion control are: Grass Matting

Fiber Matting

Mulch Matting

Wood Matting

The 4 mentioned matting types are deigned the same.

The matting will sit directly on top of the soil.

It then acts like a shelter for the soil and will prevent the harsh impact of wind and

water on the soils surface.

The matting allows the soil to breathe and retain moisture.

Matting is recommended to be used for long terms of 12 months. Once the 12

months is up your soil should be controlled and free of soil erosion.


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Self purification on river

Self purification exists in form of a biological cycle which is able to adjust itself,

within limits, to change in environmental condition.

Self purification Cycle

Purification of water in liquid form ultimately depends on natural filtration, chemical

absorption and adsorption by soil particles and organic matter, living organism

uptake of nutrients, and living organism decomposition processes in soil and water

environments.

Soils, especially in wetland and riparian areas, along with vegetation and

microorganisms play very important roles in natural water purification.

Microorganisms in soils, wetlands and riparian areas either utilize or breakdown

numerous chemical and biological contaminants in water.

Wetlands serve as ecological kidneys and can remove 20 to 60 percent of metals in

water, trap and retain 80 to 90 percent of sediment from runoff, and eliminate 70 to

90 percent of the nitrogen in water.

Riparian (streamside) forests also act as living filters that intercept sediments,

absorb and store excess nutrients, and transform and remediate the effects of many

water contaminants and pollutants carried in runoff from adjacent lands.

Riparian areas can reduce the nitrogen concentration in storm water runoff by up to

90%, and can reduce phosphorus levels by as much as 50 percent.

Self purification involves one or more following process:

1.

Sedimentation

possibly assisted by biological and mechanicalflocculation. The deposited solid will form benthic deposit which if

organic will decay anaerobically and which if resuspended by flood

flow can exert sudden high oxygen demand on the system.

2. Chemical Oxidation reducing agent such as sulphides.

Wastewater

Algae

Protozoa

Fish

Man

Natural

Organic/

Inorganic


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3. Bacterial Decay due to inhospitable environment for enteric and

pathogenic bacteria in natural water.

4. Biochemical oxidation most important process to maintain aerobic

condition, this mean that the balance between oxygen consumed by

BOD and the supplied by reaction from the atmosphere is not

drastically disturbed.

The processes of oxidation give rise to deoxygenating of the river-water, and the

extent of deoxygenating depends on the strength of the sewage, the degree of

dilution afforded by admixture with the river-water, and the velocity of the river.

If the concentration of oxidisable material be excessive, the river-water will suffer

considerable or complete deoxygenating, and a nuisance will result owing to the

septic condition caused by the anaerobic decomposition of the organic matter.

In the other hand, if there be sufficient dilution, the organic matter can be oxidized

and thus destroyed without depriving the river-water of oxygen to any appreciable

degree. The suspended matter will also be sediment in the form of a thin film

distributed over a considerable area of river-bed, and no nuisance will thus result

through the formation of foul mud-banks.

Mass balance on liquid

To assess the effect of particular polluting discharge on receiving water in

quantitative term, we have to utilize a mass balance approach.

Figure below shows a river receiving pollutant discharge and it is possible to

determine downstream concentration of pollutant, assuming instantaneous mixing

with conservation of mass

(Q1 X C1) + (Q2 X C2) = (Q3 X C3)

Since the assume of the flows arriving and leaving the discharge point must be equal

(i.e Q3=Q1+Q2) the downstream concentration is easily calculated. Depending upon

the nature of pollutant it will then be possible to calculate the concentrations at point

River

Flow Q1

Concentration C1

Flow Q2

Concentration C2

Discharge

Flow Q3

Concentration C3


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further downstream from discharge, knowing the velocity of flow and hence the time

travel between the point.

Example calculation of mass balance:

A stream with flow of 0.1 m3/s and chloride concentration 0f 52 mg/l receives a

discharge of mine drainage water with a flow of 0.025 m3

/s and chloride

concentration is 1250mg/l. Find downstream concentration.

Solution:

Q1X C1 = (0.1 X52) =5.2

Q2X C2 = (0.025 X1250) =31.25

Q3 =Q1+ Q2= (0.1 +0.025) =0.125

Hence Downstream concentration = (5.2 + 31.25)/0.125 = 291.6 mg/l.

Chloride is a conservative pollutant so that the concentration will be only reducing

below 291.6 mg/l if additional water with lower chloride concentration enters the

stream below the drainage discharge.

In case of non-conservative pollutants the initial concentration will decrease

downstream due to decay reaction.

Dissolved Oxygen

The concentration of dissolved oxygen [DO, units of milligram per liter (mgL-1)] is

perhaps the single most important feature of water quality. It is an important

regulator of chemical processes and biological activity.

Most forms of aquatic life require oxygen (DO). For example, certain combinations

of low temperature and high DO concentrations are required for the maintenance of

a cold water sport fishery (such as trout and salmon).

Plant photosynthesis produces oxygen within the region below the water surface

with adequate light (photic zone).

Carbon dioxide+Water-------------->Oxygen+Carbon-rich foods

CO2 H2O O2 C6H12O6

Microbial (for example, bacteria) respiratory and organic decay processes consume

oxygen. Near the reservoir surface, oxygen can move between the water and air.

The rate and direction of this exchange is dependent on the wind speed and status

of the surface waters with respect to the equilibrium or saturation concentration.

Dissolved oxygen is measured using a DO probe. The DO probe consists of small

silver anodes and a gold cathode. These electrodes are separated from the

surrounding lake water by a Teflon membrane. Dissolved oxygen diffuses across


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the membrane and is reduced to OH- ions at the cathode and AgCl is formed at the

anode. The current associated with this process is proportional to the DO in the

surrounding water

Oxygen is moderately soluble in water. The solubility limit, or saturation

concentration of DO is largely regulated by temperature. Concentrations that

exceed the saturation value are described as supersaturated. Such conditions

reflect high photosynthetic activity (i.e. during an algal bloom). Undersaturated

conditions prevail when the DO concentration is less than the saturation value,

indicating oxygen-demanding processes exceed the sources of DO.

Dissolved oxygen is one of many measures of water quality, but an important one for

aquatic life. Like land animals, fish and shellfish require oxygen to survive. When

oxygen levels fall below 5 mg/l, fish are stressed. At oxygen levels of 12 mg/l, fish

die.

The amount of oxygen that can dissolve in water (i.e., the saturating concentration

of oxygen) depends on water temperature. Colder water can hold more oxygen than

warmer water.


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The above graph shows the maximum amount of oxygen that can be dissolved in

water at various temperatures. Assuming a constant atmospheric pressure, water of

low temperatures can hold more oxygen than water of high temperatures.

One unit of measure of dissolved oxygen in water is parts per million (ppm), which is

the number of oxygen (O2) molecules per million total molecules in a sample.

Calculating the percent saturation is another way to analyze dissolved oxygen levels.

Percent saturation is the measured dissolved oxygen level divided by the greatest

amount of oxygen that the water can hold at that particular temperature and

atmospheric pressure, then multiplied by 100.

Fish growth and activity usually require 5-6 ppm of dissolved oxygen. Dissolved

oxygen levels below 3 ppm are stressful to most aquatic organisms. Levels below 2

ppm will not support fish at all.

DO will decrease while the time (in min) increase

Show that DO consumption will increase every minute

The adjacent figure illustrates some of the factors that drive the eutrophication

process in an impoundment.
http://www.cotf.edu/ete/modules/waterq3/WQglossary.html#ppmhttp://www.cotf.edu/ete/modules/waterq3/WQglossary.html#ppm


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The Process of Eutrophication

In nature, eutrophication is a common phenomenon in freshwater ecosystems and is

really a part of the normal aging process of many lakes and ponds

Over time, these bodies of freshwater change in terms of how productive or fertile

they are.

While this is different for each lake or pond, those that are naturally fed rich

nutrients from a stream or river or some other natural source are described as

"eutrophic," meaning they are nutrient-rich and therefore abundant in plant and

animal life.

Natural eutrophication is usually a fairly slow and gradual process, occurring over a

period of many centuries.

Human activities almost always result in the creation of waste, and many of these

waste products often contain nitrates and phosphates.

Nitrates are a compound of nitrogen, and most are produced by bacteria.

Phosphates are phosphorous compounds. Both nitrates and phosphates are absorbed

by plants and are needed for growth


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However, the human use of detergents and chemical fertilizers has greatly increased

the amount of nitrates and phosphates that are washed into our lakes and ponds.

When this occurs in a sufficient quantity, they act like fertilizer for plants and algae

and speed up their rate of growth.

Algae are a group of plantlike organisms that live in water and can make their own

food through photosynthesis When additional phosphates are added to a body of

water, the plants begin to grow explosively and algae takes off or "blooms."

In the process, the plants and algae consume greater amounts of oxygen in the

water, robbing fish and other species of necessary oxygen.

All algae eventually die, and when they do, oxygen is required by bacteria in order

for them to decompose or break down the dead algae.

A cycle then begins in which more bacteria decompose more dead algae, consuming

even more oxygen in the process.

The bacteria then release more phosphates back into the water, which feed more

algae.

As levels of oxygen in the body of water become lower, species such as fish and

mollusks literally suffocate to death.

Eventually, the lake or pond begins to fill in and starts to be choked with plant

growth.

Example of Dead Lake :

In the 1960s and 1970s, Lake Erie was the most publicized example of

eutrophication. Called a "dead lake," the smallest and shallowest of the five Great

Lakes was swamped for decades with nutrients from heavily developed agricultural

and urban lands.

As a result, plant and algae growth choked out most other species living in the lake,

and left the beaches unusable due to the smell of decaying algae that washed up on

the shores.

New pollution controls for sewage treatment plants and agricultural methods by the

United States and Canada led to drastic reductions in the amount of nutrients

entering the lake.

Forty years later, while still not totally free of pollutants and nutrients, Lake Erie is

again a biologically thriving lake.

Summary:

1. Nitrate and Phosphate from human activity (e.g. use of detergents and

chemical fertilizers) can become fertilizer and increase plant growth.


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2. Result:

plant and algae consume greater amounts of oxygen in the water

When algae die, bacteria consume oxygen to decompose algae,

decompose algae will release more phosphate.

3. Effect:

a. Algae become bloom all water surface will covered by algae

b. species such as fish and mollusks literally suffocate to death.

c. dead lake.

How to control eutrophication :

1. planting vegetation along streambeds to slow erosion and absorb

nutrients

2. Controlling application amount and timing of fertilizer

3. Controlling runoff from feedlots

4. Researching use of biological controls; for example, the process of

denitrification uses specialized bacteria that convert nitrates to harmless

molecular nitrogen

5. Aeration system

Sources of groundwater pollution

1. From Industrial

Manufacturing and other chemical industries require water for processing and

cleaning purposes.

These used water is recycled back to water sources without proper treatment, which

in turn, results in groundwater pollution.

It is also to be noted that solid industrial wastes that are dumped in certain areas

also contribute to groundwater pollution. When rainwater seeps downwards, it

dissolves some of these harmful substances and contaminates groundwater.

2. From Domestic waste

Residential wastewater systems can be a source of many categories of contaminants,including bacteria, viruses, nitrates from human waste, and organic compounds.

Injection wells used for domestic wastewater disposal (septic systems, cesspools,

drainage wells for storm water runoff, groundwater recharge wells) are of particular

concern to groundwater quality if located close to drinking water wells


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Improperly storing or disposing of household chemicals such as paints, synthetic

detergents, solvents, oils, medicines, disinfectants, pool chemicals, pesticides,

batteries, gasoline and diesel fuel can lead to groundwater contamination. When

stored in garages or basements with floor drains, spills and flooding may introduce

such contaminants into the groundwater.

When thrown in the household trash, the products will eventually be carried into the

groundwater because community landfills are not equipped to handle hazardous

materials. Similarly, wastes dumped or buried in the ground can contaminate the soil

and leach into the groundwater.

3. Municipal Landfill

Landfills contaminate groundwater when rain water leaks into aquifers below the

landfill. Many early landfills did not have liners to trap rainwater that percolatesthrough the landfill, and some newer landfills have liners that leak.

The percolating water leaches toxic chemicals from batteries, broken fluorescent

bulbs, electronic equipment, discarded household chemicals, and paints and

solvents. Although landfills now prohibit toxic waste, and they are carefully regulated

to prevent leakage to groundwater, many older sites are unlined and leak.

4.Waste from petroleum and mining

Mining wastes include waste generated during the extraction, beneficiation, and

processing of minerals.

Extraction is the first phase of hard rock mining which consists of the initial removal

of ore from the earth. Beneficiation is the initial attempt at liberating and

concentrating the valuable mineral from the extracted ore.

This is typically performed by employing various crushing, grinding and froth

flotation techniques.

Mineral processing operations generally follow beneficiation and include techniques

that often change the chemical composition of the ore or mineral, such as smelting

(iron and steel), electrolytic refining (aluminum) and acid attack or digestion.

Coal mines are another major source of contaminants. When pyrite rocks associated

with coal mining are exposed to oxygen they are oxidized to generate acid mine

drainage. The waste then flows into streams and infiltrates into aquifers.


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5. Agriculture

Pesticides, fertilizers, herbicides and animal waste are agricultural sources of

groundwater contamination.

The agricultural contamination sources are varied and numerous: spillage of

fertilizers and pesticides during handling, runoff from the loading and washing of

pesticide sprayers or other application equipment, using chemicals uphill from or

within a few hundred feet of a well.

Agricultural land that lacks sufficient drainage is considered by many farmers to be

lost income land. So they may install drain tiles or drainage wells to make the land

more productive. The drainage well then serves as a direct conduit to groundwater

for agricultural wastes which are washed down with the runoff.

Storage of agricultural chemicals near conduits to groundwater, such as open and

abandoned wells, sink holes, or surface depressions where ponded water is likely to

accumulate.

Contamination may also occur when chemicals are stored in uncovered areas,

unprotected from wind and rain, or are stored in locations where the groundwater

flows from the direction of the chemical storage to the well.

6. Saltwater intrusion

Saltwater intrusion is a major problem in coastal regions all over the world, as it

threatens the health and possibly lives of many people who live in these areas.

It increases the salinity of groundwater and water may become unsuitable for human

use.

Salinization of groundwater is considered a special category of pollution that

threatens groundwater resources, because mixing a small quantity of saltwater in

the groundwater makes freshwater unsuitable and can result in abandonment of

freshwater supply

Due to the high population growth rate in coastal regions inhabited by about two-

thirds of the world population, water demands have increased, leading to excessive

abstraction from the aquifers and hence the migration of saltwater toward the

aquifers.

In coastal areas the aquifers are in hydraulic contact with the sea, and under normal

conditions freshwater flows into the sea.


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However, over-pumping may result in inversion of the groundwater flow from the

sea towards the interior, causing saltwater intrusion.

Furthermore, the rise in sea levels accelerates saltwater intrusion into the aquifers,

thus further reducing the fresh groundwater resources.

With the combined impact of sea level rise and over-pumping, the problem becomes

very serious and requires practical measures to protect available water resources

from pollution.

Summary:

Place of originPotential groundwater contamination source

Municipal Industrial Agricultural Individual Saltwater

At or near the

land surface

air pollution

municipal wasteland spreading

salt for de-icingstreets

streets & parking

lots

air pollution

chemicals: storage

& spills

fuels: storage &

spills

mine tailing piles

air pollution

chemical spills

fertilizers

livestock waste

storage facilities &land spreading

pesticides

air pollution

fertilizers

homes

cleaners

detergents

motor oil

paints

pesticides

Over pump

Rise of sea le

Cause of marine pollution

1. Domestic and industrial waste

Solid garbage also makes its way to the ocean. Plastic bags, balloons, glass bottles,shoes, packaging material - if not disposed of correctly, almost everything we throw

away can reach the sea.

Plastic garbage, which decomposes very slowly, is often mistaken for food by marine

animals.


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High concentrations of plastic material, particularly plastic bags, have been found

blocking the breathing passages and stomachs of many marine species, including

whales, dolphins, seals, puffins, and turtles. Plastic six-pack rings for drink bottles

can also choke marine animals.

This garbage can also come back to shore, where it pollutes beaches and other

coastal habitats. Dumping of industrial wastes into ocean is another reason for

marine pollution.

The wastes often contain toxic materials such as mercury, dioxin, PCBs, PAHs and

radioactive materials, which contaminate the water of ocean.

Toxic waste gets into seas and oceans by the leaking of landfills, dumps, mines, and

farms. Farm chemicals and heavy metals from factories can have a very harmful

effect on marine life and humans.

Many fishermen believe that the toxic chemicals in the ocean are killing much of the

fish population. One of the most harmful chemicals in the ocean is lead. Lead can

cause many health problems.

It can damage the brain, kidneys, and reproductive system. Lead can also cause

birth defects for people. It has been shown to cause low IQ scores, slow growth, and

hearing problems for small children. House and car paint and manufacturing lead

batteries, fishing lures, certain parts of bullets, some ceramic ware, water pipes, and

fixtures all give off lead.

2.Disposal of Sludge

Coastal waters receive a variety of land-based water pollutants, ranging from

petroleum wastes to pesticides to excess sediments.

Marine waters also receive wastes directly from offshore activities, such as ocean-

based dumping (e.g., from ships and offshore oil and gas operations).

One pollutant in the ocean is sewage. Human sewage largely consists of excrement

from toilet-flushing; wastewater from bathing, laundry, and dishwashing; and animal

and vegetable matter from food preparation that is disposed through an in-sink

garbage disposal.

Because coasts are densely populated, the amount of sewage reaching seas andoceans is of particular concern because some substances it contains can harm

ecosystems and pose a significant public health threat.

In addition to the nutrients which can cause over enrichment of receiving water

bodies, sewage carries an array of potentially disease-causing microbes known as

pathogens.


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Animal wastes from feedlots and other agricultural operations (e.g., manure-

spreading on cropland) pose concerns similar to those of human wastes by virtue of

their microbial composition.

Just as inland rivers, lakes, andgroundwater can be contaminated by pathogenic

microbes, so can coastal waters.

Runoff from agricultural areas also contains nutrients such as phosphorus and

nitrogen, which can cause over enrichment in coastal regions that ultimately receive

the runoff.

3. Oil Spillage Oil wastes that enter the ocean come from many sources, some being accidental

spills or leaks, and some being the results of chronic and careless habits in the use of

oil and oil products.

Most waste oil in the ocean consists of oily storm water drainage from cities and

farms, untreated waste disposal from factories and industrial facilities, and

unregulated recreational boating.

It is estimated that approximately 706 million gallons of waste oil enter the ocean

every year, with over half coming from land drainage and waste disposal; for

example, from the improper disposal of used motor oil.

Offshore drilling and production operations and spills or leaks from ships or tankers

typically contribute less than 8 percent of the total.

The remainder comes from routine maintenance of ships (nearly 20 percent),

hydrocarbon particles from onshore air pollution (about 13 percent), and natural

seepage from the seafloor (over 8 percent).

Oil spills present the potential for enormous harm to Deep Ocean and coastal fishing

and fisheries.

The immediate effects of toxic and smothering oil waste may be mass mortality and

contamination of fish and other food species, but long-term ecological effects may be

worse.

Oil waste poisons the sensitive marine and coastal organic substrate, interrupting the

food chain on which fish and sea creatures depend, and on which their reproductivesuccess is based. Commercial fishing enterprises may be affected permanently.
http://www.waterencyclopedia.com/Ge-Hy/Groundwater.htmlhttp://www.waterencyclopedia.com/Ge-Hy/Groundwater.html

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CHAPTER 2-Water Pollution