Transcript Water Pollution: How clean is your water?

Water Pollution:
How clean is
your water?
Chapter 22 By Lakshmi
Read wastewater treatment system in Arcata, California and list
the effective use of the system followed in Arcata.
What is water pollution?
• Any physical, biological or chemical change in water
quality that adversely affects living organisms or
makes the water unsuitable for desired uses
• Two Major Categories
–Point source pollution
–Non-point source pollution
Can you give some examples?
• Non-point source pollution
• Point source pollution
Point Source pollution
• Water pollution that can be traced to a
specific origin. It is discharged into the
environment through pipes, sewers, or ditches
from specific sites such as factories or sewage
treatment plants.
• A cyanide spill contaminated the Tisza and
Danube rivers in Europe in 2000, killing
millions of fishes and shutting off downstream
water supplies.
Nonpoint source pollution
• It is also called polluted runoff, and is caused by land
pollutants that enter bodies of water over large areas
rather than at a single point. It occurs when
precipitation moves over and through the soil, picking
up and carrying away pollutants that eventually are
deposited in lakes, rivers, wetlands, groundwater,
estuaries, and the ocean.
• It includes agricultural run off(such as fertilizers,
pesticides, livestock wastes, and salt from irrigation),
mining wastes, municipal wastes, and construction
sediments. Soil erosion, logging operations, eroding
stream banks, and construction sites is a major cause
of nonpoint source pollution.
Eight categories of water pollutants
The main water pollution issue is lack of disease-free
drinking water. water pollutants are divided into eight
categories:
• Sewage
• Disease causing agents
• Sediment pollution
• Inorganic plant and algal nutrients
• Organic compounds
• Inorganic chemicals
• Radioactive substances
• Thermal pollution.
Pollution problems caused by Sewage
• Carries disease-causing agents and poses a threat to
public health.
• Causes two environmental problems
• A) enrichment and b) oxygen demand
• Enrichment is by the addition of high levels of plant
and algal nutrients such as nitrogen and phosphorus.
• Decomposition of the sewage requires oxygen and use
up most of the dissolved oxygen, leaving little for fishes
and other aquatic organisms. At extremely low oxygen
levels, fishes and other animals leave or die.
Sewage and BOD
• Biochemical oxygen demand (BOD), or biological
oxygen demand is usually expressed as milligrams
of dissolved oxygen per liter of water for a
specific number of days at a given temperature.
• A large amount of sewage in water generates a
high BOD, which robs the water of dissolved
oxygen.
• When dissolved oxygen levels are low, anaerobic
microorganisms produce compounds with
unpleasant odors, further deteriorating water
quality.
Eutrophication
• Eutrophication is a natural process that
increases the nutrient load of lakes over time as
sediment washes into them
• Artificial or cultural eutrophication is when
human activities speed up this process
Eutrophication: An Enrichment
Problem
• Lakes, estuaries, and slo-flowing streams that
have minimal levels of nutrients are unenriched
or oligotrophic. Such lakes have clear water and
support small populations of aquatic organisms.
• Eutrophication is the enrichment of a lake,
estuary by inorganic plant and algal nutrients
such as phosphorus, and such a water body is
said to be eutrophic. This increases
photosynthetic productivity.
Organisms in oligotrophic and
eutrophic lakes
Sewage- Eutrophication
• Oligotrophic
– Unenriched, clear water that supports small
populations of aquatic organisms
Sewage- Eutrophication
• Eutrophic– Slow-flowing stream, lake or estuary enriched by inorganic plant
and algal nutrients such as phosphorus
– Often due to fertilizer or sewage runoff
What is cultural eutrophication?
• Excess fertilizer,
human or animal
waste and
sediments act as
fertilizer in aquatic
ecosystems and
cause an algal
bloom.
What Eutrophication Looks Like
Next step…
• When the algae die, they sink to the lake bottom to
be eaten by decomposers. Decomposers deplete
oxygen and create Hypoxia (low oxygen levels) or
Apoxia (no oxygen).
• This kills the organisms in the water and creates a
“dead” zone
• What can be done? Aerate the water, like the
fountains in our lakes and Glenwood Lake
Disease causing Agents
• Municipal wastewater usually contains many bacteria,
viruses, protozoa, parasitic worms that cause human or
animal diseases.
• In the year 1993, a microorganism (Cryptosporidium)
contaminated the water supply in the greater
Milwaukee area. About 370,000 developed diarrhea,
making it the largest outbreak of a waterborne disease
ever recorded in the United States.
• In 2000, the first waterborne outbreak in North
America of the deadly strain of Escherichia coli
occurred in an Ontario town (Walkerton) in Canada.
Disease-causing Agents
• Infectious organisms that cause
diseases
– Originate in the wastes of infected
individuals
• Common bacterial or viral diseases:
– Typhoid, cholera, bacterial
dysentery, polio, and infectious
hepatitis
Some human diseases Transmitted by Polluted water
Disease
Infectious Agent
Type of organism
Major symptoms
Cholera
Vibrio cholerae
Bacterium
Severe diarrhea, vomiting
Dysentery
Shigella dysenteriae
Bacterium
Infection of the colon
causes painful diarrhea
with mucus and blood in
the stools
Enteritis
Clostridium perfringens
Bacterium
Inflammation in the small
intestine causes general
discomfort, loss of
appetite, and diarrhea.
Typhoid
Salmonella typhi
bacterium
Headache, fever,
followed by rash and
sometimes with
hemorrhaging in the
intestines
Infectious hepatitis
Hepatitis virus A
Virus
Inflammationof liver
causes jaundice, fever,
nausea.
Human diseases contd..
• Cryptosporidiosis caused by Cryptosprodium sp a
protozoan. Symptoms include diarrhea and cramps.
• Amoebic dysentry caused by Entamoeba histolytica, a
protozoan. Symptoms: infection of the colon causes
painful diarrhea with mucus and blood in the stools.
• Schistosomiasis caused by Schistoma sp. a fluke. It is a
tropical disorder of the liver and bladder causes blood
in urine, diarrhea, abdominal pains.
• Ancylostomiasis caused by hookworm. Symptoms are
anemia and bronchitis.
Effects of Sewage on Human Health
• Untreated or raw sewage can
transmit disease such as
cholera, dysentery and
typhoid
• About 4 billion cases of
diarrhea per year cause 1.8
million deaths, over 90 per
cent of them (1.6 million)
among children under five
(data from UNICEF, 2010)
• Famous Case of Typhoid Mary
http://cythereabast.wordpress.com/category/typhoid-mary-mallon/
You can make use of the above link to know about the famous case of Typhoid Mary
Effects of Sewage on Ecosystems
• As sewage is eaten by decomposers, it reduces
the dissolved oxygen (D.O.) content of the
water.
• All aquatic species have a range of tolerance
for D.O. and if the level is too low, they die.
This can result in fish kills.
Dissolved Oxygen Levels
• Healthy water has a high level of dissolved oxygen (>
8ppm)
• Oxygen-poor water (<2ppm) only supports detritivores
• Oxygen is added to the water by diffusion from air
(affect of temperature) and photosynthesis
• Oxygen is removed by respiration of plants and animals
• The addition of sewage and wastes stimulates oxygen
consumption by detritivores
How do you know if water is safe to
swim in?
• A test called the fecal coliform test tests for E. Coli
bacteria present in feces.
• one colony of bacteria per 100ml or greater is
considered unsafe to drink
• Safe swimming water should have no more than 200
per 100 mL of water
• Recreational water should have nor more than 2000
per 100 mL of water.
• Raw sewage may contain several million coliform
bacteria per 100 mL of water
• A good rule to follow: don’t go to the beach after it
rains
Disease-causing Agents
• Monitored by testing for presence of E. coli in
the water via a fecal coliform test
– Indicates the presence of pathogenic organisms
Monitoring for sewage
• Bacterial source tracking (BST) attempts to
make the proper identification. It has
successfully identified the source of coliform
bacteria in several cases.
Sediment and suspended solids
• Largest pollutant by volume in most parts of
world
• 25 billion metric tons of topsoil from runoff
and erosion
• 50 billion from grazing, construction etc.
• Erosion of agricultural lands, forest soils
exposed by logging, degraded stream banks,
overgrazed rangelands, strip mines…
Effects of sediment pollution
• Reduces light penetration, covers aquatic organisms, brings
insoluble toxic pollutants into the water, and fills in
waterways.
• Makes the water turbid, which inturn decreases the light
penetration.
• This in turn reduces productivity.
• Extreme turbidity reduces the number of photosynthetic
organisms which in turn results in decrease in number of
consumers.
• Sediments can clog gills of organisms
• Adversely affect water quality by carrying toxic chemicals.
• Disease causing agents are also transported into water via
sediments.
Inorganic Plant and Algal Nutrients
Chemicals such as nitrogen and phosphorus that stimulate the growth of
plants and algae
Harmful in large concentrations
Sources:
Human and animal wastes, plant residues, atmospheric deposition, and
fertilizer runoff
Causes:
Enrichment, red tides, bad odors,
a high BOD, “dead zones”
Red Tide
• When some pigmented marine algae experience
explosions or blooms, their great abundance
colors the water orange, red, or brown.
• Some of the algal species that form red tides
produce toxins that attack the nervous systems of
fishes leading to massive fish kills.
• Water birds like cormorants which eat the
contaminated fish die.
• The toxins work their way up the food web to
marine mammals and people.
Red tide (Read more on Red Tide Page
number 512)
The Dead Zone in the Gulf of Mexico
Every spring and summer, fertilizer runoff from midwestern fields and
manure runoff from livestcok operations in states such as Iowa, Wisconsin,
Illinois, find their way into the Mississippi River and from there into the
Gulf of Mexico.
Other than bacteria no life
Exists in the Dead Zone. The
Water does not have enough
Dissolved oxygen. This oxygenFree condition is known as
Hypoxia, when algae grow rapidly
And are decomposed.
What do we do?
• Reduce nitrogen runoff coming down the
Mississippi River.
• Modify farming methods so that less fertilizer is
needed.
• Reduce phosphorus as well.
• Sewage treatment plants and airborne nitrogen
oxides from automobile emissions to be
addressed.
• Restoring former wetlands will retain nutrients
such as nitrogen and phosphorus.
Organic Chemicals
• Pesticides, oils, plastics, pharmaceuticals, pigments,
detergents, cleaning solutions, and paints
Some are carcinogenic and some act as endocrine
disruptors and cause hormonal effects.
Alternative organic compounds which are less toxic and
degrade more readily so that they are not persistent
in the environment can be developed.
Tertiary water treatment effectively eliminates many
synthetic organic compounds in water.
(Page 514-List of synthetic organic compounds found in
polluted water)
Organic compounds
Chemicals that contain carbon atoms
Natural examples: sugars, amino acids, and oils
Human-made examples: pesticides, solvents, industrial
chemicals, and plastics
Human examples are more common
Toxic Inorganic materials
• Heavy metals:
– mercury, lead, cadmium and nickel
– mining wastes, mine drainage
– Arsenic in ground water
Lead
• Source – lead based paint, lead containing antiknock agents in gasoline.
• Effects : develop hypertension.
• High levels of lead in pregnant women increase
the risk of miscarriages, premature deliveries and
stillbirths.
• Children will suffer from a variety of mental and
physical impairments, including hearing loss,
attention deficit, lowered IQ, and learning
disabilities.
• Lead accumulates in bone.
Mercury
• Source: coal-fired power plants release the largest
amount of mercury.
• Municipal waste and medical waste incinerators also
release mercury. Fluorescent lights and thermostats
are examples of municipal wastes that contain
mercury, whereas thermometers and blood pressure
cuffs are examples of medical waste.
• Smelting of metals such as lead, copper, and zinc.
• Mercury is used in the chemical plants that
manufacture chlorine and caustic soda. Some of the
mercury vaporizes and enters the atmosphere.
Contd..
• Once mercury enters a body of water it settles into the
sediments where bacteria converts it to methyl
mercury compounds, a more toxic form that enters
food web. (biomagnification occurs)
• Exposure to methyl mercury causes kidney disorders
and damages the nervous and cardiovascular systems.
• The exposure of the developing fetuses to mercury is
linked to diminished cognitive function, cerebral palsy,
and developmental delays.
• Low levels caues headache, depression.
Radioactive Substances
• Contain atoms of unstable isotopes that
spontaneously emit radiation
• Sources
– Mining
– Processing radioactive
materials
– Nuclear power plants
– Natural sources
Effects of thermal pollution
• Less oxygen dissolves in warm water than in cold
water. when the level of dissolved oxygen is
lowered due to thermal pollution, a fish
ventilates its gills frequently and puts a great deal
of stress on the fish.
• It also affects the reproductive cycle, digestion
rates, and respiratory rates.
• At warmer temperature fishes require more food
to maintain body weight.
• In extreme themral pollution they die.
Thermal Pollution
• Water temperatures are usually stable so organisms
are poorly adapted to rapid change
• oxygen solubility decreases as temperature
increases
• most happens in industrial cooling
• Power plants release warmed water into rivers