Water Pollution - PowerPoint PPT Presentation

About This Presentation
Title:

Water Pollution

Description:

Chapter 21 Water Pollution – PowerPoint PPT presentation

Number of Views:118
Avg rating:3.0/5.0
Slides: 37
Provided by: you1155
Category:

less

Transcript and Presenter's Notes

Title: Water Pollution


1
Chapter 21
  • Water Pollution

2
POLLUTION OF FRESHWATER STREAMS
  • Flowing streams can recover from a moderate level
    of degradable water pollutants if they are not
    overloaded and their flows are not reduced.
  • In a flowing stream, the breakdown of degradable
    wastes by bacteria depletes DO and creates and
    oxygen sag curve.
  • This reduces or eliminates populations of
    organisms with high oxygen requirements.

3
Water Pollution Problems in Streams
  • Dilution and decay of degradable,
    oxygen-demanding wastes and heat in a stream.

Figure 21-4
4
POLLUTION OF FRESHWATER STREAMS
  • Most developed countries have sharply reduced
    point-source pollution but toxic chemicals and
    pollution from nonpoint sources are still a
    problem.
  • Stream pollution from discharges of untreated
    sewage and industrial wastes is a major problem
    in developing countries.

5
Global Outlook Stream Pollution in Developing
Countries
  • Water in many of central China's rivers are
    greenish black from uncontrolled pollution by
    thousands of factories.

Figure 21-5
6
Case Study Indias Ganges River Religion,
Poverty, and Health
  • Religious beliefs, cultural traditions, poverty,
    and a large population interact to cause severe
    pollution of the Ganges River in India.
  • Very little of the sewage is treated.
  • Hindu believe in cremating the dead to free the
    soul and throwing the ashes in the holy Ganges.
  • Some are too poor to afford the wood to fully
    cremate.
  • Decomposing bodies promote disease and depletes
    DO.

7
Case Study Indias Ganges River Religion,
Poverty, and Health
  • Daily, more than 1 million Hindus in India bathe,
    drink from, or carry out religious ceremonies in
    the highly polluted Ganges River.

Figure 21-6
8
POLLUTION OF FRESHWATER LAKES
  • Dilution of pollutants in lakes is less effective
    than in most streams because most lake water is
    not mixed well and has little flow.
  • Lakes and reservoirs are often stratified and
    undergo little mixing.
  • Low flow makes them susceptible to runoff.
  • Various human activities can overload lakes with
    plant nutrients, which decrease DO and kill some
    aquatic species.

9
Cultural Eutrophication
  • Eutrophication the natural nutrient enrichment
    of a shallow lake, estuary or slow moving stream,
    mostly from runoff of plant nutrients from the
    surrounding land.
  • Cultural eutrophication human activities
    accelerate the input of plant nutrients (mostly
    nitrate- and phosphate-containing effluents) to a
    lake.
  • 85 of large lakes near major population centers
    in the U.S. have some degree of cultural
    eutrophication.

10
POLLUTION OF GROUNDWATER
  • Groundwater can become contaminated with a
    variety of chemicals because it cannot
    effectively cleanse itself and dilute and
    disperse pollutants.
  • The drinking water for about half of the U.S.
    population and 95 of those in rural areas comes
    from groundwater.

11

Polluted air
Pesticides and fertilizers
Hazardous waste injection well
Deicing road salt
Coal strip mine runoff
Buried gasoline and solvent tanks
Gasoline station
Pumping well
Cesspool, septic tank
Water pumping well
Waste lagoon
Sewer
Leakage from faulty casing
Landfill
Accidental spills
Discharge
Unconfined freshwater aquifer
Confined aquifer
Confined freshwater aquifer
Groundwater flow
Fig. 21-7, p. 501
12
POLLUTION OF GROUNDWATER
  • It can take hundreds to thousand of years for
    contaminated groundwater to cleanse itself of
    degradable wastes.
  • Nondegradable wastes (toxic lead, arsenic,
    flouride) are there permanently.
  • Slowly degradable wastes (such as DDT) are there
    for decades.

13

Leaking tank
Aquifer
Bedrock
Water table
Groundwater flow
Free gasoline dissolves in groundwater (dissolved
phase)
Gasoline leakage plume (liquid phase)
Migrating vapor phase
Water well
Contaminant plume moves with the groundwater
Fig. 21-8, p. 502
14
POLLUTION OF GROUNDWATER
  • Leaks from a number of sources have contaminated
    groundwater in parts of the world.
  • According the the EPA, one or more organic
    chemicals contaminate about 45 of municipal
    groundwater supplies.
  • By 2003, the EPA had completed the cleanup of
    297,000 of 436,000 underground tanks leaking
    gasoline, diesel fuel, home heating oil, or toxic
    solvents.

15
Case Study Arsenic in Groundwater - a Natural
Threat
  • Toxic Arsenic (As) can naturally occur at high
    levels in soil and rocks.
  • Drilling into aquifers can release As into
    drinking water supplies.
  • According to WHO, more than 112 million people
    are drinking water with As levels 5-100 times the
    10 ppb standard.
  • Mostly in Bangladesh, China, and West Bengal,
    India.

16
OCEAN POLLUTION
  • Oceans, if they are not overloaded, can disperse
    and break down large quantities of degradable
    pollutants.
  • Pollution of coastal waters near heavily
    populated areas is a serious problem.
  • About 40 of the worlds population lives near on
    or near the coast.
  • The EPA has classified 4 of 5 estuaries as
    threatened or impaired.

17
OCEAN POLLUTION
  • Harmful algal blooms (HAB) are caused by
    explosive growth of harmful algae from sewage and
    agricultural runoff.

Figure 21-11
18
Oxygen Depletion in the Northern Gulf of Mexico
  • A large zone of oxygen-depleted water forms for
    half of the year in the Gulf of Mexico as a
    result of HAB.

Figure 21-A
19

Missouri River
Mississippi River Basin
Ohio River
Mississippi River
MS
LA
LOUISIANA
Mississippi River
TX
Depleted oxygen
Gulf of Mexico
Gulf of Mexico
Fig. 21-A, p. 507
20
Case Study The Chesapeake Bay An Estuary in
Trouble
  • Pollutants from six states contaminate the
    shallow estuary, but cooperative efforts have
    reduced some of the pollution inputs.

Figure 21-12
21
OCEAN OIL POLLUTION
  • Most ocean oil pollution comes from human
    activities on land.
  • Studies have shown it takes about 3 years for
    many forms of marine life to recover from large
    amounts of crude oil (oil directly from ground).
  • Recovery from exposure to refined oil (fuel oil,
    gasoline, etc) can take 10-20 years for marine
    life to recover.

22
OCEAN OIL POLLUTION
  • Tanker accidents and blowouts at offshore
    drilling rigs can be extremely devastating to
    marine life (especially diving birds, left).

Figure 21-13
23
PREVENTING AND REDUCING SURFACE WATER POLLUTION
  • The key to reducing nonpoint pollution most of
    it from agriculture is to prevent it from
    reaching bodies of water.
  • Farmers can reduce runoff by planting buffers and
    locating feedlots away from steeply sloped land,
    flood zones, and surface water.

24
PREVENTING AND REDUCING SURFACE WATER POLLUTION
  • Most developed countries use laws to set water
    pollution standards, but such laws rarely exist
    in developing countries.
  • The U.S. Clean Water Act sets standards fro
    allowed levels of key water pollutants and
    requires polluters to get permits.
  • EPA is experimenting with a discharge trading
    policy similar to that for air pollution control.

25
Reducing Water Pollution through Sewage Treatment
  • Septic tanks and various levels of sewage
    treatment can reduce point-source water pollution.

Figure 21-15
26
Reducing Water Pollution through Sewage Treatment
  • Raw sewage reaching a municipal sewage treatment
    plant typically undergoes
  • Primary sewage treatment a physical process that
    uses screens and a grit tank to remove large
    floating objects and allows settling.
  • Secondary sewage treatment a biological process
    in which aerobic bacteria remove as much as 90
    of dissolved and biodegradable, oxygen demanding
    organic wastes.

27
Reducing Water Pollution through Sewage Treatment
  • Primary and Secondary sewage treatment.

Figure 21-16
28
Reducing Water Pollution through Sewage Treatment
  • Advanced or tertiary sewage treatment
  • Uses series of chemical and physical processes to
    remove specific pollutants left (especially
    nitrates and phosphates).
  • Water is chlorinated to remove coloration and to
    kill disease-carrying bacteria and some viruses
    (disinfect).

29
Reducing Water Pollution through Sewage Treatment
  • Sewage sludge can be used as a soil conditioner
    but this can cause health problems if it contains
    infectious bacteria and toxic chemicals.
  • Preventing toxic chemicals from reaching sewage
    treatment plants would eliminate such chemicals
    from the sludge and water discharged from such
    plants.

30

Odors Odors may cause illness or indicate
presence of harmful gases.
Dust Particles Particles of dried sludge carry
viruses and harmful bacteria that can be inhaled,
infect cuts or enter homes.
BUFFER ZONE
Exposure Children may walk or play in fertilized
fields.
Livestock Poisoning Cows may die after grazing
on sludge-treated fields.
Sludge
Groundwater Contamination Harmful chemicals and
pathogens may leach into groundwater and
shallow wells.
Surface Runoff Harmful chemicals and pathogens
may pollute nearby streams,lakes, ponds, and
wetlands.
Fig. 21-17, p. 513
31
Reducing Water Pollution through Sewage Treatment
  • Natural and artificial wetlands and other
    ecological systems can be used to treat sewage.
  • California created a 65 hectare wetland near
    Humboldt Bay that acts as a natural wastewater
    treatment plant for the town of 16,000 people.
  • The project cost less than half of the estimated
    price of a conventional treatment plant.

32
Reducing Water Pollution through Sewage Treatment
  • Water pollution laws have significantly improved
    water quality in many U.S. streams and lakes but
    there is a long way to go.
  • Some want to strengthen the U.S. Clean Water Act
    (CWA) to prevent rather than focusing on
    end-of-the-pipe removal.
  • Many farmers and developers see the CWA as
    limiting their rights as property owners to fill
    in wetlands.

33
DRINKING WATER QUALITY
  • Centralized water treatment plants and watershed
    protection can provide safe drinking water for
    city dwellers in developed countries.
  • Simpler and cheaper ways can be used to purify
    drinking water for developing countries.
  • Exposing water to heat and the suns UV rays for
    3 hours can kill infectious microbes.

34
Using Laws to Protect Drinking Water
  • While most developed countries have drinking
    water quality standards and laws, most developing
    countries do not.
  • The U.S Safe Drinking Water Act requires the EPA
    to establish national drinking water standards
    (maximum contaminant levels) for any pollutant
    that may have adverse effects on human health.

35
Using Laws to Protect Drinking Water
  • The U.N. estimates that 5.6 million Americans
    drink water that does not meet EPA standards.
  • 1 in 5 Americans drinks water from a treatment
    plant that violated one or more safety standard.
  • Industry pressures to weaken the Safe Drinking
    Act
  • Eliminate national tests and public notification
    of violations.
  • Allow rights to pollute if provider cannot afford
    to comply.

36
Is Bottled Water the Answer?
  • Some bottled water is not as pure as tap water
    and costs much more.
  • 1.4 million metric tons of plastic bottles are
    thrown away.
  • Fossil fuels are used to make plastic bottles.
  • The oil used to produce plastic bottles in the
    U.S. each year would fuel 100,000 cars.
Write a Comment
User Comments (0)
About PowerShow.com