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Water Treatment

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Water Treatment - Pearland Independent School District ... Water Treatment – PowerPoint PPT presentation

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Title: Water Treatment


1
Water Treatment
2
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.

3
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.

4
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.

5
Bottled Water is NOT 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.

6
Reducing Water Pollution through Sewage Treatment
  • Septic tanks and various levels of sewage
    treatment can reduce point-source water pollution.

Figure 21-15
7
Municipal Sewage Treatment
  • There are three steps to cleaning sewage
  • Primary Treatment
  • Secondary Treatment
  • Tertiary Treatment (sometimes)
  • Only after sewage has been treated is it safe to
    reintroduce to water supply

8
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9
Primary Treatment
  • Goal Removal of solids from waste water
  • 1. Bar screens remove large solids from water
  • 2. Settling basins allow small particles to
    settle
  • The solids removed in these steps are called
    sludge

10
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11
Secondary Treatment
  • Goal Clean water of chem. bio. pollutants
  • 1. Aeration adds D.O. to water for bacteria
  • 2. Bacteria in tanks digest majority of organics
  • 3. Chlorination tanks kill off bacteria
  • 3. Settling tanks collect more sludge (bacteria)

12
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13
Tertiary Sewage Treatment
  • Goal Clean additional pollutants from water
  • 1. Chemical and physical processes used
  • 2. Lagoons or wetlands used for purification
  • 3. Sampling to see if water meets WQS
  • 4. Disinfect with chlorine again (if necessary)
  • 5. Release into nature

14
Sludge Treatment Options
  • Digesters with aerobic bacteria
  • Produces CO2 as by product (undesired)
  • Digesters with anaerobic bacteria
  • Produces methane/biogas (can burn for
    electricity)
  • Composting
  • Mix sludge with bacteria, straw, wood chips, etc.
  • High levels of heat, kills parasites/microorganism
    s
  • Use as fertilizer

15

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
16
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.

17
20-1. What are the causes and effects of water
pollution?
  • Concept 20-1A Water pollution causes illness and
    death in humans and other species and disrupts
    ecosystems
  • Concept 20-1B The chief sources of water
    pollution are agricultural activities, industrial
    facilities, and mining, but growth in population
    and resource use makes it increasingly worse.

18
WATER POLLUTION SOURCES, TYPES, AND EFFECTS
  • Water pollution is any chemical, biological, or
    physical change in water quality that has a
    harmful effect on living organisms or makes water
    unsuitable for desired uses.

19
POINT SOURCE
NONPOINT SOURCE
Gargas, France
Farmland sediment
Pollutants enter water at specific location
(drain pipes, ditches, sewer lines)
Pollutants cannot be traced to a single site of
discharge (atmospheric deposition, agricultural /
industrial / residential runoff)
20
Leading Causes of Water Pollution
  • Most water pollution comes from
  • Agriculture
  • Fertilizers, pesticides, bacteria, food wastes
  • Industrial Facilities
  • Inorganic and organic chemicals
  • Mining
  • Sediment erosion, toxic chemical runoff/leaching

21
Major Water Pollutants Have Harmful Effects
  • 3.2 million die annually due to polluted sources
    of water (almost 9,000 per day)
  • 1.2 billion people have no access to clean
    drinking water
  • 1.9 million killed each year due to diarrhea
  • The majority of deaths come from children younger
    than five years old!

22
Common Diseases Transmitted Through Water
23
S. typhi -Typhoid Fever
Polio
Hook worm (Ancylosomiasis)
24
Major Water Pollutants and Their Effects
  • Water quality and dissolved oxygen (DO) content
    in parts per million (ppm) at 20C.
  • Only a few fish species can survive in water less
    than 4ppm at 20C.

Pg 535
25
20-2. What are the major water pollution problems
in streams and lakes?
  • Concept 20-2A While streams are extensively
    polluted worldwide by human activities, they can
    cleanse themselves of many pollutants if we do
    not overload them or reduce their flows.
  • Concept 20-2B Addition of excessive nutrients to
    lakes from human activities can disrupt lake
    ecosystems, and prevention of such pollution is
    more effective and less costly than cleaning it
    up.

26
Streams and Rivers
  • Streams and rivers can cleanse themselves if they
    are not overloaded
  • Initial breakdown of waste by bacteria causes
    lack of oxygen
  • Time and space can recover oxygen and eliminate
    some wastes in water

27
  • Heat can also pollute streams
  • As temperature increases, dissolved oxygen
    decreases
  • B.O.D. Oxygen used my microorganisms to
    decompose waste
  • As long as stream isnt overwhelmed, it can
    bounce back

Fig. 20-5 oxygen sag curve
28
Another Example
29
Developed vs. Developing Countries
  • Since mid-20th century, water quality has
    improved in developed countries
  • Elimination of many point sources
  • Increased awareness/prevention of non-point
  • Increase effectiveness and number of sewage
    treatment plants
  • Developing countries lag behind
  • Lack of , resources, large populations, lax
    environmental laws
  • 90 waste into river, half of top 500 polluted
    rivers

30
Groundwater Pollution
  • 50 of U.S. uses ground water (95 rural)
  • Groundwater sources cannot effectively cleanse or
    dilute itself (like rivers/lakes)
  • Sources include spills, leaking underground
    pipes/tanks, seepage
  • Takes 100 to 1000 years to degrade wastes
  • Nonbiodegradable wastes (arsenic, etc.) stay
    there permanently!

31
Sources of Groundwater Pollution
Fig. 20.11
32
Groundwater Pollution Movement
Fig. 20.12
33
Groundwater Pollution
  • According to the EPA
  • One or more organic chemicals contaminate 45 of
    municipal water supplies
  • 90 of U.S. aquifers are contaminated with VOCs
  • Out of 26,000 industrial waste ponds, only 1/3
    have a protective liner

34
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.

35

Solutions
Groundwater Pollution
Cleanup
Prevention
Pump to surface, clean, and return to aquifer
(very expensive)
Find substitutes for toxic chemicals
Keep toxic chemicals out of the environment
Inject microorganisms to clean up contamination
(less expensive but still costly)
Install monitoring wells near landfills and
underground tanks
Require leak detectors on underground tanks
Pump nanoparticles of inorganic compounds to
remove pollutants (may be the cheapest, easiest,
and most effective method but is still being
developed)
Ban hazardous waste disposal in landfills and
injection wells
Store harmful liquids in aboveground tanks with
leak detection and collection systems
Fig. 21-9, p. 504
36
U.S. Clean Water Act
  • Passed in 1972-helps keep waters swimmable,
    fishable, safe for consumption.
  • Variety of rules/regulations with the goal of
  • Reduce point source pollution into waterways
  • Finance waste water facilities
  • Manage polluted runoff
  • Establishing water quality standards (WQS)
  • Early focus on point-source, now a focus on
    nonpoint sources

37
Clean Water Act Terminology
  • Designated Uses (DU)
  • Drinking water, recreation, fishing, aquatic
    life, agricultural or industrial water supply
  • Water Quality Standards (WQS)
  • Acceptable conditions for water body based on DU,
    must be approved by EPA
  • Total Maximum Daily Loads (TMDLs)
  • Amount of contaminant water can receive and still
    achieve WQS

38

Solutions
Water Pollution
Prevent groundwater contamination
Reduce nonpoint runoff
Reuse treated wastewater for irrigation
Find substitutes for toxic pollutants
Work with nature to treat sewage
Practice four R's of resource use (refuse,
reduce, recycle, reuse)
Reduce air pollution
Reduce poverty
Reduce birth rates
Fig. 21-18, p. 517
39

What Can You Do?
Water Pollution
Fertilize garden and yard plants with manure
or compost instead of commercial inorganic
fertilizer.
Minimize your use of pesticides.
Do not apply fertilizer or pesticides near a
body of water.
Grow or buy organic foods.
Do not drink bottled water unless tests show
that your tap water is contaminated. Merely
refill and reuse plastic bottles with tap water.
Compost your food wastes.
Do not use water fresheners in toilets.
Do not flush unwanted medicines down the
toilet.
Do not pour pesticides, paints, solvents, oil,
antifreeze, or other products containing harmful
chemicals down the drain or onto the ground.
Fig. 21-19, p. 517
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