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Water Pollution and Its Prevention

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Title: Water Pollution and Its Prevention


1
Water Pollution and Its Prevention
  • Chapter 17

2
  • Water Pollution
  • defined as the presence of a substance in the
    environment that, because if its chemical
    composition or quantity, prevent the functioning
    of natural processes and produces undesirable
    environmental and health effects.
  • almost always the byproducts of worthy and
    essential activities
  • producing crops,
  • creating comfortable home
  • providing energy and transportation
  • manufacturing products
  • removing biological wastes.

3
.
  • Many materials used widely are nonbiodegradable
  • They resist attack and breakdown by detritus
    feeders and deecomposers.
  • Examples include plastics. Aluminum cans and
    synthetic organic chemicals
  • Any part of the environment may be affected
  • Our goal should be to manage materials that are
    man made so that the environment will not be
    jeopardized for future generations.

4
Identify the material or
  • Strategy to avoid or manage pollutants
  • Identify the sources of the pollutants
  • Identify the material or materials that are
    causing the pollution
  • Develop and implement pollution control
    strategies to prevent the pollutants from
    entering the environment
  • Develop and implement alternative means of
    meeting the need that do not produce the
    pollution by-product.

5
  • Water Pollution Sources, Type, Criteria
  • point and nonpoint sources
  • Point sources discharge pollutants at specific
    locations through pipes, ditches or sewers into
    bodies of surface water.
  • These can include factories, sewage treatment
    plants and abandoned underground mines.
  • These are fairly easy to identify.
  • In developed countries, many industrial
    discharges are strictly controlled, whereas in
    most developing countries, this type of discharge
    is largely uncontrolled.

6
  • Nonpoint sources
  • These are sources that cannot be traced to any
    single site of discharge.
  • They are usually large land areas or watersheds
    that pollute water by runoff, subsurface flow or
    deposition from the atmosphere.
  • This could include stormwater, seepage into the
    ground from croplands, livestock feedlots, logged
    forests, streets, lawns, and parking lots.

7
  • Pathogens
  • these include bacteria, viruses and other
    parasitic organisms.
  • A person or animal may till harbor low
    populations of a pathogen even after symptoms of
    the disease disappear.
  • These are called carriers.
  • These measures are more important than modern
    medicine
  • purification and disinfection of public water
    supplies with chlorine
  • sanitary collection and treatment of sewage
    wastes
  • maintenance of sanitary standards in food
    facilities
  • education in personal and domestic hygiene

8
  • Sanitation_
  • prevention of disease is good medicine, this has
    been done through public health measures
  • over 1 billion people do not have access to safe
    drinking water
  • 2.5 billion people live in areas having poor or
    no sewage collection or treatment
  • 3 million deaths each year due to waterborne
    diseases.

9
  • Over 1 billion people do not have access to safe
    drinking water
  • 2.5 billion people live in areas having poor or
    no sewage collection or treatment.
  • Over 3 million deaths each year are traced to
    waterborne diseases.
  • One of the Millennium Development Goal (MGD)
    targets is to reduce by half the number of people
    without sustainable access to safe drinking
    water.

10
  • Cholera is a disease that is related to
    unsanitary conditions of areas where there is no
    sewage treatment.
  • A cholera outbreak in Peru killed several
    thousand people in Peru in 1990.
  • The problems with civil disorder in Liberia led
    to an outbreak of cholera in 2003.
  • WHO reports many cholera outbreaks annually and
    cases number in the thousands with hundreds of
    deaths.

11
  • Organic Wastes
  • Human and animal wastes contain organic matter.
    Other organic matter (leaves, grass clippings,
    trash) enter bodies of water and can cause
    excessive aquatic plant growth.
  • When bacteria and detritus feeders decompose
    organic matter they consume oxygen gas dissolved
    in the water.
  • DO is directly related to temperature. Cold
    water holds many times more oxygen than warm
    water.

12
  • If there is organic material to consume, bacteria
    growth will be high and DO kept low.
  • BOD (biochemical oxygen demand) a measure of
    the amount of organic material in water in terms
    of how much oxygen will be required to break it
    down biologically, chemically, or both.
  • The Gulf of Mexico has a region that is larger
    than the state of Massachusetts.
  • This is due to organic material washed down the
    Mississippi from the Midwest.

13
  • Chemical Pollutants because water is an
    excellent solvent, it is able to hold many
    chemical substances.
  • Inorganic chemicals include heavy metals, acids
    from mine drainage, acid precipitation, road
    salts,
  • Organic chemicals include petroleum products,
    pesticides, polychlorinated biphenyls, cleaning
    solvents and detergents.
  • Many of these are toxic at low concentrations
  • Some may become a part of the food chain and be
    passed along through biomagnification.

14
  • Sediments
  • These enter water as natural landforms weather,
    especially during storms.
  • Erosion from farmland, construction sites, mining
    sites, overgrazed rangelands.
  • When erosion is slight, streams and rivers run
    clear, supporting aquatic plants.
  • Sediment entering water in large amounts have a
    large impact
  • Silt, sand, clay and organic particles are
    separated because they are carried at different
    rates
  • Clay and humus are carried in suspension- makes
    the water muddy, reduces the amount of light
    penetrating the water reduces photosynthesis

15
  • As the material settles, it coats everything,
    continues to block photosynthesis
  • Kills animals by clogging their gills and feeding
    structures
  • Eggs are particularly vulnerable
  • Bed load sand and silt which is not readily
    carried in suspension but is washed along the
    bottom. This scours organisms from the rocks,
    buries and smothers the bottom life, fills in
    hiding and resting places of fish and crayfish.

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  • Aquatic plants are prevented from reestablishing
    themselves because the bottom is constantly
    shifting
  • Modern storm water management is designed to
    reduce the bed load.
  • Many housing developments include storm water
    retention reservoirs.
  • This creates a small area of wetland.
  • Nutrients phosphorus and nitrogen are the two
    most important elements for aquatic plant growth.
    Often they are in low supply in water.
  • Nutrients become water pollutants when they
    stimulate undesirable plant growth.

18
  • the most serious source of excessive nutrients
    are sewage outfalls. If the sewage is not
    treated, high levels of nutrients will enter the
    water.
  • Agricultural runoff is the most notorious source
    of excess nutrients. Runoff from lawns and
    feedlots are also culprits,
  • Criteria Pollutants What concentration is
    worrisome?
  • There are standards set by the EPA. There are 158
    chemicals identified as pollutants. The list
    also has recommendations of concentration or
    freshwater, salt water and human consumption.

19
  • Standards for drinking water are much higher
  • Read in your book on page 472 how the EPA define
    a potential toxin an responds.
  • 94 of the US is served with drinking water that
    meets the drinking water standards

20
  • Eutrophication
  • This term means well nourished
  • Benthic plants are plants that grow attached to
    or rooted to the bottom of the water.
  • Phytoplankton species of photosynthetic algae.
  • If phytoplankton grows in the extreme, the water
    may become pea-soup green and block all light.

21
  • Impacts of nutrient enrichment
  • Oligotrophic lakes or waters are clear. The lack
    of nutrients renders the water clear it allows
    sunlight to pass through the water to support the
    growth of SAV.
  • Eutrophication if an oligotrophic body becomes
    enriched with nutrients, rapid growth and
    multiplication of phytoplankton increase the
    turbidity of the water,

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23
  • Combating eutrophication
  • Attack the symptom
  • Go to the root cause
  • Attacking the symptoms include chemical
    treatments of the weeds, aeration harvesting the
    weeds, drawing the water down.
  • Herbicides are used to control the growth of
    nuisance plants. Copper sulfate and diquat are
    frequently used. Sometimes glyphosate and 2,4, D
    are used,
  • These products are sensitive to fish.
  • Fish can be killed by the plant material rotting
    depleting the oxygen supply.

24
  • Aeration can be done to increase dissolved
    oxygen.
  • Harvesting where it is possible, bottom rooted
    vegetation is harvested.
  • Drawdown - The lake is lowered to kill rooted
    aquatic plants. They usually grow back over
    time.
  • Getting at the root cause
  • Identify the major point and nonpoint sources of
    nutrients and sediments.

25
  • The EPA has established ecoregional nutrient
    criteria.
  • these criteria measures causative factors
    (nitrogen and phosphorous) and criteria of
    response factors. These numbers differ for
    different regions of the country.
  • Control strategies for Point Sources
  • In heavily populated areas the most common source
    (of phosphate) is sewage treatment plants.
  • In regions where eutrophication s a problem,
    detergents containing phosphates have been
    banned.
  • Some dishwashing detergents are still high in
    phosphates..
  • Eliminating phosphates from detergents has had a
    profound impact on waterways that were heavily
    damaged by effluents.

26
  • Control Strategies for Nonpoint Sources Farm
    and urban runoff are the culprits here.
  • The source could be thousands or millions of
    individual property owners
  • The EPA has established regulations
  • Identify the pollutants responsible for degrading
    the water
  • Estimate the pollution coming from all sources
    (point and nonpoint)
  • Estimate the ability of the body of water to
    assimilate the pollutants while remaining below
    the threshold designating poor or inadequate
    water quality.
  • Within a margin of safety, allocate the allowable
    level of pollution among the different sources
    such that the water quality standards are
    achieved.

27
  • BMPs
  • (best management practices)
  • Reducing or eliminating pollution will require
    different strategies for different sources.
  • Farm activities causing erosion due to erosion
    and leaching and runoff of animal wastes will be
    different from urban runoff problems.
  • If standards are not met, the TMDL process must
    be revisited and new pollution allowances
    allocated (total maximum daily load).

28
  • Recovery
  • The good news is that water pollution and
    cultural eutrophication can be reversed.
  • The Chesapeake Bay suffered from heavy nutrient
    pollution destroying all but 1/10 of the 600,000
    acres of sea grasses.
  • Lake Washington, east of Seattle, has undergone a
    great change
  • In the 1940s and 50s sewage effluent was sent
    into the water at a rate of 20 million gallons
    per day.
  • By 1968, the effluent was put into Puget Sound
    where the effluent was mixed with ocean water.
  • By 1975, the recovery was complete

29
  • Sewage Management and Treatment
  • Before the late 1800s, the management of waste
    was the outdoor privy.
  • This was a problem where the outdoor privy was
    close to the well the household used for drinking
    water
  • Seepage occurred causing many infectious diseases
  • The result was the invention of the flush toilet.
    So then people began draining their wastes into
    the same place the storm sewers drained - the
    water ways.

30
  • Sewage treatment plants were first built in 1900.
  • People quickly realized that household waste
    needed to be treated separately from storm
    drains.
  • Even in the US as late as the 1970s there were
    still areas in the US that discharged untreated
    sewage into waterways.
  • Only about 10of waste water is collected in
    developing countries
  • Even where there are treatment plants, many do
    not operate effectively.

31
  • The pollutants in raw sewage
  • About 99.9 water since we use so much water to
    flush
  • 150 200 gallons per person per day
  • Debris and grit coarse sand, gravel
  • Particulate organic materials fecal matter food
    from garbage disposals, toilet paper
  • Colloidal and dissolved organic matter urine,
    soaps detergents
  • Dissolved inorganic materials nutrients from
    excretory wastes, nitrogen phosphorus.
  • Some pesticides, heavy metals, etc.

32
  • Steps taken to treat the sewage
  • Preliminary treatment
  • Remove grit and debris water passes through a
    series of screens. The water is slowed to allow
    the grit go settle out. This is taken to a land
    fill. (youd be amazed at what goes down a
    toilet)
  • Primary treatment the water goes to a settling
    basin. The particle matter settles out and is
    collected as raw sludge. This is treated
    separately

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  • Secondary treatment
  • This is also called biological treatment
  • it uses organisms and their metabolism to feed
    on the colloidal and dissolved organic material
    and break it down to CO2 and water. The water
    flows over a series of rocks on which live
    organisms, detritus feeders, live. Oxygen is
    provided for the system.
  • The organisms that live on these rocks represent
    a food web. The organisms consist of bacteria,
    rotifers (which feed on protozoans), protozoans,
    various small worms and other detritus feeders.

35
  • The activated sludge is also processed by
    detritus feeding organisms. The water is aerated
    (this is the activation part) as it moves through
    the system. As organisms feed on each other they
    form clumps called floc, This water goes into
    another settling tank where the organisms settle
    out. It is mostly water . 90 of the organic
    material is removed. The organisms that settle
    out are put back into the clarifier tank.
    Surplus amounts of the activated sludge are taken
    out from time to time and put in with the raw
    sludge. So the end product is carbon dioxide,
    water and mineral nutrients that remain in the
    water solution

36
  • After the secondary treatment the resultant
    mixture is very nutrient rich. Heretofore, this
    was not considered a problem. Now we know that
    extra nutrients leads to cultural eutrophication.
    Today, secondary activated sludge systems have
    been added to remove nutrients ad oxidize
    detritus. This is called biological nutrient
    removal.

37
  • Which nutrients are problems?
  • Nitrogen
  • phosphorus

38
BNR, Biological Nutrient Removal
  • Nitrogen is removed by denitrification. The
    activated sludge goes into four different zones
    where denitrifying is controlled
  • Phosphorus phosphate is removed as bacteria
    utilize it in their cells.
  • Final cleansing and disinfection wastewater is
    treated with chlorine, basically Clorox
  • Another method of disinfecting water is to use
    ozone. It kills microorganisms and produces
    oxygen gas.
  • It can also be passed through an array of UVB
    lights in the water. UV light kills bacteria.

39
  • Now, how is the sludge treated?
  • Sludge contains lots of bacteria. It is
    considered a biologically hazardous material.
  • Anaerobic digestion - Bacteria feed on detritus
    in the absence of oxygen, The end products are
    CO2, methane, and water. So one of the products
    is biogas. This can be used as fuel.
  • The biogas fuel is commonly used to heat the
    sludge digesters because the bacteria work best
    at about 104 degrees F.

40
  • After 4-6 weeks, anaerobic digestion is more or
    less complete
  • Now it is called treated sludge or biosolids,
    Most pathogens are gone.
  • It could be used as a fertilizer for lawns or
    agricultural fields. Usually it is a liquid,
    although it can be dehydrated to form sludge
    cake.
  • Composting
  • This can be done where the raw sludge is mixed
    with wood chips and placed in long narrow piles
    to break down with bacteria. It can then be used
    as a soil treatment.
  • Pasteurization
  • after the water is removed from the sludge, it
    can be put in ovens and pasteurized. The
    resulting material can be used as fertilizer.
    Milwaukee uses sludge from the brewing process
    and sells it as Milorganite

41
  • Onsite waste water treatment
  • Septic tanks wastewater flows into a tank, The
    solid material settles to the bottom. Water
    containing colloidal and dissolved organic
    material flows into the drain field and
    percolates into the soil. Accumulated biosolids
    in the tank must be pumped out every three to
    five years.
  • Onsite systems regularly fail.
  • Some common problems include, grease, cat litter,
    pesticides, household chemicals being rinsed down
    drains or flushed down toilets.
  • Have the septic system inspected frequently
  • Keep heavy equipment off the drain field
  • Garbage disposals are not good for septic tanks.

42
  • Using effluents for irrigation
  • Effluents are used in some towns to irrigate and
    fertilize residential lawns and open spaces.
  • Purple pipes in Cary
  • Reconstructed Wetland systems
  • Wetlands are good nutrient absorbers
  • in the 60s and 70s some wetlands were converted
    to pasture
  • They have now been reclaimed and converted back
    to wetlands.
  • These wetlands are being used as a treatment for
    effluent before it goes back into the James
    River.

43
  • Public Policy
  • The foundation for public policy and the laws
    that the EPA can enforce have to come from
    Congress
  • The Clean Water Act required permits for all
    poi8nt source discharges of pollutants
  • The Clean Water Act has funds for building and
    replacing treatment facilities
  • Reauthorization of the Clean Water Act is long
    overdue it has gotten very political
  • Nonpoint source pollution is the nations number
    one water pollution problem
  • New wastewater treatment facilities not far behind

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