Water and Its Pollution by 6983Shf6

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									     Lecture 9




Water and Its Pollution
     A Glimpse Into Water’s Unique
              Properties
Liquid water dissolves a variety of compounds

 -     known as the universal solvent

 -     is easily polluted by water-soluble
       wastes

 -     in living organisms: carry dissolved
       nutrients; flush waste products
            Main Uses of Water

1. Domestic Use
    -   domestic and municipal use account for
        6 - 8% of worldwide withdrawals

    -    improved water supply helps reduce
         diseases

    -    humans are approx. 70% water
         Main Uses of Water cont’d
2. Industrial Use
     -    worldwide withdrawals of water for
          energy production & industrial
          processing is ~ 23%

     -    most water is used for cooling &
          cleaning

     -    it takes 100,000 gallons (380,000 litres)
          to make an automobile
          Main Uses of Water cont’d
3. Agricultural Use
    -    consumes the greatest quantity of fresh
         water

     -    globally ~ 69% of the water withdrawn
          is used for irrigation

     -    irrigation water efficiency is < 30%
       Main Uses of Water cont’d
4. Transport

    - use of seas and rivers

    - e.g., river barges, freight ships
         Main Uses of Water cont’d
5. Recreation / Tourism

    -    use of seas and rivers

    -    e.g., rafting, canoeing, snorkeling,
         swimming, river-boat casinos, scuba
         diving, cruise ships
WHERE IS OUR WATER STORED?

Watershed
 - also called drainage basin or catchment area
 - areas of land that drain into bodies of water

Surface Water
  - precipitation that does not soak into the
     ground or return to the atmosphere
  - forms streams, lakes, wetlands
Surface Runoff
  - water flowing off the land into bodies of
     surface water



Groundwater
 - water that sinks into the soil and is stored in
    slow flowing and slowly renewed
    underground reservoirs

  -   underground water
       Groundwater Pollution
- groundwater is easy to deplete and pollute
  because it is renewed very slowly

- pesticides and nitrates are the most common
  contaminants

- pollution is caused from: landfills, underground
  storage tanks, hazardous waste dumps, leaking
  underground sewers, industrial-waste storage
  lagoons e.g. red mud lakes
             Water Pollution
Water is becoming scarce in some parts of the world
  & its quality is being degraded.
    8 Principal Water Pollutants
1. Sediment
2. Inorganic Plant Nutrients
3. Pathogens
4. Organic Chemicals
5. Inorganic Chemicals
6. Radioactive Chemicals
7. Thermal Pollution
8. Sewage
1. Sediment (or suspended matter)
- insoluble particles of soil and other solids that are
  suspended in water

- occurs mostly when soil is eroded from land

- biggest water pollutant

- clouds water
  (lowers rate of photosynthesis)
2.   Inorganic Plant Nutrients
     (excess nutrients)
 - come from soil erosion and human & animal
   waste

 - water-soluble nitrates and phosphates can cause
   excessive growth of algae

 - causes eutrophication:
  over-nourishment of aquatic ecosystems with
   plant nutrients
3.   Pathogens (disease-causing agents)
 - from sewage and livestock wastes

 - include disease-causing bacteria, parasitic worms,
   protozoa and viruses

 - greatest cause of sickness and death in LDCs
4. Organic Chemicals / Compounds
- include oil, gasoline, plastics, pesticides, cleaning
  solvents, detergents

- threaten human health

- harm aquatic life
5. Inorganic Chemicals
- consist of acids, salts & compounds of toxic
  chemicals, e.g., mercury, lead

- high levels can:
     · make water unfit to drink
     · harm aquatic life
     · depress crop yields
     · accelerate corrosion of equipment
6. Radioactive Chemicals
- can cause birth defects, cancer, genetic damage

- capable of being biologically amplified to higher
  concentrations as they pass through food webs

- e.g.     DDT (Dichloro-Diphenyl-Trichloroethane)
           PCBs (Polychlorinated Biphenyls)
7. Thermal Pollution
- is an increase in water temperature that has
  harmful effects on aquatic life

- generally caused by heat that is absorbed by
  water used to cool electric power plants

- water temperature increase lowers oxygen content

- aquatic organisms more vulnerable to disease
8. Sewage & other oxygen demanding wastes
 - organic wastes that an be decomposed by aerobic
   bacteria

 - can lead to depletion of oxygen and death of
   aquatic life
     Sources of Water Pollution
Point Source
 - single, identifiable source that discharges
 pollutants into the environment

  - e.g., the drainpipe of a meat packing plant
  Sources of Water Pollution cont’d
Non-point Source
 - large or dispersed land areas, e.g., crop fields,
 streets & lawns, that discharge pollutants into the
 environment over a large area
    MAIN SOURCES OF WATER
          POLLUTION

• Agriculture

• Municipal Waste

• Industrial Waste
AQUATIC ECOSYSTEMS
   UNDER THREAT
               Coral Reefs
- the most threatened ecosystem in the coastal
  zone

- greatest threats come from eroded soil

     produced by:    deforestation
                     construction
                     agriculture
                     poor land management
                 Wetlands
- under severe human attack

- cut & converted to wood chips

- cut and drained for farmland & aquaculture
  ponds

- drained & dumped up for housing development
                    Oceans
- covers > 70% of Earth’s surface

- water evaporates as part of the water cycle

- mix and dilute many human-produced wastes to
  less harmful levels, if they are not overloaded

- affected by oil pollution
    Sustainable Use of Water
•    Conservation
•    Recycling
•    Rainwater harvesting
•    Efficient sewage treatment
•    Proper solid waste disposal
•    Soil conservation
•    Population control

								
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