Water Pollution

Distribution of Water

  • Characteristics of a given watershed include its area, length, slope, soil, vegetation types, and divides with adjoining watersheds.

    1. How will changing climate affect the availability and distribution of water?

    2. How do human activities affect the occurrence of droughts?

    3. How do so many people live with so little water?

    4. Why do people use so much more water than they used to?

    5. Why don't localities and people use water in the most efficient way, rather than sometimes in wasteful ways?

    6. Globally, how many people do not have access to water that is safe for drinking and washing?

Water Pollution and Sources

  • Organisms have a range of tolerance for various pollutants. Organisms have an optimum range for each factor where they can maintain homeostasis. Outside of this range, organisms may experience physiological stress, limited growth, reduced reproduction, and in extreme cases, death.

  • Heavy metals used for industry, especially mining and burning of fossil fuels, can reach the groundwater, impacting the drinking water supply.

  • Increased sediment in waterways can reduce light infiltration, which can affect primary producers and visual predators. Sediment can also settle, disrupting habitats.

  • When elemental sources of mercury enter aquatic environments, bacteria in the water convert it to highly toxic methyl-mercury.

  • Thermal pollution occurs when heat released into the water produces negative effects to the organisms in that ecosystem.

  • Variations in water temperature affect the concentration of dissolved oxygen because warm water does not contain as much oxygen as cold water.

    1. What is the toll of waterborne diseases?

    2. What are the indicators of water quality?

    3. What type of pollutants do urban areas create?

    4. How do pollutants enter the groundwater?

    5. How do agricultural practices cause water pollution?

    6. What causes land subsidence and where are the places where this is a problem?

    7. How can heat be a pollutant and what damage can it cause?

    8. Is keeping water from becoming polluted easier, less expensive, and safer than cleaning it after it is polluted?

    9. What can individuals do to protect water quality?

    10. What is the purpose of the Clean Water Act?

Marine Pollution

  • Coral reefs have been suffering damage due to a variety of factors, including increasing ocean temperature, sediment runoff, and destructive fishing practices.

  • Oil spills in marine waters cause organisms to die from the hydrocarbons in oil. Oil that floats on the surface of water can coat the feathers of birds and fur of marine mammals. Some components of oil sink to the ocean floor, killing some bottom-dwelling organisms.

  • Oil that washes up on the beach can have economic consequences on the fishing and tourism industries.

  • Litter that reaches aquatic ecosystems, besides being unsightly, can create intestinal blockage and choking hazards for wildlife and introduce toxic substances to the food chain.

  • Wetlands are areas where water covers the soil, either part or all of the time.

  • Wetlands provide a variety of ecological services, including water purification, flood protection, water filtration, and habitat.

  • Threats to wetlands and mangroves include commercial development, dam construction, overfishing, and pollutants from agriculture and industrial waste.

Wastewater Treatment

  • Primary treatment of sewage is the physical removal of large objects, often through the use of screens and grates, followed by the settling of solid waste in the bottom of a tank.

  • Secondary treatment is a biological process in which bacteria break down organic matter into carbon dioxide and inorganic sludge, which settles in the bottom of a tank. The tank is aerated to increase the rate at which the bacteria break down the organic matter.

  • Tertiary treatment is the use of ecological or chemical processes to remove any pollutants left in the water after primary and secondary treatment.

  • Prior to discharge, the treated water is exposed to one or more disinfectants (usually, chlorine, ozone, or UV light) to kill bacteria.

    1. How is wastewater treated?


  • Eutrophication occurs when a body of water is enriched in nutrients.

      1. Where do these nutrients typically come from?

      2. What are the two most common nutrients causing eutrophication?

  • The increase in nutrients in eutrophic aquatic environments causes an algal bloom. When the algal bloom dies, microbes digest the algae, along with the oxygen in the water, leading to a decrease in the dissolved oxygen levels in the water. The lack of dissolved oxygen can result in large die-offs of fish and other aquatic organisms.

  • Hypoxic waterways are those bodies of water that are low in dissolved oxygen.

      1. What causes hypoxia during the process of eutrophication?

  • Compared to eutrophic waterways, oligotrophic waterways have very low amounts of nutrients, stable algae populations, and high dissolved oxygen.

      1. How can you tell an oligotrophic waterway from a eutrophic one by looking at it?

  • Anthropogenic causes of eutrophication are agricultural runoff and wastewater release.

      1. What are some practical solutions to reduce agricultural runoff and wastewater release?

  • Oceanic dead zones are areas of low oxygen in the world’s oceans caused by increased nutrient pollution.

  • An oxygen sag curve is a plot of dissolved oxygen levels versus the distance from a source of pollution, usually excess nutrients and biological refuse.

  1. What is the process of eutrophication?

  2. What are some negative environmental, economic, and societal problems with eutrophication?