Unit 8, Module 48: Water Pollution

Overview of Topics

  • Non-chemical Pollution
    • Eutrophication
    • Sedimentation
    • Thermal Pollution
    • Noise Pollution
  • Changing Bodies of Water
    • Human Impact on Natural Water
    • Desalination of Water

Eutrophication

  • Definition: An increase in the nutrients in water, particularly nitrogen (N) and phosphorus (P).
  • Possible Sources of Eutrophication:
    • Agricultural Fertilizers: Used in farming practices, contributing excess nutrients to water bodies.
    • Manure and Human Sewage: Runoff containing organic waste increases nutrient levels.
    • Certain Industrial Wastewater: Industrial processes may release nutrient-rich wastewater into water bodies.

Algal Blooms and Dead Zones

  • Algal Bloom: A rapid increase in the population of algae in aquatic systems due to nutrient enrichment.
  • Dead Zones: Areas in water bodies where oxygen levels are too low to support marine life, often resulting from high nutrient inputs.

Biological Oxygen Demand (BOD)

  • Definition: The amount of oxygen required by aquatic organisms to decompose organic matter in water.

Oxygen Sag Curve

  • Definition: A graph representing the changes in oxygen levels in a water body over distance, showing the relationship between BOD and the availability of oxygen.
  • Direction of River Flow: The oxygen sag curve often declines downstream, indicating areas of higher BOD.

Risks to Human Health

  • Certain algal species can produce toxins harmful to both aquatic life and humans, posing health risks when contaminated water is consumed.

Sedimentation

  • Definition: The process by which sediment settles at the bottom of a body of water.
  • Mechanism: Rivers carry sediment as a result of erosion.
    • Types of Sediment:
    • Clay-sized particles
    • Sand grains
    • Gravel-sized sediments
  • Effects of Sedimentation:
    • Clay-sized particles tend to settle farthest fromshore in calm waters, whereas larger particles settle closer.
  • Human Impact on Sedimentation:
    • Natural Origin vs. Human Activity: 30% of sediment is from natural sources, while 70% is attributable to human activities such as construction, farming, and mining.
    • Consequences of Excess Sedimentation:
    • Turbidity (cloudy water)
    • Reduced sunlight penetration
    • Decreased oxygen levels
    • Increased nutrient levels
    • Clogged gills of aquatic organisms
    • Reduction in water depth as sediment accumulates on the bottom.

Thermal Pollution

  • Definition: The degradation of water quality due to a change in water temperature, most often caused by water discharged from industrial facilities.
  • Mechanism: Power plants and factories often use water as a coolant and release it back at temperatures 10 to 15°C hotter than the source.
  • Impacts on Ecosystems:
    • Many aquatic organisms may struggle to survive in altered temperatures.
    • Warmer water holds less dissolved oxygen.
    • Increased metabolic rates in ectothermic animals lead to higher oxygen demands.
    • Potential for species migration to cooler environments.
  • Possible Solutions:
    • Cooling towers for dissipating heat into the atmosphere
    • Recycling cooling water within power plants to minimize environmental discharge.

Noise Pollution

  • Definition: Underwater noise pollution primarily results from human activities, affecting marine animal communication and behavior.
  • Mechanism of Sound Travel: Sound travels 4 times better underwater than through air, making it crucial for the navigation and hunting of aquatic species.
  • Sources of Noise Pollution:
    • Ships
    • Submarines
    • Offshore drilling platforms
    • Sonar operations
  • Consequences of Noise Pollution:
    • Disruption of animal communication
    • Interference with echolocation for navigation and hunting
    • Potential forced migration of species to unfamiliar areas
    • Increased instances of beaching among whales and dolphins.
  • Possible Solutions:
    • Redesigning ships for quieter operation
    • Using alternate shipping routes to avoid critical habitats
    • Reducing sonar usage where possible.

Controlling Water

  • Overview: Humans depend on water but face dangers from flooding and other natural disasters. Strategies to manage these risks include:
    • Levees: Earth embankments to prevent flooding from rivers.
    • Dikes: Embankments to protect against sea flooding.
    • Dams: Barriers to control river flow and create reservoirs.
    • Aqueducts: Systems transporting water from one location to another.
Levees
  • Purpose: To keep riverbanks from overflowing during floods.
  • Construction: Usually made from earth, designed to protect land on the dry side.
  • Disadvantages:
    • Reduced fertility of floodplains
    • Increased development near rivers, posing risks if levees fail.
Dikes
  • Purpose: To control flooding by seas and oceans, creating protection for lands typically underwater.
  • Function: They can also reclaim land from aquatic areas, as seen in the Netherlands, where a significant area lies below sea level.
Dams
  • Definition: Structures designed to restrict and control water flow in streams and rivers, creating reservoirs.
  • Purposes of Dams:
    • Water supply
    • Recreation
    • Electricity generation
    • Flood prevention
  • Advantages and Disadvantages:
    • Advantages:
    • Provides water supply
    • Enables recreational activities
    • Generates renewable energy
    • Controls flooding risks downstream.
    • Disadvantages:
    • Alters nearby ecosystems
    • Hinders natural fish migrations
    • Displacement of local communities during construction.
Aqueducts
  • Definition: Systems of canals and ditches to transport water from one location to another.
  • Advantages:
    • Efficient distribution of water to needed areas.
  • Disadvantages:
    • Redistribution may change the hydrology of originating rivers or lakes.
  • Notable Example: The environmental crisis of the Aral Sea, due to water diversion for irrigation.

Access to Safe Drinking Water

  • Global Statistics:
    • 1 in 6 people lacks access to safe drinking water.
    • Annually, approximately 3,400,000 deaths are attributable to water-related diseases.
  • Cholera Death Rates by Region (Notable Statistics):
    • Papua New Guinea: 330,000
    • Chad: 160,000
    • Guinea: 140,000
    • Mozambique: 60,000

Desalination of Water

  • Overview: Desalination is the process of removing salt from seawater to produce potable (drinkable) fresh water.
  • Methods of Desalination:
    1. Distillation:
    • Involves boiling seawater to create vapor, leaving salt behind (brine).
    • Disadvantage: Requires a significant amount of energy; disposal of brine can be problematic.
    1. Reverse Osmosis:
    • Forces saltwater through a semi-permeable membrane, allowing water to pass while blocking salt.
    • Disadvantage: More cost-effective than distillation, but still expensive to implement; brine disposal remains a challenge.