Water Pollution Notes

4.4 Water Pollution

  • Environmental Systems and Societies

Review Questions

  • What is the difference between point source and non-point source pollution? Provide an example of each.
  • Explain the three levels of pollution management strategies.

Point vs. Non-Point Sources

  • Point Sources:
    • Wastewater treatment plants
    • Factories
  • Non-Point Sources:
    • Urban streets
    • Suburban development
    • Rural homes
    • Cropland
    • Animal feedlots

Types of Water Pollutants

  • Chemical: Toxic metals
  • Physical: Noise and thermal pollution
  • Biological: Invasive species
  • Organic material
  • Floating debris
  • Plant nutrients
  • Light pollution

Movement of Pollutants

  • Pollutants can move between the atmosphere, lithosphere, and hydrosphere.
  • Lithosphere (Crust and Mantle)
  • Atmosphere
  • Hydrosphere
  • Biosphere

Ocean Currents and Pollution

  • Ocean currents play a role in distributing pollutants.
  • Example: Rubber ducks lost in the Pacific Ocean in January 1992 were found in various locations including Australia, Alaska, USA, Arctic, Scotland, and Chile.

Sources of Water Pollution: Inland and Coastal Waters

  • Domestic sewage: organic matter (soaps, detergents)
  • Industrial discharge: organic matter, toxic metals, non-biodegradable compounds
  • Agricultural run-off: pesticides, fertilizers, manure
  • Urban run-off: organic waste, suspended solids, oil, toxic metals
  • Land development: suspended sediments
  • Acid mine drainage: sulfuric acid
  • Atmospheric input: toxic metals and synthetic compounds

Sources of Water Pollution: Marine Based Sources

  • Outfall pipes: treated or untreated sewage, cooling water from stations
  • Dumped materials: sewage sludge, ammunitions, fly ash
  • Shipping activities: litter, oil spills
  • Exploitation of resources: oil or gravel extraction

Effects of Water Pollution

  • Eutrophication: Increased amounts of nitrogen (N) and/or phosphorus (P) lead to nutrient enrichment.
    • Turbidity increases, reducing light penetration.
    • Increased decomposition of sediments.
    • Less dissolved oxygen.

Eutrophication Impacts

  • High nitrate concentrations may affect human health (linked to stomach cancer).
  • Reduced recreational use of water (boating, swimming, fishing).
  • Water becomes unsuitable for drinking.
  • Reduced commercial value of the aquatic ecosystem.

Eutrophication Process

  1. Nutrient load up: Excessive nutrients from fertilizers are flushed from the land into rivers or lakes by rainwater.
  2. Plants flourish: These pollutants cause aquatic plant growth of algae, duckweed, and other plants.
  3. Algae blooms, oxygen is depleted: Algae blooms prevent sunlight from reaching other plants. The plants die, and oxygen in the water is depleted.
  4. Decomposition further depletes oxygen: Dead plants are broken down by bacteria (decomposers), using up even more oxygen in the water.
  5. Death of the ecosystem: Oxygen levels reach a point where no life is possible. Fish and other organisms die.

Impacts of Water Pollution

  • Toxic metals:
    • May interrupt cellular processes.
    • Bioaccumulation and biomagnification can occur.
  • Synthetic compounds:
    • Accumulate in organisms.
    • Inhibit phytoplankton/oyster shell growth.
    • Suppress the immune system in birds.
    • Cause reproductive failure of organisms.
  • Inert suspended solids: Prevent light penetration.
  • Hot water: Elevates water temperature.
  • Oil:
    • Prevents gas exchange, leading to O2O_2 depletion.
    • Prevents light penetration.
    • Causes birds to lose their plumage.
  • Pathogens: Health hazard
  • Plastic debris: Organisms are entangled or ingest them, affecting their digestive system or hormone levels.
  • Artificial light: Disorients turtles
  • Noise: Beaching of whales and dolphins
  • Invasive species: Competition for resources

Impact of Oil Contamination on Birds

  • Contamination of plumage
  • Loss of water repellency
  • Water penetration and air displacement
  • Loss of buoyancy and thermal insulation
  • Bird sinks
  • Increased metabolism
  • Death by drowning
  • Exhaustion, hypothermia

Case Study: Water Contamination in Flint, Michigan

  • The city was provided with drinking water from the Flint River (2014).
  • Water treatment process against lead and copper was delayed.
  • People noticed issues with water color, taste, and smell.
  • The water carried E. coli, TTHMs (disinfection byproducts), and lead from pipes.
  • Health effects: liver, kidney, and nervous system problems, low IQ in children, shortened attention span, increased violent and antisocial behavior, and irreversible effects on reproductive organs.

Assessing Water Quality

  • Chemical and Physical Indicators:
    • pH, BOD, temperature, turbidity, dissolved oxygen, etc.
  • Biological Indicators:
    • Examining fish, insects, and other invertebrates.
    • Many species indicate good water quality; few species suggest poor water quality.

Physical and Chemical Parameters

  • pH: Discharged water can alter pH, affecting reproduction and growth rates.
  • Temperature: Affects dissolved gasses. Colder temperatures hold more oxygen.
  • Suspended solids: Block sunlight, reducing photosynthesis; block feeding and respiratory systems of organisms.
  • Turbidity: Determines the amount of light scattered by particles.
  • Conductivity: Indicates the amount of salts present.
  • Nitrates and phosphates
  • Biochemical Oxygen Demand (BOD): Measures the amount of oxygen used by organisms in the water sample.
    • Indicates pollution with organic matter.
    • Organic pollutants increase organism populations that break down pollutants, consuming oxygen.
  • Metals: Certain concentrations can adversely affect aquatic ecosystems or humans.
    • Example: arsenic from mining

*Limitations: These parameters provide information for a specific sample at a particular time. Chemical pollution can be quickly washed away.

Biological Monitoring

  • Biological organisms can indicate whether the water quality has declined and whether there have been episodes of pollution between periods of sampling.

Biotic Index

  • Determines water quality using aquatic organisms.
  • Principles:
    • High biodiversity indicates little pollution.
    • Indicator species reflect specific conditions.
      • Some species are more sensitive to pollution; others are more tolerant.

Microbial Test

  • If the water is to be used for recreation or drinking purposes, it will be tested for pathogens of fecal origin.
  • Examples: Escherichia coli and Faecal Streptococci are used for analysis.
  • These are absent in unpolluted water.
  • It is an expensive process that requires a large amount of equipment.

Water Pollution Management

  • Altering Human Activity Producing Pollution
    • Ban or limit detergents.
    • Use eco-detergents without phosphates.
    • Use buffer zones between fields and water courses to absorb excess nutrients.
    • Compost garden or food waste.
    • Educate farmers about more effective timing for fertilizer application.
  • Regulating and Reducing the Pollutants at the Point of Emissions
    • Divert a polluted watercourse away from a sensitive ecosystem.
    • Increase the price of polluting products.
    • Regulate fertilizer dosage on agricultural lands or use organic matter instead.
  • Clean Up and Restoration
    • Precipitation of phosphates in water (treatment with Al)
    • Dredging sediments with high nutrient levels.
    • Mud pumping - removing nutrient enriched sediments
    • Removal of biomass and using it for fuel

Wastewater Treatment Process

  1. Screening: Removes large objects (diapers, nappies, cotton buds, plastics).
  2. Primary treatment: Separation of organic solid matter (human waste). Wastewater is placed in settlement tanks for the solids to sink to the bottom of the tank.
  3. Secondary treatment: Water is placed in aeration lanes. Air is pumped into the water for bacteria to break down tiny bits of sludge.
  4. Final treatment: Water is passed to a settlement tank. More sludge is formed at the bottom from bacterial activity. Water is then filtered through a bed of sand to remove any additional particles.

Sources of Water Pollution

  • Freshwater pollution
    • Runoff
    • Sewage
    • Industrial discharge
    • Solid domestic waste
  • Marine pollution
    • Rivers
    • Pipelines
    • Atmosphere
    • Activities at sea such as oil extraction

Specific Sources of Water Pollution and Examples

  • Industrial waste: Small/large industries release untreated effluents with Hg, Pb, Cr, nitrates, phosphates, and sulphates.
    • Examples: Dye manufacturing, chemical plants, textile units. The Yamuna River, India.
  • Sewage & wastewater: Treated/untreated household sewage carries harmful bacteria/chemicals.
    • Example: Ganges River in India, where over 3 billion liters of untreated sewage are dumped daily.
  • Mining activities: Extraction processes release toxic metals/chemicals, posing health risks to humans.
    • Example: The Hienghène River, New Caledonia (Nickel Mining).
  • Marine dumping: Paper, aluminum, rubber, glass, plastic & food from households takes years to decompose and endangers wildlife.
    • Example: The Great Pacific Garbage Patch - between Hawaii & California.
  • Oil Leakage: Oil does not dissolve with water causing problems for marine wildlife.
    • Example: Deepwater Horizon Oil Spill (2010), Gulf of Mexico.
  • Burning of Fossil Fuels: Coal/oil are burnt and release toxins that contribute to acid rain & global warming.
    • Example: Acid Rain in the Northeastern United States (1970s - 1990s) due to burning of coal in power plants. pH less than 4.4 - normal pH 5.6
  • Chemical fertilizers/pesticides: Run-off from farms can harm aquatic organisms.
    • Example: Lake Erie in North America.
  • Leakage from sewer lines: Sewer system aging and poorly maintained. It contaminates underground water, a breeding ground for mosquitoes, public health crisis.
    • Example: Kolkata, India.

More Water Pollutants

  • Floating debris
  • Organic material (human waste, food particles, soap and biodegradable organic substances).
  • Synthetic compounds: PCBs, DDT, PPCPs, PFAS, TCE
  • Oil
  • Microbial pollution: Cholera

Airborne Pollution Impact on Water

  • Airborne sulfur and nitrogen compounds contribute to acid rain, which recharges to groundwater and surface water.
  • Urban runoff
  • Landfills
  • Pesticides and fertilizers
  • Hazardous waste dump sites
  • Automobiles
  • Manure
  • Septic systems
  • Gas stations

Assessing Water Quality: Direct and Indirect Measures

  • Direct Measures/Chemical Indicators: pH, BOD, temperature, turbidity, dissolved oxygen, biochemical oxygen demand (BOD), chemical oxygen demand (COD), ammonia, heavy metals, etc.
  • Indirect Measures/Biological Indicators: examining fish, insects and other invertebrates. If there are many species - water quality is very good. If not…