Water Contamination: Sources, Effects, and Mitigation

Posted on Dec 2, 2024 in Geology

Water Pollution: An Overview

Water pollution is the introduction of harmful materials, energy, or conditions that degrade water quality. It stems from the release of substances or energy forms that alter the natural composition of water, with the degree of contamination depending on its intended use. Water pollution is primarily caused by human activities.

Types of Contamination

Diffuse: This type of contamination has a wide area of impact and no specific point source (e.g., natural runoff).

Point Source: This type originates from a specific, identifiable source and affects a localized area (e.g., industrial wastewater discharge).

Sources of Pollution

Natural Contamination: The presence of natural substances in water without human intervention.

Urban Origin: Wastewater from homes, businesses, etc., containing fecal waste, food residues, and chemical products.

Agricultural Origin: The use of pesticides, herbicides, biocides, and fertilizers. These contaminants can be carried by irrigation water, leading to the introduction of salts, nitrogen, sulfur, and organochlorine elements into groundwater through leaching.

Industrial Sources: Industrial activities produce a wide range of materials and energy sources that contribute significantly to water pollution.

Anthropogenic Origin: Landfill waste, fuel spills, leaks from industrial and non-industrial channels and deposits, and oil spills.

Factors Affecting Contamination Levels

Receiver Characteristics:

  • Type of receptor (surface or underground)
  • Quantity and quality of the receiving water body
  • Dynamic or static characteristics (influencing dispersion and purification capacity)
  • Biocenosis (the presence of organisms that degrade organic matter in water)

Physical Water Contaminants

Temperature: Industrial discharges and dam turbines can increase water temperature, reducing dissolved oxygen levels, affecting species growth cycles, and causing abnormal breeding patterns.

Radioactive Particles: Waste and sludge from nuclear power plants, which can accumulate and pose risks through radon inhalation.

Suspended Solids (Inorganic and Organic): Originating from domestic and industrial wastewater, soil erosion, and uncontrolled infiltration. These solids increase turbidity, reduce light penetration, alter food chains, affect aquatic organism mobility and respiration, and modify the physical properties of water.

Chemical Water Pollutants

Chemical pollutants alter the properties of water.

Pollution of Rivers and Lakes: Eutrophication

The effects of pollution in rivers and lakes include restricted water use, changes in wildlife, and unpleasant aesthetics. Rivers have a natural defense mechanism due to their dynamic flow, while lakes are more vulnerable due to their static nature.

Eutrophication: Increased primary productivity caused by the introduction of bionutrients from agricultural and domestic discharges.

The process of eutrophication is as follows:

  1. Phosphorus (P) and nitrogen (N) from detergents and fertilizers are utilized by phytoplankton.
  2. Phytoplankton photosynthetic activity increases surface oxygen, which escapes into the atmosphere.
  3. Reduced light penetration decreases photosynthetic activity and dissolved oxygen (O2) levels.
  4. Nitrogen depletion leads to phytoplankton death and the proliferation of blue-green algae, which fix atmospheric nitrogen and continue to grow due to phosphorus accumulation.
  5. Increased organic matter intensifies aerobic bacteria activity, consuming large amounts of O2 to oxidize organic matter.
  6. Harmful algal blooms (red tides) can occur, coloring the sea and producing toxins harmful to fish.

Measures to mitigate eutrophication:

  • Limit domestic and agricultural discharges into aquatic ecosystems with reduced or low dynamics.
  • Treat wastewater before releasing it into receiving waters.
  • Reduce polyphosphates in detergents.
  • Inject pure O2 into affected lakes and reservoirs.
  • Add nitrogen to prevent the growth of blue-green algae.

Groundwater Contamination

Groundwater contamination can be point source (affecting specific areas near the source) or diffuse (affecting a large area of the aquifer). It originates from municipal waste discharge or industrial overexploitation. Over-extraction of groundwater can lower water tables, reducing their usability and causing saltwater intrusion, where seawater invades the aquifer and contaminates freshwater resources.

Pollution of Seawater

While oceans and seas have a larger volume of water and greater purification capacity than rivers, they are still susceptible to pollution from dumping, rubbish, and oil spills, which can form black tides. Oil spills can cause the death of marine animals through drowning, ingestion, or habitat destruction, leading to significant ecological damage.

Processes that remove oil from water:

  • Evaporation of light hydrocarbons
  • Photooxidation of components on the sea surface
  • Dispersion of heavy components into droplets, facilitated by waves