Water Pollution

Definition and Scope of Water Pollution

• General Definition: Water pollution refers to the contamination of various water bodies, including but not limited to lakes, rivers, oceans, and groundwater. This phenomenon is predominantly driven by human activities.

• Technical Definition: It is characterized by any change or modification in the physical, chemical, or biological properties of water that results in detrimental consequences for living organisms.

• Mechanism of Occurrence: Pollution occurs when pollutants are discharged into water bodies—either directly or indirectly—without sufficient treatment to eliminate or neutralize harmful compounds.

• Primary Drivers: Pollutants enter the water cycle mainly through human factors or specific anthropogenic causes.

• Environmental Status: Along with air pollution, water pollution is identified as the second most imperative environmental concern globally.

Sources of Water Pollution

• Water pollution levels and sources are subject to various classifications, though two chief sources are recognized:

  • Point Source Pollution:

    • Definition: These are specific, identifiable sources that discharge water pollutants directly into a water body.

    • Examples: Oil wells located near water bodies, industrial factories, power plants, and underground coal mines.

  • Non-Point Source Pollution:

    • Definition: These sources do not have a specific, single location for discharging pollutants into the water body.

    • Examples: Run-offs from agricultural fields, residential gardens, construction sites, and urban infrastructure such as roads and streets.

Major Types of Water Pollution

• Nutrient Pollution:

  • Cause: wastewater, sewage, and fertilizers containing high concentrations of nutrients.

  • Impact: Elevated nutrient levels stimulate the excessive growth of weeds and algae.

  • Consequences: The water becomes undrinkable and can clog filtration systems. Moreover, excessive algae consume the available dissolved oxygen, leading to the death of other aquatic organisms via oxygen starvation.

• Surface Water Pollution:

  • Definition: This involves the pollution of natural water found on the Earth's surface, such as oceans, lagoons, rivers, and lakes.

  • Process: Occurs when hazardous substances come into contact with surface water, dissolving in it or mixing with it physically.

• Oxygen Depleting Pollution:

  • Microbiology Level: Water bodies house both aerobic and anaerobic microorganisms.

  • Mechanism: When excessive amounts of biodegradable matter enter the water, it triggers rapid microorganism growth. These organisms consume high volumes of oxygen.

  • Outcome: As oxygen is depleted, aerobic organisms die. This allows anaerobic organisms to proliferate, which produce high levels of harmful toxins such as ammonia ($NH_3$) and sulfides.

• Groundwater Pollution:

  • Process: Human application of pesticides and chemicals to soil allows these substances to be washed deep into the earth by rainwater.

  • Contamination: These chemicals reach the water table and underground water reserves.

  • Precaution: Water extracted from wells and boreholes must be rigorously checked for pollution before consumption.

• Suspended Matter (Particulate Matter):

  • Definition: Some pollutants, including specific substances, particles, and chemicals, do not dissolve easily in water.

  • Mechanism: These materials remain suspended or eventually settle at the bottom of the water body.

  • Impact: Sediments can harm or kill aquatic life living on the floor of the water body.

• Chemical Water Pollution:

  • Industrial/Agricultural Source: Use of chemicals to control pests, insects, and weeds.

  • Pollutants: Industrial solvents and metals.

  • Effect: These are highly poisonous to aquatic life, leading to slowed development, infertility, and death.

• Oil Spillage:

  • Scope: Spills typically have localized effects on wildlife initially but can spread across many miles.

  • Direct Impact: Oil causes fish mortality and sticks to the feathers of seabirds, stripping them of their ability to fly.

Primary Water Pollutants and Their Origins

• Domestic Sources: Sewage discharged directly from residential areas located on riverbanks.

• Urban/Industrial Sources: Effluents from urban areas containing high concentrations of detergents, heavy metals, and oils.

• Agricultural Sources: Plant remains and chemical inputs such as herbicides, insecticides, pesticides, and fertilizers.

• Nuclear Sources: Radioactive waste generated by nuclear reactors.

• Biological Sources: Human and animal excretory wastes deposited into water bodies.

Environmental and Health Effects

• Variability of Impact: The specific effects of pollution depend on the types of chemicals dumped and the location of the water body.

• Urban Pollution: Water bodies near urban centers are often highly polluted due to garbage dumping by individuals and the legal or illegal disposal of hazardous chemicals by manufacturing industries, schools, market places, and health centers.

• Human Health in India:

  • Polluted water consumption is a primary cause of ill health in India.

  • Associated Diseases: Cholera, diarrhea, dysentery, jaundice, and tuberculosis.

  • Statistic: Approximately $80\%$ of stomach-related diseases in India are attributed to the consumption of polluted water.

Eutrophication

• Definition: The enrichment of water with nutrients (specifically nitrates and phosphates) that triggers the rapid growth of green algae.

• Process Detail:

  1. Sewage or fertilizer runoff from agricultural fields enters the water.

  2. Nutrient content in lakes becomes enriched (Eutrophication).

  3. Algae multiply rapidly to create an "algal bloom."

  4. Algae consume dissolved oxygen and eventually begin to die.

  5. Decomposers (bacteria) multiply as they break down dead algae, further consuming oxygen.

  6. Higher organisms (such as fish) die due to a lack of dissolved oxygen.

Toxic Pollutants and Biomagnification

• Toxic Pollutants: Comprised of pesticides, heavy metals, and individual xenobiotic pollutants.

• Trace Metals: While some metals like Manganese ($Mn$), Zinc ($Zn$), and Copper ($Cu$) are essential in trace amounts for physiological functions, others cause severe toxicological damage to humans and ecosystems.

• Biomagnification Process:

  • Definition: The entry of harmful non-biodegradable chemicals into the food chain in small concentrations, which then accumulate in increasingly higher concentrations at each trophic level.

  • Example (DDT): Non-biodegradable pesticides like DDT are used for crop protection and mosquito control.

  • Trophic Level Accumulation (Concentration Gradient):

    • Water: $0.2\,\text{ppm}$

    • Algae: $77\,\text{ppm}$

    • Fish: $500\text{-}600\,\text{ppm}$

    • Pelican Bird (Top Consumer): $1700\,\text{ppm}$

  • Top Consumer Impact: In birds, high DDT concentrations cause adverse effects such as the weakening of eggshells, leading to a decrease in the total population.

Control and Prevention of Water Pollution

• Technological and Procedural Measures:

  • Implementation of water recycling and reuse programs.

  • Treatment of industrial effluents prior to discharge.

  • Creation of separate channels for sewage and river water to prevent mixing.

• Behavioral Changes:

  • Avoiding the use of natural bodies (rivers, lakes, ponds) for bathing or washing clothes.

  • Prohibiting the disposal of food materials, paper, biodegradable vegetables, plastics, and general waste into open drains.

• Governance and Awareness:

  • Consultation with qualified and experienced professionals for effective pollution control strategies.

  • Initiating public awareness campaigns via media to educate on the adverse effects of water pollution.

  • Establishing and modifying laws, standards, and practices based on current technological advancements and environmental requirements.