Environmental pollutants of water are substances that contaminate water bodies (rivers, lakes, oceans, and groundwater), rendering them harmful to humans, animals, and ecosystems.
In the Indian legal context, Section 2(e) of the Water (Prevention and Control of Pollution) Act, 1974, defines water pollution broadly as any contamination or alteration of the physical, chemical, or biological properties of water that creates a nuisance or renders it harmful to public health, safety, or legitimate uses.
Classification of Water Pollutants
Water pollutants are typically categorized by their nature and the source of contamination.
1. Pathogenic Microorganisms (Biological Pollutants)
These are disease-causing organisms that typically enter water through untreated domestic sewage or animal waste.
Examples: Bacteria (e.g., E.
coli, Vibrio cholerae), viruses (Hepatitis A), and protozoa. Impact: Leading cause of waterborne diseases like cholera, typhoid, and dysentery.
2. Organic Waste (Oxygen-Demanding Waste)
This includes biodegradable matter from sewage, food processing plants, and paper mills.
The BOD Factor: When these substances decompose, they consume dissolved oxygen.
This is measured as Biochemical Oxygen Demand (BOD). Impact: High BOD levels lead to oxygen depletion, causing "dead zones" where fish and other aquatic life cannot survive.
3. Inorganic Chemicals and Heavy Metals
These often originate from industrial effluents and mining activities.
Heavy Metals: Lead, Mercury, Arsenic, Cadmium, and Chromium.
Inorganic Salts: Nitrates and Phosphates (often from agricultural runoff/fertilizers).
Impact: These substances often bioaccumulate in the food chain.
For example, mercury poisoning (Minamata disease) or arsenicosis from contaminated groundwater.
4. Synthetic Organic Compounds
Man-made chemicals that are often persistent in the environment (Non-biodegradable).
Examples: Pesticides (DDT), insecticides, plastics, detergents, and industrial solvents (PCBs).
Impact: Many are toxic or carcinogenic and can cause long-term reproductive and neurological issues in wildlife and humans.
5. Sediments and Suspended Solids
Soil particles, silt, and sand washed into water bodies through erosion, construction, or deforestation.
Impact: Increases turbidity (cloudiness), which blocks sunlight for aquatic plants (photosynthesis) and clogs the gills of fish.
6. Thermal Pollution
The discharge of heated water from power plants and industrial cooling systems.
Impact: Warmer water holds less dissolved oxygen and can cause "thermal shock" to aquatic organisms tailored to specific temperature ranges.
7. Radioactive Substances
Waste from uranium mining, nuclear power plants, and medical/research facilities.
Examples: Radon, Uranium, and Thorium.
Impact: Causes genetic mutations, cancer, and long-term environmental toxicity.
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