Water Pollution

INTRODUCTION
Water is called the “universal solvent” because it can dissolve more substances than any other liquid. This property makes water extremely useful for life, but it also makes water very vulnerable to pollution. When harmful chemicals, wastes, or microorganisms enter rivers, lakes, oceans, ponds, groundwater, or wetlands, the water becomes unsafe for humans, animals, and the ecosystem. This is called water pollution.

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CATEGORIES OF WATER POLLUTION
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1. POINT SOURCE POLLUTION
Pollution coming from a single, identifiable source.
Examples:
• Discharge from factories  
• Oil refineries  
• Sewage treatment plants  
• Leaking septic tanks  
• Chemical or oil spills  
Although the source is one place, the pollution can spread over long distances.

2. NON-POINT SOURCE POLLUTION
Pollution coming from many scattered sources, making it difficult to trace.
Examples:
• Agricultural runoff  
• Stormwater runoff  
• Waste washed into drains during rains  
Very difficult to regulate because there is no single culprit.

3. TRANSBOUNDARY POLLUTION
Polluted water crossing national boundaries.
Examples:
• Oil spills from one country reaching another  
• Industrial chemicals slowly flowing downstream to another country  

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CAUSES OF WATER POLLUTION
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SEWAGE AND URBAN WASTE
• Discharge of untreated sewage  
• Plastics and microbeads entering water (90% of marine floating debris is plastic – UNEP)  
• Oil leaks from tankers (Ennore, Mumbai tar balls, Deepwater Horizon)  
• Ballast water discharge from ships  
• Deep sea mining increases heavy metals in water  

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DISSOLVED OXYGEN (DO)
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DO is extremely important for survival of fish and aquatic life.

• DO below 8 mg/L = contaminated water  
• DO below 4 mg/L = highly polluted water  

Factors affecting DO:
• Photosynthesis  
• Waste decomposition  
• Temperature  
• Water movement  

More waste = more decomposition = less oxygen.

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BIOCHEMICAL OXYGEN DEMAND (BOD)
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• BOD measures the amount of oxygen required by bacteria to break down organic waste.  
• High BOD = high pollution and low DO  
• Only measures biodegradable wastes, so it is not fully reliable.

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CHEMICAL OXYGEN DEMAND (COD)
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• Measures oxygen required to oxidise both biodegradable & non-biodegradable substances.  
• Better indicator of industrial pollution.

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INDUSTRIAL WASTES
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Industries discharge toxic metals and chemicals.
Examples:
• Petroleum refineries  
• Paper mills  
• Mining  
• Chemical industries  

Common pollutants: arsenic, chromium, cadmium, lead, nickel, benzene, plastics etc.

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AGRICULTURAL RUNOFF
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Contains:
• Fertilisers (N, P, K)  
• Pesticides (often non-degradable)  
• Animal excreta  
• Soil sediments (caused by erosion & deforestation)

Excess chemicals leach into groundwater or wash into rivers.

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THERMAL & RADIATION POLLUTION
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Power plants release hot water into rivers:
• Raises temperature by 10–15°C  
• Reduces DO  
• Kills fish and aquatic organisms

Radiation exposure results from:
• Nuclear waste  
• Nuclear accidents  
• Medical waste  

It causes:
• DNA mutations  
• Cancer  
• Thyroid damage (radioactive iodine)

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MARINE POLLUTION
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Oceans receive pollutants from:
• Coastal city waste  
• Oil spills  
• Radioactive waste  
• Ship discharge (oil, detergents, sewage)

OIL SPILLS:
• Oil floats, blocks oxygen  
• Kills fish, plankton, birds  
• Long-term ecosystem damage  

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INVASIVE SPECIES
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• Water hyacinth (Terror of Bengal)  
• Grows aggressively in nutrient-rich (eutrophic) waters  
• Blocks sunlight  
• Reduces oxygen  
• Causes stagnation  

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GROUNDWATER POLLUTION
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Pollutants enter groundwater through:
• Industrial seepage  
• Landfills  
• Sewage  
• Agricultural runoff  

Major contaminants:
• Nitrates – cause blue baby syndrome (methemoglobinemia)  
• Arsenic – causes cancer, black-foot disease  
• Fluoride – causes dental & skeletal fluorosis, knock-knee syndrome  

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EFFECTS OF WATER POLLUTION
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ON HUMAN HEALTH:
• Typhoid, cholera from sewage  
• Arsenic → cancer, skin thickening  
• Mercury → Minamata disease (neurological damage)  
• Lead → lead poisoning  
• Cadmium → Itai-Itai disease (bone pain)

ON ENVIRONMENT:
• Algal blooms → eutrophication → lake ageing  
• Biomagnification (DDT, mercury)  
• Bird populations decline due to thin eggshells  
• Oxygen deficiency kills fish  

ON AQUATIC ECOSYSTEM:
• Low DO eliminates sensitive species  
• Only tolerant species (Tubifex worms) survive  
• Hot water reduces oxygen further  

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WATER POLLUTION CONTROL MEASURES
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GOVERNMENT INITIATIVES:
• Ganga Action Plan (1985)  
• Coastal Regulation Zone (CRZ) Rules  
• Blue Flag beach certification (SICOM)  
• Classification of water bodies based on “designated best use”  
• National River Action Plan  

SOLUTIONS:
• Desiltation of lakes  
• Prevent encroachments & fencing  
• Allow only stormwater into lakes  
• Install biogas plants for animal waste  
• Plastic ban and proper waste disposal  
• Sewage treatment before discharge  
• Reduce fertiliser and pesticide use  
• Promote organic farming  
• Use water hyacinth to absorb toxins  
• Oil spill cleanup using bregoli  
• Plant eucalyptus near sewage ponds for water uptake  

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BIOREMEDIATION
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Use of microorganisms to clean polluted sites.

• **In situ bioremediation:**  
  - Bioventing – supply of air/nutrients  
  - Biosparging – inject air below water table  
  - Bioaugmentation – add helpful microbes  

• Oilzapper and Oilivorous-S (TERI) for oil-spill cleanup.

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WATER ACT, 1974
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Main objectives:
• Maintain & restore water quality  
• Prevent pollution  

Key provisions:
• Establish CPCB & SPCBs  
• Control industrial discharge  
• Prohibit release of poisonous substances  
• Penalties include fines & imprisonment  
• Powers to close polluting industries  

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WATER QUALITY MONITORING (WQM)
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India’s rivers depend on monsoon and often run dry for months, carrying untreated waste.  
CPCB collects and analyses water data for policymaking.

 

 

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Subject: Environment

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