Detection of Some Gases
- Introduction of unwanted substances to the water bodies that affects the natural quality of water decreasing its usability
- Ways to identify polluted water:
- Foul smell
- Bad taste
- Oil or grease floating on the surface
- Excessive algal growth
- Growth of weeds
- Household detergents
- Domestic and industrial waste
- Oil spills
- Thermal pollution
Causes of Water Pollution
Pathogens − Enter water from sewage and animal excreta
E.Coli and S.faecalis cause gastrointestinal diseases.
Organic wastes − Leaves, grass trash, etc. reach water with run off.
- Oxygen dissolved in water is called dissolved oxygen (DO). DO in water (10 ppm) is very less as compared to air (200,000 ppm).
- For decomposition of organic matter, oxygen is required by bacteria. Therefore, presence of organic matter in water depletes the DO of water.
- If DO reaches less than 6 ppm, then the growth of fish gets inhibited.
- If there is deficiency of oxygen in water, then anaerobic bacteria start degrading the organic matter, resulting in foul small and harmful effects on human health.
- Biochemical Oxygen Demand (BOD) − Amount of oxygen required by bacteria to break down organic matter present in water.
- Therefore, BOD represents the amount of organic matter present in water.
- Less polluted water has lower BOD value and vice-versa.
- Heavy metals dissolved in water are harmful as our body cannot excrete them. These metals cause damage to kidneys, CNS, liver, when accumulated beyond tolerance limit in body.
- Acids and raw salts (used to melt ice) also act as water pollutants.
- Organic chemicals such as petroleum products (from oil spills), pesticides, industrial chemicals such as PCBs, detergents also fall under category of chemical water pollutants.
- Fertilizers also cause water pollution. These fertilizers contain phosphates, which enhance algae growth (algae bloom). Algae consume a major part of dissolved oxygen, thus depriving aquatic plants and animals of it, hence killing them. This condition is called Eutrophication.
- pH value
- Presence of pollutants alters the natural pH (7) of water.
- This causes harm to aquatic plants and animals
- pH value less than 7 indicates water is acidic.
- pH value greater than 7 indicates water is basic.
- Presence of bacteria can be detected by observing samples of water from a source under microscope at regular intervals.
- Presence of bacteria in water indi…
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