Definition
Sewage: Water carried waste matter from homes or industries #BiologyDefinitions
Untreated sewage → should not be discharged into rives / lakes → as it may contain disease causing organisms such as bacteria.
- If these disease causing organisms → get into drinking water → may infect large number of people in community with diseases
- Cholera and typhoid → examples of water borne disease caused by bacteria
Untreated sewage → contains phosphates and nitrates.
- These are nutrients for algae and water plants. When untreated sewage → enters water bodies → can result in excessive growth of algae and water plants.
- Can promote bacterial growth
Other organisms in water → may die → due to lack of oxygen.
- Can lead to eutrophication
- Besides untreated sewage → eutrophication → can also be caused by excessive amounts of inorganic chemical fertilisers → entering water bodies
Definition
Eutrophication → process by which → water receives excess nutrients → like phosphates and nitrates → causing excessive growth of algae + water plants #BiologyDefinitions
Process of Eutrophication
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Untreated sewage + fertilisers → that are not absorbed by crops → may be washed by rainwater → into nearby rivers or lakes
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Nitrates and phosphates in fertilisers / untreated sewage → enhance growth of algae and water plants. → they are used in synthesis of proteins and nucleic acids
- Leads to increase growth + multiplication → of algae and floating water plants in rivers or lakes. Phenomenon → called eutrophication
- Overgrowth (overcrowding) → of algae and floating water plants → prevent sunlight from reaching submerged plant
- Submerged algae and water plants → die due to lack of sunlight.
- Dead algae and water plants → decomposed by aerobic bacteria and fungi
- As the bacteria feed on the decaying organic matter, they grow and multiply rapidly, using up the oxygen in the water
- Other organisms → such as fish → die due to lack of oxygen