Question 3.
Why is air along with microorganisms bubbled into the sewage treatment tanks? Answer
(a)After separating sludge from the sewage, the wastewater is transferred into large tanks where air along with microorganisms is bubbled into the tank.
(b)The wastewater is held in the aerated tanks for 48 hours.
(c)During this period, the microorganisms decompose most of the organic matter still present in the sewage. Decomposition breaks down waste matter into harmless substances.
(d)Oxygen in the air is used by the microorganisms to respire.
Question 4.
What will you do to reduce household waste water? Answer
Do not wash clothes, utensils or vehicles using running water. This will save much water and reduce waste water.
Question 5.
A septic tank is a mini sewage treatment plant. Explain? Answer
A septic tank is a mini sewage treatment plant. It is suitable for places having sandy soil as the outlet pipe gets blocked in clayey soil. A cluster of 4 to 5 houses can install and maintain a common septic tank. With a few modifications, a septic tank can be converted into an efficient biogas plant.
Question 6.
Why are open drainage systems harmful? Answer
In some towns and cities there are open drainage systems. An open drainage system is a health hazard. It is not only a breeding place for mosquitoes and flies but also spreads water-borne diseases and contaminates water sources during monsoon.
Question 7.
Why does untreated wastewater kill fish? Answer
(a)Large amounts of organic waste (present in untreated water) would lead to growth of microorganisms in a waterbody.
(b)The microorganism would decrease the amount of dissolved oxygen in the water.
(c)Most aquatic organisms use oxygen dissolved in the water to live. Once the level of dissolved oxygen falls, fish and most other aquatic animals begin to die.
Question 8.
A lot of dead fish were found floating on the surface of a lake. What could be the reason? Answer
If untreated wastewater is let off into the water bodies likely then it leads to an increase in algal growth called algal blooms. This causes depletion of oxygen in the water bodies making them unable to support aquatic life, which will lead to the death of the fishes.
Question 9.
How can you control the generation of sewage at home? Answer
Sewage generation can be minimised by monitoring what is thrown in the drain.
(a)Oil and fats must always be disposed off in dustbins.
(b)Chemicals like paints, solvents, insecticides, motor oil and medicines may kill decomposer microbes that help purify water. So, these must never be thrown down the drain.
(c)Used tea leaves, solid food remains, soft toys, cotton napkins etc. should also be thrown into the dustbin.
Question 10.
Explain the importance of sanitation?
Answer
Sanitation is the hygienic practice of ensuring cleanliness of our surroundings to maintain good health. Sanitation can be maintained by the proper disposal of refuge or the waste produced due to human activities. This can be done by ensuring the proper usage of toilets, sewer systems, treatment of wastewater, safe disposal of garbage and implementing personal hygiene practices.
A few steps that can be taken for better sanitations are as follows:
(a)People in rural and urban areas should be educated about sanitation.
(b)The government should provide monetary aid for the construction of proper sewerages.
(c)Wash basin with clean water supply and soap should be provided.
(c)Proper dustbins should be provided for the disposal of refuse.
(e)All the open drain should be covered.
