Q1. Fill in the blanks.
Cleaning of water is a process of removing pollutants.
Wastewater released by houses is called sewage.
Dried sludge is used as manure.
Drains get blocked by cooking oil
By-products of wastewater treatment are sludge
Clean water is a basic need of human being.
Used water is clean water. False
Treatment plants reduce pollutants in
wastewater to a level where nature can take care of it. True
Open drain system is a breeding place for
flies, mosquitoes and organisms which cause diseases. True
People should defecate in the open. False
Q3. Which day is celebrated as World Water Day?
Q4. Name two chemicals used to disinfect water.
chemicals used to disinfect water are chlorine
Q5. What is sewerage?
is like a transport system that carries sewage from the point of being produced
to the point of disposal, i.e. treatment plant.
Q6. Why chemicals should not be thrown down the drain?
Ans. Chemicals should not be thrown down the drain
because chemicals like paints, solvents, insecticides, motor oil and medicines
may kill microbes that help purify water.
Q7. What are the reasons for scarcity of freshwater?
of freshwater due to population growth, pollution, industrial development, mismanagement
and other factors.
Q8. What is waste water?
Rich in lather, mixed with oil, black– brown water that goes down the drains from
sinks, showers, toilets, laundries is dirty. It is called wastewater.
Q9. What are the harmful effects of drinking contaminated water?
Contaminated drinking water is the cause of a large number of diseases such as
cholera, typhoid, polio, meningitis, hepatitis and dysentery.
Q10. What causes blockage of the drain?
Used tealeaves, solid food remains, soft toys, cotton, sanitary towels, etc. should
be thrown in the dustbin. These wastes cause blockage of the drain.
Q11. Why air is pumped into clarified water?
is pumped into the clarified water to help aerobic bacteria to grow.
consume human waste, food waste, soaps and other unwanted matter still
remaining in clarified water.
Q12. Why should eucalyptus trees be planted along sewage ponds?
has been suggested that we should plant eucalyptus trees all along sewage ponds.
These trees absorb all surplus wastewater rapidly and release pure water vapour
into the atmosphere.
Q13. Write two uses of ozone.
uses of ozone are:
It is used to disinfect water.
It absorbs ultraviolet rays.
Q14. Why are bacteria important in sewage treatment?
Ans. Bacteria are important in sewage treatment
because it consume human waste, food waste, soaps and other unwanted matter
still remaining in clarified water.
Q15. What is cleaning of water?
of water is a process of removing pollutants before it enters a water body or
is reused. This process of wastewater treatment is commonly known as “Sewage Treatment”.
Q16. Why should oils and fats be not released in the drain?
and fats should not be released in the drain because they can harden and block
the pipes. In an open drain the fats clog the soil pores reducing its
effectiveness in filtering water.