Wastewater story Class 7 Worksheet Science Chapter 13

Q.1.  Fill in the blanks.
(i) Cleaning of water is a process of removing _______ .

pollutants

(ii) Wastewater released by houses is called ______.

sewage

(iii) Dried ____ is used as manure.

sludge

(iv) Drains get blocked by ____ and ____.

 cooking oil, fats

(v) By-products of wastewater treatment are ____ and ____ .

sludge, biogas

Q.2. State True (T) or False (F).
(i) Clean water is a basic need of human being.

True

(ii) Used water is clean water.

False

(iii) Treatment plants reduce pollutants in wastewater to a level where nature can take care of it.

True

(iv) Open drain system is a breeding place for flies, mosquitoes and organisms which cause diseases.

True

(v) People should defecate in the open.

False

Q.3.  Name two chemicals used to disinfect water.

Two chemicals used to disinfect water are chlorine and ozone.

Q.4. What is sewerage?

It is like a transport system that carries sewage from the point of being produced to the point of disposal, i.e. treatment plant.

Q.5. Which day is celebrated as World Water Day?

22 March

Q.6. Why chemicals should not be thrown down the drain?

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. 

Q.7. 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.

Q.8. 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.

Q.9. What are the reasons for scarcity of freshwater?

There is scarcity of freshwater due to population growth, pollution, industrial development, mismanagement and other factors.

Q.10. 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.

Q.11. Why air is pumped into clarified water?

Air is pumped into the clarified water to help aerobic bacteria to grow. Bacteria consume human waste, food waste, soaps and other unwanted matter still remaining in clarified water.

Q.12. Why should eucalyptus trees be planted along sewage ponds?

It 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.

Q.13. Why are bacteria important in sewage treatment?

Bacteria are important in sewage treatment because it consume human waste, food waste, soaps and other unwanted matter still remaining in clarified water.

Q.14. Why should oils and fats be not released in the drain? Explain.

Oils 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.

Q.15. Write two uses of ozone

Two uses of ozone are:
(i) It is used to disinfect water.
(ii) It absorbs ultraviolet rays.

Q.16. What is cleaning of water?

Cleaning 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”.

Q.17. What is sewage treatment?

Cleaning 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”. It takes place in several stages.

Q.18. Outline your role as an active citizen in relation to sanitation.

As an enlightened citizen we should approach the municipality or the gram panchayat if we see open drains and insist that the open drains be covered. If the sewage of any particular house makes the neighbourhood dirty, we should request them to be more considerate about others’ health.

Q.19. How can we contribute in maintaining sanitation at public places?

All of us can contribute in maintaining sanitation at public places. We should not scatter litter anywhere. If there is no dustbin in sight, we should carry the litter home and throw it in the dustbin.

Q.20. Explain the function of bar screens in a wastewater treatment plant.

A bar screen is a mechanical filter used to remove large objects, such as rags and plastics, from wastewater. Wastewater is passed through bar screens. Large objects like rags, sticks, cans, plastic packets, napkins present in waste water are removed.