Wastewater Story Class 7 Extra Questions and Answers Science Chapter 18

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Class 7 Science Chapter 18 Extra Questions and Answers Wastewater Story

Extra Questions for Class 7 Science Chapter 18 Wastewater Story with Answers

Wastewater Story Class 7 Extra Questions Very Short Answer Type

Question 1.
Which day is celebrated as the ‘World Water Day’?
Answer:
22nd March.

Question 2.
What do you understand by ‘wastewater’?
Answer:
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.

Question 3.
Which period has been proclaimed as the International decade for action on “Water for life”?
Answer:
United Nations proclaimed the period 2005-2015 as the International Decade for action on “Water for life”.

Question 4.
What do you mean by cleaning of water?
Answer:
Cleaning of water is a process of removing pollutants before it enters a water body or is reused.

Question 5.
What is sewage treatment?
Answer:
The process of wastewater treatment is commonly known as “Sewage Treatment”.

Question 6.
Why is the speed of incoming wastewater decreased in the grit and sand removal tank?
Answer:
The speed of the incoming wastewater in the grit and sand removal tank is decreased to allow sand, grit and pebbles to settle down.

Question 7.
Why should we plant eucalyptus along sewage ponds?
Answer:
Eucalyptus absorb all surplus wastewater rapidly and release pure water vapour into the atmosphere.

Wastewater Story Class 7 Extra Questions Short Answer Type 1

Question 1.
How do sand, grit and pebbles settle down in the grit and sand removal tank?
Answer:
Jn grit amLsand removal tank, the speed of the incoming wastewater is decreased to allow sand, grit and pebbles to settle down.

Question 2.
Why is air pumped into clarified water?
Answer:
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.

Question 3.
How is dry sludge used?
Answer:
Dried sludge is used as manure, returning organic matter and nutrients to the soil.

Question 4.
What is done to improve sanitation?
Answer:
To improve sanitation, low-cost onsite sewage disposal systems are being encouraged. Examples are septic tanks, chemical toilets, composting pits. Septic tanks are suitable for places where there is no sewerage system, for hospitals, isolated buildings or a cluster of 4 to 5 houses.

Wastewater Story Class 7 Extra Questions Short Answer Type 2

Question 1.
What is vermi-process toilet?
Answer:
Vermi-processing toilet is a design of a toilet in which humans excreta is treated by earthworms. It has been found to be a novel, low water-use toilet for safe processing of human waste. In the vermi processing toilet, the human excreta is completely converted to vermi cakes – a resource is much needed for soil.

Question 2.
What is done with the sludge produced in Wastewater Treatment Plant? Is it useful to us? If yes, how?
Answer:
The sludge produced IP Wastewater Treatment Plant is transferred to a separate tank when it is decomposed by the anaerobic bacteria. The biogas produced in the process can be used as fuel or can be used to produce electricity.

Question 3.
Why is air pumped into the clarified water? What is the role of aerobic bacteria in cleaning of water?
Answer:
Air is pumped into the clarified water to help aerobic bacteria to grow. These bacteria consume human waste, food waste, soaps and other unwanted matter still remaining in clarified water.

Wastewater Story Class 7 Extra Questions Long Answer Type

Question 1.
Suggest some better housekeeping practices.
Answer:
(i) Cooking oil and fats should not be thrown down the drain. They can harden and block the pipes. In an open drain the fats clog the soil pores reducing its effectiveness in filtering water. Oil and fats should be thrown in the dustbin.
(ii) Chemicals like paints, solvents, insecticides, motor oil, medicines may kill microbes that help purifying water. So, they should not be thrown in the drain.
(iii) Used tea leaves, solid food remains, soft toys, cotton, sanitary towels, etc. should also be thrown in the dustbin. These wastes choke the drains. They do not allow free flow of oxygen. This hampers the degradation process.

Question 2.
What is the composition of sewage?
Answer:
Sewage is a complex mixture containing suspended solids, organic and inorganic impurities, nutrients, saprotrophic and disease-causing bacteria and other microbes.

Organic impurities – Human faeces, animal waste, oil, urea (urine), pesticides, herbicides, fruit and vegetable waste, etc.

Inorganic impurities – Nitrates, Phosphates, metals.
Nutrients – Phosphorus and Nitrogen.
Bacteria – Such as which causes cholera and typhoid.
Other microbes – Such as amoeba which cause dysentery.

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