Saturday, January 26, 2013

NCERT/CBSE -7th Science Assignment Chapter –Waste Water Story

Q1) Fill in the blanks:-

(a) The World Water Day is on __________.

(b) The activated sludge is about __________ water.

(c) Water is disinfected by using chemicals like __________ and __________.

(d) __________ and __________ are water borne diseases

(e)The sewage system were ------ type in olden days.

Q2) What is sewage? What does it contain?

Q3) Give two examples of organic and inorganic impurities present in sewage.

Q4) What is meant by waste water?

Q5) How many processes are involved in the treatment of waste water? Name them.

Q6) What is the function of the bar screen used in a Wastewater Treatment Plant?

Q7) What is sludge?

Q8) What is clarified water? Explain.

Q9) What is the difference between aerobic and anaerobic bacteria?

Q10) Give reasons

a. Eucalyptus trees are grown all along sewage ponds.

b. Used tea leaves, solid food remains, cotton etc. should be thrown in the dustbin.

c. Large amount of waste generated at public places must be disposed off properly.

d. Untreated human excreta is a health hazard.


a) Eucalyptus trees are grown near sewage ponds as they can grow in contaminated soils and soil containing high amount of salt and organic matter. Also, they absorb the metals, organic matter, nutrients and water from the sewage.

b) These wastes choke the drains. They do not allow free flow of oxygen. This hampers the degradation process.

c) Large amount of waste generated at public places must be disposed off properly otherwise epidemics could break out. 

d) Since a very large fraction of our people defecates in the open, on dry riverbeds, on railway tracks, near fields and many a time directly in water.It may cause water pollution and soil pollution

Q11) Write a short note on “vermiprocessing toilet”.

Q12) What can we do to reduce the load of pollutants in waste water and the pressure on Wastewater Treatment Plant?

Q13) Each tree can make its own manure. How?

Q14) How is sea wage treated?

Q15) What are the technique of waste water managements?

CBSE 7th Waste Water Story management Solved Test Paper Click here

CBSE 7th Waste Water Story management Solved questionsr Click here


J Sunil said...

What is sludge? Explain how it is treated.

Answer: The solid waste which settles at the bottom of the sedimentation tank is called sludge. The sludge is further treated by the process of aeration. This helps in growth of bacteria which eat away the human waste.

J Sunil said...

Q8) What is clarified water? Explain.

Ans: Clarification consists in removing all kind of particles, sediments, oil, natural organic matter and colour from the water to make it clear.

J Sunil said...

What is a Skimmer?

A skimmer is a type of a machine that helps to separate liquid or suspended particles from another Liquid. Skimmer is usually used to separate oil from water after oil spill on large water bodies

J Sunil said...

what is the process of waste water treatment plant? Ans:
Waste water treatment consists of four stages:-
1. Preliminary treatment:- At this stage the waste water is passed through a screen that removes all the
solid waste like paper, plastic of cloth.
2. Primary stage:- After preliminary stage is over the water is send to the sedimentation tank where all the solid particles of organic materials are removed using gravity setting.
3. Secondary stage:- At this stage microorganisms are used to remove all dissolved and suspended organic material. This is known as a activated sludge process.
4. Tertiary stage:- At this stage chlorine is used for killing all pathogens present in the water

J Sunil said...

Q.What is Sewage? Explain why it is harmful to discharge untreated sewage into river or sea?

Ans: Sewage is the wastewater containing both liquid and solid wastes produced by human activities from homes, industries, hospitals, offices , etc. Sewage contains various contaminants including disease-causing bacteria and other microbes. If untreated sewage is discharged into rivers or seas, then the water in the rivers or seas would also get contaminated. If this contaminated water is used for drinking, then it can cause diseases such as cholera, typhoid, dysentery, etc. which may lead to death. That is why it is harmful to discharge untreated sewage into r

J Sunil said...

Q. What is the difference between aquifers and ground water?
Ans: The water that is found under the surface of the Earth and is responsible for the presence of water in the wells, tube wells, and springs is called ground water. The porous regions in the soil and gaps in between the rocks are filled with this ground water. Rain water and water from the other water bodies on the surface of the Earth seeps down into the soil and is stored as ground water. This passing down of water through the soil is known as infiltration.
This infiltrated water accumulates in the deep underground, where a layer of impermeable rocks blocks the water from seeping down further. Such places that have an impermeable layer of rocks leading to the accumulation of water over it are known as aquifers .

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