RBSE Class 7 Science Important Questions Chapter 18 Wastewater Story

Rajasthan Board  RBSE Class 7 Science Important Questions Chapter 18 Wastewater Story  Important Questions and Answers.

RBSE Class 7 Science Chapter 18 Important Questions Wastewater Story

Multiple Choice Questions

Question 1. 
Sewage can be defined as :
(a) liquid waste 
(b) solid waste 
(c) gaseous waste 
(d) all of these
Answer:
(a) liquid waste 

Question 2. 
Which chemical is used to disinfect the water?
(a) Biogas 
(b) Chlorine
(c) Nitrogen 
(d) Oxygen
Answer:
(b) Chlorine

Question 3. 
Which of the following is wastewater?
(a) Water coming out of the tap
(b) Water flowing in the river
(c) Water coming out of the chemical factory
(d) Water left in a glass
Answer:
(c) Water coming out of the chemical factory

Question 4. 
The system of pipes used to take away wastewater from home to the treatment plant is known as :
(a) sewage 
(b) wastewater
(c) sewerage  
(d) transporting pipe
Answer:
(c) sewerage  

Question 5. 
In a wastewater treatment plant, water is filtered using a layer of:
(a) cans and plastic
(b) sand and clay
(c) clay and fine gravel
(d) sand, fine gravel, and medium gravel
Answer:
(d) sand, fine gravel, and medium gravel

Question 6. 
Ozone is used to :
(a) increase microbes
(b) disinfect water
(c) remove solid waste
(d) all of these
Answer:
(b) disinfect water

Fill in the blanks

Question 1. 
United Nations assembly proclaimed 2005-2015 as the International Decade for action on....................for life.
Answer:
water

Question 2. 
Wastewater treatment plant converts wastewater into....................water.
Answer:
clarified

Question 3. 
Pumping air into clarified water helps in the growth of....................
Answer:
aerobic bacteria

Question 4. 
Poor....................and contaminated drinking water is the cause of a large number of disease.
Answer:
sanitation

Question 5. 
Solid waste should always be thrown in....................
Answer:
dustbin

State Whether True or False

Question 1. 
Water treatment plants completely remove all sorts of pollutants from wastewater.
Answer:
False

Question 2. 
Chemical industries require a large amount of water for their daily activities.
Answer:
True

Question 3. 
Ozone is used for the absorption of oxygen dissolved in water.
Answer:
False

Question 4. 
Biogas produced during sludge decomposition can be used as a fertilizer.
Answer:
False

Question 5.
A bar screen removes large objects like rags, sticks, cans, napkins, etc. 
Answer:
True

Match the following

Column I	Column II
1. Disinfection	(a) Faeces
2. Diarrhea	(b) Sewage transport
3. Onsite sewage	(c) Chlorine, ozone
4. Organic impurity	(d) Cooking oil
5. Sewerage	(e) Vermi-composting
6. Blocking of pipes	(f) Scarcity of water
7. Earthworms	(g) Sewage treatment
8. Population	(h) Skimmer growth
9. Removing pollutants	(i) Compost pit
10. Floatable solids	(j) Waterborne diseases

Answer:

Column I	Column II
1. Disinfection	(c) Chlorine, ozone
2. Diarrhea	(j) Waterborne diseases
3. Onsite sewage	(i) Compost pit
4. Organic impurity	(a) Faeces
5. Sewerage	(b) Sewage transport
6. Blocking of pipes	(d) Cooking oil
7. Earthworms	(e) Vermi-composting
8. Population	(f) Scarcity of water
9. Removing pollutants	(g) Sewage treatment
10. Floatable solids	(h) Skimmer growth

Very Short Answer Type Questions

Question 1. 
Name the bacteria that causes cholera and typhoid.
Answer:
Vibrio cholera causes cholera and Salmonella paratyphi causes typhoid.

Question 2. 
Why are manholes built?
Answer:
Manholes are built as an access point to enable easy maintenance of the underground network of sewers if required. 

Question 3. 
Is clarified water fit for consumption? 
Answer:
No, clarified water still contains many low-level organic impurities and is not fit for consumption.

Question 4. 
What is activated sludge?
Answer:
The sludge collected at the bottom of the aeration tank (where clarified water is aerated) is called activated sludge.

Question 5 
What is the purpose of bar screens? 
Answer:
Bar screens are used for the removal of large suspended objects in the wastewater such as plastics, cloth, rags, sticks, cans, etc.

Question 6. 
Name diseases caused as a result of lack of proper sanitation.
Answer:
Diseases caused due to the lack of proper sanitation:

1. Diarrhea, 
2. Dysentery,
3. Polio, 
4. Typhoid.

Question 7. 
Give three examples of alternative arrangements for sewage disposal. 
Answer:
Alternate arrangements of sewage disposal are:

1. Safety tank 
2. Chemical toilets
3. Compost pits.

Short Answer Type Questions

Question 1. 
Define wastewater.
Answer:
Wastewater is the water that contains dissolved or suspended substances released from homes, hospitals, agriculture or any other establishment. It is basically polluted and dirty water.

Question 2. 
What should be the fate of wastewater?
Answer:
The wastewater should be recycled and treated in appropriate ways to make it fit for use again. The pollutant should be removed by treatment of wastewater.

Question 3. 
What do you mean by sewage treatment?
Answer:
Sewage treatment refers to the removal of various pollutants from the wastewater, before releasing into the water bodies like seas and oceans.

Question 4. 
List some applications of water. 
Answer:
Applications of water :

1.  Drinking and cooking 
2. Washing and cleaning
3. Industrial use i.e. chemical industries
4. Irrigation in agriculture
5. In-car radiators to keep it cool
6. In water coolers to increase the moisture and coolness of surrounding air.

Question 5. 
What do you mean by organic impurities?
Answer:
Organic impurities are primarily derived from plants or animals. Examples include:

1. Human excreta 
2. Animal excreta
3. Oil 
4. Urea
5. Pesticides 
6. Herbicides
7. Fruits and vegetables.

Question 6. 
What is sewage treatment?
Answer:
Sewage treatment refers to the process of removing contaminants from wastewater. It involves several physical, chemical and biological processes for the removal of contaminants.

Question 7. 
How is sewage is treated in industries?
Answer:
In the industries, sewage is treated by an efficient treatment plant. These plants are specially designed to remove industrial waste for its reuse and safe release into the environment.

Question 8. 
List the sequence involved in the treatment of wastewater in a WWTP. 
Answer:
Steps in the treatment of wastewater :

1. Passing through bar screens.
2. Sedimentation of sand, grit, and pebbles.
3. Removal of sludge and skimming of surface oil or floating substances.
4. Decomposition of sludge for production of biogas.
5. Production of clarified water.
6. Aeration of clarified water.

Question 9. 
What is sludge? 
Answer:
Sludge refers to the semisolid viscous mixture primarily consisting of feces that settle at the bottom of the sewerage treatment tank and has to be scrapped away for anaerobic decomposition and production of biogas.

Question 10. 
Why is wastewater aerated? 
Answer:
Aeration of wastewater has main purposes that are:

1. To remove carbon dioxide, sometimes produced in excess due to the decomposition process.
2. To promote the growth of aerobic microbes that feed on organic matter.

Question 11. 
Why is it suggested to plant eucalyptus trees all along with sewage ponds?
Answer:
It has been suggested to plant eucalyptus trees all along with sewage ponds because these trees absorb all surplus wastewater rapidly and release pure water vapor into the atmosphere.

Question 12. 
What are the causes of groundwater pollution?
Answer:

1. Defecation in the open area,
2. Defecation in dry riverbeds,
3. Defecation on the railway tracks, or
4. Defecation in the water bodies themselves.

Question 13. 
How is excreta used as a source of cooking gas?
Answer:
The anaerobic decomposition process of excreta as well as other organic matter such as kitchen waste results in the production of biogas, which can be supplied to homes and used as a means of cooking fuel or cooking gas.

Long Answer Type Questions

Question 1. 
Why is the period from 2005 to 2015 considered important in relation to the significance of water?
Answer:
This decade is considered the International Decade for action on “water for life”. It increased awareness about the need for better management of water as many parts of the world are in severe water crises. Water being essential for many life activities, this period saw a significant increase in awareness among the people regarding the importance and conservation strategies.

Question 2. 
Why is there a shortage of water on earth despite so much water everywhere?
Answer:
A large amount of water present on the Earth is salty and cannot be consumed. Only a little water is available for consumption on Earth's surface. The main reason for the shortage is the imbalance in demand and supply! With the increase in population, pollution, industrialization and lack of management practices, most of the World’s places face an acute shortage of water. 

Question 3. 
What are the components of sewage? 
Answer:
Sewage in primarily composed of:

1. Organic impurities e.g. human feces.
2. Inorganic impurities e.g. metallic wastes
3. Nutritional impurities e.g. nitrogen, phosphorous.
4. Bacteria e.g. Vibrio cholera, Salmonet la paratyphi.
5. Other microbes e.g. Protozoans.

Question 4. 
Why is water treated with ozone or chlorine before released into the ocean?
Answer:
Ozone is used for the disinfection of water as well as to oxidize some metals so that they could precipitate out of the water. Chlorine is mainly used for disinfection as it is very effective in killing certain bacteria that cause waterborne diseases e.g cholera.

Question 5. 
How should solid and chemical wastes be disposed of?
Answer:
Solid wastes such as sanitary towels, solid food remains, soft toys, etc. should be thrown in a dustbin.
Chemical wastes such as paints, solvents, medicines, motor oils, insecticides, etc. should be discarded in leakproof and lidded containers specially meant for this purpose.

Question 6. 
What are septic tanks? Where are they used?
Answer:
Septic tanks are a type of low-cost onsite sewage disposal facility, generally used in areas that are not well connected to a sewerage system. It is a primary wastewater collection tank, situated underground that uses the natural process of sedimentation to separate the solid and liquid components of the sewage. It also allows for the anaerobic growth of microbes which helps in the decomposition process. They are used in hospitals, isolated buildings, rural areas, etc.

Question 7. 
What is vermicomposting?
Answer:
Vermicomposting is a technique of onsite disposal of domestic waste with the help of worms (earthworms). This technology uses very less water for flushing, it is also called “dry toilets”. The worm ingests and degrades organic waste converting them to nutrients rich manures that can be added to the soil in the form of cakes, called vermin-cakes.

Question 8. 
List five ways in which you can contribute to sanitation at parks, cinema halls, fairs, etc.
Answer:
Five methods to maintain sanitation at public places:

1. Avoid spitting in public places.
2. Discard plastic waste in special containers/bins for non-biodegradable wastes. 
3. Discard leftover food products in the appropriate, a bin for biodegradable food products.
4. In case no dustbin is around, carry the litter at home.
5. Avoid urinating or defecating in the open, always use public toilets.