Wastewater Story Worksheet Science CBSE Class 7 Sample Paper

Wastewater Story Worksheet

Objective Type Questions

Match the following:
Rearrange the letters to form meaningful words based on the clues provided.
i. A substance which pollutes the environment - nctnmaoitan
ii. Solids like faeces settle at the bottom of water treatment plant – dsglue.
iii. The process of keeping places free from dirt, infection, disease, etc., by removing trash and garbage – itnsoanait.
Fill in the blanks:
i. _______ is a liquid waste which causes water and soil pollution.
ii. By-products of wastewater treatment are _____ and _____.
iii. Rich in lather, mixed with oil, black brown water that goes down the drains from sinks, showers, toilets, laundries is dirty is called ______.
Complete the figure:

Multiple Choice Questions
A community leader in a small village wants to build a septic tank for a nearby residential complex. Where the septic tank should be connected to the existing sewer system

(a) Point A
(b) Point B
(c) Point C
(d) Point D
Which of the following is not a factor that contributes to the increasing scarcity of fresh water?
(a) Population growth
(b) Industrial development
(c) Excessive use of fertilizers and pesticides
(d) Mismanagement of water resources
What is the point of origin of chemicals in sewage?
(a) Households
(b) Industries
(c) Rivers and lakes
(d) Wastewater treatment plants
An art festival was organised in a remote village of India where electric and water supply is limited. What type of toilets are most suitable for holding such a festival such that they are cost effective and use less space?
(a) Septic tanks
(b) Chemical toilets
(c) Composting toilets
(d) Vacuum toilets
Rajiv and his friends made a filtration system using layers of fine sand, coarse sand and gravel. They tested this system in the lab using 1 litre of wastewater sample.

In order to upscale their design, they added a settling tank after the filter. What should they add before their filtration system?
(a) A wire mesh
(b) Disinfectants
(c) An aeration tank
(d) A mechanical skimmer
A local textile industry is currently releasing their wastewater directly into the sewerage system of the nearby town, causing a burden on the wastewater treatment plant. Seema, who is a local official, needs to take action to effectively address this issue.

Which of the following actions would be the most appropriate for Seema to take?
(a) Instruct the industry to stop producing all industrial wastes
(b) Request the factory to relocate to another municipality
(c) Ask the factory to discharge their wastewater into the local lake
(d) Advise the industry to pre-treat their wastewater before release

SAQs
What are the benefits of planting eucalyptus trees along the sewage ponds?
What are some common sources of water contamination in rural areas of India and how can they be addressed?
What are the consequences if a significant amount of waste generated in public places is not disposed off correctly?
Draw a labelled sketch of a wastewater treatment plant.
Describe the various steps involved in separating clear water from wastewater. Which fuel can be extracted during this process?

Assertion-Reasoning Questions

Select the correct answer to these questions from the codes (a), (b), (c) and (d) as given below:
Assertion: Open defecation is one of the common sources of water contamination in rural areas of India.
Reason: Human waste contains harmful bacteria and viruses that can contaminate water sources.
Assertion: Chlorination is a method of disinfection of wastewater.
Reason: Chlorine is added to the water to remove any bad smell.
Assertion: In 2020, the Indian government launched a new initiative called "Swachh Bharat." The program includes various drives, such as providing clean drinking water and distributing sanitary pads to all.
Reason: The government wanted to accelerate efforts to achieve universal sanitation coverage and put a focus on sanitation.
Assertion: Collective action can have a significant impact on improving sanitation practices.
Reason: Individual initiative is not important for improving sanitation practices.

Case-Based Questions
Ravi is a part of the student organization located in a rural village in India. Recently, the village has seen a rise in waterborne illnesses like cholera and typhoid. To combat this issue, the group has taken the initiative to conduct a survey on water contamination. Their goal is to pinpoint the potential sources of contamination and implement good sanitation practices to prevent further outbreaks.
i. What are some potential sources of water contamination that Ravi and his group should investigate in their survey?
ii. What methods can Ravi and his group use to collect data on water contamination in their village?
A.Take water samples from various sources such as wells, rivers, and lakes, and test them for contaminants.
B. Conduct surveys among the villagers to gather information about their water usage and sanitation practices.
C. Request villagers to stop drinking water from wells and rivers until the cause of spread was determined.

Choose the correct statement among the following.
(a) Only statement A is correct.
(b) Only statement B is correct.
(c) Both statement A and B are correct
(d) Both statement A and C are correct

iii.State any two good sanitation practices that Ravi and his group could implement to prevent further outbreaks of waterborne illnesses.
iv.How can Ravi and his group educate the villagers about the importance of good sanitation practices and the prevention of contagious diseases?

Objective Type Questions

Match the following:

Correct answer: I-B, II-D, III- A, IV- C
Solution:
Rearrange the letters to form meaningful words based on the clues provided.
i. A substance which pollutes the environment - nctnmaoitan
ii. Solids like faeces settle at the bottom of water treatment plant – dsglue.
iii. The process of keeping places free from dirt, infection, disease, etc., by removing trash and garbage – itnsoanait.*
Solution:
i. contaminant
ii. sludge
iii. sanitation
Fill in the blanks:
i. _______ is a liquid waste which causes water and soil pollution.
ii. By-products of wastewater treatment are _____ and _____.
iii. Rich in lather, mixed with oil, black brown water that goes down the drains from sinks, showers, toilets, laundries is dirty is called ______.
Solution:
i. Correct answer: Sewage
Sewage is a liquid waste which causes water and soil pollution.
ii. Correct answer: sludge, biogas
By-products of wastewater treatment are sludge and biogas.
iii. Correct answer: Wastewater.
Rich in lather, mixed with oil, black brown water that goes down the drains from sinks, showers, toilets, laundries is dirty is called wastewater.
Complete the figure:

a

Solution:

Multiple Choice Questions
A community leader in a small village wants to build a septic tank for a nearby residential complex. Where the septic tank should be connected to the existing sewer system

(a) Point A
(b) Point B
(c) Point C
(d) Point D
Correct answer: (a) - Point A
Solution:
Septic tanks are low-cost onsite sewage disposal systems suitable for places where there is no sewerage system. It can be used for hospitals, isolated buildings or a cluster of houses.
In the given case, the local community leader must connect the septic tank at point A so that sludge can be separated, and wastewater can enter the wastewater treatment plant.
Which of the following is not a factor that contributes to the increasing scarcity of fresh water?
(a) Population growth
(b) Industrial development
(c) Excessive use of fertilizers and pesticides
(d) Mismanagement of water resources
Correct answer: (c) - Excessive use of fertilizers and pesticides
Solution:
The increasing scarcity of fresh water is mainly caused by factors such as population growth, industrial development, and mismanagement of water resources. Excessive use of fertilizers and pesticides can lead to water pollution, but it does not directly contribute to the scarcity of fresh water.
What is the point of origin of chemicals in sewage?
(a) Households
(b) Industries
(c) Rivers and lakes
(d) Wastewater treatment plants
Correct answer: (b) - Industries
Solution:
Chemicals in sewage originate from industries, where they are used in the manufacturing processes and discharged into the wastewater system.
An art festival was organised in a remote village of India where electric and water supply is limited. What type of toilets are most suitable for holding such a festival such that they are cost effective and use less space?
(a) Septic tanks
(b) Chemical toilets
(c) Composting toilets
(d) Vacuum toilets
Correct answer: (b) – Chemical toilets
Solution:
Chemical toilets do not require water for flushing and use chemicals to break down the waste and control odours. They are easy to install and maintain and can be used for short-term events like festivals. Septic tanks and composting toilets require more space and maintenance, while vacuum toilets are expensive and require a constant source of electricity.
Rajiv and his friends made a filtration system using layers of fine sand, coarse sand and gravel. They tested this system in the lab using 1 litre of wastewater sample.

In order to upscale their design, they added a settling tank after the filter. What should they add before their filtration system?
(a) A wire mesh
(b) Disinfectants
(c) An aeration tank
(d) A mechanical skimmer
Correct answer: (c) - An aeration tank
Solution:
Aeration in an activated sludge process is based on pumping air into a tank, which promotes microbial growth in the wastewater.
The microbes feed on the organic material, forming flocs, which can easily settle out and be removed by the filtration system made by Rajiv.
A local textile industry is currently releasing their wastewater directly into the sewerage system of the nearby town, causing a burden on the wastewater treatment plant. Seema, who is a local official, needs to take action to effectively address this issue.

Which of the following actions would be the most appropriate for Seema to take?
(a) Instruct the industry to stop producing all industrial wastes
(b) Request the factory to relocate to another municipality
(c) Ask the factory to discharge their wastewater into the local lake
(d) Advise the industry to pre-treat their wastewater before release
Correct answer: (d) - Advise the industry to pre-treat their wastewater before release.
Solution:
Seema's best course of action in addressing the issue of the local textile industry dumping wastewater directly into the sewerage system of a nearby town would be to advise the industry to pre-treat their wastewater before releasing it. This would lessen the strain on the wastewater treatment plant and aid in the prevention of pollution in the local environment.

SAQs
What are the benefits of planting eucalyptus trees along the sewage ponds?
Solution: Eucalyptus trees planted along the sewage ponds help to quickly absorb excess wastewater and emit pure water vapour into the atmosphere. They also add a lot of oxygen to the atmosphere.
What are some common sources of water contamination in rural areas of India and how can they be addressed?
Solution:
Water contamination is a significant issue in rural areas of India. Some common sources of this contamination include open defecation, improper disposal of waste, and agricultural runoff.
To address these issues, individuals can promote safe water practices such as:
• boiling or treating water before drinking,
• building toilets and encouraging proper waste disposal,
• adopting sustainable agricultural practices such as organic farming
• reducing the use of chemical fertilizers and pesticides.
What are the consequences if a significant amount of waste generated in public places is not disposed off correctly?
Solution: Improper disposal of waste can lead to several problems, including the spread of diseases due to inadequate disposal of human waste, damage to the ecosystem, death of living organisms, and contamination of the entire environment.
Draw a labelled sketch of a wastewater treatment plant.
Solution: Wastewater treatment includes physical, chemical as well as biological processes.
Describe the various steps involved in separating clear water from wastewater. Which fuel can be extracted during this process?
Solution:
The steps involved in the treatment are as follows:
• Screening - Waste water is passed through bar screens. Large and easily visible objects such as sticks, cans, plastic packets and napkins are removed.
• Grit and sand removal - Water then enters a grit and sand removal tank. Water is passed slowly to allow sand, grit and pebbles to settle down.
Water is allowed to settle in a large tank which slopes towards the middle. Solids (e.g., faeces) settle at the bottom and are removed with a scraper. This is sludge. A skimmer removes the floatable solids (e.g., oil and grease). Water so cleared is called clarified water. The sludge is then transferred to a separate tank where anaerobic bacteria decompose it. The biogas produced in the process can be used to produce electricity.
• Aeration: Anaerobic bacteria are allowed to grow by pumping in air into clarified water. Bacteria consume the unwanted matter still present in the clarified water.
From the aeration tank, treated water is sent to another sedimentation tank, where, after several hours, the suspended microbes settle down as activated sludge and the water from the top is removed. As this activated sludge is about 97% water, sand drying beds or machines are used to remove water. The dried sludge is now used as manure, thereby returning the organic matter and nutrients to the soil.
• The treated water has a very low level of organic and suspended matter and is hence discharged into seas, rivers or into the ground.
• Sometimes, chemicals such as chlorine and ozone are used to disinfect water before releasing it into the distribution system.
During this process we get Biogas and manure as a bioproduct.

Assertion-Reasoning Questions

Select the correct answer to these questions from the codes (a), (b), (c) and (d) as given below:
Assertion:Open defecation is one of the common sources of water contamination in rural areas of India.
Reason:Human waste contains harmful bacteria and viruses that can contaminate water sources.
Correct answer: a- Both A and R are true, and R is the correct explanation of the assertion.
Solution: The assertion is true, as open defecation is a common source of water contamination in rural areas of India. The reason is also true, as human waste contains harmful bacteria and viruses that can contaminate water sources and make the water unfit for use.
Assertion:Chlorination is a method of disinfection of wastewater.
Reason:Chlorine is added to the water to remove any bad smell.
Correct answer: c- A is true but R is false.
Solution:
The assertion is true, as chlorination is a method of disinfection of wastewater. However, the reason is not true, as chlorine is added to the water to kill harmful bacteria and other microorganisms and disinfect water.
Assertion:In 2020, the Indian government launched a new initiative called "Swachh Bharat." The program includes various drives, such as providing clean drinking water and distributing sanitary pads to all.
Reason: The government wanted to accelerate efforts to achieve universal sanitation coverage and put a focus on sanitation.
Correct answer: d- A is false, but R is true.
Solution:
In the year 2016, the Government of India has initiated a new mission known as “Swachh Bharat” under which a lot of drives such as proper sewage disposal and providing toilets for everyone have been started to accelerate efforts to achieve universal sanitation coverage and put a focus on sanitation.
Assertion:Collective action can have a significant impact on improving sanitation practices.
Reason:Individual initiative is not important for improving sanitation practices.
Correct answer: c - A is true, but R is false.
Solution:
The assertion is true, as collective action can have a significant impact on improving sanitation practices by promoting community involvement and awareness. However, the reason is false, as individual initiative is important for improving sanitation practices by promoting personal responsibility and behaviour change.
Case-Based Questions
Ravi is a part of the student organization located in a rural village in India. Recently, the village has seen a rise in waterborne illnesses like cholera and typhoid. To combat this issue, the group has taken the initiative to conduct a survey on water contamination. Their goal is to pinpoint the potential sources of contamination and implement good sanitation practices to prevent further outbreaks.
i. What are some potential sources of water contamination that Ravi and his group should investigate in their survey?
ii. What methods can Ravi and his group use to collect data on water contamination in their village?
A.Take water samples from various sources such as wells, rivers, and lakes, and test them for contaminants.
B. Conduct surveys among the villagers to gather information about their water usage and sanitation practices.
C. Request villagers to stop drinking water from wells and rivers until the cause of spread was determined.

Choose the correct statement among the following.
(a) Only statement A is correct.
(b) Only statement B is correct.
(c) Both statement A and B are correct
(d) Both statement A and C are correct

iii.State any two good sanitation practices that Ravi and his group could implement to prevent further outbreaks of waterborne illnesses.
iv.How can Ravi and his group educate the villagers about the importance of good sanitation practices and the prevention of contagious diseases?
Solution:
i. Some potential sources of water contamination that Ravi and his group should investigate in their survey include sewage and wastewater from households and industries, agricultural runoff containing fertilizers and pesticides, and improper disposal of hazardous waste.
ii. Correct answer: c – Both statement A and B are correct
Ravi and his group can use several methods to collect data on water contamination in their village. They could take water samples from various sources such as wells, rivers, and lakes, and test them for contaminants. They could also conduct surveys among the villagers to gather information about their water usage and sanitation practices.
iii. Some good sanitation practices that Ravi and his group could implement to prevent further outbreaks of waterborne illnesses include:
• promoting proper hand washing and hygiene,
• ensuring safe disposal of human waste,
• educating the villagers about the importance of boiling or treating their drinking water.
iv. To educate the villagers about the importance of good sanitation practices and the prevention of contagious diseases, Ravi and his group could organize awareness campaigns and workshops. They could also distribute informational materials such as pamphlets and posters, and work with local health officials to provide access to medical care and vaccinations.

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