Class 7 Exam  >  Class 7 Notes  >  Science Class 7  >  Very Short Question Answers: Waste Water Story

Class 7 Science Chapter 13 Question Answers - Wastewater Story

Very Short Q & A :


Q1: What is sewage?

Ans : Waste water released by houses is called sewage.


Q2: What per cent of earth’s water is fresh?

Ans : 3 per cent.


Q3: What constitutes waste water?

Ans : It can include human waste, food scraps and chemicals.


Q4: State one of the reasons for increasing scarcity of fresh water.

Ans : Population growth.


Q5: Which day is celebrated as World Water Day?

Ans : 22 March


Q6: What is cleaning of water?

Ans : Cleaning of water is the process of removing pollutants before it enters a water body or is reused.


Q7: In order to have safe drinking water, it should be ________.

Ans : Boiled


Q8: What are the adverse effects of drinking contaminated water?

Ans : Drinking contaminated water results in diseases such as cholera, typhoid and diarrhoea. Polluted water can also prove fatal.


Q9: Water gets contaminated and scarcity of clean water is due to :

  • People take baths and wash clothes in rivers and lakes.
  • Many people bathe their animals in rivers and lakes.
  • Increase in the population, industries and improper disposal of waste
  • All of the above.

Ans : All of the above.


Q10: What is sewage treatment?

Ans : Pollutants in waste water can be removed in several stages, and this process is called “sewage treatment.


Q11: Sewage contains organic and _______________ impurities.

Ans : Inorganic


Q12: Sewage contains disease-causing bacteria. True/False

Ans : True


Q13: Saprotrophic bacteria feed on dead organisms.True/False

Ans : True


Q14: Sewage contains some harmful nutrients, such as ______________and nitrogen.

Ans : Phosphorous


Q15: Wastewater has many impurities and these impurities should be removed by _______________.

Ans : Water treatment.


Q16: What is the purpose of filtering waste water?

Ans : To remove large impurities.


Q17: What is a clarifier?

Ans : A clarifier is a tank with its central part inclined downwards so as to allow faeces to settle down. The inclined waste is then removed using a scraper.


Q18: Name some biological contaminants in water.

Ans : bacteria and microbes


Q19: Name the chemical used in water plant to clean water

Ans : Chlorine tablets or ozone.


Q20: Dried _ is used as manure.

Ans : Sludge


Q21: List the substances responsible for blockage of drain.

Ans : Tealeaves, solid food remains, soft toys, cotton, and sanitary towels.


Q22: Why should used tea leaves, solid food remains, etc. not be released in 

the drains?

Ans : Used tea leaves, solid food remains etc. should not be thrown down the drain as they may choke the drain.


Q23: What is the function of bar screens in waste water treatment plant?

Ans : The bar screen remove the large objects like rags, sticks, cans, plastics packets etc. from the sewage.


Q24: Why waste water is passed through bar screen?

Ans : Waste water is passed through bar screens to remove big objects like cans, sticks, rags etc.


Q25: What is the function of a skimmer?

Ans : A skimmer removes the floatable solids like oil, grease etc.


Q26: Why air is pumped into clarified water?

Ans : Air is pumped into clarified water to help aerobic bacteria to grow.


Q27: The suspended microbes in water treatment plant settle at the __________& the water is removed from the_____

Ans : Bottom and top.


Q28: State various uses of water.

Ans : Water is used for:

  • Drinking
  • Cooking
  • Washing clothes, utensils
  • Generating electricity
  • Bathing


Q29: What is the actual reason behind improper sanitation?

Ans : Lack of knowledge and of money, illiteracy, large population and lack of social awareness results in improper sanitation


Q30: Onsite sewage disposal systems collect human excreta and store it in a hole or a pipe, and later direct it to a sewage treatment plant. True/False.

Ans : True


Q31: Septic tanks are not suitable for places such as hospitals, isolated buildings and clusters of houses where there is no sewage.True/False

Ans : False


Q32: What kind of toilets are in aeroplanes and trains?

Ans : Chemical toilets


Q33: Public places such as railway stations, bus depots, airports and hospitals generate a lot of waste, which leads to diseases. True/False.

Ans : True


Q34: Solids like faeces settle at the bottom by _____________ and are removed with a scraper.

Ans : Sedimentation

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FAQs on Class 7 Science Chapter 13 Question Answers - Wastewater Story

1. What is wastewater?
Ans. Wastewater is any water that has been used and discarded, such as water from toilets, sinks, showers, and industrial processes. It contains various pollutants and contaminants that need to be treated before it can be safely released back into the environment.
2. Why is wastewater treatment important?
Ans. Wastewater treatment is important because it helps remove harmful substances and pollutants from the water, making it safe to be reused or returned to the environment. It helps protect public health, prevents water pollution, and preserves ecosystems.
3. How is wastewater treated?
Ans. Wastewater is treated through a series of processes. First, physical processes like screening and sedimentation are used to remove large solid particles. Then, biological processes are employed to break down organic matter using bacteria and other microorganisms. Finally, chemical processes like disinfection and filtration are used to remove remaining pathogens and pollutants.
4. What are the benefits of wastewater recycling?
Ans. Wastewater recycling has several benefits. It helps conserve freshwater resources by reusing treated wastewater for non-potable purposes like irrigation, industrial processes, and toilet flushing. It also reduces the strain on natural water sources and can help mitigate water scarcity issues in regions with limited water supply.
5. How does wastewater impact the environment?
Ans. If untreated or poorly treated, wastewater can have significant negative impacts on the environment. It can contaminate water bodies, leading to the death of aquatic life and the spread of waterborne diseases. Wastewater can also pollute soil and affect plant growth. Proper wastewater treatment is crucial to minimize these environmental impacts.
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