Important Questions for Class 7 Science Chapter 13 Waste Water Story

Important Questions for CBSE Class 7 Science Chapter 13 Waste Water Story

Here are the important questions beneficial for Important Questions for CBSE Class 7 Science Chapter 13 Waste Water Story-

Very Short Answer Questions: (1 Mark)

1. The United Nations declared the period from 2005-2015 as the International Decade for _______________.

Ans: Action on the water for life.

2. The suspended impurities in sewage are called _________________.

Ans: Contaminants.

3. The network of small and big pipes that is used for the transport of sewage from the point of production to the point of treatment is called __________________.

Ans: Sewerage.

4. The sewage that originates from the kitchen is called as _____________.

Ans: Sullage.

5. Foul waste originates from __________________.

Ans: Toilets and bathrooms.

6. Wastewater generated by the industries is called as __________________.

Ans: Trade water.

7. _____________ are used to remove large objects from wastewater.

Ans: Bar screens.

8. Solid component of sewage is called as _______________.

Ans: Sludge.

9. Aerobic bacteria that settle in the bottom of the tank after clarification are referred to as ________________.

Ans: Activated sludge.

10. Septic tanks, chemical toilets, and composting pits are examples of ___________________.

Ans: On-site composting.

Short Answer Questions: (3 Marks)

1. What is the importance of sewage treatment?

Ans: Sewage treatment is crucial as it removes harmful contaminants from wastewater before it is discharged into natural water bodies. Untreated sewage contains pathogens and pollutants that can cause diseases and environmental degradation. Treatment processes help to cleanse the wastewater, making it safer for the environment and public health.

2. How is activated sludge formed?

Ans: Activated sludge forms during the secondary treatment phase of sewage treatment. After the sewage is clarified in the primary treatment stage, it is transferred to an aeration tank. In the aeration tank, aerobic bacteria decompose organic matter present in the sewage. These bacteria grow and form a biomass known as activated sludge, which settles to the bottom of the tank and is periodically removed for further processing.

3. What is the role of grit and sand removal tanks?

Ans: Grit and sand removal tanks are designed to remove heavy, inert particles like sand and grit from the wastewater. These particles settle out due to their weight and are collected at the bottom of the tank. This process prevents damage to equipment in downstream treatment processes and ensures that only fine, organic materials enter the subsequent stages of sewage treatment.

4. How is water clarified in a water clarifier?

Ans: In the water clarifier, sewage is allowed to settle for several hours. During this time, heavier solid particles, including organic matter and sludge, settle to the bottom of the tank. These solids are periodically removed as sludge. The clarified water, free from suspended solids, is then discharged to further treatment stages or directly to natural water bodies. This process reduces the turbidity and improves the quality of the water.

5. What are onsite composting methods?

Ans: Onsite composting methods treat sewage directly at the point of origin. Techniques like septic tanks, chemical toilets, and compost pits involve the biological decomposition of sewage by microorganisms. The composted material is rich in nutrients and can be used as manure, while the treated wastewater can be safely discharged into the environment. These methods are particularly useful in rural or dispersed communities where centralized sewage treatment is not feasible.

Long Answer Questions: (5 Mark s)

1. Suggest better housekeeping practices that can be adopted to reduce waste generation.

Ans: To reduce waste generation, better housekeeping practices include not disposing of cooking fats and oils down the sink, which can solidify and clog drains. Avoiding the flushing of chemicals like cleaners or medicines into the toilet, as they can harm essential sewage-treatment bacteria. Solid wastes like food scraps should not be poured into the sink as they can obstruct drains and affect the treatment process. Lastly, proper disposal of garbage and avoiding littering can significantly reduce waste in our environment.

2. Poor sanitation leads to diseases. Justify.

Ans: Poor sanitation refers to inadequate disposal of human waste and lack of hygiene. When sanitation is poor, harmful pathogens can breed, leading to outbreaks of diseases like cholera, typhoid, and dysentery. The improper disposal of sewage allows these pathogens to enter water sources, contaminating them and posing a risk to public health. Safe sanitation practices, therefore, are essential for preventing the spread of such diseases and maintaining a healthy community.