Year 10 Chemistry: Purification of Drinking Water and Purification of Sewage Water

Introduction

Hello Year 10! Today, we are going to learn about two very important processes: the purification of drinking water and the purification of sewage water. These processes are crucial for keeping our water safe and clean for us and for the environment.

Purification of Drinking Water

Why is it Important?

Drinking water must be clean and safe to prevent diseases. Contaminated water can have harmful bacteria, viruses, and chemicals.

Steps in Purification

1. Sedimentation: In this first step, water is allowed to sit in a large tank. Heavy particles like dirt and sand settle at the bottom. This is called sedimentation.
2. Filtration: After sedimentation, the clearer water on top is passed through filters. Filters can be made of sand, gravel, and charcoal to remove smaller particles and impurities.
3. Disinfection: Finally, the water is treated with chemicals, usually chlorine, or UV light to kill any remaining germs. This makes the water safe to drink.

Tips for Understanding

• Remember the three main steps: Sedimentation → Filtration → Disinfection.
• Think of it like cleaning out a dirty sponge: first, you let the dirt settle, then you rinse it, and finally, you sterilise it!

Purification of Sewage Water

Why is it Important?

Sewage water, which comes from toilets and sinks, can contain harmful substances. It’s essential to purify it before it goes back into rivers or oceans to protect our environment.

Steps in Purification

1. Preliminary Treatment: Large objects like sticks and plastics are removed from sewage water through screens and grates.
2. Primary Treatment: The sewage is allowed to settle in a tank. Heavy solids form sludge at the bottom, while liquid waste moves to the next stage.
3. Secondary Treatment: Bacteria are used to break down organic matter in the water. This is often done in aeration tanks where air is pumped in to help bacteria thrive.
4. Tertiary Treatment: The water may go through additional filtering and chemical treatment to remove any remaining pollutants, making it safe to return to nature or to be reused.

Tips for Understanding

• Remember the steps of sewage purification: Preliminary → Primary → Secondary → Tertiary.
• Visualise it like cleaning out a messy room: first, you remove the big trash, then tidy up, and finally, you polish everything to make it shine!

Questions

Easy Level Questions

1. What is the first step in purifying drinking water?
2. What do we use to kill germs in drinking water?
3. Name one impurity that might be found in drinking water.
4. What happens to heavy particles during sedimentation?
5. Why is it important to purify sewage water?
6. What is the purpose of filtration?
7. What type of water is treated with chlorine?
8. Name one method used to disinfect drinking water.
9. What do we call the solid waste that settles at the bottom during primary treatment?
10. What type of bacteria are used in secondary treatment?
11. What is the last step in purifying drinking water?
12. What is the purpose of aeration in sewage treatment?
13. Why do we need to remove large objects from sewage water?
14. What type of water comes from sinks and toilets?
15. What is tertiary treatment?
16. What is one way to visually understand sedimentation?
17. How does filtration help clean water?
18. What do we call the clear water after sedimentation?
19. Why is chlorine used in water treatment?
20. What happens to the sludge after primary treatment?

Medium Level Questions

1. Explain how sedimentation works.
2. Why is disinfection important in the purification process?
3. What are some materials used in water filtration?
4. Describe the role of bacteria in secondary sewage treatment.
5. How does aeration help the treatment of sewage water?
6. What are the environmental consequences of not purifying sewage water?
7. Why might we need to use UV light instead of chlorine for disinfection?
8. What are common contaminants found in sewage water?
9. Explain the difference between primary and secondary sewage treatment.
10. Why is it important to have multiple steps in water purification?
11. What might happen if we skip the filtration step?
12. How do we ensure that drinking water is safe for consumption?
13. What is the purpose of using gravel and sand in filtration?
14. How does chlorination work to disinfect water?
15. In what ways can purified sewage water be reused?
16. What happens to the remaining solid waste after secondary treatment?
17. Describe the process of aeration in your own words.
18. How do screens and grates function in preliminary treatment?
19. What are the potential risks of drinking contaminated water?
20. Why is it important to monitor water quality after purification?

Hard Level Questions

1. Discuss the chemical reactions that occur during chlorination.
2. Compare and contrast the purification processes for drinking water and sewage water.
3. Evaluate the effectiveness of different disinfection methods.
4. How does the presence of heavy metals affect water purification?
5. Explain the concept of biological oxygen demand (BOD) in relation to sewage treatment.
6. What role does pH play in water purification?
7. Describe how new technologies are improving water purification methods.
8. What are the long-term effects of untreated sewage on aquatic ecosystems?
9. Discuss the importance of regulations in water quality management.
10. How do climate change and pollution influence water purification processes?
11. Explain the role of activated sludge in secondary sewage treatment.
12. What are the challenges faced in purifying drinking water in developing countries?
13. Discuss the importance of community involvement in water purification efforts.
14. How do we test water quality after purification processes?
15. Explain the significance of removing nutrients like nitrogen and phosphorus in sewage treatment.
16. What are some alternative methods for disinfecting water besides chlorine and UV light?
17. How does the treatment of greywater differ from blackwater?
18. Discuss the economic implications of water purification technologies.
19. How can water reuse contribute to sustainability?
20. Investigate the impact of pharmaceuticals in sewage water and their treatment.

Answers and Explanations

Easy Level Answers

1. Sedimentation
2. Chlorine
3. Bacteria, dirt, chemicals
4. They settle at the bottom.
5. To prevent pollution and protect ecosystems.
6. To remove smaller particles.
7. Drinking water.
8. Chlorination or UV light.
9. Sludge.
10. To break down waste.
11. Disinfection.
12. To enhance bacteria growth.
13. To prevent blockages and pollution.
14. Sewage water.
15. To remove remaining pollutants.
16. Think of it as letting dirt settle.
17. It removes small particles.
18. Clear water after sedimentation.
19. To kill harmful germs.
20. It can be processed into fertiliser or compost.

Medium Level Answers

1. Heavy particles settle at the bottom as the water sits.
2. To eliminate harmful microorganisms.
3. Sand, gravel, charcoal.
4. They consume organic matter, breaking it down.
5. It adds oxygen, helping bacteria grow.
6. It can harm wildlife and water quality.
7. UV light is effective against chlorine-resistant pathogens.
8. Viruses, bacteria, chemicals.
9. Primary is physical separation; secondary uses biological processes.
10. Each step targets different contaminants.
11. Filtration prevents larger particles from damaging later processes.
12. To avoid health risks and ensure safety.
13. They trap and filter out contaminants.
14. Chlorine kills microorganisms.
15. For irrigation and industrial uses.
16. It may be used as fertiliser.
17. It introduces air to the water, helping bacteria.
18. They prevent large solids from entering treatment tanks.
19. Illness from pathogens.
20. To ensure it meets safety standards.

Hard Level Answers

1. Chlorination produces hypochlorous acid, killing germs.
2. Drinking water focuses on health; sewage on ecosystem protection.
3. UV light is immediate; chlorine has residual effects.
4. They require special treatment processes.
5. BOD measures the amount of oxygen needed to decompose organic matter.
6. It affects solubility and effectiveness of treatments.
7. Technologies like membrane filtration and advanced oxidation.
8. It leads to algae blooms, harming aquatic life.
9. Regulations ensure safety and effectiveness of treatments.
10. They affect water availability and quality.
11. It helps purify sewage by fostering microbial breakdown.
12. Limited resources and infrastructure challenge effective treatment.
13. Community input can enhance awareness and funding.
14. Tests measure contaminants, pH, and turbidity.
15. To prevent eutrophication in water bodies.
16. Ozone and hydrogen peroxide are alternatives.
17. Greywater is less contaminated and can be reused directly.
18. Investments in water treatment can be high but necessary.
19. Reuse reduces demand on fresh water supplies.
20. Pharmaceuticals can disrupt treatment processes and harm wildlife.

This concludes our lesson on water purification. Remember, clean water is vital for everyone! If you have any questions, feel free to ask!