Question 1. Fill in the blanks:
(a) Cleaning of water is a process of removing ____________.
(b) Wastewater released by houses is called ____________.
(c) Dried ____________ is used as manure.
(d) Drains get blocked by ____________ and ____________.
Solution 1.
(a) Cleaning of water is a process of removing pollutants.
(b) Wastewater released by houses is called sewage.
(c) Dried sludge is used as manure.
(d) Drains get blocked by cooking oil and fats.
Question 2. What is sewage? Explain why it is harmful to discharge untreated sewage into rivers or seas.
Solution 2. Sewage is the wastewater released by our houses. Sewage is full of pollutants and harmful micro-organisms so it should not be directly discharged into the sea before treating it well. This sewage contaminates water which causes disease in people using it.
Question 3. Why should oils and fats be not released in the drain? Explain.
Solution 3. Cooking oil and fats block the drain system which is why oils and fats should not be released in the drain.
Question 4. Describe the steps involved in getting clarified water from wastewater.
Solution 4. Following are the steps involved in getting clarified water from wastewater:
- Firstly, pass the water through the bar screen to remove all the physical impurities like stones, plastic bags, cans etc.
- Then impurities are removed by a process called sedimentation.
- Now all the impurities are collected from the bottom like solid impurities and faeces. These impurities are called sludge.
- This clarified water is then further cleaned by the aerator.
- At last, chlorination is done to remove all disease-causing bacteria.
Question 5. What is sludge? Explain how it is treated.
Solution 5. The solid impurities like faeces that settle down at the bottom during wastewater treatment are called sludge.
Sludge can be treated in the following ways:
- By using a skimmer sludge can be removed and then transferred to a tank.
- In this separate tank, sludge can be decomposed by anaerobic bacteria.
- Activated sludge can be used as manure.
Question 6. Untreated human excreta is a health hazard. Explain
Solution 6. Untreated human excreta is a health hazard because it contains microorganisms and pollutants that will contaminate the soil and water resources causing various diseases. People who use water from these contaminated water resources would likely suffer diseases like cholera, typhoid, dysentery and hepatitis.
Question 7. Name two chemicals used to disinfect water.
Solution 7. The name of two chemicals that are used to disinfect water are- Chlorine and Ozone.
Question 8. Explain the function of bar screens in a wastewater treatment plant.
Solution 8. The function of bar screens in a wastewater treatment plant is to remove all the large objects like rags, sticks, cans, plastic packets and napkins.
Question 9. Explain the relationship between sanitation and disease.
Solution 9. Sanitation is directly related to diseases because lack of sanitation causes various diseases and good sanitation practices prevent many diseases.
Question 10. Outline your role as an active citizen in relation to sanitation.
Solution 10. Every citizen should participate in maintaining proper sanitation. For this we should do the following things:
- Keep our surroundings clean.
- Bifurcate our domestic waste before throwing it into the drains.
- In case of any leakage in the sewage pipes report immediately to the concerned authoritive.
Question 11. Study the following statements about ozone:
(a) It is essential for the breathing of living organisms.
(b) It is used to disinfect water.
(c) It absorbs ultraviolet rays.
(d) Its proportion in the air is about 3%. Which of these statements is correct?
(i) (a), (b) and (c)
(ii) (b) and (c)
(iii) (a) and (d)
(iv) All four
Solution 11.
(ii) (b) and (c)