Notes

Question 2
Why should oil and fats be not be released in the drain? Explain.
Answer 2
Cooking oils and fats should not be thrown down the drain. They can harden and block the pipes. In an open drain, fats clog the soil pores reducing its effectiveness in filtering water. Throw oils and fats in dustbin.
Question 3
Describe the steps involved in getting clarified water from waste water.
Answer 3
Treatment of waste water involves physical, chemical and biological processes:
1
Waste water is passed through bar screens. Large objects like rags, sticks, cans, plastic packets, napkins etc are removed.
2
Water then gets to grit and sand removal tank. This allows sand, grit and pebbles to settle down.
3
The water is then allowed to settle in a large tank which is sloped towards the middle. Solids like feces settle at the bottom and are removed with a scrapper. This is the sludge.
4
Air is pumped into the clarified water to help aerobic bacteria to grow. Bacteria consumes unwanted matter still remaining in the clarified water.
5
Sometimes it may be necessary to disinfect water with chemicals like chlorine and ozone before releasing into the distribution system.
Question 4
What is the sludge? Explain how it is treated.
Answer 4
Solids like feces that settle at the bottom of sedimentation tank are called sludge. The sludge is transferred to a separate tank where it is decomposed by the anaerobic bacteria. The biogas produced in the process can be used as a fuel or can be used to produce electricity.
Question 6
Untreated human excreta is a heath hazard. Explain.
Answer 6
The sewage contains human excreta. If it is discharged into rivers without treating then the drinking water will get contaminated. Contaminated water can cause so many disease causing microbes grow into it. By drinking such contaminated water, people may suffer from diseases like cholera, hepatitis and dysentery. Thus, this untreated human excreta is a heath hazard.
Question 7
Name two chemicals used to disinfect water.
Answer 7

1
Chlorine
2
Ozone
Question 8
Explain the function of bar screen in bar screens in a waste water treatment plant.
Answer 8
The bar screen removes the large rubbish objects like rags, tins, plastic etc from the sewage. These large objects cannot pass through the holes of the bar screen.
Question 9
Explain the relationship between sanitation and disease.
Answer 9
Sanitation and diseases are directly related. Poorer the sanitation, more are the diseases. Whereas better sanitation minimizes diseases. Poor sanitation and contaminated drinking water is the cause of large number of diseases in our country.
Question 10
Explain your role as an active citizen in relation to sanitation.
Answer 10
Our roles as an active citizen in relation to sanitation are:
1
We must realize our responsibility in maintaining the water sources in a healthy state
2
Adopting good sanitation practices should be our way of life
3
As an agent of change, our individual initiative will make a great difference
4
A lot can be done if people work together
Mahatma Gandhi once said: No one need to wait for anyone to adopt a humane and enlightened course of action.
END OF CHAPTER

Writing Skills
Speech writing
Cleanliness is next to godliness
Respected chairperson, principal, worthy teachers and my dear friends. I am Sakshi of class 7th B and today I stand before you to express my views on the topic Cleanliness is next to godliness.
It has been rightly said that Cleanliness is next to godliness. It is so because god loves cleanliness. A clean heart is god’s temple. That is why temples, mosque and churches are kept clean. We go to temple only after taking a bath. Thus, clean heart, clean body and clean surroundings are the essentials of good life. But the saying means much more than that. The value of cleanliness is known to modern science. Most of the diseases we suffer form are a result of dirty surroundings. If our surroundings are clean, and we get clean air, clean water and clean food we may live a long and healthy life. So, for a happy and healthy life we must learn to be clean. Without it we will miss the world as well as god.