NCERT Book Class 7 Science Wastewater Story

18 Wastewater Story

All of us use water in our homes and make it dirty. Dirty! Are you surprised? 

Rich in lather, mixed with oil, black– brown water that goes down the drains from sinks, showers, toilets, laundries is dirty. It is called wastewater. This used water should not be wasted. We must clean it up by removing pollutants. Have you ever thought where the wastewater goes and what happens to it?

18.1 WATER, OUR LIFELINE

Clean water is a basic need of human being. Let us make a mindmap of the many uses of clean water. Clean water that is fit for use is unfortunately not available to all. It has been reported that more than one billion of our fellow human beings have no access to safe drinking water. This accounts for a large number of water-related diseases and even deaths. Women and girls walk for several kilometres to collect clean water, as you read in Chapter 16. Is it not a serious matter for human dignity? 

You have studied in Chapter 16 about the increasing scarcity of freshwater due to population growth, pollution, industrial development, mismanagement and other factors. Realising the urgency of the situation on the World Water Day, on 22 March 2005, the General Assembly of the United Nations proclaimed the period 2005–2015 as the International Decade for action on “Water for life”. All efforts made during this decade aim to reduce by half the number of people who do not have access to safe drinking water. Cleaning of water is a process of removing pollutants before it enters a water body or is reused. This process of wastewater treatment is commonly known as “Sewage Treatment”. It takes place in several stages.

18.2 WHAT IS SEWAGE?

Sewage is wastewater released by homes, industries, hospitals, offices and other users. It also includes rainwater that has run down the street during a storm or heavy rain. The water that washes offroads and rooftops carries harmful substances with it. Sewage is a liquid waste. Most of it is water, which has dissolved and suspended impurities. These impurities are called contaminants.

Exercises

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 ____________.

2. What is sewage? Explain why it is harmful to discharge untreated sewage into rivers or seas.

3. Why should oils and fats be not released in the drain? Explain.

4. Describe the steps involved in getting clarified water from wastewater.

5. What is sludge? Explain how it is treated.

6. Untreated human excreta is a health hazard. Explain.

7. Name two chemicals used to disinfect water.

8. Explain the function of bar screens in a wastewater treatment plant.

9. Explain the relationship between sanitation and disease.

10. Outline your role as an active citizen in relation to sanitation.

Please refer to attached file for NCERT Class 7 Science Wastewater Story