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Practice each question, then open the answer or worked solution.
Here is a crossword puzzle: Good luck!
Across
3. Liquid waste products
4. Solid waste extracted in sewage treatment
6. A word related to hygiene
8. Waste matter discharged from human body
Down
1. Used water
2. A pipe carrying sewage
5. Micro-organisms which causes cholera
7. A chemical to disinfect water
Across
3. Sewage
4. Sludge
6. Sanitation
8. Excreta
Down
1. Wastewater
2. Sewer
5. Bacteria
7. Ozone
Study the following statements about ozone:
(a) It is essential for breathing of living organisms.
(b) It is used to disinfect water.
(c) It absorbs ultraviolet rays.
(d) Its proportion in air is about 3%. Which of these statements are correct?
(i) (a), (b) and (c)
(ii) (b) and (c)
(iii) (a) and (d)
(iv) All four
The answer is (ii) (b) and (c)
Introduction to NCERT Solutions Class 7 Science Chapter 18 Wastewater StoryThis chapter specifically deals with the issue of contaminants in water. Water is an important resource not just for humans but for all the organisms on earth. Therefore, contaminating this natural resource has dire consequences. The main reasons for water pollution are our commercial and industrial activities. All the waste effluents that reach water bodies results in water pollution. In the long run, this can cause many diseases and health hazards for us.
For instance, in Minamata City, Japan, mercury runoff from a factory polluted the waters, and the poisoning went undetected for decades. It came to notice only when the people saw their newborns had birth defects. It was found that the mercury runoff had contaminated the marine ecosystem, resulting in fish species ingesting the mercury. Over a period of time, mercury accumulation in fish species got transferred into humans who consumed contaminated fish. This adversely affected bodily functions and caused a lot of problems for the people and their descendants. Hence, we need to take care of such issues by preventing industrial effluents which pollute our most precious resource – water.