BIOLOGY rivers, estuaries and oceans are becoming polluted in several parts of the world. Realising the importance of maintaining the cleanliness of the water bodies, the Government of India has passed the Water(Prevention and Control of Pollution)Act,1974 to safeguard our water resources. 16.2.1 Domestic Sewage and Industrial Effluents As we work with water in our homes in the cities and towns, we wash everything into drains. Have you ever wondered where the sewage that comes out of our houses go? What happens in villages? Is the sewage treated before being transported to the nearest river and mixed with it? A mere 0.1 per cent impurities make domestic sewage unfit for human use (Figure 16.2). You have read about sewage treatment plants in Chapter 10. Solids are relatively easy to remove, whatFigure 16.2 Composition of waste water is most difficult to remove are Figure 16.3 Effect of sewage discharge on some important characteristics of a river

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