People use water for many purposes. In the home we use it to bathe, to wash the dishes and to flush the toilet. The dirty water runs into the sewers. Then the polluted water runs into rivers and then to the sea. The polluted water kills all living things in the rivers.
Water is also largely polluted by industrial waste. Industrial waste from making paper and lather flow into the sewers. Chemical products are used to clean engines. The waste is dumped with the rubbish. When these waste materials are buried they remain there for along time. Sometimes they get into the water used in the house.
Another source of pollution is agricultural waste. Farmers use fertilizers and pesticides. They get into rivers and lakes and pollute the water. Some of these chemicals are dangerous to human beings.
In some places the polluted water does not flow into the rivers. It stays in ponds or lakes. Soon a thick, green, algae forms on the surface. The algae grow quickly in the polluted water. This is dangerous to fish and to human being.
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