March 22nd is World Water Day. It started in1993. It not only makes us think about the importance of water, but also calls on(号召）us to1and protect water. Today, we're facing terrible water problems. Among them, wastewater problem is especially 2. And the subject of World Water Day in 2017 is "Wastewater".
What is wastewater? It is used water. Usually, wastewater comes from homes, 3, hospitals and so on. It is produced by different kinds of activities, including washing the clothes, taking showers and using the kitchen. The rain also4 wastewater when it is running down the street during a storm. No matter where it comes from, this kind of water is sure to have5harmful in it.
6must we treat（处理）wastewater? Wastewater has a big influence on our life. It causes both illness for us and pollution for the environment. We must care for our environment and our own7.
How can we treat wastewater? Different kinds of wastewater need different ways of treatment. Wastewater8 homes can be reused. Then there will be9 wastewater. Also, factory wastewater has to be cleaned 10 it goes back to nature.
