雅思小作文范文:雨水成为饮用水的过程

　　The flow chart above shows the process of purification of rain for drinking water in Australian. Overall, 4 main stages are involved: collection, filtration, storage and treatment.

　　Firstly, rain falling on the roof, the raw material for drinking water, flows down along gutters and into drains, which then direct the water into underground filtration system. Next, water goes through a physical filter slowly which serves to remove particulates from rainwater. After percolation, the water is delivered by the pipe to a large cube-shaped container and be stored carefully.

　　For the purpose of producing drinkable water, there is another stage for further treatment. Specifically, the water is transferred into a bigger tank, in which some chemicals are added and mixed with stored water. This chemical reaction is able to fully eliminate impurities, thus enhancing the quality of water up to a safe and potable level for human.

　　Finally, through water pipe, the well-treated water is pressed and directed to the resident house for daily use.

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