The government of Singapore has created a highly developed system that turns wastewater into drinking water. The system involves a network of tunnels and high technology treatment centers.

The system helps reduce ocean pollution, as only a small amount of the treated water is sent into the sea. The United Nations estimates that 80 percent of the world’s wastewater flows back into the oceans without being treated or reused.

Singapore has few natural water sources. The island nation has long had to depend mostly on supplies from neighboring Malaysia.

Low Pei Chin, an expert, told reporters, “Singapore lacks natural resources, and it is limited in space, which is why we are always looking for ways to explore water sources and stretch our water supply. One major plan is to collect every drop and reuse endlessly.”

Parts of the water treatment center are underground. Wastewater enters the center through a 48- kilometer tunnel that is linked to sewers. The center contains a large system of steel pipes, tubes, tanks, cleaning systems and other machinery. It can treat up to 900 million liters of wastewater a day.

In one building, a network of air flow systems has been put in place to keep the air smelling as fresh as possible. Waste that arrives at the plant goes through a cleaning process before powerful pumps send it flowing to areas above ground for more treatment. There, the treated water receives additional cleaning. Bacteria and viruses are removed through highly developed cleaning processes and then disinfected with ultraviolet radiation (紫外线).

Singapore is also in the process of expanding its recycling system. The country will add another underground tunnel and a major water treatment center to serve the western half of the island. Officials expect work on the center to be completed by 2025. By the time the expansion is finished, Singapore will have spent about $7.4 billion on its water treatment systems.

【小题1】What can we infer from the second paragraph?

A．The world’s oceans are polluted by wastewater.

B．Only a small amount of the treated water is suitable to drink.

C．Wastewater is usually treated before being sent into the oceans.

D．80 percent of the water in the oceans can be used as drinking water.

【小题2】What can we know from the passage?

A．Singapore plans to get help from Malaysia.

B．The wastewater is cleaned underground in the whole process.

C．900 million liters of wastewater can be cleaned in the center a day.

D．The recycled water enters the sea through a highly developed system.

【小题3】How are bacteria and viruses of treated water removed?

A．Purifying water by itself.

B．Through a special kind of chemical.

C．With ultraviolet radiation.

D．Through cleaning processes and disinfection.

【小题4】Which of the following is the best title for the passage?

A．Singapore turns wastewater into drinking water.

B．Collect and rescue: the future of Singapore.

C．The importance of sea water in Singapore.

D．Water source protection matters.