Far below every town and city lies an invisible network of pipes crucial to the lives of their residents. Once water disappears down a pipe or toilet, it’s out of sight, out of mind. The water flows into containers that carry rainwater, wastewater and solid waste away. There are three main types of sewers (下水道): sanitary sewers, storm sewers and combined sewers. Among them, sanitary sewers function as a city’s veins (静脉). Water containing human and industrial waste is collected in sanitary sewers and carried to wastewater treatment plants. There, the solid waste is separated from the water, which is then purified before being released back into the environment. It will be reused for industrial, agricultural or environmental purposes. Furthermore, the gas from water treatment can be used to produce energy. They not only contribute to a healthy environment and good quality of life, but also achieve the goal of sustainable development.
While wastewater collection and treatment are critical to the health of urban residents, storm sewers also play an important role. In urban areas, green has given way to concrete. As a consequence, there has been a loss of the land’s natural water retention as concrete cannot take in rainwater. When an extreme weather event causes heavy rain, storm sewers must cope with the water, so it does not flood the city. However, storm sewers are only part of the solution to water management and flood prevention.
To reduce flooding, an integrated urban management plan has been adopted, where all the factors — storm sewers, land planning and economic development — are considered together. Engineering innovations, additional facilities and increased green space requirements in new development projects have improved water retention in cities.
Sewers help improve urban public health, prevent urban flooding and boost environmental protection. Together they protect vital water resources and maintain the safety of people and property.
【小题1】What’s the function of sanitary sewers?| A．Cleaning dirty water. | B．Collecting solid waste. |
| C．Delivering used water. | D．Producing useful gas. |
| A．Absorption. | B．Treatment. | C．Purification. | D．Distribution. |
| A．To explain a complicated theory. | B．To provide supporting facts. |
| C．To raise improved suggestions. | D．To describe a recent phenomenon. |
| A．Urban Unseen Network | B．Modern City’s Management |
| C．Extreme Weather’s Solution | D．Wastewater’s Potential Threat |
