What is the role of urban drainage system in modern society?

In densely populated urban areas, a large amount of wastewater is produced every moment. These wastewaters include domestic sewage, industrial wastewater and natural precipitation (rain and snow). Among them, industrial wastewater and domestic sewage contain a large number of harmful and toxic substances and a variety of bacteria, which seriously pollute the natural environment, spread various diseases, and directly endanger people's health. . In addition, if rainwater cannot be removed in time, it will flood the streets, interrupt traffic, and make people unable to live and produce normally. Therefore, in order to ensure a good living and production environment in cities and towns, urban wastewater must be reasonably collected, transported, treated, utilized and discharged, and the task of this task is the urban drainage system, collectively referred to as drainage engineering or sewer engineering.

Drainage engineering is one of the important infrastructures in urban construction. After the establishment of China, especially since the reform and opening up, with the rapid development of urban and industrial construction, the construction of urban drainage projects has also developed greatly. Taking Beijing as an example, in the early days of the founding of New China, there were only 220km of old ditches in the city, which were in disrepair, collapsed and silted up, and could not be used normally. The length of the pipe network is 2887km. With the development of drainage engineering construction, a professional team of sewer maintenance has been gradually formed, which has laid a foundation for the development of sewer maintenance technology and scientific management.

Mixing all kinds of wastewater, that is, domestic sewage, industrial wastewater and rainwater, in the same pipeline is called a combined drainage system. Most of the early urban drainage systems were combined systems. The mixed sewage in this system is generally only treated simply, or directly discharged into the natural water body without treatment. This kind of drainage system can be used when the amount of domestic sewage and industrial wastewater in small and medium-sized towns is relatively small and the amount of rainwater is relatively large.