What are the advantages and disadvantages of a combined sewer system?

Benefits

• Compared to the complete divergence system in which sewage pipes and rainwater pipes, only one pipe is required and construction costs are lower.
• Since only one pipe is required, competition with other underground buried objects such as gas pipes and water pipes is reduced, and construction is relatively easier than the diverted type system.
• There is only one from the drainage system to the public sewer, and the pipe system is simpler than the diversion type, making it easier to maintain and manage.

Demerits

• When the amount of rainwater exceeds a certain magnification of the amount of sewage in rainy weather, it is discharged into rivers and the sea from the rain spillway room, etc., which is likely to cause water pollution.
• In the combined sewer system, the pipe diameter is large and the slope is small, so pollutants tend to accumulate in the pipe when fine weather is fine.
• In rainy weather, the flowing water into the water reclamation center involves some rainwater in addition to sewage, so the amount of treated water increases.