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

Merit

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

Demerits

• In rainy weather, if the amount of rainwater exceeds a certain magnification against the amount of sewage, it is released from the spillway room to rivers and the sea, and 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 in fine weather.
• In rainy weather, the amount of treated water increases because some rainwater is added to the water flowing into the water reclamation center in addition to sewage.