4. Storm basin on combined sewer system

4.1 General principle

• A "storm basin" or "buffer basin" is a stormwater management structure often used in combined sewer systems. Its role is twofold.

  • Hydraulic role

    The storm water basin is used to temporarily store excess effluent during rainy periods. During heavy rainfall, the volume of water reaching the treatment plant can exceed its treatment capacity. The buffer structure regulates flow by storing excess water and gradually releasing it back to the treatment plant, or reinjecting it into the network once the rain has passed and treatment capacity has been restored. This avoids direct overflow into the environment (rivers, sea, etc.), which can cause major pollution.

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