Abstract:Megacities are densely populated and have high pipe network density, and the management of rainwater and sewage mixing is particularly complex. In the case of a megacity, since 2015, a series of rainwater and sewage mixing treatment actions have been carried out to achieve the remarkable results in river water quality and sewage collection and treatment efficiency. However, in the process of treatment, there are still many difficulties in pipeline inspection and management. In order to further improve the effectiveness of treatment, a comprehensive policy of technical and institutional methods is put forward, aiming to systematically solve the problem of rainwater and sewage mixing and improve the management efficiency of drainage system in megacities.