Rainwater collection on building roofs is suitable for residential, public buildings, and factory roofs. The collected rainwater in such scenarios has good water quality and relatively small waste flow. Road and hardened ground rainwater collection is mainly used in municipal roads, squares, and parking lots. Due to the heavy pollution of rainwater in these areas, it is necessary to increase the amount of abandoned water to ensure the quality of collected water. Rainwater collection in sponge city construction projects is commonly used in scenarios such as rain gardens and biological retention facilities. These facilities mainly serve as pre-treatment units for rainwater collection, laying the foundation for subsequent treatment. The rainwater reuse in industrial parks mainly targets the rainwater collection and utilization system in the factory area. The core requirement is to remove the initial pollution load of rainwater and ensure that the reused water quality meets the standard. Modular rainwater treatment systems are mostly integrated underground integrated machines, which have the functions of waste disposal, filtration, storage, and upgrading, and can flexibly adapt to the treatment needs of various rainwater collection scenarios.