Aiming at the problems of low filtration efficiency in fine screens, high failure rates of sand pumps in the aerated grit chamber, and poor grit-water separation existing in the Zhengzhou New District Wastewater Treatment Plant Phase I Project, taking the Phase II Project as the research object, the targeted design optimizations are implemented. The optimized contents include (1) replacing the drum-type fine screens with inward-flow panel fine screens to enhance the retention capacity of fibrous debris; (2) installing the overflow bypass channels to deal with the risk of high-pressure flushing water supply interruption; (3) adopting the dry-type sand pumps to reduce the mechanical wear, optimizing the hydraulic retention time of the grit separation chamber to 5.5 minutes, and deploying the variable-frequency screw conveyors to improve the grit separation efficiency. The results show that the average annual output of screen residue from the fine screens of the Phase II Project reaches 0.219 m³/10⁴ m³ of sewage, which is 2.5 times higher than that of the Phase I Project, and the problem of scum in the biological reaction tank has been basically eliminated. The maintenance frequency of sand pumps has been reduced from once a month to once every three months. The efficiency of sand particle separation has been increased by 57%. The optimization measures have significantly enhanced the operational stability and treatment efficiency of the pretreatment units