With Chemically Enhanced Primary Treatment (CEPT) as the short-term process, the capacity of Bailonggang Wastewater Treatment Plant accounts for almost 25% of the total capacity of wastewater treatment in Shanghai, China. However, shortly after this plant was placed in operation in 2004, it was found that the effluent of CEPT couldn't meet the new national discharge criteria. Although the removal of phosphate is almost 80%, chemical oxygen demand (COD) and ammonia nitrogen (NH3-N) in the effluent is frequently found to exceed the standards. The primary goal of this research is to investigate the possibility of optimizing the CEPT to make it meet the discharge criteria before it is upgraded to a secondary treatment. An oxidant is adopted to remove NH3-N, and a high performance polyaluminum chloride (HP-PACl) is synthesized to enhance the removal of COD. It is found that HP-PACl improves the removal of COD, and the oxidant enhances NH3-N removal effectively. However, to meet the requirement of a newly implemented stricter discharge standard, it is necessary to upgrade this CEPT to a secondary treatment. The results of this study provide scientific evidence for the upgrade of the Bailonggang Wastewater Treatment Plant.