Abstract: Since the mud cake from groundwater plants contains manganese oxides that can be utilized as potential catalytic oxidation materials for ammonia removal in water, and the presence of transition metal elements can enhance the catalytic activity of manganese oxides, this study aimed to investigate the impact of five types of transition metal ions (Mn²⁺, Fe²⁺, Cu²⁺, Co²⁺, Ni²⁺) on the activation process of the catalytic oxidation of mud cake. The operability of mud cake-loaded quartz sand filter material with the most effective activation was assessed. The findings revealed that the co-addition of two different transition metal ions or the individual addition of Cu²⁺, Co²⁺, and Ni²⁺ could impede the ammonia removal activity of the mud cake. The addition of Mn²⁺ or Fe²⁺ was found to enhance the formation of effective ammonia removal activity. Specifically, adding 0.5 mg of Fe²⁺ per gram of mud cake resulted in optimal performance, leading to a nearly 30% increase in catalytic oxidation capability, with an ammonia removal rate of 0.234 mg/(g·h). Under these conditions, the initiation time of the filter column was reduced by almost 10 days post-mud cake loading, and the continuous operation for 13 days achieved a 96.7% ammonia removal rate, demonstrating suitability for both groundwater and surface water environments. Characterization analysis indicated that Fe²⁺ activation led to the augmentation of iron phases, predominantly in the form of Fe₂O₃ and FeOOH, which provided active oxygen atom sites conducive to the ammonia reaction. Furthermore, the contents of Mn(Ⅲ), metal—O, and metal—OH increased, intensifying the mud cake's catalytic oxidation activity. The activated mud cake and its reaction solution were free of pathogenic microorganisms, did not exceed permissible levels of heavy metal elements, and yielded satisfactory effluent quality post-application of the loaded filter material. This research offers a novel approach for the effective reutilization of waste resources and enhances the efficiency of ammonia removal in water treatment plants, showcasing practical significance.