Spent metalworking fluids constitute a significant environmental problem due to their high content of organic substances, the presence of stable oil-in-water emulsions, and chemical additives that hinder their treatment. The aim of this study was to assess the effectiveness of chemical coagulation for a real pooled industrial batch of spent metalworking fluid accumulated from multiple machining units. In the first series, tests were performed to provide a preliminary assessment of the possibility of emulsion destabilization. In the second series, the effectiveness of industrial coagulants used in municipal wastewater treatment plants, including the Municipal Wastewater Treatment Plant in Białystok, was investigated; these included the iron-based coagulants PIX 111, PIX 113, and PIX 211. Based on observations, the most promising coagulant was selected and then subjected to further dose assessment in the third series of tests. The influence of the PIX 113 coagulant dose and the addition of silica on the physicochemical parameters of the samples was analyzed, including pH, specific conductivity, salinity, turbidity, color, chemical oxygen demand (COD), and the mass of the sludge formed. PIX 113 showed the most visible destabilization among the tested coagulants; the dose of 1004 mg Fe/L should be interpreted only as the best-performing tested dose under the applied jar-test conditions, not as a universal optimum. Intense flocculation and partial clarification of the supernatant were observed, but the reduction in turbidity and color was incomplete, while pH decreased to the range of 3-4, accompanied by substantial production of secondary sludge. For the investigated batch, chemical coagulation alone was insufficient to achieve final effluent quality, indicating the need for additional treatment stages. Extended characterization of the same raw batch confirmed a highly loaded, hydrocarbon- and surfactant-containing industrial waste matrix. The results show that coagulation substantially reduced selected indicators but remained insufficient as a stand-alone treatment process under the tested conditions.