Abstract
This paper presents the results of a study on the efficiency of treating oil-containing wastewater from a locomotive depot using combined physicochemical processes. The relevance of the study is conditioned by the high aggregative stability of oil-in-water emulsions formed in wastewater from railway enterprises, as well as the necessity to meet regulatory discharge standards for centralized sewerage systems. The mechanisms of oil emulsion formation and their influence on treatment processes were analyzed. The methodology included the sequential application of gravitational sedimentation, coagulation–flocculation using iron(II) sulfate with pH adjustment by lime, and filtration–adsorption polishing using wood shavings and sulfonated carbon. Laboratory experiments were conducted using real wastewater samples from a locomotive depot with an initial petroleum hydrocarbon concentration ranging from 40 to 150 mg/L. The results demonstrated the low efficiency of mechanical settling in the presence of stable emulsions. The most significant reduction in petroleum hydrocarbon concentration was achieved during the coagulation stage at pH 8.0–8.5, where the treatment efficiency reached up to 98%. The final filtration–adsorption stage provided additional removal of residual hydrocarbons, reducing their concentration to approximately 2 mg/L. The discussion confirms that the combination of coagulation and filtration–adsorption processes represents an optimal approach for treating oil-containing wastewater from transport enterprises. The developed technological scheme ensures compliance with regulatory requirements while maintaining relatively low operational costs and can be recommended for practical implementation.