IC 7894 Abating Stream Pollution By Recovering Waste Oil From Steel Rolling Mills ? Summary

This report presents the results of a research and development program in recovering waste-rolling oils conducted by the Bethlehem Steel Co., before 1954 at its Sparrows Point plant, Sparrow Point, Md., with the cooperation of the Bureau of Mines, U. S. Department of the Interior, College Park, Md. The objective of the program was twofold: First, to recover oil for reuse in the plant; and second, to stop pollution, by oil, of the stream and harbor areas in the immediate vicinity of the plant. The sequence of the investigations was laboratory and pilot plant studies on sedimentation, simple aeration, and flotation for the separation of oil and water; and construction of a production unit using standard flotation equipment. This work was only preliminary for the Bethlehem Steel Co. and it has continued research on this problem. Recent progress indicates that new, improved processes will soon replace the flotation units described in this report. The first efforts to separate oil and water by simple sedimentation were unsuccessful. To establish the cause of this failure, microscope examinations and measurements were made on cold-reduction rolling mill cooling-water effluents containing oil in suspension. It was discovered that an average oil globule, held in suspension, was only 0.001 inch in diameter and would not coagulate with other globules for normal sedimentation at room temperature. The next step in the sequence of studies was to coagulate the oil suspension by simple aeration with air under slight pressure. The aeration methods studied were effective in removing up to 68 percent of the total oil but were approaching flotation in principle. The final investigation of the series was flotation of the oil in conventional laboratory-size flotation cells. The small-bubble method, without reagents, floated up to 89 percent of the total oil held in suspension and was the process selected for pilot-plant development.