Wastewater Resulting from the
Benefication of Low Grade Iron Ore
C. ROBERT BAILLOD, Assistant Professor
GEORGE R. ALGER, Associate Professor
HENRY S. SANTEFORD, JR., Instructor
Department of Civil Engineering
Michigan Technological University
Houghton, Michigan
INTRODUCTION
Over the past 25 yr, the iron mining industry has witnessed a trend toward the
exploitation of low grade ore deposits. Formerly, nearly all of the ore shipped
consisted of richer, natural ores (usually the brown and red hematites) which required little or no processing (beneficiation) at the mine site. As the high grade ore
deposits became more scarce, technological improvements in beneficiation processes
made the exploitation of low grade ore deposits economically attractive. The term
taconite, although descriptive of a hard, dense Minnesota rock with 25 to 35 per cent
iron content, is sometimes loosely used as a general term for low grade ore formations. In 1945, only 23 per cent of the ore shipped resulted from beneficiation
processes. However, in 1965 77 per cent of the 87 million tons of useable ore had
been beneficiated (1). The Lake Superior district accounted for three-fourths of this
production. It is anticipated that this trend will continue in the future.
In contrast to the old underground mines, the newer open pit mining and
beneficiating operations are more visible and make use of more land surface. Because
of its concern with the impact of mining operations on the environment, the Cleveland-Cliffs Iron Co., for itself and its Associated Companies, initiated a program of
environmentally oriented investigations in cooperation with Michigan Technological
University. This paper presents some results of a study conducted to delineate the
problems encountered in the operation of a tailings impoundment and water clarification system at the Marquette Iron Mining Co., Republic Mine. Additional aspects
of the program concerned with revegetation of the basins, mechanical properties of
the deposits, and biological effects on the receiving stream are not covered in this
paper.
IRON ORE BENEFICIATION
The beneficiation process is essentially a concentrating process whereby the
low grade ore (25 to 35 per cent Fe) is concentrated to 55 to 70 per cent Fe. This
results in a waste material containing 10 to 20 per cent Fe. Thus, for every four tons
of ore at 35 per cent iron, 1.8 tons of concentrate at 65 per cent iron would be
produced. The 2.2 remaining tons at 10 per cent iron would be discharged to the
tailings deposit. The concentrated ore is pelletized in a heat hardening operation with
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