Section 15. STEEL AND FOUNDRY WASTES
QUANTIFICATION OF THE INFLUENCE OF STEEL INDUSTRY TRACE
ORGANIC SUBSTANCES ON BIOLOGICAL NITRIFICATION
Jeffrey H. Greenfield, Graduate Student
Ronald D. Neufeld, Associate Professor
Civil Engineering Department
University of Pittsburgh
Pittsburgh, Pennsylvania  15261
Biological nitrification, the removal of ammonia-nitrogen (NH3-N) from wastewater, is
required by EPA due to [ 1 ]:
1. the considerable oxygen demand ammonia exerts upon the receiving waters;
2. the extra chlorine demand ammonia exerts via chloramination upon treated waters;
and
3. the toxicity of ammonia to aquatic life.
Ammonia in aqueous municipal waste discharges is created through ammonification,
the bacterial decomposition of organic nitrogen. Typical aqueous industrial discharge sources
are from byproducts of coking, refining, fertilizer and organic chemical industries.
Domestic wastewater NH3 discharges are often in the 10 mg/l to 20 mg/l range, and are
usually oxidized completely, with an occasional accumulation of nitrite (N02). However,
in the cases of industrial wastes where high concentrations of reduced nitrogen (100-300
mg/l) are present, complete nitrification often does not occur.
Coking is the heating of bituminous coal in the absence of air; gases are given off and
a residue remains in the oven. The residue is coke, which is a major ingredient in the blast
furnace manufacturing of pig iron. In a by-products coking operation, the gases are captured
for further processing. These gases are cooled prior to distillation and refining into tar and
light oils. Cooling is accomplished by drawing the gas through water sprays. The water
saturated with gas vapor is known as flushing liquor. Condensate is also formed and combined with the flushing liquor. A second cooling phase forms additional condensate which
is joined with the flushing liquor and first stage condensate in a decant tank where the
tars are removed by gravity separation. The underflow from the decant tank is often recycled for gas cooling. These processing steps produce excess waste water known as weak
ammonia liquor. This liquor contains the majority of the waste ammonia from the coking
operation. This excess waste water can be discharged directly, used in quenching, stripped
only of its contained ammonia, or processed to recover both its phenol and ammonia constituents, and then either discharged, used in quenching or biologically treated.
LEGISLATIVE ASPECTS
In the January 7, 1981 Federal Register [21, the F.PA published effluent limitation
guidelines for the by-product coke category of the Iron and Steel Industry. Table I summarizes these guidelines. The average of daily values for 30 consecutive days is 15.3 mg/l
NH3 based on 150 gallons wastewater per ton coke product.
In the January 3, 1980 [11 Federal Register, the F.PA proposed that ammonia be removed from the non-conventional pollutant list, and be added to the list of "priority pollutants" as originally developed under section 307 (a) of the Clean Water Act.
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