BIOPHYSICAL TREATMENT OF COKE PLANT WASTEWATERS
Gerald L. Bauer, Director of Research Engineering
Michael G. Hardie, Senior Systems Engineer
Thomas J. Vollstedt, Process Development Engineer
Zimpro Inc.
Rothschild, WI 54474
INTRODUCTION
Coke plant wastewaters are generally a composite of waste ammonia liquor, hght od plant
wastewater, and several lesser streams, all generated in the byproduct area of coke plants.
The contaminants present in these wastewaters are pyrolysis products from coke manufacturing and include tars, ammonia, cyanide, thiocyanate, phenoUcs, and other organic
substances.
Current EPA regulations require removal of phenol, ammonia, cyanide, suspended soUds,
and od and grease from the wastewaters prior to discharge to a receiving stream. Under consideration now and anticipated to be in force by 1984 are tighter restrictions on these five
pollutants and additional requirements for removal of BOD, sulfide and perhaps selected
priority pollutants [ 1 ]. Table I shows the standards proposed for 1984.
As currently envisioned, treatment of coke plant wastewaters wUl consist of a pretreatment for removal of tars and most ammonia, followed by a biological treatment for
removal of phenol, BOD, sulfide, cyanide, and the remaining ammonia. Because of the
limitations inherent in ammonia stripping, and because the metaboUsm of thiocyanate and
cyanide yield ammonia as an intermediate product, the biological system must be capable
of achieving nitrification. A final, fUtration step wUl be necessary to meet the suspended
solids requirements.
Beginning in 1976, Zimpro Inc. carried out a series of investigations to evaluate the
suitabUity of the biophysical treatment system (the combination of powdered activated
carbon and biological solids) for the treatment of coke plant wastewaters to meet the
present and proposed regulations. Biophysical treatment in conjunction with wet air regeneration seemed to offer an attractive method for treatment of coke plant wastewaters for
a number of reasons: the biophysical treatment system is capable of a high degree of poUutant removal from concentrated waste streams in a single stage; it is more resistant to upset
conditions than that normally associated with conventional biological systems; and when
used in conjunction with wet air regeneration technology, it eUminates the handling of
secondary soUds and the problems associated with the landfUling of sludges which may contain toxic substances.
Table I. Proposed 1984 Discharge Standards for Coke Plant Wastewaters
Analysis Limit (mg/l)
pHa 6-9
BOD 10
phenol 0.5
CN (amenable)13 0.25
NH3-N 10
Oil and grease 10
Suspended solids 10
S= 0.3
apH has no units,
cyanide amenable to chlorination.
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