									Draft

									February 5, 2009

									Ref: PF/NPDES/PER

The blast furnace recycle system consists of two thickeners (i.e., one
for each furnace), a cooling tower and a pump house for recirculating
treated process water for reuse at the blast furnaces. Periodic blowdown
from or lake water make-up to this system occurs throughout the day in
order to maintain a hydraulic balance within the recycle system. The
blowdown is discharged to the plant’s dirty industrial wastewater
(DIW) sewer system for further treatment at the Secondary Wastewater
Treatment Plant (SWTP) prior to discharge to surface waters of the
State. In the event the recycle system experiences elevated
concentrations of cyanide, a steady-state blowdown can be directed to an
alkaline chlorination system to destroy the cyanide before discharge to
the SWTP.

The sinter plant has its own dedicated treatment plant that receives all
of the gas cleaning blowdown from the sinter plant and minor quantities
of filtrate from the mechanical dewatering of BOF sludge.  Excess
moisture is added to this system by virtue of the process and is blown
down to the Reclamation Services Building (RSB) for treatment. After pH
adjustment (we try to maintain a pH of about 9.3) and the addition of
flocculation/coagulation polymers, the wastewaters are directed to the
final thickener for preliminary clarification.   The effluent of the
final thickener discharges to the Dirty Industrial Wastewater (DIW)
sewer system for further treatment at the SWTP. 

The basic oxygen furnace recycle system consists of two thickeners that
treat the gas cleaning process waters prior to recycling back to the gas
cleaning system or blowdown to the DIW sewer system for further
treatment at the SWTP.

The continuous casters (2) are equipped with scale pits for the removal
of suspended solids and oil. The hot forming mills (two plate mills and
the hot strip mill) are also equipped with scale pits and oil skimming
equipment. The facilities recycle a portion of the scale pit effluent
water for use in the production process and the balance is discharged to
the DIW sewer system for further treatment at the SWTP.

Wastewaters generated from the hot dip (galvanizing) coating line are
filtered prior to discharge to the DIW in order to remove particulate
zinc. Waste pickling acids are either used on site to neutralize
wastewaters, sold for off-site recycling or disposed of by deep well
injection. Pickling rinsewaters and fume scrubber blowdowns are combined
with pretreated wastewaters from the cold rolling operations and
directed, via the DIW sewer system, to the SWTP for final treatment.

Contaminated groundwater from the ore dock area is recovered and used as
a replacement for lake water in the gas cleaning systems of either the
Sinter Plant or the Blast Furnaces. As noted above, the blowdowns from
these systems receive initial treatment at the generation site and
secondary treatment at the SWTP.

Most of the facility’s wastewaters receive primary treatment at their
source and final treatment at the SWTP. Final treatment includes pH
adjustment, oil separation, flocculation/coagulation and clarification
prior to discharge through several open channel conveyances before
reaching the East Branch of the Little Calumet River. Sludges generated
by the SWTP will be disposed on-site in a permitted Type 1 solid waste
landfill (to be constructed). Any leachate generated by the landfill
will also undergo preliminary treatment prior to discharge to the DIW
and SWTP.  

The SWTP effluent is routed through two lagoons prior to discharge
through internal Outfall 011 and final Outfall 001 into the East Branch
of the Little Calumet River. The lagoons are equipped with aerators for
temperature control. Lake Michigan water can also be added to the
Outfall 011 discharge during warm weather months for additional
temperature control.

 

 

