Air Flotation Treatment and Reuse of
Refinery Wastewater
JAMES A. HART, Conservation Specialist
Mobil Oil Corporation
East Chicago Refinery
East Chicago, Indiana
INTRODUCTION
Mobil Oil Corporation's East Chicago Refinery is located on the Indiana
Harbor Ship Canal, which discharges into Lake Michigan.
The Great Lakes-Illinois River Basin Survey (GLIRB) made by the Health,
Education, and Welfare Department in 1963, indicated a need for improving the
quality of waste waters discharged into this Canal.
At that time Mobil's waste treatment facilities consisted of two ballast water
settling tanks and two parallel API Separators which processed all the oily waste
water. Sanitary sewage was discharged into the City sewer system and was treated by
the City of East Chicago.
A Sour Water Stripper installation had been budgeted, for removing sulfides
and ammonia from the refinery's catalytic cracker condensate.
This paper will present Mobil's experiences in operating a Sour Water Stripper
and an Air Flotation Unit. Results of water reuse in cooling towers will also be
discussed.
WASTE WATER QUALITY IMPROVEMENTS, 1965-1967
In February 1965, the Sour Water Stripper was put into service, producing
dramatic results. The API Separator effluent water's visual appearance was greatly
improved by the complete elimination of a black precipitate which the sulfides had
caused. The Sour Water Stripper Bottoms was of excellent quality, containing
essentially no sulfide and only 15 mg/1 of ammonia-nitrogen. Reuse of the Sour
Water Stripper Bottoms as Desalter wash water achieved a reduction of 90 per cent in
phenol content.
These operations, plus several improvements in housekeeping practices,
resulted in the following improvements in API Separator effluent quality, compared
with that shown by the 1963 GLIRB Survey:
Per Cent
Pollutant Reduction
Sulfides 99.9
Ammonia-Nitrogen     95.0
Phenols    91.0
BOD    43.0
To maintain consistent waste water quality, it is necessary that the Sour Water
Stripper operate essentially 100 per cent of the time, while the catalytic cracker is on
stream. Figure 1 shows a simplified flow diagram of the Stripper and the locations of
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