A NOVEL CHEMICAL APPROACH FOR THE TREATMENT
OF OILY WASTEWATERS
Kerstin E. Katnik, Product Specialist
Audrone M. Pavilcius, Chemist
Nalco Chemical Company
Oak Brook, Illinois 60521
INTRODUCTION
July  1, 1977 has passed.   The EPA estimates that most major industrial dischargers
of point source water pollutants   were in compliance with the first Clean Water Act
deadline for best practicable technology.    These larger plants have successfully treated
wastewaters to reduce fats, oils and grease (FOG), biochemical oxygen demand (BOD),
chemical oxygen demand (COD), and suspended solids (SS).    Many have used chemical
primary treatment programs such as cationic polyelectrolytes plus inorganic coagulants.
Typically, the most effective treatment processes have been coagulation-flocculation with
air flotation or sedimentation and they have been made even more efficient with chemical treatment [1,2,3,4,5].    With good operator "control, plants using the combination of
chemicals and properly selected equipment are capable of discharging the best water
quality at the lowest overall cost.
However, smaller plants which typically generate less than 300,000  gallons per
day of wastewater, have experienced more difficulties achieving compliance.    For these
plants, the overall economics of the conventional treatment programs are poor because
of their smaller flow and more variable wastewater.   These plants find it difficult to
support the full time operator and the treatment equipment required to apply conventional programs.
Thus, the need has developed for a treatment which is easy to apply and control or
in short-a very forgiving program which would minimize feed equipment and manpower
requirements.
This paper addresses itself to the problems of the waste treatment plant handling
smaller volumes of water.
CONVENTIONAL TREATMENT PROGRAMS
Chemical treatment of industrial oily wastewaters using  cationic   polyelectrolytes
and/or inorganic metallic salts is an established and defined technology [1,4].
A typical plant flow diagram for this process is shown in Figure 1.   The wastewater
flows into a primary oil-water separator where free oil is removed.    These separators
may be the American Petroleum Institute (API) design, the corrugated plate design, or
simply a holding tank equipped with surface skimmers to remove free-floating oil.
These are typically not treated with chemicals.
After the free oil is removed the wastewater is allowed to mix and become homogeneous in large holding tanks. This step is very important as it provides a consistent
quality of wastewater which can be treated effectively without varying the chemical
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