73    TREATMENT OF STORM RUNOFF BY OIL-WATER
SEPARATION,
FLOTATION, FILTRATION, AND ADSORPTION.
PART B: WASTE SLUDGE MANAGEMENT
Lawrence K. Wang, Director
Mu Hao S. Wang, Professor
Lenox Institute for Research Inc.
Lenox, Massachusetts 01240
William J. Mahoney, Technical Director
Imperial Oil Company Inc.
Morganville, New Jersey 07751
INTRODUCTION
The combined storm runoff and process water from an oil blending company in the northeast was
successfully treated by an innovative system consisting of oil-water separation, dissolved air flotation
(DAF), optional filtration, and optional granular activated carbon (GAC) adsorption. This chapter
presents and discusses the sludge management technologies developed by the performing
organizations.
Initially the oil and grease (O&G) in the combined storm runoff and process water was removed by
three API oil-water separators in series. The separated oil was in virgin form, and was, therefore,
skimmed off, dried and reused.
The oil-water separator effluent was treated by a required Supracell DAF with sodium aluminate
and ferric chloride. Further tertiary wastewater treatment by filtration and GAC adsorption was
optional, and highly recommended by the authors. The oil company did install GAC adsorbers for
possible post-treatment of Supracell DAF effluent, but needed not to operate the adsorbers because
arsenic in wastewater was not as high as anticipated.
The major waste sludge generated from the wastewater treatment system was the DAF floated
sludge which amounted to 0.7% of influent wastewater flow.
No coliform bacteria could survive in the DAF floated sludge which contained arsenic. Therefore
microbiological stabilization of DAF sludges was not required. The DAF liquid sludge which had
0.85-0.96% in consistency was concentrated to a 21% sludge cake by a precoat vacuum filtration
unit. The filtrate was recycled to DAF for reprocessing.
The DAF sludge before dewatering by vacuum filtration did not posses any characteristic of
Extraction Procedure Toxicity and was not hazardous. The dewatered sludge cake met the current
State limits on heavy metals for land application.
Alternatively either the thickened wet sludge or the dewatered sludge cake could be easily solidified
with commercial concrete mix to form concrete blocks which could then be safely disposed of by
sanitary landfill.
WASTE SLUDGE AND RESIDUES
Figure 1 illustrates the oil company's wastewater treatment system, waste sludge and residues
produced from the system and a waste sludge management plan.
There are only three sources of waste sludge and residues: 1) the floated oil from oil-water separators; 2) the floated sludge from Supracell dissolved air flotation (DAF) clarifier; and 3) the spent
granular activated carbon (GAC) from stand-by GAC adsorbers.
The virgin oil recovered by the oil-water separators is reused.
44th Purdue Industrial Waste Conference Proceedings, © 1990 Lewis Publishers, Inc., Chelsea, Michigan 48118.
Printed in U.S.A.
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