21    BIODEGRADATION/PARTITIONING OF BENZO(A)PYRENE
IN LIQUID/SOLIDS SUSPENDED GROWTH SYSTEMS
Robert E. Marks, Graduate Research Assistant
Stephen D. Field, Associate Professor
Department of Civil Engineering
Andrew K. Wojtanowicz, Associate Professor
Department of Petroleum Engineering
Louisiana State University
Baton Rouge, Louisiana 70803.
INTRODUCTION
The scope of this research is to study the biodegradation and partitioning of benzo(a)pyrene (B[a]P)
contained in sludges in continuous growth systems with the longer term goal of developing engineering parameters for design of pilot plant systems which will be more effective than existing alternative
technologies in reducing accumulations of persistent polynuclear aromatics (PNA's) at Superfund
sites. Design parameters will also be developed for the addition of an online waste reduction process
as a cleanup stage for detoxification of hazardous organic compounds contained in the waste sludge
generated from petroleum refineries and petrochemical plants.
Deposition rates of PNA's from all sources are exceeding the natural destruction rates by microbial
decomposition and photo-oxidation, and accumulations in the land/water ecosystems are occurring.'
The majority of the accumulations are from anthropogenic sources and contain the semi-volatile
condensed 4-5 aromatic ring compounds. Five of these PNA's are considered by the Environmental
Protection Agency (EPA) to be carcinogens and include: benzo(a)anthracene (B[a]A), ben-
zo(b)fluoranthene (B[b]F), B[a]P, chrysene, and dibenzo(a,h)fluoranthene (DB[a,h]F). B[a)P is considered strongly carcinogenic based on cancers induced in small animal laboratory experimentation.2
These compounds are typically solids at ambient temperatures, and are characterized by their high
organic partition coefficients, very low aqueous solubility, low vapor pressures and tendency to
bioaccumulate in the natural environment.
EPA has developed a listing of national sites containing hazardous materials and has established an
order of priority for cleanup of these sites —National Priorities List (NPL). Many of these sites are
contaminated with PNA's. The EPA Office of Emergency and Remedial Response (OERR) has the
responsibility for developing treatment strategies which can be applied to these sites. Three basic
treatment mechanisms are favored by EPA.3 The treatment options include: a) destruction of the
contaminant through chemical alteration to less toxic compounds (thermal destruction, dechlorination, and bioremediation); b) transfer of the contaminants to other waste streams for subsequent
treatment (low temperature thermal desorption, chemical extraction, and soil washing); and c) contaminant bonding to waste media (immobilization). The current preferred methodology is thermal
combustion (incineration), but costs are high and available capacity falls far short of the accumulated
and projected industrial production of hazardous wastes. The second choice is bioremediation where
costs factors are low but biodegradation times are comparatively long. A bioremediation solution
must insure that the contaminated soils or sludges are detoxified to permit safe release to the environment, and all other products associated with the process such as recovered oils, surface scums,
aqueous discharges, and decontaminated solids also meet current disposal regulations or are directed
to further treatment.
The two hazardous wastes selected for this study are sludges from API separators. The first sludge
was obtained from one of 16 API separators from a fully integrated crude oil refinery while the
second sludge was obtained from an API separator in a petrochemical complex.
45th Purdue Industrial Waste Conference Proceedings, © 1991 Lewis Publishers, Inc., Chelsea, Michigan 48118.
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