6    ADVANCED BIOLOGICAL TREATMENT OF HAZARDOUS
CONSTITUENTS IN K051 PETROCHEMICAL SLUDGES
Robert E. Marks, Graduate Research Assistant
Stephen D. Field, Adjunct Associate Professor
Department of Civil Engineering
Andrew K. Wojtanowicz, Associate Professor
Department of Petroleum Engineering
Gary A. Breitenbeck, Associate Professor
Department of Agronomy
Louisiana State University
Baton Rouge, Louisiana 70803
INTRODUCTION
A trend is developing in insitu cleanup of hazardous waste sites of: using initial biologically-driven
suspended growth processes for primary destruction of hazardous constituents, followed by land
treatment for final polishing of the biological products.1 This application of biological processes for
the treatment of organic sludges and contaminated soils offers a promising new technology and an
alternative to incineration as a method for destroying or altering hazardous constituents. The application of the biological suspended growth process, however, is not well defined and this project will
obtain data for developing engineering parameters which will make the process more efficient and
thus reduce cost factors and cleanup times. A well engineered approach will permit faster reductions
in constituent toxicity thus further restricting the opportunity for migration potential of the hazardous constituents into surface and ground waters. The development of an alternative technology for
treatment of refining and petrochemical wastes is driven by impending restrictive disposal regulations2
due to provisions of the Resource Conservation and Recovery Act (RCRA). These provisions regulate
the future use of land disposal for hazardous wastes and also mandate that the volume, toxicity and
mobility of the wastes be reduced. The statutes stress that permanent, cost-effective solutions are
employed that are acceptable to the public, to the maximum extent possible. An alternative technology based on biological processes will limit the toxicity and migration potential of many organic
compounds found in petrochemical and other industrial wastes.
1. Current Research
The current research is centered on biodegradation of recalcitrant petrochemical sludges in sealed
continuous stirred tank reactors (CSTRs). The specific sludge to be used in the research contains eight
polynuclear aromatics (PNAs) cited by the United States Environmental Protection Agency (USEPA)
as hazardous wastes. Benzo(a)pyrene [B(a)P] was selected in this research as the primary target
contaminant due to its strong carcinogenic nature and low allowable release concentrations in sludges.
Chemical properties of eight key PNAs are shown on Table 1 (Chemical Properties of Key PNAs).
The low solubility of B(a)P of 0.003 mg/1 is considered to be the rate limiting step in biodegradation
reactions where B(a)P is a constituent.3 Equilibrium conditions in the vigorously stirred aerobic 1 liter
reactors were confirmed by daily monitoring of key parameters which include: sludge oil & solids
mass balances, B(a)P mass balances, pH, culture plating, carbon dioxide respiration, and total
suspended solids (TSS). B(a)P loadings are increased from 286 mg/kg of dry feed solids to 34,896 mg/
kg. Test reactors processing solid wastes at B(a)P feed rates of 286-289 mg/kg, met the 1990 USEPA
constituent concentration limit (CCL) for B(a)P of 12 mg/kg for allowable land disposal.
An anionic surfactant, Triton N-101, was added to all petrochemical sludges augmented with B(a)P
at loadings of 1,600 mg/kg and higher. All sampling and analytical protocols followed USEPA
methodologies.4 Mass balance removals of B(a)P and other similar aromatic hydrocarbons were
found to exceed 90%.
46th Purdue Industrial Waste Conference Proceedings, 1992 Lewis Publishers, Inc., Chelsea, Michigan 48118.
Printed in U.S.A.
45