7    TREATMENT OF PETROLEUM OILY SLUDGES IN
LIQUID/SOLIDS CONTACT REACTORS - RESULTS OF
BATCH TESTING
Marwan F. Salameh, Environmental Engineer
Randolph M. Kabrick, Principal
Remediation Technologies, Inc.
Austin, Texas  78705
INTRODUCTION
A new technology that is proving to be technically reliable, economically feasible and environmentally sound for the treatment of oily sludges is biological liquid/solids contact (LSC) treatment in
engineered units.1 LSC treatment of oily sludges offers the following advantages:
• Ability to treat concentrated sludges avoiding the need for dilution and related large
reactors;
• Rapid biodegradation due to intimate mixing of the contaminant solids in the liquid
phase with the microbial population and higher mass transfer rates of contaminants and
oxygen into the aqueous phase;
• Little or no risk of off-site contamination; and
• Greater control over environmental conditions.
LSC treatment has been used to biologically treat hazardous and non-hazardous sludges from the
petroleum and petrochemical industries.2,3 These units are generally operated as batch systems.
However, operations in a continuously fed mode are also feasible. The process is used to reduce the
toxicity and migration potential of many organic compounds present in these sludges via bio-
oxidation of these compounds.
DESCRIPTION OF THE LSC PROCESS
The LSC process is analogous to the suspended growth processes (SGP) such as the activated sludge
process. However, LSC reactors are designed to treat wastes high in solids content (up to 50 percent).
LSC reactors do not employ biosludge recycling and therefore are typically operated at long hydraulic
residence times (HRTs) (days to weeks). LSC reactors are designed to process wastes that are more
difficult to degrade, less soluble and are more concentrated (COD > 100,000 mg/L) than SGP. The
high viscosity of the oily sludges treated in LSC reactors requires special operational and mixing
equipment. Due to the presence of potentially hazardous volatile organic carbons (VOCs) in these
sludges, the reactors are generally equipped with emission control equipment. A general schematic
diagram for a complex LSC process employing three continuously fed reactors in series is shown in
Figure 1.
The ability of LSC reactors to significantly reduce the level of contaminants in a waste stream
involves the following phenomena:
• The extraction (solubilization) of the organics into the aqueous phase.
• The biodegradation of the extracted organics into less toxic forms (ultimately C02 and
H20).
• The removal (stripping and biodegradation) of volatile contaminants from the hydrocarbon and the aqueous phases.
Biodegradation of oily sludges results in complete degradation of some compounds and transformation of other compounds into other polar intermediates. Several factors affect the performance of
the LSC process. These factors are:
46th Purdue Industrial Waste Conference Proceedings, 1992 Lewis Publishers, Inc., Chelsea, Michigan 48118.
Printed in U.S.A.
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