16    CASE HISTORY: GROUNDWATER REMEDIATION USING
SEQUENCING BATCH REACTORS. REMOVAL OF
VOLATILE AND SEMIVOLATILE COMPOUNDS AT A
SUPERFUND SITE IN NORTHWEST INDIANA
Diane R. Martini, Project Scientist
Mark J. Knight, Senior Project Manager
Ariadne Lytwyn, Project Geologist
James L. Kilby, Manager, Remedial Projects
Monsanto Agriculture Company
St. Louis, Missouri 63617
INTRODUCTION
Remediation is ongoing at a Superfund site in Indiana where hazardous wastes, including a combination of oily wastes and solvents known collectively as light, non-aqueous phase liquids (LNAPL),
were disposed during the early 1970s. Remedial activities include a soil-bentonite slurry wall, LNAPL
recovery, groundwater treatment, and a separate surface water treatment system. Construction was
completed in 1991 and the systems began operating in February 1992.
Groundwater treatment consists of LNAPL separation, followed by permanganate oxidation and
chemical coagulation to remove iron, then by biological treatment to remove organic chemicals using
Sequencing Batch Reactors (SBRs). Results from the first year of operation indicate >99% removal
of Volatile Organic Compounds and Carbonaceous Biochemical Oxygen Demand, and >90%
removal of Semivolatile Organic Compounds from site groundwater. Chemical Oxygen Demand
(COD) removal has averaged 92%. Nitrification was not observed during the first year of operation.
Site groundwater is salty, with a Total Dissolved Solids (TDS) content of 5000 mg/L. This salt did not
appear to inhibit the SBR system.
The following discussion addresses removal of BETX compounds, chlorinated solvents, polynu-
clear aromatic hydrocarbons and phthalates.
BACKGROUND
During the 1970s, the site was used for disposal of construction debris, liquid chemical wastes, and
some solidified chemical waste materials. Operations at the site were centered around drum recycling.
Some drummed materials were disposed, but only when the drum could not be easily salvaged. As a
result, the site contains a wide variety of free-phase chemicals including oily wastes and solvents which
combine to form a light non-aqueous phase liquid (LNAPL) phase which has been contained and is
being recovered.
A soil-bentonite slurry wall defines the boundaries of the site and prevents offsite migration of
contaminants as illustrated in Figure 1. The area within the slurry wall is known as the exclusion zone.
The slurry wall and associated LNAPL recovery and treatment systems are known as the Interim Site
Remedy (or 1SR). The Final Site Remedy (or FSR) will commence after ISR operations are completed
as determined by the termination of LNAPL recovery. Recovered LNAPL at the site has been shown
to contain low levels of Polychlorinated Biphenyls (PCBs), as well as chlorinated solvents and petroleum distillates.
PROCESS DESCRIPTION
The Groundwater Treatment System first uses physical-chemical processes to recover LNAPL and
remove iron and other scaling agents from site groundwater, then uses biological treatment to remove
organic constituents. Treated water is returned to the exclusion zone via an infiltration gallery to
facilitate additional flushing of contaminants from site soils. The design flow capacity for the system
49th Purdue Industrial Waste Conference Proceedings, 1994 Lewis Publishers, Chelsea, Michigan 48118. Printed in
U.S.A.
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