Section Three
SITE REMEDIATION
A. BIOREMEDIATION
13    IN-SITU GROUNDWATER BIOREMEDIATION
Ralph E. Moon, Technical Director, Engineering
Gregory J. Rorech, Senior Associate
Geraghty & Miller Inc.
Tampa, Florida, 33618
INTRODUCTION
A site investigation and in-situ bioremediation were conducted at a manufacturing facility to
identify and to remove a prominent source of odor, metal corrosion, and groundwater contaminants.
Three acres of a 20 acre facility were seriously affected. A soil-gas sampling program revealed that a
rotten egg odor originated from a variety of subsurface sources including groundwater monitor wells,
subsurface conduits (telephone, electrical lines), and persisted in wind-protected areas of the facility.
Soil-gas samples contained highly elevated hydrogen sulfide (H2S) concentrations (up to 7000 ppm)
and little or no oxygen (< 5%).
The project strategy proposed a two-phased approach: (1) the rapid exchange of subsurface vapors
with ambient air to remove the odor and to promote aerobic conditions, and (2) a groundwater
recovery, treatment and injection program to remove the groundwater contaminants, and to improve
the rate of natural aerobic bioremediation in the aquifer. Because a highly anaerobic subsurface
environment was suspected, an in-situ bioremediation system was considered ideal to remove the
contaminant source.
A soil vacuum extraction (SVE) system was also used to assist the in-situ bioremediation system and
is reported in detail elsewhere.1,2 It was recognized that the SVE alone would neither remove the
source of hydrogen sulfide vapors permanently nor significantly lessen the concentration of organic
contaminants in the groundwater.
The in-situ bioremediation system was based on the results obtained from four major activities: (1)
groundwater investigation, (2) soil-gas investigation, (3) bacterial evaluation, and (4) groundwater
modeling. The methods used and results obtained from these activities are presented below; they
provided the basis to design the treatment program. The site investigation was conducted between
July 1988 and September 1990. Groundwater remediation began December 1991 and is expected to
continue for several more years.
Facility History
During initial facility construction in the 1960's and expansion in the 1970's, subsurface pipelines
were installed to transfer domestic and industrial wastes to either a waste-water treatment or solvent
recycling facilities. Over a 15-year period, subsurface pipelines deteriorated and released liquid wastes
into the subsurface. Accidental surface spills and solvent delivery system failures may have also
contributed chemicals to the aquifer via storm drains.
Although hydrogen sulfide odors were evident for 10 to 15 years before the investigation, severe
metal corrosion problems and increased hydrogen sulfide odor complaints prompted a subsurface
investigation to locate and remove the source. Samples obtained from groundwater monitor wells and
soil-gas probes indicated that the hydrogen sulfide source was generated from a subsurface source,
most likely a groundwater plume.
48th Purdue Industrial Waste Conference Proceedings, 1993 Lewis Publishers, Chelsea, Michigan 48118. Printed in
U.S.A.
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