EPA/540/A5-91/009
January 1993
Pilot-Scale Demonstration of a
Slurry-Phase Biological Reactor for
Creosote-Contaminated Soil
Applications Analysis Report
Risk Reduction Engineering Laboratory
Office of Research and Development
U.S. Environmental Protection Agency
Cincinnati, Ohio 45268
Printed on Recycled Paper
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Notice
The information in this document has been funded by the U.S. Environmental Protection Agency
(EPA) under ContractNo. 68-C9-0036 and the Superfund Innovative Technology Evaluation (SITE)
Program It has been subjected to the Agency's peer and administrative review and has been approved
for publication as an EPA document Mention of trade names or commercial products does not
constitute endorsement or recommendation for use.
11
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Foreword
The Superfund Innovative Technology Evaluation program was authorized in the 1986 Superfund
amendments. The program is a joint effort between EPA's Office of Research and Development and
Office of Solid Waste and Emergency Response. The purpose of the program is to assist the
development of hazardous waste treatment technologies necessary to implement new cleanup
standards that require greater reliance on permanent remedies. This is done through technology
demonstrations designed to provide engineering and cost data on selected technologies.
This project describes the pilot-scale demonstration of a slurry-phase bioremediation process
performed at the EPA's Test and Evaluation Facility in Cincinnati, OH. The demonstration was used
to obtain information on the ability of this technology to biodegrade creosote contamination in soil
from the Burlington Northern Superfund Site in Brainerd, MN. The data obtained from this
demonstration will be used in part to develop Best Demonstrated Available Technology standards for
contaminated soil in support of the land disposal restrictions under the 1984 Resource Conservation
and Recovery Act Hazardous and Solid Waste Amendments. The data will also be used to evaluate
this technology for its applicability in remediating selected Superfund sites. The demonstration is
documented in two reports: a previously published Technology Evaluation Report describing the
demonstration activities and laboratory results, and this Applications Analysis Report, which provides
an interpretation of the data and discusses the potential applicability of the technology.
A limited number of copies of this report will be available at no charge from EPA's Center for
Environmental Research Information, 26 Martin Luther King Drive, Cincinnati, OH 45268 Requests
should include the EPA document number found on the report's cover. When the limited supply is
exhausted, additional copies can be purchased from the National Technical Information Service
Ravensworth Building, Springfield, VA 22161, (703) 487-4600. Reference copies will be available
at EPA libraries in the Hazardous Waste Collection.
E.Timothy Oppelt, Director
Risk Reduction Engineering Laboratory
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Abstract
In support of the U.S. Environmental Protection Agency's (EPA) Superfund Innovative Technology
Evaluation (SITE) Program, a pilot-scale demonstration of a slurry-phase bioremediation process was
performedMay 1991 at the EPA's Test & Evaluation Facility in Cincinnati, OH. In this 12-wk study,
acreosote-contaminated soil from the Burlington Northern Superfund site in Bramerd, MN, was used
to test the slurry-phase bioreactors. During the demonstration, five 64-L stainless-steel bioreactors,
equipped with agitation, aeration, and temperature controls, were used. The pilot-scale study
employed a 30% soil slurry, an inoculum of indigenous polynuclear aromatic hydrocarbon (PAH)
degraders, an inorganic nitrogen supplement in the form of NH4-N, and a nutrient broth containing
potassium, phosphate, magnesium, calcium, and iron.
During the course of the study, levels of soil-bound and liquid-phase PAHs, total petroleum
hydrocarbons, nutrients, pH, dissolvedoxygen, temperature, toxicity, and microbial populations were
monitored. The total percent reduction of soil-boundPAHs over 12-wk of testing ranged from greater
than 72% to greater than 90% (average reduction exceeded 87%).
This Applications Analysis Report presents an evaluation of treatment efficiency and technical and
economk: applicability of this technology based on results from the SITE demonstration and from
three case studies. The conclusions from the pilot-scale SITE demonstration and case studies are (1)
the slurry-phase biological treatment can be used to effectively remediate soils and sludges contami-
nated with polynuclear aromatic hydrocarbons (PAHs) to below regulatory standards, (2) tiie
technology can potentially be implemented at nearly any site with applicable wastes, and (3) costs tor
the technology range from about $50 to $250 per yd3 and largely depend on site-specific factors such
as the type of contamination, quantity of waste, emission control needs, materials handling, and
cleanup criteria.
IV
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Contents
Notice _
Foreword ...
m
Abstract .
* iv
Figures
Tables
Abbreviations and Symbols
Acknowledgments
1. Executive Summary ,
Introduction _ ,
Overview of the SITE Demonstration l
Results of the SITE Demonstration 2
Results from the Case Studies 2
Economics ~
Conclusions 2
2. Introduction ,
Purpose, History, and Goals of the SITE Program , 3
SITE Program Reports 3
Key Contacts ; 4
3. Technology Applications Analysis 5
Introduction , ,
Effectiveness of Slurry-Phase Bioremediation 5
SITE Demonstration Results 5
Results of Three Case Studies <-
o
Performance Evaluation of Slurry-Phase Bioremediation 7
Slurry-Phase Treatment Options 7
In-Situ Treatment _ 7
Ex-Situ Reactor System : g
Factors Influencing Effectiveness 9
Waste Characteristics o
Operating Parameters 9
Maintenance Requirements , 1
Site Characteristics . 1
Materials Handling Requirements tl
Personnel Requirements
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Contents (continued)
Health & Safety Concerns 13
Potential Community Exposures 13
n
Regulatory Requirements J
Comprehensive Environmental Response, Compensation, and Liability Act 13
Resource Conservation and Recovery Act 13
Occupational Safety and Health Act of 1970 14
Clean Air Act -15
Clean Water Act 15
The Future of Bioslurry Technology 15
4. Economic Analysis
Introduction "
Site-Specific Factors Affecting Cost 17
18
Basis of Economic Analysis 10
19
Cost Categories
19
Site Preparation Costs
Permitting and Regulatory Costs 19
19
Capital Equipment Costs
Startup and Fixed Costs
90
Labor Costs zu
20
Supply and Consumable Costs
Utility Costs - 20
Effluent Treatment and Disposal Costs 20
Residuals and Waste Shipping, Handling, and Transportation Costs -20
90
Analytical Costs zu
Equipment Repair and Replacement Costs 20
*71
Site Demobilization Costs
21
Case Study Costs
23
References
25
Appendices
A. Description of Treatment Technology 25
B. SITE Demonstration Results "
C. Case Studies 37
References for Appendices "
VI
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Figures
1. In-situ slurry-phase bioremediation 7
2. Tank-based slurry-phase bioremediation g
3. Slurry-phase treatment process flow chart 19
A-l EIMCO Biolift reactor 26
B-l Burlington Northern Superfund site, Brainerd, MN 30
B-2 Demonstration reactor setup 31
B-3 Total PAH levels in reactor soil samples as determined by GC/MS 35
B-4 Total PAH levels in reactor soil samples as determined by HPLC 35
C-l Plan view of slurry-phase reactor ; 30
C-2 Cross-section of slurry-phase reactor 33
C-3 Sheridan waste slurry bioremediation process schematic 45
C-4 French Limited site schematic 55
C-5 Benzene by composite number _ 5^
C-6 Vinyl chloride by composite number 57
C-7 Total PCBs by composite number 57
C-8 Arsenic by composite number 5g
C-9 Benzo(a)pyrene by composite number 5g
vu
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Tables
1. Standard Bioslurry Reactor Operating Conditions 10
2. Estimated Costs Associated with Slurry-Phase Reactor Systems 18
3. Costs for Slurry-Phase Biotreatment of 1-Million-Gallon of Refinery Waste:
RETEC Demonstration 21
4. Costs for French Limited Superfund Site Remediation: French Limited Task Group, Inc.
Demonstration 22
B-l Concentrations of Total, 2- and 3-Ring, and 4- through 6-Ring PAH Levels in
Soil Samples Determined by GC/MS 32
B-2 Percent Degradation of Total, 2- and 3-Ring, and 4- through 6-Ring PAH Levels in
Soil Samples, Determined by GC/MS < - 32
B-3 Concentrations of Total Petroleum Hydrocarbons (TPH) in Soil 33
B-4 Percent Total, 2- and 3-Ring, and 4- through 6-Ring PAH Degradation Rates in
Soil Samples Analyzed by HPLC 34
C-l Analytical Results for Percent Solids, Nutrients, and Bacterial Enumerations 41
C-2 Reactor PAH Mass Balance 42
C-3 Waste Sludge and Excavated Soil Conventional Analyses 44
C-4 Chemical Classification of Feed Streams 44
C-5 Personal Protective Equipment Requirements 4?
C-6 Summarized Test Results of 30-Day Residence Time Load Condition 48
C-7 Summarized Test Results of 15-Day Residence Time Load Condition 48
C-8 Summarized Mass Flow Rates for 30-Day HRT Load Condition Test Period 49
C-9 Summarized Mass Flow Rates for 15-Day HRT Load Condition Test Period 49
C-10 Measured Range of Ambient Air Concentrations at Four Sheridan Perimeter
Monitoring Locations Versus the Consent Decree Limits 51
C-l 1 Maximum Measured Emission Rates of VOCs (BETXS) for All Sources and
Activities in This Study 51
C-12 Analytical Methods and Their Scheduling Used to Evaluate Variables of the
Slurry Bioremediation Process 52
C-13 Contaminant Concentrations in Sludge, French Limited Site 59
C-14 French Limited Air Monitoring Response Plan 62
vui
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Abbreviations and Symbols
AAR
ARAR
BETXS
BOAT
BN.
BOD
CERCLA
CPU
CFR
C:N:P
COD
COI
CS&D
CSTR
DO
ECOVA
EPA
FLTG
ft
g
gal
GC/MS
gpm
hr
hp
HPLC
HRT
HSWA
in.
IT
kw
L
LDR
LOD
m
mg/kg
Applications Analysis Report
applicable or relevant and appropriate
requirements
benzene, ethylbenzene, toluene, xylene,
styrene
best demonstrated available technology
Burlington Northern
biochemical oxygen demand
Comprehensive Environmental Response,
Compensation, and Liability Act
colony forming units
Code of Federal Regulations
carbon:nitrogen:phbsphorus ratio
chemical oxygen demand
contaminant of interest
contaminated soil and debris
continuously stirred tank reactors
dissolved oxygen
ECOVA Corporation
U.S. Environmental Protection Agency
French Limited Task Group, Inc.
feet/foot
gram(s)
gallon(s)
gas chromatography/mass spectroscopy
gallons per minute
hour
horsepower
high performance liquid chromatography
hydraulic retention time
Hazardous and Solid Waste Amendments
inch(es)
IT Corporation
kilowatt
liter
Land Disposal Restrictions
limit of detection
meter(s)
milligram per kilogram
mL
NCP
NPDES
OSHA
OUR
OVM-PID
PAH
PCB
PEL
POTW
PPE
ppm
RA
RCRA
RFP
ROD
SARA
SCOD
SITE
SVOC
T&E
TER
THC
TKN
TM
TPH
TSCA
TSS
TVSS
VOC
wk
w/v
w/w
yd
micrometer
milliliter
National Contingency Plan
National Pollutant Discharge Elimination
System
Occupational Safety and Health
Administration
oxygen uptake rate
organic vapor meter-photo ion detector
polynuclear aromatic hydrocarbons
polychlorinated biphenyls
permissible exposure limit
publically owned treatment works
personal protective equipment
parts per million
remedial action
Resource Conservation and Recovery Act
request for proposal
record of decision
Superfund Amendments and
Reauthorization Act
soluble chemical oxygen demand
Superfund Innovative Technology Evaluation
semivolatile organic compounds
Test and Evaluation Facility
(USEPA, Cincinnati, OH)
Technology Evaluation Report
total hydrocarbons
total kjeldahl nitrogen
Trade Mark
total petroleum hydrocarbons
Toxic Substance Control Act
total suspended solids
total volatile suspended solids
volatile organic compounds
week(s)
weight per volume
weight per weight
yard
IX
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Acknowledgments
This report was prepared by IT Corporation (Cincinnati, OH) under the direction and coordination
of Dr. Ronald Lewis, Superfund Innovative Technology Evaluation (SITE) Technical Project
Manager, U.S. Environmental Protection Agency (EPA), Risk Reduction Engineering Laboratory,
Cincinnati, OH. The information on case studies was provided by Dr. Alan Jones of ECOVA
Corporation, Dr. Frank Castaldi of Radian Corporation, Mr. Randolph Kabrick of RETEC, and Mr.
Richard Sloan of French Limited Task Group, Inc. Dr. Michael Taylor of IT Corporation was the
Senior Reviewer.
Mr. Majid Dosani and Ms. Jennifer Platt of IT Corporation, Cincinnati, OH, prepared this report for
EPA's SITE Program under Contract No. 68-C9-0036.
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Section 1
Executive Summary
Introduction
IT Corporation (IT) in conjunction with ECO VA Corpora-
tion (ECOVA) evaluated ECOVA's slurry-phase bioreme-
diation technology under U.S. Environmental Protection
Agency's (EPA) Superfund Innovative Technology Evalu-
ation (SITE) program. The technology demonstration was
conducted at EPA's Test and Evaluation (T&E) Facility in
Cincinnati, OH, from May 8 through July 31,1991.
In this process, the soil is suspended in water to obtain a
pumpable slurry, then pumped into a 64-L, continuously
stirred tank reactor (CSTR). The CSTR can be supple-
mented with air, nutrients, or as was the case in this demon-
stration, an inoculum of microorganisms to enhance the
biodegradation process. This treatment method has several
advantages because an optimal environment for biodegra-
dation of the organic contaminants can be maintained with
a high degree of reliability. Biological reactions can pro-
ceed at accelerated rates in a slurry system because limiting
nutrients can be supplied and contact between contami-
nants and microorganisms can be increased by effective
mixing and maintenance of high bacterial populations.
The objectives of the technology demonstration were:
1. Evaluate the ability of slurry-phase bioreactor to de-
grade polynuclear aromatic hydrocarbons (PAHs)
presentincreosote-contaminatedsoil from the Burlington
Northern (BN) Superfund site in Brainerd, MN.
2. Evaluate the performance of the slurry-phase bioreac-
tor process, its removal efficiencies for PAHs, and the
overall effect on soil toxicity.
3. Determine the air emissions resulting from the volatil-
ization of the reactor contents during treatment.
4. Provide technical data to assistEPA in establishing best
demonstrated available technology (BDAT) standards
for the level of treatment required before land disposal.
5. Develop information on capital and operating costs for
the full-scale treatment system.
The purpose of this report is to present information from the
SITE demonstration and from three case studies to evaluate
the technical and economic applicability of slurry-phase biore-
mediatipn technology to the remediation of soil- and sludge-
bound hazardous contaminants. Section 2 of this report
presents an overview of the SITE program. Section 3 dis-
cusses information relevant to the technology's application,
including site characteristics, waste characteristics, operation
and maintenance requirements, materials handling require-
ments, personnel requirements, potential community expo-
sures, and potentially applicable environmental regulations.
Section 4 summarizes the costs associated with implement-
ing the technology. Appendices A through C include: a
description of treatment technology, SITE demonstration re.
suits, and three case studies.
Overview of the SITE Demonstration
The slurry-phase demonstration technology was developed
and tested by ECOVA Corporation at the bench-scale level
at ECOVA's laboratories in Redmond, WA. IT, working
with ECOVA, developed materials handling and scaleup
parameters during the pilot-scale SITE demonstration.
Five 64-L (working volume) EIMCO Biolift reactors,
operated in batch mode, were used to test the degradation
of soil-bound PAHs in a biologically active soil slurry.
Creosote-contaminated soil from the BN site was passed
through a 1/2-in. screen to remove oversized material. Af-
ter screening, the soil was mixed with water to form a 30%
slurry. The slurry was then poured into a ball mill, milled
to reduce the particle size, and screened on exit from the
ball mill through a No. 8 sieve to produce a slurry with a
grain size distribution suitable for charging EIMCO Biolift
reactors. Following milling, 66 L of the soil slurry was
transferred into each of the five reactors.
After the reactors were charged with the soil slurry, a concen-
trated inoculum of indigenous bacteria was added to each of
the reactors. For optimal microbial activity, nutrient amend-
ments, including ammonia, phosphate, magnesium, calcium,
iron, and ammonium molybdate, were added to the reactors.
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Sampling and analysis activities performed during the pilot-
scale demonstration involved collecting composite samples
from each of the reactors for pre- and posttreatment analyses
and sampling throughout the demonstration to monitor sys-
tem operation. During the demonstration, soil-bound and
liquid-phase PAHs, total petroleum hydrocarbons (TPHs),
nutrients, pH, dissolved oxygen (DO), temperature, toxicity,
microbial phenotypes, and microbial activity were moni-
tored. Composite samples were collected from three sam-
pling ports located along the side of each reactor at different
vertical locations. Soil-slurry samples were taken from the
reactors over a 12-wk period. In the ninth week of operation,
four of the bioreactors were reinoculated with an additional 125
mL of the inoculum to stimulate the PAH degradation process.
Results of the SITE Demonstration
The pilot-scale demonstration achieved significantly re-
duced PAH concentrations in the soil matrix. Results
indicate that an average of greater than 87% of total PAHs
were removed over all five operating reactors after the 12th
week of the demonstration period. Air samples taken
continuously during the first 5 days and thereafter periodi-
cally through the ninth week of the demonstration show
that volatilization of organics was initially significant.
Semivolatile emissions peaked at 38.9 mg/m3 on the first
day of operation. By the fifth day of operation, volatiliza-
tion of organic chemicals decreased to near or below detec-
tion limits. Microtox analysis, performed over the course
of the study to monitor toxicity levels of the slurried soil,
showed that toxicity also decreased to low levels during
slurry-phase biological treatment.
Results from the Case Studies
Information on the technology's performance at three addi-
tional hazardous waste sites was evaluated to provide addi-
tional performance data.
RETEC Corporation performed a 56-day, 1-million-gallon
slurry-phase tank demonstration for a major Gulf Coast
refinery. The concentration of most PAH species was
reduced by greater than 90% in 56 days of treatment.
A Radian Corporation pilot-scale remediation study on
petrochemical waste-contaminated soils and sludges at a
Texas site employed four 10,000-L CSTRs. At HRTs of
17.5 and 42 days of treatment more than 80% removal was
observed for most compounds; removals of many com-
pounds approached 100%.
The French Limited Task Group, Inc. (FLTG) has imple-
mented in-situ, slurry-phase bioremediation at the French
Limited Superfund site in Crosby, TX. Preliminary results
indicate that constituents of interest are being reduced and
that treatment objectives will be achieved if not exceeded.
Economics
Economic analysis of this technology is based on cost
information provided by ECOVA and case study costs
provided by RETEC and FLTG. (At the time of writing,
cost information for the study performed by Radian was not
available.) Conclusions of the economic analysis are:
Costs are site-specific.
Costs range typically from $50 to $250/yd3.
Labor costs associated with materials handling and
operation can account for more than half of the cost
incurred.
Conclusions
Slurry-phase bioremediation technology may be broadly
applicable for treating soils and sludges contaminated with
organic, biodegradable hazardous wastes, and it is a cost-
effective alternative to cumbersome and often less-effec-
tive treatment methods. Advantages include onsite treat-
ment and, in some cases, in-situ treatment, thus minimizing
materials handling activities. Also, slurry-phase bioreme-
diation can be implemented on sites with complex mixtures
of organic wastes. The cost of slurry-phase implementa-
tion ranges from about $50 to $250/yd3; the cost depends
largely on site/waste characteristics and remediation goals.
Because the fate of recalcitrant organics biodegraded in the
slurry-phase technology is largely unknown, future studies
should include the fate of degradation products and lexico-
logical evaluation of bioremediated soils and sludges.
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Section 2
Introduction
This section presents information about the SITE Program,
discusses the purpose of this Applications Analysis Report,
and provides a list of key personnel who may be contacted for
additional information.
Purpose, History, and Goals of the SITE
Program
In response to the Superfund Amendments and Reauthoriza-
tion Act of 1986 (SARA), the EPA Office of Solid Waste and
Emergency Response and Office of Research and Develop-
ment established a formal program called the SITE Program
to promote the development and use of innovative technolo-
gies to clean up Superfund sites across the country. The
primary purpose of the SITE Program is to enhance the
development and demonstration of innovative technologies
applicable to Superfund sites so as to establish their commer-
cial availability.
The SITE Program comprises four major elements:
Demonstration Program
Emerging Technologies Program
Measurement and Monitoring Technologies Program
Technology Transfer Program
The objective of the SITE Demonstration Program is to
develop reliable engineering performance and cost data on
selected technologies so that potential users can evaluate each
technology's applicability to a specific site and compare it
with the applicability of other alternatives. Demonstration
data are used to assess the performance and reliability of the
technology, the potential operating problems, and approxi-
mate capital and operating costs.
Technologies are selected for the SITE Demonstration Pro-
gram through annual requests for proposal (RFPs). EPA
reviews proposals to determine the technologies with the
most promise for use at Superfund sites. To qualify for the
program, a new technology must have been developed to
pilot- or full-scale and must offer some advantage over exist-
ing technologies.
Once EPA has accepted a proposal, the Agency and the
developer work with the EPA regional offices and state
agencies to identify a site containing wastes suitable for
testing the capabilities of the technology. The developer is
responsible for demonstrating the technology at the selected
site and is expected to pay the costs to transport, operate, and
remove the equipment The EPA is responsible for project
planning, sampling and analysis, quality assurance and qual-
ity control, preparing reports, and disseminating information.
The Emerging Technology Program of the SITE Program
fosters further investigation and development of treatment
technologies that are still at the laboratory scale. The third
component of the SITE Program, the Measurement and Moni-
toring Technologies Program, provides assistance in the de-
velopment and demonstration of innovative measurement
and monitoring technologies.
In the Technology Transfer Program, technical information
on technologies is exchanged through various activities that
support the SITE Program: Data from the Demonstration
Program and existing hazardous waste remediation daja are
disseminated in an effort to increase awareness of alternative
technologies available for use at Superfund Sites.
S/TE Program Reports
The results of each SITE demonstration are incorporated in
two documents: the Technology Evaluation Report (TER)
and the Applications Analysis Report (AAR). The TER
provides a comprehensive description of the demonstration
and its results. This report is intended for engineers and
scientists prforming a detailed evaluation of the technology
for aispecific site and waste situation. The purpose of these
technical evaluations is to obtain a detailed understanding of
the performance of the technology during the demonstration
and to ascertain the advantages, risks, and costs of the tech-
nology for the given application. This information is used to
produce conceptual designs in such detail that cost estimates
can be prepared.
The purpose of the AAR is to estimate the Superfund
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applications and costs of a technology based on all available
data. The report compiles and summarizes the results of the
SITE demonstration, the vendor's design and test data, and
other laboratory and field applications of the technology. It
discusses the advantages, disadvantages, and limitations of
the technology. Estimated costs of the technology for differ-
ent applications are based on available data from pilot- and
full-scale applications. The report discusses factors, such as
site and waste characteristics, that have a major effect on
costs and performance.
The amount of available data for the evaluation of an innova-
tive technology varies widely. Data may be limited to labora-
tory tests on synthetic wastes or may include performance
data on actual wastes treated at pilot- or full-scale. The
conclusions regarding Superfund applications that can be
drawn from a single field demonstration are also limited. A
successful field demonstration does not necessarily ensure
that a technology will be widely applicable or fully developed
to the commercial scale. The AAR attempts to collate avail-
able information and draw reasonable conclusionsa docu-
ment useful to those considering the technology for Super-
fund cleanups. It represents a critical step in the development
and commercialization of the treatment technology.
Key Contacts
Additional information on the pilot-scale demonstration of slurry-phase bioremediation of creosote-contaminated soil at
EPA's T&E or the SITE Program can be obtained from:
Pilot-Scale Demonstration at T&E Facility
Majid Dosani
IT Project Manager
IT Corporation
11499 Chester Road
Cincinnati, OH 45246
(513) 782-4700
The SITE Program
Dr. Ronald Lewis
SITE Technical Project Manager
U.S. Environmental Protection Agency
Office of Research and Development
Risk Reduction Engineering Laboratory
26 West Martin Luther King Drive
Cincinnati, OH 45268
(513) 569-7856
Information on Case Studies
Dr. Frank J. Castaldi, P.E.
Principal Engineer
Radian Corporation
P.O. Box 201088
Austin, TX 78720-1088
(512)454-4797
Dr. Alan B. Jones
Project Scientist
ECOVA
18640 ME 67th Court
Redmond, WA 98052
(206) 883-1900
Randolph M. Kabrick
Principal
RETEC
1301 West 25th Street
Suite 406
Austin, TX 78705
(512) 477-8661
Richard L. Sloan
Project Manager
French Limited Task Group, Inc.
1024 Gulf Pump Road
Crosby, TX 77532
(713) 328-1648
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Section 3
Technology Applications Analysis
Introduction
This section addresses the applicability of slurry-phase
bioremediation technology for treating contaminated soils
and sludges. The technology's applicability is presented
based on results from the pilot-scale demonstration per-
formed under the SITE program and from supporting infor-
mation on field-scale remediations provided by the vendors.
The effectiveness of the slurry-phase technology is sum-
marized in this section, followed by treatment options,
factors influencing its effectiveness, mechanical require-
ments, site characteristics, materials handling requirements,
personnel requirements, health and safety concerns, poten-
tial community exposure, regulatory requirements, and>the
future of bioslurry technology. Three case studies included
in Appendix C of this report are:
RETEC's study of a 1-million-gallon petroleum sludge
tank;
Radian's study of four, 10,000-L petroleum sludge/
soil CSTRs; and
FLTG's remedial action of an in-situ 34-milIion-gal-
lon sludge/subsoil impoundment.
Effectiveness of Slurry-Phase
Bioremediation
The effectiveness of the slurry-phase bioremediation tech-
nology presented in this section is based on results from the
SITE demonstration and the three case studies of the tech-
nology.
SITE Demonstration Results
The SITE demonstration was performed by FT in conjunction
with ECOVA at EPA's T&E Facility in Cincinnati, OH, during
May through July 1991. During the pilot-scale demonstration,
creosote-contaminated soil from the BN Superfund Site in
Brainerd, MN, was used in evaluating slurry-phase technology.
The objectives of the technology demonstration performed
under the SITE program were:
1. Evaluate the ability of the slurry-phase bioreactor to
degrade PAHs present in creosote-contaminated soil
from the BN Superfund Site in Brainerd, MN.
2. Evaluate the performance of slurry-phase bioreactor
and its removal efficiencies for PAHs and.soil toxicity.
3. Determine the air emissions during biodegradation in
the reactor.
4. Provide technical data to assist EPA in establishing
BOAT standards for the level of treatment required
before land disposal.
5. Develop information on capital and operating costs for
the full-scale treatment system.
In this demonstration, five 64-L EIMCO reactors were
charged with a 30% slurry (dry weight) composed of
screened and milled contaminated soil suspended in water.
Air, nutrients, and microbial additions were added as supple-
ments to the slurry. The concentration of PAHs and toxic-
ity of the slurry were monitored weekly for 12 wk.
Appendix B summarizes the demonstration test results.
Key findings of the demonstration are given below.
PAH Removal Efficiency
The pilot-scale biodegradation demonstration significantly
reduced PAH concentrations in the soil matrix. An average
of greater than 87% of total PAHs were degraded in the five
operating reactors after the 12th week of the demonstration
period. The initial concentration of creosote PAHs was 2460
mg/kg, as determined by gas chromatography/mass spectros-
copy (GC/MS) method (SW-846, Method 8270).1 After 12
wk of treatment, the concentration of the 2- and 3-ring
compounds had declined by >98% from 1490 mg/kg to <35
mg/kg. The concentration of the 4-, 5-, and 6-ring com-
pounds declined 72% from 960 mg/kg to <270 mg/kg. The
more complete degradation of the lower molecular-weight
PAHs is probably due in part to higher bioavailability of 2-
and 3-ring PAHs compared to the 4- through 6-ring PAHs.
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Slurry Toxlcity Reduction
Although monitoring contaminant levels by analytical meth-
ods can show removal of contaminants, such methods do
not directly indicate the effect of residual contaminants and
metabolites in the treated slurry on biological systems.
Microtox analysis was performed over the course of the
study to monitor toxicity levels of the treated slurry to
determine if toxicity decreased during slurry-phase bio-
logical treatment. The toxicity of the treated soil declined
markedly over the 12 wk. After 4 wk of treatment, evi-
dence of toxicity was obtained for each of the five reactor
slurries; at week 9, Reactors 5 and 6 still appeared to have
some residual toxicity. However, by week 10, either mar-
ginal or no toxicity was associated with the slurries.
Results of Air Monitoring
For the first few days of the demonstration, air emissions
were continuously monitored for total hydrocarbons (THCs),
semivolatile organics compounds (SVOCs), and volatile
organics compounds (VOCs). The VOCs and SVOCs
were then monitored periodically through week 9. THC
emissions data show high emissions during the first 2 days
of process operation, followed by a steady decline to base-
line recordings by the fifth day of operation. The VOC
volatilization was high the first 2 days of operation and
decreased to near analytical detection limits by the third
day of operation. SVOC emissions (naphthalene, 2-meth-
ylnaphthalene, acenaphthylene, acenaphthene, dibenzofuran,
fluorene, phenanthrene, and anthracene) were detectable
during the first 4 days of sampling. Beginning the sixth day
of operation, very small quantities (at or below detection)
of semivolatiles were found.
Results of Three Case Studies
Three, comparatively large-scale slurry-phase remediations
performed by other vendors are offered in this report as
case studies (summarized in Appendix C). A brief sum-
mary of the effectiveness of these operations is presented
below.
In the first case study, RETEC Corporation conducted a 56-
day, single-batch treatment of petroleum sludge for a major
Gulf Coast refinery. For the study, an onsite 1-million-
gallon, abandoned concrete clarifier was retrofitted to be
operated as a bioreactor. Sludge from an impoundment
onsite was pumped to the bioreactor and was mixed with
water to create a 10% slurry. Mixing and aeration of the
slurry were provided by float-mounted mixers and aerators.
Hydrocarbon-degrading microorganisms were used to seed
the slurry; nutrient additions and pH adjustments were
made periodically as indicated by system monitoring.
The concentrations of most PAH species decreased by
greater than 90% in 56 days of treatment Because the
technology requires high mixing and aeration rates, the loss
of volatile hydrocarbons due to volatilization was significant.
In the second case study, Radian conducted a pilot-scale
remediation study of soils and sludges contaminated with
petrochemical waste at a site in Texas. Three aerobic
10,000 L CSTRs were operated in a continuous-flow op-
eration with a target hydraulic retention time (HRT) of 15
and 30 days. Hazardous waste constituents in the soils and
sludges included PAHs; amines; benzene, ethylbenzene,
toluene, xylene, and styrene (BETXS); ketones; phenols;
polychlorinated biphenyls (PCBs); phthalates; and volatile
chlorinated organics. After actual system volumetric resi-
dence times of 17.5 and 42 days of treatment, more than
80% removal was observed for most compounds; removals
of many compounds approached 100%.
In Radian's study, data indicate that removal rates for most
compounds were lower for the 15-day HRT than for the 30-
day HRT test as a result of both operating temperature
(26.3°C for the 15-day HRT test vs 33.3°C for the 30-day
HRT test) and higher contaminant load conditions during
the 15 day HRT test. Due to the higher contaminant load of
the 15-day HRT test, however, the total mass reduction of
priority pollutants was higher for the 15-day HRT test than
the 30-day HRT test. In addition, a much smaller percent
of volatile hydrocarbons was lost to volatilization during
the 15-day test as a result of the lower average operating
temperature and the comparatively lower vapor pressures
of the contaminants.
In the third case study FLTG conducted a slurry-phase
bioremediation at the French Limited site. The French
Limited site consists of a 7.3-acre, 34-million-gallon la-
goon in which petroleum wastes were deposited for several
years. Slurry-phase bioremediation was chosen as the
remedial technology after the process applicability was
verified through a series of laboratory, pilot, and in-situ
tests.
For full-scale, in-situ treatment, the lagoon was divided
initially into two cells of equal 17-million-gallon volumes,
using a sheet pile wall placed across the lagoon. Aeration
and mixing equipment were installed in the first cell under-
going bioremediation. Pure oxygen is introduced into the
lagoon with the use of the Linde Mixflo Oxygenation
System. The Linde system allows optimum aeration and
mixing of lagoon contents with minimum surface distur-
bance; this minimizes volatilization of volatile organics.
Horizontal flow mixers submerged below the surface pro-
vide additional mixing and allow bottom solids suspension.
Skid-mounted dredges transfer contaminated subsoil into
the active cell mixed liquor. Amendments to the system
include lime to maintain a neutral pH, and diammonium
and monosodium phosphate as nutrient supplements. Oxy-
gen uptake rate (OUR), total suspended solids (TSS), total
volatile suspended solids (TVSS), and heterotrophic mi-
crobial plate counts are monitored to evaluate the
technology's performance. Preliminary results indicate
-------
that constituents of interest are being reduced and treatmen t
objectives will be achieved if not exceeded.
Performance Evaluation of Slurry-Phase
Bioremediation
Slurry-phase bioremediation technology has, during re-
cently completed studies, been found to be an effective as
well as economically feasible treatment for soil and sludges
contaminated with certain organic, biodegradable hazard-
ous wastes. Compounds that have been tested with bioslurry
technology include PAHs and other elements of creosote,
pesticides, diesel, and petroleum products including those
of high molecular weight. Advantages include onsite treat-
ment, and often, in-situ treatment, thus minimizing materi-
als handling activities. The overall results achieved through
application of this technology, however, depend on the
experience and knowledge of the operators involved. Suc-
cessful implementation of bioslurry technology, as with
many bioremediation processes, requires far more exper-
tise than merely combining soil and water in a tank reactor
and hoping for the best. Proper and thorough preparation
and knowledge of the soil characteristics, the contami-
nants, and the dynamics of the biodegradative process oc-
curring within the slurry are important. Bench- or pilot-
scale treatability studies must initially be performed to
determine the feasibility of the process. Optimization of
the process is also necessary to achieve the lowest possible
retention time to minimize labor cost for the entire project.
Performance of this technology depends not only on the
nature of the contaminants but also on site age, contaminant
concentration in the solid matrix, soil type, and the presence
of other organic materials, hazardous or otherwise, that could
potentially compete with the contaminant as metabolic sub-
strates for the bacteria. Bioslurry treatment may be sufficient
in and of itself to reduce levels of certain biodegradable
hazardous materials to regulatory clean-up levels. However,
the range of organic contaminants which can be treated using
this process has not yet been established.
Slurry-Phase Treatment Options
Various process configurations as indicated in the above
discussion have been successfully implemented in the slurry-
phase treatment of soils and impoundment sludges:
in-situ batch treatment of the entire sludge impound-
ment in a single operation or by sections;
ex-situ treatment of soils and sludges in a sequenced
batch reactor or a continuously fed, stirred-tank reactor.
A brief description of each of these process options is
presented in the following subsections.
In-Situ Treatment
Small sludge impoundments or lagoons (<2 acres) can be
considered for remediation by in-situ batch treatment in a
single operation. Impoundments larger than 2 acres, how-
ever, may be inhomogeneous and may require in-situ treat-
ment by sections or ex-situ treatment by dredging and
transfer of sludge to a smaller sequenced-batch or to con-
tinuous treatment operations. Tank-based reactor systems
may not be suitable for treating impoundment sludge be-
cause the necessary HRTs are too long (20 to 30 days) and
the corresponding tank volume requirements are high (i.e.,
> 106 gal) for economically practical sludge feed rates. Fig-
ure I2 shows one type of in-situ sludge impoundment pro-
cess.
For contaminated sludge, the geometry and depth of an
impoundment, the nature and integrity of the impoundment
liner (if present), characteristics of the sludge, and thick-
ness of the sludge layer all must be considered in optimiz-
ing the engineering design for slurry-phase treatment Mix-
ing and treatability tests can be performed on representa-
tive samples of waste from a particular impoundment to aid
in the engineering design. A total solids, content of between
5% and 20% is typical for in-situ impoundment closures. If
the thickness of the sludge layer precludes complete sus-
Nutrients
Aeration
I Microorganisms
\
X c=
Water 1
:=> <5lii/HriQ . 1 *
' '
/
yT
Figure 1.2 In-situ slurry-phase bioremediation.
Source: Derrick Ross, 1990/91.
-------
pension and treatment in a single batch operation, then in-
situ treatment of the material may require isolating a smaller
section of the impoundment for use as a treatment cell
where the solids loading can be controlled. Alternatively,
the material can be dredged from the impoundment and
treated in a separate, sequenced-batch or continuous-reac-
tion system.
Bioremediation of impoundment sludges by slurry-phase
biotreatment will often involve a sequence of unit opera-
lions. In this regard, the technology is quite similar to
conventional activated sludge treatment of municipal or
industrial wastewaters where primary solids removal, equal-
ization, and clarification operations are fundamental to the
overall treatment scheme. The only situation in which
multiple unit operations are not needed is for strictly in-situ
applications where treated sludge residuals are destined to
remain in place. Even here, dredging of contaminated soil
may be needed so the soil can be treated simultaneously
with the sludge. Removal of residual water and in-situ
solidification and capping of residual solids may also be
required.
Ex-Situ Reactor System
Tank-based reactor systems are used to treat contaminated
soils when excavation is required. A schematic representa-
tion of a tank-based process is shown in Figure 2.3 For
tank-based treatment of soil, the reactor is operated in
either of two basic modes: continuous-flow or batch. The
many important factors in selecting the reactor mode in-
clude reaction kinetics, soil type, diffusibility of the con-
taminants, bacterial phenotypes, etc. With the continuous-
flow reactor, a feed stream containing a high concentration
of contaminants is fed continuously into a steady-state
slurry containing very low levels of contaminants, thereby
instantaneously diluting the feed stream. The concentration
of contaminants in the reactor are maintained at the same
level as the concentration of contaminants in the effluent.
This is done by initially charging and then operating the
reactor in a recirculation mode. In this mode, the bacteria
will degrade the contaminants down to the concentration
suitable for discharge. At this point, the reactor is changed
to a continuous-flow mode complete with a contaminated
influent stream and a clean effluent stream. As the con-
taminated influent enters the reactor, it is immediately
diluted by the large volume of clean reactor contents.
This process allows a continuous feed supply to the flour-
ishing bacterial population but with a much lower concen-
tration of hazardous compounds. As a matter of reaction
kinetics, this process design also proceeds best with a zero
order reaction. That is, the rate of the degradation of the
hazardous material depends entirely on the concentration
of the bacteria and not on the concentration of the hazard-
ous material. Thus, maintaining growth conditions for a
vigorous population of bacteria results in the highest pos-
sible rate of biodegradation of the hazardous compounds,
regardless of the concentration of the compounds in the
slurry. This information can only be determined in the
laboratory optimization study. Several advantages accrue
from reactor operation in the continuousrfeed mode. This
process does not require a system of holding tanks for each
successive batch of slurry to be treated. There is also an
instantaneous dilution of any toxic component in the feed-
stream and a stable, steady-state condition that fosters a
Excavation
Screening
Nutrients
Aeration
Microorganisms
Dewatered
Slurry
Dewatering
Slurry Bioreactors
Figure 2.3 Tank-based slurry-phase bloremediation process.
Source: Derrick Ross, 1990/91.
-------
stable distribution of bacterial population levels is main-
tained in the reactor.
Batch-style reactors are useful for sites with small amounts
of material to be treated or when the reaction kinetics of the
degradation are first order. For example, if the experimen-
tally determined reaction rate depends primarily on con-
centration of the hazardous material, then a first order (or
pseudo first order) reaction is indicated (thus, the rate will
proceed more quickly, the higher the concentration of haz-
ardous material). To optimize reactor use and reduce total
project time, batch-style reactors also, necessarily, require
holding tanks in which to prepare the succeeding slurry
batch that can be immediately pumped into the reactor
when the preceding batch is drained.
Considerable differences can exist among applications in
which slurry-phase biotechnology is a viable remedial op-
tion. For example, the physical and chemical nature of the
waste solids, volumes requiring treatment, remedial objec-
tives, and various site characteristics all influence optimal.
system design. Therefore, selection of the most appropri-
ate operational sequence must be determined on a case-
specific basis.4
Factors Influencing Effectiveness
Several factors influence the effectiveness of slurry-phase
treatment technology. These factors can be grouped into
three categories: (1) waste characteristics, (2) operating
parameters, and (3) maintenance requirements. Each of
these is discussed below.
Waste Characteristics
Waste is defined here as the combination of the chemical
contaminants themselves and the solid matrix onto which
the contaminants are adsorbed. The essential, rate-limiting
step in many bioslurry treatment processes that involve
hydrophobic contaminants is the desorption of the con-
taminants from the solid matrix and their dissolution into
the aqueous phase. Once present in the aqueous phase,
suspended bacteria that utilize the contaminant compounds
for carbon, energy, or both, readily metabolize the material.
A number of bom contaminant and matrix characteristics
will affect the efficacy and even the feasibility of bioslurry
technology for remediation.
The most pertinent waste characteristic for this technology
is the biodegradability of the waste contaminants. In addi-
tion, a method must be either known or developed to desorb
the compounds from the solid matrix. The timely desorp-
tion of chemical compounds from the soil or sludge particle
surface (both interior and exterior) is controlled by the
"mass transfer effect" and is a direct reflection of the
maximum path length that a molecule of chemical adsorbed
to the centermost surface of the particle must traverse to
reach the very outside of the particle and dissolve in the
aqueous phase. Because chemicals adsorb and desorb from
the particle surface, the amount of chemical adsorbed to the
solid particle at any given time in a slurry is a function of
the solubility of the chemical in the aqueous phase. Fur-
ther, as bacteria metabolize the dissolved chemical in the
aqueous phase, a gradient is created that continually draws
additional chemical from the soil phase and the aqueous
phase. Severely hydrophobic compounds may require the
assistance of a surfactant or solubilizer.
If a particular chemical is very hydrophobic, its solubility
in the aqueous phase will be quite low and the rate at which
it desorbs can also be quite low. A chemical that is thus
tightly adsorbed onto the particle surface or has a very low
diffusivity through the aqueous medium can prolong the
treatment time and also cause appreciable analytical prob-
lems. Specifically, when an analytical method is not prop-
erly optimized for the chemical and solid matrix, extraction
of the chemical for analytical purposes can be hindered or
only partially successful.
Chemical contaminants, particularly those at a weathered
site (usually an older site that has been exposed to climatic
forces that have removed volatile, accessible, or otherwise
easily degradable components of the hazardous material),
may have entered the interstices of soil particles and "set-up"
over time. Effective desorption of compounds from weath-
ered soil can be an intractable problem. Soils and sludges are
known to have varying degrees of cation- and anion-ex-
change capacity, essentially retarding the efficient desorption
of a chemical compound intended for biodegradation.
Operating Parameters
Operating parameters are those process parameters that can
be varied during treatment to achieve desired removal effi-
ciencies. Many process parameters are measured routinely
during testing to determine the progress of biological deg-
radation of the contaminants of interest and to maintain an
environment that is optimized for biological degradation.
Typical monitoring parameters include levels of the
contaminant(s), nutrient levels, pH, levels of DO, tempera-
ture, toxicity, and enumeration and characterization of mi-"
crobial populations. Table I5 shows typical operating con-
ditions, including acceptable parameter ranges and sug-
gested sampling frequencies. Actual parameters moni-
tored and frequency of monitoring will depend on the
testing goals and resource availability. Following is a
comprehensive list of common start-up and process moni-
toring parameters.
Test Parameters
Physical, chemical, microbiological soil characteristics
of pretreated waste matrix
Indigenous microbial enumeration/characterization and
bioaugmentation
Solids loading (total solids)
-------
Table 15. Standard Slurry-Phase Reactor Operating Conditions
Parameter
Acceptable Range
Suggested Sampling
Frequency
Dissolved oxygen (DO)
PH
Dissolved Oxygen uptake rate (DOUR)
Aqueous phase ammonia-nitrogen
Aqueous phase ortho-phosphate
Headspace total organic carbon (TOC),
using a volatile organics analyzer/PID or
FIDb
Off-gas contaminants of interest (COI)C
Aqueous phase COI concentration
Soil COI concentration
Microbial plate counts
Surfactant concentration
>2.0 ppm Daily
6.0 - 7.5 Daily
>6.0 ppm/hra Daily
>20 ppm Daily
>5.0 ppm 3 x Weekly
Decreasing over time Daily
Decreasing over time Weekly
Decreasing over time Weekly
Decreasing over time Weekly
Increasing initially, Weekly
decreasing toward end
At least 50% of dose Weekly
a Soils containing high concentrations of relatively easy-to-degrade compounds can have
DOURs in excess of 30 ppm/hr. DOUR is site- and condition-specific. The real value of this
parameter as a process control parameter is that it offers a cheap and real-time method of
monitoring the progress of the system microbiology.
b PID = photo ion detector; FID = flame ion detector.
c COI should include site contaminants, cometabolites, and potential intermediates.
Particle size
Viscosity
Mixing rate
Aeration rate
Surfactant foaming potential
Surfactant chemical leaching'potential
Nutrient amendments (i.e., nitrogen, potassium, phos-
phorus, carbon, trace metal salts)
Dissolved oxygen
pH
Temperature
Critical contaminants) and degradation products (gas,
slurry, reaction vessel walls)
Slurry matrix toxicity
Oxygen/carbon dioxide influent (gas)
Oxygen/carbon dioxide effluent (gas)
Dissolved oxygen uptake rate
Heterotrophic plate counts
Microbial characterization
Biochemical oxygen demand
Chemical oxygen demand
Total suspended solids/volatile suspended solids
Total solids/volatile solids
Alkalinity
Volatile organic carbon (gas)
Surfactant degradation
Anti-foam additions
Cometabolite utilization
Total Kjeldal nitrogen/ammonia-nitrogen
Total organic carbon
Dissolved organic carbon
Total phosphorus/orthophosphate
Other ions (i.e., chlorine, fluorine)
Several process parameters are determined before the study
begins. The largest particle size fraction that can be sus-
pended at a given lower limit of percent solids6 is deter-
mined for solids loading of the reactor. If a particle size in
the slurry is too large for the anticipated slurry loading,
then, at worst, the slurry will fail to. remain suspended and,
at best, stratification will exist in the slurry column.
Chemical requirements for slurry-phase systems are asso-
ciated primarily with providing nutrients and controlling
pH. Nitrogen and phosphorus are the key nutrients typi-
cally amended. Other nutrients (i.e. carbon, potassium and
trace metals) are naturally present in quantities generally
sufficient to be nonlimiting.
10
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A carbon:nitrogen:phosphorous (C:N:P) ratio of 100:5:1 is
suitable for most slurry-phase systems. Nitrogen can be
provided in the form of readily available nitrate fertilizers
or urea. Ammonium fertilizers should be avoided because
the nitrification process can contribute to significant oxy-
gen consumption rates that may limit the usefulness of this
parameter in evaluating heterotrophic activity levels. In
addition, nitrification can consume enough alkalinity to re-
quire the addition of lime or caustic to maintain a neutral pH.
Phosphorus is best provided in the form of phosphate salts
in bulk quantities. Although agricultural superphosphate
can be used, it is more difficult to solubilize; when added to
a reactor, it can settle out and thus reduce its availability.
Although liquid phosphoric acid can be used, it may sig-
nificantly depress pH and in turn, necessitate using lime to
counter the acid effect on pH.
In bioslurry treatment systems, more nitrogen and phos-
phate are needed at the beginning of treatment during the
microbial log growth phase. Toward the end of treatment,
the demand for nitrogen and phosphate diminishes as less
carbon becomes available and as cell decay increases
nitrogen and phosphate concentrations in solution. Over-
all addition of nitrogen and phosphorus should, through
the course of treatment, achieve a minimum C:N:P ratio
of approximately 100:5:1 based on the carbon concentra-
tion in the waste matrix. In practice, the concentration of
these nutrients should be kept above target set-point val-
ues (e.g., 10 ppm orthophosphate and 50 ppm nitrate-
nitrogen).
The pH should be maintained between 6.0 and 7.5 for best
results. Lime or caustic soda can be added when the pH
declines below this range. To avoid rapid changes in pH,
equimolar quantities of mono- and dibasic potassium phos-
phate (KH2PO4 and K2HPO4) should be used to enhance the
medium's buffering capacity.
Nontoxic antifoaming agents may, under some condi-
tions, be necessary to control excessive foaming. Foam-
ing is typical in slurry-phase treatment systems and is
believed to occur as a result of natural biosurfactant pro-
duction. In some applications, commercially available
surfactants are added to the system to facilitate the des-
orption of hazardous materials from surfaces of soil par-
ticles. Before using such surfactant in a reactor system,
however, it should be tested for efficacy, biodegradability
(competition with the hazardous compound to be de-
graded), foaming, interference with the analytical method,
and toxicity.7
Maintenance Requirements
A bioslurry system involves mechanical and electrical main-
tenance requirements which will be specific to the system
installed. Typical considerations include frequency and
cost of equipment repair and maintenance.
Site Characteristics
Bioslurry technology can be located at virtually any con-
taminated site: mobile CSTRs are commercially available,
impoundments can be modified to operate as in-situ CSTRs,
and batch or continuously fed, stirred tank reactors can be
constructed onsite. The requirements for the machinery
and equipment are limited in terms of space, power, and
emissions to the surrounding environment The contami-
nant must be organic, and it should be known that bacteria
exist (preferably indigenous) that can effectively biode-
grade the contaminant.
A site can be especially amenable to remediation by slurry-
phase biotechnology if:
the amount of available land for other, technologies is
limited,
the soil or sludge is only contaminated with organic,
biodegradable compounds,
the soil or sludge is not sterile,
the contaminating materials are soluble,
applicable regulations allow the discharge of treatment
water,
the remediation project is schedule-driven,
- a slurry evaluation test shows that the soil or sludge can
produce a pumpable, suspendable slurry, and/or
the solid matrix is either of such a consistency that it can
produce a slurry without any treatment or it can be
treated by soil washing or milling to create a useful slurry.
To be economically feasible, the site should consist of at
least 10,000 yd3 of contaminated soil. The soil at the site
should contain enough fines, or large particles that could be
crushed to produce fines, so that a thick, viscous slurry can
be produced when combined with water. There must not be
a toxic element that cannot be biodegraded, such as high
levels of heavy metals (e.g., mercury, cadmium) that could
effectively sterilize the waste material. An assessment of
the treatability of the contaminated soil or sludge can only
be made by a thorough treatability study in the laboratory.8
Materials Handling Requirements
Materials handling is important for the effective applica-
tion of this technology to a specific site. For contaminated
soils, excavation and particle size/type reduction are typi-
cally necessary. A minimum proportion of fines in the soil
must be present to create the necessary viscosity to suspend
high-density, large-diameter particles (> No. 10 mesh).
11
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Consequently, soils with high contents of sand, gravel, or
rocks are not amenable to bioslurry technology without
some form of pretreatment.
Soil composed of a high proportion of gravel, sand or large
inclusions of sediment or solidified product can be pre-
treated by one or a combination of the following:
screening to exclude oversize particles;
milling with either a rod or ball mill to crush the
material into smaller, suspendable particles that will
yield a larger percentage of fines to increase slurry
viscosity and provide for hindered settling of the solids;
attrition scrubbing with the use of high-shear impellers
and a very high soil load, to reduce soil particle size
and transfer the contaminants from large, coarse par-
ticles to smaller particles;
soil washing to transfer the contaminants from the
coarser-grained material to a bulk aqueous phase en-
riched in soil particulates less than 100 mesh size;9 or
hydrocycloning a pumpable slurry to remove gravel
and sand particles from the more heavily contaminated
clay particles.
After pretreatment, the slurry may be collected within a
hopper and pumped directly into the reactor as a continu-
ous-feed operation. To pump the slurry, a centrifugal or a
diaphragm elastomer-lined slurry pump will be necessary.
Except for in-situ applications, contaminated sludge must
be removed from the source impoundment and transported
to the treatment system. Dredging is generally preferred
over excavation, because dredging minimizes exposure of
workers and the environment (e.g., VOC emissions) to
sludge constituents. The surface water covering pumpable
sludges must be able to support low-draft dredging vessels.
VOC emissions are lower under these circumstances be-
cause of a protective water cover and the fact that the slurry
is contained within a pipe during transport.10
Equalization of the impoundment sludge may be an indi-
cated pretreatment step in some cases. This process step
maintains reasonable uniformity in the physical and chemi-
cal characteristics of the waste, which, in turn, minimizes
disruptions from shock loading or the introduction of in-
hibitory substances.
To manage the bioremediated residuals from a slurry-phase
treatment system, several posttreatment operations can be
considered to dispose of the solids and discharge the water.
The conventional approach would be to gravity thicken the
effluent slurry, filter the solids for disposal by landfill, and
discharge the thickener overflow and filtrate to a wastewa-
ter treatment plant. Alternative scenarios for solids dis-
posal include discharge to drying beds or immediate stabi-
lization of the thickener underflow (i.e., depending on mois-
ture content) followed by backfilling onsite, landfilling, or
land treatment. Additional water treatment may be re-
quired under some circumstances. Typically, water not
recycled for use in the reactor could be discharged to an
existing wastewater treatment system at acceptably low
hydraulic loadings.11
Personnel Requirements
Although personnel requirements for slurry-phase
biotreatment systems are operation-specific, some general
guidelines can be given. For full-scale treatment of con-
taminated soil, using bioslurry technology, at least two
persons are needed onsite to:
excavate and screen the soil,
charge the mill,
monitor the mill operation,
monitor reactor charging,
monitor reactor operation and take samples regularly
for laboratory analysis,
recycle water from the treated slurry, and
backfill and compact the dewatered, treated soil.12
For treatment of contaminated sludge using bioslurry tech-
nology, two persons are also needed onsite to:
monitor reactor dredging operation and reactor charg-
ing/feeding,
monitor reactor operation and take samples regularly
for laboratory analysis, and
perform post-treatment materials handling such as
sludge-dewatering and backfill of the dewatered, treated
sludge.
These operations require the crews to work typically 8 to
12 hr/day.13
A project manager and an available commercial laboratory
or a field laboratory and chemist would be needed for the
duration of the entire project. Physical, chemical, and
biological monitoring is needed for the reactor conditions,
the slurry, the feed-stream, the recirculated and discharged
water, and the posttreatment materials handling.
Engineering and construction assistance is needed during
the initial stages of the project to erect and assemble the
12
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reactor as well as the milling, screening, and pumping
equipment for ex-situ soil treatment. For in-situ sludge
treatments, engineering and construction assistance is needed
initially for impoundment conversion to treatment cell(s);
in addition for ex-situ sludge remediation, assistance is
needed for setup of dredging operations.
Health & Safety Concerns
Health and safety concerns of biosluny treatment include
the chemical hazards peculiar to the chemicals involved
and physical hazards peculiar to the operation of heavy
equipment. Chemical hazards are of most concern during
pretreatment handling and system acclimation. Appropri-
ate personal protective equipment must be worn and may
include air purifying respirators, Tyvek coveralls, chemi-
cally resistant gloves and boots, safety glasses, hearing
protection, and safety helmets. During steady-state opera-
tions, chemical hazards may be of less concern because of
less contact with the waste material, decreased toxicity of
the waste material, and decreased volatilization and/or in-
creased air e'mission control. Physical hazards of concern
that may be encountered include material handling activi-
ties in which heavy equipment is operated; electrical, me-
chanical, and structural construction, maintenance, and re-
pair; trip and fall hazards encountered during normal sys-
tem monitoring.
Potential Community Exposures
Because of the design of typical bioslurry reactor systems,
exposure of the surrounding community to harmful influ-
ences should be minimal. Hazardous air emissions during
materials handling activities such as excavation and mill-
ing are the primary concern. The slurry treatment is
performed within a reactor system where, at any given
time, the concentration of dissolved volatile contaminants
in the slurry is extremely low. During the materials han-
dling and system operation, appropriate air emission con-
trols and monitoring should be in place.
Regulatory Requirements
Comprehensive Environmental Response,
Compensation, and Liability Act
The Comprehensive Environmental Response, Compensa-
tion, and Liability Act (CERCLA) of 1980 authorizes the
federal government to respond to releases or potential re-
leases of any hazardous substance into the environment, as
well as to releases of pollutants or'contaminants that may
present an imminent or significant danger to public health
and welfare or to the environment.
The Superfund Amendments and Reauthorization Act of
1986 (SARA) amended CERCLA and directed EPA to:
* Use remedial alternatives that permanently and sig-
nificantly reduce the volume, toxicity, or mobility of
hazardous substances, pollutants, or contaminants.
Select remedial actions that protect human health and the
environment, are cost-effective, and involve permanent
solutions and alternative treatment or resource recovery
technologies to the maximum extent practicable.
Avoid offsite transport and disposal of untreated haz-
ardous substances or contaminated materials when prac-
ticable treatment technologies exist [Section 121 (b)j.
As part of the requirements of CERCLA, EPA has prepared
the National Contingency Plan (NCP) to address responses
to releases of hazardous substances. The NCP (codified in
40 CFR Part 300) delineates the methods and criteria used
to determine the appropriate extent of removal and cleanup
for hazardous waste contamination.
In general, two types of responses are possible under
CERCLA: removal and remedial actions. Excavation and
air emission control technologies can be part of both types.
If the removal action is part of a remedial action, the
removal action will be limited in the amount of time and
money spent to implement the response. In most cases,
Superfund-financed removal actions cannot last more than
12 months nor cost more than $2 million [Section 104(c)(l)].
Under SARA, remedial actions should permanently reduce
the volume, toxicity, and mobility of hazardous substances,
pollutants, or contaminants at a site. Section 121(c) of
CERCLA, as amended by SARA, requires EPA to review
any remedial action in which hazardous substances, pollut-
ants, or contaminants remain at the site.
Because each hazardous waste is unique and has specific
contamination characteristics, a discussion of all potential
applicable or relevant and appropriate requirements (ARAR)
for a given remedial action involving excavation and air
cannot be covered in this regulatory analysis. Onsite reme-
dial actions must comply with federal and more stringent
state ARARs; these actions are determined on a site-by-site
basis. The ARARs will dictate the degree of cleanup
necessary at CERCLA sites, and CERCLA provides only
six waivers to meeting ARARs during a remedial action
[Section 121(d)(4)]. Section 121(e)(l) specifies that no
federal, state, or local permit is required for the portion of
any removal or remedial action conducted entirely on the
site; however, the remediation must comply with all sub-
stantive regulatory requirements.
Resource Conservation and Recovery Act
The Resource Conservation and Recovery Act (RCRA), an
amendment to the Solid Waste Disposal Act, was passed in
13
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1976 to address the problem of how to manage and dispose
of municipal and industrial solid wastes safely. Specifi-
cally, RCRA addresses the identification and management
of hazardous wastes. The Hazardous and Solid Waste
Amendments of 1984 (HSWA) significantly expanded the
scope and requirements of RCRA, including prohibiting
the land disposal of hazardous wastes that do not meet
promulgated treatment standards.
The RCRA regulations concerning hazardous waste identi-
fication and management are specified in 40 CFR Parts
124,260-272. EPA and RCRA-authorized states can imple-
ment and enforce RCRA and state regulations.
The key to determining if RCRA regulations apply is
whether the waste material is a hazardous waste. The EPA
defines hazardous waste in 40 CFR Part 261. If hazardous
wastes are to be treated, the owner/operator of the treat-
ment or disposal facility must obtain a RCRA permit from
EPA or a RCRA-authorized state. The RCRA require-
ments for permits are specified in 40 CFR Part 260. Re-
quirements for hazardous waste generators, specified in 40
CFR Part 262, include obtaining an EPA identification
number before treating hazardous wastes.
If hazardous wastes are generated in batches and must be
stored onsite before treatment, other RCRA regulations
may apply. These regulations may include complying with
90-day accumulation limits for facilities without hazardous
waste storage permits (40 CFR Section 262.34) and com-
plying with 40 CFR Part 264 or Part 265, Subpart I if
hazardous wastes are stored in containers.
A RCRA operating permit (Hazardous Waste Permit to
Operate, Part B) is required. A state agency (e.g., Califor-
nia) or EPA may issue this permit. To acquire the permit,
the reactor structure, the foundation, and the safety mecha-
nisms on the reactor, screen, tractors, mill, and associated
machinery must be examined. Although a full permit can
require nearly a year to acquire, a RCRA permit-to-operate
package can often be acquired in considerably less time at
less cost. The process of acquiring permits typically re-
quires the energies of one engineer for 1 month.
RCRA Land Disposal Restrictions
The HSWA mandated that EPA develop land disposal re-
strictions (LDR) prohibiting the placement of untreated haz-
ardous waste in land disposal units. The EPA set treatment
standards for restricted hazardous wastes based on the BOAT
determined for each waste. When a restricted waste has been
treated to meet treatment standards, it may be disposed on land.
The EPA may grant national variances to the LDRs if it
determines that the capacity to treat restricted wastes is
unavailable. Other variances to the restrictions are issued
on a case-by-case basis and may extend for up to 2 yr. A
restricted waste may be disposed on land without treatment
under such variances; however, the land disposal unit re-
ceiving the waste must comply with minimum technologi-
cal requirements specified in Section 3004(o) of RCRA.
The EPA may also grant treatability variances in cases
where the restricted wastes were formed by inadvertent mix-
ing or where the restricted wastes are different in physical
form from those wastes used to set the treatment standards.
RCRA Corrective Action
The HSWA greatly expanded EPA's authority under RCRA
to require corrective action. Section 3004(u) of HSWA
requires corrective action for releases of hazardous wastes
or their constituents from any solid waste management unit
at a storage, treatment, or disposal facility that is seeking or
is otherwise subject to a RCRA permit. Section 3004(u)
also requires that these permits contain assurances of finan-
cial responsibility for complying with corrective action.
Moreover, Section 3004(v) authorizes EPA to require cor-
rective action beyond the facility boundary. Section 3008(h)
of HSWA authorizes EPA to require corrective action or
other necessary response measures whenever it is deter-
mined that a release of hazardous wastes or their constitu-
ents has occurred from a facility authorized to operate
under Section 3005(e) of RCRA. Under RCRA regula-
tions, the facility owner or operator is responsible for con-
ducting the corrective action.
Occupational Safety and Health Act of 1970
Under this act, the Occupational Safety and Health Adminis-
tration (OSHA) was created to reduce hazards in the work-
place. Employers and employees engaged in operations at
CERCLA sites are covered in 29 CFR 1910.120; RCRA
corrective action sites; RCRA-regulatcd treatment, storage, and
disposal facilities; and most other hazardous waste operations.
Under these regulations, OSHA requires:
employee health and safety training;
employee medical surveillance programs;
hazardous-waste-site control programs to prevent ac-
cidental employee exposures;
engineering controls, work practices, and personal pro-
tective equipment to reduce employee exposure to
below permissible limits (29 CFR 1910.120 and
1910.132-135 set forth the standards for personal pro-
tective equipment);
air monitoring to determine appropriate levels of em-
ployee protection; and
development and implementation of site-specific health
and safety plans and emergency response plans for
hazardous waste operations.
14
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Under 29 CFR 1910.134, OSHA requires employers to
establish respiratory protection programs. This regulation,
along with 30 CFR Part 11, outlines specific requirements
for approval and use of respiratory protection devices.
In 1971, OSHA promulgated permissible exposure limits
(PELs) for worker exposure to certain airborne chemicals.
The PELs are found in 29 CFR 1910.1000 and are legally
applicable to all workplaces including hazardous waste
operations.
The National Institute for Occupational Safety and Health
and OSHA have developed exposure guidelines for use in
selecting appropriate respiratory protection. The Immedi-
ately Dangerous to Life and Health levels represent the
maximum concentration of a particular chemical from which
one could escape within 30 min without any impairing
symptoms or irreversible health effects.
Clean Air Act
The Clean Air Act of 1970 requires that treatment, storage,
and disposal facilities comply with primary and secondary
National Ambient Air Quality Standards (Section 109).
Section 112 of the 1990 Clean Air Act amendments lists
189 hazardous air pollutants and requires EPA to establish
Maximum Achievable Control Technology (MACT) stan-
dards for each "major" source of these pollutants.
In general, emissions from Superfund remedial activities
are not expected to qualify as major sources under federal
law; however, state or local air program requirements may
be more strict Fugitive emissions from the excavation and
processing of waste material may therefore require treat-
ment in accordance with these standards.
A permit will be required from the local or state department
of air quality because the venting for the aerobic treatment
reactor represents a point source of pollution. In some
localities, merely the excavation of the contaminated soil
will require an air quality permit.
Clean Water Act
The principal requirements for permitting concern the dis-
charge of a portion of the aqueous phase of the slurry
following treatment in the reactor. Most water recovered
from the settling of slurry will, under favorable circum-
stances, be recirculated through the mill and reactor. A
National Pollutant Discharge Elimination System (NPDES)
permit (or state equivalent) is needed for the direct dis-
charge of process water to a receiving water. Discharges to
a publicly owned treatment works (POTW) must comply
with all applicable effluent discharge limits. A permit to
discharge to a POTW is required.
The Future of Bioslurry Technology
Bioslurry technology is a treatment regimen for soil or
sludges contaminated with organic, biodegradable hazard-
ous wastea technology that will become more commonly
used as the industry, owners, and regulatory agencies be-
come more familiar with it. It is a cost-effective alternative
to cumbersome and often less-effective methodsan alter-
native that effectively reduces the risk to future users of the
site and the surrounding community.
Much more development must be done, however, in optimiz-
ing the slurry conditions for bacterial degradation, in treating
heterogeneous soils, and in defining the nature of metabolic
products of the bioremediation process. Fate studies that
define the end-products for the metabolism of most common
hazardous wastes are vital to the long-term acceptance of this
technology by all regulatory agencies. Although ideally, all
hazardous waste is mineralized to carbon dioxide and water,
this is most certainly not the case with the bioremediation of
all hazardous compounds in the environment. Metabolic
products of some compounds may even be more harmful
than the original compound. Studies of this nature require
careful and thorough research, probably involving radioac-
tive isotopes to track the fate of metabolic end-products.
The education of owners and regulators is important in pre-
venting the development and propagation of unrealistic ex-
pectations in the potential of bioslurry treatment. The educa-
tion of the industry itself is necessary to temper unrealistic
claims. The scientific basis for bioslunry remediation is
sound and continues to increase in scope and depth. In time,
this technology is expected to become the technology of
choice for the treatment of a great many hazardous wastes
presently contaminating soil.14
15
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-------
Section 4
Economic Analysis
Introduction
The costs associated with slurry-phase biological treatment
are highly variable and case-specific especially when con-
sidering the pre- and posttreatment requirements that may
be necessary as part of the overall remedial program. Be-
fore initiating the full-scale remediation, however, a con-
siderable portion of the costs is incurred during the initial
optimization studies. During this phase, a variety of surfac-
tants are often tested, several nutrient loadings are studied,
bacterial phenotypes are characterized, inoculum develop-'
ment occurs, and a factorial-design experiment is typically
established and conducted. These procedures are necessar-
ily labor-intensive because the small-scale volumes and
large number of variables incorporated in the testing.
As mentioned in Section 3, several physical process con-
figurations are possible when considering slurry-phase
treatment, i.e., in-situ batch treatment of sludge impound-
ment or ex-situ treatment of soil and sludge in tank reac-
tors. The overall remediation cost will vary depending on
the in-situ or ex-situ treatment option selected for a par-
ticular site. A summary of treatment cost per cubic yard
of contaminated matrix for each of these process options
is presented below.
The lowest treatment costs involve in-situ treatment of
contaminated sludge when neither emission controls nor
remediation of underlying soils is required. Mixers and
aerators are placed in the impoundment and the sludges are
bioremediated in a single batch operation. The treated
solids may then be dewatered and stabilized in place after
which the impoundment may be capped. Costs for this
treatment option generally fall in the range of S50 to $75/
yd3. Batch treating large impoundments (i.e., >5 mil gal) in
a single operation is, however, often impractical and costly.
For large impoundments, sheet piling or other structures
can be installed to create smaller treatment cells, and the
impoundment can then be remediated in more than one
batch operation. This will typically add 10% to 15% to the
overall project cost.
Although ex-situ treatment in tank reactors is probably
unsuitable for impoundment closures because of the large
reactor sizes required, there are situations when tank reac-
tors are used for sludge treatment. Assuming that the
treated sludges can be left in place or returned to the
original impoundment and be dewatered and stabilized, the
treatment costs increase to between $75 and $125/yd3'. If
treated sludge solids must be removed from the impound-
ment, stabilized, and disposed in a separate on- or offsite
landfill to allow remediation of underlying soils or con-
taminated groundwater, then costs can increase to between
$100and$150/yd3.
Tank-based treatment is generally considered only for treat-
ment of contaminated soils in which excavation is required.
Costs for disposal in an onsite land treatment unit without
dewatering or stabilizing the treated impoundment sludge
will range between $100 and $150/yd3 for an existing reac-
tor. If a new reactor is required, treatment and disposal
costs can exceed $200/yd3.15
Site-Specific Factors Affecting Cost
Several major factors affecting the cost of the slurry-phase
treatment system are highly site specific. The factors that
will affect the cost generally include: volume of contami-
nated matrix to be treated; extent of contamination; treat-
ment goals; physical site conditions; and permit require-
ments. -
Soil characteristics can dramatically affect the cost of the
soil remediation because of the materials handling cost.
This is a labor-intensive aspect of the technology, and
complications, such as the lack of sufficient fines, the
presence of a great deal of unmillable overage, or a very
high proportion of sand can complicate the application of
the technology. If the bulk of the contamination exists
within the treatable small particle fractions and not on a
very large proportion of unmillable but screenable overage,
the cost could be appreciably reduced.
A major portion of cost incurred during the field-scale
remediation of sludge or soil is labortypically about 50%
of the total remediation cost. To reduce labor cost, the size
of the reactor and the process should be appropriately
designed so the least amount of time is spent onsite per-
forming the remediation. For sites where treatment is
17
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expected to be completed in less than 1 yr, portable reactors
should be considered to avoid the cost of erecting large-
scale, permanently sited equipment.16
Basis of Economic Analysis
This economic analysis is based on the costs associated
with a tank reactor system at a hazardous waste site for
treating contaminated soil. The cost information in this
economic analysis was provided by ECOVA and is based
on their knowledge and experience on actual, large-scale,
tank-based remediation. The costs have been placed into
the 12 categories that reflect typical cleanup activities at
Superfund and RCRA corrective action sites. The esti-
mated cost analysis presented in Table 2 is based on the
discussions of each of the cost categories included in this
'section. These costs reflect 1993 prices. Percent variances
are meant to convey the element of difficulties and contin-
gencies that may be encountered at different sites.
For the purpose of this economic analysis, it will be as-
sumed that 20,000 yd3 of soil contaminated with organic,
biodegradable material will be treated. The soil has a density
of 1.3 g/mL, a moisture content of 25%, and evaluation has
already confirmed that a 30% slurry (w/v) with a specific
gravity of 1.074 will be the most efficient load. It is assumed
that a continuous-flow treatment system with a retention time
of 2 wk will be used. The treatment costs are indicated for
two different sizes of reactor and are based on the assumption
Table 2: Estimated Costs Associated
Cost
Category
Site preparation
Excavation
Decontamination facilities
Utility connections
Emergency & safety equipment
Permitting and Regulatory
Capital equipment
Mill
Screen
Reactor & mechanism
Engineering
System design
System construction
Startup & fixed
H&S monitoring
Establish operating procedures
Equipment mobilization
Scale up optimization
Labor
Supply and consumable
Utility
Effluent disposal (soil backfill)
Residuals and waste shipping, handling and
transportation
Analytical
Equipment repair and replacement
Site demobilization
Total
Cost/yd3
with Slurry-Phase Reactor
cost,
275m3
80,000
8,500
35,000
12,000
15,000
65,000
20,000
125,000
41 ,500
23,000
120,000
2,000
9,000
7,500
50,000
3,750,000
27,000
110,000
100,000
N/Aa
1,120,000
95,000
75,000
5,897,000
294
$
1,125m3
80,000
8,500
35,000
12,000
15,000
65,000
20,000
256,000
41 ,500
23,000
241 ,000
2,000
9,000
7,500
50,000
1 ,290,000
15,000
43,000
100,000
N/A
470,000
40,000
75,000
2,905,000
145
Systems
Magnitude
+50% to -30%
+50% to -30%
+50% to -30%
+50% to -30%
+50% to -30%
+50% to -30%.
+50% to -30%
+50% to -30%
+50% to -30%
+50% to -30%
' +50% to -30%
+50% to -30%
+50% to -30%
+50% to -30%
+50% to -30%
+50% to -30%
+50% to -30%
+50% to -30%
+50% to -30%
N/A
+50% to -30%
+50% to -30%
+50% to -30%
+50% to -30%
. +50% to -30%
aN/A = not applicable
18
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that the remediation will follow the treatment process as
shown schematically in Figure 3. The larger reactor is a
1,125m3 reactor containing approximately 1,100,000 L
(290,000 gal); the smaller reactor is a 275 m3 reactor contain-
ing approximately 265,000 L (70,000 gal).
Cost Categories
A discussion of each of the 12 cost categories in Table 2 are
discussed in the following subsections.
Site Preparation Costs
The costs associated with site preparation include the plan-
ning and management involved with system design and
construction, legal searches, access rights and roads, prepa-
rations for support facilities and decontamination facilities,
design and pouring a concrete reactor pad, erection of the
reactor tank and operating mechanism, utility connections,
and installation of emergency and safety equipment. Site
preparation costs depend on the type, condition, and geo-
graphical location of the site.
For ex-situ treatment of contaminated soil, the contaminated
soil must be excavated before treatment. For this analysis,
the cost of excavating contaminated soil is included in the site
preparation costs. The total site preparation costs are esti-
mated to be approximately $175,000. This cost is the same
for both the smaller and the larger reactor systems.
Permitting and Regulatory Costs
Permitting and regulatory costs can depend on whether treat-
ment is done at a Superfund or a RCRA corrective action site.
At Superfund sites, Section 121(d) of CERCLA as amended
by SARA requires that remedial actions be consistent with
any ARAR. At RCRA-corrective action sites, regulatory
costs will increase since analytical protocols and monitoring
reports need to be maintained during operation of the treat-
ment system. Permitting and regulatory costs also depend on
how the liquid waste stream is disposed. Permits are required
for any discharges to POTW or any surface water bodies.
Permitting and regulatory costs are assumed to be approximately
$15,000 for both sizes of reactor systems. This analysis assumes
that treatment is being conducted as part of a RCRA remedial
action and that the effluent is discharged to a POTW.
Capital Equipment Costs
The capital equipment costs include the cost of milling and
screening equipment, cost of reactor, and operating mecha-
nism. Milling and screening equipment are estimated to
cost $65,000 and $20,000, respectively, for either reactor
size. The cost for the smaller reactor (275 m3 EIMCO
Biolift Reactor) includes $23,000 for system design,
$41,500 for engineering, $42,000 for the tank, $83,000 for
Pretreatment
'. "'
Excavation
' " - * -
Screening
-:t ' 1 -
* x s^ssss s\ \Uf
'"^T
Washing and/or Milling and
Slurry Preparation
1
-
Treatment
Reactor Operation and
Treatment
Posttreatment
1
Dewatering
1
Disposal
I -
Liquid Waste Stream + Soil
1
Figure 3: Slurry-phase treatment
process flow chart.
the operating mechanism, and $120,000 for erection at the
site. Thecostof thelargerreactor (1,125 m3EIMCO Biolift
Reactor) includes $23,000 for system design, $41,500 for
engineering, $75,000 for the tank, $181,000 for the operating
mechanism, and $241,000 for erection at the site.
Total capital cost is, therefore, estimated to be $394,500 for
the smaller reactor system and $646,500 for the larger reactor
system.
Startup and Fixed Costs
Startup and fixed costs include those required to mobilize
equipment, perform initial shakedown of equipment, train
19
-------
operators, establish operating procedures, and perform health
and safety monitoring. Mobilization and shakedown costs
include transporting the equipment to the site, initial setup,
and evaluating the system's performance to determine the
proper operating parameters for treatment
For this analysis, it is assumed that a thorough evaluation of
the operating parameters will be done in a laboratory setting
before initiating the onsite treatment The evaluation cost is
estimated at approximately $50,000. The other startup and
fixed costs include establishing operating procedures and
mobilization of equipment These costs are estimated to be
516,500 for either reactor system. The total startup and fixed
costs for either reactor system are estimated to be $66,500.
Labor Costs
The cost of labor to monitor the reactor over the duration of
the project largely depends on the size of the reactor. The
smaller reactor's capacity dictates that 320 reactor volumes
would be required to treat the entire 20,000 yd3, assuming
no overages (from screening) and all excavated material
would be treated. Each reactor volume will be treated for
the equivalent of a 2-wk retention time. Thus, 640 wk
(12.3 yr) are estimated to complete the project.
The larger reactor's capacity dictates that 77.2 reactor volumes
would be required to treat the entire 20,000 yd3, assuming no
overages (from screening) and all excavated material would be
treated. Thus, 153 wk (3 yr) are estimated complete the project
Personnel required to monitor the larger or smaller system
includes two persons working 8 to 12 hr/day, $60/hr. Their
duties would be materials handling, reactor charging, process
monitoring (i.e., flow rates, nutrient additions, pH, D.O.), and
sampling. Per diem allowances and lodging are included in
labor costs. Labor costs also include screening and milling,
which ECOVA estimates can account for approximately 50%
of the total labor costs. (Note that excavation costs are
included in the subsection titled "Site Preparation Costs.")
For the smaller reactor system, the total labor costs to treat the
entire volume of soil is estimated to be $3,750,000. For the
larger reactor system, the total labor cost is estimated to be
SI 290,000.
Supply and Consumable Costs
Supplies and consumables for the slurry-phase treatment
system include lime to maintain pH and nutrients such as
nitrogen and phosphorus to maintain microbial nutritional
needs. The cost of supplies and consumables are estimated
at approximately $27,000 for the smaller reactor system
and $15,000 for the larger reactor system.
Utility Costs
Utility costs include the amount of electricity needed to
operate pumps, air blowers, mixers, etc. of the reactor system.
For this analysis, it is assumed that the power cost is S0.10/
Kw-hr. It should be noted that the cost of power can vary by
as much as 50%, depending on the local utility rates. The cost
of utilities, therefore, is estimated at approximately SI 10,000
for the smaller reactor system (operating 12.3 yr) and $43,000
for the larger reactor system (operating 3 yr). The preceding
costs are based on the assumption that the power requirement
of the larger reactor system is higher than the power require-
ments of the smaller reactor system.
Effluent Treatment and Disposal Costs
This analysis assumes that water from the reactor system is
clean enough to meet regulatory standards and hence can be
directly discharged to a POTW without further treatment.
The dewatered soil from the treatment system can be treated
as clean soil. It is commonly used as backfill. For the
purpose of this analysis, it is assumed that soil wilt be back-
filled and compacted back to the site. The cost to backfill and
compact treated soil onsite is estimated to be $100,000 (±20%)
for either of the two reactor systems.
Residuals and Waste Shipping, Handling, and
Transportation Costs
Since this analysis assumes that the effluent water will be
discharged to a POTW and dewatered soil will be backfilled
on to the site, no cost will be incurred for waste shipping and
transportation. The solid wastes generated from this process
are assumed to consist only of contain inated health and safety
gear having a negligible disposal cost.
Analytical Costs
Analytical costs constitute a major percent of the total
remedial cost. These costs depend primarily on the types
of analyses performed, the frequency of analyses, the
duration of the remediation, and the relative per analysis
cost of the analytical laboratory. The types of analyses
include routine monitoring such as DO and pH, usually
performed in the field for a low cost per sample, as well as
analysis of samples for critical contaminants. The nature
of the critical contaminants and the sample matrix dictates
the types of analyses performed and the relative cost per
analysis. The duration of the remediation may affect the
analytical cost, although the cost could be offset by reduc-
ing the frequency of sampling. The cost of the analytical
laboratory can also affect the total cost; in some situa-
tions, an onsite field laboratory may prove cost effective.
For this cost analysis, the analytical costs are estimated at
$1,120,000 for the smaller reactor system and 5470,000
for the larger system.
Equipment Repair and Replacement Costs
Equipment repair and replacement costs include mechanical
and electrical repair and replacement of items such as matcri-
20
-------
als handling equipment and reactor and reactor-associated
components. An estimated $95,000 is needed to maintain the
equipment for the smaller reactor system and $40,000 is
needed for the larger reactor system.
Site Demobilization Costs
Site demobilization include operation shutdown and de-
commissioning of equipment, site cleanup and restoration,
disconnection of utilities, and disposal of wastes. Site
demobilization costs depend on whether the treatment op-
eration occurs at a Suprfund site or at a RCRA corrective
action site. Demobilization at a RCRA-corrective action
site will require detailed closure plans and permits, which
are not required at a Superfund site.
For this analysis, the site demobilization cost is estimated to
be $75,000 for either of the two reactor systems.
Case Study Costs
Cost information for the case studies was provided by
RETEC and FLTG for their respective remediations. At
the time of writing, the cost information for the Radian
study was not available.
The total cost of RETEC Corporation's slurry-phase
biotreatment of 1-million-gallon of petroleum refinery waste
was $252,500 or $50.50 per yd3 of petroleum sludge. Costs
included $35,500 to retrofit an existing tank to a treatment
reactor, $139,000 for the combined costs of capital equip-
ment, startup and fixed labor, and supply and consumables,
including air monitoring and reporting. Utility costs for the
56-day treatment were $8,000. No costs were incurred for
effluent disposal or residual and waste shipping, handling,
and transportation because treated effluents were recycled
to an onsite refinery water treatment plant. Analytical costs
were $50,000. Equipment repair and replacement costs
were $5,000. The cost of site demobilization was S15,000.
A summary of the RETEC pilot-scale demonstration costs
is provided in Table 3.
Costs incurred and projected for the French Limited Super-
fund slurry-phase biological remediation of 34-million-
gallons of lagoon sludge and subsoil and the adjacent slough
area subsoil are shown in Table 4. Costs include detailed
technology development, a high degree of analytical and
technical documentation as well as EPA/regulator oversight
associated with Superfund-site remediations. It should be
noted that the French Limited site is the first slurry-phase
biological treatment Superfund remedial action, and in this
experience, costs have proven to be highly site-specific.
Table 3. Costs for Slurry-Phase Biotreatment of 1-Million-Gallon of Refinery Waste3:
RETEC Demonstration
Cleanup Activity
Site preparation
Permitting and regulatory
Capital equipment
Startup and fixed
Labor
Supplies and consumables
Utilities
Effluent disposal
Residuals and waste shipping, handling and
transportation
Analytical
Equipment repair and replacement
Site demobilization
Total
Cost, $
35,000
NA
NA
139,000b
8,000
NA
NA
50,000
5,000
15,000
252,500
Cost/Yd3, $
7
28
1.5
10
1
3
50.5
b Combined cost for capital equipment, startup and fixed, labor, and supplies and consumables.
21
-------
Table 4. Costs for French Limited Superfund Site Remediation:
French Limited Task Group, Inc. Demonstration
Cleanup Activity
Cost, $millions Cost/Ton, $ Cost/Yd3, $
Lagoon Remediation3
Development
Floodwall
Operations, maintenance, analytical
Dewatering
Fixation
Technical support
Administrative
Demobilize
EPA oversight
Total
Slough area subsoil remediation13
Investigation
Remediation
12.2
2.3
21.8
0.6
0.4
2.3
3.1
1.9
2.3
46.9
0.4
1.6
40.6
7.6
72.6
2.0
1.3
7.7
10.3
6.3
7.6
156.0
36.4
145.5
60.9
11.4
108.9
3.0
1.95
11.6
15.5
9.5
11.4
234.0
54.6
218.2
Total
2.0
181.8
272.7
a300,000 tons sludge and soil
b11,000 tons soil
22
-------
References
1. EPA Test Methods for Evaluating Solid Waste. 1986. Volume IB. Laboratory Manual of Physical/
Chemical Methods. SW-846, Third Edition. Office of Solid Waste, Washington, D.C.
2. Ross, Derek. 1990/91. Slurry-Phase Bioremediation: Case Studies and Cost Comparisons. Remediation
1:1:61-73.
3. Ross, Derek. 1990/91. Slurry-Phase Bioremediation: Case Studies and Cost Comparisons. Remediation,
1:1:61-73.
4. Information provided by RETEC.
5. Adapted from Zappi, M. E., Gunnison, D., Teeter, C. L., Francinques, N. R. 1991. Development of a
Laboratory Method for Evaluation ofBioslurry Treatment Systems. Hazardous Materials Control/Super-
fund '91,12th Annual National Conference and Exhibition, p. 267.
6. Soil Slurry Evaluation for Use in the EIMCO Biolift Reactor, EIMCO Corp., 669 West Second South,
Salt Lake City, UT, provided by Mr. Gunter Brox.
7. Information provided by RETEC.
8. Information provided by ECOVA.
9. Information provided by ECO VA.
10. Information provided by RETEC.
11. Information provided by RETEC.
12. Information provided by ECO VA.
13. Information provided by RETEC and Radian.
14. Information provided by ECO VA.
15. Information provided by RETEC.
16. Information provided by ECOVOA.
17. Information provided by ECOVA.
23
-------
-------
Appendix A
Description of Treatment Technology
Introduction
Biological treatment entails degradation of organic com-
pounds by microorganisms. The desired end products of
aerobic biodegradation are carbon dioxide, water, inor-
ganic salts, and other relatively harmless products of mi-
crobial metabolism. In treating hazardous wastes or
remediating contaminated soil, nutrients and microorgan-
isms are often added to enhance biodegradation.
In the slurry-phase biological process, soil is suspended in
water to obtain a pumpable slurry that is fed to a large-
capacity CSTR. The reactor is then supplemented with
oxygen, nutrients, and when necessary, a specific inoculum
of microorganisms to enhance the biodegradation process.
This treatment method.has several advantages because an
optimal environment for biodegradation of the organic con-
taminants can be maintained with a high degree of reliability.
Biological reactions can proceed at an accelerated rate in a
slurry system because of the increased contact efficiency that
can be achieved between contaminants and microorganisms
by successfully maintaining higher bacterial populations. A
slurry-phase process can also be operated as a continuous-
flow system since the impact of toxic waste levels is reduced
by instantaneously diluting the feed stream as it enters the
reactor; In addition, toxic end products of microbial metabo-
lism, which may repress bacterial activity, typically do not
accumulate to inhibitory levels in the continuous-flow mode.
Specifications of Slurry-Phase Reactor
used During SITE Demonstration
The EIMCO Biolift Reactor (nominal volume of 64-L)
used during the SITE demonstration, shown diagrammati-
cally in Figure A-1,1 is constructed of stainless steel and
equipped with agitation, aeration, and temperature controls.
Specifications for the 60-L EIMCO Biolift reactor2 are:
Reactor is made of 304 stainless-steel plate, 3/16-in.
thick. Interior tank diameter is 15 in. Total height is
36 in. Usable volume is approximately 60 L.
Two airlift pipes and rake arm mechanisms are made
of 304 stainless steel.
Two elastomeric membrane diffusers are mounted on
rake arm. Diffuser membrane consists of NBR rubber;
other rubber materials are available depending on ap-
plication.
Air to diffusers is supplied via a rotary air valve. Air to
airlift is supplied through a connection in the bottom
plate of reactor.
Drive motor for the rake arm is a Dayton, permanent-
magnet, DC gear motor: power input 1/12 hp; 0.83
amps; 9.9 rpm; gear ratio 167:1; 228 in.lb torque; a
Dayton Motor Speed Control 3 amps (max). Power
transmission is by a timing belt.
Drive motor for the impeller is a Dayton, permanent-
magnet DC gear motor: power input 1/10 hp; 0.89
amps; 110 rpm; gear ratio 37:1; 34 in. Ib torque; a
Dayton Motor Speed Control 3 amps (max). Power
transmission is by timing belt.
Reactor is heat traced electrically: chromolox on/off
proportional temperature controller with digital indica-
tor.
Axial flow impeller with pitched blades is mounted on
drive shaft.
Flowmeters for airlift and diffusers are Dwycr Instru-
ments RMB type.
All the necessary tabs, fittings, and plugs allow inser-
tion of DO, pH, and temperature probes.
The single stage, single-cylinder, oilless, diaphragm
compressor is Thomas Industries Model 917CA22; I/
8 hp shaded pole motor, single phase; 1 lOv, 60 Hz; or
alternatively, a filter regulator for hook-up to high
pressure house air.
A mechanical foam breaker with 1/6 hp variable speed
motor is optional.
The reactor's contents are agitated by three mechanical
methods. First, a rake mechanism moves the settled mate-
25
-------
Diffuser
Air Supply
Sample and
Drain Valves
Rake Drive
Gearmotor
Impeller Drive
Gearmotor
Rake Blades
Airlift Supply
Figure A-11. EIMCO Biolift reactor.
26
-------
rial from the bottom of the reactor to the second agitation
mechanism, an airlift circulation system, which circulates
the material to the top of the reactor. The third agitation
mechanism is a low-shear impeller located approximately
in the center of the central shaft of the reactor. Aeration is
supplied by a set of air diff users attached to the rake arm at
the bottom of the reactor. Temperature is maintained by a
heat tape system equipped with a digital readout
The contents of the EIMCO Biolift Reactor can be
sampled in two ways. An opening at the front top of the
reactor allows access at the top surface of the liquid. This
permits visual inspection of the mechanical actions within
the reactor as well as data collection with hand-held instru-
ments that can be inserted into the slurry from the top.
Samples can also be collected from the three sampling
ports located along the side of the reactor at three vertical
positions along the reactor wall. Each port represents a
distinct zone of the slurry: the bottom sampling port pro-
vides material from within the rake mixing zone where the
heaviest particles are likely to be present; the middle sam-
pling port, from within the most well-mixed zone of optimal
grain size; the top sampling port, from the layer containing
the finest particles. Samples of contaminated material can be
taken from each of these three ports to permit an evaluation of
the mixing efficiency of the reactor.
27
-------
-------
Appendix B
SITE Demonstration Results
Introduction
IT Corporation in conjunction with ECOVA Corporation
evaluated ECO VA's slurry-phase bioremediation technology
under U.S.EPA's SITE program. The technology demon-
stration was conducted at the EPA's T&E Facility in Cincin-
nati, OH, during May through July, 1991. In this 12-wk
study, creosote-contaminated soil from the BN Superfund
site in Brainerd, MN, was used to test the slurry-phase pro-
cess. This appendix briefly describes the BN Superfund site
and summarizes the SITE demonstration activities and dem-
onstration results.
Site Description
The BN Superfund Site is located on the border between
Baxter and Brainerd, MN. State Highway 371 is approxi-
mately 800 to 1000 ft north of the site, and the Mississippi
River flows about 3000 ft east of the plant Residential
areas are located within 1000 feet to the northeast and
southeast of the site. BN has owned and operated the
railroad tie treatment plant on this site since 1907. The
plant uses creosote mixtures to preserve railroad ties. Dur-
ing the 1950s, BN began blending creosote with No. 5 fuel
oil in a 1:1 ratio. At some undetermined time, this mixture
was changed to creosote and coal tar, which are currently
being used at the plant in the ratio of 7:3.
Historically, wastewater generated from the wood-treating
process was sent to shallow, unlined surface impound-
ments for disposal. The first impoundment, which covered
an area of approximately 60,000 ft2, eventually became
filled with sludge, and in the 1930s, it was buried under
clean fill. A second, newer impoundment was used until
October 1982, when a wastewater pretreatment plant was
completed. The discharge of wastewater to the disposal
ponds generated a sludge and leachate that contaminated
both the soil and groundwater beneath both ponds. As a
result, the site was included on the proposed National
Priorities List issued by the EPA in December 1982. Fig-
ure B-l is a map of the BN Superfund Site.
The Record of Decision (ROD) for the BN Superfund Site
was signed by the Regional Administrator on June 4,1986.
The ROD specifies that only visibly contaminated soils and
sludges will be excavated from the site for onsite treatment.
Visibly contaminated soil was characterized as being heavily
stained, dark brown to black in color, visibly oily, and
usually having a pronounced creosote odor. The second
impoundment from which wastewater and creosote were
removed contained an estimated 6000 yd3 of contaminated
soil and 1000 yd3 of contaminated sludge. The first imr
poundment, which was closed in the 1930s, contained an
additional 2500 yd3 of contaminated soil. Together, the
two impoundments contained an estimated 9500 yd3 of
contaminated material.
Waste Characteristics
Initial sampling showed the primary constituents of con-
cern to be PAHs, heterocyclic compounds, and phenols.
Concentrations of these contaminants ranged from 34,388
mg/kg total PAHs and heterocyclics and 16 mg/kg total
phenols in the first impoundment to 134,044 mg/kg total
PAHs and heterocyclics and 130 mg/kg total phenols in the
second impoundment. Groundwater monitoring results
indicated that the groundwater contamination is restricted
to a relatively small area downgradient from the site. All
contaminated soils were excavated from the lagoon areas
and stored in a waste pile on a site just east of the existing
lagoon area. The contaminated soil is a fine, sandy soil, of
which 75% has a grain size between 0.1 and 0.4 mm in
diameter. The soil has a relatively low moisture content
(10%) and a heat value below 500 Btu/lb.
In November 1989, IT sent a sampling team to the BN site
to excavate soil for treatability studies. Soil was removed
to a depth of 2 to 6 ft and placed in 55-gal drums. The
drummed soil from this original excavation was stored at
the BN site for nearly one year. In October 1990, IT
returned to the site to collect four pails of contaminated soil
for the bioslurry demonstration. Prior to collection of the
soil for the bioslurry demonstration, the soil from the drums
was homogenized. Three drums of homogenized soil were
shipped to the T&E facility in Cincinnati, OH, for use in the
pilot-scale bioslurry demonstration.
29
-------
RIVERSIDE
SCHOOL
t22tl30-,l7teS8S)
BRAINERD
0*»n«ir*i«
uilon
LCOfNO
I AppretitniH «if»nf »t eenlamlneiltil
grtuntmaltr pbm* £. JOOnj/l
f.J lf*oiur»rf Conctntratien
for»rej» 6/04 - 4/05)
tr*ii Sir*
BRAINERO
JR. COLLEGE
Figure B-1. Burlington Northern Superfund site, Brainerd, MN.
Source: Summary of Remedial Alternative Selection, Burlin'gton Northern Hazardous Waste Site, Brainerd, MN.
Environmental Protection Agency, Region V. 1985.
Process Description
The pilot-scale demonstration of slurry-phase bioremedia-
tion was performed from May 8 through July 31, 1991 at
the EPA's T&E Facility in Cincinnati, OH. In this 12-wk
study, creosote-contaminated soil from the BN Superfund
Site in Brainerd, MN, was used to test the slurry-phase
bioremediation process. During the demonstration, five
64-L EIMCO Biolift reactors were used. Figure B-2
contains a photograph of the experimental setup.
The normal operational volume of the EIMCO Biolift
reactor is 60 L. Because of the large volumes of slurry to be
removed for analytical sampling at the initial time point, it
was concluded that each reactor should initially be loaded
to a volume of 66 L. This volume was immediately de-
creased after collecting the first sample set; this allowed for
the maximum loading of the batch slurry reactor. Quanti-
ties of nutrients and inoculum added to each reactor at the
start of the demonstration were calculated on the basis of a
66-L initial reactor volume at 30% slurry.
Before initiating the pilot-scale slurry-phase demonstration,
the soil was shoveled from a 55-gal drum (in which it had
been transported from the BN site) and passed through a 1/2-
in. screen to remove oversized material. As received, the soil
was brown-to-black, fine-to-medium-grained sand with some
minor gravel content, and somewhat resilient and greasy.
Following initial screening, the soil was mixed with water to
form a 30% slurry (W/V). The slurry was then poured into a
30
-------
Figure B-2. Demonstration reactor setup.
ball mill to reduce the particle size and continuously screened
with a No. 8 sieve at the outlet of the mill to produce a slurry
with a grain size distribution suitable for charging to the
EIMCO Biolift reactors. Following milling, 66 L of the
soil slurry was transferred into each of the five reactors.
After the reactors were charged with the soil slurry, 66 mL
of a concentrated inoculum of indigenous bacteria (Pseudo-
monas stutzeri, Pseudomonasfluorescens, and Pseudomonas
stutzeri strain FLN-1) was added to each of the reactors.
Based on the titre of bacteria present in the inoculum, a total
of 1.98 x 1012 colony forming units (CPU) was added per
reactor. Furthermore, because the amount of free nitrogen,
measured as ammonia nitrogen, needed for optimal microbial
activity was quite low, ammonia supplementation was deemed
necessary. Nutrient amendments added to the reactors in-
cluded ammonia, phosphate, and trace amendments of mag-
nesium, calcium, iron, and ammonium molybdate.
Sampling and analysis activities performed during the pi-
lot-scale demonstration involved collection of composite
samples from each of the reactors for pre- and posttreaJ-
ment analyses and sampling throughout the demonstration
to monitor system operation. During the demonstration,
soil-bound and liquid-phase PAHs, TPHs, nutrients, pH,
DO, temperature, toxicity, and microbial populations were
monitored. Composite samples were collected from the
three sampling ports located along the side of each reactor
at three different vertical locations. All parameters of the
demonstration were monitored in accordance with the sam-
pling and analysis plan prepared for the project Soil-slurry
samples were taken from the reactors over a 12-wk period.
In the ninth week of operation, four of the bioreactors were
reinoculated with an additional 125 mL of the inoculum to
stimulate the PAH degradation process. Results of the
demonstration are summarized below.
Results of Pretreatment and
Posttreatment Soil Samples Analyzed by
GC/MS Method
The pre- and posttreatment soil and liquid samples were
analyzed for critical contaminants (PAHs) and TPH. The
air samples were analyzed for volatile and semivolatile
organics and total hydrocarbons (THCs). All the PAH
analyses on soil and liquid samples were performed by the
EPA-approved GC/MS method (SW-846, Method 82703).
The pretreatment samples were collected at the start of
testing (Week T0) to determine the baseline concentration
of the critical semivolatile contaminants in the soil treat-
ment. The posttreatment samples were collected 9 weeks
(T9) and 12 weeks (T12) after the start of testing to deter-
mine the levels of the critical contaminants remaining in
the soil after treatment.
The concentrations of the PAH contaminants in the pre-
treatment soil samples ranged from 5.5 to 840 mg/kg. The
concentrations of total, 2- and 3-ring, and 4- through 6-ring
PAH level and the degradation rates determined by GC/MS
are given in Tables B-l and B-2. The concentrations of the
PAHs in posttreatment samples indicated a significant re-
31
-------
Table B-1. Concentrations of Total, 2- and 3-ring, and 4- through 6-Ring PAH Levels in
Soil Samples, Determined by GC/MS, mg/kg
Week
Reactor
2- and 3-Ring PAHs
Reactor 1
Reactor 2
Reactor 4
Reactor 5
Reactor 6
Total
4- through 6-Ring PAHs
Reactor 1
Reactor 2
Reactor 4
Reactor 5
Reactor 6
Total
Total PAHs
Reactor 1
Reactor 2
Reactor 4
Reactor 5
Reactor 6
Total
0
2299
1418
390.5
2644
718.6
1494.0
1410
775
288
1836
502
962.2
3709
2193
678.5
4480
1220.6
2456.2
9
<31.4
5.5
<32.3
31.5
18
<23.7
<273.7
<65.2
<357.9
<308.9
182.3
<237.6
<305.1
<70.7
<390.2
<340.4
200.3
<261.3
12
<49.5
<23.8
8.1
<46.3
<44.7
<34.5
316.4
<267.5
<91.3
404.6
<291.8
274.3
<365.9
<291.3
<99.4
<450.9
<336.5
308.8
Table B-2. Percent Degradation of Total, 2- and 3-ring, and 4- through 6-Ring PAH Levels in
Soil Samples, Determined by GC/MS
Week
Reactor
2- and 3-Ring PAH Degradation Rate
Reactor 1
Reactor 2
Reactor 4
Reactor 5
Reactor 6
Mean Percent
9
>98.63
99.61
>91.73
98.81
97.50
>98.41
4- through 6-Ring PAH Degradation Rate
Reactor 1 >80.59
Reactor 2 >91 .59
Reactor 4 >-24.3
Reactors >83.18
Reactor 6 63.69
Mean Percent
Total PAH Degradation Rate
Reactor 1
Reactor 2
Reactor 4
Reactors
Reactor 6
Mean Percent
>75.31
>91.77
>96.77
>42.50
>92.40
83.59
>89.36
12
>97.85
>98.32
97.93
>98.25
>93.78
>97.69
77.56
>65.48
>68.30
77.96
>41.87
>71.49
>90.10
>86.72
>85.35
>89.94
>72.43
>87.43
32
-------
duction of PAHs in the soil matrix. The percent reduction of
total PAH for Week Tu samples for the five reactors ranged
from >72% to >90%. Results indicate that an average of
>87% of total PAHs were degraded over all five operating
reactors after the 12th week of the demonstration period.
Initial levels of the hazardous component of creosote PAHs
were 2460 mg/kg, as determined by GC/MS. After twelve
weeks of treatment, the concentration of the easily-de-
graded 2- and 3-ring compounds had declined by >98%
from 1490 mg/kg to <35 mg/kg. The concentration of the
much more intractable 4-, 5- and 6-ring compounds de-
clined >72% from 960 mg/kg to <270 mg/kg.
The more complete degradation of the lower molecular-
weight PAHs reflects, in part, the higher bioavailability of
2- and 3-ring PAHs than 4- through 6-ring PAHs. Four-
and higher-ring PAHs are considerably less soluble than
simpler-ring PAHs.
The degradation rates of the different PAHs varied apprecia-
bly during the course of the study and reflect changes in the
reactor environments. After nine weeks of testing, Reactors 2
and 4 were inoculated with fresh bacterial populations, and
Reactors 5 and 6 were both reinoculated and amended with
the surfactant Tween 80. Reactor 1 was not amended in any
way. .Results from Week 12 indicate that additional spiking
during Week 9 did not assist in further degradation of the
complex PAHs. On the contrary, the level of contamination
due to the presence of the more complex PAHs was greater in
Week 12 than in Week 9. The lower level of PAH contami-
nation in Week 9 soil samples may have resulted from labora-
tory procedures. To extract PAHs, the analytical laboratory
used a sonication method (EPA Method 3550) that calls for a
2-minute sonication period. This may not have been enough
time for the entire soil sample to intimately contact the ex-
traction solvents and may have led to some inconsistent
results for higher ring PAHs.
IT monitored TPH by infrared spectroscopy analysis over
the course of the study. The data for soil-bound TPH
indicate that, as with the PAH data, variations occurred in
TPH levels in the slurry (Table B-3). As with the PAHs,
the greatest decline in TPH occurred in the first 2 wk of the
study. A rise in the levels of TPH occurred at Week T6,
however, this is 2 wk after total PAHs rose in the slurries.
This delay could reflect the actual production of TPH com-
pounds as metabolic products of the biodegradation of the
PAHs. It could also reflect a simple rise in extraction
efficiency resulting from soil particle comminution.
GC/MS Analytical Results of
Pretreatment and Posttreatment Liquid
Samples
The concentrations of the PAH contaminants in the pre-
treatment liquid samples ranged from 0.006 to 18 mg/L.
The concentrations for the majority of PAHs in the post-
treatment samples were below the established MDLs for
the instruments. After 9 wk of treatment, only the more
recalcitrant, complex PAHs remained in the liquid matrix.
These contaminants ranged in concentration from 0.013 to
0.14 mg/L. Results from Week 12 indicated a further
reduction in liquid phase contaminants as the levels of
PAHs in the soil were further diminished, and the MDLs
for the contaminants from Week 12 were lower than those
for Week 9.
Results of Pretreatment and
Posttreatment Soil Samples Analyzed by
High Performance Liquid
Chromatography (HPLC) Method
In addition to IT's sampling and analyses, ECOVA per-
formed PAH analyses on soil samples. IT analyzed samples
from Weeks T0, T9, and T12 for PAHs; ECOVA, from
Weeks T0, tlt T2t T,, T4, T6, T9, T10, Tu, and TI2. The
ECOVA Laboratory in Redmond employed HPLC (mod-
ified EPA SW-846, Method 8310) to analyze for PAHs.
The baseline soil (Week T0) characterization showed that
naphthalene, acenaphthene, and fluoranthene were the con-
stituents present at the highest levels (range of 2170 ± 250
ppm), followed by fluorene and benzo(a)anthracene (range
Table B-3. Concentrations of Total Petroleum Hydrocarbons (TPH) in Soil, mg/kg
Week
Reactor
1
2
4
5
6
0
35000
17500.
13000
16000
19500
2
7200
2600
2700
3600
2400
4
1800
1800
1600
2300
2400
6
3100
2300
2100
2900
3600
9
1800
3200
1800
1700
2200
11
1900
1700
1700
3700
4900
12
1700
1800
1900
2700
2700
33
-------
of 960 ± 8 ppm). Total PAH levels in these soils were
determined to be 10,970 ppm. The. 2- and 3-ring PAHs
constituted 5890 ppm of the total, and the 4- through 6-ring
PAHs accounted for 5080 ppm.
The PAH degradation rates over all five operating reactors
during the 12-wk study are presented in Table B-4. As seen
in Table B-4, after the initial 2 wk of slurry-phase treat-
ment, 90% of the total PAHs were degraded. Degradation
rates (mg/kg/wk) for 2- and 3-ring PAHs were somewhat
higher at 2 wk (96%) than they were for 4- through 6-ring
PAHs (83%). The final levels at Week T,2 were 653.5 mg/
kg for total PAHs, 152.1 mg/kg for 2- and 3-ring PAHs,
and 501.4 mg/kg for 4- through 6-ring PAHs.
Comparison of Analytical Results
Obtained by GC/MS and HPLC Methods
The GC/MS results indicate total PAHs were degraded by
more than 87% for all reactors during a 12-wk study.
Degradation rates for 2- and 3-ring PAHs (over 98%) were
much higher than they were for 4- through 6-ring PAHs
(72%). These observations agreed in proportion (although
not in absolute concentration) with those obtained in the
ECOVA HPLC study. The HPLC results show 94% reduc-
tion of total PAHs, 97% reduction of 2- and 3-ring PAHs
and 90% reduction of 4- through 6-ring PAHs. Figures B-
3 and B-4 compare the total mean PAH concentration at
Weeks T0, T9, and T12, as determined by GC/MS and HPLC.
Results of Air Monitoring
Air monitoring of total hydrocarbons (THCs), semivolatile
organic compounds (SVOCs), and volatile organic com-
pounds (VOCs) were performed continuously for the first
few days of the demonstration. The VOCs and SVOCs
were monitored periodically through the 9th week. THC
emissions data show high emissions the first two days of
process operation, followed by a steady'decline to baseline
recordings by the fifth day of operation. The VOC volatil-
ization was high the first two days of operation, decreasing
to near analytical detection limits by the third day of opera-
tion. The SVOC emissions (naphthalene, 2-methylnaph-
thalene, acenaphthylene, acenaphthene, dibenzofuran,
fluorene, phenanthrene, and anthracene) were detectable
during the first four days of sampling. Beginning the sixth
day of operation, very small quantities (at or below detec-
tion) of semivolatiles were found.
Table B-4. Percent Total, 2- and 3-Ring, and 4- through 6-Ring PAH Degradation Rates in
Soil Samples Analyzed by HPLC*
Week
Reactor
1
2
3
4
6
9
10
11
12
2- and 3-Ring PAH
Reactor 1
Reactor 2
Reactor 4
Reactor 5
Reactor 6
Mean Percent
4- through 6-Ring
Reactor 1
Reactor 2
Reactor 4
Reactor 5
Reactor 6
Mean Percent
Total PAH
Reactor 1
Reactor 2
Reactor 4
Reactor 5
Reactor 6
98.53
84.25
' 56.64
81.82
88.79
PAH
35.54
34.10
-79.11
28.65
47.60
61.86
60.15
-10.75
56.72
71.34
92.87
97.39
97.17
95.52
96.40
96.14
70.41
83.46
87.28
80.83
85.90
82.89
82.86
90.70
92.26
88.58
91.95
90.00
99.14
99.10
99.38
97.74
98.29
87.37
91.56
93.79
83.36
83.35
93.89
95.48
96.61
90.95
91.96
84.41
95.98
97.76
90.43
97.15
50.80
77.56
90.22
60.76
83.35
69.42
87.13
94.02
76.43
91.30
99.28
96.54
95.02
98.16 .
99.39
88.15
80.13
72.28
64.95
93.53
94.31
88.65
83.73
82.48
96.91
98.56
98.11
98.15
97.74
97.83
98.06
93.23
91.86
93.19
83.65
95.59
92.22
96.18
95.10
95.69
91.09
96.88
95.35
98.71
98.82
95.41
91.54
99.22
86.65
90.30
92.37
86.64
91.99
93.33
94.73
93.90
89.23
96.16
86.28
92.00
91.77
97.87
99.50
85.11
91.16
92.72
80.54
88.50
85.76
91.60
92.24
89.69
94.84
98.21
98.45
98.43
93.36
97.25
97.42
86.16
92.41
94.32
82.34
90.07
90.13
92.83
95.55
96.39
88.16
94.21
94.04
aHPLC = High performance liquid chromatography.
34
-------
6 8 10 12
Week
Figure B-3. Total PAH levels in reactor soil samples as determined by GC/MS.
Figure B-4. Total PAH levels in reactor soil samples as determined by HPLC.
35
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-------
Appendix C
Case Studies
Case Study 1: Slurry-Phase Biological
Treatment of 1 "million-gallon Petroleum
Refinery Waste Sludge Performed by
nETEC
Introduction
A pilot-scale demonstration of slurry-phase treatment was
conducted at a major Gulf Coast refinery to evaluate bio-
logical, treatment as a potential option for remediation of a
large impoundment containing petroleum sludge The treat-
ment goal was to achieve substantial reductions in Skinner
List* organic compounds. In this case, the only Skinner
List compounds present were volatile aromatics and PAH
~Jmf lf batch of sludge was treated for 56 days in a 4.8 x
1U m (Imilgal)bioreactor. The operation was conducted
at a nominal solids loading of 10%.
The overall objective of the field demonstration was to
generate treatment performance information that would
enable evaluation and design of a full-scale biological treat-
ment for the impoundment. The study was designed to
obtain information essential for determining:
the rate and extent of treatment,
the rate and extent of volatile hydrocarbon emissions
during slurry-phase treatment,
engineering design parameters for full-scale treatment
and '
estimated costs for full-scale treatment.
Technical Approach
An abandoned concrete clarifier was retrofitted to be oper-
ated as a batch slurry-phase reactor. Sludge was dredged
from the impoundment and pumped to the reactor Mixing
and aeration were provided by float-mounted mixers and
aerators. The reactor was seeded with a mixed culture of
hydrocarbon-degrading organisms (from an activated sludge
system) suitable for treating refinery wastewater. Reactor
performance was tracked by a combination of daily moni-
toring of and periodic sampling and analysis of the mixed
liquor (i e the suspension .of biological solids, organic and
inert solids, and organic sludge residues) for selected pa-
rameters. Volatile hydrocarbon emissions during treat-
ment were also evaluated.
Materials and Equipment
*
A plan view and cross section of the slurry-phase reactor are
presented in Figures C-l and C-2, respectively. The reactor
consisted of an abandoned, concrete, wastewater clarifier
tank, float-mounted aerators, float-mounted mixers, electri-
cal control panel, and a nutrient delivery system.
The clarifier had a47 m (155 ft) diameter. It was 4 3 m (14 ft)
high at die center and 2,7 m (~9 ft) high at the wall. The floor
of toe clanfier sloped from the wall to the center with a 6%
grade. The operating capacity of the clarifier was approxi-
mately 4.8 x 103 m3 (1.3 x Iff gal).
Aeration was supplied using updraft float-mounted aera-
tors (19 kw; Aqua Aerobic Systems, Inc.) positioned ap-
proximately equidistant from one another at 15 2 m from
the reactor center. Four aerators were used during the
initial 2 wk of treatment to accommodate the high oxygen
demand at startup. One aerator was then taken out of
service for the remainder of the treatment program Each
aerator was fitted with a low trajectory disk to minimize
aerosol formation while maintaining efficient oxygen trans-
ter into the aqueous phase. Mixing was provided by two 30
kw float-mounted mixers spaced approximately 6 m from
the center of the reactor on opposite sides of the center-
drive. A third 19 kw mixer equipped with a 90° discharge
elbow was installed 3 m from the wall to resuspend settled
material in the shallow region near the reactor wall The
latter unit could be repositioned to enable full perimeter
coverage. All three mixers were manufactured by Aqua
Aerobics Systems, Inc. Nutrients and lime (for pH control)
ZL^rrV" 3 3u78°-L (1'000
pumped to the slurry-phase reactor.
37
-------
3,780 Liter
Nutrient Mix Tank
3,780 m3
Liquid/Solids Reactor
Grade
(not to scale)
Power
Control
Panel
Electrical Cable
30 kW Mixer
,19 kW Aerator
Figure C-1. Plan view of slurry-phase reactor.
Mixer
Figure C-2. Cross-section of slurry-phase reactor.
38
-------
Operations and Maintenance
Startup
Sludge was dredged from the impoundment to the reactor
in increments over a period of several days. Sludge ob-
tained from an inline sampling port between the dredge and
the reactor was analyzed daily for solids content (i.e., dry
weight). Values ranged from 7% to 22% by weight. The
target solids concentration was 10%. To achieve this tar-
get, clear supernatant water was decanted from the reactor
on two separate occasions during the loading process; the
amount of water was recorded. By using data from the
inline composite samples and decanted water volumes, the
initial total solids concentration was estimated at approxi-
mately 12%. The total initial slurry volume in the reactor
was 3.6 x 103 m3 (950,000 gal).
Mixing and aeration equipment were installed the day after
the sludge was loaded in the reactor. Mixing began the
following day. The aerators were started incrementally
over a 3-day period to minimize volatile emissions, which are
most significant during the initial stages of batch treatment
Activated sludge from a refinery wastewater treatment sys-
tem was transferred to the slurry-phase reactor 1 day after
mixing began. Approximately 83 m3 (22,000 gal) of acti-
vated sludge, which contained TSS of 3,200 mg/L, were
transferred. The solids transferred to the reactor represented
slightly less than 0.1% of the total solids present at startup.
Mixing and Aeration
This slurry was continuously mixed and aerated during
treatment except for brief periods when certain pieces of
equipment were serviced or the locations of aerators or
mixers were adjusted. The initial mixer/aerator arrange-
ment presented in Figure C-l was modified only slightly
over the 8 wk treatment period to provide maximum solids
suspension. Modifications consisted of periodically rotat-
ing the positions of the 30-kw mixers to suspend solids in
zones of low mixing energy and moving the 19-kw mixer
about the perimeter to scour solids in the shallower areas of
the clarifier.
Nutrient and Lime Additions
Nutrients and lime were added incrementally over the course
of the treatment program in response to weekly analytical
results. The overall target C:N:P ratio for the pilot study
was 100:5:1. Slurries of nitrogen and phosphorus fertiliz-
ers, and slaked lime (Ca(OH)2) were added to the reactor as
required. Nitrogen was added in the form of prilled ammo-
nium nitrate (NH^NC^) and phosphorus as prilled super-
phosphate (P2O5). The superphosphate was later replaced
with 75% phosphoric acid. This material was discharged
directly into the reactor. Lime was added only twice to
prevent excessive declines in mixed-liquor pH.
Performance Monitoring
Reactor operating conditions were monitored daily to de-
termine how well the treatment system was functioning.
Routine monitoring parameters included temperature, pH,
and DO concentration arid uptake rate. These parameters
were determined by using standard methods published by
the American Public Health Association. In addition, the
reactor liquid level, amperages drawn by the mixing/aera-
tion equipment, and any pertinent visual observations were
recorded.
An abbreviated set of chemical analyses was periodically
conducted at the onsite field laboratory. Total solids, soluble
chemical oxygen demand (SCOD) of the mixed liquor, and
soluble nutrients (NH^N and PO4-P) were determined us-
ing HACK test kits.
Sampling and Analysis
Slurry samples were periodically collected from the reactor
with the use of a stainless-steel bailer with dual check
valves. Grab samples were collected from several loca-
tions in the reactor and combined in a single container.
Sampling locations away from the catwalk were accessed
from a boat. Composite samples were homogenized,
subsampled, and submitted for selected chemical analyses.
At the end of the treatment program, sampling included
collecting both suspended and settled-solids materials, which
were analyzed separately. This information was vital for
constituent mass balance calculations. Grab samples of settled
solids were obtained with the use of an extensive sampling
grid. The thickness of the settled solids layer was determined
at each grid location to estimate the volume of settled mate-
rial. Equal portions of settled-solids grab samples were
combined and homogenized to form a grand composite sample
for analysis. This material was analyzed in duplicate for total
solids, oil and grease, PAH, and Skinner List metals.
Results
Waste Characteristics
The petroleum sludge treated in this study was weathered
from years of accumulation in the impoundment. Analyses
of slurry obtained from the slurry-phase startup were com-
pared with analyses of a composite sample obtained "inline"
during the sludge transfer operation. The inline sample
was eentrifuged before analysis to determine both aqueous
and solid-phase constituent concentrations. The aqueous
phase concentrations were negligible in comparison with
the solid-phase concentrations.
The data indicated that the sludge was a good candidate for
biological treatment. The distribution of PAH was weighted
toward the low-molecular-weight end of the spectrum (i.e.,
39
-------
2- and 3-ring compounds predominate): These compounds
rapidly degrade in biological treatment systems.5 Other
semivolatile base/neutral compounds (e.g., phthalates) and
acid compounds were below detection limits.
Operating Conditions
A significant head of foam (12 to 25 cm) developed on the
surface of the slurry early in the treatment operation and
persisted to the end of the study. The development of foam
is typical for aerated biological systems.
The mixers and aerators were generally well suited for
operating in the high-solids environment of the reactor.
The poor reactor geometry (i.e., shallow mixing depths and
sloped bottom), however, limited the diameter over which
the 30-kw mixers were effective so that a settled solids
layer formed near the reactor wall and along the axis bisect-
ing the mixers. The 19-kw mixer was used to periodically
scour settled solids near the wall along the entire perimeter.
A solids mass balance at the end of the study was based on
both suspended mixed liquor solids and settled solids in the
reactor. The settled material represented approximately
25% of the total solids in the reactor at the end of treatment.
A net solids reduction of approximately 10% occurred
during treatment.
The temperature of the mixed liquor ranged between 20°C
and 25°C with an average of 22.6 ±0.6°C (n=50) in re-
sponse to climatic conditions at the site. DO concentra-
tions remained above 2 mg/L during the majority of the
treatment program; this is sufficient to maintain healthy
aerobic conditions. The pH of the mixed liquor was stable
near 6.0 for the majority of the study. Two lime amend-
ments of 114 kg each precluded a drop below pH 6.0.
The OURs were measured as an index of biological activity
levels. The OUR data fluctuated near 0.20 mg/L/min from
day 20 to the end of treatment. Trends of increasing OUR
during this period may have been in response to nutrient
additions. Generally, the low OUR values reflected the
highly weathered nature of the sludge in the impoundment.
The SCOD in filtered mixed liquor was determined at least
once each week. Clarified water from the original dredge
slurry had a COD of approximately 350 mg/L. The COD
steadily increased as treatment progressed and reached an
apparently stable level of approximately 900 mg/L at the end
of treatment. A combination of compound solubilization
from biosurfactant activity and the biological production of
soluble metabolites probably caused the observed increase.
Analytical Results
Table C-l contains the results of total solids, nutrient, and
microbial enumeration analyses. Total solids in the mixed
liquor were initially lower than the 12% expected at startup
because some solids were not suspended. A combination
of evaporative concentration and repositioning the mixing
equipment to reduce settling slightly increased the total
solids. Microbial plate counts for total heterotrophic or-
ganisms showed concentrations ranged between 107 and
10s CFU/mL; this indicated that a substantial and healthy
biomass had developed in the reactor and that there were no
significant toxicity effects.
Ammonia-nitrogen concentrations averaged approximately
10 mg/L during the study. Levels on the order of 1 mg/L
occurring during weeks 3 and 4 indicated a possible nitro-
gen limitation during this period. The analytical laboratory
reported that dissolved orthophosphate concentrations were
difficult to determine because of matrix interferences. All
values reported by the laboratory were below the detection
limit. Separate tests, however, were conducted onsite us-
ing a HACH molybdovanadate colorimetric test method.
Results of this testing (not shown) demonstrated that dis-
solved orthophosphate exceeded 1 mg/L only twice (1.5
and 2 mg/L). These data were supported by "standard-
additions" quality assurance testing and suggested a poten-
tial limitation of phosphorus to the biological system. Sorp-
tion of nutrients to solid constituents may have limited the
free aqueous phase concentrations.
Concentrations of BETXs in the mixed liquor were reduced
to below detection limits in 1 day, primarily as a result of
stripping. Volatile hydrocarbon emissions from the slurry-
phase biological treatment reactor were evaluated in a com-
prehensive study that is reported elsewhere.6 Briefly, emis-
sions of total nonmethane hydrocarbons were reduced to
background levels by day 6.
The time required to reach a 50% reduction in oil and
grease, based on a calculated linear rate, was between 80
and 90 days. This loss rate is at the lower end of the range
observed in other studies (25 to 50 days) for degradation of
petroleum sludges in slurry systems. The time required to
achieve a 50% reduction in oil and grease is typically
between 40 and 60 days at temperatures of 20° to 25°C.
The low removal rates observed for oil and grease in the
reactor are related to the weathered sludge conditions
whereby the easy-to-degrade organics were absent.
Most of the PAHs present in the original sample were
substantially degraded after 2 wk of treatment. The report
for the 4-wk samples had one detected value for phenan-
threne (0.6 mg/Kg) and one for pyrene (0.% mg/Kg) in the
same individual sample. The 4-wk samples were centri-
fuged before analysis and therefore contained a signifi-
cantly higher fraction of solids than did the mixed-liquor
samples receiving no pretreatment in the form of centrifu-
gation. The detection limits of both the 2- and 4-wk
analyses were very low, at approximately 0.5 mg/kg.
Each dredge composite sample was centrifuged before
analysis, which accounts for the high solids concentra-
40
-------
Table C-1. Analytical Results for Percent Solids, Nutrients, and Bacterial Enumerations
Elapsed
Time, day Mixed Liquor Total
Solids, %
Date
9/26/89
10/3/89
10/10/89
10/17/89
10/24/89
10/31/89
11/7/89
11/14/89
7
14
21
28
35
42
49
56
Sample
9.0
9.1
8.0
10.4
8.7
9.6
9.5
Sample Dupa
8.0
9.0
8.0
10.4
9.1
9.4
9.6
9.7
Nitrogen, mg/L
N-Ammonia N-Nitrate
12.3 <1
9.4 5
<1 <1
2.1 <1
4.9 <1
15.7 18.8
45.7 <1
22 3.8
Ortho-
Phosphate,
mg/L
<31
<31
<374
<377
<379
<379
<152
<150
Aerobic Bacteria
Population Densities,
CFU/g
Sample
>6.1E+06
>6.1E+06
2.1E+07
4.2E+08
6.1E+07
Sample Dup
_
1 .7E+07
1.9E+07
tions reported. The concentrations of PAH in the aqueous
phase of this sample were negligible and are therefore not
reported here. The end-of-treatment settled solids and
centrif uged mixed-liquor solids contained substantially lower
concentrations of PAH than those observed in the dredge
sample; this indicates that significant degradation occurred.
Discussion
Performance Summary
The treatment system generally performed well for reduc-
ing organic constituents to nondetectable levels in the mixed
liquor.
Volatile hydrocarbons were rapidly lost through a combina-
tion of volatilization and biodegradation. The fraction lost by
volatilization was significant because the treatment demon-
stration was conducted in batch mode that necessitated aera-
tion of 100% untreated sludge in the presence of a low initial
concentration of biomass. An estimated 910 kg of nonmethane
hydrocarbons were emitted for the approximately 425,000 kg
of solids treated. To minimize air emissions, requirements to
control air emissions are likely to be common for full-scale
impoundment closures in the future. One approach to reduc-
ing emissions is to conduct slurry-phase treatment in a con-
tinuous system where full advantage can be taken of biologi-
cal removal mechanisms at low equilibrium slurry concentra-
tions. Minimizing surface disturbances (e.g., providing oxy-
gen by submerged diffusion of pure oxygen or using downdraft
aerators) would also reduce emissions. Finally, slurry-phase
biological treatment systems could be designed with a pre-
treatment step to physically remove and capture volatiles
(i.e., stripping followed by carbon adsorption, combustion, or
biofiltration) before slurry-phase treatment.
Semivolatile constituents were rapidly degraded in the treat-
ment demonstration. PAHs in mixed liquor solids were all
below detection limits after week 4 of treatment. A mass
balance on PAH compounds was done with the use of data
from the inline dredge composite sample and reactor settled
solids PAH concentrations obtained at the end of treatment
(Table C-2). The mass of settled solids that had accumu-
lated at the reactor bottom was estimated, as discussed
earlier. The estimate indicated that approximately 20% of
the reactor solids were settled at any given moment. Ad-
justments in the positions of mixing equipment during the
study helped to cycle much of the settled material into the
suspended mixed liquor where aerobic biodegradation could
occur. Overall,PAHremovalsweregreaterthan90%. Greater
reductions would probably have been achieved had mixing
maintained a greater percentage of solids in suspension.
When an impoundment sludge is regarded as a listed petro-
leum waste and land disposal of the treated residue is being
considered, BOAT standards would apply. Results of this
demonstration program indicate that BDAT levels can be
achieved by slurry-phase treatment especially when the
PAH constituents in the sludge are predominantly 2- and 3-
ring compounds.
Case Study 2: Slurry-Phase Biological
Treatment of Petrochemical Waste-
Contaminated Soils and Sludges
Performed by Radian
Introduction
A slurry bioremediation process developed by Radian Cor-
poration for the treatment of contaminated sludges and
soils was pilot tested at the Sheridan Disposal Services Site
near Hempstead, TX. This study involved pilot-scale test-
41
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Table C-2. Reactor PAH Mass Balance
Beginning of Treatment3
Solids mass (kg)
Sample replicate
PAH Mass (kg)
Naphthalene
1-methy [naphthalene
Phenanthrene
Pyrene
Benzo(a)anthracene
4.29E+05
Sample
14.12
14.12
14.12
3.62
1.77
,
Sample Dupc
16.42
16.42
24.63
16.42
4.41
9.85
Avg.
15.27
15.27
19.38
10.02
4.41
5.81
End of Treatment13
9.26E+04
Sample
1.39
1.20
1.44
0.37
0.99
0.19
Sample Dup
1.16
1.45
1.89
0.96
2.50
0.81
Avg.
1.27
1.32
1.66
0.67
1.75
0.50
% Reduction
91.7
91.3
91.4
93.4
60.5
91.4
Initial masses calculated from results of inline dredge composite analyses.
b Final masses calculated by using results of settled sludge analyses. Mixed jiquor analyses were all less than
detection limits (<0.6 mg/kg) after 4 weeks.
c Dup - Duplicate.
ing of a slurry bioremediation process that Radian had
evaluated on the bench-scalea process to treat waste
sludges from petrochemical production.7 The bench-scale
studies with petrochemical waste sludges and tars found
that compounds typical of the Sheridan waste (those with
high vapor pressures and especially those with low water
solubility) were rapidly dispersed within a slurry bioreac-
tor; those kinds of wastes were more likely to be removed
from solution during the early stages of system acclimation
by volatilization. This effect is most pronounced in a batch
biooxidation process because the point when waste con-
stituent loading is highest is also the point when the accli-
mated microbial population is lowest.
Therefore, it was postulated that the use of continuous or
semicontinuous feeding should reduce the degree of volatile
hydrocarbon loss during biooxidation. This would level the
waste loadings on the reactor and thereby permit biodegrada-
tion to compete favorably with the rate of constituent volatil-
ization. Recycle of biomass also was hypothesized as an
effective way to maintain high concentrations of acclimated
microorganisms within the process while sustaining a high
organic loading on the system. Radian conducted additional
research on methods of treating organic-laden wastes, like the
Sheridan wastes, during the period between the bench-scale
study and the development of the pilot system test plan. From
this, Radian concluded that a continuous flow process was
viable, and that Sheridan waste was appropriate for multi-
stage reactor applications. Reactors commercially available
from the EIMCO Process Equipment Company were judged
to be desirable for the aerobic treatment of the Sheridan class
of wastes (Le., tarry, oily sludges, and soils).
Study Objectives
The objectives of the pilot-scale bioremediation study were
to achieve the performance levels obtained during earlier
bench-scale batch treatability studies. A continuous-flow
process was to be used one operating between 30 and 15
days of HRT and with a minimum of volatile organic com-
pound loss to the surroundings. The Radian slurry bioreme-
diation process8 minimized volatile organic compound emis-
sions by implementing the following design specifications:
. maintaining a low hydraulic shear environment in the
slurry bioreactors,
using a high-efficiency, gas transfer system to reduce
the volume of air supplied to the reactors,
using biomass recirculation to control the waste-to-
microorganism ratio of the process during continuous
or semicontinuous operation,
using bioaugmentation and the principles of continu-
ous culture microbial enrichment to promote the de-
velopment of microorganisms highly acclimated to the
degradation of volatile aromatic hydrocarbons found
in Sheridan site wastes, and
using a covered tank reactor design.
Study Activities
The pilot-scale slurry bioremediation study included the
following program activities:
A materials handling demonstration that evaluated a
pond sludge, a soil removal strategy, and a method for
pond partitioning. Additionally, a demonstration of an
appropriate method of pond partitioning and sludge
removal for the full-scale remediation was performed.
42
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A pilot-scale biotreatment study that included material
handling, bioseed acclimation, bioreactor system quasi-
steady-state performance testing, biotreatment residue
characterizations, and data analysis for design and scaleup.
An air emissions characterization study that examined
both source emissions and ambient air quality during
the materials handling demonstration, pilot-scale
biotreatment acclimation, and pilot-scale biotreatment
steady-state performance testing.
Site Description
The Sheridan Disposal Services site is located 9 mi northwest
of the City of Hempstead in Waller County, TX. The facility
covers 110 acres of a 700-acre tract that is bordered on the
north by the Brazos River and on the south by Clark Bottom
Road. The site includes a 12- to 15-acre pond included in a
17-acre diked area, a 42-acre evaporation area, and a group of
abandoned structures located inside the pond dike.
The pond contains approximately 23,000 m3 of tarry, petro-
leum-based sludge and an additional estimated 7,700 m3 of
contaminated soil. The sludge is contaminated with vola-
tile aromatic compounds, polynuclear aromatic compounds,
phenol and substituted phenols, polychlorinated biphenyls,
and other constituents.
The pilot-scale slurry bioremediation process was constructed
on the eastern dike of the pond near the abandoned structures.
This area was selected because it provided a relatively large
flat surface near the pond and is accessible by existing roads.
The area also is near existing electric utility lines.
Waste Characteristics
The conventional pollutant constituents measured for the
waste sludges and excavated soils at the Sheridan site are
summarized (Table C-3). These data indicate that the
waste-sludge constituent concentrations were higher during
the 15-day HRT test period than that measured during the 30-
day HRT test period. This results from thicker waste sludges
being collected from the pond during the 15-day HRT test
period. Probably thicker slurries were obtained from the
pond because the dredge operation improved during the
project. As the operation of the dredge became more routine,
the average total solids concentration of the waste sludge
increased from about 38% to 58%. The viscosity also in-
creased significantly from the 30-day HRT to the 15-day
HRT test period. The actual tarry waste viscosity averaged
approximately 1-mil centipoise when measured in the pond.
Values for the toxic organic pollutant constituent classes
measured for the waste sludges and excavated soils at the
Sheridan site (Table C-4) are averages for each class of
substance found in the waste sludges and excavated soils
during the 30- and 15-day HRT test periods. Over the
course of the study, more than 60 organic compounds were
identified in the input and output streams of the slurry
bioremediation process.
During the 30-day HRT test period, the waste sludge con-
tained higher levels of 2- and 3-ring PAHs, phthalates, and
volatile chlorinated organics than did the 15-day waste
sludge; during the 15-day HRT test period, the waste sludge
composition contained more amines, BETXS, and ketones.
This variation in composition is not unexpected because of
the number of waste constituents present in the pond. The
concentrations of PCBs as Aroclors and congeners were
relatively unchanged over the study period. The phenol
class also was constant and represented the highest
concentration of identified substances in the waste.
Pilot-Plant Description
The Sheridan site pilot bioremediation system (Figure C-3)
consisted of front-end waste storage facilities, four
bioprocessing reaction vessels, and solids separation vessels.
Sludge was dredged periodically from the pond and stored in
a conical-bottom, fiberglass tank. Soils collected from a
dewatered area of the pond at the start of testing were stored
on a plastic liner. As required, the waste sludge, soil, re-
cycled biomass, and nutrients were added to the first-stage,
waste-dissolution reactor, a stirred-tank reactor in which dis-
solution of the tar components begins. Dissolution of the
waste sludge was the primary objective of this reactor. Air
was not intentionally introduced into the dissolution reactor;
however, because the sludge level dropped during process-
ing, limited aeration probably occurred in this tank, which led
to the biooxidation of some easily degradable compounds. A
peristaltic pump with a time-actuated feed valve transferred
this waste-biomass slurry to the first of three aerobic bioreactors.
The aerobic vessels were 10,000 L BioLift reactors sup-
plied by the EIMCO Process Equipment Company, Salt
Lake City, UT. The BioLift reactors employed an airlift,
an auxiliary mixer, and diffused aeration to achieve aera-
tion and mixing. The diffusers consist of fine bubble,
nitrile-butadiene rubber membranes. A thickener was used
at the end of processing to separate treated residue from
biomass and decant water. The biomass and decant water
were returned to the dissolution reactor for blending with
fresh waste sludge and soil.
Materials Handling Requirement
Four major activities were related to materials handling
during the pilot-scale slurry bioremediation program at the
Sheridan site:
waste sludge dredging operations,
pond partitioning,
43
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Table C-3. Waste Sludge and Excavated Soil Conventional Analyses
30-Day HRT Test
15-Day HRT Test
All Values
Stream Analysis
Waste sludge
Viscosity, cps
Total COD, mg/kg
Total solids, mg/kg
TVS, mg/kg
O&G, mg/kg
Specific gravity
Soil
Total COD, mg/kg
Total solids, mg/kg
TVS, mg/kg
O&G, mg/kg
Specific gravity
Average
248,872
290,400
382,464
279,610
51,058
1.084
127,592
785,680
150,794
51,951
1.660
Std. Dev.
442,559
80,566
166,193
146,176
16.401
0.024
61,139
71,426
58,483
18,280
0.154
Average
1,202,500
490,000
585,059
480,007
371,859
1.045
122,280
773,441
142,994
48,446
1.477
Std. Dev.
514,093
345,893
120,350 .
126,920
181,245
0.028
69,741
65,434
46,176
19,379
0.100
Average
725,686
390,200
483,762
379,809
211,459
1.064
124,936
779,560
146,894
50,199
1.581
Std. Dev.
676,045
259,086
173,535
166,767
208,102
0.032
61,894
64,899
49,847
17,856
0.157
Table C-4. Chemical Classification of Feed Streams, mg/kg, as received basis
Organic
Pollutant
Waste Sludge
2-3 Ring PAHs
4-6 Ring PAHs
Amines
BETXS
Furans
Ketones
PCB Aroclors
PCB Congeners
Phenols
Phthalates
Volatile chlorinated organics
Soil
2-3 Ring PAHs
4-6 Ring PAHs
Amines
BETXS
Furans
Ketones
PCB Aroclors
PCB Congeners
Phenols
Phthalates
Volatile chlorinated organics
Average of All
Values
847
30
272
3,270
48
283
54
45
5,680
217
185
22
5,2
18
116
0.98
4.9
7.6
7.1
13
21
1.8
30-Day HRT
Average
1,015
20
177
1,912
48
239
54
39
5,655
261
247
20
4.4
13
26
0.82
0.52
7.9
7.2
8.1
27
0.35
15-Day HRT
Average
680
38
367
4,628
NDa
327
55
50
5,705
174
123
23
6.3
24
207
1.3
7.1
6.4
7.0
22
14
3.3
aND = not detected
44
-------
soil excavation and storage, and
routine feed slurry preparation for bioremediation pro-
cessing.
Dredging Operations
A commercial-scale hydraulic dredge (IMS Versi-Dredge-
Model 3100), with a submerged hydraulically driven pump
that used winches to pull the pump head into the face of the
sludge blanket, proved effective for removing the Sheridan
site waste sludge from the pond bottom. This method of
dredging was selected because bottom sludge could be
removed from the pond without disturbing the water layer
above. The hydraulic dredge was capable of pumping
waste sludge from the pond without the addition of large
amounts of water and the subsequent liberation of volatile
organic compounds to the atmosphere.
During the demonstration of the dredge operation, two "Baker"
tanks were filled with sludge from the southeast comer of the
pond while VOC emissions were monitored. Flux chamber
measurements at the surface of the pond near the pump head also
were performed to obtain air emission values from the pond
surface during dredging operations. The dredge successfully
cleaned the pond bottom so that soil could be excavated.
Pond Partitioning
The Sheridan site Record of Decision (ROD) specified that
the first 6 in. of soil below the pond sludge also were to be
biotreated.9 To remove bottom soil from the pond, a tem-
porary, nonintrusive method of segregating dredged areas
from undredged areas was developed. A polyethylene
plastic tube that can be inflated to create a temporary water
dam partitioned the pond. The device, manufactured by
Water Structures Inc., consists of two internal tubes inside
an outer tube. When both tubes are inflated with pond
water, frictional resistance prevents the structure from mov-
ing laterally. This equipment can be installed with minimal
exposure of personnel to the sludge.
A single 100-ft section of this water-structure devise was
positioned across a corner section of the sludge pond.
When the structure was inflated with pond water, a dam
was created which separated a dredged area from the main
body of the pond. The enclosed section of pond was dewa-
tered, and the water structure was able to maintain the cor-
doned area with minimal seepage for approximately 30 days.
Soil Excavation
Immediately after dewatering the partitioned pond seg-
ment, flux chamber measurements were made for deter-
mining emission levels from the freshly exposed bottom
soil. A track hoe then excavated approximately 20 yd3 of
soil to a depth of 6 in. This soil was stored on a synthetic
plastic liner (covered by another liner) for use as feed in the
bioremediation pilot study. During feed preparation, the
cover was pulled back and a small front-end loader loaded
Waste Sludge
from Dredge
Raw Waste
Storage Tank
Soils from
Storage
Liquid Residue (Decant)
Sent to Pond
Waste Dissolution
Reactor Reactor
Feed Pump
Air Intake**
Air Compressors
(1 functional; 2 standby)
T VIV.J1U1IJP | ICV^yirlC
Biological Residue Tank & Pump
(Product)
to Product Storage Drums
Figure C-3. Sheridan waste slurry bioremediation process schematic8.
"Castaldi, F.J., U.S. PTO Serial No. 07/733,344, patent pending.
45
-------
the soil into the pilot-plant dissolution reaction vessel.
Routine Feed Preparation
A waste-sludge storage vessel held dredged material from the
pond. A conveyance line from the hydraulic dredge, (a
flexible hose connected to a 12-in.-diameter aluminum-pipe
header on the dike adjacent to the pond) supplied freshly
pumped waste sludge to the sludge storage vessel twice
weekly. The dredge's forward speed, cutter head depth, and
pumping rate were controlled so the pond bottom sludge
provided to the pilot system contained minimal water. This
way the percent solids of the waste were maintained close to
that normally seen in the pond. After some experimentation
with dredge operation, the dredge pump was capable of
moving a waste sludge slurry consisting of 50 % solids at flow
rates of between 100 and 200 gpm. This solids level was
considered adequate for full-scale operation of the process.
Because the dredge cable was anchored at several points on
either side of the pond, the dredge could operate at many
different locations in the pond. The material collected with
the dredge pump was, therefore, representative of the entire
pond. Between 1000 and 1500 gal of thickened raw waste
sludge from each dredging event was used for feed preparation.
Waste sludge and soils were fed into the first-stage, waste
dissolution reactor where the solids were slurried with
active biomass and kept in suspension by a mixer. Volatil-
ization of organics to the ambient air was minimized by using
a low-speed, radial, flat-blade turbine mixer in the reaction
vessel. Feed mixtures were prepared on a batch basis when
the slurry level in the waste dissolution reactor was low.
Nutrients as ammonium sulfate and diammonium phosphate
were added to the slurry at the time of feed preparation.
The slurry mixture in the waste dissolution reactor was con-
tinuously pumped from the vessel bottom, through a
recirculation loop, and back into the reactor where it was
reblended with the bulk slurry. A timer-actuated, electric ball
valve diverted slurry feed material to the aerobic bioreactor
train on a semicontinuous basis (i.e., 1 to 2 min. every quarter
hour). From that point on, slurry flowed continuously through
the process. The aerobic bioreactor train was fed 96 times
each day to achieve as near a continuous feed rate as practi-
cable at the scale of the test conditions. (On pilot scale, true
continuous flow could not be achieved because of the viscos-
ity of the waste slurry and the potential for pump clogs that
result from low-flow conditions with such materials.)
Personnel Requirement
A field engineer and a field chemist manned the pilot-scale
process 12 to 14 hr/day. The field engineer's responsibility was
for the pilot-plant operations and process equipment mainte-
nance; the field chemist's responsibility was onsite sampling and
analytical work. A mechanical technician visited the site weekly
to repair and/or maintain all motors, pumps, compressors, and
other mechanical equipment Less frequent site visits were made
by an electrical technician to repair and/or maintain electrical
equipmentduringtheproject An additional field engineer would
spend several hours a week at the site assisting with the dredging
and other materials handling activities.
The pilot plant also had an automatic-dialing, remote, monitoring
system for periods when the equipment was not manned (i.e.,
between 9:00 p.m. and 7:00 am. the next day). This system was
alerted when one of the four alarm points was not operating:
aerobic reactor slurry circulation pump (cascaded so
that there was only one contact for all three aerobic
reactors);
compressors (cascaded so that there was only one
contact for all compressors);
slurry feed pump; and
dissolution reactor mixer.
There also was a general power failure alarm that indicated
a utility power outage, even though an auxiliary generator
would have kicked in to provide the system power.
Regulatory Requirement
The ARARs for the Sheridan study indicate that the appro-
priate regulatory requirements are covered by 40 CFR Sec-
tions 264.14 (site security); 264.17 (incompatible waste
storage); 264.114 (equipment decontamination); and Part
761, Subpart G (PCB spill policy), and Section 4.01 of the
Texas Clean Air Act.
To ensure compliance with all relevant and appropriate
requirements for the protection of groundwater and air
quality at the site, the pilot study provided periodic ambient
monitoring of both groundwater and air to verify that site
conditions were not causing or contributing additional pol-
lution. The pilot study was designed to ensure that emis-
sions were in compliance with the ARARs.
Health and Safety Requirements
The major chemical and physical hazards associated with
the study were:
Chemical HazardsThe potential chemical hazards,
identified with handling the waste material from the
pond, were PCBs (primarily Aroclor-1242 and -1260),
volatile organics (particularly benzene), and
semivolatile organics (primarily phenol).
Physical HazardsThe primary physical hazards in-
46
-------
eluded mechanical hazards, electrical hazards, noise,
heat stress, and general site hazards (slips, trips, and
falls).
The personal protective equipment used at the Sheridan site
during the study is summarized (Table C-5). Based on
results of the personnel monitoring program, the actual
levels of protection required for the waste material collec-
tion and pilot-plant activities were modified.
Performance of Technology
Bioremediation Process Performance
The pilot-scale process was operated at two target experi-
mental HRTs: 30 days and 15 days, which correspond to
conceptual waste load conditions of a full-scale, aerobic,
bioreactor train. Actual system residence times at these
experimental load conditions were 42 days and 17.5 days
respectively. The process was operated over three HRTs
during each experimental load condition. The sampling sched-
ule developed for the program involved characterizing all
process streams twice per system HRT (every 2 wk during
30-day HRT testing, weekly during 15-day HRT operation)
Priority constituents were generally sampled after one full-
system HRT to allow for process stabilization at the load
condition of interest The waste sludge, soil, and biotreated
residue were analyzed four times during each test period for
volauleandsemivolatilecompoundsandPCBAroclors Each
waste stream was also analyzed twice for PCB congeners The
pdot-scalebiotreatedresiduequalily is compared with inequality
of the Shendan waste sludge and excavated soil (Tables C-6 and
C-7) for the 30- and 15-day HRT load conditions.
The biotreated residue analyses (Table C-6) for the 30-day
HRT load condition show excellent removal for all priority
constituents (i.e., constituent concentrations in the treated
residue at less than 1.0 mg/kg), except for the pollutants
bis(2-ethylhexyl)phthalate and the PCB Aroclors. Both of
these pollutants were present in waste streams examined in
earlier bench-scale laboratory studies, but they were found at
higher concentrations in the Sheridan site waste sludges and
soils during the pilot demonstration of the process The
slightly higher volatile hydrocarbon concentrations in
biotreated residue obtained during the first sampling event
may have resulted from steady-state residue contamination
with material that accumulated in the treated residue separa-
tor from the previous process acclimation period The sepa-
rator was cleaned after the first sampling event, and treated
residue qualities for volatile hydrocarbons improved thereaf-
ter. During the 30-day HRT load condition, the concentration
of most pollutant constituents in the waste sludge increased
with each sampling event (Table C-6). Nevertheless the
Table C-5. Personal Protective Equipment Requirements'
Task
Waste sludge and
soils collection
Process feed
collection
Waste dissolution
reactor loading
Process acclimation
period
Process steady-
state operation
Packaging and
shipping samples
Sample prep and
analysis
Personnel
Dredge operator
and all
exclusion zone
workers
Support zone
personnel
Exclusion zone
personnel
Worker directly
handling waste
Exclusion zone
personnel
Exclusion zone
personnel
Sample controller
Analyst
Respirator11
Yesc
Available
for use
Yesc
Yesc
Yes9
Available
for use
Available
for use
Available
Coveralls
Yesd
Available
for use
Yesd
Yesd
Available
for use
Availabfe
for use
No
No
Chemically
Resistant
Gloves
Yese
Available
for use
Yese
Yes»
Available
for use
Available
for use
Available
for use
Available
for use
Neoprene
Safety
Boots
Yes
Available
for use
Yes
Yes
Available
for use
Available
for use
No
No
Safety
Glasses
No'
Yes
No'
No'
Yes
Yes
Yes
Yes
1 niuMMutjuiiuiHuiiis were modit.ed when the. results of personnel monitnrinn i^,^ «, r»L« __
Splash
Goggles
No'
Available
for use
No'
No'
Available
for use
Available
for use
No
Available
Ear
Plugs/
Muffs
Available
for use
Available
for use
No
Available
for use
Available
for use
Available
for use
No
No
Safety
Hel-met
Yes
Yes
Yes
Yes
Yes
Yes
No
No
not being exceeded.
b All respirator cartridges were changed on a daily basis.
< Full facepiece with combination organic vapor/high efficiency paniculate filters
Polyethylene-coated with attached boots and hood.
e Nitrite outer gloves with inner vinyl gloves.
f Full facepiece respirator used.
3 Half-face respirator with combination organic vapor/high efficiency paniculate filters.
47
-------
Table C-6. Summarized Test Results of 30-Day Residence Time Load Condition, mg/kg
Compound
Percent Moisture
Benzene
Ethyl benzene
Methyl ethyl ketone
4-Methyl-2-pentanone (MIBK)
Styrene
Tetrachloroethene
Toluene
Xylenes
Ws(2-Ethylhexyl)phthalate
2,4-Dichtorophenol
2,4-Dlmethylphenol
2-MethylnaphthaIene
Naphthalene
Phenanthrene
Phenol
PCB-1242
PCB-1260
1
77
95
55
16
38
38
8.7
71
160
13
ND
280
59
62
38
490
16
ND
Waste Sludge
Sampling Event3
2 3
77 71
260 696
'85 570
ND ND
100 199
100 325
11 46
170 615
310 1447
69 590
ND ND
340 1200
ND 530
81 490
71 ND
520 2700
42 70
3.7 14
5
48
330
400
ND
ND-
250
44
470
1200
360
ND
1500
550
590
230
4500
59
12
Excavated Soil
Sampling Event3
1
27
1.7
13
ND
ND
ND
0.42
4.5
33
5.1
ND
ND
ND
ND
ND
ND
6.3
ND
2
8.1
NDb
ND
ND
ND
ND
ND
ND
ND
59
ND
ND
ND
ND
ND
ND
5.4.
2
3
24
0.24
1.7
ND
ND
ND
ND
0.45
4.5
19
ND
ND
ND
ND
ND
8.7
7.8
3.9
5
31
2.3
9.3
ND
ND
ND
ND
3.4
31
. 11
ND
ND
5.3
ND
5.7
ND
4.3
2
Treated Residue
Sampling Event3
1
87
ND
0.15
ND
ND
0.18
ND
0.12
0.78
19
ND
ND
ND
ND
ND
ND
10
ND
2
67
. ND
ND
ND
ND
ND
ND
ND
ND
120
ND
ND
ND
ND
ND
ND
22
3.5
3
78
ND
ND
ND
ND
ND
ND
ND
ND
23
ND
ND
ND
ND
ND
ND
23
3.2
5
64~
ND
ND
ND
ND
ND
0.23
0.1
ND
85
ND
ND
ND
ND
ND
ND
31
4.7
a Sampling events denote the points where priority constituents were sampled.
residence times at the test conditions evaluated.
b ND * Not detected.
These events represent 1.5/2.0/2.5/3.0 hydraulic
Table C-7. Summarized Test Results of 15-Day Residence Time Load Condition, mg/kg
Waste Sludge
Sampling Event3
Compound
Percent moisture
Benzene
Ethyl benzene
Methyl ethyl ketone
4-Methyl-2-pentanone (MIBK)
Styrene
Tetrachloroethene
Toluene
Xylenes
bis(2-Ethylhexyl)phthalate
2,4-Dichlorophenol
2,4-Dimethylphenol
2-Methylnaphthalene
Naphthalene
Phenanthrene
Phenol
PCB-1242
7
45
300
520
ND
170
430
39
800
1600
ND
ND
540
150
150
63
1400
49
5.5
8 9
54 53
450 520
690 870
ND ND
320 350
660 750
36 58
1200 1500
2100 2600
ND ND
ND ND
620 1100
ND ND
150 270
ND ND
1600 3100
36 41
5.7 7.2
10
49
300
470
ND
ND
390
33
760
1600
380
ND
1200
ND
320
ND
3100
47
5.6
Excavated Soil
Sampling Event3
7
30
24
75
ND
ND
ND
3.4
49
230
ND
ND
ND
ND
ND
'ND
ND
5.6
0.77
8
28
NDb
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
3.9
1.1
9
27
2.8
16
ND
ND
ND
1.1
9.3
59
14
ND
ND
ND
ND
ND
9.9
1.8
0.58
10
31
21
64
ND
2.5
1.9
1.7
44
230
11
ND
6.9
6.3
7
8.5
19
5.3
2
Treated Residue
Sampling Event3
7
87
ND
4.6
ND
2.5
ND
ND
2.2
14
ND
ND
ND
ND
ND
ND
ND
8
76
ND
2.5
ND
ND
0.55
ND
1.7
13
13
ND
ND
10
ND
16
ND
16 18
2.1
1.5
9
87
ND
1.3
ND
ND
ND
ND
1.1
7.7
9.2
ND
ND
7.1
ND
11
ND
18
3.1
10
82~
ND
18
ND
ND
2.9
0.8
6.6
42
22
ND
17
13
7
22
11
6.7
1.5
a Sampling events denote the points where priority constituents were sampled.
residence times at the test conditions evaluated.
b ND - Not detected.
These events represent 2.i
48.
-------
apparent biotreated residue quality remained consistent
throughout this test period.
Table C-7 presents similar data for the 15-day HRT load
condition. During this test, the waste sludge composition
showed less variability, with only phenol reporting an in-
creasing concentration trend with sampling event. This prob-
ably resulted from the apparendy improved operation of the
hydraulic dredge, which averaged a sludge moisture level of
approximately 50%.
During the 15-day, residence-time load condition, the
biotreated residue contained higher concentrations of priority
constituents than those found in treated residue from the 30-
day HRT test. The system operating temperatures during the
15-day HRT load condition were generally lower than sys-
tem temperatures recorded at the 30-day residence time load
(i.e., 26.3°C versus 33.3°C for the 15- and 30-day HRT loads,
respectively). The combination of the higher waste load and
lower operating temperatures during the 15-day HRT load
condition were responsible for the reduced biodegradation of
priority constituents. All other parameters (e.g., biochemical
oxygen demand [BOD], oil and grease) used to track perfor-
mance of the treatment system also indicated reduced
biotreatment effectiveness at this load condition.
Tables C-8 and C-9 present mass flow rates of the various
classes of compounds for the 30- and 15-day HRT load
condition test periods, respectively. The stream mass rates
are based on the average flows measured during the test
Tables C-8. Summarized Mass Flow Rates for 30-Day HRT Load Condition Test Period, g/day
Chemical Class
Stream mass,3''5 kg/day
Moisture '
2-3 Ring PAHs
4-6 Ring PAHs
Amines .
Benzene
BETXS
Furans
Ketones
PCS Aroclors
PCB congeners
Phenols
Phthalates
Volatile chlorinated organics
Sludge
139
61.8%
369
7
64
125
695
17
87
20
14
2058
95
90
Soil
77
21.4%
2.0
0.4
1.3
0.1
2.5
0.1
0.1
0.8
0.7
0.8
2.6
0.0
Residue
98
75.4%
4.0
4.0
0.0
0.0
0.1
0.0
0.0
10.7
8:3
0.0
25.8
0.2
Decant
Liquid
64
0
0
0
0
0.05
0
0.02
0
0.001
0.01
0.05
0.05
Vent Air
Flow
2500
0
NAC
NA
16
41
NA
NA
NA
NA
NA
NA
27
Percent
Biodegraded
98.9%
48.4%
100.0%
87.2%
94.1%
100.0%
100.0%
47.4%
43.9%
100.0%
73.5%
Percent
Volatilized
0.0%
NA
NA
1 2.8%
5.9%
NA
NA
NA
NA
NA
NA
b Average system temperature 33.3°C.
0 NA = not available because parameter was not monitored in vent air.
Tables C-9. Summarized Mass Flow Rates for 15-Day HRT Load Condition Test Period, g/day
Chemical Class
Stream mass,a'b kg/day
Moisture
2-3 Ring PAHs
4-6 Ring PAHs
Amines
Benzene
BETXS
Furans
Ketones
PCB Aroclors
PCB congeners
Phenols
Phthalates
Volatile chlorinated organics
Sludge
359
41.5%
417
23
225
241
2838
0
201
34
31
3499
107
75
Soil
127
22.7%
3.8
1.0
4.0
2.0
34
0.2
1.2
1.1
1.2
3.6
2.3
0.5
Residue
432
74.1%
83
6.7
6.7
0.2
44.2
1.5
5.0
24.0
80.9
6.7
21.7
0.8
Decant
Liquid
108
0.11
0
0
0.04,
5.4
0
0.19
0.02
0.01
0
0.05
0.24
Vent Air
Flow
2000
0
NAC
NA
9.8
14.7
NA
NA
NA
NA
NA
NA
0.4
Percent
Biodegraded
80.2%
97.1%
97.1%
95.9%
97.8%
97.4%
30^9%
2.9%
99.8%
80.1%
Percent
Volatilized
0.0%
NA
NA
4.0%
0.5%
NA
NA
NA
NA
NA
NA
b Average system temperature 26.3°C.
c NA = not available because parameter was not monitored in vent air.
49
-------
periods and on the average of the analytical measurements
made for each constituent class. This can be considered an
overall substance balance, i.e., sludge and soil entered the
pilot system and residue, decant liquid, and vent air exited
the material balance boundary. As can be seen, for both
test periods, the mass reduction of most chemical classes is
impressive.
These data also indicate that although a higher concentra-
tion of volatile hydrocarbon (e.g., benzene, volatile chlori-
nated organics) material remained in the treated residue at
the 15-day HRT load condition (than at 30-day HRT condi-
tion), a much smaller percent of the constituent was lost
with the vent gas at this condition than was experienced at
the 30-day HRT loading. This is probably a direct conse-
quence of the operating temperature of the process and of
the vapor pressure of the compounds of interest.
Air Quality and Emissions Monitoring
The air quality monitoring system for the pilot study was
designed to simultaneously measure air quality parameters
both at source locations and at potential receptor sites on or
near the property fence line. To monitor air quality param-
eters at source locations, direct emission measurements were
made from surfaces (pond water or bottom soil) or from
waste storage tank and bioreactor vents. At the fence line,
chemical concentrations in the ambient air were measured.
The measured parameters included emission rates and am-
bient air concentrations of BETXS, together with several
other groups of chemicals. Two major project activities
were of concern: (1) materials handling conducted at the
level of the full-scale remediation, and (2) the test runs of
the pilot-scale slurry bioremediation process. Each activity
had several time periods that were monitored for emissions
and potential contributions to ambient air levels.
For materials handling, emissions were measured for base-
line conditions (presludge disturbance) during dredging
and transfer of sludge to waste storage tanks and after the
pond bottom soil was exposed. During the test runs of the
slurry bioremediation process, the monitored time periods
were the first week of pilot system acclimation and after
quasi-steady-state operation was achieved. Ambient air
sampling at four fence-line points measured concentrations
of VOCs, phenols, PCBs, and metals during five time
periods periods that concurred with source emission mea-
surements. Monitoring stations were set up at points north,
south, east, and west of the Sheridan site pond. These
stations monitored the migration of emissions off the site.
A portable meteorological station, installed at the southeast-
em segment of the Sheridan site fence line, collected wind
speed, wind direction, and temperature data.
The Sheridan Consent Decree10 established limits for ambi-
ent air concentrations of the target chemicals at the fence
line during all phases of the pilot study and full-scale
remediation. In Table C-10, the range of ambient air
concentrations for all target chemicals measured at the four
fence line sampling locations can be compared with the
Consent Decree limits. It can be seen that the maximum
detected ambient air concentration was a factor of about
1000 below the limit. Many of the target chemicals were
not detected in the ambient air at the fence line. The
highest limit of detection (LOD) was a factor of 10 below
the regulatory limit. Therefore, none of the ambient air
limits were exceeded or even approached during any pilot
study activity.
Emission rate measurements were made for BETXS at
eight separate times or locations. The maximum emission
rates for the sum of VOCs (i.e., BETXS) in each of the
cases are given in Table C-l 1. Note that the units are (Jg/
m2/min for waste surfaces and mg/min for slurry bioreme-
diation pilot system process vents.
All of the measured emission rates were low. Estimates of
the total VOC emissions that would be generated by dredg-
ing operations during the full-scale remediation were based
on the maximum emission rate of 5,000 ng/m2/min in Table
C-ll. The total VOC emission for dredging the whole
pond at a pump rate of 1000 gal/min would be about 1.5 kg,
or 0.002% of the total VOC content of the Sheridan site
waste sludge. Similarly, at a dredge pump rate of 1000 gal/
min, the VOC emissions at the waste sludge storage tank
vent would be about 30 kg, or 0.036% of the total VOC
content in this sludge. These are considered conservative
estimates. The low emission rates are consistent with the
low ambient air measurements reported in Table C-10.
The volatilization from dewatered and exposed soils in the
Sheridan site pond can be estimated from the flux value
shown in Table C-l 1, a surface area of 17 acres, and a 1-hr off-
gassing period for emission of VOCs. This produces an esti-
mated loss of 4 kg over the total remediation period or 0.005%
of the total VOC content of the Sheridan site waste sludge.
Canisters were used to measure VOC concentrations in the
headspace above each of the four slurry bioremediation
process vessels and the overall pilot system vent. Ten sets
of canister measurements were made, five per test period.
Tables C-10 and C-ll summarized the average emissions
from the pilot system for benzene, BETXS, and other chemi-
cal classes. As shown, the pilot-scale emissions are on the
order of 10 to 20 kg/yr. Emissions from the full-scale system
are expected to be 50 to 100 times more than the pilot system.
Testing Procedures
The testing procedures used during the Sheridan study are
presented in Table C-12. This table shows the schedule of
steady-state performance evaluation analytical testing for
each slurry bioreactor in the reaction train (Figure C-3)
The streams were analyzed for the presence of BOD, COF
total solids, total volatile solids, and oil and grease. Chs
50
-------
Table C-10. Measured Range of Ambient Air Concentrations at Four Sheridan Perimeter Monitoring
Locations versus the Consent Decree Limits
Ambient Air Target Chemical
by Monitoring Group
Volatile organic compounds
benzene
toluene
ethyl benzene
xylenes
styrene
trichloroethylene
tetrachloroethylene
naphthalene
Phenols
phenol
2,4-dimethylphenol
PCBs
Aroclor 1 232
Metals
chromium
lead
nickel
zinc
Sheridan Site Consent
Decree Perimeter Limits,3
u.g/m3
3,520
41 ,470
47,740
47,740
.23,650
2.9,590
37,290
5,720
2,090
2,420d
55
550
16
110
110
Measured Range of Ambient Air
Concentrations at Site Perimeter,13
u,g/m3
0.9 to 3.7
2.2 to 14.0
ND(<1)C
\ /
1 .2 to 5.5
ND (<1)
ND(<1)
ND(<1)
ND(<1)
ND (<4)
ND (<4)
ND (<6)
ND(<1)to~1
ND(<1)
ND(<1)
ND(<1)to~1
The consent decree ambient air concentration limits at the Sheridan Site perimeter (fence
line) were set at 11% of the 1988-89 Threshold Limit Values (TLVs as established by the
American Conference of Governmental Industrial Hygienists, Cincinnati, Ohio). The values
in this column are 11 % x TLVs.
b This is the range (minimum - maximum) of ambient air concentrations measured by Radian
at four locations on the fence line of the Sheridan Site for all periods during this study-
April 30 - August 28,1991.
0 ND (
-------
Table C-12. Analytical Methods and their Scheduling Used to Evaluate Variables of the
Slurry Bioremediation Process
Parameter
Analytical Method
Frequency/Reactor3
Onsite analyses
Temperature
pH
Dissolved oxygen
Total and soluble COD
Total and soluble BOD
Total solids/total
Volatile solids
Alkalinity
Chloride
Oil and grease
Oxygen uptake
Phosphate
EPA 1 70.1 b
EPA 1 50.1 b
EPA 41 0.1 b
SM52100
EPA 1 60.3/1 60.4b
EPA 310.1 b
EPA 325.3b
EPA 41 3.1 b
SM 271 0 B°
EPA 365.2b
Daily
Daily
Daily
3/week
2/week
3/week
1/week
1/week
1/week
3/week
1/week
Offsite analyses
Ammonia
Kjeldahl nitrogen
Metals
Purgeable organics
Extractable organics
PCBs
PCS congeners
Microtox
Total plate count
VOC speciation
Viscosity
Specific gravity
EPA 350.2b
EPA 351 .3b
EPA* 601 Od
EPA* 8240d
EPA* 8270d
EPA* 8080d
EPA* 680d
EPA 921 5d
EPATO-14
1/week
1 /month
1/Test Period8
4/Test Period8
4/Test Period6
4/Test Period8
2/Test Period8
1/week
1/week
5f/Test Period6
5/Test Period6
5/Test Period8
a Samples collected from waste dissolution reactor and each aerobic reactor in the treatment
system as shown in Figure C-3.
b U.S. EPA; Methods for Chemical Analysis of Water and Wastes, March 1983.
c APHA, AWWA, WPCF, Standard Methods for the Examination of Water and Wastewater,
17th ed., 1989.
d U.S. EPA/SW846, Test Methods for Evaluating Solid Wastes, 3rd ed., 1986; and U.S. EPA,
Methods for Organic Chemicals Analysis of Municipal and Industrial Wastewater, July 1982.
8 Test period is defined as a system hydraulic residence time load condition (e.g., 30 days or
15 days).
f Samples collected from the waste dissolution reactor vent, each aerobic reactor vent in the
treatment system, and the total of all aerobic reactor vents as shown in Figure C-3.
52
-------
acterization testing included analysis for metals, purgeable
and extractable organics, PCBs, and PCB congeners.
Characteristics Influencing Process Performance
The evaluations were conducted to establish the treatability
of the Sheridan wastes and to develop engineering data for
designing a biological waste treatment system. As dis-
cussed previously, waste sludge and pond bottom soils
were fed into the waste dissolution reactor where the solids
were slurried with water and with active microorganisms
recovered from previously treated wastes11. The resultant
slurry feed was then pumped in a semicontinuous manner
to three, aerobic, cascaded CSTRs. This waste slurry was
fed to the aerobic, cascaded CSTRs at approximately four
cycles per hour (96 times per day). As a consequence, the
slurry bioremediation process pilot system operated as close
to continuous flow as is practicable for a treatment system
of its size handling highly viscous waste material.
The following factors influenced process performance:
the rate that stable emulsions of waste tars and oils
formed in water during the initial waste dissolution
stage of the process;
the quantity and type of microorganisms cultured within
the process and their ability to affect continuous
bioemulsification of the waste sludges;
the number of aerobic, cascaded CSTRs used to achieve
treatment;
the operational slurry-phase temperature of the pro-
cess;
the presence of fine-grain soils within the process, and
the ability of the microorganisms to access the pollut-
ants that might be associated with them;
the levels of hydraulic shear experienced by the mi-
crobes in the slurry bioreactors; and
the equilibrium DO levels maintained within the biore-
actors during periods of optimum waste biodegradation.
Conclusions
The following are the major conclusions of the Sheridan
waste slurry bioremediation process pilot-scale evaluation:
Acclimated microorganisms, cultured to effect bioemulsi-
fication from stable emulsions of waste tars and oils in
water in a waste dissolution reactor. Slurry suspensions
in excess of 25 wt. % solids were practicable under the
operating conditions of the test program.
An airlift bioreactor with auxiliary mixing effectively
maintained sludge and soil slurry suspensions up to 25
wt. % solids in a low hydraulic shear environment.
The nitrile-butadiene rubber membrane diffusers, pro-
vided for aerobic bioreactor mixing and aeration, were
chemically resistant to the tars and oils. They may,
however, have been affected by the low-molecular-
weight aromatics also present in the waste. Problems
primarily occurred in the first stage aerobic bioreactor
where diffuser deformation was most apparent
Cascades of continuous-flow stirred tank reactors were
effective for aerobic microbial treatment of waste slur-
ries from the Sheridan site.
Significant waste solids destruction (greater than 80%)
occurred at temperatures above 30°C and at a system
volumetric residence time of 42 days. '
More total and soluble fraction conventional pollut-
ants were removed when the temperature was above
30°C and the residence time was 42 days.
When temperatures were above 30°C, the majority of
the volatile and semivolatile priority constituent or-
ganics were removed from the reaction slurries before
reaching the third-stage aerobic bioreactor.
All priority constituent organics were at higher con-
centrations when temperatures were below 30°C and
the volumetric residence time of the process was 17.5
days. This condition coincided with higher concentra-
tions of most total and soluble fraction conventional
pollutants in the reaction slurries.
Aromatic hydrocarbons were at lower concentrations in
the headspace of the bioreactors during the 15-day HRT
load condition test than during the 30-day HRT loading
test. This occurred despite much higher aromatic hydro-
carbon concentrations in the reaction slurries during the
15-day HRT load condition test. A lower system operat-
ing temperature is the probable reason.
Case Study 3: Slurry-Phase Biological
Treatment of 34-million-gallon Lagoon
Performed by FLTG.
Introduction
The French Limited site is an abandoned industrial waste
management facility in Harris County, TX, east of Hous-
ton. The 22.5-acre site contains a 7.3-acre, 34-million-
gallon lagoon into which approximately 70-million-gallons
of waste materials were placed from mid-1966 through
53
-------
early 1971. Surrounding sloughs have received spills and
overflow of waste constituents from ihe lagoon. In 1981,
the EPA proposed the French Limited site for the "Interim
National Priority List."
As part of the remedial investigation, a site assessment was
completed, and as part of the feasibility study, screening,
remedy selection, and remedy design treatability studies
were completed. The EPA issued a final ROD March 24,
1988. The ROD concluded that the slurry-phase bioreme-
diation process developed during the field-scale, in-situ,
biodegradation demonstration was the appropriate technol-
ogy for the final French Limited site remediation. The
remedial action (RA), initiated after issuance of the ROD is
the first Superfund in-situ slurry-phase bioremediation.
Lagoon remediation is expected to be completed in March
1993.
The French Limited site RAs were designed to achieve
predefined remedial objectives established in the ROD.
Bioremediation objectives included reducing health haz-
ards from direct contact with sludges and waste-affected
soils by reducing the toxicity and/or volume of the wastes.
The bioremediation clean-up levels for indicator param-
eters in sludge and subsoils are:
Parameter
PCBs
Benzo(a)pyrene
Benzene
Vinyl chloride
Arsenic
System Design
Concentration Level
23ppm
9ppm
14ppm
43ppm
7ppm
The bioremediation process design is based on dividing the
French Limited Lagoon with sheet pile into two primary
treatment cells, Cell E and Cell F. The lagoon treatment
cell configuration is shown schematically in Figure C-4.
Each treatment cell has the same total volume of treatment
media (water and sludge/subsoil). Subsoil from the con-
taminated slough area was excavated and placed into a
treatment cell for bioremediation. Sludge and subsoil
from three small portions of the original lagoon, cells A, B,
and D, were dredged and placed in one of the two large
treatment cells. Contaminated water from a small aquifer
is added to offset evaporative loss to maintain lagoon liquid
level. After treatment cell E is remediated, the process
equipment will be moved to cell F for its remediation.
The in-situ reactor is the lagoon treatment cell, amended
with oxygenation, mixing, and dredging devices. Bioreme-
diation is performed by optimizing conditions for micro-
bial degradation of contaminants. Chemical additions made
to the treatment cell during bioremediation include nitro-
gen and phosphorus for microbial nutrition and lime for pH
control. Process equipment used to optimize oxygenation
and microbial/contaminant contact includes mechanical
aerators, centrifugal pump sludge mixers, and hydraulic
dredge subsoil mixers. The oxygenation system is de-
scribed below.
The Linde Mixflo Oxygenation System is used in this
bioremediation process. In designing the Mixflo system
for the French Limited process, the following design crite-
ria were used:
Temperature = 40?C
Oxygen requirement = 2500 Ib/hr
Liquid depth = 10 ft
Pump efficiency = 75%
Saturation oxygen concentration = 27.5 ppm
The Linde Mixflo system dissolves oxygen in a two-
stage process. First, water is pumped from the treatment
area and pressurized to between 2 and 4 atmospheres. Then
pure merchant oxygen gas is injected into the water, on the
pump discharge. The resulting two-phase mixture passes
through a pipeline contactor in which approximately-60%
of the injected oxygen dissolves. At the elevated operating
pressure, the solubility of oxygen in the water increases
substantially, and therefore, the rate at which oxygen dis-
solves is increased and the contactor length necessary to
dissolve the oxygen is minimized. The amount of water
pumped also decreases as the pressure increases because a
given water volume has greater DO capacity at elevated
pressures.
Linde calculations show the predicted saturated oxygen
concentration in the French Limited mixed liquor at 105°F
is 82.4 ppm. The actual DO concentration in the pipeline
contactor is predicted to be 43.4 ppm, or approximately
one-half saturation concentration at pipeline pressure.
For the French Limited project, oxygen is injected in eight
pipeline contactors where it mixes with mixed liquor at en-
hanced pressure. The mixed liquor is pressurized by pumps
located on two pontoons, one near each bank of the lagoon.
The treatment cell circulation flow pattern established by the
eductors' discharge is supplemented and enhanced by also
using three raft-mounted, self-powered circulation mixers.
To supply the oxygen to the project, liquid oxygen is
trucked from one of several facilities in the Houston area.
A liquid trailer holds approximately 550,000 scf of oxygen.
At the designed use rate of oxygen, a delivery is needed
every 16 hr on the average. The liquid is off loaded into a
11,000-gal cryogenic storage tank using pumps mounted
on the delivery trailer. This tank, which holds approxi-
54
-------
LOCATION OF WALL
DIVIDING CELL E
AND CELL F
SHEET HIE ROOD WAU.
-T=rA-L_iJ-l) U-JLJ-L-LJLJ.J-1-Ll-LJ-J-LT^
:==L -w^gMPQBARYGATE GU1> PUMP ROAD EAST!
EAST TEMPORARY GATE
MAIN GATE
Figure C-4. French Limited site schematic.
-------
mately 1-1/2 days of the process requirements, provides a
safety margin of storage should demand fluctuate or in the
event a delivery cannot be made because of weather condi-
tions or other unforeseen circumstances. A second 11,000-
gal tank will be added when an increase in flow rate war-
rants its installation. The onsite storage tanks are leased
from Linde.
Effectiveness ofln-Situ Slurry-Phase
Bioremediation
At the time of this writing, Cell E remediation is almost
complete. The concentrations of the five indicator param-
eters present in the lagoon bottom subsoil are below or near
the remedial objective concentrations set in the ROD. Data
from the first 11 bottom sampling events are shown in Fig-
ures C-5 through C-9 for the five indicator parameters. The
concentration of benzo(a)pyrene remains above the decon-
tamination objective in all composite samples and is there-
fore the compound that will determine the confirmational
sampling dates. Confirmational sampling will be done as
described in the subsection "Operation and Maintenance,"
below. Remediation of Cell F will be initiated after comple-
tion of Cell E remediation.
Site Characteristics
Site characteristics are the single most important factor in
the applicability, effectiveness, and cost of slurry-phase
bioremediation. Site characteristics and a willingness of the
potentially responsible party to consider bioremediation made
this technology applicable to the French Limited site.
Characteristics include the waste matrix, the technical fea-
sibility, the cost, and the site location. The French Limited
site waste constituents are biodegradable, and an onsite
lagoon was amended to an in-situ reactor. Contaminated
subsoil located outside the lagoon was excavated and placed
in the lagoon for remediation. Contaminated groundwater
is used for lagoon volume control. Critical supplies, such
as oxygen, are available locally.
Waste Characteristics
Samples taken from the French Limited site indicated that
hazardous chemicals were present in the lagoon sludges, in
the soils underlying the lagoon sludges, and to a lesser extent,
in the lagoon water and groundwater. Levels of contaminant
concentrations in the sludge samples are given in Table C-13.
10000=
1000=
100=
o
I
10; :
1=
0.1
rSuWOJSframCewAiB
-J
--14 ppm-
96 110 124 145 166 187 201 215 229 239 253 264 271 273
Project Day
#1 HI #2 ggg #3
#4 F~] #5 | 1 #6
Figure C-5. Benzene by composite number.
56
-------
1000:
Objective-» 43 opm
96 110 124 145 166 187 201 215 229 239 253 264 271 273
0.1
Project Day
#1 mm #2 sss #3
Figure C-6. Vinyl chloride by composite number.
<
1000
100- -
10=
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n i .
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96 110 124 145 166 187 201 215 229 239 253 264 271 273
Project Day
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Figure C-7. Total PCI3s by composite number.
57
-------
"IfiOO-
100=
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96 110 124 145 166 187 201 215 229 239 253 264 271 273
Project Day
I 1 #4 r] #5 Q #6
Figure C-8. Arsenic by composite number.
iWiH-
1000=
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Figure C-9. Benzo(a)pyrene by composite number.
58
-------
A series of laboratory screening tests determined that the
waste constituents were biodegradable, and thus, biological
treatment methods could remediate the sludge/subsoil at
the French Limited site.
Material Handling Requirements
Materials handling of the waste matrix is technically fea-
sible. Materials handling includes excavating slough-area
subsoil and placing it in the lagoon; mixing and dredging
lagoon sludge and subsoil; dewatering the lagoon matrix
after treatment; and backfilling, or stabilizing and offsite
disposing of solid material after treatment and dewatering.
Operation and Maintenance
Chemical Additions
Simple batch systems for chemical addition are used to
control the pH and nutrient chemistry of the mixed liquor
during bioremediation treatment. Experience during the
field-scale, in-situ demonstration and other bioremediation
Table C-13. Contaminant Concentrations in Sludge, French Limited Site
Compounds
Concentration, ppm
I. Volatile Organics
Benzene
1,2-DichIoroethane
Chloroform
Ethylbenzene
Toluene
II. Acid Extractable Organics
Phenol
III. Base/Neutral Extractable Organics
Acenapthene
Fluoranthene
2,6-Dinitrotoluene
Di-N-Butyl Phthalate
Benzo(a)anthracene
Crysene
Acenaphthalene
Anthracene
Naphthalene
Fluorene
Phenanthrene
Pyrene
IV. Pesticides and PCBs
Total priority pollutant pesticides
Total priority pollutant PCBs
V. Inorganics
Chromium
Lead
Mercury
Copper
Nickel
Zinc
Beryllium
150
230
160
150
130
30
430
170
160
10
55
80
200
230
1800
500
900
270
up to 427
110
110
2
385
280
630
59
-------
projects for petrochemical wastes showed that these treat-
ments become progressively acidic and thus require routine
base additions to achieve pH control. Numerous alkaline
chemicals are available to control pH. Based on safety,
cost and availability considerations, a 35% solution of
hydrated lime was selected for the French Limited biore-
mediation. The lime is diluted onsite to 15% concentration
for ease of handling.
Nutrient must be regularly added to maintain the proper
concentration of nitrogen and phosphorus required for the
growth and active metabolism of the biomass. By a
variety of mechanisms, nitrogen and phosphorus are lost
or sequestered from the treatment system. They are both
consumed by being incorporated into the biomass. Much
of this nitrate and nitrite nitrogen is lost to the water or air
because of microbial denitrification as relatively inert
nitrogen (Nj). Phosphate can be sequestered from the
treatment biomass by precipitation reactions with divalent
cations or by binding to the cationic sites on the solids.
To offset these nutrient losses, nitrogen is added as hy-
drated urea and phosphorus is added as liquid ammonium
phosphate. Urea (46% nitrogen by weight) is the process
design nitrogen source. Urea is economically available
locally as a 45% to 50% solution in water (20% to 23%
nitrogen). Water solutions of urea do not produce noxious
fumes, will remain in solution at normal environmental
temperatures, and present no materials handling hazard.
The source for nutrient phosphorus is ammonium phos-
phate. Ammonium phosphate is economical, is commer-
cially available in a concentrated solution, is not a corrosivity
hazard, is readily compatible with the nutrient nitrogen
source, and requires no special material for tankage or
piping. Ammonium phosphate is applied through a small
mixing tank and injection system. The ammonium phos-
phate solution can be mixed with the urea solution when
both need to be added. To prevent the undesirable precipi-
tation of phosphate by calcium, however, concentrated am-
monium phosphate is not added at the same time or at the
same injection point'as concentrated slaked lime.
The system facilities allow batches of up to 1,500 gal of
chemicals to be added to the lagoon at two locations.
Storage to accommodate 4,500 gal truck deliveries are
provided for lime and urea. Because the requirement for
phosphorus is low, a 600-gal tank is provided for small-
quantity truck shipments.
Mixed-Liquor Sampling
The mixed-liquor sampling design provides for a program
of sampling and analyses in the treatment cell that enables
the bioremediation process to be monitored and controlled
on a long- and short-term basis. Bioremediation processes
produce changes in many of the physical and chemical
parameters of the matrix being remediated. Generally,
microorganisms function optimally in a stable, unchanging
environment. This is the basis of "steady state," continu-
ously fed reactors that give optimum microbial perfor-
mance. If significant changes occur, the performance of
the microorganisms declines, the rate of remediation drops,
and the total time of treatment is lengthened. Because of
the constant mixing of sludge and soils into the mixed
liquor, the French Limited bioremediation treatment cell is
similar to a continuously fed batch reactor.
Mixed-liquor samples are taken at two locations in the
treatment cell One sample is obtained from the middle of
the walkway across the sheetpile wall that separates the two
treatment cells; here, the mixed liquor flows toward the
wall in its circulation pattern created by the Mixflo sys-
tem eductors and the circulation mixers. Because of the
circulation pattern, samples from this location should be
representative of the mixed-liquor chemistry. A second
sample is taken at the middle of the treatment cell; the site
workboat provides access to the location.
To verify that the mixed-liquor samples are representative,
extra samples are taken (from the workboat deck) from
various points in the treatment cell during the initial opera-
tion period. Results of this verification activity are then
compared with samples taken from the two regular loca-
tions, and appropriate action is taken to obtain representa-
tive samples for the remainder of the bioremediation opera-
tion. This review of the sampling is completed by day 60 of
cell remediation.
Mixed-Liquor Parameters
Parameters of the mixed liquor are analyzed to provide the
basis for controlling and monitoring the bioremediation
process. The microbial plate count (or CPU) measurement
is included to provide an indicator of biomass growth with
time, during the early stages of treatment in a cell.
The mixed liquor parameters selected for controlling the
bioremediation process are listed below with the frequency
of analysis that is followed to achieve the required process
control.
Parameter Frequency
pH 1/8-hr shift
Dissolved oxygen (DO) 1/8-hr shift
Oxygen uptake rate (OUR) 1/8-hr shift
Nutrient nitrogen 1/8-hr shift
Nutrient phosphorus I/day
Temperature I/day
- Total/volatile suspended solids,
(TSS/VSS) , ,1/wk
Total petroleum hydrocarbons,
(TPH) 1/wk
Microbial plate count (CPU) I/week
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Measured Parameter Control Range
During bioremediation operation, chemicals are added pe-
riodically with the objective of controlling each parameter
at approximately midway within the concentration range
described below. These ranges represent the concentration
extremes within which mixed-liquor chemistry may vary
without incurring irreversible damage to the biological popu-
lation. Chemical additions are made at a frequency and in
sufficient volume to maintain these parameters within the
specified range. Nutrient nitrogen and nutrient phospho-
rous concentrations above the minimum of the acceptable
range do not require a chemical addition response.
Measured Parameter
PH
Dissolved oxygen
Nutrient nitrogen
Nutrient phosphorus
Acceptable Range
6.0-8.0 pH
0.5-4.0mg/L
1.0-2.0mg/L
1.0-2.0mg/L
Measuring the Progress of the Remediation
To provide a series of measurements that asses the progress
of bioremediation treatment, the following parameters are
measured at the frequency indicated. The measurement
program is not begun until after the first 60 days of biore-
mediation (in each treatment cell, E and F).
Parameter
Measurement Frequency
after Dav 60
1/wk
TPH
Five site criteria compounds
(benzene, vinyl chloride,
benzo(a)pyrene, arsenic, PCBs) I/month
Fixed Solid/Volatile Solid I/month
During each weekly measurement sampling event, approxi-
mately 25% of 52 grid sampling locations in the treatment
cell are sampled. Four adjacent samples are composited
into a single sample and analyzed for TPH. This results in
four TPH analyses obtained each week. Each week, a
different quarter of the cell is sampled, so that no quarter is
sampled a second time until all quarters have been sampled.
A Giddings core sampling device on the workboat is used
to take samples of lagoon sludge or subsoil. A core sample
that imbeds into the subsoil under the sludge is held in the
coring device while the core is lifted from the treatment
cell. The organic vapor meter-photo ion detector (OVM-
PID) measures volatile organic concentrations along the
surface of the core, and the sludge sample is taken from the
sludge layer at the point of highest volatile organic concen-
tration. The remainder of the core is returned to the lagoon.
The subsoil sample is a composite of the subsoil from the
upper 4-ft layer of subsoil collected in each core. Once per
month, sludge or subsoil samples are collected and ana-
lyzed for the five criteria compounds. All 52 grid locations
are sampled, and approximately eight adjacent samples are
composited for one analysis. This results in six analyses
per month for tracking remediation progress.
The bioremediation facilities are shutdown for 16 hr before
these sampling events to allow waste material to settle to
the lagoon bottom.
During the sludge-mixing phase, the core sampling activities
described above, observations, and measurements are taken
to visually assess the sludge layer thickness (depth). A
combination of sludge-layer thickness (in inches), with O VM-
PID organic vapor concentrations taken at the sample sur-
face, are obtained on each sample. These data are tabulated
to identify and track the untreated sludge-layer thickness
across the treatment cell. Although precise criteria for the
final sludge-layer thickness cannot be established, this track-
ing chart provides another indicator of when sludge mixing is
complete and subsoil mixing should begin by showing when
the sludge-layer thickness is not longer decreasing. The
objective is to reduce the sludge- layer thickness to essen-
tially zero before initiating subsoil mixing. A sludge-layer
thickness survey is taken at all sampling grid intersects before
startup of bioremediation operations to provide a base for
comparing the tracking measurements. This survey is also
used to determine an initial sludge volume and mass that
exists in each treatment cell.
The OUR data that are used to assess the mixed-liquor
biological activity are also tabulated in a tracking chart to
describe the OUR trend as treatment progresses. These
data provide another indicator of when the sludge treatment
phase is completed and subsoil treatment should begin.
These analyses and sludge-thickness results are plotted to
track remediation progress and form the overall data base
used in deciding when to change the process from sludge
pump mixing to subsoil cutterhead mixing. After subsoil mix-
ing begins, the same sampling and analysis program is used
to determine when subsoil remediation is near completion.
Subsoil Remediation Verification
When bioremediation of subsoil is considered complete,
based on analyses taken as part of the progress tracking
program, the treatment cell is shut down and allowed to
naturally settle for a 48-hr period. Water spray is used
during this period to cause crust to float or settle to the
lagoon bottom as much as possible. Samples of the lagoon
bottom subsoil are taken at each of the grid sampling
locations in that treatment cell. These samples of sludge or
subsoil are taken from the lagoon bottom with the use of the
core sampling device on the workboat. The sample is a
composite of the subsoil from the upper 4-ft layer of sub-
soil collected in each core. Eight adjacent subsoil samples
are composited into one sample and analyzed for the five
remediation criteria compounds. After sampling, bioreme-
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diation operations are resumed until analytical results are
received.
After these results are compared with the five remediation
criteria concentrations and reviewed with EPA, a decision
is made to continue the bioremediation treatment or deter-
mine that the site remediation criteria have been met and
discontinue cell remediation.
Bioremediation Air Monitoring
An ambient air monitoring program included two types of
action to monitor potential releases of VOCs from the
French Limited operation: short-term monitoring and long-
term, time-integrated monitoring.
Instrumentation for the short-term monitoring program pro-
vides a continuous instantaneous reading of total VOC
concentration in ambient air. Measurements are taken at
five strategic locations around the operating bioremedia-
tion treatment cell at the top of the French Limited lagoon
flood wall. Measurements from these locations are con-
tinuously monitored by automatic instrumentation to deter-
mine whether control adjustments are necessary in the
bioremediation process to maintain total VOC concentra-
tion within preapproved limits established by EPA.
Additionally, these measurements are continuously recorded
for historical purposes, and each measurement will trigger
a process control alarm signal if it exceeds a preset reading.
The selected alarm point ensures control action is taken
before the preapproved EPA limits are reached.
Any time total VOC concentrations exceed predetermined
action limits at a monitoring location at the top of the flood
wall, response actions are implemented in accordance with
a response plan (Table C-14) until concentrations return to
normal.
The long-term monitoring program provides a 24-hr/day, 7
day/wk continuous sampling of organic compounds in the
ambient air at three sites on the French Limited property
line. These locations are directly between the bioremedia-
tion cell in operation and the three nearest potential recep-
tors. The samples are analyzed daily to provide a time-
integrated measurement of the 35 VOCs on the EPA's
Hazardous Substances List The concentrations determined
in these measurements are then processed mathematically
to identify the dispersion that will occur between the French
Limited property line and the three potential receptor loca-
tions. The potential receptor concentrations are compared
with the acceptable concentration criteria.
These daily, long-term measurements are continuously accu-
mulated and averaged to derive a cumulative average on a
weekly basis. This average is used to determine the projected
2-yr concentration that will result from the bioremediation
operation. Comparison of these projections is used to deter-
mine if adjustments are necessary in the bioremediation op-
eration to ensure maintenance of die acceptable 2-yr ambient-
air criteria established by EPA.
Personnel Requirements
The French Limited remediation operation is staffed with an
appropriate number of technicians and operators 24-hr/day, 7
days/wk to ensure the process systems are operated in accor-
dance with the pre-approved plans and procedures.
Assignments for each technician or operator are flexible, with
each individual trained to perform multiple tasks.
The staffing level during the initial remediation operations
included 16 people for 10 positions:
one lead operator per shift
one operator per shift
two operators on straight days
five dredge mixer operators on straight days (6 during
subsoil mixing phase)
Table C-14. French Limited Air Monitoring Response Plan
Site Operational
Condition
Green
Yellow
Red
White
Total VOC
Concentration
0-5 ppm
5-11 ppm
5-11 ppm
>1 1 ppm
Duration
Indefinite
More than 5 minutes
More than 30 minutes
More than 30 minutes
Response Action
Normal operation
Reduce aeration and mixing
intensity
Shut down aeration and mixing;
conduct specific target volatile
sampling at top of flood wall
Evacuate onsite personnel
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one air monitoring technician
The staffing level is modified as experience is gained during
the operation activities.
Health and Safety
The following health and safety measures have been taken
for the French Limited RA include:
risk analysis
personnel monitoring requirements
protective measures
health and safety responsibility
hazard communications
health and safety training
medical surveillance
site control
decontamination procedures
A risk analysis identified potential hazards as either physical
or chemical. Physical hazards are those encountered by
onsite workers while performing operating and monitoring
duties, e.g., slips, falls, cuts, drowning, pinches, hit-by-fall-
ing-object Chemical hazards involve the potential for:
direct skin or eye contact with sludge, lagoon water,
shallow alluvial groundwater, or process chemicals,
ingestion of sludge, lagoon water, shallow alluvial ground-
water, or process chemicals, or
prolonged inhalation of air emissions from the bioreme-
diation process, if organic concentrations in the air ex-
ceed predefined limits.
The French Limited facilities were designed to protect the
health and safety of onsite workers and the general public.
The facilities comply with OSHA requirements for industrial
facilities and were designed to allow proper site access con-
trol and safe access to all onsite operational facility locations.
All regular project operations employees are included in
health and safety activities: health and safety indoctrination
(raining and weekly and daily health and safety meetings.
Operating procedural controls are designed to ensure safe
implementation of all regular operating duties and project
personnel are trained in these procedures. Periodic health and
safety inspections verify that the procedures are maintained.
Field personnel safety rules ensure safety in field activities.
These include using the "buddy system" in all site exclusion
zones (where contact with the waste is possible), avoiding
contamination, exercising proper hygiene, and communicat-
ing by two-way radio in field activities, when indicated.
The Site Health and Safety Officer conducts daily health and
safety inspections. All personal protective equipment is
inspected to verify it is clean, in good repair, and ready for
use. The Site Manager regularly inspects all site offices,
change room, and process facilities to ensure that site house-
keeping standards are continuously maintained. The quar-
terly inspections and annual health and safety audits are
maintained in the project file.
Personal protective equipment (PPE) are used when appropriate.
Other health and safety protective measures include electrical
lockout, confined space entry procedures, and noise protection.
In compliance with the OSHA 29 CFR 1910.120 (i) hazard
communication requirements, project personnel are informed
of each individual's responsibility to ensure that the hazards
of all chemicals acquired, used, and/or encountered at the site
are recognized, understood, and controlled. Information re-
garding hazard, proper handling, and precautions is readily
available through material safety data sheets.
Health and safety training is conducted in compliance with
the requirements of Occupational Safety and Health Guid-
ance for Hazardous Waste Site Activities, 29 CFR 1910.
Medical surveillance is provided as required in OSHA 29
CFR 1910.120 (f). Training and medical surveillance records
are maintained onsite.
Onsite work zones were established to demark the degree of
risk. In the exclusion zone, there is potential for contact with
the site's waste material. The decontamination zone provides
a location for removing contaminated PPE, personnel wash-
ing, and equipment decontamination. The clean zone, main-
tained free of waste materials, includes the administration
area and the parking lot.
In general, everything that enters the exclusion zone at the
site must be either decontaminated or properly discarded
upon leaving die zone. Decontamination procedures were
established for personnel, equipment, and disposal.
Potential Community Exposures
Bioremediation of the French Limited lagoon results in the
emission of VOCs into the atmosphere. During bioremedia-
tion of the lagoon, the goal is to limit VOC concentrations in
the air to levels that protect the health of individuals residing
near the lagoon. By setting emission limits that protect the
most-exposed nearby residents, people with lower exposures,
e.g., those living farther away or those who occasionally pass
through the area, will also be protected.
Air monitoring, previously described, provides measurements
of daily air concentrations of VOC at the fence line. Results
are then used to estimate the VOC concentrations to which
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residents living in the nearby subdivisions may be exposed.
To protect public health, the goal of this project is to limit the
potential increase in a person's excess lifetime cancer risk to
no more than one in a million per chemical and to limit the
hazard index for potential noncarcinogenic effects to no more
than one per chemicaL
Regulatory Requirements
The SARA. (1986) amended the CERCLA to require that
Superfund RAs comply with the technical standards and
requirements of ARAR federal and state laws and to specifi-
cally exclude compliance with their administrative and per-
mitting aspects. The following paragraphs describe the de-
sign or operational features that have been provided in the
biorernediation facility in response to ARAR requirements.
In some' cases, the ARAR provision is met by operating
procedures implemented during remedial operations: ,
Facilities are designed to prevent release of contami-
nated material during a 100-yr flood event of the San
Jacinto River in accordance with RCRA.
The Site Contingency Plan provides procedures for con-
trol of potential spills and volatile releases, as required
by the Clean Water Act and RCRA.
All remediation facilities and site operating procedures are
specified to achieve and maintain compliance with OSHA
regulations relating to an industrial facility and a hazardous
waste site. A partial list of provisions applicable to the
shallow aquifer, subsoil remediation, and design and operat-
ing procedures for the lagoon facility in compliance with
OSHA requirements are:
ladder/handrail design
health and safety training
onsite protective equipment
hazard communications standards
tanks and equipment design in compliance with OSHA-
specified codes
health and safety records maintenance
walking/working surface design
fire extinguishers
floor loading limits
rotating machinery guards
medical surveillance
emergency response plan
decontamination procedures
area lighting
fixed machinery anchoring
noise exposure.
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References
1. Adapted from information provided by EMCO Process Equipment Company, Salt Lake City, UT.
2. Information provided by EMCO Process Equipment Company, Salt Lake City, UT.
3. EPA Test Methods for Evaluating Solid Waste. 1986. Volume IB. Laboratory Manual of Physical/
Chemical Methods. SW-846, Third Edition. Office of Solid Waste, Washing, D.C.
4. 40 CFR, Part 264, Appendix IX.
5. Sims, R.C., and Overcash, M. R. 1983. Fate of Polynuclear Aromatic Compounds in Soil-Plant Systems
Residue Reviews, 88:1-68.
6. Remediation Technologies, Inc. (RETEC),Kent,WA. 1990. Monitoring Air Emissions from a Pilot-Scale
Biological Treatment Reactor. Report prepared for Mittelhouse Corp., Chicago, IL.
7. Castaldi,F.J. and Ford, D. 1992. Slurry Bioremediation of Petrochemical Waste Sludges. Water Science
and Technology, 25:3:207-212.
8. Castaldi,F.J. U.S. PTO Serial No. 07/773344, Patent Pending.
9. Record of Decision for Sheridan Disposal Services Site, Waller County, TX. Prepared by the U S EPA
December 1988. *-/»
10. Administrative Order on Consent, Docket Number CERCLA VI-19-90, Sheridan Disposal Services Site
Waller County, TX."
11. Castaldi,'F. J. U.S. PTO Serial No. 07/733344, Patent Pending.
65
U. S. GOVERNMENT PRINTING OFFICE: 1993-753-293
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