United States
Environmental Protection
Agency
Office of Research and
Development
Washington, DC 20460
EPA/600/R-92/028
April 1992
Eighteenth Annual
Risk Reduction Engineering
Laboratory Research
Symposium
Abstract Proceedings
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EPA/600/R-92/028
April 1992
Eighteenth Annual
Risk Reduction Engineering Laboratory Research Symposium
Abstract Proceedings
Sponsored by the U.S. EPA, Office of Research and Development
Risk Reduction Engineering Laboratory
Coordinated by:
Science Applications International Corporation
Ft. Washington, PA 19034
Project Officers:
Gordon Evans
Emma Lou George
MarkStutsman
RISK REDUCTION ENGINEERING LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
CINCINNATI, OH 45268
Printed on Recycled Paper
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NOTICE
These Proceedings have been reviewed in accordance with the U.S. Environmental
Protection Agency's peer and administrative; review policies and approved for presentation and
publication. Mention of trade names or commercial products does not constitute endorsement
or recommendation for use. i
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FOREWORD
Today's rapidly developing technologies and industrial practices frequently carry with
them the increased generation of materials, that if improperly dealt with, can threaten both
public health and the environment. The U. S. Environmental Protection Agency is charged by
Congress with protecting the Nation's land, air, and water resources. Under a mandate of
national environmental laws, the Agency strives to formulate and implement actions leading to
a compatible balance between human activities and the ability of natural systems to support and
nurture life. These laws direct the EPA to perform research to define our environmental
problems, measure the impacts, and search for solutions.
The Risk Reduction Engineering Laboratory is responsible for planning, implementing,
and managing research, development, and demonstration programs to provide an authoritative,
defensible engineering basis in support of the policies, programs, and regulations of EPA with
respect to drinking water, wastewater, pesticides, toxic substances, solid and hazardous waste,
and Superfund-related activities. This publication is one of the products of that research and
provides a vital communication link between researchers and users.
These Abstract Proceedings from the 1992 Symposium provide the results of projects
recently completed by RREL and current information on projects presently underway. Those
wishing additional information on these projects are urged to contact the author or the EPA
Project Officer.
RREL sponsors a symposium each year in order to assure that the results of its research
efforts are rapidly transmitted to the user community.
E. Timothy Oppelt, Director
Risk Reduction Engineering Laboratory
in
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ABSTRACT
The Eighteenth Annual Risk Reduction Engineering Laboratory Research Symposium was
held in Cincinnati, Ohio, April 14-16, 1992. The purpose of this Symposium was to present the
latest significant research findings from ongoing and recently completed projects funded by the
Risk Reduction Engineering Laboratory (RREL).
These Proceedings are organized into two sections, Sessions A and B, which contain
extended abstracts of the paper presentations. A list of poster displays is also included. Subjects
include remedial action, treatment, and control technologies for waste disposal, landfill liner and
cover systems, underground storage tanks, and demonstration and development of
innovative/alternative treatment technologies for hazardous waste. Alternative technology
subjects include thermal destruction of hazardous wastes, field evaluations, existing treatment
options, emerging treatment processes, waste minimization, and biosystems for hazardous waste
destruction. !
IV
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TABLE OF CONTENTS
Session A
Solidification/Stabilisation of High Level Inorganic and Organic
Soils at Robins Air Force Base . . . . .
1
Review of Soil Vapor Extraction Microcomputer Models .5
Remediation of Lead Contaminated Soil .....;... •-. •... .11
Destruction of Organic Wastes Using Concentrated Solar Radiation 16
Assessment of Relative POHC Destruction at EPA's Incineration
Research Facility .20
PACS vs CO as Surrogates for Trace Combustibles 25
High Energy Electron Beam Irradiation: An Emerging Technology
for the Destruction of Organic Contaminants in Water, Wastewater,
and Sludge 28
Carbon Dioxide Cleaning of Contaminated Surfaces 32
Evaluation of Three Oil Filter Designs for Pollution Prevention
Effectiveness 36
The Waste Reduction Evaluations at Federal Sites Program 39
Measuring Pollution Prevention .43
Two Pollution Prevention Technology Evaluations for the Printed
Circuit Board Industry 46
Evaluation of Emulsion Cleaners at Air Force Plant Number 6 50
Evaluation of Filtration and Distillation Methods for Recycling
Automotive Coolant 55
The Use of Hydraulic Fracturing to Enhance In Situ Bioremediation 59
In Situ Treatment of Soil Contaminated with PAHs and Phenols 62
Long-Term Durability of Solidified/Stabilized Materials 67
V
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Session A (continued)
Page
Metals Partitioning Resulting from Rotary Kiln Incineration
of Hazardous Waste • 72
Engineering Analysis of Metals Emissions from Waste '
Incinerators Field Data 77
Effect of Municipal Waste Combustion Ash Monofill Leachate
on Selected Containment Barrier Components 81
Solidification/Stabilization for Lead Battery Site - A Two
Stage Program 86
Rotary Kiln Incineration of Spent Pdtiiner from
the Manufacturer of Aluminum . .,. 90
Selective Recovery of Nickel and Cobalt from Electromachining
Process Solutions . 96
Session B
r -T--' ^ I
Treatment of Dilute Hazardous Waste Streams by
Sorption/Anaerobic Stabilization ..;.... ..."... 101
i
Development of a Novel Biofilter for Aerobic Biodegradation
of Volatile Organic Compounds (VOCs) 110
Onsite Biological Pretreatment Followed by POTW Treatment
of CERCLA Leachates .......' . . . . 114
Two U.S. EPA Bioremediation Field Initiative Studies:
Evaluation of In-Situ Bioventing . 118
Measurement of the Effect of Temperature on Oxygen Uptake ........... 124
A Fundamental Kinetic Study of the Anaerobic Biodegradation
of Chloroform and its products with Various Co-Substrates
in Mixed Culture Chemostats . . .'• 130
i
Emissions of Organics from Bioslurry Reactors Treating Soil
Contaminated with Wood Preserving Waste 135
Design of Full Scale Debris Washing System 138
VI
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Session B (continued)
Page
Treatment of Hazardous and Toxic Liquids Using Rochem
Disc Tube Technology . . 143
The Site Demonstration of the Retech Plasma Centrifugal Furnace 146
Site Demonstration of the Soiltech Anaerobic Thermal Processor 149
The Site Investigation Robot 152
Evaluation of the Air-Sparged Hydrocyclone 155
Assessment of Binding Energies Between Organic Contaminants
and Soils and Sediments 160
Bioavailability and Biodegradation Kinetics of Organics in Soil 163
Removal of Creosote from Soil by Thermal Desorption 170
Slurry Reactor Bioremediation of Soil-Bound Polycyclic Aromatic
Hydrocarbons 174
Adsorptive Filtration for Treatment of Metals at Superfund Sites 179
Phase Separation and Soluble Pollutant Removal By Means of
Alternating Current Electrocoagulation 184
Fluid Extraction-Biological Degradation of Organic Wastes 189
Remediation of Leaking USTS on Native American Lands 194
Laboratory Study of Interactions Between Polychlorinated
Biphenyls and Quicklime . . . ; . 200
Risk Reduction Engineering Laboratory (RREL) Treatability Database 205
Development of Biodegradation Kinetics for Mixed Substrate System 206
VII
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LIST OF POSTER DISPLAYS
I
Remedy Screening Tests for Extraction Technologies
Ari Selvakumar, FW Enviresponse
Ozone/Ultraviolet Light Treatment of Dithiocarbamate Pesticides in WasteWatef
Mark Briggs, Radian Corp ;
Alternatives for "Clean" Production ; • ' .. '
Mary Ann Curran, U.S. EPA, RREL '
Research Study Opportunities at EPA's Test and Evaluation Facility
Francis Evans, U.S. EPA, RREL :
I
RREL Superftind Technical Support Program
Ben Blaney, U.S. EPA, RREL j
\
Development of Small-Scale Evaluation Techniques for Fungal Treatment of Soils*
Frederic Baud-Grasset, U.S. EPA, RRELi
[
Subsurface Remediation of Gasoline by Air Sparging and SVE
Chien Chen, U.S. EPA, RREL
I " •-•
Ultrasonic Enhancement of Soil Washing
Asim Ray, FW Enviresponse |
Innovative Clean Technologies Project i
Angel Martin-Dias, Center for Hazardous (Materials Research
Onsite Anaerobic Biological Process Addressing Explosives and Pesticides
Ronald Crawford, University of Idaho j
Screening Methodology for Assessing Cleanup Technologies for Leaking Underground Storage
Tank Sites !
Chi-Yuan Fan, U.S. EPA, RREL
Pesticide Treatability Data Base i
David Ferguson, U.S. EPA, RREL
Development of Biodegradation Kinetics for Mixed Substrate Systems
Rakesh Govind, University of Cincinnati j
i
Waste Analysis Plan Review Advisor (WAPRA) to Assist RCRA Permit Reviewers
Daniel Greathouse, U.S. EPA, RREL ! ,
VIII
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Leachate Recirculation as a Remedial Action at Problematic Municipal Solid Waste Disposal
Sites
Stephen Harper, Engineering Science
RREL Remedy Screening Lab
Gerard Roberto, Center Hill Facility
Pilot Program for the Treatment of Mining Wastes, Butte, Montana
Jonathan Herrmann, U.S. EPA, RREL
Results from the U.S. EPA Municipal Solid Waste Innovative Technology Evaluation Program
(MITE)
Lynann Kitchens, U.S. EPA, RREL
RREL RCRA Corrective Action Technical Support Program
Doug Grosse, U.S. EPA, RREL
Characterization of Inorganic Wood Preserving Waste: F035
DanPatel, SAIC
SITE Demonstration of the Horsehead Resource Development Co., Inc.
(HRD) FLAME REACTOR
Marta Richards, U.S. EPA, RREL
NATO/CCMS: Pollution Prevention Strategies for Sustainable Development
Harry Freeman, U.S. EPA, RREL
Pollution Prevention in Public Agencies
Emma Lou George, U.S. EPA, RREL •
Treatability Tests on Ash from Incineration of Spent Potliner Waste (KO88)
Vijay Rao, IT Corporation
Feasibility of Rubber Battery Casings as a Fuel Substitute
James Stumbar, FW Enviresponse
U.S. EPA Waste Minimization Assessment Centers
William Kirsch, University City Science Center
California EPA WRITE Program
Robert Ludwig, California Dept. of Toxic Substances Control
Contaminated Soil and Debris Technology Transfer Program
Joyce Perdek, U.S. EPA, RREL
IX
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CERCLA Treatability Guidance \
Jim Rawe, SAIC
Evaluating Physical and Biological Changes in Soils Caused by Superfund Treatment
Pat Lafornara, U.S. EPA, RREL
i
The Municipal Waste Landfill as a Biological Reactor
Norbert Shoemaker, Gulf Coast Hazardous Substance Research Center
Scanning Electron Microscope Monitoring of Biological Granular Activated Carbon Hazardous
Waste Treatment Processes \
Steven Safferman, U.S. EPA, RREL i
Utilization of the Incineration Research Facility for Superfund Treatability Testing
Howard Wall, U.S. EPA, RREL j
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SOLIDIFICATION/STABILIZATION OF
HIGH LEVEL INORGANIC AND ORGANIC
SOILS AT ROBINS AIR FORCE BASE
Terry Lyons
U.S. EPA, RREL
26 Martin Luther King St.
Cincinnati, OH 45268
(513) 569-7589
Paul V. Dean
PRC Environmental Management, Inc.
1505 Planning Research Dr., Suite 220
McLean, VA 22102
(703) 883-8806
INTRODUCTION
Solidification/stabilization technologies have been applied widely and generally have been
effective in immobilizing metal and other inorganic contaminants at hazardous waste sites. Solidifica-
tion/stabilization technologies have been less effective in immobilizing organic contaminants, because
solidification alone may not reduce the mobility and toxicity of hydrophobia constituents. In addition,
treatment of wastes containing volatile organic compounds (VOC) by solidification/stabilization generally
has consisted of partitioning VOCs to the air either through aeration (such as materials handling and
mixing) or through heat of reaction with treatment reagents.
To constitute treatment under Superfund, a solidification/stabilization technology must
demonstrate a significant reduction (90 to 99 percent) in the concentration of chemical constituents of
concern. During the last 10 years, various innovative solidification/stabilization technologies have
emerged that are capable of treating wastes containing organic as well as inorganic contaminants.
These innovative solidification/stabilization technologies have involved the use of surfactants and other
reagents that chemically stabilize contaminants in conjunction with solidification.
One innovative solidification/stabilization technology, developed by Wastech, Inc., is currently
being tested in the U.S. EPA Superfund Innovative Technology Evaluation (SITE) program at Robins Air
Force Base (Robins AFB) in Warner Robins, Georgia. An on-base landfill cell of approximately 1.5 acres
was used for the disposal of industrial wastewater treatment sludge, as well as solvents, cleaners, paint
removers, hydraulic fluids, and oils. Those wastes were deposited in the cell over a period of
approximately 16 years ending in 1978. Soils at the site are contaminated with a variety,of VOCs, such
as 1,2-, 1,3-, and 1,4-dichlorobenzene, trichloroethylene, benzene, toluene, ethylbenzene, and xylenes,
and with chromium, nickel, and lead.
The Wastech solidification/stabilization technology is being evaluated to determine the
effectiveness of the technology in treating organic and inorganic contaminants. The evaluation of the
Wastech technology will include determining the structural properties of the treated waste and assessing
the loss of VOCs during the treatment process and during post-treatment curing.
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METHODOLOGY !
The first phase of the Wastech treatrhent technology involves adding proprietary liquid chemicals
and catalysts to the waste, which will result in the formation of micelles. According to Wastech, after
exposure to the liquid reagents, the contaminants are chemically stabilized and volatilization stops. The
second phase of the treatment involves physical solidification and stabilization in a mixture of pozzolanic
binders and Portland cement The resulting grout-like mixture is deposited into containers or in
engineered excavations for curing and disposal.
The evaluation of the Wastech technology will consist of a pilot-scale demonstration at Robins
AFB. The evaluation will be based primarily 0n 1) determining if the technology can reduce the level of
organic contaminant extractability as measured by total waste analysis (SW 846 Methods 8240 and
8270), and 2) determining if the Wastech technology reduces leachability and mobility of both organic
and Inorganic contaminants as measured byithe Toxicity Characteristic Leaching Procedure (TCLP) and
other leaching procedures such as TCLP-Disjtilled Water. The technology evaluation also will be based
on the structural properties of the treated waste, the loss of VOCs during treatment and curing, the
volume and mass increase of the treated waste, and treatment variability from batch to batch.
Contaminated soil from the Robins A'FB site will be excavated, screened, and conveyed by a
screw auger to the treatment mixer. At each excavation location, a 4-foot diameter casing,
approximately 10 feet long, will be driven into the landfill, using a vibrating hammer. The casing will
allow clean removal and temporary storage of overburden without adjacent overburden collapsing into
the hole. After the overburden has been augered out, a modified mud bucket will collect the
contaminated soil in single 1- to 2-cubic-yard lifts. The excavated waste will be transported directly to
the screen and screw conveyor in the mud bucket, minimizing material handling and attendant VOC
emissions. The overburden will be used to backfill the excavation following waste removal.
The mixer is trailer-mounted and contains mixing paddles and two high-speed rotary cutting
blades. Calibrated load cells (scales) are located under each leg of the mixer, providing the accurate
weight of all materials added. With the mixer in the trailer are storage tanks for water, liquid reagent and
catalyst, pozzolanic binders, and portland cement, as well as a control booth and wet scrubber/carbon
adsorption system to control air emissions, the mixer will be kept under negative pressure, with the air
drawn through a tank of scrubber water and then through two canisters of granular activated carbon that
are staged in series. :
Raw- and treated-waste samples collected during the technology demonstration will be analyzed
by a variety of chemical and physical tests (Such as Methods 8240, 8270, TCLP and unconfined
compressive strength). To account for any interferences introduced by the treatment reagents and
process water, a reagent mix "blank" batch will be run using clean sand. The sand and water, as well as
the "treated" material, will be sampled and analyzed upon discharge from the mixer.
Loss of VOCs during treatment and curing will be measured in two ways. First, for each batch
of soil treated in the mixer, the scrubber water and carbon canisters will be analyzed for VOCs.
Sampled clean water and carbon will be used for each treatment batch. Second, upon discharge of
treated waste, a tared 5-gallon bucket will be filled with the waste, immediately covered, weighed, and
placed inside a glove box with Inflow and outflow ports (see figure). The glove box then will be sealed
and purged with nitrogen, using a low-volume air pump. Activated carbon tubes, in series to prevent
breakthrough, will be attached to the outflow port and the bucket cover removed. Carbon tubes will be
changed daily for one week and analyzed for VOCs.
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REPRESENTATIVE GLOVE BOX
SOIL
MIXER
RESULTS
A borehole program at the Robins AFB site to identify excavation locations for the technology
demonstration was conducted in July and August 1991. Soil samples were collected from various
locations at a depth of 6 to 8 feet. Representative results of the borehole sampling program are shown
in Tables 1 to 3.
CONCLUSIONS
Bench-scale testing results should be available in March or April 1992. A pilot-scale field
demonstration currently is scheduled for April or May 1992.
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TABLE 1. VOCs AT ROBINS AFB - METHOD 8240
I
Concentrations are in mg/Kg (ppm)
Sample Location
1 ,2-DIchloroethene (total)
Trichloroethene
Tetrachloroethene
Chlorobenzene
1 ,2-Dichlorobenzene
1 ,3-Dichlorobenzene
1 ,4-Dichlorobenzene
TEX*
i 98
1!,388
[298
, 33
6,638
366
3,288
86
19
119
32
17
815
80
479
145
235
2,613
161
ND
3,700
146
1,800
ND
97
624
58
21
1,838
86
1,138
149
TEX » Total toluene, ethylbenzene, and total xyienes; no benzene detected.
TABLE 2. SEMIVOLATILE ORGANIC COMPOUNDS AT ROBINS AFB - METHOD 8270
I
Concentrations are in mg/Kg (ppm)
1 ,2-Dichlorobenzene
1 ,3-Dichlorobenzene
1 ,4-Dichlorobenzene
1 ,2,4-TrichIorobenzene
Naphthalene
2-Methyl naphthalene
I
I
; A
4,867
i 336
, 2,560
127
105
327
Sample Location
B
658
72
415
ND
ND
59
_C_
5,083
293
2,867
ND
ND
329
TABLE 3. METALS AT ROBINS AFB - TCLP
Concentrations are in mg/L (ppm)
Sample Location
Chromium
Nickel
Lead
i 0.371
I 0.371
1.125
0.358
0.867
0.221
0.370
0.656
0.325
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REVIEW OF SOIL VAPOR EXTRACTION MICROCOMPUTER MODELS
Chi-Yuan Fan
Superfund Technology Demonstration Division
Risk Reduction Engineering Laboratory
U.S. Environmental Protection Agency
2890 Woodbridge Avenue
Edison, New Jersey 08837
INTRODUCTION
Soil Vapor Extraction (SVE) is a process in which volatilization of
residual organics is enhanced and contaminated gas is removed from subsurface
soils. The technology is commonly used to remediate volatile organic
compounds released from underground storage tank (UST) systems. Across the
nation, numerous consultants have designed and operated SVE for cleaning up
gasoline and solvents contaminated soil. However, despite the wide
application of SVE systems, only scanty information is available for
evaluating the feasibility of SVE technology and predicting the efficiency of
system performance.
The US EPA Risk Reduction Engineering Laboratory has recently prepared a
document to provide guidance for designing and implementing a soil vapor
extraction treatability study in support of remedy selection at Comprehensive
Environmental Response, Compensation, and Liability Act (CERCLA) sites. As
stated in the guidelines, screening and evaluation of the SVE technology
applicability necessitates understanding SVE processes through modeling
techniques at an early stage of the technology implementation.
A model is a physical or mathematical construct that simulates or
approximates the behavior of an actual physical process. Models are used to
understand processes or portions of processes that have a high degree of
complexity or cannot be readily understood by direct observation. In leaking
underground storage tanks site or hazardous waste site evaluations, models are
particularly valuable since modeling the behavior of a soil-vapor-groundwater
system prior to the construction of a remediation system can reduce the cost
associated with trial and error system design and operation.
If SVE processes can be adequately modeled, then the remedial design
consultant will be better able to examine the process feasibility, to predict
potential performance, and to develop system engineering design criteria prior
to SVE implementation. This paper presents a brief overview of the identified
micro-computer models that simulate soil vapor transport due to the influences
of a SVE system and evaluate the feasibility of using SVE system for site
remediation.
SOIL VAPOR EXTRACTION MODELS
To effectively design a SVE system, an understanding of the mechanisms
controlling the fate and transport processes and the site characteristics
which affect them is required. The major processes that affect SVE are
advection, diffusion, dispersion, partitioning, and abiotic and biological
transformations.
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Mathematical models have been developed to describe results of
laboratory SVE column experiments, as well as results from field scale
implementation of SVE. In order to identify models which are applicable for
use in evaluating SVE systems, a larger group of models, subsurface vapor
transport models, was examined. The models within this group consist of seven
model types: , ,
i
Models developed to simulate laboratory column studies.
Models developed to simulate laboratory pilot (sandbox) studies.
SVE screening models.
Models developed to simulate the effect of SVE at the field scale.
3-D vapor flow models for field scale applications.
3-D multi-phase fate and transport models having a vapor flow
component for field scale applications.
Groundwater flow models used to approximate vapor flow.
Radon gas fate and transport models.
While each of these types of models is important in describing some
portion of subsurface vapor transport, this presentation addresses only those
models which can simulate SVE systems on a personal computer. Table 1
summarizes four general types of models which are discussed in the following
sections.
1. Column Models — Column models are developed to simulate laboratory
column studies that gauge the relative importance of various fate and
transport processes under simplified land controlled column conditions. SVE
treatability study and research have been conducted with column studies with
computer modeling.
Wilson (1991) developed a SVE column model to simulate one dimensional
flow in laboratory column studies. The model considered local equilibrium
betv/een vapor phase, aqueous phase, adsorbed state, and nonaqueous liquid
phase.^ Advection and diffusion/dispersion in the vapor and aqueous phases are
taken into account, and biological degradation is also modeled as a first-
order process occurring in the aqueous phase. In addition, the user can
determine the sorption parameters based on the test results according to
Freundlich, Langmuir, and BET adsorption isotherms characteristics.
i
2. Screening Models - SVE screening models are models which are
primarily used in a semi-quantitative fashion to estimate whether SVE is
feasible for application at a specific site. In addition, such a model may
provide estimates of some design parameters for sizing a SVE system. Johnson
et al. (1990, 1990a) presented a practical approach to screening the
feasibility of using SVE at a particular site. The approach is based on
equations which estimate VOC removal rates and pressure distributions related
to various SVE design parameters. Based on this approach two models.
HYPERVENTILATE and VENTING, were developed.
HYPERVENTILATE was developed as a user friendly, interactive, software
guidance system that operates as a "decision tree" for investigating the
potential implementation of SVE at a ^iven site. It was designed for the
Apple Macintosh HyperCard environment, and consequently requires the HyperCard
program for operation. The model will not completely design a vapor
extraction system, predict exactly how many days it should be operated, or
6
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predict the overall effectiveness of a SVE system. It was designed to be used
as a guide to a structured thought process to: (a) identify and characterize
required site data, (b) decide if soil venting is appropriate at a site, (c)
evaluate air permeability test results, (d) estimate the minimum number of
extraction wells, and (e) estimate how resultsat agiven site might differ from
the ideal case. The organizational basis used in Hyperventilate is a system
of multiple card files. The main card stack is called "Soil Venting Cards".
Since individual cards within this stack may require further explanation,
there are secondary card stacks that can be accessed through individual cards.
These secondary stacks include the "Soil Venting Help Stack", the "Air
Permeability Test" stack, the "Aquifer Characterization" stack, and the
"System Design" stack. Most of the SVE system parameters are estimated under
the topics that deal with SVE feasibility, system design and field testing.
VENTING — This screening model for estimating the VOC removal rate from
the vadose zone under SVE conditions assumes steady gas flow, equilibrium
partitioning between the free product and vapor phases and complete mixing of
free product and vapor to estimate the reduction in mass of each component of
the contaminant over the time of extraction. The mass balance portion only
considers partitioning from the free product phase into the vapor phase. It
assumes contributions to the vapor phase by the aqueous and adsorbed phases
are negligible. The key parameter which controls the results of VENTING is
the volumetric gas flow rate which is in contact with the contaminated soil.
The flow rate may either be input directly based on field measurements or may
be estimated from the gas permeability of the soil and the vent pressure. If
the gas permeability is not known, "VENTING" provides a method of estimating a
value for this parameter using air permeability test data.
3. Three-Dimensional Vapor Flow Models — This category of subsurface
vapor transport models addresses the three-dimensional flow of soil vapor
through a porous medium due to the pressure gradient established by an
extraction well. Such models do not consider the contaminant concentrations
in the soil vapor but do simulate the compressibility of the vapor. CSUGAS is
one of this type models. It is a three dimensional, finite difference model
which numerically simulates the flow field of a compressible gas in a porous
medium due to the influences of a SVE system. The finite difference method is
used to numerically approximate a solution to the system of equations. Use of
this method allows for application to a heterogeneous and isotropic porous
medium with gaseous flow under steady state or transient conditions. The
model can be used to select design parameters, determine the feasibility of
SVE at a particular site, or evaluate proposed modifications to existing SVE
systems.
4. Ground Water Flow Models — Another approach which has been used to
predict the pressure distribution and flow of a SVE system for design purposes
is to use ground water flow models. The equations describing vapor and ground
water flow in a porous medium are similar enough to warrant the use of ground
water flow models to approximate the pressure field and flow of a given system
design. The advantages of using ground water models are that many of these
models are readily available, well documented, validated, and may already be
familiar to the user. MODFLOW is a commonly used ground water flow model.
This model is a three-dimensional, finite difference ground water flow model
developed by the USGS as a modular model capable of simulating many hydrologic
systems (McDonald and Harbaugh 1985). It has several optional features which
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are not applicable for simulating air flow. The model is divided into
'packages", each of which represents a hydrologic or computational featurel
Packages are further divided into ''modules" which are subroutines designed for
use in a particular package. For $VE applications, the two packages that are
the most important are the Block Centered Flow (BCF) Package which simulates
flow within a porous media and the Basic Package. The Basic Package includes
definition of: the number of rows; columns and layers in the finite
difference grid, timing of the analysis, the initial pressures (head for
ground water), the boundary conditions, the timing and format of the output
and a volumetric balance. [
CONCLUSIONS i
Recent designs of SVE systems for VOC removal have mostly been
empirically based due to the simplicity of the process and to a lack of
analytical tools capable of aiding in system design. While it is possible to
empirically design a SVE system which will extract VOC vapors, design of an
efficient system which will effectively target the entire contaminated soil
volume and reduce VOC residuals to an acceptable level, requires predictive
capabilities, especially at sites with very heterogeneous soils and/or widely
varying topography. Predictive capabilities such as those provided by a
correctly applied model are needed to estimate the change in effectiveness of
a system due to varying the blower ;size, well configuration, screened
interval, and other system parameters.
Many numerical model have beeri used in actual field situation to evaluate
the effectiveness of SVE in removing organic vapors. Modeling yields
meaningful results when the appropriate background information is used.
Sensitivity analyses reveal the importance of soil moisture, temperature,
heterogeneities of the soil and other factors in controlling the migration of
volatile constituents through the u'nsaturated zone. Furthermore, the process
of contaminants desorption from soil particles, which occurs through three
consecutive mass transport steps, plays an important role in determining final
cleanup efficiency and will generate significant differences in removal rate
between the various types of soils and volatile organic components.
Acknowledgments. The author thanks Dr. John Eisenbeis of Camp Dresser & McKee
Inc., Denver, Colorado for his study on the soil vapor extraction numerical
models assessment under EPA Contract No. 68-03-3409, WA 3-09.
REFERENCES
Johnson, P.C.; C.C. Stanley, M.W. Kemblowski, D.L. Byers and J.D. Colthart
1990. A Practical Approach to the Design, Operation, and Monitoring of In Situ
Soil Venting Systems. Ground Water Monitoring Review, 10(2) p. 159.
Johnson, P.C.; M.W. Kemblowski and J.D. Colthart. 1990a. Quantitative Analysis
for the Cleanup of Hydrocarbon Contaminated Soils by In Situ Soil Ventina
Ground Water, 28(3) p. 413.
McDonald, M.G. and A.W. Harbaugh. 1988. A Modular Three Dimensional Finite
Difference Ground Water Flow Model. USGS Book 6.
8
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Sabadell, G.P.; J.J. Eisenbeis, D. VanZyl and O.K. Sunada. 1988. CSUGAS -
Flowfield Model For In Situ Volatilization of Organic Compounds in Soils,
Colorado State University Report to Argonne National Laboratory.
Wilson, D.J. 1991. Movement of a Volatile Organic Compound in a Soil Vapor
Extraction Column. (Unpublished paper)
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CONTAMINATE:
by
Walter Urban
Foster Wheeler Enviresponse, Inc.
2890 WoodbrkJge Avenue
Edison, New Jersey 08837
and
S. Krishnamurthy
Risk Reduction Engineering Laboratory
2890 Woodbridge Avenue
Edison, New Jersey 08837
INTRODUCTION
Lead contaminated soil in urban areas is of major concern because of the potential health risk to
children. Many studies have established a direct correlation between lead in soil and elevated blood lead
levels in children (Fairey and Gray, 1970; Neri et al., 1978; and Rabinowitz and Bellinger, 1988). In
Minneapolis, Minnesota, Mielke et al. (1983) reported that 50% of the Hmong children with lead poisioning
were in areas where soil lead levels were between 500 and 1000 micrograms per gram (ug/g), and 40% of
the children suffering from lead poisioning lived in areas where soil lead levels exceeded 1000 ug/g.
In urban areas, lead pollution in soil has come from many different sources. The sources include
lead paint, lead batteries and automobile exhaust. Olson and Skogerbee (1975) found the following lead
compounds in soils where the primary source of pollution was from automobiles: lead sulfate, lead oxide,
lead dioxide, lead sulfide, and metallic lead. The primary form of lead found was lead sulfate. Lead batteries
contain metallic lead, lead sulfate, and lead dioxide. The primary form of lead found is lead sulfate. Lead
sulfate, lead tetraoxide, white lead, and other forms of lead have been used in the manufacture of paints for
houses.
At present, two remediation techniques, solidification and Bureau of Mines fluosilicic acid leaching,
are available for lead-contaminated sites. The objective of the present investigation at the Risk Reduction
Engineering Laboratory(RREL), Edison, was to try to solubilize the lead species by appropriate reagents and
then recover the contaminants by precipitation as lead sulfate, using environmentally acceptable methods.
A multistep extraction process was developed. The apparatus used for mixing was a LabMaster mixer, with
variable speed and high-shear impeller.
Previous work had used nitric acid for dissolving metallic lead. Owing to the environmental
concerns, it was decided to use acetic acid in the presence of oxygen. The theoretical justification for this
approach is the favorable redox potential for the reaction between metallic lead, acetic acid, and gaseous
oxygen.
In the first step a water slurry of lead-contaminated soil is reacted with ammonium carbonate to
convert lead sulfate to lead carbonate. After filtration, the soil is reacted with gaseous oxygen in an acetic
acid medium. In this second step metallic lead and lead carbonates are solubilized as lead acetate. The
soil is filtered and then reacted (third step) with manganese acetate. This step converts lead dioxide to
soluble lead acetate, leaving insoluble manganese compounds as a byproduct. The filtrates from the three
steps are combined to precipitate insoluble lead sulfate, which is a usable product.
11
-------
METHOD
To determine what mixing speed and oxygen flow rate to use, 5.0 grams of metallic lead was mixed
at different mixing speeds and at different oxygen flow rates in the presence of sand for one hour. The sand
was added to keep the metallic lead dispersed throughout the solution. At the beginning and end of the
runs, the pH of the lead-sand-acetic acid mixture was measured to determine if the desired reaction was
occurring. The dissolved oxygen concentration was measured every 10 minutes. At the end of the run, three
samples were taken for determination of lead by atomic absorption spectroscopy.
The second experiment performed was a rate of reaction study. In this study, every ten minutes
a sample was taken out for lead determination to find how long it takes for maximum metallic lead solubility
to occur in the presence of the oxygen. These tests were done for 70 minutes. Three different sets of
conditions were studied. In the first set of conditions, 10,000 milligrams per liter (mg/L) of metallic lead was
mixed in 1.0M acetic acid with an oxygen flowj rate of 73.4 milliliters per minute (mL/min). In the second
set of conditions, 20,OOOmg/L of metallic lead was mixed in 0.01 Molar(M) acetic acid with an oxygen flow
rate of 73.4ml_/min. In the third set of conditions, 10,000 mg/L of metallic lead was mixed in 0.1 M acetic
acid with an oxygen flow rate of 73.4 mL/min. Temperature pH, and oxygen solubility were also determined.
The lead concentrations in the sample were determined via atomic absorption spectroscopy.
The solubilization of lead dioxide involves the use of manganese acetate to reduce and solubilize
the lead dioxide. 1.15 grams of lead dioxide was added to a beaker containing 500 mL of 1.0 M acetic acid.
To twelve beakers of this mixture, manganese acetate was added at the following levels: 0.5, 1.0, 1.5, 2.0,
2,5 and 3.0 grams. The contents were mixed for a period of one hour, then filtered. Three samples were
taken from the filtered solution for lead determination.
i
In separate experiment, samples of silt loam from Bayou Bonfouca, Louisiana were spiked with
10,000, 5,000 and 1,000 milligrams per kilograms (mg/kg) of lead. Four different types of lead were added
to the silt loam. Lead sulfate, white lead, lead dioxide, and metallic lead were added to the soil in the ratio
6:2:1:1. The extracting solutions in the following steps were added at a ratio of 8:1. The first step was to
add ammonium carbonate solution to convert the lead sulfate to lead carbonate The sample was mixed for
5 minutes. Three samples were taken from the filtrate for lead analysis. The second step was to add 1.0
M acetic acid to the sample in the presence of oxygen to solubilize the lead carbonate, metallic lead, and
white lead. The lead in solution was determined by atomic absorption spectroscopy. After the second step,
the residue was leached with deionized water. The leachate was analyzed for lead. The filial step involved
the use of manganese acetate in 1.0 M acetic acid as a means of removal of the lead dioxide from the soil.
At the 10000 parts per million(ppm) lead level, the above procedure was done twice to see if any additional
lead could be extracted.
RESULTS
The solubilization of metallic lead in a sand medium showed the importance of choosing the proper
mixing speed and oxygen flow rate. As the oxygen flow rate was increased from 24.1 ml/min to 59.5
ml/min, an increase in the solubility of metallic lead was observed. Oxygen flow above 59.5 ml/min did not
result in an increase in metallic lead solubility. Increasing the mixing speed from 400 revolutions per minute
rpm) to 800 rpm caused almost a 25% increase|in metallic lead solubility. Metallic lead solubility at 400 rpm
averaged 63%, while at 800 rpm mixing speed^ metallic lead solubility averaged 84%.
The complete results for the manganese acetate test can be found in Table 1. The use of
manganese acetate showed that, when added at a level of 1.0gram/500 milliliter (g/mL), more than 55% of
the lead dioxide (2000mg/L) dissolved. Additional manganese acetate appeared to result in a slight
decrease in lead dioxide solubility.
12
-------
TABLE 1. LEAD DIOXIDE SOLUBILITY AS AFFECTED BY THE LEVEL OF MANGANESE ACETATE ADDED.
Manganese Acetate Used
(g/500mL)
0.5
1.0
1.5
2.0
2.5
3.0
Lead Added
(ppm)
2000
2000
2000
2000
2000
2000
Lead in Solution
(ppm) (%)
654
1185
1038
997
945
979
33
59
52
50
47
49
In the rate of reaction studies, the solubilization of lead varied depending upon the ratio of metallic
lead to acetic acid. When metallic lead was added at 10000 mg/L rate to a 1 M solution of acetic acid
representing approximately 10 to 1 reagent to lead ratio, 72% of the added lead was in solution in 10
minutes. After 20 minutes, 89% of the added metallic lead was found to have dissolved. The increase in
metallic lead solubility was then much slower and levels off at 60 minutes with 95.5% of the lead going into
solution. When the ratio of reagent to metallic lead was 1.3 to 1, 73.3% of the metallic lead went into
solution within 10 minutes. After seventy minutes, the metallic lead solubility had only increased to 80.2%
of the added lead. When lead was added at 20,000 mg/L to a 0.01 M acetic acid solution, lead solubility
leveled off at 10 minutes of 4.8% of the added lead going into solution. After the first ten minutes, lead
solubility decreased and pH rose above 9.6.
The results of experiments with lead-contaminated soils are summarized in Table 2. Using soil
spiked with lead at 5000 mg/kg of soil, approximately 82% of the lead went into solution from the above
procedure. In the first step where carbonation was done, only 0.7% of the lead went into solution. In the
oxidation step, 63.8% of the applied lead went into solution. Leaching the residue with water resulted in an
additional 3.5% of the lead being removed from the soil. The final step where manganese acetate was
added resulted in an additional 14.2% of the added lead going into solution.
Using soil spiked with lead at 1000 mg/kg of soil, approximately 80% of the lead went into solution.
The carbonation step resulted in 1.9% of the lead going into solution. The oxidation step resulted in 57.6%
of the lead going into solution. Leaching the residue with deionized water resulted in the removal of
additional 4.4% lead from the soil. The addition of manganese acetate resulted in 15.9% of the added lead
going into solution.
The 10000 mg Pb/kg of soil sample was run through the three-step process twice. After the first
run through the three-step extraction procedure, 82.9% of the lead added was in solution. The second run
through the three-step procedure resulted in an additional 6.4% of the added lead being solubilized. A total
of 89.3% of the added lead was solubilized by duplicating the three step process. The oxidation step in
the first set of extractions resulted in 65.1% of the lead going into solution. The manganese acetate
extraction step resulted in 13.8% of the added lead being solubilized. The second set of extractions resulted
in an additional 4.6% of the lead being removed in the oxidation step with the remaining lead removal being
divided between the deionized water and manganese acetate leaching steps.
After the above treatment, the soil was subjected to the Toxicity Characteristic Leaching Procedure
(TCLP) test. The soil passed the test with a value of 3 parts per million (ppm) in the leachate.
13
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TABLE 2. LEAD REMOVAL EFFICIENCY IN THE THREE-STEP PROCESS IN A SILT I 0AM WITH
DIFFERENT LEVELS OF INITIAL LEAD
Step
1
2
3
Total
1
2
3
Total
Reagent used
Ammonium Carbonate
Oxygen and Acetic Acid
Deionized Water
Manganese Acetate
Ammonium Carbonate
Oxygen and Acetic Acid
Deionized Water
Manganese Acetate
Lead input
(ppm)
1000
1000
1000
1000
1000
I
2000
2000
2000
2000
2000
Lead in solution
(ppm)
2.6
75.3
24.1
21.3
123.4
5.5
428.6
94.4
96.6
625.1
Removal efficiency
(%)
1.9
57.6
4.4
15.9
79.7
0.6
63.8
3.5
14.2
82.2
1
2
3
Total
2
3
Total
Ammonium Carbonate
Oxygen and Acetic Acid
Deionized Water
Manganese Acetate
Ammonium Carbonate
Oxygen and Acetic Acid
Deionized Water
Manganese Acetate
Deionized Water
First Extraction
10000 5.0
10000 847.3
10000 207.3
10000 183.2
10000 1242.8
Second Extraction*
10000 0.7
10000 62.6
10000 32.7
10000 12.2
10000 5.2
10000
113.6
0.4
65.1
3.7
13.8
82.9
0.1
4.5
0.7
0.9
0.1
6.4
* Here the removal efficiency was calculated bn the starting concentration in the first step.
CONCLUSIONS I
The results in the silt soil show that a three step process involving manganese acetate, ammonium
carbonate, acetic acid and oxygen has the potential for effectively removing lead sulfate, lead dioxide,
metallic lead, and white lead from a soil. The three step extraction process resulted in 80% or greater
solubilization of the lead that was added to a silt loam.
At present, research is continuing on the study of this process for removing the lead compounds
of concern in urban environments and more data will be available when the conference is held.
14
-------
REFERENCES
1. Fairey, F. and Gray, J. 1970. Soil lead and pediatric lead poisoning. S. C. Med. Assoc. 66:79-82.
2. Neri, I., Johansen, J,, Schmitt, N,, Pagan, R,, and Hewitt, D. 1978. Blood lead levels in children in
two British Columbia communities, in Hemphill, D. ed. Twelfth Trace Substances Conference. Univ.
of Missouri, Columbia, MO. pp 403-410.
3. Rabinowitz, M. B. and Bellinger, D. C. 1988. Soil lead-blood lead relationship among Boston
children. Bull. Environ. Contam. Toxicol. 41:791-797.
4. Mielke, H. W., Blake, B., Burroughs, S., and Kissinger, N. 1983. Urban lead levels in Minneapolis:
The case of the Hmong children. Environ. Res. 34:64-76.
5. Olson, K. W. and Skogerbee, R. K. 1975. Identification of soil lead compounds from automotive
sources. Environ. Sci. Technol. 9:227-230.
15
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DESTRUCTION OF ORGANIC WASTES USING CONCENTRATED SOLAR RADIATION
Barry Bellinger, John L. Graham, and Joel M. Berman
Environmental Sciences Group
University of Dayton Research Institute
300 College Park
Dayton,;OH 45469-0132
(513)229-2846
INTRODUCTION
We have recently demonstrated that the rate of many gas-phase photochemical reactions can be increased
by initiating these reactions at elevated temperatures i(e.g., > 400°C) (1,2). The development of very high-
temperature photochemistry has raised exciting possibilities for applications such as the destruction of toxic
organic wastes (1-3). Since concentrated sunlight contains a considerable quantity of near-UV photons (X. > 300
nm) that can be used to initiate photochemical reactions, as well as infra-red (IR) photons that can serve as a
source of considerable thermal energy, the solar induced thermal/photolytic destruction of hazardous organic
wastes appears to be technically feasible.
Our initial laboratory studies using simulated, broad-band, solar radiation (filtered xenon arc emission) in
conjunction with a thermoelectrically heated flow reactor have clearly shown that the destruction rates of target
compounds can be significantly increased and the production of stable reaction intermediates reduced as
compared to identical thermal exposures (1,2). We have developed relatively simple global kinetic and
photochemical models that empirically describe the experimental results. However, the details of the
photochemistry and spectroscopy are poorly understobd and the need for further investigation is clear. In this
paper, we present the results of a detailed study of the high-temperature photolysis of chlorobenzene in a gas-
phase, oxidative environment using a new flow reactor system utilizing a pulsed, tunable laser system as the near-
UV photon source.
METHODOLOGY
The experimental portion of this research program was conducted on two dedicated instrumentation
systems. Absorption spectra were obtained on a system referred to as the High Temperature Absoiption
Spectrophotometer (HTAS), while the reaction data was taken with a system called the Advanced
Thermal/Photolytic Reactor System (ATPRS). •
The HTAS consists of a specially designed high-temperature absorption cell illuminated by a deuterium
lamp, with the absorbed radiation dispersed by a 0.25'M monochrometer and detected with a 512 channel optical
multichannel analyzer. Temperature dependent absorption spectra were obtained up to 750°C.
The ATPRS is a modular instrument comprised of a tunable pulsed laser illumination system, high
temperature reactor, and dedicated analytical systems. The tunable pulsed laser system consists of a Nd:YAG
laser (Continuum, Model 682-20) coupled to a dye laser (Continuum, Model TDL-51). The reactor is a slender
cylinder measuring 4 mm by 250 mm. Downstream of the reactor is a cryogenic trap that is cooled to -160°C
16
-------
using chilled nitrogen. For analysis, the exhaust gases are purged to an in-line programmed temperature GC
(Hewlett-Packard, Model 5890) fitted with a hydrogen flame ionization detector and a mass selective detector
(Hewlett Packard, Model 5970) which was operated in a scanning mode. During normal operation the GC is fitted
with dual columns for simultaneous mass spectrometric (GC/MS) and hydrogen flame ionization (GC/FID)
detection of the effluent from the cryogenic trap. Alternatively, for analysis of light species (e.g., carbon
monoxide, methane, etc.), the GC was operated as a conventional system using gas samples collected in Tedlar
bags attached to the cryogenic trap's exhaust port.
RESULTS
Figure 1 presents data on the thermal and thermal/photolytic destruction of chlorobenzene. As can
readily be seen by comparison of theseFigures, the rate of destruction of chlorobenzene is accelerated with the
addition of ultra-violet radiation. Furthermore, fewer (and different) products are formed following
thermal/photolytic treatment that are decomposed a lower temperatures than the products formed under purely
thermal degradation conditions.
The photochemical quantum yield for chlorobenzene destruction was calculated to achieve a maximum
of 0.536 at 700°C and the destruction of chlorobenzene was also enhanced by a factor of 4300 at this temperature.
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100
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Phenol
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fxpnvt Tetperttwi, C
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Figure 1. Comparison of product yields from the thermal and thermal/photolytic oxidation of monochlorobenzene
at I0 - 883 mW/cm2 @ 280 nm. [ClBz]0 = 2.95 x 10'5 mol/L. R.T. = 10.0 s. Of particular note is the reduction
in quantity, yield, and stability of the thermal/photolytic by-products. Significantly, this is an apparent change in
oxidation mechanism resulting in different products.
17
-------
CONCLUSIONS
Data on this and other compounds demonstrate the potential viability of destruction of toxic wastes using
concentrated solar radiation. ;
There appears to be several advantages of solar destruction over thermal destruction which include:
1. Increased destruction efficiency of the parent and by-products;
2. Control of vaporization of toxic metals through lower operating temperatures;
3. Control of NOX formation through lower operation temperatures;
4. Recovery of excess thermal energy that can be used for thermal desorption
of solids and sludges;
5. Control of CO, CO2, and toxic organic emissions through substitution of solar
energy for conventional fuels; j
6. Cost savings due to lower fuel costs, increased materials lifetime, and reduced size
and complexity of air pollution control devices;
7. Increased public acceptance through iise of a renewable, non-polluting
energy source for a non-incineration waste disposal technology.
Apparent major disadvantages include:
1. The unreliable availability of solar radiation;
2 Cost of collection and concentration Of solar radiation;
3. Lack of an off-the-shelf technology to construct a working pilot-
or full-scale system.
Our task is to develop an approach that utilizes the advantages and to minimize the disadvantages.
One approach that has been previously proposed is to develop a hybrid two-stage system targeted for
detoxification of contaminated soils and other solids [3]. With this concept, a hybrid primary unit (possibly an
indirectly-fired rotary drum design) may be used to thermally desorb organics from solids, while a secondary solar
reactor would be used to thermal/photolytically destroy the desorbed organics. An auxiliary heat source is
necessary to operate the process continuously during intermittent cloud cover and maintain night-time operation.
The desorbed organic matter during dark operation may be stored by cryogenic trapping or sorption on carbon for
destruction during light periods. Since the total volume of material desorbed is small, the photolytic reactor
should readily handle the stored off-gases during light operation. This approach maintains the previously listed
advantages for solar based waste destruction while minimizing two of the three disadvantages. The hybrid
primary unit allows continuous operation, thus eliminating the concern over the unreliability of sunlight.
REFERENCES
1. Graham, J. L. and Dellinger, B. Solar Therinal/Photolytic Destruction of Hazardous Organic Wastes.
Energy, 12, No. 3/4, pp . 303-310,1987.
2. Graham, J. L., Dellinger, B. and Klostermaii, D., Glatzmaier, G., and Nix, G., Disposal of Toxic Wastes
18
-------
Using Concentrated Solar Radiation. In: Emerging Technologies in Hazardous Waste Management II,
American Chemical Society, Washington, DC, Chapter 6,, April 1991, pp. 83-104.
3. Bellinger, B., Graham, J. G., Herman, J. M., and Klosterman, D. High Temperature Photochemistry
Induced by Concentrated Solar Radiation. In: Proceedings of the National Academy of Sciences on
Potential Applications of Concentrated Solar Photons. Solar Research Institute. National Research
Council. 1990.
19
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ASSESSMENT OF RELATIVE POHC DESTRUCTION
AT EPA'S INCINERATION RESEARCH FACILITY
Gregory J. Carroll
U.S. Environmental Protection Agency
Risk Reduction Engineering Laboratory
Cincinnati, Ohio 45268
Johannes W. Lee
Acurex Corporation
Jefferson, Arkansas 72079
INTRODUCTION
As part of their permitting process, hazardous waste incinerators must
undergo demonstration tests, or "trial burns", during which their ability to
meet EPA performance standards is evaluated. Among the performance standards
is a minimum destruction and removal efficiency (ORE) for principal organic
hazardous constituents (POHCs) in the incinerator waste feed.
In accordance with the regulations promulgated under the Resource
Conservation and Recovery Act (RCRA), selection of POHCs for incinerator trial
burns is to be based on "the degree of difficulty of incineration of the
organic constituents in the waste land on their concentration or mass in the
waste feed." (I) In order to predlict the relative difficulty of incinerating
specific compounds, several "incinerability" ranking approaches have been
proposed, including a system based on POHC heats of combustion and a system
based on thermal stability under pyrolytic conditions. (£)
i
The latter ranking system was'developed by the University of Dayton
Research Institute (UDRI) under contract to the U.S. EPA Risk Reduction
Engineering Laboratory (RREL). The system is supported largely by non-flame,
laboratory-scale data and is based on kinetic calculations indicating that
post-flame pyrolysis of poorly-mixed waste/air pockets is the primary
contributor to emissions of undestroyed organic compounds. (2-4) The subject
tests were conducted to develop data on POHC behavior in a larger-scale,
conventional incineration environment.
METHODOLOGY
Testing took place in the rotary kiln incineration system (RKS) at the
U.S. EPA Incineration Research Facility (IRF) in Jefferson, Arkansas. The RKS
consists of a primary combustion chamber and a secondary (afterburner)
chamber. Flue gas exiting the afterburner flows through a quench section,
which is followed by a venturi scrubber and a packed-column scrubber.
Downstream of the packed column is a secondary air pollution control system
(APCS) consisting of a demister, activated-carbon adsorber, and a high-
efficiency particulate filter. >
20
-------
Mixtures of 12 POHCs, consisting of compounds from each of 7 proposed
incinerability classes, were formulated for the tests. Table 1 lists the test
compounds in decreasing order of predicted thermal stability.
Feed batches, consisting of 3 Ib of POHC mixture added to 5 Ib of a clay
adsorbent material, were fed to the kiln in 1.5 gal fiberpack-containers.
Compound concentrations in Mixture #1 (Tests 1, 2, and 3) ranged from 8 to 10%
by weight, with the exception that n-nitroso-di-n-butylamine was present at
only 2% for safety reasons. POHC concentrations in Mixture #2 (Tests 4 and 5)
were tailored to achieve the desired hydrogen/chlorine ratio.
Five kiln operating modes were investigated: a baseline condition; 3
failure modes (thermal, mixing, and matrix); and a worst-case combination of
the 3 failure modes. Target conditions for key test parameters are indicated
in Table 2.
Permit restrictions and health and safety concerns precluded operating
the entire system (kiln, afterburner, APCS) under failure mode. Therefore,
failure mode operation was attempted in the kiln only and it was the kiln exit
(as opposed to the stack) at which flue gas POHC concentrations were measured
in order to determine relative DREs. (J5)
RESULTS
No semivolatile POHCs were detected in the kiln exit gas during Test 1
(baseline), Test 3 (mixing failure), and Test 4 (matrix failure). Only low
levels of volatile POHCs were observed in these 3 tests. In contrast, Test 2
(thermal failure) and Test 5 (worst-case) yielded detectable levels of 3 of
the 7 semivolatile POHCs and significant levels of all 5 volatile POHCs.
Table 3 presents kiln-exit POHC DREs for each test. A "greater than" ORE
in the table indicates that the POHC was not detected in the kiln-exit flue
gas for that test. The lower ORE limit in such cases is calculated using the
practical quantitation limit (PQL) for the POHC in the exit gas. Since the
exact POHC concentration may be anywhere between zero and its PQL, the exact
POHC ORE may be anywhere between this lower bound and 100%.
In the following discussions, "incineration failure" refers to poor
destruction of POHCs in the kiln, resulting in low (less than 99.99%) kiln-
exit DREs. As expected, incineration failure does not appear to have taken
place during the baseline operating conditions. Likewise, the attempts to
achieve incineration failure in Test 3 (mixing failure) and Test 4 (matrix
failure) appear to have fallen short. DREs during each of those three tests
were uniformly above 99.99%. The close distribution of DREs among the POHCs
makes identification of a correlation between predicted and observed POHC
ranking extremely difficult. Interpretation of the data is further
complicated by the fact that kiln-exit concentrations of 7 of the POHCs Were
below their PQL. While it may be said that DREs for those POHCs are "greater
than VX%'", their exact values are not known.
21
-------
TABLE 1. POHC MIXTURE COMPOSITIONS
Component
J-99-
Concentration (wt %}
Mixture 1 Mixture 2
Benzene
Chlorobenzene
Tetrachloroethene
l,2,2-Trichloro-l,l,2
trifluoroethane
(Freon 113)
Nitrobenzene
Hexachlorocyclo-
hexane (Lindane)
Hexachloroethane
1,1,1-Tri chloroethane
Diphenyl disulfide
p-Dimethylaminoazo
benzene (Methyl yellow)
Nicotine
N-nitroso-di-n-butyl
amine
1150
990
890
780
655
640
590
545
500
405
300
130
8
8
8
8
8
10
10
10
8
10
10
2
4
4
33
4
5
25
5
4
5
5
2
Temperature required to achieve 99% destruction in 2 sec under
pyrolytic conditions; based on experimental, laboratory studies of
mixtures (4) ,
TABLE 2. TARGET TEST CONDITIONS
Test
1
2
3
4
5
Failure
mode
Baseline
Thermal
Mixing
Matrix
Worst-case
Kiln-exit
Feed (Ki
temperature ;
In)
H/C1
[°C (°F)] [molar]
871
649
871
871
649
(1600)
(1200)
(1600)
(1600)
(1200)
3
3
3
1
1
.6
.6
.6
.2
.2
(22.
(22.
(22.
(15.
(10.
8)
8)
8)
7)
3)
Charge
weight Charges/
[kg
3.
4.
7.
3.
7.
6
5
2
6
2
(lb)]
(8)
(10)a
(16)
(8)
(16)
hr
12
12
6
12
6
Includes 0.9 kg (2 Ib) water added.
22
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TABLE 3. KILN-EXIT POHC DREsa (%)
POHC
Benzene
Chlorobenzene
Tetrachl oroethene
Freon 113
Nitrobenzene
Lindane
Hexachloroethane
1,1,1-Trichloroethane
Diphenyl disulfide
Methyl yellow
Nicotine
N-nitroso-di-n-butyl
amine
Test 1
(baseline)
99.9943
99.9988
99.998
99.9966
>99.99961b
>99. 99969
>99. 99969
99.9971
>99. 99922
>99. 99969
>99. 99969
>99.9983
Test 2
(thermal )
99.989
99.88
99.4
98.7
99.84
99.9927
99.966
99.993
>99. 99901
>99. 99961
>99. 99961
>99.9979
Test 3
(mixing)
99.9987
99.99962
99.99947
99.99935
>99. 99957
>99. 99966
>99. 99966
99.99928
>99. 99914
>99. 99966
>99. 99966
>99.9979
Test 4
(matrix)
99.99916
99.99937
99.99929
99.99946
>99. 99909
>99. 99928
>99. 99986
99.99982
>99.9982
>99. 99928
>99. 99928
>99.9977
Test 5
(worst-
case)
99.954
99.9948
99.9925
99.77
99.958
99.9989
99.9925
99.84
>99.9984
>99.9994
>99.9994
>99.998
* Based on feed formulation data.
">" indicates POHC not detected in kiln exit gas; lower-bound ORE computed
using PQL.
Tests 1, 3, and 4 did yield measurable emissions of the 4 POHCs which
were predicted to be most difficult to destroy. As would be expected, this
resulted in lower DREs for those POHCs than for the majority of the other
POHCs. Among the more significant anomalies was 1,1,1-trichloroethane, which
sometimes had measured DREs substantially lower than similarly-ranked POHCs.
This may be due to the fact that 1,1,1-trichloroethane is a common product of
incomplete combustion (PIC), and can be reformed during the incineration
process.
Incineration failure does appear to have taken place during the thermal
failure and worst-case modes (Tests 2 and 5). Low to moderate DREs were
quantifiable for 8 of the 12 POHCs in those two tests, and the 4 POHCs not
detected are those predicted to be the easiest to destroy. In contrast to the
1,1,1-trichloroethane discussion above, the unexpectedly-low ORE for Freon 113
in Tests 2 and 5 cannot be explained by PIC formation. Nonetheless, despite
the fact that the four predicted most-difficult-to-destroy compounds did not
23
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follow the expected rank order in tests 2 and 5, a strong correlation with the
ranking system predictions exists for the two tests. (5)
CONCLUSIONS I
As discussed above, each of the tests yielded emissions of some POHCs at
concentrations below their PQLs. This presents a challenge in that the exact
DREs for such compounds are essentially unknown; they are greater than the
DREs computed using the PQLs. As a result of the unknowns, exact ordering of
observed POHC ranking is not possible. This was the case with diphenyl
disulfide, methyl yellow, nicotine and n-nitroso-di-n-butylamine during each
of the five tests, and with nitrobenzene, lindane and hexachloroethane during
Tests 1, 3 and 4. !
i
i
In order to evaluate how well the observed POHC incinerability ranking
order correlated with that predicted by the UDRI ranking system, a statistical
test was applied to the data. The:Spearman rank-order coefficient provides a
measure of the confidence with which it can be stated that a statistically-
significant correlation exists. i
Because the exact DREs for several POHCs are unknown, discrete rank-order
coefficients could not be determined. Rather, ranges of coefficients based on
assumed DREs were computed. Best-case assumptions suggest that a
statistically-significant correlation at the 99% confidence level between the
predicted and observed ranking orders may exist for each of the five tests.
If one were to adopt the worst-case assumptions, the correlation between
predicted and observed orders would be below the 90% confidence level for
Tests 1, 3, and 4. However, it can be concluded with certainty that
statistically-significant correlations exist for Test 2 and Test 5 at the 99%
and 95% confidence levels, respectively, even under the worst-case scenario.
I
REFERENCES j
1. Code of Federal Regulations; iTitle 40, Part 264, Subpart 0.
2, Guidance on Setting Permit Conditions and Reporting Trial Burn Results:
Volume II of the Hazardous Waste Incineration Guidance Series.
EPA/625/6-89/019, U.S. Environmental Protection Agency, 1989.
3. Dellinger, B., P. Taylor, and D. Tirey. Minimization and Control of
Hazardous Combustion Byproducts. EPA/600/52-90/039, 1991.
4. Taylor, P., B. Dellinger, and C. Lee. Development of a Thermal-
Stability-Based Ranking of Hazardous Organic Compound Incinerability.
Environ. Sci. Techno!.. Vol. 24, No. 3, 1990.
i
5, Lee, J., W. Whitworth, and L. Waterland. Pilot-Scale Evaluation of the
Thermal Stability POHC Incinerability Ranking - Draft Test Report.
U.S. Environmental Protection Agency Contract No. 68-C9-0038, 1991.
24
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PACS VS CO AS SURROGATES FOR TRACE COMBUSTIBLES.
J.H.J. Thijssen, M.A. Toqan, A.F.S. Sarofim, andJ.M. Beer
Dept of Chemical Engineering and Energy Laboratory
Massachusetts Institute of Technology
60 Vassar Street 31-261
Cambridge, MA 02139
Tel. : (617) 253 0876
INTRODUCTION
In the continuous monitoring of trace combustibles we are presented with two fundamental problems:
there are too many trace combustibles regulated to be able to practically monitor all those compounds
individually in real time, and the control of the combustion and incineration devices according to hundreds
of parameters would be impractical. Therefore, surrogates, that can be easily monitored, are necessary to
represent the concentrations of large groups of those trace combustibles. Traditionally, carbon monoxide
has been used for this purpose because of its role in the final oxidation step of all hydrocarbons. However,
it has been found frequently, that CO concentrations measured correlate poorly with concentrations of air-
toxics obtained from stack sampling. This is plausible if one realizes that the critical role of CO presumes
that the trace combustibles should remain reactive to the point of sampling. However, when trace
combustibles escape to low temperature regions of the combustion system (eg. because of poor mixing),
oxidation rates might become so low that the trace combustibles become largely unreactive, not forming
any CO in the process. Thus the trace combustibles might go undetected by the surrogate monitoring
system.
It was thus proposed that surrogates are measured which are more chemically similar to the trace
combustibles and which are equally, or preferentially more, refractory than the trace combustibles. PACs
were found to be very refractory to oxidative destruction and they can be measured in low concentrations
in real time (1). In experiments being carried out the use of PACs as surrogates for trace combustibles
emissions is compared to the use of CO for that purpose. In the experiments the formation and •
destruction of PACs, as well as of CO, is studied in detail in a turbulent natural gas diffusion flame which is
doped with an aromatic compound (toluene). CO measurements are made using a conventional CEM
apparatus, and PACs are monitored by means of the MIT laser induced fluorescence (now LIF) system
which has been developed under a separate project(2), and characterized in detail by a physical sampling
method described elsewhere.
METHODOLOGY
All combustion experiments are carried out in the M.I.T. Combustion Research Facility (CRF), a tunnel
furnace with a maximum thermal input of 3.0 MW. The CRF consists of a number of separate, water cooled,
sections, a variable number of which may be refractory lined on the inside. It is equipped with a Variable Swirl
Burner (VSB) which allows the flow and mixing pattern in the near burner region to be controlled.
25
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Secondary ("overfire") air can be introduced through a, separate, secondary air injection section and
dopants may be injected through probes. The pRF allows both physical and optical access to the
horizontal plane of symmetry through ports in all sections. For the experiments described in this paper the
CRF was configured as shown in Fig. 1. A detailed description of the MIT CRF is given in Beer et at2.
All fluorescence experiments are done using the LIF/LLS system depicted in Fig. 2. The excitation source
is a 5 W (multi line) argon ion laser, operated at;its 488 nm line. The laser beam, modulated (at 1000 Hz) by'
a light chopper, is directed to the sampling volume by two beam steerers. A sampling volume, of 2 mm
diameter and 60 mm length, is observed by the detection system which consists of a single lens, colored
(OG 515) fitters, a Jarrell Ash 25 cm focal length monochromator (with a stepper motor wavelength
selector) and an EMI 9558 QB photomultiplier tube, thermoelectrically cooled to 263 K. The PMT output is
collected by an EG&G 5105 lock-in amplifier, tjjned to the chopper reference frequency. An IBM PC/AT
serves for data acquisition and process control The attenuation of the laser beam by the flame, necessary
for correction of the LIF signal, is determined by the use of a power meter in the port opposite to the LIF
instrument. I
In the combustion experiments, no windows are used to avoid effects of fouling, inevitably associated with
windows. The furnace, under normal operation^ is operated with a slight underpressure, so as to avoid
possible damage to the optical equipment by Combustion fluctuations. Due to the underpressure, and the
favorable geometry of the power meter (narrow view angle), there is no observable effect, of the radiation
from the flame upon the measured signal.
i
Physical samples from the CRF are drawn through a stainless steel water cooled probe into a
Dichloromethane (DCM) Sampling system, consisting of two refrigerated baths of DCM in series (243 K
and 203 K respectively) in which the PACs are to be dissolved. The DCM sample (with the PACs),
including the amount used for rinsing the probe, is-concentrated by Kuderna Danish evaporative
concentration and analyses by HPLC-UV, GC-FID and GC-MS(SIM)
RESULTS
In all experiments, the fire box is run at a near stoichiometric fuel equivalence ratio. Secondary fuel, in the
form of a monocyclic aromatic compound, in particular toluene, is added in the entrance of the cylindrical
section. This fuel has a small concentration (order of 102 ppm), so that the fuel equivalence ratio is only
marginally affected. Secondary air, to yield an oxygen mole fraction of --0.06, is injected in the cylindrical
section to oxidize the PACs formed.
i '
Test are run with equal amounts of the secondary fuel injected, as well as one blank test, in which no
secondary fuel is injected at four different temperatures (in the range between 1400 and 2000 K). In each
test detailed measurements are made of temperatures, velocities, and major species and trace
hydrocarbon species, along all axial center linelstations of the furnace in both fuel rich and fuel lean zones
of the combustion system. :
Those measurements illustrate the processes by which PACs, trace combustibles, and CO are being
formed and destroyed and thus the propensity of both PACs and CO as surrogates for trace combustibles
can be assessed from a fundamental point of view.
i
REFERENCES
1. J. M. Beer, W. F. Farmayan, J. D. Teare, M. A. Toqan, (Electric Power Research Institute, 1985),
2, J. H. J. Thijssen Toqan, Majed A., Beer,, Janos M., Sarofim, Adel F., in Second International
Congress on Toxic Combustion By-Products: Formation and Control R. Seeker Koshland, C.,
Eds. Salt Lake City, Utah, U.S.A., 199t),
26
-------
natural
gas
feed
secondary
fuel
primary air
1 i
T5I fire box _
ri n
iii iii
secondary
III 1 1
V
variable
swirl
burner
i i
sampling ideations
Figure 1 : configuration of the MIT CRF
to stack
A
•fffffitfftfttfftif.
_X monochromator
r—r—t-
PMT
s
telescope
5 W argon laser
power meter chopper
Figure 2 : Schematic of the MIT LIF System
27
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HIGH ENERGY ELECTRON BEAM IRRADIATION: AN EMERGING TECHNOLOGY FOR THE
DESTRUCTION OF ORGANIC CONTAMINANTS IN WATER. WASTEWATER AND SLUDGE
William J. Cooper1
Thomas D. Waite2
Charles N. Kurucz3
Michael G. Nickelsen1
Kaijun Lin1
i
1 Drinking Water Research Center
Florida International University
Miami, FL33199
.(305) 348-3049
2 Department of Civil and Architectural Engineering
University of Miami
Coral Gables, FL 33124
(305) 284-3467
3 Department of Management Science and Professional Engineering
University of Miami
Coral (Sables, FL 33124
(305) 284-6595
INTRODUCTION
As a result of the widespread presenbe of hazardous organic contaminants in aqueous
matrices, considerable research is being conducted on treatment technologies for removing these
compounds from contaminated environments. Historically treatment process efficiency focused
only on the removal of the solute of interest Ifrom solution, with little or no concern for the
formation of potentially hazardous reaction by-products. An extension of this approach is the use
of carbon adsorption and aeration stripping. In the case of carbon the solutes are concentrated and
then incinerated during the carbon regeneration process. Aeration stripping for the removal of
volatile chemicals at worst transfers the problem directly into the atmosphere and at best transfers
it to carbon or another adsorbent.
A more realistic approach to the problem of the disposal of toxic and hazardous organic
waste chemicals will be the development of treatment processes that result in, or facilitate, the
mineralization of the chemicals. Probably the best known process to achieve this is the use of
ozone, O3, most often in the presence of various catalysts for its decomposition, e.g. ultraviolet
(UV) light and/or hydrogen peroxide, H2O2. Other chemical/physical processes that are receiving
attention are supercritical oxidation and wet oxidation. Bioremediation can also be considered an
ultimate disposal process. Incineration of wastes has certain demonstrated advantages, but also a
high potential for the formation of reaction by-products that may be as bad or in some instances
worse than the starting materials.
The current innovative treatment process being evaluated is the use of high energy
electrons for the ultimate disposal of hazardous organic contaminants from aqueous matrices.
When high energy electrons impact an aqueous solution reactive transient species are formed. The
28
-------
three transient species of most interest, in the removal of hazardous contaminants from aqueous
matrices, are the aqueous electron, e"«,, the hydrogen radical, H-, and the hydroxyl radical, OH-.
This paper describes the use of high energy electrons for the destruction of chloroform,
trichloroethylene (TCE), tetrachloroethylene (PCE), benzene, toluene, and phenol from aqueous
solution. The experimental parameters examined are: absorbed dose, water quality (with and
without the addition of 3% clay), and carbonate ion concentration.
METHODOLOGY
The Electron Beam Research Facility (EBRF) is located at the Miami-Dade Central District
Wastewater Treatment Plant located on Virginia Key, Miami, Florida. The facility consists of a
horizontal 1.5 MeV insulated-core transformer (ICT) electron accelerator capable of delivering from
0 to 800 krads absorbed dose. The electron beam is scanned at 200 Hz to give a coverage of 48"
wide and 2" high.
Influent streams at the EBRF are presented to the scanned beam in a falling stream
approximately 48" wide and at the design flow of 120 gpm is 0.15" thick. Total power
consumption, including pumps, chillers and other auxiliary equipment is about 120 kW.
The experiments presented in this paper were conducted by preparing 3,000 gallon (11,355
L) solutions of the compounds slated for study in either a 4,600 or 6,000 gallon tanker. The
tanker is then directly connected to the influent of the EBRF, where the solution is pumped and
irradiated. All contaminants were studied at 0.1, 1.0, and 10 mg L1, pH 5, pH 7 and pH 9, with
and without the addition of 3% clay.
RESULTS
Initial results using high energy electron radiation were presented at the 17th Annual RREL
Research Symposium. By changing the experimental design and eliminating the use of methanol,
as a carrier for the organic contaminants studied, we have begun to develop a better understanding
of the removal processes and more realistic estimates of removal efficiency than previously
reported.
Tables 1 -3 summarizes the calculated d0 B0, d0.90, and d0.a9 values for TCE with and without
the addition of 3% clay at three different pH levels. That is, the absorbed irradiation dose required
to remove 50%, 90%, and 99% of the initial concentration of TCE from solution. From these
results, it appears that our initial removal efficiency estimates were at least 10-fold higher than
when methanol is eliminated from the experimental matrix. That is, equivalent solute removal is
now possible with about 10-fold less energy. In addition to increased removal efficiency we have
conducted extensive studies on solutions of up to 3% clay and have show that the presence of the
suspended matter only moderately affects removal efficiency and in some instances actually
increases removal efficiency.
Since carbonate ion is an excellent scavenger of OH-, the in situ concentration of carbonate
ion was controlled by pH adjustment. For trichloroethylene and tetrachloroethylene lowering of the
pH (i.e., less available carbonate ion) did not seem to enhance removal efficiency. This is because
these halogenated compounds are primarily removed by e'^,. Chloroform, however, did show a
29
-------
decrease in removal efficiency at lower pH values. This is opposite from what was expected. At
this time the reason for this phenomenon is unknown. For the aromatic compounds benzene,
toluene, and phenol removal efficiency was enhanced by pH adjustment. This is attributed to the
lower carbonate ion concentration available at lower pH values. That is, less OH- scavenging by
carbonate ion. \
Reaction by-products identified for a majority of the compounds studied included: chloride
ion, low molecular weight aldehydes and low molecular weight carboxylic acids. All organic
reaction by-products were identified in sub-micromolar concentrations. From these results it
follows that the remaining concentration of starting material was completely mineralized to halide
acids, carbon dioxide, and water.
CONCLUSIONS
In conclusion, the use of high energy electrons appears to be a promising treatment
technology for the ultimate destruction of hazardous contaminants from aqueous matrices. This
innovative treatment technique has the ability:to completely mineralize a variety of hazardous
compounds without the added problem of a secondary treatment technique for ultimate
contaminant disposal as in carbon adsorption iand/or aeration stripping. Furthermore, high energy
electron radiation has demonstrated the destruction of these hazardous contaminants in a variety of
water qualities ranging from treated groundwgter to water containing up to 3% suspended solids.
PUBLICATIONS PERTAINING TO THIS PROJECT
Kurucz, C.N., T.D. Wait, W.J. Cooper and M.C3. Nickelsen. Full-Scale Electron Beam Treatment of
Hazardous Wastes - Effectiveness and Costs in Proceedings of the 45th Annual Purdue University
Industrial Waste Conference. Lewis Publishers, Inc., 1991, pp 539-545.
Kurucz, C.N., T.D. Waite, W.J. Cooper and M.G. Nickelsen. High-Energy Electron Beam Irradiation
of Water, Wastewater and Sludge, in Advances in Nuclear Science and Technology. Volume 23, J.
Lewins and M. Becker, Eds., Plenum Press, N.Y. N.Y., 1991 (in press).
Nickelsen, M.G., W.J. Cooper, T.D. Waite, an
-------
Table 1. Summary of the Doses Required to Remove 50%, 90%, and 99% of TCE From
Aqueous Solution.
Table 2. Summary of the Doses Required to Remove 50%, 90%, and 99% of TCE From
Aqueous Solution.
PH
Target at 7.62 fitt (1,000 ng/L)
Table 3. Summary of the Doses Required to Remove 50%, 90%, and 99% of TCE From
Aqueous Solution.
Target at 76.2
5 Rep #1
Rep #2
7 Rep #1
Rep #2
31
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CARBON DIOXIDE CLEANING OF CONTAMINATED SURFACES
I
Thomas J. Powers
Risk Reduction Engineering Laboratory
Office of Environmental Engineering Technology and Development
Office of Research and Development
United States Environmental Protection Agency
26 West Martin Luther King Drive
Cincinnati, Ohio 45268
Phone Number: (513) 569-7550
INTRODUCTION
Cleaning of contaminated surfaces presents many challenges. Surfaces can be cleaned in many
ways and, depending on the cleaning method,;produce many waste by-products. Many of the wastes
produced will be hazardous or toxic and therefore require proper containment, capture and disposal.
One cleaning or surface preparation method is, blast finishing. Blasting technology is not new. Within
the past two decades, modified or specialized blast media have been selected to enhance the surface
cleaning and preparation process. Older methods utilize natural abrasives such as water and sand.
The newer methods employ glass beads, steel shot, steel grit, aluminum oxide, silicon carbide, garnet
grain, walnut or pecan shells and plastic beads to create variations in abrasive action.
A ranging study was conducted to determine the applicability of pelletized carbon dioxide as a
media for removal of lead-based paint from wooden doors, and to characterize the occupational
exposures to airborne lead and total particulate. Personal breathing zone and work area samples were
collected to assess the airborne concentrations of lead particulate. Aerodynamic particle size
distribution were determined using Marple Series 290 Cascade Impactors. Residual surface levels of
lead were determined using the Housing and Urban Development (HUD) wet-wipe method and a
particulate adhesive sampler (PAS).
METHODOLOGY OF THE BLAST CLEANING PROCESS
The blast cleaning of surfaces is an art form which has been used throughout industry as a quick
and highly efficient method of surface preparation for coatings or reuse. Certain applications have
become more sophisticated due to environmental constraints. As a result of these considerations,
containment systems and pollution recovery systems are expected. Current regulations in many states
require adequate capture and disposal of blasting sand that has been used to clean chromium, lead or
other coating materials. ' . •
The use of carbon dioxide as a blast media, can offer several advantages over other materials
and methods. One positive feature of using CO2 is the reduced volume of solid and liquid waste
requiring disposal. A fifty to one ratio is not uncommon. A second favorable feature is that the surface
finish of metals may not be altered; if desired, the degree of removal may be tailored so that original
undercoat is left and thus remains for refinishing. One disadvantage to the use of this process is the
CO2 level in the work area may be high and a second drawback would be that while CO2 pellets
remove most rust, sand or some other abrasive media; blast may be required to meet current paint
preparation specifications related to profiling and "white metal" surface.
A video dramatically presents the blasting cleaning process using pelletized CO2. This video
explains applications which have a proven performance history. Carbon dioxide surface cleaning can
be an effective method if it is applied properly.
32
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Each cleaning process has five factors for evaluating the effectiveness of cleaning contaminated
surfaces:
1. Surface to be cleaned,
2. Penetration of cleaning agents,
3. Type of contamination to be removed and disposed of,
4. Disposal method, and
5. Total cleaning cost.
The cleaning process can be physical/mechanical or chemical or a combination of both.
Common physical/mechanical methods include polishing, sanding, grinding and blasting. The chemical
methods typically are acids, alkalies, solvents, and water. Almost any combination can be used in a
variety of sequences to produce the desired effect.
The most common surfaces to be cleaned are metals, concrete, plastic, fabrics, and wood.
These surfaces may be contaminated with benign compounds, unknown substances, toxic substances,
hazardous wastes, and radioactive substances.
The factors for evaluating the effectiveness of cleaning a surface will depend upon:
1. Thickness of contaminant,
2. Penetration of the substrate
3. Bonding characteristics,
4. Required reaction, and
5. By-products.
A good cleaning process requires surface decontamination, sub-surface removal, preparing the surface
for sealant and proper collection and disposal of residues. Surface cleaning methods available should
include but not necessarily be limited to, 1) mechanical wipe, 2) chemical wipe/rinse, 3) physical
abrasion, 4) chemical penetration, and 5) penetration by mechanical means. The selection of abrasive
cleaning agents will depend upon the surface contamination, hardness of surface, and blasting material
hardness. The blasting process can be both a cleaning and a finishing method. Blasting can remove
surface contamination and roughen the surface for the application of paint. Blasting is also used to
remove surface irregularities and create a specific surface finish.
The CO2 process utilizes pelletized carbon dioxide, which is metered into an air stream on
demand. This air stream is then directed through a nozzle at high velocity and the solid CO2 particles
impinge on the article to be cleaned. The collision between pellets and the work piece causes the
kinetic energy of the pellets to be rapidly converted to heat which causes the CO2 to sublime.
The cleaning effectiveness of carbon dioxide pellets relative to the substrate being cleaned is
determined by:
33
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1. Composition of substrate [
2. Mass and density of CO2 pellets !
3. Velocity of CO2 pellets
4. Dwell time of CO2 pellets
5. Angle of impact
i
6. Temperature of the surface ',
7. Distance between nozzle and surface to be cleaned.
The proven applications of carbon dioxide cleaning include material preparation, technical cleaning,
paint removal, and decontamination. \
RESULTS
The ranging study conducted on lead paint removal from wood doors revealed some very
important aspects of using the pelletized CO2 process:
1. Personal breathing zone and work area concentrations respectively, were approximately 2
and 4 times the OSHA Permissible Exposure Limit (50 (xg/m3) for lead during removal of
lead-based paint from wooden doors. Work area sample concentrations are higher than
the personal breathing zone concentrations because they represent concentrations
measured closest to the point of generation of the participate (i.e.r the samples were
positioned approximately 2 feet from the workpiece).
i '
2. Cascade Impactors were used to determine the cumulative particle size distribution of lead
and total paniculate aerosol. The jmass median diameter (MMD) of total particulates for
two personal breathing zone and two work area samples are 13.5 and 10.5 microns and 28
and 24 microns, respectively. The MMD of lead for two personal breathing zone and two
work area samples are 13 and 17imicrons and 38 and 41 microns, respectively. Particles
larger than 10 micron equivalent diameter are essentially all removed in the nasal chamber.
3. Samples collected for assessing lead-particulate fall-out in the test room showed
concentrations that ranged from 730 to 1,300 (ig/ft2.
4. Residual surface concentrations of lead using the wet-test method ranged from 330 to
5,000 jig/ft* (average = 3,500 ng/ft2). All but one of these samples exceeded the
Department of Housing and Urban Development (HUD) interim surface guidelines of 200 to
800 |ig/ft2. Residual surface concentrations of lead using the tape-lift method ranged from
84 to 3,800 ng/ft2 (average = 1,320 jig/ft2). Half of these samples were less than the HUD
interim surface guidelines.
34
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5. Baseline concentration of gaseous carbon dioxide in the test room was 1,000 parts per
million (ppm). Measurements made at approximately 15-minute intervals during the carbon
dioxide blasting ranged from 2,000 to 30,900 ppm (n = 11, arithmetic average = 10,700
ppm). By comparison, the OSHA PEL's 10,000 ppm for an 8-hour time weighted average,
30,000 ppm for a 15-minute short-term excursion limit, and 50,000 ppm for an immediately
dangerous level to health.
Sampling and analytical methods used to measure surface cleanliness have been investigated
recently by the Risk Reduction Engineering Laboratory. A dozen sampling methods were investigated
and each technique appeared to have certain advantages. The analytical quantatfoe and qualitative
methods will vary with the type of contamination on the surface. All of the cleaning procedures require
a surface testing method to determine the appropriate cleaning agents and system to produce the
desired result - a "clean" surface. The question becomes "how clean is clean?" This can only be
defined using the proper sampling and analytical methods.
CONCLUSIONS AND RECOMMENDATIONS
Major conclusions on the pelletized carbon dioxide cleaning process are:
1. Selecting proper sequence of methods for each application produces high efficiency.
2. Surface testing is a mandatory requirement for evaluation.
3. Several cleaning methods used together may enhance efficiency.
Pelletized carbon dioxide blasting appears to be a viable technology to remove lead-based paint
from wooden surfaces (e.g., doors). The removal efficiency of the technology can be enhanced by final
cleaning procedures. Environmental control systems can be developed to minimize fugitive paniculate
release and gaseous carbon dioxide. This technology can significantly reduce the quantity and nature
of the waste generated during paint removal and produces no liquid waste. Hence, it offers
outstanding environmental gains regarding hazardous waste minimization.
35
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EVALUATION OF THREE OIL FILTER DESIGNS
FOR POLLUTION PREVENTION EFFECTIVENESS
Lisa M. Brown
U.S. Environmental Protection Agency
26 W. Martin Luther King Dr.
Cincinnati, Ohio 45268
INTRODUCTION
Used oil and discarded oil filters are a major source of
waste in the U.S. Two possible ways of minimizing these wastes
are the use of reusable oil filters and the use of filters that
extend oil life. Reusable filters may reduce waste since they
can be cleaned and reused instead of being discarded. Filters
that reduce the rate at which engine oil deteriorates in quality,
allowing the oil to be used longer between oil changes without
harm to engine life, generate less oil and filter wastes due to
fewer oil changes. >
A oil filter testing program was started in January 1991 as
a part of the California/EPA Waste Reduction Innovative
Technology Evaluation (WRITE) Program. The California/EPA WRITE
program is now in its third year of technically and economically
evaluating waste reduction technologies. The WRITE Program is a
national research demonstration program designed to evaluate the
use of innovative engineering and scientific technologies to
reduce the amount and/or toxicity of wastes generated from the
manufacture, processing, and use of hazardous materials. This
work was done under a Mission of Support Policy Agreement between
the U.S. EPA and the California Department of Toxic Substances
Control.
[
In this testing program, three types of diesel engine bus
oil filters (reusable wire mesh, disposable fiber, and disposable
paper) underwent an engineering and economic evaluation at the
Orange County Transit Association (OCTA) in Garden Grove, CA.
The two major objectives of the testing were (1) to assess the
performance of three different types of oil filters and (2) to
determine if the oil life could be extended. Testing parameters
included efficiency, ease of use, economics, and environmental
impacts, such as the reduction of number of oil filters and/or
the frequency of oil changes.
[
METHODOLOGY '.
This program was designed !to test alternative filters on
twelve OCTA fleet buses with Detroit 6V92T diesel engines. The
twelve test buses selected were identical in manufacturer and age
and were dispatched from the same division. The buses were as
similar as possible in mileage, type of service route, and
previous routine oil analysis results. Three sets of buses were
grouped at random; each set included four buses with identical
primary filters and secondary centrifugal filters. Four buses
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were the baseline test vehicles with regular spin-on pleated
paper primary filters. The second set of four buses were
equipped with a composite synthetic media primary filter. The
third set of buses used a reusable screen for the primary filter.
During the 4-month test period the twelve selected buses
were sampled weekly each Saturday between the dates of May 18
through September 21, 1991. On each bus a special device was
installed that allowed extraction of a sample of the circulating
oil. A brass fitting called a "probalyzer" was installed on the
oil recirculation line downstream from the primary filter. The
fitting had an internal valve that could be opened to access the
flow of oil while the motor was running. The oil samples were
analyzed weekly for a series of physical and chemical properties.
These parameters Were used as a tool to monitor and evaluate the
adequacy of the motor and engine oil. In addition, biweekly
particle counting tests were conducted on the samples in an
attempt to gauge the particle removal efficiencies of the
filters.
Data were analyzed for the following parameter groups:
1. Wear elements - Iron, Chromium, Lead, Copper, Tin, Aluminum,
Nickel, Silver, Manganese, Antimony, Cadmium, Titanium
2. Contaminants - Silicon, Boron, Sodium
3. Additives - Magnesium, Calcium, Barium, Phosphorus, Zinc,
Molybdenum
4. Physical and Chemical Parameters - Flash point, Fuel,
Viscosity, Water content, Percent solids, Glycol, Soot, TEN
5. Particle Counts - >5, >10, >15, >25, and >50 urn
Test parameters can be grouped into those that primarily
reflect the quality of the oil and those that are indicative of
potential engine problems. Viscosity and percent solids indicate
oil quality. Metallic wear elements, water content, glycol
content and contaminants are indicators of potential engine
problems. These parameters were monitored based upon guidelines
provided by the Detroit Engine Company.
RESULTS
Overall, no differences could be observed among the twelve
buses except for wear metals and particle counts <25 urn. Samples
from the buses with synthetic fiber filters had slightly higher
metal concentrations than those with other filters due to one bus
that had consistantly higher concentrations throughout the test.
Samples from these buses also had the lowest concentrations for
particles with diameters <25 urn. These buses were followed by
the buses with reusable filters, then by buses with regular
filters. In addition, all of the buses went beyond the 6,000
miles oil filter change limit currently in place by OCTA. Ten of
the twelve buses operated the full 4-month period without an oil
and filter change. Miles traveled ranged from 14,429 miles to
21,571 miles.
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CONCLUSIONS
Using conventional oil test methods (excluding particle
count analyses) no significant differences were observed in
recirculating oil quality between the reusable and non-reusable
filters. With regard to partiple count, the composite synthetic
media filters maintained significantly lower particle counts for
particles less than 25 urn in sjize than the other two filters.
Considering the pleated paper filter versus the reusable filter,
the reusable filters showed better performance for the particles
<25 urn. The differences in performances between filters
disappeared as particle sizes -Increased.
Oil and filter changes at OCTA are currently performed
approxiamately every 6,000 milies. This program found that the
test buses were able to travel far; beyond this distance without
unacceptable deterioration of oil quality. The type of filter
used appeared to have no significant effect. It appears that bus
engine manufacturer recommendations for oil change intervals are
highly conservative and may be safely increased for fleets that
conduct routine oil quality mohitoring like OCTA.
Oil filter changes not including the cost of oil are
estimated to cost $30 each for the pleated paper filter and $40
each for the composite synthetic media filter. Since the
reusable filter is not replaced at each oil change, it is
necessary to amortize its $364'installed cost over an estimated
10 year life. Adding labor and expendable parts cost (e.g. .
gaskets) the estimated cost of cleaning the reusable filter is
slightly lower at $27.50 per cleaning, based upon 8 cleanings per
year. Fewer cleanings result in a higher cost per cleaning due
to constant amortization cost. Basically, there is no
significant difference in the comparative cost of using the three
filters tested. However, the use of the reusable reduces the
disposal of 8 filters per year per bus. For a fleet of 450 buses
(OCTA), this is 100 drums of oil filter waste per year.
If the interval between oil changes were increased from
6,000 to 18,000 miles, the annual cost savings would be
approximately $350 per bus per year and annual oil disposal would
be 170 gal per bus per year less based on 48,000 miles driven per
year. For OCTA this would be a savings of $157,000 per year and
decreased oil disposal of 1390 drums per year.
As stated previously, synthetic filters did a better job of
filtering out particles <25 microns in the oil. The reduction of
these particle counts may be helpful in extending the engine's
life. However, research is needed to quantify the relationship
between engine oil particle counts and engine life between
overhauls. If reduced particle counts should have a significant
effect in increasing engine life, the potential economic benefits
are large.
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THE WASTE REDUCTION EVALUATIONS AT FEDERAL SITES PROGRAM
James S. Bridges
Risk Reduction Engineering Laboratory
26 W. Martin Luther King Drive
Cincinnati, Ohio 45268
INTRODUCTION
The Waste Reduction Evaluations At Federal Sites (WREAFS) Program is a cooperative research,
development and demonstration (RD&D) program between the US Environmental Protection Agency and
the Federal community at large. The three primary objectives of the WREAFS Program are to : 1)
conduct waste minimization assessments and case studies; 2) conduct pollution prevention research
and demonstration projects jointly with other Federal activities; and 3) provide technology and
information transfer of pollution prevention results. Since the initiation of the WREAFS Program in 1988
within the Risk Reduction Engineering Laboratory's Pollution Prevention Research Branch, the Federal
community has initiated constructive action and demonstrated awareness of the significance of pollution
prevention in the production and consumption of goods and services for the Federal government
nationwide and abroad. This abstract provides a summary of the current cooperative RD&D projects
within the Federal community under the aegis of the WREAFS Program.
WASTE MINIMIZATION ASSESSMENTS
The waste minimization assessments are conducted by an assessment team that is composed
of personnel from EPA, personnel from the cooperating Federal facility, and others who can provide
technology and processing expertise. The assessments follow the procedures described in the EPA
report, Waste Minimization Opportunity Assessment Manual. (EPA/625/7-88/003) which is available from
the Center for Environmental Research Information (CERI), Publications Unit, 26 West M. L. King Dr.,
Cincinnati, Ohio, 45268. This Manual provides a systematic procedure for identifying ways to reduce or
eliminate waste generation. The conduct of a waste minimization assessment results in the waste
generating activity identifying solutions and RD&D needs. The active participation as part of the waste
minimization assessment team also provides on-site training for Federal personnel, encouraging
continued use of the EPA Manual at other waste generating activities within a Federal Department. This
hands-on experience is one reason for targeting at least one joint waste minimization assessment
between EPA and each of the fourteen Federal Departments. Results from completed waste
minimization assessments are documented with a report and project summary for technology transfer to
both the public and private sectors.
Completed waste minimization assessments available through CERI include:
EPA/600/S2-90/046
Waste Minimization Opportunity Assessment:
Philadelphia Naval Shipyard
EPA/600/S2-90/031
Waste Minimization Opportunity Assessment: Fort Riley,
Kansas
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EPA/600/S2-90/062
EPA/600/S2-91/030
EPA/600/S2-91/024
EPA/600/S2-91/031
EPA/600/S2-91/054
EPA/910/9-91-017
EPA/910/9-91-018
Waste Minimization Opportunity Assessment: US Coast
Guard Support Center, Governors Island, New York
'Waste Minimization Opportunity Assessment: Naval
Undersea Warfare Engineering Station, Keyport,
Washington
Hospital Pollution Prevention Case Study
Waste Minimization Opportunity Assessment: Optical
Fabrication Laboratory, Fitzsimmons Army Medical
Center, Denver, Colorado
| Waste Minimization Opportunity Assessment: Scott Air
Force Base
Waste Minimization Opportunity Assessment: US Coast
iGuard Base Ketchikan, Alaska and
Waste Minimization Implementation Plan: US Coast
Guard Base Ketchikan, Alaska are results of a joint
project between EPA's Region 10 Federal Facilities
Program and RREL
Other planned and ongoing waste minimization assessments to be completed in FY 92 include
joint assessments with the Department of Interior's Bureau of Mines, the US Army's facility in Ft. Carson,
Colorado, the Department of Agriculture's Research Service in Beltsville, Maryland, the Department of
Treasury's Bureau of Engraving and Printing and the US Department of Energy's Sandia National
Laboratories. ;
The Tidewater Interagency Pollution Prevention Program (TIPPP) is a cooperative effort among
EPA, DOD, and NASA to take advantage of the (capabilities of well-defined communities to develop a
pilot program, establishing an integrated multi-media pollution prevention plan that includes both short-
and long- term projects with results that will be transferable to other Federal and public communities.
Through a number of WREAFS sponsored pollution prevention assessments at selected operations at
each of the host facilities, pollution prevention recommendations will be considered for implementation
or further demonstration. The host facilities are located at Ft. Eustis, Langley AFB, Langley NASA, and
Navy Base Norfolk. WREAFS is also developing a series of Pollution Prevention Fact Sheets on
processes, products, and various activities prevalent at TIPPP installations to assist with more generic
short-term issues. It is anticipated that TIPPP facility managers will utilize the P2 information to reduce
the generation of wastes from selected processes and each alternative will be documented and
transferred throughout the Federal community. At the end of FY 92 RREL support to TIPPP should
Include up to thirty waste minimization assessments and fifteen P2 Fact Sheets. Due to the importance
and widespread transferability of the results from RREL support to the TIPPP, the majority of WREAFS
resources have been allocated for the TIPPP projects.
i
RESEARCH, DEVELOPMENT, AND DEMONSTRATION
A number of RD&D needs have arisen from the conduct of waste minimization assessments
since there are not optimum solutions available for every waste generating problem. When a solution is
not technically sound or does not exist, or solutions are not economically feasible, the stage is set for
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RD&D. The WREAFS Program has concentrated on waste minimization assessments during the first
three years and with the successful completion of these assessments and case studies, it is felt the
WREAFS Program will target RD&D within the Federal community for the next several years. The
Pollution Prevention Research Branch has conducted RD&D activities within the Federal community over
the past three years such as: the evaluation of emulsion cleaners at US Air Force Plant No. 6; waste
reduction from chlorinated and petroleum-based degreasing operation with Auburn University for Tyndall
AFB; the evaluation of a wet to dry Navy spray paint booth; reclaiming fiber from newsprint with USDA;
and investigating and developing wood/plastic composites with USDA's Forests Product Laboratory.
RD&D projects planned and on-going for FY 92, in addition to what will result from the TIPPP,
include support to the Air Force and Navy. The WREAFS Program is planning technical support to the
Naval Civil Engineering Laboratory (NCEL) for a joint project with a FY 92 start regarding industrial
wastewater treatment plants (IWTP). This in-house study calls for a feasibility analysis to determine
future needs which consider pollution prevention solutions to current and future pollution generating
issues as well as emerging waste management technologies. The initial meeting for this technical
support project is for RREL to host a workshop on January 29, 30, and 31.
Tinker AFB and RREL are working on a joint RD&D project designed to evaluate five major
chemical waste generators as the overhaul/repair processes associated with CFC's, electroplating,
component cleaning, painting/de-painting, and vapor degreasing. The objective of this project is to
identify and assess alternative processes that will enable the Oklahoma City - Air Logistics Center to
minimize waste generation while meeting overall mission objectives. By the end of FY 92, completed
activities will include baseline data gathering, alternative identification and characterization, alternative
assessment, and selection of alternatives.
The objective of another Tinker AFB - RREL joint RD&D project is to minimize the amount of
hazardous chemicals used in plating by implementing electrochemical metallizing (EM). Using
computerized numerical control, serni-automatic, or fixed station systems for EM plating of parts which
are currently bath plated, EM plating will reduce chemical usage thus reducing the amount of hazardous
wastes being generated in the repair and overhaul of gas turbine engines. This project includes seeking
an acceptable substitute for chrome plating, providing a demonstration line for semi-automatic EM nickel
plating, performing cost comparisons between tank plating and EM, and assessing the quality of the
parts being plated. The impact of EM plating could be substantial for reducing chemical requirements.
TECHNOLOGY TRANSFER
Technology transfer continues to result from project reports and project summaries of
completed WREAFS projects. As noted earlier, the waste minimization assessments provide an
opportunity for training and change in culture to thinking pollution prevention rather than end-of-pipe
control. It is important for the Federal community to be leaders in pollution prevention and to provide
examples to others in the private and public sectors. A number of pollution prevention
workshops/conferences or parts of environmental conferences which include pollution prevention have
participants from the Federal community. This technology transfer allows for an integrated approach to
the problems of waste generation in the United States. Stepping down from the aloofness of sovereign
immunity, the Federal government and business are working together toward pollution prevention
solutions. The WREAFS Program is providing the forum and technical foundation for the
encouragement of pollution prevention research in the Federal community. Using lessons learned RD&D
for pollution prevention answers throughout the Federal community, joining RD&D resources to find
solutions to common waste generating problems, and working together to bring about the cultural
change in thinking pollution prevention are the goals of the WREAFS technology transfer efforts.
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Federal scientists and engineers are invited to share RREL facilities and interact with RREL
scientists and engineers in promoting a research cooperative for Federal facilities. It is the vision of
RREL that scientists and engineers from other Federal Agencies would be assigned to RREL for a
specified period to work on a pollution prevention research project of that Agency or assist RREL with
pollution prevention research projects that will be applicable to all Federal facilities. The contacts, joint
RD&D, and training will benefit both EPA and the other Agencies. Participation in this "cooperative" is
strictly voluntary. ;
WREAFS PROGRAM SUMMARY
The WREAFS Program takes on many facets in its endeavor to support the Federal community
with pollution prevention research. There has been a number of RD&D products that have been
completed and a number of on-going efforts, but perhaps the most important impact will come from any
resulting cultural change brought about by conducting a waste minimization assessment or reading a
RD&D report. The Federal facilities "cooperative" is one idea that should be a big benefit for the Federal
community and pollution prevention once support is provided. It is necessary for all of the fourteen
Departments to take an active role in pollution prevention and be an example to the rest of the world.
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MEASURING POLLUTION PREVENTION
David G. Stephan
and
James S. Bridges
Risk Reduction Engineering Laboratory
Cincinnati, Ohio 45268
(513)569-7896
INTRODUCTION
To assess progress in pollution prevention, estimates or measurements of the amounts of
pollution actually prevented have to be made. Such estimates or measurements tell us how far we have
come and, possibly, how much farther there is to go in utilizing pollution prevention as a tool for
improving environmental quality. They can, theoretically, be used to assess progress on a scale ranging
from the individual facility or even the individual process or activity generating wastes to a scale as large
as a geographical area such as a county, a state or even the United States as a whole.
INDUSTRIAL SOURCES .
A major step in being able to assess pollution prevention progress by industry was the provision
in the recent Pollution Prevention Act requiring the addition of a "toxic chemical source reduction and
recycling report" to the annual Toxics Reduction Inventory (TRI). This report, beginning in 1992, will
attempt to quantify the pollution prevention progress actually occurring with respect to certain toxic
chemicals used by industry. Progress will be assessed through the tabulation of such information as the
quantities of the chemicals entering wastes or otherwise released to the environment, the amounts
recycled at the facility or elsewhere, etc.
Roughly a year ago, an early version of this source reduction and recycling report was evaluated
"in the field" by Battelle Columbus Operations under a Pollution Prevention Research Branch support
contract (1). The draft report form was distributed to nine companies which had volunteered their
services to "test" it. The companies were provided with the form and its instructions and asked to
complete the form and then to meet with Battelle evaluators. By interviewing the companies, the
evaluators tried to ascertain 1) the clarity/understandability of the form and its instructions, 2) the ease or
difficulty of responding to the questions, 3) the reliability and meaningfulness of the data reported, 4) any
concerns over confidentiality of the data requested and 5) the overall "burden" of responding and to
obtain suggestions for improvement:
In addition, the draft report form was sent to several industrial trade associations and public
interest environmental groups for their reactions.
As might be expected, the field test participants and the trade associations had very similar
comments but the environmental groups commented from a different perspective. All commenters
agreed that the purpose of the forms should be to collect the data needed to describe pollution
prevention progress, to encourage pollution prevention, to express progress to the public and to identify
opportunities for further pollution prevention. Commenters also agreed that the definition of terms
needed to be clarified, especially terms such as open-loop and closed-loop recycling.
On the other hand, industry and public interest groups differed on how closely the TRI and RCRA
reporting processes should be connected. Environmental groups wanted to see a close tie between
these reports while industry reviewers felt that even the qualitative connection proposed in the form would
be difficult to implement. There was also considerable variance in views as to the level of detail available
or appropriate for reporting. Industry commenters expressed concern that the report would not always
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f
capture a true picture of their pollution prevention activities. They also felt that requirements to report
expected progress might be converted into auditable goals. A major issue involved the "starting point" to
be used as a baseline for assessing progress. It was felt that firms that had already aggressively
implemented pollution prevention would suffer in comparison with firms that had done nothing to date
and still had "the low-hanging fruit to pick." Another item that elicited much comment related to the so-
called Production Ratio or Activity Index aimed at normalizing data from year to year based on the level of
production or activity taking place at a facility. Itjwas urged that flexibility be allowed in choosing the most
appropriate Index for each chemical being reported.
With the passage of the Pollution Prevention Act, a mandated set of source reduction and
recycling questions will be added to the TRI beginning in 1992. These questions and the instructions
related to them have benefitted from the results pf this field test and from considerable other input from a
wide variety of industrial, public interest and other groups over the last year or so.
AGRICULTURAL SOURCES
Battelle was also asked to develop a methodology for measuring pollution prevention progress in
the agricultural sector (2). Focus was placed on: three types of agricultural pollution: fertilizers, pesticides
and concentrated animal wastes. With regard to fertilizers and pesticides, it was felt that application rates
could serve as simple surrogates for "wastes generated" and that, generally speaking, reductions in
amounts applied from one year to another would approximate pollution prevented. It was recognized,
however, that many factors other than the introduction of pollution prevention techniques affect amounts
applied. For fertilizers, amounts are impacted, for example, by type of crop, crop rotations, weather and
market factors. For pesticides, one must also consider, for example, cyclical infestations and pesticide
fo'rmulations available. The pesticide situation is, of course, considerably more complicated because of
the many, many different types and potencies of [pesticides whereas fertilizer pollution is essentially limited
to the three major nutrients, potassium, phosphqrus and nitrogen. Because of the normal year-to-year
variations, it was felt that data on application rates would have value only to detect trends over extended
periods such as 5 or 10 years. '
With respect to animal wastes, the possibilities for accomplishing true "source reduction" are
quite limited. The primary methodology examined from the standpoint of how to assess pollution
prevention progress was the use of growth hormones to increase the amount of product (meat, milk,
eggs) per unit of manure excreted.
In all cases, Battelle's proposal was to survey a representative sample of farmers to determine the
rates at which various pollution prevention techniques were being applied. From this information along
with data on how much pollution is prevented by: each technique, an estimate of overall pollution
prevented could be made.
Battelle's findings in the agricultural area, while not providing any specific methodology ready for
field testing, should help in providing a basis for 1) refining and expanding the list of pollution prevention
practices applicable to agricultural activities, 2) measuring reduced fertilizer or pesticide use rates under
different circumstances and 3) estimating the adoption rate for various agricultural pollution prevention
practices.
PROGRESS RESULTING FROM PRODUCT DESIGN DECISIONS
A third task assigned to Battelle (3) was to develop a methodology for measuring pollution prevention
progress occurring as a result of actions or decisions taken during the design stage of a product. This is
important since the TRI will collect information only on pollution prevented during the manufacturing
stage. Yet, through astute product design decisions, much pollution can and will be prevented during
other stages of the product's life than the manufacturing stage; most importantly, perhaps, pollution
prevention as a result of product design will primarily occur during product use and at the time the
product's useful life ends and the product, itself, becomes a waste.
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Since a designer is able to influence the raw materials used, the production process employed,
the way in which the product is used, its life, its "repairability," its recyclability and even the mode of its
eventual disposal, product design decisions which beneficially influence any of the above potential
environmental impacts should be acknowledged. This effort is an attempt to define how this might be
done.
REFERENCES
1. Otfenbuttel, R. F. and Smith, L. A. Source Reduction Measurement Methodology for Consumer
Products. Unpublished final report (Task 1, WA 0-12, Contract No. 68-CO-0003, Battelle
Columbus Operations), Risk Reduction Engineering Laboratory, U.S. Environmental Protection
Agency, Cincinnati, Ohio, 1991.
2. Concepts for Measuring Pollution Prevention Progress in United States Agriculture. Unpublished
final report (Task 2, WA 0-12, Contract No. 68-CO-0003, Battelle Columbus Operations), Risk
Reduction Engineering Laboratory, U.S. Environmental Protection Agency, Cincinnati, Ohio, 1991.
3. Source Reduction Measurement Methodology for Consumer Products. Unpublished final report
(Task 3, WA 0-12, Contract No. 68-CO-0003, Battelle Columbus Operations), Risk Reduction
Engineering Laboratory, U.S. Environmental Protection Agency, Cincinnati, Ohio, 1991.
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TWO POLLUTION PREVENTION TECHNOLOGY EVALUATIONS
FOR THE PRINTED blRCUIT BOARD INDUSTRY
Teresa M. Harten
U.S. Environmental Protection Agency
26 W M L King Drive
Cincinnati, Ohio 45268
(513) 569-7565
INTRODUCTION
The Minnesota/EPA Waste Reduction Innovative Technology Evaluation (WRITE) Program is
one of seven programs nationwide in which EPA and cooperating states or local governments
evaluate and demonstrate the engineering and ^conomic feasibility of selected waste reducing
technologies in a manufacturing or fully operational setting. The program in Minnesota, which began
in mid 1989, targets the metal finishing industry; specifically rinsing operations within metal finishing
operations, as the focus of the evaluations. The 5 technology evaluation projects planned for the full
life of the Minnesota/EPA Program and subsequent technology transfer activities are intended to
speed the early introduction of cleaner, pollution preventing technologies in the metal finishing
Industry. This extended abstract presents final results from the first project and preliminary results
from the second project conducted under the Program.
PROJECT 1
PROCEDURE :
Micom, Incorporated is a medium-sized job shop circuit board manufacturer employing
approximately 240 people at its plant in New Brighton, Minnesota. Under a number of military and
commercial contracts the company produces an average of 1000-1200 square feet of double sided
multilayered panels per day. In 1989, annual revenue was $17 million.
The evaluation took place at the sensitize, line where a number of process baths including
etchant ("micro-etch"), activator, accelerator, electroless copper and rinse tanks, first etch and then
chemically deposit copper onto the insides of the circuit board holes. Drag out from two of the line's
process baths, the micro-etch and the electroless copper baths, was a significant source of waste
copper discharged in the rinse water waste stream leaving the line. This rinse water had to be treated
by an on-site ion exchange unit for copper removal before it could be discharged to public sewer.
Baseline samples and measurements were taken over a two week period to determine the
initial drag out rate in milliliters per square foot of board plated. Enough sample sets were taken to
calculate 12 values for the drag out which were then averaged.
For the first modification, the hoist system was slowed from the baseline withdrawal rate of 100
ft/min for the micro-etch line and 94 ft/min for the electroless copper line to 11 ft/min for the micro-
etch line and 12 ft/min for the electroless copper line. Samples were taken and measurements made
to determine the drag out after modification 1 was put in place. Again, the number of sample sets
enabled 12 drag out values to be calculated.
For the second modification, the withdrawal rate was set at an intermediate rate between
baseline and modification 1, and the drain time over the bath was increased. Withdrawal rates were
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40 ft/min for both micro-etch and electroless baths, and drain time was increased from a baseline of
3.4 seconds to 12.1 seconds for the micro-etch line and for the electroless line from 5.2 seconds to
11.9 seconds. Samples were taken to provide 12 calculated values for drag out.
RESULTS
Both modifications reduced drag out significantly. Baseline drag out from the micro-etch bath,
12.1 ml/tf , was reduced to 6.7 ml/fl2 or 45% by modification 1, and the electroless copper bath drag
out was reduced from 6.0 ml/ft2 at baseline to 3.0 ml/ft2 after modification 1, for a reduction of 50%.
After modification 2, the micro-etch drag out was 7.1 ml/fl2, a reduction of 41% from baseline, and for
the electroless bath, drag out was 2.9 ml/fl2, a reduction of 52%.
By reducing drag out in these amounts, 203 and 189 grams of copper per day were prevented
from being discharged as waste in the rinse water waste stream, for modifications 1 and 2
respectively. Because copper concentration in rinse water was reduced, the potential for conserving
rinse water flows was also shown, although this was not directly tested. Rinse water flows could be
turned down proportionate to the reduction in drag out and still maintain the same rinsing efficiencies.
The economic savings due to these reductions were calculated by taking into consideration
avoided cost of treatment of the rinse water and avoided charges for water and sewer service. If
implemented, the first modification would save the company $3350 - $2640 savings in treatment costs
and $710 in avoided water and sewer costs. The same figures for implementing the second
modification would be $3120 - $2460 in treatment costs and $660 in avoided water and sewer
charges. Since no capital costs were incurred in making the changes, payback would be immediate.
CONCLUSION
In the first project, the waste reducing capabilities of two simple rinsing modifications were
demonstrated at a Minneapolis area printed circuit board manufacturer. The no cost, low technology
changes made were 1) slowing the withdrawal rate of racks containing the printed circuit boards as
they were pulled from an etchant process tank and an electroless copper process tank and
2) combining an intermediate withdrawal rate with a longer drain time over the process tanks. Both
modifications significantly reduced drag out of concentrated copper containing bath solutions into the
rinse water systems.
PROJECT 2
PROCEDURE
The second project took place at a flexible circuits manufacturer which employed
approximately 1800 and had annual sales of $92 million in 1989. Two technologies were tested for
their ability to reduce waste: 1) soft absorbent polyvinyl alcohol (PVA) rollers replacing hard rubber
squeegees to reduce drag out in a horizontal cleaning operation and 2) adding a conductivity
activated flow controller to reduce rinse water in a tin lead plating line. The company had identified
the cleaning operation and the tin lead line as its largest waste generators and the areas it believed
offered the largest potential for waste reduction. Waste streams from both lines were treated on site
by lime precipitation, sludge pressing and drying and off site sludge disposal as hazardous waste.
Treated waste water was discharged to sewer.
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Initial testing was conducted in May, 1991. While testing was completed for the conductivity
flow controller evaluation at that time, the company continues to monitor the cleaning line to
determine sponge roller effects on cleaning ba^h life.
The PVA "sponge" type rollers were tested for drag out reduction at an acid cleaning tank
which was part of a larger cleaning operation that removed oil, grease, and chromate conversion
coating from flexible copper sheets in preparation for the application of photoresist. In testing the
sponge rollers, baseline samples taken over a two hour period included enough sample sets to
provide 10 drag out values. During baseline testing the line was operated using the hard rubber
squeegees that come as standard equipment with the cleaning units. Next, for the evaluation phase,
the squeegees were removed and replaced with PVA sponge rollers. Sampling again was performed
over a two hour period to provide 10 sets of samples for drag out calculation. Samples were
analyzed for copper concentration as an indicator of drag out. In both baseline and evaluation
sampling, flexible circuit throughput was also tracked to enable a drag out per square foot calculation.
In the second evaluation at the flexible circuits manufacturer, a conductivity sensor and flow
controller were installed at a tin lead plating line to reduce rinse water flow from the triple
countercurrent rinse system. Before installation of the flow controller, baseline flow was measured
using a totalizing flow meter at the influent line to the rinse system. Flows were recorded every 8
hours for a one week period; conductivity was &lso recorded over this period to help establish a set
point for the conductivity flow controller. :
After baseline sampling, a conductivity sfensor was installed in the final rinse tank and
connected to a controller. The controller was set to activate a valve at the rinse water influent line
when the sensor reached the set point of 30 mS. When conductivity reached this level in rinse water,the
valve opened and allowed rinse water to flow to the rinse tanks. The 30mS level was chosen as the
approximate median level of the conductivity readings found during baseline testing. The company
believed this to be a conservative estimate for the contamination that could be tolerated by the
system and still maintain effective rinsing. Again during evaluation, flow was recorded every 8 hours
over a one week operating period. During baseline and evaluation monitoring, throughput of flexible
boards was also tracked.
RESULTS
Testing of the sponge rollers for drag out reduction at the cleaning line showed the sponge
rollers to be successful in reducing drag out. Baseline testing of the hard rubber rollers determined
that drag out was originally occurring at the rate of 27.6 ml/fr. After installation of the sponge rollers
drag out was reduced to 9.8 ml/ft2, a 64% reduction from baseline. Rinse water could be
proportionately reduced without compromising rinsing efficiency.
f
While drag out, as measured by copper concentration in the bath and rinse tank following it,
was reduced, the increased rate of copper build-up in the cleaning bath tank suggested that the tank
would have to be replaced more frequently since the company used bath copper concentration as a
measure of bath contamination and as an indicator for bath replacement. At present, the company is
conducting a longer term study to determine the impact of the rollers on bath life. This information is
critical to drawing a comparison between waste generated using hard rubber versus sponge
squeegees. The economic evaluation will also have to await this information before the two can be
compared.
48
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For the other evaluation conducted at the flexible circuits manufacturer, baseline testing of the
rinse flows to the tin lead line showed that 1.41 gallons/fl? of rinse water were used in the triple
countercurrent rinse system before installation of the flow controller. After the conductivity sensor and
flow controller were installed rinse water flow was reduced to 0.64 gallons/fl2, a reduction of 55%.
The economic analysis showed that this reduction in rinse water would save $132/yr in avoided
water and sewer utility charges and $877/yr in avoided rinse water treatment costs. The total savings
per year of $877 divided into the $500 installed cost of the flow controller/sensor combined with its
$50/yr operating cost, results in a payback of 7.5 months.
CONCLUSION ,
The evaluation of the flow controller at the flexible circuits manufacturer clearly showed that
waste could be reduced and savings achieved when used on a tin lead line rinse system. The results
are not yet available for the sponge rollers installed at a cleaning line; although it reduced drag out
significantly, the increased build up of copper in the cleaning bath required more frequent bath
replacement. The company continues to monitor the change in bath life to provide a more complete
picture of waste generated and associated costs before and after the change to sponge rollers.
49
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EVALUATION OF EMULSION CLEANERS
AT AIR FORCE PLANT NUMBER 6
Johnny Springer, Jr.
Waste Minimization, Destruction
and Disposal Research Division
Risk Reduction Engineering Laboratory
Cincinnati, Ohio 45268
(513) 569-7542
Gary Baker
Science Applications International Corporation
635 West 7th Street, Suite 403
Cincinnati, Ohio 45203
(513)723-2611
INTRODUCTION
The eva'uation of emulsion cleaners at Air Force Plant 6 project is an offshoot of the Waste
Reduction Evaluation at Federal Sites (WREAFS)S Program conducted within the Pollution Prevention
Research Branch. The WREAFS program consists of a series of demonstration and evaluation projects
for waste reduction conducted cooperatively by the U.S. Environmental Protection Agency (EPA) and
various divisions of other federal agencies. The purpose of this project is to provide assistance to Air
Force Plant 6 personnel by documenting the relevant work by other aircraft fabrication facilities to
support comparison of cleaner qualification performance with trichloroethylene for the vapor degreaser
operations at Air Force Plant 6.
METHODOLOGY
Air Force Plant No. 6, located in Marietta, Georgia, is operated for the Air Force by Lockheed
Aeronautical Systems Company. The facility is part of the Aeronautical Systems Division (ASD), whose
headquarters is located at Wright-Patterson Air Force Base near Dayton, Ohio. There are six vapor
degreaser units that utilize trichloroethylene (TCE) to prepare steel and aluminum parts for a variety of
subsequent manufacturing steps in the production of C-130 aircraft.
Although the usage of trichloroethylene has decreased from 1.2 million pounds in 1988 to about
650,000 pounds in 1990, the decrease has been largely due to a diminishing workload at the plant.
Lockheed Environmental Department and Materials and Processes Department staffs are interested in
substitution of the current solvent with appropriate cleaners due to concerns about worker safety and
health in addition to the environmental impacts of the current solvent. The eventual goal of the facility is
to substitute water-soluble emulsion cleaners to pbviate use of 650,000 pounds of TCE.
During the initial phases of this project, it was decided to investigate research conducted by other
aircraft manufacturing entities prior to conducting full scale testing of a targeted list of cleaners. As a
result of canvassing various businesses within the aircraft manufacturing industry, it was determined that
a substantial amount of research was currently being conducted. The facilities conducting research
were cooperative in sharing information and as a result, it was decided to document research currently
befng conducted and submit a report to Lockheed to use as a starting point for determining where to
begin their research.
50
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The information for this report was developed by documenting research performed by Boeing
Aircraft, Air Force Engineering Service Center (AFESC), General Dynamics, Lockheed Missile and Space
Company (LMSC), Martin Marietta and Northrop. This research information was particularly useful since
Lockheed qualification criteria are based on Air Force (military specifications), Lockheed and Boeing
tests. Lockheed currently conducts significant subcontractor work for Boeing. Also, data and
information for the report was accumulated from emulsion cleaner manufacturers/suppliers and an
international workshop on solvent substitution.
Boeing Aircraft -
Boeing Aircraft Corporation has been investigating the replacement of solvent and vapor degreasing
processes for the past three years. Specifically, Boeing has ongoing research efforts with requirements
similar to Air Force Plant 6 at three locations. Boeing is evaluating cleaners at its Wichita, Puget Sound,
and Kent Space Center facilities in actual shop trials. Shop trials are pilot programs designed to
evaluate the performance of a given solvent during actual production. The Puget Sound plant
manufactures commercial aircraft; the other two facilities are strictly involved in military aircraft
production. The Boeing site that offers data most relevant to the Plant 6 program is located at the Kent
Space Center.
Air Force Engineering Service Center (AFESC)
AFESC has been active in solvent substitution over the past several years. One of their projects is
substitution of cleaners with biodegradable solvents. This project was conducted in three phases.
During Phase I, nearly 200 companies were contacted and 185 different solvents were obtained for
testing. These tests looked at biodegradability, ability to dissolve soils, cleaning efficiency, and
corrosiveness (if able to pass the other three). From these tests, the most promising were identified for
further testing in Phase II.
During Phase II testing, solvents were subjected to extensive performance testing at the field test
facility at Tinker AFB, Oklahoma. AFESC evaluated enhancement methods (ultrasonic and mixer
agitation at various temperatures) on a revised list of solvents which originated in Phase I. Phase III
tests evaluated solvents during implementation. The cleaners evaluated in Phase III were the same
cleaners evaluated in Phase II.
The U.S. DoE is sponsoring continuation work. They are working on a related project which will
study solvents and their ability to clean approximately 20 different "soils" (this term is Used to refer to any
processing contaminant that must be removed from a part surface). These tests will focus on
performance and corrosion rather than biodegradability. Once the most promising cleaners are
identified, additional tests will be performed for recyclability and VOC emissions. It is hoped that the
information from the earlier report can complement this report in order to form a comprehensive
database on solvents.
General Dynamics
Of the research efforts investigated for this study, General Dynamics is the most comprehensive
program. The program is being conducted at the Fort Worth Division and is currently in shop trial. The
program initially evaluated 40 cleaners and screened to five cleaners. One of the five cleaners was
eliminated due to corrosion test concerns. The four remaining candidate cleaners were optimized with
General Dynamics' input. One product is compatible with the solvent regeneration process in use at
General Dynamics and is currently being used in the shop trial program.
51
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Lockheed Missile and Space Company (LMSC)j
LMSC staff have been involved in evaluating non-hazardous cleaners since August 1989. Their goal
has been to find suitable replacements for l.l.t-trichloroethane (TCA) used in vapor degreasers. The
LMSC program seeks to replace all TCA used in a variety of processes throughout their facility.
Cleaning performance, compared with TCA, as well as the etching and corrosion effects on magnesium
and aluminum surfaces were evaluated. |
Martin Marietta
Martin Marietta staff in Denver have completed an aggressive solvent substitution program that
sought to replace TCA. Numerous tests were performed on cleaners to clean aluminum soiled with fish
oil, mineral oil, glycerine, machining oil, layout Clye, and aluminum mill stamps.
Northrop
Northrop used a different strategy for evaluating cleaners: they simply told the manufacturers to send
them their best formula with instructions for use and the product would either pass or fail. No
experimentation or cleaning optimization was attempted.
RESULTS
The final report has been compiled for this project. The report contains information on the
evaluation of various substitute cleaners on the conformance of the emulsion cleaners to be
Implemented at Air Force Plant No. 6 with specific qualification test criteria. The document contains the
specifications for qualification tests in 17 areas. The 17 test areas are:
pH
Corrosh/eness
Cleaning
Corrosion between
faying surfaces
Foaming
Effect on Cd plated
surfaces
Effect on Adhesion
Water break-free
Visual
Etching
Sandwich corrosion
Intergranular Attack
Corrosion Resistance
Paint Adhesion
Sulfur
Phosphates
Chromates
It also contains a list of ten cleaners that were targeted for evaluation. Table 1 presents a summary of
the cleaners evaluated by the various organizations in the determination of a substitute for halogenated
solvents. This table provides information on what cleaner(s) were tested. It also provides the reason
why a cleaner was disqualified from further testing and which cleaners are currently being investigated in
pilot tests. Although in most cases the companies conducting the research sought to replace TCA, the
industrial processes are analogous to those conducted at Air Force Plant 6.
52
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TABLE 1. SUMMARY OF CLEANER SUBSTITUTES EVALUATED BY VARIOUS ORGANIZATIONS
* Grace Duraclean 282
* Turco 6778
* Turco 4215 NCLT
• Turco 3878
* Blue Gold
* Brulin 815 GD
* Hurri-Klean
* Quaker 624 GD
* Polychem 2000
* Novamex
* Rochester-Midland
(Biogenic SE373
Bioact EC7
Simple Green
Coors Bio T
Oakite Inproclean 2500
3D Supreme
RB Degreaser
Boeing
b
b
b
d
d
AFESC
d
d
d
d
d
a
General
Dynamics
a
b
b
b
a
LMSC
b
b
aO)
a
a(4)
Martin
Marietta
c
a
a
a(2)
a
a(2)
Northrop
a(3)
b
b
* Lockheed Air Force Plant 6 target cleaners
a - Evaluated
b - Selected for implementation or further evaluation
c - Implemented
d - To be evaluated
Eliminated due to:
(1) Phosphates
(2) Flammability concerns
(3) Not easily recyclable
(4) Unacceptable etching of magnesium substrate
The document concludes with a chart that compares the performance criteria of the various companies
to the criteria required by Lockheed.
53
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CONCLUSIONS
EPA is continuing to work in cooperation with Lockheed Aeronautical Systems Company-
Georgia and Air Force Aeronautical Systems Division to investigate the potential for implementing
emulsion cleaners as a replacement for trichloroethylene (TCE). The substitution of emulsion cleaners
for TCE Is currently being implemented at Air Force Plant No. 6. Lockheed has selected cleaner Brulin
815 GD from this report for pilot testing. As a follow-up to successful pilot testing, further testing is
planned in 800 gallon and 3400 gallon tanks respectively. Lockheed is providing funding for the pilot
testing.
It Is anticipated that this substitution will function as a degreasing solvent as well as an alkaline
cleaner. It will reduce tankage and eliminate or reduce substantially the use of chlorinated solvents at
Air Force Plant 6. EPA will be cooperating with Lockheed and Air Force personnel to document the
successes, problems and costs associated with the change. The results can then be transferred to
similar facilities in the Department of Defense or the Department of Energy, and can serve to expedite
the use of emulsion cleaners at other facilities.
54
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EVALUATION OF FILTRATION AND DISTILLATION
METHODS FOR RECYCLING AUTOMOTIVE COOLANT
Paul M. Randall
U.S. Environmental Protection Agency
Pollution Prevention Research Branch
Cincinnati, Ohio 45268
and
Arun R. Gavaskar
Battelle
Columbus, Ohio 43201
INTRODUCTION
Government regulations and high waste disposal cost of spent automotive coolant have driven
the vehicle maintenance industry to explore on-site recycling. The USEPA in cooperation with the New
Jersey Department of Environmental Protection (NJDEP) and the New Jersey Department of
Transportation (NJDOT) evaluated two commercially available technologies that have potential for
reducing the volume of spent automotive coolant. The objective of this study was to evaluate the
quality of the recycled coolant, the pollution prevention potential, and the economic feasibility of the
technologies.
METHODOLOGY
Engine coolants are intended to provide protection against boiling, freezing, and corrosion.
Through use, the coolants lose some measure of these functions because of accumulation of
contaminants and the depletion of additives such as corrosion inhibitors and anti-foam agents. The
recycling process attempts to restore the functions of the coolants to standards specified in ASTM D
3306-89 and SAE J1034 (for automotive coolants) and ASTM D 4985 and SAE J1941 (for heavy-duty
coolants).
The first technology involved chemical filtration to recycle spent coolant and was manufactured
by FPPF Chemical Co. This technology consisted of two separate units; a fleet size unit that operates
on up to 100 gal of stored spent coolant and a smaller portable unit that operates on a per vehicle
basis and does not require prior collection and storage. The process for both units is similar. The
stored spent coolant is drawn into a 100 gal plastic holding tank from which it is circulated through
filters, aerated to form oxides of dissolved metals, and refiltered. The coolant pH is measured after
initial filtration and compared to a chart that shows how much additive is needed to raise the pH to 9.5.
The high pH helps to reduce the corrosivrty of the coolant. In addition to raising the pH, the hydroxide
portion of the additive precipitates soluble metals which are continuously filtered out. The additive also
contains a blend of inhibitors, polymers, and surfactants to improve coolant quality. Following pH
adjustment, the freezing point of the coolant is checked with a hand-held refractometer. A chart tells
the operator how much virgin coolant must be added to achieve a freezing point of -34 F or lower. The
portable unit had an ion exchange column to further reduce metals.
55
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Primary batches of spent coolant (as received) were run through the fleet-size unit and portable
unit. The primary batches represented stored spent coolant from the automotive and heavy-duty
vehicles operated by NJDOT. Three "spiked" (altered spent coolant) batches were also run. The
purpose of these salts- and acid- spiked batches was to create exaggerated conditions to test the limits
of the recycling process. A blank, consisting of virgin coolant and tap water, was run through the fleet-
size unit. Samples of the spent, virgin, and recycled coolant were collected for analysis.
The second technology evaluated was one of distillation to recover automotive and heavy duty
engine coolant. This coolant recycling unit was: manufactured by Finish Thompson, Inc (FTI). The unit
operates on up to 15 gallons of spent coolant per batch. Spent coolant is poured into the distillation
still along with an additive to control boiling. The unit is switched on and allowed to operate until water
and ethylene glycol are distilled off into two separate clean drums outside the unit. This may take
about 12 to 15 hours for a full 15-gallon load of spent coolant depending upon the amount of water
present. Water distills out first at atmospheric pressure into the processed water drum. As the
temperature rises, the vacuum pump switches on automatically and starts drawing out the glycol. The
vapors are condensed by using tap water as the heat exchanger fluid or by using an optional chiller.
The condensate enters the primer tank, where it mixes with the primer (ethylene glycol) and overflows
into the processed glycol drum. The processed [glycol and processed water can then be mixed in equal
proportions. Three gallons of distillation residue collects at the bottom of the still and is emptied out,
typically after five batches. Primary and spiked batches of spent coolant, similar to those run on the
filtration units, were also tested on this distillation unit.
RESULTS
In this study, results of the analyses were compared against ASTM and/or SAE standards. After
recycling with the filtration unit, the boiling and freezing points of the coolant were brought as close to
standard as possible through use of the hand-held refractometer and alteration of the glycol-to-water
ratio. None of the recycled samples from the primary batches met the corrosion standards as
measured by the ASTM D 1384 and D 4340 tests. The spiked recycled samples, however, met the
corrosion standards for the ASTM D 1384 test.( This variation may be because the amount of corrosion
Inhibitor added is based on the pH of the spent coolant. Since the acid-spiked samples had lower pHs,
adding more corrosion inhibitor to the coolant resulted in better corrosion resistance.
j "
The spent and recycled coolants from the filtration units were characterized chemically and
levels of contaminants, such as metals, chlorides, oil and grease, etc., were measured to determine if
these constituents affected performance. After recycling, although levels of chlorides and sulfates were
not noticeably reduced in the coolant, the level of metals was considerably reduced. This retention of
chlorides and sulfates in the recycled coolant may contribute to corrosion.
After recycling with the distillation unit, freezing point was measured by a hand-held
refractometer and the ratio of processed water |o processed glycol was adjusted to meet freezing point
specifications. The freezing and boiling points were in agreement with the recommended standard.
Both pH and corrosivity of the recycled coolant were also within specified limits. Corrosivity was
measured in terms of the weight loss of metal test specimens exposed to the coolant for two weeks.
The recycling process was able to restore the spent coolant to within specifications as compared to the
ASTM D 3306 standard. The aluminum corrosion test (ASTM D 4340) was also run. This test
evaluates the effectiveness of recycled coolant to inhibit corrosion of cast aluminum alloys under heat
transfer conditions. This test is important because of the growing usage of aluminum instead of cast
fron In automotive engines. The batches were recycled to within the acceptable standard for this test.
56
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The spent and recycled coolants were characterized chemically and contaminant levels were also
measured to determine if these constituents affected performance. The levels of calcium, magnesium,
iron, and zinc were reduced considerably in the recycled coolant. Changes in levels of lead and
aluminum were hard to estimate due to low analytical recoveries and low starting levels of these metals
in the spent coolant.
For both filtration and distillation, the pollution prevention potential was measured in terms of
the volume and hazard reduction. Volume reduction addresses gross wastestreams (i.e. spent
coolant, filters). Hazard reduction involves individual pollutants( i.e. ethylene glycol, heavy metals )
contained in the wastestreams. The estimate of the amount of coolant that NJDOT disposes of
annually was based on the amount of new coolant that NJDOT uses annually decreased by 10% to
account for the environmental loss of coolant through leaks in the vehicles cooling systems. Because
the coolant is recycled rather than disposed of, the volume reduction was calculated to be 8,812 gals.
The volume of sidestreams generated for disposal during recycling for filtration (e.g. filters) and
distillation { e.g. residue ) were approximately equal.
For filtration, the economic evaluation took into account the capital and operating costs of the
recycling equipment as well as the savings provided by decreasing the amount of raw materials (virgin
coolant, water) and reducing disposal costs. Because of the relatively high price of virgin coolant and
the high volume of virgin coolant purchased by NJDOT, the recycling process was found to have a
payback period of less than one year. This is assuming that the filtration unit is able to produce coolant
that meets quality standards.
For distillation, the economic evaluation also took into account the capital and operating costs
of the recycling equipment as well as the savings provided by decreasing the needed amount of raw
materials (virgin coolant and water) and by reducing disposal costs. The purchase price of the
recycling unit at the time of this evaluation was $ 5,115. Due to the relatively high price of virgin
coolant and high volume of virgin coolant purchased by NJDOT, the payback period was much less
than one year. The payback varies depending on the amount of spent coolant generated annually by
the user. For example, if a generator purchases 100 gals of coolant annually, the recycling unit may
not be economical. A slightly larger generator, with 500 gal/yr of purchased coolant, would have a
payback period of approximately seven(7) years. The payback improves as the amount of coolant
purchased becomes larger.
CONCLUSION
Although recycling by filtration has great waste reduction and economic potential, the filtration
unit evaluated in this study would require additional improvements to ensure an acceptable quality of
the recycled product. Some possible areas of improvement are adjusting the method of determining
the amount of additive used and implementing a means of anion (chlorides and sulfates, etc.) removal
such as ion exchange.
The distillation evaluation also shows good waste reduction and economic potential. The
NJDOT facility could potentially reduce waste from over 8000 gals to approximately 400 gal/yr. The
recycled product in the distillation evaluation also fared very well in the selected ASTM performance
tests and the chemical characterization analyses. Boiling point, freezing point, pH, and corrosion
resistance function of the coolant were restored to specifications. Metals, salts, and organic
contaminants were also removed.
Several automotive and heavy-duty engine manufacturers are also beginning to evaluate
57
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recycling. Such studies involve relatively expensive testing which may be costly for small repair shops
to conduct on their own. Some repair shops have already undertaken recycling based on information
provided by vendors to address the increasing cost of disposal. But in general, initial reaction to
recycling coolants in the automotive industry has been cautious, given the demanding nature of the
application.
This study was funded by the U.S. Environmental Protection Agency under Contract No. 68-
CO-0003 to Battelle. It has been reviewed in accordance with the EPA peer and administrative review
policies and approved for presentation and publication. Mention of trade names or commercial
products does not constitute endorsement or recommendation for use.
58
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THE USE OF HYDRAULIC FRACTURING TO ENHANCE IN SITU BIOREMEDIATION
Stephen Vesper . Lawrence Murdoch
Mark Kemper, David Kreuzmann',
Rebecca Brand1, Phillip Cluxton
1
Frank Sheehy
1
K. Pete Paris'
Wendy Davis-Hooven,
Department of Civil and Environmental Engineering,
Center Hill Laboratory,
Cincinnati, Ohio 45224,
US EPA, Risk Reduction Engineering Laboratory
Municipal Solid Waste Research Management Branch
Soils & Research Section
Center Hill Laboratory,
Cincinnati, Ohio 45224
1
INTRODUCTION
Bioremediation was determined to be a viable method of degrading the hydrocarbon
contaminants at a fuel distribution and storage facility in Dayton, Ohio. Laboratory tests done by the on-
site contractor indicated that percolating water containing oxygen and nutrients through the soil would
result in biodegradation of the contaminants. The site is underlain by silty clay till of relatively low
hydraulic conductivity, so conventional methods of delivery were expected to result in either slow rates of
percolation, and thus slow rates of remediation, or excessive drilling costs. Therefore, the site was
selected as a candidate for hydraulic fracturing, a technique of creating high permeability channel ways
in tight soils.
METHODOLOGY
The site was divided into two areas: one to be treated by using hydraulic fracturing (HF) and the
other to be treated using a conventional well (CW). The same injection fluid was to be introduced into
each. The two areas were sampled at the beginning of the project then again during treatment.
Hydraulic fractures were created by injecting cross-linked gel at a constant rate into a lance-like
device composed of a casing and an inner rod, both of which are tipped at one end with a hardened
cutting surfaces that form a conical point. A drive head at one end of the lance secures both the casing
and the rod. Individual segments of the rod and casing are 1.5m long and they are threaded together
as required by the borehole depth.
During the field work, the lance was driven to depths of as much as 4 meters. The rod and point
were removed, leaving soil exposed at the bottom of the casing. Another device composed of steel
tubing with a narrow orifice at one end, was inserted into the casing. Water pumped into the device
formed a jet that cut laterally into the soil. The jetting device was rotated, producing a disc-shaped notch
extending 10 to 15 cm away from the borehole. A simple measuring apparatus, built from a steel tape
extending the length of the tube and making a right angle bend at the end of the tube, was inserted into
the casing to verify and measure the radius of the slot.
Hydraulic fractures were created by injecting the cross-linked guar gum gel into the casing.
Injection rates of 60 to 90 liters per minute were used for the tests. Lateral pressure of the soil on the
outer wall of the casing effectively sealed the casing and prevented leakage of the slurry. The fractures
nucleated at the notch and grew away from the borehole.
59
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During a typical procedure to create the fractures, the onset of pumping was marked by a sharp
Increase in pressure of the injection fluid to between 200 and 350 kPA (30 and 50 psi). This onset of
fracture propagation, however, was marked by an abrupt decrease in pressure, with pressures in the
range of 70 to 170 kPa (10 to 25 psi) during propagation. After one fracture was created, the rod and
point were inserted and the lance driven to a greater depth where another fracture was formed.
The conventional well was created by drilling a 10 cm borehole to a depth of 4 m. This hole was
filled with sand to a depth of 1.5 meter, a half inch PVC pipe was inserted, then sealed in place by filling
the rest of the borehole with bentonite.
The week after the fractures were created, continuous split spoon samples were taken to
determine the location of the hydraulic fractures, to determine the soil stratigraphy and to study the
chemical and microbial conditions in the soil. The borings were made at radial distances of 1.5, 3.2, arid
5 meters with respect to the fractured and unfractured wells. Samples for BETX (benzene, ethyl
benzene, toluene and xylene) were taken directly from the split-spoon and placed in 300 ml of methanol.
The remaining sample was sealed in ziplock bags and placed in iced coolers for analysis of TPH (total
petroleum hydrocarbons), moisture, and pH in the lab.
Microblal populations were determined by aseptically removing 1 gram samples, sonicating to
release the organisms from the soil, then plating on R2A medium incubated at 29°C. To determine the
number of gasoline degrading microorganisms; in 1 gram, the samples were plated on non-nutritive salts
medium and the plates incubated at room temperature in a gasoline-fume atmosphere. Microbial activity
was determined by monitoring the hydrolysis of fluorescein diacetate (FDA). Fluorescein diacetate was
dissolved in acetone at a concentration of 2 mg/ml. One gram of soil plus 0.5 ml of the FDA solution
were added to 100 ml of 60 mM phosphate buffer (pH7.6). These were incubated on a shaker at 12°C
for 24 hrs. The cultures are centrifuged, then filtered and the color development measured at 490 nm.
Water containing oxygen and nutrients is currently being injected into the wells. The flow rates
and pressures are being monitored. At 8 week intervals the site is resampled for chemical, physical and
microbial conditions.
RESULTS
Four hydraulic fractures were created in the contaminated area (HF). The depth of each fracture
was 2.3 m (HF2.3), 2.6 m (HF2.6), 3.2 m (HF3.2), and 4 m (HF4). We have estimated the general
geometry along cross-sections through HF (Figure 1). The fractures appear to be roughly flat-lying to
gently dipping toward the parent borehole. The uppermost fractures at HF appear to have the steepest
dip, roughly 30°, as it climbs from the parent borehole to the ground surface north of the borehole. The
other three fractures at HF dip from approximately 30° within 1.5 m of the borehole, but then flatten to
dips of 10° to 15° at greater distances on the northern side of the borehole. None of the deeper fractures
reached the ground surface. Two fractures were discovered 3.2 m south of HF and they were inferred to
be the lowest two fractures, as shown on the crdss-section. The geometry of the fractures is locally
inconclusive due to lack of recovery.
Creating the fractures produced broad domes at the surface, with maximum displacements of 12
to 23 mm, over areas roughly 9 to 14 m in maximum dimension. Most of the domes are roughly equant
in plan, although the point of maximum uplift is almost always at a point other than the point of injection.
As a result, the fractures appear to be asymmetric with respect to the points of injection.
The results of the chemical, physical and microbiological analyses of the initial soil condition are
complete. The contaminant concentrations at the site were nonuniform but the whole area was
60
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contaminated. For example, benzene ranged from a maximum of about 14 ppm to a minimum of 1 ppm.
Ethyl benzene ranged from 40 ppm to about 1 ppm. The pH of the soil was between 7.2 and 8. Starting
soil moistures are in the range of 9 to 16%. The number of gasoline degrading and heterotrophic
microbes ranged between 104 and 105 CPU (colony forming units)/ gram soil. .
CONCLUSIONS
Hydraulic fracturing was shown to be a feasible procedure at this contaminated site. The size
and shape of the fractures were as planned. Enough information was gathered at the site in the initial
assessment to evaluate the post treatment effects of the hydrofracturing as compared to a conventional
injection well arrangement. The site conditions make it conducive to bioremediation (e. g. pH about
neutral, significant hydrocarbon degrading microbial population). Significant progress is expected in the
coming months and an update will be given at the meeting.
FRACTURING BOREHOLE
CROSS SECTION OF HYDRAULIC FRACTURES
5'
Scale
Fill (crushed .limestone)
Light Brown Silty Clay
Olive Green Clay/No Clasts
Light Grey Silty Clay with Rock Fragments
Light Brown Stiff Mottled Clay with Rock Fragments
No Sample Recovery
Fracture
Fracture #
1
2
3
Figure 1. Cross section showing stratigraphy and hydraulic fractures in the HF treatment area.
61
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IN SITU TREATMENT OF SOIL CONTAMINATED WITH PAHs AND PHENOLS
I
Guggilam Sresty, Harsh Dev, and Joseph Chang.
IIT Research Institute, 10 W. 35th Street, Chicago, II 60616
Janet Houthoofd
RREL, USEPA, 5995 Center Hill Road, Cincinnati, Oh 45224
INTRODUCTION
The wood preserving industry1 uses more pesticides than any other
industry worldwide (1). The major chemicals used are creosote,
pentachlorophenol, and CCA (copper, chrome and arsenate). It is reported that
between 415 to 550 creosoting operations within the United States consume
approximately 454,000 metric tons of creosote annually. When properly used
and disposed off, creosote does nof: appear to significantly threaten human
health. However, due to improper disposal and spillage at old facilities,
creosote and other wood preserving chemicals have found their way into surface
soils. Active wood preserving sites generate an estimated 840 to 1530 dry
metric tons of hazardous contaminated sludge annually, which is classified as
K001.
Creosote, obtained from coal tar, contains a large number of chemical
components. The three main families of compounds represented in creosote are;
polycyclic aromatic hydrocarbons (PAH), phenolic, and heterocyclic compounds.
Creosote is composed of approximately 85% PAHs, 10% phenolic compounds and 5%
heterocyclic compounds. There are approximately a total of 17 PAHs present in
creosote. The four most prominent compounds belonging to the PAH family are
naphthalene, 2-methylnaphthalene, phenanthrene, and anthracene. These four
compounds represent approximately 52% of the total PAHs present in creosote.
There are approximately 12 different phenolic compounds present in creosote
among which phenol is the most abundant, representing 20% of the total
phenolics. In addition, the various isomers of cresol represent about 30% and
pentachlorophenol (PCP) represents 10% of the total phenolics. There are
approximately 13 different heterocyclic compounds present in creosote. Among
these the nitrogen containing compounds are the most abundant, representing
approximately 70% of the total heterocyclics. The balance is distributed
between sulfur and oxygen containing heterocyclics.
; I '
All of these compounds possess toxic properties and some of them, for
example, PCP, when subjected to high temperature environments are suspected
precursors in the formation of dioxins.
In this paper the results of an ongoing, USEPA funded, cooperative
agreement(are described. The purpose of this project is to determine the
treatability conditions for the removal of wood preserving contaminants
present in soil by in situ thermal -treatment. The goal was to find
appropriate time and temperature conditions for the treatment of soils by the
in situ radio frequency (RP) soil decontamination process. The in situ RF
heating process utilizes electromagnetic energy in the radio frequency band to
heat up the soil rapidly, uniformly, and without .injection of heat transfer
media or on site combustion. The in situ RF process can be used to heat the
soil to a temperature range of 150°-200°C. The contaminants are vaporized
and or boiled oat along with water vapor formed by the boiling of native soil
moisture. The gases and vapors formed upon heating the soil are recovered for
on site treatment by means of a gas collection system.,
62
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The feasibility of the in situ RF soil decontamination process was first
demonstrated for petroleum hydrocarbons at a site of a jet fuel spill (2). In
this field experiment approximately 500 cu. ft. of sandy soil was heated to a
temperature range of 150-160° C. It was demonstrated that 94 to 99 percent of
the aliphatic and aromatic hydrocarbons present in the spill site were removed
(2). In various other laboratory feasibility studies, the treatment
conditions for the removal of the following contaminants has been established:
perchloroethylene and chlorobenzene from sandy soil (3), jet fuel from clayey
soil (4), PCBs from sandy/clayey soils (3), phenanthrene, pentachlorophenol
and phenol from sandy/clayey soils (5). All of these studies except the one
with jet fuel were done with clean soils which were spiked with the
contaminants in the laboratory. In this paper we present the results of
feasibility studies performed with contaminated soil obtained from a wood
preservative site. • .
METHODOLOGY
Full Scale Implementation; The RF soil decontamination process is a two-step
process which operate simultaneously once the average temperature of the soil
exceeds 50° C. These steps are: heating of the soil, and vaporization and
recovery of the contaminants.
In the first step of the process, the soil is heated to temperatures of
150° to 200° C by means of an electrode array inserted in bore holes drilled
through the soil. Selected electrodes are specially designed to permit both
the application of RF power while collecting vapors by application of a vacuum
down hole. The vapor collection system is an integral part of the electrode
array since vapor collection points are physically integrated and embedded in
the array. A vapor containment barrier is used to prevent fugitive emissions,
and provide thermal insulation to prevent excessive cooling of the near
surface zones.
Prior laboratory and field experiments (2-5) have shown that high boiling
contaminants can be boiled out of the soil at much lower temperatures than
their actual boiling point. This occurs due to the presence of an
autogenously established steam sweep which helps to improve the rate of
vaporization of such high boiling materials. Another phenomenon which
operates during in situ heating is the development of effective permeability
to gas flow. The increase in permeability is confined to the heated zone,
thus creating a preferred path of gas and vapor flow towards the soil surface.
The second step of the process is the collection, recovery, and on-site
treatment of the vapors and gases formed by heating of the soil. The
collected waste gases are transported to an on-site treatment system. The
first vapor treatment step is cooling and condensation of the vapors from the
gas stream. The uncondensed gases are further treated to remove contaminants.
This treatment may consist of carbon adsorption, combustion in a gas-fired
afterburner, and/or gas scrubbing in an alkaline scrubber. The specific gas
treatment steps used depend upon the nature and amount of contaminants
expected in the gas stream.
The liquid phase is separated on site into two fractions: the aqueous
phase and the organic phase. The aqueous phase is treated on site through a
carbon bed and a filter. The organic phase is stored, pending ultimate
destruction at an approved treatment facility.
63
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Tgeatabilitv Study; The soil treatability experiments were performed by
heating a 3-ft column of soil packed into a 1.5 in. diameter, 4-ft long
stainless steel pipe. The pipe was connected at the top via heat traced
tubing to a glass water-cooled condenser. The outlet of the condenser was
connected to a vacuum flask which was pre-charged with 50 to 70 mL of
methanol. The side-leg of the vacuum flask was connected to a wet-test meter.
The flask was kept in an ice bath.
The bottom port of the reactor was connected to a source of heated nitro-
gen or superheated steam. Zero grade nitrogen was obtained from a cylinder,
heated through a heat traced line and delivered at the base of the soil col-
umn. When steam was needed, a three-way valve was used to pump water into the
heat traced line. The water was pumped by a positive displacement metering
pump, capable of delivering 0 to 10 mL/min. The temperature of both nitrogen
and steam was adjusted to approximately match the average temperature of the
soil in the reactor. The soil column was heated by externally wrapped heating
tapes. Both internal and external thermocouples were used to make sure that
the soil was at the desired temperature.
The results of the treatability experiment were determined by analyzing
and comparing the results of soil samples taken while the reactor was being
packed and of treated soil removed .from the reactor at the end of an
experiment. The variables being studied in these experiments are the
treatment temperature, time, flow rate of steam, type of flowing fluid sweep,
viz., nitrogen versus steam and type of soil matrix (field soil versus
Standard Analytical Reference Matrix or SARM I soil as prepared by EPA). In
selected experiments mass balance will be made by analyzing the aqueous
condensate phase collected in the water cooled condenser.
TABLE 1. EXPERIMENTAL CONDITIONS
Soil type
Soil weight, g.
Contaminants spiked
Treatment temp. , °c
Treatment time at temp., hrs.
Sweep Gas
Type
Flow rate, L/min
Time, hrs.
Type
Flow rate, L/min*
Time, hrs.
Experiment No.
1
Field
1620
—
200
23
N2
0.60
22
H20(v)
1.0
20
2
Field
1685
Aroclor
1242
200
70
N2
0.63
24
H20(v)
0.50
70
3
Field
1772
Aroclor
1242
230
70
M
0.56
12
H20.(v)
0.30
63
4
Field
1748
Aroclor
1242
200
70
N
0.58
8
H20(v)
0.16
68
5
Field
1689
Aroclor
1242
200
71
No
"2
0.51
8
H20(v)
0.17
66
* at treatment temperature
The experimental conditions for five experiments are summarized in Table
1 (additional experiments are underway). All experiments were performed with
64
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soil obtained from the wood treatment site. In experiments 2 to 5, Aroclor
1242 was spiked on the soil to determine the removal efficiency of PCB by the
in situ process.
RESULTS
TABLE 2. REMOVAL DATA FOR PAH AND PHENOLIC COMPOUNDS
Analyte
Boil-
ing
Point
°C
Melt-
ing
Point
°C
Treatment Temperature, ° C
Treatment Time at temp., hr
Acenaphthalene
Acenaphthene
Fluorene
Pentachlorophenol
Phenanthrene
Anthracene
Fluoranthene
Pyrene
Benzoanthracene
Chrysene
Benzo ( b ) f luorant hene
Benzo ( k ) f luoranthene
Benzo ( a ) pyrene
I ndenopyr ene
D ibenzo ( a , h ) anthracene
Benzo ( g , h , i ) perylene
278
278
294
309
340
342
393
393
439
448
495
524
>500
95
95
115
189
100
218
111
156
254
196
266
278
Percentage Removal
Experiment No.
1
200
23
53
100
100
100
41
66
69
69
13
10
0
5
15
3
8
2
2
200
70
100
—
100
100
_
100
_
100
17
25
6
10
23
8
-28
7
3
230
70
100
100
100
100
73
64
90
94
45
60
45
48
43
20
15
19
4
200
70
84
100
100
100
74
84
88
89
60
46
12
21
34
34
35
30
5
200
71
95
100
_
100
81
68
78
77
40
43
16
21
31
23
17
22
The results of experiments 1 to 5 are summarized in Table 2. In this
table the percentage removal for PAHs and PCP is presented. The results show
that treatment at a temperature of 200 to 230° C for a period of 70 hr. is
sufficient to remove the PCP and the three ring PAHs to their analytical
detection limit. Thus nearly 100 percent removal of these compounds from the
soil can be achieved. High removal efficiency was also obtained for pyrene, a
four-ring PAH. All of these compounds have a normal boiling point less than
400° C. For other compounds with higher boiling points and having four or
more rings, the removal efficiency was (lower. In experiments 2 through 5,
Aroclor 1242 was spiked into the soil. The initial concentration of Aroclor
was 1078, 1150, 1240, in experiments 2 to 4, respectively. The final Aroclor
65
-------
concentration in the soil from these three experiments was 48, 14,and 34 ppm.
Thus the average removal of the Aroclor in the three experiments was 95.6,
98.8 and 97.3 percent. Thus treatment at 230° C can reduce the PCB
concentration below 25 ppm. Additional analyses of the condensate are being
performed to close the mass balance for the PAHs, PCP and the Aroclor. More
experiments are being done on SARMfl soil to provide comparative data for the
standardized soil.
CONCLUSION
The results of the treatability experiments performed have shown that
heating of soil to a temperature range of 200° to 230° C is sufficient to
remove PCP and all the four-ring PAHs with boiling .point of less than 400° C.
As before, it was again demonstrated that it is not necessary to heat the soil
to the boiling point of the pure component in order to obtain substantial
removal from soil. The results have also demonstrated the feasibility of the
removal of Aroclor 1242 from soil in the temperature range of 200-230° C.
REFERENCES
1. Mueller, J. G., P. J. Chapman, and P. HapPritchard. Creosote
Contaminated Sites. Environmental Science and Technology, 23(10):1179-
1201, 1989.
2. Dev, H., Enk, J., Sresty, G., Bridges, J. In Situ Decontamination by
Radio Frequency Heating—Field Test. IIT Research Institute. Final
Report C06666/C06676. Prepared for USAF, HQ AFESC/RDV, Tyndall AFB,
Fla., May 1989.
3. Dev, H., J. Bridges, G. Sresty, J. Enk, N. Mshaiel, and M. Love. Radio
Frequency Enhanced Decontamination of Soils Contaminated with
Halogenated Hydrocarbons. EPA/600-2-89/008. U.S. Environmental
Protection Agency, Cincinnati, Ohio, 1989
4. Dev, H., and G. Dubiel. Optimization of Radio Frequency (RF) In Situ
Soil Decontamination Process. Draft Final Report, IITRI Project No.
C06691. ANL Contract No. 83482402. June 1990.
5. Sresty, G.C., Dev, H., Gordon, S. M., and Chang, J. Methodology for
Minimizing Emissions by Remediation of Environmental Samples? Containing
Wood Preserving Chemicals, Draft Final Report, IIT Research Institute.
US EPA Contract No. 69-D8-0002, Work Assignment No. 22, IITRI Project
No. C06693C022.
66
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LONG-TERM DURABILITY OF SOLIDIFIED/STABILIZED MATERIALS
Diana R. Kirk
U.S. EPA
Risk Reduction Engineering Laboratory
5995 Center Hill Avenue
Cincinnati, Ohio 45224
(513) 569-7674
Paul L Bishop
Department of Civil and Environmental Engineering
741 Baldwin Hall (ML #71)
University of Cincinnati
Cincinnati, Ohio 45221-0071
(513) 556-3675
INTRODUCTION
One of the major concerns with the solidification/stabilization (S/S) process for final containment of
hazardous wastes or other teachable materials is the uncertainty relative to long term stability of the
material in the environment, where it will be exposed to many influences which may cause deterioration.
The potential for and degree of weathering needs to be evaluated.
This research addresses the potential weathering of waste forms and the effects of aging and
weathering on leaching from these waste forms. The overall objectives of this research are to assess the
long-term durability of stabilized/solidified wastes from Superfund sites and to verify existing
durability/leaching models. Specific objectives include the development of accelerated aging and
weathering tests for determining long-term durability, evaluating the influence of wet/dry cycling on
durability and leaching characteristics, evaluating the influence of waste form cracking on sample
porosity and permeability, and use of the results obtained to validate existing durability and leaching
models.
METHODOLOGY
The stabilized/solidified waste samples were prepared from sludges containing .02 M concentrations
of lead nitrate, sodium arsenite and cadmium nitrate with a water/binder ratio of 0.7. The sludge was
solidified with different waste-binder ratios of portland cement, iime/flyash, and kiln dust using ASTM C-
109 into 3" diam x 6" cylinders, 2" x 2" x 2" cubes, and 3" diam x 1" disks and cured for 28 days. These
samples were then aged in weathering chambers, which allow specimens to be exposed to static
conditions (elevated temperatures and/or pressures and/or submersions) and recirculating sprays for
simulated times of 20, 50, and 100 years. The set of control samples (not aged) and the test samples
(aged) were then tested for porosity, permeability, leach tested (TCLP, ANSI 16.1, and Sequential
Leaching), wet/dry cycles, unconfined compressive strength, and acid weathering.
67
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Stabilized/solidified samples were subjected to Arrhenius aging techniques to accelerate the aging
process. Accelerated aging refers to accelerating the conditions a treated waste will experience during
the aging process. Many environmental factors may affect a material over its lifetime, such as changes
due to wet/dry, wind and rain erosion and weathering or erosion due to groundwater action. The
procedure developed for artificially aging the waste forms is based on the Arrhenius model. The
equivalent age function is based on the activation energy of the material.
The age function, known as the Arrhenius equation is:
where:
t. = service time
ta = accelerated time
Ea = activation energy
k = Boltzman's constant
Ts = service temperature
Ta = accelerated temperature
This formula provides a means for determining the equivalent age (service time, ts) a specimen would
experience at a given natural temperature (service temperature, Ts). These times and temperatures are
modelled as accelerated temperature (U for a given accelerated time (tj for the material specific
activation energy (£„).
In this research, Thermogravimetric Analysis (TGA) was used to determine the waste specific kinetic
parameters for the Arrhenius aging equation. Thermogravimetry measures the weight changes in a
sample as a function of temperature or time. The mode of thermogravimetry used for this study is
known as dynamic thermogravimetry, in which (different sample types were heated in an environment
whose temperature changed in a pre-determined manner at a linear rate. The resulting mass change
versus temperature curve provided information concerning the thermal stability and composition of the
sample. This information was then used to determine kinetic parameters of the material, specifically the
activation energy.
Cement-based immobilization systems rely heavily on pH control for stabilization of metal
contaminants. Over time, acid in leachants in contact with the waste form will penetrate the specimen
and gradually leach waste matrix materials and |metals into the surrounding environment. An intensive
study was undertaken to identify the leaching rnechanisms involved by evaluating the pH profiles within
leached specimens and the physical and chemical properties of the leached material. The pH profile
along the acid penetration route in the cement-based waste forms was identified by splitting the samples
and applying various pH color indicators. The effect of acid attack on density and porosity changes and
pore size distribution was also studied.
Monolithic and crushed test specimens which have been subjected to accelerated aging procedures
68
-------
based on the Arrhenius model were acid weathered using a leachant with an acidity comparable to that
expected to be encountered by the waste form over the period of time simulated by the aging process.
The monoliths were suspended in an extractor at a 10:1 (g leachant/sq cm monolith surface area) ratio
for 48 hours. Crushed samples were extracted for 48 hours at a 20:1 (W/W) leachant: solid ratio. Aged
samples were analyzed for leaching depth, leached zone porosity and wet/dry resistance, and the
leachate is analyzed for contaminants. The resulting samples, which simulate aged and weathered
waste forms, were then subjected to various leaching tests, including the TCLP and the ANSI 16.1 test to
determine whether the aged specimens leach differently than control samples.
The possibility of leaching hazardous substances from solidified wastes in land disposal sites is
increased if the solidified monolith is fractured during weathering. It is, therefore, desirable to determine
if the monolith fractures during weathering and, if it is fractured, what is the extent of fracture. The
method used to determine the amount of surface fracture was laser holographic interferometry.
Holograms were made by recording a diffraction grating on a photographic plate. The interference of a
reference beam and an object beam created by a laser beam created the fringe patterns on the
photographic plate. Cracks were seen in the hologram as a discontinuity in the fringe pattern. The
object (sample), optics, and plates were placed on an isolation table consisting of a 3000 pound granite
table top. Epoxy dye injection was used to determine the inner fractures and cracks.
Another technique used to evaluate deterioration of solidified wastes include resonance frequency
and pulse velocity. This was done in collaboration with the Department of Energy (DOE) to evaluate this
technique for assessing waste form durability. The evaluation of this parameter required the
determination of the natural frequency of the specimens after each aging cycle. In resonance frequency
testing a sample was excited by the application of an ultrasonic wave generator. The frequency of the
waves was varied until the specimen vibrated in a resonant mode.; As specimens sustain damage, the
resonant frequency changes and this change can be used to assess the damage.
RESULTS
Thermogravimetric Analysis (TGA) was run on pieces from three crushed cylinders of waste forms
made from a sludge containing lead nitrate, sodium arsenite and cadmium nitrate. Each sample was
analyzed under different physical conditions (small solidified pieces or as powder); under different
moisture conditions (saturation, air-dried, dried at 60° C and dried at 110° C); and for four different
temperature ramps from 2° C/min to 16° C/min, in order to investigate the effect that the physical
properties of the samples exhibited on the resulting TGA analysis.
Using the Arrhenius Equation and the kinetic parameters determined from the TGA data, an
accelerated aging schedule was developed. The Arrhenius equation uses the activation energy (EJ
found from the TGA, Boltzman's constant (k), and a given accelerated operating temperature (TJ for the
aging chambers. The service time (t.) was chosen to model two different times in the future, 50 and 100
years. The service temperature to be modelled was taken from the average temperature in the greater
Cincinnati area over the last 100 years (Ts = 54.6° F).
The time of contact of a waste form with leachant could significantly alter the potential for leaching
because it results in increased porosity and creation of a chemically altered surface layer. The pH in the
surface altered layer was found to vary from 5.0 to 6.0, which is very close to the pH in the bulk
69
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leachate. A reacting zone, where the pH abruptly changed from 6 to 12, sharply divided the altered
surface layer from the remaining unleached waste form or "kernel". The reacting zone was white in color
and was about 100 microns in width for the samples with 0.6 water-cement ratio leached in 0.4 N acetic
add solution for a total period of 29 days (Figure 1). SEM/EDX analysis indicated that in the surface
layer, most of the calcium and the stabilized metals were removed by the leachants. The metal
contents of the kernel, however, were very close to those of the original material. It was believed that
the leaching boundary was formed by the inwarg1 diffusion and reprecipitation of calcium hydroxide
crystals in front of the acid. i
\=
Leached Cement—Based Waste Form
Leached Layer -| Unleached Kernel
Acetic Acid
Solution
Medium
Grey
pH>12
Light
Grey
• Solid/solution
Interface
White Remineralization
Region (100 microns in width)
Figure 1. Schematic profile,of a leached cement-based waste form.
The porosity of the kernel was essentially the same as for the unleached controls, but the porosity of
the leached layer increased significantly. The pore distribution in the kernel was the same as in the
unleached samples, but the leached zone was significantly different. The gel porosity of the leached
layers increased greatly due to the dissolution of calcium silicate hydrate matrix.
i ' - ' '
The leaching of metals was controlled by the acidity available in the leachant. Dissolution of alkaline
materials left a silica-rich layer on the surface of khe cement-based waste from. This surface layer
exhibited different properties than those of the unleached material. The surface layer had a higher water
content, was lighter weight, and was soft and friable. Furthermore, the abundant silicate content on the
solid surface detained a portion of the leached metals, while they moved through the leached layer into
bulk solution. The leaching mechanisms of metals was idealized as five steps: (1) mass transfer of acids
from bulk liquid to solid surface, (2) transport of acids through leached layer, (3) diffusion-controlled fast
dissolution reactions at leaching boundary, (4) transport of metals through leached layer, and (5) mass
transfer of metals from solid surface Into bulk liqbid.
70
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CONCLUSION
The leaching of metals is a consequence of acid penetration. The distance from the solid/solution
interface to the front of the leaching boundary can be regarded as the depth of the leaching zone, where
the metals dissolve and diffuse out of the waste form.
The position of the leached layer can be predicted by knowing three measurable factors- the acidity
consumed in the leachant, leach time, and the buffering capacity of the waste form. By knowing the
leachable fraction of metal contaminant, the total amount of metal leached can be estimated from the
thickness of the leached layer.
These studies have shown that leaching is directly correlated to the amount of acid in contact with
the waste form, and that the leaching front moves progressively into the sample rather than being
diffused throughout the waste form depth. Further studies indicate that the amount and extent of
leaching is essentially the same for samples exposed to a weak acidic leachant over a long time period
as for a strongly acid leachant over a short time interval. Thus, the effect of acid leaching over a 50 or
100 year period can be simulated by using proper strength acid leachant, equivalent to that specimen
would see over the exposure period.
Sample porosity and pore size distribution is very important in determining the degree of leaching
that will occur in a waste, since leaching is largely controlled by the amount of available surface area. A
study conducted on solidified/stabilized fly ash and flue gas desulfurization (FGD) sludge wastes
showed that acetic acid leaching increases pore volumes and pore sizes. It was found that pore
structures varied depending upon the wastes used and the solidification mix formulations tested. The
higher the alkalinity in a sample, the greater the change of pore structure due to leaching. Changes in
pore structure were primarily due to leaching of calcium hydroxide, resulting from the attack of hydrogen
ions in the leachant. These findings essentially coincide with the porosity results for the metal sludge
used in this project.
Future work will include the testing of radioactive/mixed waste samples obtained from DOE for
utilization in the weathering chambers. Many ideas about optimum S/S techniques have originated from
actual laboratory investigations and use of chemical and physical tests, but there has never been a
concrete relation between field leachate quality and laboratory leachate quality. The application of leach
tests in conjunction with weathering and aging techniques on field waste samples will provide valuable
data on existing short-term laboratory tests. This will aid in devising better techniques for making
predictions on the long-term durability of S/S waste forms.
71
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METALS PARTITIONING RESULTING FROM\ ROTARY KILN INCINERATION OF HAZARDOUS WASTE
Marta K. Richards
USEPA/RREL/WMDDRD/TDB/TRS
26 West Martin Luther King Drive
Cincinnati, Ohio 45268
(513) 569-7783
Donald J. Fournier, Jr.
Acurex Corporation
Environmental Systems Division
NCTR Building 45
Jefferson, Arkansas 72079
(501) 541-0004
INTRODUCTION
In response to the need for data on the partitioning of trace metals from hazardous waste
incinerators, an extensive series of tests was conducted in the summer of 1991 at the USEPA
Incineration Research Facility (IRF) in Jefferson, Arkansas. These tests were conducted in the IRF's
rotary kiln incinerator system (RKS) equipped with a pilot-scale Calvert Flux-Force/Condensation
scrubber as the primary air pollution control system (ARCS). The purpose of this test series was to
extend the data base on trace metal partitioning and to investigate the effects of variations in incinerator
operation on metal partitioning. Another objective was to evaluate the effectiveness of the scrubber for
collecting flue gas metals. This series is a continuation of an ongoing IRF research program
Investigating trace metal partitioning and ARCS collection efficiencies. Two previous test series were
conducted using the RKS equipped with a venturi/packed-column scrubber and a single-stage ionizing
wet scrubber.
The primary objective of this test series was to determine the fate of six hazardous and four
nonhazardous trace metals fed to the RKS in a synthetic, organic-contaminated solid waste matrix. The
six hazardous trace metals used were arsenic, barium, cadmium, chromium, mercury, and lead. The
four nonhazardous trace metals-bismuth, copper, magnesium, and strontium-were included primarily to
supply data to evaluate their potential for use as surrogates. The test variables were kiln exit gas
temperature, waste feed chlorine content, and scrubber pressure drop. The test program objectives
were to identify
• The partitioning of metals among kiln ash, scrubber liquor, and flue gas,
• Changes in metal partitioning related to variations in kiln exit gas temperature and waste feed
chlorine content, ; .
• The efficiency of the Calvert scrubber for collecting flue gas metals, and
• The effects of scrubber pressure drop on metal collection efficiencies.
i
METHODOLOGY
The IRF RKS consists of a rotary kiln primary combustion chamber, a transition section, and a fired
afterburner chamber. The refractory lined kiln is 2.5 m long with an internal diameter of 1.0 m. The
afterburner chamber is also lined with refractory and measures 3.0 m long by 0.9 m in diameter. For
these tests, both the kiln and afterburner were fired on natural gas. Total heat input to the kiln varied
with test conditions, ranging from 200 to 580 kW (0.7 to 2.0 MMBtu/hr). Calculated gas-phase residence
time through the kiln and afterburner sections averaged 2.3 seconds.
i
The main components of the Calvert scrubber ARCS used during these tests were the
condenser/absorber, Calvert Collision Scrubber,™ entrainment separator, wet electrostatic precipitator,
72
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caustic tank and injection pump, and variable-speed induced draft fan. A schematic of the scrubber
system is shown in Figure 1. In its normal configuration the Calvert scrubber pilot plant also includes a
quencher/saturator and a cooling tower. However, these components were not used for this test
program because their functions were equivalently met by the existing RKS spray quench and closed-
loop heat exchanger.
FROM IRF
HEAT
EXCHANGER
PUMP CONDENSOR
ABSORBER
FAN
(VARIABLE SPEED)
WET
ELECTROSTATIC
PRECIPITATOR
Figure 1. Schematic of the Calvert scrubber system.
The combustion gas exiting the afterburner was saturated and cooled by the IRF spray quench to
approximately 82°C (180°F), then directed to the Calvert scrubber system. The first component of the
Calvert scrubber is the condenser/absorber, which is designed to sub-cool the flue gas to about 50 °C
(122°F) and to scrub acid gases. The condenser/absorber is followed by the Collision Scrubber.™ The
Collision Scrubber™ splits the flue gas into two streams then uses a head-on collision to create fine
droplets and a large surface area to enhance the removal of paniculate and remaining acid gases as the
flue gas passes through the venturi. The pressure drop through the scrubber is controlled through the
use of a variable speed induced draft fan, which provides an operating range of 7.4 to 17.4 kPa (30 to 70
in WC). A three-stage entrainment separator follows the Collision Scrubber™. For this test series, Calvert
Environmental installed a down-flow, tube type wet electrostatic precipitator with an entrainment
separator between the first entrainment separator and the induced draft fan. Scrubber liquor collected in
the sump of the condenser/absorber was pumped to either the IRF heat exchanger or quench system
recirculation tank.
The synthetic waste fired throughout the test program consisted of a mixture of organic liquids
added to a clay absorbent material. The base solid material was a calcined clay sold commercially as a
granular absorbent for spill cleanup. The main components of the clay are hydrated aluminum-
magnesium silicate, free silica, dolomite, and calcite. The organic liquid base for the synthetic waste
consisted of toluene with varying amounts of tetrachloroethene and chlorobenzene added to provide a
range of synthetic waste chlorine contents. Waste chlorine content in the combined feed was varied
from zero (no chlorinated organics added) to nominally four percent. After mixing, the clay/organic
mixture remained a free flowing solid, similar to the unspiked clay absorbent. The synthetic waste was
continuously fed to the rotary kiln via a screw feeder at a nominal rate of 63 kg/hr (140 Ib/hr) of which
approximately 14 kg/hr (30 Ib/hr) was the organic liquid matrix. For all tests, the kiln rotation rate was
held constant to provide a solids residence time of about an hour.
73
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0™o «it ?!, H.estl excef?t chromium and magnesium, were fed to the kiln by metering an
S £ « S°l iu" ? ,theTmetals Into the clay/°raanic liquid mixture at the screw feeder, just prior to
£ ±25"t0 he WrV Tt? !fSt meta'S Were added to the sPikin9 solution as sol^le ni rate salts,
S" °-f arsenicr W,hich was added as As*°3- Tne sPjke so1*'™ was metered at a rate that
on fol|owmg nominal synthetic waste feed concentrations in mg/kg: As-35; Ba-420- Bi-400-
' ~u'425: prb-5°: H9-5? Sr-430. Chromium and magnesium are native to the clay absorbent at '
concentrations of about 50 mg/kg and 2 percent, respectively, and so were not spiked.
The test variables were kiln exit gas temperature, chlorine content of the synthetic waste feed and
Calveit scrubber pressure drop. The test program consisted of 11 test points, with each parameter
varied over three levels. Achieved conditions for the test variables are shown in Table 1 Taraet kiln exit
gas temperatures were 538°, 816°, and 927°C (1000°, 1500°, and 1700°F). Target feed chlSrine
concentrations were 0, 1, and 4 percent. Thei scrubber pressure drop for Tests 1 through 9 was held
asTiTn^ Test points 10 and 11 were at the same nominal condftons
as test point 8, but with scrubber pressure drops of 8.7 and 17.4 kPa (35 and 70 in WC), respectively
All tests were performed at the same nominal afterburner exit flue gas O2 (9 percent) and afterburner exit
e kiln '
TABLED. TEST CONDITIONS
Test
Date
Average Kiln Exit
Gas Temperature
Waste Feed
Chlorine Content
Scrubber
Pressure Drop
(kPa) (in WC)
1
2
3
4
5
6
7
8
9
10
11
6/5/91
6/6/91
6/13/91
6/18/91
6/19/91
6/21/91
6/25/91
6/28/91
7/9/91
7/11/91
7/16/91
541
819
909
555
842
919
543
817
944
829
827
1,006
1,507
1,669
1,031
1,547
1,686
1,010
1,502
1,731
1,524
1,521
0.0
0.0
0.0
0.6
0.6
0.8
3.6
3.4
3.1
2.3
3.4
12.9
12.4
12.4
12.4
12.4
12.4
12.4
12.4
12.2
8.2
16.9
52
50
50
50
50
50
50
50
49
33
68
The sampling and analysis protocols were designed to track the partitioning of the test metals
among the RKS discharge streams (incinerator ash, scrubber liquor, and flue gas). For each test
composite samples of the clay/organic liquid mixture, aqueous metals spike solution, kiln ash and
scrubber liquor were collected. The feedrates and total quantity fed of the clay/organic liquid mixture
and the metals spike solution were carefully noted. Kiln ash weights and scrubber liquor volumes were
also determined for each test. The flue gas was sampled for metals at the quench and scrubber system
exits using a Method 101A train for mercury and a Method 5 train modified for multiple metals capture
for the remaining metals. , ^
Sample preparation and analysis methods documented in EPA SW-846 were used for most
ffIIP ^Zherdig,fst.ion and ana|ysis of samples for mercury were in accordance with the procedures of
Method 7470 for liquid samples and Method 7471 for solid samples, with analysis by cold vapor atomic
absorbtion spectroscopy. Solid samples analyzed for the remaining test metals were digested following
the procedures of ASTM Method E886, Method A. The samples were fused in a flux containing a 4 to 1
74
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ratio of lithium metaborate and lithium .tetraborate, followed by a final dissolution of the melt in dilute HCI.
The liquid samples were prepared for metals analysis in accordance with the procedures of Method
3010. Metals analysis was primarily by ICAP spectroscopy in accordance with the procedures of Method
6010, although graphite furnace atomic absorbtion spectroscopy in accordance with Methods 7060 and
7000 were used to analyze most samples for arsenic and bismuth, respectively.
RESULTS
Note: At the time this abstract was prepared, the only laboratory data received were for samples
analyzed for mercury. However, it is anticipated that data on the remaining metals will be
received in time for presentation at the symposium.
Table 2 summarizes the mercury partitioning as a percent of the mercury fed. For all tests mercury
concentrations in the kiln ash were below detection limits of 0.1 mg/kg. This is expected based on
mercury's high vapor pressure. Table 2 shows that mercury recovery in the flue gas at the quench exit
ranged from 17 to 113 percent of the mercury fed, averaging 66 percent. It is interesting to note that
although the recovery of mercury in the quench flue gas was good, the downstream recovery in the
scrubber liquor and scrubber exit flue gas was much lower. An explanation for this observation is
provided by Figure 2, which shows the mercury partitioning to the scrubber liquor as a function of the
waste feed chlorine content. For the three tests with no chlorine in the waste feed, mercury
concentrations in the scrubber liquor were reported below detection limits of 0.004 mg/L. With
increased feed chlorine content to about 0.6 percent, mercury partitioning to the liquor increased to
about 7 percent of the mercury fed. Mercury partitioning to the liquor increased to approximately 30
percent with a further increase in waste feed chlorine content to about 3.5 percent. In the case of no
chlorine in the waste feed, mercury is expected to be found in the flue gas in its elemental form or as
mercuric oxide. Both are practically insoluble in water, but would still be expected to be scrubbed from
the flue gas at the low temperatures reached in the Calvert scrubber. However, once collected in the
TABLE 2. MERCURY PARTITIONING AND SCRUBBER COLLECTION EFFICIENCIES
Mercury Partitioning (% of mercury fed) Mass Balance Closure (%)
Waste Feed Quench Scrubber
Chlorine Exit Exit
Test
1
2
3
4
5
6
7
8
9
10
11
Content
(%)
0.0
0.0
0.0
0.6
0.6
0.8
3.6
3.4
3.1
2.3
3.4
Kiln
Ash
<2.9
< 1.2
< 0.9
NA+
< 1.0
< 1 .0
< 1.0
< 0.8
< 1.1
< 1.2
< 1.1
Flue
Gas
112.7
23.0
16.8
93.8
67.8
86.5
69.2
NA
NA
77.0
75.1
Flue Scrubber
Gas
< 1.4
0.6
3.9
5.6
25.6
10.4
28.7
NA
NA
32.5
15.0
Liquor
< 1.8
< 1.3
< 1.0
5.2
6.8
9.9
30.2
29.3
29.3
34.9
15.4
Around Kiln
Ash and
Quench Exit
Flue Gas
115.6
24.2
17.7
93.8
68.8
87.5
70.2
NA
NA
78.2
76.2
Around Kiln
Ash and
Scrubber
Discharges
6.1
3.1
5.8
10.8
33.4
21.3
59.9
NA
NA
68.6
31.5
Calvert
Scrubber
Collection
Efficiency (%)
> 99
97
77
94
62
88
59
NA
NA
58
80 .
* Calculated as a percent of mercury fed using detection limit values for samples reported below
detection limits.
+ NA - Data not available.
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scrubber liquor, these insoluble forms of mercUry likely settled to the bottom of the liquor storage tank
and were not collected when the liquor sample was taken, even though the storage tank was mixed
before the sample was collected. For the tests: with chlorine in the feed, mercuric chloride may have
formed in the flue gas. Mercuric chloride is soluble in water and is more likely to be collected during
sampling of the scrubber liquor. The scrubber liquor partitioning data further suggests that the
conversion to mercuric chloride was directly related to the amount of chlorine available.
Waste Feed Chlorine Content (°/
Figure 2. Mercury partitioning to the scrubber liquor versus waste feed chlorine content.
Table 2 also shows the efficiency of the Calvert scrubber for removing mercury from the flue gas.
Scrubber efficiencies were determined by comparing the emission rate of mercury measured at the exit
of the quench and at the exit of the Calvert scrubber system. Thus, no credit is given for removal by the
quench. Collection efficiencies ranged from 58 to greater than 99 percent, averaging 79 percent.
Comparing Tests 10 and 11 with the remaining tests shows no apparent relationship between scrubber
pressure drop and collection efficiency over the range tested. Measured mercury flue gas
concentrations ranged from 0.034 to 0.21 mg/dscm at the quench exit and from less than 0.001 to 0.028
mg/dscm at the scrubber exit.
CONCLUSIONS
Although most of the metals data were not [received from the laboratory in time for this abstract, the
following conclusions can be made based on the mercury data received to date.
• As expected, mercury was volatile and was not found above detection limits in the kiln ash.
• The recovery of mercury in the scrubber liquor increased directly with increased chlorine content
in the waste feed. Insoluble elemental mercury or mercuric oxide are the expected forms in the
flue gas for the tests without chlorine, wfiile the presence of soluble mercuric chloride is
• suspected in cases with chlorine present.
• Calvert scrubber collection efficiencies for mercury ranged from 58 to greater than 99 percent,
averaging 79 percent. These efficiencies exclude any contribution by the quench for collecting
mercury.
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Engineering Analysis of Metals Emissions
from Waste Incinerators Field Data
R. G. Rizeq, W. Clark, and W. R. Seeker
Energy and Environmental Research Corporation
18 Mason, Irvine, CA 92718
To be presented at the
18th Annual RREL Research Symposium
Cincinnati, Ohio, April 14-16, 1992
EXTENDED ABSTRACT
Hazardous metals emitted from waste combustion devices pose a significant risk to human
health. In recognition of this, EPA/RREL has initiated a study to collect and evaluate all possible metal
emissions information from all combustion sources. This paper is a summary of this ongoing study.
The EPA has established risk-based limits on emissions of metals from waste combustion
systems. These limits are established in the form of regulations for boilers and industrial furnaces firing
hazardous waste and in the form of permitting guidelines for hazardous waste incinerators. The limits
can be quite restrictive and can often be the limiting factor on the design of air pollution control devices
for such facilities or on the types and quantities of wastes which can be burned. Over the past several
years, a significant body of data has been accumulated on metals emissions from full scale waste
combustion devices including:
• municipal solid waste incinerators,
sewage sludge waste incinerators,
hazardous waste incinerators,
boilers and industrial furnaces,
medical waste incinerators, and
mixed waste incinerators.
In addition, a number of laboratory and pilot scale studies on metals emissions and control have been
conducted. These data have been collected from tests with varying degrees of control, data quality,
and completeness of reporting. Often there has been little attempt to analyze the data beyond the
specific goals for which each test was conducted. Additionally, there have been few attempts to collate
the data and analyze it as a single unit.
Scope and Advantages of this Study
This presentation describes the analytical efforts of a project to assemble all available data on
metals emissions from waste combustion devices into a single data base, and to analyze the,data in an
attempt to isolate and explain the fundamental parameters which control metals emissions from waste
combustion devices. In particular, several concepts/questions based on fundamental mechanisms or
on common observations of metals emissions from combustion systems are proposed and examined in
light of the data:
Does metals volatilization dominate partitioning ?
Is volatilization controlled by combustion zone thermodynamic equilibrium ?
Does the metal feed rate control metals emissions ?
77
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Does the air pollution control device determine emissions ?
Data and theory are analyzed and arguments are advanced to support and/or refute some of these
concepts and their applications to metals behavior in waste combustion systems.
This analysis will help identify the factors which control metals emissions from waste
combustion devices. Understanding of these factors and their implications will ultimately help the
regulatory and permitting authorities to:
set flexible testing procedures for facilities to show,compliance with emission limits,
determine reasonable default values for estimation of air pollution control device
efficiency, and
• assess the maximum achievable control technology for metals emissions from waste
combustion devices.
In addition, the analysis will help the designers, and operators of waste combustion systems to minimize
metals emissions. •
Approach
The approach is to apply the current understanding to develop hypotheses on metals behavior based
on fundamental concepts and common observations. These hypotheses are then examined against
data relating metals emissions to waste characteristics and design/operating parameters. The steps to
this approach are: ;
I ' '
determine the fundamental concepts/questions of metals behavior that need to be
investigated and correlated to data,
gather data and develop a data base,
analyze data in light of the fundamental concepts/questions proposed and link metals
emissions data with theory,
identify correlations with design and operating parameters, and
draw conclusions from the analysis and provide recommendations for further work or
testing improvements. j
Availability and Assembly of Field Data
A data base is being established through collection of experimental data and fundamental
studies taken from various types of waste incinerators equipped with different types of air pollution
control devices (APCDs) at various operating conditions. The database includes detailed information of
each facility's hardware and operating parameters such as:
f
size and type of incinerator,
type of APCD, ;
primary and secondary combustion zone temperatures,
uncontrolled metals emissions,
• controlled metals emissions with detailed APCD operating parameters,
• feed rates of all wastes and metals,
• waste chlorine content, and
• other pertinent information.
The database allows the data to be easily retrieved and classified to aid comparison and analysis of the
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behavior of metals and other pollutant emissions from various facilities under selected operating
conditions.
Data Analysis
This section presents the fundamental points of investigation in light of their relation to the
engineering analysis of field test data. Discussion focuses on:
Statement of the fundamental concept of metals behavior
Theoretical background
Results from the engineering analysis of field data
• Conclusions / recommendations
The key fundamental concepts will highlight what influences metals emissions in practical waste
combustion systems. Therefore, to help set a base for a unified understanding of metals partitioning
behavior in various types of incinerators, several concepts can be developed. Some detail of each
concept follows.
Importance of Volatilization
The influence of variation in volatilization temperature on the removal of metals from the bottom
ash from field data is analyzed. Additional data are available for the impact of temperature on metals in
kiln ash and fine particulates, and on the flyash enrichment of volatile metals. It is concluded that
metals volatilization dominates partitioning. Notable exceptions are arsenic under certain conditions.
Metals Emissions may be Predicted by Equilibrium Thermodynamics
If thermodynamic equilibrium is controlling, then important parameters may include:
Combustion zone temperature: Temperature strongly influences the emissions of
volatile metals.
Amount of chlorine in waste: Chlorine in waste increases emissions of most metals.
Metals volatility: Metals emissions are related to their volatility if the metals
concentration in the combustion gas is the equilibrium saturated concentration. Data
for the emission concentrations of some metals as a function of metals volatility ranking
are available from trial burns of several hazardous waste facilities including Aptus, 3M,
Bros, and DuPont.
Field data shows that trends in metals emissions are consistent with the assumption of
combustion zone thermodynamic equilibrium. Effects of temperature and chlorine on metals emissions
can also be thermodynamically predicted.
Do Metals Feed Rates Control Metals Emissions ?
If a metal's concentration is undersaturated in the combustion gas, due to the vaporization of all
of the metal fed to the combustor, then the metal's emission rate is dominated by the feed rate of the
metal rather than its saturated concentration. Theoretical arguments and figures for the expected
behavior of metals emission rates as a function of metals feed rates are discussed. A comparison plot,
generated from field test data, for metals emission rates as a function of feed rates shows that metals
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emissions are influenced by feed rates when all of the metal vaporizes (i.e., the metal is unsaturated in
the combustion gas). . ,
How Much are Metals Emissions Dictated by APCDs ?
t
There are several types of air pollution control devices (APCDs). Theoretical descriptions of
key APCDs are discussed and field test data for control efficiencies of various types of APCDs are
presented including:
• Particulate emissions from trial burns of several hazardous waste facilities with diverse
APCDs including ESPs, baghouses, Venturis, scrubbers, and HEPA filters.
• Metals control efficiencies from various APCDs installed at municipal waste incinerators.
• Scrubber efficiency versus volatility temperature of several metals in a rotary kiln.
Venturi/packed bed scrubber control efficiency as a function of volatility temperature of
various metals for data obtained from the Mobay/EPA trial burn test program, 1988.
Baghouse control efficiency versus metals (ranked according to their volatility) from the
Aptus/EPA trial burn test program, 1989.
In conclusion, analyses of the above mentioned data indicate that air pollution control devices
dictate emissions.
Recommendations for Necessary Work .
Remaining research issues include:
Metals management requires more detailed understanding of the impact of systems
design/operation and waste parameters on metals behavior.
Important data gaps: '
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
Acknowledgement
Kinetics of metals transformation under conditions simulating waste combustion.
Hexavalent chromium chemistry.
Arsenic volatilization chemistry.
Innovative techniques to change the size distribution of metals.
Fragmentation and fly ash particle size and dependence on waste stream
properties.
Interactions of metals with Ca, Al, Si within burning beds of metal containing
materials.
Impact of physical/chemical of the waste on the behavior of metals.
High temperature liquid metal viscosity.
Monitoring strategies for fine particulate matter and metals emissions.
Waste characterization techniques for metals behavior.
Support for this project provided by the'U.S. EPA, Risk Reduction Engineering Laboratory
(Project No. 68-CO-0094) under the direction of Dr. C. C. Lee is gratefully acknowledged.
80
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EFFECT OF MUNICIPAL WASTE COMBUSTION ASH MONOFILL LEACHATE
ON SELECTED CONTAINMENT BARRIER COMPONENTS
David A. Carson
U. S. EPA
Risk Reduction Engineering Laboratory
26 West Martin Luther King Drive
Cincinnati, Ohio 45268
(513) 569-7527
Thomas A. Janszen
IT Corporation - Environmental Programs
11499 Chester Road
Cincinnati, Ohio 45246
(513) 782-4700
INTRODUCTION
This study was initiated to investigate the effects of municipal waste combustion (MWC) ash
monofill leachate on lining components of an MWC monofill. This includes geosynthetic materials and
natural clay (soil) liners. The ability of these materials to perform their design function for the life of the
facility and post-closure period is best estimated through accelerated test methods described herein.
The study consisted of two separate testing efforts, one aimed at evaluating selected natural clay linings
and the other at evaluating selected geosynthetics. Both tests were performed using the same waste.
Leachate was collected from two sources, one considered modern, and the other considered
older technology. Site A was a state-of-the-art MWC ash monofill leachate facility. This facility had a
scrubber, and ash disposed of in the monofill contained bottom ash, fly ash, and scrubber residue. Site
B was an older MWC ash monofill leachate facility. This facility did not have a scrubber. Ash disposed
of in the monofill contained bottom ash and fly ash.
The following generic geomembrane types were selected at random to be tested: high-density
polyethylene (HOPE), reinforced chlorosulfonated polyethylene (CSPE-R), and polyvinyl chloride (PVC).
One filtration/separation geosynthetic was tested: a nonwoven polyester geotextile. Three compacted
soils (Illinois, Lufkin, and Nacogdoches) were evaluated to determine their resistance to the two MWC
ash leachates.
The chemical resistance of three types of geomembranes and a nonwoven polyester geotextile
with samples of two MWC ash leachates was investigated in accordance with EPA Method 9090 and
associated supplementary guidance by determining whether the analytical and physical properties of
these materials were adversely affected by exposure to the two leachates. Analytical testing was
performed to fingerprint the geomembranes and the geotextile so that the results of these compatibility
studies could be used for comparison to help assess other geosynthetics that might be potential
candidates for use in constructing lining systems for MWC ash monofills. In addition, a series of pouch
tests was performed in which samples of the two leachates were sealed in the pouches prepared from
the three respective geomembranes.
81
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Part of the study was performed to determine any changes in the hydraulic conductivity of
compacted soils exposed to MWC leachate. The purpose of this study was to determine if the selected
compacted soils are chemically resistant to MWC ash leachate. Three compacted soils were evaluated
to determine their resistance to two MWC ash leachates. Samples of the three soils were compacted to
90 percent of proctor compaction (ASTM D 693) in double-ring permeameters. The compacted soils
were then permeated with water, followed by the MWC ash leachates, to determine the hydraulic
conductivity of the soil.
The objectives of this study were: 1) to evaluate the hydraulic conductivity changes of MWC ash
leachate on natural clay liners; 2) to provide study results to support requirements for lining MWC ash
disposal facilities; and 3) to determine if high-salt content of MWC ash leachate will affect the
permeability of natural clay liners; and 4) to determine the chemical resistance of geosynthetic products
to the collected leachates. ;
METHODOLOGY
A Sampling and Analysis Plan (SAP) was developed to establish procedures for obtaining
samples of ash and leachate from two MWC facilities selected for this study. Leachate was collected
from operating MWC facilities and their disposal monofills for use in conducting compatibility testing with
geosynthetic materials, and natural clay liners.
The results of analyzing the leachate saimples at the end of each exposure period show that the
contents of the cells remained essentially constant throughout the exposures. . ,
Natural Lining Components ,
Permeability changes to clay soils upon exposure to the two ash leachates were assessed using
SW 870's Appendix III C method, "Test Method for the Permeability of Compacted Clay Soils." Stainless
steel double-ring permeameters were used to evaluate the compatibility of three compacted soils with
two MWC ash leachates. Six samples of each of the soils were compacted to 90 percent of standard
proctor compaction (ASTM D 693) in 15-cm permeameter molds.
The compatibility test involved determination of the hydraulic conductivity of the compacted soil
to a standard leachate (0.005 N CaS04) followed by one of the two MWC ash leachates. MWC ash
leachates from Sites A and B were used in this study.
Compacted soil samples were prepared for hydraulic conductivity testing and their bulk density
was estimated. A double-ring insert, filter, and insert guide were carefully lowered over permeameter
molds until the inserts were firmly seated in the compacted soil samples. The base plate/mold
assemblies were turned over and geotextile filter material was placed over each compacted soil surface.
Water (0.005 N CaSO4 solution) was poured on each soil sample and a top plate was placed on each
mold. Air pressure over the water was slowly increased until 3 to 5 psi was attained along with stable
baseline hydraulic conductivities. The water was then removed from the surface of the soil samples and
replaced with MWC ash leachate.
The pore volumes of leachate that passed through the soil samples and the time increments
over which the leachate was collected were recorded for each compartment (inner and outer rings) of
the double-ring permeameters. The collected data were used to calculate both the total pore volume of
leachate that passed through each soil sample and the hydraulic conductivity of each sample.
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Electrical conductivity (EC) was used as an index parameter to document the breakthrough of
the leachate through the soil samples. Leachate that permeated the soil samples was collected and
divided into two 15-mL aliquots. EC measurements were made of the saturated paste extract of each
soil type, the water used in the study, and each of the MWC ash leachates.
Geosynthetics
Tests were performed on the unexposed and exposed geomembranes. This testing protocol
conformed to the testing requirements of Method 9090. U.S. EPA Method 9090, which was specifically
designed to assess the chemical resistance of geomembranes and waste liquids, is divided into two
parts; the first part deals with the exposure of geomembrane samples to a waste liquid, and the second
part is concerned with the specific tests performed on the geomembranes before and after exposure. In
this test, slab samples are immersed for up to 4 months at 23° and 50 °C in a representative sample of
the waste liquid or leachate that would be contained by the geomembrane. Analytical and physical tests
are performed on the unexposed geomembranes for baseline data and on samples exposed to the
waste liquid for 30, 60, 90, and 120 days.
Current U.S. EPA regulations require that all geosynthetics used in constructing a RCRA
hazardous waste management facility must be tested for chemical resistance with the waste to be
contained. Therefore, the U.S. EPA has proposed supplementary guidelines so that geosynthetics other
than geomembranes can be tested in accordance with Method 9090. This guidance states that all
geosynthetics are to be exposed under the conditions described in Method 9090.
The analytical properties and the extractables of the exposed samples were measured in
duplicate for the unexposed geomembranes, but only single determinations were made of the volatiles
contents. The volatiles and extractables were measured in accordance with Matrecon Test Methods 1
and 2. The tests indicate the type of leachate constituents that may have been absorbed by the
geomembrane (i.e., volatile or nonvolatile constituents) and whether the leachate extracted components
of the geomembrane compound such as plasticizers or antioxidants.
Integrity changes to geomembranes and a geosynthetic material were tested by exposing three
geomembranes and one geosynthetic material to the two field-collected ash leachates. Standardized
Method 9090 and current U.S. EPA guidance-specified test conditions were maintained; test criteria for
assessing integrity changes specified in Method 9090 and U.S. EPA guidance were also utilized.
RESULTS
Natural Lining Components
The passage of more than two pore volumes of MWC ash leachate (from Sites A and B) through
three compacted soil samples (Illinois, Lufkin, and Nacogdoches) showed no significant changes in
hydraulic conductivity of these soils. Because the hydraulic conductivity values of the three soils to both
MWC ash leachates did not significantly increase over the values to water, the soils were considered to
be chemically resistant to both MWC ash leachates used in the study.
Geosynthetics
The results of the chemical resistance test of the three geomembranes and the nonwoven
polyester geotextile at both 23° and 50 °C indicated that, within the 4 months of exposure to the two
83
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MWC ash leachates, the changes in analytical and physical properties were comparatively small. The
results for the HOPE geomembrane and the polyester geotextile indicate that neither of these materials
were affected by the immersion and thus are Considered to be chemically resistant to the two MWC ash
leachates to which they were exposed. The GSPE-R geomembrane showed essentially no change in
strength characteristics; however, the analytical properties which relate to the CSPE coatings showed
slight increases in volatiles and weight and a decrease in extractables. The values of all three of these
properties were continuing to change at the end of the 4 months of exposure. Also, there was a slight
trend downward in ply adhesion. During the 4 months of exposure, the PVC geomembrane also
exhibited little change in properties, indicating short-term compatibility. During the last 2 months of
exposure, however, the PVC showed a trend that could indicate long-term lack of chemical resistance.
To determine whether the trend is continuing, testing is underway with results expected in 1992.
The results for the CSPE-R geomembrane samples in each leachate indicate that the polyester
fabric reinforcement maintained its strength during the 5 months of exposure and showed no trends
toward change. The strength was judged by hydrostatic resistance, puncture resistance, and tensile
properties. Thus, like the polyester geotextile, this fabric is considered to be chemically resistant to each
of the MWC ash leachates. The CSPE coating showed slight effects of the immersion, however, and
slight continuing trends in the analytical properties. For example, the results of testing the CSPE-R
geomembrane showed that the geomembrane increased in weight (up to 7.4 percent), but that this
Increase resulted predominantly from water absorption. There were slight decreases in extractables, in
the case of the slabs immersed at 50°C. Also, there was a slight decrease in the ply adhesion between
the two layers of CSPE, which may reflect complete loss of adhesion to the fabric or some apparent loss
caused by the stiffening of the CSPE-R as a result of crosslinking.
In the case of the HOPE geomembrane, there were slight increases in the values for tensile at
yield, modulus of elasticity, tear strength, hydrostatic resistance, and hardness. These changes may
probably be attributed to a slight increase in crystallinity and hardening of the HOPE geomembrane
during the course of the exposure. There was! also a trend toward a slight loss in weight during
exposure, which may be a reflection of the extraction of the antioxidants from the HOPE compound.
During the 4 months of exposure to the two leachates, the PVC geomembrane samples showed
an increase in volatiles contents, a decrease in weight, and signs of a slight loss of plasticizer, especially
on exposure to the leachate with the higher concentration of salts. In physical properties, the tensile
strength tended to decrease, and the elongation at break tended to increase. In stresses at 100 and 200
percent elongation, the trends for most of the samples were slightly downward, except during the last
2 months, when the trends were upward, as were the puncture and hydrostatic resistances. The
hardness changes were small, but generally the trends were downward.
CONCLUSIONS
Tests were conducted on selected natural and synthetic lining components involving exposure to
specific collected MWC ash monofill leachate. Testing of natural lining components involved
observations of hydraulic conductivity and electrical conductivity. Testing of the geosynthetics involved
U. S. EPA Test Method 9090 with modifications where required. The results of the testing indicate that
with proper engineering considerations, carefully selected materials can be expected to perform as
designed.
These test results indicate a series of tests that are likely to be performed during the permitting
and prior to construction of any waste disposal facility and are to be considered results specific to the
two leachate samples and selected barrier components collected for the purposes of this study. No
84
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inferences are to be made regarding the materials or procedures used herein regarding any other
combination of lining materials or waste that is intended to be contained. Site specific testing and
analyses are the only accurate way to determine lining component chemical resistance with the waste to
be contained. The test methods used in this study are currently accepted methods of accelerating long-
term exposure.
The intention of this study was to determine if existing lining technologies were capable of
serving to contain MWC ash monofills. This study has determined that there are materials that do exist
that proved their potential utility under these accelerated exposure testing scenarios, on two specific
leachates. Soil, geosyntetic material and leachate quality variations preclude the authors from
extrapolating any chemical resistance issues beyond the components and procedures discussed in the
study and project final report.
REFERENCES
Koerner, Robert M., editor. 1990. "Chemical Resistance Evaluation of Geosynthetics Used In Waste
Management Applications," Geosynthetic Testing for Waste Containment Applications. ASTM STP-1081.
American Society for Testing and Materials, Philadelphia, PA, 1990.
United States Environmental Protection Agency. 1986. Test Methods for Evaluating Solid Waste. 3rd
Edition. EPA/SW-846. Office of Solid Waste and Emergency Response, Washington, DC.
United States Environmental Protection Agency. 1988. Lining of Waste Containment and Other
Impoundment Facilities. EPA/600/2-88/052 (NTIS PB-89-129670). Risk Reduction Engineering
Laboratory, Office of Research and Development, Cincinnati, Ohio.
85
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SOLIDIFICATION/STABILIZATION FOR LEAD BATTERY SITE
A TWO STAGE PROGRAM
Jerry Isenburg
University of Cincinnati
USEPA Center Hill Facility
5995 Center Hill Rd.
Cincinnati, Ohio 45224
513-569-7663
Extended Abstract
INTRODUCTION
Solidification/Stabilization (S/S) technology uses binders added to hazardous waste such as
contaminated soil to accomplish two goals:
1. to render the toxic metal in the soil insoluble (stabilize) and
2. to develop physical strength for handling and disposal (solidify).
The binders contain a net alkalinity which resists leaching by acidic TCLP (EPA SW846, Method 3811)
solutions and also react to form hydraulic binding constituents. The two goals are not necessarily
synonymous however. Some solidifiers do not stabilize and some stable systems are soil like or even
slurries. For disposal in land fills, both properties are desirable. The goal of this project was to collect
data on these properties to support S/S as a Best Demonstrated Available Technology (BOAT) for soils
contaminated by lead. This abstract is a partial summary of the on site engineering report (1).
This project consisted of two stages. Both stages are presented here chronologically since they
were not planned together but do depend on each other. Both stages subjected a soil typical of lead
battery sites to a spectrum of carefully designed S/S recipes. These recipes used only generic binder
systems. The primary target for the project was to attain TCLP lead concentrations below 5 mg/l, and
a secondary target was a minimum unconfined compressive strength (UCS) of 345 kPa (50 psi).
Site And Soil Characteristics
The site chosen to supply the waste was a battery breaking site in Pennsylvania. This choice
was made because the primary contaminant was lead, the site was accessible, and contamination from
organic wastes was a minimum. Four samples were taken. Results of an on site survey with a field
x-ray spectrophotometer indicated that two samples would contain over 20,000 ppm lead and the
other two would contain a little less than 10,000 ppm lead. The composite was expected to fall in
the range of 15,000 to 20,000 ppm lead. All soil was screened on site to pass a 3/8-inch sieve to
omit battery pieces, and the appearance of the soil was a dark damp silty-clay-peat.
Analyses of the untreated soil after compositing of the four samples showed the following:
1. Metals analysis of solids
Iron 21000 ppm
Lead 21000 ppm
Aluminum 6700 ppm
All others below 1000 ppm
86
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2. TCLP: elements failing Toxicity Characteristics level
Lead: 91 mg/l, limit: 5 mg/l
3. Total Organic Carbon: 170,000 ppm
4-. Moisture: 27.7%
5. pH: 4.3
METHODOLOGY I
We have previously demonstrated a method to design S/S recipes that will pass the TCLP test
(2). The objective of this method is to create conditions at the end of the TCLP test which minimize
the solubility of lead. Lead exhibits minimum solubility at about pH 8 to 10. To attain this desired pH
at the end of the TCLP test, the indigenous alkalinity of contaminated soils needs to be augmented by
the amount that will neutralize the acid specified by the TCLP plus enough to raise the pH to 8 to 10.
We have previously developed a laboratory procedure to measure the acid neutralization capacity of
solids (3). This test has been used to determine the acid neutralization capacity of several binders (4).
These binder values have been previously used in a procedure to select types and amounts of binders
for treating a lead contaminated soil at a battery disposal site (5).
In this project three binder types were selected:
1. all portland cement- has a dependable chemistry and high alkalinity
2. 3 parts Type F fly ash to 2 parts quicklime- minimum weight of alkaline binder
3. 2 parts cement kiln dust to 1 part Type F fly ash- both waste products having low cost
The mix design plots of p.H versus acid reactant added allow prediction of one mix design for
minimum lead in TCLP leachate and another for minimum binder added to pass the TC list limit. These
two criteria lead to the following recipes:
mix #1.16% portland cement- minimum cement level
2. 20% portland cement- minimum lead in leachate
3. 8.5% quicklime + 12.75% fly ash- minimum binder
4. 10.5% quicklime + 15.75% fly ash- minimum lead in leachate
5. 24% cement kiln dust + 12% fly ash- minimum kiln dust level
6. 28% cement kiln dust + 14% fly ash- minimum lead in leachate
These six mixes were prepared in a standard laboratory mixer with sufficient water to reach
a common flow table consistency. They were cast in cylinders and cured in a 100% relative humidity
chamber for 28 days while set was being monitored by penetrometer on small samples. Mixes one
and two set hard. Mixes three and four stiffened but did not set completely. Mixes five and six did
not set by 28 days. The UCS values for the six mixes were, in order, 462, 503, 241, 207, 0, 0 kPa.
87
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RESULTS I
The TCLP test were run on the UCS fragments. All the samples failed the TC level of 5 mg/l
of lead. In addition, the pH's at the end of leaching were, in order, 5.26, 6.31, 5.3, 6.12, 5.44, 5.73
where the target pH was 8 to 9.75. j . ,
CONCLUSIONS I
Another EPA project at Center Hill was evaluating the GANC/MANC test. The UCS fragments
from the first phase of this project were tested using the GANC/MANC test (5). The acid neutralization
capacity of the samples cured for the standard 28 days was less than was predicted from an algebraic
combination of the 24 hour GANC test values for the mix ingredients. Measurements of the lead
released during the GANC test (MANC) at various pH's showed that the lead in the leachate would
have been low enough to pass the TC level if the pH had been in the target range of 8 to 1.0.
METHODOLOGY II ,
-'-'''
The original mix calculations were studied in relation to the actual GANC results for the mixes.
For each binder type, there seemed to be a single multiplier that would increase the GANC equivalents
of acidity measured on the waste such that the prediction equation would give the GANC values
actually demonstrated by the mixes. These factors were used to predict the increase in binder required
to bring the pH to the desired level. The essence of this assumption is that the waste is more acid
than the GANG showed it to be in 48 hours of contact. The following three mixes were designed by
increasing the acidity of the soil by a constant factor and increasing the binder quantities accordingly.
Note that the price of the high organic content was at least a doubling of the binder requirement.
mix # 7. 45% Portland cement
8. 31 % quicklime + 46.5% fly ash
9. 93% cement kiln dust + 46.5% fly ash ...-.,•
A major change in acid neutralization capacity during curing of the sample has not been
observed in previous applications of the GANC test to mix designs. A study of the literature for factors
that could change the acidity of a soil between 2 and 28 days in these conditions led to identification
of possible organic reactions. Cellulose molecules can be oxidized to acid groups when they are
activated by alkaline exposure. That suggests that the problem is the 17% total organic carbon tied
up in the soil. To test this hypothesis, one more mix was prepared which removed most of the organic
materials by ashing the soil at 300°C and then preparation of one of the failed mixes with correction
for the loss in water and organics weight during ashing. The following mix was chosen to complete
Phase II of this work:
mix #10. 20% Portland cement based on weight before ashing- comparable to mix 2.
The ashing process showed 17% weight loss from ignition excluding the water loss on drying.
This is not a complete removal of organics but the structures are probably oxidized enough to show
little further changes in acidity.
The mixes all set by 28 days. The UCS values were, in order, 2612, 197, 178, 1618 kPa.
while the second and third mixes did not achieve the 345 kPa level desired, they did develop sufficient
strength for many disposal situations and can be expected to develop strength over a longer time.than
the cement samples.
88
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RESULTS II
The pH at the end of the TCLP leaching tests was, in order, 11.11, 10.52, 11.65, and 8.90.
All of these would be predicted to pass the TC level of 5 mg/l of teachable lead. The actual results
from the TCLP were, in order, Below Detection Limit (BDL) of 0.2 , 1.5, 0.51, BDL mg/l. All samples
of Stage II passed the TC level for lead!
CONCLUSIONS AND RECOMMENDATIONS
1. S/S is recommended as a BDAT for lead contaminated soil.
2. Natural peat type organic materials in the soil appear to interfere with the effectiveness of
the binders. This can increase the binder requirement for effective stabilization to over twice
the level required in the absence of the organics.
3. The current GANG test for raw soil is not able to detect the longer time organic reactions
shown by this soil.
4. Any of several generic binder systems can be used to achieve TC levels of lead teachability.
5. Portland cement sets faster and provides the best strength at one month age when used at
the level required for stabilization.
6. These mix design procedures will work reliably if all the acid/base reactions are detected.
Recommendations
1. The GANG test should be revised to account for organic acid/base reactions.
2. Binder selection can be based on alkalinity and cost instead of previous testing only.
3. Biological reduction of total organic carbon contents should be researched for sites such as
the Brown's Battery Breaking site. Composting is a much more desirable treatment than
burning to prepare the soil for S/S.
REFERENCES
Report 1. "Onsite Engineering Report For Solidification/Stabilization Treatment Testing Of Contami-
nated Soils," IT Environmental Programs Inc., USEPA Contract No. 68-C9-0036, Manager:
R. P. Lauch, RREL, in preparation.
Paper 2. Isenburg, J. E. and McCandless, R. M.,"Engineering The Solidification/Stabilization Of Heavy
Metal Contaminated Wastes," presented at WASCON Conference, Maastrict, Netherlands,
November, 1991, publication pending.
Paper 3. Isenburg, J. E. and Moore, M. R., "Generalized Acid Neutralization Procedure (GANG),"
Stabilization and Solidification of Hazardous, Radioactive, and Mixed Wastes, 2nd Volume,
ASTM STP 1123, T.M. Gilliam and C. C. Wiles, Eds., American Society for Testing and
Materials, Philadelphia, 1992, pp. 361-377.
Report 4. Isenburg, J. E., "Binder Characterization Study," report in process
Report 5. "Solidification/Stabilization Treatability Assessment Report, Kassouf-Kimmerling Battery
(KKB) NPL Site," by University of Cincinnati for USEPA Region IV, Atlanta, Georgia,
September 1990.
89
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ROTARY KILN INCINERATION OF SPENT 'PQTLINER FROM THE MANUFACTURE OF ALUMINUM
Ronald J Turner
U.S. Environmental Protection Agency
26 West Martin Luther King Driye
Cincinnati, Ohio 45268
INTRODUCTION
The process of developing treatability information on the RCRA listed
waste, K088 (spent potliner from the primary reduction of aluminum), consisted
of waste characterizations at three facilities, selection of the "worst case"
with respect to cyanide and fluoride, and incineration. These data were made
available to ERA'sOffice of Solid Wastes and the aluminum industry.
Incineration was selected as an appropriate treatment process as the spent
potliner samples contained over 30 percent fixed carbon, greater than 5000
BTU/lb heat values, and cyanide is destroyed by thermal incineration.
INDUSTRY AND WASTE CHARACTERIZATION
All primary aluminum produced in the United States is made by the Hall-
Heroult Process. Aluminum is refined by dissolving alumina in a molten
cryolite (NagAlF6) bath and then introducing electric current. The reduction
takes place in carbon-lined steel and refractory cells or pots. The carbon
liner serves as the cathode. This lining becomes impregnated with the
cryolite and metal over time and failures occur. A service life of 3 to 5
years for a potliner is common. The upper portions of the carbon lining from
the bottom and side walls is "first cut" and is classified as K088. The
"second cut" material is thermal insulation and is not K088. The mechanism by
which cyanide is formed in the potliner is not discussed in the literature,
but carbides and nitrides of aluminum are known to be present in the carbon
lining. Table 1 presents a summary of the K088 waste characterizations.
Facility Three was selected for the test burn program.
INCINERATOR TEST CONDITIONS ;
The objectives for these tests were to establish whether the potliner
could be incinerated and to characterize the residuals. The rotary kiln
incineration system at the Incineration Research Facility, Jefferson, AK.
was employed for the tests. Cyanide was considered as the principal organic
hazardous constituent (POHC), and is the primary constituent of concern.
Three tests were conducted under essentially the same operating conditions,
except for exit temperatures. The planned incinerator operation conditions
are summarized in Table 2. These conditions were chosen to maximize the
carbon burn out. The actual kiln operating conditions achieved for each test
are summarized in Table 3. f
TEST RESULTS
Three composite waste feed samples and two composite kiln ash samples
were collected. One set of flue gas: analyses was completed each test day. The
90
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scrubber system was operated at total recycle for the three test days, and one
composite scrubber liquor sample was collected. Table 4 summarizes the
proximate and silica analysis results. Approximately half of the original
carbon content was oxidized during the incineration test. About 80 percent of
the ash content was discharged as kiln ash; the remainder was either
volatilized or entrained as particulate in the flue gas.
Table 5 summarizes the cyanide concentrations for all samples analyzed.
The first test samples contained an average of 5,200 mg/kg total cyanide. The
waste fed during the second and third days contained less cyanide, or about
3,500 mg/kg. Kiln ash cyanide content varied from test to test, and from
sample to sample within a test day. Measured levels were in the range of 60
to 330 mg/kg. Kiln ash leachates contained estimated cyanide levels, ranging
from 0.5 to 0.6 mg/L for the Test 1 ash, and 3 to 4 mg/L for Test 2 and 3 ash.
No cyanide was detected in the scrubber liquor or scrubber exit flue gas
samples.
The cyanide destruction/removal efficiency (ORE) data are given in Table
6. The DREs were better than 99.9999 percent at both the scrubber exit and at
the stack for Test 1, and 99.99987 for Tests 2 and 3. The fraction of cyanide
remaining in the kiln ash was calculated to be 2.7 percent of the feed, so
97.3 percent was removed by the incineration process.
Kiln ash fluoride levels were comparable to the waste levels (1.3 to 6.8
percent). The leachate levels were generally less than 100 mg/L (one sample
result was 668 mg/L fluoride). The kiln ash contained about 64 percent of the
waste feed fluoride.
CONCLUSIONS
The kiln ash contained measurable cyanide and carbon burn out was not
complete. The K088 material formed slag at temperatures above 1800 degrees F.
This was in contrast to the results of the preliminary ash fusion tests which
indicated a 2700 degree F fusion temperature. About 20 percent of the kiln
ash collected was slag removed from the kiln after completion of the tests.
About a 30 percent reduction in waste weight occurred with this incineration
test. Tests will be conducted to determine whether the fluoride in the kiln
ash requires further treatment to restrict its Teachability.
REFERENCES
Whitworth, W.E., Lee, J.W., Waterland, L.R. Pilot-Scale Incineration Tests of
Spent Potliners from the Primary Reduction of Aluminum (K088). U.S.
Environmental Protection Agency, Cincinnati, Ohio
91
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TABLE 1. K088 CHARACTERIZATION DATA SUMMARY
Constituent
Fluoride
Cyanide
Arsenic
Barium
Cadmi urn
Chromium
Lead
Mercury
Selenium
Silver
Nickel
Percent Moisture
Percent Ash
Percent Volatile
Percent Fixed Carbon
Btu/lb
Ash Fusion Temp (°F)
Facility 1
(mq/kq)
I
17,700
810
<2.2j
145 i
<0.42
35.9^
8.7 1
<0.085
<3.4;
<0.025
13.7;
0.02!
47.79
0.05[
52.14
7338!
2220!
Facility 2
(mq/kq)
18,000
1,010
<25.7
153
<0.28
18.4
11.7
<0.097
<2.2
<0.37
6.0
0.78
53.04
3.32
42.86
6074
2275
Facility 3
(mq/kq)
20,000
9,190
<1.1
149
0.69
41.1
16.7
<0.093
10.8
<0.39
52.3
0.37
59.21
4.18
36.24
5394 '
2700+
TABLE 2. TARGET TEST CONDITIONS
Total waste feedrate
Kiln temperature
Kiln exit flue gas 02
Afterburner temperature j
Afterburner exit flue gaj> 02
Scrubber blowdown flowrate
Scrubber liquor flowrate|
Scrubber pressure drop
Scrubber liquor pH
68 kg/hr (150 Ib/hr)
980 °C(1,800°F) ,
10 percent
1,090°C(2,000°F)
7 percent
0 L/min (total recycle)
230 L/min (60 gpm)
1.5 kPa (6 in WC)
7.5 to 8.0
TABLE 3. KILN OPERATING CONDITIONS
Parameter
Test 1
(1/15/91)
Test 2
(1/16/91)
Test 3
(1/17/91)
Average natural gas feedrate
scm/hr 49!
(scfh) (H720)
kW 504
(kBtu/hr) (H720)
46
1,609)
471
(1,609)
43
1,526)
447
(1,526)
92
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TABLE 3. KILN OPERATING CONDITIONS (continued)
Parameter
Test 1 Test 2
(1/15/91) (1/16/91)
Test 3
(1/17/91)
Average combustion air flowrate
scm/hr 408 410 395
(scfh) (14,400) (14,470) (13,950)
Average total air flowrate
scm/hr 1,297 1,320 1,249
(scfh) (45,790) (46,610) 44,090)
Average kiln draft
Pa 12 15 15
(in WC) (0.05) (0.06) (0.06)
Exit temperature
Range, °C 962-1,062 954-1016 922-1012
Range, (F) (1,764-1,944) (1,7649-1,861) (1,692-1,853)
Average, °C 999 984 972
Average, (°F) (1,830) (1,803) (1,781)
Exit 02
Range, % 9.6-12.3 9.9-12.8 9.7-11.4
Average, % 11.0 11.6 11.4
Average waste feedrate
kg/hr 66.4 62.2 66.8
(Ib/hr) (146) (137) (147)
TABLE 4. PROXIMATE AND SILICA ANALYSIS RESULTS
Concentration, wt %
Samp! e
Test 1 (1/15/91):
Waste la
Kiln ash la
Waste Ib
Kiln ash Ib
Waste Ic
Test 2 (1/16/91):
Waste 2a
Kiln ash 2a
Waste 2b
Kiln ash 2b
Waste 2c
Test 3 (1/17/91):
Waste 3a
Kiln ash 3a
Waste 3b
Kiln ash 3b
Waste 3c
Fixed
carbon
33.0
21.5
34.7
25.4
31.3
34.2
27.7
34.8
26.1
33.8
37.4
28.9
36.4
20.3
38.8
Volatile
matter
2.4
2.1
2.5
1.3
,3.1
3.5
4.0
4.8
3.7
3.6
-5.4
2.3
5.4
3.6
4.0
Total Fixed
plus volatile
35.4
23.6
37.2
26.7
34.4
37.7
31.7
39.6
29.8
37.4
42.8
31.2
41.8
23.9
42.8
Moisture Ash Silica
0.1
0.1
0.02
0.1
0.2
0.2
0.1
0.2
0.1
0.2
0.1
0.1
0.2
0.1
0.2
64.6
76.3
62.7
73.2
65.4
62.1
68.2
60.2
70.1
62.4
57.1
68.7
58.0
76.0
57.6
3.4
7.3
3.3
4.0
3.7
5.6
5.5
5.3
5.4
5.7
5.9
5.6
5.5
5.7
6.3
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TABLE 5. CYANIDE ANALYSIS RESULTS
Sample
Test 1 (1/15/91):
Waste la, mg/kg
Kiln ash la, mg/kg
Kiln ash la TCJ.P leachate, mg/L
Scrubber liquor filtrate la, mg/1
Scrubber liquor solids la, mg/kg
Waste Ib, mg/kg
Kiln ash Ib, mg/kg
Kiln ash TCLP leachate, mg/L
Scrubber liquor filtrate Ib, mg/L
Scrubber liquor solids Ib, mg/kg;
Waste Ic, mg/kg
Scrubber exit flue gas, /tg/dscm
Stack gas, /ig/dscm
Test 2 (1/16/91):
Waste 2a, mg/kg
Kiln ash 2a, mg/kg i
Kiln ash 2a,TCLP leachate, mg/L
Scrubber liquor filtrate 2a, mg/L
Scrubber liquor solids 2a, mg/kg
Waste 2b, mg/kg
Kiln ash 2b, mg/kg
Kiln ash 2b TCLP leachate, mg/L ;
Scrubber liquor filtrate 2b, mg/L
Scrubber liquor solids 2b, mg/dscm
Waste 2c, mg/kg
Scrubber exit flue gas, /ig/dscm i
Stack gas /ig/kg ;
Test 3 (1/17/91):
Waste 3a, mg/kg
Kiln ash 3a, mg/kg
Kiln ash 3a TCLP leachate, mg/L
Scrubber liquor filtrate 3a, mg/L
Scrubber liquor solids 3a, mg/kg
Waste 3b, mg/kg
Kiln ash 3b, mg/kg
Kiln ash 3b TCLP leachate, mg/L
Scrubber liquor filtrate, mg/L
Scrubber liquor solids 3b, mg/kg
Waste 3c, mg/kg
Scrubber exit flue gas, /ig/dscm
Stack gas, /ig/dscm
Total CN
5,290
60
0.51
<0.005
<5
4,550
130
0.58
<0.0005
<5
5,880
<0.16
<0.14
3,200
90
3.1
<0.005
<5
3,500
330
3.2
<0.005
<5
3,500
<0.15
<0.14
3,390
260
4.0
<0.005
<5
3,500
130
3.3
<0.500
<5
3,800
<0.16
<0.15
Amenable Fraction
CN amenable, %
5,120
36
0.21
NAa
NA
4,430
40
1.17
NA
NA
5,780
NA
NA
2,700
20
<0.005
NA
NA
2,970
170
<0.005
NA
NA
3,000
NA
NA
2,930
190
1.6
NA
, NA
2,900 '
90
<0.005
NA
NA
3,100
NA
NA
96.8
60.0
41.2
97.4
30.8
98.3
84.4
22.2
<0.2
84.9
51.5
<0.2
85.7
86.4
73.1
40.0
'
82.9
56.3
<0.2
81.6
•
"NA « Not analyzed.
performed.
If total CN not detected, amenable CN analysis'not
94
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TABLE 6 CYANIDE DREs
Parameter
Test 1
d/15/91)
lest z
(1/16/91)
lest 3
d/17/91)
Waste Feed:
Waste feedrate, kg/hr 72 68 72
Average CN concentration, mg/kg 5,240 3,4QO 3,560
CN feedrate, g/hr 377 231 . 256
Scrubber exit flue gas:
CN concentration, /zg/dscm <0.16 <0.15 <0.16
Flue gas flowrate, dscm/min 29.5 34.6 35.2
Flue gas CN emission rate, /fg/hr <280 <310 <340
CN ORE, % >99.99993 >99.99987 >99.99987
Stack gas:
CN concentration, /zg/dscm <0.14 <0.14 <0.15
Flue gas flowrate, dscm/min 33.0 , 35.5 36.6
Flue gas CN emission rate, #g/hr <280 <300 <330
CN DRE,% >99.99993 >99.99987 >99.99987
95
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SELECTIVE RECOVERY OF NICKEL AND COBALT FROM ELECTRQMAGHINING PROCESS
SOLUTIONS
David Dahnke, Dale Flynn, Scott Shuey and Larry Twidwell
INTRODUCTION
Department of Metallurgical and Mineral Processing Engineering
Montana College of Mineral Science and Technology
Butte, Montana 59701
(406) 496 4208
Background
An extremely large data base has been generated at Montana Tech for the treatment of a wide
variety of sludge materials. Emphasis has been given to the treatment of electroplating and
electromachining sludge materials. These investigations have shown that a series of hyclrometallurgical
unit operations can be performed to selectively recover all metal values from the hydroxide waste
materials. Four publications (1-4) and ten master of science theses (5-14) have been completed that are
directly related to this project, e.g., the theses include the following: Laney has investigated the
effectiveness of leaching electroplating and electromachining sludge materials in sulfuric acid and the
use of solvent extraction reagents to recover copper and zinc from the produced multicomponent sludge
leach solutions (5); Dahnke has summarized research on zinc and iron solvent extraction, and his work
produced the initial data upon which the phosphate process is based (6); Arthur investigated the
application of the phosphate process to chloride-bearing sludge leach solutions (7); Konda investigated
Iron-zinc separations from high zinc solution in a sulfate solvent matrix (8); McGrath studied the
speclation of chromium in phosphate-bearing solutions and the kinetics of chromium phosphate
precipitation (9); Rapkoch studied the phosphate precipitation of trivalent cations from the
ammonia/ammonium sulfate system (10); Nordwick conducted studies on the rate of conversion of ferric
phosphate to ferric hydroxide (11); Quinn investigated the conversion of chromium phosphate to other
more marketable products by soda ash fusion (12); Flynn investigated the use of cyanide complexation
for separation of nickel from cobalt (13); and Shuey (14) is presently investigating refinements on the
cyanide process for selectively separating nickel from cobalt and subsequently recoveririq the cobalt in a
high purity form.
Because of the problem of summarizing and representing such a large amount of data in the
brief space available, the approach used in this presentation is to summarize the results and conclusions
without including a great deal of detail concerning the separation process. The authors are, therefore,
relying on the reader to solicit copies of individual theses and publications of interest. The emphasis in
this presentation will be placed on the treatment of electrochemical machining sludges; especially on the
selective separation of nickel from cobalt. Also, research that is presently in progress will be reported
and discussed in the oral presentation, i.e., methods studied to recover high purity cobalt from nickel
depleted cyanide solutions.
ECM Sludges
Electrochemical machining (ECM) sludge materials are produced as a result of electrolyte
solution treatment. During the ECM process, the work piece is dissolved into the electrolyte by an
electrochemical depleting reaction. Because the efficiency and control of the ECM process is partly
dependent on the chemistry of the electrolyte solution, simple water treatment technologies are used to
control the concentration of dissolved metals in'the electrolyte. A highly oxidized Heavy metal hydroxide
sludge results from the electrolyte treatment operations. After filtration, the sludge materials are
generally supplied as a feed material to a pyrometallurgical operation or are disposed of in hazardous
waste sites. The waste material contains appreciable metal values.
METHODOLOGY
Phosphate precipitation has been investigated and demonstrated to be successful for selectively
separating trivalent cations from divalent cations in complex mixed metal leach solutions produced from
electroplating sludge materials by Twidwell, Dahnke, and others (1-4). These investigators, have also
shown that trfvatent chromium can be effectively separated from trivalent iron in the presence of divalent
nickel and cobalt (4). The flowsheet for the phosphate process is presented in Figure 1.
96
-------
The application of phosphate precipitation technology also has been shown to be appropriate
for treating ECM sludge leach solutions for the removal of iron and the recovery of chromium (2).
However, the separation of divalent cations such as nickel and cobalt one from the other requires an
approach other than phosphate precipitation. Figure 2 shows the unit operation sequence for the
treatment of ECM hydroxide sludge materials using cyanide complexation, nickelic hydroxide
precipitation, and cobalt recovery by acid baking, redissolution and electrowinning.
SLUDGE
T-KTC
pH-12
TO NON- *—I / L,
HAZARDOUS
DISPOSAL
pH-3
T-25'C
Zn
SX
I
Ni/Co PRECIPITATION
ZnS04
CRYSTALLIZATION
1 CAUSTIC 21
TO NI/Co SEPARATION
I
TO WASTEWATER TREATMENT
AND/OR RECYCLE
NaCN
NaOH
BLEACH
NICKEL-COBALT
DISSOLUTION
NlgO 3 PRODUCT
Co METAL PRODUCT
Figure 1. Metal value recovery from electroplating
and electromachining sludges.
Figure 2. Selective separation of nickel and
cobalt by cyanide complexation.
The nickel-cobalt starting materials were prepared by treating ECM sludge by the flowsheet (2)
presented in Figure 1, e.g., the sludge was leached in sulfuric acid, filtered, iron was precipitated and
filtered as ferric phosphate, chromium was precipitated and filtered as chromium phosphate, and
nickel/cobalt was precipitated and filtered as hydroxides. The starting ECM sludge material was
supplied by Lehr Corporation and its composition is presented in Table 1. The resulting nickel/cobalt
hydroxide material composition is presented in Table 2.
The nickel/cobalt material was treated as depicted in the flowsheet presented in Figure 2.
Bench scale tests were conducted in one-liter reaction vessels and large scale tests were conducted in
twenty liter batches. Solution pH, Eh, and temperature were monitored throughout each test. Solutions
and solids were sampled periodically during each test to establish the influence of time on the test
results. Solids were examined by both x-ray diffraction and scanning electron microscopy/energy
dispersive (SEM/EDX) analysis. Solid compositions were determined by digestion and induction
coupled plasma (ICP) analysis. Solutions were analyzed by ICP procedures.
97
-------
Source
TABLE 1. AS-RECEIVED ELECTROCHEMICAL MACHINING SLUDGE:
Solids Composition, %
Fe Cr Ni Co Nb Ti Mo Al Ca Na
LehrCorp. 11.34 4.88 14.88 3.97 0.78 p.28 1.5 0.03 0.68 11.20
Starting Material Solid Content: 35.27%
TABLE 2. NICKEL/COBALT HYDROXIDE STARTING MATERIAL COMPOSITION
Batch
Solids Composition, %
Ni
Co
Fe
Cr
Lehr#1,Dry
Lehr #2, Wet
Lehr #3, Wet
Lehr #4, Wet
mean
mean
mean
mean
15.97
3.98
4.19
6.63
3.97
1.04
1.13
1.75
0.05
0.01
0.01
0.01
0.23
0.03
-------
precipitate containing a nickel/cobalt ratio of 692/1 and a cobalt solution free (within detection limits)
of nickel within ten minutes.
• The influence of the amount of added cyanide on the purity of the nickelic hydroxide precipitate and
cobalt bearing leach solution was evaluated for the following conditions: five gpl nickel, 1.25 gpl
cobalt, pH 14, one hour residence time, and amount/rate of hypochlorite as above. The
stoichiometric requirement for cyanide (for complete complexation) is eight moles of cyanide per
mole of nickel plus cobalt. Any cyanide above this amount would have to be oxidized prior to the
oxidation of the nickelo-tetracyano complexes thus requiring the expense of additional oxidant.
Therefore, the smallest addition of cyanide that produces acceptable products should be used. The
following stoichiometric amounts were experimentally investigated: 0.5, 0.75, 1.0, 1.5.
The influence of the stoichiometric amount of cyanide is not important with respect to effective
removal of nickel from the solution phase but is very important with respect to the purity of the
nickelic hydroxide solid. A deficiency of cyanide in solution significantly increases the level of cobalt
contamination in the nickelic hydroxide precipitate. Therefore, an excess above the stoichiometric
amount is required to maintain a high purity solid product. The nickel/cobalt and cobalt/nickel ratios
in the solid phase and in the solution phase were (at 1.5 times the stoichiometric requirement) 690/1
and 186/1, respectively.
• The influence of the amount of added oxidant on the purity of the nickelic hydroxide precipitate and
cobalt bearing leach solution was evaluated for the following conditions: five gpl nickel, 1.25 gpl
cobalt, pH 14, one hour residence time, and 1.5 times the stoichiometric requirement of cyanide. The
following hypochlorite (5.25%) amounts were investigated: addition (at a rate of 10 ml/minute) of 25
ml (13.125 gpl), 50 ml (26.250 gpl), 75 ml (39.375 gpl), and 100 ml (52.500 gpl) per 100 ml of starting
solution.
The influence of the amount of oxidant is not important with respect to the purity of the precipitated
nickelic hydroxide but is important with respect to the effective removal of nickel from the solution
phase. Greater than 75 ml of oxidant were required for effective nickel removal from solution. The
nickel/cobalt ratio in the solid phase for this condition was 591/1 and the solution nickel content was
below the ICP detection limit (therefore, the cobalt/nickel ratio in the solution was greater than
228/1).
Cobalt Recovery by Acid Baking
A survey of techniques to recover cobalt from the cobalt hexa-cyano complex was conducted
by Flynn (13). The techniques experimentally investigated included: direct electrowinning cobalt from
solution, acid baking/electrowinning of cobalt metal, and high temperature fusion. The only treatment
technique shown to be feasible was acid baking/electrowinning.
Preliminary test work was conducted to establish reagent requirements. Evaporation of one liter
of cobalt solution resulted in the formation of 194 grams of solid product. The off-gases were collected,
scrubbed and analyzed for cyanide during the bake operation. No cyanide was detected. This is in
agreement with literature statements that no undecomposed cyanide is produced during the
decomposition process. X-ray diffraction analysis of the acid bake product confirmed that the product
was cobalt sulfate and other sodium, chlorine, and sulfate compounds. The cobalt concentration in the
product was approximately three percent.
Sufficient quantity of this residue was produced to investigate electrowinning. The solid was
dissolved in sufficient water to produce a solution containing 20 gpl cobalt (pH 5.9). This solution was
placed in a small electrowinning cell using titanium anodes and lead cathodes with surface areas of 0.25
drrr. At a current density of 1.5 amperes and 6.5 volts, a deposit of 99+% cobalt metal was produced in
five hours.
Other test work presently underway includes: destruction of the nickel cyanide complex by
hydrogen peroxide with subsequent recovery of the cobalt by electrowinning; and recovery of the cobalt
by precipitation as a cobalt naphthate solid (a marketable product).
99
-------
1.
2.
CONCLUSIONS
Experimental test work has shown that nickel and cobalt can be effectively separated and
recovered in the form of marketable products from mixed metal hydroxide electrochemical machining
sludge materials by first producing a mixed nickel/cobalt hydroxide material. The nickel/cobalt
hydroxide materials can be redissolved in a calistic cyanide solution. Nickelic hydroxide can be
selectively and effectively precipitated from the solution by a dilute hypochlorite solution. The resulting
cobalt bearing solution can be reacted by acid baking/electrowinning to recover metallic cobalt.
References
Twidwell, LG. and Dahnke, D.R. Metal Value Recovery from Metal Hydroxide Sludqes: Removal of
Iron and Recovery of Chromium. NTIS PB-88176078. Cincinnati, OH. Dec. 1987. *
Twiawell, LG. and Dahnke, D.R. Metal Value Recovery from Alloy Chemical Milling Waste: Phase
II. EPA Contract No. 68-02-4432. Dec., 1987.
3. Twidwell, LG., Dahnke, D.R., and McGratH, S.F. Detoxification of and Metal Value Recovery from
Metal Finishing Sludge Materials, jn: H. Freeman (ed.), Innovative Haz. Waste Treatment
Technology Series, Physical Chemical Processes. Vol. 2, Chapter 2.6. 1990. pp 515-61.
Dahnke, D.R., Twidwell, LG. and Robins, R.G. Selective Iron Removal from Process Solutions by
Phosphate Precipitation. Jn: J.E. Dutrizac and A. J. Monhemius (ed.), Iron Control in
Hydrometallurgy, Ellis Horwood, Publisher; Chapter 23. 1986. pp 477-503.
Laney, D.G. The Application of Solvent Extraction to Complex Metal-Bearing Solutions. M.S.
Thesis. Montana College of Mineral Science and Technology, Butte, MT. 1984. 140 pp.
Dahnke, D.R. Removal of Iron from Acidic Aqueous Solutions. M.S. Thesis. Montana College of
Mineral Science and Technology, Butte, MT. 1985.
7. Arthur, B. Treatment of Iron, Chromium, and Nickel Aqueous Chloride Acidic Solutions by
Phosphate Precipitation. M.S. Thesis. Montana College of Mineral Science and Technology, Butte
MT. May 1987.
8. Konda, E. Study of Ferric Phosphate Precipitation as a Means of Iron Removal from Zinc Bearing
Acidic Aqueous Solutions. M.S. Thesis. Montana College of Mineral Science and Technology,
Butte, MT. May 1986. » ay,
9. McGrath, S. Rate of Chromium Precipitation from Phosphate Solutions. M.S. Thesis. Montana
College of Mineral Science and Technology, Butte, MT. May 1992.
10. Rapkoch, J. Effects of Substituting Ammonium Hydroxide for Sodium Hydroxide on Metal
Phosphate Solubilities in Complex Metal Bearing Solutions. M.S. Thesis. Montana College of
Mineral Science and Technology, Butte, Mf. May 1988.
11. Nordwick, S. Conversion of Ferric Phosphate Dehydrate to Ferric Hydroxide. M.S. Thesis.
Montana College of Mineral Science and Technology, Butte, MT. May 1987.
12, Quinn, J. Conversion of Chromium Phosphate by Sodium Carbonate Fusion. M.S. Thesis. Montana
College of Mineral Science and Technology, Butte, MT. May 1988.
13. Rynn, D.R. Recovery of Nickel and Cobalt from Electromachining Process Solutions. M.S. Thesis.
Montana College of Mineral Science and Technology, Butte, MT. May 1990.
t
14. Shuey, S., New Techniques for Separating Nickel from Cobalt. M.S. Thesis, Montana College of
Mineral Science and Technology, May 1992.
4.
5.
6.
100
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U.S. EPA Symposium Presentation
Treatment of Dilute Hazardous Waste Streams by Sorption/Anaerobic StabUization
Margaret J. Kupferle*
Tsaichu Chen
Vicente J. Gallardo
David E. Lindberg
Paul L. Bishop
University of Cincinnati
Department of Civil and Environmental Engineering
Cincinnati, Ohio 45221-0071
DolloffF. Bishop
Steven I. Safferman
U.S. Environmental Protection Agency
Risk Reduction Engineering Laboratory
26 W. Martin Luther King Drive
Cincinnati, Ohio 45268
ABSTRACT
Many wastewater streams contain dilute concentrations of organic pollutants that
are not treated effectively by conventional activated sludge processes. These
pollutants, however, can often be treated effectively anaerobically. If the pollutants
were treated anaerobically, pass-through of the pollutants to the receiving stream and
stripping of volatile compounds during aeration could be minimized. To treat the entire
wastewater stream in an anaerobic digester would not be economical. However, if the
bulk liquid stream could first be passed through a sorbent bed such as granular
activated carbon (GAC) prior to aeration, only the sorbent material, a much smaller
volume, would require anaerobic stabilization at elevated temperatures.
* Presenter
101
-------
Feasibility studies have been completed for a system employing GAC coated with
anaerobic biomass as the sorbent material. Two 87 L/day bench-scale systems were
operated for 331 days, one treating unspiked primary effluent and one treating primary
effluent spiked with 5% landfill leachate and fourteen hazardous organic compounds
(Table 1). Each system had two stages (Figures 1 and 2). The first stage was operated
as a sorption unit, and the second stage was operated as a stabilization unit. The
sorption stage was operated at a two-day carbon retention time (CRT) and an empty
bed contact time of 30 minutes. The target CRT in the stabilization stage was 15 days;
the hydraulic retention tune in this stage approached infinity because the supernatant
associated with the GAC exchanges was separated from the GAC and returned to the
reactor.
In order to establish system capacity for removal of the spiked organic
compounds, grab samples of the sorption stage influent and effluent were collected for
GC/MS analysis of volatiles (EPA Method 1624B) and semivolatiles (EPA Method
1625B) two tunes every three weeks. Grab samples of the off-gases were tested for
spiked volatile compounds several times during the course of the study using gas
chromatography with a PID/Hall detector. Sorption stage influent and effluent samples
for monitoring total and soluble chemical oxygen demand removals initially were
collected as daily grab samples and later as two-day composites. Samples for
monitoring sulfate reduction and for assessing the impact of the sorption stage on other
wastewater characteristics important to the downstream aerobic process, e.g., total
i
suspended solids, nitrogen forms and total phophorus were collected and analyzed
102
-------
according to EPA methods. In addition, pH, bicarbonate alkalinity, volatile acids, gas
production and composition, temperature, GAC bed volume, and influent, spike and
recirculation flowrates were routinely monitored throughout operation of the
experimental systems.
Background concentrations of the selected organics in the primary effluent and
landfill leachate used as feed stock for the study varied substantially with time; the
chemical oxygen demand (COD) also varied substantially. The variability is related to
the diverse industrial contributions and combined sewer stormwater flows received by
the Mill Creek Plant, the source of primary effluent in the study. The variability of the
concentrations of the organics and COD entering the sorption stage of the process
provided a real world test of the process on low strength but complex wastewater.
The spiked organic compound removal data for the year-long study are
summarized in Table 1. Average removals were the highest for the aromatic
compounds. Five of the sk aromatics added were removed at over 95% and the sixth,
phenol, had an 85% removal. Removals of chlorinated aliphatic compound ranged
from 50% for methylene chloride to 95% for trichloroethylene. Removals of phthalate
compounds were approximately 60%. Removals of ketones ranged from 24% for
acetone to 93% for methyl isobutyl ketone. Analytical interferences due to the
ubiquitous presence of methylene chloride in the analytical laboratory may have
contributed to the low removals of methylene chloride. The spiked organics that
substantially passed through the process (acetone and the phthalates) are readily
removed by subsequent efficient aerobic treatment.
103
-------
The data for the wastewater characteristics of the sorption stage influent and
effluent samples are sumarized in Table 2 for both the unspiked and spiked systems.
Average COD removals in both the unspiked and spiked systems consistently
remained at 40-50% throughout the year-long study. The resulting reduced COD
loading to the aeration process would substantially reduce air requirements and waste
aerobic biomass (such as waste activated sludge) in subsequent aerobic treatment.
Sulfate reduction in the range of 15% was observed in the two systems. Total and
volatile suspended solids (TSS and VSS) removals in the range of 20-25% and 4-7%
were observed in the unspiked and spiked systems, respectively. The difference in
removal efficiency may be related to the presence of methanogenic activity in the
sorption stage of the spiked system. Even at the short hydraulic retention time used in
the sorption stage, methanogenic activity was noted in the spiked system; it was not
observed in the unspiked system. Methanogenic activity in the spiked system was
stimulated by the readily-degradable substrate, methanol, which was used as a carrier
for the spike. The other parameters, i.e., nitrogen species and total phophorus, were
i
not significantly affected by the presence of the sorption stage.
This feasibility study, performed at bench-scale with complex real-world wastes,
demonstrated that the experimental system was capable of consistently removing
40-50% of the influent COD for a year-long period. No GAC replacement was
necessary during this time. The reduction of COD discharged to the aeration basin
would reduce aeration requirements as well as aerobic sludge production in actual
application. In addition, the stabilization process produces methane from the removed
104
-------
COD which potentially would be recoverable as fuel for heating the reactor. When
hazardous compounds are present in the influent waste, the sorption stage is capable
of trapping significant amounts, preventing their pass-through to the aeration basin and
subsequent volatilization of the strippable chemicals. The sorption stage also
attenuates the effects of shock loads of compounds which may be toxic to the aerobic
portion of the plant. In addition, the combined sorption/anaerobic stabilization stage
retention time for GAC, and, therefore, biomass and sorbed organics, is extremely high,
maximizing the potential for degradation of compounds which are normally recalcitrant
at conventional treatment plant retention times.
105
-------
CD
CD
"o
o
cu
=©=
D
Recycle pump
-©—
Spike
Syringe pump
T
Influent
Feed pump
Primary
Effluent
and
Leachate
Feed Drum
Figure 1. Sorption Stage of the Experimental
Bench-Scale System
106
-------
Sight tube
Sampling
port for
supernatant
Diaphragm
pump for —
recirculation
of supernatant
Flexible sleeve
coupling for
GAC/biomass
transfers
GAC/biomass
ready for
transfer
Figure 2. Stabilization Stage of the Experimental
Bench-Scale System
107
-------
TABLE 1. Spiked Compound Removals in the Sorption Stage of the Spiked System
Influent
(ug/L)
Mean §D*
VOLATILES
Acetone*
Methyl Ethyl Ketone1
Methyl Isobutyl Ketone*
Toluene2
Ethylbenzene2
Chlorobenzene2
Methylene Chloride3
1,1-Dichloroethane3
TricHoroethylene3
SEMIVOLATILES
Dibutylphthalate4
Bis(2-Ethylhexyl)phthalate 4
Nitrobenzene2
Trichlorobenzene2
Phenol2
2340
599
640
483
72
83
44
65
57
47
129
129
55
132
i
1440
410
495
291
61
49
28
55
36
50
267
108
44
97
Effluent
(ug/L)
Mean SD
1770
144
45
18
2.3
3
21
14
2.6
16
56
4
3
20
1170
80
40
14
3.5
3
29
10
2.4
33
82
10
6
19
Percent
Removal
24
76
93
96
97
96
50
78
95
66
57
97
95
85
* SD » Standard Deviation
L Ketone 2 Aromatic 3 Chlorinated aliphatic 4 Phthalate
108
-------
TABLE 2. Wastewater Characteristics Data Summary for Sorption Stage
PARAMETER
Total COD**
Soluble COD**
Sulfate#
##
TSS#
##
VSS#
##
TKN-N #
NH3-N#
NO3-N #
NO2-N #
Total P #
UNSPIKED SYSTEM
Influent Effluent Percent
mg/L mg/L Removal
Mean SD* Mean SD
241
149
238
165
68
62
54
40
31
24
0.22
<0
3.51
* SD = Standard Deviation
96
59
56
37
53
20
42
15
10
8
0.16
.1
1.11
**
145
80
239
137
50
49
42
32
29
24
0.22
<
3.54
59
37
70
27
44
25
37
16
9
8
0.18
0.1
1.40
4/23/90-3/20/91
40
46
0
17
25
21
22
20
6
0
0
-1
SPIKED SYSTEM
Influent Effluent Percent
mg/L mg/L Removal
Mean SD Mean SD
352
252
228
176
91
73
68
47
42
35
0.27
<
3.56
100
92
59
45
51
26
41
16
8
7
0.18
:0.1
1.01
#4/23/90-9/29/90
200
111
231
151
87
68
64
45
40
35
0.26
<
3.51
58
44
64
41
73
24
43
15
7
7
0.18
0.1
1.41
43
56
-1
14
4
7
6
4
5
0
4
-
1
##10/23/90-3/20/91
109
-------
IENT OF A NOVEL BIOFILTER FOR AEROBIC BIODEGRADATION OF
VOLATILE ORGANIC COMPOUNDS (VOCs)
Rakesh Govind, Vivek Utgikar, Y. Shan, Wang Zhao, Department of Chemical
Engineering, University of Cincinnati, Cincinnati, OH 45221 (513) 556-2666
Gregory D. Sayles, Dolloff F. Bishop, Steven I. Safferman, U.S. EPA,, RREL,
Cincinnati, OH 45268 (513) 569-7629
INTRODUCTION
In recent years, the emission into the atmosphere of volatile organic
compounds (VOCs) has undergone increased regulation by EPA, OSHA and other
government agencies due to potential human health hazards. The sources of these
VOCs include releases during industrial production arid use, from contaminated
wastewaters in collection systems and treatment plants, and from hazardous wastes in
landfills and contaminated ground water.
Conventional methods for treating VOC emissions include adsorption on solids.
absorption in solvents, incineration and catalytic oxidation. One alternative to these
conventional treatment methods is the biological destruction of the VOCs On gas phase
biofilters. This method has the advantage of pollution destruction (as compared to
transfer to another medium) at lower operation and maintenance costs. The biofilter
method also can be combined with various stripping or vapor extraction separation
processes which effectively transfer VOGs from liquid or solid matrices into the gas
phase entering biofilters.
i
Many immobilized-cell reactors contain films of biomass growing on some type
of adsorbent particle. They include trickling filters used for wastewater treatment,
packed beds proposed for ethanol production, and several fluidized bed designs for
anaerobic fermentations and aerobic and anaerobic wastewater treatment. Fluidized
beds of floe particles, such as tower fermenters and sludge-blanket reactors can also
be considered immobilized cell reactors because they represent the limiting case as
the size of the support particle goes to zero.
Immobilized cell reactors provide several advantages, the principal differences
being superior mass transfer at higher cell densities, no washout problems, and
capability to operate in a continuous fashion.
However immobilized cell reactors share the common problem of mass transfer
resistance associated with the biomass film, i.e., the substrate must diffuse in and
product must diffuse out. This creates a region of low substrate and high product
concentration on the inside surface of the biofilm, thereby severely inhibiting
metabolic activity. This requires that biofilm thickness should be minimized to prevent
diffusional limitations from occuring in the process.
Furthermore, for packed bed designs, growth of biomass causes plugging of
the bed, causing high pressure drop problems in the operation. The growth of
biomass is especially rapid in aerobic systems. Hence, control of biofilm thickness is
an important part of immobilized-cell reactor design.
Traditionally, the term 'biofilter* has been used to define processes that use
compost, peat, bark, soil, or mixtures of these substances as the filter medium. These
media serve as a support system for a microbial population. Filter media is underlain
110
-------
with a gas distribution system, commonly perforated pipe. Gases flow through the bed
where the pollutants are adsorbed to the filter media. After contact with the
microorganisms the pollutants are broken dqwn thus regenerating the adsorption
capacity of the bed. Water is sprayed over the bed's surface or by humidifying the
influent gases. The terms "soil filters", "soil biofilters", or "soil beds" delineate
processes where the filter media is soil. Soil biofilters are generally less permeable to
gas flow than biofliters that use compost, peat, or bark media thus a larger soil biofilter
area is required for the same back pressure.
Biofilters and soil filters have been applied to control odors from wastewater
treatment plants and industrial processes since 1953 (1). Recently, these processes
have been used for volatile organic compound emisssions removal from chemical and
process industries (2,3,4). Other processes mentioned in the literature that employ
biological treatment of waste gases include bioscrubbers and tricking filters (4,5).
Recently, experimental data has been obtained on a packed bed biofilter for the
biodegradation of methylene chloride, trichioroethylene, and toluene (6,7). Complete
removal of these compounds from air was demonstrated using the packed bed biofilter
system.
METHODOLOGY
This paper reports on the experimental study of the biodagradation of volatile
organic compounds present in the landfill leachates in a novel aerobic biofilter. The
most abundant compounds in leachate streams were targeted for study. A stripping
study was carried out on the selected compounds to confirm Henry's law constant
values.
The predominant VOCs from a landfill leachate stream were treated in a bench
scale biofilter. The following five chemicals (substrates) were targeted for this study at
the following feed concentrations: Toluene: 450 ppm; Methylene Chloride: 150 ppm;
Trichioroethylene: 25 ppm, Chlorobenzene: 40 ppm, and Ethyl benzene: 20 ppm. The
compounds were fed in vapor form to the biofilter in air. The required composition of
the compounds in the gas phase was achieved by making the synthetic gas mixtures in
a cylinder and blending with air. This was done to ensure a uniform feed concentration
to the biofilter. Nutrient solution was circulated countercurrent to the gas through the
bed. The inlet and outlet gas streams were analyzed for the above five chemicals using
a gas chromatograph (EPA standard method 602).
The biomass acclimated to the above compounds was obtained in the following
manner: Biomass from a pilot scale activated sludge plant treating hazardous waste
was suspended in the bioreactor (column 100 mm dia., 700 mm height). The bioreactor'
was fed daily With the five compounds. Nutrients necessary for biomass growth were
added periodically. The biomass from the bioreactor was transferred to the biofilter by
circulating the bioreactor suspension through the biofilter. It was found that the
biomass could be effectively transferred from the bioreactor to the support media in
the biofilter.
The novel biofilter, developed through our research, consists of a square cross-
section (100 mm x 100 mm) extruded ceramic monolith structure (celite, Manville
Corporation, CA), with 99 square straight passages (6 mm x 6 mm). The biomass
111
-------
exists as a uniform film immobilized on the inner surface of each straight passage. The
biofilm is attached to the support material and enables simultaneous diffusion and
degradation of the organics.
The major differences between the novel biofilter and the other immobilized cell
bioreactors are as follows:
1. The immobilized cell biofilter contains straight passages for the flow of
gas/liquid phase, thereby providing liquid phase shear, to maintain a. thin biofilm
on the support structure. This is distinctly different from a packed bed
containing support particles, wherein the excessive biomass that shears off the
particles becomes lodged in the interstitial spaces between the packed
particles, and cannot leave the bed easily. In the biofilter, the straight
passages enable the excessive biomass growth to leave the biofilter due to the
shear forces exerted by the flow of liquid through the straight passages.
2. The straight passages for gas flow also minimizes the pressure drop in the
biofilter. In the case of expanded packed beds, or fluidized beds, for typical
adsorbents, such as activated carbon, there is significant liquid pressure
needed to expand the packed bed of particles or fluidize them. Minimizing the
pressure drop also minimizes the pumping cost for the gas phase, which
constitutes the major operating cost for the biofilter process.
3. Stratification of the microorganisms in the biofilter occurs for a gas stream
containing mixed substrates. In mixed substrate systems, the biomass culture
immobilized in the biofilter at different heights gets naturally adapted to
different organics, depending on their biodegradation kinetics. This
stratification of the culture, not present in well-mixed systems, is a distinctive
feature of plug-flow type bioreactors.
RESULTS
Removal efficiency of the biofilter for a compound was defined as the amount of
compound removed from the gas phase;expressed as a percentage of the amount of
that compound fed to the biofilter through the gas phase. The removal efficiency can
be calculated simply by taking the ratio of the difference in the inlet and outlet
concentrations of the compound in the gas phase to the concentration of the
compound at the inlet. It was found that the amount of compound removed from the
gas phase that can be accounted for by the increase in the liquid phase concentration
of the compound was negligible. This meant that the compound removed in the
biofilter by the trickling nutrient flow was negligible as compared to the feed rate of
the compound.
Figure 1 shows the percent removal efficiency for the five influent compounds
as a function of time. Note that the percent removal efficiency for TCE is increasing as
the microorganisms are getting acclimated to the chemical. Measurements of the
cumulative net increase in carbon dioxide concentration, between the inlet and outlet
gas streams, have been made to confirm the overall carbon balance. Measurements of
the increase in concentration of the chloride ion in the liquid nutrient flow have been
made to confirm the degradation of the chlorinated compounds. No degradation
products were found to exist, as determined by GC and GC/MS analysis, in the outlet
gas stream. Careful measurement of the total gas phase pressure drop allows an
indirect measurement of the average biofilm thickness. This parameter has been used
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to confirm the validity of a lumped parameter dimensionless mathematical model, which
can be used to scale-up the biofilter.
CONCLUSIONS
It has been shown that a biofilter is a viable technology for treating gas phase
organic contaminants. Complete aerobic degradation of trichloroehylene, although at
less than 100% removal efficiency, has been demonstrated in the novel biofilter.
Furthermore, it has been demonstrated that the straight passages biofilter does not
plug-up due to biomass growth, as in the case of packed beds, and has an overall
lower gas phase pressure drop.
REFERENCES
1.
2.
3.
4.
5.
6.
7.
Carlson D.A. and Leiser, C.P. Soil beds for the control of sewage odors. J. Wat.
Pollut. Contr. Fed. 38: 829, 1966.
Ottengraf S.P.P. and van den Oever, H.C. Kinetics of organic compound
removal from waste gases with a biological filter. Biotech. Bioeng. 25: 3089,
1983.
Ottengraf S.P.P., et. al. Biological Elimination of Volatile Xenobiotic
Compounds in Biofilters. Bioprocess Engineering. (Netherlands) 1: 61, 1986.
Ottengraf S.P.P. Biological Systems for Waste Gas Elimination., Trends
Biotechnol. (Netherlands), 5/5, 132, 1987.
Brauer H. Biological Purification of Waste Gases. International Chemical
Engineering. 26, 3, 387, 1986.
Bishop F. and Govind, R. Degradation of gas phase contaminants in a Biofilter
Disclosure. August 7, 1990.
Govind R. Biodegradation of organics in a Biofilter, Quarterly Reports
Submitted to the Project Officer, U.S. EPA, 1990-1991.
100
u
c
0)
o
e
0)
o:
0 30
Time (day")
Figure 1: Removal Efficiency for the straight passages biofilter
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ONSITE BIOLOGICAL PRETREATMENT FOLLOWED BY
POTW TREATMENT OF CERCLA LEACHATES
E. Radha Krishnan, Roy C. Haught, Ruma Nath, and Srinivas Krishnan
IT Corporation
11499 Chester Road
Cincinnati, Ohio 45246
Makram T. Suidan and Mohammed N. Islam
Department of Civil and Environmental Engineering
University of Cincinnati
Cincinnati, Ohio 45221-0071
Richhrd C. Brenner
U.S. Environmental Protection Agency
26 W. Martin Luther King Drive
Cincinnati, Ohio 45268
INTRODUCTION
A study was conducted at the U.S. EPA's Test & Evaluation (T&E) Facility in Cincinnati, Ohio, to
investigate the effectiveness of two types of anaerobic fixed-film biological reactors in pretreating
hazardous landfill leachates containing synthetic organic chemicals (SOCs) prior to discharge to publicly
owned treatment works (POTWs). Various anaerobic treatment processes have been used successfully
In the past to treat municipal leachates, with emphasis placed on chemical oxygen demand (COD)
removal. This study evaluated the processes of anaerobic biodegradation using upflow, packed-bed,
anaerobic filters (bench-scale and pilot-scale) and an upflow, granular activated carbon (GAC),
expanded-bed, anaerobic reactor (bench- scale). These units are highly suited for treating high strength,
Inhibitory wastes similar in characteristics to the leachate used in this study.
Conventional wastewater treatment plants are often incapable of satisfactory removal of hazardous
substances from polluted water. The current method for treating hazardous landfill leachates usually
involves aerobic treatment, which may be inadequate under the Comprehensive Environmental
Response, Compensation, and Liability Act (CERCLA) because of the following reasons:
a) Air stripping of volatile organic compounds,
b) Incomplete treatment of semivolatile organic compounds, and
c) Difficulty in degrading chlorinated compounds.
i . .
Anaerobic biological pretreatment is expected to reduce such problems because of the
substantially smaller volume of exhaust gas produced and the reductive dehalogenation capabilities of
anaerobic microorganisms. The leachate for th? study was obtained from a large commercial municipal
landfill (Rumpke) in Georgetown, Ohio. The leachate was rendered hazardous by supplementing it wjth
a mixture of ten volatile and four semivolatile organic compounds. A list of these 14 toxic; organic
compounds, with their corresponding target concentrations, is provided in Table 1.
The goals of this study were to: 1) establish the effectiveness of anaerobic pretreatment using
GAC, expanded-bed, anaerobic reactors and upflow, packed-bed, anaerobic filters in removing organic
compounds, Including chloroform; 2) compare the performance of the bench-scale, upflow, packed-bed,
anaerobic filter (B1) versus the GAC, expanded-bed, anaerobic reactor (B2); 3) compare the
performance of the bench-scale, upflow, packed-bed, anaerobic filter (B1) versus a similarly-operated
pilot-scale, packed-bed, anaerobic filter (P1); 4) evaluate the toxicity of chloroform in removal of toxic
114
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organics in the leachate in each of the three bioreactors; 5) observe potential problems such as bed
plugging and calcium carbonate deposition on the GAG medium; and 6) determine the actual retention
time of the contaminants in the bench- and pilot-scale, packed-bed, anaerobic filters using lithium
chloride as a tracer material. This paper reports on the performance of these systems over a period of 2
years during which effective process control was maintained. The experimental treatment systems were
operated at the U.S. EPA T&E Facility in Cincinnati, Ohio.
TABLE 1. COMPOSITION OF SOC SUPPLEMENT TO THE LEACHATE
Compounds
Concentration (ua/L)
VOLATILE ORGANIC COMPOUNDS
Acetone 10,000
Methyl Ethyl Ketone 5,000
Methyl Isobutyl Ketone 1,000
Trichloroethylene 400
1,1-Dichloroethane 100
Methylene Chloride 1,200
Chloroform 0 to 2,000
Chlorobenzene 1,100
Ethylbenzene 600
Toluene 8,000
SEMIVOLATILE ORGANIC COMPOUNDS
Phenol 2,600
Nitrobenzene 500
1,2,4-Trichlorobenzene 200
Dibutyl Phthalate 200
METHODOLOGY
The bench-scale anaerobic pretreatment units consisted of an upflow, packed-bed, anaerobic filter
(B1) and a GAG, expanded-bed, anaerobic reactor (B2). These units were fabricated using plexiglass
and installed to treat municipal leachates rendered hazardous by the addition of 14 SOCs. The growth
support medium in the B1 column (15.2 cm diameter x 122 cm high) was 2.54-cm diameter
polypropylene pall rings. The growth support medium in the B2 column (10.2 cm diameter x 106 cm
high) was 1.0 kg of 16 x 20 U.S. Mesh Granular Activated Carbon (GAC). Each of these bioreactors was
coupled with a second-stage, bench-scale, aerobic treatment system (simulating a POTW) consisting of
a primary clarifier, aeration basin, and secondary clarifier. Raw municipal leachate was fed to each
bench-scale anaerobic reactor from a sealed, chilled, mixed, oxygen-free, stainless steel reservoir
through stainless steel lines. A stock solution of the SOCs was fed into the suction side of each recycle
loop along with the leachate. The pilot-scale pretreatment system (P1) consisted of a 129-cm diameter
by 229-cm high upflow anaerobic filter, packed with polypropylene rings, coupled with a second-stage,
pilot-scale, primary clarification/activated sludge aerobic system. All three anaerobic pretreatment units
were operated at 35°C and a pH range of 7-7.5.
All the bioreactors were fed with the Rumpke leachate, which was characterized by COD levels
ranging between 400 and 2,500 mg/L. Due to its relatively low biodegradable content during the first 6
months of the project, the leachate was supplemented with a mixture of equal portions of organic acids
(acetic, propionic, and butyric) to maintain the bioreactor influent COD at 1,600 mg/L This practice was
discontinued during the course of the study in order to evaluate biodegradation under the natural
varying COD concentrations of the leachate. Leachate sulfate concentrations ranged from 3 - 300 mg/L.
115
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The flow rate to the B1 and B2 columns was nominally set at 10 L/day. The leachate flow rate into
P1 was Initially regulated at 0.57 L/minute. Off gases from each of the bioreactors were measured using
wet-tip gas meters, connected at the top of each of the units. Daily measurements of total gas
production, feed flow rates, spike flow rates, reactor temperatures, and reactor pH values were recorded.
Samples were analyzed throughout the test period for SOCs, total and soluble COD, sulfate, and off-gas
composition. Metals, SOC composition in the off gas, total and volatile suspended solids, and ammonia
nitrogen were measured weekly on selected sampling periods.
The experimental period can be divided into five distinct phases for the B1, B2, and P1 bioreactors.
During Phase 1, each of the systems was acclimated for approximately two months to the Rumpke
leachate. In this phase, the leachate flow rates in the bioreactors were gradually increased and adjusted
at design specifications. The leachate flow rate was adjusted to 10 L/day in each of the bench-scale
bioreactors. This resulted in an empty-bed contact time (EBCT) of 2 days in bioreactor B1, and an
unexpanded EBCT of 8 hours in bioreactor B2. During this phase, the P1 bioreactor was adjusted to an
EBCT of 4 days corresponding to a leachate flow rate of 0.57 L/minute (820 L/day). Bioreactors B1, B2,
and P1 were inoculated with 100% concentrations (Table 1) of 13 of the 14 synthetic organic
compounds (SOCs) within one month at incremental rates of 33% and 66% of the target level;
chloroform was not introduced until the later stages of the study because of its potential toxicfty. Phase
2 experienced the design flow rates and 100% SOC concentrations (without chloroform) for five months.
During Phase 3, the leachate flow rate was doubled for pilot-scale bioreactor P1, thus establishing an
EBCT of 2 days similar to that in bioreactor B1. Recirculation rate ratios were also made comparable for
bioreactors B1 and P1 during this phase. During Phase 4, chloroform was included in the SOC mixture
(at a concentration of 2 mg/L) for all three bioreactors. Phase 5 can be divided into several distinct
stages for the three anaerobic pretreatment units. First, leachate flow rates were doubUsd (20 L/d) for
bioreactors B1 and B2, thereby halving the EBCT in B1 and B2 to 1 day and 4 hours, respectively.
Second, carbon washing was initiated on bioreactor B2 to evaluate the effects of carbon washing on the
GAC system. Third, chloroform was removed from bioreactor P1 's SOC spike because of possible toxic
effects, and the system was monitored to determine if performance could be recovered to pre-
chloroform addition levels.
RESULTS AND CONCLUSIONS
Both B1 and B2 bioreactors were capable of removing through biodegradation most of the
CERCLA compounds at efficiencies of 90% or higher, with the exception of 1,1-dichloroethane and
dibutyl phthalate (which were removed at 80%! efficiency). The packed-bed bioreactors removed
ketones more efficiently than the expanded-bed bioreactor. Over 90% removal was observed for the
following compounds in B1, B2 and P1 systems: acetone, methyl ethyl ketone, methyl isobutyl ketone,
trlchloroethylene, methyiene chloride, nitrobenzene, and phenol. All the semivolatile compounds, with
the exception of dibutyl phthalate, were removed at 95% efficiency in the B1 and B2 systems. In the P1
bforeactor, over 75% removal was observed for toluene, over 60% removal for ethylbenzene and
chlorobenzene, and over 80% for 1,2,4-trichlorpbenzene and dibutyl phthalate. All of the volatile
aromatics showed higher removal efficiencies in the expanded-bed bioreactor compared to the packed-
bed bioreactors.
The COD removal efficiency in the B1 and B2 systems averaged 42% and 48%, reispectively.
During the period of the volatile acids addition, the primary COD removal mechanism was
methanogenic. After the volatile acids addition was stopped and the feed COD decreased, the COD
removal mechanism was due to a combination of methanogenesis and sulfate reduction. The average
sulfate reductions in the GAC expanded-bed bioreactor and the anaerobic filters were 71 % and 65%
respectively, corresponding to an Influent sulfate concentration of 116 mg/L.
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The performance of the B1, B2 and P1 systems was similar prior to the introduction of chloroform
in the spike solution. Within 3 weeks after the addition of chloroform into the three units, however, the
P1 bioreactor showed a decline in the removal of some of the SOCs (including chloroform). SOC
removals continued to decline over a period of 4 months, at which time chloroform addition to the spike
mixture was discontinued for the P1 bioreactor. The B1 and B2 systems continued to receive
chloroform at a concentration of 2 mg/L until the termination of the study because the removal
efficiency in both bioreactors averaged 95%.
During the initial period of the study (about 350 days of bioreactor operation), the less
biodegradable but more adsorbaWe aromatic compounds were removed more efficiently in the GAG,
expanded-bed anaerobic reactor than in the upflow, packed-bed, anaerobic filter. However, after about
400 days of operation, problems such as bed plugging and calcium carbonate deposition on the GAG
medium disrupted the methanogenic activity in the B2 column. This problem was circumvented by
periodically washing 5% of the total carbon contained in the expanded-bed system using 0.1N HCI.
Therefore, in the long run, the anaerobic upflow packed-bed filter systems were less susceptible to
operational problems and more conducive to the growth of methanogens compared to the expanded-
bed anaerobic unit. It should be noted, however, that the bench-scale, GAG, expanded-bed bioreactor
operated at one-sixth the empty-bed contact time of the bench-scale anaerobic filter and, for part of the
study, at one-twelfth the empty-bed contact time of the pilot-scale anaerobic filter.
In order to verify the actual retention time of leachate in the B1 and PI packed-bed systems,
lithium chloride tracer studies were conducted. The tests were conducted first, after the fourth phase of
the study (without cleaning the bioreactor media), and then after completion of the study (following
cleaning and repacking of the media). Results of the first tracer study indicate some plugging in the P1
bioreactor. Results of the second tracer study are expected shortly. The observed media plugging and
probable channeling in the.P1 unit may explain, at least in part, the poorer performance of the pilot-scale
anaerobic filter compared to the bench-scale anaerobic filter.
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TWO U.S. EPA BIORBMBDIATION FIELD INITIATIVE STUDIES: EVALUATION
OF 77V-S77I/BIOVENTING
j
Gregory D. Sayles1, Robert E. Hinchee2, Richard C. Brenner', Catherine M. Vogel3 and
Ross N. Miller4
1 U.S. EPA, Risk Reduction Engineering Laboratory, Cincinnati, OH 45268
2Battelle Laboratories, Columbus Division, Columbus, OH 43201
3 U.S. Air Force Engineering Services Center, Tyndall Air Force Base, FL 32403
4 U.S. Air Force, Center for Environmental Excellence, Brooks Air Force Base, TX 78235
INTRODUCTION
Bioventing is the process of supplying oxygen in-situ to oxygen-deprived soil microbes by forcing air
through contaminated soil at low air flow rates. Unlike soil venting or soil vacuum extraction technologies,
bioventing attempts to stimulate biodegradative activity while minimizing stripping of volatile organics. The
process destroys the toxic compounds in the ground. Bioventing technology is especially valuable for treating
contaminated soils in areas where structures and utilities cannot be disturbed because the equipment needed (air
injection/withdrawal wells, air blower, and soil gas monitoring wells) is relatively non-invasive.
The U.S. EPA Risk Reduction Engineering Laboratory, with resources from the U.S. EPA
Bioremediation Field Initiative, began two parallel 2-year field studies of in-situ bioventing in the summer of
1991 in collaboration with the U.S. Air Force. The field sites are located at Eielson Air Force Base (AFB)
near Fairbanks, Alaska, and Hill AFB near Salt Lake City, Utah. Each site has jet fuel JP-4 contaminated
unsaturated soil where a spill has occurred in association with a fuel distribution network. With the pilot-scale
experience gained in these studies and others, bioventing should be available in the very near future as an
inexpensive, unobtrusive means of treating large quantities of organically contaminated soils.
METHODOLOGY
Eielson AFB
At Eielson AFB, we are studying bioventing in shallow soils in a cold climate in conjunction with soil
wanning methods to enhance the average biodegradation rate during the year. Roughly 1 acre of soil is
contaminated with JP-4 from a depth of roughly 2 ft to the water table at 6-7 ft. Initial (pre-bioventing) soil gas
measurements taken in July 1991 ranged from 600-40,000 ppm total hydrocarbons, 0-13% O2, and 10-18%
CO2, indicating oxygen-limited biological activity and a high degree of contamination. Thus, addition of oxygen
as air to the site would be expected to increase the rate of biodegradation. In comparison, atmospheric air
composition includes 21% O2 and 0.03% CO2.
The test area was established by laying down a relatively uniform distribution of 24 air
injection/withdrawal wells and constructing test plots within this test area (see Figure 1). Air is injected from 2-
6 ft deep at an overall rate of 60 cfm to the test area or 2.5 cfm to each active well. Thus, the test plots should
receive relatively uniform aeration. Three 50-ft square test plots were established. One plot is being used as a
control, i.e., bioventing only, no heating. The remaining two plots are being used to evaluate separately the
following two strategies of combining bioventing with wanning of the soil above ambient temperature to
increase the rate of biodegradation year-round: (1) passive solar warming using plastic covering, and (2) active
warming by applying warm water from soaker hoses just below the surface. Water is applied at roughly 35°C
and an overall rate of roughly 1 GPM to the actively-warmed plot.
In addition to the network of air injection/withdrawal wells, three-level soil gas monitoring wells and
three-level temperature probes were installed throughout the site between 2 and 6 ft deep. In addition, one air
injection/withdrawal well and one soil gas monitoring well was installed in a nearby uncontaminated area for
118
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background measurements. The venting of air and the trickling of unheated water to the actively-warmed plot
began in September 1991. Warming of the water began in October, 1991. A plan view of the installation is
presented in Figure 1.
Periodically, in-situ respirometry tests are conducted to measure the in-situ microbial oxygen uptake
rates. Such measurements indicate the relative rate of biodegradation of the contaminants. These tests involve
temporarily (4 to 8 days) shutting the air off and monitoring the soil gas oxygen concentration with time. The
decrease in oxygen concentration with time indicates a relative biodegradation rate at that time during the study.
Oxygen uptake due to oxygen demands other than biological activity is calculated by conducting a parallel shut-
down test in the (uncontaminated) control area. These tests allow estimation of the biodegradation rate as a
function of ambient temperature and soil warming technique. Quarterly in-situ respiration tests will be
conducted.
os-io
-too-
TaxJwuy
- Groundwat*r mentoring vwl
• • Air InjMtion/wtthdrawal ml
S - Thr»-l«wl sol gai prob*
T - Thr»-towl thwmocoupte prob*
O - Air InjaeOon/wtthdraml MX
(Currant* not h UM)
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I
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Figure 1. Plan view of the joint U.S. EPA and U.S. Air Force bioventing activities at Eielson AFB.
HillAFB
At Hill AFB in Utah, we are evaluating bioventing at greater depths. A 1-acre site is contaminated
with JP-4 from depths of approximately 35 ft to perched water at roughly 95 ft. Here, bioventing, if
successful, will stimulate biodegradation of the fuel plume under roads, underground utilities, and buildings
without disturbing these structures. A plan view of the installation is shown in Figure 2. The air injection well
is indicated. "CW" wells are soil gas "cluster wells" where independent soil gas samples can be taken at 10-ft
intervals from 10-90 ft deep, and "WW" wells are groundwater monitoring wells. A cross-sectional view along
the path AA' in Figure 2 is shown in Figure 3. Air is currently being injected from one well into the plume at
a rate of 40 cfm at depths from 30-95 ft.
An inert gas tracer study, regular soil gas measurements at several locations and depths, and semi-
annual in-situ respiration tests are planned to demonstrate the effectiveness of delivering oxygen and stimulating
119
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biodegradation in a large volume of soil of substantial depth. The inert gas tracer study involves temporarily .,.
replacing the injection of air with the injection of argon or helium and observing the transport of gas in the soils
by monitoring for the inert gas at the various soil gas wells. The air injection rate will be increased semi-
annually to evaluate the trade-off between the gain in area of influence of the injected air for bioremediation and
the additional loss of air and volatilized organics to the atmosphere at the soil surface.
Figure 2. Plan view of the joint U.S. EPA and U.S. Air Force bioventing activities at Hill AFB. CW are
cluster soil gas monitoring wells, WW are groundwater monitpring wells, and the air injection well is indicated.
Path AA' indicates the location of the cross-sectional view shown in Figure 3.
RESULTS , "
EielsonAFB
Progress to date includes installation of the pilot-scale equipment and initial soil sampling for total
hydrocarbons during July and August 1991, continuous soil temperature monitoring since August 25, and an
initial pre-heating in-situ respiration test conducted in early October (data not available at this time). Figure 4
shows soil temperatures at one location at three different depths for the actively-warmed and (uncontaminated)
background area as a function of time through November 15, 1991 (data for the other plots was; not available at
this time). Clearly, the active-warming strategy is functioning well: as ambient temperatures fell during the
fall, the actively-warmed plot remained above 10°C (except for a short period when soil temperature decreased
to between 8 and 9°C), while the temperature at the background location dropped steadily toward 0°C. The
background area should drop well below 0°C during the winter since the annual average soil temperature at this
location in Alaska is only about -2°C. Note that the active warming is maintaining the temperature in the
actively-warmed plot near the average summer temperature of about 11°C.
Several problems caused inefficient performance of the actively-warmed plot in its early operation.
The first problem encountered was reduced water flow rate from,the buried soaker hoses due to the ;
accumulation of silt around the hoses. The low water flow rate resulted in the steady decline of the temperature
120
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between Day 30 and Day 56 (Figure 4). Our goal was to maintain the soil in the actively-wanned plot between
10 and 20°C. To remedy this situation, weekly high-pressure pulses are employed to clear the hoses. The
pulsing began on Day 56 and quickly resulted in increased soil temperatures (Figure 4).
4790
4770-
4750 -
4730-
4710-
4690-
4S7O - [E
CW - Son Gas Clutter Well
03 • Sand with Gravel and day
D • Screened Interval fHM - Sand wtth Clay Cloto
=|-SiltySand | |- Sand
4790
<- 4770
-4750
4730
4710
r4690
4670
Perched Water
(Approx. Surtece)
Figure 3. Cross-sectional view at Hill AFB along path AA' (Figure 2) showing the relative locations of the air-
injection well, soil gas cluster and groundwater monitoring wells, and some geological features of the site.
40
Time (Days)
Figure 4. Temperature as a function of time at one location and three depths within the background and
actively-warmed plots at Eielson AFB.
121
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Second, the soils were not being adequately aerated, probably because a large fraction of soil pore :
volume flooded due to the continuous trickling of water onto the plot. Table 1 shows the range in soil oxygen
concentration measured in the three plots immediately before the initial respiration test. Ideally, the forced
aeration should result in a soil oxygen composition of at least 5-10% to avoid oxygen-limited microbial activity.
The low oxygen concentration observed in some portions of the actively-warmed plot indicated rapid microbial
activity, but also demonstrated that air was not being delivered efficiently to those areas. In December, semir ,
weekly cycling of the water flow rate from high to very low was initiated to decrease the average amount of
water held in the soil in an attempt to increase the water-free pore volume.
TABLE 1. RANGE OF SOIL OXYGEN LEVEL DURING BIOVENTING PRIOR TO WATER FLOW
RATE CYCLING. DATA ARE FROM TWO WELLS IN EACH PLOT, THREE DEPTHS EACH
Plot
Active
Passive
Control
Background
Oxygen Cone. Range, %
1-15
20-21
7-20
21
HillAFB
Progress to date at Hill AFB includes completion of the installation of the wells shown, in Figures 2 and
3 and initial soil sampling for total hydrocarbon levels as a function of depth. An example of one total
hydrocarbon distribution is shown in Figure 5 for soil taken during installation of well CW6. This initial
characterization will be compared to final soil sampling planned for Summer 1993 to calculate net loss of
hydrocarbons due to bioventing. The inert gas tracer study is planned for Spring 1992.
u -
10-
20-
30 -
40-
60 -
7O -
80 -
90 -
inn -
#!#^5#^
-------
CONCLUSIONS
This paper summarizes the first 6 months of a 2-year joint U.S. EPA/U.S. Air Force study of in-situ
bioventing. Already, the work at Eielson AFB has shown that active soil warming techniques are successful in
maintaining soil at warm temperatures during cold ambient temperatures. The most efficient means of
delivering warm water to avoid blockage of the buried hoses, and the optimal water and air flow rates that
provide adequate warming and aeration, continue to be investigated.
The bioventing studies at Hill and Eielson AFBs are generating valuable pilot-scale performance data
and field operational experience for a technology that in the near future could provide an cost-effective means of
in-situ cleanup of organically contaminated unsaturated soils. In addition, the soil warming techniques
investigated here will be applicable to enhancing biological treatment rates of unsaturated soils for any
bioremediation technology at any location where a significant portion of the year is too cold to allow satisfactory
biological activity.
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MEASUREMENT OF THE EFFECT OF TEMPERATURE ON OXYGEN UPTAKE
John R. Haines,1 Todd Harrington,2 Mohammed Islam,2
Kevin Strohmeier,2 and Albert D. Venosa1 .
and Environmental Engineering
Mail Location 71, University of Cincinnati
Cincinnati, OH 45221
2U.S. EPA, Risk Reduction Engineering Laboratory
Cincinnati, OH 45268
INTRODUCTON
The effectiveness of bioremediation products intended for use on spilled
petroleum or refined petroleum products must be evaluated prior to a spill
occurrence. The need for development of a test protocol for product
evaluation has led to initiation of work at RREL in Cincinnati. Biological
degradation of petroleum hydrocarbons requires molecular oxygen as a terminal
electron acceptor. The current method for testing efficacy of bioremediation
products involves monitoring disappearance of oil constituents over time by
gas chromatography (GC) and gas chromatography/mass spectrometry (GC-MS), both
of which are tedious and expensive. Our laboratory is developing methods by
which 02 consumption and C02 production can be correlated with disappearance
of oil compounds. This correlation, once established, will permit examination
of bioremediation products based oh 02 consumption/C02 production with minimal
chemical analysis. The goal of this work is to establish reliable methods for
assaying potential effectiveness of bioremediation products under various
conditions.
Protocol development will encompass seawater, freshwater, sediments,
beach material, and soils. Various types of crude oil or refined products
will be examined as well as the effects of temperature and salinity on the
efficacy of bioremediation products. Oxygen consumption, bacterial numbers,
and changes in oil chemistry will be measured over time. When data collection
is completed, the various parameters will be correlated with oil disappearance
as measured by gas chromatography, and simpler, less expensive methods will be
proposed as a measure of bioremediation product effectiveness.
This paper reports on the effect of temperature on microbial degradation
of crude oil in closed systems. Degradation was tracked by measuring oxygen
uptake in respirometers, decreases in aliphatic constituents of the oil, and
changes in oil degrader population^ over time. Results will have an impact on
how bioremediation protocols will be conducted for determining product
efficacy.
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changes in oil degrader populations over time. Results will have an impact on
how bioremediation protocols will be conducted for determining product
efficacy.
METHODOLOGY
Inoculum cultures were maintained by periodic (three week) transfers
into Bushnell-Haas salts medium supplemented with 1.0% w/v Alaska North Slope
(ANS) crude oil. Inocula were prepared by centifuging 300 ml of culture and
resuspending the pellet in a final volume of 60 ml of culture supernatant.
Each respirometer flask was inoculated with 1 ml "of the concentrated culture,
except those flasks serving as unihoculated controls. The inoculum yielded
about 2.5 X 104 cells/ml final concentration. Flasks containing oil received
5000 mg/L of the ANS oil.
Oxygen consumption was measured using N-CON respirometers
(Larchmont, NY). The N-CON system uses sensitive pressure switches to measure
pressure drops in sealed flasks caused by oxygen consumption. The system then
activates microsolenoid valves to feed 02 from a cylinder to balance the
pressure in the flasks with reference pressure cells. The computer then
calculates oxygen consumption based on the solenoid valve volume and number of
pulses required to balance the system. The flask caps also include a
reservoir for KOH solution for absorbing C02 produced by oil degrading
microorganisms. The KOH traps can be renewed by means of a syringe valve and
cannula penetrating the flask cap.
Populations of microorganisms in the flasks were measured each time a
sample series was collected for chemical analysis. Small samples (10-15 ml)
of the flasks' contents were placed in a sterile reservoir on a Beckman Biomek
1000 laboratory robot. The Biomek fills a 96 well tissue culture plate with
sterile medium, transfers and performs serial 10 fold dilutions of the sample,
and layers oil (2 uL No. 2 fuel oil) on the surface of each well
automatically. The plates thus prepared are then covered and insulated in the
dark at room temperature (22°C) for 14 days. After incubation, a multichannel
pipettor is used to deliver 50 uL of a 0.1% w/v solution of
p-iodonitrotetrazolium violet to each well of each plate. After 30 minutes,
positive wells were scored by counting the pink wells in each row of
dilutions. The data produced were for an eight tube Most Probable Number
(MPN) procedure and the MPN of oil degraders per ml was computed using a PC
based Fortran program.
The remaining contents of each respirometer flask were treated by adding
50 ml of CH2C12 to initiate extraction. The samples were extracted with
CH2C12 and had the CH2C12 exchanged with hexane prior to silica gel
chromatography. The crude hexane extract was applied to a 60-200 mesh silica
gel column for fraction separation. The alkarie fraction was eluted by washing
the column with hexane and the aromatic fraction was eluted by washing
the column with benzene: hexane (1:1) after the hexane washing.
The respective fractions were then concentrated to a standard volume and
analyzed by GC and GC-MS. The analytical conditions were: injector
125
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temperature, 250°C; oven temperature programmed from 5 min initial hold at
50°C to 300°C at 7°C/nrm; with a hold at 300°C for 35 min; FID detector, 350°C.
In the case of the GC-MS the ionization voltage was 70 ev. The carrier gas
was He at 5 mL/min and the column was a 0.75mm X 30mm DB-5 from Supelco,
Supelco Park, PA. The GC was a Hewlett Packard 5880A and the GC-MS was a
Hewlett Packard 5970A with a 0.25mm X 30mm DB-5 column. The other parameters
were the same as for the GC except the program rate was 8°C/nrin. Oil residue
weight was measured by drying a portion of the CH2C12 extract and weighing the
dried residue.
RESULTS ' ' :
The oxygen uptake curves at 15° and 25°C produced by microorganisms
incubated with ANS crude were quite different. At 15°C, the onset of oxygen
uptake occurred at 3 days and slowed in rate at 6 days. At 25°C oxygen uptake
was rapid after 2 days and slowed after 5 days. Uptake was more rapid at 25°
than at 15°. At 15°C, oxygen uptake was about 2500 mg/L, which is about 23%
of theoretical. At 25°C, oxygen uptake was about 4500 mg/ L, which is about
42% of theoretical. Potential oxygen uptake was calculated based'on complete
conversion of oil carbon to C02. Total conversion would have consumed about
10,600 mg/L 02. The carbon content of the ANS crude was 82% based on
elemental analysis of duplicate samples by an independent laboratory.
Over the period of this experiment, numbers of oil degraders followed a
typical growth and decline pattern (Fig.l). At day zero the population in
each flask was about 2.5 X 104 cells per mL. By day 9 the population had
increased by over five orders of magnitude, thereafter the population
declining slowly to about 107 cells per mL.
Analysis of the oil content of flasks over the period of the experiment
yielded interesting results. During incubation at 15°C, 95% of the resolvable
alkanes were consumed by day 5 of the experiment. No aromatic hydrocarbon
data were available at this writing. Degradation of labile alkanes was
essentially complete by day 5. Oxygen uptake was still active after day 5,
indicating that microorganisms wefe consuming less readily resolved
hydrocarbons. Analysis of the data showed very little preference for
degradation of normal alkanes over branched alkanes such as pristane.
Pristane decreased in concentration almost as rapidly as heptadecane. This
indicates some organisms can adapt to utilize branched chains as well as
straight chains quite readily. Oil residue weight had declined from about
3500 mg/L to 3200 mg/L at the end of the experiment. Figure 2 shows the
results of oil analyses from this experiment.
Even though easily analyzed hydrocarbons were consumed, significant
quantities of oil persisted in the flasks. The easily resolved hydrocarbons
measured by GC represent a small fraction of the total oil mass. Our
laboratory estimates the n-alkane fraction to be.about 1% of the oil.
The difference between oxygen uptake and oil residue weights may be due to
the fact that oil residue methods only provide a general mass estimate. The
extraction procedure will extract any compound that preferentially partitions
126
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into CHjClj over water. Some of these compounds will include partially
metabolized oil compounds and cellular lipids.
A subsequent experiment was conducted to evaluate the response of
microorganisms to six different kinds of oil or refined products. Crude oils,
light Arabian (LA), South Louisiana (SL), Prudhoe Bay (PB), and Weathered PB
(WP) and Number 2 (F2), and Number 6 (F6) fuels were incubated at 15 and 25°C
as previously described. Trials were conducted with nutrients or without
added nutrients at both temperatures. In general, oxygen uptake at 15°C was
lower than at 25°C. At 15°C, oxygen consumption was about 3700 mg/L for LA,
3200 mg/L for F2, 2700 mg/L for SL, 1600 mg/L for PB and WP, and 1000 mg/L for
F6 with nutrients. Without nutrients 02 consumption was lower. The onset and
early rate of oxygen uptake was the same for LA and PB crudes beginning at
three days. Degradation of LA continued rapidly until 12 days and slowed.
Degradation of PB slowed after six days. Degradation of SL began at four days
and slowed at seven days. WP oxygen uptake began at five days and slowed at
seven days. Oxygen uptake with F2 began at five days and remained mostly
constant until 18 days. F6 oxygen uptake started at five days and remained
slow for the entire experiment.
CONCLUSIONS
The results of work to date show that the performance of microorganisms
degrading oil varies significantly with temperature and "nutrients as expected.
Our results indicate that the major portion of oxygen consumption is
complete by less than 14 days of incubation at either 15 or 25°C. The readily
degraded compounds are largely consumed in this period and therefore
experiments evaluating bioremediation products may be completed in less than
30 days. Oil residue weight may not be a good indicator of degradation. Long
period studies can concentrate on metabolism of resistant structures left in
crude oils after preliminary weathering. The variation in 02 consumption
resulting from different kinds of oils shows that bioremediation products may
need to be tailored for the specific type of oil involved in a spill.
The data obtained with multiple oils also will aid in planning future
experiments with regard to sample collection and analysis. The lighter fuels
and crude oils yielded the highest 02 consumption. The lowest 02 uptake was
associated with the heavy No.6 fuel and weathered PB oils.
Testing of bioremediation products will require careful attention to the
parameters of microbial growth in the testing sequence. The type of product,
the oil product the remedial product is intended for, the environmental
parameters affecting the remedial product, and the time scale that remedial
products are intended to act in, will require that testing protocols be
flexible in methodology and interpretation.
Future work will expand upon the preliminary results obtained to date in
this work.
127
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CO
DC
UJ
Q
<
CC
O
ill
Q
O
u.
O
•
O
z
10 15 20 25
30
TIME, DAYS
Figure 1. Most Probable Number of Oil Degraders over Time.
128
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40000
35000 -*=•
30000 --
25000 --
J 20000 H-
o
15000 --
10000
5000 --
target alkanes
residue weight
— 4000
— 3500
— 3000
— 2500
i
2000 -
->- 1500
1000
— 500
0 2 4 6 8 10 12 14 16 18
time, days
Figure 2. Decline in Target Alkanes and Residue Weight as a Function of Time at
15°C
129
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A FUNDAMENTAL KINETIC STUDY OF THE ANAEROBIC BIODEGRADATION OF CHLOROFORM AND
ITS PRODUCTS WITH VARIOUS CO-SUBSTRATES IN MIXED CULTURE CHEMOSTATS
l - i
Ashutosh Gupta1, Joseph R. V. Flora1, Gregory D. Sayles?, Makram T. Suidan1
1 Civil and Environmental Engineering
Mail location 71, University of Cincinnati
Cincinnati, OH 45221
U.S. EPA, Risk Reduction Engineering Laboratory
Cincinnati, OH 45268
INTRODUCTION
The highly chlorinated methanes biologically degrade only extremely slowly
under aerobic conditions. For example, in conventional wastewater treatment
facilities, these toxic compounds would likely be untreated and either pass
through the aerobic bioreactor and appear in the plant effluent or be stripped
to the atmosphere by the aeration. Cost-effective technologies to destroy
these priority pollutants are required due to their prevalence at Superfund
sites, in landfill leachates and in industrial effluents. For example, the
1986 National Priorities List (NPL) database indicates that chloroform and
carbon tetrachloride appear at 24% and 7% of all NPL sites, respectively.
It is well known that anaerobic biological treatment can degrade the
highly chlorinated methanes efficiently while metabolizing more easily
degradable primary substrates. However, recently completed research by the
U.S. EPA Risk Reduction Engineering Laboratory revealed that chloroform can
severely limit the ability of methanogenic anaerobic treatment systems to
process readily, biodegradable and more refractory constituents of a
multicomponent hazardous waste stream. :
The type of anaerobic environment utilized appears to influence the impact
that these compounds have on an anaerobic process. Recent data collected from
a leachate-treatability study conducted at the U.S. EPA Test and Evaluation
Facility using parallel anaerobic reactors operating under methanogenic and
sulfate-reducing conditions, respectively, revealed that sulfate-reduction
promoted efficient chloroform degradation while, once again, methanogenic
activity was adversely affected by increased levels of chloroform in the
feed.
Thus, the objective of this study is to rigorously investigate the
anaerobic biodegradability of chlorinated methanes with primary emphasis on
chloroform. The fundamental kinetics of transformation of carbon
tetrachloride, chloroform, dichloromethane and chloromethane are studied under
methanogenic and sulfate-reducing environments. These kinetics are evaluated
in the presence of the co-substrates methanol, formate and acetate.
METHODOLOGY
Six 10-liter stainless-steel chemostats were assembled. Each chemostat is
equipped with two constant speed masterflex pumps to feed the nutrients and
130
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the buffer. The nutrients contain the necessary inorganic salts and vitamins,
while the buffers maintain a constant pH. The masterflex pumps are channelled
through timers to enable variable flows. The organic substrates are injected
with a 10-ml syringe pump. The contents of the chemostats are kept completely
mixed with the aid of a variable speed mixer. The primary substrate in the
feed to each chemostat and the corresponding anaerobic environment are listed
in Table 1. The chloromethane will be an additional organic feed component.
TABLE
Chemostat
I
II
III
IV
V
VI
1. KEY CONSTITUENTS OF THE CHEMOSTAT FEED
Environment
Methanogenic
Methanogenic
Methanogenic
Sulfate-reduction/methanogenic
Sul fate-reduction/Methanogenic
Sulfate-reduction/Methanogenic
Co-Substrate
Methanol
Acetate
Formate
Methanol
Acetate
Formate
The chemostats are operated at a 3 g/day COD loading. Daily and weekly
analyses are performed to monitor the performance of the chemostats. The
daily analyses include recording the feed rates of the buffer, nutrient, and
syringe pump (COD feed) solutions, and measuring the pH, total gas production,
and temperature. Appropriate adjustments in the buffer solutions are made to
keep the pH constant at 7.2. Weekly analyses include measuring the COD and
sulfate concentration, volatile suspended solids (VSS), and volatile fatty
acids (VFA) in the effluent. The percent composition of the effluent gas is
also determined. These measurements allow calculation of the fraction of the
COD removal attributable to methanogenesis (methane formation), to sulfate-
reduction (oxidation of the organic feed components by the reduction of
sulfate), and to biomass production. An example of the weekly COD balance is
presented in Figure 1. Steady state is confirmed and characterized by
constant levels of all parameters including measurement of the oxidation-
reduction potential (ORP).
In the methanogenic/sulfate-reducing systems, an abundance of iron is
required as a microbial nutrient and to precipitate the inhibitory sulfide
that is produced. Iron is introduced in the chemostats with the nutrient
solution. Organic chelating agents have been used in the past to solubilize
iron in nutrient,solutions, but these agents are not desirable as they serve
as another source of COD. A detailed investigation of the chemistry of the
anaerobic environment resulted in an alternative procedure that does away with
these chelating agents.
RESULTS
As of December 1991, the first phase of the project was complete. The
goal of the first phase was to obtain an initial steady-state operation for
all the chemostats without the presence of chloromethanes. Over four months
131
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of stable operating data, and weekly COD balance on all the chemostats
indicate that the initial steady-state was achieved (an example of the weekly
COD balance for Chemostat I is presented in Figure 1). To confirm steady-
state, in-situ ORP measurements were performed repeatedly. The steady-state
values for selected parameters are shown in Table 2. Note that the sum of the
percent of COD removal by methanogenesis and by sulfate-reduction does not
equal 100 because a fraction of the inlet COD is used to produce biomass.
•o
Q
O
O
2 -
1 -
O influent
V gas + effluent
D effluent
20
120
140
Figure 1. Weekly COD balance for chemostat I through December 4, 1991.
^ A computer model was developed to study the interactions of the various
ions present in the systems. The main motivation for this task was to study
the effect of these interactions on the availability of the nutrients,
especially in the case of the sulfate-reducing systems where large amounts of
sulfide are produced that can cause precipitation of the important nutrient
metals. A non-steady CSTR model was prepared to simulate equilibrium
interactions. Refinement of this model is continuing. The results from the
132
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model will be compared with experimental data. These results will also be
presented at the symposium.
TABLE 2. STEADY STATE RESULTS FROM CHEMOSTAT I
Chemostat
I
II
III
IV
V
VI
. • '• '
Removal of Inlet
COD %
98
96
97
96
94
95
Fraction of C
Methanogenesi
s %
85
83
81
0
84
40
OD Removal by
Sul fate-
reduction %
0
0
0
66
0
27
CONCLUSIONS
As expected, the methanogenic systems consumed the primary substrates very
efficiently with all chemostats exhibiting above 95% COD removal (Table 2).
However, the sulfate-reducing systems exhibited some more interesting
behavior:
i. Acetate was readily consumed by the sulfate reducers
(chemostat IV).
ii. Although there was an abundance of sulfate in this
chemostat feed (4500 mg/1), methanol was not consumed
by the sulfate reducers in chemostat V and no COD was
utilized via sulfate-reduction. While both the
chemostats with methanol feed (chemostats II and V)
exhibited methanogenesis exclusively, differences were
observed in their operation. The most important was
the difference in the ORPs, where the absolute value
of the ORP of the chemostat with sulfate was more than
twice that of the chemostats with no sulfate.
Consequently, very different behaviors between the two
reactors are expected once the chloroform feed starts.
iii. A competition was observed between sulfate reducers
and methanogens for formate utilization (chemostat
VI). Batch tests will be performed on the chemostat
contents to evaluate the kinetic parameters in order
to explain this behavior.
The second phase of the project is due to start shortly. During this
phase of the study, chloroform feed to the chemostats will begin. The results
of part of the second phase will also be presented at the symposium.
133
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EMISSIONS OF ORGANICS FROM BIOSLURRY REACTORS TREATING
SOIL CONTAMINATED WITH WOOD PRESERVING WASTE
Ronald F. Lewis
U.S. EPA
26 West M. L. King Drive
Cincinnati, Ohio 45268
Michael Smith, Judy Hessling, and Majid Dosani
International Technology Corporation
11499 Chester Road
Cincinnati, Ohio 45246
INTRODUCTION
This paper is a part of the work conducted for a joint
Superfund Innovative Technology Evaluation (SITE) project and a
study for the EPA's Office of Solid Waste and Emergency Response
(OSWER) that is developing information for Best Demonstrated
Available Technology (BOAT). The project was conducted at the U.S.
EPA Test and Evaluation Center located at the Gest Street Waste
Water Treatment Plant in Cincinnati, Ohio. The contaminated soil
chosen for the test of the effectiveness of bioslurry reactors for
the degradation of wood preserving wastes was a soil from the
Burlington Northern NPL site in Brainerd, Minnesota. The overall
results of the soil treatment are presented in a paper titled
"Slurry Reactor Bioremediation of Soil-Bound Polycyclic Aromatic
Hyrocarbons" by Alan Jones, Madonna Brinkmann, and William Mahaffey
of Ecova Corporation.
Air sampling was conducted to characterize the off-gases
emitted from the bioreactors during the operations and to determine
organic constituent loss through volatilization.
METHODOLOGY
All five reactors were vented through stainless steel piping
into a manifold system before carbon filtration and eventual
exhausting to the outside air. The air monitoring was conducted at
a point prior to the collective mainfold to obtain emissions from
two individual reactors.
Two sampling trains were constructed to collect samples for
volatile and semivolatile organics. Volatile organics were
collected in a SUMMA passivated canister, and semivolatiles were
collected in XAD-2 resin tubes. The canisters and XAD-2 resin
tubes were installed in the venting systems for the tested
reactors.
Four consectutive sets of samples were collected from each of
the two tested reactors during the first week of operation. Two
sets of samples were collected during weeks 2 through 5, and one
135
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set of samples was collected during weeks 6, 7, and 9.
The air sampling program measured semivolatile, volatile, and
total hydrocarbons during the first nine weeks'of treatment. Total
Hydrocarbons (THC) as methane was determined according to
procedures in U.S. EPA Method 25A. This sampling was conducted
continuously at the main exhaust line for the first five days of
operation. Sampling for volatiles (by modified Method TO14) and
semivolatiles (by modified Method TO13) was conducted periodically
during the first nine weeks of operation.
RESULTS
The background ambient air showed THC
averaging 3ppm on a dry basis. During the charging
THC emissions gradually increased ;with peak
averaging 390 ppm or 0.014 Ib/hr from 17:51 to
1991. A table will be presented showing the
emission rates, and flow rates used to calculate
data are reported as methane because it was used as
gas during the sampling.
concentrations
of the reactors'
concentrations
18:00 oh May 8,
concentrations,
emissions. All
the ceil ibration
The emissions of THC dropped to 0.007 Ib/hr in a little over
6 hours, and to 0.00176 Ib/hr in,just 24 hours. Within 48 hours
the THC emissions were down to less than 0.0003 Ib/hr and by
72hours were less than 0.0002 Ib/hr.
Semivolatile polynuclear aromatics were detected during the
first four days of operation with napthalene found at 8600
ug/sample, 2-methylnaphthalene at 1500ug/sample,and acenahpthene,
fluorene, phenanthrene, and anthracene going in order from 703'
ug/sample to 23 ug/sample. After four days all samples were below
15ug/sample. By day 3 the most volatile compounds, naphthalene and
2-methylnaphthalene had already declined to less than 20 ug/sample.
The volatile organics found in greatest abundance were:
xylene, toluene, ethylbenzene; benzene, and styrene. Table 1 shows
the results of the first 4 days of measurement of 12 volatile
compounds. The samples again show that themajority of emissions
occurred during the first few days of operation of the slurry
bioreactors.
Conclusions
It has often been stated that liquid aerated biotreatment of
hazardous compounds should be avoided because of the potential for
air pollution during the treatment. The testing of air emissions
during this project shows that the major emissions are during the
charging of the vessels and a small amount may continue for the
first few days. The problem of air emissions during charging of a
reactor can be similar or even greater in charging incinerators or
other non-biological treatment units.
136
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The levels of both semivolatile and volatile organics found in
the air emissions of the bioreactors dropped back to near the
background level within four days. Emission control systems can be
devised for operation of bioslurry reactors, but the cost benefit
may be low when there are no major concentrations of volatile
compounds present in the waste. The microbes are quite efficient
in capturing and using most of the semivolatile compounds that can
be biodegraded.
TABLE 1. Volatile Organic Emissions
Concentration
Compound
carbon disulfide
methylene chloride
chloroform
1,1, 1-trichloroethane
benzene
toluene
tetrachloroethane
chlorobenzene
ethy Iben z ene
m- and/ or p-xylene
o-xylene
styrene
DAY 1
ppb
67.0
—
_ •
—
45.0
230.0
—
_
160.0
800.0
320.0
44.0
DAY 2
ppb
17.0
0.8
—
1.6
2.3
4.6
—
_
3.4
17.0
14.0
3.6
DAY 3
ppb
5.0
9.2
0.7
2.8
2.4
8.0
1.6
0.9
1.5
7.3
3.5
0.9
Day 4
ppb
20.0
1.1
1.1
1.6
1.2
3.2
—
_
0.9
3.0
1.4
0.5
137
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DESIGN OF FULL SCALE DEBRIS WASHING SYSTEM
Michael L. Taylor, Majid A. Dosani, John A. Wentz, and Avinash N. Patkar
IT Corporation
11499 Chester Road
Cincinnati, Ohio 45246
Telephone: (513) 782-4700
Naomi P. Barkley
U.S. Environmental Protection Agency
Risk Reduction Engineering Laboratory
Cincinnati, Ohio 45268
Telephone: (513) 569-7854
BACKGROUND
In conjunction with promulgating Land Ban Disposal Regulations, the United States Environmental
Protection Agency (EPA) published (Federal Register, May 30,1991) an Advanced Notice of Proposed Rule
Making (ANPR) In which definitions for debris and contaminated debris were suggested as quoted below:
Debris means solid material that: (1) has been originally manufactured or processed, except for
solids that are listed wastes or can be identified as being residues from treatment of wastes and/or
wastewaters, or air pollution control devices; or (2) is plant and animal matter; or (3) is natural
geologic material exceeding a 9.5 mm sieve size including gravel, cobbles, and boulders (sizes as
classified by the U.S. Soil Conservation Service), or is a mixture of such materials with soil or solid
waste materials, such as liquids or sludges, and is inseparable by simple mechanical removal
processes.
Contaminated Debris means debris which contains RCRA hazardous waste(s) listed in 40 CFR
Part 261, Subpart D, or debris which otherwise exhibits one or more characteristics of a hazardous
waste (as a result of contamination) as defined in 40 CFR Part 261, Subpart C.
The ANPR also contains suggested techniques for decontaminating debris prior to disposal. The
options listed include high pressure washing based, to a large extent, on work performed by EPA/RREL.
This paper gives an overview of the development and assessment of high pressure washing technology
and presents an update on EPA's efforts to develop a full scale, semi-automatic, debris washing system
INTRODUCTION
Since 1987, IT Environmental Programs Inc. (ITEP, a subsidiary of International Technology
Corporation) in conjunction with EPA/RREL in Cincinnati, Ohio, have been developing and conducting
bench scale and pilot scale testing of a transportable debris washing system which can be used on-site for
the decontamination of debris (1).
During the initial phase of the debris decontamination project, a series of bench scale tests were
performed in the laboratory to assess the ability of the system to remove contaminants from debris and to
facilitate selection of the most efficient surfactant solution. Five nonionic, non-toxic, low foaming,
surfactant solutions (BG-5, MC-2000, LF-330, BB-100, and L-422)3 were selected for an experimental
evaluation to determine their capacity to solubilize and remove contaminants from the surfaces of
corroded steel pieces. The pieces of corroded steel were coated with a heavy grease mixture prepared in
Manufacturers of these surfactants are: BB-ldO, Bowden Industries, Huntsville, AL; BG-5, Modern
Chemical, Jacksonville, AR; MC-2000, Alcolac, Baltimore, MD; LF-330, GAF Chemicals Corporation,
Wayne, NJ; and L-422, DuBois Chemicals, Cincinnati, OH.
138
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the laboratory and these pieces of "debris" were placed in a bench scale spray tank on a metal tray and
subjected to a high-pressure spray for each surfactant solution for 15 minutes. At the end of the spray
cycle, the tray was transferred to a second bench scale system, a high-turbulence wash tank, where the
debris was washed for 30 minutes with the same surfactant solution as that used in the spray tank. After
trie wash cycle was completed, the tray was removed from the wash tank and the debris was allowed to air-
dry. Before and after treatment, surface-wipe samples were obtained from each of the six pieces of
"debris" and were analyzed for oil and grease. Based on the results, BG-5 was selected as the solution
best suited for cleaning grease-laden, metallic debris.
PILOT SCALE DEBRIS WASHING SYSTEM
Based on the results obtained from bench scale studies, a pilot scale debris washing system
(DWS) was designed and constructed. The pilot scale DWS consists of a 300-gallon spray tank, a 300-
gallon wash tank, a surfactant holding tank, a rinse water holding tank, an oil/water separator, and a
solution-treatment system consisting of a diatomaceous earth filter, an activated carbon column, and an
ion-exchange column. The pilot scale DWS was demonstrated at a PCB-contaminated site in Hopkinsville,
Kentucky, and a pesticide-contaminated site in Chickamauga, Georgia.
Demonstration at the Ned Gray PCB Site. Hopkinsville. KY — This site covers approximately 25 acres.
From 1968 to 1987 a metal reclaiming facility was operated at the site, which involved open burning of
electrical transformers to recover copper for resale. Approximately 70 to 80 burned-out, PCB-
contaminated transformers were on site, along with large amounts of other materials, including asbestos-
covered pipes, automobiles, and miscellaneous scrap metal. The entire DWS was transported to the
Hopkinsville, Kentucky site on a 48-foot semitrailer and reassembled on a 24 ft x 24 ft concrete pad. A
temporary enclosure, approximately 25 ft high, was also built on the concrete pad to enclose the DWS
and to protect the equipment and surfactant solution from rain and cold weather. The demonstration took
place during December 1989 when ambient temperatures at the site during the demonstration ranged
from near 0° to 50°F.
Prior to the initiation of the cleaning process, the transformer casings, ranging from 5 gallons to
100 gallons in size, were cut into halves with a metal-cutting saw. A pretreatment sample was obtained
from one half of each of the transformer casings by using a surface wipe technique (2). The transformer
halves we"e placed into a basket and lowered into the spray tank of the DWS, which was equipped with
multiple w, .ter jets that blast loosely adhered contaminants and dirt from the debris. After the spray cycle,
the basket was removed and transferred to the wash tank, where the debris was immersed into a high-
turbulence washing solution. Each batch of debris was cleaned for a period of 1 hour in the spray tank and
1 hour in the wash tank. During both the spray and wash cycles, a portion of the cleaning solution was
cycled through a closed-bop system in which the oil/PCB-contaminated cleaning solution was passed
through an oil/water separator, and the clean oil-free solution was then recycled into the DWS. After the
wash cycle, the basket containing the debris was returned to the spray tank, where it was rinsed with fresh
water. Upon completion of the cleaning process, posttreatment wipe samples were obtained from each of
the transformer pieces to assess the residual levels of PCBs. The before-treatment concentrations
ranged from 0.1 to 98 u.g/100 cm2. The posttreatment analyses showed that all the cleaned transformers
had a PCB concentration lower than the acceptable level of 10 u.g/100 cm2.
After treatment of all transformers at the site, the spent surfactant solution and the rinse water
were neutralized to a pH of approximately 8 by using concentrated sulfuric acid and were treated in the
water treatment system.The before- and after-treatment water samples were collected and analyzed for
PCBs and selected metals (cadmium, copper, chromium, lead, nickel, and arsenic).
The PCB concentration in the water was reduced by the treatment system to below the detection
limit of 0.1 u.g/L. The concentrations of each of the selected metals (except arsenic) were reduced to the
allowable discharge levels set by the city of Hopkinsville for discharge into the sanitary sewer. Upon
receipt of the analytical results of the water, the treated water, which was stored in the holding tank, was
pumped into a plastic-covered, 10,000-yd3 pile of contaminated soil at the site. During this site cleanup,
75 transformers were cleaned in the DWS. All of these transformers were considered to be free of PCB
contamination and were sold to a scrap smelter.
139
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Demonstration at the Shaver's Farm Srte. Chickamauga. GA - The second demonstration of the DWS was
conducted at a drum disposal site in August 1990. Fifty-five gallon drums containing varying amounts of a
herbicide, Dicamba (2-methoxy-3,6-dichlorobenkoic acid), and benzonitrile, a precursor in the
manufacture of Dicamba, were buried on this 5-acre site. An estimated 12,000 drums containing solid and
liquid chemical residues from the manufacture of Dicamba were buried there during August 1973 to
January 1974. EPA Region IV had excavated more than 4000 drums from one location on the site when
this demonstration occurred. The pilot scale DWS and the steel-framed temporary enclosure used
previously at the Hopkinsville, Kentucky Site were transported to this site in a 48-foot semitrailer and
assembled on a 24 ft x 24 ft concrete pad. Ambient temperature at the site during the demonstration
ranged from 75 to 105°F. .
Prior to treatment in the DWS, the 55-galIon, pesticide-contaminated, empty drums were sawed
into four sections. Pretreatment surface-wipe samples were obtained from each section. The drum
pieces were placed in the-spray tank of the DWS for 1 hour of surfactant spraying, then placed in the wash
tank for an additional hour of surfactant washing, followed by 30 minutes of water rinsing in the spray tank.
The drum pieces were then allowed to air-dry before posttreatment surface-wipe samples were obtained.
Ten batches of one to two drums per batch were treated during this demonstration. Pretreatment
concentrations of benzonitrile in surface-wipe samples ranged from 8 to 47,000 u.g/100 crn2 and
averaged 4556 |ig/100 cm2. Posttreatment levels of benzonitrile ranged from below detection limit to
117 u.g/100 cm2 and averaged 10 uxj/100 cm2. Pretreatment Dicamba values ranged from below
detection limit to 180 u.g/100 cm2 and averaged 23 u.g/100 cm2, whereas posttreatment concentrations
ranged from below detection limit to 5.2 u.g/100 Cm2 and averaged 1 u.g/100 cm2. The detection limit for
wipe samples for dicamba and benzonitrile was 5 ug/100 cm2.
Upon completion of the treatment, the spent surfactant solution and rinse water were treated in
the water treatment system. The before- and after-treatment water samples were collected and analyzed
(in duplicate) for benzonitrile and Dicamba. The concentration of benzonitrile in the pretreatment water
samples was 250 and 400 u.g/L, and the posttreatment concentration was below the detection limit of 5
u,g/L The concentration of Dicamba in the pretreatment samples was 6800 and 6500 u.g/L, and the
posttreatment concentration was estimated to be less than or equal to 630 ug/L (value estimated due to
matrix interferences). Since the concentration of Dicamba in the posttreated water sample was possibly as
high as 630 u7L, the treated water stored in the polyethylene holding tank was pumped into an onsite
water-treatment system for further treatment by EPA. Although the concentration of Dicarnba in
posttreatment water was ;n estimated value, it was decided to send the water to the onsite water-
treatment system prior to discharge as a precautionary measure.
The test equipment was decontaminated with a high-pressure wash. The wash water generated
during this decontamination was collected and pumped into the onsite water-treatment system. The
system and the enclosure were disassembled and transported back to Cincinnati in a semitrailer.
FULL SCALE DEBRIS WASHING SYSTEM
The extensive experience gained under actual field conditions with the pilot scale DWS lead to
the following conclusions regarding the technology: 1) the desired results were obtained using the pilot
scale DWS - a marked reduction of organic contaminants on actual metallic debris from CERCLA sites was
achieved; 2) the generation of large volumes of contaminated waste water was avoided by employing a
process water filtration system which operates concurrently with the debris cleaning process; and 3) the
pilot scale system as constructed is mechanically reliable and proved to be very rugged and amenable to
being transported from site to site. Thus the field studies convincingly demonstrated that the DWS
technology has definite promise for addressing the problem of decontaminating metallic debris at
hazardous waste sites. In addition, important information was also gained during these field
demonstrations which indicate areas where improvements in the full scale system design could be made
and these are summarized in the following paragraphs.
140
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The pilot scale system is not a high throughput device and extensive manual handling of debris is
required. Due to the relatively small size of the spray and wash tanks debris larger than approximately
30" x 15" x 30" must be cut to size. Debris must be manually placed into a basket which is lifted using a
fork-lift and then lowered into the spray tank. The efficiency of the spraying treatment is limited by the fact
that the wire mesh on the sides of the basket interferes with the spray which emerges from nozzles on the
sides of the spray tank. It was determined that during the one hour spray cycle the best results were
obtained when the spray cycle was momentarily interrupted and the debris was manually repositioned to
enhance contact between the debris surfaces and the spray. The spray intensity was found to be
incapable of removing all of the heavy clay deposits from surfaces of drums excavated in Chickamauga.
As indicated in the above discussion, it is clear that the overall pilot scale process, although generally very
effective for removing hazardous contaminants, is labor intensive.
When approaching the design of the full scale system the following goals were established:
1) the manual handling of debris is to be kept to a minimum, if not eliminated; 2) the overall throughput of
debris/day is to be markedly increased (on the order of ten-fold) while not diminishing the effectiveness of
the process; 3) the usage of water is to be increased somewhat, however recycling of process water to
minimize generation of wastewater is essential; 4) the full scale system should be mounted on one or two
normal-sized semitrailers which require no special permits; 5) the system is to be rugged enough to be
transported from site to site with minimal time and costs for mobilization/demobilization; 6) the system is to
include appropriate features to ensure the safety of workers operating the system and to ensure
containment of emissions potentially harmful to the environment. In an effort to address the goals for the
full scale DWS the following features have been incorporated into the design. A schematic representation
of the full scale system is shown in Figure 1.
The unit operations will entail initially loading a heavy duty basket with approximately two tons of
debris (typically metallic debris) which will then be lifted by means of a crane and placed in a 3000 gallon
tank. An innovative system will permit the debris to be directly impacted by high intensity detergent spray
while the debris is subjected to a tumbling action. In addition to the spray/tumbling phase, the debris will
be cleaned using a wash cycle in which the debris is immersed in cleaning solution and then a final
spray/rinse will be utilized to remove residual contaminated liquid from the surfaces of the debris. The
contaminated liquids (detergent solution, rinse solution) will be continuously treated using a transportable
process water treatment system which will include various treatment modules which will be implemented to
decontaminate the process water. In th?s fashion, the quantity of process water generated during the
debris cleaning process will be significar ly minimized. The full scale DWS will be mounted on two
semitrailers. Site preparation will be minimal and is expected to entail leveling and placing of gravel or
crushed stone on which the trailers will be parked.
REFERENCES
1) Technology Evaluation Report: Design and Development of a Pilot Scale Debris
Decontamination System, U.S. Environmental Protection Agency. EPA 540/5-91-006a,
August 1991.
2) Field Manual for Grid Sampling of PCB Spill Sites to Verify Cleanup, U. S. Environmental
Protection Agency, EPA 560/5-86/017, May 1986.
ACKNOWLEDGMENTS
This research was funded in its entirety by the United States Environmental Protection Agency's
Risk Reduction Engineering Laboratory under Contract No. 68-03-3413. Naomi Barkley is the Technical
Project Monitor.
141
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142
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TREATMENT OF HAZARDOUS AND TOXIC
LIQUIDS USING ROCHEM DISC TUBE TECHNOLOGY
David LaMonica
President
Rochem Separation Systems
3904 Del Amo Boulevard, Suite 801
Torrance, California 90503
(310) 370-3160
INTRODUCTION
Rochem Separation Systems, established in 1990 as a subsidiary of the international Rochem
Group, has advanced the treatment of hazardous and toxic liquids with its unique, patented Disc Tube
technology. Developed in 1987 at Rochem's design arid production facilities in Hamburg, Germany, the
,Disc Tube technology is a series of membrane modules that greatly reduce the problems that hamper the
effectiveness of other treatment technologies (i.e. fouling, scaling, cost, etc.). Applications of the Disc
Tube technology include reverse osmosis and ultrafiltration. Rochem was recently accepted into the
EPA Superfund Site program as a result of its Disc Tube technology.
METHODOLOGY
The Rochem Disc Tube is constructed from a series of octagonal membrane cushions separated
by a series of plastic spacer discs. The discs support the membrane cushions but leave an open channel
flow path through the module (see Figure 1). The minimum clearance in the feed water flow path of the
Disc Tube is approximately one millimeter. The flow path through the module is radial, progressing from
the center of one disc to the edge of the cushion. The flow then makes a 180 degree turn and flows
inward over the other side of the membrane cushion. The flow path repeats for each membrane cushion
in the stack. The flow reverses direction every three inches. The turbulence created by the flow reversal
eliminates the concentration polarization, minimizing scaling and fouling while maintaining high energy
efficiency. Also, the Disc Tube operates effectively at increased turbidity and Silt Density Index (SDI)
levels.
RESULTS ,
Rochem is currently operating its Disc Tube technology in reverse osmosis (RO) systems at
various hazardous landfill leachate sites throughout Europe, including one at Schwabach, Germany. The
RO systems are being used at the sites to treat leachate seeping into the ground and contaminating
valuable ground water. The effluent produced from the ieachate treatment process meets applicable
discharge standards by removing up to 99% of all dissolved solids and BOD (see Table 1).
CONCLUSIONS
The use of membranes for the reduction of difficult hazardous liquids was not economically
feasible prior to the advent of Rochem's Disc Tube concept. Due to the Disc Tube's unique design,
liquids that traditionally inhibit the use of membranes as a result of scale formation and biological fouling
143
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are handled efficiently. In addition, by utilizing a combination of membrane systems to treat hazardous
liquids such as multi-component waste found at hazardous landfills, cost effective and efficient
treatment can be achieved. The most significant advantage this technology has over single membrane
systems is that all major contaminants are reduced to within prescribed regulatory limits. Also,
membrane performance is improved by selecting membranes chemically compatible with the waste to be
treated.
FIGURE 1
DISC TUBE MEMBRANE MODULE
HYDRAULIC FLOW SCHEMATIC
FEED
PEHMEATE 3R1NE
HYDRAULIC DISC
MEMBRANE CUSHION
TENSION ROD
144
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TABLE 1
LANDFILL LEACHATE TREATED BY TWO-STAGE REVERSE OSMOSIS
PLANT AT SCHWABACH LANDFILL SITE
Parameter Untreated Leachate
El Conduct (u,s/cm)
PH Value (mg/l)
COD (mg02/l)
BOD (mgO2/l)
TOC (mg/l)
Hydrocarbons (mg/l)
Sulfate (mg/l)
Ammonium (mg/l)
Arsenic (mg/l)
Cyanide (mg/l)
Vanadium (mg/l)
12.25
7.7
2,619
184
289.0
13.40
22093.0
380
0.25
2.35
290.0
Second Stage Permeate Rejection
382
6.6
1.2
2.5
4.0
0.3
.4.8
0.4
ND
ND
2.2
99.9%
99.9%
98.6%
98.6%
97.8%
99.9%
99.9%
>99.99%
>99.99%
99.2%
145
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THE SITE DEMONSTRATION
OF THE
RETECH PLASMA CENTRIFUGAL FURNACE
Laurel Staley
Chemical Engineer
Superfund Technology Demonstration Division
Risk Reduction Engineering Laboratory
U.S. Environmental Protection Agency
Cincinnati, Ohio 45268
(513) 569-7863
INTRODUCTION
Plasma is highly ionized gas that contains equal numbers of positively
and negatively charged particles. Plasmas can be created by passing gas
through an electrical discharge and thereby ionizing it. The Plasma
Centrifugal Furnace (PCF), developed by Retech Inc. of Ukiah, California, uses
plasma generated by a transferred-arc torch to vitrify contaminated soil. In
this system, soil contaminated with .organic chemicals and metals is fed to the
rotating PCF vessel. The plasma torch is used to heat and melt the soil at a
temperature of approximately 3000°F., As the soil melts, organic contamination
is driven into the gas phase which is at an average temperature of 2000°F.
Organic contamination is thermally destroyed at these temperatures. Exhaust
gas from the PCF is treated downstream to remove any unburned hydrocarbons,
acid gas and particulate. Melted soil is intermittently discharged from the
PCF and allowed to air cool into a glass-like solid mass.
METHODOLOGY
The PCF was demonstrated as part of the EPA's Superfund Innovative
Technology Evaluation (SITE) program in July 1991 at the U.S. Department of
Energy's Magnetohydrodynamics Component Development and Integration Facility
(CDIF) in Butte, Montana. During th^ demonstration, the PCF. treated 1440 Ib
of soil contaminated with 28000 ppm zinc oxide, 1,000 ppm hexachlorobenzene
and 10% by weight No. 2 diesel oil. This material was fed to the PCF at 120
Ib/hr. To evaluate the performance of the system, the EPA sampled the feed
and all effluent streams from the process. On cooling, the treated soil
formed a glass-like matrix. During vitrification, organic contamination in
the soil was volatilized and thermally destroyed.
RESULTS
Preliminary results from the demonstration indicate that the PCF
effectively immobilized the zinc contamination while thermally destroying the
hexachlorobenzene. The vitrified soil produced by the PCF did not produce
Teachable quantities of zinc. In fact, while the feed soil produced leachate
146
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containing 982 mg/L zinc, the vitrified soil produced leachate that contained
only 0.30 - 0.45 mg/L zinc. While much of the zinc was volatilized during
vitrification, acid digestion of the slag revealed that it still contained
between 6000 ppm and 9000 ppm zinc. Although zinc is not regulated under the
TCLP rule, these results clearly indicate that the PCF was able to immobilize
the zinc that remained in the slag. The Destruction and Removal Efficiency
for hexachlorobenzene was greater than 99.99%. Benzene was the only Products
of Incomplete Combustion detected at significant levels.
Particulate emissions were 0.374 grains/dscf which exceeds the RCRA
regulatory limit of 0.08 grains/dscf. Emissions of NO averaged 5000 ppm.
Because the flowrate of the stack gas is very low in the PCF, NOX emissions
did not exceed regulatory limits. These emissions remain a concern, however.
In full-scale PCF applications,
necessary.
NO and additional particulate control may be
CONCLUSIONS
The results of the SITE demonstration of the Retech Plasma Centrifugal
Furnace indicate that it may be a practical vitrification technology.
Additional particulate and NOX control may be necessary, but such control is
readily available and should not prevent this technology from being used at
sites where it is otherwise applicable.
147
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SITE DEMONSTRATION OF THE
SOILTECH ANAEROBIC THERMAL PROCESSOR
Paul R. de Percin
Superfund Technology Demonstration Division
Risk Reduction Engineering Laboratory
Cincinnati, Ohio 45268
INTRODUCTION
In 1986, the U.S. Environmental Protection Agency (USEPA)
established the Superfund Innovative Technology Evaluation (SITE)
program to promote the development and use of innovative
technologies to clean up Superfund sites. A SITE program field
demonstration was performed on the SoilTech Anaerobic Thermal
Processor (ATP) at the Wide Beach Development site in Brant, New
York during May 1991. This technology is designed to thermally
desorb organic contaminants such as polychlorinated biphenyls
(PCBs) from soils and sludges. During this demonstration, the
ATP was used in conjunction with dehalogenation using alkaline
polyethylene glycol (APEG) reagents to chemically destroy PCB
contaminants.
PROCESS DESCRIPTION
The SoilTech ATP is an innovative, indirectly-heated rotary
kiln system, using a physical separation process that thermally
desorbs organics from soils and sludges. Dehalogenation is
accomplished by spraying the contaminated soil with a diesel fuel
and oil mixture which acts as a carrier for the APEG. The kiln
provides intimate soil and reagent mixing combined with elevated
temperature and residence time to accelerate the APEG
dechlorination reactions.
149
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The ATP kiln is innovative because it has four distinct
zones. The first section is the preheat zone where the
contaminated feed temperature is elevated to about 500°F. The -
next section is the retort zone where the soil is heated to
900°F, either volatilizing or coking the hydrocarbons under
anaerobic conditions. The third section is the combustion zone
where the kiln is heated and non-condensable hydrocarbons are
destroyed. The last section is the cooling zone in which the
soil is cooled by heating the preheat zone. Sand seals allow-the
different zones to have separate operating conditions. ,
The unit is designed to handle 10 to 15 tons per hour 'of
solids containing up to 20 percent moisture and 10 percent
hydrocarbon content. Wastes with greater than 20 percent
moisture require dewatering to improve process economics and
wastes with greater than 10 percent hydrocarbon content may
require multiple passes through the unit.
During the remediation, the contaminated soils were
excavated from yards and roadways, and staged in the contaminated
feed storage area. Prior to entering the processor, contaminated
soil passed through a grinder.
SITE DESCRIPTION
Between 1968 and 1978, about 40,950 gallons of waste oil,
some contaminated with PCBs, was applied to area roadways for
dust control. In 1980, a sanitary sewerline was installed, and
PCB-contaminated soils were excavated and used as fill in several
residences. As a result of these activities, approximeitely
42,000 tons of soil were contaminated with PCBs. Conteimination
levels in these soils ranged from the low tens of parts per
million (ppm) to over 5,000 ppm.
DEMONSTRATION OBJECTIVES
The SITE technology demonstration had the following
obj ectives:
1) Assess the technology's ability to remove PCBs and
other organic contaminants from the soil,
2) Determine whether polychlorinated debenzo-p-dioxins
(PCDD) or polychlorinated dibenzofurans (PCDF) are
produced in the system,
3) Document the operating conditions of the SoilTech ATP,
4) Determine capital and operating costs of the ATP
Technology.
150
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SITE DEMONSTRATION
For the SITE demonstration, three tests were conducted
during full-scale remediation while the ATP was operated under
typical operating conditions. Each test run consisted of 5.5
hours of solids and liquids sampling and 5 hours of concurrent
stack sampling. The solid and liquid samples included
contaminated feed soil, treated soil, combined flue gas cyclone
fines and baghouse dust, preheat vapor cyclone fines, scrubber
liquor, condensed water (before and after treatment), vapor
scrubber oil, and preheat oil. In addition to stack gases, the
non-condensable preheat and retort off-gases also were sampled
during each run. Laboratory analyses included analyses of solid,
liquid and stack gas for PCBs, dioxins/furans, volatile organic
compounds (VOCs), and semivolatile organic compounds (SVOCs).
Extractable organic and inorganic chlorides were also analyzed in
an attempt to trace the fate of chlorine throughout the system.
A variety of other general chemistry and macronutrient analyses
were performed to characterize the feed and treated soils.
The unit was operated at an average 6.3 tons per hour during
the three runs. Other parameters, such as kiln temperature,
stack flow rates, etc., were maintained at essentially constant
conditions.
DEMONSTRATION RESULTS
Key findings from the Wide Beach SITE demonstration are:
1) The SoilTech ATP removed PCBs from the contaminated
soil to levels below the EPA-required cleanup
concentration of 2 ppm. The highest average treated
soil PCB concentration was 0.073 ppm.
2)
3)
4)
5)
Dioxins and furans did not seem to be created.
No_major operational problems affecting the ATP's
ability to treat the contaminated soil were observed.
The average stack gas emissions were:
Particulate
HCL
PCB
Dioxins/Furans
0.362 gr/dscf (7% O2)
0.054 Ib/hr
3.87 x 10'4 Ib/hr
1.37 x 10"7
Ib/hr
No VOC and SVOC degradation products were found in the
soil.
151
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EXTENDED ABSTRACT
for the
US EPA Risk Reduction Engineering Laboratory Research Symposium
Cincinnati, OH ,
April 14-16,1992 '
THE SITE INVESTIGATION ROBOT
JimOsborn "
Field Robotics Center
Carnegie Mellon University . , .
Pittsburgh, PA 15213 ' '
Non-invasive imaging of the underground is an essential component of hazardous waste site
investigations, yet, despite advances in sensjor technology, high quality maps of the subsurface
are difficult to obtain. Subsurface mapping depends on the spatial correlation of individual
sensor measurements taken at multiple locations. Current manual data collection techniques,
however, are subOptimal for precisely positioning subsurface imaging sensors and
-------
obstacles while maximizing coverage of the surface.
At each point in sampling grid, a pulse is transmitted into the ground and the energy
reflected to the receiving antenna is recorded, digitized and pre-processed to remove pulse
transmission effects and noise. Three dimensional data arrays are then formed using the position
information associated with the records. The waveform recorded at each grid point is actually a
composite of all radar reflections within the antenna's conical beam pattern due to the poor
focusing of the GPR antenna. However, since the spacing between surface grid points is
accurately measured, we are able to correlate all of the measurements and synthetically focus the
antenna. Vertical-and horizontal sections of the resulting subsurface map are then displayed as
color or gray-scale images and enhanced further with several filtering and feature detection
algorithms.
SIR is an example of an emerging class of robots dedicated to the solution of hazardous waste
problems. The spatially correlated information that Site Investigation Robot generates will be
used to more effectively conduct the costly phase of site remediation. This, along with reduction
of human exposure will ultimately lower the expense of site cleanups. This project is a
preliminary step towards broader capabilities in automated waste site investigations, such as
acquisition of a wider variety of data, environmental sampling, centralized site databasing, and
computer-aided site modeling.
153
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Figure 1. The Site Investigation Robot prototype
154
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EVALUATION OF THE AIR-SPARGED HYDROCYCLONE
Theodore S. Jordan
Metallurgical Engineering Department
Montana College of Mineral Science & Technology
Butte, Montana 59701
INTRODUCTION
Throughout history, both the mining of ores and the extraction of metals from them has been guided
by economic considerations. Thus, the miner took those ores that were easiest to mine and the
processor extracted those values that came out readily. Processing focused on improving metal
.- reqpyery to the extent that the cost of increased yields was more than.conipensated by,the values
recovered, but those minerals whose extraction cost exceeded their value were left behind. The result
has been the accumulation of thousands of tons of partially depleted mineral resources, generally known
as mil) tailings. .-;", ,,
Over one hundred years of extensive mining and milling operations has left the area of Butte,
Montana, 'The Richest Hill on Earth", with millions of tons of tailings containing varying amounts of
metallic minerals. The initial mode of occurrence of these minerals was in the form of sulfides, the
primary source of base metals such as copper.lead, zinc, nickel, etc. Substantial amounts of such
minerals remain in the tailings impoundments. Through exposure tolthe atmpspherei the elements and
bacterial action, the sulfides, which are relatively insoluble in water, oxidize to soluble sulfates, creating
acidic drainage, laden with heavy metals and harmful to plant, animal and aquatic life. The watershed
from this area, known as the Clark Fork Drainage, comprises the largest collection of Superfund Sites in
the United States. ; r;
Naturally, extraction technologies have improved over the course of Butte's mining history, while ore
grades have progressively diminished. Thus, the oldest tailings are those containing the highest content
of sulfides. Sometimes overlain by more recently-produced and cleaner tailings, they still produce acidic
effluent. , , . : , • , : , :
The work undertaken in this project is directed toward developing means to reprocess old tailings in
order to remove a substantial percentage of the acid producers and, hopefully, to recover sufficient
mineral values to offset some of the cost of removal and refreatment.
The most modern method of separating sulfide minerals is froth flotation (hereinafter referred to
simply as flotation), wherein mineral surfaces are selectively rendered water repellent by subjection to a
suitably controlled chemical environment within an aqueous slurry. Prior to the advent of flotation early
in the 20th century, the primary method of separating sulfides from associated waste minerals was by
gravity concentration, which is quite sensitive to particle size. While the lower particle size that can be
separated by gravity concentration is in the range of 300 micrometers, flotation reduced the lower size
limit to about 50 micrometers. This development was especially significant in the processing of Butte
ores, since the values in them are concentrated in the finer size fractions.
The Butte area thus contains two general types of tailings, those from older gravity operations and
more recently produced flotation tailings. As would be expected, the flotation tailings have been ground
to a finer size and contain less mineral values than do the gravity tailings. Thus, the older gravity tailings
are the more obvious target for remediation through removal of sulfides left behind by earlier processors,
but retreatment of either type of tailing would be enhanced by the development of technology that would
recover particles finer in size than those recoverable by flotation.
155
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Tailings from the old Colorado Mill, a Superfund site containing about 250,000 cubic yards of gravity
concentration tailings, was the initial target of this project. Preliminary tests indicated that this material
was an ideal candidate for retreatment through the Air-Sparged-Hydrocyclone (ASH), to be described
later. A proposal to evaluate the ASH with Colorado tailings was submitted to the U. S. Environmental
Protection Agency (EPA), but shortly after its acceptance, the Potentially Responsible Party (PRP) for
Colorado Mill tailings withdrew permission for removal of a quantity of the material for the work.
Subsequently, a more recent tailing, resulting from a flotation operation, was obtained and tested.
METHODOLOGY
Rotation is conventionally carried out in stirred tank reactors in which ground mineral particles are
held in suspension in water, which disperses the necessary chemical reagents and to which air is added
and fractionated into fine bubbles by a rotor/ stator arrangement. In the agitated slurry, particles and
bubbles collide, with water repellent particles adhering to bubbles when collision takes place. The
bubble/particle agglomerate levitates to the slurry surface and overflows to a suitable container, thus
separating water repellant from water wettable particles. Poor flotation recovery of small particles is
thought to result from low probability of collision due to the reduced inertia attendant with light weight.
Most of the attempts to develop more effective means of flotation have focused on flotation machine
design. One such device is the Air-Sparged Hydrocyclone (ASH), which was developed! by Dr. J. D.
Miller of the University of Utah in the 1980's. The ASH, diagrammed in Figure 1, increases the
probability of particle/bubble collision in two ways: 1) particles enter the ASH at a high tangential
velocity and, 2) the porous inner wall of the ASH admits a great number of fine air bubbles in a swirling
layer in line of contact with the particle stream. As in conventional hydrocyclones, lighter particles exit
upwards through the vortex finder and heavier particles leave through the bottom of the device. In the
ASH, the lighter particles are the particle/bubble agglomerates.
OVERFLOW
SLURRY
AIR
NIPPLE
UNDERFLOW CONTROL SLEEVE
UNDERFLOW DISC
UNDERFLOW
DISC WtTH DESIRED DIAMETER IS INSERTED
TO CONTROLTHE UNDERFLOW
Figure 1. Air-Sparged Hydrocyclone
156
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The ASH is licensed in Montana to Hydroprocessing and Mining of Montana (HPM), who have set up
a,pilot plant for its evaluation.
RESULTS
Chemical analyses of the metal content of various size fractions of a randomly-selected sample of
Colorado Mill tailings, before and after size reduction by grinding, are presented in Table 1.
TABLE 1. METAL DISTRIBUTION IN SIZE FRACTIONS OF COLORADO TAILINGS
Tyler Mesh
As Received
+35
—35 + 48
-48 + 65
-65 + 100
-100 + 150
-150 + 200
-200
Calculated Head
After Grind
+35
-35 + 48
-48 + 65
-65 + 100
-100 + 150
-150 + 200
-200
Calculated Head
Weight %
42.3
18.3
14.7
9.7
4.8
3.0
7.2
Assay
NIL
0.9
11.0
17.5
18.8
11.0
40.8
Assay
_Pb_
.04
.04
.04
.05
.06
.07
.42
.07
.04
.04
.04
.05
.05
.16
.09
Assay. %
_Zn_
.12
.17
.26
.43
.82
1.30
1.77
.37
.15
.06
.09
.20
.32
.57
.33
Distribution. %
Cu
.11
.08
.10
.12
.15
.20
.80
.16
.08
.04
.04
.05
.07
.30
.16
Pb
24.9
10.2
8.2
6.7
4.1
2.8
43.1
0.4
4.8
7.6
10.2
6.0
71.0
Zn
13-9
8.5
10.4
11.3
10.7
10.4
34.7
0.4
2.0
4.8
11.4
10.7
70.7
Cu
29.2
9.2
9.3
7.3
4.5
3.7
36.7
0.5
2.9
4.6
6.2
5.1
80.8
Inspection of the table points out the tendency of the metal-bearing minerals to report in the finer size
fractions.
Ground material was then passed through the ASH repeatedly to see if repeated treatment5
("scavenging") would bring about progressive flotation of a number of potentially toxic elements.
Resulting data are summarized in Table 2, in which UF signifies the underflow or rejected portion and
OF the overflow or concentrate. (Underflow from the first cycle becomes feed to the second cycle and
underflow from the second cycle is feed to the third cycle.) Since concentrate is removed after each
test, feed to the succeeding cycle is lower in grade, which accounts for the progressive decrease in both
157
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underflow and overflow grade. In commercial milling operations, it is normal practice to scavenge the
ore stream to the extent required to give a desired recovery. The lower grade concentrates are returned
to preceding process cycles in order to achieve acceptable concentrate grades.
TABLE 2. METAL CONTENT OF PRODUCTS AFTER REPEATED PASSAGE OF UNDERFLOW
THROUGH THE ASH
Analysis in Milligrams per Kilogram (ppm) in Solids
Element
Arsenic
Barium
Cadmium
Copper
Chromium
Gold
Iron
Lead
Manganese
Mercury
Selenium
Zinc
Silver
UF#1
980
< 5.0
30.60
288
7.49
1.12
4,108
5.00
158
0.004
< 0.2
2,640
48.55
UF#2
820
< 5.0
13.75
285
1.87
0.28
3,694
3.75
147
< .002
< 0.2
2,420
18.14
UF#3
790
< 5.0
12.00
220
1.56
0.28
2,656
30.20
140
< .002
< 0.2
1,870
14.51
OF#1
10,780
< 5.0
78.75
6,278
29.60
56.08
35,628
8,152
383
0.77
< 0.2
35,350
473.78
from:
OF #2
8200
< 5.0
28.50
3,100
23.80
13.95
30,598
5,280
315
0.51
< 0.2
15,150
405.70
OF #3
4650
< 5.0
27.00
1,550
13.10
5.30
20,958
866
225
0.09
< 0.2
14,170
202.85
The above results led to submission of the proposal to EPA. Due to the refusal of the PRP to supply
sufficient material for complete testing, a sample of about 28 tons of tailings from the defunct Marget
Ann mill was obtained from New Butte Mining Company, who are interested in ASH technology and had
earlier cooperated with HPM in testwork on dump ore from the Butte area. The Marget mill operated
briefly In the 1950's and appears to have been a technical success but an economic failure.
Preliminary examination showed the material to be quite low in metal values and somewhat
contaminated with organic matter. It was also found that, like most local tailings, metal content
increased with decreasing particle size. This is illustrated in Table 3.
Three factorial design experiments at different levels of grind, collector and activator showed only
minor concentration of lead or zinc by flotation in a conventional laboratory machine. Tests in the ASH
pilot plant were carried out under various conditions, since success with this difficult material would
Indeed demonstrate the utility of the ASH in the flotation of fine mineral particles.
a :
Nine campaigns were completed with,results similar to those obtained from the conventional
flotation machine. The low grade of the starting material made accurate analysis difficult and material
accounting was poor. Work on Marget Ann tailings was terminated after analysis of data from the ninth
run and remaining material and test products were returned to the tailings site.
158
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TABLE 3. LEAD AND ZINC DISTRIBUTION IN MARGET ANN TAILS SIZE FRACTIONS
Tyler Mesh Weiaht %
+ 100 7.0
-100 + 200 12.6
-200 (Dry) 3.0
-200 (Wet) 77.4
Calculated Head Assay
Pb
, , .042
.062
.077
.086
.080
Assav. %
Zn
.076
.138
.141
.139
.134
Distribution. '
Pb
3.7
9.8
2.9
83.6
%
Zn
4.0
12.9
3.1
80.0
CONCLUSIONS
It is concluded that the Air-Sparged-Hydrocyclone shows promise for recovering sulfide minerals
from materials typified by Colorado Mill tailings but thai each candidate for such treatment must be
evaluated by testing.
Pilot plant work in the immediate future will focus on the quantity of Colorado Tailing that remained
after the preliminary work that led to submission of the project proposal. If this shows promise, another
tailing sample will be sought. If results are negative, the project will be terminated.
159
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ASSESSMENT OF BINDING ENERGIES BETWEEN ORGANIC
CONTAMINANTS AND SOILS AND SEDIMENTS"
Walter J. Weber, Jr., and Thomas M. Young
Department of Civil and Environmental Engineering
The University of Michigan
Ann Arbor, Michigan 48109-2125
(313) 763-1464
INTRODUCTION
Accurate assessment of the extents to which various hydrophobia organic contaminants will sorb
to different types of soils is critical to the development of realistic models of contaminant fate and
transport, as well as to the selection of effective remedial strategies. Results of field studies show that
hydrophobia organic compounds persist longer and migrate more slowly than predicted by commonly
used ground water transport models, which are predicated on simple linear, reversible, equilibrium
sorption phenomena. The goals of this research are to develop: 1) an improved model of complex
sorption behavior in soils and, 2) a protocol which can be employed as a basis for the more realistic
selection of appropriate transport models and remedial technologies for contaminated subsurface sites.
CONCEPTUAL MODELS FOR SORPTION REACTIONS
Three general classes of binding interactions between contaminants and soils can be identified
(1). Chemical sorption occurs when a bond, having all of the characteristics of a true covalent bond, is
formed between a functional group on the soil surface and the sorbed chemical. A second type of
interaction, which is common for polar solutes, is electrostatic or ionic bonding between the solute and
charged functional groups on the soil surface; an example is the bindjng of calcium ions to a clay. Non-
polar solutes are typically bound to soils by relatively low energy dipole interactions with functional groups
on the soil surface. Adsorption of a hydrophobia compound results from the cumulative effect of these
binding interactions and repulsive interactions between the solute and the solvent that seive to drive
solute molecules out of solution and onto soil surfaces.
The wide range of forces contributing to sorption phenomena results in great variations in binding
energies between particular solutes and soils. Most soils are intrinsically heterogeneous, generally being
comprised of a conglomeration of various mineral and organic surface types. The binding strength and
isotherm shape for sorption of a given contaminant on a given soil surface is determined by the
distribution of the energies of individual soil fractions. Uniform distributions of binding energies usually
result in linear isotherms at low surface coverages, while variations in the binding energies of the various
components comprising a soil will commonly yield non-linear isotherms (2).
Sorption of hydrophobia organic contaminants on soils is frequently described by models that are
predicated on the assumptions that 1) soil organic matter is the principal, if not the only, soil fraction
exhibiting significant reactivity and 2) all soil organic matter has similar binding energies for non-polar
organic compounds. Sorption is therefore treated in these models as a linear, reversible process
dominated by weak physical binding reactions. Several investigators have generalized this concept by
developing correlations that allow the prediction of partition coefficients from the knowledge of a solute's
hydrophobicity and a soil's organic carbon content (3).
A number of limitations have been observed in applying these correlations to diverse soil
systems. The correlations generally fail for soils pf low organic carbon content, such as those typically
found in subsurface environments. Non-linear isotherms have been reported for a number of low organic
carbon subsurface soils (4,5). The nature of the organic carbon present in the soil has also been shown to
influence the sorption of non-polar organic molecules. More reduced organic matter, reflected by higher
C/O or H/O ratios, has a higher capacity to adsorb organic compounds than more oxidized organic matter
(2,6,7). Furthermore, the assumption of local equilibrium between contaminants and soils in ground water
systems has been shown to be invalid in a number of experiments (1,8). Explanations for non-equilibrium
160
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include extremely slow sorption rates (1,8,9) or hysteretic effects (10). Consequently, contaminants
present in a soil for an extended time period may be more difficult to desorb than freshly added material
(11). The total effect of the foregoing limitations is to call into question the accuracy of the microscopic,
linear, reversible, local equilibrium sorption model for despribing macroscopic solute transport in many
subsurface contamination situations.
IMPLICATIONS FOR FIELD SCALE MODELING
Selection of an inappropriate microscopic model of contaminant sorption can lead to significant
macroscopic modeling errors. For example, when a literature correlation developed for high organic
carbon surface soils is used to predict linear partitioning coefficients for low organic content subsurface
soils, the amount of sorption may well be underestimated, and the time required to complete a pump-and-
treat remedial scheme may therefore be far longer than predicted. Problems with literature correlations
can be avoided by conducting laboratory studies to generate isotherms specific to the soil-contaminant
system at a particular site. This method is not without pitfalls, however. When the data span too small a
range of solution concentrations, isotherm non-linearities may be overlooked. Short equilibration times in
the laboratory may cause hysteresis or aging effects to be missed, resulting in underestimates of true
levels of contaminant binding by soils in the system. In each case the results will be overly optimistic
estimates of the ease of soil remediation. Ideally, the reactivity of each type of soil fraction could be
measured and a soil's binding strength for a contaminant could be calculated by using an appropriate
distributed reactivity model (2). The complexity, immense diversity, and unknown structure of most soil
organic matter represent great obstacles to obtaining the data needed for routine use of this approach.
Alternatively, a tool might be developed to quantify binding strengths between specific contaminants to
be removed and soil samples from the site in question.
SUPERCRITICAL FLUID EXTRACTION IN SOIL SORPTION STUDIES
Supercritical fluid extraction using non-polar gases such as carbon dioxide appears to offer a
reasonable basis for development of such a tool. The chief advantage in using non-polar supercritical
fluids as extraction solvents lies in their controllable solvent strength and minimal solvent-solute
interactions. The solvent strength of supercritical fluids is directly related to their density, which can be
varied easily by changing the pressure in the extraction vessel. Moreover, mass transfer is often orders of
magnitude faster in supercritical fluids than in liquid solvents because supercritical fluids have more
favorable diffusivities and viscosities. Finally, supercritical fluids offer important practical advantages
because they are usually inert, non-toxic and relatively inexpensive. Efficiencies approaching or
exceeding those of Soxhlet extractions have already been demonstrated for removing several organic
solutes from soil and other solid matrices using supercritical carbon dipxide-cosolvent mixtures. Solutes
studied include polynuclear aromatic hydrocarbons (12,13), polychlorinated biphenyls and DDT (14)
In order to quantify the binding strength between a contaminant and a soil, non-quantitative
extractions can be performed at different pressures. Successive increases in extraction efficiency with
increasing energy input at higher pressures can then be used to calculate a distribution of binding
energies for the contaminant/soil system of interest. Changes in binding strength with aging of the
contaminant will be measured to develop a model of contaminant aging effects. Finally, the binding
strengths measured in the supercritical fluid extraction experiments will be compared with the
effectiveness of remedial schemes for soils including bioremediation, soil washing, and pump-and-treat
methods. If a correlation is found, supercritical fluid extraction may be a useful screening tool for
predicting remedial effectiveness.
CONCLUSION
Supercritical fluid extraction appears to have great potential as a new tool for examining the
sorptive behavior of soils based on the results of studies that have already been conducted in this area.
The need to improve our understanding of these processes is amply demonstrated by the number and
severity of soil and sediment contamination incidents that have been reported and by current difficulties in
modeling the removal of hydrophobia compounds from soils and sediments. It is our objective that the
research being conducted under this project will improve our knowledge of the microscopic sorption
161
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mechanisms operative in diverse types of soils and, consequently, increase the accuracy with which
macroscopic transport and remediation of contaminants can be predicted.
ACKNOWLEDGEMENTS |
This work is supported in part under Cooperative Agreement No. 818213 with the U.S.
Environmental Protection Agency. The Project Officer is Dr. John E. Brugger, Releases Control Branch,
Risk Reduction Engineering Laboratory, U.S. EPA, Woodbridge Avenue, Edison, NJ 08837-3679.
REFERENCES
(1) Weber, W.J., Jr., McGiniey, P.M., and Katz, L.E. Sorption phenomena in subsurface systems:
concepts, models and effects on contaminant fate and transport. Water Res. 25:499-528,1991.
(2) Weber, W.J., Jr., McGiniey, P.M., and Katz, L.E. A distributed reactivity model for sorption by soils
and sediments: conceptual basis and equilibrium assessments. Environ. Sci. Technol. in review,
1992.
(3) Karickhoff, S.W., Brown, D.S., and Scott, T.A. Sorption of hydrophobic pollutants cm natural
sediments. Water Res. 13:241-248,1979.
(4) Miller, C.T. and Weber, W.J., Jr. Modeling organic contaminant partitioning in ground water
systems. Ground Water 22:584-592. 1984.
(5) Miller, C.T. and Weber, W.J., Jr. Sorption of hydrophobic organic pollutants in saturated soil
systems. J. Contam. Hydrol.1:243-261, 1986.
(6) Garbarini, D.R. and Lion, L.W. Influence of the nature of soil organics on the sorption of toluene
and trichloroethvlene. Environ. Sci. Technol. 20:1263-1269, 1986.
(7) Grathwohl, P. Influence of organic matter from soils and sediments from various origins on the
sorption of some chlorinated aliphatic hydrocarbons: implications on Koc correlations. Environ.
Sci. Technol. 24:1687-1693. 1990.
(8) Miller, C.T. and Weber, W.J., Jr. Modeling the sorption of hydrophobic contaminants by aquifer
materials-ll Column reactor studies. Water Res. 22:465-474,1988.
(9) Bali, W.P. and Roberts, P.V. Long-term sorption of halogenated organic chemicals by aquifer
material. 1.Equilibrium. Environ. Sci. Technol. 25:1223-1235,1991.
(10) Horzempa, L.M. and DiToro, D.M. The extent of reversibility of polychlorinated biphenyl
adsorption. Water Res. 17(8): 851-859,1983.
(11) Steinberg, S.M., Pignatello, J.J., and Sawhney, B.L. Persistence of 1,2-dibromoethane in soils:
entrapment in intraparticle micropores. Environ. Sci. Technol. 21:1201-1208,1987.
(12) Hawthorne, S.B. and Miller, D.J. Extraction and recovery of polycyclic aromatic hydrocarbons from
environmental solids using supercritical fluids. Anal. Chem. 59:1705-708.1987.
(13) Hawthorne, S.B. and Miller, D.J. Extraction and recovery of organic pollutants from environmental
solids and Tenax-GC using supercritical CO2- J. Chrom. Sci. 24:258-263,1990.
(14) Brady, B.O., Kao, C.C., Dooley, K.M., Knopf, F.C., and Gambrell, R.P. Supercritical extraction of
toxic oraanics from soils. Ind. Eno:. Chem. Res. 26:261-268,1987.
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BIOAVAILABILITY AND BIODEGRADATION KINETICS OF ORGANICS IN SOIL
Henry H. Tabak, U.S. EPA, RREL, Cincinnati, OH 45268 (513) 569-7681
Rakesh Govind, Chao Gao, In-soo Kim, Lei Lai, Department of Chemical Engineering,
University of Cincinnati, OH 45221 (513) 556-2666
INTRODUCTION
As EPA begins to remediate Superfund sites using permanent treatment
technologies, such as bioremediation, a fundamental understanding of the kinetics
and the factors that control the rate of bioremediation will be required (1). Biological
treatment technologies hold considerable promise for safe, economical, on-site
treatment of toxic wastes (2). A variety of biological treatment systems designed to
degrade or detoxify environmental contaminants are currently being developed and
marketed. Knowledge of the kinetics of biodegradation is essential to the evaluation
of the persistence of most organic pollutants in soil (3,4). Furthermore, measurement
of biodegradation kinetics can provide useful insights into the favorable range of the
important environmental parameters for improvement of the microbiological activity and
consequently the enhancement of contaminant biodegradation.
A major effort is currently underway to clean up aquifers and soils that are
contaminated by organic chemicals, which has generated increased interest in the
development of in situ bioremediation technologies. Although considerable data
exists for rates of biodegradation in aquatic environments, there is little information on
biodegradation kinetics in soil matrices, where irreversible binding to the soil phase
may limit the chemicals bioavailability and ultimate degradation. Knowledge on
biodegradation kinetics in soil environments can facilitate decisions on the efficacy of
in situ bioremediation.
Recently, increased interest has been directed towards obtaining quantitative
information on pollutant sorption equilibria in soils, since the physical state of the
compound can influence its bioavailability. Information concerning the availability of
hydrocarbons sorbed on soil can be useful in choosing the appropriate technology to
treat subsurface contamination by gasoline, which is released to the environment as a
result of accidental spills and leaking underground storage tanks.
The main objective of this research is to quantitate the bioavailability and
biodegradation kinetics of organic chemicals in surface and subsurface soil
environments, examine the effects of soil matrices and soil conditioning (drying,
aging, compaction), and develop a predictive model for biodegradation kinetics
applicable to soil systems.
METHODOLOGY
Four separate soil microcosm reactors were designed, assembled and installed,
to simulate contaminated sites. Each microcosm reactor consisted of a glass
aquaraium (12 in.x 20 in.x 12 in.) with about 6 in. depth of soil. Undisturbed,
uncontaminated forest soil from Northern Kentucky was placed in each microcosm
reactor. The reactor was then brought into the laboratory, and contaminated with a
known class of compounds. Initially, our study was confined to phenols, PAHs,
163
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chlorinated phenols, and aromatic hydrocarbons. Nutrients were periodically sprayed
on top of the soil surface, to simulate rainfall. A known flow rate of carbon dioxide free
air was introduced into the headspace of each microcosm reactor, and the carbon
dioxide concentration in the exit gases was carefully monitored.
Each microcosm reactor represents a controlled contaminated site, which
eventually will have acclimated microorganisms for the contaminating organics.
Samples were taken from the microcosm reactors for measuring oxygen uptake
respirometrically, carbon dioxide generation kinetics, and other studies.
Studies were conducted with soil slurry reactors, wherein the oxygen uptake
was monitored respirometrically (5). Various concentrations of soil (2%, 5%, 10%) and
compound were mixed with the nutrient medium and stirred in the reactor flask. The
flask was connected to the oxygen generation flask and pressure cell of a 12 unit
VOITH electrolytic respirometer.
The oxygen uptake data was then analyzed on the computer, using the Monod
equation combined with a linear adsorption isotherm, to determine the soil adsorption
parameter, and the Monod biodegradation parameters. The model equations for a soil
slurry respirometer reactor flask have been summarized below.
(1)
dt
dSs
~BT
dSp
dt
KS+SS
(4)
(5)
where
Caq soil concentration [ mg/L ]
Kd soil adsorption coefficient [ L/mg ]
KS Michaelis constant [ mg/L ]
C^ oxygen uptake [ mg/L ]
Saq substrate concentration in aqueous phase [mg/L]
164
-------
, ,Sp byproduct [mg/L]
Ss substrate [ mg/L ]
„. , t time[HrJ „ ,. ,;
i ,Y , yield coefficient [ mg/mg ] ,
Yp bioproduct yield coefficient [ mg/mg ]
••:•••.. •& . .-...growth coefficient [1/Hr]
; Carbon dioxide generation rates were measured in shaker flasks, wherein the
.soil sample was shaken with the nutrients and compound. A packed bed of soda lime
pellets was used to absorb the generated carbon dioxide. The upper bed of soda lime
pellets was used to absorb the carbon dioxide from the influent air, and the lower bed
of soda lime pellets was used to absorb carbon dioxide generated in the flask, due to
biodegradation. ,
The soda lime pellets were then removed periodically from the shaker flask, and
analyzed for the amount of carbon dioxide generated.
RESULTS
Three chemical compounds, phenol, p-cresol, and 2,4 dimethyl phenol, were
selected for the soil respirometric degradation test. Three different compound
concentrations: 50 mg/l, 100 mg/l, and 150 mg/l, and three different soil
concentrations, 2%, 5% and 10% were selected for the initial studies.
Figure 1 shows the oxygen uptake curve for phenol at 100 mg/l concentration
and various soil concentrations: 2%, 5%, and 10%.
A newly developed adaptive random search technique was used to determine
these parameters from the experimental data. Table 1 presents the results of the
analysis for the experimental data presented earlier in Figure 1. it can be seen that
the Monod biokinetic parameters, u and Y do not vary with soil concentration, while
other parameters change dramatically at 10% soil concentration. This is expected due
to the fact that at higher soil concentrations, significant mass transfer effects occur in
the bioreactor system. This finding can have a significant impact on the design and
operation of soil slurry reactors. Furthermore, the physical soil adsorption parameter,
Kd, decreases as the substrate concentration increases, which is expected from a
nonlinear adsorption isotherm.
The experimental value for the soil adsorption parameter, KOc reported in the
literature (6) is 27. Since Kd is defined as KOc x (percent organic carbon in soil), the
experimental value of Kd is 27 x 0.06 = 1.62. The soil adsorption parameter values
obtained from respirometry are in the range of 1.02 - 3.899.
165
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Figure 2 shows the cumulative carbon dioxide generation data for 5% soil
concentration and phenol concentration Varying from 0 to 150 mg/l. The total amount
of carbon dioxide generated increases with the compound concentration.
The carbon dioxide generation data provides unambiguous measurement of
biodegradation kinetics for complete mineralization of the compounds. Reconciliation
of carbon dioxide generation data with oxygen uptake information is important in
determining the biokinetics of not only biotransformation reactions, but also for
complete mineralization of the compound.
CONCLUSIONS
Respirometric studies with soil slurry reactors provides valuable insight into the
biodegradation kinetics of compounds adsorbed in soil phase. It has been shown that
a Monod kinetic equation in conjunction with a linear adsorption isotherm can provide
reliable estimates of the Monod kinetic parameters. Experiments conducted in our
laboratory have demonstrated that cumulative carbon dioxide measurement can be
made for soil slurry systems.
REFERENCES
(1) Goring, C.A.I., Hamaker, J.W., Organic Chemicals in the Soil Environment,
Marcel Dekker, New York, 1972.
(2) Boethling, R.S., Alexander, M., Microbial degradation of organic compounds at
trace levels, Environ. Sci. Techno!., 13: 989-991, 1979.
(3) Brunner, W., Focht, D.D., Deterministic three-half-order kinetic model for
microbial degradation of added carbon substrates in soil, Appl. Environ.
Microbiol, 47: 167-172, (1984).
(4) Anderson, J.P.E., Domsch, K.H., Quantification of bacterial and fungal
contributions to soil respiration, Arch. Mikrobiol. 93: 113-127, 1973.
(5) Tabak, H.H., Govind, R., Determination of Biodegradation kinetics with the use
of respirometry for development of predictive structure-b!odegrada1:ion
relationship models, Paper presented at the IGT Symposium, Colorado Springs,
CO, December 1991.
(6) Kenega, E.E., Goring, C.A.I., Relationship between water solubility, soil
adsorption, Octanol-water partition, and Bioconcentration of Chemicals in Biota,
In Eaton, J.C., Parrish, P.R., Hendricks, A.C. (Eds.) Aquatic Toxicology, ASTM
STP 707, Philadelphia, PA: American Society for Testing and Materials, 1980.
166
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FIGURE i Phenol biodegradalion in soil slurry reactor
Phenol concentration = 100 mg/L
34
Time (hr)
180
CL
D
C
0)
O)
X
o
160-
140-
120-
roo-
80
60-
40-
20-
0
FIGURE 2 Phenol biodegradation in soil slurry reactor
Phenol concentration = 150 mg/L
,U*1
456
Time (hr)
10
167
-------
Table 1: Phenol concentration = 100 rag/1
Soil concentration :
2%
5% 10%
Monod parameters:
H [1/hrJ
Ks [me/Li
Y [me/me]
Yp Crne/me]
b fl/hrl
0.577
14.6
0.499
0.0304
0.0110
0.535 0.551
11.4 1.12
0.477 0.388
0.0209 0.00709
0.0295 0.00709
Adsorption parameter :
Kd IL/Bl
3.899
3.84 2.54
RSSE:
13.3
3.84 16.5
RSSE: Residual sum of squared errors
All mass measurements are as COD
Table 2: .Phenol concentration = 150 mg/1
Soil concentration :
• 2%
5%
10%
Monod
parameters:
u. [1/hr]
Ks fmz/Ll
Y [me/msl
Yp (me/me) ;
b fl/hrl
0.388
29.9
0.406
0,0360
0.0299
0.327
24.7
0.272
0.0782
0.0234
0.342
1.94
0.369
0.00103
0.0162
Adsorption parameter :
Kd FL/el
1 .02 -
1.22
3.07
RSSE:
185
139
318
RSSE: Residual sum of squared errors
All mass measurements are as COD
168
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o> g> E E
p E o o
C O O LO
O IT) T- -I—
^ c\r oT ^
I
Q
^ LJJ
1/Boi 'Q31Va3N3O 2OO
169
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REMOVAL OF CREOSOTE FROM SOIL BY THERMAL DESORPTION
by
Judy L Hessling, Edward S. Alperin, and Arend Groen
IT Corporation
11499 Chester Road
Cincinnati, Ohio 45246
(513) 782-4700
Richard P. Lauch and Jonathan G. Herrmann ^
Risk Reduction Engineering Laboratory
U.S. Environmental Protection Agency
26 West Martin Luther King Drive .
Cincinnati, Ohio 45268
(513) 569-7237
INTRODUCTION
Contaminated soil and debris (CS&D) pose a special problem because of their complexity and
high degree of variability. Therefore, the EPA has determined that a detailed evaluation of treatment
technologies for CS&D is needed to develop separate Land Disposal Restriction (LDR) standards
applicable to their disposal. These standards are being developed through the evaluation of best
demonstrated available technologies (BDATs). Once these LDRs are promulgated, only CS&D wastes
that meet the LDR standards will be permitted to be disposed of in land disposal units.
As part of the effort to establish the standards, a thermal desorption treatability study was
performed for the U.S. EPA to supply information as part of the data base on BDATs for CS&D
remediation. Thermal desorption has been successfully tested at both the bench and pilot scale on a
wide range of organic contaminants. During this'study, thermal desorption was investigated for removal
of creosote from soil at a process temperature of 550°C.
The contaminants of concern in the soil were polycyclic aromatic hydrocarbons (PAHs),
semivolatile contaminants that boil at temperatures ranging from approximately 215°C to greater than
525°C. Vapor pressures of these compounds vary depending on whether the contamination consists of
one compound or a mixture of compounds. Because the -boiling points 'of various' mixes of
contaminants are not known, bench-scale thermal desorption tests were performed to determine the
optimum temperature and residence time required for removal of these compounds from the soil. The
thermal desorption study was performed in two phases-bench-scale and pilot-scale. Based on the
results of the bench test, a pilot-scale test for the thermal desorption technology was performed at an
operating temperature of 550°C and a residence time of 10 minutes to reduce the PAHs present in the
soil.
METHODOLOGY
The thermal desorption pilot plant evaluated under this project consisted of a continuously
rotating desorber tube partially enclosed within a gas-fired furnace shell. Small baffles were located at
Intervals within the tube to provide soil mixing. A stationary thermowell was extended from the dis-
charge end into the tube with six thermocouples to monitor the soil temperature and three to monitor
the gas temperature along the tube length. The furnace was a refractory-lined chamber. The 14 equally
170
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spaced burners were controlled by a standard burner control system with appropriate safety features.
Temperature measurements for furnace burner control or monitoring were taken by four thermocouples
that contact at various locations on the outer metal wall of the rotating tube beneath the furnace
refractor. The furnace flue gas was discharged directly to the atmosphere through a remotely positioned
exhaust duct. The desorber was rated at 320,000 British thermal units (Btu) maximum heat duty. A
nitrogen purge was continuously introduced to the desorber at a low rate of 2 cubic feet per minute to
help flush contaminants and to maintain an atmosphere that does not support combustion (i.e., <6
percent oxygen). The residence time was measured before the study by placing colored aquarium
gravel into the feed hopper and visually observing its discharge from the desorber. The average
retention or residence time in the tube was calculated as the difference between the time the colored
gravel was placed in the screw feeder and the time it was discharged. Solids discharged from the
desorber during steady-state operation were weighed on a digital electronic scale to determine the soil
feed rate.
The Superfund soil that was tested during the project was a fine, sandy soil (75 percent of the
particles were between 0.1 and 0.4 mm in diameter). The soil had a relatively low moisture content of
approximately 10 percent and a heating value below 500 Btu/lb.
Various temperatures and soil residence times were evaluated throughout the bench-scale
testing program. The results obtained for the removal of semivolatile organics from the soil under
various operating conditions are summarized as follows:
Run No. 1 (300°C at 10 min.) removed 96.4 percent
Run No. 2 (425° C at 10 min.) removed 99.97 percent
Run No. 3 (550°C at 10 min.) removed 99.995 percent
Run.No. 4 (300°C at 20 min.) removed 97.4 percent
Run No. 5 (550°C at 5 min.) removed >99.9999 percent
Based on the results obtained during the bench-scale study, temperature and residence time
operating conditions of 550°C and 10 minutes were established for the pilot-scale testing program. The
total residence time for the soil in the thermal desorption system was 20 minutes. This total residence
time included three phases: 1) bringing the soil to 550°C, 2) treating the soil at that temperature for 10
minutes, and 3) cooling the soil before its discharge. Although the bench-scale results indicate that the
run at 550°C and a 5-minute residence time provided the highest removal efficiencies for the semivolatile
contaminants, larger particles were expected to be introduced into the pilot-scale unit, in which case the
feed streams might not be totally uniform and could contain "hot spots." Therefore, a temperature of
550°C and a residence time of 10 minutes were chosen to obtain better treatment of the contaminated
soil.
Six sets of temporally related soil samples (waste feed and treated residual) were collected
during the thermal desorption pilot test to evaluate the performance of the technology for the treatment
of creosote-contaminated soil. Additional samples of the off-gases were collected to characterize the
emissions from the unit prior to the air pollution control equipment to determine if any degradation
products were being formed.
RESULTS
Table 1 presents the average concentrations of organic contaminants in the soil before and after
treatment on a dry weight basis. On the average, total semivolatile organic contaminants were reduced
from 4635 milligrams/kilogram (mg/kg) to less than the detection limit. Hence, average removal of total
semivolatile organics was greater than 99.9 percent.
171
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TABLE 1. AVERAGE CONCENTRATION OF SEMIVOLATILE
ORGANIC CONTAMINANTS IN TREATMENT SOIL
(mg/kg)
a
Contaminant
Phenol
2-Methylphenol
4-Methylphenol
2,4-DimethyIphenol
Naphthalene
2-MethyInaphthalene
Acenaphthylene
Acenaphthene
Dibenzofuran
Fluorene
Phenanthrene
Anthracene
Fluoranthene
Pyrene
8enzo(a)anthracene
Chrysene
Benzo(b)fluoranthene
Benzo(k)fluoranthene
Benzo(a)pyrene
lndeno(1 ,2,3-cd)pyrene
Dibenzo(a,h)anthracene
Benzo(g,h,i)perylene
Pretest
<2.5
<1.4
<2.0
<7.0
14.3
180
38
342
237
388
1028
415
668
580 ,
172
158
158
77
25
<1.0
26
Total 4635
Posttest
< 0.043
< 0.023
< 0.033
<0.120
<0.016
<0.190
< 0.007
<0.210
< 0.081
< 0.020
< 0.034
< 0.073
<0.010
< 0.052
< 0.023
<0.120
< 0.047
<0.110
< 0.035
<0.016
< 0.320
<1.35
% Removal
NAa
NA
NA
NA
> 99.99
> 99.89
> 99.98
> 99.94
:> 99.97
:> 99.99
100.00
> 99.98
100.00
> 99.99
:> 99.99
> 99.92
> 99.97
> 99.86
> 99.86
NA
> 98.77
> 99.97
NA = Not applicable.
172
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No appreciable reduction in lead or arsenic was observed during the study because of the low
operating temperature in relation to the boiling points of lead and arsenic; however, mercury, which has
a boiling point of 356°C, was reduced from 19.3 mg/kg to 0.8 mg/kg.
Air sampling was performed to characterize the gases coming off the treatment system before
they reached any air pollution control equipment. The results of the air analyses showed a
predominance of aromatic compounds. All of the more complex aromatics detected in pretreatment soil
were also detected in the off-gas. In addition, phenolic compounds as well as volatile organic
compounds such as benzene, toluene, and xylene were detected in the air samples. The fact that these
compounds were not detected in the soil indicates they could have been masked by the more concen-
trated contaminants in the soil or the possible degradation of the more complex PAHs to form lower-ring
compounds.
CONCLUSIONS
Bench tests should be performed first to determine the best operating temperature and
residence time for the pilot-scale desorber with specific soils. For this study, a residence time of 10
minutes at a temperature of 550°C was selected from bench-test results for optimum operation of the
pilot-scale desorber. Volatile organic contaminants were below the detection limit in both the
pretreatment soil and the posttreatment soil.
On the average, the pilot-scale desorber reduced total semivolatile organic contaminants from
4635 mg/kg to less than the method detection limit, a removal rate of greater than 99.9 percent. All of
the individual semivolatile organics were reduced to concentrations below the method detection limits.
The highest average individual contaminant concentration in the pretreatment soil was 1028 mg/kg for
phenanthrene, and this concentration was reduced to less than the method detection limit of 0.034
mg/kg in the posttreatment soil.
The off-gas from the pilot-scale desorber contained all of the semivolatile organics in
approximately the same proportions that were present in the pretreatment soil. Some phenols and
volatile organic compounds (e.g., benzene, toluene, and xylene) were detected in the off-gas. This
indicates that some degradation of the higher-ring compounds to lower-ring compounds was taking
place.
No appreciable volatilization of lead or arsenic occurred in the pilot-scale desorber. Mercury,
which has a boiling point of 356°C, was 90 percent vaporized from the soil in the pilot-scale desorber.
Release of the mercury to the atmosphere was prevented by the high-efficiency paniculate air (HEPA)
filter and carbon adsorber. .
REFERENCES
IT Environmental Programs, Inc. 1991. On-Site Engineering Report for the Low-Temperature Thermal
Desorption Pilot-Scale Test on Contaminated Soil. Volumes I and II. Prepared for the U.S.
Environmental Protection Agency, Office of Research and Development, Risk Reduction Engineering
Laboratory, under Contract No. 68-C9-0036.
173
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SLURRY REACTOR BIOREMEDIATION OF SOIL-BOUND POLYCYCLIC AROMATIC
HYDROCARBONS
Alan B. Jones, Madonna R. Brinkmann and William R. Mahaffey
ECOVA Corporation
18640 - N. E. 67th Court
Redmond, Washington 98052
(206) 883-1900
INTRODUCTION
ECOVA Corporation conducted pilot-scale process development studies in 1991 using a slurry-
phase blotreatment design to evaluate bioremediation of polycyclic aromatic hydrocarbons (PAHs) in
creosote-contaminated soil collected from a superfund site. Bench-scale studies were performed as an
antecedent to pilot-scale evaluations in order to collect data which would be used to determine the
optimal treatment protocols. This study was performed for the U.S. EPA to supply information as part of
the database on Best Demonstrated Available Technology (BOAT) for soil remediation. The database will
be used to develop soil standards for land disposal restrictions. This paper is a summary of the
complete on-sfte engineering (OER) report that is available from the U.S. EPA.
The site is a former railroad tie-treating facility. Two surface impoundments were used for the
disposal of wastewater generated from wood-treating processes (Resource Conservation and Recovery,
Act waste code K001). Although all wastewater and liquid creosote have been removed from the
Impoundments, there is an estimated 12,500 cubic yards of soil and sludge remaining that is
contaminated with 2-, 3-, and 4+-ring PAHs. There is also some groundwater contamination restricted
to a relatively small area downgradient from the site.
A landfarming operation has been conducted on contaminated soil and sludges at the site since
1986. Although this work has attained significant reductions in 2- and 3-ring PAHs, the degradation of
the 4+-ring PAHs and benzene-extractaWe hydrocarbons has been less successful. A significant
improvement In blodegradation rates of the 4-ring and larger PAHs is possible through the* use of slurry-
phase biological treatment vs. landfarming. In this process, the soil is suspended to obtain a pumpable
slurry which Is fed to a large-capacity continuously stirred tank reactor (CSTR). The reactor is then
supplemented with oxygen, nutrients, and, when! necessary, a specific inocula of microorganisms to
enhance the biodegradation process. This method of treatment has several advantages because the
engineering and biotechnology required to provide an optimal environment for biodegradation of the
organic contaminants can be controlled with a high degree of confidence. Often, biological reactions
can be accelerated in a slurry system-because of the increased contact efficiency between contaminants
and microorganisms due to the higher sustained levels of bacterial populations in the aqueous phase
(e.g., 10-109 colony-forming units/millilrter (cfu/mL)). In a 30% slurry this translates to 109-101°
cfu/gram of sol! which is 10- to 100-fold higher than typically attainable in solid-phase treatment
processes.
METHODOLOGY
Physical characterization of the site soils indicated that there was a substantial amount of heavy,
coarse-grained particles. The percentage volume of soil fines which was less than 100 mesh was only
9%. This suggested that there would be appreciable difficulties in generating a manageable slurry with
this soil. Another important observation was the presence of hardened inclusions of creosote which
were pulverized when substantial shearing forces were applied. Consequently, a soil pretreatment was
required prior to charging pilot-scale reactors. Normally, a soil of this nature would be subjected to soil
washing to remove contaminants from oversize materials (+100 mesh) and yield a pregnant slurry
enriched in smaller particulates (-100 mesh). However, to meet the requirements of the EPA's program,
the pretreatment step chosen was a soil milling process which crushed larger particles yielding a soil
enriched in -100 mesh particles.
174
-------
Pilot-scale bioreactors (5) were EIMCO 64-liter stainless steel containers incorporating an airlift
system and rotating rake attachment. The reactors were filled with a 30% slurry (w/v, soil in water)
amended with nutrients and an inocula of PAH-specific degrading microorganisms. Nutrients were
adjusted to provide an optimal ratio of Total Organic Carbon (TOC) : Nitrogen (N) : Phosphorous (P). A
microbial evaluation of the contaminated soil was conducted to determine the size and diversity of
bacterial populations and the ability of these organisms to degrade polycyclic aromatic hydrocarbons.
Enrichment culture techniques and selective plating procedures were used to isolate and characterize
PAH degrading organisms. Reactors were inoculated with specific PAH degrading organisms
indigenous to the soil (P. fluorescens, P. stutzeri, and Alcaligenes sp.) at a concentration of 9.3 x107
per gram of soil. Rake speed, airlift volumes, temperature, pH, dissolved oxygen, and foaming were all
monitored over the course of the study.
Chemical analyses were performed on composited soil samples to determine contaminant levels.
Analysis for semivolatile contaminant levels was performed according to EPA Method 8270 (SW-846). In
addition, soil was analyzed for polycyclic aromatic hydrocarbons by HPLC (ECOVA Site Support
Chemistry [SSC-6]), total petroleum hydrocarbon (TPH) by infrared spectroscopy (IR) (EPA method
418.1), and total organic carbon (TOG) and inorganic nutrient ions (NO3, NH4, PO4, SO4) by standard
chemical methods (ECOVA SSC-17, ECOVA SSC-14, ECOVA SSC-15, and EPA 375.4, respectively). The
inorganic nutrient data were used to determine whether, based upon TOC, the levels and ratio of
nitrogen (N), o/ffto-phosphate phosphorous (P), and sulphur (S) were sufficient to support optimal
microbial activity. In addition, a soil toxicity test was performed using Microtox procedures. The pilot-
scale study was conducted for 12 weeks.
RESULTS .
This project demonstrated
optimum treatment of PAHs by
slurry-phase biotreatment in stirred
batch reactors. Baseline analyses
of PAH concentrations in the soil
are illustrated in Table 1.
Naphthalene, acenaphthene and
fluoranthene were the constituents
present at the highest levels. Total
PAH levels in these soils averaged
10,970 ± 1,515 gr. / kg dry soil
(parts per million, ppm). The 2- &
3-ring PAHs constituted 5,890 ±
1,469 ppm and the 4- to 6-ring
PAHs constituted 5,080 ± 367 ppm
of the total.
TABLE 1 '. BASELINE SOIL PAH
CONCENTRATIONS
PAH
Naphthalene
Acenaphthylene
Acenaphthene
Fluorene
Phenanthrene
Anthracene
Fluoranthene
Pyrene
Benzo(a)Anthracene
Chrysene
Benzo(b)Fluoranthene
Benzo(k)Fluoranthene
Benzo(a)Pyrene
DiBenzo(a,h)Anthracene
lndeno(1 ,2,3-cd)Pyrene
Mean (5)
(ppm)
2143.3
17.4
1937.1
967.8
518.9
307.0
2428.7
161.1
957.2
468.1
389.4
279.6
260.2
119.9
17.2
Std Dev.
(ppm)
710
7.6
1016.8
288.4
12.1
34.7
732.6
51.2
284.8
129.6
112.7
83.1
75.4
94.1
4.8
175
-------
Pilot-scale results for
reductions In total PAH of 89.
with an overall PAH
reduction of 93.4 ±
3.2% over 12 weeks.
With respect to the
more biodegradable
and bioavailable 2- & 3-
ring PAHs, a reduction
of 95.9 ± 1.8% occurred
within two weeks with
only a slightly increased
overall reduction to
97.14 ± 2.2% over 12
weeks (see Figure 2).
Reductions in the 4- to
6-ring PAHs, which are
less biodegradable and
bioavailable and usually
are not preferred
carbon sources for
bacterial growth, were
81.58 ± 6.7% after two
weeks. After 12 weeks,
further significant
reductions were
observed in the 4- to 6-
ring PAHs totalling
89.06 ± 4.8% (see
Figure 3). After nine
weeks, two of the five
reactors were
resuppiemented with
inoculum and two with
inoculum and surfactant
(Tween 80). These
amendments did not
stimulate further
reductions in PAHs
during the time period
from week 9 to week
12.
Specific PAH-
degrading bacterial
populations were
monitored over time.
Bacteria were grown on
mineral salt agar and
sallcylate-amended
mineral salt agar with
phenanthrene or pyrene
as carbon sources.
Sallcyiate-amended
PAH biodegradation paralleled the bench-scale study results. Optimum
3 ± 3.9% occurred during the first two weeks of treatment (see Figure 1)
16000
14000
inonn ,
5 8000 i
6000
2000
0 J
C
' ^-"i : ! ' ' ' !•'•''
*^( A . , . ; i ; — • — * Reactor #1
t\ ' -\-— "-~: •"*-• ' — ••---- .•---.; -.--' ;
V \ \ " " .1 L — D — Reactor #2
\lir V ; ; ; ! ! ~~° — "Reactor #5
--^4;^^^^--— --^ —Reactor^
; y=»~-<^— * ^HZ^^^^f *— 4
1 2 3 4 6 9 10 11 12
WEEKS
Figure 1. Total Polycyclic Aromatic Hydrocarbons
9000 i
8000
7000
ci_ i
2000
1000
C
.it ii
r r ' ' '< " " " '"" r r "
\ • • i • i • i i ma i jii
Vsj™,1 '• _; : ' ! [ -'—a— Reactor #2
L\\ : ...;:' :
V\\\i : : i ! f I , • , ~ — • — Reactor #4
\\ V •'.•:;,;
\v \ ! ~ ~ ~! r~ ~"! I""" ; "" 1 ~^<> — Reactor #5
1 2 3 4 6 9 10 11 12
WEEKS
Figure 2. 2- & 3-Ring Polycyclic Aromatic Hydrocarbons
• Reactor #i
• Reactor #2
• Reactor #4
• Reactor #5
Reactor #6
Figure 3. 4- to 6-Ring Polycyclic Aromatic Hydrocarbons
176
-------
media was used to screen for strains which might be capable of cooxidizing PAH's while growing on an
alternate carbon source. Specific PAH degrader population levels declined over the course of the
project (see Figure 4). The PAH cooxidizing populations exhibited the most significant and rapid
declines. This may reflect that bacteria that utilize salicylate are more likely to degrade naphthalene.
Once naphthalene levels have been depleted, these populations may become carbon-source limited and
death will occur. An interesting observation is that populations capable of utilizing pyrene and
phenanthrene as sole
carbon sources appear
to be sustained
throughout the study.
Between weeks 10 and
12, pyrene degraders
exhibit the most
significant population
declines. Total
heterotrophic bacterial
counts also do not
appear to decline over
the 12 weeks. These
data suggest subtle
shifts in bacterial
populations from low-
molecular weight PAH
degraders to higher-ring
PAH degraders.
1.00E + 10
1.00E + 09
1.00E + 08
2 1.00E+07
1.00E+06
1.00E+05
1.00E+04
IHMi IT II I! ! ? ri H H 3ftn i Iff la; i 4 jj 3 3K i [ [313 JI911 if walgj (M
•PCA
• PMSS-PHEN
' PMSS-PYFt
PMS-PHEN
PMS-PYR
Figure 4. Mean Value of Microbial Enumerations
0.15
0.11
0.08
0.05
0.01
MESH SIZING IN MILLIMETERS
PRE-MILLING
POST MILLING
8 WEEKS
An important
phenomenon that
occurred with these
soils in the continuously
stirred tank reactors
(CSTRs) was a further
comminution of the soil
despite extensive ball
milling. Figure 5 shows
the effect of both the
milling and CSTR
comminution on particle
size distribution. After
milling, there was an
enrichment of the
particle fraction smaller
in size than 0.21 mm at
the expense of larger
size particles. This
allowed development of
a manageable slurry.
After 8 weeks of CSTR stirring there was an enrichment in the fraction with particle sizes Jess than 0.15
mm. This resulted in an appreciable thickening (viscosity) of the slurry itself and also an increase in the
extraction efficiency of PAHs from soil particles. Between weeks 3 and 9 the levels of PAHs increased
with the most significant increases observed in the 4-to 6-ring PAH fraction. These phenomenon may
reflect the increased bioavailability of soil-bound PAHs due to comminution of soil particles which would
also contribute to increased slurry viscosity. PAHs were reduced by 94%, of which 2- and 3-ring
compounds were degraded 97% and 4- to 6-ring compounds degraded by 90%. Factors contributing to
Figure 5. Particle Sizing Data
177
-------
the lack of further decline of total PAHs may be: bacterial utilization of metabolic degradative
Intermediates as a preferential carbon source, a reduction of the more readily biodegradable 2- and 3-
ring PAHs to below levels which sustain an acclimation of biomass, the low bioavailability of the more
recalcitrant 4-, 5-, and 6-ring PAHs, or the generation of inhibitory metabolic end-products which repress
catabollc activity.
CONCLUSIONS
Slurry-phase biotreatment of creosote-contaminated soils offers an efficient and rapid process
for reducing the toxic PAH components of this waste class (K001). Soils from this superfund site
possess a robust population of PAH degrading bacteria capable of efficient biodegradation of these
compounds. Optimal biotreatment of these waste components can be stimulated by adjusting inorganic
nutrient levels, providing adequate aeration with mixing, and controlling the pH, Finally, material
characterization of soils is critically important in assessing the feasibility of using slurry-phase reactors to
bloremediate contaminated soils.
REFERENCES
1. Onsite Engineering Report Of The Slurry-Phase Biological Reactor For Pilot-Scale Testing On
Contaminated Soil, Vols. I & II, by IT Environmental Programs, Inc, Cincinnati, OH. Technical Project
Monitor: Richard P. Lauch, Water and Hazardous Waste Treatment Research Division, Risk Reduction
Engineering Laboratory, Cincinnati, OH. October, 1991 (in review). , . ,
ACKNOWLEDGEMENTS
The authors gratefully acknowledge the technical assistance of Christopher M. Krauskopf and
the expertise and assistance of Harlan A. Borow, both of ECOVA Corporation. The authors wish to also
thank Richard Lauch, U.S. EPA/Cincinnati, for his helpful comments and guidance.
178
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ADSORPTIVE FILTRATION FOR TREATMENT OF METALS AT SUPERFUND SITES
Mark M. Benjamin and Ronald S. Sletten
Dept. of Civil Engineering FX-10, University of Washington
Seattle, WA 98195, Tel: 206-543-7645
INTRODUCTION
This project investigated the potential application of a combination adsorbent-filtration media for
treatment of heavy metals from Superfund sites. The media is comprised of ordinary filter sand onto
which a layer of iron oxide had been coated. The coating was applied by heating a solution of iron nitrate
to dryness under controlled conditions in the presence of the sand. The final product was about 1 to 2%
Fe by weight. The coating was a few micrometers thick on sand grains of diameter around 400 mm, and
it increased the surface area of the bulk solid from about 0.04 to about 7 m2/g.
Since iron oxide is known to be a good adsorbent for heavy metals, it was hoped that the
modification of the surface of the sand would allow the sand grains to adsorb soluble heavy metals as
they passed through a column packed with the media. At the same time, it was anticipated that the
coated sand would perform comparably to plain sand as a media for collecting particulate metals. Thus;
the goal of the project was to assess the ability of the coated sand media to remove soluble and
particulate metals simultaneously as water containing those species passed through the column.
METHODOLOGY
Runs were conducted using synthetic influents and a treated, metal-bearing water from a
Superfund site. Preliminary runs used laboratory-prepared solutions containing 0.5 or 5.0 mg/L each of
three metals (Cu, Cd, and Pb). Most of these tests were conducted at pH 9.0 using a 2-minute empty
bed detention time, corresponding to a hydraulic loading rate of about 11 gal/min-fr. Runs were also
conducted to characterize the effects on metal behavior of ammonia (as a complexing agent), EDTA (as
a chelating agent), or sodium dodecyl sulfonate (a surfactant) in the influent solution, and of biogrowth in
the column. At the end of the project, a few tests were run with a solution collected from a Superfund site
where conventional treatment is currently being applied. During all runs, influent and effluent metals
concentrations were monitored, and, in most cases, soluble and particulate metals were analyzed
independently.
After most runs, the media was backwashed to remove the particulates that had been collected.
It was then regenerated at pH around 2.0 to remove the soluble metals that had sorbed. The
backwashing step was skipped if the influent in the previous run did not contain particulate matter.
Regeneration efficiency was monitored and characterized as a function of operating conditions during the
regeneration step.
RESULTS
In runs with 0.5 mg/L each of uncomplexed Cu, Cd, and Pb in the influent, the majority of the
influent metal load was soluble. Between 7000 and 13000 bed volumes of influent were treated
179
-------
effectively prior to substantial metal breakthrough. Before breakthrough, the metal concentrations in the
effluent were quite steady, with virtually no short-term fluctuations. Typical effluent concentrations of total
Cu, Cd, and Pb were substantially less than 0.1 mg/L each.
In the runs with influent nominally containing 5 mg/L of each uncomplexed metal (in reality,
influent metal concentrations varied between about 3 and 7 mg/L), most of the influent metal load was
particulate; soluble influent concentrations were typically around 1.5 mg Cd/L, 0.8 mg Pb/L, and 0.2 mg
Cu/L. For the purposes of this discussion, a "run" is defined as the time between sequential regeneration
cycles. Several batches of influent were treated during each run. During the course of these runs, the
media was backwashed over 20 times and regenerated about 10 times over a period of a few months,
with no apparent deterioration in performance.
Atypical breakthrough curve for these tests is shown in Figure 1. The total concentrations
(corrected for background) of all the metals in the effluent were well below 0.1 mg/L until about 150 to
200 bed volumes had been treated. Removal of soluble metal was always significant throughout these
runs, and was very good at least until the point of particulate breakthrough. Particulate rnetals began
breaking through the column after about 200 to 400 bed volumes had been treated over a 6- to 12-hour
period. Typical removal efficiencies for soluble metals in the influent were 80% for Cu, 90% for Pb, and
98% for Cd, and typical overall removal efficiencies (comparing total effluent and total influent) were 99%
or greater for all three metals (Table 1).
1 T
0.8 - -
•S 0.6 -•
0.4
0.2 •"•
Pb
Cd
Cu
100
200
300
400
Bed volumes
500
600
700
800
Figure 1. Breakthrough curve showing total and soluble metals in column effluent as a function
of the volume of water treated. Influent conditions: Cu = Cd = Pb = 5mg/L; pH = 9.0, Empty bed
detention time = 2 min.
180
-------
TABLE 1 . Soluble metals in column influent and effluent at various times during'run 1 5.
Time of Sample
Batch 1 , BV 3
Batch 1,BV 13
Batch 2, BV 3
Batch 2, BV 45
Batch 2, BV 63
Batch 3, BV 6
Batch 3, BV 260
Soluble Influent, mg/L
Cu Cd Pb
98 825 523
105 863 548
355 933 468
127 1603 683
160 1891 739
77 578 392
248 1710 697
Soluble Effluent, mg/L
Cu Cd Pb
23 26 3
23 17 39
.16 0 0
/ 25 27 84
24 31 140
23 12 83
63 59 109
% Removal of Soluble
Metals ,
Cu Cd Pb
77 97 99
78 98 93
95 >99 >99
80 98 88
85 . 98 81
70 ' 98 79
75 97 84
Headless usually reached 25 psi near the time when particulate breakthrough occurred. At this
point, the column was backwashed with pH 9.0 water, and the next batch of influent was fed into the
system. The backwash water typically contained a few hundred mg/L of each metal. After the first batch
of water had been treated, particulates broke through relatively soon after each backwash step. Thus,
backwashing with water adjusted to pH 9.0 did not return the column to its original filtration capacity.
However, despite the fact that particulates broke through the column more rapidly in batches 2 and 3
than in batch 1, the effluent values prior to breakthrough during treatment of all three batches were
comparable. When breakthrough did occur, it was due to particulate metals passing through the column;
the columns did not appear to reach adsorptive saturation in any of the three batches. Thus, it appears
that additional batches could have been run successfully before the column needed to be regenerated.
The regeneration protocol was to circulate either 4 or 8 bed volumes of water adjusted to pH 2.0
through the column. After two hours, an additional 4 to 8 bed volumes was passed through the column
and not recirculated. The metal concentration in the recirculation fluid increased rapidly at first and then
only slowly thereafter. Based on these results, it appears that a recirculating period as short as 10
minutes would release a large fraction of the available metal. Metal concentrations in the first and second
regenerant solutions were as high as 3000 and 500 mg/L after the 5 mg/L runs, and about a factor of 5
lower after the 0.5 mg/L runs. ;
Interestingly, only about 40 to 75% of the particulate metal load that was removed by the column
was recovered during the backwashing step. Most of the remainder was recovered during the acid
regeneration step, suggesting that once the particles collide with the media, they form strong bonds to it.
Overall recovery efficiencies (backwash plus regeneration) Were almost always greater than 80% and
were often 100% ± 10% (Table2). ... •
181
-------
TABLE 2. Recovery of metals from the column after various treatments after run 15.
Metal,
Batch #
Pb,1
Pb,2
Pb,3
Cd,1
Cd,2
Cd,3
Cu,1
Cu,2
Cu,3
Estimated
Cumulative
Particulate
Me Removed
(mg)
80.7
63.0
163.9
307.6
119.0
41.4
158.8
319.2
109.3
85.1
201.4
395.8
Metal
Recovered
by
Backwashing
(mg)
35.4
67.3
150.1
252.7
29.0
54.3
135.9
219.2
46.2
84.7
164.0
294.9
Cumulative
Soluble Me
Removed
(mg)
29
36
37
102
47
85
71
209
5.5
12.3
11.0
28.8
Metal
Recovered
by
Regeneration
(mg)
161.1
234.1
59.8
Total Metal
Recovery
Efficiency
101
86
84
When sufficient ammonia was added to the solution to keep all of the influent Cu and Cd (5 mg/L)
soluble, about 4000 mg each of Cu and Cd could be sorbed onto the media at pH 10. Regeneration of
this column using a total of 16 bed volumes of regenerant solution at pH 2.0 recovered 93% of the sorbed
Cd and 100% of the Cu. Thus, at least some complexing agents do not interfere with the performance of
the media. On the other hand, when EDTA was added at a ratio of 1.25 mols EDTA/mol metal,
breakthrough occurred very quickly, both at pH 10 and pH 4.5. The adsorptive filtration process appears
not to be applicable for waters containing such a strong chelator. In situations where complexed metals
need to be treated, tests investigating the behavior of the specific complex will be required.
Sodium lauryl sulfonate is a surfactant that might interfere with the process by interacting either
with the metals or the surface of the media. Thirty mg/L of this surfactant had no noticeable effect on
metal sorption.
In the one test that was run using media on which biogrowth had occurred, the biofilm apparently
reduced the capacity of media for the metals by about 50%. This interference could probably be
reversed by exposing the column to a high pH solution, which would solubilize a substantial amount of the
biofilm.
One set of tests was conducted using a treated, metal-bearing wastewater from a Superfund site.
Unfortunately, this solution could not be treated under optimal conditions for our process, since massive
amounts of CaCO3 precipitated when the pH was raised to 9.0. Therefore, the water was treated at pH
8.0. The only metal present in significant quantities in this water was Zn, for which the total and soluble
concentrations were in the ranges 0.6 to 4.0 and 0.3 to 0.6 mg/L, respectively. As shown in Figure 2,
typical total and soluble Zn concentrations in the effluent were 0.15 and 0.05 mg/L, respectively. Thus,
even though the test could not be run under optimal conditions, it did demonstrate that the adsorptive
filtration process could work on such a water. Chances are that the outcome would have been more
impressive if a water with lower Ca or alkalinity had been chosen for the test.
182
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1.0 -r
0.8 --
fi
I
0.6 --
0.4 --
0.2 --
0.0
• Filtered Effluent
* Unfiltered Effluent
° Zinc blanks
4 *** *»» ^AAAA****.* *
-°-t-
•H-
.
500 1000 1500 2000 2500 3000 3500 4000 4500
Bed volumes
5000
Figure 2. Breakthrough curve showing total and soluble Zn in the column effluent during
treatment of water from a Superfund site (Run 3). Prior treatment involved precipitation and
settling at pH = 8.0. Influent Zn concentrations quite variable with a mean value and standard
deviation of 0.73 ± 0.28 mg/L total and 0.40 ± 0.22 mg/L soluble Zn.
CONCLUSIONS
To summarize, simultaneous sorption and filtration of Cu, Cd, and Pb are feasible using iron
oxide-coated sand under reasonable engineering conditions. Soluble effluent concentrations of a few
tens of fig/L or less are achievable. The media can remove particulate metals simultaneously from the
water, probably with an efficiency comparable to that achievable with conventional sand filtration. The
media can be regenerated by exposure to an acid solution, yielding regenerant solutions containing metal
concentrations a few hundred times as concentrated as the influent. In our tests, filtration limited process
performance moreso than sorption, although this outcome is not generalizable: the limiting factor would
certainly depend on the specific chemical composition of the influent solution.
183
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PHASE SEPARATION AND SOLUBLE POLLUTANT REMOVAL
BY MEANS OF ALTERNATING CURRENT ELECTROCOAGULATION
Clifton W. Farrell
and
Thomas W. Gardner-Clayson
Electro-Pure Systems, Inc.
10 Hazelwood Drive
Amherst, NY 14228-2298
Tel: (716) 691-2610
INTRODUCTION
Electro-Pure Systems (EPS) has undertaken a two-year laboratory program to investigate the
technical and economic viability of alternating current electrocoagulation technology (ACE Technology)
for Superfund site remediation. The ACE Technology offers a technologically simple mechanism to
achieve phase separation of liquid-solid slurries and liquid-liquid emulsions, and to remove soluble ionic
pollutants (metals, alkaline metals, phosphate) from solution. Alternating current electrocoagulation was
originally developed as a treatment technology in the early 1980s to break stable aqueous suspensions
of clays and coal fines in the mining industry. The technology offers a replacement for primary chemical
coagulant addition to simplify effluent treatment, realize cost savings, and facilitate recovery of fine-
grained products that would otherwise have been lost. The traditional approach for treatment of such
effluents entails addition of organic polymers or inorganic salts to promote flocculation of fine
partlculates and colloidal-sized oil droplets in aqueous suspensions. These flocculated materials are
then separated by sedimentation or filtration. Unfortunately, chemical coagulant addition generates
voluminous, gelatinous sludges which are difficult to dewater and slow to filter. As an alternative to
chemical conditioning, alternating current electrocoagulation introduces into an aqueous medium highly-
charged polymeric aluminum hydroxide species which will neutralize the electrostatic charges on
suspended solids and oil droplets to facilitate their agglomeration (or coagulation). These species will
also coprecipitate many soluble ions. ACE Technology prompts coagulation without adding any soluble
species and produces a sludge with a lower contained water content and which will filter more rapidly.
Through separation of the hazardous components from an aqueous waste, the volume of potentially
toxic pollutants requiring special handling and disposal can be minimized. Waste reduction goals may
be accomplished by integrating this technology into a variety of operations which generate contaminated
water.
Presented in this paper are preliminary results from the laboratory testing program conducted by
EPS under the auspices of the U. S. EPA's Superfund Innovative Technology Evaluation (SITE) program.
Performance data from a field test of a pilot-scale alternating current electrocoagulation unit are
summarized as well.
METHODOLOGY
Laboratory experiments were conducted in a bench-scale electrocoagulation apparatus, referred
to as an ACE Separator™, on a series of synthetic wastes. Two designs of the ACE Separator™ were
used: a Parallel Electrode unit in which a series of parallel, vertically-oriented, aluminum electrodes form
a series of monopolar electrolytic cells up through which the effluent passes, and a Fluidized Bed unit
which consists of non-conductive cylinders equipped with rectilinearly-shaped, non-consumable metal
electrodes between which is maintained a turbulent, fluidized bed of aluminum alloy pellets. Application
of an alternating current field to the electrodes prompts dissolution of the aluminum and formation of
highly reactive polymeric hydroxide species. The Parallel Electrode ACE Separator™ was used in the
first year EPS participated in the SITE program when the basic mechanism of electrocoagulation was
184
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believed to be electrostriction (polarization of electrical charges on colloidal particles by imposition of an
alternating current electric field). Experiments conducted with this version of the ACE Separator™
primarily addressed the influence of frequency, residence time, field strength (electrode spacing), and
current density of the applied AC current field. The realization that treatment efficiency was primarily
dependent upon aluminum ion production instead of upon the characteristics of the applied AC current
field prompted development of the Fiuidized Bed ACE Separator™ which dissolves aluminum at least one
order of magnitude more efficiently than the Parallel Electrode ACE Separator™. Experiments in the
second year were conducted primarily with this newly-designed ACE Separator™.
Experiments were conducted on two surrogate wastes which were prepared by EPS by
combining measured quantities of the EPA's Synthetic Soil Matrix (SSM), supplied to EPS by EPA's
Edison, NJ laboratory, with hydrocarbon and/or metal contaminants selected by EPS. Both were
prepared as stable aqueous suspensions of silt, clay and top soil containing approximately 1%
suspended solids, with or without spikes of toxic metals (Cd, Cr, Cu, Pb) and diesei fuel. The clay
surrogate waste contained solely the -40 mesh synthetic soil matrix fines while the second incorporated
the fines fraction mixed with 1.5% No. 2 diesel fuel and 1% of a strong surfactant. Experiments on
metals and phosphate reductions were conducted on aqueous end-member solutions at neutral pH at
two solution conductivities (1,500 and 3,000 (iS/cm). Metals and phosphate matrix experiments were
conducted to determine the treatment conditions that would yield both acceptable metal reductions and
a reasonable operating cost (electrical power, aluminum consumption). Electrocoagulation treatment
efficiency was primarily determined by reductions achieved in the supernant phase of total suspended
solids (TSS), turbidity, and soluble contaminant concentrations (metals, Chemical Oxygen Demand
(COD) for diesel fuel-spiked surrogates). Improvements in solids settling rates and decreases in the
moisture content of coagulated solids filter cakes were also measured. Based upon the encouraging
results of bench-scale tests of the Fiuidized Bed ACE Separator™, a portable, pilot-scale ACE
Separator™ of this design with a nominal throughput capacity of 70 gpm was designed, fabricated and
tested for recovery of suspended colloidal-sized pigment (TiO2) from an industrial waste stream. The
results for treatment of the clay suspension surrogate, diesel-fuel contaminated soil slurry and metals-
bearing solutions are summarized below.
RESULTS
• Clay-Metals Surrogate
The clay suspension surrogate was spiked with four metal salts (Pb(NO3)2, CuSO4 • 5 H2O,
CdCI2 • V4 H2O, CrCI3 • 6 H2O) at concentrations of 10-50 mg/l, thoroughly mixed, and
electrocoagulated at operating conditions found to be optimum for effecting separation of clays from the
surrogate. While a majority of the soluble metals strongly adhere to the clays, electrocoagulation
enables agglomeration of the colloidal, metal-bearing clays and significant (>90%) reductions in the
soluble metals loadings (Table 1). The filtration time for the treated surrogate decreased to
approximately 50% of that required for the untreated surrogate waste (3:02 minutes versus 6:00
minutes). Comparative chemical coagulant experiments with alum (AI2(SO4)3) and organic cationic
polyelectrolyte flocculants (Drew Polymer 485) were also conducted on the surrogate waste.
Electrocoagulation yielded a faster filtration rate (2:15 minutes for 100 mis) than for either the untreated
slurry (7:30 minutes) or the alum-treated solution (3:53 minutes). Polymer treatment had the same
filtration rate. Filter cake volume expressed as a percentage of the pre-filtered sludge volume seemed to
be a minimum for ACE Separator™ treatment (6%) compared to alum and polymer treatment (13-15%)
The volume data indicate that the ACE Separator™-treated solids cakes are more compact and easier to
dewater than those for coagulant-treated samples. Particle size analyses of the treated and untreated
slurries indicated that the mean size of the ACE Separator™-treated solids both in the supernant and
filtrate (25.2 and 35.1 microns, respectively) increased by a factor of 3-4 over that in the original slurry
185
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(9.1 microns). Larger particulate growth occurred as a result of electrocoagulatiqn than by either
polymer or alum addition (15 and 10 microns, respectively).
TABLE 1. CLAY- METALS-SPIKED SURROGATE EXPERIMENTS
ACE SEPARATOR TREATED
ANALYTICAL
PARAMETERS
TOTAL SOLIDS
TOTAL SUSPENDED SOLIDS
TOTAL ORGANIC CARBON
TOTAL METALS:
CADMIUM
CHROMIUM
COPPER
LEAD
MOISTURE CONTENT
UNTREATED
SLURRY
(mg/l)
17,000
22,000
220
7.9
16
44
32
N.D.
SUPERNANT
(mg/l)
1,700
25
1.8
0.89
0.074
0.13
0.11
N.D.
FILTRATE
(mg/l)
1,700
3.0
26
2.2
0.018
0.053
1.7
N.D.
FILTER CAKE
(ug/i)
540,000
N.D.*
: N.D.
340
1,100
2,400
2,700
42.4
*N.D.: Parameter not determined.
• Clay-Metals-Diesel Fuel Surrogate
Electrocoagulation of the clay surrogate waste containing 1.5% diesel fuel and metals (Cu, Cd,
Cr, Pb) produced effective reductions in suspended solids (112 to 12 mg/l), total carbon (230 to 110
mg/l) and total inorganic carbon (28 to 12 mg/l). Copper is reduced by 90-94%, cadmium and
chromium by 91-97% apd lead by 86-89% (Table 2). No appreciable change in TOC loadings in the
supernant resulted from treatment; the TSS was reduced by approximately 90% from 222 to 19 mg/l.
Comparative chemical coagulant addition experiments were conducted for the diesel fuel contaminated
slurry. The following generalizations can be made for the treatment: alum and polymer treatments
generally required approximately 30% longer filtration times, ACE Separator™ and polymer treatments
reduce the total solids (TS) and TSS loadings to an equivalent degree (equal to four times the reduction
achieved by alum treatment) and better reductions in soluble metal concentrations were usually achieved
with polymer and electrocoagulation treatment. Particle size data confirm the appreciable enhancement
In the clay fraction as a result of electrocoagulation. The mean size of the ACE Separator™-treated
particulates both in the supernant and filtrate (188 and 20 microns, respectively) has increased by a
factor of approximately 85 and 8, respectively, over that in the original slurry (2.2 microns).
186
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TABLE 2. CLAY- DIESEL- METALS-SPIKED SURROGATE EXPERIMENTS
ACE SEPARATOR TREATED
ANALYTICAL
PARAMETERS
TOTAL SOLIDS
TOTAL SUSPENDED SOLIDS
TOTAL INORGANIC CARBON
TOTAL ORGANIC CARBON
TOTAL CARBON
TOTAL METALS:
CADMIUM
CHROMIUM
COPPER
LEAD
UNTREATED
SLURRY
„ ..(Pig/I)
' 1,870
222
15
.130
150
, 0.5
0.31
0.30
0.72
SUPERNANT
(mg/I)
1,480
4.5
7.8
6.6
20
0.15
0.024
0.085
0.09
FILTRATE
.Jmg/JL,,
-N:D*
N.D.
N.D.
N.D.
1,300
0.28
0.01
0.44
0.16
FILTER CAKE
(ug/0
1,000,000
N.D.
: N.D.
N.D.
N.D.
289
721
, 650
3,700
*N.D.: Parameter not determined.
• Metals and Phosphate Experiments . . ...:.'
Matrix electrocoagulation experiments on the surrogate metals and phosphate-bearing solutions
indicated excellent nickel, copper and phosphate concentration reductions. Electrocoagulation by
means of either design of the ACE Separator™ enabled in excess of 90% (concentration basis) of the
phosphate and copper to be removed from solution at low aluminum and electrical power requirements.
Reductions in the nickel concentration varied between 78 and 91% (concentration basis). Table 3
presents the analytical results for reductions for these three species from neutral solutions by means of
both the Fluidized bed and Parallel Electrode ACE Separators™ for representative matrix experiments.
« Pilot-Scale ACE Separator™ Demonstration
A pilot-scale, portable Fluidized Bed ACE Separator™ equipped with four, 6" diameter'
electrocoagulation cells having a combined nominal throughput capacity of 70 gpm was designed and
manufactured. This unit was field-tested at a TiO2 pigment manufacturer to recbver fine-grained (<30n)
product from the overflow of a clarifier which contains 500-3,000 mg/l TjQ2. Electrocoagulation of the
overflow at a rate of 1-2 ampere-minutes/liter, corresponding to introduction of «15-17. mg/l aluminum,
followed by 5-10 minutes of gravity settling allowed recovery of 85-95% of the pigment! . Such treatment
reduces the TSS of the overflow stream from 2,000 mg/I to «50 mg/l; direct electrocoagulation of the
filtrate entering the, clarifier is another treatment possibility for enhancing its "operation. The. direct
operating cost for this ACE Separator™ treatment required 5 KWH/1000 gallon's of electrical power and
«0.25 Ib. AI/1000 gallons for a total treatment cost of $0.50/1000 gallons. Electrocoagulation enabled
recovery of »17 Ibs. TiO2/lOOO gallons that would otherwise have been lost to a settling lagoon-'
Assuming a pigment price of $0.85/Ib. and an electrocoagulation operating cost of $0.50/1000 gallons
ACE Separator™ treatment will enable recovery of *$14.00 of TiO2 from every 1000 gallons of clarifier
overflow.
187
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TABLE 3. PHOSPHATE, NICKEL AND COPPER REDUCTIONS
EXPERIMENT* AND ACE SEPARATOR
OPERATING CONDITIONS
INITIAL
CONCENTRATION
(mg/l)
FINAL
CONCENTRATION
(mg/l)
• PHOSPHATE
FB 1.1 AMP, 180 SEC RT, 123 VAC
FB 1.5 AMP, 540 SEC RT, 74 VAC
PP 11.2 AMP, 240 SEC RT, 16 VAC
PP 19.6 AMP, 168 SEC RT, 27 VAC
• NICKEL
FB 2.7 AMP, 150 SEC RT, 130 VAC
FB 4 AMP, 120 SEC RT, 120 VAC
PP 22.6 AMP, 144 SEC RT, 20 VAC
PP 31.9 AMP, 221 SEC RT, 13 VAC
- COPPER
FB 1.1 AMP, 144 SEC RT, 97 VAC
FB 2.3 AMP, 14 SEC RT, 111. VAC
PP 23.8 AMP, 60 SEC RT, 110 VAC
PP 21 AMP, 225 SEC RT, 23 VAC
75
95
98
98
91
87
100
100
84
47
75
50
6.7
1.8
18
6.2
22
13
24
8.6
1.9
0.38
1.4
4.3
"ABBREVIATIONS:
FB: Fluidized Bed ACE Separator™, PP: Parallel Electrode ACE Separator11
RT: Retention Time
CONCLUSIONS
ACE Separator™ treatment is effective in removing particulates from the soil suspensions,
Increasing the resulting mean particle size and, consequently, improving filtration properties. The
technology has proven effective in reducing the metal concentrations in such slurries both by removing
the clays to which metal ions have adsorbed and by coprecipitating soluble species. The ACE
Technology is particularly applicable to zero discharge applications in which addition of chemicals, and
the inevitable build-up of residual concentrations would adversely affect the effluent quality or inhibit its
reuse. Other applications of the ACE Separator™ are foreseen for the remediation of groundwater and
leachates (metals, COD/BOD removal), for enhancement of clay separation from aqueous chemistries
used in soil-washing operations, for the breakage of oil-in-water emulsions produced in the pumping of
hydrocarbon-contaminated groundwater and for removal of suspended solids from storm water runoff.
Industrial applications are envisioned for fine-grained product recovery (pigments, PVC) and for
extraction of suspended solids from waste streams which contribute to high BOD and COD loadings and
thus reduce POTW discharge surcharges. Overall treatment operating costs are nearly equivalent to
those for traditional chemical treatment; refinement in the engineering design of the electrodes and
process control mechanism are expected to further reduce these costs and thereby enhance the
economic attractiveness of this innovative treatment technology.
188
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FLUID EXTRACTION-BIOLOGICAL DEGRADATION OF ORGANIC WASTES
David M. Rue and Robert Kelley
Institute of Gas Technology
3424 S. State St.
Chicago, IL 60616
(312) 567-3711, (312) 567-3809
Annette M. Gatchett
U.S. Environmental Protection Agency
Risk Reduction Engineering Laboratory,
26 W. Martin Luther King Drive
US EPA Cincinnati, OH 45268
(513) 569-7697
INTRODUCTION
The Institute of Gas Technology (IGT) Fluid Extraction-
Biological Degradation (FEED) Process extracts hydrocarbon
contaminants from soil and then biologically degrades the
pollutants in aerobic bioreactors. The FEED process has the
potential to be an environmentally benign means of safely and
economically degrading pollutants by overcoming bioavailability
limitations of the pollutants in soil. The process consists of
three stages; extraction, separation, and biodegradation.
Contaminants are first removed from the soil by solubilization in
supercritical carbon dioxide in an above-ground extraction
vessel. The hydrocarbon contaminants are then collected in a
separation solvent, and clean CO? is recycled to the extraction
stage. Separation solvent containing the organic wastes is sent
to the biodegradation stage where the wastes are converted to
CO2, water, and biomass. All stages of the FEED process have
been successfully demonstrated.
The extraction stage of the FEED process relies on the
unique properties of supercritical .fluids (SCF) to remove organic
contaminants from soil. An SCF is a compound at conditions
exceeding its critical temperature and pressure. Fluids in the ••'
supercritical range have viscosities and diffusivities between
liquids and gases with densities close to those of liquids.
Supercritical fluids have the solution characteristics of liquids
with better mass transfer capabilities. Extraction and
separation are easily controlled because changes in the pressure
(density) of an SCF can be used to change the solvation ability
of the fluid (1).
Different compounds and classes of compounds have varying
degrees of solubility in individual SCFs. Hydrocarbon compound
solubilities in supercritical CO2 as a general rule decrease with
increasing molecular size and with increasing aromaticity (2).
Alkanes are highly soluble, in supercritical CO2/ and larger
molecules as diverse as phenols, pesticides, PCBs, dioxins, and
coal tar residues have been extracted from soils with
supercritical CO2.
189
-------
The biodegradation stage of the FEED process uses an aerobic
bioreactor. In studies reported here an aerobic, PAH degrading
mixed-culture derived from contaminated soil was used. The
bacterial cultures used for biodegradation at a specific site
will be selected based on site-specifics of the particular
contaminants.
METHODOLOGY .. - .
The soil used for testing the FEED process was collected and
provided to IGT by Biotrol, Inc. (Chesha, MN). Three soil
samples were taken by Ebasco from the North Cavalcade Superfund
Site in northeast Houston, Texas near the intersection of
interstate 610 and U.S. highway 59. Biotrol mixed the three
samples and generated a composite sample which was sent to IGT.
The site was a wood preserving business, and the principal
pollutants are polynuclear aromatic hydrocarbons (PAHs) present
in creosote used as the wood preservative. The soil was. stored
frozen at IGT until needed. Analysis of the composite soil
labeled FEBD-1 by EPA method SW-846, 8100 revealed a total of
1925 ppm of PAH compounds. This includes 50 ppm of 2-ring, 1132
ppm of 3-ring, 670 ppm of 4-ring, and 73 ppm of 5-6 ring PAHs.
Extraction tests were performed in a batch supercritical
fluid extraction (SFE) unit purchased from LDC Analytical, Inc.
and modified at IGT. Three 316 stainless steel vessels; a 55 ml.
extraction cell and two 150 ml separation vessels, are connected
in series and have individual pressure regulators and heaters. A
metering pump with head chiller supplies CO2 to the system.
Before each extraction test, 35 grams of soil is placed
between inlet and exit screens in the extraction cell. Methylene
chloride is placed in the separation vessels. The extraction
cell is pressurized with supercritical CO2, and the separation
vessel pressures are set at 500 and 200 psig, well below the
critical pressure of CO2. The extraction cell temperature is
then set. •
Extraction of contaminants begins when supercritical CO2 is
passed through the extraction cell. After leaving the extraction
cell, the CO2 passes through an on-line UV spectrophotometer and
the two separation vessels. Contaminants are collected in the
separation solvent and the scrubbed, depressxlrized CO2 is vented
from the unit through an activated carbon filter. The fluid flow
is continued until the desired fluid to contaminant ratio is
reached. After a test is completed, both the extracted soil and
the separation solvents are analyzed.
All biodegradation tests were performed in batch mode in
clean 1000 ml Erlenmeyer flasks containing 250 ml of Basal Salts
Medium (BSM). FEBD-1 soil extracts in ethanol (2.5 ml) were
added to the flasks. A 250 ul of 0.1 OD at 550 nm bacterial
suspension was added to the flasks which would give about 105
cells per ml. The flasks were incubated at 30°C on a rotary
shaker operating at 150 revolutions per minute throughout the
experiment. Triplicate or duplicate flasks we're sacrificed at
190
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each sampling time to monitor bacterial numbers as measured by
viable cell counts, biomass as measured by protein content, and
residual PAH levels. Bacterial cell counts were performed using
the drop plate method (3). Biomass was measured as ug of protein
per ml of culture using a protein assay kit by Pierce Chemicals.
RESULTS '
More than twenty supercritical carbon dioxide extraction
tests have been conducted with sample FEBD-1 in the lab-scale SFE
unit. The base test conditions were 2000 psig at 115°F using a
CO2 to contaminate ratio of 6800 Ib/lb and no methanol additive.
These four operating variables were changed in the test matrix.
When the extraction pressure was 2000 psig and the
temperature was 90, 115, and 170°F, the highest extraction levels
were achieved at 115°F. Extraction of 2 to 6 ring compounds
increased from 90.6 percent at 90°F to 93.7 percent at 115°F and
declined significantly to 79.3 percent at 170°F. The largest
declines in extraction levels at high temperature were for the
heavier 4 to 6 ring compounds.
The effect of the ratio of carbon dioxide to contaminants on
extraction levels was studied with ratios of 2200 to 12300 Ib/lb.
Extraction levels of 2 to 6 ring compounds increased from 84.2
percent at 2200 Ib/lb to 93.7 percent at 6800 Ib/lb. No increase
in extraction was obtained with higher CO2/contaminant ratios.
Pressure effects on extraction were studied between 1100 and
4000 psig, all in the supercritical range. The results of tests
conducted with and without 5 weight percent methanol added as an
extraction modifier are summarized in Table 1.
Table 1. THE EFFECTS OF PRESSURE AND METHANOL ADDITIVE ON
EXTRACTION AT 115°F USING 6700 lb CO2/lb CONTAMINANT
Test E-5 E-4 E-3 E-6 E-12 E-13
Pressure; psig 1100 1500 2000 2000 4000 4000
Methanol, % 0 00 5 0 5
PAH Removal, %
Naphthalene 99.2 97.8 98.7 98.2 99.4 98.5
Phenanthrene 97.0 97.9 98.0 97.8 98.1 98.8
Benzo(a)pyrene 78.0 81.4 78.9 93.1 90.4 93.7
2 Ring PAH 99.2 97.8 98.7 98.2 99.4 98.5
3 Ring PAH 96.7 97.4 97.3 97.5 97.4 98.6
4 Ring PAH 90.0 91.9 90.9 97.2 96.2 97.1
5-6 Ring PAH 52.1 53.5 58.2 90.6 70.4 84.3
Total PAH 92.6 93.8 93.7 97.2 96.0 97.5
Extraction levels increase with increasing pressure between
1100 and 4000 psig. The largest extraction increases are
obtained for the heavier 4 to 6 ring compounds. Adding 5 weight
percent methanol to the extraction CO, significantly increases
the extraction levels. The greatest increases are again for the
191
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heavier 4 to 6 ring contaminants. A comparison of contaminant
levels in the soil after extraction using CO2 with and without
the methanol additive is presented in Figure 1. Total
contaminants in the soil are reduced from 1925 to 50 ppm using
carbon dioxide with 5 percent methanol.
The biodegradation of PAHs present in supercritical extracts
of FEBD-1 soil is presented in Figure 2. The cells used for
biodegradation were pregrown in naphthalene and phenanthrene and
were washed thoroughly in BSM before inoculation. After a lag
period of 40 hours, the total PAHs concentration reached a
treatmentendpoint of 52 percent of the initial concentration in
30 hours. The same trends are evident with 2 through 6 ring PAH
compounds.
In a second series of similar batch experiments, the lag
period observed in the earlier experiments was eliminated by
pregrowing the culture in an ethanol Soxhlet extract of FEBD-1
soil. Growth, as measured by protein content or bacteria
numbers, indicates that there is no increase in cell numbers due
to the presence of supercritical extract containing PAHs.
However, there is a significant increase in the protein content
due to the presence of supercritical extract.
CONCLUSIONS
All three stages of the FEED process; extraction,
separation, and biodegradation have been studied in batch
reactors on the laboratory scale. Supercritical carbon dioxide
extraction at 2000 psig and 115°F successfully removed more than
93 percent of 2 to 6 ring PAHs from a contaminated soil. The
addition of 5 weight percent methanol as an extraction modifier
increased the extraction levels to more than 97 percent and
enhanced particularly the removal of heavier 4 to 6 ring PAHs.
The concentration of PAH compounds extracted with
supercritical CO, was decreased by 53 percent in a bioreactor
after a 40 hour lag time and a 30 hour incubation time. The lag
period was eliminated by pregrowing the bacterial culture in an
ethanol extract of the FEBD-1 soil.
REFERENCES
1. McHugh, M. and Krukonis, V. Introduction. In:
Supercritical .Fluid Extraction, Principles and Practice.
Butterworths, 1988.
2. Francis A Ternary Systems of Liquid Carbon Dioxide. J,
Phvs- Chem. 58: 1099-1114, 1954.
3. Hoben, H.J. and Somasegaran, P. Comparison on the Pour,
Spread, and Drop Plate Methods for Enumeration of iRhizobium
Spp. in Inoculants Made From Presterilized Peat. Appl.
Environ. Microbiol. 44: 1246-7, 1982.
192
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FIGURE 1: METHANOL EFFECTS ON EXTRACTION
2 Rings
3 Rings
4 Rings
5-6 Rings
Total
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m\\\\\\\\\\\\\\\\\\\\\\\\\\\\\j t i i
im/i/iiiiiifiliiiiili\ < •- i
™™y j . j j j
• • ' 1 !
Initial Concentration, pptn
2-fing | 50
3-ring 1132
5-6 ring I 73
total 1925
\ \
| I
\\\\\\\\\\\\\\\\\\\v\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\^^^
J ' '
1 1 1 1
r
:
i
\\\\\\\M
i
i
20 40 60 80 100 120
Concentration in Soil, ug/g
CO2, 2000 psig IHH CO2/MeOH, 2000 psig
CO2, 4000 psig HI CO2/MeOH, 4000 psig
140
Temperature • 115 F
CO2/Contaminants • 6700 Ib/lb
CO2/MeOH - 95 % CO2, 5 % Methanol
FIGURE 2: BIODEGRADATION OF PAHs PRESENT
SUPERCRITICAL EXTRACTS OF FEBD-1 SOIL
PAH CONCENTRATION, ppm
20
40 60 80
TIME, hours
100
120
140
TOTAL PAHs
4 RING
2 RING
5 & 6 RING
3 RING
NO BACTERIA
193
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REMEDIATION OF LEAKING USTS ON NATIVE AMERICAN LANDS
Robert W. Hi Tiger
Superfund Technology Demonstration Division
Risk Reduction Engineering Laboratory
U.S. Environmental Protection Agency
2980 Woodbridge Avenue
Edison, New Jersey 08837 .. . ,
INTRODUCTION
Cleaning up sites contaminated by releases from leaking underground
storage tanks (LUSTs) has become a priority issue for EPA as the gap between
known releases and sites remediated continues to widen. Nowhere is this gap
more prevalent than on the Native American reservations in this country. In
most States it is common to see mounds of contaminated soil being removed from
service stations; old rusty tanks being removed and new tanks being installed.
These activities are promising signs that owners and operators of UST/LUST
facilities are trying to comply with the Federal and State regulations.
Unfortunately, such common occurrences outside the reservation are uncommon
within.
This problem is primarily attributed to jurisdiction in that most of the
funds that support UST/LUST activities are being channeled into State programs
which employ anywhere from 10 to 50 employees. These programs are not
responsible for managing or implementing UST/LUST regulations on Native
American lands. Although the Indian lands represent a small percentage of the
National UST population, a unique situation is created whereby only one or two
Federal employees are responsible for overseeing and enforcing the Federal
UST/LUST regulations from regional offices. Region 9, for example, has only
one FTE (full time employee) to manage the UST/LUST activities on reservations
in California, Arizona, New Mexico, Nevada, and Utah. Clearly, this is a
difficult if not an impossible task. ,
Recently, however, a few programs are being established within some of
the Tribal governments to address LUST issues and ensure compliance and
enforcement. The first steps taken in tackling the LUST issue was the
development of an UST/Lust tracking and prioritization system for managing
sites and ensuring that those sites which pose the greatest environmental
threat are addressed first. The system would be utilized by both the US EPA
in Region 9 and by Tribal authorities on different reservations.
SYSTEM DESIGN ;
' i
The new system, named RUST! (Reservation UST Information), was developed !
by the Risk Reduction Engineering Laboratory and the EPA Region 9 UST/LUST
program. RUSTI enables users to manage all UST related activities using a PC*.
The system was written in Clipper V. 5.01 with several functions coded in
Microsoft C. These languages offer considerable flexibility in operating
system environments (eg. LAN, stand-alone PC, multi-user PC) as well as
allowing for easy modification of the code.
194
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LUST sites involve enormous amounts of file review and paperwork; RUSTI
greatly simplifies and automates this "paper trail" by means of a customized,
electronic filing system and database. Key UST/LUSt information is stored and
presented in the system in an easy to use and comprehend manner. For examplei
if an individual needed to access information on a particular site, one could
access RUSTI and pull up a comprehensive file that illustrates all previous
activities (ie: tank removals, site assessments, etc.) conducted at that
site. Even an individual not directly involved with the site could quickly
understand the previous actions which occurred there; answer site-related
questions or make an educated decision as to the next logical step of
remediation. ,
A set protocol established by the Regional office dictates the kind of
information needed to manage UST/LUST sites from new installations through
tank removals and closure. The following UST/LUST activities represent the
bulk of their program:
Tracking UST/LUST Notification Forms
Oversight of UST Removals and Site Assessments
Enforcing Leak Detection Requirements
Managing Financial Responsibility
Evaluation of Corrective Actions for Site Remediation
Technical Support to Owners and Operators
Compliance and Enforcement of Federal Regulations
These activities are stored in three primary files, each file related irt
some way to each other. These files are:
TRIBE: Tribe name/code
Associated correspondences
SITE: Site specific information
Owner/operator information .
Tracking information
Prioritization information
Narrative sections
TANK: Site tank information
All of these files are accessed either directly or indirectly via the .
user interface of the system. RUSTI is tailored in such a way that user£ can
make quick assessments of the above activities within any of the three primary
files with just a few simple key strokes. For example: If the User were to
receive a telephone call requesting information about a site on the Nav^jO
Nation, the user would search the "Tribe" files under Navajo. Other tribes
on-line would be filtered out, and the user would be presented a list of sites
which reside on the NAVAJO nation..
Additional searches can be made on any field which exists in any of
related databases previously mentioned. These searches can then be combined
using "AND" or "OR" conjunctions and the results displayed as in any simple
search. Such search mechanisms, which are currently being used in many large
and small scale database systems, provide unlimited flexibility in tailoring at
search to meet any users' needs.
195
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After performing the search and selectively filtering it using "AND" or
"OR" combinations, one or more records are presented which adhere to the
search criteria. The user then selects the site of interest by scrolling
through a list of sites. The Site Information Screen (see Figure 1) is then
displayed.
NAVAJO - SITE #3
Name: Chevron - St. Michaels
Contact: Dan J. Gallagher
Add 1: AZ State Highway 264
Add 2:
City/St: St. Michaels AZ
Zip/Tel:
Chevron USA, Inc.
Dan J. Gallagher
PO Box 2833
1300 South Beach Blvd.
La Habra CA
90632-2833 (213)694-7903
RP EPA
Notific. Form:
Removal Noti.:
Removal Appr.:
UST Removal: 05/01/87
Confirmed Rel: 05/01/87
LUST Resp Let:
Site As. Recv: 12/13/89
RP Workpl Rec: 10/11/90 04/18/91
Remed. Init.:
Remed. Compl:
Site Clos App:
Installation (Y/N):
Operation (Y/M):
Closure (Y/N):
Abandonment (Y/N!):
Subst. Rel.: GASOLINE
Qty. Rel.: UNKNOWN
Violation (Y/N): N
EPA Enforcement:
EPA PM:
Class: 3 No. Tank Records: 5 Groundwater Cont.: YES Soil Cont.: YES
Enter , , , , , , , , or ?
Figure 1
This screen display gives the user a comprehensive account of the Site
activities, dates of correspondence, EPA approvals, release information, soil and
groundwater contamination data, telephone numbers and addresses of
owners/operators, classification rating and violation information. A variety of
selections are available at the bottom of the Site Information Screen that pull
up other files relevant to the Site selected. For example: if the user was
interested in searching information on the types of tanks and contents stored at
the example Navajo Site, they would select <"T"> and tank screen information
would be displayed (see Figures 2 and 3).
In addition RUSTI allows users to enter and edit specific site information
into narrative files using standard word processor functions. By selecting
on the site information screen (figure 1), the user accesses a menu for the
narratives which include: (1) General information, (2) Site characterization,
(3) Effects, (4) Corrective actions, (5) Operational considerations, (6)
Enforcement, (7) Accounting information, and (8) Circuit Rider notes. These
narrative "notepads" provide the user with a mechanism for managing and
documenting all UST/LUST activities beyond the basic Regional protocol.
196
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NAVAJO - SITE #3
Name
Contact
Add 1
Add 2
City/St
Zip/Tel
No.
1
1
2
3
4
: Chevron -
St. Michaels
: Dan J. Gallagher
: AZ State
•
•
Highway 264
: St. Michaels AZ
*
•
Capacity
6000
6000
4000
3000
550
Select tank record
Contents
PETROLEUM
PETROLEUM
PETROLEUM
PETROLEUM
USED OIL
Chevron USA, Inc.
Dan J. Gallagher
PO Box 2833
1300 South Beach Blvd.
La Habra CA
90632-2833 (213)694-7903
to view/edit
Const. Mat. Rel.
STEEL, SINGLE WALL Y
STEEL, SINGLE WALL Y
STEEL, SINGLE WALL Y
STEEL, SINGLE WALL Y
STEEL, SINGLE WALL N
Figure 2
NAVAJO - SITE # 3 - TANK # 1
Confirmed Release (Y/N): Y
Tank Capacity:
6000
Installation Date: 01/03/80
Removal Date: 05/01/87
Material of Construction: STEEL, SINGLE WALL
Tank Contents: PETROLEUM
Corrosion Protection: UNKNOWN
Piping: UNKNOWN
Ownership: PRIVATE/CORPORATE
Compliance: INVENTORY RECONCIL.
Overfill Protection (Y/N): Y
Upgrade (Y/N): Y
Financial Responsibility (Y/N): N
Comments:
During the transfer of hydrocarbon product from one tank to another
for the installation of cathodic protection equipment, inattentive
workers allowed approx. 200 gallons to spill into the subsurface.
Figure 3
197
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PRIORITIZATION/CLASSIFICATION
The prioritization algorithm utilized in this system provides a
methodology for site ranking using a variety of site characteristics. These
characteristics are determined by posing a series of questions for the site.
Several answers are available for each question with each answer having a
different point value. These values are summed and a classification number is
determined from this total. Ten questions are provided and are as follows:: :
Soil contamination (Y/N)
Volume of soil contaminated
TPH level in situ soil
TPH level in stockpiled soil
Groundwater contamination (Y/N)
Free product on groundwater
Contamination near domestic well
Contamination near municipal well
Benzene concentration
• Health / environmental risk (Y/N)
A classification scheme was developed which associates a class number to
the site based upon the point summation from the above questions. The classes
are summarized as follows:
Class 1
Class 2
Class 3
Class 4
Class 5
Class 6
CONCLUSION:
This is the most severe classification which represents
significant human health and environmental risk.
This is the second most severe classification which represents
significant soil and groundwater contamination. TPH levels in
soil exceed 2000 ppm and free product contamination is near either
municipal or domestic wells.
This class represents significant soil contamination and low level
groundwater contamination. Groundwater contamination is not in
the proximity of municipal/domestic wells.
This class indicates soil contamination that requires remediation.
No groundwater contamination is present at this site.
This is the least severe classification denoting minimal soil
contamination and no groundwater contamination.
Insufficient/incomplete prioritization information.
A centralized computer tracking and prioritization system serves as a
powerful and versatile tool for users that must deal with the remediation of a
large number of UST/LUST sites. RUSTI provides considerable information at
the touch of a keystroke on all UST/LUST activities on Native American Lands
and classifies the sites based on potential and real environmental risk. More
importantly, RUSTI provides the users with up-to-date information so that the
likelihood of work duplication is minimized both in the Regional offices and
in the Tribal governments.
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RUSTI also provides a standard reference structure to EPA and Native
American personnel not familiar with UST/LUST operating protocols. By
prompting for data in a systematic format, users are made aware of what site-
related questions should be asked. They are also reminded if critical site
information is missing from a given site file. The system generates reports
and statistical information required by the Program Office quickly,
efficiently, and with a high degree of accuracy. RUSTI may not be the answer
to the limited staff assignments that are responsible for the Native American
lands, but it does help EPA arid Tribal authorities maximize their efficiency
and productivity when cleaning up UST releases.
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LABORATORY STUDY OF INTERACTIONS BETWEEN
POLYCHLORINATED BIPHENYLS AND QUICKLIME
Patricia M. Erickson
U.S. EPA
Risk Reduction Engineering Laboratory
5995 Center Hill Avenue
Cincinnati, Ohio 45224
(513)569-7884
Robert L Einhaus and Issa Honarkhah
Technology Applications, Inc.
26 W. Martin Luther King Drive
Cincinnati, Ohio 45268
(513) 569-7415
INTRODUCTION
Pdychlorinated biphenyl (PCB) contamination is a major concern at many sites across the
country, including more than 10% of the Superfund sites for which Records of Decision are available.
Under the Toxic Substances Control Act, material containing more than 50 parts per million (ppm) PCBs
must be treated by incineration (or equally effective treatment) or disposed in a chemical waste landfill.
Chemical destruction techniques equivalent to incineration have been the subject of numerous research
projects over the past 10-20 years. High cost is the main disadvantage of conventional remediation
techniques; siting of both incinerators and landfills is becoming an additional obstacle.
Liquids and sludges that contain PCBs are often solidified to improve waste handling
characteristics prior to remediation. Solidification usually involves the addition of an alkaline material,
such as quicklime (calcium oxide, CaO) or cement kiln dust. In the course of such bulking operations,
EPA staff noted an apparent reduction in PCB levels following solidification, which might be attributable
to dilution during treatment, vapor phase emissions, decomposition, or incomplete extraction of PCBs
from the solidified matrix prior to analysis.
A laboratory study on this process commissioned by EPA yielded a draft final report in which the
principal investigator concluded that quicklime could completely destroy PCBs. Reviewers determined
that the experiments and results described in the report did not justify the conclusions. Therefore, EPA
began a study to repeat and expand the initial study, as well as to confirm field observations (1).
METHODOLOGY
The basic experimental approach was patterned after the experimental design us5ed in the initial
laboratory study conducted for EPA1. A stock solution containing 1330 milligrams per liter (mg/L) 3,5-
dichlorobiphenyl (DCBP), 1050 mg/L3,3',5,5'-tetrachlorobiphenyl (TCBP), and 1330 mg/L 2,2'4,4',5,5'-
hexachlorobiphenyl (HCBP) were prepared in methylene chloride/methanol solvent. The stock solution
was used to spike a matrix comprised of equal-weight parts of diatomaceous earth, silicon dioxide and
Reference 1 includes experimental details and the draft final report on the initial laboratory study.
200
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acid-washed Ottawa sand. Replicate 50-g samples of the matrix were prepared, spiked with 50 mL of
the PCS stock solution, and allowed to dry at ambient temperature or at about 80 °C on a hotplate,
yielding matrix contaminated at 1330 ppm DCBP, 1050 ppm TCBP, and 1330 ppm HCBP.
A series of open-vessel tests were conducted in which each of 10 PCB-spiked samples was
mixed with 120 g quicklime (91.4% CaO by Ca content). At the start of the test, 50 mL reagent grade
water was added to each sample with vigorous manual stirring to promote lime slaking (hydration), a
strongly exothermic reaction. After cooling to <100°C, water was added to the treated mixture to
produce a thick slurry; the beaker was covered with a watch glass and the slurry was heated at 80-90°C
for 3 hours (h), then left at ambient temperature. Duplicate samples were acidified and prepared for
analysis at nominal times of 5-72 h after lime slaking. In addition to the treated samples, 5 control
samples were prepared exactly as described, with the exception that no quicklime was added.
A series of four 24-h closed-vessel tests was performed in which 50-g PCB-spiked samples were
treated with 120 g alkaline material and a solvent. The alkaline materials used in three tests were
quicklime, kiln dust, and an equal-mass mixture of the two, each slaked with 50 mL water. The fourth
experiment used quicklime slaked with 50 mL water/methanol (9:1 volumetric). The reaction was carried
out in a resin reactor, fitted to connect a mechanical mixer, a thermocouple, a slaking-solvent reservoir,
and a solvent-trap system to collect volatiles and particulates emitted during the reaction. At the start of
each experiment, the vessel was charged with a well-mixed sample of PCB-spiked matrix and dry
alkaline material. After connecting the lid, a slight vacuum was drawn at the end of the solvent trap
(cold trap and bubbler). The slaking solvent was added to the dry mixture and stirred mechanically,
while vapor temperature and steam evolution were monitored. After slaking appeared complete, the
treated mixture was allowed to cool, then slurried and heated as described for the open-vessel tests.
Acidification of the treated mixtures with 7.2 molar hydrochloric acid was used to terminate any
reaction between hydrated lime and PCBs. Control samples received 600 mL water instead of acid.
After settling, the aqueous layer was decanted. The solid residue underwent three sequential
extractions, using methanol, 50% methanol/50% methylene chloride, and methylene chloride. After each
solvent addition, the mixture was sonicated and then centrifuged. All solvent phases were combined
with the aqueous layer in a separatory funnel, shaken and allowed to separate. The methylene chloride
layer was drained through sodium sulfate and diluted quantitatively with additional solvent. Analysis was
performed by gas chromatography/mass spectrometry (GC/MS). The. overall method performance on
PCB-spiked matrix samples carried through the extraction and analysis procedure was 87.3-93.1%
recovery of the three congeners at relative standard deviations of 1.5-2.0%.
A field sample was obtained from a site where lime solidification was applied to PCB-containing
sludges. The sample was homogenized, then portions were acidified and extracted as described above.
Additional portions were extracted by the Soxhlet method (EPA Method 3540) using methylene chloride.
The extracts from both methods were subjected to additional florisil and gel permeation chromatography
to remove interfering constituents. Cleaned extracts were analyzed by gas chromatography on a fused
silica capillary column followed by electron capture detection.
RESULTS
Open-Vessel Tests
Open-vessel tests showed large losses of PCBs following the addition of quicklime and water
(Table 1). The greatest incremental decrease in concentration was observed at a nominal reaction time
of 5 h, immediately following the heating induced by quicklime slaking and subsequent heating on a
hotplate. As soon as water was added to the spiked matrix/quicklime mixture, the temperature rose to a
201
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maximum of 171-189°C and a particulate-laden steam column emanated from the beaker, suggesting
that vaporization or steam stripping could be occurring. A substantial fraction of the DCBP loss in
treated samples can be attributed to vapor losses, since the control (no quicklime) samples also showed
high losses of DCBP. The control samples showed much lower losses of TCBP and HCBP, indicating
that these congeners have lower vapor pressures in the temperature range from ambient to 90°C.
TCBP and HCBP losses in the treated samples could be due to vaporization and/or steami stripping at
the higher temperature attained during quicklime slaking, as well as decomposition.
Table 1.
Percent PCB content remaining* at various times in open-vessel tests.
TIME
h
0
5
12
24
48
72
DCBP
treated
100
28
23
13
8.5
21
DCBP
control
100
44
39
32
18
47
TCBP
treated
100
41
32
25
21
18
TCBP
control
100
96
93
93
85
82
HCBP
treated
100
16
17
13
9.7
5.5
HCBP
control
100
101
99
95
75
85
Values for treated samples are averages of two; controls were not duplicated.
Extracts of the quicklime-treated materials were analyzed for possible PCB decomposition
products. Tentative identifications were based on comparison of measured mass spectra with library
spectra of known compounds. Concentration estimates were based on a response factor for each
product equal to that of deuterated chrysene. Products included lesser-chlorinated biphenyls (mono-
penta congeners), and chlorinated biphenyls in which a methoxy or hydroxy group was substituted for
one chlorine. In addition, tetrachlorodibenzofuran (TCDF) was observed in all treated samples at
concentrations ranging from 1 to 14 ppm (0.07-1% of starting HCBP concentration). This is the only
product where a response factor was calculated for the pure compound; a response factor of 0.359
relative to deuterated chrysene was calculated.
Total product concentrations were estimated to range from 12 to 229 ppm, with a striking
dependence on how the spiking solvent was removed from the sample prior to treatment. In four
samples that were evaporated solely at ambient temperature, cumulative product concentrations were 48
to 229 pprn; three of these four samples produced 205-229 ppm total products, 1-5 ppm TCDF, and
peak temperatures above 180°C. The remaining six samples were heated at about 80°C prior to
treatment to remove residual spiking solvent. These pre-heated samples yielded total products of 12-50
ppm, Including TCDF concentrations of 4-14 ppra It appears that the presence of residual spiking
solvent favors formation of all observed products except TCDF.
Total product concentrations in the open-vessel samples after 5 to 72 h reaction times ranged
from 0.3-6% of initial PCB concentration. These products in no way account for the bulk of the absent
PCB mass. Losses to the vapor phase were suspected, based on DCBP loss in the control sample and
apparent temperature dependence of losses of each congener. A wipe test of interior surfaces of the
glove box In which these experiments were conducted showed significant contamination by all three
congeners. Modelling showed that the observed time-dependent loss of PCBs was consistent with
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volatilization expected for Aroclor mixtures at the experimental temperatures.
Closed-Vessel Tests
Closed-vessel tests were conducted to determine if PCB losses observed in the open-vessel
tests were, in fact, due to vapor-phase losses of the spiked congeners, and not losses of decomposition
products. The apparatus was under slight negative pressure to prevent vapor concentration buildup
above the reaction mass. Four tests were carried out, each allowing 24 h reaction time after the addition
of alkaline material and water. Test results are shown in Table 2. Extracts prepared from the solids in
the reaction vessel and solvent in the cold trap were analyzed separately for residual PCB and
decomposition products.
Table 2. Percent recovery of PCB congeners from closed-vessel tests after 24 h reaction time.
PCBs from the solid matrix plus the cold traps are summed to yield total recovery.
TREATMENT
Quicklime
Quicklime/Methane!*
Kiln dust
Quicklime/Kiln dust
DCBP
50 + 17 = 67
84 + 3.9 = 88
102 + 3.5 =106
87 + 6.7 = 94
TCBP
75 + 2.0 = 77
89 + 1.3 = 90
110 + 1.0 =111
102 + 1.0 =103
HCBP
64 + 1.0 = 65
89 + 0.5 = 90
122 + 1.0 =123
87 + 2.5 = 90
Water added to slake the lime was spiked with 10% methanol (v:v).
This set of experiments yielded essentially full recovery of the spiked PCBs in three of the four
variations. In the first experiment, using quicklime alone, some PCBs may have been lost due to vapor
emission through poorly-fitted thermocouple and stirrer ports, or due to incomplete extraction of solids
adhering to reaction vessel walls, lid and cold trap connections. Vapor or paniculate emissions are
consistent with increasing recoveries of all congeners observed as quicklime was replaced with kiln dust:
the temperature should have decreased as CaO content in the alkaline material decreased, thereby
decreasing the tendency of gaseous species to escape the vessel. Temperature could not be measured
during the reaction, since the thermocouple interfered with the stirrer.
Although the closed vessel tests were expected to yield higher total recoveries than the open-
vessel tests if vapor phase losses were dominant in the latter, we expected higher recoveries of PCBs
from the cold trap in the closed vessels. At 24 h, open-vessel samples had lost 75-87% of the initial PCB
spikes, with less than 6% accounted for in reaction products. Closed-vessel tests yielded only 0.5-17%
of the initial spikes in the solvent traps at the same reaction time. Vapor condensation and paniculate
deposition on reaction vessel surfaces were visually observed during the closed-vessel tests. These
factors probably account for the apparent reduction in PCB volatilization but could not be quantified
separately from the bulk solid matrix. Another factor that may have contributed to reduced volatilization
is reduced reaction temperature, resulting from poorer mixing (thus slower slaking) or from lower CaO
concentration in kiln dust (thus less heat of hydration produced).
Field Sample
A sample was obtained from a site where lime was used to solidify PCB-containing waste.
According to sample documents, a bucket of material had been taken after various wastes were
composited and solidified, and then stored on-site.
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The sample was homogenized and then sub-sampled as needed for analysis. Four replicate
samples were acidified and extracted using the same procedure applied to open- and closed-vessel test
samples. Two additional samples were extracted using the Soxhlet method. Gas chromatography with
electron capture detection (GC-ECD) was applied to cleaned extracts. Peak profiles were compared to
Aroclor standards; the best agreement was found for a mixture of Aroclors 1242 and 125-1; equal mass
mixtures of these Aroclors were then used for calibration to quantify the field sample extracts.
The acidification/extraction procedure yielded an average PCB concentration of 200 ppm with a
relative standard deviation of 4.2% for four replicate samples. The Soxhlet procedure yielded 218 and
222 ppm PCBs on duplicate samples. Prior to treatment, samples taken at various locations across the
field site were reported to contain up to 157 ppm PCBs. The field sample analyzed in this study snowed
that the treatment did not destroy PCBs to any measurable extent. Although both extraction procedures
successfully extracted PCBs in this study, the characteristic Aroclor pattern was completely indiscernible
when extracts were analyzed by GC/MS, owing to interference by numerous other compounds extracted
from the sample. If an analytical laboratory attempted to analyze PCBs by GC/MS techniques, heavily
contaminated samples might result in non-detection owing to masking by other contaminants. GC-ECD
Is less subject to these interferences.
CONCLUSIONS
Addition of quicklime and water to PCBs on an inert matrix resulted in very little PCB
decomposition. Less than 6% of the starting material was identified in reaction products. Products
found routinely included partially-dechlorinated biphenyls, hydroxy-substituted PCBs, and TCDF. The
variety of products was decreased and total concentration of products was less than 1.4% of starting
PCB content when heat was applied to remove spiking solvent prior to treatment. These heated
samples typically exhibited more TCDF than unheated samples, but lower concentrations and less
variety of other compounds. Only the unheated samples yielded methoxy derivatives.
Vapor-phase losses of PCBs were significant in open-vessel tests. The effect was temperature
dependent, with the dichloro congener quite susceptible to evaporation at 90°C or lower, and the other
congeners more subject to evaporation or steam stripping at higher temperatures. High temperatures
were achieved by slow water addition and vigorous mixing.
A stored sample from PCB-containing sludge solidified with lime was found to contain about 200
ppm PCBs as Aroclors 1242 and 1254. The PCB content was extractable by both the
acidlfication/sonication/extraction procedure used in this study and the more conventional Soxhlet
extraction. No conclusions can be drawn regarding previous reports of PCB losses since splits were not
reserved of samples analyzed by other laboratories.
Treatment of PCB-contamlnated materials by quicklime and water, as performed in these
experiments, did not result in the degree of dechlorination required for remediation of contaminated
sites.
REFERENCES
(1) Einhaus, R. L, Honarkhah, I., and Erickson, P. M. Fate of Polychlorinated Biphenyls (PCBs) in
Soil Following Stabilization with Quicklime. EPA/600/2-91/052, U.S. Environmental Protection
Agency, Cincinnati, Ohio, 1991,114 p.
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RISK REDUCTION ENGINEERING LABORATORY (RREL)
TREATABILITY DATABASE
. Glenn M. Shaul
(513) 569-7408 Fax (513)t 569-7787
Chief, Chemical Engineering Section
Toxics Control Branch
Water and Hazardous Waste Treatment Research Division
1. Purpose
The purpose of the RREL Treatability Database is to provide a ,
thorough review of the removal/destruction of chemicals in
various types of media, including water, soil, debris, sludge and
sediment. There are currently thirty-three treatment
technologies, thirteen aqueous matrices and five solid matrices
presented in the database. Version 4.0 was released in January
1992 and is free of charge.
2. Target Group
The users of the database include federal, state and local
governments, universities, industry and consulting engineers.
These diverse groups share a common interest in needing reliable
treatability data for specific chemicals of environmental
interest. Current distribution is approximately 1500.
3. Organization
The program contains physical/chemical properties for each
compound, as well as treatability data. The treatability data,
summarizes the types of treatment used to treat the specific
compound; the type of waste/wastewater treated; the size of the
study/plant; and the treatment levels achieved. In addition,
each data set is referenced with respect to source of information
and each reference is quality-coded based upon analytical
methods, reported quality assurance and quality control efforts
and operational information on process(es) sampled.
4. Computer Hardware and Software
The requirements are as follows: IBM personal computer or
compatible; 8 megabyte hard disk storage; 640 K RAM memory; DOS
version 2.0 to 5.0, except version 4.0; and a 12 pitch printer.
The program has been compiled and does not require any
specialized software to operate it and it is menu driven for ease
of use. The program can also be accessed through EPA's
Alternative Treatment Technology Information Center (ATTIC).
Please contact Joyce Perdek at 908-342-4380 for additional
information.
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DEVELOPMENT OF BIODEGRADATION KINETICS FOR MIXED SUBSTRATE SYSTEMS
Rakesh Govind, Chao Gao, Department of Chemical Engineering, University of
Cincinnati, Cincinnati, Ohio 45221 (513) 556 2666
Henry H. Tabak, U.S. EPA, RREL, Cincinnati, OH 45268 (513) 569 7681
INTRODUCTION
Mixed substrate systems are often encountered in pharmaceutical, food,
wastewater processes and chemical manufacturing industries. In wastewater treatment
systems, a number of organic compounds are present at the same time. In these cases
it is inevitable that the toxic, or inhibitory substrates will be found in mixtures with
nontoxic, or conventional wastes. In the presence of alternative carbon sources, a
number of possible substrate interactions can occur. Extensive studies on
biodegradation of single components have been conducted (1). However, there is
insufficient information on the performance of biological treatment facilities for the
removal of a specific chemical from wastewater, consisting of a mixture of organic
pollutants. There is a strong need for extensive studies of multisubstrate systems. A
broad data base will help to understand the interaction and removal rates of organic
compounds in mixtures. These studies will also help to establish control mechanisms
that regulate the relative utilization rates of mixtures. In this paper, emphasis will be
given on a comprehensive review of mechanisms, experimental methods, and
modeling studies for biodegradation of mixed substrates.
In biological treatment plants, the substrate removal pattern in a multisubstrate
system may include simultaneous, preferential, or sequential utilization. The diauxi'c
growth observed by Monod (2) in Escheiichia coli suggests that the very presence of a
particular substrate in a wastewater stream might prevent an organism from
acclimatizing to another substrate until the first one has been completely metabolized.
The blockage of metabolism of one compound by another may lead to preferential or
sequential substrate removal from a multisubstrate environment. Chian and Dewalle
(3) have presented evidence for the sequential removal of waste components during
biological treatment of a leachate from a sanitary landfill. Deshpande and Chakrabarti
(4), in a batch reactor, demonstrated preferential removal of m-nitrobenzenesulfonate,
sodium salt (m-NBS), from a mixture of m-NBS and resorcinol, compounds that are
known to be present in m-aminophenol (m-AP) manufacturing wastewaters,
The mechanism of substrate utilization by a bacterial cell can be generally
described as a sequence of three complex processes: contact of a cell with the
molecule of a substrate; transport of the molecule into the cell; and formation of the
substrate Intermediate. On the basis of this general mechanism, it is possible to
classify various types of substrates into three main groups: (a) single components
substrates, which are directly transportable; (b) multicomponent substrates, which are
represented by a mixture of several single substrates; (c) complex substrates, which
have to be changed externally prior to transportation into the cell.
The specific research objectives of this project are as follows: (l)IEvaluate the
effect of co-metabolites on biodegradation kinetics; (2)Develop appropriate kinetic
data for organics with a variety of functional groups; (3)Develop appropriate kinetic
data of a toxic organic in presence of multiple toxics from homologous and non-
homologous series, as sole carbon source or in wastewaters containing background
concentrations of biogenic or toxic organics; and (4)Validate the structure-activity
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relationship model for the biodegradation kinetics of the toxic compounds as single or
multiple components in a variety of municipal / industrial wastewaters.
METHODOLOGY
Experiments were conducted using a 12 unit VOITH electrolytic respirometer for
the following mixed substrates: (1)Mixture of chemical and raw wastewater from the
primary effluent stream of a domestic activated sludge treatment plant; four chemicals
were studied at a concentration level of 100 mg/l : Aniline, Catechol, Phenol and
Benzene. (2)Mixture of chemical and wastewater from the secondary basin of a
domestic activated sludge treatment plant; four chemicals were studied at a
concentration of 100 mg/l: Aniline, Catechol, Phenol and Benzene. (3)Raw wastewater
from the primary effluent stream with no compound; and (4)Wastewater from the
secondary basin with no compound.
The VOITH electrolytic repirometer consists of a temperature controlled
waterbath, containing measuring units, an on-line microcomputer for data sampling,
and a cooling unit for continuous recirculation of waterbath volume. Each measuring
unit consists of a reaction vessel, with the microbial inoculum and test compound, an
oxygen generator, comprised of an electrolytic cell containing copper sulfate and
sulfuric acid solution, and a pressure indicator which triggers the oxygen generator.
The carbon dioxide generated is absorbed by soda lime, placed in the reaction flask
stopper. Atmospheric pressure fluctuations do not affect the results since the
measuring unit forms an air sealed system. The uptake of oxygen by the
microorganisms in the sample during biodegradation is compensated by the
electrolytic generation of oxygen in the oxygen generator, which is connected to the
reaction vessel. The amount of oxygen supplied by the electrolytic cell is proportional
to its amperage requirements, which is continously monitored by the microcomputer
and the digital recorder.
The nutrient solution used in our studies was an OECD synthetic medium (5)
consisting of measured amounts per liter of deionized distilled water containing (1)
mineral salts solution; (2) trace salts solution; and (3) a solution (150 mg/l) of yeast
extract as a substitute for vitamin solution.
The microbial inoculum was an activated sludge from The Little Miami
wastewater plant in Cincinnati, Ohio, receiving municipal wastewater. The activated
sludge sample was aerated for 24 hours before use to bring it to an endogenous
phase. The sludge biomass was added to the medium at a concentration of 30 mg/l
total solids. Total volume of the synthetic medium was 250 ml in the 500 ml capacity
reaction vessels. Reactor flasks either contained 62.5 ml of primary effluent
wastewater mixed with 164 ml of deionized distilled water or 125 ml of secondary
wastewater mixed with 101 ml of deionized distilled water.
In a typical experimental run, duplicate flasks were used for the test mixture,
and reference compound (aniline). The reaction vessels were incubated at 25° C in
the temperature controlled bath and stirred continuously throughout the run. The
microbiota of the activated sludge were not preacclimated to the substrate. The
incubation period of the experimental run was between 28-50 days. A comprehensive
description of the procedural steps involved in the respirometric tests have been
presented elsewhere (6).
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Kompala et al. (7) studied the cybernetic modeling of microbial growth on
multiple substrates. In this model, the internal regulatory processes, which underlie a
variety of behavior in microbial growth on multiple substrates, are viewed «is a
manifestation of an invariant strategy to optimize some goal of the cells. The model
proposed in this paper for describing the degradation of multiple substrates is based
on the cybernetic model, and allows the prediction of microbial growth behavior based
on growth data for single substrates. The framework of this model can be applied to
batch or continuous culture growth of several bacteria on different combinations of
substrates.
In the sequential growth on multiple substrates, the cells grow first on the
fastest assimilated substrate in the medium. The cells may have acquired such a
strong capability to optimize their growth behavior in the following manner: Assume
that in a multisubstrate environment, there exist cells with different strategies of
responding to the environment. The cells that arbitrarily choose to grow first on the
fastest substrate available proliferate much faster than the cells that responded
differently. Very quickly all the cells that remain in that environment will be those that
have responded in the most optimal manner. Hence, it is reasonable to postulate that
over many years of evolutionary processes, in environments with varying menus of
substrates, microbes have acquired the capability to control their regulatory processes
to optimize their pattern. The basic merit of the cybernetic approach is that it adopts a
mathematical simple description of a complex organism but compensates for the over-
simplification by assigning an optimal control motive to its response.
The microbial growth on multiple substrates can be simplistically represented by
the following equation:
E,
B + S| (1+Y,)B + Pr (1)
B
B~
(2)
where: B is the biomass excluding the key enzyme Er.
Instantaneous maximum biomass productivity model was proposed by Kompla
(6). This model proposes that, in a multiple substrate environment, at any instant t,
the organism chooses to synthesize the enzyme for the substrate which maximizes the
biomass growth rate at that instant. The major limitations of the cybernetic model is
that it only predicts an optimal allocation of existing resources to the enzyme
synthesis alternatives .
The cybernetic model equations for biodegradation of multiple substrates are
given below:
rB,l
e, S, C
K? K8f + S,
a, S) C
K
(3)
(4)
8f
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dt K?K8f + S, dt
dS, !
"dT - - Tt re''v'
dC
dt
dS
(Ln C ) e, - p,e,
Pi
dt
where:
v.
max (rBJ)
rB,i
where:
B
C
ei
E,
K°
Kl
rB,i
pi
(5)
(6)
(7)
(8)
(9)
(10)
(11)
biomass
biomass concentration [ mg/l ]
specific enzyme level
ith key enzyme [ mg/l ]
Michaelis constant [mg/l ] for pure compound i
inhibition factor for Michaelis constant
ith bioproduct [ mg/l ]
rate of biomass production through consumption of S; [ mg/I/Hr ]
rate of Ef synthesis [ mg/I/Hr ]
ith substrate [ mg/l ]
ith bioproduct concentration [ mg/l ]
time[Hr]
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U|, cybernetic model variables
V| cybernetic model variables
Y| yield coefficient [ mg/mg ]
Yp| ith product yield coefficient [mg/mg]
ctj enzyme synthesis rate constant [1/1 ]
Pi enzyme decay rate constant [ 1/1 ]
H° growth coefficient [1/1 ] for pure compound i
(if inhibition factor for growth coefficient
Note that the Monod equations in the cybernetic model was modified to include
inhibition from other substrates, products or biomass as initially proposed by
Levenspiel (8).
The cybernetic model equations were used to obtain the kinetic parameters
from the cumulative oxygen uptake data obtained for mixed substrate systems.
RESULTS
Figures 1 through 4 show the cumulative oxygen uptake curves for aniline,
catechol, phenol and benzene in clean water, primary effluent and secondary effluent.
The oxygen uptake curve obtained for the wastewater without the compound has been
shown for comparison.
Similarly, oxygen uptake curves were obtained for binary mixtures of the four
chemical compounds in clean water, primary effluent and secondary effluent. Figure 5
shows the oxygen uptake curve for a mixture of benzene and aniline in clean water.
The cybernetic model was applied using the single compound Monod parameters, and
the calculated and experimental curve for clean water are shown in the Figure. The
cybernetic model parameters are summarized in Table 1.
CONCLUSIONS
It has been shown that the Monod kinetic parameters obtained for the
degradation of single compounds in wastewater are statistically the same as those
obtained in clean water. This result is significant, since most of the available Monod
kinetic parameters in the literature, were obtained using clean water. Furthermore, it
has been demonstrated that the oxygen uptake curves for binary mixtures of
compounds can be derived from single compound Monod kinetic parameters using the
cybernetic model. This allows the prediction of biodegradation of compound mixtures
in clean water systems from single compound studies. The extention of this result for
dirty wastewater is currently being developed.
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REFERENCES
1 . Tabak, H.H., Govind, R., Determination of biodegradation kinetics with the use
of respirometry for development of predictive structure-biodegradation
relationship models, Paper presented at the ACS I&EC Division Special
Symposium on "Emerging Technologies for Hazardous Waste Management",
Atlanta, GA, 1991.
2. Monod, J. Recherche suila croisceance des Cultures Bacteriennos; Hermann:
Paris, 1942.
3. Chian, E. S. K.; Dewalle, F. B. Prog. Water Technol. 1975, 7, 235.
4. Deshpande, S. D.; Chakarabarti, T. Proceeding of the National Symposium on
Biotechnology; Jain, S. C., Ed.; Punjab University: Chandigarh, India, 1982; pp
83-99.
5. OECD guidelines for testing of chemicals. EEC directive 79/831, Annex V, part
C: Methods for determination of ecotoxicity, 5.2 Degradation, Biotic degradation,
Manometric respirometry, Method DGX1, Revision 5. pp. 1-22, 1983.
6. Tabak, H.H., Govind, R., Determination of biodegradation kinetics with the use of
respirometry for development of predictive structure-biodegradation relationship
models, Paper presented at the IGT Symposium, Colorado Springs, CO, 1991.
7. Kompala, D. S.; Ramkrishna, D.; Tsao, G. T., Cybernetic Modeling of Microbial
Growth on Multiple Substrates, Biotechnol. Bioeng., Vol. XXVI, 1272-1281,
1984.
8. Keehyun Han, Levenspiel, Octave, Extended Monod Kinetics for Substrate,
Product, and Cell Inhibition, Biotechnol. Bioeng., Vol. 32, 430-437,1988.
Table 1 Values for the cybernetic model parameters
(For all substrates, a; =0.001, (3j= 0.05, e10/e2o = 4.47/84.8)
Substrate
H
Ks
Y
YD
Pf
Ksf
Aniline
0.25
28.9
0.43
0.01
1.26
5.34
Benzene
0.28
6.50
0.27
0.02
1.52
7.55
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250
50
100 150 200
TIME (HE)
250
300
FIGURE 1. Cumulative oxygen uptake curve for the following
mixtures: [1] Primary effluent and aniline (100 mg/l); [2] Secondary
effluent and aniline (100 mg/I); [3] Clean water and aniline (100
mg/i); Primary effluent; [5] Secondary effluent.
20 40 60 80 100 120 UO 160 180
TIME (HE)
FIGURE 2. Cumulative oxygen uptake curve for the following
mixtures: [1] Primary effluent and catechol (100 mg/i); [2]
Secondary effluent and catechol (100 mg/l); [3] Clean water and
catechol (100 mg/l); Primary effluent; [5] Secondary effluent.
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300
mg/I);
20
40 6° 8™r^° 12° U° 16° 18°
TIME (HR)
300
20
60
80 100 120 UO 160 180
TIME(HR)
FIGURE 4. Cumulative oxygen uptake curve for the following
mixtures: [1] Primary effluent and benzene (100 mg/I); [2]
Secondary effluent and benzene (100 mg/l); [3] Clean water and
benzene (100 mg/I); Primary effluent; [5] Secondary effluent.
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400
350
10 15 20 25 30 35 40 45 50
FIGURE 5. [1] Concentration of aniline varying as a function of
time, during the biodegradation of a mixture of benzene and
aniline; [2] Concentration of benzene changing as a function of
time, during the biodegradation of a mixture of benzene and
aniline; [3] Experimental oxygen uptake curve for a binary mixture
of aniline and benzene; [4] Calculated oxygen uptake curve using
the cybernetic model; [5] Biomass concentration in COD units.
*U.S. GOVERNMENT PRINTING OFFICE: 1 9.9 2 16 K 8 - 0 0 3ft H 7 m
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