United States
Environmental Protection
Agency
Center for Environmental
Research Information
Cincinnati OH 45268
EPA/625/4-89/020
September 1989
Technology Transfer
&EPA Seminar Publication
Corrective Action:
Technologies and
Applications
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EPA/625/4-89/020
September 1989
Seminar Publication
Corrective Action:
Technologies and Applications
U.S. Environmental Protection Agency
Cincinnati, OH 45268
Printed on Recycled Paper
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Disclaimer
This document has been reviewed in accordance with U.S. Environmental Protection
Agency policy and approved for publication. Mention of trade names or commercial
products does not constitute endorsement or recommendation for use.
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Preface
This seminar publication is wholly based on edited versions of presentations made at U.S.
Environmental Protection Agency (EPA) Technology Transfer Seminars entitled
"Corrective Actions: Technologies and Applications". These seminars were held in
Houston, Texas (March 30-31,1988); Atlanta, Georgia (April 19-20, 1988); Chicago.lllinois
(May 25-26, 1988); Philadelphia, Pennsylvania (June 7-8, 1988); and Los Angeles,
California (June 14-15, 1988).
The following lists the authors whose presentations are summarized in this publication and
who participated in the seminar series.
- Ken Whitaker - Engineering Science
- Brent Huntsman - Terran Corporation
- Charles Parmele - IT Corporation
- Evan Nyer and George Skladany - DETOX, Inc.
- Fred Hall - PEI
- Ed Martin - PEER Consultants, P.C.
- James Nash - Roy F. Weston
- Barbara Cormier - PEER Consultants, P.C.
H. Douglas Williams (EPA Center for Environmental Research Information, Cincinnati, OH)
provided guidance and review for this document. Editorial and review assistance was
provided by Dr. J.T. Swartzbaugh and Mr. Robert Mentzer of PEER Consultants, P.C.
This report has been reviewed by the U.S. Environmental Protection Agency and approved
for publication. The process alternatives, trade names, and commercial products are
presented as examples and are not endorsed or recommended by the EPA. Other
alternatives may exist and may be developed. In addition, the information in this document
does not necessarily reflect the policy of the EPA, and no official endorsement should be
inferred.
Ml
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Abstract
The Corrective Action Program is currently under development by the RCRA Enforcement
Division in the Office of Waste Programs Enforcement. To provide engineers and
scientists involved in RCRA Corrective Action activities, from a industrial perspective, with
insight into the selection and evaluation of technologies suitable for application in the
containment and treatment of hazardous releases.
Rve seminars were held in the spring and summer of 1988 in Houston.Texas; Chicago,
Illinois; Atlanta, Georgia; Philadelphia, Pennsylvania; and Los Angeles, California. Support
for the seminars came from the RCRA Enforcement Division of the Office of Waste
Program Enforcement. This publication contains edited versions of what was presented at
each of the five seminars.
The seminar publication provides information on the identification, selection and application
of technologies suitable for controlling and treating releases of hazardous wastes or their
constituents from RCRA treatment, storage and disposal facilities. Applications of
technologies are presented, where appropriate, to demonstrate the suitability of treatment
options for specific waste types. In addition, factors to consider when implementing
corrective measures at operating facilities are reviewed. Whenever possible, information
has been updated and revised to take into account recent changes in the regulations.
This publication is not a design manual, nor does it include all the technologies available
for corrective action. Additional sources should be consulted for more detailed information
and design criteria. State and local authorities should be contacted for regulations as
needed in local areas.
IV
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Contents
Preface mj
Abstract .- '.'.'.'.'.'.'.'.'.'.'.. iv
Tables vi
Figures '.'.'..'.'.'.'.' vii
List of Acronyms jx
Chapter 1 Engineering Overview of the Corrective Action Program 1
What Triggers Corrective Action 1
The Corrective Action Plan '.'.'.'. 2
Interim Measures 2
References '.'.'.'. 4
Chapter 2 Engineering Considerations in the Facility Investigation 5
Pre-lnvestigation Evaluation of Corrective Measures
Technologies 5
Field Diagnostic Tools '.'.'.'.'.'.'.I'.'.'.'. 6
Laboratory and Bench-Scale Studies '.'.'.'.'.'.'.'.'.'.'.'.' 17
References 17
Chapter 3 Containment Options -j g
Groundwater Containment 1 g
Containment and Control Options for Gaseous Wastes from Soils 22
Methods to Control Releases from Surface Impoundments 24
References 25
Chapter 4 Engineering Considerations for the Corrective Measures Study 27
Identification and Development of Corrective Measures Alternative(s) 27
Evaluation of the Corrective Measure Alternative(s) 28
References ^
Chapter 5 Technology Options for the Treatment of Wastes and Waste Streams 31
Chemical Treatment Processes for Corrective Action 31
Biological Processes for Corrective Action 37
Thermal Processes for Corrective Action '.'.'.'.'.'.'.'.'.'.'.'.'.'.'. 47
References 57
Chapter 6 Pretreatment and Post Treatment Options 5g
Separation Techniques (Pretreatment Options) 5g
Solidification/Stabilization Processes (Post Treatment Options) '.'.'.'.'.'.'.'.'. 64
References 73
Chapter 7 Engineering Considerations for Corrective Measures Implementation 75
Corrective Measures Design 75
References 77
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Tables
No.
1 Examples of Interim Measures
2 Containment/Recovery Options and Data Needs by Media
3 Summary of Important Geologic Information
4 Summary of Basic Technologies and Data Needs to Modify
the Degree of Hazard of Wastes
5 Important Physical Treatment Data Needs
6 Geophysical Techniques, Their Application and Limitations
at Hazardous Waste Sites .
7 Comparison of Precipitation Reagents •
8 Biodegradable RCRA-Regulated Organic Compounds . . .
9 Nutrients for Biological Treatment
10 Incineration Type for Various Waste Matrices
11 Debris Identification :
12 Applicability of Solidification/Stabilization for
Specific Contaminants .; .
Page
3
7
8
g
11
12
33
40
40
51
60
67
VI
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Figures
No.
Page
1
2a
2b
3a
3b
4
5
6
7a
7b
8
9a
9b
9c
10a
10b
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
Alteration of function and data needs
Boundaries of a contaminant plume
Subsurface stratigraphic relationship
Cross-section of seismic refraction measuring technique
Log of seismic refraction results
Soil vapor probe and sampling train
Comparison of TCE and TCA concentration distribution by
groundwater and soil gas samples, southwestern U.S. study
Containment options
Containment using extraction wells
Plume diversion using injection wells
The use of subsurface drainage to contain a leachate plume
Plan of downgradient placement
Plan of upgradient placement with drain
Plan of circumferential wall placement
Passive gas control using a permeable trench
Passive gas control synthetic membrane
Gas collection/recovery system
Chemical processes
Flow diagram of a generic chemical treatment process
pH adjustment system
Solubilities of metal hydroxides as a function of pH
General process flowsheet for chemical oxidation
Hydrolysis of refractory organics
Photolysis flow diagram
Site of formaldehyde release
Diagram of in-situ treatment
Biological processes
Diagram of the suspended growth system
Life-cycle design - installed system at southern Texas
site (treating phenol in a brine aquifer)
Diagram of the film flow reactor
DETOX H-series submerged fixed-film biological reactor
Process diagram for revised groundwater and solvent
wastes biological treatment system
Houston Chemical Co. response actions
Conceptual strategy for determining burnability
Pretreatment option logical decision flow chart
Liquid injection incineration system
Schematic of plasma arc system
Rotary kiln incineration system
Fluidized bed reactor
Circulating fluidized bed boiler
Process flow diagram of infrared incineration system
Separation techniques for various particle sizes
Cyclone
Jigging
7
13
13
14
14
14
16
19
20
20
21
22
22
22
23
23
24
32
32
33
34
34
36
36
37
38
38
42
42
43
44
44
46
49
50
52
53
54
55
56
56
62
63
63
VII
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Figures (Continued)
39
40
41
42
43
44
45
Magnetic separator 63
API oil/water separator 64
Shell corrugated-plate interceptor 65
Mobile soils washing system 66
Separator nozzle • • • • ^7
Cernent-based stabilization process 69
Lime-based (pozzolanic) stabilization process 71
VIII
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List of Acronymns
ARC Air Pollution Control
ARC Dir Pollution Control Device
BOD Biochemical OxygenDemand
CAP Corrective Action Plan
CFR Code of Federal Regulations
CM Corrective Measures
CMI Corrective Measures Implementation
CMS Corrective Measures Study
COD Chemical Oxygen Demand
DRE Destruction Removal Efficiency
EM Electromagnetic Conductivity
EP Tox Extraction Procedure Toxicity Test
EPA Environmental Protection Agency
FML Flexible Membrane Liner
GC Gas Chromatograph
GC/MS Gas Chromatograph/Mass Spectrophotometer
gpm gallons per minute
GPR Ground Penetrating Radar
HHE Human Health and the Environment
HWF Hazardous Waste Fuel
kw kilowatt
Ib/hr pound per hour
MAG Magnetometry
MD Metal Detection
MEK Methyl Ethyl Ketone
mg/€ milligrams per liter
MMBtu/hr million Btu per hour
ORP Oxidation Reduction Potential
PAC Powdered Activated Carbon
PCB Polychlorinated Biphenyl
ix
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List of Acronyms (Continued)
PGP Pentachlorophenol
PID Photoionization Detector
ppb parts per billion
ppm parts per million
PVC Polyvinyl Chloride
RBC Rotating Biological Contactor
RCRA Resource Conservation and Recovery Act
RFA RCRA Facility Assessment
RFI RCRA Facility Investigation
SBR Sequencing Batch Reactor
SITE Program Superfund Innovative Technology Evaluation
Program
TCDD Trichlorodibenzodioxin
TCLP Toxicity Characteristic Leaching Procedure
TOC Total Organic Carbon
tph tons per hour
USATHAMA U.S. Army Toxic and Hazardous Materials;
Agency
UV Ultraviolet
VOC Volatile Organic Compounds
p.g/f micrograms per liter
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Chapter 1
Engineering Overview of the Corrective Action Program
The technical differences between site problems at
RCRA facilities and CERCLA sites sometimes may
be difficult to distinguish, owing to similarities in
present or past uses of the site, in hydrogeologic
setting, and/or in the types of substances disposed,
spilled, or otherwise managed at the site.
Consequently, many technical aspects of the study
and remediation of releases of hazardous wastes and
constituents from RCRA facilities often will closely
parallel those at Superfund sites, and cleanups under
both statutes must achieve similar goals for
protection of public health and the environment.
Additionally, activities which would be termed
removal actions or expedited response actions under
CERCLA may be undertaken by owners and
operators under RCRA. In the RCRA context, such
actions are termed interim measures, as will be
discussed in subsequent chapters.
Differences between the two programs may arise in
several areas: (1) who performs the work, (2) extent of
the analyses and/or cleanup performed, (3) factors
considered in selecting a final remedy, and (4) use of
the site following cleanup. First, a Superfund cleanup
may be undertaken by EPA under CERCLA Section
104, or by the responsible parties under EPA or state
supervision under CERCLA Section 106. Corrective
actions at RCRA facilities, on the other hand, are
developed and implemented by the owner/operator
under EPA or state supervision, either through the
facility permit or an enforcement order. Second, at
some RCRA facilities the Corrective Action process
may be somewhat more streamlined than at a
CERCLA site. This could occur in situations where
much is already known about the wastes and the site
at the initiation of Corrective Actions from the Part B
permit application and other submittals; and, where
the release problem is relatively minor or the
remedial alternatives to address it are relatively
minor or the remedial alternatives to address it are
relatively straightforward or self-evident. Third,
while the remedy selection factors in the draft RCRA
Corrective Action regulations (40 CFR 264 Subpart
S) are expected generally to parallel those offered in
the proposed revisions to Superfund's National
Contingency Plan, cost and cost-effectiveness may
not be used as a basis for selecting remedies under
the RCRA statute. Finally, in many cases Corrective
Actions at a RCRA facility may culminate in its
return to normal operating status; while at most
Superfund sites (and at some RCRA facilities
undergoing Corrective Action), these activities
typically culminate in final cleanup or closure of the
site. These and other factors might lead to selection
and implementation of different corrective measures
at otherwise similar RCRA and Superfund sites.
As of this writing, the proposed Subpart S
regulations describing many procedural aspects of
the RCRA Corrective Action program have not been
published. However, two documents provide the
framework for directing the development of the site-
specific work to be performed by the owner/operator
in the facility's Corrective Action program: the
RCRA Corrective Action Plan - Interim Final (U.S.
EPA, 1988a) and RCRA Corrective Action Interim
Measures - Interim Final (U.S. EPA, 1988b). These
can be used to develop site-specific schedules of
compliance for incorporation into a permit or an
enforcement order. From an engineering perspective,
these documents provide scopes of work that can
assist owner/operators and engineers in planning
each phase of a facility-wide Corrective Action
program, and in the formulation and implementation
of interim measures, respectively. Additional
guidance currently is under development.
What Triggers Corrective Action
A common question is "What triggers Corrective
Action?" There is no single answer. In general, any
indicator that a release of hazardous wastes is
occurring (or has occurred) can serve as a trigger.
Thus, a fish kill, a reported spill, contaminated
drinking water or contamination in monitoring wells
are some examples of conditions that may result in
the EPA's initiating a Corrective Action program. An
initial step may be a RCRA Facility Assessment
(RFA), which is conducted by the EPA and intended
to identify releases or potential releases of hazardous
wastes and/or constituents. Usually the RFA is
completed before the Corrective Action process is
initiated. If releases or potential releases are found
that may threaten public health and the
environment, the Agency may require the owner
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and/or operator to develop a Corrective Action Plah to
address the releases.
The Corrective Action Plan
The Corrective Action Plan (CAP) relies on }the
sequential performance of activities which are
conventional engineering practices. These activities
include problem identification, development and
evaluation of alternatives, and the implementation of
the selected alternative. The three analogous phases
identified in the CAP are as follows:
• RCRA Facility Investigation (RFI) - site
characterization and pre-investigation
identification of possible containment/treatment
technologies', ,
Corrective Measures Study (CMS) - the conduct
of detailed feasibility studies of the cleanup
alternatives identified;
• Corrective Measures Implementation (CMI) -
those activities associated with the design and
construction of the technology options selected
and with performance monitoring.
The CAP can serve as the technical framework for a
Corrective Action program. The CAP provides a
"menu" of activities or information requirements
that may be necessary for each phase of the process.
Site-specific conditions and the nature and extent of
the contamination will determine which tasks will be
necessary. The necessary tasks will be enforceable
through permit conditions or by an administrative
order or judicial action. The CAP can serve as a
flexible engineering guide for the regulajtory
community in implementing their own Corrective
Action Program.
Interim Measures
At this writing, the Interim Final guidance for the
regulatory community with regard to interim
measures is available (U.S. EPA, 1988). Based on
this guidance, the general concepts for the
application of interim measures can be identified.
Where there is an imminent threat to human health
and the environment, as well as in some non-
emergency situations, the regulatory agency may
ascertain that a response is appropriate prior to the
completion of the RCRA Facility Investigation or the
Corrective Measures Study. Hence, the decision for
interim measures can be made based on the
immediacy as well as the magnitude of the potential
threat to human health or the environment; the
nature of appropriate Corrective Action; the
implications of deferring Corrective Action until the
RCRA Facility Investigation and Corrective Measure
Study is complete; and other factors.
Once a decision is made that interim measures are
needed, then the next question is what interim
measures might be required for this particular
situation. Examples of interim measures for various
RCRA treatment, storage and disposal facilities, and
for various release types are listed in Table 1. Note
that these are examples; their inclusion does not infer
either guidance or approval.
Interim measures may be separate from the
comprehensive Corrective Action plan but should be
consistent with, and integrated with, any longer-
term Corrective Action (e.g., corrective measure
through an order, an operating permit, a post-closure
permit or interim status closure requirements). To
the extent possible, interim measures should not
seriously complicate the ultimate physical
management of hazardous wastes or constituents,
nor should they present or exacerbate a health or
environmental threat. Interim measures may add
additional costs or work to the comprehensive
Corrective Action. Such added costs or work do not
preclude implementation of an interim measure.
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Table 1. Examples of Interim Measures
The following is a list of possible interim measures for various units and release types. This list is not
considered to be all-inclusive. More information is available through the Interim Measures Guidance •
Interim Final (U.S. EPA, 1988b).
Containers
1.
2.
3.
4.
5.
6.
Tanks
1.
2.
Surface Impoundments
1.
2.
3.
4.
5.
6.
7.
Landfills
1.
2.
3.
4,
5.
6.
7.
Waste Piles
1.
2.
3.
4.
Soils
1.
2.
3.
Ground water
1.
2.
3.
4.
5.
Surface Water Releases
(Point and Non-point)
1.
2.
3.
4.
5.
Overpack/Redrum
Construct Storage Area; Move to New Storage Area
Segregation
Sampling and Analysis
Treatment, Storage and/or Disposal
Temporary Cover
Overflow; Secondary Containment
Leak Detection/Repair; Partial or Complete Removal
Reduce Head
Remove Free Liquids and Highly Mobile Wastes
Stabilize/Repair Side Walls, Dikes or Liner(s)
Temporary Cover
Run-off/Run-on Control (Diversion or Collection Devices)
Sample and Analyze to Document the Concentration of Constituents
Left in Place When a Surface Impoundment Handling Characteristic
Wastes is Clean Closed
Interim Groundwater Measures (See Groundwater Section of this
table)
Run-off/Run-on Control (Diversion or Collection Devices)
Reduce Head on Liner and/or in Leachate Collection System
Inspect Leachate Collection/Removal System or French Drain
Repair Leachate Collection/Removal System or French Drain
Temporary Cap
Waste Removal (See Soils Section of this table)
Interim Groundwater Measures (See Groundwater Section of this
table)
Run-off/Run-on Control (Diversion or Collection Devices)
Temporary Cover
Waste Removal (See Soils Section of this table)
Interim Groundwater Measures (See Groundwater Section of this
table)
Sampling/Analysis; Disposal
Run-off/Run-on Control (Diversion or Collection Devices)
Temporary Cap/Cover
Delineation/Verification of Gross Contamination
Sampling and Analysis
Interceptor Trench/Sump/Subsurface Drain
Pump and Treat; In-situ Treatment
Temporary Cap/Cover
Overflow/Underflow Dams
Filter Fences
Run-off/Run-on Control (Diversion or Collection Devices)
Regrading/Revegetation
Sample and Analyze Surface Waters and Sediments or Point Source
Discharges
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Table 1. (Continued)
Gas Migration Control
1.
Particulate Emissions
1.
2.
3.
Other Actions
1.
2.
3.
4.
5.
S.
Barriers/Collection/Treatment/Monitoring
Truck Wash (Decontamination Unit)
Revegetation
Application; of Dust Suppressant
Fencing to, Prevent Direct Contact
Sampling Off-site Areas
Alternate Water Supply to Replace Contaminated Drinking Water
Temporary Relocation of Exposed Population*
Temporary or Permanent Injunction"
Suspend or Revoke Authorization to Operate Under Interim Status*
'Model language not included in Interim Measures Guidance - Interim Final.
References
U.S. EPA. 1988a. RCRA Corrective Action Plan -
Interim Final EPA/530- SW-88-028, OSWER 9902.3,
Office of Solid Waste and Emergency Response,
Washington, D.C., June 1988.
U.S. EPA. 1988b. RCRA Corrective Action Interim
Measures Guidance - Interim Final EPA/530-SW-88-
029, OSWER 9902.4, Office of Solid Waste and
Emergency Response, Washington, B.C., June 1988.
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Chapter 2
Engineering Considerations in the Facility Investigation
If the RFA or other information has indicated a
release of hazardous constituents, then from the
owner/operator's perspective, the Corrective Action
process truly begins. The first step in the process, the
RCRA Facility Investigation (RFI), is directed
toward development of the engineering information
about the site necessary to permit selection and
evaluation of remedial alternatives. The main
engineering thrust of the RFI is the characterization
of site conditions by defining the nature and extent of
the problem.
The data collection efforts for site characterization
may be expensive and time consuming. Certain
additional data will be needed to evaluate potential
Corrective Action options. Therefore, it is postulated
that if a preliminary screening of possible Corrective
Action options is made before data collection for site
characterization begins, the data necessary to
evaluate candidate Corrective Action options can be
collected concurrently with the site characterization
data. For example, the nature of the identified
release, as well as the owner/operator's knowledge of
hazardous materials used in the past, can give some
indication of the media contaminated and the
possible type(s)^ of contamination. Such information
gives the engineer guidance in identifying potential
Corrective Action technologies. Furthermore,
because the time normally required to conduct the
RFI can be as long as 24 months; lab, bench and pilot
tests can be conducted to confirm the applicability of
candidate technologies and to develop system design
information, if deemed appropriate.
Design of the RFI should incorporate the following
considerations:
• Both containment and treatment may be options;
• Different options may be selected t-o address
different units;
• At any given unit/area, a combination of
technologies (e.g., treatment train) may be
needed to fully address the problem.
Identification of what contaminants are in what
media is only part of the objectives of the RFI. In
addition, treatability information is required which
addresses the physical/chemical properties of the
contaminated media.
From an engineering standpoint, the initial step in
the RFI would be to collect historical information
about past practices to provide insight into the
possible source(s) of the release, the type and
quantities of releases, and potential pollutant
migration pathways. The next step would be to
identify possible technologies which may be needed to
halt the migration of the pollutant and to remove
and/or treat the contaminants in the various media
(i.e., soil, groundwater, etc.) in which the
contaminants are found. Through identification of
what is known about the site and what possible
Corrective Action and/or containment scenarios
might be needed for cleanup, a plan can be developed
to fill the data gaps during the RFI. This chapter is
directed toward the following RFI engineering
activities:
• Pre-investigation identification of candidate
treatment options for containing and/or treating
contaminants;
• Field diagnostic tools which can be used to
characterize the site;
• Bench- and pilot-scale study considerations.
Pre-lnvestigation Evaluation of Corrective
Measures Technologies
During the RFI stage of a Corrective Action program,
only limited information about the site and waste
may be available. Some historical data about the
facility and its past practices and operating
conditions may be developed from plant records. In
addition, the RFA may provide some information
about the contaminants and contaminated media.
Because such information is limited, only general
classes of treatment technologies can be identified
initially .(e.g., the material is organic, so thermal
processes might work). Such identification of general
treatment options is helpful in planning, since the
data collection for site characterization and
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treatment selection can be dealt with
simultaneously. This approach makes the fi|eld
sampling program more cost effective and efficient.
Strategy for Containment Selection:
Early in the Corrective Action process, a decision
may be made concerning whether or not containment
is necessary to protect human health and the
environment (HHB). If the release or threatened
release presents danger to HHE, immediate action
must be taken to halt migration. Under these
circumstances, actions termed "Interim Measures"
may be required, and excavation or containment
measures may be directed by the regulatory agency.
However, the Owner/Operator will be responsible for
their implementation. In the event that containment
is not required as an interim measure, containment
may still be needed as part of the overall Corrective
Action to halt the pollution migration if wastes or
contaminants are to be left on-site.
Based on the existent site information, the questions
which need to be answered to determine if
containment is needed are:
In what medium is the contamination located?
What is the source of contamination?
What are pollutant migration pathways?
What are the potential receptors?
Can the contamination be contained?
Once the medium and a general understanding of the
chemical composition of the waste or contaminant is
known, a number of containment alternatives can be
identified. Table 2 presents the general classes of
containment technologies for various contaminated
media along with data needs for technology
evaluation. Table 3 presents a summary of important
geological information required as part of the dat|a to
be collected to support selection of containment
technologies.
Strategy For Treatment Selection
The purpose of treatment is to alter the function,
form or quantity of the waste, or media contaminated
by the releases, by changing its mobility, its volume,
or its toxicity. The hierarchy of hazardous waste
management establishes that a change (reduction) in
toxicity is the main treatment objective. The next
level of acceptable objectives is providing a change
(reduction) in mobility. The least desirable strategy,
other than storage, is producing a change in volume,
unless producing that change will facilitate
treatment by another means. The general options for
treatment based on these alterations are shown in
Figure 1.
If the primary intent is to detoxify the waste, then the
characteristics of the waste which make the waste
hazardous (and whether the contaminant is organic
or inorganic) become issues. Accordingly, the
questions then become the following:
• Is it toxic?
• Is it reactive?
• Is it corrosive?
• Is it ignitable?
Table 4 allows a generic identification of the various
technology options suitable for treating wastes based
on their hazardous characteristics and physical form.
Table 4 also identifies the kinds of data which must
be collected to perform a valid evaluation of those
technologies. The physical treatment data needs for
different media shown in Table 5 are typically
required in addition to those presented in Table 4.
Field Diagnostic Tools
There are many field diagnostic tools available for
characterization of a contaminated site. In the
preliminary site investigation, screening techniques
can be used to locate areas of contamination by non-
invasive methods. Then in the detailed site
investigation, sampling and monitoring techniques
which provide greater quantification of contaminants
can be focused on those areas identified. As would be
expected, screening techniques are typically rapid
and qualitative as well as being less expensive than
detailed sampling and monitoring techniques.
Preliminary site investigation (screening) techniques
typically include geophysical surveys, soil gas
monitoring, surface water sampling, and limited
groundwater sampling. Of fchese, geophysical
techniques (which measure some physical property of
the soil or contaminant) are useful for locating buried
wastes, contaminated soils and groundwater.
Screening techniques would not usually incorporate
the drilling of wells for core analysis or groundwater
sampling.
Detailed sampling can include, but is not limited to,
the installation of monitoring well networks. After
the wells have been installed, aquifer tests are
typically performed. Once the aquifer tests are
performed and the aquifer characteristics are
determined, time series sampling for a given
contaminant, or a surrogate, is undertaken. The
combined results of these efforts provide the basis for
development of a treatment strategy. Modeling can
be used as part of this effort to help determine the
best technical and most cost-effective techniques to
be used at a site.
Geophysical Techniques
Geophysical techniques can be used for many
purposes, such as to: (1) map hidden hydrogeologic
features, (2) map leachate plumes and zones of
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Figure 1 Alteration of function and data needs.
Volume
Reduction
Quantity
V
-p
Possible
Technology
Classes
Separation
k
Data Needs
Which Chemicals at What
Concentrations?
Phase?
Media?
Mobility
Toxicity
• • t
k
Change of
Function
Change of
Chemical
Form
>.
k
Technology
Classes
Containment
Solidification
Possible
Technology
Classes
Biological
Thermal
Chemical
k
Data Needs
Short/Long Term Risk Areas?
Potential Pathways?
Volume?
Data Needs
Which Chemicals at What
Concentrations?
Phase*^
Media?
Table 2. Containment/Recovery Options and Data Needs by Media
Principal Option
for
Containment/
Recovery
Soils
Excavation
Vacuum extraction
Temporary cap/cover
Hydraulic modification
No action
Groundwater
Groundwater pumping
Subsurface drains
Hydraulic barriers
Low permeability barriers
No action
Surface Water/Sediments
Overflow/underflow
containment (i.e. oil booms)
Run off/run on control
Diversion/collection
No action
Air
Capping/insulation
Operations modifications
Gas collection/removal
No action
Data needed
Soil stratigraphy
Soil hydrology
Surface topography
Engineered features
Chemical composition of
contacted soil
Subsurface soil conditions
Aquifer properties
Geochemical environment
Hydrogeologic setting
Chemical composition of
contaminated plume
Climatic conditions
Geographic conditions
Surface water category
Hydrogeologic setting
Chemical composition of
surface water
Climate
Site-specific weather conditions
Site topography
Physical features
Chemical composition of waste
contamination where electrical conductivities vary
markedly from background levels, (3) locate trenches
in which wastes may have been buried, and (4) to
locate and define buried metallic objects. Such
studies are generally less expensive than well
installations. (This includes the costs for
development, maintenance, sampling and priority
pollutant analyses). In some geologic settings,
geophysical investigations are the most suitable
method for investigating groundwater flow paths.
When a geophysical investigation points to a possible
geologic anomaly or otherwise unrecognizable
feature (natural or man-made), one or a few
appropriately sited wells can be drilled to examine
the subsurface directly; this saves the often
unnecessary and expensive task of drilling many
wells on a grid system to investigate the subsurface
geology of the site. Geophysical techniques include
Ground Penetrating Radar (GPR), Electromagnetic
Conductivity (EM), Electrical Resistivity Surveys, or
Seismic Surveys.
It is important to understand that any geophysical
method which is successful at one site may or may
not have the same success at another site. There are
many variables associated with all geophysical
techniques as presented in Table 6. Someone with the
experience to know the limitations of each of the
techniques should be consulted prior to developing a
large geophysical reconnaissance program.
Ground Penetrating Radar:
This technique uses high-frequency radio waves
sensitive to interfaces between materials with
differing electrical conductivities. These waves are
-------
Table 3. Summary of Important Geologic Information (EPA 540/G-85/002)
Appropriate Collection Methods
Information Needed
Purpose or Rationale
Primary
Secondary*
Structural Features:
• Folds, faults
• Joints, fractures,
interconnected voids
Stratigraphic Characteristics:
• Thickness, areal extent,
correlation of units,*
extent (horizontal and
vertical) of aquifers and
confining units
• Mineral composition,
permeability, and
porosity, grain-size
distribution, in-situ
density, moisture
content
Groundwater Occurrence:
• Aquifer boundaries and
locations
• Aquifer ability to transmit
water
Groundwater Movement
• Direction of flow
• Rate of flow
Groundwater
Recharge/Discharge:
• Location of
recharge/discharge
areas
• Rate
Groundwater Quality
pH, total dissolved
solids, salinity, specific
contaminant
concentrations
Determine natural flow
barriers or controls
Existing geologic maps, field
surveys
Predict major boundaries, Existing geologic profiles,
avenues of groundwater flow pump tests
Determine geometry of
aquifers and confining layers,
aquifer recharge and
discharge
Determine groundwater
quality, movement,
occurrence, productivity
Define flow limits and degree
of aquifer confinement
Determine potential quantities
and rates for treatment '
options
Identify most likely pathways
of contaminant migration
Determine maximum potential
migration rate and dispersion
of contaminants ;
Determine interception points
for withdrawal options, areas
of capping
Determine variability of
loading to treatment options
Determine exposure via
groundwater; define
contaminant plume for
evaluation of interception
methods
Existing geologic maps,
observation wells
Laboratory analysis, existing
geologic literature
Existing literature, water
resource atlases
Pumping and injection tests
of monitor wells
Existing hydrologic literature
Existing hydrologic literature
Existing site data, hydrologic
literature site inspection
Existing literature
Existing site data
Remote sensing, aerial
photography, geophysical
techniques '
Borehole logging and
mapping, geophysical
techniques (limited)
Borehole logging and
mapping, geophysical
techniques (limited)
Existing literature
Borehole logging, regional
water level measurements
Water level measurements in
monitor wellis
Hydraulic gradient,
permeability, and effective
porosity from water level
contours, pump test results,
and laboratory analyses
Comparison of water levels in
observation wells,
piezometers, lakes and
streams
Water balance calculations
aided by geology and soil
data
Analysis of groundwater
samples from observation
wells, geophysics
"May be appropriate if detailed information is required or if it is the only method due to a paucity of published data.
-------
Table 4. Summary of Basic Technologies and Data Needs to Modify the Degree of Hazard of Wastes
Waste Type Form Technology Options Preliminary Technology Data Needs
Corrosive
Liquid
Chemical pH
Constituent analysis
Oil and grease content
Total suspended solids
Total dissolved solids
Ignitable
Liquid
Chemical
Biological
Thermal
Gas
Solid
Thermal
Pretreat to get to
treatable form by
Chemical and
Biological means
Biological
Thermal
PH
Constituent analysis
Gross organic components (BOD.TOC)
Dissolved oxygen
Nutrients analysis (NH3, PO4> NO3)
pH
Priority pollutant analysis
ORP
Heat content
Ash content
Halogen content
Moisture content
Heavy metal content
Volatile matter content
Heat content
Halogen content
Gross organic components (BOD.TOC)
Nutrient analysis (NH3, PO4, NO3)
Priority pollutant analysis
PH
Heat content
Volatile matter content
Ash characteristics
Ash content
Halogen content
Moisture content
Heavy metals content
Reactive
Liquid
Chemical
Biological
Gas
Solid
Thermal
Thermal
Pretreat to get to
treatable form by
Chemical and
Biological means
Biological
PH
Constituent analysis
Gross organic components (BOD.TOC)
Dissolved oxygen
Nutrients analysis (NH3 , PO4, NO3)
pH
Priority pollutant analysis
ORP
Heat content
Ash content
Halogen content
Heavy metal content
Volatile matter content
Heat content
Halogen content
Gross organic components (BOD.TOC)
Nutrient analysis (NH3, PO4, NO3)
Priority pollutant analysis
pH
-------
Table 4. (Continued)
Waste Type
Form
Technology Options Preliminary Technology Data Needs
Thermal Heat content
Volatile matter content
Ash characteristics
Ash content
Halogen content
Moisture content
Heavy metals content
Toxic-Inorganic
Liquid Chemical
Gas Pretreatment required
to get to liquid phase
for chemical treat-
ment or solid phase
for solidification/
stabilization
Solid Solidification/
Stabilization
PH
Constituent analysis
Oil and grease content
Total suspended solids
Total dissolved solids
Solubility (in H20, organic)
Solvents, oils, etc.
Size distribution
Constituent analysis
Organics
Liquid
Gas
Solid
Chemical
Biological
Thermal
Thermal
iPretreat to get to
|treatable form by
Chemical and
'Biological means
Biological
Thermal
PH
Constituent analysis
Halogen content
Total suspended solids heavy metals
content
Gross organic components (BOD.TOC)
Dissolved oxygen
Nutrient analysis (NH3, PO4, NO3)
pH
Priority pollutant analysis
ORP
Heat content
Ash content
Halogen content
Heavy metals content
Volatile matter content
Heat content
Halogen content
Gross organic components (BODTOC)
Nutrient analysis (NH3, PO4, NO3)
Priority pollutant analysis
PH
Heat content
Volatile matter content
Ash characteristics
Ash content
Halogen content
Moisture content
Heavy metals content
10
-------
Table 5. Important Physical Treatment Data Needs
Data Need
Purpose
For Solids
Absolute Density
Bulk Density
Size Distribution
Friability
Solubility (in H20, organic solvents, oils, etc.)
For Liquids
Specific Gravity
Viscosity
Water Content (or oil content, etc.)
Dissolved Solids
Boiling Pt/Freezing Point
For Liquids/Solid Mixtures
Bulk Density
Total Solids Content
Solids Size Distribution
Suspended Solids Content
Suspended Solids Settling Rate
Dissolved Solids Content
Free Water Content
Oil and Grease Content
Viscosity
For Gases
Density
Boiling (condensing) Temp.
Solubility (in H20, etc.)
Density Separation
Storage Volume Required
Size Modification or Separation
Size Reduction
Dissolution
Density Separation
Pumping & Handling
Separation
Separation
Phase Change Separation, Handling and Storage
Storage & Transportation
Separation
Separation
Separation
Separation
Separation
Storage & Transport
Separation
Pumping and Handling
Separation
Phase Change Separation
Dissolution
sent and received (usually) from the same antenna,
with variations in the returning signals being
recorded continuously. The resulting subsurface
profile shows features such as bedding, voids and
fractures. There are depth limits to this technique,
with signal attenuation becoming more important at
depths where subsurface materials have low
electrical conductivities, i.e., where pore fluids are
present in quantity. What this means is that optimal
conditions for this technique are sandy or rocky soils
in the vadose zone or bedrock with low permeability
where water is not permanently present. Clay-rich
sediments (which by their nature retain water more
than most sediments) and otherwise damp or
saturated sediments will generally yield poorer
results. However, reliable data are obtainable in
settings where pore fluids have a low specific
conductance, e.g., where significant amounts of
petroleum products are present. Ground penetrating
radar gives the highest resolution among the various
techniques discussed herein, and a radar survey can
be done relatively quickly at hazardous waste sites.
Electromagentics:
The electromagnetic method measures electrical
conductivity values of subsurface materials. Where
pore fluids are present, it is their conductance values
that are measured. A transmitter emits an
electromagnetic field that sets up induced eddy
currents, which are intercepted by a receiver,
producing an output voltage that is related to
subsurface conductivities. Paralleling the results
obtained with radar, electromagnetic methods reveal
changes in soil conductivity which are normally
related to pore fluids. For example, in instances
where leaking drums were buried in shallow
trenches, the contaminated zone contrasted sharply
with surrounding sediments. Because this technique
produces data in conductivity units directly, the data
can be used in the field immediately after the survey.
This can allow for quick, "best-educated guess"
decisions if necessary.
11
-------
Tablo 6. Geophysical Techniques, Their Application and Limitations
Utilization at Hazardous
Technique Technology Description Waste Sites
at Hazardous Waste Sites (Johnson, 1986)
Limitation on Application
Ground
Penetrating
Radar (GPR)
Electromagnetic
(EM)
Conductivity
Seismic
Refraction (SR)
DC Resistivity
Magnotomeby
(MAG)
Metal Detection
(MD)
An electromagnetic
pulse is sent into the
ground. The reflected
pulses are detected by
an antenna held at the
surface of the ground.
Measures the electrical
conductivity of materials
In microohms over a
range of depths
determined by the
spacing and orientation
of the transmitter and
receiver coils, and the
nature of the earth
materials.
Induced compression
waves are reflected at
the interface of the
subsurface elements and
refract differently based
on the properties of the
new medium of
propagation.
Measures the voltage
drop between two
electrodes in the ground
after an electric current
has been put into the
ground between two
other electrodes.
Measures the intensity
of the earth's magnetic
field and local magnetic
anomalies. By
electronically filtering out
the earth's magnetic
field and nulling the
instrument, the local
magnetic anomalies
created by ferro-
magnetic objects can be
qualified.
MD measures
instrument responses to
deposits of ferrous and
nonferrous metals up to
10 to 20 ft deep.
In real-time, shallow earth
profiles of dielectrical dis-
continuities related to sub-
surface conditions such as
moisture content, >lithology,
bedding, voids, fractures,
man-made objects. Can be
used to detect buried plas-
tic containers and areas of
excavation boundaries.
Delineates areas of soil and
groundwater contamination
and the depth to bedrock or
buried objects. Surveys to
depths of 50 to 100 ft are
possible.
Estimates the depth of
bedrock, rock strength
(density), depth to
saturated soil or rocks and
soil layering in general.
Used to locate fractures in
the bedrock that act as
conduits for the
contamination in otherwise
impervious strata.
Metal can be detected to
depths up to 60 ft
Frequently a gradiometer,
basically two
magnetometers ih one with
the sensors at different
levels, is more efficient than
the single sensing unit.
Detection of high-density
deposits in shallow depths.
Good inexpensive
preliminary survey tool.
• Adverse soil conditions - Radar waves will not effectively
penetrate damp, low-resistance clay or other conductive
material.
• Improper antenna - Several frequencies should be tried before
selecting the optimum frequency and antenna.
• Adverse surface conditions - Grooming of the surface may be
required. Long grass and rough ground cause problems with
radar penetration and patterns. Surface and subsurface metal
can distort the GPR record.
• Improper calibration - Depth is difficult to derive from a single
antenna receiver unless a specific target can be identified.
• Power lines, underground cables, transformers and other
electrical sources severely distort the measurements.
• Low resistivities of surficial materials makes interpretation
difficult. The top layers act as a shunt to the introduction of
energy into lower layers.
• Capabilities for defining the variation of resistivity with depth are
limited.
• In cases where the desired result is to map a contaminated
plume in a sand layer beneath a surficial clayey soil in an area
of cultural interference, or where chemicals have been spilled
on the surface, or where clay soils are present, it is probably
not worth the effort to conduct the suivey.
• Fill material must be evaluated with extreme caution.
Substantially more shot locations should be made than needed
for a conventional survey.
• Industrial sites produce a lot of background noise, and it is
necessary to utilize sources of energy more powerful than for
normal suivey work.
• Correlating data from site borings are required to obtain
meaningful results from interpretations of the data.
• The Wenner array should not be used unless the expected
ground conditions are fairly simple. The Schlumberger array is
less sensitive to lateral resistivity variations.
• Meaningful resistivity results cannot be expected on top of the
area of buried debris (landfill), dry sand, frozen ground, or near
fences, or railroad tracks and underground pipes.
• The resistivity survey cannot interpret information from a
horizon beneath an aquifer.
• Contour maps of apparent resistivity can be misleading.
Electrode spacing should, not be considered to have a linear
relationship with depth of penetration.
•The most effective survey lines orient N/S.
• Readings every 10 ft are needed on survey lines 30 ft apart.
• Surface ferrous items should be noted.
• Many anomaly patterns can exist due* to other site activities
than waste disposal.
• Anomaly patterns of a gradiometer are more difficult to interpret
than those of the magnetometer. :
• Background conductivities greater than 40 millimhos/meter
impairs results.
• Wet clay soils impair resluts.
12
-------
Because most groundwater contamination problems
involve anionic/cationic species or organic chemicals,
a change in background conductance levels will occur
when a significant amount of contaminant is present
in the subsurface. In the case of polar species (such as
heavy metals, nitrates, chlorides, and other
electrolytes) the specific conductance will, in most
settings, be increased greatly over background levels.
With organic contaminants such as nonpolar
chlorinated solvents, specific conductance levels will
decrease. In either case, an electromagnetic survey
will commonly be able to detect the contaminant
plume, define its boundaries and, in some cases,
indicate the flow direction.
Resistivity
These surveys measure the electrical resistivity of
subsurface materials, which is just the opposite of the
electromagnetics survey. As one might expect, the
advantages and disadvantages of each method are
not the same. Resistivity methods use a pair of
electrodes at the ground's surface to set up an
electrical current in the subsurface, and the resultant
voltage is measured by a second pair of electrodes.
Resistivity is then calculated using site-specific
variables in a standard equation. The effectiveness of
a resistivity survey is basically dependent on pore
fluid composition, as with electromagnetics, and the
results can be used in a similar way. For example, the
survey can be used to define the boundaries of a
contaminant plume or to establish subsurface
stratigraphic relations (Figures 2a and 2b).
Figure 2b Subsurface stratigraphic relationship
(Universal Oil Prod., 1972).
Figure 2a
v- Electric
\Timer
Boundaries of a contaminant plume (Universal
Oil Prod., 1972).
Shock Points at
10' Intervals
Water-Bearing
'- Sand
X .' '-. .(
Bedrock
A comparison of resistivity and electromagnetic
techniques (resistance versus specific conductance)
shows that resistivity surveys are slower because the
technique is necessarily limited to measurements at
the fixed electrode points, which must be moved for
each new survey. Electromagnetic surveys are not
limited by fixed points. Also, certain applications of
resistivity methods are best suited for sites where the
0.040
0.030
0.020
0.010
V3 = 8,300 fps
0 10 20 30 40 50 60 70 80 90 100
Distance in Feet
stratigraphic column is fairly uniform over the entire
area. Resistivity surveys, however, are generally
more effective than electromagnetics in profiling
vertical variations in the subsurface. Furthermore,
results of resistivity can be evaluated in the field
qualitatively or semi-quantitatively. An additional
capability of resistivity is that a first approximation
of lithologic compositions can be made, particularly
when outcrops are lacking in an area and wells are
widely separated or absent altogether.
Seismic Refraction
This technique measures the travel time or velocity
of seismic waves to map depths to and thicknesses of
particular stratigraphic units or other significant
layers (e.g., the water table or the base of landfills
and trenches) in the subsurface. This is not the same
as the seismic reflection technique commonly used in
oil and gas exploration. The seismic reflection
technique is ineffective at the relatively shallow
depths in which contamination occurs at most
hazardous waste sites. Seismic waves are sent out by
introducing energy at the surface and recording
direct and/or refracted waves with geophones spaced
at regular intervals (Figures 3a and 3b). This method
is inherently susceptible to severe disturbance by
stray vibrations, which can be set up by nearby
footsteps, cars, trains, etc., and the investigator must
be aware of the potential problems such vibrations
may cause in the data.
Seismic studies are very useful when information is
lacking on subsurface stratigraphy, or when the
depth to bedrock, the water table, a particular bed or
formation, or some other layer in the subsurface must
be determined without drilling. Seismic lines can be
set up to produce stratigraphic cross sections and
they can be a very useful "non-invasive" inves-
13
-------
tigative technique, particularly if correlated with a
core-measured section or geophysical well log. The
lack of "hard" stratigraphic data from a core, well log,
etc., means that the interpretation of the "soft"
seismic data is much more subjective. This may not
be a problem in a small study area, but when the goal
is subsurface stratigraphic interpretation over a
large area, the results would probably be considered
speculative until a well was drilled and logged or an
outcrop measured, and this stratigraphic information
was convincingly correlated with the seismic data.
Once again, note the importance of mapping the site
geology to determine field relations of the various
strata present. Without this information, much of the
interpretation of information gathered from seismic
studies is necessarily speculative. :
Figure 3a Cross-section of seismic refrac*'on measuring
technique (Zhody, 1974).
Potential Electrode •
Current
Source
-W«—
Milliommeter
Potentiometer
L-*
Current
Electrode
*f*****l£ Ui»« MM"I »• -t w.«l»!.»«.•. ' ^M^IMMgpMr**.
;.—^lh£>-.-i^c^..^^^?^-;j^v:-_=j-=£F-^-^~i; v
• Moist Silt & Clay J?fe>fSr-lr*"^ai^X>. r;
< (Low Resistivity) \$£z^SJK*. wfc^.=-z.-^.,
-
L.x--N
*..-»7Xi*-v«
Resistivity of This •
Region Measured
^^
;^V£>
•Xv>if«J Sand & Gravel
TfT^.y;- (H'flh resistivity)
Figure 3b Log of seismic refraction results (Zhody,
1974).
Honzontal Distance in Meters
100 200 300 400
500
0 200 400 600 800 1000 1200 1400 1600
West Horizontal Distance in Feel East
Soil Gas Monitoring
VOCs on the "surface" of groundwater volatilize into
the voids in the soil above the groundwater. Soil gas
collection and sampling procedures have been
developed that are simple and quick to implement
(Lappala, 1984; Quinn, 1985; Nadeau', 1985). In one
method as shown in Figure 4, a small diameter (1-in.)
steel probe is inserted to a depth of 3 feet. A vacuum
pump pulls the VOC that is present between the
interspaces or voids of the soils into a sample tube.
The sealed tube is taken to a laboratory for analysis
by Gas Chromatography (GC). The sample train is
decontaminated before use in the next probe hole by
pumping ambient air through the system. A portable
photoionization detector (PID) gas chromatograph
can be used in the field prior to putting the sample
into the collection tube.* By first passing a sample
through this device, a quick determination of the
presence of VOCs can be made. If there is no reading,
then no sample need be analyzed in the laboratory.
Figure 4. Soil vapor probe and sampling train (Nadeau,
1985).
- Air Sampling Bag
Vacuum
Pump
As shown in Figures 5a, 5b, 5c and 5d, the soil gas
sampling procedure can quickly produce isopleths of
VOC concentrations over a large site and indicate
possible source areas. While not exactly analogous to
the VOC concentrations in groundwater, the results
can be utilized to develop a borehole and monitoring
well program with a minimum number of wells
because of this prior knowledge of the site conditions.
The soil gas sampling procedure is low cost, produces
low site disturbance and can be used at sites with
difficult access.
Detection limits of 0.0001 to 0.01 mg/P in. soil
samples and 0.1 to 1.0 mg/€ in water samples have
been reported. Lappala (1984) reported the results of
repeated sampling on successive days at a
14
-------
southwestern United States site using these soil gas
sampling techniques. The results of successive days'
samples showed no significant difference by
Student's "t" Test. However, Karably (1987) reported
significant variations in soil gas sample point
readings (i.e., magnitude of VOC detected) over an
extended time period caused by environmental
variables. However, the general trend of contaminant
levels and plume geometry were roughly the same.
Soil gas concentrations were found to be affected by
temperature and infiltrating groundwater.
A second factor affecting the repeatability of the soil
gas sampling techniques was the length of time to
draw the sample at each station. Karably (1987)
reported that results of repeated sampling at the
same station suggest that a specific volume of soil gas
must be evacuated to obtain a representative sample,
and that this volume would differ among hazardous
sites. This required volume would need to be
determined at each site as part of the sampling
protocol. Results and effectiveness have been found to
be sensitive to repeated spill incidents on the same
site and to fluctuations of the groundwater table.
Sites with tight, saturated clay layers or an expected
contaminated layer below a clean layer of
groundwater are not good applications for soil gas
sampling (Lappala, 1984). A sampling probe length
of 3 feet has been used on sites with groundwater
down to 36 feet, while a length of 10 feet is needed for
groundwater down to 100 feet. If the detected
concentration decreases with depth, then the source
of the VOC is a surface spill. If the concentration
increases, this indicates that the VOC is on the
surface of the groundwater. The sampling procedure
has limited usefulness for deep groundwater (75 to
100 feet).
For air sampling of unknown contaminants, a
multistage tube was developed to provide a quick
profile of organic compounds (Turpin, 1984). Solid
sorbent media require minimal processing to produce
a suitable sample for injection into GC/MS analytical
equipment, a rapid qualitative and quantitative
device for characterization of unknown mixtures.
This procedure reduces the number of air samples
needed, improves turnaround time, and identifies a
wide variety of chemicals in the screening process.
The sample is collected in a two-stage tube consisting
of Tenax-GC packing in the first tube and
Chromosorb® 102 sorbent in the second. Some
chemicals such as tricresyl phosphate, isopropyl
alcohol, chlordane, Aroclor 1254, and naphthalene
were not collectible by this tube configuration.
Use of Surrogates
During a preliminary investigation, much of the
expense associated with analytical activities can be
reduced by using surrogate or good indicator
parameters. These are typically nonspecific.
Examples would be: total organic carbon, total
organic halogens, specific conductance or, if dealing
with gases, organic volatile measurements. It should
be emphasized that these analyses measure a class or
a group of compounds and may not directly quantify
the specific compound or contaminants of concern.
Care must be exercised when correlating these
nonspecific measurements with the total movement
of the contaminant.
Core Sampling
To make the most of monitoring well installations, it
should be decided if continuous coring with core
recovery should be performed during well drilling
activities. The study of cores is the best way to
examine rocks in the subsurface, and if there are
unresolved questions about porosity, hydraulic
conductivity, fracturing, etc., the detailed lithologic
log produced from core logging will often provide
answers. Cores give a more complete picture of the
subsurface geology and contaminant location than do
cuttings alone, and therefore, coring is preferred.
Monitoring Well Networks
Pumping tests or single well tests are probably the
most utilized tool to determine the aquifer properties.
There are a number of different type tests, but as
with any other type of testing program, selecting the
sampling point(s) is critical in order to obtain good
results. An effective preliminary survey can produce
significant cost savings by specifying the optimum
locations for a minimum number of required wells.
Before any site-specific groundwater sampling is
done, soil and waste characterization should be
completed.
When groundwater contaminant plumes are
suspected of having significant depth as well as
lateral distribution, a three-dimensional array of
monitoring points is needed to identify and
characterize such plumes. Thus, groundwater data
must be obtained from a number of different locations
and from a number of different depths at each
location. As a result, either a large number of
drillholes are required, each with separate
instrumentation installed, or instruments must be
combined and installed at multiple levels in each of a
smaller number of drillholes.
Several downhole sampling devices have been
developed to sample at discrete and multiple levels
within the well. Discrete sampling can be utilized to
identify the location for the well screening to assure
extraction of the contaminant during pumping. The
sampler can be lowered into a borehole to
increasingly lower depths until the proper level is
identified. The sampler is then removed and the well
is developed for extraction. If the well were being
developed as a monitoring well, then the sampler can
15
-------
Figure 5. Comparison of TCE and TCA concentration distribution by groundwater and soil gas samples, southwestern U.S.
study (Lappala, 1984).
Plant —' «- Solvent Sump
Log of TCE in Groundwater
Figure 5a.
Plant
- Solvent !3ump
Log of TCE in Soil Gas
Figure 5b.
Plant
V
Solvent Sump
Plant
Solvent Sump
Log of TCA in Groundwater
Figure 5c
Legend:
• Monitoring Well
* Soil Gas Probe
r-f 3.1 Log of TCE or TCA Concentration in Groundwater
/-x 3.1 Log of TCE or TCA Concentration in Soil Gas
Log of TCA in Soil Gas
Figure 5d.
100 200 Meter
16
-------
be left in place. A multiple level sampler can be used
to take many samples over the depth of the well
without having to be moved if such sampling is
required.
Conceptual Model
Upon completion of both the preliminary and detailed
site investigation, a conceptual model can be
prepared. A conceptual model is essentially a site
model which includes all of the information that has
been acquired for the site from both preliminary and
detailed investigations, as well as other
investigations not directly related to the site. The
conceptual model can be anything from simple
diagrams to detailed computer simulations,
depending upon the complexity of the site. The model
must be continually updated to include new
information as it is developed.
Once the conceptual model is operating, it can be
utilized to help develop a technically sound, cost-
effective recovery and treatment system. Potential
uses for a conceptual model include provision of
continual updates of project developments, provision
of a yardstick to measure what has been done and
what needs to be done, and helping prioritize areas
for Corrective Action. Ultimately, the principal use
for a conceptual model is to help determine what
Corrective Actions or alternatives are applicable to
the site.
Laboratory and Bench-Scale Studies
Bench- or pilot-scale studies are necessary to
demonstrate the ability of a technology to effectively
treat a specific waste. Waste characteristics vary
from site to site and because of this, the effect of a
treatment technology with that particular waste may
not be known, given the site-specific factors and
conditions. Also, the proposed treatment technology
may be new or unproven.
Thus, bench or pilot studies are necessary to avoid
technology misapplication in the field. The loss of
time in treatment or the requirement to provide
additional treatment for the waste is very expensive.
Therefore, the relatively small costs and time needed
for these studies make them useful tools in treatment
selection. Bench-scale treatability studies for
demonstrated technologies can cost between $10,000-
$50,000 and take up to 6 weeks. Demonstrated
technologies are those for which the major design
parameters and treatment efficiencies are well
understood. Innovative (and some biological
processes) will require substantially more time (4-16
weeks) and money ($25,000-> $200,000). These are
estimates, and actual time and costs are going to
depend on what kind of technology is under
consideration.
Pilot-scale studies for demonstrated technologies can
cost from $25,000 to more than $100,000 and
typically require 2-12 weeks. For innovative
technologies, the cost for pilot testing can start at
$100,000 and exceed $1,000,000 and require 3 to 12
months.
Aside from size considerations, the primary
difference between bench-scale and pilot-scale work
is that bench-scale tests are conducted in the
laboratory; pilot-scale testing is usually carried out
on the site. Pilot tests are subject to a whole range of
problems, such as siting, health and safety, obtaining
clearances, installation and operation. However, the
data obtained from pilot-scale tests are much more
appropriate and useful because they reflect what is
actually occurring in the field.
The choice of the kind of testing (bench or pilot-scale)
to be performed is going to hinge on the balance
between the level of certainty that the technology is
going to work (and be effective for the site) against
the risk of failure if the technology does not work for
the unique mix of contaminants and contaminated
media (air, water, soils, sediments) found at that site.
The risks of failure include the cost and time needed
to perform another test or to implement another
technology if the first one selected fails. Obviously,
pilot-scale studies may not be needed if there is a
high level of certainty that the particular technology
will work (i.e., there is a low risk of failure). Pilot-
scale studies also may be unnecessary if there is
going to be very little cost or time penalty for
identifying a new treatment system, given failure of
the first. On the other hand, if there is a low level of
certainty that the technology is appropriate and
there is a very high risk of failure, one needs to
carefully consider that it may be more prudent to
spend the time and money for bench-scale testing.
Pilot-scale testing, without prior bench-scale testing,
should be employed only when there is a moderate
level of certainty that the technology is going to be
effective and there is only a moderate risk of failure.
References
Johnson Division-Universal Oil Products Company,
Groundwater and Wells, St. Paul, Minnesota, 1972,
p. 177.
Johnson, W. and P. Johnson. "Pitfalls of Geophysics
in Characterizing Underground Hazardous Waste,"
In: Management of Uncontrolled Hazardous Waste
Sites Proceedings, Hazardous Materials Control
Research Institute, Washington, D.C., p. 227-232,
1986.
Karably, L. and K. Babcock. Effects of
Environmental Variables on Soil Gas Surveys In:
Superfund '87, The 8th National Conference
17
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Proceedings, Hazardous Materials Control Research
Institute, Washington, D.C., 1987.
Lappala, E. and G. Thompson. Detection of
Groundwater Contamination by Shallow Soil Gas
Sampling in the Vadose Zone and Applications. In:
Management of Uncontrolled Hazardous Waste Sites
Proceedings, Hazardous Materials Control Research
Institute,Washington, D.C., 1984.
Nadeau, R., J. Lafornara, G. Klinger and T. Stone.
Measuring Soil Vapors for Defining Subsurface
Contaminated Plumes. Management of Uncontrolled
Hazardous Waste Sites Proceedings, Hazardous
Materials Control Research Institute, Washington,
D.C.,1985.
Quinn, K., S. Wittmann and R. Lee. Use of Soil Gas
Sampling Techniques for Assessment of
Groundwater Contamination. In: Management of
Uncontrolled Hazardous Waste Site Proceedings,
Hazardous Materials Control Research Institute,
Washington, D.C., 1985.
Turpin, R., K. Vora, J. Singh, A. Eissler, and D.
Stranbergh. "On-Site Air Monitoring Classification
by the Use of a Two-Stage Collection Tube,":
Management of Uncontrolled Hazardous Waste Sites
Proceedings, Hazardous Materials Control Research
Institute, Washington, D.C., 1984.
Zohdy, A., G. Eaton, and D. Mabey. Application of
Surface Geophysics to Groundwater Investigation,
Techniques of Water Resource Investigation, Book II
Chapter Dl, U.S. Government Printing Office,
Washington, D.C., 1974, p.14.
18
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Chapter 3
Containment Options
If hazardous wastes or hazardous constituents are
found to be migrating from a RCRA-regulated
facility, an initial response might be directed toward
implementation of methods to control their spread.
Once the site investigation provides sufficient
information about the nature and extent of the
contamination and the medium in which the
contaminant is located, actions to limit the spread of
the contaminant can be developed, if deemed
necessary. Note that the containment technology
selected depends upon the medium in which the
contaminant is found and the general containment
options available for common situations encountered
are shown in Figure 6. These situations include
contaminated groundwater and gaseous emissions
from landfills or surface impoundments.
Groundwater Containment
Contaminants from a hazardous waste site can enter
the groundwater system through a variety of
mechanisms: (1) surface water infiltration, (2)
groundwater passage through the waste, and (3)
liquid waste flow through permeable soil. Control of
contaminant migration involves containment of the
contaminated groundwater plume and the
prevention of further dissolution of contaminants by
water entering the waste area. Infiltration of
rainwater to the contaminated medium can be
controlled by capping and surface water diversion
techniques. A more difficult problem arises when
trying to contain the movement of uncontaminated
groundwater through a waste or of a plume of
contaminated groundwater. However, before a
specific containment strategy can be selected and
subsequently located in the field, it is important to
have a good understanding of the hydrogeologic
setting and the subsurface behavior of the
contaminants.
With an understanding of the site geology and
hydrology and the behavior of the contaminants in
the subsurface, the selection of containment/recovery
technology can begin. Typical ways to contain and/or
recover contaminated groundwater plumes include
groundwater pumping, subsurface drains and barrier
walls. Barrier walls are a passive option typically
aimed at containment whereas groundwater
Figure 6. Containment options.
Surface water diversion and
capping can be used to prevent
further infiltration of rainwater or
runoff.
pumping and subsurface drains can be used to control
pollutant migration as well as to extract
contaminated groundwater for subsequent
treatment.
Groundwater Pumping
Groundwater pumping can be used to manipulate
and manage groundwater for the purpose of
removing, diverting, and containing a contaminated
plume or for adjusting groundwater levels to prevent
plume movement. For example, pumping systems
consisting of a series extraction wells located directly
down-gradient from a contaminated source can be
19
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used to collect the contaminated plume. Water can
also be injected into the subsurface to move the plume
away from an area that must be protected, such as a
domestic drinking water source (Figure 7a and 7b).
The success of any contaminant capture system based
upon pumping wells is dependent upon the rate [of
groundwater flow and the rate at which the wellj is
pumped. Thus, the zone of capture for the pumping
system must be established. :
Figure 7a. Containment using extraction wells (U.S. EPA,
1985).
Domestic
Well
Extraction Wells
with Radium of
Influences
Figure 7b.
Plume diversion using Injection wells (U.S. EPA,
1985).
Injection
Wells
Domestic Wells
Corrective Action Application
The Fairchild Camera and Instrument Corporation
site in South San Jose, California, proved to be a
complex and difficult groundwater contamination
cleanup action (U.S. EPA, January 1987). Over
43,000 gallons of organic chemicals were lost into the
•soil, contaminating four aquifers? beneath the site.
Groundwater in the shallow aquifers was initially
contaminated by the chemicals. Subsequently,
contaminants migrated into the lower aquifers
through interconnecting sand beds, existing wells,
and slow seepage through separating strata. The first
action taken for plume containment was the
installation of an extraction well to create a zone of
influence to draw the plume back. The initial
pumping rate was 500 gpm, but this was increased to
1500 gpm when the lower rate failed to contain the
plume spread. To further control the spread of the
plume, three rows of extraction wells were installed
near the source of the contaminant. The combined
pumping dewatered two aquifers, but left the
contaminant behind in the unsaturated soil.
Subsequently, contaminants continued to migrate to
lower aquifers. Finally, the source was contained
with a 3500-ft long, 70 to 140-ft deep, 3-ft wide slurry
wall.
Subsurface Drains
Pumping techniques represent an aggressive
approach which requires ongoing maintenance and
operation throughout the life of the Corrective
Action. By contrast, subsurface drains (and barrier
walls, described below) represent a passive design
which do not require a high level of ongoing
maintenance. Subsurface drains are most useful in
preliminary containment applications for controlling
pollutant migration while a final treatment design is
developed and implemented. They also provide a
measure of long-term protection against residual
contaminants following conclusion of treatment and
site closure.
Subsurface drains are essentially permeable barriers
designed to intercept the groundwater flow. The
water must be collected at a low point and pumped or
drained by gravity to the treatment system (Figure
8). Subsurface drains can also be used to isolate a
waste disposal area by intercepting the flow of
uncontaminated groundwater before it enters into a
contaminated site.
Corrective Action Application
The use of a drain system permits the quick
construction of a collection/removal system which
also serves as a barrier for leachate from large,
shallow sites. At the Sylvester hazardous waste site
in Nashua, New Hampshire, a groundwater
interception and recirculation system was installed
as a method to retard further spread of the leachate
plume until a remedial cleanup action could be
implemented. The system was operated for 1 year
until a containment wall and cap were constructed
over the 20-acre site (McAneny, 1985).
20
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Figure 8. The use of subsurface drainage to contain a leachate plume (U.S. EPA, 1985).
Waste Disposal Site
Contaminated "%.
Groundwater Plume t?
Groundwater Flow
Direction
Map View
Subsurface Drainage
5 ^3-'- -" '
rfT> /
Collected
Groundwater is
Pumped into
Treatment System
Cross Section
Waste Disposal Site
Original Water
Table
Contaminated
Groundwater Plume
Barrier Walls
Low permeability barriers are used to direct the
uncontaminated groundwater flow around the
disposal site or to prevent the contaminated material
migrating from the site. Figures 9a, 9b and 9c
illustrate typical configurations for barrier walls.
Barrier walls can be made of a wide variety of
materials as long as they have a lower permeability
than the aquifer. Typical materials include mixtures
of soil and bentonite, mixtures of cement and
bentonite, or barriers of engineered materials (sheet
piling). A chemical analysis of wall/contaminant
compatibility is necessary to the final selection of
materials. The installation of a low permeability
barrier usually entails a great deal of earth moving,
requires a significant amount of land area, and is
expensive. However, once in place, they represent a
long-term, low maintenance system. Once in place,
active gradient controls (i.e., pump and treat)
required by some installations will add to the long
term operating costs of these systems.
Corrective Action Application
At one Superfund site, a slurry wall was placed
around a landfill containing municipal waste and
industrial hazardous wastes (solid and liquid). In
addition to installing the slurry wall, a cap over the
site was constructed simultaneously. Due to the onset
of winter, the capping of the site had to be halted.
During the subsequent winter months, an
extraordinary amount of rainfall was experienced.
The area within the slurry wall began to fill with
water (the bathtub effect). A pumping and treatment
system had to be installed to reduce and treat the
water which collected within the slurry wall. Some
portions of the slurry wall required repair due to the
large hydraulic gradient produced by the high water
levels inside the wall (U.S. EPA, 1987).
This case serves to point out the importance of
maintaining a constant hydraulic gradient on the
inside and outside of a slurry wall. This can also
become a factor if slurry walls are used with
groundwater pumping systems (extraction wells).
Then water must be reinjected to maintain a
21
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Figure 9a. Plan of downgradient placement (Spooner et al.,
1984). |
Groundwater Divide
Extraction
Walls
Slurry
* Wall
Figure 9b. Plan of upgradient placement with drain
(Spooner et al., 1984).
Figure 9o. Plan of circumferential wall placement
(Spooner et al., 1984).
Qroondwater Flow
Slurry Wall
Extraction
Wells
relatively constant hydraulic gradient on both sides
of the slurry wall.
Containment and Control Options for
Gaseous Wastes from Soils
Gaseous wastes may introduce an additional range of
problems which must be addressed in the design of a
containment plan. Gaseous wastes will migrate
vertically or horizontally along: the path of least
resistance. Control systems fall into three general
categories: (1) passive perimeter gas control systems,
(2) active perimeter gas control systems, and (3) ,
active interior gas collection/recovery systems. All of
these systems assume the installation of a cap to
prevent vertical escape of gaseous wastes.
Passive Perimeter Gas Control! Systems
Passive perimeter gas control systems are designed to
alter the path of contaminant flow through the use of
trenches or wells, and typically include synthetic
flexible membrane liners (FMLs) and/or natural
clays as containment materials. The membrane is
held in place by a backfilled trench, the depth of
which is determined by the distance to a limiting
structure, such as groundwater or bedrock. A
permeable trench installation functions to direct
lateral migration to the surface, where the gases can
be vented (if acceptable) or collected and conveyed to
a treatment system (Figure lOa and lOb).
Corrective Action Applications
At the Lipari Landfill site in New Jersey, the gas
venting system installed in 1983 consisted of two
underground 4-inch (10-cm) perforated PVC pipes
and five vent risers. Two parallel PVC pipes were
installed 200 feet apart prior to cap emplacement
during the period of wall construction and were
placed about 3 feet beneath the finished grade. The
vent risers were connected to the buried manifold
pipes and consisted of open pipe installed
perpendicular to the underground pipes and the
ground surface. Filters were not attached to the riser
exit points (U.S. EPA, 1987).
Active Perimeter Gas Control Systems
An active perimeter gas control system can have any
of the same configurations as a passive perimeter
system with the addition of any combination of gas
extraction wells, gas collection headers, vacuum
blowers or compressors. Their ultimate purpose is to
direct the gas to a treatment or utilization system.
Active Interior Gas Collection/FJecovery Systems
Active interior gas collection and recovery systems
are designed to supplement capping and to prevent
22
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Figure 10a. Passive gas control using a permeable trench (U.S. EPA, 1985).
Section A-A
4" PVC, Vent Pipe'
(Space @ 50' ± O.C.)
4" PVC Perforated Collector
(Continuous)
Drainage
Swale
Monitoring
Probe
Gravel
or Stone
(i" Min. Size)
Low Groundwater Table, Bedrock
Source: SCS, 1980
"For applications where
venting of gases to
atmosphere is acceptable.
"Collector can be used to
convey gases to a
treatment system.
Figure 10b. Passive gas control synthetic membrane
(U.S. EPA, 1985).
Section A-A
Groundwater
' Table, Bedrock, etc.
tsi
Monitoring
Probe
Synthetic
Membrane
Natural
Ground
Trench
Backfill
Area to be
Protected
Any Convenient Width
Source: SCS, 1980
lateral gas migration. Gas extraction wells are a
principal component of such systems. Active interior
systems are quite similar to perimeter gas control
systems and differ primarily in terms of scale (Figure
11). Active interior systems represent the most
effective means of containing and controlling gaseous
wastes and can be designed using conventional
equipment with little time required for
implementation. The reliability of such systems is
limited by their dependence on mechanical and
electrical components.
Corrective Action Application
At the Taylor Road landfill (originally intended for
the disposal of municipal refuse only), unknown
quantities of hazardous wastes from industrial and
residential sources were deposited. During the period
when the landfill was active, soil and groundwater
samples collected at the site were found to contain
concentrations of volatile organic compounds and
metals above acceptable safe drinking water
standards. Analysis of samples collected from private
drinking water wells indicated that contamination
23
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Figure 11. Gas collection/recovery system (U.S. EPA, 1985).
Refuse Fill
was also present down-gradient from the Taylor Road
site. After the Taylor Road site was closed, methane
gas was detected off-site near adjacent residences.
To handle the methane gas generated from the 42.5-
acre site, an active interior gas collection system was
installed as shown in Figure 11. The installation
consisted of 42 recovery wells, a gas collection header
system, condensate traps, blower station and a fjare
station. In addition, a methane monitoring system
consisting of thirty-two 2-inch wells was installed
around the site (U.S. EPA, 1987).
Methods to Control Releases from
Surface Impoundments
Surface impoundments are a significant source of
gaseous emissions which can be controlled through a
wide range of strategies. These approaches include
enclosure, covering the surface with floating solid
objects, the addition of surface coatings, shape
modification and aerodynamic modification.
Documentation of specific application of these
technologies is limited.
Enclosures
An enclosure is usually an air-supported structure
which permits the collection and treatment of
gaseous wastes produced by surface impoundments.
Enclosures are susceptible to wind damage and can
be harmed by the wastes they cover. Subject to these
limitations, control effectiveness approaches 100
percent (University of Arkansas? and Louisiana State
University, 1985).
Floating Objects
A variety of containment strategies employ floating
solid objects to control the rate of gaseous emissions
from surface impoundments. These include: synthetic
membrane covers, rafts, and hollow plastic spheres.
Synthetic membrane covers are feasible where the
out-gassing of volatiles due to biological activity is
not expected. Selection of the liner material must be
24
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based on permeability and resistance to the gases to
be contained. Membrane covers are subject to damage
by weathering or by contact with wastes. They are
similar to enclosures in effectiveness, i.e., greater
than 90 percent (University of Arkansas and
Louisiana State University, 1985).
Rafts are designed to restrict the surface area
exposed to air so as to reduce oxygen absorption. They
are subject to damage by direct waste contact and can
achieve efficiencies of up to 90 percent.
Floating hollow spheres are made of polypropylene
with projections to prevent rotation. They restrict
oxygen absorption and reduce emissions with an
effectiveness of 80 to 90 percent. High winds can pose
serious problems by blowing the spheres away
(University of Arkansas and Louisiana State
University, 1985).
Surface Coatings
Floating oil layers and surfactants constitute a liquid
alternative to floating solid objects. An immiscible
liquid floating on the surface has been found to be
effective in reducing air emissions by up to 90
percent. However, windy conditions can result in a 50
to 80 percent loss of efficiency (University of
Arkansas and Louisiana State University, 1985).
Shape Modification
Shape modification strategies involve lagoon design
and construction to reduce the ultimate rate of
volatile emissions. Adjusting berm height achieves
this effect by reducing wind-caused emissions.
Increasing the ratio of depth-to-surface area also
produces reduced emissions. Orienting the lagoon
with its long axis perpendicular to prevailing winds
helps reduce emissions by maximizing the surface
area which benefits from proximity to shoreline
protection.
Aerodynamic Modification
Aerodynamic modification through the use of wind
fences represents another strategy for reducing
emissions under wind-enhanced conditions. Porous
wind fence material (such as that used for dust
control) is superior to solid fences. This material can
achieve emission and oxygen absorption reductions of
up to 80 percent. The wind fence can be aligned to
protect from several wind directions and can be used
to complement the effects of lagoon orientation and
floating covers. Reduction of wind velocity can be
expected for a distance of 1 to 5 fence heights
downwind of the installation. Fences should be
composed of polyester or other high-strength
materials to ensure their resistance to wind damage
(University of Arkansas and Louisiana State
University, 1985).
References
McAneny, C..and A. Hatheway. Design and
Construction of Covers for Uncontrolled Landfill
Sites. In: Management of Uncontrolled Hazardous
Waste Sites Proceedings, Washington, B.C., 1985
p.331.
Spooner, P.A., et al. Slurry Trench Construction for
Pollution Migration Control, EPA/540/2-84/001,
1984a.
U.S. EPA. Case Studies Addendum: 1-8 Remedial
Response at Hazardous Waste Sites. Office of
Research and Development, Cincinnati, Ohio, 1987.
U.S. EPA. Handbook-Remedial Action at Waste
Disposal Sites (Revised). EPA/625/6-85/006. Office of
Emergency and Remedial Response, Washington,
D.C., 1985.
U.S. EPA. Leachate Plume Management. EPA/540/2-
85/004. Office of Solid Waste and Emergency
Response, Office of Emergency and Remedial
Response, Washington, D.C., 1985.
U.S. EPA. Underground Storage Tank Corrective
Action Technologies, EPA/625/6-87/015, January,
1987.
University of Arkansas and Louisiana State
University. In-Situ Methods for the Control of
Emissions from Surface Impoundments and
Landfills. Draft Final Report. Prepared for U.S.
Environmental Protection Agency. Contract No.
CR810856. June 1985. pp. 95.
25
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Chapter 4
Engineering Considerations for the Corrective Measures Study
The Corrective Measures Study (CMS) elements as
outlined in the EPA document entitled RCRA
Corrective Action Plan - Interim Final (U.S.EPA,
1988) provides guidance to the regulatory community
on the steps practiced by the engineering community
in the conduct of a feasibility study. These steps
include:
• Identification and development of Corrective
Measure Alternatives
• Evaluation of Alternatives
• Selection of a Corrective
Implementation.
Measure(s) for
This logical process ensures that all appropriate
technologies are identified and evaluated on an equal
basis.
Screening of Corrective Measures Technologies
The first step in the screening process is to review the
results of the RFI and reassess the preliminary
corrective measure technologies identified therein
along with any supplemental technologies which
have come to light. By compiling a listing of all
possible treatment alternatives suitable for the site,
an engineer can then eliminate (1) those that may
prove infeasible to implement, (2) those that rely on
technologies unlikely to perform satisfactorily or
reliably, or (3) those that do not achieve the
corrective measure objective within a reasonable
time period. From an engineering standpoint, the
screening process focuses on eliminating those
technologies which have severe limitations for a
given set of wastes and site-specific conditions. The
screening step may also eliminate technologies based
on inherent technology limitations. Site, waste and
technology characteristics which are used to screen
inapplicable technologies are described in more
detail below.
Identification and Development of
Corrective Measures Alternative(s)
In order to begin the process of identification and
development of Corrective Measure Alternatives, it is
necessary first to define the problem in terms of the
site conditions determined as a result of the RCRA
Facility Investigation (RFI). Then, site-specific
objectives for the corrective action need to be
established to serve as a basis for technology
assessment and to establish the end point for cleanup
activities. These objectives are generally based on
public health and environmental criteria,
information gathered during the RFI, EPA guidance,
and the requirements of any applicable Federal or
state statutes. For example, all corrective actions
concerning groundwater releases from regulated
units must be consistent with, and as stringent as,
those required under 40CFR264.100. With
information on current site conditions and with
cleanup objectives defined, it becomes possible to
develop corrective measure alternatives by screening
the possible technologies and combinations of
technologies identified early in the RFI.
Site Characteristics
Site data should be reviewed to identify conditions
that may limit or promote the use of certain
technologies. Technologies whose use is clearly
precluded by site characteristics should be
eliminated from further consideration.
Waste Characteristics
Identification of waste characteristics that limit the
effectiveness or feasibility of technologies is an
important part of the screening process. Technologies
clearly limited by these waste characteristics should
be eliminated from consideration. Waste
characteristics particularly affect the feasibility of
on-site methods, direct treatment methods, and land
disposal (on/off-site).
Technology Limitations
During the screening process, the level of technology
development; performance record; and inherent
construction, operation, and maintenance problems
27
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should be identified for each technology considered.
Technologies that are unreliable, perform poorly, or
are not fully demonstrated may be eliminated in the
screening process. By contrast, certain treatment
methods have been developed to a point where they
can be implemented in the field without extensive
technology transfer or development.
Through a stepwise approach to the screening pf
alternatives, the engineer can gain confidence that
technologies which may be applicable for site cleanup
are not overlooked. In addition, the rationale for the
elimination of specific technologies is available to
justify these engineering decisions to management,
or the regulatory community, and the public.
Identification of the Corrective Measure
AJternative(s)
Based on the screening activities, several
alternatives may be identified which are viable
options for the cleanup of the site. These alternatives
can consist of an individual technology or a
combination of technologies which appear to be
appropriate for the given site conditions and appear
to be capable of meeting the cleanup objectives.
Evaluation of the Corrective Measure
Alternative(s)
Once the candidate corrective measure alternatives
have been identified, a more detailed evaluation of
each alternative needs to be undertaken. From an
engineering perspective, the first step in the
evaluation process would include the development of
a conceptual design for each alternative. The
conceptual design would consist of a process
description, a process flow diagram and a layout
drawing. Preliminary sizing of equipment and utility
and land requirements would be developed. In
addition, chemical requirements and residuals
produced can be estimated. From the conceptual
design, permitability and residuals disposal issues
can be identified and addressed.
Evaluation Criteria
After the conceptual designs for each candidate
corrective measure alternative have been developed,
each can be compared using the following evaluation
criteria:
Technical Criteria
• Performance of the corrective measure based on
the effectiveness of the technology to perform its
intended function and the length of time the level
of effectiveness can be maintained.
• Reliability of the corrective measure based on
operating and maintenance requirements and
the demonstrated reliability. (This criterion is
concerned with the complexity of a system and its
impact on operation, maintenance and potential
for failure.)
• Implementability of the corrective measure is
concerned with the constructability of the
facilities (i.e., site constraints, permitability,
equipment availability, and the time it takes to
implement and to operate and maintain the
facility.)
• Safety issues include threats to the safety of
workers or nearby communities during the
implementation or operation, of the corrective
measures (i.e., fire, explosion and exposure to
hazardous substances).
Environmental Criteria
An Environmental Assessment for each alternative
(focusing on the facility conditions and pathways of
contamination actually addressed by each
alternative) should be prepared. Issues to be reviewed
include: the short- and long-term beneficial and
adverse effects of the response alternative; any
adverse effects on environmentally sensitive areas;
and an analysis of measures to mitigate adverse
effects.
Human Health Criteria
Each alternative should be assessed in terms of the
extent to which it mitigates short- and long-term
potential exposure to any residual contamination and
protects human health, both during and after
implementation of the corrective measure.
Institutional Criteria
Institutional needs for eaqh alternative must be
developed as part of the technology evaluation.
Specifically, this should address the effects of federal,
state and local environmental and public health
standards, regulations, guidance, advisories,
ordinance or community relations on the design,
operation and timing of each alternative.
Cost Estimate
An estimate of the cost for each corrective measure
alternative should be developed, including capital,
operating and maintenance costs. Capital costs
consist of direct (construction) and indirect
(nonconstruction and overhead) costs.
• Direct capital costs include:
Construction costs
28
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Equipment costs
Land and site-development costs
Buildings and service costs
• Indirect capital costs generally include:
Engineering expenses
Legal fees and license or permit costs
Start-up and shake-down costs
Contingency allowances
Operation and maintenance costs are post-
construction costs necessary to ensure continued
effectiveness of a corrective measure. The following
are examples of typical operation and maintenance
costs:
• Operating labor costs
• Maintenance materials and labor costs
• Auxiliary materials and energy
• Purchased services
• Disposal and treatment costs
• Administrative costs
• Insurance, taxes and licensing costs
Justification and Recommendation of the
Corrective Measure(s)
After each issue outlined in the evaluation criteria
has been developed for each corrective measure, the
selection of the most appropriate alternative can be
made. Trade-offs among health risks, environmental
effects and other pertinent technical, environmental
and human health factors enter into this decision-
making process. In the RCRA context, cost is not a
factor in the selection process except when two or
more corrective measure alternatives are determined
by EPA to provide similarly adequate levels of
protection of human health and the environment.
References
U. S. EPA. RCRA Corrective Action Plan • Interim
Final, EPA/530-SW-88-028, Office of Solid Waste and
Emergency Response, Washington, B.C., 1988.
29
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Chapter 5
Technology Options for the Treatment of Wastes and Waste Streams
In nearly every phase of the Corrective Action
process, some information about treatment
technologies is needed - e.g., in the pre-investigation
planning for data gathering, in the screening and
evaluation of candidate remediations, in lab and pilot
studies, and in design, implementation, operation
and monitoring of the selected remedy. Many
documents exist which describe candidate
technologies in detail and give their respective
applicability and limitations. One intent of the
seminar on which the present document is based is to
present a broader perspective on several types of
remedial technologies, their applicability and limits
from a CA perspective and an understanding of how
process residuals may themselves require additional
treatment to achieve protection of human health and
the environment (HHE).
equipment, the process controls, and the ancillaries
necessary to make the reaction proceed in a full-scale
facility. Figure 13 represents a flow diagram of a
generic chemical treatment process showing the
inputs and outputs which require consideration.
Before the selection of a specific treatment
technology can be made, an understanding of the site-
specific factors which drive the selection of that
technology is required because these factors can
influence the evaluation of the advantages and
limitations of competing technologies. The
information required to resolve these site-specific
issues falls into four categories: waste composition
and matrices, waste quantity, treatment objectives,
and the reactions involved in the treatment of the
contaminated material.
Chemical Treatment Processes for
Corrective Action
What Is Chemical Treatment?
Chemical treatment is a class of processes in which
specific chemicals are added to wastes or to
contaminated media in order to achieve
detoxification. Depending on the nature of the
contaminants, the chemical processes required will
include pH adjustment, lysis, oxidation, reduction or
a combination of these. Thus, chemical treatment is
used to effect a chemical transformation of the waste
to an innocuous or less toxic form. In addition,
chemical treatment is often used to prepare for or
facilitate the treatment of wastes by other
technologies. Figure 12 identifies specific treatment
processes which perform these functions.
To understand chemical treatment processes, it must
be remembered that a reaction is not a process. A
reaction involves the chemical transformation of a
material, whether this is carried out on a lab-scale or
an industrial-scale. A process, on the other hand, is a
series of actions or operations needed to make such a
reaction occur in a controlled manner. Thus, the
development of a process requires the design of the
Applicability Based On Waste Type
In general, chemical treatment processes are
applicable to a broad range of organic and inorganic
wastes. For example, they can be used for the
oxidation of organics, for pH adjustment to
precipitate heavy metals, and for lysis of chlorinated
organics to cleave chlorine atoms from organic
molecules in preparation for subsequent oxidative
processes. It should be remembered that chemical
processes are very specific as to the waste that they
treat. Thus, it is frequently necessary to link several
unit operations together to effect the desired removal
objectives. Other waste components must also be
carefully considered because they can affect the
chemical process by consuming more reagents,
generating unwanted precipitates, inhibiting the
reaction or creating safety issues when their presence
is not recognized (e.g., the production of
intermediates such as CN-, S-2).
Applicability Based On Waste Form
Chemical treatment processes rely on the intimate
mixing of reagents with the waste. Thus, the wastes
generally treated by chemical means must be in an
aqueous or slurry form.
31
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Figure 12. Chemical processes.
Chemical processes
Neutralization
Chemical
Precipitation
PPt
— Hydrogen Perox.
— Ozone
— Air
- KMnO4
— CI2
— Ferrous Sulfate
— Ferrous Chloride
— Sulfur Dioxide
— Sodium
Metabisulfite
•— Alkali Metal
Dechlorination
— Hydrolysis
— Photolysis
Catalysis
Figure 13.
Flow diagram of a generic chemical treatment,
process.
Treatment
Chemicals
Energy
Contaminated ^
Material
Contan
Generic
Treatment
Process
—
I \
linants By-products
Treated
Material
Treatment Options and Their Applications
pH Adjustment
The function of pH adjustment is to neutralize acids
and bases and to promote the- formation of
precipitates (especially of heavy metal precipitates)
which can subsequently be removed by conventional
settling techniques. These purposes are not mutually
exclusive, precipitates can be formed as the result of
neutralizing a waste. Conversely, neutralization of
the waste stream can result when adjusting the pH to
effect chemical precipitation. Typically, pH
adjustment is effective in treating inorganic or
corrosive wastes. Figure 14 is a general flow
schematic which illustrates the pH adjustment
process.
pH Adjustment for Neutralization
Technology Description: Neutralization is a process
used to treat acids or alkalis (bases) in order to reduce
their reactivity or corrosiveness. Neutralization can
be an inexpensive treatment if waste alkali can. be
used to treat waste acid and vice versa. Typical
neutralizing reagents include:
Acid: H2SO4, HC1 and HN03
Base: Ca(OH)2, CaO, NaOH, NaHCO3,
Na2CO3andMg(OH)2
Applicability: Neutralization would be appropriate
for acidic and basic wastes. The process should be
performed in a well-mixed system. Care should be
taken to ensure compatibility of the waste and
treatment chemicals to prevent the formation of more
toxic compounds.
Residuals Produced: The resulting effluent may
contain dissolved inorganic salts at concentrations
which may be unacceptable for discharge. Based on
the chemical composition of the waste stream, a
precipitate may be formed which may require
removal and disposal.
32
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Figure 14. pH adjustment system.
Wastewater Treatment System
Metal Finishing Industries
Metal Sludge
(30 - 50%)
Corrective Action Application: An acidic ground water
at a Florida site (pH 2.5-3) required treatment. The
groundwater was collected by extraction wells,
pumped to an above-ground reactor, and neutralized
with lime. In the course of neutralizing the waste
stream, precipitates were formed which were
removed by clarification and filtration prior to
discharge. Sludges produced from the clarification
and filtration steps were dewatered by a filter press.
pH Adjustment to Effect Chemical Precipitation
Technology Description: To achieve precipitation,
acid or base is added to a solution to adjust the pH to a
point where the constituents to be removed have
their lowest solubility. Chemical precipitation
facilitates the removal of dissolved metals from
aqueous wastes. Metals may be precipitated from
solutions as hydroxides, sulfides, carbonates, or other
soluble salts. A comparison of precipitation reagents
is presented in Table 7. Solid separation is effected by
standard flocculation/ coagulation techniques.
Table 7. Comparison of Precipitation Reagents
Lime
least expensive, generates highest sludge volume
Caustic and more expensive than lime, generates smaller
Carbonates amount of sludge, applicable for metals where their
minimum solubility within a pH range is not sufficient
to meet clean-up criteria
Sulfides
effective treatment for solutions with lower metal
concentrations
Sodium expensive reagent, produces small sludge volumes
borohydride which can be reclaimed
Applicability/Limitation: This technology is
applicable for aqueous wastes containing heavy
metals (i.e., Cd, Cr (III), Pb, Ni). The optimum pH for
minimum solubility of various metals is not the
same, therefore, solutions containing mixed metals
introduce a limitation to the system. Figure 15
graphically shows the solubility of metal hydroxides
as a function of pH. Chelating or complexing agents
present in the waste stream may inhibit the
formation of a desired precipitate.
Residuals Produced: Resulting metal sludges from
the chemical precipitation process may require
further treatment prior to disposal. The effluent pH
may require an adjustment before it may be
discharged. Dissolved inorganics present in. the
effluent may pose a problem for direct discharge.
Corrective Action Application: Gulf Coast Lead is a
small, secondary lead smelting facility in Florida,
which recovers lead from discarded lead acid
batteries and lead from other battery breakers.
Contaminated ririsewater and battery casings were
dumped into an unlined surface depression causing
the soil and the shallow groundwater to become
heavily contaminated with sulfuric acid and heavy
metals. A groundwater treatment and recovery
system was installed consisting of primary
clarification followed by pH adjustment (using lime
or caustic soda) and final clarification. The system
reduced lead concentrations from 6 ppm to below 0.3
ppm and adjusted the pH from 1.5 to 9.7. The cleanup
objectives required that the effluent be below 0.3 ppm
lead and the discharge volume from the treatment
system be 20,000 gpd.
Oxidation and Reduction Processes
Oxidation and reduction must both take place in any
such reaction. In any oxidation reaction, the
oxidation state of one compound is raised (i.e.,
oxidized) while the oxidation state of another
33
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Figure 15. Solubilities of metal hydroxides as a function of
pH. i
100
8 9
Solution pH
compound is lowered (i.e., reduced). Oxidation and
reduction reactions are utilized to change the
chemical form of a hazardous material in order to
render it less toxic or to change its solubility,
stability, separability or otherwise change it for
handling or disposal purposes. In the reaction, the
compound supplying the oxygen (or chlorine or other
negative ion) is called the oxidizer or oxidizing agent
while the compound accepting the oxygen (He.,
supplying the positive ion) is called the reducing
agent. The reaction can be enhanced by catalysis,
electrolysis or photolysis.
Chemical Oxidation
Technology Description: Oxidation processes involve
the conversion of organics to CO2, H2O, HC1, NO2
and SOa or the conversion of inorganics to a more
desirable form. For both organic and inorganic
wastes, the function of chemical oxidation is to
change the chemical form of the molecular structure
for the purpose of detoxification. Typical oxidants
used for oxidation processes are:
Air
02
H202
03
C12
C102
KMnO4
NaS2O7
Oxidation processes may rely on pH adjustment to
enhance the chemical reaction. Figure 16 illustrates
the typical configuration of a chemical oxidation
process. The major engineering considerations for
chemical oxidation include: reaction kinetics, mass
transfer, by-products, temperature, oxidant
concentration, pH and vent gas scrubbing.
Figure 16. General process flowsheet for chemical
oxidation.
Feed Vent Gas
J L
Acid or
Base
Catalyst
Recovery
If Required
Effluent
Applicability/Limitations: The process is nonspecific.
Solids must be in solution. Reactions can be
explosive. Waste composition must be well known to
prevent the inadvertent production of a more toxic or
more hazardous end product. Oxidation processes are
applicable for the following classes of organic
contaminants:
• High reactivity contaminants: phenols,
aldehydes, aromatics, amines, some sulfur
compounds.
• Medium reactivity contaminants: alcohols,
ketones, organic acids, esters, alkyl-substituted
aromatics, nitro-substifcuted aromatics,
carbohydrates.
• Low reactivity contaminants: halogenated
hydrocarbons, saturated aliphatics, benzene.
• Cyanide-bearing wastes.
34
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The reaction mechanism depends on the chemistry of
the active oxidant and chemical contaminants.
Multiple sequential and parallel reaction steps occur
frequently. Partial oxidation produces noxious by-
products.
Residuals Produced: Typical residuals resulting from
oxidation are partial oxidation products (e.g.,
chlorinated organics) and inorganic salts (e.g., NaCl,
Mn02). Additional treatment may be required to
permit disposal.
-Corrective Action Application: At a hazardous waste
treatment storage and disposal facility in
Washington State, a cyanide-bearing waste required
treatment. The influent waste stream contained 15
percent cyanide. Electrolytic oxidation was used to
reduce the cyanide concentration to less than 5
percent. Alkaline chlorination was used to further
reduce the cyanide concentration to 50 mg/1 (the
cleanup objective). The electrolytic process was used
as a first stage treatment because the heat of
reaction, using alkaline chlorination to treat the
concentrated cyanide waste, would be so great that it
would melt the reactor tank.
Chemical Reduction
Technology Description: The function of reduction
processes is to convert inorganics to a less toxic
and/or more easily treated form. It also serves as a
pretreatment step for inorganics in which chemical
precipitation is used to remove the metal hydroxide
from solution.
Applicability/Limitations: Reduction processes are
applicable for:
Hexavalent chromium waste
Mercury wastes
Hexavalent selenium
Organic lead compounds
Chelated-metal-bearing wastes
Chemical reduction process limitations include the
following:
• Reducing agents are non-selective.
• Violent reactions are possible.
• Air emissions and odors can.be produced.
• Slurries, tars or sludges are difficult to treat.
Residuals Produced: The reaction products are
usually inorganic salts.
Corrective Action Application: At a RCRA site in the
southwest, a waste stream containing hexavalent
chromium was reduced to the trivalent form. The
trivalent chromium was then removed using ion
exchange. The influent hexavalent chromium
concentration was less than 50 ppm, and the effluent
concentration was 0.5 mg/1 (the cleanup objective).
Alkali Metal Dechlorination
Technology Description: Chlorinated organics
represent a large class of toxic and hazardous
substances that are difficult to treat. The purpose of
this process is to displace the chlorine from the
chlorinated compound. By-products include chloride
salts, which can be removed by centrifugation and
filtration. The reagents used are metallic sodium and
potassium in conjunction with proprietary reagents.
For the sodium based processes, the reagents are
suitable for treating oils containing less than 1000
ppm PCBs.
Applicability/Limitations: Alkali metal
dechlorination is applicable to chlorinated
hydrocarbons such as:
• PCBs (e.g., transformer decontamination)
• Dioxins
• Solvents
• Pesticides
Alkali metal dechlorination processes are water
sensitive. Soil moisture content can adversely affect
the reaction in in-situ soil applications. The
application of alkali metal dechlorination is
generally expensive.
Residuals Produced: The residual produced from the
alkali metal dechlorination of soils is reported to be
an alkaline soil which requires neutralization.
Corrective Action Application: At a Navy facility in
Guam, approximately 25 tons of PCB contaminated
soil was treated using the KPEG (potassium
polyethylene glycol) process. PCB concentrations
were reduced from 3000 ppm to less than 5 ppm.
Upon completion of treatment using the KPEG
process, the soil was neutralized from a pH of 14 to 7.
A full-scale system for this process is currently under
development.
Lysis Processes
The basic function of lysis processes is to split
molecules to permit further treatment. Hydrolysis is
a chemical reaction in which water reacts with
another substance. In the reaction, the water
molecule is ionized while the other compound is split
into ionic groups. Photolysis, another lysis process,
breaks chemical bonds by irradiating a chemical with
ultraviolet light. Catalysis uses a catalyst to achieve
bond cleavage.
35
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Hydrolysis
Technology Description: Hydrolysis is the process of
breaking a bond in a molecule (which is ordinarily
not water-soluble) so that it will go into ionic solution
with water. Hydrolysis can be achieved by the
addition of chemicals (e.g., acid hydrolysis), by
irradiation (e.g., photolysis) or by biological action
(e.g., enzymatic bond cleavage). The cloven molecule
can then be further treated by other means to reduce
toxicity.
Applicability/Limitations: Hydrolysis is suitable for
pretreating difficult-to-treat wastes and for organics
with substituents, such as phenols or chlorinated
organics with reactive chlorine atoms. Hydrolysis is
specific for only a limited number of contaminants.
Residuals Produced: The resulting residuals from a
hydrolysis process are an aqueous effluent and
insoluble organics. ;
Corrective Action Application: Hydrolysis was
favorably applied to a site in which the wastewater
contained very soluble, refractory organics. In
addition, tars were being produced in high quantities
on this site. Both of these problems were solved using
a hydrolyzer. Figure 17 illustrates a flow diagram of
this process. As a result, the wastewater treatment
goals were achieved, and the production of tar was
reduced.
Hydrolysis of refractory organics.
Water, acid or base
Energy
By-products
Ultraviolet Photolysis
Technology Description: Ultraviolet (UV) photolysis
is a process that destroys or detoxifies hazardous
chemicals in aqueous solutions utilizing UV
irradiation. Absorption of UV energy results in a
molecule's cleavage, increasing the ease of
subsequent oxidation of the molecule. For example,
ultraviolet light has been used for degradation of
dioxins in waste sludge. This process required
extraction (into a clean, transparent solvent) of the
waste to be destroyed. Reaction products were
dechlorinated materials and free chlorine gas. In
addition, the use of UV photolysis on nitrated wastes
has been successfully demonstrated on a pilot scale.
Applicability/Limitations: Photolysis is appropriate
for difficult-to-treat chemicals (e.g., pesticides,
dioxins, chlorinated organics), nitrated wastes, and
those chemicals in media which permits photolyzing
the waste. The waste matrix can often shield
chemicals from the light (e.g., ultraviolet light
absorbers, suspended solids, solid wastes). The
photolysis process typically requires pretreatment to
remove suspended materials, and the by-products
formed may be more toxic than the parent molecules.
Residuals Produced: Photolysis produces
decomposition products of dechlorinated material
and free chlorine gas.
Corrective Action Application: At a manufacturing
site, photolysis was used to cleave chlorine atoms
from tetrachlorodibenzodioxin (TCDD). The basic
flow diagram for the process is shown in Figure 18.
The wastes from a hexachlorophene process were
stored in an underground tank which held 4300
gallons of the oily residuals containing 343 ppm
TCDD. This material required removal and
treatment. The selected treatment system consisted
of a batch solvent extractor to transfer the TCDD into
a cleaner fluid more amenable to photolysis. The
solvent was separated from the oil, circulated
through a bank of eight 10-kW ultraviolet lights,
recovered and recycled. Effluent from this process
contained 0.15 ppm TCDD.
Figure 18. Photolysis flow diagram.
UV Light
Effluent
In-Situ Chemical Treatment
Technology Description: In-situ chemical treatment
uses the same principles employed for above-ground
chemical processes. Materials are added to
neutralize, oxidize or remove contaminants in
groundwater or soils in order to avoid digging or
pumping of the contaminated waste above ground for
36
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treatment. The reagents which have been used for in-
situ chemical treatment include:
Figure 19. Site of formaldehyde release.
Dilute acids or bases
Hydrogen peroxide
Water
Water with additives
Air
Applicability/Limitations: In-situ treatment can be
used when it is uneconomical to haul or when
infeasible or uneconomical to dig or pump the
contaminated 'waste matrix for treatment in a
reactor. This approach should be used whenever
excavation or removal causes an increased threat to
human health. It can reduce the cost of a remediation
program. Because chemicals are applied to the
contaminated waste matrix, specifically soil and
groundwater, a potential exists for reaction with the
soil. Permeability problems can occur as the result of
precipitate formation. This can result in inadequate
mixing of the contaminant with the treatment
chemical. Gas generation may also occur.
Corrective Action Application: A case involving the
cleanup of a 20,000 gallon formaldehyde release
utilized in-situ treatment due to the- location of the
spill. The release occurred from a break in an
underground pipeline at a tank farm (Figure 19). The
soil could not be excavated because it served as a road
for trucks. The objectives were to remediate the
release; reduce the long-term liability for oxidizing
the formaldehyde; and reduce the time and cost for
groundwater treatment without interfering with
operations in the area. The process (Figure 20)
involved slowly injecting alkaline hydrogen peroxide
into the clay till to oxidize the formaldehyde without
creating excessive temperature and pressure
increases. The results were that the formaldehyde
was reduced from percent concentrations to 1-18 ppm.
The permeability of the soil improved, arid the overall
treatment costs were significantly less than removal
followed by above-ground treatment.
Biological Processes for Corrective
Action
What is Biological Treatment?
Biological treatment is a destruction process relying
primarily on oxidative or reductive mechanisms.
Enzymatic activity can effect lysis (e.g., hydrolysis or
dehalogenation). Further, biological activity can
result in pH changes in the waste stream which may
require adjustment by chemical means. The use of
biological treatment processes is directed toward
accomplishing (1) destruction of organic
contaminants, (2) oxidation of organic chemicals
whereby the organic chemicals are broken down into
smaller constituents, and (3) dehalogenation of
Failed Formaldehyde Pipeline
organic chemicals by cleaving a chlorine atom(s) or
other halogens from a compound. Specific engineered
systems to effect oxidation and reduction for different
matrices are presented in Figure 21. Biological
treatment processes have certain advantages over
other common treatment technologies, namely, the
organic contaminants to be destroyed are used and
transformed by bacteria or other organisms as a
source of food. These processes can be employed in
soils, slurries, or waters (ponds, groundwater, etc.) to
aid in the remediation of a site.
Applicability Based on Waste Type
Biological processes can be used on a broad class of
biodegradable organic contaminants. Table 8
presents some common RCRA-regulated organic
compounds which are susceptible to biodegradation.
Some compounds, called refractiles, are persistent
compounds which are not readily biodegradable. It
should be noted that very high concentrations as well
as very low concentrations of organic contaminants
are difficult for biological processes to treat.
Applicability Based on Waste Form
Biological treatment processes can be used to treat
organic contaminants in liquid, slurry, and soil
matrices. However, it should be remembered that
moisture is an essential need of the biomass both for
37
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Figure 20. Diagram of In-sltu treatment.
H202
Tracer
Water
Figure 21. Biological processes.
Biological Processes
1 Oxidation of Organics
I
Biological Processes
Aerobic Processes
— Soils
L
in-situ
Liquids
I— in a
reacto'r
I Liquids - in
a reactor
— Suspended growth
— Fixed film
' Hybrid
Liquids
In-situ
Lin ar
in-si1
in a reactor
in-situ
growth and to provide mobility either of the food to
the biomass or the biomass to the organic. Thus,
matrices which do not have sufficient moisture will
not support biodegradatioh, and methods to add
moisture may have to be engineered into the system.
Environmental Factors Necessary to Maintain the
Biomass
Since microorganisms need appropriate conditions in
which to function, an engineer must provide an
optimum environment, whether above ground in a
reactor or below ground for an in-situ application.
The primary environmental factors which can affect
the growth of the microbial community - in addition
to providing them with sufficient food (organic
material) - are pH, temperature, oxygen
concentration, nutrients, and toxicity.
pH
Typically, the biological treatment system operates
best when a waste stream is at a pH near 7. However,
waste treatment systems can operate (with some
exceptions) between pH values of 4 and 10. The
38
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exceptions are aerobic systems in which ammonia is
oxidized to NOX as well as anaerobic methane
fermentation systems. For these, the pH should be
between 6 and 8. At the extremes of this range, the
system will function, but efficiency will suffer.
Temperature
Waste treatment systems can function over a very
wide temperature range, e.g., 5° to 60°C. However,
there are three rather distinct ranges in which
different groups of organisms function:
Psychrophilic
Mesophilic
Thermophilic
<15°C
15°to45°C
>45°C
Most waste treatment systems operate in the
mesophilie region. The expense of altering the
temperature of wastes encountered in abnormally
cold or warm environments indicates the desirability
of developing organisms which are suited to extremes
of ambient waste temperatures.
Oxygen
Microorganisms need a certain amount of oxygen not
only to survive, but also to mediate their reactions.
Therefore, the residual dissolved oxygen
concentrations should be maintained at
approximately 2 mg/€ or greater within a typical
liquid biotreatment system. Having this much
oxygen "left over" indicates that sufficient oxygen
was available for the biological process.
Nutrients
Nutrients can be classified into three groups based on
levels required in waste treatment systems. These
are given in Table 9. The major nutrients can be
identified from the generalized biomass formula (Cgo
Hg2 C>23 Ni2 P). The actual quantity needed depends
on the biochemical oxygen demand (BOD) of the
waste. The higher the BOD the greater the quantity
of cells produced. The minor and trace nutrients are
needed in small quantities and are given in terms of
concentration because these are the levels needed in
solution to force the small amount required inside the
cell across the cell-wall membrane.
For many of the trace nutrients, it will be difficult to
find literature references to the concentrations
required. It is only recently that it has been realized
that these trace nutrients are required, because they
were only present as contaminants in biological
preparations. Indeed, many other substances may be
required nutrients but at such low levels that their
requirement is not easily manifest.
Toxicity
The presence of toxic substances will obviously
produce adverse conditions in a biological system.
Unfortunately, it is difficult to cite specific toxic
materials because toxicity depends on concentration.
All of the nutrients previously mentioned can be
toxic if their concentration is excessive. All types of
organic compounds which can be used as food by
bacteria can be toxic if the level is high enough. Thus,
our concept of a toxic substance is a substance which
is toxic at, a very low concentration. (Little detailed
information on ranges in which substances are toxic
is available.) In addition, phenomena such as
acclimation, antagonism and synergism will alter
toxicity effects. Frequently, toxicity concerns can be
avoided by waste dilution and by microbe
acclimation. Acclimation is most important when
dealing with "toxic waste". For example, with
unacclimated biomass, a few milligrams per liter of
phenol can produce toxicity; but after acclimation,
waste treatment systems can easily handle wastes
containing up to 500 mg/t of phenol.
Biological Processes and Their Applications
Engineered Processes to Achieve Oxidation
Aerobic processes are oxidative processes and are the
most widely used biological treatment processes for
organic wastes. These processes rely on providing the
basic environmental conditions required for
biological growth but use differing methods for
maintaining the microorganisms in the system and
contacting the organic material with the biomass.
Since these systems require a supply of molecular
oxygen, the cost of supplying oxygen frequently sets
an economic limit on the concentration of organics
which can be present in the wastewater. For
conventional systems, a limit of approximately
10,000 mg/€ BOD is a good rule of thumb. For
situations where the flow is low, however, higher
concentrations can be economically biodegraded.
Engineered aerobic processes include suspended
growth systems, fixed-film systems, hybrid reactors
and in-situ application.
Suspended Growth Systems
Technology Description: Suspended growth systems
maintain the biomass suspended in the aqueous
waste to be treated. Intimate mixing brings the food
and the microorganisms into contact and permits
biodegradation to occur. The biomass is captured as it
is washed out of the reactor. Typically, a clarifier is
used to capture washout. The biomass is concentrated
as sludge and a portion is recycled back to the reactor
to maintain the concentration of biomass in the
reactor while the remainder is dewatered and
disposed. This system allows a long contact time
between the organic waste and the biomass. Figure
39
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Table 8. Biodegradable RCRA-Regulated Organic Compounds, (USEPA, 1985)
Respiration
Substrate Compounds
Aerobic Anaerobic Fermentation Oxidation Co-oxidation
Straight Chain Alkanes
Branched Alkanes
Saturated Alkyl Halides
Unsaturated Alkyl Halides
Esters, Glycols, Epoxides
Alcohols
Aldehydes, Ketones
Carboxylic Acids
Amides
Esters
Nitrites
Amines
Phthalate Esters
Nitrosatnines
Thfols
Cyclic Alkanes
Unhalogenated Aromatics
Halogenated Aromatics
Simple Aromatic Nitro Compoufids
Aromatic Nitro Compounds with Other
Functional Groups
Phenols
Hatogenated Side Chain Aromatics
Fused Ring Hydroxy Compounds
Nitrophenols
Halophenols
Phenols - Dihydrides Polyhydrides
Two & Three Ring Fused Polycyciic
Hydrocarbons
Biphenyls
Chlorinated Biphenyls
Four Ring Fused Polycyciic Hydrocarbons
Five Ring Fused Polycyciic Hydrocarbons
Fused Polycyciic Hydrocarbons
Organophosphates
Pesticides and Herbicides
-h
•I-
+
+
+
+
Table 9. Nutrients for Biological Treatment
Major (Quantity depends on waste strength)
carbon, hydrogen, oxygen, nitrogen, phosphorus
Minor l-100mg/£
sodium, potassium, ammonium, calcium, magnesium, iron, chloride, sulfur
Trace Less than 1 mg/€
manganese, cobalt, nickel, vanadium, boron, copper, zinc, various organics (vitamins),
molybdenum
40
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22 represents a general illustration of a suspended
growth system.
Applicability/Limitations: Suspended growth systems
are applicable to organic wastes with a moderate to
high organic load. In addition, these systems are less
susceptible to shock and thus are suitable where
fluctuations in influent feed are anticipated.
Limitations to the use of suspended growth systems
are generally associated with lower level
concentrations of organics in the feed. In these cases,
the maintenance of the biomass within the system is
not possible because of the low food to mass ratio. In
addition, if the growth rate of a viable biomass
population is sufficiently slow, then a more positive
means for maintaining the biomass in the system is
required.
Residuals Produced: The residuals produced from
suspended growth systems are the excess biomass
produced as the result of biodegradation. In general,
this biomass can be disposed without further
treatment. However, site-specific conditions may
require stabilization prior to disposal.
Corrective Action Application: Under a Gulf Coast
hazardous waste site in Robstown, Texas, a portion of
the brine groundwater had become contaminated
over the course of several years. The sources of
contamination were removed, and the plume was
confined to the site boundary. The cleanup of the
groundwater was the only remaining (and the most
difficult) task to perform. The combined influent
water had an average concentration of 15,000 mg/£
dissolved solids and 1300 mg/€ total organic carbon
(TOG) with the main component being 400 mg/€ of
phenol. For reinjection, the influent had to be treated
to background quality (< 18 mg/€ TOC). Since the
natural groundwater is brine, the dissolved solids
were not removed. The optimum pumping rate from
the wells was determined to be 23,000 gal/day. At
this rate of removal and recharge, the design life of
the treatment system was projected at 10 years.
The process selection for the treatment system
considered several important and unique problems
concerned with the treatment of a brine groundwater.
The most critical problem was a decrease in the
concentration of organics in the groundwater with
time as the treated water was returned to the ground
and forced back to the central wells. Before the full-
scale system was put into service, a large-scale pilot
plant was run to ensure that the assumptions made
from the laboratory data were correct. In 1984, the
full-scale system (as shown in Figure 23) included the
following components: a first stage activated sludge
system; a second stage fixed-film biological reactor; a
dual media filter; and a carbon adsorption column.
Using these components of the full-scale system,
groundwater was pumped out of the ground, treated,
and then recharged back into the ground (Nyer,
1987). As the concentration of the effluent decreases,
the system configuration is modified (Figure 23).
Fixed-Film Systems
Technology Description: Fixed-film reactors rely on
maintaining the biomass on some media and passing
the contaminated organic material over that media to
promote biological activity. In classical municipal
treatment, trickling filters are an example of a fixed-
film system. In the industrial and hazardous waste
treatment arena, fixed-film reactors make use of
rotating biological contactors (RBC) or packed media
reactors. Oxygen transfer is promoted by (1) in the
case of the RBC, rotating the discs into and out of the
waste stream, and (2) in the case of packed media
reactors, passing a thin liquid layer over the media.
The advantages of these processes include the
following:
• The biomass is retained in the reactor on inert
media.
• The design of the bioreactor is based on the
specific surface area.
• High concentrations or high mass of viable
bacteria can be maintained in a relatively small
volume.
• BOD removal is approximately 85 to 90 percent.
An illustration of a fixed-film reactor system is
presented in Figure 24.
Applicability/Limitations: Fixed-film reactors are
applicable to influents containing lower
concentrations of organics or for maintaining a
specialized, slow growing biomass such as would be
required to degrade complex organic wastes. A
variation of this concept is a kind of in-situ or on-site
treatment in which the soil serves as the media and
nutrients are passed through the soil to promote
bacterial growth. Because the flow through these
systems is essentially plug flow, fixed-film reactors
are adversely impacted by shock loadings. In
addition, high concentrations of organics in the feed
can produce excessive amounts of biomass which can
clog or (by sheer weight) destroy the media
supporting the biomass.
Residuals Produced: The residuals produced in a
fixed-film reactor are normally small when compared
to the residuals produced in a suspended growth
system. There can be some sloughing of biomass
during system operations, and this may need to be
separated from the effluent. The residuals, depending
on site-specific requirements, may require additional
treatment prior to ultimate disposal.
Corrective Action Application: At a dry cleaning
facility in a desert area of California, an underground
solvent storage tank was found to have leaked for
many years. The soil from the 100-ft x 160-ft by 20-ft
41
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Figure 22. Diagram of the suspended growth system.
Mixer
Waste
Clarified
Effluent
Biomass Recycle
Excess Biomass
Figure 23. Llfe-cycla design - Installed system at southern Texas site (treating phenol in a brine aquifer) (Nyer, 1987).
1300 mg/l TOC
<900 mg/LTOC
H/TOX
^-farJLr
Clarifer
Aeration "*"""*~j |
Blowers
Dual Media CarbQn
Filter Adsorption
<100 mg/lTOC
-JlT
Carbon
Adsorption
deep site was excavated. The pit was lined with
plastic and covered by gravel for drainage. The soil
was put back into the lined pit. Nutrient rich water
was allowed to percolate down through the soil to feed
the indigenous microbes. The water was recovered
from a ground drain (O. Russ, EMCON Associates,
personal communication, 1988).
Some key issues learned from this case were:
• Injection of acidic, nutrient-rich water into the
highly alkaline soils resulted in "cementing" of
the soils.
• To alleviate this "cementing", the microbes were
grown above-ground in a 500-gal container. They
were then allowed to percolate down through the
soil. This inoculum had a neutral pH and did not
react with the soil.
42
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Figure 24. Diagram of the film flow reactor.
Flow Distributor
Inert Packing
Waste
Effluent Recycle
• At a percolation rate of 500 gal/day, the time for
cleaning the soil is projected to be 6 months.
Hybrid Reactors
Technology Description: Hybrid reactors, as the name
implies, are a combination of suspended growth and
fixed-film reactor principles. In these systems, the
fixed film is submerged and the reactor contents are
continuously stirred. A large amount of biomass is
maintained in the system.
Applicability/Limitations: Hybrid reactors,
depending upon their configuration, can handle high
organic loads (i.e., in the range of 50 to 10,000 ppm).
Because these reactors are a completely mixed
system, they are less affected by shock loadings.
Hybrid reactors are designed to compensate for the
principal limitations of fixed-film and suspended
growth reactors. However, set-up and operation of
hybrid reactors will tend to be somewhat more
technically demanding than either fixed-film or
suspended growth systems.
Residuals Produced: As with the suspended growth
and fixed-film systems, some biomass is produced
which will require disposal. The pretreatment and
disposal practices required will depend on site-
specific requirements.
Corrective Action Application: Case 1 - Groundwater
at the MEMOREX Computer Tape Plant (Santa
Clara, California) was contaminated by a leaking
underground solvent storage tank (Skladany et al.,
1987). Chemical analysis of the groundwater
identified the presence of methyl ethyl ketone (MEK)
up to 500 ppm; xylenes together with ethyl benzene
up to 40 ppm; cyclohexanone up to 30 ppm;
cyclohexanol up to 10 ppm; acetone up to 10 ppm; and
toluene, tetrahydrofuran, 2-butanol, and methyl
propyl ketone each less than 1 ppm. A biological
system consisting of two submerged fixed-film
biological reactors in series was designed for
treatment of the contaminated groundwater, as
shown in Figure 25. By operating the reactors in
series, the first unit was used to remove the bulk of
the contaminants present. The second unit acted as a
biological polishing unit. The design permitted one of
the bioreactors to be removed or bypassed as the
groundwater contaminant concentration decreased
over time. Following the bioreactors, to ensure that
the effluent met all applicable discharge criteria,
were cartridge filters (to remove suspended solids)
and two carbon units (each containing 600 pounds of
carbon). The treatment system was designed to
handle a continuous flow of 15 gallons per minute
(gpm) and to attain effluent MEK concentrations of
less than 1 ppm and other total organics
concentrations of less than 100 ppb. Initial influent
analysis indicated that MEK concentration to the
biotreatment system was in the order of 510 ppm, at a
flow rate of 8 gpm. Subsequently, additional solvent-
contaminated wastes at the site also required
treatment; therefore, the groundwater/solvent wastes
biotreatment system was revised as shown in Figure
26. The major contaminants treated at the plant
continued to be MEK and cyclohexanone.
Case 2 - The Hyde Park Landfill site, located in an
industrial complex in the extreme northwest corner
of Niagara, New York, was used from 1953 to 1975 as
a disposal site for an estimated 80,000 tons of
chemical waste, including chlorinated hydrocarbons.
A compacted clay cover was installed in 1978 over the
landfill and a tile leachate collection system was
installed in 1979. Hazardous compounds such as
ortho-, meta- and para-chlorobenzoic acid; toluene;
ortho- and meta-chlorotoluene; 3,4-dichlorotoluene;
and 2,6-dichlorotoluene were detected in the leachate
(Irvine et al., 1984). Since 1979, the existing leachate
treatment system has used activated carbon as the
technology for removing organic carbon. Although
43
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Flfluro 25. DETOX H-series submerged fixed-film biological reactor (Skladany et al., 1987).
High' Surface Area
Plastic media
Influent
Water
! Media
Support
Aeration Piping
Air Inlet
Effluent Outtfi
Figure 26. Process diagram for revised groundwater and solvent wastes biological treatment system.
I
Extraction Well
Complete Mixed Bioreactor
#1
Clarifier
Complete Mixed Bioreactor
#2
producing a suitable quality effluent, the treatment
of Hyde Park leachate by conventional carbon
technology was unacceptable from an economic
standpoint. For the purchase of carbon alone, the cost
forecast was $21 million over a 10-yr period (Irvine et
al., 1984).
Review of several alternative technologies to reduce
the load of organic carbon on the activated carbon
system produced the following conclusions. The
organic constituents of the leaehate (which accounts
for about 60 percent of the combined wastewater
volume but more than 80 percent of the total organic
44
-------
loading to the existing adsorption system) were found
to be easily biodegraded. Biological pretreatment of
the combined wastewater in SBRs was capable of
reducing the carbon requirements by 90 percent
(Yingetal.,1986).
Subsequently, biological/physical treatment of
leachate with an activated carbon-enhanced
sequencing batch bioreactor (PAC-SBR) was
analyzed to determine whether the improved
treatment by simultaneous adsorption and
biodegradation in the SBR would produce an
acceptable effluent without post-treatment in the
existing granular activated carbon adsorber (Ying et
al.f 1986). *
In-Situ Biological Treatment
Because biological activity is frequently occurring in
the natural environment, the key to in-situ
bioremediation involves providing those conditions
which will enhance biodegradation. In-situ biological
treatment requires the application of fundamental
nutrients or feed augmentation to promote biological
growth to a contaminated groundwater or soil.
Technology Description: In-situ biological treatment
is site-specific, but in general may require the
injection of nutrients, oxygen and microbial
populations to degrade the organic material present.
Usually, extraction wells are used to pump
groundwater from beneath the site for use as a
carrier for the supplemental materials which need to
be applied (either to the groundwater or the soil) in
order to provide the appropriate environment for
biodegradation.
Applicability/Limitations: In-situ treatment is
applicable to sites where the removal of the
contaminated material would be difficult and in
which biodegradation is currently taking place to a
limited degree. This would include sites close to
structures, along active railroad tracks, and where a
large volume of contaminated soil or groundwater
requires treatment. The limitations of in-situ
bioremediation are associated with the ability to
achieve adequate contact of the biomass with the
waste in the underground environment and to
determine the degree of degradation achieved by the
treatment process.
Corrective Action Application: Case 1 - A spill
occurred at the Houston Chemical Company (located
in Texas County, Missouri) in June 1979 (U.S. EPA,
1984). An estimated 15,000 gallons of a 5 percent
solution of pentachlorophenol (PCP) in diesel oil was
released as shown in Figure 27. The emergency
physical cleanup operations performed at the site
were:
• Skimming and vacuuming floating PCP/oil
from the catch basin and pond;
• Excavating and removing contaminated soil
from the PCP/oil spill path and from the farm
pond bottom;
• Constructing surface water diversions
around the farm pond; and
• Sealing of the well at the plant site.
The water in the farm pond was treated by carbon
adsorption and returned to the pond. The
biotreatment operations performed at the pond
consisted of the inoculation with nonindigenous
microbes for the purpose of degrading the low
concentrations of PCP/oil remaining in the water and
soil. Mechanical aerators were installed to provide
oxygen. PCP levels were reduced using a
bioremediation from a range of 250-400 ug/€ to a
value of 10 ug/€ (the clean up objective).
Subsequently, these concentrations rose to 400 ug/€,
but it was anticipated that continued biodegradation
at the site would occur. Since this was an emergency
response action, no follow up monitoring of the site
was performed.
Case 2 - At a midwestern industrial facility, two of
the seven 6000-gal storage tanks were leaking fuel
oil and waste solvents. The underground vault (25 ft
x 70 ft x 12 ft deep) contained seven 6000-gal tanks ,
for storing clean fuel oils and waste solvents from the
laboratory facility. Groundwater contamination was
confined primarily to the underground vault, but
some dissolved hydrocarbons were detected in the
clay stratum immediately adjacent to the tank. Soils
throughout the vault were saturated with aromatic
and aliphatic hydrocarbons. Total contamination was
calculated to be 655 gallons of free products
(solvents/fuel mixture) and 300 to 900 gallons of
adsorbed hydrocarbons (Brenoel and Brown, 1985). A
two phase remediation approach was chosen. In the
first phase, free products were recovered. In the
second phase of remediation, biostimulation was
employed. The basic elements of the installed
biostimulation process included a groundwater
circulation system to sweep the contaminated area
(i.e., a system of injection and recovery wells) and.
nutrient and oxygen injection capabilities. The
nutrients were required for stimulation of the
bacteria and controlled degradation of hydrocarbons.
Two formulations were used: a blend of ammonium
chloride and sodium phosphates and a formulated
oxygen-enhancement solution. Because the available
oxygen level was considered critical to maintaining a
rapid rate of degradation, the oxygen-enhancement
solution was added continuously. An activated
carbon system was utilized for further reduction of
residual hydrocarbons in the groundwater in the
final step of remediation. The dissolved hydrocarbon
levels were reduced to less than 10 ppb (Brenoel and
Brown, 1985,1984).
45
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Figure 27. Houston Chemical Co. response actions (EPA/540/2-84/002b, 1984).
Houston Chemical Co.
Response Actions
Hwy. 63
Spillway
Service
Road
Carbon Filtration
Ruptured Tank
Main Flow of Oil
Decontamination Trailer
Equipment Trailer
On-Site Lab
Command Post
Kitchen
Engineered Processes to Achieve Reduction
Anaerobic treatment of hazardous wastes has not
been widely used in above ground reactors or in situ.
All anaerobic biological treatment processes achieve
the reduction of organic matter to methane and
carbon dioxide in an oxygen-free environment. This
is accomplished by using cultures of bacteria which
include facultative and obligate anaerobes.
Anaerobic bacterial systems include hydrolytic
bacteria (catabolize saccharides, proteins, lipids);
hydrogen producing acetogenic bacteria (catabolize
the products of hydrolytic bacteria, e.g., fatty acids
and neutral end products); homolactic bacteria
(catabolize multicarbon compounds to acetic acid);
and methanogenic bacteria (metabolize acetic and
higher fatty acids to methane and carbon dioxide).
The strict anaerobes require totally oxygen-free
environments and oxidation reduction potentials of
less than -0.2V. Microorganisms in this group are
commonly referred to as methanogenic consortia and
are found in anaerobic sediments or sewage sludge
digesters. These organisms play an important ro!0 in
reductive dehalogenation reactions, nitrosamine
degradation, reduction of epoxides to olefins,
reduction of nitro groups, and ring fission of aromatic
structures.
Technology Description: Available anaerobic
treatment concepts are based on such approaches as
the classic well-mixed system, the two-stage system
and the fixed bed. In the well-mixed digester system,
a single vessel is used to contain the wastes being
treated and all bacteria must function in that
common environment. Such systems typically
require long retention times and the balance between
acetogenic and methanogenic populations is easily
upset. In the two stage approach, two vessels are used
to maintain separate environments, one optimized for
the acetogenic bacteria (pH 5.0), and the other
optimized for the methanogenic bacteria (pH 7.0).
Retention times are significantly lower and upsets
are uncommon in this approach. The fixed bed
approach (for single or 2-staged systems) utilizes
inert solid media to which the bacteria attach
themselves and low-solids wastes are pumped
through columns of such bacteria-rich media. Use of
such supported cultures allows reduced retention
times since bacterial loss through washout is
minimized. Organic degradation efficiencies can be
quite high. A number of proprietary engineered
processes based on these types of systems are actively
being marketed, each with distinct features but all
utilizing the fundamental anaerobic conversion to
methane and carbon dioxide.
46
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Applicability/Limitation: These processes are used to
treat aqueous wastes with low to moderate levels of
organics. Anaerobic digestion can handle certain
halogenated organics better then aerobic treatment.
Stable, consistent operating conditions must be
maintained. Anaerobic degradation can take place in
native soils but when used as a controlled treatment
process, an air-tight reactor is required. Since
methane and CC>2 gases are formed, it is common to
vent the gases or burn them in flare systems.
However, volatile hazardous materials could readily
escape via such gas venting or flare systems. Thus,
controlled off-gas burning is required. Alternatively,
depending on the nature of the waste to be treated,
the off-gas could be used as a source of energy.
To date, the logistics for achieving controlled
anaerobic conditions for in-situ surface treatment
have not been developed. In the subsurface
environment, it has been shown that anaerobic
conditions can be achieved after aerobic
biodegradation has depleted the oxygen. Anaerobic
conditions can be controlled in above-ground
reactors. Thus aqueous waste streams can be
anaerobically biodegraded whether in a reactor or in
situ. Soils can also be anaerobically treated in an
above ground reactor. The amount of oxygen present
in subsurface soils and surface soils cannot be easily
controlled, therefore anaerobic treatment is not
generally appropriate.
Residuals Produced: Some biomass is produced
which will require disposal. The disposal practices
required will depend on site-specific requirements.
Corrective Action Application: At the Turi Landfill in
Orange County, New York, bench-scale studies at
room temperature were conducted for the anaerobic
treatment of sanitary landfill leachate. Leachate
collected directly from the Turi landfill site was used
in test runs conducted in continuous operation for
more than 6 months. Highly variable characteristics
of the leachate used in the study was exemplified by
CODs ranging from 2,000 to 35,000 mg/€, BOD5s
from 1,800 to 24,000 mg/€, and ammonia nitrogen
from 50 to 500 mg/€. Concentrations of detectable
priority pollutants were also found in the leachate.
An anaerobic fixed-film reactor (with a volume of
5.78 gal and with a controlled rate of sludge
recycling) was operated with upflow feeding at
organic loadings between 0.51 and 5.46 Ib COD/ft3-
day and hydraulic detention times of 6.9 to 10.3 days
(Mureebe et al., 1986). The test runs resulted in
filtered COD removals from 92 to 94 percent,
unfiltered BOD5 removals of 90 to 94 percent, and
ammonia removal from 40 to 50 percent.
Thermal Processes for Corrective Action
What is Incineration?
Corrective Action utilizing incineration can be
applied to most organic-bearing wastes under various
conditions. Wastes may be burned which contain
relatively high water content, are largely inorganic
in nature (i.e., they possess high ash content), or are
in the solid or semi-solid state. The primary question
is: When should incineration be chosen for
application as opposed to other technologies? To
decide whether incineration is the best technology for
a specific waste, consideration must be given to the
following issues:
1. Limitations which arise from the quantity or
nature of the waste;
2. The environmental impact of incineration,
including stack and fugitive emissions;
3. The requirements for disposal of residues,
i.e., ash and air pollution control (APC)
residues;
4. Permitting issues.
Incineration is an oxidative process which is used for:
• detoxification and sterilization
• volume reduction
• energy recovery
• by-product chemical recovery
The incineration process may be viewed as consisting
of four parts: (1) preparation of the feed materials for
placement in the incinerator (pretreatment), (2)
incineration or combustion of the material in a
combustion chamber, (3) cleaning of the resultant air
stream by air pollution control devices (APCDs)
which are suitable for the application at hand, and (4)
disposal of the residues from the application of the
process (including ash, and air pollution control
system residues).
Applicability Based on Waste Type
Thermal processes are typically used for highly toxic
waste or highly concentrated organic wastes. If the
waste contains PCB, dioxins, or other toxic
substances, incineration should be chosen in order to
assure destruction. If the wastes contain greater than
1000 parts per million of halogens (chlorinated
materials), it would probably be desirable to select
incineration of these wastes, after consideration of
other options. In any case, a material may be
incinerated or used as a fuel if the heat content is
greater than 8500 BTUs per pound or, if between
2500 and 8500, it may be incinerated with auxiliary
fuel. The waste components of concern are halogens,
alkali metals and heavy metals.
47
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Applicability Based On Waste Form
Incineration processes are available to destroy
organics in liquids, solids/sludges, soils and gases.;
Selection Strategy
Simple strategies (as shown in Figures 28 and [29)
exist for evaluating incineration as an'option, given
the waste's characteristics. This decision logic will
assist in planning for possible use of incineration for
hazardous waste applications. If the wastes contain
highly toxic substances (e.g., dioxins), or compounds
of special interest such as PCBs, the incineration or
destruction option is an attractive one (the first two
decision diamonds on Figure 28). If wastes contain
high concentrations of halogens or recoverable heat
value (the next two decision diamonds), the
possibility for recovery and/or alternate pretreatment
should be examined. For this option, the series of
boxes to the right of the diagram should be used.
Finally, waste with low-heat value could be burned
with supplemental fuel. Thus, the process shown on
Figure 29 may be used to evaluate incineration
among the treatment technologies available. If
incineration is selected, the next step is the selection
of the type of combustion device. The physical form,
metal content, and water content are the major
considerations for the selection. Pretreatment
methods exist for wastes prior to incineration.
Thermal Processes and Their Application
Once the decision is made to incinerate'the material,
the type of incinerator which is selected is largely
dependent on the matrix in which the waste is
located. Table 10 indicates the application of various
thermal processes for liquids, solids/sludges, soil and
gases. i
Incineration of Liquids
The types of incinerators which can be employed for
incineration of liquid wastes include:
• Liquid injection furnaces
• Plasma arc incinerators
• Rotary kilns (discussed under the
incineration of solids)
Liquid Injection
Technology Description: Liquid waste material is
introduced to the combustion chamber by means of
specially designed nozzles. Different nozzle designs
result in various droplet sizes which mix with air and
fuel as needed. Following combustion, the resulting
gases are cooled and treated to remove particulates
and to neutralize acid gases. Pretreatment (such as
blending) may be required for feeding some wastes to
specific nozzles in order to provide efficient mixing
with the oxygen source and to maintain a continuous
homogeneous waste flow. In general, the more finely
atomized liquids will combust more rapidly and more
completely. Operating temperatures range from 1200
to 1300°F and the gas residence time ranges from 0.1
to 2 seconds. Typical heat output ranges from 1 to 100
MMBtu/hr. A typical configuration for a liquid
injection incinerator is presented in Figure 30.
Applicability/Limitations: Liquid injection incin-
eration can be applied to all pumpable organic wastes
including wastes with high moisture content. Care
must be taken in matching waste (especially
viscosity and solids content) to specific nozzle design.
Particle size is a relevant consideration so that the
wastes do not clog the nozzle. Emission control
systems will probably be required for wastes with ash
content above 0.5 percent (particulate control) or for
halogenated wastes (acid gas scrubbers).
Residuals Produced: Liquid injection incinerators
produce ash which may require application of a post
treatment technology prior to disposal. The by-
products from the emission control devices may also
require further treatment prior to disposal.
Plasma Arc
Technology Description: The developmental plasma
arc process functions by contacting the waste feed
with a gas which has been energized into its plasma
state by an electrical discharge. The plasma torch
acts as one electrode and the hearth at the bottom of
the reactor acts as the second electrode. The
discharge of electricity between the two electrodes
causes the centerline temperatures in the plasma to
reach 9000°F. A small amount of gas is introduced
into the centerline region and is ionized. The ionized
gas molecules transfer energy fco the waste to cause
pyrolysis of the waste. Since the process is pyrolytic,
the scale of the equipment Is small, especially
considering the high throughput rates. This
characteristic makes it potentially attractive for use
as a mobile unit. Gaseous emissions (mostly Hg, CO),
acid gases in the scrubber and ash components in
scrubber water are the residuals. The system's
advantages are that it can destroy refractory
compounds and typically the process has a very short
on/off cycle. The system components for the plasma
arc process is presented in Figure 31.
Applicability: This process is applicable to liquid
(pumpable) organic wastes and finely divided,
fluidizable sludges. It may be particularly applicable
to the processing of liquid wastes with a. high
chlorine, pesticide, PCB or dioxin content. Sludges
must be capable of being fluidized by the addition of a
liquid. Waste streams must be free of (or preprocessed
to remove) solids, which prevent satisfactory
atomization.
48
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Figure 28. Conceptual strategy for determining burnability.
Start
Does Waste Contain
Dioxins or Furans?
Does Waste Contain
>50 ppm PCBs?
Identify all State-of-the
Art Disposal and
Treatment Options
Does Waste Contain
>1000 ppm
Halogens?
Assess Relative Hazard
to HHE for Each Option
Compared to Incineration
Is the Waste a
Characteristic"
Waste?
Estimate Costs of Each
Option Having Acceptable
"Hazard" Level
Is Heat Content (as
Received) >8500
BTU/lb?
Scinerate or \
se as Fuel )
Is Heat Content (
Received) Between
2500 and 8500
BTU/lb?
Use Lowest Cost
Acceptable" Option
Incinerate with >>
Auxiliary Fuel )
49
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Figure 29. Pretreatment option logical decision flow chart.
Other
Alternatives
Is Gross Physical
Form O.K.?
Modify Physical
Form as Needed
Dewatenng
Process
Is Moisture Content
Too High?
Solids Removal
Process
Is Solid Content Too
High?
Metal Removal/
Reduction
Process
Is Metals Content Too
High?
Augment with
High BTU
Waste or
Auxiliary Fuel
Is BTU Content Too
Low?
©
I
Estimate Probable Emissions
-Bottom Ash
-Fly Ash
-Scrubber Waters
-Paniculate Emissions
-Gaseous Emissions
Assemble List of All
Pretreatment Residues
-Liquids
-Solids
-Sludges
Identify Bat for Treatment/
Disposal of All Residues
(Incinerator and Pretreatment)
Perform Composite Risk
Assessment for All Emissions
and All Disposal Residues
Assess Total Process Cost for
Incineration with Pretreatment
Compare Cost "Effectiveness"
with Other
Incineration/Pretreatment
Combinations or Other
Competing Technologies
I Use Most Cost
Effective Option
50
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Table 10. Incineration Type for Various Waste Matrices
Liquids Solid/Sludges Soil Gases
Liquid injection incinerator x
Plasma Arc x
Rotary Kiln x x
Fluidized Bed x x
Circulating Bed x
Infrared x x
In-situ Vitrification x
Afterburners x
Residuals Produced: The plasma arc process
produces ash which may require post treatment to
make it suitable for disposal. The wet scrubber
blowdown may require treatment prior to disposal.
Solids/Sludges
The thermal processes applicable to detoxify organics
in a solid/sludge matrix include the following
incinerators:
• Rotary kiln
• Fluidized bed
• Circulating bed
• Infrared
Rotary Kiln
Technology Description: A rotary kiln incinerator is
essentially a long, inclined tube that is rotated
slowly. Wastes and auxiliary fuels are introduced to
the high end of the kiln and the rotation constantly
agitates (tumbles) the solid materials being burned.
This tumbling causes a great amount of solids mixing
and allows for improved combustion. Rotary kilns are
intended primarily for solids combustion, but liquids
and gases may be co-incinerated with solids. Exhaust
gases from the kiln pass to a secondary chamber or
afterburner for further oxidation. Ash residue is
discharged and collected at the low end of the kiln.
Figure 32 illustrates a rotary kiln system.
Applicability/Limitations: Most types of solid, liquid,
and gaseous organic waste or a mixture of these
wastes can be treated with this technology. Explosive
wastes and wastes with high inorganic salt content
and/or heavy metals require special evaluation. This
operation can create high particulate emissions
which require post-combustion control.
Residuals Produced: Exhaust gases require acid gas
and particulate removal through the use of a gas
scrubber and the ashes may require solidification
before landfilling.
Corrective Action Applications: Case 1 - The U.S.
Army Toxic and Hazardous Materials Agency
(USATHAMA) completed a trial burn of explosive,
contaminated soil in a rotary kiln (Noland, 1984).
Soil contaminated from red and pink water lagoons
was successfully burned. A transportable rotary kiln
system was set up. The technology by Therm-All,
Inc., had been used in industry for destruction of solid
wastes. The normal screw feed system was not used,
due to fear of a soil explosion during the extruded
plug feed process. Therefore, the soil was placed in
combustible buckets and individually fed by a ram
into the incinerator. The feed rate was 300 to 400
Ib/hr and the operational temperature was 1200° to
1600°F in the kiln and 1600° to 2000°F in the
secondary chamber.
A ORE of 94.99 percent was reported. The flue gases
were cooled in a heat exchanger prior to entering a
baghouse for particulate emissions control.
Case 2 - A mobile rotary kiln incinerator was used at
the Sidney Mines site, Hillsborough County, Florida,
to burn nonhazardous oil-contaminated sand and
sludge (Hatch, 1985). The site did not require a
RCRA permit since the waste matrix passed the EP
toxicity test and was not hazardous. The dry
processed soil was captured in a bin and tested by the
EP toxicity method for leachable heavy metals prior
to disposal at the nearby county landfill. The flue
gases were cooled by a boiler prior to entering a water
quench and steam ejector particulate system. The
boiler generates steam to operate the particulate
emissions control ejector. The steam ejector also
serves as the source and regulator for the negative
draft through the combustor, and thus the system
does not have an induced-draft fan.
The incinerator processed about 2.25 tph due to the
high thermal value of the oil. The system could
handle 4 to 6 tph of low-energy soils. The system
experienced the following problems:
• clogging of front-end waste feed equipment,
• loss of refractory bricks sooner than expected,
and
• carry-over of fine solids into the horizontal
secondary chamber and restriction of the flue
gas flow.
Fluidized Bed
Technology Description: Fluidized bed incinerators
utilize a very turbulent bed of inert granular
material (usually sand) to improve the transfer of
heat to the waste streams to be incinerated. Air is
blown through the granular bed materials until they
are "suspended" and able to move and mix in a
manner similar to a fluid, i.e., they are "fluidized'Mn
this manner, the heated bed particles come in
intimate contact with the wastes being burned. The
process requires that the waste be fed into multiple
injection ports for successful treatment. Advantages
51
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Figure 30. Liquid Injection Incineration system
Flue Gas
Steam
Liquid .
Waste
Fuel
Air-
i i Incinerator
Acid
Solution
Salt
Solution
of this technology include excellent heat transfer to
the material being incinerated and a long solids-
retention time. An off-shoot of this technology is a
circulating bed combustor. The configuration of a
fluidized bed reactor is presented in Figure 33.
Applicability/Limitations: Fluidized beds require
frequent attention for maintenance and cleaning
purposes. This treatment is ideal for slurries and
sludges but not for bulky or viscous wastes. The
waste particles should be of a certain size and be
homogeneous. Wastes must have a low sodium
content and a low heavy metal content. Some
refractory wastes may not be fully destroyed since
these units operate at low combustion temperatures
(750°tolOOOeC).
Residuals Produced: Fluidized bed incineration
produces no separate ash as such, but solids are
carried over in the gas stream and will require
removal. Residuals from the air pollution control
devices may require additional treatment prior to
disposal.
Corrective Action Application: Fluidized bed
incineration has been used to incinerate municipal
wastewater treatment plant sludge, oil refinery
waste, some pharmaceutical wastes, and some
chemical wastes including phenolic waste, and
methyl methacrylate. Heat recovery is possible.
Circulating Bed
Technology Description: The circulating bed
combustor (Figure 34) is designed to be an
improvement over conventional fluidized beds. The
system operates at higher velocities and finer
sorbents than fluidized bed systems. This permits a
unit that is more compact and easier to feed. The unit
also produces lower emissions and uses less sorbent
materials than the fluidized bed systems. No off-gas
scrubber is necessary in the circulating bed
combustor and heat can be recovered as an added
benefit. The key to the high efficiency of the
circulating bed combustor is the high turbulence that
is achieved within the combustor. This feature allows
efficient destruction of all types of halogenated
hydrocarbons including PCBs and other aromatics at
temperatures less than 850°C. Acid gases are
captured within the combustion chamber by
limestone in the bed. A baghouse is needed for
particulate control. Compounds containing high
levels of phosphorus, sulfur, cyanide,' etc. can be
processed with low emissions of NOX, CO and acid
gases. In addition to the turbulence, a large
combustion zone with uniform and lower
temperature throughout also contributes to high
efficiency. The circulating bed combustor also
features longer residence time of the combustibles
and sorbents in the combustion zone.
Applicability/Limitations: The system is capable of
treating solids, sludges, slurries and liquids. The
high degree of turbulence a.nd mixing ensures
treatment of a wide variety of wastes. The waste
52
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Figure 31. Schematic of plasma arc system.
Process Water
Off Gases to Flare
n
Power
Cooling Water
Emergency
Carbon
Filter
Gas Chromatograph
Mass Selectivity Unit
Laboratory
Analysis
Equipment
Gas Chromatograph
Salt Water to Drain
Source: Westinghouse Plasma Systems
however, must be fairly homogeneous in composition
when fed to the combustor, since it is usually
introduced at only one location. An additional benefit
of the circulating bed combustor is the possibility of
heat recovery. The combustion chamber can be of
"waterwall" construction.
Residuals Produced: Circulating bed incinerators
produce no ash. Solids are carried over in the gas
stream and require removal. Residuals from the air
pollution control device may require further
treatment prior to disposal.
Corrective Action Application: Circulating fluidized
bed incinerators are ready for full-scale testing under
the EPA SITE Program. A unit is now in the RCRA
permitting process.
Infrared
Technology Description: Infrared radiators can be
used as the heat source in the destruction of
hazardous waste. This system (Figure 35) is made up
of a primary chamber consisting of a rectangular
carbon steel box lined with layers of a light weight,
ceramic fiber blanket. Infrared energy is provided by
silicon carbide resistance heating elements. The
material to be processed is conveyed through the
furnace on a woven wire belt. Solids are pyrolyzed on
the hearth. Sufficient air (or oxygen) is introduced to
fully combust the off-gases. When the waste reaches
the discharge end of the furnace it drops off the belt
into a hopper. Advantages include a quiescent
combustion zone, which results in low particulate
emissions; reduced gaseous pollutant emissions; low
fossil fuel usage; and up to 50 percent operational
turndown capacity. This system allows a high degree
of control, and long-residence times for solids are
achievable.
Applicability Limitation: This technology is used
primarily to treat solids, sludges and contaminated
soils, but liquid or gaseous injection systems are
available.
So//s
Applications of thermal processes to contaminated
soils are somewhat limited. Two processes, rotary
53
-------
Figure 32. Rotary kiln Incineration system.
Steam
Ram, Auger
Concentrated
Brine Solution
kilns and in-situ vitrification, offer a mechanism to
detoxify organic contaminated soils.
Rotary kilns, as described previously, can be used to
incinerate materials which can be excavated and fed
into the kiln. Vitrification is a process, which can be
used without removing the soil and is described
below.
Vitrification
Technology Description: Vitrification is a process
whereby hazardous wastes are converted into a
glassy substance by means of very high
temperatures. The process is carried out by inserting
large electrodes into contaminated soils, which must
contain significant levels of silicates. Graphite on the
surface connects the electrodes to the soil. High
current of electricity passes through the electrodes
and soil. The resultant heat in the soil causes a melt
that gradually works downward through the soil.
Some organic contaminants are volatilized and
escape from the soil surface and must be collected by
a vacuum system. Inorganics and some organics are
trapped in the melt, which, as it cools, becomes a form
of obsidian or very strong glass. When the melt is
cooled, it forms a stable noncrystalline solid.
Applicability/Limitation: Vitrification was originally
tested as a means of solidification/immobilization of
low level radioactive materials. It may also be useful
for forming barrier walls. This latter use needs
testing and evaluation to determine how uniform the
wall would be and to evaluate the stability of the
material over a period of time.
Residuals Produced: Off-gases from the melting
require treatment for volatile organics.
Corrective Action Application; This technology is
currently being evaluated under the Superfund
Innovative Technology Evaluation (SITE) Program.
54
-------
Figure 33. Fluidized bed reactor.
Sight Glass
Exhaust
Pressure Tap
Access
Doors
Preheat
Burner
Thermocouple
Fluidized
Sand
Sludge
Inlet
Fluidizing
Air Inlet
55
-------
Figure 34. CIrculaIng fiuidized bed boiler.
Convection
Pass
_ Flue
4-Recycle ^^ Gas
Secondary
Heat Exchanger
(Optional)
Primary
Air
Figure 35. Procass Itow diagram of infrared incineration system.
Material Processing/De-Watering
_a
Secondary Combustion
Chamber
Feed Metering
11^0 *• <2==3~" *
t,7~u .. — -=c —
lIQJ 1
-ft — II
^_ ^J -»—
1
u
Ash Discharge
Primary Combustion Chamber
Source: Shirco Infrared Systems, Inc.
56
-------
References
Brenoel, M. and R.A. Brown. Remediation of a
Leaking Underground Storage Tank with
Enhanced Bioreclamation. In: Proc. 5th National
Symposium and Exposition on Aquifer Restoration
and Groundwater Monitoring, National Water
Well Association, Worthington, Ohio, 1985. pp.
O« i.
Hatch, J. and E. Hayes. "State-of-the-Art Remedial
Action Technologies Used for the Sydney Mine
Waste Disposal Site Cleanups," In: Management of
Uncontrolled Hazardous Waste Sites Proceedings
Washington, D.C., 1985, pp. 285.
Irvine, R.L., S.A. Sojka and J.F. Colaruotolo.
Enhanced Biological Treatment of Leachates from
Industrial Landfills. Hazardous Waste Vol 1 No
1,1984. pp. 123-135.
Mureebe, A.K., D.A. Busch and P.T. Chen. Anaerobic
Biological Treatment of Sanitary Landfill
Leachate. In: Hazardous Wastes and Hazardous
Materials, Atlanta, Georgia, 1986.
Noland, J. and W. Sisk. "Incineration of Explosives
Contaminated Soils," In: Management of
Uncontrolled Hazardous Waste Sites Proceedings
Washington, D.C., 1984, pp. 203.
Nyer, E.K. Innovative Biological Treatment of
Contaminated Groundwater. In: First National
Outdoor Action Conference on Aquifer
Restoration, Groundwater Monitoring, and
Geophysical Methods, May, 1987.
Skladany, G.J., J.M. Thomas, G. Fisher and R.
Ramachandran. The Design, Economics and
Operation of a Biological Treatment System for
Ketone Contaminated Ground and Solvent
Recovery Process Waters. Presented at the 42nd
Annual Purdue Industrial Waste Conference,
Purdue University, West Lafayette, Indiana, 1987.
U.S. Environmental Protection Agency. Case Studies
No. 1-23: Remedial Response at Hazardous Waste
Sites, EPA/540/2/84-002b, March, 1984.
U.S. Environmental Protection Agency. Case Studies
Addendum 1-8: Remedial Response at Hazardous
Waste Sites., Office of Research and Development
Cincinnati, Ohio, EPA/540/2-88-001, April 1988
U.S. Environmental Protection Agency. Remedial
Action at Waste Disposal Sites, EPA/625/6-85/006
October, 1985.
Ying, W.C., R.R. Bonk and S.A. Sojka. Treatment of
Landfill Leachate in Powered Activated Carbon
Enhanced Sequencing Batch Bioreactors. In: Proc
of the 18th Mid-Atlantic Ind. Waste Conference,
Technomic Publishing Company, Inc., Lancaster!
Pennsylvania, 1986.
57
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Chapter 6
Pretreatment and Post Treatment Options
Once the primary treatment alternatives have been
identified for the detoxification of the waste or waste
stream, other treatment technologies may be
required to prepare the waste for treatment.
Similarly, additional treatment technologies may be
required to prepare residues from the treatment
- process for ultimate disposal. As shown in the review
of biological processes, some technologies (e.g., pH
adjustment) were needed to permit other technologies
to proceed. Physical separation techniques are
frequently required to prepare a waste for treatment.
These pretreatment technologies are directed toward
concentrating or sizing the waste to facilitate
treatment. Furthermore, most treatment processes
produce residues which may require additional
treatment before land disposal. Solidification/
stabilization processes are frequently used as post-
treatment technologies to immobilize hazardous
constituents in chemical sludges and incinerator ash.
These solidification/stabilization technologies can
also be applied to high volume, low toxicity wastes
without treatment by other technologies.
Separation Techniques (Pretreatment
Options)
Most treatment options for detoxifying the hazardous
constituents from RCRA facilities must have a
uniform feed to the process. However, the media in
which hazardous constituents are located are not
generally homogeneous. Thus, some form of
pretreatment of the waste or waste medium will
probably be required to prepare the waste for further
treatment by chemical, biological or thermal means.
A Separation Strategy
With few exceptions, treatment technologies are
limited to some extent by the size of the material that
they are able to process. These limitations can apply
to the throat of the feed devices, the inner workings of
the equipment, the treatment mechanisms, or the
process elements. To make these remedial
technologies efficient and cost effective, separation
techniques are used to make the feed stream uniform
or to isolate specific contaminants from the waste
stream.
In developing a separation strategy, the size
distribution of the components found in the
contaminated medium can be used as a starting
point. As an initial step, debris (such as rocks, etc.)
can be separated from the remainder of the waste.
After the debris is removed, other separation
techniques can be employed to concentrate the waste
further or physically manipulate the waste into a
form suitable for treatment.
Debris Separation
In order to develop measures for removal of debris
from the waste matrix, the general types of debris
anticipated need to be identified. A composite list,
based on debris found at 29 Superfund sites, was
developed. The list includes cloth, glass, ferrous
materials, nonferrous materials, metal objects,
construction debris, electrical devices, wood existing
in a number of different forms, rubber, plastic, paper,
etc., as presented in Table 11. Similar types of debris
would be expected at RCRA sites.
Debris with particularly good absorbent qualities
such as wood, some paper products, paper, cloth
materials, etc., are good candidates for shredding so
that they can be included in the remediation process.
Materials that are not porous and are not adsorbent
are glass, plastic, metal objects, some types of
construction debris, tanks, etc., are good candidates
for manual or magnetic separation.
After the debris has been separated or removed, there
are basically four options available for dealing with
the debris:
• Do nothing.
• Pile it off to the side to be treated later.
• Shred the material so that it does not interfere
with the process.
• Separate it and not include it in the process.
59
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Tablo 11. Debris Identification
Cloth
-Rags
-Tarps
- Mattresses
Glass
-Bottles
-(white, brown, green, clear, blue)
Windows
Ferrous Metals
-Cast Iron
-Tin cans
-Slag
Nonferrous Metals
-Stainless steel
-Aluminum
-Brass
-Copper
-Slag
Metal Objects
-Autos/vehicles
-55-galIon drums/containers
-Refrigerators
-Tanks/gas cylinders
-Pipes
-Nails
-Nuts and bolts
-Wire and cable
-Railroad rails
-Structural steel
Construction Debris
-Bricks
-Concrete blocks
-Asphalt
-Stones and rocks
-Reinforced concrete pipe
-Wood
-Steel beams
-Asbestos insulation and
roofing/siding shingles
- Fiberglass insulation
- Fiberglass tanks
Paper
- Books
-Magazines
-Newspaper
-Cardboard
- Packing
Plastic
-Buckets
-Pesticide containers
-Six-pack retainer rings
-Thin plastic sheets
-Plastic bags
-Battery cases
Rubber
-Tires
-Hoses
- Insulation
- Battery cases
Wood
-Stumps and leaves
- Furniture
-Pallets
- Plywood
-Railroad ties
Electronic/Electrical
-Televisions !
-Transformers
-Capacitors
-Radios
Separation Analysis
In selecting or investigating alternative separation
and treatment technologies, there are some rules of
thumb which can be useful. For example,
contamination occurs on the surface of soil particles.
The smaller the size of the particle, the greater is its
proportionate surface area; consequently, the smaller
particles have a greater relative capacity for
contamination. In general, in a soil matrix that
consists of large particles and small particles,' a high
level of contamination would be expected in the finer
fraction. Experience in site remediation has indeed
shown that to be the case. Making use of this feature
can reduce volumes of waste to be treated and
thereby minimize treatment costs.
It should be remembered that while it is generally
true that the heavier contamination is found in the
finer fractions, it is not totally true. Coarser fractions
can have cracks where there is room for large
quantities of contamination.
In lagoons where there is liquid on the surface and a
highly viscous fluid below the liquid surface,
separating the water from the waste and sludge may
be appropriate. The expenses for incineration of the
removed sludge could be greatly reduced by removal
of the water.
The chemical properties of the contaminants have to
be considered when selecting separation techniques.
Some of the liquids are absolutely immiscible in
water, and if the process stream involves water and
the contamination is liquid/liquid, then the
separation technique can greatly reduce the volume
of contaminated water. For example, if acetone is the
contaminant of concern, a simple vapor stripping
technique can be effective in making a separation. In
the case of refined oil, which has a solubility limit of
approximately 50 ppm, one of the oil/water
separation techniques could be effective. Some
general guidelines to consider are:
• If the waste stream has a high content of fine
particulate matter then, by isolating particulate
matter, most of the contamination wotald be
isolated.
• If the chemicals of concern contain more than
eight carbon atoms, then they tend to have a high
soil adsorption.
In general, when separating two liquids, they must
be immiscible and have different specific gravities
before a separation technique-such as oil/water
separation-would be effective. In the case of finely
dispersed liquids or finely dispersed solids, if the
dispersed material is below one micron in particle
size, centrifuging should be considered. The use of
centrifugal force on the differing densities of the
material can facilitate the separation technique.
Sizing Methodology for Solids
Once the debris has been removed from the waste
material, the preparation of the waste for treatment
can begin. Over the years, the construction, mining,
and manufacturing industries have developed
various pieces of equipment that are geared for the
specific purpose of separating materials and making
process streams uniform. The raw materials
60
-------
themselves can range in size from 1 meter down to 1
angstrom (10-1° meters) . There are a number of
devices that can be used to separate materials
depending upon the form of the waste and the particle
size (Figure 36). These devices utilize a difference in
size, density, or their electrical or magnetic
properties to make the separation. The use of any of
these technologies or a combination of these
technologies may be required to prepare the waste for
further treatment.
Separation Technologies
The size of the particles, the medium, and the
contaminant are all important factors in the selection
of a separation technique. Another important
consideration in selecting a separation technique is
whether the process is intended to make the waste
stream uniform or to isolate a portion of the waste
stream for treatment.
Scree/75
The screen is a simple device used for the grading or
separating of particles by size. Vibrating and
oscillating screens are used for the same purpose, but
the passing of the material is enhanced by a vibrator
or oscillator, respectively. The centrifugal screen
enhances the passing of the material by making use
of centrifugal force and the density of the material.
Tabling
Another type of separation that utilizes the difference
in densities of material is called tabling. The process
can be performed either wet or dry, with dry tabling
having the broader particle size range where it can be
used. The device uses slotted incline planes, and the
surface oscillates to move the solids. In the case of wet
tabling, washing fluid removes the less dense solid
fractions, and the heavier solids are collected in the
grooves and moved to the collection point by the table
oscillation. For example, dry tabling is used
extensively in the coal industry. The undesired
mineral content of mined coal is much more dense
than the actual bituminous, anthracite, or lignite
fractions of the coal. The ash content of the mineral-
containing fraction is much higher than that of the
coal fraction making separation desirable.
Another type of the tabling process is called
agglomerate tabling. Here, pretreatment is involved
to precipitate a particular constituent of the material
so that it can be separated by the tabling process.
This type of tabling is particularly useful for sludges
that require pretreatment.
Cyclones
Cyclones, hydrocyclones and centrifuges utilize
centrifugal force to separate material of differing
densities. The principle in the operation of these
devices is that the heavier materials are thrown to
the outside, and the lighter materials remain near
the inside where they can be drawn off (Figure 37).
Jigging
Jigging is a separation process in which material of
similar size but different densities can be separated
by immersing them in a fluid that is less dense than
either material. Pulsating the material up and down
in the fluid is done in such a manner that different
buoyancy factors are imparted to particles of
differing densities (Figure 38). The lighter materials
separate to the top; the heavier materials settle to the
bottom. This process can also be used .to separate
material of the same density but different particle
size. The jigging process is used extensively in the
mining industry, particularly coal mining and
uranium mining.
Magnetic Separator
The magnetic separator is typified by a rotating drum
surrounded by four stationary magnets. The material
coming in from the top is composed of magnetic and
non-magnetic material. As the material falls past the
drum, the magnetic field will hold the magnetic
material in place until it can drop down into a
separate chute for magnetic materials. The non-
magnetic materials, of course, will drop off prior to
that point and down another chute (Figure 39).
Oil/Water Separators
Oil/water separators are another class of devices that
utilize density to achieve separation. Oil/water
separators have wide application at petroleum
refineries, shipboard bilge water processing, and
metal processing where oil and water emulsions are
used as lubricants. Most oil/water separators depend
upon gates or weirs and baffles to effect the oil and
water separation without disturbing the operation of
the rest of the device (Figure 40). This device can also
include a scraper for solids removal. The effluent is
discharged into the sewer or a holding basin.
Another kind of oil/water separator is a coalescing
system which involves packs of parallel, inclined
plates. The oil-laden fluid passes down from top to
bottom across the parallel plates. As the water passes
through the plates, oil tends to coalesce on the plates.
The water is not passed through the plates fast
enough to capture the droplets of coalescing oil. Due
to the buoyant effect in the water, the coalesced oil
will go back up the plates. The oil globules escape and
create an oil layer at the top of the device where it can
be skimmed off with a physical skimming device. The
coalescing oil/water separators utilize a sediment
trap so that solids do not get into the parallel plates.
The treated water, after going through the plates,
61
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Figure 36. Separation techniques for various particle sizes.
Reverse
Osmosis
Hyper
Filtration
Micro Filtration
Ultra Filtration
Ultra
Centrif.
Super
Centrifuge
Vibrating Screen
High Speed
Vibrating Screen
Rod-deck
Screen
_L
Oscillating Screen
Grizzly
Rod Grizzly
Sifter Screen
1
T
Centrifugal Screen
Static Sieve
_L
Revolving Filter Screen
Particle Filtration
T
Wet Classifiers
Centrifuge
Revolving Screen, Trommels,
Scrubbers
Jigging
Hydroseparator
Wet Tabling
Dry Tabling
(Coal) j
Agglomeration
Table
Spiral
Concentration
Dense-Medium
Separator
10-9
10-8
10-7
10'6
10-5 10'4
Meters
10-3
10-2
10-1 10-°
goes into an outlet chamber where residual oi,l will
tend to float. The chamber outlet is below the outer
surface so there is less likelihood of taking the
residual oil product to the outlet valve (Figure 41).
The parallel plate process is not the only type of
coalescent equipment that is used. There are a
number of different types of coalescent elements.
So//s Washing System
A soils washing system is a system designed to
separate soil into component parts and, in the
process, do some scrubbing and washing of
contaminants (Figure 42). The one shown is a mobile
sysbem developed by the EPA. The waste feed is
placed in the top hopper. Inside the first chamber is a
screen section. This is a rotating screen or trommel. It
has a wedge wire screen, and is designed so that if
particles do get slightly caught in the mouth jof the
opening, then they will not become permanently
wedged between two bars. The wedge allows it to pass
through if it is just barely passable going through the
opening. The material that passes through is finer
than gravel. The sand, 2 millimeters and finer, goes
into a sump and then goes onto the next device. The
gravel and material larger than 2 millimeters go into
a rotating drum where they tumble around for up to
15 minutes, then are passed to a second screen for a
final washing prior to being discharged down the
chute into a hopper. This produces a gravel mix that
has the majority of its finer than 2 millimeter
material removed. The less than 2 millimeter
material then passes on into this device which is
basically a froth flotation unit with hydrocyclones.
The fluid swirls around inside the apex. The bottom
of the hydrocyclone is where the concentrated slurry
of the material passes. None of these hydrocyclones
can work beyond a 10 percent slurry.
62
-------
Figure 37. Cyclone.
Figure 38. Jigging.
This process removes the coarser fractions in the
hydrocyclones. Hydrocyclones basically operate
within the sand region, and if there is material that
is finer than sand (material that passes a 200 mesh
screen), then approximately 100 percent of that
material will pass out the top. The finer fractions and
the wastewater that overflow from the hydrocyclone
are not treated any further. The contaminants that
reside on the finer fractions adhere fairly well to such
particles,, therefore, it does not make any processing
sense to try and remove them. The coarser fractions
then subsequently move down into the next cells. The
fluid movement from right to left and the solid
Figure 39. Magnetic separator.
Non-Magnetic
Magnetic
movement from left to right (as they pass through
each of these hydrocyclones) gives this device its
name, a countercurrent unit. The coarse fractions
pass through the cleanest water just prior to leaving
the system and the finest fractions traveling away
from the system in the direction of the most
contaminated fluids.
Gas Separation
Gas separation can be achieved with centrifugal
separation techniques. Gas is forced through a
63
-------
Figure 40. API oil/water separator.
U_ — Separator Channel — —
_j
Diffusion Device
(Vertical-Slot Baffle
\
Gateway Pier \
\ \
-V
Flight Scraper
Chain Sprocket
/
Rotatable OIN
Skimming Pipe
\
\
Oil-Retention
Baffle
s
Effluent
Weir and
Wall
Forebay
Slot for
Channel Gate
Sludge-Collecting
Hopper
Efluent Flume '
''
Etfluent Sewer
Sludge Pump
Suction Pipe
separation nozzle which is circular in shape. The
input gas is entered at supersonic speed and the
higher density material tends to go to the outside of
the separation nozzle and the less dense remain on
the inner side. The separation knife will then sheer
the heavy fraction on the outside from the lighter
inner fraction (Figure 43).
Solidification/Stabilization Processes
(Post Treatment Options)
Solidification/stabilization technologies are
techniques designed to be used as final waste
treatment. A major role of these processes is post-
treatment of residuals produced by other processes
such as incineration or chemical treatment. In some
cases, solidification/ stabilization processes can serve
as the principal treatment of hazardous wastes for
which other detoxification techniques are not
appropriate. High volume, low toxicity wastes (such
as contaminated soils) are an example of this
application.
The intent of solidification/stabilization processes is
to immobilize these toxic or hazardous constituents
in a waste by:
• Changing the constituents into immobile
(insoluble) forms;
• Binding them in an immobile, insoluble matrix;
and/or
• Binding them in a matrix which minimizes the
waste material surface exposed to solvent.
Often, the immobilized product has a structural
strength sufficient to prevent fracturing over time.
Solidification accomplishes the objective by changing
a non-solid waste material into a solid, monolithic
structure that ideally will not permit liquids to
percolate into or leach materials out of the mass.
Stabilization, on the other hand, binds the hazardous
constituents into an insoluble matrix or changes the
hazardous constituent to an insoluble form. Other
objectives of solidification/stabilization processes are
to improve handling of the waste and produce a stable
solid (no free liquid) for subsequent use as a
construction material or for landfilling.
As a first step in the selection process, the
applicability of the various solidification/
stabilization processes for specific contaminants can
be determined using Table 12. Since these waste
treatment systems vary widely in their applicability,
cost, and pretreatment requirements, many are
limited as to the types of waste that can be
economically processed. Waste characteristics such
as organic content, inorganic content, viscosity and
64
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Figure 41. Shell corrugated-plate interceptor.
Oil Globules
\\\\\\\\\\\\\\\\
1
M^ *
*
• 9
1
\
\
t <
^r^
Inlet
A
\\\\ \\V\\\\\Y\\\\\
Sediment Trap
"^ Packs of Corrugated
Parallel Plates
Treated Water Outlet
Channel
sL
V^— — Sludge Pit
particle size distribution can affect the quality of the
final solidified product. These characteristics inhibit
the solidification process by affecting the
compatibility (or incompatibility) of the binder and
the waste, and the completeness of encapsulation and
development of preferential paths for leaching due to
spurious debris in the waste matrix. Selection of any
particular technique for waste treatment must
include careful consideration of the intended purpose
for the action, the cost of processing, the increase in
bulk of material produced and the changes in the
handling characteristics of the resultant by-products.
The design and location of any placement area or
landfill that eventually receives the treated waste is
also a major consideration in deciding on the physical
properties that will be required of the stabilization
process.
Solidification/stabilization processes are not "off-the-
shelf" technologies, thus, it is not unusual for
modifications to the additives required for a specific
waste. For this reason, some pilot testing of the
solidification reagents may be required to develop the
ultimate characteristics desired in the final product.
As part of the quality control procedures for
solidification technologies, raw materials used must
be checked as well as the waste and the final product.
The raw materials may vary from supplier to
supplier and from batch to batch. In order to achieve
a consistent solidified product, tests should be run to
check raw material inputs and match them to plant
operations. More important, the waste must be tested
before processing. To this end, samples are taken for
treatability studies during the facility investigation
as well as during processing of the waste on a routine
basis. When an incoming waste is received at a
solidification treatment facility, it must be rapidly
tested for selected parameters which may interfere
with the solidification process. This testing can be
complicated, and there is little time available to
match the incoming wastes' characteristics with
those previously determined to be acceptable for a
solidification process designed specifically for the
waste. The waste characteristics must be consistent
between shipments (within an acceptable range): if it
does not meet the requirements, the shipment may be
rejected on this basis. As a last quality check, the
final product must undergo preselected physical and
65
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Figure 42. Mobile soils washing system.
Coo laminated
Soil in
To Vapor
Control
Soil Feed
Motor
First
Screen
-«— Clean Wash Fluid
Rotating Drum (2-14 rpm)
^'•'•.';'.•. + 2mm Gravel with Some -2mm•:';
A A L
Second
Screen
\ X
J
ute Slurry
- 2mrn
+ 2m
Spent Wash Fluid
Clean Wash
Fluid to Cell 4
Clean Soil Slurry
chemical tests, and the results must fall within
acceptable ranges.
Physical and chemical tests of the final product may
need to address two concerns: (1) whether the
solidified waste exhibits any RCRA defined toxicity
characteristics or could be delisted; and (2) the
potential long term fate of treated materials iii the
disposal environment. Three tests are available
which address the first concern. These are( the
Extraction Procedure (EP Tox) (40 CFR 261,
Appendix II, 1980) and the Toxicity Characteristic
Leaching Procedure (TCLP) (40 CFR 261, Appendix
II, 1986), and the Multiple Extraction Procedure Test
(40 CFR 261, Appendix II, January 1989). It is
important to note that these tests are not indicators
of expected leachate quality but of potentials. A
solidified product which cannot pass the appropriate
test (EP Tox or TCLP) would be subject to
classification as a hazardous waste.
A wide variety of tests may be useful in assessing the
long term fate of a solidified product. An appropriate
combination of tests would deprend on the nature of
the waste, the treatment technology employed, and
the final disposal environment of the treated waste.
Performance test methods for a number of these
testing procedures are currently being evaluated by
the U.S. EPA Risk Reduction Engineering
Laboratory in Cincinnati, Ohio. General information
is provided through the Handbook for
Stabilization/Solidification of Hazardous Wastes
(U.S. EPA, 1986).
Available Solidification/Stabilization Technologies
and Their Application
Major categories of industrial waste
solidification/stabilization systems are cement-based
processes, pozzolanic processes (not including
cement), thermoplastic techniques, organic polymer
techniques, surface encapsulation techniques, and
self-cementing techniques (for high calcium sulfate
sludges). Vitrification (discussed previously) can also
be considered a solidification process.
66
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Figure 43. Separator nozzle.
Table 12. Applicability of Solidification/Stabilization for Specific Contaminants
Process
Micro-
encapsulation
Asphalt-
based
Polymer-
based
Macro-
enoapsulation
with
polyethylene
Stabilization
Cement-
based
Pozzolanic
Organic
Heavy Metals Solvents3
Applicable Applicable
Applicable Applicable;
impeded
setting11
Applicable Applicable if
contaminant is
adsorbed onto a
solid
Applicable Applicable;
impeded setting
Applicable Applicable;
impeded setting
Solid Orgahics
(excluding
explosives)
Applicable;
contaminant
may act as a
binding agent
Applicable;
impeded setting
Applicable
Applicable
Applicable
Acidic Wastes
(from explosives
manufacturing Oxidants
Applicable if Not applicable
waste is first
neutralized
Applicable Not applicable
Applicable if Not applicable
waste is first
neutralized
Applicable Applicable
(contaminant is
neutralized by
the basic
cement)
Applicable Applicable
Sulfates
Not applicable
Applicable
Applicable
Applicable if an
additive used to
prevent spelling
Applicable
a May volatilize upon heating.
b "Impeded setting" does not preclude the existence of an additive that could counteract this effect.
Source: R.F. Weston
67
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Cement-based Pozzolan
Technology Description: To understand the cement-
based pozzolan solidification/stabilization process, it
is necessary to first understand the binding material.
Common (portland) cement is produced by firing a
charge of limestone and clay or other silicate
mixtures in a kiln at high temperatures. The
resulting clinker is ground to a fine powder to
produce a cement that consists of approximately 50
percent tricalcium and 25 percent dicalcium silicates
(also present are about 10 percent tricalcium
aluminate and 10 percent calcium aluminoferrite).
The cementation process is brought about by the
addition of water to the anhydrous cement powder.
This first produces a colloidal calcium silicate-
hydrate gel of indefinite composition and structure.
Hardening of the cement is a lengthy process brought
about by the interlacing of thin, densely packed,
silicate fibrils growing from the individual cement
particles. This fibrillar matrix incorporates the added
aggregates and/or waste into a monolithic, rock-like
mass.
A number of additives (many proprietary) have been
developed for use with cement to improve the
physical characteristics and to decrease the leaching
losses from the solidified mass. Experimental work
on the treatment of radioactive waste has shown that
nuclear waste retention improvements can be
achieved by cement-based stabilization processes
with the addition of clay or vermiculite as
absorbents. Soluble silicates have reportedly been
used to bind contaminants in cement solidification
processes, but this additive causes an increase in
volume to occur during the setting of the cement-
waste mixture. A recently proposed modification of
this technique involves dissolving the metal-rich
waste with fine-grained silica at low pH and then
polymerizing the mixture by raising the pH to 7. The
resulting contaminated gel is mixed with cement and
hardens within 3 days. The equipment used for the
cement-based pozzolan process is similar to that used
in a cement batching plant as illustrated in Figure
44.
Applicability: Most hazardous waste slurried in
water can be mixed directly with cement, and the
suspended solids will be incorporated into the rigid
matrices of the hardened concrete. This process is
especially effective for waste with high levels of toxic
metals since at the pH of the cement mixture^ most
multivalent cations are converted into insoluble
hydroxides or carbonates. Metal ions also may be
incorporated into the crystalline structure of the
cement minerals that form. Materials in the waste
(such as sulfides, asbestos, latex and solid plastic
wastes) may actually increase the strength and
stability of the waste concrete. It is also effective for
high-volume, low-toxic, radioactive wastes.
The presence of certain inorganic compounds in the
hazardous waste and the mixing water can be
deleterious to the setting and curing of the waste-
containing concrete. Also, impurities such as organic
materials, silt, clay or lignite may delay the setting
and curing of common portland cement for as long as
several days. Dust-like, insoluble materials passing
through a No. 200 mesh sieve (74 X 10-6m particle
size) are undesirable, as they may coat the larger
particles and weaken the bond between the particles
and the cement. Soluble salts of manganese, tin, zinc,
copper and lead may cause large variations in setting
time and significant reduction in physical strength.
In this regard, salts of zinc, copper and lead are the
most detrimental. Other compounds such as sodium
salts of arsenate, borate, phosphate, iodate and
sulfide will retard setting of portland cement even at
concentrations as low as a few tenths of a percent of
the weight of the cement used. Wastes containing
large amounts of sulfate (such as flue-gas cleaning
sludges) not only retard the setting of concrete, but,
by reacting to form calcium sulfoaluminate hydrate,
cause swelling and spalling in the solidified waste-
containing concrete. To prevent this reaction, a
special low-alumina cement was developed for use in
circumstances where wastes containing high sulfate
levels are encountered.
Advantages: Cement-based solidification systems are
an economically feasible process having the following
advantages:
(1) The amount of cement used can be varied to
produce high-bearing capacities thereby
making the waste/concrete material a good
subgrade and subfoundation material.
(2) Low permeability in the product can also be
achieved by varying the amount of cement
used.
(3) Raw materials are plentiful and inexpensive.
(4) The technology and management of cement
mixing and handling is well known; the
equipment is commonplace and specialized
labor is not required.
(5) Extensive drying or dewatering of the waste
is not required because cement mixtures
require water in the hydration process, and
thus the amount of cement added can be
adjusted to accommodate a wide range of
waste water contents.
(6) The system is tolerant of most chemical
variations. The natural alkalinity of the
cement used can neutralize acids. Cement is
not affected by strong oxidizers, such as
nitrates or chlorates.
68
-------
Figure 44. Cement-based stabilization process (Roy F. Weston).
Mixing Pump
(Sodium J
Silicate Tank J
Stabilized Waste
(7) Pretreatment is required only for materials
that retard or interfere with the setting
action of cement.
(8) Leaching characteristics can be improved,
where necessary, by coating the resulting
product with a sealant.
Disadvantages: Disadvantages include the fact that
relatively large amounts of cement are required for
most treatment processes (but this may partly be
offset by the low cost of material). The weight and
volume of the final product is typically about double
those of other solidification processes. Uncoated
cement-based products may require a well-designed
landfill for burial. Experience in radioactive waste
disposal indicates that some hazardous constituents
are leached from the solidified concrete, especially by
mildly acidic leaching solutions. Extensive
pretreatment and the use of more expensive cement
types or additives may be necessary for waste
containing large amounts of impurities, such as
borates and sulfates which can effect the setting or
curing of the waste-concrete mixture. If ammonia is
present in the waste, the alkalinity of cement drives
off ammonium ions as ammonia gas. Finally, if
energy cost increases dramatically, the cost of cement
will likely follow because cement is an energy-
intensive material.
Corrective Action Application: At the James River
site in Virginia, cement-based solidification was
performed on kepone-contaminated sediment.
Testing indicated that the cementitious agents were
ineffective in reducing kepone concentrations in
water leachate (Tittlebaum et al., 1985). This was
attributed to the high pH of the cementitious
stabilization agents required in the curing process.
Although the elevated pH proved to effectively
contain heavy metals, it resulted in increasing the
water solubility of the kepone in the sediment
(Tittlebaum et al., 1985). This example serves to
show how contaminant-specific, cement-based
solidification processes are.
Pozzo/an/c Processes (Not Containing Cement)
Technology Description: Waste solidification
techniques based on lime products usually depend on
the reaction of lime with a fine-grained silica
69
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(pozzolanic) material and water to produce a
concrete-like solid (sometimes referred to as a
pozzolanic concrete). The most common pozzolanic
materials used in this solidification process are fly
ash, ground blast-furnace slag and cement-kiln dust.
All of these materials are themselves waste products
with little or no commercial value. The use of these
waste products to consolidate another waste is often
advantageous to the processor, who can treat two
waste products at the same time. For example, by
making use of the pozzolanic reaction, power-plant
fly ash can be combined with flue-gas-cleaning
sludge and lime (along with other additives) to
produce an easily handled solid. Figure 45 illustrates
the configuration of equipment used for this process.
Applicability: Pozzolanic processes are suitable for
high-volume, low-toxicity wastes containing
radioactive materials or heavy metals with an
organic content below 10 percent.
Advantages: The advantages of lime-based
solidification techniques that produce pozzolanic
concrete are: solidified material produced! has
improved handling and permeability characteristics;
materials required for the process are often very low
in cost and widely available; little specialized
equipment is required for processing; the chemistry
of lime-pozzolanic reactions are relatively well-
known; sulfate content of the waste does not cause
spalling or cracking; and extensive dewatering is not
necessary because water is required in the setting
reaction.
Disadvantages: The lime-based systems have many
of the same potential disadvantages as cement-based
techniques including: the lime and other additives
add to the weight and bulk of the resultant product to
be transported and/or landfilled; uncoated lime-
treated materials may require specially designed
landfills to guarantee that the material does not lose
potential pollutants by leaching; the process is
temperature sensitive; the waste may require
pretreatment; the setting characteristics of the
pozzolanic concrete are sensitive to organic content;
and the process has a potential for producing fugitive
dust emissions.
Corrective Action Application: In Massachusetts, a
municipal wastewater treatment plant receives a
number of wastestreams containing heavy metals
from local industries. When tested, the dewatered
sludge failed the EP toxicity test. In order to permit
landfill disposal of the sludge, solidification processes
were examined. A soluble, silicate-based system,
developed by Chemfix, was ultimately selected which
produced a product whose leachate passed the EP
toxicity test (Sullivan, 1984).
Cement-Pozzolanic Processes
Certain treatment systems fall in the category of
cement-pozzolanic processes and have been in use for
some time outside the U.S. In these systems, both
cement and lime-siliceous materials are used in
combination to give the best and most economical
containment for the specific waste being treated. In
general, the bulk of the comments (under both
classifications above) hold for techniques using a
combination of treatment materials.
Thermoplastic Microencapsul&tion
Technology Descriptions: The use of thermoplastic
solidification systems in radioactive waste disposal
has led to the development of waste containment
systems that can be adapted to industrial waste. In
processing radioactive waste with bitumen or other
thermoplastic material (such as paraffin or
polyethylene), the waste is dried, heated and
dispersed through a heated, plastic matrix. The
mixture is then cooled to solidify the mass.
The process requires some specialized (expensive)
equipment to heat and mix the waste and plastic
matrices, but equipment for mixing and extruding
waste plastic are commercially available. The plastic
in the dry waste must be mixed at temperatures
ranging from 130° to 230°C, depending on the
melting characteristics of the material and type of
equipment used.
A variation of this process uses an emulsified
bitumen product that is miscible with a wet sludge.
In this process, the mixing can be performed at any
convenient temperature below the boiling point of the
mixture. The overall mass must still be heated and
dried before it is suitable for disposal. Ratios of
emulsions to waste of 1:1 to 1:1.5 are necessary for
adequate incorporation.
Applicability: Thermoplastic microencapsulation is
commonly used for high-toxicity, low-volume wastes
and is suitable for inorganic and most organic waste.
In many cases, the waste type can rule out the use of
an organic-based treatment system. Organic
chemicals that are solvents for the matrix obviously
cannot be used directly in the treatment system.
Strong oxidizing salts (such ass nitrates, chlorates or
perchlorates) will react with the organic matrix
materials and cause slow deterioration. At the
elevated temperatures necessary for processing, the
matrix-oxidizer mixtures are extremely flammable.
Leach or extraction testing undertaken on anhydrous
salts embedded in bitumen as a matrix indicates that
rehydration of the embedded compound can occur.
When the sample is soaked in water, the asphalt or
bitumen can swell and split apart, thereby greatly
increasing the surface area &nd rate of waste loss.
70
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Figure 45. Lime-based (pozzolanic) stabilization process (Roy F. Weston).
Pozzolanic
silo
Waste
Lime
silo
1
f
Feeder
units
i
f
-Landfill
Stabilized waste
Some salts (such as sodium sulfate) will naturally
dehydrate at the temperatures required to make the
bitumen plastic; thus, these easily dehydrated
compounds must be avoided in thermoplastic
stabilization.
Advantages: The major advantages of the
thermoplastic-based disposal systems are: by
disposing of the waste in a dry condition, the overall
volume of the waste is greatly reduced; most
thermoplastic matrix materials are resistant to
attack by aqueous solutions; microbial degradation is
minimal; most matrices adhere well to incorporated
materials, therefore, the final product has good
strength; and materials embedded in a thermoplastic
matrix can be reclaimed if needed.
Disadvantages: The principal disadvantages of the
thermoplastic-based disposal systems are the
following: (1) expensive, complicated equipment
requiring highly specialized labor is necessary for
processing; (2) the plasticity of the matrix-waste
mixtures may require that containers be provided for
transportation and disposal of the materials, which
greatly increases the cost; (3) the waste materials to
be incorporated must be dried, which requires large
amounts of energy; (4) incorporating wet wastes
greatly increases losses through leaching; (5) these
systems cannot be used with materials that
decompose at high temperatures, especially citrates
and certain types of plastics; (6) there is a risk of fire
in working with organic materials such as bitumen
at elevated temperatures; (7) during heating, some
mixes can release objectionable oils and odors,
causing secondary air pollution; (8) the incorporation
of tetraborates of iron and aluminum salts in
bitumen matrices causes premature hardening, and
can clog and damage the mixing equipment; (9)
strong oxidizers usually cannot be incorporated into
organic materials without the occurrence of oxidizing
reactions (High concentrations of strong oxidizers at
elevated processing temperatures can cause fires.);
and (10) dehydrated salts incorporated in the
thermoplastic matrix will slowly rehydrate if the
mixture is soaked in water. The rehydrated salt will
expand the mixture causing the waste block to
71
-------
fragment thereby increasing the exposed surface
area.
Corrective Action Application: Documentation 0^1 the
application of this technology is limited for RCRA
sites.
Surface Encapsulation
Technology Description: Many waste treatment
systems depend on binding particles of waste
material together. To the extent to which the binder
coats the waste particles, the wastes are
encapsulated. However, the systems addressed by
surface encapsulation processes are those in which
the waste has been pressed or bonded together and
then is enclosed in a coating jacket of inert material.
A number of systems for coating solidified industrial
waste have been examined. In most cases, coated
materials have suffered from lack of adhesion
between coatings and bound wastes, and lack of long-
term integrity in the coating materials.
Applicability: Surface encapsulation (macroeiicap-
sulation) is appropriate for both organic and
inorganic wastes.
Surface coating of concrete-waste composites has
been examined extensively. The major problems
encountered have been poor adhesion of the coating
onto the waste or lack of strength in the concrete
material containing the waste. Surface coating
materials that have been investigated include
asphalt, asphalt emulsion and vinyl. THowever, no
surface coating system for cement-solidified material
is currently being advertised.
Advantages: Major advantages of an encapsulation
process involve the fact that waste materials never
come into contact with water, therefore, soluble
materials (such as sodium chloride) can be
successfully surface-encapsulated. The impervious
jacket also eliminates all leaching into contacting
waters as long as the jacket remains intact.
Disadvantages: A major disadvantage of surface
encapsulation is that the resins required for
encapsulating are expensive. The process requires
large expenditures of energy in drying, fusing the
binder and forming the jacket. Polyethylene is
combustible (with a flash point of 350°C) making
fires a potential hazard. The system requires
extensive capital investment and equipment. Skilled
labor is required to operate the molding and fusing
equipment.
Corrective Action Application: TRW Corporation has
developed one type of encapsulation system (U.S.EPA
1980). The TRW surface encapsulation requires that
the waste material be thoroughly dried. The dried
waste is stirred into an acetone solution of modified
1,2-polybutadiene for 5 min. The mixture is allowed
to set for 2 hr during which time a solid block is
formed. The optimum amount of binder for
encapsulation is 3 percent to 4 percent of the fixed
material on a dry-weight basis. The coated material
is placed in a mold, subjected to slight mechanical
pressure, and heated to between 120° and 200°C to
produce fusion. The agglomerated material is a hard,
tough, solid block. A polyethylene jacket 2.5 mm
thick is used to encapsulate the solid block and
adheres to the polybutadiene binder.
No field tests or pilot applications of this process have
been performed to date. The product does well in
bench tests in which the polyethylene jacket remains
intact Destructive bench tests which grind the
product (such as the EP Tox or TCLP) defeat the
purpose of the encapsulating jacket.
Self-Cementing
Technology Description: Some industrial wastes such
as flue-gas-cleaning sludges contain large amounts of
calcium sulfate and calcium sulfite. A technology has
been developed to treat these types of wastes so that
they become self-cementing. Usually a small portion
(8 percent to 10 percent by weight) of the dewatered
waste sulfate/sulfite sludge is calcined under
carefully controlled conditions to produce a partially
dehydrated cementitious calcium sulfate or sulfite.
This calcined waste is then reintroduced into the
waste sludge along with other proprietary additives.
Fly ash is often added to adjust the moisture content.
The finished product is a hard, plaster-like material
with good handling characteristics and low
permeability.
Applicability: Self-cementing processes require large
amounts of calcium sulfate and calcium sulfite and
are appropriate for immobilizing heavy metals.
Advantages: The primary advantage for using a self-
cementing process is the material produced is stable,
nonflammable and nonbiodegradable. There are
reports of effective heavy me.'tal retention, which is
perhaps related to chemical bonding of potential
pollutants. Other advantages are: (1) no major
additives have to be manufactured and shipped to the
processing site; (2) the process is reported to produce
a faster setting time and more rapid curing than
comparable lime-based systems; and (3) these
systems do not require completely dry waste because
the hydration reaction uses up water.
Disadvantages: The disadvantages associated with
self-cementing processes include: the self-cemented
sludges have much the same leaching characteristics
as cement- and lime-based systems; only high
calcium sulfate or sulfite sludges can be used; and
additional energy is required to produce the calcined
cementitious material. The process also requires
72
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skilled labor and expensive machinery for calcining
waste and for mixing the calcined wastes with the
bulk waste and the proprietary additives.
Corrective Action Application: Documentation on the
application of this technology for RCRA waste is
limited.
References
Tittlebaum, Marty E., Roger Seals, Frank Cartledge,
Stephanie Engels, Louisiana State University. State
of the Art on Stabilization of Hazardous Organic
Liquid Wastes and Sludges. Critical Reviews in
Environmental Control, Volume 15, Issue 2,1985.
Sullivan, Tim, "SESD is Treating Sewage Again -
With Time to Spare", The Salem, Massachusetts,
Evening News - 3, July 1984. •
U.S. Environmental Protection Agency, "Guide to
the Disposal of Chemically Stabilized and Solidified
Waste", SW-872, Office of Water and Waste
Management, Washington, D.C., 1980.
U.S. Environmental Protection Agency, "Handbook
for Stabilization/ Solidification of Hazardous
Wastes", EPA/540/2-86/001.
Federal Register - Extraction Procedures 40 CFR
261, Appendix II, 1980.
Federal Register - Toxicity Characteristic Leaching
Procedure, Revised 40 CFR 261, Appendix II, 1986.
Federal Register - Multiple Extraction Procedure
Test, Revised 40 CFR 261, Appendix II, January
1989. *
73
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Chapter 7
Engineering Considerations for Corrective Measures Implementation
The Corrective Measures Implementation (CMI)
phase of the Corrective Action Process can present a
difficult task for engineers involved in implementing
the corrective action(s) selected. Up to this point,
activities have been directed toward those
engineering matters associated with site
characterization and remedy selection, along with
routine interface with the regulatory community. As
the work proceeds into the corrective measure
implementation (design and construction) phase, the
company management becomes more involved in the
process, primarily as a result of the need to commit
funds. In addition, the engineer must now come face-
to-face with the complexities of the site in terms of
the installation of facilities. Thus, the engineer's
efforts are directed toward the parallel, yet
interconnected, activities associated with satisfying
the regulatory requirements, dealing with
management's needs, and developing facilities
consistent with the site conditions. Using the
elements of the Corrective Measures Implementation
outlined in RCRA Corrective Action Plan - Interim
Final (U.S. EPA, 1988) specifically the CMI Plan
Development, the Corrective Measures (CM) Design
and CM Construction the implications of each
element can be viewed in the context of conventional
engineering activities.
CMI Plan Development
From an engineering perspective, it is normal
practice to identify a project management team and
project strategy prior to beginning the design phase.
It is at this point that the methods for handling the
design, preparation of specifications, and
construction are decided. In essence, a plan (although
not formalized in great detail) is defined for the
design phase and generalized for the construction
phase. The EPA's proposed guidance suggests that
the management plan for Corrective Actions be
formalized similar to plans submitted for Superfund
cleanup projects.
A community relations plan is suggested for
corrective action projects. For most projects, such
activities are reserved for public relations personnel.
However, because of the technical aspects of
corrective action projects, engineering attention may
be required to alleviate public, concern with noise,
odors and other nuisances associated with corrective
action activities. It is important to work closely with
the local residents so that these problems can be
identified and handled effectively when they occur.
For example, on one stabilization job, a new
solidifying agent was brought to the site which
caused some dusting problems. The dust got on a
number of neighbor's cars. Because of the public
participation program, the problem was quickly
identified; a solution was found to prevent the dust
emissions; and the contractor paid to have all of the
affected automobiles cleaned. The project was only
shut down for one day while the dust collecting
measure was implemented. A much longer delay
would have occurred without the presence of a public
participation program which avoided the
development of antagonism between local residents,
the contractor, and the company implementing the
program.
Corrective Measures Design
The design phase of an engineering project normally
consists of the following activities:
• Defining the design basis.
• Preparing preliminary and detailed design
drawings.
• Development of equipment lists and
specifications.
• Developing material and energy balances.
Based on the in-house engineering capabilities,
management philosophy, and the complexity of the
project, there are a number of ways a company may
wish to approach these activities. In some cases, a
turnkey approach where an engineering firm'is
retained to design and construct the required
facilities is preferred. In other cases, the design,
specification, preparation and construction
management activities are performed by the
company, and the equipment and construction
activities are purchased. However, it is not
uncommon for construction of facilities to begin prior
to the completion of the design. Most companies have
mechanisms for the routine review of a project at
various phases of completion. These project review
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requirements parallel those of the regulatory
community. For corrective action projects, it will be
necessary to take into consideration the needs of the
regulatory community in the scheduling and
recording of activities as they are performed.
Operations and Maintenance Manuals are typically
developed for most industrial facilities. The
development of these documents usually takes place
after all equipment is purchased and during the
installation and shake-down of the facilities. These
manuals cover normal operation and maintenance of
equipment, including troubleshooting instructions
and preventive and routine maintenance needs of the
equipment. The items suggested in the CAP that are
not normally addressed by operation and
maintenance manuals are issues such as a
description of potential operating problems which
evolve from human health and environmental
considerations; a description of alternate operating
and maintenance activities which recognize possible
aspects for system failure; a description of routine
monitoring and laboratory testing; and a safety plan.
For example, machinery that has been contaminated
during remediation of the site may have to be
maintained on site or decontaminated prior to
maintenance. Depending on the nature of the work,
the health and safety of the personnel performing
maintenance may require extraordinary procedures
in order to perform what may otherwise be routine
tasks (e.g., lubrication of heavy equipment while
wearing protective equipment).
Other, engineering considerations which are
routinely addressed in the design phase are the
development of a project schedule and cost estimate.
Most companies or contractors for those companies
have developed construction quality assurance
programs which are based on good engineering
practice and state and local building requirements.
Regulatory considerations and data reporting may
impact on the quality assurance program and
construction schedules. The design is based on the
information generated during the facility assessment
and the facility investigation. During construction,
additional information is generated that may alter
the process requirements and operating parameters,
forcing schedule changes.
In addition to regulatory requirements, the practical
matters associated with maintaining product and
personnel flow to and from operating facilities must
be addressed. For example, it may be difficult to
remove a rail spur for remediation of a contaminated
bed, if the only means to deliver a feedstock into the
facility or ship a product from the facility is this rail
line. In-situ flushing or some other form of non-
invasive treatment would be required to address such
a problem. Similarly, personnel access may have to
be addressed in the planning for a corrective
measures program. This is especially true in older or
more crowded facilities. People and material must be
allowed to move around so that operations may
continue at the facility in as normal a fashion as
possible.
Corrective Measures Construction
From an engineering perspective, the general
corrective measures construction activities identified
in the CAP conform with typical construction
management activities, but are more rigorous. The
planning, inspection, and quality assurance
activities in the CAP focus on issues of concern to the
regulatory community to ensure that the completed
corrective measures meet or exceed the cleanup
objectives. In addition to the regulatory needs, the
facility engineer is also concerned with these issues
from the perspective of ensuring efficient
construction of facilities, and that the facilities
installed meet the design specifications, plant safety
requirements, and building codes. As most
construction projects proceed, a "punch" list of items
requiring completion, modification to meet safety
codes, or repairs identified during equipment
checkout is developed; and system start-up and
shake-down procedures are developed. Periodic
review and resolution of each item is required before
the construction phase is considered complete.
Another issue that the engineer must consider is the
training of operating personnel. This can be handled
by the contractor or by the equipment supplier. In
some cases, personnel who will be responsible for the
operation of the facilities are on the project team from
its inception, as part of their training. In other cases,
the operating team is assembled for training during
the start-up and shake-down procedures. In any
event, careful training of personnel before the
contractor completes the project appears to be an
effective way to ensure proper- operation of the
facility over the long term.
As with most pollution control projects, the
effectiveness of the design is demonstrated by some
type of performance testing. This generally occurs
after the equipment is operating "normally". For
corrective action projects, certain facilities (such as
organized above-ground treatment systems) may be
able to demonstrate effectiveness through the
performance testing mechanism. However, other
systems (such as groundwater pumping to
control/recover a contaminant plume) may require
ongoing monitoring to assess its effectiveness.
Sampling and testing protocols may have to be
developed and implemented to demonstrate the
performance of these systems.
Summary
The CMI requires close cooperation between the
regulatory community and the engineering and
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management team of the company performing the
corrective action. Through cooperation and good
planning, the Corrective Action Process can proceed
in a timely fashion. Without such cooperation and
planning, time and money can be misdirected and
necessary protection of HHE can be delayed. Thus,
from the start of the Corrective Action Process, it is
important to work closely with the regulatory
community in all phases of the project.
References
U.S. EPA. 1988a. RCRA Corrective Action Plan -
Interim Final EPA/530-SW-88-028, OSWER 9902.3,
Office of Solid Waste and Emergency Response,
Washington, B.C., June 1988.
•U.S. Government Printing Office: 1992— 648-003/41850
77
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